Abstract: An improved wet-laid nonwoven fabric for a battery separator wherein 20 to 95% by weight of thermoplastic staple fibers having a single fiber diameter of 20 .mu.rm, or less are three-dimensionally entangled with hot-melt fibers having a melting point lower by 20.degree. C. than that of the thermoplastic staple fibers so that a mean fiber entangling point interval is 300 .mu.m or less, wherein at least part of the hot-melt fibers are fused to bond the fibers with each other to fix the nonwoven structure. The nonwoven fabric has a basis weight in a range from 10 to 350 g/m.sup.2, a thickness in a range from 30 to 1000 .mu.m and an apparent density in a range from 0.26 to 0.7 g/cm.sup.3, and is excellent in uniformity and mechanical strength. The wet-laid nonwoven fabric is particularly excellent in air permeability, liquid holding capability, liquid retention capability and liquid absorption rate and satisfies the requirement for a battery separator.

Abstract: Disclosed is a composite sheet for a reinforcing material, which comprises a web comprised of a reinforcing filament bundle and a thermoplastic polymer fiber in the form of single filaments, and this composite sheet is characterized in that the thermoplastic polymer fiber is involved in the web-constituting filaments in an entangled and integrated state. This composite sheet is prepared by a process comprising depositing and incorporating the thermoplastic polymer fiber in the form of single filaments in the web comprising the reinforcing filament bundle, and applying a jet stream of a fluid to the assembly.