Verfahren zur Herstellung von siliciumhaltigen Produkten

1,186,771. Silicious products. CONTEKI DEVELOPMENTS Ltd. 25 April, 1968 [12 May, 1967; 28 July, 1967], Nos. 22190/67 and 34884/67. Headings C3C, C3N and C3R. Silicious products are prepared by reacting an aqueous solution of an alkali metal silicate with an organic isocyanate or isothiocyanate. The isocyanate or isothiocyanate is preferably a polyisocyanate or polyisothiocyanate and more preferably is 4,41-diphenylmethane diisocyanate or a tolylene diisocyanate. It is preferred to use sodium silicates of formula Na 2 O.SiO 2 , wherein the Na 2 O: SiO 2 ratio may be from 1À6 to 3À3. The reaction may be carried out in the presence of a catalyst, e.g. a tertiary amine or an organometallic compound. The reaction conditions may be such as to produce cellular products by the evolution of carbon dioxide. Conventional blowing agents and surfactants may be added to the reaction mixture to assist in the foam production. Polyols may also be added to the reaction mixture, as may polymers and fillers in fibrous or particulate form. The filler materials may be sand, alumina, alumino-silicates, magnesia, metal fibres, asbestos, glass fibre, rock wool, aluminosilicate fibres, calcium silicate fibres, wood flour, coke, paper pulp, cotton waste, cotton jute, sisal, hemp, flax, rayon, or synthetic fibres such as polyester, polyamide and acrylonitrile fibres. The particulate material may also comprise ingredients which react together exothermically when ignited, e.g. aluminium, oxidizing agent therefor alone or together with a particulate refractory material. In the case of foamed products a non-foamed surface layer may be provided by defoaming the surface during manufacture or by providing the foamed material with a facing layer. Foundry moulds and cores may be prepared by incorporating sand into the reaction mixture.