Non-woven fabric sheet separator material for storage batteries and method for making the same

摘要

The invention is to a non-woven fabric sheet for a storage battery separator. The sheet has an excellent property of holding electrolyte by using conjugate fibers having a specific sectional form. The sheet comprises an ethylene copolymer having a specific structure which can introduce a desirable amount of sulfo groups efficiently under mild reaction conditions. Conjugate fibers having a split sectional form include a first component and a second component having a radial arrangement. The conjugate fibers are obtained by forming an ethylene based random copolymer containing a unit represented by a formula -CH2CH(COOH)-, with polypropylene. Subsequently, a non-woven fabric sheet of a thermally bonding type is obtained by mixing the conjugate fibers with polypropoylene fibers. Subsequently, a non-woven fabric sheet for a storage battery separator is obtained by sulfonating the non-woven fabric sheet using gas such as SO3 to form a unit of the formula -CH2C(SO3H)(COOH)-.