| 摘要 |
1360392 Foamable thermoplastic compositions and foams thereof FISONS Ltd 5 July 1971 [31 July 1970 5 Aug 1970 20 Aug 1970] 37047/70 37779/70 and 41006/70 Heading C3C [Also in Division B5] A foamed plastics material is made by heating a foamable thermoplastic composition comprising a thermoplastic material selected from olefin polymers and copolymers, styrene polymers and copolymers, and rigid polyvinyl chloride; azodicarbonamide; and at least one finely divided material having a BET surface area of 200-350 m.<SP>2</SP>/g. The latter material is preferably one that contains water (free or combined) that can be released at temperatures below 250‹ C., particularly fume and colloidal silicas, gypsum, CaCO 3 .6H 2 O, CaO.6H 2 O, hydrated potassium carbonate, copper, ferric, and magnesium sulphates, hydrated magnesium benzoate and cerous acetate and nitrate. The compositions may also contain dyes, pigments, stabilizers, dispersants, fillers, extenders, other blowing agents, e.g. benzene sulphon hydrazide, and kickers, the latter including compounds of Zn, Cd Sn, Pb, urea, ethanolamine, glycols. Preferred additives are Mg, Zn or Ba stearates, and also oxamide (as nucleating agent). The composition may be fused, prior to foaming, by heating at 100-150‹ C. for 2À5-0À5 min., as is normally foamed at 150-280‹ C. It may be formed into a sheet by extrusion, casting, calendering or spreading as a powder blend; also applied to a backing member optionally overcoated with a plastics layer, or it may be moulded by conventional techniques. Examples detail compositions prepared from polyethylene, azodicarbonamide and either silica, optionally with magnesium stearate, MgSO 4 .7H 2 O or CaSO 4 .2H 2 O. |
