Polyacrylic acid copolymer emulsion. It is generally made by copolymerizing acrylic acid low ester organic substances such as methyl acrylate as the main monomer with acrylonitrile, styrene, dibutyl maleate, methacrylate, vinyl chloride, vinylidene chloride or vinyl acetate. Sometimes, in order to give the polymer emulsion some special properties, functional monomers are introduced, such as (meth) acrylic acid, maleic acid, fumaric acid, (meth) acrylamide, etc.