Patent GB-888777-A (GB)
Title: Silicone rubber foam compositions
IPC: C08J9/06
Filed: 1958-08-14
Abstract: A room temperature vulcanizable silicone rubber foam composition comprises (A) a diorganopolysiloxane polymer of the average formula XO[R2SiO]nX in which each X is alkyl, aryl or hydrogen, each R is alkyl or aryl, and n has an average value of at least 50, (B) one or more organic silicon compounds for cross-linking, (C) a vulcanizing catalyst, (D) a nitroso compound in which the nitroso group is bound to a carbamic nitrogen atom and (E) an activating agent.  Both (C) and (E) may be provided by a single substance.  The polymer A is preferably solvent-soluble with an average degree of substitution of 2\sB0,01, e.g. a benzene-soluble hydroxyl end-blocked dialkyl polysiloxane.  Suitable organic silicon compounds for (B) may be one or more of (i) silanes of the formula RmSiY4-m in which each R is as for (A) above and each Y is an alkoxy, aryloxy or amino group, and m has an average value of 0 to less than 2, (ii) alkylpolysilicates, (iii) siloxanes of the formula <FORM:0888777/IV (a)/1> in which each R and m have the meanings given above and (iv) alkoxylated siloxane resins containing from 1 to 1,5 organic radical, i.e. alkyl or aryl, per silicon atom.  As vulcanizing catalyst (C) dibutyl tin dilaurate, zinc octoate, chrome acetyl carbonate, lead or mercury oxide, boric acid or oleic acid, triethanolamine, polyethyleneimine and butylamine, are specified; and preferred nitroso compounds (D) include nitrosomethylurea, nitrosomethylurethane, N-methylN-nitroso-N1-nitroguanidine and dinitroso-terephthalic-N:N-dialkylamide.  Suitable activating agents (E) are trialkanolamines such as triethanolamine, and dibutylamine, methylamine, ethylenediamine, butyltriamine, alcoholic potash lye, sodium ethylate, potassium hydroxide, may also be used.  A preferred composition comprises 100 parts by weight of (A), 0,5 to 10 parts of (B), 0,1 to 5 parts of (C), 6 to 12% of (D) based on (A)+(B)+(C) and on the same basis 0,1 to 5% of (E).  The composition may be prepared by mixing the constituents in any order and pigments, oxidation inhibitors, flame retardants may be incorporated in the mix.ALSO:A room-temperature vulcanizable silicone rubber foam composition comprises (A) a diorganopolysiloxane polymer of the average formula XO [R2SiO]nX in which each X is alkyl, aryl or hydrogen, each R is alkyl or aryl, and n has an average value of at least 50, (B) one or more orgno silicon compounds for cross-linking, (C) a vulcanizing catalyst, (D) a nitroso compound in which the nitroso group is bound to a carbamic nitrogen atom and (E) an activating agent; (C) and (E) may be provided by a single substance.  The polymer (A) is preferably organic soluent-soluble with an average degree of substitution of 2 \sB 0.,01, e.g. a benzene-soluble hydroxyl end-blocked dialkyl polysiloxane.  Suitable organic silicon compounds for (B) may be one or more of (i) silanes of the formula Rm SiY4-m in which each R is as for (A) above and each Y is an alkoxy, aryloxy or amino group, and m has an average value of 0 to less than 2, (ii) alkyl-polysilicates, (iii) siloxanes of the formula <FORM:0888777/V/1> in which each R and m have the meanings given above and (iv) alkoxylated siloxane resins containing from 1 to 1,5 organic radicals per silicon atom, i.e. alkyl or aryl radicals.  As vulcanizing catalysts (C) dibutyl tin dilaurate, zinc octoate, chrome acetyl carbonate, lead or mercury oxide, boric acid or oleic acid, triethanolamine, polyethyleneimine and butylamine are specified and preferred nitroso compounds (D) include nitroso-methyl urea, nitroso methyl-urethane, N-methyl -N-nitroso-N1-nitroguanidine and dimetrosoterephthalic-N; N-dialkylamide.  Suitable activating agents (E) are trialkanolamines such as triethanolamine, and dibutylamine, methylamine, ethylenediamine, butyltriamine, alcoholic potash lye, sodium ethylate, potassium hydroxide may also be used.  A preferred composition comprises 100 parts by weight of (A), 0,5 to 10 parts of (B), 0,5 to 5 parts of (C) 6 to 12% of (D) based on (A) + (B) + (C) and on the same basis 0,5 to 5% of (E).  The composition may also include pigments, oxidation inhibitors flame retardants, and the constituents may be mixed in any order to produce vulcanized foamed silicone rubber.