FIELD: process engineering.
SUBSTANCE: invention relates to production of microporous polyolefin membranes to be used in storage battery separators. Membrane comprises polyethylene resin and features (a) trip temperature of 135°C or lower whereat air permeability on heating at 5°C/min rate reaches 1×105 s/100 cm3, (b) maximum shrinkage at 40%-smelting or less in crosswise direction at 135-145°C that is determined thermo mechanically at load of 2 gf at temperature increase rate of 5°C/min and (c) melting point of 150°C or higher whereat air permeability measured at subsequent heating after reaching trip temperature becomes, again, equal to 1×105 s/100 cm3 Membrane is produced by mixing polyethylene resin melt with membrane-forming solvent in two-screw extruder in extruding produced solution through die. Cooling is performed to produce gel sheet. Said sheet is stretched at 1-80%/s-rate to provide 100%-length before stretching, and solvent is removed from sheet.
EFFECT: better trip melting properties of proposed membrane.
4 cl, 6 dwg, 1 tbl, 9 ex
