Hydrophilic polymer coated microporous membranes capable of use as a battery separator

DETAILED DESCRIPTION What is claimed is: 1.
A process for rendering a normally hydrophobic microporous membrane hydrophilic and reducing the electrical resistance thereof which comprises applying a coating to the surface of said membrane in a manner sufficient to achieve a coating thickness when dry of from about 1 to about 25 microns, said coating being selected from the group consisting of cellulose esters, and polyvinyl alcohol, and impregnating said membrane with a surfactant in a manner and in at least an amount sufficient to render the membrane hydrophilic in the absence of said coating.
2.
The process of claim 1 wherein the polymer coating is applied as a solution or dispersion and the surfactant is impregnated in the substrate membrane by mixing it with said polymer coating solution or dispersion.
3.
The process of claim 2 wherein the polymer coating is cellulose acetate.
4.
A process for reducing the penetration, of a battery separator which is disposed between a zinc anode and a cathode which constitute the electrodes of at least one rechargeable electrolytic cell employing an alkaline electrolyte, by electrode derived ions which comprises employing as the battery separator at least one normally hydrophobic microporous membrane which has been rendered hydrophilic by applying a coating to the surface of said membrane in a manner sufficient to achieve a coating thickness when dry of from about 1 to about 25 microns, said coating being selected from the group consisting of cellulose esters, and polyvinyl alcohol, and impregnating said membrane with a surfactant in a manner and in at least an amount sufficient to render the membrane hydrophilic in the absence of said coating.




Description:
BACKGROUND OF THE INVENTION The present invention relates to coated microporous membranes which exhibit improved wettability and can be used in alkaline storage batteries and particularly in batteries having electrode systems containing zinc and silver electrodes, e.
g.
, nickel-zinc and silver-zinc, and a process for making the same