GB1317694A - Polyarylene polyether membrane - Google Patents

Abstract

1317694 Polyarylene-ether coated fabrics RHONE-POULENC SA 26 Oct 1971 [27 Oct 1970] 49757/71 Heading B2E [Also in Divisions B5 and C3] A membrane consisting essentially of a polyarylene polyether comprising recurring units of the formula: in which Q represents a phenyl radical, Q' represents a phenyl radical, a phenyl radical substituted by 1 to 5 alkyl radicals having 1 to 8 carbon atoms, or a biphenylyl, terphenylyl or naphthyl radical, A, (which may either be a substituent on the basic phenylene chain member or a substituent on Q or Q') represents a halogen atom, y, the value of which can vary from one recurring unit to another, is 0, 1, 2, 3 or 4 and x is such that the specific viscosity of the polyether is 0.3-1.5, measured at 25‹C, as a 5g/litre solution in cyclohexanone, the membrane comprising a dense layer of average thickness 0.01-10Á, and thereunder a porous layer, with open pores, of average thickness 30Á-1mm., the total volume of the pores representing 20-80% of the total volume of the membrane, is prepared by a) casting onto a support a solution of the polyarylene polyether in a binary mixture of two solvents for the polymer, having boiling points differing by at least 30‹C, onto a support; b) removing at least a part of the more volatile solvent without exceeding the boiling point of this more volatile solvent; c) treating the resulting film thus obtained with a coagulating liquid; and d) drying the film resulting from c). Suitable solvents used are aliphatic and aromatic hydrocarbons, halogenated hydrocarbons and aprotic polar solvents such as N-methylpyrrolidone-2, dimethylformamide and dimethylacetamide. A suitable solvent mixture is dichloromethane and N-methylpyrrolidone-2. Examples of coagulating liquid are water, alcohols and ketones. A particularly preferred coagulating liquid is methanol. In general the weight of the more volatile solvent in the solvent mixture is 10-70% by weight of the solvent mixture and the concentration of polymer in the solution is 5-40% by weight based on the weight of solution 15-100% by weight of the more volatile solvent may be removed prior to step c). The object of treating with coagulating liquid is to set or gel the polymer solution or to complete any initial gel formation. This treatment is preferably carried out at room temperature. The final stage may be carried out at temperatures up to 100‹C. The support used for casting may be a glass plate or a metal belt (continuous casting). Depending on the shape of the support membranes of various shapes, e.g. planar and tubular, may be made. The membrane may also be reinforced by a fabric screen such as a woven fabric, e.g. a polyamide or polyester woven fabric, or a non-woven fabric of natural or synthetic fibres. Such membranes are prepared by casting onto the screen borne by the support. The membranes of the invention find application in the fractionation of gas mixtures.