GB954202A - Microporous thermoplastic material - Google Patents

Abstract

Microporous material is produced by mixing two incompatible thermoplastic resins under sufficient heat and pressure to produce a plasticized mass, shaping the mass e.g. by calendering or extrusion, and backing out one resin with a solvent which does not affect the other. An ion exchange polymer and/or graphite may be added to the plasticized mixture of two resins. Medicaments, e.g. antiseptics, insecticides or bactericides may similarly be incorporated into the microporous material. The amount of soluble resin may be adjusted to yield pores which exactly accommodate the increase in volume of the ion exchange resin on its conversion to the salt form, thus yielding a continuous ion exchange membrane. Suitable insoluble resins are polyethylene, polypropylene, polystyrene and polyvinyl chloride. Suitable water-soluble resins for backing out are polyethylene oxide, polyethylene glycol and polyvinyl pyrrolidone. In Example I, polyethylene is mixed with polyethylene oxide under pressure at 220 DEG -250 DEG F., on a mill, the mixture is calendered to sheet form at 250 DEG F., and then immersed in water for 1/2 to 4 hours. II is similar, but methylcellulose is introduced into the pasturized mix to give a porous film suitable for use in dry batteries. III. polymeric methacrylic acid was introduced into the plasticized mix of resins to produce after backing a cation exchange diaphragm. IV. uses polystyrene sulphonic acid instead of polymethacrylic acid to give an ion exchange diaphragm. V. The ion exchange resin incorporated was a weakly boric one obtained by aminating with diethylenetriamine a chlormethylated copolymer of styrene and divinyl benzene VI. A strongly basic anion exchange material obtained by aminating and quaternating a chlormethylated styrene-divinyl benzene co-polymer with trimethylamine was used. Specification 896,800 is referred to.