GB629486A - Improvements in and relating to methods of preparation of dimethyl silicone gums - Google Patents

Abstract

A dimethyl silicone (dimethyl polysiloxane), preferably a liquid polymer having a methyl-to-silicon ratio of about 1.98 to 2, is treated with a sulphuryl halide to produce an elastic gum which may be compounded with fillers (such as titanium dioxide, lithopone, zinc oxide, talc ferric oxide) and accelerators (such as benzoyl peroxide) and heat cured to give an elastomer having rubber-like properties. The sulphuryl halide may be from 1 to 50 per cent by weight of the dimethyl silicone and the treatment may be at from room temperature (10 to 40 days) to about 150 DEG C. (about 12 hours). In an example about 600 parts of dimethyl dichlorosilane containing about 0.4 mol. per cent trichlorosilane were hydrolysed with water; to 200 parts of the dimethyl silicone were added 100 parts of sulphuryl chloride and the mixture was heated, first at 85 DEG to 90 DEG C. for 6 1/2 hours and then at 175 DEG C. for 48 hours to give an elastic gum. 36 Parts of the gum were milled with 72 parts titanium dioxide and 0.72 parts benzoyl peroxide, pressed into a sheet first at 150 DEG C. for 10 minutes under 500 lbs./sq. inch and then at 200 DEG C. for 48 hours. Specifications 586,188, 586,189 and 594,481 are referred to.