GB746037A - Production of aqueous silanol dispersions of superior stability - Google Patents

Abstract

Stable aqueous silanol dispersions are prepared by bringing to a pH between 3 and 7 by means of the hydrogen form of a cation exchanger an aqueous solution of a siliconate of an alkali or alkaline earth metal, preferably sodium or potassium. The siliconate should have from 0.5 to 3 hydrocarbon groups per silicon atom, the hydrocarbon groups being saturated or olefinically unsaturated groups having one to five carbon atoms or phenyl, tolyl or benzyl. A long list of hydrolysable silicones from which the siliconates may be prepared is given, including silanes having two or three silicon atoms joined by hydrocarbon groups and silanes having hydrogen attached to silicon. The siliconates may be prepared by hydrolysis in strongly alkaline solution or by solution in alkali of the normal hydrolysis products of the silanes. In addition to halogen, alkoxy, amino, aroxy and acyloxy groups, hydrogen and b -halo-substituted alkyl and b -g -unsaturated groups are specified as hydrolysable radicals. In examples vinyl triethoxy silane, phenyl triethoxysilane, ethyl triethoxysilane and a mixture of butyl triethoxy silane and ethyl orthosilicate are hydrolysed with aqueous caustic soda and ethanol and the products distilled to remove ethanol. In another example vinyl trichlorosilane is added to concentrated hydrochloric acid and the precipitate dissolved in aqueous caustic soda. The resulting siliconate solutions are converted to silanols by diluting to 98 per cent water and passing the solutions through a column containing a cation-exchanger. The resulting solutions are useful for imparting water repellency to various materials.ALSO:Stable aqueous silanol dispersions are prepared by bringing to a pH between 3 and 7 by means of the hydrogen form of a cation exchanger an aqueous solution of a siliconate of an alkali or alkaline earth metal, preferably sodium or potassium. The siliconate should have from 0.5 to 3 hydrocarbon groups per silicon atom, the hydrocarbon groups being saturated or olefinically unsaturated groups having one to five carbon atoms or phenyl, tolyl or benzyl. A long list of hydrolysable silanes from which the siliconate may be prepared is given, including silanes having two or three silicon atoms joined by hydrocarbon groups and silanes having hydrogen attached to silicon. The siliconates may be prepared by hydrolysis in strongly alkaline solution or by solution in alkali of the normal hydrolysis products of the silanes. In addition to halogen, alkoxy, aroxy, amino and acyloxy groups, hydrogen and b -halo-substituted alkyl and b -g -unsaturated groups are specified as hydrolysable radicals. In examples, vinyltriethoxysilane, phenyltriethoxysilane, ethyl triethoxysilane and a mixture of butylttriethoxy silane and ethylorthosilicate are hydrolysed with aqueous caustic soda and ethanol and the products distilled to remove ethanol. In another example vinyl trichlorosilane is added to concentrated hydrochloric acid and the precipitate dissolved in aqueous caustic soda. The resulting siliconate solutions are converted to silanols by diluting to 98 per cent water and passing the solution through a column containing a cation exchanger. The resulting solutions are useful for imparting water repellency to various materials.ALSO:Materials such as magnesium silicate, cellulose, porous ceramic ware, glass (bottles, fibres and cloth), clay, noncarbonaceous masonry, sand, ores (for flotation), wood products, paper, mica, talc (for use as fillers in moulding compounds), asbestos and related materials, are waterproofed by the application at a pH between 3 and 8, of an aqueous dispersion of a silanol (see Group IV(a)). The materials are dipped in the dispersion or the dispersion is applied to the materials, followed by drying, whereupon the silanol condenses to form an insoluble water-repellent silicone. The silanol may be applied in amounts of from 0.001 to 2 per cent by weight of the material.ALSO:Ores (for flotation) are waterproofed by the application, at a pH between 3 and 8, of an aqueous dispersion of a silanol (see Group IV(a)) The materials are dipped in the dispersion or the dispersion is applied to the materials, followed by drying, whereupon the silanol condenses to form an insoluble water-repellent silicone. The silanol may be applied in amounts of from 0,001 to 2 per cent by weight of the material.ALSO:Materials such as mica, asbestos and related materials, are waterproofed by the application, at a pH between 3 and 8, of an aqueous dispersion of a silanol (see Group IV(a)). The materials are dipped in the dispersion or the dispersion is applied to the materials, followed by drying, whereupon the silanol condenses to form an insoluble water-repellent silicone. The silanol may be applied in amounts of from 0.001 to 2 per cent by weight of the material.