• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The invention is directed to the provision of polyimide fibers which are suitable for high temperature applications such as protective clothing, insulation or hot gas filtration and which better maintain elastic properties and strength and show little shrinkage, especially at temperatures above 260 ° C.
    公开号:AT17296U1
    申请号:TGM50146/2020U
    申请日:2020-07-22
    公开日:2021-11-15
    发明作者:
    申请人:Evonik Fibres Gmbh；
    IPC主号:
    专利说明:

    description
    POLYIMIDE FIBERS FOR HOT GAS FILTRATION
    FIELD OF THE INVENTION
    The invention is directed to the provision of polyimide fibers that are suitable for high temperature applications, such as protective clothing, insulation or hot gas filtration and that better maintain elastic properties and strength and show little shrinkage, especially at temperatures above 260 ° C.
    BACKGROUND OF THE INVENTION
    In a dry spinning process from a polyimide solution by evaporation of the solvent spun and then stretched at high temperatures fibers made from a 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride (= BTDA) and a mixture of 4,4'-methylenebis ( phenyl diisocyanate) (= MDI) and 2,4- and 2,6-toluene diisocyanate (= TDI) are known from US Pat. No. 3,985,934 and US Pat. No. 4,801,502 and are commercially available from Evonik Fibers GmbH under the trade name P848®. These fibers have good stability at temperatures up to 260 ° C and can be used to manufacture filters for hot gas filtration. Bag filters, which include needle felts made from P84® fibers, are commonly used for hot gas filtration in cement production and in power plants.
    No. 5,120,814 discloses a polyimide produced from 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride and a mixture of only 2,4- and 2,6-toluene diisocyanate in the presence of a sodium methylate catalyst, with a higher glass transition temperature and improved thermal stability, which is dry-spun Fibers.
    No. 5,384,390 discloses the production of polyimide fibers by a dry spinning process with subsequent heat treatment in the undrawn state. The resulting fibers show little shrinkage at temperatures of up to 280 ° C, but have a lower strength of 15-22 cN / tex than drawn P84® fibers, which makes them less suitable for hot gas filtration and protective clothing.
    WO 2011/009919 and WO 2014/202324 disclose the production of hollow fiber membranes for gas separation from a mixture of 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride and 1,2,4,5-benzenetetracarboxylic dianhydride (= PMDA ) and a mixture of 2,4- and 2,6-toluene diisocyanate polyimide produced by a wet spinning process with phase inversion coagulation of the polyimide. Hollow fibers obtained by this wet spinning process have a macroporous structure and a circular cross-section.
    SUMMARY OF THE INVENTION
    In the course of the present invention it has now been found that the polyimide fibers of the prior art used for hot gas filtration suffer a loss of elastic properties when used at temperatures above 260 ° C, whereby the filter cake removal from hot gas filtration bag filters is less efficient, which leads to increased Loss of pressure in the filter and requires more frequent filter cleaning by means of pressure pulses. Maintaining elasticity is a critical property for the polyimide fiber when used in hot gas filtration as well as in textile fiber applications such as protective clothing. Here, the elastic properties of the polyimide fiber are a prerequisite for the garment to keep its shape and not become stiff and inflexible over time. These elastic properties can be assessed using the bending length in accordance with DIN EN ISO 9073-7 and DIN 53362. In the course of the invention it was also found that from a mixture of 3,3 ', 4,4'-benzophenonetetracarboxylic acid dianhydride and 1,2,4,5-benzene tetracarboxylic acid dianhydride and a mixture of 2,4- and 2,6-toluene diisocyanate Polyimide fibers produced by a dry spinning process show their elastic properties at higher levels
    Maintain temperatures above 260 ° C. Hot gas filters made from these new polyimide fibers are therefore less susceptible to performance losses as a result of their maximum operating temperature being exceeded than filters made from polyimide fibers of the prior art. In the course of the invention it was also found that drawn fibers made from this polyimide have a high strength, but surprisingly show much less shrinkage, in particular at temperatures of more than 260 ° C., than drawn polyimide fibers of the prior art from a dry spinning process.
    The invention therefore provides a polyimide fiber comprising a polyimide which comprises monomer units of the formula (I):
    oO Oo (*) N RA N— RB (**) sy
    {))
    where R * is selected from the group consisting of 3,3 '', 4,4'-Benzophenontetrayl (R "') and 1,2,4,5 Phenylenetetrayl (R" ),
    where the molar ratio of R “': R * in the monomer units of the formula (I) in the polyimide is 95: 5 to 50:50,
    where R is selected from the group consisting of 2,4-toluenediyl and 2,6-toluenediyl,
    wherein the polyimide fiber has a strength of more than 30 cN / tex
    and where the radicals RP ”in the monomer units in the polyimide are the same or different and where the bond indicated by“ (*) ”binds a monomer unit to the bond indicated by“ (**) ”of the adjacent monomer unit.
    A second aspect of the present invention is a method of making a polyimide fiber comprising the steps of:
    (a) Preparing a solution of a polyimide comprising monomer units of the formula (I):
    Oo oO (*) LS Re (**) a!
    ())
    where R * is selected from the group consisting of 3,3 ', 4,4'-Benzophenontetrayl (R "') and 1,2,4,5Phenylenetetrayl (R" ), where the molar ratio of R "': R" in the monomer units of the formula (I) in the polyimide is 95: 5 to 50:50, where R is selected from the group consisting of 2,4-toluenediyl and 2,6-toluenediyl, the polyimide fiber having a strength of more than 30 cN / tex and the radicals R in the monomer units in the polyimide are the same or different and where the bond indicated by "(*)" binds a monomer unit to the bond indicated by "(**)" of the adjacent monomer unit, in a dipolar aprotic solvent;
    (b) spinning the obtained solution by a dry spinning method in a gas atmosphere having a temperature of 160 ° C to 350 ° C to obtain a fiber;
    (c) drying the fiber at a temperature of 180 ° C to 220 ° C to obtain a dried
    neten fiber; and (d) drawing the dried fiber at a temperature of 280 ° C to 440 ° C by a factor of 1: 2 to 1: 6.
    Detailed description of the invention
    The polyimide fiber according to the first aspect of the invention comprises a polyimide comprising monomer units of the formula (I):
    oO oO (*)> RR (**) X
    oO O (N
    where R * from the group consisting of R “'= 3,3', 4,4'-Benzophenontetray and R * = 1,2,4,5phenylenetetrayl is selected,
    where the molar ratio of R * ': R “ in all monomer units of the formula (I) in the polyimide is 95: 5 to 50:50, preferably 65:35 to 55:45, more preferably 60:40,
    where R is selected from the group consisting of 2,4-toluenediyl, 2,6-toluenediyl,
    wherein the polyimide fiber has a strength of more than 30 cN / tex, preferably from 35 to 60 cN / tex, even more preferably from 40 to 50 cN / tex
    and where the radicals RP in the monomer units in the polyimide are identical or different, preferably different,
    in those preferred cases in which the polyimide 2,4-toluenediyl and 2,6-toluenediyl as R comprises, it is preferred that the molar ratio of groups 2,4-toluenediyl: 2,6-toluenediyl in all monomer units of the formula (I) in the polyimide is 1: 9 to 9: 1, more preferably 3: 1 to 17: 3, is very particularly preferably 4: 1,
    and where the bond indicated with “(*)” binds a monomer unit to the bond indicated with “(**)” of the adjacent monomer unit.
    It was surprisingly discovered that the fiber according to the invention has a strength of more than 30 cN / tex, preferably 35 to 60 cN / tex, even more preferably 40 to 50 cN / tex, very particularly preferably 42 cN / tex. This strength distinguishes the fiber of the invention from the fibers of the prior art. The characteristics of the manufacturing process for the fiber described below give the fiber other, advantageous structural properties, which are reflected in this higher strength. Because of its higher strength, the fiber according to the invention is particularly suitable for textile applications.
    “Strength” is determined in accordance with DIN EN ISO 5079 in the context of the present invention. The unit “cN / tex” is known to the person skilled in the art and means the average maximum tensile strength per textile fiber as determined in accordance with DIN EN ISO 5079, where “tex” means 1 g per 1 km of fiber.
    In formula (I), R "is from the group consisting of R" '= 3,3', 4,4'-Benzophenontetrayl and RR - 1,2,4,5-phenylenetetrayl selected.
    In the polyimide, the molar ratio of R "* 'to R" in all monomer units of the formula (I) in the polyimide 95: 5 to 50:50, preferably 65:35 to 55:45, more preferably 60:40. “The molar ratio of R” * 'to R * in all monomer units of formula (I) in the polyimide "refers to the molar ratio of R" 'to R " over all monomer units of the formula (I) in a given polyimide polymer chain.
    This molar ratio can be controlled by the respective amounts of BTDA and PMDA which are added in the synthesis of the polyimide. In a given polyimide
    this molar ratio can be determined by hydrazinolysis and HPLC analysis.
    The polyimide preferably comprises at least 10 monomer units of the formula (1), even more preferably at least 100 monomer units of the formula (I), even more preferably 100 to 10,000, even more preferably 100 to 5000 and even more preferably 100 to 1000 monomer units Formula 1).
    In formula (I), R selected from the group consisting of 2,4-toluenediyl and 2,6-toluenediyl. In the monomer units of the formula (I) in the polyimide, the RP radicals are identical or different. They are preferably different, which means that the polyimide comprises 2,4-toluenediyl and 2,6-toluenediyl as R®. In those preferred cases in which the polyimide comprises 2,4-toluenediyl and 2,6-toluenediyl as R®, it is more preferred that the molar ratio of groups 2,4-toluenediyl: 2,6-toluenediyl in all monomer units of the Formula (I) in which the polyimide is 1: 9 to 9: 1, more preferably 3: 1 to 17: 3, very particularly preferably 4: 1.
    "The molar ratio of groups 2,4-toluenediyl: 2,6-toluenediyl in all monomer units of the formula (I) in the polyimide" refers to the molar ratio of 2,4-toluenediyl to 2,6-toluenediyl over all Monomer units of the formula (I) in a given polyimide polymer chain.
    This molar ratio can be controlled by the respective amounts of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate which are added in the synthesis of the polyimide. In a given polyimide, this molar ratio can be determined by hydrazinolysis and HPLC analysis.
    In a preferred embodiment, the polyimide fiber of the present invention has a fineness (fiber diameter) of 0.6 to 10 dtex, preferably 1.0 to 5.5 dtex. According to the invention, “fineness (fiber diameter)” is measured in accordance with DIN EN ISO 1973, point 8.2 (vibroscope method).
    It is further preferred that the polyimide fiber of the invention has a non-circular cross-section with a perimeter that has both convex and concave portions. This is advantageous because the fiber has a higher specific surface and thus a higher filtration efficiency compared to round-shaped fibers.
    The end group of the first repeating unit of the polyimide according to the invention, which is present for this in the formula (I) at the bond defined by "(*)", and the end group of the last repeating unit of the polyimide according to the invention, which is for this in the formula ( I) at the bond defined by “(**)” are not particularly limited and result from the polymerization process used in the process for producing the polyimide according to the second aspect of the invention. These end groups composed of hydrogen, hydroxyl and a phenyl radical, which may optionally be replaced by at least one composed of NH; and -COOH selected group may be substituted. These end groups are more preferably selected from 4-aminophenyl and a phenyl group substituted by two —COOH groups.
    The polyimide of the invention preferably comprises at least 80% by weight of monomer units of the formula (I), more preferably at least 90% by weight of monomer units of the formula (|), even more preferably at least 95% by weight of monomer units of the formula ( 1), even more preferably at least 99% by weight of monomer units of the formula (I), even more preferably at least 99.9% by weight of monomer units of the formula (I). The polyimide according to the first aspect of the invention very particularly preferably consists of monomer units of the formula (I), the end group of the first repeating unit of the polyimide according to formula (I) at the bond defined by “(*)” and the end group of the last repeating unit Polyimides according to formula (I) on the bond defined by “(**)” from the group consisting of hydrogen, hydroxyl and a phenyl radical, which is optionally replaced by at least one of NH; and -COOH selected group may be substituted. These end groups are more preferably selected from the group consisting of 4-aminophenyl and a phenyl group substituted by two —COOH groups.
    The polyimide fiber of the invention preferably comprises more than 90 wt .-%, preferably more than 99.7 wt .-%, more preferably more than 99.9 wt .-%, of the polyimide of the formula (I), where it The remainder is a content of final treatment agents, such as finishing agents, antistatic agents and residual solvents, which is normally below 10% by weight, more preferably below 0.3% by weight, very particularly preferably below 0.1% by weight. %, lies.
    The polyimide fibers according to the invention retain their elastic properties and show much less shrinkage than fibers of the prior art at higher temperatures of more than 260.degree. C., preferably in a range from 280.degree. C. to 550.degree. C., more preferably 280 ° C to 450 ° C.
    The polyimides which are part of the polyimide fiber according to the present invention are produced by a process for producing a polyimide fiber comprising the steps of:
    (a) Preparation of a solution of a polyimide of the formula (I):
    oO oO (* LS Re (+) N oO Oo {l)
    where R “from the group consisting of R“ '= 3,3', 4,4'-Benzophenontetrayl and R * = 1,2,4,5-phenylenetetrayl is selected, the molar ratio of R * ': R * in all monomer units of the formula (I) in the polyimide is 95: 5 to 50:50, preferably 65:35 to 55:45, more preferably 60:40, where R is selected from the group consisting of 2,4-toluene diyl, 2,6-toluene diyl, the polyimide fiber having a strength of more than 30 cN / tex, preferably from 35 to 60 cN / tex, even more preferably from 40 to 50 cN / tex, and where the radicals R® in the monomer units in the polyimide are the same or different, it being preferred in those preferred cases in which the polyimide comprises 2,4-toluenediyl and 2,6-toluenediyl as R ”that the molar ratio of groups 2,4-toluenediyl: 2,6-toluenediyl in all monomer units of the formula (I) in the polyimide is 1: 9 to 9: 1, more preferably 3: 1 to 17: 3, very particularly preferably 4: 1, and wherein the bond of one monomer unit indicated by “(*)” binds to the bond indicated by “(**)” of the adjacent monomer unit, in a dipolar aprotic solvent;
    (b) spinning the obtained solution by a dry spinning method in a gas atmosphere having a temperature of 160 ° C to 350 ° C to obtain a fiber;
    (c) drying the fiber at a temperature of 180 ° C to 220 ° C to obtain a dried fiber; and
    (d) drawing the dried fiber at a temperature of 280 ° C. to 440 ° C., preferably 280 ° C. to 420 ° C., by a factor of 1: 2 to 1: 6, preferably 1: 4.
    Step (a) of the method for producing a polyimide fiber is known to the person skilled in the art and is described, for example, in WO 2014/202324 A1.
    A solution according to step (a) of the method for producing a polyimide fiber is preferably produced by first producing the polyimide. The polyimides used according to the present invention can be prepared by polycondensation of a mixture of the two dianhydride compounds, which are used in the respective molar ratio of 95: 5 to 50:50, preferably 65:35 to 55:45, more preferably 60:40, namely 3.4 , 3 ', 4'-Benzophenonetetracarboxylic acid dianhydride (= BTDA) and 1,2,4,5-Benzoltetracarboxylic acid dianhydride (= PMDA) with one or both of the compounds 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate
    Release of carbon dioxide can be produced. In those preferred embodiments in which 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate are used in step (a) of the process for preparing a polyimide according to the invention, it is further preferred that the in step (a) of the process for Preparation of a polyimide fiber according to the invention, the molar ratio of 2,4-tolylene diisocyanate to 2,6-tolylene diisocyanate used is 1: 9 to 9: 1, more preferably 3: 1 to 17: 3, most preferably 4: 1.
    The polymerization is preferably carried out in an aprotic dipolar solvent. The aprotic dipolar solvent is preferably at least one from the group consisting of dimethylformamide, dimethylacetamide, N-methylpyrrolidone, N-ethylpyrrolidone and sulfolane.
    Here, the mixture of aromatic dianhydrides is preferably dissolved in such a way that the sum of the concentration of both dianhydrides is in the range between 10% by weight and 40% by weight, preferably between 18% by weight and 32% by weight and more preferably between 22% by weight and 28% by weight in an aprotic dipolar solvent. The mixture obtained is then preferably heated to 50.degree. C. to 150.degree. C., preferably 70.degree. C. to 120.degree. C. and more preferably 80.degree. C. to 100.degree. This solution is preferably 0.01% by weight to 5% by weight, preferably 0.05% by weight to 1% by weight and more preferably 0.1% by weight to 0.3% by weight mixed with a basic catalyst. The basic catalyst is preferably at least one from the group consisting of tertiary amines, alkali or alkaline earth metal hydroxides, alkali or alkaline earth metal methoxides, alkali or alkaline earth metal ethoxides, alkali or alkaline earth metal carbonates and alkali or alkaline earth metal phosphates.
    Alkali or alkaline earth metal hydroxides, methoxides, ethoxides, carbonates and phosphates are even more preferably selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium carbonate, sodium hydrogen carbonate, potassium carbonate, potassium hydrogen carbonate, potassium phosphate, Potassium hydrogen phosphate and potassium dihydrogen phosphate were selected.
    Tertiary amines are even more preferably selected from the group consisting of trimethylamine, triethylamine, tripropylamine, diazabicycloundecane, diazabicyclooctane and dimethylaminopyridine.
    Preferably, water is also added to the solution. If water is mixed into the solution, it is even more preferred to use water in an amount of 0.001% by weight to 1% by weight, preferably 0.013% by weight to 0.65% by weight, more preferably 0.026% by weight. % to 0.26% by weight, more preferably 0.0325% by weight to 0.195% by weight, more preferably 0.039% by weight to 0.1625% by weight, very particularly preferably 0.15% by weight. -%, to be added, based on the total amount of 3,4,3 ', 4'-benzophenonetetracarboxylic dianhydride and 1,2,4,5-benzenetetracarboxylic dianhydride used in step (a) of the process.
    Then the diisocyanate, d. H. 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, both of which are mixed in, preferably over a period of 1 to 25 hours, more preferably 3 to 15 hours and even more preferably 5 to 10 hours.
    The molar ratio of the total molar weight of the sum of BTDA and PMDA to the total molar weight of the sum of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate is preferably in the range from 1.1: 0.9 to 0.9: 1.1, more preferably 1: 1.
    With the polymers used according to the present invention, a clear golden yellow to dark brown polymer solution with a viscosity between 1 and 300 Pa.s, preferably 20 and 150 Pa.s and more preferably 40 and 90 Pa.s. is produced in this way. The molar masses Mp are preferably above 100,000 g.mol ”.
    In the context of the present invention, "viscosity" refers to the dynamic viscosity n. The dynamic viscosity n is determined by shearing the polymer solution in a cylindrical gap at a constant temperature of 25 ° C. once by specifying various speeds Q (or Shear gradient y) and then by specifying different
    The measuring instrument used is a HAAKE RS 600 with a liquid-heated measuring cup holder TEF / Z28, a cylindrical rotor Z25DIN53019 / 1S03219 and an aluminum disposable measuring cup Z25E / D = 28 mm. The shear stress T is measured at a special shear gradient. The dynamic viscosity n is calculated from the following formulas and is given in Pa.s. for a shear gradient of 10 s *.
    T
    2 Z5N * Y Y
    The viscosity is a function of the real shear gradient yv = M * Q TtT shear stress n dynamic viscosity M shear factor of the rotor: 12350 rad / s Q angular velocity
    After the above process steps, the polyimide polymer of the present invention is obtained as a solution in an aprotic dipolar solvent. There are no disruptive accompanying substances or by-products in the polymer solution. For this reason it is also economically advantageous not to precipitate the polymer and then redissolve it in the same solvent. The solutions are therefore preferably used directly for producing the spinning solution without isolating the polymer and preferably also without any other further treatment.
    The polymer solutions obtained from the polycondensation preferably have a solids content between 15% by weight and 35% by weight, more preferably between 22% by weight and 30% by weight, even more preferably between 22% by weight and 29% by weight and very particularly preferably 25% by weight and can be used to produce the spinning solution without further treatment.
    The spinning solution is then preferably filtered. In the preferred cases in which it is filtered, it is even more preferred that the solution is degassed and freed from air bubbles after the filtration. This is generally done by applying a negative pressure with the help of a vacuum pump.
    The polyimide obtained after step (a) of the method and its preferred embodiments are as described for the polyimide in the polyimide fiber according to the invention.
    In step (b) of the process, the solution obtained from step (a) is spun in a dry spinning process in a gas atmosphere at a temperature of 160 ° C. to 350 ° C., and a fiber is obtained. Such a dry spinning process step differs from the wet spinning process described in WO 2014/202324 A1. Dry spinning processes are known to the person skilled in the art and are described, for example, in US Pat. No. 4,801,502, US Pat. No. 5,120,814 and US Pat. No. 5,384,390.
    A dry spinning process is known to the person skilled in the art and is characterized in that the solution containing the polymer, such as the spinning solution obtained in step (a), is spun through a spinneret and then, preferably partially, dried by a hot gas atmosphere, for example hot air. In step (b) of the method for producing a polyimide fiber, the solution obtained in step (a) is spun in a hot gas atmosphere having a temperature of 160.degree. C. to 350.degree.
    In step (b) of the method, the solution obtained in step (a) is preferably pressed through a circular opening in the spinneret. After drying, this typically leads to a non-circular cross-section of the fibers, which then has a circumference with both convex and concave sections. Such polyimide fibers with a non-circular cross-section with a circumference that has both convex and concave sections are particularly preferred because of their higher specific surface area and thus higher filtration efficiency compared to round-shaped fibers.
    The solution is preferably spun through a spinneret with at least 100, preferably at least 200, more preferably at least 400, even more preferably at least 600 and very particularly preferably at least 800 openings. The openings are preferably circular and even more preferably have a diameter of 1 to 1000 µm, more preferably 100 µm to 500 µm, even more preferably 200 µm.
    In step (b) of the process, there is preferably partial drying, i. H. partial evaporation of solvent from the fiber. “Partial” evaporation means that the solvent is not completely evaporated from the fiber. This more preferably means that at the end of step (b) the fiber contains up to 20% by weight of solvent, more preferably between 5 to 20% by weight of solvent, even more preferably between 10 to 15% by weight of solvent .
    In step (c) of the method, the fiber obtained in step (b) is then dried at a temperature of 210 ° C to 240 ° C and a dried fiber is obtained. This means that after step (b) the solvent content of the fiber is reduced and, in those cases in which partial solvent evaporation takes place in step (b), it is further reduced.
    At the end of step (c), the fiber preferably contains less than 5% by weight of solvent, more preferably less than 4% by weight of solvent, even more preferably less than 3.1% by weight of solvent, even further preferably less than 3% by weight of solvent.
    Step (d) of the method is the distinguishing step. In this step, it is preferred to draw the dried fiber obtained in step (c) at a temperature of from 280 ° C. to 440 ° C., preferably from 280 ° C. to 420 ° C., by a factor of 1: 2 to 1: 6 by a factor of 1: 3 to 1: 5, more preferably by a factor of 1: 3.5 to 1: 4.5, even more preferably by a factor of 1: 3.9 to 1: 4.1, completely particularly preferably carried out by a factor of 1: 4.
    This stretching step is typically carried out on a stretching unit consisting of heated rolls. Each roller has an individual temperature. The fiber bundles are wound around the rollers starting with the roller with the lowest temperature, and the last roller has the highest temperature. The draw ratio is set by different speeds of the inlet drive and the outlet drive, which carry the fiber bundle, and a gradual increase in the speed of the heated rollers. In a preferred embodiment, the speed of the first roller with the lower temperature is between 1 m / min to 30 m / min, preferably 5 m / min to 20 m / min, even more preferably 10 m / min, and the speed of the last roller is by a factor of 2 to 6, preferably by a factor of 3 to 5, more preferably by a factor of 3.5 to 4.5, even more preferably by a factor of 3.9 to 4.1, very particularly preferred by a factor of 4, higher. The temperature range between the roller with the lowest temperature and the roller with the highest temperature is preferably in the range from 280 ° C to 440 ° C, more preferably in the range from 280 ° C to 420 ° C.
    After step (d) of the process, a polyimide fiber according to the invention is obtained. This polyamide fiber is characterized in that it has a strength of more than 30 cN / tex, preferably from 35 to 60 cN / tex, more preferably from 40 to 50 cN / tex. This strength is much higher than in the case of the comparable fibers of the prior art (such as that described in WO 2014/2023241) and makes the polyimide fibers according to the invention much better for use as textile fibers (for example for weaving or for the production of needle felts) for hot gas filtration or heat protection equipment.
    After step (d), the method preferably contains a further step (e) in which the polyimide fiber obtained in step (d) is treated by a standard method such as crimping, coating.
    The following examples illustrate the invention without restricting it in any way.
    EXAMPLES
    EXAMPLE E1: PREPARATION OF A P84-HT FIBER ACCORDING TO THE INVENTION Step 1: Preparation of a P84-HT polyimide solution in dimethylformamide
    In a 2.5 m ° stainless steel reactor with stirrer, reflux condenser, two inline viscometers and a liquid metering system, 1775 kg of anhydrous dimethylformamide are presented at 80 ° C. 350 kg of 3,3 ‘, 4,4‘-benzophenonetetracarboxylic dianhydride (BTDA) and 158 kg of pyromellitic dianhydride (PMDA) are added as a solid to the reactor and dissolved in the solvent at 80 ° C. 500 g of sodium hydroxide and 770 g of water are added to the solution under nitrogen. After stirring for 15 minutes, 314 kg of a mixture of 80% 2,4-toluene diisocyanate and 20% 2,6-toluene diisocyanate are metered in under high pressure over a period of 7 hours with elimination of O »as a by-product until the target viscosity is reached. The highly viscous solution obtained has a golden color and a viscosity of 70 Pa.s. The molar masses are determined by gel permeation chromatography as follows:
    The molecular weights Mw, Mp and Mn were determined by means of gel permeation chromatography with calibration against polystyrene standards. The molecular weights given are therefore relative molecular weights.
    The following parameters and devices were used:
    WATERS 2690/5 (pump), 2489 UV detector
    HPLC guard column PSS SDV guard column 5 6 A column PSS SDV 10 at 1000, 10 ° and 10 ° A
    Eluent 0.01 M LiBr + 0.03 M H3sPO «4 in DMF (filtered with 0.45 µm)
    Flow rate 1.0 ml / min, run time 43 min
    Pressure 1100 psi 270 nm
    Detection wavelength
    50 ul or 20 ul (for solutions c> 19g / l) PS (polystyrene) standards (closely spaced, 600-3x106, PSS)
    Injection volumes
    Standards
    The following molecular weights were measured: Mn = 75,500 g: mol‘1, Mp = 122,200 g: mol 1, Mw = 150,900 g: mol: 1; PDI = 2.00.
    Mn is the number average molecular weight and is the statistical average molecular weight of all polymer chains in the sample: Mn = (ZNiM;) / ZN; where Mi is the molecular weight of the chain and N; is the number of chains with that molecular weight.
    Mw means the weight average molecular weight and is represented by Mw = (ZN; M; ’) / ZNiM; Are defined. Mp means the molecular weight of the highest peak.
    PDI means polydispersity index and is calculated by PDI = Mw / Mn.
    Step 2: Spinning process and post-processing of P84-HP fiber
    The P84-HT solution obtained was continuously degassed at 500 mbar (abs.) And filtered with a filter with a mesh size of 25 μm. The solution is fed to the spinning head of a dry spinning shaft via a gear pump. It is spun through a spinneret having 850 orifices, the orifices being circular and 200 µm in diameter. The temperature of the spinning solution before it enters the spinneret block
    is 69 ° C. The spinning gas temperature at the spinning nozzle block is 340 ° C and at the end of the 8 m high spinning shaft 142 ° C, with a spinning gas quantity of 75 Nm ”/ h. The thread speed was set to 336 m / min.
    The freshly spun fiber bundle, which has a total denier of 6842 dtex and a residual dimethylformamide content of 15% by weight, based on dry polymer, is taken up on bobbins.
    Some of these coils are combined into a larger bundle and fed into a continuous process. The fiber bundle is coated with an antistatic preparation (e.g. Leomin AN from Archroma) in an immersion bath, dried in circulating air at 210 ° C. and then stretched in a ratio of 1: 4 using a cylinder dryer. The stretching ratio is set by varying the speed of the cylinder dryer with the stretching ratio increasing from 1: 1.2 to 1: 2. The surface temperature of the cylinder dryer is in the range of 280 ° C (first cylinder) to 420 ° C (last cylinder). The stretched bundle obtained is coated (e.g. with Leomin LS), crimped in a stuffer box crimping machine at 330 ° C., finished with a finishing agent (e.g. Leomin LS) and cut into staple fibers with a length of 60 mm. The fibers, which have a final denier of 2.2 dtex (determined in accordance with DIN EN ISO 1973, point 8.2 (vibroscope method) as described in paragraph [019]) have a strength of 42 cN / tex (determined in accordance with DIN EN ISO 5079 as described in paragraph [011]), the fiber elongation at break being 28%.
    The glass transition temperature of the fiber obtained was determined by differential calorimetry with a temperature program as follows:
    1st min hold at 50 ° C.
    2. Heat from 50 ° C to 450 ° C at 20 ° C / min. 3. Hold at 450 ° C for min.
    4. Cooling from 450 ° C to 50 ° C at 50 ° C / min. 5. Hold at 50 ° C for 1 min.
    6. Heat from 50 ° C to 450 ° C at 20 ° C / min.
    The glass transition temperature of the fiber according to the invention was determined to be 384 ° C. (measured in step 6) and was accordingly much higher than the glass transition temperature given in the prior art. For example, fibers made from the polyimide described in US Pat. No. 5,120,814 have a glass transition temperature of 340.degree. No PMDA is used in the manufacturing processes for these prior art fibers.
    As a further parameter, the shrinkage of the fiber according to the invention and a fiber obtained according to column 4 of US Pat. No. 5,120,814, right column of Table 1, was compared. The shrinkage measurements are carried out by allowing the fibers to act at a temperature of 240 ° C. for 15 minutes without placing them under tension. The lengths of the fibers are measured before and after the heat exposure. The average shrinkage measured for the new P84 fibers was in the range of 0.72%, whereas the nominal shrinkage for standard commercially available P84 textile fibers according to US Pat HT fibers were drawn, is in the range of 3%. This shows that the shrinkage observed for the fibers according to the invention is much smaller than for the fibers of the prior art. As a first conclusion it is surprisingly found that the fibers according to the invention show a much higher glass transition temperature and a lower shrinkage than the fibers of the prior art listed in US Pat. No. 5,120,814. This shows that the fibers of the invention are much better suited for use in textile applications, especially when exposed to high temperatures.
    COMPARATIVE EXAMPLE V1: PRODUCTION OF A P84-HT FIBER WITHOUT DRAWING
    The fiber according to the invention obtained according to E1 was compared with a further fiber of the prior art, namely the fiber obtained in the process according to US Pat. No. 5,384,390 without a drawing step.
    P84-HT polyimide solution in dimethylformamide is prepared and processed as in Example E1, step 1).
    The spinning process for the freshly spun P84-HT fibers follows the parameters given in Example E1, step 2). Some of these bobbins of the freshly spun bundle are combined into a larger bundle and fed into a continuous process. The fiber bundle is coated with an antistatic preparation in an immersion bath, dried in circulating air at 210 ° C. and then further dried on the cylinder dryers without any stretching (all cylinder dryers rotate at the same speed). The surface temperature of the cylinder dryer is in the range of 280 ° C (first cylinder) to 420 ° C (last cylinder). The bundle obtained is coated (e.g. with Leomin LS), crimped in a stuffer box crimper at 330 ° C. and cut into staple fibers with a length of 60 mm. The fibers have a strength (measured according to the method discussed in paragraph [011] above) below 30 cN / tex and thus a lower strength than the fibers obtained in example E1 according to the invention.
    From the comparison of E1 and V1, the conclusion can be drawn that the drawing step surprisingly makes it possible to obtain a fiber with higher strength, which makes it suitable for textile applications.
    COMPARATIVE EXAMPLE V2: COMPARISON WITH A FIBER OBTAINED BY WET SPINDING
    The textile properties of P84-HT fibers produced using the dry spinning process described above (inventive example E1) and a hollow fiber produced from the same polymer using a wet spinning process according to WO 2014/202324 or WO 2011/009919 were compared. Strength and fiber diameter are measured according to the guidelines mentioned in paragraphs [011] and [019], respectively.
    Fiber diameter Tear strength Elongation [dtex] [cN / tex] [%] P834-HT textile fiber 2.2 41.7 28.8 (according to inventive example E1) P84-HT hollow fiber for 309 6.38 25.5 membrane applications
    From the above data it can be seen that the fiber according to the invention obtained by a dry spinning process according to example E1 according to the invention shows better properties in terms of strength and elongation compared to a fiber obtained by a wet spinning process according to WO 2014/202324 or WO 2011/009919.
    COMPARISON OF TEXTILE PROPERTIES OF THE INVENTION FIBER PRODUCT WITH THE FIBER PRODUCT OF THE PRIOR ART
    A further investigation of the properties of the new P84-HT fiber synthesized according to Example E1 according to the invention was carried out using needle felts produced therefrom in the process
    carried out in the same way as an equivalent product produced with P84 standard fibers type 70 according to US Pat. No. 5,120,814 A, Table 1, right column.
    A needle felt, as used for dry filtration applications, is a three-layer structure consisting of a layer of fibers on the filtration side, a mesh fabric in the middle and a further layer of fibers on the clean gas side. It is made through the following process steps:
    First, a nonwoven web is formed for both fiber layers. By guiding the fibers through a carding unit and a transverse panel to obtain a homogeneous fleece, a fiber layer with a weight of approximately 200 g / m educated.
    Both fleece layers and the mesh fabric are then entangled and compressed with one another in the needling process.
    Another optional process is the heat setting of the fiber to relieve internal stresses in the structure after the needling process and the application of coatings to increase the water repellency.
    For the following comparative tests, felts made from the new P84-HT fiber and the standard commercially available P84 fiber (right column of Table 1 in US 5,120,814) were made on the same equipment using the same PTFE mesh and the same Settings of the carding and needling machines made. Both felts have a comparable weight of around 520 g / m®.
    Before testing the residual flexibility of both needle felts, the samples were exposed to a temperature of 280 ° C. for 21 days. This should simulate the thermal conditions of an insulation material or a needle felt in a technical application.
    The bending length, a measure of the flexibility, was determined in accordance with DIN EN ISO 9073-7 using the ACPM200 apparatus from the University of Dresden.
    Average bending length bending stiffness
    [mm] [mN * cm] P84-HT felt according to E1 57.9 35.23 P84 standard felt (as of | 94.9 69
    Technology)
    A longer flex length means that the material is stiffer. It can be clearly seen that the new fiber is much more flexible at elevated temperatures than the standard P84 fibers according to the prior art, namely US 5120814 A. The fiber of the invention is thus better in all high temperature applications such as protective clothing, insulation and filtration.
    COMPARISON OF FILTRATION PERFORMANCE OF THE FIBER PRODUCT OF THE INVENTION WITH THE FIBER PRODUCT OF THE PRIOR ART
    Another specific investigation into filtration application was carried out with the following test. Again samples of a felt with P84-HP fibers according to example E1 according to the invention and the standard P84 fibers according to the right column of Table 1 in column 4 of US Pat. No. 5,120,814 were thermally aged for 28 days at 280 ° C. Other samples were exposed to a temperature of 240 ° C for 48 days. This should simulate the effect of elevated temperatures in a hot gas filtration process.
    Next, both sample types were assessed in simulated filter tests according to VDI guideline 3926 at a filtration speed of 2 m / min with Pural NF as test dust in a concentration of 5 g / m®. This type of filter test has an initial phase of 30
    Cycles with an upper pressure loss setpoint of 1000 Pa to assess the initial filtration properties of a filter material. This phase is followed by accelerated aging, a series of 10,000 short filtration cycles with a time-controlled cleaning sequence of 5 seconds to simulate a long period of time in a filter system. The last phase is again controlled by pressure loss. The sequence is initiated by 10 stabilization cycles followed by 30 cycles, preferably at the same pressure loss level as before aging at 1000 Pa. Differences in the achieved cycle time and the residual pressure loss of the medium, which are recorded directly after the pulse cleaning, are measures for the performance of a filter material.
    During a filtration cycle, particulates will accumulate on the filter media. They are removed with a pulse of compressed air. The time between two cleaning pulses is called the cycle time. If a significant amount of dust cannot be removed from the filter media, the residual pressure drop, which is the pressure drop measured immediately after pulsing, is high. As a further result, less dust can be collected on the filter element during the filtration cycle 20. As a result, the filter element has to be cleaned more frequently and the cycle time is reduced.
    Therefore, the longer the cycle time, the better the filtration efficiency of the felt. The smaller the pressure loss after aging, the better the filtration efficiency of the felt.
    Thermal base fiber residual residual cycle time cycle time aging before | material of
    the Filtrati- | Felt pressure loss pressure loss
    onstest Before After Before After Aging Aging Aging Aging [Pa] [Pa] [Ss] [Ss] 240 ° C / P84 (status 68 403 295 97 48 days of technology) P834 HT 50 312 312 134 280 ° C / P84 (status 138 775 287 16 28 days of technology) P84 HT 72 454 333 82
    The results are as follows:
    The better filtration performance of the HT fiber felt produced with fibers according to Example E1 according to the invention can already be seen at 240.degree. It already performs slightly better than the prior art fiber.
    The effect is even more pronounced at samples exposed to a temperature of 280 ° C. At a temperature of 280 ° C, the cycle time of the HT type is much better than the cycle time observed for the prior art fiber. This shows that stable operation in a filter unit is only possible for the HT felt type according to the invention.
    While the felt sample produced from P84-HT fibers produced according to the invention Example E1 still works stably even after the simulated filtration aging, the felt sample from the P84 standard felt shows a very short cycle time and a high pressure loss. This suggests that this felt would no longer work stably in a filtration process and must be replaced.
    权利要求:
    Claims (1)
    [1]
    Claims 1. Polyimide fiber comprising a polyimide comprising monomer units of the formula (I): Oo OÖ (*) —N RA N-RB— (**) oO © (N
    where R * is selected from the group consisting of 3,3 ', 4,4'-Benzophenontetrayl (R “') and 1,2,4,5Phenylenetetrayl (R“ ),
    where the molar ratio of R * ': R * in the monomer units of the formula (I) in the polyimide is 95: 5 to 50:50,
    where R® is selected from the group consisting of 2,4-toluene diyl and 2,6-toluene diyl, the polyimide fiber having a strength of more than 30 cN / tex
    and wherein the RP radicals in the monomer units in the polyimide are the same or different
    and where the bond indicated with “(*)” binds a monomer unit to the bond indicated with “(**)” of the adjacent monomer unit.
    2. The polyimide fiber according to claim 1, wherein the polyimide comprises at least 10 monomer units of the formula (I).
    3. Polyimide fiber according to claim 1 or 2 with a fineness of 0.6 to 10 dtex.
    4. Polyimide fiber according to one of claims 1 to 3, wherein the molar ratio of RA ’: RA in the monomer units of formula (I) in the polyimide is 55:45 to 65:35.
    5. Polyimide fiber according to one of claims 1 to 4, wherein the polyimide 2,4-toluene diyl and toluene diyl as R includes.
    6. The polyimide fiber according to claim 5, wherein the molar ratio of 2,4-toluenediyl: toluenediyl groups in the monomer units of formula (I) in the polyimide is 1: 9 to 9: 1.
    7. Polyimide fiber according to one of claims 1 to 6, wherein the polyimide comprises at least 80% by weight of monomer units of the formula (I).
    8. Polyimide fiber according to one of claims 1 to 7, comprising more than 90 wt .-% of the polyimide of formula (I).
    9. A polyimide fiber according to any one of claims 1 to 8 having a non-circular cross-section with a periphery having both convex and concave portions.
    No drawings for this
    类似技术:
    公开号 | 公开日 | 专利标题
    DE60029085T2|2007-01-11|METHOD FOR PRODUCING META-AROMATIC POLYAMIDE FIBERS
    DE60317627T2|2008-10-30|NON-THERMOPLASTIC STARCH FIBERS AND STRENGTH COMPOSITION AND METHOD FOR THE PRODUCTION THEREOF
    DE10355665B4|2005-12-15|A process for producing a polyurethane elastic fiber and the polyurethane elastic fiber thus prepared
    DE4230323B4|2005-07-28|Asymmetric gas separation membrane
    DE4444140A1|1996-06-13|Solvent-spun cellulosic filaments
    EP0119185B1|1989-01-18|Method for the preparation of highly fire-retarding, heat-resisting polyimide fibres
    EP3010630A1|2016-04-27|Method for producing polyimide membranes
    DE2543824C3|1980-05-14|Process for producing fibrils from poly | resins and the fibrils from these resins
    DE3246417A1|1984-06-20|WATER-INSOLUBLE FIBERS MADE OF CELLULOSE ACETATE, CELLULOSE PROPIONATE AND CELLULOSE BUTYRATE WITH AN EXTREMELY HIGH ABSORPTION CAPACITY FOR WATER AND PHYSIOLOGICAL LIQUIDS
    DE2646332C3|1979-12-06|
    AT17296U1|2021-11-15|Polyimide fibers for hot gas filtration
    EP0918894B1|2003-05-02|Method for producing cellulose fibres
    DE2232504C3|1975-07-17|Aromatic copolyhydrazide fibers and process for their manufacture
    DE3914226A1|1990-10-31|FIBER MATERIALS FROM HOMOGENEOUS ALLOYS FROM AROMATIC POLYAMIDES AND POLY-N-VINYLPYRROLIDONE, METHOD FOR THE PRODUCTION THEREOF AND THEIR USE
    DE3535368C2|1993-12-09|Polyacrylonitrile fiber with high strength and high modulus of elasticity
    DE2543816C3|1980-09-25|Use of fibrils made from aromatic poly | resins for the production of paper and textile-like flat structures
    DE2239651A1|1973-02-22|Process for the production of glossy yarns
    DE2044281A1|1971-03-11|Porous fibers or threads and their manufacture
    DE1694767A1|1970-12-03|Process for making elastomeric products
    DE2800744B2|1979-06-07|Threads made from a copolyamide derived from at least 3 polyamide-forming monomer components
    DE1300824B|1969-08-07|Use of incompletely regenerated viscose threads cut to the length of staple fibers for the production of fiber nonwovens or paper-like structures on the wet route without the addition of a binder
    DE2340400A1|1974-02-21|NEW FEDES, FIBERS, FILMS AND FOILS MADE OF ARYLALIPHATIC POLYMERS AND METHODS FOR THEIR PRODUCTION
    DE69915892T2|2005-02-03|SPANDEXFIBER POLYURETHANE UREA POLYMERE MANUFACTURED BY USING 1,3-DIAMINOPENTAN AS CHAIN EXTENDER
    EP0918893B1|2003-10-01|Cellulose microfibre
    DE3115281C2|1990-03-08|
    同族专利:
    公开号 | 公开日
    DE202020003237U1|2020-08-27|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    DE2442203A1|1973-10-12|1975-04-17|Upjohn Co|MIXED POLYIMIDE FIBERS AND FIBERS AND THE PROCESS FOR THEIR MANUFACTURING|
    EP0119185B1|1983-03-09|1989-01-18|Lenzing Aktiengesellschaft|Method for the preparation of highly fire-retarding, heat-resisting polyimide fibres|
    US5384390A|1990-10-15|1995-01-24|Lenzing Aktiengesellschaft|Flame-retardant, high temperature resistant polyimide fibers and process for producing the same|
    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    EP19187771|2019-07-23|
    [返回顶部]