Composite hydrogel-forming article and method of making same

Claim 1

A composite article comprising (A) a layer of an optically clear blend of (1) 40 to 98% by weight, based on the total weight of the blend, of a water-soluble polymer of a vinyl lactam having the structure ##STR5## in which X represents an alkylene bridge having three to five carbon atoms, or a water-soluble copolymer thereof with 1 to 90 mole percent of copolymerizable monomer containing a polymerizable ethylenic unsaturation, said polymer or copolymer having a molecular weight from 10,000 to 1,000,000 and (2) 2 to 60% by weight of a water-insoluble copolymer consisting essentially of 50 to 90% by weight, based on the total weight of the copolymer, of a hydrophobic water-insoluble ethylenically unsaturated monomer, 2 to 12% by weight of an ethylenically unsaturated monomer containing an acid group, and 0 to 50% by weight of a hydrophilic ethylenically unsaturated monomer free from acidic groups, and (B) adherent thereto a layer of solid high molecular weight water-resistant polymeric material which is compatible with said vinyl lactam polymer or copolymer in the unhydrated state as determined by optical clarity of a mixture of said polymeric material with said vinyl lactam polymer or copolymer, said layers being in face to face adherent contact with each other, and said layer (A) being capable of absorbing more than 45% of its weight of water without dissolution at room temperature to form a hydrogel adherent to layer (B).