ADHESIVE LATEXES OF VINYL ACETATE/ETHYLENE/N-METHYLOLACRYLAMIDE TERPOLYMERS

摘要

Latex adhesives with excellent resistance to cold flow and peel are prepared by a method comprising (a) maintaining about 50-300 psi ethylene pressure on an aqueous emulsifying composition containing a partially hydrolyzed polyvinyl alcohol and a free-radical donor selected from alkali metal and ammonium persulfates and peroxydiphosphates, (b) causing said free-radical donor to initiate interpolymerization while (c) gradually adding vinyl acetate (VAc) and N-methylol acrylamide (NMA) monomers in substantially constant NMA/VAc weight ratio of about 0.5 to 2.0 percent, wherein said polyvinyl alcohol and free-radical donor are used in amounts respectively of about 2.5-8.0 percent and 0.5-2 percent based on the total weight of vinyl acetate used and wherein the rates of monomer addition are sufficient to cause interpolymerization of the vinyl acetate, ethylene and NMA, but insufficient to permit the quantity of unpolymerized vinyl acetate in the aqueous composition to rise higher than about 3.5 percent by weight of the composition during the preparation of at least 75 percent of said interpolymerization.