To improve affinity with an electrolyte, smoothly pass oxygen gas generated at charging time, and prevent an internal pressure increase by absorbing the gas by a negative electrode by performing surface treatment on a base material composed of nonwoven fabric or woven fabric using a polyolefine resin as a main constitutive material by glow discharge plasma.
This separator contains epoxy radical denatured polyvinyl alcohol whose number average molecular weight expressed by a formula is 8000 to 220000. Here, R1 to R4 of the formula are a hydrogen atom or an alkyl group, and R5 is an alkyl group, and (n1) is 1 or 2, and (n2) is 1, 2 or 3, and (i, j and k) are an integer to satisfy (i+j+k=200 to 3500). The composition of the epoxy radical denatured PVA is selected from a range of a vinyl alcohol unit of 99.99 to 70 mole %, a vinyl ester unit of 0 to 29 mole % and an expoxy radical containing monomer unit of 0.01 to 10 mole %. Therefore, it can be used as an excellent battery separator which has high liquid preserving rate and alkali resistance and by which battery performance is not reduced.
YOKOUCHI HIDEYUKI
TOYOSHIMA SETSUO
Next Patent: POLYMER SEPARATOR, ITS MANUFACTURE, AND BATTERY CONTAINING THE SEPARATOR