GB836243A - Copolymers of vinyl acetate with higher vinyl esters - Google Patents

Abstract

A mixture of vinyl esters of acetic acid and another carboxylic acid, for use in the production of copolymers of vinyl acetate with other vinyl esters of carboxylic acids (see Group IV (a)) is prepared by reacting at least ten molar proportions of vinyl acetate with one molar proportion of the carboxylic acid in the presence of a mercuric salt of a strong acid as catalyst, to give a mixture of vinyl acetate, vinyl ester, acetic acid, and a small proportion of unconverted carboxylic acid, the organo-mercury complexes are decomposed and mercury compounds and acetic acid are removed from the mixture. By carboxylic acid is meant a higher fatty acid containing not less than five carbon atoms, e.g. caprylic, lauric, stearic, or oleic acid, or a half-ester of a dicarboxylic acid, e.g. butyl hydrogen phthalate. The mercuric salt is of a strong inorganic or organic acid, e.g. sulphuric, phosphoric, nitric, periodic, p-toluene sulphonic, trichloracetic, or formic acid and may be formed in situ by adding a mercuric salt of a weak acid such as acetic acid to the reactants and then treating with a strong acid. The decomposition of the organo-mercury complexes is achieved either by treating the reaction mixture with the sulphide of an alkali metal such as sodium sulphide in aqueous solution and removing the precipitated mercuric sulphide, or by converting the mercury of the complexes into a water-soluble complex ion by addition of cyanides, hydriodic acid, or potassium iodide. In one method aqueous potassium iodide solution is added with an alkali such as sodium carbonate or bicarbonate, thus removing mercury compounds and acetic acid simultaneously.ALSO:Copolymers of vinyl acetate with a vinyl ester of (a) a higher fatty acid containing at least 5 carbon atoms per molecule, e.g. caprylic, lauric, stearic, and oleic acids, or (b) a half-ester derived from a dicarboxylic acid and an alkanol such as butyl hydrogen phthalate, are produced by reacting at least 10 molar proportions of vinyl acetate with one molar proportion of the higher fatty acid or half-ester in the presence of a mercuric salt of a strong acid as catalyst to give a mixture of vinyl acetate, vinyl ester and acetic acid, together with a small proportion of unconverted higher fatty acid or half-ester, decomposing any organo-mercury complexes and removing substantially all mercury compounds and the acetic acid from the mixture, and then copolymerizing the vinyl acetate and the vinyl ester of the higher fatty acid or half ester. Suitable proportions by weight of vinyl acetate to vinyl ester in the final copolymerisable blend are in the range 95/5% to 75/25% . The reaction of vinyl acetate with the higher fatty acid or half-ester may be effected below 40 DEG C. without using a polymerization inhibitor, or at higher temperatures, e.g. boiling under reflux, when such an inhibitor is used, the inhibitor being subsequently removed from the reaction mixture. The mercuric salt of a strong inorganic or organic acid, e.g. sulphuric, phosphoric, nitric, periodic, p-toluene sulphonic, trichloracetic, or formic acid, is employed as catalyst, or the catalyst may be formed in situ by adding a mercuric salt of a weak acid such as acetic acid to the reactants and then treating with a strong acid. The decomposition of the organo-mercury complexes is achieved either by treating the mixture with the sulphide of an alkali metal such as sodium sulphide in aqueous solution and removing the precipitated mercuric sulphide, or by converting the mercury of the complexes into a water-soluble complex ion by addition of cyanides, hydriodic acid, or potassium iodide. In one method aqueous potassium iodide solution is added with an alkali such as sodium carbonate or bicarbonate, thus removing mercury compounds and acetic acid simultaneously. Polymerization is effected preferably in emulsion in aqueous phase, a dispersing agent being employed, such as methyl cellulose, benzyl cellulose, natural gums such as gum arabic and tragacanth, and polyvinyl alcohols such as are obtained by the partial hydrolysis of polyvinyl acetate. Anionic surface-active agents such as organic sulphates and sulphonates, e.g. the sodium salt of the sulphonic acid of dioctyl succinic ester, may be used in conjunction with the above dispersing agents. Polymerization catalysts such as persulphates and peroxides, e.g. ammonium persulphate, are preferably present, and the polymerization may be effected in an atmosphere of inert gas such as nitrogen.