this invention relates to improved textile fibers having deposited thereon a coagulable , multi - stage , latex binder . in addition , this invention relates to a method for improving the stiffness of textile materials by depositing thereon an acid - resistant , coagulable , multi - stage , latex binder wherein one stage enhances the stiffness of the textile fibers and another stage controls the coagulation temperature of the latex binder . the latex binder is particularly suitable for use in battery separators .