Crosslinked membrane and polymer for making same and method of using membrane

Abstract

A composition of and a method of making high performances crosslinked membranes are described. The membranes have a high resistance to plasticization by use of crosslinking. The preferred polymer material for the membrane is a polyimide polymer comprising covalently bonded ester crosslinks. The resultant 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 membrane from a monesterified polymer followed by final crosslinking after the membrane is formed.

1 . A polymer membrane comprising:
 a crosslinked polymer having covalent ester crosslinks formed from a crosslinkable polymer; and   having a CO 2  permeance of at least 20 GPU and a CO 2 /CH 4  selectivity of greater than 20, at 35 degrees C. and a pressure of 100 psia.   
   
   
       2 . The polymer membrane of  claim 1  wherein:
 the crosslinkable polymer has an average molecular weight of between 20,000 and 200,000.   
   
   
       3 . The polymer membrane of  claim 1  wherein:
 the crosslinkable polymer has an average molecular weight of between 30,000 and 160,000.   
   
   
       4 . The polymer membrane of  claim 1  wherein:
 the crosslinkable polymer has an average molecular weight of between 40,000 and 140,000.   
   
   
       5 . The polymer membrane of  claim 1  wherein:
 the cross linkable polymer has an average molecular weight of between 60,000 and 120,000.   
   
   
       6 . The polymer membrane of  claim 1  wherein:
 the crosslinkable polymer has an average molecular weight greater than the entanglement molecular weight of the polymer.   
   
   
       7 . The polymer membrane of  claim 1  wherein:
 the polymer is selected from the group consisting of polyimides, polyletherimides, polyethersulfones and polysulfones.   
   
   
       8 . The polymer membrane of  claim 7  wherein:
 the polymer is made using analogs of 6FDA.   
   
   
       9 . The polymer membrane of  claim 8  wherein:
 the polymer is a polyimide.   
   
   
       10 . The polymer membrane of  claim 1  wherein:
 the ester crosslinks are made using 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.   
   
   
       11 . The polymer membrane of  claim 1  wherein:
 the crosslinkable polymer is formed by the monoesterification of a polymer having carboxylic acid sites incorporated therein, with a diol.   
   
   
       12 . The polymer membrane of  claim 11  wherein:
 the dial is selected from the group consisting of ethylene glycol, propylene glycol 1,3 propanediol, 1,4 butanediol, 1,2 butanediol, benzenedimethanol, and 1,3 butanediol.   
   
   
       13 . The polymer membrane of  claim 1  wherein:
 the membrane is a composite membrane with a porous support supporting a crosslinked polymer wherein the porous support is a polymer selected from the group consisting of substituted or unsubstituted polymers, polysulfones, poly(styrenes), including styrene-containing copolymers including acrylonitrilestyrene copolymers, styrene-butadiene copolymers and styrene-vinylbenzylhalide copolymers, polycarbonates, cellulosic polymers including cellulose acetate-butyrate, cellulose propionate, ethyl cellulose, methyl cellulose, nitrocellulose, polyamides and polyimides, including aryl polyamides and aryl polyimides, polyethers, polyetherimides, polyetherketones, polyethersulfones, poly(arylene oxides) including poly(phenylene oxide) and poly(xylene oxide), polyesteramide-diisocyanate), polyurethanes, polyesters (including polyarylates), such as polyethylene terephthalate, poly(alkyl methacrylates), poly(acrylates), poly(phenylene terephthalate), polypyrrolones, polysulfides, polymers from monomers having alpha-olefinic unsaturation including poly (ethylene), poly(propylene), poly(butene-1), poly(4-methyl pentene-1), polyvinyls including poly(vinyl chloride), poly(vinyl fluoride), poly(vinylidene chloride), poly(vinylidene fluoride), polyvinyl alcohol), poly(vinyl esters) including poly(vinyl acetate) and polyvinyl propionate), poly(vinyl pyridines), poly(vinyl pyrrolidones), polyvinyl ethers), poly(vinyl ketones), poly(vinyl aldehydes) including polyvinyl formal) and poly(vinyl butyral), poly(vinyl amides), poly(vinyl amines), polyvinyl urethanes), polyvinyl ureas), poly(vinyl phosphates), and poly(vinyl sulfates), polyallyls, poly(benzobenzimidazole), polyhydrazides, polyoxadiazoles, polytriazoles; poly (benzimidazole), polycarbodiimides, polyphosphazines, and interpolymers, including block interpolymers containing repeating units including terpolymers of acrylonitrile-vinyl bromide-sodium salt of para-sulfophenylmethallyl ethers.   
   
   
       14 . A polymer comprising:
 a polymer which has been monoesterified with a diol to form a crosslinkable polymer having an average molecular weight of between 20,000 and 200,000 and which can be formed into a membrane and transesterified to provide a crosslinked membrane having a CO 2  permeance of at least 20 GPU and a CO 2 /CH 4  selectivity of greater than 20, at 35 degrees C. and a pressure of 100 psia.   
   
   
       15 . The polymer of  claim 14  wherein:
 the crosslinkable polymer has an average molecular weight of between 30,000 and 160,000.   
   
   
       16 . The polymer of  claim 14  wherein:
 the crosslinkable polymer has an average molecular weight of between 40,000 and 140,000.   
   
   
       17 . The polymer of  claim 14  wherein:
 the crosslinkable polymer has an average molecular weight of between 60,000 and 120,000.   
   
   
       18 . A process for producing hydrocarbon products comprising separating two gases having different molecular sizes in a feedstream including these two gas components, the process including: (a) providing a crosslinked polymer having covalent ester crosslinks and having a CO 2  permeance of at least 200 GPU and a CO 2 /CH 4  selectivity of greater than 20, at 35 degrees C. and a pressure of 100 psia, the membrane having feed and permeate sides and which is selectively permeable to a first gas component over a second gas component; and (b) directing a feedstream including the first and second gas components to the feed side of the membrane and withdrawing a retentate stream depleted in the first gas component and withdrawing a permeate stream enriched in the first gas component from the permeate side of the membrane.