GB788815A - Improvements in and relating to porous plates - Google Patents

Abstract

A porous plate particularly for use as a battery separator plate is formed by coalescing a mixture of granular ebonite and at least one granular thermoplastic synthetic resin by the action of heat and/or pressure. Preferably the plate comprises 3 to 15 parts by weight of ebonite and 100 parts by weight of a thermoplastic material selected from polymers, copolymers and polymer mixtures of vinyl compounds, e.g. esters of acrylic and methacrylic acids. A mixture comprising ebonite and thermoplastic particles of about the same size, in the range of 0.01 to 0.3 mm. may be sintered in two stages, either by partially sintering by heating to approximately the sintering temperature and completing the sintering by applying pressure, or by partially coalescing by applying pressure thereto at room temperature and thereafter heating to complete the sintering. A number of plates may be manufactured by a continuous process in which the mixture is carried by a movable support through a heating zone to effect partial sintering, whereafter the web thus obtained is pressed, cooled and divided into lengths. In one example a mixture of 95 parts by weight of polystyrene and 5 parts of ebonite dust, both of particle size of approximately 60 microns, are heated on metal moulds for 18 minutes at about 280 DEG C. The material is then pressed while still hot for about 5 seconds at 3 kg/square cm. pressure. In further examples the mixes comprise (a) 80 parts polystyrene, 10 parts diatomaceous earth and 10 parts ebonite dust; (b) 90 parts polyvinyl chloride, 10 parts ebonite dust; and (c) 45 parts polyvinyl chloride, 45 parts polystyrene, 10 parts ebonite dust.ALSO:A porous plate particularly for use as a battery separator plate is formed by coalescing a mixture of granular ebonite and at least one granular thermoplastic synthetic resin by the action of heat and/or pressure. Preferably the plate comprises 3 to 15 parts by weight of ebonite and 100 parts by weight of a thermoplastic material selected from polymers, copolymers, and polymer mixtures of vinyl compounds e.g., esters of acrylic and methacrylic acids. A mixture comprising ebonite and thermoplastic particles of about the same size in the range of 0,01 to 0,30 mm. may be sintered in two stages, either by partially sintering by heating to approximately the sintering temperature and completing the sintering by applying pressure, or by partially coalescing by applying pressure thereto at room temperature and thereafter heating to complete the sintering. A number of plates may be manufactured by a continuous process in which the mixture is carried by a movable support through a heating zone to effect partial sintering, whereafter the web thus obtained is pressed, cooled, and divided into lengths. In one example a mixture of 95 parts by weight of polystyrene and 5 parts of ebonite dust, both of particle size of approximately 60 microns, are heated on metal moulds for 18 minutes at about 280 DEG C. The material is then pressed while still hot for about 5 seconds at 3 kg./square cm. pressure. In further examples the mixes comprise (a) 80 parts polystyrene, 10 parts diatomaceous earth, and 10 parts ebonite dust, (b) 90 parts polyvinyl chloride, 10 parts ebonite dust, and (c) 45 parts polyvinyl chloride, 45 parts polystyrene, 10 parts ebonite dust.