Patent GB-542655-A (GB)
Title: Methyl silicone condensation products
IPC: C08G77/00
Filed: 1940-08-01
Abstract: 542,655. Organo-silicon compounds ; synthetic resins. BRITISH THOMSONHOUSTON CO., Ltd. Aug. 1, 1940, No. 12466. Convention date, Aug. 1, 1939. [Class 2 (iii)] By hydrolysing a methyl silicon halide and allowing the hydrolysed product to condense, viscous products, suitable for adhesives, impregnation &c., are obtained which may be further condensed by heating to obtain rubbery to glossy products. Methyl silicon chlorides are preferred and are prepared by adding slowly, with rapid stirring, an ether solution of methyl magnesium bromide to an ether solution of silicon tetrachloride cooled to -20‹ C., the temperature being kept below 0‹ C. and preferably at -20‹ C. or lower ; the cold re-action mixture, with or without separation of magnesium salts, is poured on to cracked ice and the ether solution of the hydrolysed and partly condensed product separated, washed free of acid and, if desired, concentrated to a viscous liquid. In examples, the molar ratios of methyl magnesium bromide to silicon tetrachloride are (1) 1.75/1, (2) 1/1 and (3) 2-2“/1. The initial condensation product of Ex. 1 on heating to 100-200‹ C. and maintained at 200‹ C. yields a clear, colourless horny solid ; that of Ex. 2, heated between 20-100‹ C. hardens to a hard, brittle solid ; the initial product of Ex. 3, after removal of ether, is an oily liquid which is converted to a soft, rubbery, infusible gel by heating to 120‹ C. in air. Compounds having a particular CH 3 /Si ratio may be obtained by co-condensing different methyl silicon halides,. or by mixing, in powder form, the individual solid condensates. The products are particularly useful for high temperature insulation. Metallic conductors, bars, &c. covered with asbestos, glass fibres, cotton or paper, may be coated with an ether solution of the partially condensed product, and, if desired, wound into a coil, and heated to complete condensation. Sheet insulation may be prepared by treating fabrics with the partially condensed product, which may also be used as a binder for flaky material, e.g. mica ; films or sheets of clay, e.g. bentonite, may be similarly treated, more particularly sheets containing embedded glass &c. fibres, described in Specification 539,797, [Group VIII]. The powders may also be used for coating glass bulbs and, with pigments, e.g. graphite, metallic surfaces, e.g. of metal vacuum tubes ; for resistance paints ; as sealing compositions, e.g. in making vacuumtight joints between metal and glass. They may also be compounded with other materials, e.g. natural and synthetic rubber, tars, asphalts,. pitches and natural and artificial resins ; or the hard, brittle products may be pulverized and used as fillers for such substances. Low molecular weight products may be dissolved or dispersed in oils, e.g. linseed, chinawood, perilla or soya bean, alone or mixed with solvents, pigments, plasticizers, driers &c. to form coating-compositions adapted to : be rendered heat resistant by baking. Sheet materials may be impregnated and laminated under heat and pressure. Moulding compositions, which may include fillers, e.g. asbestos, glass fibres, talc, quartz powder or wood flour may also be made.