GB1101204A - Cementing compositions - Google Patents

Abstract

A copolymer, for use in cement compositions (see Division C1) comprises (a) vinylidene chloride, (b) acrylonitrile and (c) a monoethylenically unsaturated carboxylic acid wherein at least 65% by wt. of the units are derived from (a), 11 to 30% from (b) and 0.5 to 5% from (c). The monoethylically unsaturated acid is preferably acrylic or methacrylic acid. The copolymer may be prepared in aqueous dispersion in the substantial absence of emulsifiers but when conventional emulsifiers are used a non-ionic surface-active agent, e.g. an alkyl phenyl ether of a polyoxyethylene glycol may be added in an amount of 0.5 to 10% by wt. based on the weight of the copolymer. A silicone defoaming agent may also be present. In the examples, ammonium persulphate is used as catalyst.ALSO:A cement composition comprises an hydraulic cement, e.g Portland or plaster of Paris, optionally aggregates, and 5-40% by weight, based on the weight of the cement of a copolymer of (a) vinylidene chloride, (b) acrylonitrile, and (c) a monoethylenically unsaturated carboxylic acid, said copolymer containing at least 65% by weight of units derived from vinylidene chloride, 11 to 30% of units derived from acrylonitrile and 0.5-5% by weight of units derived from said monoethylenically unsaturated carboxylic acid which may be acrylic, methacrylic, vinyl acetic, crotinic acid or a polycarboxylic acid such as maleic, fumaric, itaconic, aconitic, citraconic and mesaconic acid. The copolymer may be added to the cement in the form of an aqueous dispersion which may be prepared in the absence of an emulsifier. A non-ionic surface active agent in amount 0.5 to 10% by weight may be added as stabilizer, e.g. alkyl phenyl ether of a polyoxyethylene glycol and a silicone-defoaming agent may also be present. The aggregates may be sand, lime or gravel.