superabsorbent polymer showing rapid absorption, its manufacturing process, and absorbent article

专利摘要:
SUPERABSORVENT POLYMER HAS FAST ABSORPTION. The present invention relates to a particulate superabsorbent polymer composition having rapid absorption and a particle superabsorbent manufacturing process comprising a monomer solution comprising a foaming agent and a mixture of a lipophilic surfactant and a hydrophilic surfactant. polyethoxylate where the particulate superabsorbent polymer composition has an average particle size distribution of 300 to 500 micrometers and a vortex time of 30 to 60 seconds. The present invention further includes superabsorbent polymer compositions in surface particles treated with other components. The present invention further includes absorbent cores and articles including particulate superabsorbent polymer compositions.
公开号:BR102015007414B1
申请号:R102015007414-0
申请日:2015-04-01
公开日:2021-01-12
发明作者:Michael Azad；Rani M. Wieand；Regina Gilmer；Geoff Blake；Ronald W. Wiedbusch；David L. Bergman；Andrew J. Lang
申请人:Evonik Corporation；
IPC主号:

专利说明:

[0001] [001] The present invention relates to superabsorbent polymers that absorb water, aqueous liquids and blood where the superabsorbent polymers of the present invention have rapid absorption. The present invention also relates to the preparation of these superabsorbent polymers with rapid absorption and their use as absorbents in hygiene articles. Background of the Invention
[0002] [002] A superabsorbent polymer generally refers to a polymer, or material, insoluble in water, swellable in water, capable of absorbing at least 10 times its weight, and up to about 30 times or more of its weight in a solution aqueous solution containing 0.9 weight percent sodium chloride solution in water. Examples of superabsorbent polymers may include a partially neutralized, crosslinked acrylate polymer, and the formation of superabsorbent polymer hydrogel from polymerization, and formation of particulate superabsorbent polymer compositions capable of retaining aqueous liquids under a certain pressure according to the generic definition of superabsorbent polymer.
[0003] [003] The superabsorbent polymer hydrogel can be formed in particles, generically referred to as superabsorbent polymer in particles, where the superabsorbent polymer in particles can be treated on the surface with surface crosslinking, and other surface treatment and post treated after surface crosslinking to form particulate superabsorbent polymer compositions. The acronym SAP can be used in place of superabsorbent polymer, superabsorbent polymer composition, particulate superabsorbent polymer compositions, or variations thereof. In general, these particulate superabsorbent polymer compositions have a centrifugal retention capacity (CRC) of at least 25 grams of 0.9 weight percent per gram of sodium chloride solution of the polymer. Compositions of particulate superabsorbent polymer are also designed to quickly absorb body fluids, which require high gel bed permeability (GBP).
[0004] [004] Commercial particulate superabsorbent polymer compositions are widely used in a variety of personal care products, such as baby diapers, children's training pants, adult incontinence product, female care products, and the like.
[0005] [005] Absorption speed and increased speed is an aspect of superabsorbent polymer. Addition of a foaming agent such as sodium carbonate or sodium bicarbonate to the superabsorbent polymer prior to polymerization has been shown as a way to increase the absorption rate of the superabsorbent polymer. Use of a foaming agent results in a pyrolytic bubble formation process in the superabsorbent polymer and relies on the heat generated by polymerization to initiate foaming. This foaming process has problems such as the polymerization in process resulting in a large change in volume, not allowing easy control, and producing a polymer with a lack of homogeneity in quality and presenting a particularly high content of insoluble components in water and the foam produced lacking pore diameter and distribution stability and not allowing sufficient control of the absorption speed.
[0006] [006] When this process is carried out through the use of an azo-based polymerization initiator, the amount of this initiator is generically increased to form bubbles in an amount sufficient to improve the absorption rate and consequently the content of water-insoluble components in the polymer produced tends to increase. Also, the process using the azo-based polymerization initiator, similarly to the process using the foaming agent, has the problem that the process polymerization will result in a large volume change and consequently will not allow easy particle control of pore and bubble distribution.
[0007] [007] When this process implements polymerization in the presence of dispersion of such a water-insoluble foaming agent as a volatile organic compound, although polymerization can be carried out relatively stably, the process incurs heavy energy discharge, provides capacity of impractical and expensive service, because the polymerization requires a special apparatus from the safety point of view due to the use of the volatile organic compound and the used volatile organic compound is discharged from the system.
[0008] [008] These superabsorbent polymers in particles, however, are invariably at a disadvantage in showing insufficient absorption speed without and under load, not allowing easy drying, suffering a great load during spraying, lacking uniform pore diameter, and presenting a high content of water-soluble components.
[0009] [009] An object of this invention, therefore, is to provide a superabsorbent polymer in particles capable of rapid water absorption and a process for its production. That is why it is an object of the present invention to provide a superabsorbent polymer that exhibits an increased water absorption rate as well as maintaining excellent properties. The present invention made a water-absorbent resin that allows the production of a uniform foam in bubble distribution, allows rapid absorption of water, and a process for its production. Summary of the Invention
[0010] [0010] The present invention is directed to a superabsorbent polymer comprising a foaming agent, lipophilic non-ionic surfactant and a polyethyl-ethoxylated hydrophilic non-ionic surfactant where the particulate superabsorbent polymer has a vortex time of 30 to 60 seconds.
[0011] [0011] The present invention is also directed to a particulate superabsorbent polymer comprising an internal cross-linking structure, from about 0.05 to about 2.0% by weight of a foaming agent and a hydrophilic polyethoxy ethyl surfactant. do, the particle presenting a surface that has been subjected to a crosslinking treatment for surface crosslinking, the superabsorbent polymer in particles having a vortex time of 30 to 60 seconds.
[0012] [0012] The present invention is also directed to a process for the manufacture of a superabsorbent polymer in particles with rapid water absorption comprising the steps of:
[0013] [0013] a) preparation of an aqueous monomer solution from a mixture of a monomer containing polymerizable unsaturated acid group and an internal cross-linking agent monomer where the aqueous monomer solution comprises dissolved oxygen;
[0014] [0014] b) spreading of aqueous step monomer solution a) including adding an inert gas to the aqueous step monomer solution a) to replace the dissolved oxygen from the aqueous monomer solution;
[0015] [0015] c) polymerization of aqueous solution of monomer from step b) including the steps of
[0016] [0016] c1) addition to the aqueous solution of step a) monomer: i) an aqueous solution comprising from about 0.05 to about 2.0% by weight, based on the total amount of the polymerizable unsaturated acid group containing solution monomer of a foaming agent; and ii) an aqueous solution comprising from about 0.001 to about 1.0% by weight, based on the total amount of the monomer solution containing polymerizable unsaturated acid group from a mixture of a lipophilic surfactant and a polyethoxylated hydrophilic surfactant;
[0017] [0017] c2) treatment of step monomer solution c1) for high speed shear mixing to form a treated monomer solution, where components i) an aqueous solution comprising from about 0.05 to about 2.0 % by weight of the foaming agent; and ii) an aqueous solution comprising from about 0.001 to about 1.0% by weight of a mixture of the lipophilic surfactant and the polyethoxylated hydrophilic surfactant is added to the aqueous monomer solution after step b) of spreading aqueous monomer solution and before step c2) high speed shear mixing of the aqueous monomer solution;
[0018] [0018] c3) formation of a hydrogel by adding a polymerization initiator to the treated monomer solution from step c2) where the initiator is added to the treated monomer solution after the foaming agent and the surfactant mixture, where the polymer is formed to include bubbles of the foaming agent in the polymer structure; and
[0019] [0019] d) drying and crushing hydrogel of step c) to form particulate superabsorbent polymer; and
[0020] [0020] e) surface crosslinking of superabsorbent polymer in step d particles with a surface crosslinking agent where the crosslinked surface superabsorbent polymer has a vortex time of about 30 s to about 60 s.
[0021] [0021] With the foregoing in mind, it is a feature and advantage of the invention to provide particle superabsorbent polymer composition and particle superabsorbent polymer composition speed increase processes. Numerous other features and advantages of the present invention will appear from the description that follows. Brief Description of Drawings
[0022] [0022] Fig. 1 is a side view of the test apparatus used for the Free Swelling Gel Bed Permeability Test.
[0023] [0023] Fig. 2 is a cross-sectional side view of a cylinder / cup assembly used in the Free Swelling Gel Bed Permeability Test apparatus shown in Fig. 1;
[0024] [0024] Fig. 3 is a top view of a plunger used in the Free Swelling Bed Permeability Test apparatus shown in Fig. 1;
[0025] [0025] Fig. 4 is a side view of the test apparatus for the Load Absorption Test; and
[0026] [0026] Fig. 5 shows a top plan view, partially cut from an absorbent article in a stretched condition and left flat with the surface of the article that contacts the user's skin facing the observer. Definitions
[0027] [0027] Within the context of this specification, each term or phrase below will include the following meaning or meanings.
[0028] [0028] It should be noted that when used in the present exhibition, the terms "comprises", "comprising", and other derivatives of the root term "understand" are intended to be open-ended terms that specify the presence of any established characteristics , elements, integers, steps, or components, and are not intended to prevent the presence or addition of one or more other characteristics, elements, integers, steps, components, or a group thereof.
[0029] [0029] As used herein, the term "fence" modifying the amount of an ingredient in the compositions of the invention or used in the processes of the invention refers to the variation in the numerical quantity that can occur, for example, through typical measurement and handling processes of liquids used to manufacture concentrates or solutions used in the real world; through inadvertent error in these procedures; through differences in the manufacture, source, or purity of the ingredients used to make the compositions or perform processes; and the like. The term about also encompasses amounts that differ due to different equilibrium conditions for a composition resulting from a particular initial blend. Whether or not modified by the term "fence", the claims include equivalent amounts.
[0030] [0030] The term "Centrifugal Holding Capacity (CRC)" as used herein refers to the ability of the particulate superabsorbent polymer to retain liquid there after being saturated and subjected to centrifugation under controlled conditions and is established as grams of liquid retained per gram of sample weight (g / g) as measured using the Centrifugal Holding Capacity Test shown here.
[0031] [0031] The terms "crosslinked", "crosslinked", "crosslinked" as used herein refer to any means for making materials normally soluble in water substantially insoluble in water but intumescible. Such a crosslinking means can include, for example, physical entanglement, crystalline domains, covalent bonds, ionic complexes and associations, hydrophilic associations such as hydrogen bonding, hydrophobic associations, or Van der Waals forces.
[0032] [0032] The term "internal crosslinker" or "crosslinker monomer" as used herein refers to the use of a crosslinker in the monomer solution to form the polymer.
[0033] [0033] The term "superabsorbent polymer composition in dry particles" as used here generally refers to the superabsorbent polymer composition having less than about 20% moisture.
[0034] [0034] The term "gel permeability" is a property of the mass of particles as a whole and is related to the distribution of particle size, particle shape, and the ability to connect the open pores between the particles, shear modulus, and surface modification of the swollen gel. In practical terms, the gel permeability of the superabsorbent polymer composition is a measure of how quickly liquid flows through a mass of swollen particles. Low gel permeability indicates that liquid cannot flow easily through the superabsorbent polymer composition, which is generically referred to as gel blocking, and any forced liquid flow (such as a second application of urine during diapering) must take a alternate path (for example, diaper leak).
[0035] [0035] The acronym "HLB" means the hydrophilic - lipophilic balance of a surfactant and is a measure of the degree to which it is hydrophilic or lipophilic, as determined by calculating values for the different regions of the molecule. The HLB value can be used to predict the surfactant properties of a molecule where an HLB value <10 is soluble in lipid (insoluble in water) and an HLB value> 10 is soluble in water (insoluble in lipid).
[0036] [0036] The term "mass average particle size" of a given sample of particles of superabsorbent polymer composition is defined as the particle size, which divides the sample in half on a mass basis, that is, half the sample by weight it has a particle size larger than the mass average particle size, and half of the mass sample has a particle size of less than the mass average particle size. Thus, for example, the mass average particle size of a sample of particles of superabsorbent polymer composition is 2 microns if half of the samples by weight are measured as more than 2 microns.
[0037] [0037] The term "moisture content" when used here must mean the amount of water contained in the particular particle superabsorbent polymer composition as measured by the Moisture Content Test.
[0038] [0038] The term "non-ionic surfactants" is a non-charged surfactant and can greatly reduce the surface tension of water when used in very low concentrations. They do not ionize in aqueous solutions because their hydrophilic group is not dissociable.
[0039] [0039] The terms "particle", "in particles", and the like, when used with the term "superabsorbent polymer", refer to the form of discrete units. The units may comprise flakes, fibers, agglomerates, granules, pulverized, spheres, pulverized materials, or the like, as well as combinations thereof. The particles can have any desired shape: for example, cubic, rod-like polyhedron, spherical or semi-spherical, rounded or semi-rounded, angular, irregular, etc.
[0040] [0040] The terms "superabsorbent particulate polymer" and "superabsorbent particulate polymer composition" refer to the superabsorbent polymer form and superabsorbent polymer compositions in discrete form, where the "superabsorbent particulate polymer" and "polymer compositions" particulate superabsorbent "may have a particle size of less than 1000 micrometers, or from about 150 micrometers to about 850 micrometers.
[0041] [0041] The term "permeability", when used here, should mean a measure of the effective connectivity of a porous structure, in this case, crosslinked polymers, and can be specified in terms of the void fraction, and extent of connectivity of the superabsorbent polymer composition in particles.
[0042] [0042] The term "polymer" includes, but is not limited to, homopolymers, copolymers, for example, block, graft, random, and alternating copolymers, terpolymers, etc., and combinations and modifications thereof. In addition, unless otherwise specifically limited, the term "polymer" should include all possible configurational isomers of the material. These configurations include, but are not limited to, isotactic, syndiotactic and atactic symmetries.
[0043] [0043] The term "polyolefin" as used herein generically includes, but is not limited to, materials such as polyethylene, polypropylene, poly isobutylene, polystyrene, ethylene-vinyl acetate copolymer, and the like, homopolymers, copolymers, terpolymers, etc., and their combinations and modifications. The term "polyolefin" should include all of its possible structures, which include, but are not limited to, isotactic, syndiotactic, and random symmetries. Copolymers include atactic and block copolymers.
[0044] [0044] The term "superabsorbent polymer" as used herein refers to water-insoluble organic or inorganic materials, water-swellable or inorganic materials including superabsorbent polymers and superabsorbent polymer compositions capable, under the most favorable conditions, of absorbing by hair. at least about 10 times its weight, or at least about 15 times its weight, or at least about 25 times its weight in an aqueous solution containing 0.9 wt% sodium chloride.
[0045] [0045] The term "superabsorbent polymer composition" as used herein refers to a superabsorbent polymer comprising a surface additive according to the present invention.
[0046] [0046] The term "surface crosslinking" as used herein refers to the level of functional crosslinking in the vicinity of the surface of the superabsorbent polymer particle, which is generally greater than the level of functional crosslinking within the superabsorbent polymer particle. As used here, "surface" describes the boundaries facing the exterior of the particle.
[0047] [0047] The term "thermoplastic" as used herein describes a material that softens when exposed to heat and that substantially returns to an unheated condition when cooled to room temperature.
[0048] [0048] The term "vortex time" measures the amount of time in seconds required for 2 grams of an SAP to close a vortex created by shaking 50 milliliters of saline at 600 rpm per minute on a magnetic stirring plate. The fear that it takes for the vortex to close is an indication of the free swelling absorption rate of SAP.
[0049] [0049] The term "% by weight" or "% wt" as used herein and referring to components of the dry particle superabsorbent polymer composition, is to be interpreted as based on the weight of the dry superabsorbent polymer composition, the unless otherwise specified herein.
[0050] [0050] These terms can be defined in additional language in the remaining portions of this specification including the following Detailed Description. Detailed Description of the Invention
[0051] [0051] Although typical aspects of realization and / or realizations have been shown for the purpose of illustration, this Detailed Description and accompanying drawings should not be considered to be a limitation on the scope of the invention. In the same way, various modifications, adaptations, and alternatives can occur to those skilled in the art without departing from the spirit and scope of the present invention. By means of a hypothetical illustrative example, the exposure in this specification of a range from 1 to 5 should be considered to support claims of any of the following ranges: 1-5; 1-4; 1-3; 1-2; 2-5; 2-4; 2-3; 3-5; 3-4; and 4-5.
[0052] [0052] According to the invention, a superabsorbent polymer composition in particles showing rapid absorption can be obtained using the processes described herein. The present invention further includes an absorbent article comprising a topsheet; a backsheet; and an absorbent core disposed between the topsheet and the backsheet, the absorbent core comprising the various embodiments of the particulate superabsorbent polymer composition of this invention.
[0053] [0053] The present invention is also directed to a particulate superabsorbent polymer comprising an internal cross-linking structure, from about 0.05 to about 2.0% by weight of a foaming agent, and about 0.001 at about 1.0% by weight of a mixture of a lipophilic surfactant and a hydrophilic polyethoxylated surfactant in an interior of the particle, the particle having a surface that has undergone a cross-linking treatment for surface cross-linking, the superabsorbent polymer in particles presenting a vortex time of 30 to 60 seconds.
[0054] [0054] The present invention is also directed to a superabsorbent polymer in particles where the lipophilic surfactant has an HLB of 4 to 9 and the hydrophilic polyethoxylated surfactant has an HLB of 12 to 18; or where the mixture of a lipophilic surfactant and a polyethoxylated hydrophilic surfactant has an HLB of 8 to 14; or where the lipophilic surfactant is a sorbitan ester and the polyethoxylated hydrophilic surfactant is a polyethoxylated sorbitan ester; or where the lipophilic surfactant is non-ionic and the polyethoxylated hydrophilic surfactant is non-ionic; or where the foaming agent is selected from an alkali metal carbonate or alkali metal bicarbonate where the alkali metal can be sodium or potassium; or where the superabsorbent polymer has a Pressure Absorbance Index of about 120 to about 150: or where the internal crosslinking agent comprises a silane compound comprising at least one vinyl group or allyl group and at least one Si-O bond where the vinyl group or allyl group is directly attached to a silicon atom.
[0055] [0055] The present invention is also directed to a particulate superabsorbent polymer comprising an internal cross-linking structure, from about 0.05 to about 2.0% by weight of a foaming agent, and from about 0.001 At about 1.0% by weight of a mixture of a lipophilic nonionic surfactant and a polyethoxylated hydrophilic nonionic surfactant in an interior of the particle, the particle having a surface that has undergone a crosslinking treatment for surface crosslinking, the particulate superabsorbent polymer having a vortex time of 30 to 60 seconds and the particulate superabsorbent polymer has a particle diameter greater than 600 micrometers in an amount of about 6% by weight to about 15% by weight of the superabsorbent polymer in particles as specified by standard sieve classification; or having an average particle diameter by weight (D50) specified by classification on a standard sieve of 350 micrometers to about 500 micrometers; or the particulate superabsorbent polymer having a particle diameter of less than 600 microns and greater than 150 microns in an amount of not less than about 85% by weight of the particulate superabsorbent polymer composition and as specified by standard sieve classification; or featuring particles having particle diameters less than 600 microns and greater than 150 microns in an amount of not less than about 90% by weight of the particulate superabsorbent polymer composition and as specified by standard sieve classification and particles having a diameter particle size (D50) specified by classification on a standard sieve of 300 to 400 micrometers.
[0056] [0056] The present invention is also directed to a particulate superabsorbent polymer comprising having an internal cross-linking structure, from about 0.05 to about 5.0% by weight of a foaming agent, and about 0.001 to about 1.0% by weight of a mixture of a lipophilic nonionic surfactant and a polyethoxylated hydrophilic nonionic surfactant in an interior of the particle, the particle having a surface that has undergone a crosslinking treatment for surface crosslinking, the particulate superabsorbent polymer having a vortex time of 30 to 60 seconds and the particulate superabsorbent polymer further comprising a clay to form a superabsorbent polymer hydrogel - clay comprising from about 90% to about 98%, by weight of superabsorbent polymer and from about 0.5% to about 10% by weight of the clay; or comprising from about 0.001 to about 10 parts by weight per 100 parts by weight of the particulate superabsorbent polymer; or further comprising from about 0.05 to about 5.0% by weight of a foaming agent added to the aqueous hydrogel.
[0057] The present invention is directed to a particulate superabsorbent polymer comprising having an internal cross-linking structure, from about 0.05 to about 2.0% by weight of a foaming agent, and about from 0.001 to about 1.0% by weight of a mixture of a lipophilic nonionic surfactant and a polyethoxylated hydrophilic nonionic surfactant in an interior of the particle, the particle having a surface that has undergone a crosslinking treatment for surface crosslinking , the particulate superabsorbent polymer having a vortex time of 30 to 60 seconds and the particulate superabsorbent polymer further comprising a chelating agent where the chelating agent is selected from amino carboxylic acids with at least three carboxyl groups and their salts.
[0058] [0058] The present invention is also directed to a particulate superabsorbent polymer comprising having an internal cross-linking structure, from about 0.05 to about 2.0% by weight of a foaming agent, and about 0.001 to about 1.0% by weight of a mixture of a lipophilic nonionic surfactant and a polyethoxylated hydrophilic nonionic surfactant in an interior of the particle, the particle having a surface that has undergone a crosslinking treatment for surface crosslinking, the particulate superabsorbent polymer having a vortex time of 30 to 60 seconds and the particulate superabsorbent polymer further comprising from about 0.01 to 0.5% by weight of a thermoplastic polymer based on dry weight of pulverized polymer; or where the thermoplastic polymer is selected from polyethylene, polyesters, polyurethanes, linear low density polyethylene (LLDPE), ethylene and acrylic acid copolymer (EAA), styrene copolymers, ethylene copolymer and alkyl methacrylate (EMA), polypropylene ( PP), ethylene and vinyl acetate copolymer (EVA) or their combinations, or their copolymers; or where the thermoplastic polymer is added to the particulate superabsorbent polymer with the surface crosslinking agent.
[0059] [0059] The present invention is directed to a particulate superabsorbent polymer comprising having an internal crosslinking structure, from about 0.05 to about 2.0% by weight of a foaming agent, and about 0.001 about 1.0% by weight of a mixture of a lipophilic nonionic surfactant and a polyethoxylated hydrophilic nonionic surfactant in an interior of the particle, the particle having a surface that has undergone a crosslinking treatment for surface crosslinking, the particulate superabsorbent polymer having a vortex time of 30 to 60 seconds and further comprising from 0.01% by weight to about 5% by weight based on the weight of particulate superabsorbent polymer composition of a neutralized aluminum salt applied to the surface of the particulate superabsorbent polymer, in the form of an aqueous solution of neutralized aluminum salt having a pH value of about 5.5 to about 8.
[0060] The present invention is also directed to a particulate superabsorbent polymer comprising having an internal cross-linking structure, from about 0.05 to about 2.0% by weight of a foaming agent, and about 0.001 to about 1.0% by weight of a mixture of a lipophilic nonionic surfactant and a polyethoxylated hydrophilic nonionic surfactant in an interior of the particle, the particle having a surface that has undergone a crosslinking treatment for surface crosslinking, the particulate superabsorbent polymer having a vortex time of 30 to 60 seconds and having a Centrifugal Retention Capacity (CRC) of about 25 grams to about 40 grams of 0.9 percent aqueous sodium chloride weight per gram of the composition of superabsorbent polymer in particles; or having a water content of about 2 to about 10% by weight of the particulate superabsorbent polymer; or having a Free Swelling Gel Bed Permeability (FSGBP) of about 20x10-8 cm2 to about 200 x 10-8 cm2; or having a 60-minute absorption capacity of about 15 g / g to about 26 g / g under a load of 4.83 kPa to 0.9% by weight.
[0061] [0061] The present invention is also directed to a process for the manufacture of a superabsorbent polymer in particles with rapid water absorption comprising the steps of:
[0062] [0062] a) preparation of an aqueous monomer solution from a mixture of a monomer containing polymerizable unsaturated acid group is an internal crosslinking agent monomer where the aqueous monomer solution comprises dissolved oxygen;
[0063] [0063] b) spreading of aqueous step monomer solution a) including adding an inert gas to the aqueous step monomer solution a) to replace the dissolved oxygen of the aqueous monomer solution;
[0064] [0064] c) polymerization of aqueous solution of monomer from step b) including the steps of
[0065] [0065] c1) addition to the aqueous solution of step a) monomer: i) an aqueous solution comprising from about 0.05 to about 2.0% by weight, based on the total amount of the monomer solution containing acid group polymerizable unsaturated foaming agent; and ii) an aqueous solution comprising from about 0.001 to about 1.0% by weight, based on the total amount of the monomer solution containing polymerizable unsaturated acid group from a mixture of a lipophilic non-ionic surfactant and a hydrophilic non-ionic surfactant polyethoxylated.
[0066] [0066] c2) treatment of step c1) monomer solution for high speed shear mixing of at least 2500 rpm to form a treated monomer solution, where the components i) an aqueous solution comprising from about 0.05 to about 2.0% by weight of a foaming agent; and ii) an aqueous solution comprising from about 0.001 to about 1.0% by weight of a mixture of a lipophilic nonionic surfactant and a polyethoxylated hydrophilic nonionic surfactant is added to the aqueous monomer solution after step b) spreading. aqueous monomer solution and before step c2) high-shear mixing of the aqueous monomer solution;
[0067] [0067] c3) formation of a hydrogel by adding a polymerization initiator to the treated monomer solution of step c2) where the initiator is added to the treated monomer solution after the foaming agent and the surfactants, where the polymer it is formed to include bubbles in the foaming agent in the polymer structure; and
[0068] [0068] d) drying and crushing hydrogel d step c) to form particulate superabsorbent polymer; and
[0069] [0069] e) surface crosslinking of superabsorbent polymer in step d particles with a surface crosslinking agent where the crosslinked surface superabsorbent polymer has a vortex of about 30 seconds to about 60 seconds.
[0070] [0070] The present invention further includes an absorbent article comprising a topsheet; a backsheet; and an absorbent core disposed between the topsheet and the backsheet, the absorbent core comprising the particulate superabsorbent polymers of this invention.
[0071] [0071] An appropriate superabsorbent polymer can be selected from synthetic, natural, biodegradable, and modified natural polymers. The crosslinked term used in reference to the superabsorbent polymer refers to any means to effectively make materials normally soluble in water substantially insoluble in water but intumescible. Such a crosslinking meaning may include, for example, physical entanglement, crystalline domains, covalent bonds, complexes and ionic associations, hydrophilic associations such as hydrogen bonding, hydrophobic associations or Vander Waals forces. A superabsorbent polymer as shown in embodiments of the present invention can be obtained through initial polymerization of about 55% to about 99.9% by weight of the superabsorbent monomer polymer containing polymerizable unsaturated acid group. An appropriate monomer includes any of those containing carboxyl groups, such as acrylic acid or methacrylic acid; or 2-acrylamido-2-methyl propane sulfonic acid, or mixtures thereof. It is desirable that at least about 50% by weight, and more desirably that at least about 75% by weight of the acid groups are carboxyl groups.
[0072] [0072] The process for making a superabsorbent polymer of this invention can be obtained through initial polymerization of about 55% to about 99.9% by weight of the monomer superabsorbent polymer containing polymerizable unsaturated acid group. An appropriate polymerizable monomer includes any of those containing carboxyl groups, such as acrylic acid, methacrylic acid, or 2-acrylamido-2-methyl propane sulfonic acid, or mixtures thereof. It is desirable that at least about 50% by weight, and more desirable that at least about 75% by weight of the acid groups are carboxyl groups.
[0073] [0073] The impurities contained in acrylic acid can be defined as follows. Acrylic acid can include protoanemonine and / or furfural, which can be controlled to be in a predetermined amount or less in consideration of color tone stability or a residual monomer. The content of the protoanemonine and / or furfural, can be from 0 to about 10 ppm, or from 0 to about 5 ppm, or from 0 to about 3 ppm, or from 0 to about 1 ppm. For the same reason, acrylic acid may include a small amount (s) of aldehydes other than furfural and / or maleic acid. An amount (s) of aldehydes with respect to acrylic acid is 0 to about 5 ppm, or 0 to about 3 ppm, or 0 to about 1 ppm. Examples of other non-furfural aldehydes include benzaldehyde, acraldehyde, acetaldehyde, and the like. From the point of view of reducing a residual monomer, acrylic acid includes acrylate dimer in an amount of 0 to about 500 ppm, or from 0 to about 200 ppm, or from 0 to about 100 ppm.
[0074] [0074] The acid groups are neutralized with an alkaline base to the extent of at least about 25 mol%, or from about 50 mol% to about 80 mol%, that is, the acid groups are desirably present like sodium, potassium, or ammonium salts. The amount of alkaline base can be from about 14% by weight to about 45% by weight of the particulate superabsorbent polymer composition. The alkaline base can include sodium hydroxide or potassium hydroxide. In some respects, it is desirable to use polymers obtained by polymerizing acrylic acid or methacrylic acid, the carboxyl groups of which are neutralized in the presence of internal cross-linking agents. It is noted that neutralization can be achieved either by adding alkali to the monomer solution or adding monomer such as acrylic acid to the alkali. The temperature or neutralization (neutralization temperature) is not specifically limited, but it can be from 10 to 100oC or from 30 to 90oC.
[0075] [0075] In some respects, a suitable second monomer that can be copolymerized with the ethylenically unsaturated monomer may include, but is not limited to, acrylamide, methacrylamide, ethyl hydroxyl acrylate, (methyl) amino alkyl dimethyl acrylate, (meth) ) ethoxylated acrylates, dimethyl amino propyl acrylamide, or acrylamide propyl trimethyl ammonium chloride. Such a monomer can be present in a range from 0% by weight to about 40% by weight of the copolymerized monomer.
[0076] [0076] In the case when the monomer is acrylic acid, the partially neutralized acrylate salt is made into the polymer in the water-absorbing agent in particular following polymerization, the value converted based on acrylic acid can be determined through conversion of polyacrylate salt partially neutralized is assumed to be entirely equimolar non-neutralized polyacrylic acid.
[0077] [0077] The superabsorbent polymer of the invention also includes from about 0.001% by weight to about 5% by weight, or from about 0.2% by weight to about 3% by weight, based on the total amount of the monomer containing polymerizable unsaturated acid group of at least one internal cross-linking agent. The internal cross-linking agent generally has at least two ethylenically unsaturated double bonds or an ethylenically unsaturated double bond and a functional group that is reactive towards the acidic groups of the monomers containing polymerizable unsaturated acid group or several functional groups that are reactive towards the groups Acids can be used as the internal cross-linking component that is present during the polymerization of monomers containing polymerized unsaturated acid group. The internal cross-linking agent may contain a silane compound comprising at least one vinyl group or allyl group directly attached to a silicon atom and at least one Si-O bond.
[0078] [0078] Examples of internal cross-linking agents used in superabsorbent polymers include aliphatic unsaturated amides, such as methylene bis acrylate or methacrylamide or ethylene bisacrylamide, and in addition aliphatic esters of polyols or alkoxylated polyols with ethylenically unsaturated acids, such as di (meth) acrylates or butanediol or ethylene glycol tri (meth) acrylates, polyglycols or trimethylol propane, trimethylol propane di- and triacrylate esters which are preferably oxyalkylated, preferably ethoxylated, with 1 to 30 moles of alkylene oxide, acrylate and methacrylate glycerol esters and pentaerythritol and glycerol and ethoxylated pentaerythritol with 1 to 30 moles of ethylene oxide and in addition allyl compounds, such as (meth) allyl acrylate, (meth) alkoxylated allyl acrylate reacted with 1 to 30 moles of ethylene oxide, cyanide trialyl, trialyl isocyanurate, maleic acid diallyl ester, poly allyl esters, vinyl trimethoxy silane, vinyl silane like Dynasylan 6490, Dy nasylan 6498, vinyl alkoxy silanes such as vinyl trimethoxy silane, methyl vinyl trimethoxy silane, vinyl triisopropyl phenoxy silane, vinyl triethoxy silane, methyl vinyl triethoxy silane, vinyl methyl dimethoxy silane, ethyl vinyl dietoxy silane, ethyl vinyl vinyl silane, and vinyl tris- ( 2-methoxy ethoxy) silane; vinyl acetoxy silanes, such as vinyl methyl diacetoxy silane, vinyl ethyl diacetoxy silane, and vinyl triacetoxy silane ;. Allyl alkoxy silanes such as allyl trimethoxy silane, allyl methyl dimethoxy silane, and allyl triethoxy silane; divinyl alkoxy silanes and divinyl acetoxy silanes such as divinyl dimethoxy silane, divinyl diethoxy silane and divinyl diacetoxy silane; diallyl alkoxy silanes and diallyl acetoxy silanes such as diallyl dimethoxy silane, diallyl dietoxy silane and diallyl diacetoxy silane, vinyl triethoxy silane, poly siloxane comprising at least two vinyl groups, tetra allyoxy ethane, trialyl amine, tetra ethylene diamine, diols, polyols, hydroxy compound allyl or acrylate and allyl esters of phosphoric acid or phosphorous acid, and in addition monomers that are capable of cross-linking, such as N-methylol compounds of unsaturated amides, such as methacrylamide or acrylamide, and the ethers derived therefrom. Ionic crosslinkers such as aluminum metal salts can also be used, or other compounds containing multivalent cations can also be used. Reactive post-polymerization crosslinkers that form either additional cross-links after polymerization, for example, when fired by temperature (during drying or heat treatment, for example), or through the addition of water or another chemical compound, or through a change in pH, or some other change, for example, when coming into contact with bodily fluids. Mixtures of the mentioned crosslinking agents can also be used.
[0079] The superabsorbent polymer may include from about 0.001% by weight to about 0.1% by weight, based on the total amount of the polymerizable unsaturated acid-containing monomer of a second internal crosslinker which may comprise compositions comprising at least two ethylenically unsaturated double bonds, for example, methylene bisacrylamide or methacrylamide or ethylene bisacrylamide; in addition, esters of unsaturated mono- or polycarboxylic acids of polyols, such as diacrylates or triacrylates, for example, butanediol diacrylate or methacrylate or ethylene glycol; trimethylol propane triacrylate, as well as its alkoxylated derivatives; additionally, allyl compounds, such as allyl (meth) acrylate, trialyl cyanurate, maleic acid diallyl ester, poly allyl ester, tetra aloxy ethane, di- and triallyl amine, tetraethylene diamine, allyl esters of phosphoric acid or phosphorous acid. In addition, compounds having at least one reactive functional group towards acidic groups can also be used. Examples include N-methylol amide compounds, such as methacrylamide or acrylamide, and their ethers derivatives, as well as di- and polyglycidyl compounds. The second internal crosslinker which may comprise polyethylene glycol acrylate monoaryl ether, ethoxylated trimethylol propane triacrylate, and / or polyethylene glycol diacrylate.
[0080] [0080] The usual initiators, such as, for example, azo or peroxo compounds, redox systems or UV initiators, (Sensitizers), and / or radiation are used to initiate free radical polymerization. In some respects, primers can be used to initiate polymerization of free radicals. Suitable initiators include, but are not limited to, azo or peroxy compounds, redox systems or ultraviolet initiators, sensitizers, and / or radiation.
[0081] [0081] A polymerization initiator for use in the invention is selected as necessary according to the type of polymerization, and not specifically limited. Examples of the polymerization initiator include a thermally degradable polymerization initiator, a photodegradable polymerization initiator, and a redox-type polymerization initiator, or the like. Specific examples of the thermally degradable polymerization initiator include per-sulphate such as sodium per-sulphate, potassium per-sulphate, or ammonium per-sulphate; and, peroxide such as hydrogen peroxide, t-butyl peroxide, or methyl ethyl ketone peroxide; and azo compound with 2,2'-azo-bis- (2-amidino propane) dihydrochloride, 2,2'-azo-bis- [2- (2-imidazolin-2-yl) propane dihydrochloride], or similar. Specific examples of the photodegradable polymerization initiator include benzoyl derivative, benzyl derivative, phenone aceto derivative, benzo phenone derivative, and azo compound, or the like. An example of the redox-type polymerization initiator includes use of a reducing compound such as L-ascorbic acid or sodium hydrogen sulfite in combination with persulfate or peroxide described above. A preferable example includes use of the photodegradable polymerization initiator in combination with the thermally degradable polymerization initiator described above. A use amount of the polymerization initiator can be about 0.001 to about 1 mol%, or about 0.05 to 1.0 mol% with respect to the monomer. When the amount of use of the polymerization initiator is more than 1 mol%, the coloring of the water-absorbing resin may occur. Whereas, when the amount of use of the polymerization initiator is less than 0.0001 mol%, it can cause an increase in a residual monomer.
[0082] [0082] Meanwhile, it should be noted that, instead of using the polymerization initiator described above, the monomer can be polymerized through irradiation of activated energy rays such as radiation rays, electron beams, and UV rays. In addition, polymerization can be carried out using the polymerization initiator in combination with the activated energy rays.
[0083] [0083] The present invention further includes from about 0.05 to about 2.0% by weight, or from about 0.1 to about 1.0% by weight, based on the total amount of the monomer solution containing polymerizable unsaturated acid group of a foaming agent. The foaming agent may include a salt containing alkali metal carbonate or alkali metal bicarbonate, or mixed salt, sodium carbonate, potassium carbonate, ammonium carbonate, magnesium carbonate, or magnesium carbonates (hydroxic), carbonate calcium, barium carbonate, bicarbonates and hydrates thereof, azo compounds or other cations, as well as naturally occurring carbonates, such as dolomite, or mixtures thereof. Foaming agents can include carbohydrate salts of multiple cations, such as Mg, Ca, Zn, and the like. Although certain multivalent transition metal cations can be used, some of them, such as ferric cation, can cause color staining and can be subjected to reduction reactions - oxidation or hydrolysis equilibrium in water. This can lead to difficulties in quality control of the final polymeric product. Also, other multivalent cations, such as Ni, Ba, Cd, Hg, may be unacceptable due to potential toxic or skin sensitizing effects.
[0084] [0084] The present invention further includes an aqueous solution comprising from about 0.001 to about 1.0% by weight, or from about 0.002 to about 0.5% by weight, or from about 0.003 to about 0 , 15 by weight, based on the total amount of the monomer solution containing polymerizable unsaturated acid group from a mixture of a lipophilic surfactant and a polyethoxylated hydrophilic surfactant, where the lipophilic surfactant can have an HLB of 4 to 9 and the polyethoxylated hydrophilic surfactant has an HLB from 12 to 18; or where the lipophilic surfactant may be non-ionic or the polyethoxylated hydrophilic surfactant may be non-ionic.
[0085] [0085] Typical examples of the surfactant, polyoxyethylene alkyl aryl ethers such as polyoxyethylene laurel ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene alkyl ethers such as polyoxyethylene higher alcohol ethers, and polyoxyethylene non-ethylene phenyl ether ether ether ether ether grains ether ether etheres sorbitan mono laurate, sorbitan mono palmitate, sorbitan mono stearate, sorbitan tristearate, sorbitan mono oleate, sorbitan trioletate, sorbitan sesquioleate, and sorbitan doestearate; polyoxyethylene sorbitan fatty esters, polyoxyethylene sorbitan mono lao polyoxyethylene sorbitan palmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan monooleate, and polyoxyethylene sorbitan trioleate; polyoxyethylene sorbitol fatty esters such as polyoxyethylene sorbit tetra oleic acid; fatty esters of glycerin such as glycerol mono stearate, glycerol mono oleate, and self-emulsifying glycerol mono stearate; polyoxyethylene fatty esters such as polyethylene glycol mono laurate, polyethylene glycol mono stearate, polyethylene glycol distearate, and polyethylene glycol monoeate; polyoxyethylene alkyl amines; castor oil hardened with polyoxyethylene; and alkyl alcohol amines can be cited. The mixture of nonionic surfactants may include a mixture of lipophilic surfactant which is a sorbitan ester and the polyethoxylated hydrophilic surfactant is a polyethoxylated sorbitan ester.
[0086] [0086] The process of this invention is preferred to carry out the polymerization or copolymerization reaction in the presence of a mixture of a lipophilic surfactant and a polyethoxylated hydrophilic surfactant. The use of a mixture of two surfactants allows the bubbles to be stably dispersed. Also through appropriate control of the type and quantity of the mixture of two surfactants, the pore diameter and the water absorption rate of the hydrophilic polymer to be produced can be controlled. A process for making the particulate superabsorbent polymer with rapid water absorption of the present invention includes the steps of:
[0087] [0087] a) preparation of a monomer solution comprising
[0088] [0088] a1) from about 55 to about 99.9% by weight of monomers containing polymerizable unsaturated acid group;
[0089] [0089] a2) from about 0.001 to about 5.0% by weight of an internal cross-linking agent;
[0090] [0090] a3) from about 14 to about 45% by weight of an alkali where the composition has a degree of neutralization of about 50 mol% to about 70 mol%; and
[0091] [0091] a4) spreading the monomer solution from step c) by bubbling an inert gas into the monomer solution so that the monomer solution has less than 1% by weight of oxygen;
[0092] [0092] b) polymerization of monomer solution from step a) including the steps of
[0093] [0093] b1) addition to step a) monomer solution of the following:
[0094] [0094] i) an aqueous solution comprising from about 0.05 to about 2.0% by weight, based on the total amount of the polymer containing unsaturated acid group polymerizable from a foaming agent; and
[0095] [0095] ii) an aqueous solution comprising from about 0.001 to about 1.0% by weight, based on the total amount of the monomer solution containing polymerizable unsaturated acid group of a mixture of a lipophilic surfactant and a polyethylated hydrophilic surfactant ;
[0096] [0096] b2) monomer solution treatment of step a) and step b1) with high speed shear mixture which can be at least about 2500 rpm to form a treated monomer solution;
[0097] [0097] b3) formation of a hydrogel by adding a polymerization initiator to the treated monomer solution from step b2) where the initiator is added to the treated monomer solution after the foaming agent and the surfactants, where the polymer is formed to include bubbles of the foaming agent in the polymer structure and where the bubbles; and
[0098] [0098] c) drying and crushing of hydrogel of step b) for the formation of superabsorbent polymer in particles; and
[0099] [0099] d) surface crosslinking of superabsorbent polymer in step particles c) with a surface crosslinking agent where the crosslinked surface superabsorbent polymer has a vortex of about 30 seconds to about 60 seconds.
[0100] [00100] The temperature at the beginning of the polymerization, although variable with the type of the radical polymerization initiator to be used, can be in the range of 0-50oC, or in the range of 10oC-40oC. The polymerization temperature in the reaction process, although variable with the type of radical polymerization initiator to be used, can be in the range of 20oC-110oC, or in the range of 30oC-90oC. If the temperature at the start of the polymerization or the temperature of the polymerization in the reaction process deviates from the range mentioned above, disadvantages such as (1) an undue increase in the amount of residual monomer in the produced water-absorbing resin, (b) difficulty incurred in the control of foaming with a foaming agent that will be described here specifically below, and (c) excessive advance of the self-crosslinking reaction accompanied by an undue increase in the amount of water absorbed by the water-absorbing resin possibly following will.
[0101] [00101] The reaction time is not particularly limited but is only required to be fixed depending on the combination of an unsaturated monomer, a crosslinking agent, and a radical polymerization initiator or on such reaction conditions as the reaction temperature.
[0102] [00102] The average pore diameter of the water-absorbing resin or hydrophilic polymer that has an almost independent bubble structure is in the range of 10-500 micrometers, or in the range of 20-400 micrometers, or in the range of 30-300 micrometers , or in the range of 40-200 micrometers, or in the range of 70 micrometers to about 110 micrometers. The pore diameter mentioned above is verified by subjecting the water absorbent resin or hydrophilic polymer to a dry state to image analysis with the aid of an electron microscope. Specifically, the average pore diameter is obtained by forming a histogram representing the distribution of pore diameters of the water-absorbing resin as a result of image analysis and calculating the average number of pore diameters based on the histogram.
[0103] [00103] To further improve the properties of the particulate superabsorbent polymer, an additional amount of foaming agent as shown here can also be added to the aqueous superabsorbent polymer prior to the drying step.
[0104] [00104] The drying temperature is not particularly limited, but it is required to fall in the range of 100oC-250oC, or in the range of 120oC-200oC, for example. Although drying time is not particularly limited, it is preferred to be in the range of approximately 10 seconds - 5 hours. The hydrogel resin can be neutralized or further disintegrated for fine division before drying.
[0105] [00105] The drying process to be adopted is not particularly limited, but can be selected from several processes such as, for example, drying by heating, drying by hot air, drying under reduced pressure, drying by infrared rays, drying with microwave, drying with a drying drum, dehydration by azeotropy with a hydrophobic organic solvent, and drying of high humidity through the use of hot steam. Among the drying processes mentioned above, drying with hot air and drying with microwaves proved to be particularly favorable. When the hydrogel containing the bubbles is irradiated with microwaves, the water-absorbent resin produced still enjoys an exalted speed of water absorption because the bubbles are consequently expanded to several dozen times the original volume. Superabsorbent Particle Polymer (SAP) - Combination of Clays
[0106] [00106] As noted earlier, the polymerization reaction proceeds quickly to yield a highly viscous hydrogel that is extruded, for example, on a flat surface such as a continuously moving conveyor belt. The neutralized superabsorbent polymer hydrogel is then crushed, and the clay can be added, typically as an aqueous clay paste, and intimately mixed with the crushed superabsorbent polymer hydrogel particles. The clay can also be added as solid particles, or a spray. The hydrogel components of SAP and clay can then be intimately mixed, for example, by extrusion, to disperse the clay in, and on, the hydrogel particles. The resulting mixture of SAP - neutralized clay is then dried and carved, and optionally cross-linked to the surface to provide neutralized SAP - clay particles. Grinding of the SAP - clay hydrogel particles can be carried out simultaneously or sequentially.
[0107] [00107] After crushing, the SAP - viscous clay hydrogel particles are dehydrated (that is, dried) to obtain SAP - clay particles in a solid or pulverized form. The dehydration step can be carried out, for example, by heating particles of SAP viscous hydrogel - clay at a temperature of about 190oC to about 210oC for about 15 minutes to about 120 minutes in a forced air oven , or a period of time from about 15 minutes to about 110 minutes or from about 15 minutes to about 100 minutes, or about 20 minutes to about 100 minutes. The hydrogel of SAP - dried clay can then be subjected to further mechanical means for particle size reduction and classification including cutting, crushing, and sieving.
[0108] [00108] Such SAP - clay compositions can include superabsorbent polymer present in an amount of about 90% to about 99.5%, or about 91% to about 99%, or about 92% to about 98% by weight, and the clay is present in an amount of about 0.5% to about 10%, or about 1 to about 9% by weight, or from about 2 to about 8% in weight.
[0109] [00109] Useful clay in the present SAP particles - clay can be swelling or non-swelling clay. Intumescent clays have the ability to absorb water and are organic, layered, swellable materials. Suitable swelling clays include, but are not limited to, montmorillonite, saponite, nontronite, laponite, beidelite, hectorite, sauconite, stevensite, vermiculite, volkonskoite, magadite, medmontite, kenyaite, and mixtures thereof.
[0110] [00110] Suitable non-swelling clays include, without limitation, kaolin minerals (including kaolinite, dickite, and nacrite), serpentine minerals, mica minerals (including illite), chlorite, sepolite, paligorskite, bauxite, and mixtures thereof.
[0111] [00111] The clay can also be an organophilic clay. As used herein and hereinafter, the term "organophilic" is defined as the property of a compound absorbing at least its own weight, and preferably many times its own weight, of an organic, water-immiscible compound. An organophilic compound can optionally absorb water or a water miscible compound.
[0112] [00112] Commercially available clays include ULTRAGLOSS clays (hydrated kaolin) from BASF Corporation, Florham Park, N.J .; Purified Clay from Nanocor Technologies, Arlington Heights, III .; and HYDROGLOSS from Huber, Atlanta, Ga. Particle Size
[0113] [00113] Polymerization forms a superabsorbent polymer gel, which is granulated into particles of superabsorbent polymer, or superabsorbent polymer into particles. The superabsorbent polymer gel generally has a moisture content of about 40 to 80% by weight of the superabsorbent polymer gel. The particulate superabsorbent polymer generally includes particle sizes ranging from about 50 micrometers to about 1000 micrometers, or from about 150 micrometers to about 850 micrometers. The present invention can include at least about 40% by weight of the superabsorbent polymer particles having a particle size of about 300 microns to about 600 microns, at least about 50% by weight of the particles having a particle size of about 300 micrometers to about 600 micrometers, or at least about 60% by weight of the particles having a particle size of about 300 micrometers to about 600 micrometers as measured by sieving through a US standard 30 mesh screen and retained on a 50 standard US mesh screen In addition, the D50 mass average particle diameter can be 200 to 450 micrometers, or 300 to 430 micrometers.
[0114] [00114] Still, the percentage of particles of less than 150 micrometers is generally 0-8% by mass, or 0-5% by mass, or 0-3% by mass, or 0-1% by mass. In addition, the percentage of particles of more than 600 micrometers can be from 0 to 25% by mass, or from 3 to 15% by mass, or from 5 to 12% by mass, or 5 to 8% by mass, as measured using , for example, a RO-TAP Mechanical Sieve Shaker Model B available from WS Tyler, Inc., Mentor, Ohio.
[0115] [00115] The particle size can be adjusted by subjecting particles to dispersion polymerization and dispersion drying. However, in general, when carrying out aqueous polymerization in particular, the particles are pulverized and classified after drying, and then the average mass diameter of D50, and the amount of particles less than 150 micrometers and greater than 600 micrometers, are adjusted accordingly. to obtain a specific particle size distribution. For example, if the specific particle size distribution is obtained by decreasing the diameter of the particles having a mass average diameter from D50 to 400 micrometers or less and also reducing the amount of fine particles having diameters of less than 150 micrometers and greater than 600 micrometers, the particles can first be classified into coarse particles and fine particles after drying through the use of generic classification equipment such as a sieve. This process preferably removes coarse particles with a diameter of 5000 micrometers to 600 micrometers, or 2000 micrometers to 600 micrometers, or 1000 micrometers to 600 micrometers. Then, in the main adjustment process, fine particles of less than 150 micrometers are removed. The coarse particles removed can be discarded, but they are more likely to be sprayed again through the previous spraying process. The resulting particulate superabsorbent polymer thus produced with a specific particle size distribution through the spraying process is therefore made up of irregularly sprayed particles.
[0116] [00116] The particulate superabsorbent polymers are treated on the surface with additional chemical compounds and treatments as shown here. In particular, the surface of the particulate superabsorbent polymer can be crosslinked, generally referred to as surface crosslinking, through the addition of a surface crosslinking agent and heat treatment. In general, surface crosslinking is a process for increasing the crosslinking density of the polymer matrix in the vicinity of the particle superabsorbent polymer surface with respect to the crosslinking density of the particle interior. The amount of the surface crosslinking agent can be from about 0.01% by weight to about 5% by weight of the dry particle superabsorbent polymer composition, and as from about 0.1% by weight to about 3% by weight, and as from about 0.1% by weight to about 1% by weight, based on the weight of the dry particulate superabsorbent polymer composition.
[0117] [00117] Desirable surface crosslinking agents include chemical compounds with one or more functional groups that are reactive towards pendant groups on the polymer chains, typically acid groups. Surface crosslinking agents comprise functional groups that react with functional groups of a polymer structure in a condensation reaction (condensation crosslinker), in an addition reaction or in a ring opening reaction. These compounds can include, for example, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, polyglycerin, propylene glycol, diethanol amine, triethanol amine, polyoxy propylene, oxyethylene - oxypropylene block copolymers, sorbitan fatty acid esters, esters of fatty acid esters polyoxyethylene sorbitan fatty acid, trimethylol propane, pentaerythritol, polyvinyl alcohol, sorbitol, 1,3-dioxolan-2-one (ethylene carbonate), 4-methyl-1,3-dioxolan-2-one (propylene carbonate), or 4,5-dimethyl-1.3-dioxolan-2-one.
[0118] [00118] After the particulate superabsorbent polymer has been brought into contact with the surface crosslinking agent, or with the fluid comprising the surface crosslinking agent, the treated particulate superabsorbent polymer is heat treated to a temperature of about 50 to about 300oC, or about 75 to about 275oC, or about 150 to about 250oC and for a time of about 5 to about 90 minutes depending on the temperature, so that the outer region of the polymer structure is more strongly reticulated compared to the inner region (ie, surface reticulation). The duration of the heat treatment is limited by the risk that the desired profile of properties of the polymer structures will be destroyed as a result of the heat effect.
[0119] [00119] In a particular aspect of surface crosslinking, the particulate superabsorbent polymer is treated on the surface with ethylene carbonate followed by heating to effect surface crosslinking of the superabsorbent polymer particle, which improves the surface crosslinking density and gel resistance characteristics of the superabsorbent particulate polymer. More specifically, the surface crosslinking agent is coated onto the particulate superabsorbent polymer by mixing the particulate superabsorbent polymer with an aqueous alcoholic solution of the ethylene carbonate surface crosslinking agent. The amount of alcohol in the aqueous alcoholic solution can be determined by the solubility of the alkylene carbonate and is kept as low as possible for various reasons, for example, for protection against explosions. Suitable alcohols are methanol, isopropanol, ethanol, butanol, or butyl glycol, as well as mixtures of these alcohols. In some respects, the solvent is desirably water, which is typically used in an amount of about 0.3 wt% to about 5.0 wt%, based on the weight of the dry particulate superabsorbent polymer composition. In still other aspects, the ethylene carbonate surface crosslinking agent can be applied from a sprayed mixture, for example, with an inorganic carrier material, such as silicon dioxide (SiO2), or in a vapor state through sublimation. of ethylene carbonate.
[0120] [00120] To obtain the desired surface crosslinking properties, surface crosslinking agents, such as ethylene carbonate, must be uniformly distributed over the particulate superabsorbent polymer. For this purpose, mixing is carried out in appropriate mixers known in the art, such as fluidized bed mixers, spatula mixers, rotary drum mixers, or double endless mixers. It is also possible to coat the superabsorbent polymer in particles during one of the process steps in the production of the superabsorbent polymer in particles. In a particular aspect, an appropriate process for this purpose is the reverse suspension polymerization process.
[0121] [00121] The surface crosslinking agent solution can also include from 0% by weight to about 1% by weight, or from about 0.01% by weight to about 0.5% by weight, based on dry particle superabsorbent polymer composition of a thermoplastic polymer. Examples of thermoplastic polymers include polyolefin, polyethylene, polyester, linear low density polyethylene (LLDPE), ethylene-acrylic acid copolymer (EAA), ethylene-alkyl methacrylate (EMA) copolymer, polypropylene (PP), polypropylene malea-do , ethylene-vinyl acetate (EVA) copolymer, polyester, and combinations of all polyolefin families, such as PP, EVA, EMA, EEA, EBA, HDPE, MDPE, LDPE, LLDPE, and / or VLDPE combinations , can also be advantageously employed. In particular aspects, maleate polypropylene is a preferred thermoplastic polymer for use in the present invention. A thermoplastic polymer can be functionalized to have additional benefits such as solubility or dispersibility in water.
[0122] [00122] The heat treatment, which follows the coating treatment of the superabsorbent polymer in particles, can be carried out as follows. In general, the heat treatment is at a temperature of about 100oC to about 300oC. Lower temperatures are possible if highly reactive epoxy crosslinking agents are used. However, if ethylene carbonate is used, then the heat treatment is suitably at a temperature of about 150oC to about 250oC. In this particular aspect, the treatment temperature depends on the residence time and the type of ethylene carbonate. For example, at a temperature of around 150oC, heat treatment is carried out for an hour or more. In contrast, at a temperature of about 250oC, a few minutes (for example, from about 0.5 minutes to about 5 minutes) are sufficient to obtain desired surface cross-linking properties. Heat treatment can be carried out in conventional dryers or ovens known in the art.
[0123] [00123] Particulate superabsorbent polymer compositions can still be treated on the surface before, during or after surface cross-linking with other chemical compositions. Al sulfate insertion section
[0124] [00124] The particulate superabsorbent polymer composition of the invention may comprise from about 0.01% by weight to about 5% by weight based on the weight of the particulate superabsorbent composition of an aluminum salt applied to the surface of the superabsorbent polymer. in particles, in the form of an aqueous solution having a pH value of about 5.5 to about 8, or from about 6 to about 7. Or, the particulate superabsorbent polymer composition comprises about 6% by weight to about 15% by weight based on the weight of the particulate superabsorbent composition of an aqueous solution of aluminum salt applied to the surface of the crosslinked particulate superabsorbent polymer, where the aqueous solution of aluminum salt has a pH value of about 5.5 to about 8, or about 6 to about 7. The aqueous solution of the aluminum salt may comprise an aluminum cation and a hydroxyl ion or anion of a deprotonated organic hydroxyl acid. Examples of preferred organic acids are mono carboxylic hydroxyl acids such as lactic acid, glycolic acid, glyconic acid, and 3-hydroxy propionic acid.
[0125] [00125] The aqueous solution of aluminum salt includes the reaction product of alkaline hydroxide and aluminum sulfate or hydrated aluminum sulfate. In another embodiment, the aqueous solution of aluminum salt includes the reaction product of sodium hydroxide and aluminum sulfate or hydrated aluminum sulfate. In yet another embodiment, the aqueous aluminum salt solution comprises an aluminum compound and an organic acid. The mixture of the aluminum compound with the organic acid (salt) can be acidic or basic, and the pH can be adjusted to the desired range with a basic or acidic material. Examples of basic pH adjustment materials include, but are not limited to, sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium carbonate or sodium bicarbonate. Examples of acidic materials for pH adjustment include, but are not limited to, hydrochloric acid, sulfuric acid, methyl sulfonic acid, or carbon dioxide in water. Acidic aluminum salts, such as aluminum chloride, aluminum sulfate, aluminum nitrate and poly aluminum chloride, or basic aluminum salts, such as sodium aluminate, potassium aluminate, and ammonium aluminate, can be used also for pH adjustment.
[0126] [00126] The aqueous solution of aluminum salt can be added at various stages of the surface treatment of the particulate superabsorbent polymer. In one embodiment, the aqueous aluminum salt solution can be applied to the particulate superabsorbent polymer together with the surface crosslinking solution.
[0127] [00127] The aqueous solution of aluminum salt can be added after the surface crosslinking step, which can be called a post treatment. In one embodiment, the superabsorbent polymer in cross-linked surface particles and the aluminum salt are mixed using means well known to those skilled in the art. In particular, from about 6% by weight to about 15% by weight of an aqueous solution of aluminum salt is applied to a superabsorbent polymer composition in crosslinked surface particles.
[0128] [00128] The particulate superabsorbent polymer compositions according to the invention can be treated on the surface, before, during or after surface crosslinking with 0.01% by weight to about 5% by weight based on the weight of the superabsorbent composition particles of a compound containing one or more multivalent cations applied to the surface of the particulate superabsorbent polymer. Examples include aluminum, calcium, iron, zinc, magnesium and zirconium cations. Of these, aluminum can be used. Examples of anions in the multivalent metal salt may include halides, chlorohydrates, sulfates, nitrates and acetates. Aluminum sulphate can be used and is easily commercially available. Aluminum sulfate can be hydrated aluminum sulfate, where aluminum sulfate can have 12 to 14 hydration waters. Mixtures of multivalent metal salts can be used. In one embodiment, the invention may comprise from about 0.01% by weight to about 5% by weight based on the weight of the particulate superabsorbent composition of an aluminum salt applied to the surface of the particulate superabsorbent polymer, in the form of an aqueous solution having a pH value of about 5.5 to about 8, or about 6 to about 7.
[0129] [00129] Aqueous solution of aluminum salt may include the reaction product of alkaline hydroxide and aluminum sulfate or hydrated aluminum sulfate. In another embodiment, the aqueous solution of aluminum salt comprises a single aluminum salt such as aluminum sulfate or aluminum chloride, or mixtures with other compounds containing multivalent cation that can be applied with or without pH adjustment. In yet another embodiment, the aqueous aluminum salt solution can comprise an aluminum compound and an organic acid. The mixture of the aluminum compound with the organic acid (salt) can be acidic or basic and can be applied with or without pH adjustment. If a pH adjustment is desired, the pH can be adjusted to the desired range with an acidic or basic material.
[0130] [00130] The particulate superabsorbent polymer compositions according to the invention can be surface treated with from about 0.01% to about 2% by weight, or from about 0.01% to about 1% by weight , based on the dry composition of superabsorbent polymer of a water insoluble inorganic metal compound. The water-insoluble inorganic metal compound can include a cation selected from aluminum, titanium, calcium, or iron and an anion selected from phosphate, borate, or chromate. An example of a water-insoluble inorganic metal compound includes aluminum phosphate. The inorganic metal compound can have a mass average particle size of less than about 2 micrometers and can have a mass average particle size of less than about 1 micrometer.
[0131] [00131] The particulate superabsorbent polymer composition can include from about 0% by weight to about 5% by weight, or from about 0.001% by weight to about 3% by weight, or from about 0.01 % by weight to about 2% by weight based on the weight of the dry particulate superabsorbent polymer composition of a cationic polymer. A cationic polymer as used herein refers to a polymer or mixture of polymers comprising a group or functional groups having the potential to become positively charged ions with ionization in an aqueous solution. Suitable functional groups for a cationic polymer include, but are not limited to, amino groups, imino groups, imido groups, primary, secondary or tertiary starch groups and quaternary ammonium groups. Examples of synthetic cationic polymers include the salts or partial salts of poly (vinyl amines), poly (allyl amines), or poly (ethylene imine). Examples of naturally-based cationic polymers include partially deacetylated chitin, chitosan, and chitosan salts.
[0132] [00132] A particulate superabsorbent polymer composition can include from about 0% by weight to about 5% by weight, or from about 0.001% by weight to about 3% by weight, or from about 0.01 % by weight to about 2% by weight based on the weight of the water-insoluble, inorganic dry particulate superabsorbent polymer composition. Examples of insoluble inorganic sprays include silicon dioxide, silica, titanium dioxide, aluminum oxide, magnesium oxide, zinc oxide, talc, calcium phosphate, clays, diatomaceous earth, zeolites, bentonite, kaolin, hydrotalcite, activated clays , etc. The insoluble inorganic spray additive can be a single compound or a mixture of compounds selected from the list above. Examples of silica include smoked silica, precipitated silica, silicon dioxide, silicic acid, and silicates. In some particular aspects, microscopic non-crystalline silicon dioxide is desirable. Products include SIPERNAT 22S and AEROSIL 200 available from Evonik Corporation, Parsippany, New Jersey. In some respects, the particle diameter of the inorganic spray may be 1000 microns or less, such as 100 microns or less.
[0133] [00133] The particulate superabsorbent polymer composition can also include from 0% by weight to about 30% by weight, or from about 0.001% by weight to about 25% by weight, or from about 0.01% by weight to about 20% by weight, based on the weight of the dry particulate superabsorbent polymer composition, water-soluble polymers, such as partially or completely hydrolyzed polyvinyl acetate, polyvinyl pyrrolidone, starch or starch derivatives, polyglycols or polyacrylic acids, preferably in polymerized form. The molecular weight of these polymers is not as critical as they are soluble in water. Preferred water-soluble polymers are starch and polyvinyl alcohol. The content of such water-soluble polymers in the absorbent polymer according to the invention is 0-30% by weight, or 0-5% by weight, based on the total amount of the dry particulate superabsorbent polymer composition. Water-soluble polymers, preferably synthetic polymers, such as polyvinyl alcohol, can also serve as a graft base for the monomers to be polymerized.
[0134] [00134] The particulate superabsorbent polymer composition can also include from 0% by weight to about 5% by weight, or from about 0.001% by weight to about 3% by weight, or from about 0.01% by weight to about 2% by weight based on the weight of the dry particulate superabsorbent polymer composition, dusting agents, such as hydrophilic and hydrophobic dusting agents such as those described in US patents 6 090 875 and 5 994 440.
[0135] [00135] In some respects, additional surface additives can optionally be employed with the particulate superabsorbent polymer composition, such as odor-binding substances, such as cyclo dextrins, zeolites, inorganic or organic salts, and similar materials; anti-pie formation additives, flow modifying agents, surfactants, viscosity modifiers, and the like.
[0136] [00136] The particulate superabsorbent polymer composition of the present invention can be, after the heat treatment step, treated with an aqueous solution, such as the aqueous solution of deprotonated organic acid salt, aluminum salt, or water-soluble polymer such as polyethylene glycol.
[0137] [00137] The superabsorbent polymer composition in treated particles has a moisture content of about 3% by weight to about 15% by weight, or from about 4% by weight to about 12% by weight, or 5% by weight to about 11% by weight, based on the composition of particulate superabsorbent polymer and as measured by the Moisture Content Test contained herein.
[0138] [00138] In yet another embodiment, a chelating agent can be added and become part of the particulate superabsorbent polymer composition of the present invention. The chelating agent can be selected from specific carboxylic amino acids that can be fixed on the surface of the water-absorbent resin by mixing the polycarboxylic amino acid and the surface cross-linking agent with a water-absorbing resin before the surface cross-linking of water-absorbing resin. water, thus cross-linking the water-absorbent resin surface, or by adding polycarboxylic amino acid and water to a water-absorbent resin of specific cross-linked surface, thus granulating this resin. Because the deterioration of water-absorbing resins occurs from their surfaces, it is preferable that the chelating agent is placed in the vicinity of the surface of the particulate superabsorbent polymer composition. In carrying out the production processes of the present invention, for example, the chelating agent and the surface crosslinking agent, which is capable of reacting with a carboxyl group, are mixed with the superabsorbent polymer obtained above having a carboxyl group.
[0139] [00139] Examples of the chelating agent, as used in the present invention, include the following compounds: (1) carboxylic amino acids and their salts; (2) monoalkyl citramides, monoalkenyl citramides, and their salts; (3) monoalkyl malonamides, monoalkenyl malonamides, and their salts; (4) monoalkyl phosphoric esters, monoalkyl phosphoric esters, and their salts; (5) N-acylated glutamic acids, N-acylated aspartic acids, and their salts; (6) beta diketone derivatives; (7) tropolone derivatives; and (8) organic phosphoric acid compounds.
[0140] [00140] The amount of the chelating agent is generally from about 0.0001 to about 10 parts by weight, or from about 0.0002 to about 5 parts by weight, per 100 parts by weight of the solid content of the composition. particulate superabsorbent polymer. In the present invention, the chelating agent can be added to the particulate superabsorbent polymer both during surface crosslinking and to a crosslinked surface particulate superabsorbent polymer.
[0141] [00141] The particulate superabsorbent polymer composition of the present invention exhibits certain characteristics, or properties, as measured by Free Swelling Gel Bed Permeability (FSGBP), Centrifugal Holding Capacity (CRC), and absorption under load at about 90Kpa (0.9Psi) (90Kpa (0.9Psi) AUL). The FSGBP test is a measurement of the permeability of a swollen bed of particulate superabsorbent polymer composition in terms of 10-8 cm2 (for example, separated from the absorbent structure) under a containment pressure after what is commonly referred to as " free swelling ". In this context, the term "free swelling" means that the supra-absorbent particle polymer composition is allowed to swell without a swelling restriction charge with test solution absorption as will be described.
[0142] [00142] Permeability is a measure of the effective connectivity of a porous structure, be it a fiber mat or a foam sheet or, in the case of this patent application, superabsorbent polymer in particles and composition of superabsorbent polymer in particles, generally referred to herein as particulate superabsorbent polymer compositions, or SAP, and can be specified in terms of the empty fraction and extent of connectivity of the particulate superabsorbent polymer compositions. Gel permeability is a property of the mass of superabsorbent polymer compositions in particles as a whole and is related to particle size distribution, particle shape, open pore connectivity, shear modulus and modification of the swollen gel surface. In practical terms, the permeability of the particulate superabsorbent polymer composition is a measure of how quickly liquid flows through a mass of swollen particles. Low permeability indicates that liquid cannot flow easily through particulate superabsorbent polymer compositions, which is generically referred to as gel blocking, and that any forced flow of liquid (such as a second application of urine during diapering) has to take an alternative route (for example, diaper leak).
[0143] [00143] The Vortex Test measures the amount of time in seconds required for 2 grams of an SAP to close a vortex created by shaking 50 milliliters of saline at 600 rpm on a magnetic stirring plate. The time taken to close the vortex is an indication of the free swelling absorption rate of SAP.
[0144] [00144] The centrifugal retention capacity test (CRC) measures the ability of the particulate superabsorbent polymer composition to retain liquid there after being saturated and subjected to centrifugation under controlled conditions. The resulting holding capacity is established as grams of liquid retained by weight in grams of the sample (g / g).
[0145] [00145] The absorption under load test (AUL) measures the ability of particulate superabsorbent polymer composition particles to absorb a 0.9 weight percent solution of sodium chloride in distilled water at room temperature (test solution) while material is under a load of 90Kpa (0.9Psi).
[0146] [00146] The pressure absorbance index (PAI) is the sum of the absorbance values under load (described here below) for a SAP determined under the following loads: 690 dynes per square centimeter (0.01 pound per square inch); 19995 dynes per square centimeter (0.29 pounds per square inch); 39300 dynes per square centimeter (0.57 pounds per square inch); and 62053 dynes per square centimeter (0.90 pounds per square inch) (). That is, the absorbance values under load for a given SAP are determined under the restraining forces shown above according to the process shown below in connection with the examples. The absorbance values under load determined under the constraint loads shown above are then totaled to produce the Pressure Absorbency Index.
[0147] [00147] All values for Centrifugal Holding Capacity, Absorbency under load and gel bed permeability shown here are to be understood as being determined by the centrifugal holding capacity test, absorbency test under load, and bed permeability test. of free swelling gel as provided herein.
[0148] [00148] The superabsorbent particulate composition showing rapid absorption, manufactured through a process of the present invention can have a vortex time of about 30 to 60 seconds, or from 40 seconds to about 60 seconds, a centrifugal holding capacity of about from 25 g / g to about 40 g / g, or from about 27 to about 35 g / g; and an absorbance under load of 90Kpa (0.9Psi) of about 15 g / g to about 24 g / g, or about 16 g / g to about 22 g / g, a PAI of about 120 to about 140, and a free swelling gel bed permeability (FSGBP) of about 20x10-8 cm2 to about 200x10-8 cm2.
[0149] [00149] The particulate superabsorbent polymer compositions according to the present invention can be used in many absorbent articles including sanitary towels, diapers, or wound coverings, and they have the property that they quickly absorb large amounts of menstrual blood, urine, or other bodily fluids. Since the agents according to the invention retain the absorbed liquids even under pressure and are also capable of distributing liquid still inside the construction in the swollen state, they are more desirably employed in higher concentrations, in relation to the hydrophilic fiber material, such as as fluff, when compared to conventional current superabsorbent compositions. They are also suitable for use as a homogeneous superabsorbent layer with no fluff content within diaper construction, as a result of which particularly thin articles are possible. The polymers are furthermore suitable for use in hygienic articles (for example, incontinence products) for adults.
[0150] [00150] The particulate superabsorbent polymer compositions according to the invention are also used in absorbent articles that are suitable for further uses. In particular, the particulate superabsorbent polymer compositions of this invention can be used in absorbent compositions for absorbents for water or aqueous liquids, or in constructions for absorbing body fluids, in foamed and non-foamed sheet-like structures, in packaging materials, in buildings for plant growth, as soil improvement agents or as carriers of active compost. For this, they are processed to a weave through mixing with paper or pile or synthetic fibers or through the distribution of superabsorbent polymers between substrates of paper, pile or non-woven textiles or through processing in carrier materials.
[0151] [00151] The particulate superabsorbent polymer compositions according to the present invention can be used in many absorbent articles including sanitary towels, diapers, or wound covers, and they have the property that they quickly absorb large amounts of menstrual blood, urine, or other bodily fluids. Since the agents according to the invention retain the absorbed liquids even under pressure and are also capable of still delivering liquid within construction in the swollen state, they are more desirably employed in higher concentrations, with respect to the hydrophilic material, such as fluff , when compared to conventional current superabsorbent compositions. They are also suitable as for use as a homogeneous superabsorbent layer with no fluff content within a diaper construction, as a result of which particularly thin articles are possible. Polymers are furthermore suitable for use in hygiene articles (for example, incontinence products) for adults. For example, referring now to Figure 5, in one aspect, the absorbent article employing the particulate superabsorbent polymer composition described herein is a disposable article 10 including a backsheet or outer cover 20, a liquid-permeable top sheet or liner body side 22 positioned in relation to the outer cover 20, and an absorbent core 24, such as an absorbent pad, which is placed between the body side liner 22 and the outer cover 20. Article 10 has a outer surface 23, a front waist region 25, a rear waist region 27, and a socket region 29 connecting the front and rear waist regions 25, 27. The outer cover 20 defines a length and width that, in appearance shown, coincide with the length and width of the article 10. The absorbent core 24 generally defines a length and width that are less than the length and width of the outer cover 20, respectively . Thus, marginal portions of article 10, such as marginal sections of the outer cover 20, may extend past the end edges of the absorbent core 24. In the illustrated aspects, for example, the outer cover 20 extends outward beyond the end edge edges of the absorbent core 24 to form lateral margins and terminal margins of the article 10. The body side lining 22 is generally coextensive with the outer cover 20 but optionally can cover an area that is greater or less than the area of the outer cover 20, as desired . In other words, the body side lining 22 is connected in a superimposed relationship with the outer cover 20. The outer cover 20 and the body side lining 22 are intended to cope with the wearer's body and body, respectively, while in use.
[0152] [00152] To provide improved adaptation and to assist in reducing leakage of body exudates from article 10, the side margins of article and end margins can be made elastic with appropriate elastic members, such as a single or multiple strips of elastic. The elastic strips can be composed of natural or synthetic rubber and optionally they can be heat shrinkable or thermally elastic. For example, as illustrated representatively in Fig. 5, article 10 can include elastic legs 26 that are constructed to operably hold and fold the side edges of article 10 to provide elastic leg bands that can be closely fitted around the legs to reduce leakage and provide improved comfort and appearance. Similarly, waist elastics 28 can be employed to make the end edges of article 10 elastic to provide elastic waists. Waist elastics 28 are configured to operably attach and pleat waist sections to provide a close, comfortably resilient fit around the user's waist. In the illustrated aspects, the elastic members are illustrated in their stretched condition, not contracted for the purpose of clarity.
[0153] [00153] Fixing means, such as a hook or loop fasteners 30, can be used to hold article 10 over a user. Alternatively, other fastening means, such as buttons, pins, snap fasteners, adhesive tape fasteners, cohesives, mushroom and loop fasteners, a strap, and so on, as well as combinations including at least one of the previous fasteners can be employed. In addition, more than two fasteners can be provided, particularly if article 10 is to be provided in a pre-fixed configuration.
[0154] [00154] Article 10 can also include other layers between the absorbent core 24 and the body side liner 22 or outer cover 20. For example, article 10 can also include a thick management layer 34 located between the side liner body 22 and the absorbent core 24 to prevent assembly of exuded fluids and to further improve air exchange and distribution of exuded fluids within article 10.
[0155] [00155] Article 10 can be in various appropriate ways. For example, article 10 may have a total rectangular shape, T shape or an approximate shape of watch glass. In the aspect shown, article 10 generally has an I shape. Article 10 further defines a longitudinal direction 36 and a transverse direction 38. Other suitable article components that can be incorporated onto absorbent articles include containment flaps, waist flaps, elastomeric side panels, and the like.
[0156] [00156] The various components of Article 10 are integrally assembled using various types of bonding mechanisms such as adhesive, sonic bonds, thermal bonds, and so on, as well as combinations including at least one of the previous mechanisms. In the aspect shown, for example, the body side liner 22 and outer cover 20 are mounted to the absorbent core 24 with adhesive liners, such as a hot melt pressure sensitive adhesive. Similarly, other article components, such as elastic members 26 and 28, fastening members 30, and thick layers 34 can be mounted on article 10 using the connection mechanisms identified above.
[0157] [00157] The outer cover 20 of article 10 can include any material for such applications, such as a substantially vapor-permeable material. The permeability of the external cover 20 can be configured to improve the breathing capacity of the article 10 and to reduce the hydration of the user's skin during use without allowing excessive condensation of vapor, such as urine, on the clothing facing the surface of the external cover 20 which can undesirably dampen user's clothes. The outer cover 20 can be constructed to be permeable to at least water vapor and can have a water vapor transmission rate greater than or equal to about 1000 grams per square meter for 24 hours (g / m2 / 24 H). For example, the outer cover 20 can define a water vapor transmission rate from about 1000 to about 6000 g / m2 / 24 hours.
[0158] [00158] The outer cover 20 is also desirably substantially impermeable to liquid. For example, the outer cover 20 can be constructed to provide a hydrohead value greater than or equal to about 60 centimeters (cm), or, more specifically, greater than or equal to about 80 cm, and even more specifically, greater than or equal to about 100 cm. An appropriate technique for determining the resistance of a material to liquid penetration is the Federal Test Method Standard (FTMS) 191 Method 5514, of December 31, 1968.
[0159] [00159] As stated above, the outer cover 20 can include any material used for such applications, and desirably includes materials that directly provide the desired above levels of liquid impermeability and air permeability and / or materials that can be modified or treated in some way to provide such levels. The outer cover 20 can be a fibrous nonwoven fabric constructed to provide the required level of liquid impermeability. For example, a nonwoven web including polymer fibers blown from melting and / or bonded with spinning can be selectively treated with a water-repellent coating and / or laminated with a vapor-permeable, liquid-impermeable polymer film to provide coverage outer 20. In another aspect, outer cover 20 may include a non-woven web including a plurality of hydrophobic thermoplastic melt blown fibers, randomly deposited that are sufficiently bonded or otherwise connected to each other to provide a substantially impermeable web liquid and substantially vapor permeable. The outer cover 20 may also include a vapor-permeable non-woven layer that has been partially coated or otherwise configured to provide liquid impermeability in selected areas. In yet another example, the outer cover 20 is provided with an extensible material. In addition, the outer sheath material 20 can be stretched in the longitudinal 36 and / or transverse 38 directions. When the outer sheath 20 is manufactured from extensible or stretch materials, article 10 provides additional benefits for the user including improved adaptation.
[0160] [00160] The body side lining 22, used to help isolate the user's skin from liquids trapped in the absorbent core 24, can define a non-irritating, soft, acquiescent feeling for the user's skin. In addition, the body side lining 22 may be less hydrophilic than the absorbent core 24, to present a relatively dry surface for the user, and may be sufficiently porous to be permeable to liquid, allowing liquid to easily penetrate through its thickness. A suitable body side liner 22 can be manufactured from a wide selection of weft materials, such as porous foams, cross-linked foams, open plastic films, natural fibers (for example, wood fibers or cotton fibers), fibers synthetic (for example, polyester or polypropylene fibers), and the like, as well as a combination of materials including at least one of the foregoing materials.
[0161] [00161] Various fabrics and non-fabrics can be used for the body side lining 22. For example, the body side lining 22 can include a melt blown or spun-bonded weave (for example, from polyolefin fibers) , a carded-bonded web (for example, of natural and / or synthetic fibers), a substantially hydrophobic material (for example, treated with a surfactant or otherwise processed to provide a desired level of wetting and hydrophilicity), and similar, as well as combinations including at least one of the above. For example, the body side liner 22 may include a spun-bonded, non-woven polypropylene fabric, optionally including about 2.8 to about 3.2 denier fibers formed in a weft having a weight basis of about 22 grams per square meter (g / m2) and a density of about 0.06 grams per cubic centimeter (g / cm3).
[0162] [00162] The absorbent core 24 of article 10 may include a matrix of hydrophilic fibers, such as a fibrous web of cellulosic fibers, mixed with particles of the particulate superabsorbent polymer composition. The pulp of wood pulp can be exchanged with synthetic, polymeric, melt blown fibers, and the like, as well as a combination including at least one of the above. The particulate superabsorbent polymer composition can be mixed substantially homogeneously with the hydrophilic fibers or can be mixed non-uniformly. Alternatively, the absorbent core 24 may include a fibrous web laminate and particulate superabsorbent polymer composition and / or a matrix suitable for maintaining the particulate superabsorbent polymer composition in a localized area. When the absorbent core 24 includes a combination of hydrophilic fibers and the particulate superabsorbent polymer, the hydrophilic fibers and particulate superabsorbent polymer composition can form an average base weight for the absorbent core 24 which can be about 400 grams per square meter ( g / m2) to about 900 g / m2, or, more specifically, about 500 g / m2 to about 800 g / m2, and even more specifically, about 550 g / m2 to about 750 g / m2.
[0163] [00163] In general, the particulate superabsorbent polymer composition is present in the absorbent core 24 in an amount greater than or equal to about 50 weight percent (% by weight), or, more desirably greater than or equal to about 70% by weight, based on the total weight of the absorbent core 24. For example, in one particular aspect, the absorbent core 24 may include a laminate that includes more than or equal to about 50% by weight, or, more desirably, more than or equal to about 70% by weight of particulate superabsorbent polymer surrounded by a fibrous web or other material suitable for maintaining high absorbency material in a localized area.
[0164] [00164] Optionally, the absorbent core 24 further includes a support (for example, a substantially hydrophilic fabric or non-woven wrapping sheet (not shown)) to help maintain the integrity of the structure of the absorbent core 24. The wrapping sheet of fabric it can be placed around weft / sheet of material and / or high absorbency fibers, optionally on at least one or both of its main face surfaces. The woven sheet may include an absorbent cellulosic material, such as crepe pad or a high moisture resistant fabric. The wrapping sheet of fabric can optionally be configured to provide a twisted layer that helps to quickly distribute liquid over the mass of absorbent fibers constituting the absorbent core 24. If this support is used, the dye 40 can optionally be arranged on the support, on the side of the absorbent core 24 opposite the outer cover 20.
[0165] [00165] Due to the fineness of the absorbent core 24 and the high absorbency material within the absorbent core 24, the liquid absorption rates of the absorbent core 24, by themselves, may be very low, or may not be adequately sustained over multiple liquid insults in the absorbent core 24. To optimize the absorption of total liquid and air exchanges, article 10 can also include a liquid-permeable, porous layer of thick management layer 34, as shown in Fig. 5. The layer coarse-management 34 is typically less hydrophilic than the absorbent core 24, and can have an operable level of density and basis weight to quickly collect and temporarily retain liquid waves, to transport liquid from its initial entry point and to substantially completely release the liquid to other parts of the absorbent core 24. This configuration can help prevent liquid from being collected and collected over the portion of the a article 10 positioned against the user's skin, thereby reducing the user's feeling of moisture. The structure of the wave management layer 34 can also improve the air exchange within article 10.
[0166] [00166] Various woven and non-woven fabrics can be used to build the wave management layer 34. For example, the wave management layer 34 can be a layer including a melt blown or spun-bonded weave ( such as polyolefin fibers); a carded-bonded weave or air-laid weave including, for example, natural and / or synthetic fibers; hydrophobic material that is optionally treated with a surfactant or otherwise processed to provide a desired level of wetting and hydrophilicity; and the like, as well as combinations including at least one of the above. The bonded carded web may, for example, be a thermally bonded web that is bonded using low melting, pulverized, and / or adhesive binder fibers. The layer may optionally include a mixture of different fibers. For example, the wave management layer 34 can include a non-woven, hydrophobic material having a basis weight of about 30 to about 120 g / m2. Testing Procedures The Vortex Test
[0167] [00167] The Vortex Test measures the amount of time in seconds required for 2 grams of an SAP to close a vortex created by shaking 50 milliliters of saline at 600 rpm on a magnetic stirring plate. The time taken to close the vortex is an indication of the free swelling absorption rate of SAP. Equipment and Materials
[0168] [00168] 1. Becher of 100 mL Schott Duran and graduated cylinder of 50 mL.
[0169] [00169] 2. Programmable magnetic stirring plate, capable of providing 600 revolutions per minute (such as that commercially available from PMC Industries, under the trademark Dataplate Model # 721).
[0170] [00170] 3. Magnetic stirring bar without rings, 7.9 mm times 32 mm, coated with Teflon (such as the one commercially available from Baxter Diagnostics, under the trademark S / PRIM single pack round stirring bars with ring removable pivot).
[0171] [00171] 4. Stop watch
[0172] [00172] 5. Scale, accuracy of +/- 0.01 g
[0173] [00173] 6. Saline solution, 0.87% weight / weight Blood Blank Saline available from Baxter Diagnostics (considered for the purposes of this patent application to be equivalent to 0.9% weight saline
[0174] [00174] 7. Weighing paper
[0175] [00175] 8. Room with standard condition atmosphere: Temperature = 23oC +/- 1oC, and relative humidity = 50% +/- 2% Test Procedure
[0176] [00176] 1. Measure 50 mL +/- 0.01 mL of saline in the 100 mL beaker.
[0177] [00177] 2. Place the magnetic stir bar in the beaker.
[0178] [00178] 3. Set the magnetic stirring plate to 600 revolutions per minute.
[0179] [00179] 4. Place the beaker in the center of the magnetic stirring plate so that the magnetic stirring bar is activated. The bottom of the vortex should be close to the top of the stir bar.
[0180] [00180] 5. Weigh 2g +/- 0.01 g of SAP to be tested on weighing paper
[0181] [00181] NOTE: SAP is tested as received (ie, as it can follow in an absorbent composite like those described here). No separation for a specific particle size is made, although the particle size is known to have an effect on this test.
[0182] [00182] 6. While the saline is being stirred, quickly pour the SAP to be tested in the saline and activate the interruption clock. The SAP to be tested must be added to the saline between the center of the vortex and the side of the bécher.
[0183] [00183] 7. Stop the clock when the surface of the saline solution becomes flat and note the time.
[0184] [00184] 8. Time, noted in seconds, is reported as the Vortex Time. Centrifugal Retention Capacity Test (CRC)
[0185] [00185] The CRC Test measures the ability of the SAP composition in particles to retain liquid there after being saturated and subjected to centrifugation under controlled conditions. The resulting holding capacity is established as grams of liquid retained by weight in grams of the sample, (g / g). The SAP sample to be tested is prepared from particles that are pre-sieved through a US standard 30 mesh screen and retained on a US standard 50 mesh screen. As a result, the particulate SAP sample comprises particles of size in the range of about 300 to about 600 microns. The particles can be pre-screened manually or automatically.
[0186] [00186] The retention capacity is measured by placing about 0.20 grams of the SAP sample in pre-sieved particles in a water-permeable bag that will contain the sample while allowing a test solution (0.9 sodium chloride percent by weight in distilled water) is freely absorbed by the sample. A heat sealable tea bag material, such as that available from Dexter Corporation (having a business location in Windsor Locks, Connecticut, U.S.A.) as a model designation 1234T heat sealable filter paper works well for most applications. The pouch is formed by folding a 5-inch by 3-inch sample of the pouch material in half and sealing two of the open ends to form a 2.5-inch by 3-inch rectangular pouch. The heat seals are about 0.25 inches inside the edge of the material. After the sample is placed in the bag, the remaining open edge of the bag is also heat sealed. Empty bags are also manufactured to serve as controls. Three samples are prepared for each particulate SAP to be tested.
[0187] [00187] The sealed bags are submerged in a saucepan containing the test solution at about 23oC, ensuring that the bags are kept underneath until completely moistened. After wetting, the particulate SAP samples remain in the solution for about 30 minutes, during which time they are removed from the solution and temporarily left on a flat, non-absorbent surface.
[0188] [00188] The wet bags are then placed in the basket where the wet bags are separated from each other and are placed on the outer circumferential edge of the basket, where the basket is of an appropriate centrifuge capable of subjecting the samples to a g-force of about 350. A suitable centrifuge is a CLAY ADAMS DYNAC II, model # 0103, featuring a water collection basket, a digital rpm meter, and a machined drain basket adapted to retain and drain samples from the flat pouch. Where multiple samples are centrifuged, samples are placed in opposite positions within the centrifuge to balance the basket when rotating. The bags (including the empty, wet bags) are centrifuged at about 1600 rpm (for example, to obtain a target g-force of about 350g force with a variance of about 240 to about 360g force), for 3 minutes. G-force is defined as a unit of inertial force on a body that is subjected to rapid acceleration or gravity, equal to 32 ft / s2 at sea level. The bags are removed and weighed, with the empty bags (controls) being weighed first, followed by the bags containing the particulate SAP samples. The amount of solution retained by the SAP sample in particles, taking into account the solution retained by the bag itself, is the centrifugal retention capacity (CRC) of SAP, expressed as grams of fluid per gram of SAP. More particularly, the holding capacity is determined by the following equation:
[0189] [00189] CRC = [sample bag after centrifuge - empty bag after centrifuge - dry sample weight] / dry sample weight
[0190] [00190] The three samples are tested, and the results are averaged to determine the SAP CRC in particles. Free Swelling Gel Bed Permeability Test (FSGBP)
[0191] [00191] As used herein, the free swelling gel bed permeability test, also referred to as the 0 psi swelling pressure gel bed (FSGBP) permeability test, determines the permeability of a swollen particle bed gel (for example, such as SAP in particles, or SAP in particles before being treated on the surface), under what is commonly referred to as "free swelling" conditions. The term "free swelling" means that the gel particles are allowed to swell without a restriction load on the absorption test solution as will be described. An appropriate apparatus for conducting the Gel Bed Permeability Test is shown in Figs. 1,2, and 3 and generically indicated as 500. The test apparatus assembly 528 comprises a sample container, generally indicated in 530, and a plunger, generally indicated in 536. The plunger comprises an axis 538 having a cylinder bore perforated down the longitudinal axis and a 550 head positioned at the bottom of the axis. The shaft hole 562 has a diameter of about 16 mm. The plunger head is connected to the shaft, as well as through adhesion. Twelve holes 544 are drilled in the radial axis of the shaft, three positioned every 90 degrees with diameters of about 6.4 mm. The 538 shaft is machined from a LEXAN rod or equivalent material and has an outside diameter of about 2.2 cm and an inside diameter of about 16 mm.
[0192] [00192] The plunger head 550 has a concentric inner ring with seven holes 560 and an outer ring with 14 holes 554, all holes having a diameter of about 8.8 mm as well as a hole of about 16 mm aligned with the axis. The plunger head 550 is machined from a LEXAN rod or equivalent material and has a height of approximately 16 mm and a diameter of such size that it fits inside cylinder 534 with minimal wall clearance but still sliding freely. The total length of the plunger head 550 and shaft 538 is about 8.25 cm, but it can be machined at the top of the shaft to obtain the desired mass of the plunger 536. The plunger 536 comprises a 100 mm steel cloth screen mesh 564 which is biaxially stretched to stretch and attached to the lower end of the plunger 536. The web is attached to the plunger head 550 using an appropriate solvent that causes the web to be securely adhered to the plunger head 550. Care must be taken to avoid excessive solvent migration in the open portions of the screen and reduce the open area for liquid flow. Acrylic adhesive, Weld-On # 4, from IPS Corporation (having a business location in Gardena, California, USA) is an appropriate adhesive.
[0193] [00193] Sample container 530 comprises a cylinder 534 and a 400 mesh stainless steel cloth screen 566 which is biaxially stretched to stretch and attached to the lower end of cylinder 534. The screen is attached to the cylinder using an appropriate solvent that causes the screen to be securely adhered to the cylinder. Care must be taken to avoid excessive solvent migration in the open portions of the screen and reducing the open area for liquid flow. Acrylic adhesive, Wel-On # 4, from IPS Corporation is an appropriate adhesive. A sample of gel particle, indicated as 568 in Fig. 2, is supported on the screen 566 inside cylinder 534 during tests.
[0194] [00194] Cylinder 534 can be drilled from a transparent LEXAN rod or equivalent material, or it can be cut from LEXAN tubing or equivalent material, and has an internal diameter of about 6 cm (for example, an area of cross section of about 28.27 cm2), a wall thickness of about 0.5 cm and a height of approximately 7.95 cm. A step is machined on the outside diameter of cylinder 534 so that a region 534a with an outside diameter of 66 mm exists for the bottom 31 mm of cylinder 534. An O-ring 540 that adapts to region diameter 534a can be placed at the top of the step.
[0195] [00195] The annular weight 548 has a counter-drilled hole about 2.2 cm in diameter and 1.3 cm deep so that it slides freely over the 538 axis. The annular weight also has a hole through 548a of about 16 mm. The ring weight 548 can be made of stainless steel or other suitable corrosion resistant materials in the presence of the test solution, which is 0.9 weight percent sodium chloride solution in distilled water. The combined weight of the plunger 536 and annular weight 548 equals approximately 596 grams (g), which corresponds to a pressure applied to sample 568 of about 0.3 pounds per square inch (psi), or about 20.7 dynes / cm2 (2.07 kPa), over a sample area of about 28.27 cm2.
[0196] [00196] When the test solution flows through the test apparatus during tests as described below, the sample container 530 generally rests on a dam 600. The purpose of the dam is to deflect liquid that overflows on top of the sample container 530 and deflects the overflowing liquid to a separate collection device 601. The dam can be positioned above a scale 602 with a beaker 603 resting on it to collect saline solution by passing through a swollen sample 568.
[0197] [00197] To conduct the gel bed permeability test under "free swelling" conditions, the plunger 536, with the weight 548 resting on it, is placed in an empty sample container 530 aa height from the top of the weight 548 to the bottom of the sample container 530 is measured using an appropriate gauge accurate to 0.01 mm. The force that the thickness gauge applies during measurement should be as low as possible, preferably less than about 0.74 newtons. It is important to measure the height of each combination of empty sample container 530, plunger 536, weight 548 and keep track of which plunger 536 and weight 548 is used when using multiple test devices. The same plunger 536 and weight 548 should be used for measurement when the sample 568 is then swelled to saturation. It is also desirable that the base on which the sample cup 530 is resting is level, and the upper surface of the weight 548 is parallel to the lower surface of the sample cup 530.
[0198] [00198] The sample to be tested is prepared from the particulate SAP, which is pre-sieved through a US standard 30 mesh screen and retained on a US standard 50 mesh screen. As a result, the test sample comprises particles with sizes in the range of about 300 to about 600 microns. SAP particles can be pre-screened with, for example, a RO-TAP Mechanical Sieve Shaker Model B available from W.S. Tyler, Inc., Mentor, Ohio. Sifting is conducted for 10 minutes. Approximately 2.0 grams of the sample is placed in the sample container 530 and spread evenly over the bottom of the sample container. The container, with 2.0 grams of sample in it, without the plunger 536 and weight 548 there, is then submerged in the 0.9% saline solution for a period of about 60 minutes to saturate the sample and allow the sample swell free of any restriction load. During saturation, the sample cup 530 is placed on a screen located in the liquid reservoir so that the sample cup 530 is slightly raised above the bottom of the liquid reservoir. The screen does not inhibit the flow of saline into the sample cup 530. A suitable screen can be obtained as part number 7308 from Eagle Supply and Plastic, featuring a business location in Appleton, Wisconsin, USA Saline does not fully cover SAP particles, as evidenced by a perfectly flat saline surface in the test cell. Also, the depth of saline is not allowed to drop so low that the surface inside the cell is uniquely defined by swollen SAP, rather than saline.
[0199] [00199] At the end of this period, the plunger assembly 536 and weight 548 is placed on the saturated sample 568 in the sample container 530 and then the sample container 530, plunger 536, weight 548, and sample 568 are removed from the solution. After removal and before being measured, the sample container 530, plunger 536, weight 548, and sample 568 remain at rest for about 30 seconds on a suitable non-deformable plate of wide, flat, uniform thickness. The thickness of the saturated sample 568 is determined by re-measuring height from the top of the weight 548 to the bottom of the sample container 530, using the same thickness gauge using previously as long as the zero point is unchanged from the initial height measurement. Sample container 530, plunger 536, weight 548, and sample 568 can be placed on a large, flat, non-deformable plate of uniform thickness that will provide drainage. The plate has a total dimension of 7.6 cm by 7.6 cm, and each grid has a cell size dimension of 1.59 cm long by 1.59 cm wide by 1.12 cm deep. A suitable large, flat, non-deformable plate material is a parabolic diffuser panel, catalog number 1624K27, available from McMaster Carr Supply Company, featuring a business location in Chicago, Illinois, USA, which can then be cut to dimensions appropriate. This large, flat, non-deformable plate must also be present when measuring the height of the initial empty assembly. Height measurement should be made as soon as practicable after the thickness gauge is engaged. The height measurement obtained from measuring empty sample container 530, plunger 536, and weight 548 is subtracted from the height measurement obtained after sample saturation 568. The resulting value is the thickness, or height "H" of the swollen sample. .
[0200] [00200] The permeability measurement is initiated by releasing a flow of 0.9% saline solution in sample container 530 with saturated sample 568, plunger 536, and weight 548 inside. The flow rate of the test solution in the container is adjusted to cause the saline solution to overflow the upper part of the cylinder 534 resulting in a consistent head pressure equal to the height of the sample container 530. The test solution can be added via any means that are sufficient to ensure a small but consistent amount of overflow from the top of the cylinder, such as with a 604 delivery pump. The overflowing liquid is diverted into a separate collection device 601. The amount of solution passing through sample 568 versus time is measured gravimetrically using the 602 scale and bécher 603. Data points from the 602 scale are collected every second for at least sixty seconds once the overflow has started. Data collection can be done manually or with data collection software. The flow rate, Q, through swollen sample 568 is determined in units of grams / second (g / s) through a linear minimum square adaptation of fluid passing through sample 568 (in grams) versus time (in seconds) .
[0201] [00201] Permeability in cm2 is obtained through the following equation: K = [Q * H * μ] / [A * p * P] where K = permeability (cm2), Q = flow rate (g / s), H = swollen sample height (cm), μ = liquid viscosity (poise) (approximately one centipoise for the test solution used with this Test) , A = cross-sectional area for liquid flow (28.27 cm2 for the sample container used with this Test), p = liquid density (g / cm3) (approximately one g / cm3, for the test solution used with this Test) and P = hydrostatic pressure (dynes / cm2 (usually approximately 7797 dynes / cm2). Hydrostatic pressure is calculated from P = p * g * h, where p = liquid density (g / cm3), g = acceleration gravitational, nominally 981 cm / s2, eh = fluid height, for example, 7.95 cm for the Gel Bed Permeability Test described here.
[0202] [00202] A minimum of two samples are tested and the results are averaged to determine the gel bed permeability of the particulate SAP sample.
[0203] [00203] The FSGBP can be measured as described here before subjecting a particulate SAP to a processing test as described here. Such an FSGBP value can be referred to as the "original" FSGBP of SAP in particles. FSGBP can also be measured subsequent to subjecting SAP in particles to the Processing Test. Such an FSGBP value can be referred to as the "post-processing" FSGBP. Comparison of the original FSGBP of a particulate SAP with the FSGBP post-processing of the particulate SAP can be used as a measure of composition stability. It should be noted that all "original" and "post-processing" FSGBP values reported here were measured using a sample of particles from 300 to 600 micrometers pre-sieved. Absorbance test under load (AUL (90Kpa (0.9Psi)))
[0204] [00204] The absorbance test under load (AUL) measures the ability of SAP in particles to absorb a 0.9 weight percent solution of sodium chloride in distilled water at room temperature (test solution) while the material is under load 90Kpa (0.9Psi). The apparatus for AUL tests consists of:
[0205] [00205]. an AUL assembly including a cylinder, a 4.4 g piston, and a standard weight of 317 g. The components of this assembly are described in further detail below.
[0206] [00206]. a flat-bottomed square plastic tray that is wide enough to allow glass frits to be on the bottom without contact with the tray walls. A plastic tray that is 22.9 cm x 22.9 cm (9 "by 9"), with a depth of 1.3 cm to 2.5 cm (0.5 "to 1") is commonly used for this testing process.
[0207] [00207]. a 9 cm diameter sintered glass frit with a 'C' porosity (25-50 microns). This frit is prepared in advance by equilibrating it in saline solution (sodium chloride 0.9% in distilled water, by weight). In addition to being washed with at least two portions of fresh saline, the frit must be immersed in saline for at least 12 hours before AUL measurements.
[0208] [00208]. Whatman Grade 1.9 cm diameter filter paper circles
[0209] [00209]. A supply of saline solution (0.9% sodium chloride in distilled water, by weight).
[0210] [00210] Referring to Fig. 4, cylinder 412 of the AUL 400 assembly used to contain the particulate superabsorbent polymer composition 410 is manufactured from lightly machined 2.54 cm (one inch) thermoplastic tubing for ensure concentricity. After machining, a 400 mesh stainless steel wire cloth 414 is fixed to the bottom of cylinder 412 by heating steel wire cloth 414 in a flame until hot red, after which cylinder 412 is retained on the cloth steel wire until cooled. The soldering iron can be used to retouch the seal if unsuccessful or if it breaks. Care must be taken to maintain a uniform flat bottom and not to disturb the inside of cylinder 412.
[0211] [00211] The 4.4 g (416) piston is made of a solid material of an inch in diameter (for example, PLEXIGLAS) and is machined to adapt hermetically without connection in the cylinder 412.
[0212] [00212] A standard weight of 317 g 418 is used to provide a restriction load of 62 053 dynes / cm2 (about 90Kpa (0.9Psi)). The weight is a cylindrical 1 inch diameter (2.54 cm) stainless steel weight that is machined for tight fit without connection to the cylinder.
[0213] [00213] Unless otherwise specified, a sample 410 corresponding to a layer of at least about 300 gsm (0.16 g) of SAP particles is used for AUL tests. Sample 410 is taken from SAP particles that are pre-sieved through U.S. standard # 30 mesh and retained over U.S. standard # 50 mesh. SAP particles can be pre-screened with, for example, a RO-TAP Mechanical Sieve Shaker Model B available from W.S. Tyler, Inc., Mentor, Ohio. Sifting is conducted for about 10 minutes.
[0214] [00214] The interior of cylinder 412 is wrapped with an antistatic cloth before placing particles SAP 410 in cylinder 412.
[0215] [00215] The desired amount of the SAP sample in sieved particles 410 (about 0.16 g) is weighed on a weighing weight and evenly distributed on the wire cloth 414 at the bottom of cylinder 412. The weight of the SAP in particles at the bottom of the cylinder it is noted as 'AS', for use in the AUL calculation described below. Care is taken to ensure that no particulate SAP is adhered to the cylinder wall. After careful placement of a 4.4 g 412 piston and a 317 g 418 weight on the SAP 410 particles in the 412 cylinder, the AUL 400 assembly including the cylinder, piston, weight, and SAP particles is weighed, and the weight is noted as 'A' weight.
[0216] [00216] A sintered glass frit 424 (described above) is placed in plastic tray 420, with saline solution 422 added to a level equal to that of the top surface of glass frit 424. A single circle of filter paper 426 is placed gently on the glass frit 424, and the assembly of AUL 400 with the particulate SAP 410 is then placed on filter paper 426. The assembly of AUL 400 is then left to remain on filter paper 426 for a test period of one hour, with due attention to maintaining saline level in the constant tray. At the end of the one hour test period, the AUL apparatus is then weighed, with this value noted as 'B' weight.
[0217] [00217] AUL (90Kpa (0.9Psi)) is calculated as follows: AUL (90Kpa (0.9Psi)) = (BA) / AS Where
[0218] [00218] A = unitary AUL weight with dry SAP
[0219] [00219] B = weight of AUL unit with SAP after 60 minutes of absorption
[0220] [00220] SA = actual SAP weight
[0221] [00221] A minimum of two tests are performed and the results are averaged to determine the value of AUL under load of 90Kpa (0.9Psi). Particulate SAP samples are tested at about 23oC and about 50% relative humidity. FAT test
[0222] [00222] The Pressure Absorbency Index is the sum of the pressure absorbance values (described here below) for a SAP determined under the following loads: 690 dynes per square centimeter (0.01 pound per square inch); 19995 dynes per square centimeter (0.29 pounds per square inch); 39300 dynes per square centimeter (0.57 pounds per square inch); and 62053 dynes per square centimeter (0.90 pounds per square inch). That is, the Absorbance Under Load values for a given SAP are determined under the restraining forces shown above according to the process shown below in connection with the examples. The absorbance values under load determined under the constraint loads shown above are then totaled to produce the Pressure Absorbency Index. Moisture Content Test
[0223] [00223] The amount of water content, measured as "% moisture", can be measured as follows: 1) Weigh 5.0 grams of superabsorbent polymer (SAP) composition precisely in a pre-weighed aluminum saucepan heavy; 2) place the SAP and casserole in a standard laboratory oven preheated to 105oC for 3 hours; 3) remove and re-weigh the casserole and contents; and 4) calculate the moisture percentage using the following formula: Moisture% = {((casserole weight + initial SAP weight) - (dried SAP & casserole weight)) * 100} / initial SAP weight Examples
[0224] [00224] The following comparative examples 1-4, and Examples 1-12 and Tables 1 and 2 are provided to illustrate the inventions of products including particulate superabsorbent polymer and processes for making superabsorbent particulate polymer as shown in the claims, and not limit the scope of the claims. Unless otherwise stated, all parts and percentages are based on the dry particulate superabsorbent polymer.
[0225] [00225] Example 1 In a polyethylene vessel equipped with a stirrer and cooling spirals, 2.0 kg of 50% NaOH and 3.32 kg of deionized water were added and cooled to 20oC. 0.8 kg of glacial acrylic acid was then added to the caustic solution and the solution again cooled to 20oC. 0.6 g of polyethylene glycol monoaryl ether acrylate, 1.2 g of ethoxylated trimethylol propane triacrylate product SARTOMER 9035, and 1.6 kg of glacial acrylic acid were added to the first solution, followed by cooling to 4-6oC. Nitrogen was bubbled through a monomer solution for about 5 minutes. Dissolve 4.38 g of sodium bicarbonate, 0.0364 g of Tween 80 and 0.0364 g of Span20 in 95.55 g of water. Add the mixture to the monomer solution to mix it with Silverson High Shear Mixer at 6500 rpm for 30 seconds. The monomer solution was then discharged into a rectangular tray. 80 g of 1% by weight aqueous solution of H2O2, 120 g of 2% by weight aqueous solution of sodium persulfate, and 72 g of 0.5% by weight aqueous solution of sodium erythorbate were added to the monomer solution to start polymerization reaction. The stirrer was stopped and the initiated monomer was allowed to polymerize for 20 minutes.
[0226] [00226] The resulting hydrogel was cut and extruded with a commercial Hobart 4M6 extruder, followed by drying in a forced air oven Procter & Schwartz Model 062 at 175oC for 12 minutes with upward flow and 6 minutes with downward air flow over a tray perforated metal of 20 inches x 40 inches for a final product moisture level of less than 5% by weight. The dried material was crushed - coarse in a Prodeva Model 315-S grinder, ground in a MPI 666-F three-stage roller mill and sieved with Minox MTS 600DS3V to remove particles greater than 850 microns and less than 150 microns.
[0227] [00227] 8g of ethylene carbonate solution (50% weight / weight in water) was applied to the 400 g surface of the above particles. Use a finely atomized spread from a Paasche VL spreader while the superabsorbent polymer particles were fluidized in air and continuously mixed. The coated material was then heated in a convection oven at 185oC for 55 minutes for surface crosslinking. The cross-linked surface particulate material was then sieved with standard 20/100 mesh US sieves to remove particles greater than 850 microns and less than 150 microns. The cross-linked particulate material was cooled to below 60oC and coated with a solution containing 0.4 g of polyethylene glycol (molecular weight 8000) and 40 g of deionized water. The coated material was relaxed at room temperature for one day and then sieved with standard 20/100 mesh US sieves to remove particles greater than 850 microns and less than 150 microns.
[0228] [00228] The following is a representation of PSD and average particle diameter (D50) of example 1:
[0229] [00229] Example 2 - Same as Example 1, except that 0.364 g of Tween 80 and 0.0364 g of Span20 were replaced with 0.0364 g of Tween 80 and 0.0364 g of Span40.
[0230] [00230] Example 3 - Same as example 1, except that 0.0364 g of Tween 80 and 0.0364 g of Span20 were replaced with 0.0364 g of Tween 80 and 0.0364 g of Span60.
[0231] [00231] Example 4 - Same as example 1, except that 0.0364 g of Tween 80 and 0.0364 d of Span20 were replaced with 0.0364 g of Tween 20 and 0.0364 g of Span20.
[0232] [00232] Example 5 - Same as example 1, except that 0.0364 g of Tween 80 and 0.0364 g of Span20 were replaced with 0.0364 g of Tween 40 and 0.0364 g of Span20.
[0233] [00233] Example 6 - Same as example 1, except that 0.0364 g of Tween 80 and 0.0364 g of Span20 were replaced with 0.0364 g of Tween 60 and 0.0364 g of Span20.
[0234] [00234] Control Comparative Example 1 - Superabsorbent polymer with regular cross-linked surface without surfactant or foaming agent.
[0235] [00235] Comparative Example 2 - includes a surfactant mixture of 0.0364 g of Tween 80 and 0.0364 g of Span20 but no foaming agent.
[0236] [00236] Comparative Example 3 - Example 1 which includes only 0.025% Span20 but no Tween 80.
[0237] [00237] Comparative Example 4 - Example 1 which includes only 0.025% Tween 80 but no Span20. Neutralized aluminum salt A
[0238] [00238] 200 g of aluminum sulphate solution (20% aqueous solution) was stirred in a beaker with a magnetic stir bar. To this solution, sodium hydroxide solution (50% aqueous solution) was added until the pH of the mixture had reached 7. In total 130 g of sodium hydroxide solution were consumed. The white colloidal solution was stirred for 15 minutes and still sheared with a Turnax mixer for about 1 minute to break up lumps. The neutralized aluminum solution was used to modify the superabsorbent polymer without further purification.
[0239] [00239] Example 7 - Example 1 was changed where the material in particles of cross-linked surface was cooled to below 60oC and coated with a solution containing 16 g of Neutralized Aluminum Salt A and 0.4 g of polyethylene glycol (weight molecular 8000) and 40 g of deionized water. The coated material was relaxed at room temperature for one day and then sieved with standard 20/100 mesh US sieves to remove particles greater than 850 microns and less than 150 microns.
[0240] [00240] Example 8 - 16 g of Neutralized Aluminum Salt A and 8 g of ethylene carbonate solution (50% weight / weight in water) were applied to the surface of 400 g of SAP from Example 1 using a finely atomized spray of a Paasche VL spreader while the SAP particles were fluidized in air and continuously mixed. The coated material was then heated in a convection oven at 185oC for 55 minutes for surface crosslinking. The cross-linked surface particulate material was then sieved with standard 20/100 mesh US sieves to remove particles greater than 850 microns and less than 150 microns. The cross-linked particulate material was cooled to below 60oC and coated with a solution containing 16 g of Neutralized Aluminum Salt A and 0.4 g of polyethylene glycol (molecular weight 8000) and 40 g of deionized water. The coated material was relaxed at room temperature for one day and then sieved with standard 20/100 mesh US sieves to remove particles greater than 850 microns and less than 150 microns.
[0241] [00241] Example 9 - 0.02% by weight of thermoplastic polymer of ethylene - acrylic acid and 8 g of ethylene carbonate solution (50% by weight / weight in water) were applied on the surface of 400 g of Example SAP 1 using a finely atomized spread of a Paasche VL spreader while the SAP particles were fluidized in air and continuously mixed.
[0242] [00242] Example 10 - The particulate material of the crosslinked surface of Example 1 was cooled to below 60oC and coated with a solution containing 0.2 wt% diethylene triamine penta acetic acid salt, Na5DTPA) and 0.4 g of polyethylene glycol (molecular weight 8000) and 40 g of deionized water. The coated material was relaxed at room temperature for one day and then sieved with standard 20/100 mesh US sieves to remove particles greater than 850 microns and less than 150 microns.
[0243] [00243] Example 11 - Example 1 was changed to add 0.5% by weight of kaolin clay to the hydrogel of Example 1.
[0244] [00244] Example 12 - Same as Example 1, except that the 1.2 g of ethoxylated trimethylol propane triacrylate SARTOMER 9035 internal crosslinker is replaced with 1.705 g of Dynasylan 6490 poly siloxane (0.275% good), 0.744 g of diacrylate polyethylene glycol 300 (Peg300DA) (0.120% good), 0.12 g of mono allyl ether polyethylene glycol acrylate (PEGMAE) (0.120% good). The product of Example 12 has a 2.7 g / g CRC increase.
[0245] [00245] Notwithstanding that the numerical ranges and parameters establishing the broad scope of the invention are approximations, the numerical values shown in the specific examples are reported as precisely as possible. Elsewhere than in the operative examples, or where otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so on used in the specification and claims are to be understood as being modified in all examples by term "fence". Any numerical value, however, inherently contains certain errors, necessarily resulting from the standard deviation found in their respective test measurements.

权利要求:
Claims (20)
[0001]
Process for the manufacture of a superabsorbent polymer in particles with rapid water absorption, characterized by the fact that it comprises the steps of: (a) preparing an aqueous monomer solution from a mixture of a monomer containing polymerizable unsaturated acid group and an internal cross-linking agent monomer where the aqueous monomer solution comprises dissolved oxygen; (b) spraying the aqueous monomer solution from step (a) including adding an inert gas to the aqueous monomer solution from step (a) to replace the dissolved oxygen from the aqueous monomer solution; (c) polymerize the aqueous monomer solution from step (b) including the (c1) addition to the aqueous solution of step monomer (a): (i) an aqueous solution comprising from 0.05 to 2.0% by weight, based on the total amount of the monomer solution containing polymerizable unsaturated acid group of a foaming agent; and (ii) an aqueous solution comprising from 0.001 to 1.0% by weight, based on the total amount of the monomer solution containing polymerizable unsaturated acid group of a mixture of a lipophilic surfactant and a polyethoxylated hydrophilic surfactant; (c2) treating the monomer solution from step c1) with a high-speed shear mixture to form a treated monomer solution, the components of (i) an aqueous solution comprising 0.1 to 1.0% by weight of a foaming agent; and (ii) an aqueous solution comprising from 0.001 to 1.0% by weight of a mixture of a lipophilic surfactant and a hydrophilic polyethoxylated surfactant are added to the aqueous mo-number solution after step (b) of spreading aqueous solution of monomer and before step (c2) of high speed shear mixing of the aqueous monomer solution; (c3) form a hydrogel by adding a polymerization initiator to the step-treated monomer solution (c2) where the initiator is added to the treated monomer solution after the foaming agent and the surfactant mixture, where the polymer is formed to include bubbles of the foaming agent in the polymer structure; (d) drying and crushing hydrogel of step c) to form particulate superabsorbent polymer; and (e) surface crosslinking of superabsorbent polymer in step particles (d) with a crosslinking agent where the surface crosslinked superabsorbent polymer has a vortex of 30 seconds to 60 seconds.
[0002]
Process according to claim 1, characterized by the fact that the lipophilic surfactant is non-ionic and has an HLB of 4 to 9, and the hydrophilic polyethoxylated surfactant is non-ionic and has an HLB of 12 to 18.
[0003]
Process according to claim 1, characterized by the fact that the mixture of a lipophilic surfactant and a polyethoxylated hydrophilic surfactant has an HLB of 8 to 14.
[0004]
Process according to claim 1, characterized by the fact that the lipophilic surfactant is a sorbitan ester, and the polyethoxylated hydrophilic surfactant is a polyethoxylated sorbitan ester.
[0005]
Process according to claim 1, characterized in that the foaming agent is selected from a metal carbonate or alkali metal bicarbonate.
[0006]
Process, according to claim 1, characterized by the fact that the superabsorbent polymer has a pressure absorbance index of 120 to 150.
[0007]
Process according to claim 1, characterized by the fact that it comprises from 0.05 to 1.0% by weight, based on the total amount of the monomer solution containing polymerizable unsaturated acid group of the polymerization initiator.
[0008]
Process according to claim 1, characterized in that said particulate superabsorbent polymer composition has particle diameters less than 600 micrometers and greater than 150 micrometers in an amount not less than 85% by weight of the superabsorbent polymer composition in particles and as specified by standard sieve classification and the particles having a weight average diameter (D50) specified by standard sieve classification of 300 to 400 micrometers.
[0009]
Process, according to claim 1, characterized by the fact that it also comprises the step of: (e) mixing cross-linked surface superabsorbent polymer with a chelating agent, the amount of the chelating agent being from 0.001 to 10 parts by weight per 100 parts by weight of the particulate superabsorbent polymer.
[0010]
Process according to claim 9, characterized by the fact that the chelating agent is selected from amino carboxylic acids with at least three carboxyl groups and their salts.
[0011]
Process according to claim 1, characterized by the fact that it comprises the step of adding 0.01 to 0.5% by weight of a thermoplastic polymer based on the pulverized weight of dry polymer is applied on the particle surface, being that the thermoplastic polymer is both added to the particulate superabsorbent polymer with the crosslinking agent and applied to the particulate superabsorbent polymer before the surface crosslinking agent is added to the particulate superabsorbent polymer, thermally treating the coated superabsorbent polymer particle in a temperature between 150oC and 250oC for 0.5 to 60 minutes to effect the surface cross-linking of the superabsorbent polymer particle.
[0012]
Process according to claim 11, characterized by the fact that the thermoplastic polymer is selected from polyethylene, polyesters, polyurethanes, linear low density polyethylene (LLDPE), ethylene-acrylic acid copolymer (EAA), styrene copolymers, copolymer ethylene - alkyl methacrylate (EMA), polypropylene (PP), ethylene - vinyl acetate copolymer (EVA) or combinations thereof, or copolymers.
[0013]
Process according to claim 11, characterized in that the thermoplastic polymer is added to the superabsorbent polymer in particles with a surface crosslinking agent.
[0014]
Process according to claim 11, characterized in that the thermoplastic polymer is added to the particulate superabsorbent polymer before the surface crosslinking agent (c) is added to the particulate superabsorbent polymer.
[0015]
Superabsorbent particulate polymer, characterized by the fact that it comprises an internal cross-linking structure, produced using 0.1 to 1.0% by weight, based on the total amount of the monomer solution containing polymerizable unsaturated acid group of a forming agent foam and 0.001 to 1.0% by weight, based on the total amount of the monomer solution containing polymerizable unsaturated acid group particle, the particle presenting a surface that has been subjected to a crosslinking treatment for surface crosslinking, the particulate superabsorbent polymer having a Vortex time of 30 to 60 seconds.
[0016]
Particle superabsorbent polymer according to claim 15, characterized by the fact that the lipophilic non-ionic surfactant has a HLB of 4 to 9, the lipophilic non-ionic surfactant has a HLB of 4 to 9, and the polyethylated hydrophilic non-ionic surfactant has an HLB of 12 to 18.
[0017]
Particle superabsorbent polymer according to claim 15, characterized by the fact that the mixture of a lipophilic non-ionic surfactant and a polyethoxylated hydrophilic non-ionic surfactant has an HLB of 8 to 14.
[0018]
Superabsorbent particulate polymer according to claim 17, characterized by the fact that the lipophilic non-ionic surfactant is a sorbitan ester, and the polyethoxylated hydrophilic non-ionic surfactant is a polyethoxylated sorbitan ester.
[0019]
Particulate superabsorbent polymer according to claim 15, characterized in that said particulate superabsorbent polymer composition has particles with particle diameters of less than 600 micrometers and greater than 150 micrometers in an amount not less than 85% by weight of the superabsorbent polymer composition in particles and as specified by standard sieve classification and particles having a weight average particle diameter (D50) specified by standard sieve classification of 300 to 400 micrometers.
[0020]
Absorbent article, characterized by the fact that it comprises: a top sheet; a backsheet; an absorbent core disposed between the topsheet and the backsheet, the absorbent core comprising a particulate superabsorbent polymer composition comprising an internal crosslinking structure, from 0.1 to 1.0% by weight, based on the total amount of the solution of monomer containing polymerizable unsaturated acid group of a foaming agent, and from 0.001 to 1.0% by weight, based on the total amount of the monomer solution containing polymerizable unsaturated acid group of a mixture of a non-ionic lipophilic surfactant and a non-ionic hydrophilic polyethoxylated surfactant in an interior of the particle, the particle having a surface that has undergone a crosslinking treatment for surface crosslinking, the superabsorbent polymer in particles having a vortex time of 30 to 60 seconds.

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同族专利:

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公开号 | 公开日

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CN104974312B|2020-06-12|

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JP6087973B2|2017-03-01|

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TW201609892A|2016-03-16|

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CN104974312A|2015-10-14|

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KR101764609B1|2017-08-03|

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JP2015199958A|2015-11-12|

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KR20150116418A|2015-10-15|

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BR102015007414A2|2015-12-29|

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法律状态:
2015-12-29| B03A| Publication of an application: publication of a patent application or of a certificate of addition of invention|

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2018-02-27| B06F| Objections, documents and/or translations needed after an examination request according art. 34 industrial property law|

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2019-12-17| B06U| Preliminary requirement: requests with searches performed by other patent offices: suspension of the patent application procedure|

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2020-11-17| B09A| Decision: intention to grant|

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2021-01-12| B16A| Patent or certificate of addition of invention granted|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 01/04/2015, 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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US14/246,451|2014-04-07|

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EP14163666.2|2014-04-07|

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US14/246,451|US20150283284A1|2014-04-07|2014-04-07|Superabsorbent polymer having fast absorption|

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EP14163666.2A|EP2930191B1|2014-04-07|2014-04-07|Superabsorbent polymer having fast absorption|

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