Patent GB-1327990-A (GB)
Title: Dialysis and ultrafiltration of a liquid
IPC: A23C9/142
Filed: 1971-09-08
Abstract: 1327990 Semi-permeable membranes RHONE-POULENC SA 8 Sept 1971 [9 Sept 1970] 41936/71 Heading B5B [Also in Division B1] A semi-permeable membrane used to separate two compartments in apparatus for the fractionation of liquids is prepared by treating a film containing at least one copolymer of acrylonitrile and an ionic or ionizable olefinically unsaturated monomer with water or an aqueous non-solvent mixture at a temperature of 60-250 C. Preferably the films consist of either (a) a copolymer of acrylonitrile and at least one ionic or ionizable monomer and, optionally, a non-ionic monomer or (b) a blend of at least two copolymers defined in (a) or of at least one copolymer defined in (a) and at least one copolymer of acrylonitrile and a non-ionic monomer, the ionic or ionizable monomer units representing from 1 to 80 mole per cent of the monomer units in one of said copolymers and 1 to 50% of the total monomer units in the membrane. Suitable ionic or ionizable monomers are the ethylenically unsaturated monomers of general formula where Y is an ionic or ionizable group, particularly a sulphonate, phosphonate or quaternary ammonium group; R 1 , R 2  and R 3  are hydrogen or alkyl groups and may be the same or different; and A is either (i) a divalent purely hydrocarbon radical; or (ii) a divalent chain in which purely hydrocarbon groups are bonded to each other by an oxygen or sulphur atom or a carbonyloxy or 1-oxo-2-aza-ethylene group; or (iii) a O-A- or S-A- group wherein A is as defined in (i) or (ii); or (iv) a group as defined above in which one or more carbon atoms carries an additional substituent. Preferred ionic or ionizable monomers are the vinyl-sulphonic or -phosphonic acids or their sodium, potassium or ammonium salts and the vinyl pyridinium salts. Suitable non-ionic or non-ionizable monomers are those conventionally used in acrylonitrile copolymers, preferred monomers being methyl methacrylate, butyl acrylate, vinyl benzoate, vinylidene chloride, acrylamide and styrene. The membranes may be prepared by casting a DMF solution of suitable composition on to a glass plate, drying the resultant film at 60 C. in an oven, removing the dried film from the plate and immersing it in hot water at a temperature of from 60 C. to 250 C. or by a process in which a copolymer solution in DMF is continuously cast on to an endless steel belt and passed into an oven heated to 150 C., the resultant film being cooled to 20 C., moisturized and stripped from the belt and then passed through a bath of hot water maintained at 90 C. The film may be stretched uni- or bi-axially between 20% and 1,000% and may be reinforced with a support e.g., a fabric or net. Examples relate to the production of membranes from copolymers of acrylonitrile and sodium methallylsulphonate, potassium vinyloxybenzene-sulphonate, sodium vinylsulphonate or N-methyl-4-vinylpyridinium sulphonate with or without one of the non-ionic monomers listed above and to the use of the membranes in the ultrafiltration of aqueous solutions of cattle albumen, pepsin, dextran, lysozyme and of human blood, whey, river water, milk and an ascitic liquid.