| 摘要 |
A composition curable to an elastomer at room temperature comprises by weight (1) from 0.01 to less than 5.0 per cent of a siloxane having at least three RHSiO units per molecule, any remaining units being of the general formula R3SiO0,5, in which units each R is a monovalent hydrocarbon radical containing less than 7 carbon atoms, (2) from more than 95 to 99.99 per cent of a polysiloxane having a viscosity of at least 100 cs. at 25 DEG C. and in which all the molecules have at least 2 Si-bonded OH groups attached thereto and in which the average ratio of monovalent hydrocarbon or halogenated hydrocarbon radicals (of less than 8 C atoms) to Si atoms is from 1.9 to 2.0; and (3) as catalyst metal carboxylate or an organometallic compound. Siloxane (1) includes OH-terminated linear polymers, cyclic polymers and triorganosilyl end-blocked linear polymers, e.g. methyl-, phenyl-, ethyl-, butyl-, vinyl- and hexyl-hydrogensiloxanes, and trimethyl end-blocked methylhydrogensiloxane, dimethylhydrogen - terminated methylhydrogensiloxane and triethyl end-blocked phenylhydrogensiloxane. Siloxane (2), which may contain up to 15 per cent by weight of non-hydroxylated siloxanes, may have as Si-bonded radicals methyl, ethyl, butyl, phenyl, tolyl, vinyl, allyl, cyclohexyl, chloromethyl, pentafluoroethyl, tetrafluorocyclobutyl, chlorodifluorovinyl, a ,a ,a - trifluorotolyl, monochlorophenyl and pentabromophenyl radicals. Catalysts specified are ferric benzoate and octoate, dibutyl tin diacetate, lead, manganese and cupric octoates, monobutyl tin trilaurate and iron cyclohexoate; tetralauryl tin, tetraphenyl lead, tetraphenyl tin, tetraethyl lead and tetraallyl lead, and are used in amount, e.g. of 0.001 to 1 per cent by weight of the siloxanes. If desired, curing may be effected by heating up to 90 DEG C., and fillers, e.g. silica, diatomaceous earth, glass, asbestos, carbon black, organic fibres, metal oxides and clays, may be added. Examples are given. Uses.-The products are used in making dental impressions and impressions for patternmaking; for coating textiles and paper, as described in Specification 804,198; in the treatment of wool; and for casting or moulding articles for use as electrical insulation, heatresistant ducts, seals for closures and de-icing devices on aircraft. Specification 767,797 also is referred to. |
