GB916134A - Improvements in or relating to water-base vinyl acetate-methyl methacrylate gloss paints - Google Patents

Abstract

Binders for water-base gloss paints comprise an aqueous dispersion of a vinyl acetate-methyl methacrylate copolymer, said p copolymer containing from 5 to 40% by weight of methyl methacrylate and having a particle diameter no greater than 0,25 microns. The copolymer dispersions may be prepared by polymerizing the monomers in aqueous media in the presence of catalysts, e.g. hydrogen peroxide, organic peroxides, azo compounds, ammonium, sodium and potassium persulphates, and redox systems comprising sodium hydrosulphite, sodium metabisulphite or potassium sulphite activated with ferrous or chromous ions; protective colloids and emulsifiers, e.g. gelatine, polyvinyl alcohol, hydroxyethyl cellulose, gums, sodium sulphates or sulphonates of long chain alcohols or substituted benzenes, ethylene oxide condensates with long chain acids and alcohols and block polymers of ethylene and propylene oxides; and buffers, e.g. sodium bicarbonate, sodium acetate and sodium and potassium phosphates. The polymerization may be effected batchwise or continuously, preferably with continuous gradual addition of the monomers. The dispersions may be compounded with film fusion agents, ethylene glycol monoalkyl ethers and esters thereof, linear and branched chain alcohols containing 4 to 12 carbon atoms and glycols containing 5 to 12 carbon atoms; plasticizers, e.g. dibutyl phthalate and tricresyl phosphate; pigments and fillers, e.g. titanium dioxide; thickeners, e.g. methyl cellulose, hydroxyethyl cellulose and ammonium polyacrylate; surfactants, e.g. polyglycol esters and sodium salts of low molecular weight carboxylated polyelectrolytes; and defoamers. Preferably a pigment dispersion is prepared by grinding water, pigment, filler, surfactant, defoamer and fusion agent in a high speed paint mill and mixing the resulting dispersion with the binder.