METHOD OF MANUFACTURING MULTILAYER POLYTETRAFLUOROETHYLENE POROUS MEMBRANE AND HALF-SINTERED POLYTETRAFLUOROETHYLENE MULTILAYER FILM Russian patent published in 1999 - IPC

FIELD: electrolytic technics. SUBSTANCE: invention is concerned with production of permeable membranes for electrolysis and battery separators, filtering media for corrosive gases and liquids. Internal cavity of premolding mold is filled with at least two types of polytetrafluoroethylene powders having (i) different endothermic peaks in the curves of crystalline melting within a temperature range of 332 to 348 C as measured by scanning differential calorimeter and (ii) different crystalline conversions with difference between their minimum and maximum magnitudes 0.1 to 0.75. Powders are mixed with a liquid lubricant. Resulting multilayer blank is extruded. Extrudate is freed from lubricant and non-caked multilayer structure is heated to temperature not lower than melting temperature of caked polytetrafluoroethylene. At least one of powders contains non-fiber- forming material. EFFECT: improved quality of prepared material. 6 cl, 16 dwg, 1 tbl, 10 ex