| 摘要 |
1411132 Extruded foamed articles RHONE PROGIL 27 Nov 1972 [29 Nov 1971] 54680/72 Heading B5A [Also in Division C3] In order to form an article having a closed cell interior and a smooth skin exterior, a thermoplastics composition which includes a foaming agent and a particulate filler is extruded, with partial expansion, through a die having a temperature which is lower than that required to decompose the foaming agent but which is high enough to prevent frictional tearing of the skin, the filler particles having a mean diameter of 0À005-10 microns and a concentration of 0À5-20% by weight of the thermoplastics polymer. The temperature of the die may be 150-175‹ C. and the temperature of the extruder body may be 160‹ C. The filler may be silica, alumina, titanium dioxide, magnesia, asbestos, talc, barium sulphate, lead sulphate, calcium carbonate, silicoaluminates, sulphides, urea-formaldehyde or a polyester. The polymer may be plasticized or non-plasticized P.V.C., polystyrene, copolymers of vinyl chloride and vinyl acetate, copolymers of acrylonitrile and styrene, terpolymers of acrylonitrile, butadiene and styrene and terpolymers of methyl methacrylate, butadiene and styrene. The foaming agent has a decomposition temperature less than 180‹ C. and may be sodium bicarbonate, ammonium formate, the carbonates and bicarbonates of ammonium azodicarbonamide, and azodiisobutyronitrile. The concentration of the foaming agent is 0À5-4% by weight of the polymer. The article may have a density of 0À3-1À0 g./cm.<SP>3</SP> and a thickness of 1-100 mm. Thermal and acoustic insulators, seals, wall mouldings and plinths in construction and furnishing may be produced. |
