Aqueous emulsion-type pressure sensitive adhesives

Abstract

An aqueous emulsion-type pressure sensitive adhesive characterized in that the aqueous emulsion is prepared by (i) a first step of emulsion polymerizing an ethylenically unsaturated monomer composed essentially of at least one type of styrene, alpha-methylstyrene, acrylonitrile, methyl methacrylate and vinyltoluene in the presence of an emulsion composed of at least one tackifier resin selected from a rosin ester, a petroleum resin and a terpene resin to form an aqueous emulsion containing particles of a two-layered structure having a core layer of the tackifier resin and a layer of a polymer (polymer A.sub.1) derived from the ethylenically unsaturated monomer, and (ii) a second step of using the aqueous emulsion containing the particles of the two-layered structure as a seed and emulsion polymerizing an ethylenically unsaturated monomer composed essentially of at least one alkyl (meth)acrylate (an alkyl group has 4 or more carbon atoms) to form an aqueous emulsion containing particles of a multilayered structure having also a layer of a polymer (polymer A.sub.2) derived from the ethylenically unsaturated monomer.

Dependencies are inferred from the claim text.