Organosilicon foams

Abstract

Abstract Siloxane foams are made by mixing (1) an organo-polysiloxane having an average of 1 to 1.8 radicals selected from monovalent hydrocarbon, halogenated hydrocarbon and halophenoxymethyl radicals, per Si atom, at least 1 per cent by weight of the siloxane units having at least one silicon-bonded hydrogen atom; (2) from 0.001 to 30 per cent by weight of (1) of a catalyst which is a quaternary ammonium or alkali metal salt of a silanol or siloxanol, or alkali metal hydroxide or a tin or lead carboxylate; and (3) a non-acidic hydroxylated compound, and thereafter allowing the mixture to expand into a foam. If desired, the foams so made may be heated to further cure the resin. Silicon-bonded organic radicals specified are alkyl, alkenyl, cycloaliphatic, aryl, aralkyl, halogenated hydrocarbon and halophenoxymethyl. Numerous examples of catalysts are given. Hydroxylated compounds specified are hydroxysiloxanes, silanols, water, ethanol, butanol; ethylene, propylene, diethylene and polyalkylene glycols; glycerol, pentaerythritol; ethanolamine, triethanolamine; hydroxy esters and polyesters; hydroxy ethers; alcohols containing halo, nitro, nitrile or other functional groups; and alkali metal hydroxides. Siloxane (1) may or may not contain Si-bonded OH groups, but preferably should contain at least 0.5 per cent of such groups. Thus, when the siloxane (1) contains Si-bonded OH groups, it is unnecessary to add any additional hydroxylated compound to produce a foam. Optional ingredients specified are alkylpolysilicates, preferably containing less than 10 C atoms in each alkoxy group and used in amount of up to 8 per cent by weight of the siloxane; fillers, e.g. powdered Al, Sn, Zn or Si, silica, mica, clay or iron oxide; flame retardants, e.g. antimony oxide, calcium carbonate, polychlorinated biphenyls or paraffins, or organic sulphamates; stabilizing agents; plasticizers, e.g. liquid siloxanes; and additional catalysts, e.g. other metal carboxylates or amines. Where the siloxane is ordinarily a solid, solvents, e.g. benzene, toluene, xylene, petroleum naphtha, methylene chloride or ethylene chloride, may be added. In the examples a mixture of a hydroxylated copolymer of monoethyl-, dimethyl-, monophenyland diphenyl-siloxane units, methylene chloride, a cyclic methylhydrogenpolysiloxane and a liquid trimethylsiloxy-end blocked phenylmethyl siloxane, was foamed by adding specified catalysts. Uses.-For thermal insulation for pumps, motors, pipes, fire walls and for lightweight reinforcing material in structure members. Specifications 784,826 and 788,598 are referred to.

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