GB706719A - Improvements in or relating to co-polymeric siloxanes and the application thereof - Google Patents

Abstract

A copolymeric siloxane is made by reacting one or more silanes of the general formula RnSiX4-n and/or one or more polysiloxanes of the formula <FORM:0706719/IV (a)/1> , where R is an alkyl, monocyclic aryl or halogenated monocyclic aryl hydrocarbon radical, X is chlorine or alkoxy and n has a value of 1 to 3, the average degree of substitution of the silanes or polysiloxanes being from 2.1 to 3 R radicals per silicon atom, and at least 50 per cent. of the R radicals being alkyl, with a silica hydrosol in amount such that there is a total of at least 1 mol. of organosilicon compound per mol. of SiO2 in the hydrosol and under such conditions that the reaction mass has a pH of less than 5. The hydrosol may be formed separately or in situ by reacting a chlorosilane with an alkali metal silicate, or separately by neutralising sodium silicate solution with an acid. The desired pH may be attained by addition of hydrochloric, sulphuric, nitric, phosphoric, benzene sulphonic or trichloracetic acid. Reaction of the hydrosol with the organo-silicon compound(s), which may be effected in the presence of water-miscible solvents, e.g. fatty alcohols, dioxane, ketones and carboxylic acids or mixtures of water-soluble and water-insoluble solvents such as toluene, xylene and ether, proceeds rapidly at 30 DEG C. or above, usually with formation of an emulsion which on standing separates into two layers from which the copolymer is separated, purified and dried to yield products varying from viscous oils to thermoplastic resins. Using this procedure in the examples, a silica hydrosol, made by reacting sodium silicate solution with hydrochloric acid or trimethylchlorosilane, was reacted with (1) trimethylchlorosilane, (2) dimethylphenylchlorosilane, (3) hexamethyldisiloxane, (4) trimethylethoxysilane, (5) the hydrolysate of ethyldimethylchlorosilane, (6) hexamethyldisiloxane and cyclic dimethylsiloxane, (7) trimethylchloro- and phenyltrichloro-silanes, (8) stearyltrichlorosilane, and (9) bis-chlorophenyltetramethyldisiloxane. The copolymers are useful for waterproofing applications particularly leather, antiflotation of paint pigments, thickening liquid dimethylsiloxanes or for boot greases. Solutions in solvents e.g. petroleum hydrocarbons, benzene, toluene and xylene are usually employed and may also contain other organosilicon polymers, e.g. liquid dimethylsiloxanes, methylphenylsiloxane resins, liquid methylphenylsiloxanes, stearylsilsesquioxane, butylmethylpolysilane, phenylmethylpolysilane and stearylmethylpolysilane, specific compositions being given in examples 10 to 14.