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摘要

Heat-resistant organic foam materials are prepared by introducing into an aqueous solution containing alkali metal silicate, which may contain suspended solid water-containing alkali metal silicate, expandable finely divided synthetic resin in such quantity that the ratio of the weight of added synthetic resin to the weight of anhydrous substances contained in the solution or suspension is from 1:9 to 9:1 (preferably 3:7 to 7:3) and then foaming the mixture at a temperature above the softening point of the expandable synthetic resin to form a homogenous foam material. The mixture may be solidified at a temperature below that at which foaming takes place, prior to expansion. Substances which react with alkali metal silicates to form water-insoluble silicates, e.g. zinc oxide, talc, asbestos flour, magnesium oxide or calcium carbonate may be added to the solution before the addition of the synthetic resin particles. Fibrous materials, metal cloth or plastic cloth and mineral fibre mats may be added to the mixture, prior to expansion, to increase the mechanical stability of the foam. 1 to 10% by weight of polyhydric alcohols, e.g. glycerin and sugar such as cane sugar, may be added advantageously. The synthetic resin particles used may be pre-foamed but capable of further expansion. Suitable particles consist of polystyrene or copolymers of styrene with acrylonitrile, acrylic acid and butadiene. Particles based vinylidene chloride or chlorinated polyvinyl chloride are also suitable. Suitable expanding agents are one which do not dissolve the particles or only slightly swell them, e.g. aliphatic hydrocarbons such as propane, n-butane and n- or iso-pentane. Powdered expanding agents which liberate gas at elevated temperature, e.g. azodibutyronitrile, may also be used. The synthetic resin particles may be made flame retardant by adding inorganic halogen compounds or by mixing with chloroparaffin powder or antimony trioxide.ALSO:Formed synthetic resin material containing alkali metal silicates (see Division C3) may be provided with a protective layer, for example by applying lacquers of epoxide resins, polyamides, polyvinyl chloride or copolymers of vinylidene chloride and other polymerizable substances or by applying a coat of plaster. Synthetic resins specified are polystyrene, styrene-acrylonitrile, acrylic acid-butadiene, polyvinylidene chloride, chlorinate polyvinyl chloride. Fibrous materials, metal cloth, plastic cloth, mineral fibre mats may be added to the foamable synthetic resin mixture.