PROCESS FOR THE PRODUCTION OF POST-RETICULATED WATER-ABSORBING POLYMER PARTICLES ON THE SURFACE, POS

专利摘要:
process for producing surface post-crosslinked water-absorbent polymer particles, surface-post-crosslinked water-absorbent polymer particles, and, fluid-absorbent article. The present invention relates to a process for producing surface post-crosslinked water-absorbent polymer particles by coating water-absorbent polymer particles having a residual monomer content in the range of 0.03 to 15% by weight with at least one surface post-crosslinker and thermal surface post-crosslinking at temperature in the range of 100 to 180°C.
公开号:BR112015011531B1
申请号:R112015011531-4
申请日:2013-11-07
公开日:2021-08-24
发明作者:Thomas Daniel；Norbert Herfert；Stephan Bauer；Katrin Baumann；Birgit Reinhard；Jürgen Freiberg；Christophe Bauduin；Katarzyna Dobrosielska-Oura；Michael Mitchell
申请人:Basf Se；
IPC主号:

专利说明:

[001] The present invention relates to a process for the production of surface-crosslinked water-absorbent polymer particles by coating water-absorbent polymer particles having a residual monomer content in the range of 0.03 to 15 % by weight with at least one surface post-crosslinking and thermal surface post-crosslinking at temperature in the range of 100 to 180°C.
[002] The preparation of water-absorbent polymer particles is described in the monograph "Oqfgtp Uwrgtcduqtdgpv Rqn{ogt Vgehpqnqg{", F.L. Buchholz and AT. Graham, Wiley-VCH, 1998, on pages 71 to 103.
[003] Being products that absorb aqueous solutions, water-absorbent polymer particles are used to produce diapers, tampons, toilet paper and other hygiene items, but also as water-retaining agents in the gardening market. Water absorbing polymer particles Vcodfio u«q tefetkfqu eqoq "rqtfogtqu uwrgtcduqtxgpVgu" qw "uwretcduqtxepVeu"
[004] The preparation of water-absorbent polymer particles by polymerizing droplets of a monomer solution is described, for example, in EP 0 348 180 A1, WO 96/40427 A1, US 5,269,980, WO 2008/009580 A1, WO 2008/052971 A1 , WO2011/026876 A1 , and WO 2011/117263 A1 .
[005] Polymerization of monomer solution droplets in a hcue fe iáu swe ektewpfc cu iqVíewncu *“rqnkmerization by iqVíewnc formation”+ fkurqpkdknkzc rcrtíewncu fe rqníoetquc cduqtáu sweepvc (medium temperature). Mean sphericity is a measure of the circularity of polymer particles and can be determined, for example, with the Camsizer® image analysis system (Retsch Technology GmbH; Haan; Germany).
[006] It was an objective of the present invention to provide water-absorbent polymer particles having better properties, that is, water-absorbent polymer particles having a high centrifuge holding capacity (CRC) and a high absorption under a load of 49, 2 g/cm2 (AUHL).
[007] It was another objective of the present invention to provide particles of water-absorbent polymers that have a high centrifuge holding capacity and that provide good liquid distribution when used in toiletries.
[008] Yet another objective of the present invention is to provide particles of water-absorbent polymers that allow the reduction of use in toiletries, while maintaining excellent dryness.
[009] The objective is achieved by a process for the production of water-absorbent polymer, comprising the steps of forming water-absorbent polymer particles by polymerizing a monomer solution, coating the water-absorbent polymer particles with at least one powder. surface crosslinker and post-surface thermal crosslinking of the coated water-absorbent polymer particles, wherein the residual monomer content in the water-absorbent polymer particles prior to coating with the surface post-crosslinker is in the range of 0.03 at 15% by weight, and the temperature during post-thermal surface crosslinking is in the range of 100 to 180°C.
[0010] The present invention further provides a process for the production of water-absorbent polymer, comprising the steps of forming water-absorbent polymer particles by polymerizing a monomer solution, coating the water-absorbent polymer particles with at least one powder. surface crosslinker and post-surface thermal crosslinking of the coated water-absorbent polymer particles, wherein the residual monomer content in the water-absorbent polymer particles prior to coating with the surface post-crosslinker is in the range of 0.1 at 10% by weight, the surface post crosslinker is an alkylene carbonate, and the temperature during the thermal surface post crosslink is in the range of 100 to 180°C.
[0011] The present invention is based on the discovery that the level of residual monomers in the water-absorbent polymer particles before the thermal surface post-crosslinking, the surface thermal post-crosslink temperature, and the surface post-crosslinker in themselves have an important impact on the properties of the post-crosslinked surface water-absorbent polymer particles formed.
[0012] The result of the specific conditions according to the process of the present invention are particles of water-absorbent polymers having a high centrifuge holding capacity (CRC) and a high absorption under a load of 49.2 g/cm2 (AUHL ). This is an amazing result. Centrifuge holding capacity (CRC) is known to significantly decrease during post-thermal surface crosslinking as proven by Ullmann's Encyclopedia of Industrial Chemistry, 6th Ed., Vol. 35, page 84, Figure 7. Surprisingly additional is that the less reactive alkylene carbonate reacts under the inventive conditions at unusually low temperatures. Other cyclic surface crosslinkers, eg 2-oxazoliidinone, show very similar behavior. According to the monograph "Modern Uwrgr-absorbent Polymer Vgehponog{", F.L. Buchholz and AT. Graham, Wiley-VCH, 1998, page 98, recommended reaction temperatures for alkylene carbonates are in the range of 180 to 215°C.
[0013] The combination of having a high centrifuge holding capacity (CRC) and a high absorption under a load of 49.2 g/cm2 (AUHL) results in water-absorbent polymer particles having a high total liquid absorption in the drainage absorption test.
[0014] The specific conditions further result in the water-absorbent polymer particles having a lower pressure dependence of the swelling time characteristic in the VAUL test at high centrifuge holding capacities (CRC).
[0015] The present invention further provides surface post-crosslinked water-absorbent polymer particles having a centrifuge holding capacity (CRC) of 35 to 75 g/g, an absorption under high load (AUHL) of 20 to 50 g /g, a level of extractable constituents less than 10% by weight and a porosity of 20 to 40%.
[0016] The present invention further provides surface post-crosslinked water-absorbent polymer particles having a total liquid absorption of Y > -500 x ln(X) + 1880 where Y[g] is the total liquid absorption and X [g/g] is the centrifuge holding capacity, where the centrifuge holding capacity is at least 25 g/g and the liquid absorption is at least 30 g.
[0017] The present invention further provides surface post-crosslinked water-absorbent polymer particles having a change in characteristic swelling time of less than 0.6 and a centrifuge holding capacity of at least 35 g/g, wherein the change in characteristic swelling time is
where Z is the change in characteristic swelling time, xo.i is the characteristic swelling time at a pressure of 0.1 psi (6.9 g/cm2), and xo.s is the characteristic swelling time at a pressure 0.5 psi (35.0 g/cm 2 ).
[0018] The present invention further provides fluid absorbent articles comprising the inventive water absorbent polymer particles. Detailed Description of the Invention
[0019] The water-absorbent polymer particles are prepared by a process, comprising the steps of forming water-absorbent polymer particles by polymerizing a monomer solution, comprising a) at least one ethylenically unsaturated monomer that carries acid groups and can be at least less partially neutralized, b) optionally one or more crosslinkers, c) at least one initiator, d) optionally one or more ethylenically unsaturated monomers copolymerizable with the monomers mentioned in a), e) optionally one or more water-soluble polymers, and f) water, coating the water-absorbent polymer particles with at least one surface post-crosslinker and post-thermal surface-crosslinking of the coated water-absorbent polymer particles, wherein the residual monomer content in the water-absorbent polymer particles prior to coating with the surface post crosslinker is in the range of 0.03 to 15% by weight, the super crosslinker post Hard is an alkylene carbonate and the temperature during post-thermal surface crosslinking is in the range of 100 to 180°C.
[0020] Water-absorbent polymer particles are typically insoluble, but swellable in water.
The monomers a) are preferably soluble in water, i.e. the solubility in water at 23°C is typically at least 1 g/100 g water, preferably at least 5 g/100 g water, more preferably at least minus 25 g/100 g water, above all preferably at least 35 g/100 g water.
[0022] Suitable monomers a) are, for example, ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid and itaconic acid. Particularly preferred monomers are acrylic acid and methacrylic acid. Particular preference is given to acrylic acid.
[0023] Suitable additional monomers a) are, for example, ethylenically unsaturated sulfonic acids such as vinylsulfonic acid, styrenesulfonic acid and 2-acrylamido-2-methylpropanesulfonic acid (AMPS).
[0024] Impurities can have a strong impact on polymerization. Preference is given to especially preferred monomers a). Purification methods used are disclosed in WO 2002/055469 A1, WO 2003/078378 A1 and WO 2004/035514 A1. A suitable monomer a) is according to WO 2004/035514 A1 purified acrylic acid having 99.8460% by weight acrylic acid, 0.0950% by weight acetic acid, 0.0332% by weight water, 0.0203 by weight of propionic acid, 0.0001% by weight of furfurals, 0.0001% by weight of maleic anhydride, 0.0003% by weight of diacrylic acid and 0.0050% by weight of hydroquinone monomethyl ether.
[0025] Polymerized diacrylic acid is a source for residual monomers due to thermal decomposition. If temperatures during the process are low, the diacrylic acid concentration is no longer critical and acrylic acids having higher diacrylic acid concentrations, ie 500 to 10,000 ppm, can be used for the inventive process.
The content of acrylic acid and/or salts thereof in the total amount of monomers a) is preferably at least 50 mol%, more preferably at least 90 mol%, above all preferably at least 95 mol%.
The acid groups of the monomers a) are typically partially neutralized in the range of 0 to 100 mol%, preferably to an extent of 25 to 85 mol%, preferably to an extent of 50 to 80 mol%, more preferably to 60 to 75 mol%, for which customary neutralizing agents can be used, preferably alkali metal hydroxides, alkali metal oxides, alkali metal carbonates or alkali metal hydrogen carbonates and mixtures thereof. Instead of alkali metal salts, it is also possible to use ammonia or organic amines, eg triethanolamine. It is also possible to use oxides, carbonates, hydrogen carbonates and hydroxides of magnesium, calcium, strontium, zinc or aluminum in the form of powders, slurries or solutions and mixtures of any of the above neutralizing agents. Example for a mixture is a sodium aluminate solution. Sodium and potassium are particularly preferred as alkali metals, but very particular preference is given to sodium hydroxide, sodium carbonate or sodium hydrogen carbonate and mixtures thereof. Typically, neutralization is achieved by mixing into the neutralizing agent as an aqueous solution, as a melt or preferably also as a solid. For example, sodium hydroxide having a water content significantly below 50% by weight may be present as a waxy material having a melting point above 23°C. In this case, addition measured as part material or cast at elevated temperature is possible.
[0028] Optionally, it is possible to add to the monomer solution, or to the starting materials of this or more chelating agents to mask metal ions, eg iron, for the purpose of stabilization. Suitable chelating agents are, for example, alkali metal citrates, citric acid, alkali metal tartrates, alkali metal lactates and glycolates, pentasodium triphosphate, ethylenediamine tetraacetate, nitriloacetic triacid and all chelating agents known under the name Trilon ®, for example, Trilon® C (pentasodium diethylenetriaminepentaacetate), Trilon®D (Trisodium (hydroxyethyl)ethylenediaminetriacetate) and Trilon®M (methylglycinediacetic acid).
Monomers a) typically comprise polymerization inhibitors, preferably hydroquinone monoether, as storage inhibitor.
[0030] The monomer solution preferably comprises up to 250 ppm by weight, more preferably not more than 130 ppm by weight, above all preferably not more than 70 ppm by weight, preferably not less than 10 ppm by weight, most preferably not less that 30 ppm by weight and especially about 50 ppm by weight of hydroquinone monoether, based in each case on acrylic acid, with salts of acrylic acid salts being counted as acrylic acid. For example, the monomer solution can be prepared using acrylic acid having the appropriate hydroquinone monoether content. Hydroquinone monoethers, however, can also be removed from the monomer solution by absorption, for example, onto activated carbon.
Preferred hydroquinone monoethers are hydroquinone monomethyl ether (MEHQ) and/or alpha-tocopherol (vitamin E).
[0032] Suitable crosslinkers b) are compounds having at least two groups suitable for crosslinking. Such groups are, for example, ethylenically unsaturated groups that can be polymerized by a free radical mechanism in the polymer chain and functional groups that can form covalent bonds with the acid groups of monomer a). Furthermore, polyvalent metal ions which can form co-ordinated bonding with at least two acid groups of monomer a) are also suitable crosslinkers b).
[0033] Crosslinkers b) are preferably compounds having at least two free radical polymerizable groups which can be polymerized by a free radical mechanism in the polymer network. Suitable crosslinkers b) are, for example, ethylene glycol dimethacrylate, diethylene glycol diacrylate, polyethylene glycol diacrylate, allyl methacrylate, trimethylolpropane triacrylate, triallylamine, tetraallylammonium chloride, tetraallyloxyethane as described in EP 0 530 438 A1, di- and tri-acrylates, as described in EP 0 547 847 A1, EP 0 559 476 A1, EP 0 632 068 A1, WO 93/21237 A1, WO 2003/104299 A1, WO 2003/104300 A1, WO 2003/104301 A1 and in DE 103 31 450 A1, mixed acrylates which, as well as acrylate groups, comprise additional ethylenically unsaturated groups, as described in DE 103 314 56 A1 and DE 103 55 401 A1, or crosslinker mixtures, as described, for example, in DE 195 43 368 A1, DE 196 46 484 A1, WO 90/15830 A1 and WO 2002/32962 A2.
Suitable crosslinkers b) are, in particular, pentaerythritol triallylether, tetraallyloxyethane, polyethyleneglycol dialylethers (based on rqnkgVkngpq inkeqn Vgpfq wo rguq oqngewnct gpVtg 622 g 42222 i10qnyl-trimethylene+.N. ethoxylate, polyethylene glycol diacrylate, trimethylolpropane triacrylate and triallylamine.
Very particularly preferred crosslinkers b) are polyethoxylated and/or -propoxylated glycerols which have been esterified with acrylic acid or methacrylic acid to give di- or triacrylates, as described, for example, in WO 2003/104301 A1. Ethoxylated 3- to 18-tuply glycerol di- and/or triacrylates are particularly advantageous. Particular preference is given to ethoxylated and/or propoxylated di- or triacrylates of 1- to 5-tupli glycerol. Above all preferred are ethoxylated and/or propoxylated 3-tupli glycerol triacrylates and especially ethoxylated 3-tupli glycerol triacrylate.
[0036] The amount of crosslinker b) is preferably from 0.0001 to 0.6% by weight, more preferably from 0.001 to 0.2% by weight, above all preferably from 0.01 to 0.06% by weight based, in each case, on the monomer a). By increasing the amount of crosslinker b) the centrifuge holding capacity (CRC) decreases and the absorption at a pressure of 21.0 g/cm2 (AUL) passes through a maximum.
[0037] The post-crosslinked polymer particles on the surface of the present invention surprisingly required very little or no crosslinker during the polymerization step. Thus, in a particularly preferred embodiment of the present invention no crosslinker b) is used.
[0038] The initiators c) used can be all compounds which disintegrate into free radicals under polymerization conditions, for example peroxides, hydroperoxides, hydrogen peroxide, persulfates, azo compounds and redox initiators. Preference is given to the use of water soluble initiators. In some cases it is advantageous to use multiple initiators, for example mixtures of hydrogen peroxide and sodium or potassium peroxodisulfate. Mixtures of hydrogen peroxide and sodium peroxodisulfate can be used in any proportion.
Particularly preferred initiators c) are azo initiators such as 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride and 2,2'-azobis[2-(5) dihydrochloride -methyl-2-imidazolin-2-yl)propane], 2,2'-azobis(2-amidinopropane) dihydrochloride, 4,4'-azobis(4-cyanopentanoic acid), 4,4'- sodium salt of azobis(4-cyanopentanoic acid), 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide] and photoinitiators such as 2-hydroxy-2-methylpropiophenone and 1-[4-(2-hydroxyethoxy) )phenyl]-2-hydroxy-2-methyl-1-propan-1-one, redox initiators such as sodium persulfate/hydroxymethylsulfinic acid, ammonium peroxodisulfate/hydroxymethylsulfinic acid, hydrogen peroxide/hydroxymethylsulfinic acid, sodium persulfate/ ascorbic acid, ammonium peroxodisulfate/ascorbic acid and hydrogen peroxide/ascorbic acid, photoinitiators such as 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one and mixtures thereof. The reducing component used is, however, preferably a mixture of the sodium salt of 2-hydroxy-2-sulfinateacetic acid, the disodium salt of 2-hydroxy-2-sulfonateacetic acid and sodium bisulfite. Such mixtures can be obtained as Bruggolite® FF6 and Bruggolite® FF7 (Bruggemann Chemicals; Heilbronn; Germany). Of course it is also possible within the scope of the present invention to use the salts or purified acids of 2-hydroxy-2-sulfinatoacetic acid and 2-hydroxy-2-sulfinatoacetic acid - the latter being available as the sodium salt under the trade name Blancolen® (Bruggemann Chemicals; Heilbronn; Germany).
Initiators are used in customary amounts, for example in amounts from 0.001 to 5% by weight, preferably from 0.01 to 2% by weight, above all preferably from 0.05 to 0.5% by weight , based on monomers a).
[0041] Examples of ethylenically unsaturated monomers d) which are copolymerizable with monomers a) are acrylamide, methacrylamide, hydroxyethyl acrylate, hydroxyethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, dimethylaminopropyl acrylate and diethylaminopropyl methacrylate.
Useful e) water-soluble polymers include polyvinyl alcohol, modified polyvinyl alcohol comprising acidic side groups, e.g., Poval® K (Kuraray Europe GmbH; Frankfurt; Germany), polyvinylpyrrolidone, starch, starch derivatives, modified cellulose, such as such as methylcellulose, carboxymethylcellulose or hydroxyethylcellulose, gelatin, polyglycols or polyacrylic acids, polyesters and polyamides, polylactic acid, polyglycolic acid, co-polylactic-polyglycolic acid, polyvinylamine, polyallylamine, water-soluble copolymers of acrylic acid and maleic acid available as Sokalan® ( BASF SE; Ludwigshafen; Germany), preferably starch, starch derivatives and modified cellulose.
[0043] For optimal action, the preferred polymerization inhibitors require dissolved oxygen. In this way, the monomer solution can be free of dissolved oxygen prior to polymerization by blanketing, ie flowing through with an inert gas, preferably nitrogen. It is also possible to reduce the dissolved oxygen concentration by adding a reducing agent. The oxygen content of the monomer solution is preferably decreased prior to polymerization to less than 1 ppm by weight, more preferably to less than 0.5 ppm by weight.
[0044] The water content of the monomer solution is preferably less than 65% by weight, preferably less than 62% by weight, more preferably less than 60% by weight, most preferably less than 58% by weight.
The monomer solution has, at 20°C, a dynamic viscosity of preferably from 0.002 to 0.02 Pa s, more preferably from 0.004 to 0.015 Pa s, most preferably from 0.005 to 0.01 Pa s. The average droplet diameter in droplet generation increases with increasing dynamic viscosity.
[0046] The monomer solution has, at 20°C, a density of preferably from 1 to 1.3 g/cm3, more preferably from 1.05 to 1.25 g/cm3, above all preferably from 1.1 at 1.2 g/cm3.
[0047] The monomer solution has, at 20°C, a surface tension of 0.02 to 0.06 N/m, more preferably 0.03 to 0.05 N/m, above all preferably 0.035 to 0.045 N/m. The average droplet diameter in droplet generation increases with increasing surface tension. Polymerization
[0048] The monomer solution is polymerized. Suitable reactors are, for example, kneading reactors or belt reactors. In the kneader, the polymer gel formed in the polymerization of an aqueous monomer solution or suspension is continuously reduced, for example, by counter-rotating agitating rods, as described in WO 2001/038402 A1. Mat polymerization is described, for example, in DE 38 25 366 A1 and US 6,241,928. Polymerization in a belt reactor forms a polymer gel which has to be thinned in an additional process step, for example in an extruder or kneader.
[0049] To improve the drying properties, the thinned polymer gel obtained by means of a kneader can additionally be extruded.
[0050] In a preferred embodiment of the present invention the water-absorbent polymer particles are produced by polymerizing droplets of the monomer in a surrounding heated gas phase, for example, using a system described in WO 2008/040715 A2, WO 2008/052971 A1 , WO 2008/069639 A1 and WO 2008/086976 A1.
[0051] The droplets are preferably generated by means of a droplet plate. A droplet plate is a plate having numerous holes, the liquid entering the holes from the top. The droplet plate or liquid can be oscillated, which generates a chain of ideally monodisperse droplets in each hole at the bottom of the droplet plate. In a preferred embodiment, the droplet plate is not agitated.
[0052] In the scope of the present invention it is also possible to use two or more droplet plates with different hole diameters, in such a way that a range of desired particle sizes can be produced. It is preferred that each droplet plate carries only one hole diameter, however mixed hole diameters in one plate are also possible.
[0053] The number and size of holes are selected according to the desired capacity and droplet size. The droplet diameter is typically 1.9 times the hole diameter. What is important here is that the liquid to be formed in a droplet does not pass through the hole as quickly and the pressure drop over the hole is not very large. Otherwise, the liquid does not form a droplet, but instead the liquid jet is split (sprinkled) due to the high kinetic energy. The Reynolds number based on the flow rate per hole and the hole diameter is preferably less than 2000, preferably less than 1600, more preferably less than 1400 and most preferably less than 1200.
[0054] The bottom of the droplet plate has, at least in part, a contact angle preferably at least 60°, more preferably at least 75° and above all preferably at least 90° with respect to the water.
[0055] The contact angle can be a measure of the wetting behavior of a liquid, in particular water, with respect to a surface and can be determined using conventional methods, eg according to ASTM D 5725. A low angle contact denotes good wetting and a high contact angle denotes poor wetting.
[0056] It is also possible that the droplet plate consists of a material having a smaller contact angle with respect to water, for example a steel having the German Building Material Code Number of 1.4571 and is coated with a material having a greater contact angle with respect to water.
[0057] Useful coatings include, for example, fluoro polymers such as perfluoroalkoxyethylene, poly-tetrafluoroethylene, ethylene-chlorotrifluoroethylene copolymers, ethylene-tetrafluoroethylene copolymers and fluorinated polyethylene.
[0058] Coatings can be applied to the substrate as a dispersion, in which case the solvent is subsequently evaporated and the coating is heat treated. For polytetrafluoroethylene this is described, for example, in US-3,243,321.
[0059] Additional coating processes are to be found pc pqVc oentcl “Vjkp Hüou” pc xgtu«q gngVt»pkec fc “WHocnriu Gpekclopedia qh KpfwuVtkcn EjgokuViy” *ugzVc gfk>«q cVwcnkzcfc. 4222 GngeVtqpke Tgngcug+o
[0060] The coatings can be additionally incorporated into a nickel layer in the course of a chemical nickelization.
[0061] It is the poor wetting capacity of the droplet plate that leads to the production of monodisperse droplets of narrow particle size distribution.
[0062] The droplet plate preferably has at least 5, more preferably at least 25, above all preferably at least 50 and preferably up to 750, more preferably up to 500 holes, above all preferably up to 250. The number of holes is determined mainly due to geometric and manufacturing limitations and can be adjusted to practical conditions of use even outside the range given above. The diameter of the holes is adjusted to the desired droplet size.
[0063] The separation of the holes is normally from 5 to 50 mm, preferably from 6 to 40 mm, more preferably from 7 to 35 mm, above all preferably from 8 to 30 mm. Minor hole separations can cause polymerization droplets to agglomerate.
[0064] The diameter of the holes is preferably from 50 to 722 µo. ocku preferably fg 322 c 522 μo. cekoc fg Vwfq rtgfgtkxenogpVg fg 372 c 472 μo0
[0065] For optimization of the mean particle diameter, droplet plates with different hole diameters can be used. Variation can be done by different holes in a plate or by using different plates, where each plate has a different hole diameter. The mean particle size distribution can be monomodal, bimodal or multimodal. Above all preferably it is monomodal or bimodal.
[0066] The temperature of the monomer solution as it passes through the hole is preferably from 5 to 80°C, more preferably from 10 to 70°C, most preferably from 30 to 60°C.
[0067] A gas flows through the reaction chamber. The carrier gas is conducted through the reaction chamber in co-current to the free-falling droplets of the monomer solution, ie, from the top to the downstream. After one pass, the gas is preferably recycled at least partially, preferably up to at least 50%, more preferably up to at least 75%, in the reaction chamber as circulating gas. Typically, a portion of the carrier gas is discarded after each pass, preferably up to 10%, more preferably up to 3% and most preferably up to 1%.
[0068] The carrier gas can be composed of air. The oxygen content of the carrier gas is preferably from 0.1 to 15% by volume, more preferably from 1 to 10% by volume, most preferably from 2 to 7% by weight. Within the scope of the present invention it is also possible to use a carrier gas which is free of oxygen.
[0069] Like oxygen, the carrier gas preferably comprises nitrogen. The nitrogen content of the gas is preferably at least 80% by volume, more preferably at least 90% by volume, most preferably at least 95% by volume. Other possible carrier gases can be selected from carbon dioxide, argon, xenon, krypton, neon, helium, sulfur hexafluoride. Any mixture of carrier gases can be used. Carrier gas can also be charged with water vapors and/or acrylic acid.
[0070] The gas velocity is preferably adjusted in such a way that the flow in the reaction zone is directed, for example, no convection currents opposite the direction of the general flow are present, and is preferably from 0.1 to 2, 5 m/s, more preferably from 0.3 to 1.5 m/s, even more preferably from 0.5 to 1.2 m/s, most preferably from 0.7 to 0.9 m/s.
[0071] The inlet temperature of the gas, i.e. the temperature at which the gas enters the reaction zone, is preferably 160 to 200°C, more preferably 165 to 195°C, even more preferably 170 to 190°C, above all preferably 175 to 185°C.
[0072] The vapor content of the gas entering the reaction zone is preferably 0.01 to 0.15 kg per kg of dry gas, more preferably 0.02 to 0.12 kg per kg of dry gas, above most preferably from 0.03 to 0.10 kg per kg of dry gas.
[0073] The gas inlet temperature is controlled in such a way that the gas outlet temperature, that is, the temperature at which the gas leaves the reaction zone, is less than 150°C, preferably from 90 to 140°C, more preferably from 100 to 130°C, even more preferably from 105 to 125°C, most preferably from 110 to 120°C.
[0074] The vapor content of the gas leaving the reaction zone is preferably 0.02 to 0.30 kg per kg of dry gas, more than 0.04 to 0.28 kg per kg of dry gas, above everything from 0.05 to 0.25 kg per kg of dry gas.
[0075] Water-absorbent polymer particles can be divided into three categories: type 1 water-absorbent polymer particles are particles with a cavity, type 2 water-absorbent polymer particles are particles with more than one cavity and particles Type 3 water-absorbent polymers are solid particles with no visible cavity. Type 1 particles are represented by hollow spheres, type 2 particles are represented by spherical closed cell sponges, and type 3 particles are represented by solid spheres. Type 2 or type 3 particles or mixtures thereof with little or no type 1 particles are preferred.
[0076] The morphology of particles of water-absorbent polymers can be controlled by the reaction conditions during polymerization. Water-absorbent polymer particles having a high amount of particles with a cavity (Type 1) can be prepared using low gas velocities and high gas exit temperatures. Water-absorbent polymer particles having a high amount of particles with more than one cavity (Type 2) can be prepared using high gas velocities and low gas exit temperatures.
[0077] Water-absorbent polymer particles that contain no cavity (Type 3) and water-absorbent polymer particles having more than one cavity (Type 2) show better mechanical stability compared to water-absorbent polymer particles having only one cavity (Type 1).
[0078] As a particular advantage round-shaped particles do not have edges that can easily be broken by processing stress in diaper production and during swelling in the aqueous liquid there are no break points on the surface that could lead to loss of mechanical strength.
[0079] The reaction can be carried out at elevated pressure or at reduced pressure, preferably from 0.1 kPa to 10 kPa (1 to 100 mbar) below ambient pressure, more preferably from 0.15 to 5 kPa (1.5 to 50 mbar) below ambient pressure, above all preferably 0.2 to 1 kPa (2 to 10 mbar) below ambient pressure.
[0080] The reaction effluent, that is, the gas leaving the reaction chamber, can be cooled in a heat exchanger. This condenses water and unconverted a) monomer. The reaction effluent can then be re-heated at least partially and recirculated into the reaction chamber as circulating gas. A portion of the reaction effluent can be discarded and replaced with fresh gas, in which water and a) unconverted monomers present in the reaction effluent can be removed and recirculated.
[0081] Particular preference is given to a thermally integrated system, that is, a portion of the waste heat in the effluent cooling is used to heat the circulating gas.
[0082] Reactors can be heated by trace. In this case, the trace heating is adjusted such that the wall temperature is at least 5°C above the internal reactor temperature and condensation of the reactor walls is reliably prevented. Thermal post-treatment
[0083] The particles of water-absorbent polymers obtained by droplet formation can be heat post-treated to adjust the residual monomer content to the desired value.
[0084] Residual monomers can be removed better at relatively low temperatures and relatively long residence times. What is important here is that the water absorbent polymer particles are not very dry. In the case of excessively dry particles, residual monomers decrease only negligibly. Too high a water content increases the cake-forming tendency of the water-absorbent polymer particles.
[0085] The heat post-treatment can be done in a fluidized bed. In a preferred embodiment of the present invention an internal fluidized bed is used. An internal fluidized bed means that the product of the polymerization by droplet formation is accumulated in a fluidized bed below the reaction zone.
[0086] In the fluidized state, the kinetic energy of the polymer particles is greater than the potential for cohesion or adhesion between the polymer particles.
[0087] The fluidized state can be achieved by a fluidized bed. In this bed, there is an upstream flow towards the water-absorbing polymer particles, so that the particles form a fluidized bed. The height of the fluidized bed is adjusted by the gas rate and gas velocity, that is, through the pressure drop of the fluidized bed (kinetic energy of the gas).
[0088] The velocity of the gas stream in the fluidized bed is preferably from 0.3 to 2.5 m/s, more preferably from 0.4 to 2.0 m/s, above all preferably from 0.5 to 1 .5 m/s.
[0089] The pressure drop above the base of the internal fluidized bed is preferably 0.1 kPa to 10 kPa (1 to 100 mbar), more preferably 0.3 to 5 kPa (3 to 50 mba), most preferably 0.5 to 2.5 kPa (5 to 25 mbar).
[0090] The moisture content of the water-absorbent polymer particles at the end of the heat post-treatment is preferably from 1 to 20% by weight, more preferably from 2 to 15% by weight, even more preferably from 3 to 12% by weight weight, above all preferably 5 to 8% by weight.
[0091] The temperature of the water-absorbent polymer particles during the heat post-treatment is from 20 to 120°C, preferably from 40 to 100°C, more preferably from 50 to 95°C, even more preferably from 55 to 90 °C, above all preferably from 60 to 80 °C.
[0092] The average residence time in the internal fluidized bed is from 10 to 300 minutes, preferably from 60 to 270 minutes, more preferably from 40 to 250 minutes, above all preferably from 120 to 240 minutes.
[0093] The condition of the fluidized bed can be adjusted to reduce the amount of residual monomers of the water-absorbent polymer leaving the fluidized bed. The amount of residual monomers can be reduced to levels below 0.1% by weight by a thermal post-treatment using additional steam.
[0094] The vapor content of the gas is preferably from 0.005 to 0.25 kg per kg of dry gas, more preferably from 0.01 to 0.2 kg per kg of dry gas, above all preferably from 0.02 to 0.15 kg per kg of dry gas.
[0095] The use of additional steam from the fluidized bed condition can be adjusted to the amount of residual monomers of the water-absorbent polymer leaving the fluidized bed is from 0.03 to 15% by weight, preferably from 0.05 to 12 % by weight, more preferably from 0.1 to 10% by weight, even more preferably from 0.15 to 7.5% by weight above all preferably from 0.2 to 5% by weight, still most preferably from 0.25 to 2.5% by weight.
[0096] The level of residual monomers in the water-absorbent polymer has an important impact on the properties of the last post-crosslinked surface water-absorbent polymer particles formed. This means that very low levels of residual monomers must be avoided.
[0097] In a preferred embodiment of the present invention the post-heat treatment is completely or at least partially done in an external fluidized bed. The operating conditions of the outer fluid bed are in scope for the inner fluid bed as described above.
[0098] In another preferred embodiment of the present invention the heat post-treatment is done in an external mixer with mobile mixing tools, preferably horizontal mixers, such as screw mixers, disk mixers, screw conveyor mixers and screw mixers. Pan. Suitable mixers are, for example, Becker paddle mixers (Gebr. Lodige Maschinenbau GmbH; Paderborn; Germany), Nara paddle mixers (NARA Machinery Europe; Frechen; Germany), Pflugschar® plow mixers (Gebr. Lodige Maschinenbau GmbH; Paderborn; Paderborn). ; Germany), Vrieco-Nauta continuous mixers (Hosokawa Micron BV; Doetinchem; Netherlands), Processall Mixmill mixers (Processall Incorporated; Cincinnati; USA) and Ruberg continuous flow mixers (Gebruder Ruberg GmbH & Co KG, Nie-heim, Germany) . Ruberg continuous flow mixers, Becker paddle mixers and Pflugschar® plow mixers are preferred.
[0099] The heat after-treatment can be done in a batch external mixer or a continuous external mixer.
[00100] The amount of gas to be used in the batch external mixer is preferably from 0.01 to 5 Nm3/h, more preferably from 0.05 to 2 Nm3/h, above all preferably from 0.1 to 0.5 Nm3/h based in each case on the kg of water-absorbing polymer particles.
[00101] The amount of gas to be used in the continuous external mixer is preferably from 0.01 to 5 Nm3/h, more preferably from 0.05 to 2 Nm3/h, above all preferably from 0.1 to 0.5 Nm3/h based, in each case, on the production kg/h of the water-absorbing polymer particles.
[00102] The other constituents of the gas are preferably nitrogen, carbon dioxide, argon, xenon, krypton, neon, helium, air or air/nitrogen mixtures, more preferably nitrogen or air/nitrogen mixtures comprising less than 10% by volume of oxygen . Oxygen can cause discoloration.
[00103] The morphology of particles of water-absorbent polymers can also be controlled by the reaction conditions during post-heat treatment. Water-absorbent polymer particles having a high amount of particles with a cavity (Type 1) can be prepared using high product temperatures and short residence times. Water-absorbent polymer particles having a high amount of particles with more than one cavity (Type 2) can be prepared using low product temperatures and long residence times. Surface post-crosslinking
[00104] In the present invention the polymer particles are post-crosslinked on the surface to improve the properties.
[00105] Surface post crosslinkers are compounds comprising groups that can form at least two covalent bonds with the carboxylate groups of the polymer particles. Suitable compounds are, for example, polyfunctional amines, polyfunctional amidoamines, polyfunctional epoxides as described in EP 0 083 022 A2, EP 0 543 303 A1 and EP 0 937 736 A2, di- or polyfunctional alcohols as described in DE 33 14 019 A1, DE 35 23 617 A1 and EP 0 450 922 A2, or p-hydroxyalkylamides as described in DE 102 04 938 A1 and US 6,239,230. Also, ethyleneoxide, aziridine, glycidol, oxetane and their derivatives can be used.
[00106] Polyvinylamine, polyamidoamines and polyvinyl alcohols are examples of multifunctional polymeric surface crosslinking powders.
[00107] Furthermore, DE 40 20 780 C1 describes alkylene carbonates, DE 198 07 502 A1 describes 1,3-oxazolidin-2-one and its derivatives, such as 2-hydroxyethyl-1,3-oxazolidin-2-one DE 198 07 992 C1 describes bis- and poly-1,3-oxazolidin-2-ones, EP 0 999 238 A1 describes bis- and poly-1,3-oxazolidines, DE 198 54 573 A1 describes 2-oxotetrahydro-1 ,3-oxazine and its derivatives, DE 198 54 574 A1 describes N-acyl-1,3-oxazolidin-2-ones, DE 102 04 937 A1 describes cyclic ureas, DE 103 34 584 A1 describes bicyclic amide acetals, EP 1199 327 A2 describes cyclic oxetanes and ureas, and WO 2003/31482 A1 describes morpholine-2,3-dione and its derivatives as suitable surface crosslinking powders.
[00108] Furthermore, it is also possible to use surface crosslinking powders comprising additional polymerizable ethylenically unsaturated groups, as described in DE 37 13 601 A1.
[00109] In a preferred embodiment of the present invention at least one surface post-crosslinker is selected from alkylene carbonates, 1,3-oxazolidin-2-ones, bis- and poly-1,3-oxazolidin-2-ones, bis - and poly-1,3-oxazolidines, 2-oxotetrahydro-1,3-oxazines, N-acyl-1,3-oxazolidin-2-ones, cyclic ureas, cyclic amide acetals, oxetanes and morpholine-2,3-diones . Suitable surface post-crosslinkers are ethylene carbonate, 3-methyl-1,3-oxazolidin-2-one, 3-methyl-3-oxetanmethanol, 1,3-oxazolidin-2-one, 3-(2-hydroxyethyl)- 1,3-oxazolidin-2-one, 1,3-dioxan-2-one or a mixture thereof.
[00110] It is also possible to use any suitable mixture of surface crosslinking powders. It is particularly favorable to use mixtures of 1,3-dioxolan-2-one (ethylene carbonate) and 1,3-oxazolidin-2-ones. Such mixtures are obtained by mixing and partially reacting 1,3-dioxolan-2-on (ethylene carbonate) with the corresponding 2-amino alcohol (eg 2-aminoethanol) and may comprise ethylene glycol from the reaction.
[00111] In a more preferred embodiment of the present invention at least one alkylene carbonate is used as surface post-crosslinker. Suitable alkylene carbonates are 1,3-dioxolan-2-on (ethylene carbonate), 4-methyl-1,3-dioxolan-2-on (propylene carbonate), 4,5-dimethyl-1,3-dioxolan-2- one, 4,4-dimethyl-1,3-dioxolan-2-one, 4-ethyl-1,3-dioxolan-2-one, 4-hydroxymethyl-1,3-dioxolan-2-one (glycerin carbonate) , 1,3-dioxane-2-on (trimethylene carbonate), 4-methyl-1,3-dioxan-2-one, 4,6-dimethyl-1,3-dioxan-2-one and 1,3-dioxepan -2-one, preferably 1,3-dioxolan-2-one (ethylene carbonate) and 1,3-dioxan-2-one (trimethylene carbonate), above all preferably 3-dioxolan-2-one (ethylene carbonate) .
[00112] The amount of surface crosslinker post is preferably from 0.1 to 10% by weight, more preferably from 0.5 to 7.5% by weight, most preferably from 1 to 5% by weight based , in each case, in the polymer.
[00113] The residual monomer content in the water-absorbent polymer particles before coating with the surface crosslinker post is in the range of 0.03 to 15% by weight, preferably from 0.05 to 12% by weight, more preferably from 0.1 to 10% by weight, even more preferably from 0.15 to 7.5% by weight, above all preferably from 0.2 to 5% by weight, still most preferably from 0.25 to 2.5% by weight.
[00114] The moisture content of the water-absorbent polymer particles before the thermal surface post-crosslinking is preferably from 1 to 20% by weight, more preferably from 2 to 15% by weight, above all preferably from 3 to 10 % by weight.
[00115] In a preferred embodiment of the present invention, polyvalent cations are applied to the surface particle in addition to the surface post-crosslinkers before, during or after the thermal surface post-crosslinking.
[00116] The polyvalent cations used in the process according to the invention are, for example, divalent cations, such as zinc, magnesium, calcium, iron and strontium cations, trivalent cations, such as the aluminum, iron, chromium cations , rare earth and manganese, tetravalent cations such as titanium and zirconium cations and mixtures thereof. Possible counterions are chloride, bromide, sulfate, hydrogensulfate, methanesulfate, carbonate, hydrogencarbonate, nitrate, hydroxide, phosphate, hydrogenphosphate, dihydrogenphosphate, glycophosphate and carboxylate, such as acetate, glycolate, tartrate, formate, propionate, 3-hydroxypropionate , lactamide and lactate and mixtures thereof. Aluminum sulphate, aluminum acetate and aluminum lactate are preferred. Aluminum lactate is most preferred. Using the inventive process in combination with the use of aluminum lactate, water-absorbent polymer particles having extremely high total liquid absorption at lower centrifuge holding capacities (CRC) can be prepared.
[00117] In addition to metal salts, it is also possible to use polyamines and/or polymeric amines as polyvalent cations. A single metal salt can be used, as well as any mixture of the above metal salts and/or polyamines.
[00118] Preferred polyvalent cations and corresponding anions are disclosed in WO 2012/045705 A1 and are expressly incorporated herein by reference. Preferred polyvinylamines are disclosed in WO 2004/024816 A1 and are expressly incorporated herein by reference.
[00119] The amount of polyvalent cation used is, for example, from 0.001 to 1.5% by weight, preferably from 0.005 to 1% by weight, more preferably from 0.02 to 0.8% by weight based, in each case , in the polymer.
[00120] The addition of the polyvalent metal cation can happen before, after or concurrently with the surface post-crosslinks. Depending on the formulation and operating conditions employed it is possible to obtain a homogeneous coating and surface distribution of the polyvalent cation or a typically inhomogeneous stained coating. Both types of coatings and any mixtures between them are used within the scope of the present invention.
[00121] Surface post-crosslinking is typically carried out in such a way that a solution of the surface post-crosslinker is sprayed onto the hydrogel or dry polymer particles. After spraying, the polymer particles coated with the surface post-crosslinker are thermally dried and cooled.
[00122] Sprinkling of a surface post-crosslinker solution is preferably carried out in mixers with mobile mixing tools, such as screw mixers, disk mixers and paddle mixers. Suitable mixers are, for example, Schugi Flexomix® vertical mixers (Hosokawa Micron BV; Doetinchem; Netherlands), Turbolizers® mixers (Hosokawa Micron BV; Doetinchem; Netherlands), Pflugschar® horizontal plow mixers (Gebr. Lodige Maschinenbau GmbH; Paderborn; Germany), Vrieco-Nauta continuous mixers (Hosokawa Micron BV; Doetinchem; Netherlands), Processall Mixmill mixers (Processall Incorporated; Cincinnati; US) and Ruberg continuous flow mixers (Gebruder Ruberg GmbH & Co KG, Nieheim, Germany). Ruberg continuous flow mixers and Pflugschar® horizontal plow mixers are preferred. The surface post crosslinker solution can also be sprayed in a fluidized bed.
[00123] The surface post-crosslinker solution can also be sprayed on the water-absorbent polymer particles during post-heat treatment. In such a case the surface after-crosslinker can be added as one portion or in several portions along the axis of the after-heat mixer. In one embodiment it is preferred to add the surface post-crosslinker in the final post-heat treatment step. As a particular advantage of adding the surface post-crosslinker solution during the post-heat treatment step it may be possible to eliminate or reduce the technical effort for a separate surface post-crosslinker addition mixer.
[00124] Surface crosslinking powders are typically used as an aqueous solution. The addition of non-aqueous solvent can be used to improve surface wetting and adjust the depth of penetration of the surface post-crosslinker into the polymer particles.
[00125] The thermal surface post-crosslinking is preferably carried out in contact dryers, more preferably paddle dryers, above all preferably disk dryers. Suitable dryers are, for example, Hosokawa Bepex® horizontal paddle dryers (Hosokawa Micron GmbH; Leingarten; Germany), Hosokawa Bepex® disk dryers (Hosokawa Micron GmbH; Leingarten; Germany), Holo-Flite® dryers (Metso Minerals Industries Inc .; Danville; USA) and Nara paddle dryers (NARA Machinery Europe; Frechen; Germany). Furthermore, it is also possible to use fluidized bed dryers. In the latter case the reaction times can be shorter compared to other modalities.
[00126] When a horizontal dryer is used then it is often advantageous to adjust the dryer with an inclined angle of a few degrees depending on the surface of the earth in order to give adequate product flow through the dryer. The angle can be fixed or it can be adjustable and is typically between 0 to 10 degrees, preferably 1 to 6 degrees, most of all preferably 2 to 4 degrees.
[00127] In an embodiment of the present invention a contact dryer is used that has two different heating zones in one apparatus. For example, Nara paddle dryers are only available with one heated zone or alternatively with two heated zones. The advantage of using two or more heated zone dryers is that different phases of heat post-treatment and/or surface post-crosslinking can be combined.
[00128] In a preferred embodiment of the present invention a contact dryer with a heat first heating zone is used which is followed by a zone that maintains temperature in the same dryer. This adjustment allows for a rapid increase in product temperature and evaporation of surplus liquid in the first heating zone, while the rest of the dryer only supports the stable product temperature to complete the reaction.
[00129] In another preferred embodiment of the present invention a contact dryer with a first heating heating zone is used which is then followed by a hot heating zone. In the first heated zone the heat post-treatment is affected or completed, while the surface post-crosslinking takes place in the subsequent hot zone.
[00130] In a typical modality a paddle heater with only one temperature zone is employed.
[00131] Experts in the technology will depend on the properties of the desired finished product and the qualities of the appropriate base polymer of the polymerization step chosen in any of the same settings.
[00132] The thermal surface post-crosslinking can be carried out in the mixer itself by heating the jacket, blowing in air or hot steam. Equally suitable is a downstream dryer, for example a dryer medium, a rotary tube oven or a heatable screw. It is particularly advantageous to mix and dry in a fluid bed dryer.
[00133] Preferred thermal surface post-crosslinking temperatures are in the range from 100 to 180°C, preferably from 120 to 170°C, more preferably from 130 to 165°C, most preferably from 140 to 160°C. The preferred residence time at this temperature in the reaction mixer or dryer is preferably at least 5 minutes, more preferably at least 20 minutes, most preferably at least 40 minutes and typically at most 120 minutes.
[00134] It is preferred to cool the polymer particles after thermal surface post-crosslinking. Cooling is preferably carried out in contact coolers, more preferably paddle coolers, above all preferably disc coolers. Suitable coolers are, for example, Hosokawa Bepex® horizontal paddle coolers (Hosokawa Micron GmbH; Leingarten; Germany), Hosokawa Bepex® disc coolers (Hosokawa Micron GmbH; Leingarten; Germany), HoloFlite® coolers (Metso Minerals Industries Inc .; Danville; USA) and Nara shovel coolers (NARA Machinery Europe; Frechen; Germany). Furthermore, it is also possible to use fluidized bed coolers.
[00135] In the refrigerator the polymer particles are cooled to temperatures in the range from 20 to 150°C, preferably from 40 to 120°C, more preferably from 60 to 100°C, above all preferably from 70 to 90°C. Cooling using hot water is preferred, especially when contact coolers are used. Coating
[00136] To improve the properties, the particles of water-absorbent polymers can be coated and/or optionally wetted. The internal fluidized bed, the external fluidized bed and/or the external mixer used for the heat post-treatment and/or a separate coater (mixer) can be used to coat the water-absorbent polymer particles. Additionally, the cooler and/or a separate coater (mixer) can be used to coat/wet the post-crosslinked water absorbent polymer particles on the surface. Suitable coatings for controlling acquisition behavior and improving permeability (SFC or GBP) are, for example, inert inorganic substances such as water-insoluble metal salts, organic polymers, cationic polymers, anionic polymers and polyvalent metal cations. Suitable coatings for improving color stability are, for example, reducing agents, chelating agents and antioxidants. Suitable coatings for dust binding are, for example, polyols. Suitable coatings against the undesired cake-forming tendency of the polymer particles are, for example, fumed silica, such as Aerosil® 200, and surface active agents, such as Span® 20 and Plantacare® 818 UP. Preferred coatings are aluminum dihydroxy monoacetate, aluminum sulfate, aluminum lactate, aluminum 3-hydroxypropionate, zirconium acetate, citric acid or its water-soluble salts, di- and monophosphoric acid and its water-soluble salts, Blancolen ®, Bruggolite® FF7, Cublen®, Span® 20 and Plantacare® 818 UP.
[00137] If salts of the above acids are used instead of the free acids then the preferred salts are alkali metal, alkaline earth metal, aluminum, zirconium, titanium, zinc and ammonium salts.
[00138] Under the trade name Cublen® (Zschimmer & Schwarz Mohsdorf GmbH & Co KG; Burgstadt; Germany) the following acids and/or their alkali metal salts (preferably Na and K salts) are available and can be used in scope of the present invention, for example, to impart color stability to the finished product:
[00139] 1-hydroxyethane-1,1-diphosphonic acid, amino-tris(methylene phosphonic acid), ethylenediaminetetra(methylenephosphonic acid), diethylenetriamine-penta(methylenephosphonic acid), hexamethylene diamine-tetra(methylenephosphonic) acid, hydroxyethyl acid -amino-di(methylene phosphonic), 2-phosphonobutane-1,2,4-tricarboxylic acid, bis(hexamethylenetriamine pen-ta(methylene phosphonic).
[00140] Above all preferably 1-hydroxyethane-1,1-diphosphonic acid or its salts with sodium, potassium, or ammonium are employed. Any mixture of the above Cublenes® can be used.
[00141] Alternatively, any of the chelating agents described above for use in polymerization can be coated onto the finished product.
[00142] Suitable inorganic inert substances are silicates, such as montmorillonite, kaolinite and talc, zeolites, activated carbons, polysilicic acids, magnesium carbonate, calcium carbonate, calcium phosphate, aluminum phosphate, barium sulfate, aluminum oxide, titanium dioxide and iron(II) oxide. Preference is given to the use of polysilicic acids, which are divided between precipitated silica and pyrogenic silica, according to their mode of preparation. Both variants are commercially available under the names Silica FK, Sipernat®, Wessalon® (precipitated silicas) and Aerosil® (pyrogenic silicas) respectively. The inert inorganic substances can be used as a dispersion in an aqueous or water- or substance-miscible dispersant.
[00143] When the water-absorbent polymer particles are coated with inorganic inert substances, the amount of inorganic inert substances used, based on the water-absorbent polymer particles, is preferably from 0.05 to 5% by weight, more preferably from 0.1 to 1.5% by weight, above all preferably from 0.3 to 1% by weight.
[00144] Suitable organic polymers are polyalkyl methacrylates or thermoplastics such as polyvinyl chloride, waxes based on polyethylene, polypropylene, polyamides or polytetrafluor-ethylene. Other examples are styrene-isoprene-styrene block copolymers or styrene-butadiene-styrene block copolymers. Another example is polyvinyl alcohols bearing silanol group available under the trade name Poval® R (Kuraray Europe GmbH; Frankfurt; Germany).
[00145] Suitable cationic polymers are polyalkylenepolyamines, cationic derivatives of polyacrylamides, polyethyleneimines and polyquaternary amines.
[00146] Polyquaternary amines are, for example, condensation products of hexamethylenediamine, dimethylamine and epichlorohydrin, condensation products of dimethylamine and epichlorohydrin, copolymers of hydroxyethylcellulose and diallyldimethylammonium chloride, copolymers of acrylamide and a-methacryloyloxyethyltrimethylammonium chloride, condensation products hydroxyethylcellulose, epichlorohydrin and trimethylamine, diallyldimethylammonium chloride homopolymers and epichlorohydrin addition products to amidoamines. Furthermore, polyquaternary amines can be obtained by reacting dimethyl sulphate with polymers such as polyethyleneimines, copolymers of vinylpyrrolidone and dimethylaminoethyl methacrylate or copolymers of ethyl methacrylate and diethylaminoethyl methacrylate. Polyquaternary amines are available in a wide range of molecular weights.
[00147] However, it is also possible to generate cationic polymers on the particle surface, either through reagents that can form a network with themselves, such as epichlorohydrin addition products to polyamidoamines, or through the application of cationic polymers that they can react with an added crosslinker, such as polyamines or polyimines in combination with polyepoxides, polyfunctional esters, polyfunctional acids or polyfunctional (meth)acrylates.
[00148] It is possible to use all polyfunctional amines having primary or secondary amino groups such as polyethyleneimine, polyallylamine and polylysine. The liquid sprayed by the process according to the invention preferably comprises at least one polyamine, for example polyvinylamine or a partially hydrolyzed polyvinylformamide.
[00149] Cationic polymers can be used as a solution in an aqueous or water miscible solvent, as a dispersion in an aqueous or water miscible dispersant or substance.
[00150] When the water-absorbent polymer particles are coated with a cationic polymer, the amount of use of cationic polymer based on the water-absorbent polymer particles is usually not less than 0.001% by weight, typically not less than 0, 01% by weight, preferably from 0.1 to 15% by weight, more preferably from 0.5 to 10% by weight, most preferably from 1 to 5% by weight.
[00151] Suitable anionic polymers are polyacrylates (in acid form or partially neutralized as salt), copolymers of acrylic acid and maleic acid available under the trade name Sokalan® (BASF SE; Ludwigshafen; Germany), and polyvinyl alcohols with construction in available ionic charges under the trade name Poval® K (Kuraray Europe GmbH; Frankfurt; Germany).
[00152] Suitable polyvalent metal cations are Mg2+, Ca2+, Al3+, Sc3+, Ti4+, Mn2+, Fe2+/3+, Co2+, Ni2+, Cu+/2+, Zn2+, Y3+, Zi-4+, Ag+, La3+, Ce4+, Hf4+ and Au+/3+; preferred metal cations are Mg2+, Ca2+, Al3+, Ti4+, Zr4* and La3+; particularly preferred metal cations are Al3+, Ti4+ and Zr4*. Metal cations can be used either alone or in a mixture with one another. Suitable metal salts of the mentioned metal cations are all of which have sufficient solubility in the solvent to be used.
Particularly suitable metal salts have weakly complexing anions such as chloride, hydroxide, carbonate, acetate, formate, propionate, nitrate, sulfate and methanesulfate. Metal salts are preferably used as a solution or as a stable aqueous colloidal dispersion. Solvents used for the metal salts can be water, alcohols, ethylene carbonate, propylene carbonate, dimethylformamide, dimethyl sulfoxide and mixtures thereof. Particular preference is given to water and water/alcohol mixtures such as water/methanol, water/isopropanol, water/1,3-propanediol, water/1,2-propandiol/1,4-butanediol or water/propylene glycol.
[00154] When the water-absorbent polymer particles are coated with a polyvalent metal cation, the amount of polyvalent metal cations used, based on the water-absorbent polymer particles, is preferably from 0.05 to 5% by weight , more preferably from 0.1 to 1.5% by weight, most preferably from 0.3 to 1% by weight.
[00155] Suitable reducing agents are, for example, sodium sulfite, sodium hydrogen sulfite (sodium bisulfite), sodium dithionite, sulfinic acids and salts thereof, ascorbic acid, sodium hyposulfite, sodium phosphite and phosphinic acids and salts thereof. Preference is given, however, to salts of hypophosphorous acid, for example, sodium hyposulfite, salts of sulfinic acids, for example, the disodium salt of 2-hydroxy-2-sulfinatoacetic acid and aldehyde addition products, for example, the disodium salt of 2-hydroxy-2-sulfonatoacetic acid. The reducing agent used can, however, be a mixture of the sodium salt of 2-hydroxy-2-sulfinateacetic acid, the disodium salt of 2-hydroxy-2-sulfonateacetic acid and sodium bisulfite. Such blends are obtained as Bruggolite® FF6 and Bruggolite® FF7 (Bruggemann Chemicals; Heilbronn; Germany). Also used is purified 2-hydroxy-2-sulfonatoacetic acid and its sodium salts, available under the trade name Blancolen® from the same company.
[00156] Reducing agents are typically used in the form of a solution in a suitable solvent, preferably water. The reducing agent can be used as a pure substance or any mixture of the above reducing agents can be used.
[00157] When the water-absorbent polymer particles are coated with a reducing agent, the amount of reducing agent used, based on the water-absorbent polymer particles, is preferably 0.01 to 5% by weight, plus preferably from 0.05 to 2% by weight, above all preferably from 0.1 to 1% by weight.
Suitable polyols are polyethylene glycols having a molecular weight of 400 to 20000 g/mol, polyglycerol, 3- to 100-tupli ethoxylated polyols such as trimethylolpropane, glycerol, sorbitol, mannitol, inositol, pentaerythritol and neopentyl glycol. Particularly suitable polyols are 7- to 20-tupli ethoxylated glycerol or trimethylolpropane, for example Polyol TP 70® (Perstorp AB, Perstorp, Sweden). The latter have the particular advantage that they lower the surface tension of an aqueous extract of the water-absorbent polymer particles only insignificantly. Polyols are preferably used as a solution in aqueous or water miscible solvents.
[00159] Polyol can be added before, during or after surface crosslinking. Preferably it is added after surface crosslinking. Any blend of the polyols listed above can be used.
[00160] When the water-absorbent polymer particles are coated with a polyol, the polyol usage amount, based on the water-absorbent polymer particles, is preferably 0.005 to 2% by weight, more preferably 0.01 to 1% by weight, above all preferably from 0.05 to 0.5% by weight.
[00161] Coating is preferably carried out in mixers with mobile mixing tools such as screw mixers, disc mixers, paddle mixers and drum coater. Suitable mixers are, for example, Pflugschar® horizontal plow mixers (Gebr. Lodige Maschinenbau GmbH; Paderborn; Germany), Vrieco-Nauta continuous mixers (Hosokawa Micron BV; Doetinchem; Netherlands), Pro-cessall Mixmill mixers (Processall Incorporated; Cincinnati ; US) and Ruberg continuous flow mixers (Gebruder Ruberg GmbH & Co KG, Nieheim, Germany). Furthermore, it is also possible to use a fluidized bed for mixing. Crowding
[00162] The water-absorbent polymer particles can additionally be selectively agglomerated. Agglomeration can take place after polymerization, post-thermal treatment, post-thermal surface cross-linking or coating.
[00163] Used agglomeration aids include water and water miscible organic solvents such as alcohols, tetrahydrofuran and acetone; water soluble polymers can additionally be used.
[00164] For agglomeration a solution comprising the agglomeration aid is sprayed on the water-absorbing polymeric particles. Solution spraying, for example, can be carried out in mixers having mobile mixing implements, such as screw mixers, paddle mixers, disk mixers, plow mixers, and paddle mixers. Mixers used include, for example, Lodige® mixers, Bepex® mixers, Nauta® mixers, Processall® mixers and Schugi® mixers. Vertical mixers are preferred. Fluid bed apparatus are particularly preferred. Combination of heat post-treatment, surface post-crosslinking and optionally coating
[00165] In a preferred embodiment of the present invention the steps of post-thermal treatment and post-thermal surface crosslinking are combined in one step of the process. Such a combination allows the use of low cost equipment and, in addition, the process can be run at low temperatures, which is cost efficient and prevents discoloration and loss of performance properties of the finished product due to thermal degradation.
[00166] The mixer can be selected from any of the equipment options mentioned in the post heat treatment section. Ruberg continuous flow mixers, Becker mixers and paddle plow mixers and Pflugschar® are preferred.
[00167] In this particular preferred embodiment the post-crosslinking of the surface solution is sprayed onto the water-absorbent polymer particles by stirring.
[00168] After the heat post-treatment/surface post-crosslinking the particles of water-absorbent polymers are dried at the desired moisture level and for this step any dryer mentioned in the surface post-crosslinking section can be selected. However, as the only drying needs to be accomplished in this particular preferred modality it is possible to use simple and low cost heated contact dryers such as a heated screw dryer, eg a Holo-Flite® dryer (Metso Minerals Industries Inc.; Danville; USA). Alternatively a fluidized bed can be used. In cases where the product needs to be dried with a predetermined and narrow residence time it is possible to use disc torule dryers or paddle dryers, for example a Nara paddle dryer (NARA Machinery Europe; Frechen; Germany).
[00169] In a preferred embodiment of the present invention, polyvalent cations cited in the post-surface crosslinking section are applied to the surface of the particle before, during or after the addition of the post-surface crosslinker using different points of addition along the axis of a horizontal mixer.
[00170] In a very particular preferred embodiment of the present invention the steps of post-heat treatment, post-crosslinking of the surface and coating are combined in one step of the process. Suitable coatings are cationic polymers, surface active agents and inorganic inert substances which are mentioned in the coating section. The coating agent can be applied to the particle surface before, during or after the addition of the surface post-crosslinker also using different addition points along the axis of a horizontal mixer.
[00171] Polyvalent cations and/or cationic polymers can act as additional scavengers of residual surface crosslinking powders. In a preferred embodiment of the present invention the surface post-crosslinkers are added before the polyvalent cations and/or the cationic polymers to allow the surface post-crosslinker to react first.
[00172] Surfactants and/or inorganic inert substances can be used to prevent sticking or cake formation during this step of the process in humid atmospheric conditions. Preferred surface active agents are nonionic and amphoteric surface active agents. Preferred inert inorganic substances are precipitated silicas and pyrogenic silicas in powder or dispersion form.
[00173] The amount of total liquid used to prepare the solutions/dispersions is typically from 0.01% to 25% by weight, preferably from 0.5% to 12% by weight, more preferably from 2% to 7% by weight , above all preferably from 3% to 6% by weight, with respect to the weight of the amount of water-absorbent polymer particles to be processed.
[00174] Preferred modalities are shown in figures 1 to 12.
[00175] Fig. 1: Process scheme (without external fluidized bed)
[00176] Fig. 2: Process scheme (with external fluidized bed)
[00177] Fig. 3: Arrangement of external measurement T_
[00178] Fig. 4: Arrangement of the droplet former units
[00179] Fig. 5: Droplet former unit (longitudinal section)
[00180] Fig. 6: Droplet former unit (cross view)
[00181] Fig. 7: Inner fluidized bed base (top view)
[00182] Fig. 8: openings at the base of the internal fluidized bed
[00183] Fig. 9: Rake agitator for the internal fluidized bed (top view)
[00184] Fig. 10: Rake agitator for the internal fluidized bed (cross view)
[00185] Fig. 11: Process scheme (post-surface crosslinking)
[00186] Fig. 12: Process scheme (post-surface crosslinking and coating)
[00187] Fig. 13: Contact dryer for surface post-crosslinking
[00188] Reference numerals have the following meanings: 1 Drying gas inlet pipe 2 Measurement of drying gas quantity 3 Gas distributor 4 Droplet former units 5 Co-current spray dryer, cylindrical part 6 Cone 7 T_ output measurement 8 Tower exhaust piping 9 Chamber filters 10 Fan 11 Finishing nozzles 12 Condenser column, counter-current cooling 13 Heat exchanger 14 Pump 15 Pump 16 Water outlet 17 Fan 18 Exhaust outlet 19 Inlet of nitrogen 20 Heat exchanger 21 Fan 22 Heat exchanger 23 Steam injection through nozzles 24 Water charge measurement 25 Conditioned internal fluidized bed gas 26 Internal fluidized bed product temperature measurement 27 Internal fluidized bed 28 Rotary valve 29 Sieve 30 End Product 31 Static Mixer 32 Static Mixer 33 Initiator Feed 34 Initiator Feed 35 Monomer Feed 36 Outlet fine particle fraction for rework 37 External fluid bed 38 Fan 39 External fluid bed exhaust outlet for chamber filters 40 Rotary valve 41 Filtered air inlet 42 Fan 43 Heat exchanger 44 Vapor injection via nozzle 45 Measuring the water load 46 Conditioned external fluidized bed gas 47 T_outlet measurement (average temperature out of 3 measurements around tower circumference) 48 Droplet former unit 49 Pre-mixed monomer with initiator feed 50 Dryer tower wall per sprinkling 51 Droplet former unit outlet piping 52 Droplet former unit inlet piping 53 Droplet former cassette 54 Teflon block 55 Valve 56 Pre-mixed monomer with internal tubing connector of initiator feed 57 Plate droplet 58 Counter plate 59 Flow channels for temperature control water 60 Flow channel without dead volume for mon solution omer 61 droplet former cassette stainless steel block 62 Inner fluid bed base with four segments 63 Segment separation openings 64 Rake stirrer 65 Rake stirrer prongs 66 Mixer 67 Optional liner feed 68 Post crosslinker feed 69 Dryer thermal (surface cross-linking) 70 Cooler 71 Optional coating/water supply 72 Coating 73 Coating/water supply 74 Base polymer supply 75 Disposal zone 76 Dam opening 77 dam plate 78 Dam height 100% 79 Dam height 50% 80 Stem 81 Discharge cone 82 Angle of inclination a 85 Ugpuqtgu fg VgorgtcVwtc *Vk c Tβ+ 86 Blade (compensated stem 90°)
[00189] The drying gas is fed through a gas distributor (3) at the top of the spray dryer as shown in figure 1. The drying gas is partially recycled (drying gas loop) through a filter of chambers (9) and a column of the condenser (12). The pressure inside the spray dryer is below ambient pressure.
[00190] The spray dryer outlet temperature is preferably measured at three points around the circumference at the end of the cylindrical part as shown in figure 3. The only measurements (47) are used to calculate the average cylindrical outlet temperature of the dryer by sprinkling.
[00191] The product accumulated in the internal fluidized bed (27). Gas from the conditioned internal fluidized bed is fed into the internal fluidized bed (27) via line (25). The relative humidity of the internal fluidized bed gas is preferably controlled by adding steam via line (23).
[00192] The effluent from the spray dryer is filtered in the chamber filter (9) and sent to a condenser column (12) for completion/cooling. After the chamber filter (9) a recovery heat exchanger system for preheating the gas after the condenser column (12) can be used. The chamber filter (9) can be heated by stroke to a temperature of preferably from 80 to 180°C, more preferably from 90 to 150°C, most preferably from 100 to 140°C. Excess water is pumped out of the condenser column (12) controlling the fill level (constant) within the condenser column (12). The water inside the condenser column (12) is cooled by a heat exchanger (13) and pumped counter-current into the gas by means of termination nozzles (11) such that the temperature inside the condenser column (12) ) is preferably from 20 to 100°C, more preferably from 25 to 80°C, most preferably from 30 to 60°C. The water within the condenser column (12) is adjusted to an alkaline pH by dosing a neutralizing agent to wash away the monomer vapors a). Aqueous solution from the condenser column (12) can be sent back for preparation of the monomer solution.
[00193] The effluent from the condenser column is divided into the drying gas inlet piping (1) and the conditioned internal fluidized bed gas (25). Gas temperatures are controlled by means of heat exchangers (20) and (22). The hot drying gas is fed into the co-current spray dryer via a gas distributor (3). The gas distributor (3) preferably consists of a set of plates providing a pressure drop of preferably 0.1 kPa to 10 kPa (1 to 100 mbar), more preferably 0.2 to 3 kPa (2 to 30 mbar), above all preferably 0.4 to 2 kPa (4 to 20 mbar), depending on the quantity of drying gas. Turbulence and/or a centrifugal speed can also be introduced into the drying gas, if desired, using gas nozzles or baffle plates.
[00194] Conditioned internal fluidized bed gas is fed into the internal fluidized bed (27) via line (25). The relative humidity of the external fluidized bed gas is preferably controlled by adding steam via line (23). To avoid any condensation steam is added together with the internal fluidized bed in the heat exchanger (22). The product held in the internal fluidized bed (27) can be controlled by means of the rotational speed of the rotary valve (28).
[00195] The product is discharged from the internal fluidized bed (27) by means of a rotary valve (28). The product held in the internal fluidized bed (27) can be controlled by means of the rotational speed of the rotary valve (28). The sieve (29) is used for sieving surplus/pits.
[00196] The monomer solution is preferably prepared by first mixing monomer a) with a neutralizing agent and optionally secondly with crosslinker b). The temperature during neutralization is controlled preferably from 5 to 60°C, more preferably from 8 to 40°C, most preferably from 10 to 30°C, using a heat exchanger and pumping in a loop. A filter unit is preferably used in the loop after the pump. Initiators are metered into the monomer solution upstream of the droplet former by means of static mixers (31) and (32) by means of lines (33) and (34) as shown in Figure 1. Preferably a peroxide solution having a temperature of preferably 5 to 60°C, more preferably 10 to 50°C, most preferably 15 to 40°C is added via line (33) and preferably an azo initiator solution having a temperature of preferably 2 to 30°C, more preferably 3 to 15°C, most preferably 4 to 8°C is added via line (34). Each initiator is preferably pumped in a loop and metered via control valves to each droplet former unit. A second filter unit is preferably used after the static mixer (32). The average residence time of the monomer solution mixed with the complete initiator package in the tubing before the droplet plates (57) is preferably less than 60s, more preferably less than 30s, most preferably less than 10s.
[00197] To dose the monomer solution at the top of the spray dryer preferably three droplet former units are used as shown in figure 4. However, any number of droplet formers can be used which is required to optimize the production process and the quality of the product. Thus, in the present invention at least one droplet former is employed, and both the geometrically permitted and droplet former may be used.
[00198] A droplet former unit consists of an external tubing (51) having an opening for the droplet former cassette (53) as shown in figure 5. The droplet former cassette (53) is connected with a tubing internal (52). The inner piping (53) having a PTFE block (54) at the end, as the seal can be pushed in and out of the outer piping (51) during process operation for maintenance purposes.
[00199] The temperature of the droplet former cassette (61) is controlled to preferably 5 to 80°C, more preferably 10 to 70°C, most preferably 30 to 60°C, by water in flow channels (59 ) as shown in figure 6.
The droplet former cassette preferably has from 10 to 1500, more preferably from 50 to 1000, most preferably from 100 to 500, holes having a diameter of preferably from 50 to 500 µo. ocku preferably fg 322 c 522 μo. cekoc fg Vwfq rtgfgtkxenogpVg fg 372 c 472 μo0 Qu hwtqu rqfgo ugt fg hqtoc ektewnct. tgvcpiwnct. vtkcpiwnct qw swcnswgt another way. Circular holes are preferred. The ratio of hole length to hole diameter is preferably 0.5 to 10, more preferably 0.8 to 5, most preferably 1 to 3. The droplet plate (57) may have a thickness greater than the length of the hole when using an inlet hole channel. The droplet plate (57) is preferably long and narrow, as disclosed in WO 2008/086976 A1. Multiple rows of holes per droplet plate can be used, preferably 1 to 20 rows, more preferably 2 to 5 rows.
[00201] The droplet former cassette (61) consists of a flow channel (60) having stagnant-free volume essential for homogeneous distribution of the premixed monomer and starter solutions and two droplet plates (57). The droplet plates (57) have an angled configuration with an angle of preferably from 1 to 90°, more preferably from 3 to 45°, most preferably from 5 to 20°. Each droplet plate (57) is preferably made of a thermally and/or chemically resistant material, such as stainless steel, polyether ether ketone, polycarbonate, polyarylsulfone, such as polysulfone, or polyphenylsulfone, or fluorine polymers, such as perfluoroalkoxyethylene, polytetrafluoroethylene , polyvinylidene fluoride, ethylene-chlorotrifluoroethylene copolymers, ethylene-tetrafluoroethylene copolymers and fluorinated polyethylene. Coated droplet plates as disclosed in WO 2007/031441 A1 can also be used. The choice of material for the droplet plate is not limited, except that droplet formation should work and it is preferable to use materials that do not catalyze the initiation of polymerization on its surface.
The yield of the monomer including starter solutions per droplet former unit is preferably from 150 to 2500 kg/h, more preferably from 200 to 1000 kg/h, above all preferably from 300 to 600 kg/h. The efficiency per hole is preferably from 0.1 to 10 kg/h, more preferably from 0.5 to 5 kg/h, above all preferably from 0.7 to 2 kg/h.
[00203] The start of operation of the co-current spray dryer (5) can be done in the following sequence: - start of the condenser column (12), - start of the fans (10) and (17), - start of the exchanger heat (20), - heating the drying gas loop to 95°C, - starting nitrogen feed via the nitrogen inlet (19), - wait until the residual oxygen is below 4% by weight, - heating up to the drying gas loop, - at a temperature of 105°C, start of water feed (not shown) and - at target temperature interruption of water feed and start of monomer feed via the water former unit droplet (4)
[00204] The start of operation of the co-current spray dryer (5) can be done in the following sequence: - interruption of monomer feed and start of water feed (not shown), - start of heat exchanger operation ( 20), - cooling of the drying gas loop by means of a heat exchanger (13), - at a temperature of 105°C water supply interruption, - at a temperature of 60°C nitrogen supply interruption by means from the nitrogen inlet (19) and - air supply to the drying gas loop (not shown).
[00205] To avoid damage the co-current spray dryer (5) must be heated and cooled very carefully. Any rapid temperature changes must be avoided.
[00206] The openings in the base of the internal fluidized bed can be arranged in such a way that the water-absorbent polymer particles flow in a cycle, as shown in figure 7. The base shown in figure 7 comprises of four segments (62) . The openings (63) in the segments (62) are in the form of slits that guide the passage of the gas stream towards the next segment (62). Figure 8 shows an enlarged view of the openings (63).
[00207] The opening can be in the form of holes or slits. The diameter of the holes is preferred from 0.1 to 10 mm, more preferred from 0.2 to 5 mm, even more preferred from 0.5 to 2 mm. The slits have a preferred length from 1 to 100 mm, more preferred from 2 to 20 mm, even more preferred from 5 to 10 mm, and a preferred width from 0.5 to 20 mm, more preferred from 1 to 10 mm, above most preferred from 2 to 5 mm.
[00208] Figure 9 and Figure 10 show a rake stirrer (64) that can be used in the internal fluidized bed. The pitchforks (65) of the rake are arranged in stacks. The speed of the agitator rake is preferably from 0.5 to 20 rpm, more preferably from 1 to 10 rpm above all preferably from 2 to 5 rpm.
[00209] To begin with the internal fluidized bed can be filled with a layer of water-absorbent polymer particles, preferably 5 to 50 cm, more preferably 10 to 40 cm, above all preferably 15 to 30 cm. Water absorbent polymer particles
[00210] The present invention provides particles of water-absorbent polymers obtained by the process according to the invention.
The present invention further provides surface post-crosslinked water-absorbent polymer particles having a centrifuge holding capacity of 35 to 75 g/g, an absorption under high load of 20 to 50 g/g, a level of extractable constituents of less than 10% by weight, and a porosity of 20 to 40%.
[00212] It is particularly advantageous that the surface post-crosslinked water-absorbent polymer particles obtained by the process according to the invention have a very high centrifuge holding capacity (CRC) and a high absorption under high load (AUHL), and that the sum of the same parameters (= CRC + AUHL) is at least 60 g/g, preferably at least 65 g/g, above all preferably at least 70 g/g, and not more than 120 g/g, preferably less than 100 g/g, more preferably less than 90 g/g, and above all preferably less than 80 g/g. The surface post-crosslinked water-absorbent polymer particles obtained by the process according to the invention preferably additionally exhibit a high load absorption (AUHL) of at least 15 g/g, preferably at least 18 g/g, more preferably by the less than 21 g/g, above all preferably at least 25 g/g, and not more than 50 g/g.
[00213] Since the centrifuge holding capacity (CRC) is the maximum water holding capacity of the surface post-crosslinked water-absorbent polymer particles, it is of interest to maximize this parameter. However, High Load Absorption (AUHL) is important to allow the fiber matrix in a sanitary article to open the pores during swelling to allow additional liquid to easily pass through the article structure to enable rapid absorption of this liquid. Thus, there is a need to maximize both parameters.
[00214] The inventive water-absorbent polymer particles have a centrifuge holding capacity (CRC) from 35 to 75 g/g, preferably from 37 to 65 g/g, more preferably from 39 to 60 g/g, above all preferably from 40 to 55 g/g.
[00215] The inventive water-absorbent polymer particles have an absorbance under a load of 49.2 g/cm2 (AUHL) from 20 to 50 g/g, preferably from 22 to 45 g/g, more preferably from 24 to 40 g/g, above all preferably from 25 to 35 g/g.
The inventive water-absorbent polymer particles have a level of extractable constituents of less than 10% by weight, preferably less than 8% by weight, more preferably less than 6% by weight, most preferably less than 5% by weight.
[00217] The inventive water-absorbent polymer particles have a porosity of 20 to 40%, preferably from 22 to 38%, more preferably from 24 to 36%, most preferably from 25 to 35%.
[00218] Preferred water-absorbent polymer particles are polymer particles having a centrifuge holding capacity (CRC) of 37 to 65 g/g, an absorption upon high load (AUHL) of 22 to 45 g/g, one level of extractable constituents of less than 8% by weight and a porosity of 22 to 45%.
[00219] Most preferred water-absorbent polymer particles are polymer particles having a centrifuge holding capacity (CRC) of 39 to 60 g/g, an absorption upon high load (AUHL) of 24 to 40 g/g, a extractable constituents level of less than 6% by weight and a porosity of 24 to 40%.
Above all preferred water-absorbent polymer particles are polymer particles having a centrifuge holding capacity (CRC) of 40 to 55 g/g, an absorption under high load (AUHL) of 25 to 35 g/g , a level of extractable constituents of less than 5% by weight and a porosity of 25 to 35%.
[00221] The present invention further provides surface post-crosslinked water absorptive polymer particles having a total liquid absorption of 500 x ln(X) + 1880, preferably Y > -495 x ln(X) + 1875, more preferably Y > -490 x ln(X) + 1870, above all preferably Y > -485 x ln(X) + 1865, where Y [g] is the total liquid absorption and X [g/g] is the capacity centrifuge holding capacity (CRC), wherein the centrifuge holding capacity (CRC) is at least 25 g/g, preferably at least 30 g/g, more preferably at least 35 g/g, most preferably at least 40 g/g, and the liquid absorption is at least 30 g, preferably at least 35 g/g, more preferably at least 40 g/g, most preferably at least 45 g/g.
[00222] The present invention further provides surface post-crosslinked water-absorbent polymer particles having a characteristic swelling time change of less than 0.6, preferably less than 0.5, more preferably less than 0.45, above all preferably less than 0.4, and a centrifuge holding capacity (CRC) of at least 35 g/g, preferably at least 37 g/g, more preferably at least 38.5 g/g, above all preferably at least 40 g/g, where the characteristic swelling time change is Z < (X0.5 - X0.1) / X0.5 where Z is the characteristic swelling time change, xo.i is the time of characteristic swelling at a pressure of 0.1 psi (6.9 g/cm2) and xo.s is the characteristic swelling time at a pressure of 0.5 psi (35.0 g/cm2).
[00223] The inventive water-absorbent polymer particles have an average sphericity of 0.80 to 0.95, preferably from 0.82 to 0.93, more preferably from 0.84 to 0.91, most preferably from 0.85 to 0.90. The sphericity (SPHT) is defined as

[00224] Where A is the cross-sectional area and U is the cross-sectional circumference of the polymer particles. The mean sphericity is the mean sphericity of the volume.
[00225] Mean sphericity can be determined, for example, with the Camsizer® image analysis system (Retsch Technolgy GmbH; Haan; Germany).
[00226] For measurement, the product is introduced through a funnel and conveyed to the falling rod with a measuring channel. Although particles fall past a wall of light, they are selectively registered by a camera. The registered images are evaluated by the software, according to the selected parameters.
[00227] To characterize the circularity, the parameters designated as sphericity in the program are used. The parameters reported are the mean volume weighted sphericities, the volume of the particles being determined by the equivalent diameter xcmin. To determine the equivalent diameter xcmin, the diameter of the longest string for a total of 32 different spatial directions is measured in each case. The equivalent diameter xcmin is the smallest of the same 32 rope diameters. To record the particles, the so-called CCD-zoom camera (CAM-Z) is used. To control the measurement channel, a fraction of surface coverage in the camera's detection window (broadcast) of 0.5% is preset.
[00228] Water-absorbent polymer particles with relatively low sphericity are obtained by reverse suspension polymerization when polymer beads are agglomerated during or after polymerization.
[00229] The water-absorbent polymer particles prepared by customary solution polymerization (gel polymerization) are ground and classified after drying to obtain irregular polymer particles. The average sphericity of these polymer particles is between approximately 0.72 and approximately 0.78.
[00230] The inventive water-absorbent polymer particles have a hydrophobic solvent content of preferably less than 0.005% by weight, more preferably less than 0.002% by weight and most preferably less than 0.001% by weight. The hydrophobic solvent content can be determined by gas chromatography, for example by means of a state-of-the-art technique. A hydrophobic solvent within the scope of the present invention is both immiscible in water and only slightly soluble. Examples of typical hydrophobic solvents are pentane, hexane, cyclohexane, toluene.
[00231] Water-absorbent polymer particles that have been obtained by reverse suspension polymerization still typically comprise approximately 0.01% by weight of the hydrophobic solvent used as the reaction medium.
[00232] The inventive water-absorbent polymer particles have a dispersant content of typically less than 1% by weight, preferably less than 0.5% by weight, more preferably less than 0.1% by weight and above all preferably less than 0.05% by weight.
[00233] Particles of water-absorbent polymers that have been obtained by reverse suspension polymerization still typically comprise at least 1% by weight of the dispersant, i.e., ethylcellulose used to stabilize the suspension.
The inventive water-absorbent polymer particles have a bulk density preferably from 0.6 to 1 g/cm3, more preferably from 0.65 to 0.9 g/cm3, most preferably from 0.68 to 0 .8 g/cm3.
[00235] The average particle diameter (APD) of the particles cduqtxgpVgu fg ágwc kpxgpVkxcu fi rtgfgtkxgnogpVg fg 422 c 772 μo. ocku rtgfgtkxgnogpVg fg 472 c 722 μo. cekoc fg Vwfq rtgfgtkxgnogpVg fg 572 c 672 μo0
[00236] The particle diameter distribution (PDD) of the inventive water-absorbent particles is preferably less than 0.7, more preferably less than 0.65, more preferably less than 0.6.
[00237] The inventive water-absorbent polymer particles can be blended with other water-absorbent polymer particles prepared by other processes, i.e. solution polymerization. fluid absorbent articles
[00238] The present invention additionally provides fluid absorbent articles. The fluid-absorbing articles comprise of (A) an upper liquid-penetrable layer (B) a lower liquid-impervious layer (C) a fluid-absorbing core between (A) and (B) comprising from 5 to 90% by weight material fibrous and from 10 to 95% by weight of the water absorbent polymer particles of the present invention; preferably from 20 to 80% by weight of fibrous material and from 20 to 80% by weight of water absorbent polymer particles of the present invention; more preferably from 30 to 75% by weight of fibrous material and from 25 to 70% by weight of water absorbent polymer particles of the present invention; above all preferably from 40 to 70% by weight of fibrous material and from 30 to 60% by weight of water-absorbent polymer particles of the present invention; (D) an optional acquisition distribution layer between (A) and (C), comprising from 80 to 100% by weight of fibrous material and from 0 to 20% by weight of water-absorbent polymer particles of the present invention; preferably from 85 to 99.9% by weight of fibrous material and from 0.01 to 15% by weight of water absorbent polymer particles of the present invention; more preferably from 90 to 99.5% by weight of fibrous material and from 0.5 to 10% by weight of water absorbent polymer particles of the present invention; above all preferably from 95 to 99% by weight of fibrous material and from 1 to 5% by weight of water-absorbent polymer particles of the present invention; (E) an optional fabric layer disposed immediately above and/or below (C); and (F) other optional components.
[00239] Fluid absorbent articles are understood to be, for example, incontinence pads and incontinence pants for adults or diapers for babies. Suitable fluid absorbent articles including fluid absorbent compositions comprising fibrous materials and optionally water absorbent polymer particles to form fibrous webs or matrices for the substrates, layers, sheets and/or the fluid absorbent core.
[00240] The acquisition distribution layer acts as the transport and distribution layer for the discharge bodily fluids and is typically optimized to affect efficient liquid distribution with the stressed fluid absorbent core. Thus, for quick temporary liquid retention it provides the necessary void space, while its coverage of the stressed fluid absorbent core area should affect the required liquid distribution and is adopted for the fluid absorbent core's ability to rapidly dehydrate the fluid layer. acquisition distribution.
[00241] For fluid absorbent articles that have very good dewatering that have excellent drainability it is advantageous to use acquisition distribution layers. For fluid absorbent articles having a fluid absorbent core comprising very permeable water absorbent polymer particles a small, thin acquisition distribution layer can be used.
[00242] Suitable fluid-absorbing articles are composed of several layers whose individual elements should show a preferably defined functional parameter, such as dryness for the upper liquid-penetrable layer, vapor permeability without wetting through the lower liquid-impenetrable layer, an absorbent core a thin, flexible, vapor-permeable fluid that exhibits rapid absorption rates and is capable of retaining the greatest amounts of bodily fluids and an acquisition distribution layer between the top layer and the core. These individual elements are combined in such a way that the resulting fluid-absorbing articles meet general criteria such as flexibility, breathability of water vapor, dryness, wear comfort and protection on one side and, with respect to fluid retention, rewetting and moisture prevention through the other side. The specific combination of these layers provides a fluid absorbent article that delivers both high levels of protection as well as high consumer comfort.
[00243] The products obtained by the present invention are also very suitable to be incorporated in low-down, low-fiber, less-down or less-fiber sanitary article designs. Such designs and methods for preparing them are, for example, described in the following publications and literature cited herein and are expressly incorporated in the present invention: EP 2 301 499 A1, EP 2 314 264 A1, EP 2 387 981 A1, EP 2 486 901 A1, EP 2 524 679 A1, EP 2 524 679 A1, EP 2 524 680 A1, EP 2 565 031 A1, US 6,972,011, US 2011/0162989, US 2011/0270204, WO 2010/004894 A1, WO 2010/004895 A1, WO 2010/076857 A1, WO 2010/082373 A1, WO 2010/118409 A1, WO 2010/133529 A2, WO 2010/143635 A1, WO 2011/084981 A1, WO 2011/086841 A1, WO 2011/086842 A1, WO 2011/086843 A1 , WO 2011/086844 A1 , WO 2011/117997 A1 , WO 2011/136087 A1 , WO 2012/048879 A1 , WO 2012/052173 A1 , and WO 2012/052172 A1 .
[00244] The present invention further provides fluid absorbent articles comprising water absorbent polymer particles of the present invention and less than 15% by weight of fibrous material and/or adhesives in the absorbent core.
[00245] Water-absorbent polymer particles and fluid-absorbent articles are tested using the test methods described below. Methods:
[00246] Measurements shall, unless otherwise stated, be carried out at an ambient temperature of 23 ± 2°C and a relative atmospheric humidity of 50 ± 10%. Water-absorbent polymers are thoroughly mixed prior to measurement. vortex
[00247] 50.0 ± 1.0 mL of 0.9% NaCl solution are added to a 100 mL beaker. A cylindrical stir bar (30 x 6 mm) is added and the saline solution is stirred on a stir plate at 60 rpm. 2,000 ± 0.010 g of water absorbent polymer particles are added to the beaker as quickly as possible, starting a clock count as the addition begins. Counting on the clock is stopped when the surface of the mixture fkec “ko„xgn”. q swg means that the surface has no turbulence, and while the mixture can rotate immiscibly, the entire surface of the particles rotates as a unit. The displayed clock count time is recorded with Vortex time. Residual monomers
[00248] The level of residual monomers in the water absorbing polymer particles is determined by the recommended test method EDANA No. WSP 210.3- *3 3+ “Residual Oqpqogtu” Particle Size Distribution
[00249] The particle size distribution of water-absorbent polymer particles is determined with the Camziser® image analysis system (Retsch Technology GmbH; Haan; Germany).
[00250] For the determination of the mean particle diameter and the particle diameter distribution the proportions of the particle fractions by volume are plotted in cumulated form and the mean particle diameter is determined graphically.
[00251] The mean particle diameter (APD) here is the mesh size value that gives rise to a cumulative 50% by weight.
[00252] The particle diameter distribution (PDD) is calculated as follows:
where xi is the mesh size value giving rise to a cumulative 90% by weight and X2 is the value of the mesh size giving rise to a cumulative 10% by weight. medium sphericity
[00253] The mean sphericity is determined with the Camziser® image analysis system (Retsch Technology GmbH; Haan; Germany) using the htc>«q fq fkâogVtq fg rcttiewnc fg 322 to 3o222 μθo moisture content
[00254] The moisture content of the water absorbing polymer particles is determined by the recommended test method EDANA No. WSP 452.5 *3 3+ “Oauu Nquu Wrqp Jgatkni” Centrifuge Holding Capacity (CRC)
[00255] The centrifuge holding capacity of the water absorbing polymer particles is determined by the test method tgeqogpfcfq GFCPC Pqo YUR 463 o5 *3 3+ “Htgg Uygnn Ecrcekty kpUalkpg. Cftgt Egntriliigatiqn“. go swg rata oakqtgu xalqtgu fa earaekfafg fg tgtgp>«q of centrifuge, larger tea bags have to be used. Absorbance under no load (AUNL)
[00256] The absorbance under no charge of the water-absorbent polymer particles is determined analogously to the tgutg method tgeqogpfafq GFCPC Pqo YUR 464o5 *33+ “Itaxkogttke Fgtgtoknatkqp qh CduqtrVkqp Wpfgt Rtguuwtg”. gzegVq by using a weight of 0.0 g/cm2 instead of a weight of 21.0 g/cm2. Absorbance under load (AUL)
[00257] The absorbance under load of water-absorbent polymer particles is determined by the recommended test method GFCPC Pqo YUR 464o5 *33+ “ItcxkogVtke FgVgtoination of Absorption Wpfgt Rtguuwtg” Absorbance at high load (AUHL)
[00258] The absorbance at high load of water-absorbent polymer particles is determined analogously to the recommended test method EDANA No. WSP 242.3 (11) "(itcxiiogltie FgVgtokpcVkqp of CduqtrVkqp Wpfgt Rtguuwtg ", except using a weight of 49, 2 g/cm2 instead of a weight of 21.0 g/cm2. Porosity
[00259] The porosity of the water-absorbent polymer particles is calculated as follows:
Bulk Density/Flow
[00260] The bulk density (BD) and flow rate (FR) of the water absorbing polymer particles is determined by the recommended test method EDANA No. WSP 250.3 (11) "Gravimetric Determination of flow rate, Gravimetric Determination of Density ”. Extractables
[00261] The level of extractable constituents in the water absorbent polymer particles is determined by the recommended test method EDANA No. WSP 470.2-27 “GzVtceVcdngu” Saline Flow Conductivity (SFC)
[00262] The flow conductivity of saline is, as described in EP 0 640 330 A1, determined as the permeability in the gel layer of a swollen gel layer of fluid-absorbing polymer particles, although the apparatus described on page 19 and in figure 8 in the aforementioned patent application were modified so that the glass frit (40) is no longer used, the plunger (39) consists of the same polymer material as the cylinder (37) and now comprises 21 holes having a diameter of 9.65 mm each evenly distributed over the entire contact surface. The measurement procedure and evaluation remain unchanged from EP 0 640 330 A1. Flow is automatically recorded.
[00263] The saline flow conductivity (SFC) is calculated as follows: SFC [cm3s/g] = (Fg(t=0)xL0)/(dxAxWP), where Fg(t = 0) is the flow rate of NaCl solution in g/s, which is obtained by a linear regression analysis of the Fg(t) data from the flow determinations by extrapolation for t = 0, L0 is the thickness of the gel layer in cm, d is a density of the NaCl solution in g/cm3, A is the surface area of the gel layer in cm2 and WP is the hydrostatic pressure over the gel layer in dyn/cm2. Free swelling rate (FSR)
[00264] 1.00 g (= W1) of the dry fluid-absorbent polymer particles is weighed into a 25 mL glass beaker and is evenly distributed in the base of the glass beaker. 20 ml of a 0.9% by weight sodium chloride solution is then dispensed into a second glass beaker, the contents of this beaker are quickly added to the first beaker and a clock count is started. As soon as the last drop of salt solution is absorbed, confirmed by the disappearance of the reflection on the liquid surface, the clock is stopped. The exact amount of liquid poured from the second beaker and absorbed by the polymer in the first beaker is exactly determined by weighing the second beaker back (=W2). The time required for absorption, which was measured by clock counting, is denoted t. The disappearance of the last drop of liquid on the surface is defined as time t.
[00265] The free swelling rate (FSR) is calculated as follows: FSR [g/gs] = W2/(W1xt)
[00266] When the moisture content of the hydrogel-forming polymer is greater than 3% by weight, however, the weight W1 must be corrected for this moisture content. Absorbance in volumetric load (VAUL)
[00267] The volumetric absorbance in a charge is used in order to measure the swelling kinetics, that is, the characteristic swelling time, of the water absorbing polymer particles at different applied pressures. The height of swelling is recorded as a function of time.
[00268] The setting is shown in figure 14 and consists of - An ultrasonic distance sensor (85) type BUS M18K0-XBFX-030-S04K (Balluff GmbH, Neuhausen a.d.F.; Germany) is placed above the cell. The sensor receives ultrasound reflected by the metal plate. The sensor is connected to an electronic recorder. - A PTFE cell (86) having a diameter of 75 mm, a height of 73 mm and an inner diameter of 52 mm - A cylinder (87) made of metal or plastic having a diameter of 50 mm, a height of 71 mm and a mesh base) - A metal reflector (88) having a diameter of 57 mm and a height of 45 mm - metal ring weights (89) having a diameter of 100 mm and weights calibrated to 278.0 g or 554, 0 g.
[00269] It is possible to adjust the pressure applied to the sample by changing the combination of cylinder weight (86) and metal ring (88) as summarized in the following tables:

[00270] A 2.0 g sample of water-absorbent polymer particles is placed in the PTFE cell (86). Cylinder (equipped with mesh base) and the metal reflector (88) on top of it are placed in the PTFE cell (86). In order to apply more pressure, weights of metal rings (89) can be placed on the cylinder.
[00271] 60.0 g of aqueous saline solution (0.9% by weight) are added to the PTFE cell (86) with a syringe and recording is started. During swelling, the water-absorbent polymer particles push the cylinder (87) upwards and the changes in the distance between the metal reflector (88) and the sensor (85) are recorded.
[00272] After 120 minutes, the experiment is stopped and the recorded data is transferred from the recorder to a PC using a USB cable. The characteristic swelling time is calculated according to the equation
as described by “Modern Superabsorbent Polymer Technology” (page 155, equation 4.13) where Q(t) is the swelling of the superabsorbent that is monitored during the experiment, Qmax corresponds to the maximum swelling reached after 120 minutes (end of experiment) and k is the characteristic swelling time (k is the constant inverse rate k).
[00273] Using the Microsoft Excel software add-in “Solver” functionality, a theoretical curve can be fitted to the measured data and the characteristic time for 0.03 psi is calculated.
[00274] Measurements are repeated for different pressures (0.1 psi, 0.3 psi, 0.5 psi and 0.7 psi) using combinations of cylinder and ring weights. The characteristic swelling times for different pressures can be calculated using the equation
Drainage absorption
[00275] Drainage absorption is used in order to measure the total liquid absorption of the water-absorbent polymer particles under applied pressure. The adjustment is shown in figure 15.
[00276] A 500 mL glass bottle (90) (100 mL scale division, height 26.5 cm) equipped with a Duran® glass outlet tube is filled with 500 mL of aqueous saline solution (0.9% by weight). The bottle has an opening at the end of the base that can be connected to the Plexiglas plate via a flexible tube (91).
[00277] A scale (92) connected to a computer is placed on the Plexiglas block (area 20 x 26 cm2, height 6 cm). The glass bottle is then placed on the scale.
[00278] A Plexiglas board (93) (area: 11 x 11 cm2, height: 3.5 cm) is placed on a lifting platform. A glass frit of P1 porosity 7 cm in diameter and 0.45 cm in height (94) was swelled firmly with liquid in the Plexiglas plate, i.e. the fluid exits through the pores of the frit and neither through the edge between the Plexiglas board and the frit. A Plexiglas tube leads from the outer shell of the Plexiglas plate in the center of the Plexiglas plate to the frit to ensure fluid transport. The fluid tube is then connected with the flexible tube (35 cm long, 1.0 cm outside diameter, 0.7 cm inside diameter) to the glass bottle (90).
[00279] The lifting platform is used to adjust the upper side of the frit to the level of the end of the base of the glass bottle, in such a way that an always atmospheric flow of fluid from the bottle to the measuring apparatus is guaranteed during the measurement. The upper side of the frit is adjusted so that its surface is moist, but there is no supernatant film of water on the frit.
[00280] The fluid in the glass bottle (90) is made up to 500 mL before each run.
[00281] In a Plexiglas cylinder (95) (7 cm outside diameter, 6 cm inside diameter, 16 cm high) and equipped with a 400 mesh (36 μo) at the base, 26 g of absorbent polymer particles are placed. Water. The surface of the water-absorbent polymer particles is smoothed. The fill level is about 1.5 cm. Then a weight (96) of 0.3 psi (21.0 g/cm2) is placed on top of the water absorbent polymer particles.
[00282] The Plexiglas cylinder is placed on the frit (wet) and the electronic data logging started. A decrease in scale weight is recorded as a function of time. This then indicates how much aqueous saline solution by the gel swelling of the water absorbing polymer particles in a given time. Data is automatically captured every 10 seconds. The measurement is carried out at 0.3 psi (21.0 g/cm2) for a period of 120 minutes per sample. The total liquid absorption is the total amount of aqueous saline solution absorbed per 26 g of sample. Rewetting under load (RUL)
[00283] The test determines the amount of fluid that a fluid-absorbing article will release after being held at a pressure of 0.7 psi (49.2 g/cm2) for 10 min following multiple separate insults. Rewetting under load is measured by the amount of fluid that the fluid-absorbing article releases under pressure. In-charge rewetting is after each insult.
[00284] The fluid absorbent article is stapled non-woven side up on the inspection table. The insult point is marked in this way with respect to the type and sex of the diaper being tested (ie, in the center of the core for a girl, 2.5 cm forward for unisex and 5 cm forward for a boy). A circular weight of 3.64 kg (10 cm in diameter) having a central opening (2.3 cm in diameter) with perspex tube is placed at the previously marked insult point.
[00285] For the primary insult. 100 g of aqueous saline solution (0.9% by weight) is poured into the perspex tube in one shot. Amount of time required for the fluid to be completely absorbed into the fluid-absorbing article is recorded. After 10 minutes, the load is removed and a stack of 10 filter papers (Whatman®) having 9 cm diameter and known dry weight (W1) is placed over the insult point on the fluid-absorbing article. On top of the filter paper, the weight of 2.5 kg with 8 cm in diameter is added. After 2 the weight is removed and the filter paper is re-weighed giving the wet weight value (W2).
[00286] On-load rewetting is calculated as follows: RUL [g] = W2-W1
[00287] For in-charge rewetting of the secondary insult the procedure for the primary insult is repeated. 50 g of aqueous saline solution (0.9% by weight) and 20 filter papers are used.
[00288] For in-charge rewetting of tertiary and subsequent insults the procedure for the primary insult is repeated. For each of the following insults 3rd, 4th and 5th, 50 g of aqueous saline solution (0.9% by weight) and filter papers 30, 40 and 50 respectively are used. Rewetting value (RV)
[00289] This test consists of multiple insults of aqueous saline solution (0.9% by weight). The rewetting value is measured by the amount of fluid that the fluid-absorbing article releases under pressure. Rewetting is measured after each insult.
[00290] The fluid absorbent article is the non-woven side stapled up on the inspection table. The insult point is thus marked with respect to the type and sex of the diaper being tested (ie, in the center of the core for a girl, 2.5 cm forward for unisex and 5 cm forward for a boy). A separating funnel is positioned above the fluid-absorbing article such that the nozzle is directly above the marked insult point.
[00291] For the primary insult, 100 g of aqueous saline solution (0.9% by weight) is poured into the fluid-absorbing article via the funnel in one shot. The liquid is naturally absorbed for 10 minutes and after this time a stack of 10 filter papers (Whatman®) having 9 cm diameter and known dry weight (D1) is placed over the insult point on the fluid-absorbing article. On top of the filter paper, the weight of 2.5 kg with 8 cm in diameter is added. After 2 minutes the weight is removed and filter paper re-weighed giving the wet weight value (D2).
[00292] The rewetting value is calculated as follows: RV [g] = D2-D1
[00293] For the rewetting of the secondary insult the procedure for the primary insult is repeated. 50 g of aqueous saline solution (0.9% by weight) and 20 filter papers are used.
[00294] For the rewetting of tertiary and following insults the procedure for the primary insult is repeated. For each of the following insults 3rd, 4th and 5th, 50 g of aqueous saline solution (0.9% by weight) and filter papers 30, 40 and 50 respectively are used.
[00295] EDANA test methods are obtained, for example, from EDANA, Avenue Eugene Plasky 157, B-1030 Brussels, Belgium. Examples Preparation of the base polymer Example 1
[00296] The process was carried out in a co-current spray drying plant with an integrated fluidized bed (27) and an external fluidized bed (29) as shown in figure 1. The cylindrical part of the spray dryer (5) had a height of 22 m and a diameter of 3.4 m. The internal fluidized bed (IFB) had a diameter of 3 m and a dam height of 0.25 m. The external fluidized bed (EFB) had a length of 3.0 m, a width of 0.65 m and a dam height of 0.5 m.
[00297] The drying gas was fed through a gas distributor (3) at the top of the spray dryer. The drying gas was partially recycled (drying gas loop) through a chamber filter (9) and a condenser column (12). The drying gas was nitrogen comprising 1% to 4% by volume of residual oxygen. Before starting the polymerization the drying gas loop was filled with nitrogen until the residual oxygen was below 4% by volume. The gas velocity of the drying gas in the cylindrical part of the spray dryer (5) was 0.8 m/s. The pressure inside the spray dryer was 0.4 kPa (4 mbar) below ambient pressure.
[00298] The spray dryer outlet temperature was measured at three points around the circumference at the end of the cylindrical portion as shown in Figure 3. Three single measurements (47) were used to calculate the average cylindrical dryer outlet temperature per sprinkler. The drying gas loop has been heated and dosing of monomer solution is started. From this time on, the spray dryer outlet temperature was controlled at 117°C by adjusting the gas inlet temperature by means of the heat exchanger (20).
[00299] The product accumulated in the internal fluidized bed (27) until the height of the dam was reached. Conditioned internal fluidized bed gas having a temperature of 122°C and a relative humidity of 4% was fed into the internal fluidized bed (27) via line (25). The gas velocity of the inner fluidized bed gas in the inner fluidized bed (27) was 0.80 m/s. The residence time of the product was 120 min.
[00300] The effluent from the spray dryer was filtered in a chamber filter (9) and sent to a condenser column (12) for completion/cooling. Excess water was pumped out of the condenser column (12) controlling the fill level (constant) within the condenser column (12). The water within the condenser column (12) was cooled by a heat exchanger (13) and pumped counter-current to the gas through termination nozzles (11) such that the temperature inside the condenser column (12) ) was 45°C. The water within the condenser column (12) was adjusted to an alkaline pH by dosing sodium hydroxide solution to wash away acrylic acid vapors.
[00301] The effluent from the condenser column was separated in the drying gas inlet pipe (1) and the conditioned internal fluidized bed gas (25). Gas temperatures were controlled by means of heat exchangers (20) and (22). The hot drying gas was fed into the co-current spray dryer via a gas distributor (3). The gas distributor (3) consists of a set of plates providing a pressure drop of 0.2 to 0.4 kPa (2 to 4 mbar) depending on the quantity of drying gas.
[00302] The product was discarded from the internal fluidized bed (27) by means of a rotary valve (28) in an external fluidized bed (29). Conditioned external fluidized bed gas having a temperature of 60°C was fed into the external fluidized bed (29) via line (40). The external fluidized bed gas was air. The gas velocity of the outer fluidized bed gas in the outer fluidized bed (29) was 0.8 m/s. The residence time of the product was 1 min.
[00303] The product was discarded from the external fluidized bed (29) by means of a rotary valve (32) on the sieve (32). The sieve (33) was used for sieving surplus/pits having a particle diameter greater than 800 μθo
[00304] The monomer solution was prepared by first mixing acrylic acid with ethoxylated 3-tupli glycerol triacrylate (internal crosslinker) and secondly with 37.3% by weight of sodium acrylate solution. The temperature of the resulting monomer solution was controlled at 10°C using a heat exchanger and pumping in a loop. A filter unit having wo Vcocpjq fc maJha fg 472 μo fok wucfc pq nc>q fgrqku fc dqodCo Qu initiators were measured in the monomer solution upstream of the droplet former by means of static mixers (41) and (42) by means of lines (43) and (44) as shown in figure 1. Sodium peroxodisulfate solution having a temperature of 20°C was added via line (43) and uonw>«o fg fkenotkftcVo fg ]4,4o-azobis[ 2-(2-imidazolin-2-yl)propane] along with Bruggolite FF7 having a temperature of 5°C was added via line (44). Each initiator was pumped into a loop and metered through control valves to each droplet former unit. A second wpkfcfg fg fknvtq vgpfq wo vcocpjq fc ocnjc fg 362 μo fqk wucfq fgrqku fq static mixer (42). For the dosage of the monomer solution at the top of the spray dryer, three droplet former units were used as shown in figure 4.
[00305] A droplet former unit consisted of an external tubing (51) having an opening for the droplet former cassette (53) as shown in figure 5. The droplet former cassette (53) was connected with a tubing internal (52). The inner piping (53) having a PTFE block (54) at the end as a seal may be pushed in and out of the outer piping (51) during process operation for maintenance purposes.
[00306] The temperature of the droplet former cassette (61) was controlled at 8°C by water in flow channels (59) as shown in figure 6. The droplet former cassette (61) had 256 holes having a fkâogVtq fg 392 μo g woc ugrctc>«q fg hwtq fg 37 oθo Q ecuugVg fq droplet former (61) consisted of a flow channel (60) having volume without stagnant essential for homogeneous distribution of the pre-mixed monomer and starter solutions and a droplet plate (57). Droplet plate (57) had an angled configuration with an angle of 3°. The droplet plate (57) was made of stainless steel and had a length of 630 mm, a width of 128 mm and a thickness of 1 mm.
Feed to the spray dryer consisted of 10.45% by weight acrylic acid, 33.40% by weight sodium acrylate, 0.018% by weight ethoxylated 3-tupli glycerol triacrylate, 0.072% by weight fkenqtkftcvq fg]4.40-azobis[2-(2-imidazolin-2-yl)propane], 0.0029% by weight Bruggolite FF7 (5% by weight in water), 0.054% by weight sodium peroxodisulfate solution ( 15% by weight in water) and water. The degree of neutralization was 71%. Feed per hole was 1.6 kg/h.
[00308] The polymer particles (base polymer A1) showed the following characteristics and absorption profile: CRC of 40.2 g/g AUHL of 51.8 g/g AUL of 22.4 g/g AUHL of 8.2 g/g Porosity of 22.3% Extractables of 4.3% by weight Residual monomers of 12161 ppm Moisture content 6.1% by weight Vortex time 67 sec
[00309] The resulting polymer particles had a density crctgpVg fg 8: i1322 mN g wo fkaogVtq fg rcrtiewnc ofifkq fg 629 μo. Example 2
[00310] Example 1 was repeated, except that the resulting polymer particles having a residual monomer content of 12161 ppm were demonomerized in a plastic bottle in a laboratory oven at 90°C for 60 minutes after spraying 15% by weight of water on the polymer particles in a laboratory paddle mixer. In this way, the residual monomer content was reduced to 256 ppm and the moisture content was increased to 17.5% by weight.
[00311] The polymer particles (base polymer B1) showed the following characteristics and absorption profile: CRC of 33.1 g/g AUHL of 42.3 g/g AUL of 17.0 g/g AUHL of 8.1 g/g Porosity 21.7% Extractables 8.2% by weight Residual monomers 256 ppm Moisture content 17.5% by weight Vortexing time 54 s Example 3
[00312] Example 1 was repeated, except that the feed to the spray dryer consisted of 0.036% go"rguq"fg"fkenqtkftcvq"fg"]4.4O-azobis[2-(2-imidazolin-2-yl)propane] and that the conditioned internal fluidized bed gas had a temperature of 122°C and a relative humidity of 4% and that the residence time of the product in the internal fluidized bed was 120 min.
[00313] The polymer particles (base polymer C1) showed the following characteristics and absorption profile: CRC of 39.5 g/g AUNL of 51.4 g/g AUHL of 9.0 g/g Porosity of 23.2 % Residual monomers 1581 ppm Moisture content 10.9% by weight Post-crosslinking base polymer surface Example 4
[00314] 1200 g of the water-absorbent polymer particles prepared in example 1 (base polymer A1) having a residual monomer content of 12161 ppm were placed in a laboratory paddle mixer (model MR5, manufactured by Gebruder Lodige Maschinenbau GmbH; Paderborn; Germany). A surface solution post-crosslinker was prepared by mixing 60 g of surface post-crosslinker as described in table 1 and 60 g of deionized water, in a beaker. At a mixer speed of 200 rpm, the aqueous solution was sprayed onto the polymer particles in one minute by means of a spray nozzle. Mixing continued for another 5 minutes. The product was removed and transferred into another paddle mixer (model MR5, manufactured by Gebruder Lodige Maschinenbau GmbH; Paderborn; Germany) which was heated to 140°C beforehand. After mixing for a further 80 minutes at 140°C with sample taken every 10 minutes, the product was removed from the mixer and sieved at 150 to : 850 µm. Samples were analyzed. The results are summarized in table 1.
[00315] The resulting polymer particles that were surface cross-linked with ethylene carbonate had a bulk density of 69.0 g/100 mN, wo fkaogVto fg rcrtiewnc ofifko *ARF+ fg 6:3 μo, woc fkuVtkdwk>«o f the diameter of particle (PDD) of 0.28 and an average sphericity of 0.82. Table 1: Effect of the post-crosslinking agent
Table 1: Effect of post-crosslinking agent (continued)

[00316] EC: Ethylene carbonate; HEONON: N-(2-hydroxy ethyl)-2-oxazolidinone; EGDGE: Ethylene glycol diglycidyl ether Example 5
[00317] 1200 g of the water-absorbent polymer particles as described in table 2 having different residual monomer contents were placed in a laboratory paddle mixer (model MR5, manufactured by Gebruder Lodige Maschinenbau GmbH; Paderborn; Germany). A surface solution post-crosslinker was prepared by mixing 30 g of ethylene carbonate and 30 g of deionized water in a beaker. At a mixer speed of 200 rpm, the aqueous solution was sprayed onto the polymer particles in one minute by means of a spray nozzle. Mixing continued for another 5 minutes. The product was removed and transferred into another paddle mixer (model MR5, manufactured by Gebruder Lodige Maschinenbau GmbH; Paderborn; Germany) which was heated to 150°C beforehand. After mixing for a further 80 minutes at 150°C with sample removed every 10 minutes, the product was removed from the mixer and sieved at 150 to :72 μθo Cu coquVtcu fotco cpcnkucfcuo Qu tguwnvcfqu fotco uwoctkzcfqu pc table 2.
[00318] The resulting polymer particles based on the base polymer A1 had a bulk density of 68.0 g/100 mL, an average particle diameter (APD+ fg 5.9 μo, woc fkuVtkdwk>«o fo fkâogVtq fg rcrtiewnc ( PDD) of 0.38 and an average sphericity of 0.87.
[00319] The resulting polymer particles based on base polymer B1 had a bulk density of 64.7 g/100 ml, an average particle diameter (APD) dg 775 μo, woc fkuVtkdwk>«o fo fkâogVtq fg rcrtiewnc (PDD) ) of 0.25 and an average sphericity of 0.74.
[00320] The resulting polymer particles based on base polymer C1 had a bulk density of 69.8 g/100 ml, an average particle diameter (APD) of 399μo, woc fkuVtkdwk>«o fo fkâogVtq fg rcrtiewnc (PDD) of 0.42 and an average sphericity of 0.86. Example 6
[00321] 1200 g of the water-absorbent polymer particles as described in table 3 having different contents of residual monomers were placed in a laboratory paddle mixer (model MR5, manufactured by Gebruder Lodige Maschinenbau GmbH; Paderborn; Germany). A surface solution post-crosslinker was prepared by mixing 30 g of ethylene carbonate and 60 g of deionized water in a beaker. At a mixer speed of 200 rpm, the aqueous solution was sprayed onto the polymer particles in one minute by means of a spray nozzle. Mixing continued for another 5 minutes. The product was removed and transferred into another paddle mixer (model MR5, manufactured by Gebruder Lodige Maschinenbau GmbH; Paderborn; Germany) which was heated to 140°C beforehand. After mixing for a further 80 minutes at 140°C with sample taken every 10 minutes, the product was removed from the mixer and sieved from 150 to 850 μθo Cu coquVtcu fotco cpcnkucfcuo Qu tguwnvcfqu fotco uwoctkzcfqu pc table 3.
The resulting polymer particles based on base polymer A1 had a bulk density of 65.6 g/100 ml, a diameter of rcttiewnc ofifko *ARF+ fg 672 μo. woc fkuVtkdwk>particle diameter (PDD) of 0.32 and an average sphericity of 0.82.
The resulting polymer particles based on base polymer B1 had a bulk density of 64.7 g/100 ml, a diameter of rcttiewnc ofifko *ARF+ fg 786 μo. woc fkuttkdwk>«q particle diameter (PDD) of 0.22 and an average sphericity of 0.75.
[00324] The resulting polymer particles based on base polymer C1 had a bulk density of 70.3 g/100 ml, a diameter of rcttiewnc ofifko *ARF+ fg 5;; μo. woc fkuttkdwk>«q fq particle diameter (PDD) of 0.36 and an average sphericity of 0.84. Table 2: Effect of residual monomers
Table: Effect of residual monomers (continued)
Table 3: Effect of residual monomers
Table 3: Effect of residual monomers (continued)
Example 7
[00325] The process was carried out in a co-current spray drying plant with an integrated fluidized bed (27) and an external fluidized bed (29) as shown in figure 1. The cylindrical part of the spray dryer (5) had a height of 22 m and a diameter of 3.4 m. The internal fluidized bed (IFB) had a diameter of 3 m and a dam height of 0.25 m.
[00326] The drying gas was fed through a gas distributor (3) at the top of the spray dryer. The drying gas was partially recycled (drying gas loop) through a chamber filter (9) and a condenser column (12). Instead of the chamber filter (9) any other filter and/or cyclone can be used. The drying gas was nitrogen comprising 1% to 4% by volume of residual oxygen. Before starting the polymerization the drying gas loop was filled with nitrogen until the residual oxygen was below 4% by volume. The gas velocity of the drying gas in the cylindrical part of the spray dryer (5) was 0.82 m/s. The pressure inside the spray dryer was 0.4 kPa (4 mbar) below ambient pressure.
[00327] The spray dryer outlet temperature was measured at three points around the circumference at the end of the cylindrical part as shown in figure 3. Three single measurements (47) were used to calculate the average cylindrical dryer outlet temperature per sprinkler. The drying gas loop has been heated and dosing of monomer solution is started. From this time on, the spray dryer outlet temperature was controlled at 118°C by adjusting the gas inlet temperature by means of the heat exchanger (20). The inlet gas temperature was 167°C and the vapor content of the drying gas was 0.058 kg steam per kg of dry gas.
[00328] The product accumulated in the internal fluidized bed (27) until the height of the dam was reached. Conditioned inner fluidized bed gas having a temperature of 104°C and a vapor content of 0.058 or 0.130 kg steam per kg of dry gas was fed into the inner fluid bed (27) via line (25). The gas velocity of the inner fluidized bed gas in the inner fluidized bed (27) was 0.65 m/s. The residence time of the product was 150 min. The temperature of the water-absorbent polymer particles in the internal fluidized bed was 82°C.
[00329] The effluent from the spray dryer was filtered in a chamber filter (9) and sent to a condenser column (12) for completion/cooling. Excess water was pumped out of the condenser column (12) controlling the fill level (constant) within the condenser column (12). The water within the condenser column (12) was cooled by a heat exchanger (13) and pumped counter-current to the gas through termination nozzles (11) such that the temperature inside the condenser column (12) ) was 45°C. The water within the condenser column (12) was adjusted to an alkaline pH by dosing sodium hydroxide solution to wash away acrylic acid vapors.
[00330] The effluent from the condenser column was separated in the drying gas inlet pipe (1) and the conditioned internal fluidized bed gas (25). Gas temperatures were controlled by means of heat exchangers (20) and (22). The hot drying gas was fed into the co-current spray dryer via a gas distributor (3). The gas distributor (3) consists of a set of plates providing a pressure drop of 0.2 to 0.4 kPa (2 to 4 mbar) depending on the quantity of drying gas.
[00331] The product was discarded from the internal fluidized bed (27) by means of a rotary valve (28) on the sieve (29). The sieve (29) was used for sieving surplus/pits having a particle diameter greater than 800 μθo
[00332] The monomer solution was prepared by first mixing acrylic acid with ethoxylated 3-tupli glycerol triacrylate (internal crosslinker) and secondly with 37.3% by weight sodium acrylate solution. The temperature of the resulting monomer solution was controlled at 10°C using a heat exchanger and pumping in a loop. A filter unit having a size fc rnaJha fg 472 μo fok wucfc pq nc>q fgrqku fc dqodCo Qu kpkekcfqtgu fotc m measured in the monomer solution upstream of the droplet former by means of static mixers (41) and (42) by means of lines (43) and (44) as shown in figure1. Sodium peroxodisulfate solution having a temperature of 20°C was added via line (43) and fkenqtkftcvq fg ]4.4O-azobis[2-(2-imidazolin-2-yl)propane] solution along with Bruggolite FF7 having a temperature of 5°C was added via line (44). Each initiator was pumped into a loop and metered through control valves to each droplet former unit. A second wpkfcfg fg fknvtq vgpfq wo vcocpjq fc ocnjc fg 362 μo fqk wucfq fgrqku fq static mixer (42). For the dosage of the monomer solution at the top of the spray dryer, three droplet former units were used as shown in figure 4.
[00333] A droplet former unit consisted of an external tubing (51) having an opening for the droplet former cassette (53) as shown in figure 5. The droplet former cassette (53) was connected with a tubing internal (52). The inner piping (53) having a PTFE block (54) at the end as a seal may be pushed in and out of the outer piping (51) during process operation for maintenance purposes.
[00334] The temperature of the droplet former cassette (61) was controlled at 8°C by water in flow channels (59) as shown in figure 6. The droplet former cassette (61) had 256 holes having a fkâogVtq fg 392 μo g woc ugrctc>«o fg hwto fg 37 ooo Q ecuugVg fo droplet former (61) consisted of a flow channel (60) having a stagnant-free volume essential for homogeneous distribution of the pre-mixed monomer and starter solutions and a droplet plate (57). Droplet plate (57) had an angled configuration with an angle of 3°. The droplet plate (57) was made of stainless steel and had a length of 630 mm, a width of 128 mm and a thickness of 1 mm.
Feed to the spray dryer consisted of 10.45% by weight acrylic acid, 33.40% by weight sodium acrylate, 0.018% by weight ethoxylated 3-tupli glycerol triacrylate, 0.036% by weight fkenqtkftcvq "fg"]4,4'-azobis[2-(2-imidazolin-2-yl)propane], 0.0029% by weight Bruggolite FF7, 0.054% by weight sodium peroxodisulfate and water. The degree of neutralization was 71%. Feed per hole was 1.4 kg/h.
[00336] The resulting water-absorbent polymer particles were analyzed. The results are summarized in table 4. Table 4: Polymer bases used for surface post-crosslinking reactions
Examples 8 to 26
[00337] On a Schugi Flexomix® (model Flexomix-160, manufactured by Hosokawa Micron BV, Doetinchem, Netherlands) with a speed of 2000 rpm, the base polymer 7a or 7b was coated with a surface solution post-crosslinker using 2 or 3 round spray nozzle systems (Model Gravity-Fed Spray Set-ups, External Mix Typ SU4, Fluid Cap 60100 and Air Cap SS-120, manufactured by Spraying Systems Co, Wheaton, Illinois, USA) and then filled with medium inlet (74) and dried in a NARA heater (model NPD 5W-18, manufactured by GMF Gouda, Waddinxveen, The Netherlands) with a rod speed (80) of 6 rpm. The NARA heater has two blades with a 90° offset rod (84) and a fixed disposal zone (75) with two flexible dam plates (77). Each dam has a dam opening with a minimum dam height of 50% (79) and a maximum dam opening of 100% (78) as shown in figure 13.
[00338] The inclination angle one (82) between the floor plate and the NARA paddle dryer is approximately 3°. The height of the NARA heater dam is between 50 to 100% corresponding to a residence time of approximately 40 to 150 min, for a product density of approximately 700 to 750 kg/m3. The product temperature in the NARA heater is in a range of 120 to 165°C. After drying, the surface post-crosslinked base polymer was transported over the discharge cone (81) in the NARA cooler (GMF Gouda, Waddinxveen, Netherlands) to cool the surface post-crosslinked base polymer to approximately 60°C with a speed of 11 rpm and a dam height of 145 mm. After cooling, the material was sieved to a minimum cut size of 150 μo g wo Vcocpjq fg eqrtg oázkoq fg 932 μo.
[00339] Ethylene carbonate, water, Plantacare® UP 818 (BASF SE, Ludwigshafen, Germany) and aqueous aluminum lactate (26% by weight) was pre-mixed and spray coated as summarized in table 6. Aqueous aluminum sulphate ( 26% by weight) was spray coated separately (nozzle position = 180°). As aluminum lactate, Lothragon® Al 220 (manufactured by Dr. Paul Lohmann GmbH, Emmerthal, Germany) was used.
[00340] Measured quantities and conditions of coating on Schugi Flexomix®, conditions, formulation and values of the drying and cooling step are summarized in table 5 to 6: All physical properties of the resulting polymers are summarized in table 7 and 8 Table 5: Heat treatment process parameters in the heater
Table 5: Heat treatment process parameters in the heater (continued)

Table 6: Post-surface crosslinker formulation of heat treatment in the heater
Ethylene carbonate; bop: based on polymer Table 7: Physical properties of polymer particles after surface post-crosslinking
Table 7: Physical properties of polymer particles after surface post-crosslinking (continued)

Table 8: Physical properties of polymer particles after surface post-crosslinking
Example 27
[00341] 1200 g of the water-absorbent polymer particles prepared in example 7b (base polymer) having a residual monomer content of 4000 ppm were placed in a laboratory paddle mixer (model MR5, manufactured by Gebruder Lodige Maschinenbau GmbH, Paderborn , Germany). A surface solution post-crosslinker was prepared by mixing 12 g of 3-methyl-2-oxazolidinone as described in table 1 and 60 g of deionized water in a beaker. At a mixer speed of 200 rpm, the aqueous solution was sprayed onto the polymer particles in one minute by means of a spray nozzle. Mixing continued for another 5 minutes. The product was removed and transferred into another paddle mixer (model MR5, manufactured by Gebruder Lodige Maschinenbau GmbH; Paderborn; Germany) which was heated to 150°C beforehand. After mixing for a further 80 minutes at 150°C with sample taken every 10 minutes, the product was removed from the mixer and sieved from 150 to 850 µo Cu coquVtcu fotco cpcnkucfcUo Qu tguwnvcfqu fotco uwoctkzcfqu pc table 10.
The resulting polymer particles that were surface cross-linked with 3-methyl-1,3-oxazolidin-2-one had a bulk density of 70.4 g/100 mL and a flow rate of 11.5 g/s. Example 28
[00343] 1200 g of the water-absorbent polymer particles prepared in example 7b (base polymer) having a residual monomer content of 4000 ppm were placed in a laboratory paddle mixer (model MR5, manufactured by Gebruder Lodige Maschinenbau GmbH; Paderborn ; Germany). A surface solution post-crosslinker was prepared by mixing 6 g of 3-Methyl-3-oxethanmethanol as described in table 9 and 60 g of deionized water, in a beaker. At a mixer speed of 200 rpm, the aqueous solution was sprayed onto the polymer particles in one minute by means of a spray nozzle. Mixing continued for another 5 minutes. The product was removed and transferred into another paddle mixer (model MR5, manufactured by Gebruder Lodige Maschinenbau GmbH, Paderborn, Germany) which was heated to 150°C beforehand. After mixing for a further 80 minutes at 150°C with sample removed every 10 minutes, the product was removed from the mixer and sieved at 150 to 850 µo Cu coquVtcu fotco cpcnkucfcUo Qu tguwnvcfqu fotco uwoctkzcfqu pc Vcdgnc 10.
[00344] The resulting polymer particles that were surface cross-linked with 3-methyl-3-oxetanmethanol had a bulk density of 72.2/100 mL and a flow rate of 12.0 g/s. Example 29
[00345] 1200 g of the water-absorbent polymer particles prepared in example 7b (base polymer) having a residual monomer content of 4000 ppm were placed in a laboratory paddle mixer (model MR5, manufactured by Gebruder Lodige Maschinenbau GmbH, Paderborn , Germany). A surface solution post-crosslinker was prepared by mixing 6 g of 2-oxazolidinone as described in table 9 and 60 g of deionized water, in a beaker. At a mixer speed of 200 rpm, the aqueous solution was sprayed onto the polymer particles in one minute by means of a spray nozzle. Mixing continued for another 5 minutes. The product was removed and transferred into another paddle mixer (model MR5, manufactured by Gebruder Lodige Maschinenbau GmbH, Paderborn, Germany) which was heated to 150°C beforehand. After mixing for a further 80 minutes at 150°C with sample taken every 10 minutes, the product was removed from the mixer and sieved from 150 to 850 µo0 Cu coouvtcu fotco cpcnkucfcu0 Qu tguwnvcfou fotco uwoctkzcfou pc vcdgnc 10.
[00346] The resulting polymer particles that were surface cross-linked with 1,3-oxazolidin-2-one had a bulk density of 69.7 g/100 mL and a flow rate of 10.8 g/s. Example 30
[00347] 1200 g of the water-absorbent polymer particles prepared in example 7b (base polymer) having a residual monomer content of 4000 ppm were placed in a laboratory paddle mixer (model MR5, manufactured by Gebruder Lodige Maschinenbau GmbH, Paderborn , Germany). A surface solution post-crosslinker was prepared by mixing 6 g of 3-(2-hydroxyethyl)-2-oxazolidinone Solution and 6 g of propandiol as described in table 9 and 60 g of deionized water in a beaker. At a mixer speed of 200 rpm, the aqueous solution was sprayed onto the polymer particles in one minute by means of a spray nozzle. Mixing continued for another 5 minutes. The product was removed and transferred into another paddle mixer (model MR5, manufactured by Gebruder Lodige Maschinenbau GmbH, Paderborn, Germany) which was heated to 165°C beforehand. After mixing for a further 80 minutes at 165°C with sample taken every 10 minutes, the product was removed from the mixer and sieved at 150 to 850 µo. Cu coquVtcu fotco cpcnkucfcUo Qu tguwnvcfqu were summarized in table 10.
The resulting polymer particles which were surface cross-linked with 3-(2-hydroxyethyl)-1,3-oxazolidin-2-one and 6 g propandiol had a bulk density of 67.4 g/100 ml and a flow rate of 10.1 g/s. Example 31
[00349] 1200 g of the water-absorbent polymer particles prepared in example 7b (base polymer) having a residual monomer content of 4000 ppm were placed in a laboratory paddle mixer (model MR5, manufactured by Gebruder Lodige Maschinenbau GmbH, Paderborn , Germany). A surface solution post-crosslinker was prepared by mixing 3 g of N,N,N',N'-Tetrakis(2-hydroxyethyl)adipamide (Primid® XL 552, manufactured by Ems Chemie AG; Domat; Switzerland) as described in table 9 and 60 g of deionized water, in a beaker. At a mixer speed of 200 rpm, the aqueous solution was sprayed onto the polymer particles in one minute by means of a spray nozzle. Mixing continued for another 5 minutes. The product was removed and transferred into another paddle mixer (model MR5, manufactured by Gebruder Lodige Maschinenbau GmbH, Paderborn, Germany) which was heated to 160°C beforehand. After mixing for a further 80 minutes at 160°C with sample taken every 10 minutes, the product was removed from the mixer and sieved from 150 to 850 μθo Cu coquVtcu fotco cpcnkucfcUo Qu tguwnvcfqu fotco uwoctkzcfqu pc Vcdgnc 10.
[00350] The resulting polymer particles that were surface cross-linked with N,N,N',N'-Tetrakis(2-hydroxyethyl)adipamide had a bulk density of 65.8 g/100 mL and a flow rate of 10.2 g/s. Example 32
[00351] 1200 g of the water-absorbent polymer particles prepared in example 7b (base polymer) having a residual monomer content of 4000 ppm were placed in a laboratory paddle mixer (model MR5, manufactured by Gebruder Lodige Maschinenbau GmbH, Paderborn , Germany). A surface solution post-crosslinker was prepared by mixing 24 g of 1,3-Dioxan-2-one as described in table 9 and 60 g of deionized water, in a beaker. At a mixer speed of 200 rpm, the aqueous solution was sprayed onto the polymer particles in one minute by means of a spray nozzle. Mixing continued for another 5 minutes. The product was removed and transferred into another paddle mixer (model MR5, manufactured by Gebruder Lodige Maschinenbau GmbH, Paderborn, Germany) which was heated to 160°C beforehand. After mixing for a further 80 minutes at 160°C with sample taken every 10 minutes, the product was removed from the mixer and sieved from 150 to 850 μθo Cu coquVtcu fotco cpcnkucfcUo Qu tguwnvcfqu fotco uwoctkzcfqu pc Vcdgnc 10.
[00352] The resulting polymer particles that were surface cross-linked with 1,3-Dioxan-2-one had a bulk density of 68.4 g/100 mL and a flow rate of 10.5 g/s. Table 9: Formulation of polymer particles after surface post-crosslinking using different surface post-crosslinkers
Bop: based on polymer Table 10: Physical properties of polymer particles after surface post-crosslinking using different surface post-crosslinkers
Comparative examples
[00353] AQUA KEEP® SA60SII, AQUA KEEP® SA55XSII, AQUA KEEP® SA60SXII are water absorbent polymer particles from SUMITOMO SEIKA CHEMICALS CO., LTD, produced by a suspension polymerization process.
[00354] ASAP® 535, Hysorb® B7075, Hysorb® T9700, Hysorb® B7055, Hysorb® T8760, Hysorb® M7055N, Hysorb® B7015, Hysorb® M7015N, Hysorb® M7015 and Hysorb® 7400 are particles of water-absorbent polymers from BASF SE, produced by a polymerization process with a kneader.
[00355] CE1 and CE2 correspond to the particles of water-absorbent polymers which are prepared according to example 7 and example 26 of WO 2012/045705 A1.
[00356] CE3 corresponds to the particles of water-absorbent polymers which are prepared according to example 25 of WO 2013/007819 A1.
[00357] Figure 16 is a diagram showing the water-absorbent polymer particles according to the present invention have better overall rapid absorption compared to conventional water-absorbent polymer particles having the same centrifuge holding capacity (CRC). Table 11: Physical Properties of Comparison Example
Table 11: Physical properties of the comparison example (continued)
Example 33
[00358] A fluid absorbent article - the L-size baby diaper - which consists of 53% by weight post-crosslinked polymer on the surface of example 12, was manufactured in a standard diaper production process.
[00359] The fluid-absorbent article comprises (A) an upper liquid-penetrable layer comprising a non-woven spunbond (three paper feed pieces) having a basis weight of 12 gsm (B) a lower liquid-impenetrable layer comprising a composite of breathable polyethylene film and non-woven spunbond; (C) an absorbent core between (A) and (B) comprising 1) terry bottom layer of hydrophilic fibrous matrix of wood pulp fibers (cellulose fibers) which acts as a sweeping layer; 2) a homogeneous mixture of wood pulp fibers (cellulose fibers) and post-crosslinked polymer on the surface. The fluid-absorbent core supports 53% by weight of post-crosslinked polymer on the distributed surface, the amount of surface post-crosslinked polymer in the fluid-absorbent core is 14.5g. Dimensions of fluid absorbent core: length: 42 cm; front width: 12.8 cm; hook width: 8.4 cm; back width: 11.8 cm. The density of the fluid absorbent core is for the overall forward mean 0.23 g/cm3 for the insult zone 0.29 g/cm3 for the overall rear mean 0.19 g/cm3. The average fluid absorbent core thickness is 0.36 cm. The fluid absorbent core is packed with a spunbond - meltblown - spunbond (SMS) non-woven material having a basis weight of 10 gsm. The basis weight of the fluid absorbent core is for the front overall average 990 g/cm3, for the insult zone 1130 g/cm3, for the rear overall average 585 g/cm3. (D) an air through the acquisition distribution layer bonded between (A) and (C) having a basis weight of 60 g/m2; the acquisition distribution layer is rectangular in shape and smaller than the fluid absorbent core having a size of about 212 cm2 .
[00360] Dimension of the fluid absorbent article: length: 51 cm; front width: 31.8 cm; hook width: 22.4 cm; back width: 31.8 cm. The fluid absorbent article has an average weight of 38.1 g.
[00361] The fluid-absorbing article further comprises: a. straight rubber elastics; spandex fiber elastics: 2 elastic legs and 1 elastic cuff b. leg cuffs of synthetic fibers, non-woven material showing the SMS layer combination and having a basis weight between 15 g/m2 and a height of 3.0 cm b. mechanical closure system with 16.9 cm x 3.4 cm discharge zone and 3.1 cm x 5.4 cm flexible band closure tapes; attached to hook the 1.9 cm x 2.7 cm adjustment tape and the rewetting in load and rewetting value of the fluid-absorbing article were determined. The results are summarized in Table 12 and 13. Example 34
[00362] A fluid absorbent article - the size L baby diaper - which consists of 49% by weight post-crosslinked polymer on the surface of example 12 was manufactured in a standard diaper production process.
[00363] The fluid-absorbing article comprises the same components (A), (B) and (D) as in example 33.
[00364] The absorbent core (C) between (A) and (B) comprises 1) low-down hydrophilic fibrous matrix layer of wood pulp fibers (cellulose fibers) which acts as a sweeping layer; 2) a homogeneous mixture of wood pulp fibers (cellulose fibers) and post-crosslinked polymer on the surface. The fluid-absorbent core supports 49% by weight of post-crosslinked polymer on the distributed surface, the amount of surface post-crosslinked polymer in the fluid-absorbent core is 12.5g. Dimensions of the fluid-absorbent core are the same as in example 32. The density of the fluid-absorbent core is for the general average of the front 0.26 g/cm3 for the insult zone 0.27 g/cm3 for the average overall back 0.19 g/cm3A The average thickness of fluid absorbent core is 0.31 cm. The fluid absorbent core is packed with a spunbond - meltblown - spunbond (SMS) non-woven material having a basis weight of 10gsm. The basis weight of the fluid absorbent core is for the front overall average 971 g/cm3, for the insult zone 979 g/cm3, for the rear overall average 515 g/cm3.
[00365] Dimensions of the fluid absorbent article are the same as in example 33. The fluid absorbent article has an average weight of 35.7 g.
[00366] The fluid absorbent article further comprises: a. straight rubber elastics as in example 33 b. leg cuffs, as in example 33 c. mechanical closing system, as in example 33
[00367] The rewetting under load and rewetting value of the fluid-absorbing article were determined. The re-sets are summarized in Table 12 and 13. Example 35
[00368] A fluid absorbent article - the L-size baby diaper - which consists of 47.5% by weight post-crosslinked polymer on the surface of example 12 was manufactured in a standard diaper production process.
[00369] The fluid absorbent article comprises the same components (A), (B) and (D) as in example 33.
[00370] The absorbent core (C) between (A) and (B) comprises 1) low-down hydrophilic fibrous matrix layer of wood pulp fibers (cellulose fibers) which acts as a sweeping layer; 2) a homogeneous mixture of wood pulp fibers (cellulose fibers) and post-crosslinked base polymer on the surface. The fluid-absorbent core supports 47.7% by weight of post-crosslinked polymer on the distributed surface, the amount of post-crosslinked polymer on the surface in the fluid-absorbent core is 11.5g. Dimensions of the fluid-absorbent core are the same as in example 32. The density of the fluid-absorbent core is for the general average of the front 0.24 g/cm3 for the insult zone 0.26 g/cm3 for the average overall rear 0.18 g/cm3. The average thickness of fluid absorbent core is 0.32 cm. The fluid absorbent core is packed with a spunbond - meltblown - spunbond (SMS) non-woven material having a basis weight of 10gsm. The basis weight of absorbent core fluid is for the overall front average 928 g/cm3, for the insult zone 967 g/cm3, for the overall rear average 495 g/cm3.
[00371] Dimensions of the fluid absorbent article are the same as in example 33. The fluid absorbent article has an average weight of 34.8 g.
[00372] The fluid-absorbing article further comprises: a. straight rubber elastics as in example 33 b. leg cuffs, as in example 33 c. mechanical closing system, as in example 33
[00373] The in-load rewetting and rewetting value of the fluid-absorbing article were determined. The results are summarized in Table 12 and 13. Comparative example
[00374] A fluid-absorbent article - the L-size baby diaper - consisting of 52% by weight post-crosslinked polymer on the HySorb®B7075 surface (BASF SE, Ludwigshafen, Germany) was manufactured in a diaper production process pattern.
[00375] The fluid absorbent article comprises the same components (A), (B) and (D) as in example 33.
[00376] The absorbent core (C) between (A) and (B) comprises 1) low-down hydrophilic fibrous matrix layer of wood pulp fibers (cellulose fibers) which acts as a scanning layer; 2) a homogeneous blend of wood pulp fibers (cellulose fibers) and surface post-crosslinked base polymer (HySorb®B7075). The fluid-absorbent core supports 52% by weight of post-cross-linked polymer on the distributed surface, the amount of surface-post-cross-linked polymer in the fluid-absorbent core is 14.5 g. Dimensions of the fluid-absorbent core are the same as in example 32. The density of the fluid-absorbent core is for the general average of the front 0.24 g/cm3 for the insult zone 0.25 g/cm3 for the average overall rear 0.19 g/cm3. The average thickness of fluid absorbent core is 0.34 cm. The fluid absorbent core is packed with a spunbond - meltblown - spunbond (SMS) non-woven material having a basis weight of 10gsm. The basis weight of absorbent core fluid is for the overall front average 1013 g/cm3, for the insult zone 971 g/cm3, for the overall rear average 548 g/cm3.
[00377] Dimensions of the fluid absorbent article are the same as in example 33. The fluid absorbent article has an average weight of 38 g.
[00378] The fluid-absorbing article further comprises: a. straight rubber elastics as in example 33 b. leg cuffs, as in example 33 c. mechanical closing system, as in example 33
[00379] The in-load rewetting and rewetting value of the fluid-absorbing article were determined. The results are summarized in Table 12 and 13. Table 12. Load rewetting
Table 13. Rewetting value

[00380] The examples demonstrate that the fluid-absorbent article comprising spherically post-crosslinked polymer particles on the surface shows better rewetting performance, even when the loading of the spherically post-crosslinked polymer particles on the surface in the absorbent core is reduced by up to 20%, compared to the fluid-absorbent article containing post-crosslinked irregularly shaped polymer particles on the surface.

权利要求:
Claims (14)
[0001]
1. Process for the production of surface-crosslinked water-absorbent polymer particles, characterized in that it comprises formation of water-absorbent polymer particles by polymerizing a monomer solution, comprising a) at least one ethylenically unsaturated monomer which carries acidic groups and can be at least partially neutralized, b) optionally one or more crosslinkers, c) at least one initiator, d) optionally one or more ethylenically unsaturated monomers copolymerizable with the monomers mentioned under a), e) optionally one or plus water soluble polymers, and f) water, coating the water absorbent polymer particles with at least one surface thermal crosslinker and thermal surface crosslinker after the coated water absorbent polymer particles, wherein the residual monomer content in the particles of water-absorbent polymers before coating with the surface crosslinker post is in the range from 0.15 to 7.5% by weight and the temperature during post-thermal surface crosslinking is in the range from 100 to 180°C, wherein the surface post-crosslink water absorptive polymer particles have a capacity of centrifuge retention capacity of 35 to 75 g/g, determined by the test method recommended by EDANA WSP 241.3 (11) "Free Swell Capacity in Saline, After Centrifugation", in which for higher values of the centrifuge retention capacity, bags of larger teas must be used.
[0002]
2. Process according to claim 1, characterized in that the monomer solution comprises at least one crosslinker b).
[0003]
3. Process according to claim 1, characterized in that the surface post-crosslinker is selected from the group consisting of alkylene carbonates, 1,3-oxazolidin-2-ones, bis- and poly-1, 3- oxazolidin-2-ones, bis- and poly-1,3-oxazolidines, 2-oxotetrahydro-1,3-oxazines, N-acyl-1,3-oxazolidin-2-ones, cyclic ureas, bicyclic amide acetals, oxetanes and morpholine-2,3-diones.
[0004]
4. Process according to claim 1, characterized in that the ethylenically unsaturated monomer that carries acid groups is an ethylenically unsaturated carboxylic acid.
[0005]
5. Process according to claim 1, characterized in that the ethylenically unsaturated monomer that carries acid groups is acrylic acid.
[0006]
6. Process according to claim 1, characterized in that the moisture content of the particles of water-absorbent polymers before the thermal surface post-crosslinking is in the range of 3 to 10% by weight.
[0007]
7. Process according to claim 1, characterized in that the content of residual monomers in the particles of water-absorbent polymers before coating with the surface crosslinker is in the range of 0.25 to 2.5% in Weight.
[0008]
8. Process according to claim 1, characterized in that the surface post-crosslinker is ethylene carbonate, 3-methyl-1,3-oxazolidin-2-one, 3-methyl-3-oxetanmethanol, 1,3 -oxazolidin-2-one, 3-(2-hydroxyethyl)-1,3-oxazolidin-2-one, 1,3-dioxan-2-one or a mixture thereof.
[0009]
9. Process according to claim 1, characterized in that the temperature during the thermal surface post-crosslinking is in the range of 140 to 160°C.
[0010]
10. Surface post-crosslinked water-absorbent polymer particles prepared by the process as defined in claim 1, characterized in that the polymer particles have a high charge absorption of 15 to 50 g/g and the sum of the retention capacity of centrifuge and absorption under high load is 60 to 120 g/g, determined analogously to recommended test method EDANA No. WSP 242.3 (11) “Gravimetric Determination of Absorption Under Pressure”, except using a weight of 49.2 g /cm2 instead of a weight of 21.0 g/cm2.
[0011]
11. A fluid-absorbing article, characterized in that it comprises (A) an upper liquid-penetrable layer, (B) a lower liquid-impervious layer, (C) a fluid-absorbent core between the layer (A) and the layer (B), comprising from 5 to 90% by weight of fibrous material and from 10 to 95% by weight of water-absorbent polymer particles prepared by the process as defined in claim 1. (D) an optional acquisition distribution layer between (A) and (C), comprising from 80 to 100% by weight of fibrous material and from 0 to 20% by weight of water absorbent polymer particles prepared by the process as defined in claim 1, and (E) a layer of optional fabric arranged immediately above and/or below (C).
[0012]
12. Process according to claim 1, characterized in that the temperature during the thermal surface post-crosslinking is in the range of 100 to 170°C.
[0013]
13. Process according to claim 1, characterized in that the temperature during the thermal surface post-crosslinking is in the range of 130 to 165°C.
[0014]
14. Process according to claim 1, characterized in that the content of residual monomers in the particles of water-absorbent polymers before coating with the surface crosslinker post is in the range of 0.2 to 5% by weight.

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法律状态:
2018-03-06| B06F| Objections, documents and/or translations needed after an examination request according [chapter 6.6 patent gazette]|

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2018-03-13| B06F| Objections, documents and/or translations needed after an examination request according [chapter 6.6 patent gazette]|

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2018-03-20| B06I| Publication of requirement cancelled [chapter 6.9 patent gazette]|Free format text: ANULADA A PUBLICACAO CODIGO 6.6.1 NA RPI NO 2462 DE 13/03/2018 POR TER SIDO INDEVIDA. |

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2019-12-10| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|

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2021-03-02| B06A| Patent application procedure suspended [chapter 6.1 patent gazette]|

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2021-06-08| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|

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2021-08-24| B16A| Patent or certificate of addition of invention granted [chapter 16.1 patent gazette]|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 07/11/2013, OBSERVADAS AS CONDICOES LEGAIS. |

优先权:

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申请号 | 申请日 | 专利标题

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US201261728839P| true| 2012-11-21|2012-11-21|

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US61/728839|2012-11-21|

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EP13181703|2013-08-26|

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PCT/EP2013/073236|WO2014079694A1|2012-11-21|2013-11-07|A process for producing surface-postcrosslinked water-absorbent polymer particles|

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