Improvements in or relating to vulcanisable compositions and elastomeric compositions

摘要

A vulcanizable composition comprises: (1) a copolymer consisting essentially of (a) 75 mol. per cent or less of a siloxane having the unit formula in which each R is a perfluoroalkyl radical, n is 1 or 2, each R1 is a monovalent hydrocarbon radical and m is 0 or 1, and (b) at least 25 mol. per cent of a siloxane of the unit formula R112SiO, in which each R11 is a monovalent hydrocarbon radical, sufficient amount of (a) being present to give at least 10 per cent by weight of fluorine in the copolymer; (2) a filler; and (3) a vulcanizing agent. Each R1 and R11 may be an alkyl, alkenyl, cycloaliphatic, aralkyl or aryl radical. Fillers specified are silica, fume silica, diatomaceous earth, clay, ground glass, glass fibres, carbon black, titania and zinc, ferric, chromic and zirconium oxides, and they may be modified by having, e.g. trimethylsiloxy, ethoxy or isopropoxy groups attached to the surfaces thereof. The filler may be used in amount from 10 to 200 parts (by weight) per 100 parts of copolymer. The composition may be vulcanized by radiation, such as X-rays, or with benzoyl, 2:4-dichloro-benzoyl or cumyl peroxide, tertiary butyl paracetate; mixtures of polysilicates and metal carboxylates; and mixtures of hydrogen-containing siloxanes and metal carboxylates or chloroplatinic acid. In examples: (1) a copolymer was made by reacting the silane C3H7CH2.CH2.Si.CH3.Cl2 with conc. H2SO4 until evolution ceased, stirring in dimethyl-siloxane (cyclic tetramer) until equilibrium was reached, adding water to hydrolyse the Sibonded sulphate groups and purifying and isolating the liquid polymer; the polymer was then mixed with fume silica and benzoyl peroxide and cured at 150 DEG C; (2) the silane C7F15.CH2.CH2-Si.CH3Cl2 was co-hydrolysed with (CH3)2.SiCl2 and the resulting copolymer was milled with silica and benzoyl peroxide and cured; (3) the copolymer was made and cured as in (2); (4), (5), (6) the copolymers were made as in (1) and cured with acyl peroxides or by electron radiation. Uses.-As gaskets and hoses in fuel, hydraulic and lubricating systems for automotive vehicles, and as electrical insulation. The perfluoroalkyl-silanes used in making the above copolymers may be made (1) by reacting an olefin of the formula RCH=CH2 with a silane of the formula R1mSiHnCl4-n-m, wherein R, R1, m and n are as above defined; or (2) by reacting the olefin RCH=CH2 with HBr to give RCH2.CH2Br and thereafter preparing a Grignard reagent of this compound which can then be reacted with the silane R1mSiCl4-m. In examples, (1) the olefin C3H7CH=CH2 was reacted with CH3.H.SiCl2 in an autoclave at 250 DEG C. to give ; (2) Cl2 were made by the process of (1); (5) (C3F7CH2.CH2)2SiCl2 was made by reacting C3F7CH=CH2 with H2SiCl2; (6) (C3F7CH2.CH2) CH2=CHSiCl2 was made by reacting C3F7CH2. CH2Br with CH2=CH.SiCl3 in ether. Specifications 760,201 and 802,358 are referred to.ALSO:Olefinic compounds of the formula RCH= CH2, wherein R is a perfluoroalkyl radical, may be made by esterifying a perfluoro acid R.COOH with ethanol and reacting the resulting ester with a mixture of an isopropyl Grignard and a methyl Grignard to give an alcohol of the formula R(CH3)CH.OH, which is then dehydrated by heating with P2O5 to give the required olefin. In examples: (1) C3F7COOH was esterified with ethanol and the ester was then reacted in ether with a mixture of methyl and isopropyl magnesium bromides to give C3F7(CH3)CHOH and propylene. The alcohol was then dehydrated with P2O5 to give C3F7CH=CH2; (2) C7F15CH=CH2/t was made in a similar manner.