GB777078A - Improvements relating to the treatment of leather - Google Patents

Abstract

The water-repellency of leather is improved by treating it with an aqueous emulsion containing the polymerizable fluid intercondensed product of hydrolysis of a mixture composed essentially of 50 to 75 per cent, by weight, of dimethyldichlorosilane 1 to 10 per cent of trimethylchlorosilane, 10 to 35 per cent of methyltrichlorosilane, and up to 10 per cent of a methylchlorodisilane or mixture of methylchlorodisilanes, and a curing agent for such product, comprising a metal salt of an acid, the metal ion being present to the extent of at least 2 per cent of the weight of the hydrolysis product, and the weight of the hydrolysis product being from 0.2 to 20 per cent of that of the aqueous emulsion, and curing the said hydrolysis product. The methylchlorodisilane or mixture of methylchlorodisilanes may comprise dimethyltetrachlorodisilane, methylpentachlorodisilane and trimethyltrichlorodisilane. A suitable mixture of methylchlorosilanes may be obtained by passing methyl chloride over silicon in the presence of copper at elevated temperatures, as described in Specification 575,667, [Group IV]. Small amounts of other compounds are produced which may be removed before the mixture is hydrolysed. The salt may be a water-soluble salt of a metal of Group IV of the Periodic Table, e.g. a salt of titanium, zirconium, tin or lead or a complex of such a salt; waterinsoluble salts which are soluble in the methylpolysiloxane hydrolysis product or are dispersible therewith, e.g. zinc or tin octoates or naphthenates may also be employed. Emulsifying agents such as morpholine oleate, ammonium oleate, sulphonated amide condensation products of fatty acids with organic amines, sulphonated aromatics and mixed alkylaryl sulphonates, sulphonated esters and fatty acid amide condensates may be used in making the dispersions. Stabilizers such as 2-methylpentanediol-2,5 may be added to the diluted emulsions, as used for treatment, to prevent premature breaking thereof, and improve penetration. Plasticisers, e.g. paraffin oil, paraffin wax, neat's-foot oil, tricresyl phosphate and dimethylphthalate, bonding agents, resins, e.g. polystyrene, polyvinyl chloride, copolymers of vinyl chloride and vinyl acetate and polymethylmethacrylate, and drying oils such as chinawood oil, oiticica oil and linseed oil may be incorporated in the emulsion. Treatment may be by drumming the wetted leather, which may have been pre-treated by drumming it with dilute aqueous ammonium hydroxide, followed by neutralization and rinsing, with the methypolysiloxane emulsion, and then curing by drying, with or without heat. The leather may subsequently be treated with finishing agents, e.g. alkyl polyacrylate emulsions in conjunction with neutral or synthetic rubber latices, the adhesion of which is improved by priming its surface with organic silicates or partially hydrolysed organic silicates as described in Specification 711,374, [Group III]. Specification 745,154 and U.S.A. Specifications 2,635,059 and 2,635,060 are referred to.