Chemical modification of preformed polybenzimidazole semipermeable membrane

Claim 2

A process for chemically modifying a preformed polybenzimidazole semipermeable membrane wherein said polybenzimidazole consists essentially of recurring units of the formula ##STR7## wherein R is a tetravalent aromatic nucleus, with the nitrogen atoms forming the benzimidazole rings paired upon adjacent carbon atoms of said aromatic nucleus, and R' is selected from the group consisting of an aromatic ring; an alkylene group having from 4 to 8 carbon atoms; and a heterocyclic ring selected from the group consisting of pyridine, pyrazine, furan, quinoline, thiophene, and pyran; and wherein the chemically modified membrane exhibits improved separatory capabilities, said process comprising the steps of: (a) sulfonating said membrane with the formation of ionic bonds by contacting said membrane at a temperature within the range of approximately 5° C. to 100° C. with a sulfonating agent selected from the group consisting of (i) sulfuric acid, (ii) a complex of SO 3 with a Lewis base or other organic compound, (iii) an acyl or alkyl sulfate, (iv) sulfamic acid, (v) a halosulfonic acid, (vi) an organic sulfonic acid, and (vii) mixtures of the foregoing; and (b) heating said membrane in an inert atmosphere at a temperature and for a period of time sufficient to convert the ionic bonds formed in the sulfonating step (a) to permanent, covalent bonds, thereby providing a covalently bonded sulfonated polybenzimidazole semipermeable membrane.

Claim 3

The process of claim 1 wherein said membrane is contacted with said sulfonating agent at a temperature within the range of approximately 20° C. to 50° C.

Claim 4

The process of claim 1 wherein said sulfonating agent is sulfuric acid.

Claim 5

The process of claim 1 wherein said sulfonating agent is a complex of SO 3 with a Lewis base.

Claim 6

The process of claim 4 wherein said Lewis base is selected from the group consisting of pyridine, trimethylamine, dioxane, triethylamine, diethylaniline, thioxane, quinoline, dimethylformamide, triethylphosphate, and N-ethylmorpholine.

Claim 7

The process of claim 1 wherein said sulfonating agent is acetyl sulfate.

Claim 8

The process of claim 1 wherein said sulfonating agent is sulfamic acid.

Claim 9

The process of claim 1 wherein said sulfonating agent is a halosulfonic acid.

Claim 10

The process of claim 8 wherein said sulfonating agent is chlorosulfonic acid.

Claim 11

The process of claim 1 wherein said polybenzimidazole is poly-2,2'-(m-phenylene)-5,5'-bibenzimidazole.

Claim 12

The process of claim 1 wherein said preformed polybenzimidazole semipermeable membrane is in the form of a film.

Claim 13

The process of claim 1 wherein said preformed polybenzimidazole semipermeable membrane is in the form of hollow fibers.

Claim 14

The process of claim 1 wherein said inert atmosphere of heating step (b) is a nitrogen atmosphere.

Claim 15

The process of claim 1 wherein said membrane is heated during heating step (b) at a temperature of at least approximately 400° C.

Claim 16

The process of claim 1 wherein said membrane is heated during heating step (b) for a period of time of at least approximately 5 seconds.

Claim 17

The covalently bonded sulfonated polybenzimidazole semipermeable membrane produced by the process of claim 1.

Claim 18

A process for chemically modifying a preformed polybenzimidazole semipermeable membrane wherein said polybenzimidazole consists essentially of recurring units of the formula ##STR8## wherein R is a tetravalent aromatic nucleus, with the nitrogen atoms forming the benzimidazole rings paired upon adjacent carbon atoms of said aromatic nucleus, and R' is selected from the group consisting of an aromatic ring; an alkylene group having from 4 to 8 carbons atoms; and a heterocyclic ring selected from the group consisting of pyridine, pyrazine, furan, quinoline, thiophene, and pyran; and wherein the chemically modified membrane exhibits improved separatory capabilities, said process comprising the steps of: (a) sulfonating said membrane with the formation of ionic bonds by contacting said membrane at a temperature within the range of approximately 20° C. to 50° C. with a sulfonating agent selected from the group consisting of (i) sulfuric acid, (ii) a complex of SO 3 with a Lewis base, (iii) acetyl sulfate, (iv) sulfamic acid, and (v) chlorosulfonic acid, and (vi) mixtures of the foregoing; and (b) heating said membrane in an inert atmosphere at a temperature of at least approximately 400° C. for a period of time of at least 5 seconds in order to convert the ionic bonds formed in the sulfonating step (a) to permanent, covalent bonds, thereby providing a covalently bonded sulfonated polybenzimidazole semipermeable membrane.

Claim 19

A process for chemically modifying a preformed polybenzimidazole semipermeable membrane wherein said polybenzimidazole consists essentially of recurring units of the formula ##STR8## wherein R is a tetravalent aromatic nucleus, with the nitrogen atoms forming the benzimidazole rings paired upon adjacent carbon atoms of said aromatic nucleus, and R' is selected from the group consisting of an aromatic ring; an alkylene group having from 4 to 8 carbons atoms; and a heterocyclic ring selected from the group consisting of pyridine, pyrazine, furan, quinoline, thiophene, and pyran; and wherein the chemically modified membrane exhibits improved separatory capabilities, said process comprising the steps of: (a) sulfonating said membrane with the formation of ionic bonds by contacting said membrane at a temperature within the range of approximately 20° C. to 50° C. with a sulfonating agent selected from the group consisting of (i) sulfuric acid, (ii) a complex of SO 3 with a Lewis base, (iii) acetyl sulfate, (iv) sulfamic acid, and (v) chlorosulfonic acid, and (vi) mixtures of the foregoing; and (b) heating said membrane in an inert atmosphere at a temperature of at least approximately 400° C. for a period of time of at least 5 seconds in order to convert the ionic bonds formed in the sulfonating step (a) to permanent, covalent bonds, thereby providing a covalently bonded sulfonated polybenzimidazole semipermeable membrane.

Claim 20

The process of claim 17 wherein said membrane is contacted with said sulfonating agent at a temperature within the range of approximately 20° C. to 30° C.

Claim 21

The process of claim 17 wherein said sulfonating agent is sulfuric acid.

Claim 22

The process of claim 17 wherein said sulfonating agent is a complex of SO 3 with a Lewis base.

Claim 23

The process of claim 20 wherein said Lewis base is selected from the group consisting of pyridine, trimethylamine, dioxane, triethylamine, diethylaniline, thioxane, quinoline, dimethylformamide, triethylphosphate, and N-ethylmorpholine.

Claim 24

The process of claim 17 wherein said sulfonating agent is acetyl sulfate.

Claim 25

The process of claim 17 wherein said sulfonating agent is sulfamic acid.

Claim 26

The process of claim 17 wherein said sulfonating agent is chlorosulfonic acid.

Claim 27

The process of claim 17 wherein said inert atmosphere of heating step (b) is a nitrogen atmosphere.

Claim 28

The process of claim 17 wherein said membrane is heated during heating step (b) at a temperature within the range of approximately 450° C. to 510° C.

Claim 29

The process of claim 17 wherein said membrane is heated during heating step (b) for a period of time of approximately 8 to 30 seconds.

Claim 30

The process of claim 17 wherein said polybenzimidazole is poly-2,2'-(m-phenylene)-5,5'-bibenzimidazole.

Claim 31

A covalently bonded sulfonated polybenzimidazole semipermeable membrane produced in accordance with the process of claim 17.

Claim 32

A process for chemically modifying a preformed polybenzimidazole semipermeable membrane wherein said polybenzimidazole consists essentially of recurring units of the formula ##STR9## wherein R is a tetravalent aromatic nucleus, with the nitrogen atoms forming the benzimidazole rings paired upon adjacent carbon atoms of said aromatic nucleus, and R' is selected from the group consisting of an aromatic ring; an alkylene group having from 4 to 8 carbon atoms; and a heterocyclic ring selected from the group consisting of pyridine, pyrazine, furan, quinoline, thiophene, and pyran; and wherein the chemically modified membrane exhibits improved separatory capabilities, said process comprising the steps of: (a) sulfonating said membrane with the formation of ionic bonds by contacting said membrane at a temperature within the range of approximately 20° C. to 30° C. with a sulfonating agent selected from the group consisting of (i) sulfuric acid, (ii) a complex of SO 3 with a Lewis base, (iii) acetyl sulfate, (iv) sulfamic acid, and (v) chlorosulfonic acid, and (vi) mixtures of the foregoing; and (b) heating said membrane in an inert atmosphere at a temperature within the range of approximately 450° C. to 510° C. for a period of time within the range of approximately 8 to 30 seconds in order to convert the ionic bonds formed in the sulfonating step (a) to permanent, covalent bonds, thereby providing a covalently bonded sulfonated polybenzimidazole semipermeable membrane.

Claim 33

A process for chemically modifying a preformed polybenzimidazole semipermeable membrane wherein said polybenzimidazole consists essentially of recurring units of the formula ##STR9## wherein R is a tetravalent aromatic nucleus, with the nitrogen atoms forming the benzimidazole rings paired upon adjacent carbon atoms of said aromatic nucleus, and R' is selected from the group consisting of an aromatic ring; an alkylene group having from 4 to 8 carbon atoms; and a heterocyclic ring selected from the group consisting of pyridine, pyrazine, furan, quinoline, thiophene, and pyran; and wherein the chemically modified membrane exhibits improved separatory capabilities, said process comprising the steps of: (a) sulfonating said membrane with the formation of ionic bonds by contacting said membrane at a temperature within the range of approximately 20° C. to 30° C. with a sulfonating agent selected from the group consisting of (i) sulfuric acid, (ii) a complex of SO 3 with a Lewis base, (iii) acetyl sulfate, (iv) sulfamic acid, and (v) chlorosulfonic acid, and (vi) mixtures of the foregoing; and (b) heating said membrane in an inert atmosphere at a temperature within the range of approximately 450° C. to 510° C. for a period of time within the range of approximately 8 to 30 seconds in order to convert the ionic bonds formed in the sulfonating step (a) to permanent, covalent bonds, thereby providing a covalently bonded sulfonated polybenzimidazole semipermeable membrane.

Claim 34

The process of claim 30 wherein said sulfonating agent is sulfuric acid.

Claim 35

The process of claim 30 wherein said sulfonating agent is a complex of SO 3 with a Lewis base.

Claim 36

The process of claim 32 wherein said Lewis base is selected from the group consisting of pyridine, trimethylamine, dioxane, triethylamine, diethylaniline, thioxane, quinoline, dimethylformamide, triethylphosphate, and N-ethylmorpholine.

Claim 37

The process of claim 30 wherein said sulfonating agent is acetyl sulfate.

Claim 38

The process of claim 30 wherein said sulfonating agent is sulfamic acid.

Claim 39

The process of claim 30 wherein said sulfonating agent is chlorosulfonic acid.

Claim 40

The process of claim 30 wherein said polybenzimidazole is poly-2,2'-(m-phenylene)-5,5'-bibenzimidazole.

Claim 41

A covalently bonded sulfonated polybenzimidazole semipermeable membrane produced by the process of claim 31.

Claim 42

A covalently bonded sulfonated polybenzimidazole semipermeable membrane produced by the process of claim 32.

Claim 43

A covalently bonded sulfonated polybenzimidazole semipermeable membrane produced by the process of claim 34.

Claim 44

A covalently bonded sulfonated polybenzimidazole semipermeable membrane produced by the process of claim 35.

Claim 45

A covalently bonded sulfonated polybenzimidazole semipermeable membrane produced by the process of claim 36.