Suspension polymerisation

In the aqueous suspension polymerization of monomers such as styrene, o- or p-chlorostyrene, dichlorostyrene, methyl, ethyl, propyl or butyl styrene, divinyl benzene, butadiene, methyl methacrylate, ethyl acrylate, acrylonitrile, vinylidene chloride and mixtures, finely divided magnesium hydroxide is used as stabilizer in the presence of additional alkali, e.g. sodium, potassium and calcium hydroxides. A catalyst such as benzoyl peroxide may be used and the mixture may also contain small amounts, e.g. up to 10 per cent of the stabilizer, of a surface active agent such as the salts of organic sulphates and sulphonates, e.g. sodium octadecyl sulphate, alkali sulphite addition products of neutral esters of unsaturated polycarboxylic acids, alkyl aromatic sulphonates and aryl alkyl polyether sulphates, e.g. sulphonates of condensation products of ethylene oxide and alkyl phenols. Excess stabilizer may be removed from the polymer beads by washing with acid, e.g. sulphuric acid.