Method for graft copolymerization to natural rubber articles

Claim 1

A process for grafting a hydrophilic polymer of a carboxylic acid, or a salt thereof, onto the surface of a natural rubber article, said rubber article being selected from the group consisting of a sheet, glove and tube; and said acid being selected from the group consisting of maleic, acrylic, methacrylic, itaconic and citraconic acid; which comprises the steps of (a) contacting said rubber article with from 2 to 45 parts by weight, per part by weight of said rubber article, of an anhydride of said carboxylic acid, and 0.4 to 10 percent, based on weight of said anhydride, of a free radical polymerization initiator, at a temperature of from 50° to 150° C., in the presence of a reaction inert organic solvent which dissolves at least substantial portions of said monomeric acid anhydride and said initiator, and has no significant detrimental effect on the starting rubber article or product; (b) washing the resulting rubber article with a water miscible solvent to remove by-products and unreacted starting materials, followed by (c) hydrolysis of the washed article under aqueous alkaline conditions to convert carboxylic acid anhydride groups to carboxylate salts, and when free carboxylic acid groups are desired, acidifying with dilute aqueous or alcoholic acid.