Flexible water swellable crosslinked polyacrylate film

A flexible water swellable crosslinked polyacrylate film produced by the method which comprises

• A. applying a coating on an impervious substrate wherein the coating comprises a crosslinkable aqueous solution which is prepared by forming a polyacrylate solution having about 30 to about 70 weight percent alkali metal carboxylates by dissolving in an aqueous alkali metal hydroxide solution a polyacrylate comprising
• 1. about 30 to about 92 percent by weight of an alkyl acrylate wherein the alkyl group has 1-10 carbon atoms, an alkyl methacrylate wherein the alkyl group has 4-10 carbon atoms, or mixtures thereof,
• 2. about 8 to about 50 percent by weight of an olefinically unsaturated carboxylic acid, and
• 3. about 0 to about 15 percent by weight of an omega hydroxy-alkyl acrylate having 1-4 carbon atoms in the hydroxy alkyl group,
• heating the solution until saponification is complete, and adding to said solution about 0.1 to about 10 weight percent, based on the dissolved polymer of a water soluble crosslinking agent which is reactive with carboxylate salt groups
• B. heating said coated substrate to a temperature greater than about 30.degree. C to crosslink said polyacrylate, and
• C. separating said crosslinked film from said substrate.