Thermally, heat and chemically resistant ultrafiltration polyimide membrane and method for its production

Abstract

A thermally, heat and chemically stable polyimide asymmetric ultrafiltration membrane, is a porous film or a hollow fiber, having an anisotropic structure a selective surface layer and a substrate, wherein the selective ultraporous surface layer has size of pores 70-800 Å with thickness 0.1-10 mcm and is composed of insoluble rigid-chain aromatic (co)polyimide based on dianhydride of aromatic tetracarbonic acid and aromatic diamine and located on the microporous substrate with thickness 50-250 mcm, and the membrane has water permeability Q=(2-500)·10 −4 cm/sec atm and nominal molecular weight cutoff M L =(5-500)·10 3 g/mol, and method for producing an ultrafiltration membrane as disclosed.

1 . A thermally, heat and chemically stable asymmetric ultrafiltration polyimide membrane, comprising a porous film or a hollow fiber having anisotropic structure and includes a selective surface layer and a substrate, wherein the selective surface layer has pore sizes of between about 70 and about 800 Å with thickness of about 0.1 and about 10 mcm and is comprised of insoluble rigid-chain aromatic (co)polyimide based on dianhydride of aromatic tetracarbonic acid and aromatic diamine and located on a microporous substrate with thickness of between about 50 and about 250 mcm, and the membrane has water permeability (Q) from Q=80·10 −4  cm/sec atm to Q=320·10 −4  cm/sec atm and nominal molecular weight cutoff ML=(5-500)·10 3  g/mol. 
     
     
         2 . A membrane as defined in  claim 1 , wherein the selective surface layer is comprised of (co)polyimide based on dianhydride of aromatic tetracarbonic acid from the group consisting of dianhydride of pyromellitic acid, dianhydride of 3,3′4,4′ diphenyl tetra carbonic acid, dianhydride of 3,3′,4,4″-diphenyl oxytetra carbonic acid, dianhydride of 3,3′,4,4′-diphenylsulfone tetra carbonic acid, dianydride of 3,3′,4,4′-benzophenone tetra carbonic acid or their mixtures and aromatic diamine from the group of 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylsulfone, 4,4′-diaminodiphenylmethane, n-phenyldiamine, m-phenyldiamine, benzidine, 2,4-diaminopyrimidine or mixtures thereof. 
     
     
         3 . A membrane as defined in  claim 1 , wherein the substrate is comprised of the same polymer as the surface layer, or microporous metals or ceramics. 
     
     
         4 - 16 . (canceled)