GB798669A - Improvements in or relating to organosiloxane elastomer foams - Google Patents

Abstract

Siloxane elastomeric foams, useful in thermal insulation, are made by mixing (1) an organopolysiloxane containing Si-bonded OH groups and having a viscosity of at least 1000 cs. at 25 DEG C. and having per Si atom an average of 1.9 to 2 radicals selected from monovalent hydrocarbon and halogenated hydrocarbon radicals and H atoms, in the siloxane, there being from 1 to 75 per cent by weight of siloxane units containing at least one Si-bonded H atom and the siloxane containing an average of at least 1.25 of the defined organic radicals per Si atom; (2) up to 50 per cent by weight of (1) of a hydroxylated compound; and (3) a stannous carboxylate in amount sufficient to give from 0.1 to 10 per cent by weight of tin calculated on the weight of siloxane (1), and thereafter allowing the mixture to foam. Siloxane (1) may be a copolymer in which the Si-H and Si-OH appear in the same molecules, or it may be a mixture of a hydroxylated siloxane and an Si-H-containing siloxane, and the Si-bonded organic radicals may be alkyl, alkenyl, cycloaliphatic, aralkyl, aryl or halogenated alkyl or aryl. Hydroxylated compounds specified are silanols and siloxane diols; water; ethanol, butanol, isopropanol and tertiary butanol; ethylene, propylene and hexylene glycols; glycerine; mono- and tri-ethanolamines; hydroxy esters, hydroxylated polyesters, hydroxy ethers; alcohols containing halogen, -nitro and -nitrile groups; acetic, butyric, malonic, caproic and succinic acids. Solvents such as dioxane, ethers or benzene may be used where the hydroxylated compound is sparingly soluble in the siloxane. Catalysts specified are stannous acetate, oleate, stearate, linoleate, naphthenate, benzoate, naphthoate, succinate, sebacate, lactate, maleate, crotonate, salicylate, phthalate, mandelate, cinnamate, and phenylacetate. Fillers, e.g. titanium, zinc, ferric and magnesium oxides, clay, diatomaceous earth, fume silica, silica aerogels and xerogels, powdered glass, asbestos, silicon, powdered aluminium and carbon black, and compression set additives, oxidation inhibitors and pigments may also be added. In a typical example, two liquid hydroxylated dimethylpolysiloxanes of different viscosities, a trimethylsiloxy-methylhydrogensiloxane and diatomaceous earth were formed into a uniform mix and stannous ethylhexoate was then stirred in. Foaming began almost at once and after 10 to 15 minutes an elastomeric foam having a density of 0.5 g/c.c. was obtained. Uses-for thermal insulation, e.g. the composition can be sprayed on the inside of a car body. Specification 784,826 is referred to.