GB745927A - Improvements in or relating to emulsion polymerisation - Google Patents

Abstract

A mixture of butadiene and a compound containing a single olefinic double bond, containing less than 40 per cent butadiene, is copolymerized in the presence of an aqueous phase containing 0.05 to 0.5 per cent of an emulsifier which is an alkali metal salt of a long chain fatty acid (such as sodium or potassium stearate) or of a sulphated or sulphonated fatty acid, or sodium or potassium lauryl or cetyl sulphate, further emulsifier being added only when at least 5 per cent of the monomers have been copolymerized. The additional emulsifier may be added intermittently or continuously and, further, at the end of the reaction additional emulsifier, which may be different, e.g. condensates of ethylene oxide with oleyl alcohol or dioctyl cresol, or sodium b -naphthalene sulphonate/formaldehyde condensate, may also be added. Olefinic monomers specified are styrene, a -methyl styrene; vinyl carbazole, acetate and pyridine; acrylonitrile, methacrylonitrile; methyl acrylate, methacrylate and a -chloroacrylate; methacrylamide and methacrylic acid. Additional monomeric material and water may also be added as the polymerization proceeds. The mixture preferably contains a polymerization modifier such as mercaptans of six to eighteen carbon atoms, e.g. t-dodecyl and lauryl mercaptans, and organic polysulphides such as di(s-butyl)-, di-(2-methyl butyl)-, dialkyl xanthogen and di-o-dinitrophenyl disulphides. Catalysts, which are preferably used, include hydrogen peroxide, potassium persulphate and redox systems such as cumene hydroperoxide or benzoyl peroxide together with ferrous sulphate/potassium pyrophosphate complex and sorbose or fructose. Methanol may be included in low temperature systems and t-butyl catechol may be used as an inhibitor. Example III includes potassium hydroxide and chloride as buffer. Particles of large size may be obtained by using a portion of latex, produced as above, as seed in a second polymerization. The dispersions obtained are of high solid content and low viscosity and may be used in paints, lacquers, paper coating, leather finishing and strengthening foamed latex of natural or synthetic rubber. Specification 724,139 is referred to.