GB696066A - Polymers - Google Patents

Abstract

An acetone-soluble film-forming copolymer of methacrylonitrile and vinylidene chloride alone which contains 55 to 99 per cent of methacrylonitrile is preferably prepared in an aqueous suspension or dispersion containing methacrylonitrile and vinylidene chloride in a ratio between 52.5 : 47.5 and 90 : 10, the ratio of water to total monomer being from 3 : 1 to 6 : 1, polymerization being initiated by means of a peroxy compound. The emulsifying agent used is preferably sodium secondary octadecyl sulphate, other suitable emulsifying agents being alkali metal or ammonium salts of other long-chain alkyl sulphates, of aralkyl sulphates, of alkyl-aryl sulphonic acids or of long-chain alkyl carboxylic acids. The catalyst is preferably potassium or ammonium persulphate, other suitable catalysts being benzoyl, acetyl, lauryl and hydrogen peroxides and tertiary butyl hydroperoxide. Redox system may be employed using oxygen or one of the above catalysts in conjunction with a reducing agent such as sodium sulphinate or a sugar. Regulators such as dodecyl mercaptan, acetaldehyde and dioxane may be used to control the average molecular weight of the polymer, and polymerization may be stopped by addition of an anti-oxidant such as phenyl-beta-naphthylamine. Additions of methacrylonitrile may be made in the course of polymerization so as to keep the monomer ratio constant throughout. The copolymer may be recovered from the aqueous latex by addition of an aqueous solution containing ions capable of neutralizing the charge on the latex particles, by freezing the p latex, or by the use of a water-soluble organic precipitant such as methanol or ethanol. The copolymers of the invention may be plasticized with dialkyl and alkoxyalkyl phthalates, glycolic acid esters, dicarboxylic acid esters of cyclohexanol and its derivatives, sebacic and phosphoric acid esters, butadiene-acrylonitrile copolymers and low molecular weight condensation products of glycols with aliphatic dicarboxylic acids. Films and filaments may be made from acetone solutions of the copolymers and may be dyed by the methods used in dyeing cellulose acetate fibres. They may be stretched to many times their original length and annealed, e.g. at a temperature above 60 DEG C. Coating compositions may be made by dissolving the copolymers in volatile solvents or solvent mixtures such as one or more of acetone, methyl ethyl ketone, dioxane, dioxolane, tetrahydrofurane, nitromethane and nitroethane or in less volatile solvents such as cyclohexanone, cyclopentanone, isophorone, mesityl oxide and pyridine, and diluents such as benzene, toluene or a xylene may be added. Solvent mixtures may also include ethyl acetate, ethyl and butyl lactates, diethyl, methyl isobutyl, and methyl amyl ketones, diacetone alcohol, methylene and ethylene dichlorides, trichlorethylene, carbon tetrachloride, perchlorethylene and monochlorbenzene. Specifications 569,182, 570,711 and 629,137 are referred to.