Verfahren zur Herstellung eines Schaumgebildes

The method of expanding thermoplastic polymers disclosed in the parent Specification, in which a self-reacting exothermic material is mixed with the expandable mass, is modified by adding the expandable mass and liquid exothermic material either together or in either order to a mould without prior mixing. The thermoplastic material may be partially expanded and may completely fill the mould. The liquid exothermic material may be placed therein in a single charge or spread randomly over the granules. As it reacts and generates heat, expansion of the granules forces it throughout the mass and against the mould surfaces where it forms a skin. In addition to the compounds mentioned in the parent Specification, e.g. epoxy resins and phenolic precondensates, the exothermic material may be solutions of calcium oxide or similar metal oxide, magnesium chloride, caustic soda and mineral acids, which heat on admixture with water or each other; and sodium orthosilicate may be added to aqueous solutions. The thermoplastic material may be polymers and copolymers (including graft copolymers) of styrene and methyl- and chloro-styrenes, methyl methacrylate, vinylidene chloride, vinyl chloride, ethylene and propylene; chlorinated polyolefins, natural and synthetic rubber and cellulose ethers and esters. Specified blowing agents are dichlorodifluoromethane, chlorotrifluoromethane, carbon dioxide and pentane. Fillers may be incorporated in the polymer, e.g. saw dust, wood chips and flour, glass, cotton and nylon fibres, clay, carbon black, titanium dioxide and other pigments and dyes. A skin may also be provided on the foamed article by lining the cavity with fabric. In the examples, the exothermic materials comprise (1) a mixture of epoxy resin (from bis-phenol A), diethylene triamine and a coolant consisting of aqueous isopropanol; (3) a phenolic resin and phenolsulphonic acid activator; (4) an epoxylated Novolak resin or epoxy resin (from resorcinol) and diethylene triamine and triethylenetetramine; (5) a polyurethane resin prepared by reacting toluene diisocyanate with the reaction product of propylene oxide and glycerine and further reacted with N,N,N1,N1-tetrakis(2-hydroxy propyl) ethylene diamine.ALSO:The method of expanding thermoplastic polymers disclosed in the parent Specification in which a self-reacting exothermic material is mixed with the expandable mass, is modified by adding the expandable mass and liquid exothermic material either together or in either order