Crosslinked and crosslinkable hollow fiber mixed matrix membrane and method of making same

Abstract

A composition of and a method of making high performance mixed matrix hollow fiber membranes is described. The membranes have a high resistance to plasticization by use of a predetermined amount of crosslinking. The preferred polymer material for the membrane is a polyimide polymer contineous phase comprising ester crosslinks and a molecular sieve material dispersed within the polymer contineous phase. The resultant mixed matrix hollow fiber membrane exhibits a high permeability of CO 2 in combination with a high CO 2 /CH 4 selectivity. Another embodiment provides a method of making the mixed matrix hollow fiber membrane from a monesterified polymer followed by final crosslinking after hollow fiber formation.

What is claimed is:  
     
         1 . A hollow fiber polymer membrane, comprising: 
 a) a crosslinked polymer continuous phase; and    b) a molecular sieve material dispersed within said continuous phase;    wherein said membrane has a CO 2  permeability of at least 20 barrers and a CO 2 /CH 4  selectivity of greater than 30, at 35 degrees C. and a pressure of 100 psia.    
     
     
         2 . A hollow fiber mixed matrix polymer membrane, comprising: 
 a) a continuous phase polymer comprising a polyimide having crosslinkable sites; and    b) a molecular sieve material dispersed within said continuous phase polymer;    wherein the ratio of crosslinkable sites to imide groups is between 3:8 and 1:16.    
     
     
         3 . A hollow fiber mixed matrix polymer membrane material, comprising: 
 a molecular sieve dispersed within a continuous polymer phase wherein said continuous polymer phase comprises a polyimide polymer made from the monomers A+B+C;    where A is a dianhydride of the formula;                          where X 1  and X 2  are independently a halogenated alkyl group, phenyl or halogen;    where R 1 , R 2 , R 3 , R 4 , R 5 , and R 6  are independently H, alkyl, or halogen;    where B is a diamino cyclic compound without a carboxylic acid functionality;    where C is a diamino cyclic compound with a carboxylic acid functionality; and    wherein the ratio of B to C is between 1:4 and 8:1.    
     
     
         4 . The hollow fiber polymer membrane of  claim 1  wherein the molecular sieve material dispersed within said continuous phase has an average particle size of less than about 1 micron.  
     
     
         5 . The hollow fiber polymer membrane material of  claim 3  where X 1  and X 2  are CF 3 .  
     
     
         6 . The hollow fiber polymer membrane material of  claim 3  where R 1 , R 2 , R 3 , R 4 , R 5 , and R 6  are H.  
     
     
         7 . The hollow fiber polymer membrane material of  claim 3  wherein the dianhydride is 6FDA.  
     
     
         8 . The hollow fiber polymer membrane material of  claim 3  wherein C is DABA.  
     
     
         9 . The hollow fiber polymer membrane material of  claim 3  wherein B is a diamino aromatic compound.  
     
     
         10 . The hollow fiber polymer membrane material of  claim 3  wherein B is a diamino benzene compound having one or more methyl groups attached to the benzene ring.  
     
     
         11 . The hollow fiber polymer membrane material of  claim 3  wherein the ratio of B to C is between 17:3 and 3:2.  
     
     
         12 . The hollow fiber polymer membrane material of  claim 3  wherein the ratio of B to C is between 17:3 and 3:1.  
     
     
         13 . The hollow fiber polymer membrane material of  claim 3  wherein said membrane is subjected to esterification conditions in the presence of a diol selected from the group consisting of ethylene glycol, propylene glycol, 1,3 propanediol, 1,4 butanediol, 1,2 butanediol, benzenedimethanol, and 1,3 butanediol to form a hollow fiber polymer membrane monoester.  
     
     
         14 . The hollow fiber polymer membrane material of  claim 13  wherein at least 60% of the carboxylic acid functionality is converted to a monoester.  
     
     
         15 . The hollow fiber polymer membrane material of  claim 13  wherein the hollow fiber membrane monoester is subjected to transesterification conditions to form a crosslinked hollow fiber polymer membrane.  
     
     
         16 . The hollow fiber polymer membrane of  claim 1  wherein the molecular sieve material dispersed within said continuous phase has an average particle size of less than about 0.1 micron.  
     
     
         17 . The hollow fiber polymer membrane material of  claim 3  wherein B is diamino durene.  
     
     
         18 . The hollow fiber polymer membrane of claims  1 ,  2  and  3  wherein the molecular sieve is a zeolite.  
     
     
         19 . The hollow fiber polymer membrane of claims  1 ,  2  and  3  wherein the molecular sieve is carbon molecular sieve.  
     
     
         20 . The hollow fiber polymer membrane of claims  1 ,  2  and  3  wherein the molecular sieve is a aluminophosphate zeolite.  
     
     
         21 . The hollow fiber polymer membrane of claims  1 ,  2  and  3  wherein the molecular sieve is a borosilicate.  
     
     
         22 . The hollow fiber polymer membrane of claims  1 ,  2  and  3  wherein the molecular sieve is a SAPO.  
     
     
         23 . A method of making a crosslinked hollow fiber membrane, comprising: 
 preparing a continuous phase polyimide polymer comprising a predetermined quantity of crosslinkable sites and a molecular sieve material dispersed within said continuous phase polymer; forming a hollow fiber from said continuous phase polyimide polymer; treating the hollow fiber with a diol selected from the group consisting of ethylene glycol, propylene glycol, 1,3 propanediol, 1,4 butanediol, 1,2 butanediol, and 1,3 butanediol, at esterification conditions, to form a monoesterified hollow fiber; and subjecting the monoesterified hollow fiber to transeesterification conditions to form a crosslinked hollow fiber membrane.    
     
     
         24 . A method of making a crosslinked hollow fiber membrane, comprising: 
 preparing a polyimide polymer comprising a predetermined quantity of crosslinkable sites and a molecular sieve material dispersed within said continuous phase polymer; treating the polyimide polymer with a diol selected from the group consisting of ethylene glycol, propylene glycol, 1,3 propanediol, 1,4 butanediol, 1,2 butanediol, and 1,3 butanediol, at esterification conditions, to form a monoesterified membrane material; forming a monoesterified hollow fiber from the monoesterified membrane material; and subjecting the monoesterified hollow fiber to transesterification conditions to form a crosslinked hollow fiber membrane.    
     
     
         25 . The hollow fiber polymer membrane material of  claim 13  wherein at least 80% of the carboxylic acid functionality is converted to a monoester.