Polyimide membranes made of polymerization solutions

Abstract

The invention relates to polyimide membranes and to a phase inversion method for the production thereof. The polyimide membranes can be used to separate different gas mixtures.

Claims

1. A process for producing a polyimide hollow fiber membrane, the process comprising: (a) forming a polyimide solution comprising an aprotic dipolar solvent and a polyimide; (b) filtering and devolatizing the polyimide solution to obtain a casting solution; (c) pumping the casting solution through a two material die together with a bore solution to produce a polyimide hollow fiber by phase inversion; (d) treating the polyimide hollow fibers with a dry thermostated gas before entry into an aqueous coagulation bath to produce treated hollow fibers; and (e) dipping the treated hollow fibers into the aqueous coagulation bath to produce the polyimide hollow fiber membrane; wherein the polyimide is obtained by polymerization of an aromatic dianhydride and an aromatic diisocyanate from a reaction mixture comprising the aprotic dipolar solvent and 0.01 to 5% by weight of a basic catalyst, calculated on the combined amount of aromatic dianhydride, and aprotic dipolar solvent, and has not been isolated as a solid material and then redissolved prior to forming said polyimide solution.

2. The process of claim 1, wherein the polyimide is a polyimide of formula (I): ##STR00003## R is selected from the group consisting of ##STR00004## 0<x<0.5; 1>y>0.5; and n is a number such that a Mp of the polyimide polymer is greater than 100,000 g.Math.mol.sup.?1.

3. The process of claim 1, further comprising adding a water-soluble additive to the casting solution.

4. The process of claim 3, wherein the water-soluble additive is at least one selected from the group consisting of a water-miscible solvent, a nonsolvent, and a pore-former.

5. The process of claim 1, further comprising crosslinking the polyimide membrane with at least one amine selected from the group consisting of aliphatic diamines, oligoethyleneimine, and polyethyleneimine.

6. The process of claim 5, satisfying at least one condition selected from the group consisting of: the polyimide membrane is crosslinked with at least one aliphatic diamine selected from the group consisting of diaminoethane, diaminopropane, diaminobutane, diaminopentane, diaminohexane, diaminooctane, diaminodecane, diaminododecane, and bis-4,4-(aminomethyl)benzene; the polyimide membrane is crosslinked by dipping into a solution of said at least one amine in water or in at least one alcohol; the polyimide membrane is crosslinked at a temperature between 0 and 90? C.; the polyimide membrane is crosslinked for a time between 10 seconds and 16 hours.

7. The process of claim 1, wherein the polyimide hollow fiber produced by phase inversion is an integrally asymmetrically hollow fiber membrane and the process is continuous.

8. The process of claim 1, further comprising at least one condition selected from the group consisting of: the bore solution comprises a mixture of water and an alcohol with at least one selected from the group consisting of dimethylformamide, dimethylacetamide, N-methylpyrrolidinone, N-ethylpyrrolidinone, sulfolane, and dimethyl sulfoxide; the two-material die is at a distance of 1 to 60 cm from the aqueous coagulation bath of water into which the hollow fiber is spun and an integrally asymmetrical hollow fiber membrane is formed by precipitating the polyimide; and the dry thermostated gas is a thermostated stream of nitrogen or air.

9. A polyimide hollow fiber membrane obtained by the process of claim 1.

10. The polyimide hollow fiber membrane of claim 9, wherein an Mp of the polyimide is greater than 100 000 g.Math.mol.sup.?1 and a PDI of the polyimide is from 1.7 to 2.3.

11. The polyimide membrane of claim 9, wherein: the polyimide is a polyimide of formula (II): ##STR00005## R is selected from the group consisting of ##STR00006## 0<x<0.5; 1>y>0.5; and n is a number such that a Mp of the polyimide polymer is greater than 100,000 g.Math.mol.sup.?1.

12. The polyimide hollow fiber membrane of claim 9, in the form of: a micro-, ultra- or nanofiltration membrane suitable for separating homogeneous dissolved or particulate products from organic solvents or from water; or a no-pore membrane suitable for separation of gases.

13. The polyimide hollow fiber membrane of claim 9, wherein the polyimide membrane is an integrally asymmetrical hollow fiber membrane and the integrally asymmetrical hollow fiber membrane is suitable for separating a gas mixture.

14. The polyimide membrane of claim 13, wherein the gas mixture is selected from the group consisting of: methane and carbon dioxide; oxygen and nitrogen; hydrogen and process gases; and water vapor and a gas or a mixture of gases other than water vapor.

Description

PRODUCTION EXAMPLES

(1) The examples which follow serve to provide more particular elucidation and better understanding of the present invention, but do not limit it in any way.

(2) Producing the Polyimide Solutions

Example 1: Producing a P84 Type 70 Polyimide Solution in Dimethylacetamide

(3) A 3 l glass reactor equipped with stirrer and reflux condenser is initially charged with 1622 g of anhydrous dimethylacetamide. A quantity of 456.4 g of 3,3,4,4-benzophenonetetracarboxylic dianhydride are dissolved therein and the solution is heated to 90? C. To this solution is added 0.45 g of sodium hydroxide. Under nitrogen, 266.8 g of a mixture of 64% of 2,4-tolylene diisocyanate, 16% of 2,6-tolylene diisocyanate and 20% of 4,4-diisocyanatodiphenylmethane are metered during several hours. In the process, CO2 escapes as by-product and a polyimide results directly in solution.

(4) The highly viscous solution obtained has a golden color, a solids content of 25% and a viscosity of 49 Pa.Math.s.

(5) The molar masses are determined by gel permeation chromatography as follows: Mn=80 600 g.Math.mol.sup.?1, Mp=139 600 g.Math.mol.sup.?1, Mw=170 000 g.Math.mol.sup.?1 PDI=2.11

Example 2: Producing a P84 Type 70 Polyimide Solution in Dimethylformamide

(6) A 3 l glass reactor equipped with stirrer and reflux condenser is initially charged with 1622 g of anhydrous dimethylformamide. A quantity of 456.4 g of 3,3,4,4-benzophenonetetracarboxylic dianhydride are dissolved therein and the solution is heated to 90? C. To this solution is added 0.45 g of sodium hydroxide. Under nitrogen, 266.8 g of a mixture of 64% of 2,4-tolylene diisocyanate, 16% of 2,6-tolylene diisocyanate and 20% of 4,4-diisocyanatodiphenylmethane are metered during several hours. In the process, CO2 escapes as by-product and a polyimide results directly in solution.

(7) The highly viscous solution obtained has a golden color, a solids content of 27% and a viscosity of 48 Pa.Math.s.

(8) The molar masses are determined by gel permeation chromatography as follows: Mn=76 600 g.Math.mol.sup.?1, Mp=130 500 g.Math.mol.sup.?1, Mw=146 200 g.Math.mol.sup.?1 PDI=1.91

Example 3: Producing a P84 Type 70 Polyimide Solution in N-methylpyrrolidone

(9) A 3 l glass reactor equipped with stirrer and reflux condenser is initially charged with 1800 g of anhydrous N-methylpyrrolidone. A quantity of 456.4 g of 3,3,4,4-benzophenonetetracarboxylic dianhydride are dissolved therein and the solution is heated to 90? C. To this solution is added 0.45 g of sodium hydroxide. Under nitrogen, 266.8 g of a mixture of 64% of 2,4-tolylene diisocyanate, 16% of 2,6-tolylene diisocyanate and 20% of 4,4-diisocyanatodiphenylmethane are metered during several hours. In the process, CO2 escapes as by-product and a polyimide results directly in solution.

(10) The highly viscous solution obtained has a golden color, a solids content of 25% and a viscosity of 45 Pa.Math.s.

(11) The molar masses are determined by gel permeation chromatography as follows: Mn=65 700 g.Math.mol.sup.?1, Mp=107 200 g.Math.mol.sup.?1, Mw=147 000 g.Math.mol.sup.?1 PDI=2.24

Example 4: Producing a P84 Type 70 Polyimide Solution in N-ethylpyrrolidone

(12) A 3 l glass reactor equipped with stirrer and reflux condenser is initially charged with 1622 g of anhydrous N-ethylpyrrolidone. A quantity of 456.4 g of 3,3,4,4-benzophenonetetracarboxylic dianhydride are dissolved therein and the solution is heated to 90? C. To this solution is added 0.45 g of sodium hydroxide. Under nitrogen, 266.8 g of a mixture of 64% of 2,4-tolylene diisocyanate, 16% of 2,6-tolylene diisocyanate and 20% of 4,4-diisocyanatodiphenylmethane are metered during several hours. In the process, CO2 escapes as by-product and a polyimide results directly in solution.

(13) The highly viscous solution obtained has a golden color, a solids content of 27% and a viscosity of 87 Pa.Math.s.

(14) The molar masses are determined by gel permeation chromatography as follows: Mn=64 600 g.Math.mol.sup.?1, Mp=105 200 g.Math.mol.sup.?1, Mw=144 700 g.Math.mol.sup.?1 PDI=2.24

Example 5: Producing a P84 T100 Polyimide Solution in Dimethylformamide

(15) A 3 l glass reactor equipped with stirrer and reflux condenser is initially charged with 1800 g of anhydrous dimethylformamide. A quantity of 473.6 g of 3,3,4,4-benzophenonetetracarboxylic dianhydride are dissolved therein and the solution is heated to 90? C. To this solution is added 1.8 g of diazabicyclooctane. Under nitrogen, 254.4 g of a mixture of 2,4-tolylene diisocyanate are metered during several hours. In the process, CO2 escapes as by-product and a polyimide results directly in solution.

(16) The highly viscous solution obtained has a golden color, a solids content of 25% and a viscosity of 59 Pa.Math.s.

(17) The molar masses are determined by gel permeation chromatography as follows: Mn=82 100 g.Math.mol.sup.?1, Mp=151 500 g.Math.mol.sup.?1, Mw=181 900 g.Math.mol.sup.?1 PDI=2.21

Example 6: Producing a P84 T80 Polyimide Solution in Dimethylformamide

(18) A 3 l glass reactor equipped with stirrer and reflux condenser is initially charged with 1622 g of anhydrous dimethylformamide. A quantity of 473.6 g of 3,3,4,4-benzophenonetetracarboxylic dianhydride are dissolved therein and the solution is heated to 90? C. To this solution is added 1.8 g of diazabicyclooctane. Under nitrogen, 254.4 g of a mixture of 80% of 2,4-tolylene diisocyanate and 20% of 2,6-tolylene diisocyanate are metered during several hours. In the process, CO2 escapes as by-product and a polyimide results directly in solution.

(19) The highly viscous solution obtained has a golden color, a solids content of 27% and a viscosity of 108 Pa.Math.s.

(20) The molar masses are determined by gel permeation chromatography as follows: Mn=83 800 g.Math.mol.sup.?1, Mp=152 300 g.Math.mol.sup.?1, Mw=173 800 g.Math.mol.sup.?1 PDI=2.07

Example 7: Producing a P84 HT Polyimide Solution in Dimethylformamide

(21) A 3 l glass reactor equipped with stirrer and reflux condenser is initially charged with 1800 g of anhydrous dimethylformamide. A quantity of 316.4 g of 3,3,4,4-benzophenonetetracarboxylic dianhydride and 142.8 g of pyromellitic dianhyhdride are dissolved therein and the solution is heated to 90? C. To this solution is added 1.8 g of diazabicyclooctane. Under nitrogen, 283.4 g of a mixture of 80% of 2,4-tolylene diisocyanate and 20% of 2,6-tolylene diisocyanate are metered during several hours. In the process, CO2 escapes as by-product and a polyimide results directly in solution.

(22) The highly viscous solution obtained has a golden color, a solids content of 27% and a viscosity of 70 Pa.Math.s.

(23) The molar masses are determined by gel permeation chromatography as follows: Mn=75 500 g.Math.mol.sup.?1, Mp=122 200 g.Math.mol.sup.?1, Mw=150 900 g.Math.mol.sup.?1 PDI=2.00

Example 8: Producing a P84 MDI Polyimide Solution in Dimethylformamide

(24) A 3 l glass reactor equipped with stirrer and reflux condenser is initially charged with 1500 g of anhydrous dimethylformamide. A quantity of 369.2 g of 3,3,4,4-benzophenonetetracarboxylic dianhydride are dissolved therein and the solution is heated to 90? C. To this solution is added 1.5 g of diazabicyclooctane. Under nitrogen, 222.3 g of 2,4,6-trimethyl-1,3-phenylene diisocyanate are metered during several hours. In the process, CO2 escapes as by-product and a polyimide results directly in solution.

(25) The highly viscous solution obtained has a pale yellow color, a solids content of 25% and a viscosity of 5 Pa.Math.s.

(26) The molar masses are determined by gel permeation chromatography as follows: Mn=55 200 g.Math.mol.sup.?1, Mp=95 000 g.Math.mol.sup.?1, Mw=112 000 g.Math.mol.sup.?1 PDI=2.03

(27) Film Production and Intrinsic Gas Permeabilities

(28) The polymerization solutions are filtered neat through a 15? metal sieve. The films are produced using an instrument from Elcometer (Elcometer 4340) with an applicator. Glass plates are coated with the polymer solutions using an applicator and a gap size of 250 The solvent is subsequently evaporated off in a circulating air drying cabinet at 70? C. (0.5 h), 150? C. (2 h) and 250? C. (12 h). The films are then virtually free of solvents (content <0.1%) and are detached from the glass plates. The films obtained have a thickness of about 30 to 40 ?m. None of the films was brittle and all exhibited good mechanical properties. These films were then examined under the microscope to find imperfection-free places and circularly round samples having a diameter of 46 mm are cut out. These samples are then emplaced into the self-built gas permeation apparatus and the permeability of various gases is determined by the vacuum method.

(29) This involves pressurizing the films with a single gas (e.g. nitrogen, oxygen, methane or carbon dioxide) at various pressures and recording the increase in pressure on the permeate side. This is used to calculate the permeability in barriers (10-6 cm.sup.3.Math.cm.sup.?2.Math.s.sup.?1.Math.cmHg.sup.?1). Some examples are adduced in what follows.

Example 9: Gas Permeabilities of Various Polymers from Examples Above

(30) TABLE-US-00004 Transmembrane Thickness pressure Permeability Selec- Polymer (?m) Gas (bar) (barrer) tivity Example 2 O2 0.182 10.0 (P84 N2 0.018 type 70) CO2 0.571 67.2 CH4 0.008 Example 5 37.9 O2 10.9 0.250 30.9 (P84 37.9 N2 11.0 0.008 T100) 37.9 CO2 25.2 0.622 124 37.9 CH4 17.5 0.005 Example 6 36.0 O2 10.7 0.280 21.2 (P84 T80) 36.0 N2 11.1 0.013 36.0 CO2 28.4 0.696 237 36.0 CH4 31.5 0.003 Example 7 41.2 O2 12.0 0.53 13.2 (P84 HT) 41.2 N2 12.3 0.04 41.6 CO2 36.8 1.69 169 41.6 CH4 36.4 0.01

(31) Additizing the Polymerization Solution

Example 10: Producing a Casting Solution from P84 Type 70 for Production of Polyimide Hollow Fibers

(32) In a 3 l stirred tank of glass with powerful stirrer, 1168 g of P84 type 70 solution in dimethylformamide from Example 2 are admixed with a mixture of 94.1 g of tetrahydrofuran and 40.3 g of isopropanol added dropwise at room temperature. In the course of addition, the polymer briefly precipitates at the drop entry point, but quickly redissolves again. Stirring is continued until a homogeneous solution is produced. This homogeneous solution is then filtered through a sieve having a mesh size of 15? and left to stand for 2 days without stirring. The casting solution obtained has a solids content of 23.5%, a dimethylformamide content of 66.5%, a tetrahydrofuran content of 7% and an isopropanol content of 3%.

Example 11: Producing a Casting Solution from P84 Type 70 for Production of Polyimide Hollow Fibers

(33) In a 3 l stirred tank of glass with powerful stirrer, 1034 g of P84 type 70 solution in dimethylformamide from Example 2 are admixed with a mixture of 58.6 g of tetrahydrofuran and 46.9 g of isopropanol added dropwise at room temperature. In the course of addition, the polymer briefly precipitates at the drop entry point, but quickly redissolves again. Stirring is continued until a homogeneous solution is produced. This homogeneous solution is then filtered through a sieve having a mesh size of 15? and left to stand for 2 days without stirring. The casting solution obtained has a solids content of 23.8%, a dimethylformamide content of 67.2%, a tetrahydrofuran content of 5% and an isopropanol content of 4%.

Example 12: Producing a Casting Solution from P84 Type HT for Production of Polyimide Hollow Fibers

(34) In a 3 l stirred tank of glass with powerful stirrer, 1034 g of P84 type HT solution in dimethylformamide from Example 7 are admixed with a mixture of 47 g of tetrahydrofuran and 65 g of isopropanol added dropwise at room temperature. In the course of addition, the polymer briefly precipitates at the drop entry point, but quickly redissolves again. Stirring is continued until a homogeneous solution is produced. This homogeneous solution is then filtered through a sieve having a mesh size of 15? and left to stand for 2 days without stirring. The casting solution obtained has a solids content of 23.6%, a dimethylformamide content of 66.9%, a tetrahydrofuran content of 4% and an isopropanol content of 5.5%.

Example 13: Producing a Casting Solution from P84 T100 for Production of Polyimide Hollow Fibers

(35) In a 3 l stirred tank of glass with powerful stirrer, 1034 g of P84 T100 solution in dimethylformamide from Example 5 are admixed with a mixture of 46.8 g of tetrahydrofuran and 58.5 g of isopropanol added dropwise at room temperature. In the course of addition, the polymer briefly precipitates at the drop entry point, but quickly redissolves again. Stirring is continued until a homogeneous solution is produced. This homogeneous solution is then filtered through a sieve having a mesh size of 15? and left to stand for 2 days without stirring. The casting solution obtained has a solids content of 22.1%, a dimethylformamide content of 68.9%, a tetrahydrofuran content of 5% and an isopropanol content of 4%.

Example 14: Producing a Casting Solution from P84 Type for Production of Flat Sheet Membranes for Organophilic Nanofiltration

(36) In a 3 l stirred tank of glass with powerful stirrer, 1034 g of P84 type 70 solution in dimethylformamide from Example 2 are admixed with 258.5 g of tetrahydrofuran added dropwise at room temperature. Stirring is continued until a homogeneous solution is produced. This homogeneous solution is then filtered through a sieve having a mesh size of 15? and left to stand for 2 days without stirring. The casting solution obtained has a solids content of 21.6%, a dimethylformamide content of 58.4% and a tetrahydrofuran content of 20%.

(37) Hollow Fiber Production

Example 15: Hollow Fiber Production from a Casting Solution with P84 Type 70 in Dimethylformamide from Example 10

(38) The devolatized, filtered and additized solution of P84 type 70 in dimethylformamide from Example 10 is thermostated to 50? C. and gear pumped through a two-material die. Flux is 162 g/h. While the polymer solution is conveyed in the outer region of the two-material die, a mixture of 70% of dimethylformamide and 30% of water is conveyed in the inner region in order to produce the hole in the hollow fiber. Flux is 58 ml/h. After a distance of 40 cm, the hollow fiber enters cold water at 10? C. The hollow fiber is enveloped here with a tube. This tube is flooded with a 2 l/min stream of nitrogen, tube internal temperature being 41? C. The fiber is then pulled through a water wash bath and finally wound up at a speed of 15 m/min. After extraction with water for several hours, the hollow fibers are dipped first in ethanol and then in heptane and subsequently air dried to obtain hollow fibers having an outer diameter of 412?, a hole diameter of 250? and a wall thickness of 81?.

(39) Single gas measurements gave the following permeances for the hollow fibers at a transmembrane pressure of 5 bar:

(40) oxygen: 1.450 GPU

(41) nitrogen: 0.165 GPU

(42) carbon dioxide: 6.03 GPU

(43) methane: 0.084 GPU

(44) Single gas selectivities are thus 8.8 as between oxygen and nitrogen and 71.9 as between carbon dioxide and methane

(45) Single gas measurements gave the following permeances for the hollow fibers at a transmembrane pressure of 40 bar:

(46) carbon dioxide: 8.99 GPU

(47) methane: 0.101 GPU

(48) Single gas selectivities are 88.5 as between carbon dioxide and methane

Example 16: Hollow Fiber Production from a Casting Solution with P84 Type 70 in Dimethylformamide from Example 11

(49) The devolatized, filtered and additized solution of P84 type 70 in dimethylformamide from Example 11 is thermostated to 50? C. and gear pumped through a two-material die. Flux is 162 g/h. While the polymer solution is conveyed in the outer region of the two-material die, a mixture of 70% of dimethylformamide and 30% of water is conveyed in the inner region in order to produce the hole in the hollow fiber. Flux is 58 ml/h. After a distance of 42 cm, the hollow fiber enters cold water at 10? C. The hollow fiber is enveloped here with a tube. This tube is flooded with a 2 l/min stream of nitrogen, tube internal temperature being 46? C. The fiber is then pulled through a water wash bath and finally wound up at a speed of 24 m/min. After extraction with water for several hours, the hollow fibers are dipped first in ethanol and then in heptane and subsequently air dried to obtain hollow fibers having an outer diameter of 310?, a hole diameter of 188? and a wall thickness of 61?.

(50) Single gas measurements gave the following permeances for the hollow fibers at a transmembrane pressure of 9 bar:

(51) oxygen: 1.463 GPU

(52) nitrogen: 0.164 GPU

(53) Single gas selectivities are thus 8.9 as between oxygen and nitrogen

Example 17: Hollow Fiber Production from a Casting Solution with P84 T100 in Dimethylformamide from Example 13

(54) The devolatized, filtered and additized solution of P84 T100 in dimethylformamide from Example 13 is thermostated to 50? C. and gear pumped through a two-material die. Flux is 162 g/h. While the polymer solution is conveyed in the outer region of the two-material die, a mixture of 70% of dimethylformamide and 30% of water is conveyed in the inner region in order to produce the hole in the hollow fiber. Flux is 58 ml/h. After a distance of 42 cm, the hollow fiber enters cold water at 10? C. The hollow fiber is enveloped here with a tube. This tube is flooded with a 2 l/min stream of nitrogen, tube internal temperature being 46? C. The fiber is then pulled through a water wash bath and finally wound up at a speed of 20 m/min. After extraction with water for several hours, the hollow fibers are dipped first in ethanol and then in heptane and subsequently air dried to obtain hollow fibers having an outer diameter of 339?, a hole diameter of 189? and a wall thickness of 75?.

(55) Single gas measurements gave the following permeances for the hollow fibers at a transmembrane pressure of 9 bar:

(56) oxygen: 0.564 GPU

(57) nitrogen: 0.072 GPU

(58) carbon dioxide: 1.679

(59) methane: 0.023

(60) Single gas selectivities are thus 7.8 as between oxygen and nitrogen and 71.6 as between carbon dioxide and methane

Example 18: Hollow Fiber Production from a Casting Solution with P84 HT in Dimethylformamide

(61) The devolatized, filtered and additized solution of P84 HT in dimethylformamide from Example 12 is thermostated to 50? C. and gear pumped through a two-material die. Flux is 162 g/h. While the polymer solution is conveyed in the outer region of the two-material die, a mixture of 70% of dimethylformamide and 30% of water is conveyed in the inner region in order to produce the hole in the hollow fiber. Flux is 58 ml/h. After a distance of 15 cm, the hollow fiber enters cold water at 10? C. The hollow fiber is enveloped here with a tube. This tube is flooded with a 1 l/min stream of nitrogen, tube internal temperature being 40? C. The fiber is then pulled through a water wash bath and finally wound up at a speed of 24 m/min. After extraction with water for several hours, the hollow fibers are dipped first in ethanol and then in heptane and subsequently air dried to obtain hollow fibers having an outer diameter of 306?, a hole diameter of 180? and a wall thickness of 63?.

(62) Single gas measurements gave the following permeances for the hollow fibers at a transmembrane pressure of 10 bar:

(63) carbon dioxide: 6.0 GPU

(64) methane: 0.2 GPU

(65) Single gas selectivities are thus 30 as between carbon dioxide and methane

Example 19: Hollow Fiber Production from a Polymerization Solution with P84 HT in Dimethylformamide from Example 7

(66) The devolatized filtered solution of P84 HT in dimethylformamide from Example 7 is thermostated to 50? C. and gear pumped through a two-material die. Flux is 162 g/h. While the polymer solution is conveyed in the outer region of the two-material die, a mixture of 70% of dimethylformamide and 30% of water is conveyed in the inner region in order to produce the hole in the hollow fiber. Flux is 58 ml/h. After a distance of 15 cm, the hollow fiber enters cold water at 10? C. The hollow fiber is enveloped here with a tube. This tube is flooded with a 1 l/min stream of nitrogen, tube internal temperature being 70? C. The fiber is then pulled through a water wash bath and finally wound up at a speed of 24 m/min. After extraction with water for several hours, the hollow fibers are dipped first in ethanol and then in heptane and subsequently air dried to obtain hollow fibers having an outer diameter of 307?, a hole diameter of 189? and a wall thickness of 59?.

(67) Single gas measurements gave the following permeances for the hollow fibers at a transmembrane pressure of 10 bar:

(68) carbon dioxide: 3.37 GPU

(69) methane: 0.051 GPU

(70) Single gas selectivities are thus 66 as between carbon dioxide and methane

(71) The fiber was additionally measured at higher pressures in order to measure plasticization characteristics and pressure stability.

(72) TABLE-US-00005 CO2 Methane Pressure permeance permeance [bar] [GPU] [GPU] Selectivity 10 3.365 0.051 66 20 3.199 0.045 72 30 3.535 0.034 103 40 4.025 0.042 96 50 4.376 0.033 131 60 4.300 0.026 165 70 0.027 90 0.014

(73) Flat Sheet Membrane Production

Example 20: Producing a Flat Sheet Membrane from P84 Type 70

(74) A flat sheet membrane rig is used to produce 35 cm wide membranes from a casting solution described in Example 14. For this, the casting solution is coated using an application and a casting gap of 200? onto a calendered polyester fleece having a basis weight of 100 g/m.sup.2 and a speed of 5 m/min. The coated polyester fleece is then passed through a shaft through which nitrogen is flowed. The speed of flow is 339 m/h. The residence time thus achieved is 3 s. The coated fleece then dips into cold water at 10? C. The crude membrane is then wound up wet.

(75) Subsequently, the membrane is at 70? C. extracted in water and impregnated with a conditioning agent (25% of polyethylene glycol dimethyl ether (PGDME 250 from Clariant) in water). It is dried in a festoon dryer at a temperature of 60? C.

(76) The membrane is characterized in a Milipore stirred cell at a pressure of 5 bar. The solvent used is heptane in which hexaphenylbenzene is dissolved in a concentration of 12 mg/l. Measurement revealed a flux of 1.7 l.Math.m.sup.?2.Math.h.sup.?1.Math.bar.sup.?1 coupled with a retention of 94%

(77) The membrane is subsequently also tested at a pressure of 30 bar and 30? C. in toluene. Oligostyrenes are used as test molecules. Flux in this test with toluene was 90 l.Math.m.sup.?2.Math.h.sup.?1. The membrane exhibits very high retention over the entire molar mass range and has a sharp cut-off in the region between 200 and 300 daltons (see FIG. 3).

(78) Crosslinking the Membranes with Diamines

Example 21: Crosslinking a Flat Sheet Membrane with Amines

(79) The flat sheet membrane from Example 20 was placed for 16 h into a 0.1% ethanolic solution of an oligoethyleneimine ((#468533, Aldrich, typical molecular weight 423, contains 5-20% of tetraethylene-pentamine). The membrane crosslinks and exhibits no solubility in hexane, heptane, toluene, xylene, acetone, butanone, methanol, ethanol, isopropanol, tetrahydrofuran, dichloromethane, chloroform, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide and ethyl acetate.

(80) The membrane is characterized in a Milipore stirred cell at a pressure of 5 bar. The solvent used is dimethylformamide in which hexaphenylbenzene is dissolved in a concentration of 2.2 mg/l. Measurement revealed a flux of 1.3 l.Math.m.sup.?2.Math.h.sup.?1.Math.bar.sup.?1 coupled with a retention of 89%.

Example 22: Crosslinking a Hollow Fiber Membrane with Amines

(81) The hollow fiber membrane from Example 19 was placed for 16 h into a 0.1% solution of hexamethylenediamine in ethanol. The membrane crosslinks and exhibits no solubility in hexane, heptane, toluene, xylene, acetone, butanone, methanol, ethanol, isopropanol, tetrahydrofuran, dichloromethane, chloroform, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide and ethyl acetate.

FIGURE DESCRIPTION

(82) FIG. 1: Influence of concentrations of P84 type 70 in DMF on viscosity of solution: comparing a P84 polymerization solution and a P84 solution prepared from a precipitated and redissolved polymer at 25? C.

(83) FIG. 2: Cross sections of hollow fiber membranes with macrovoids (picture at left) and without macrovoids (picture at right)

(84) FIG. 3:

(85) Application test of membrane from Example 20.