GB699665A - Method and composition for production of cellular thermoplastic products - Google Patents

Abstract

In a method of making elongated cellular bodies, e.g. panels, planks and beams, of thermoplastic resins, particularly benzene-soluble polymers and copolymers of monoalkenyl aromatic compounds, e.g. polystyrene, a gel comprising the thermoplastic resin, 0.04 to 1 per cent of at least one of barium, calcium, lead and zinc stearates and a normally gaseous agent, e.g. methyl chloride, methyl and ethyl ethers, methyl ethyl ether or a cracked oil gas fraction rich in ethylene, propylene or butylene is formed under pressure, extruded through an orifice and, during expansion, externally pressed to a predetermined and uniform thickness. The normally gaseous agent is present in an amount sufficient to form a flowable gel and to be vaporized completely upon release of pressure and resultant expansion and cooling to a temperature between -30 DEG C. and 10 DEG above the distortion temperature of the resin. Finely divided aluminium powder, pigments, carbon black or calcium silicate may be included in the gel. Specifications 406,267, [Group V], and 661,002 are referred to.ALSO:Elongated cellular bodies of thermoplastic resins, e.g polystyrene panels, planks and beams, are formed by extruding under pressure through an orifice a flowable gel containing a normally gaseous agent (see Group IV(a)), and externally pressing to shape during the expansion to give a predetermined and uniform thickness. In an example, an orifice, 3 1/4 inches long with a minimum width of 1/8 -inch, with rounded corners and each side bowed in at the centre, has mounted over it a flared tubular shaping member in the form of a truncated rectangular pyramid having its principal axis in horizontal alignment with the orifice, and a cross-section 4 3/8 inches long with a minimum width of 1 1/2 inches at the narrow end widening to a cross-section of 11 inches and 3 3/4 inches at the outlet end. About 4 inches from the outlet a pair of endless belts spaced 5 inches apart at the inlet and 6 inches at the delivery end, and 50 feet long, receive the extruded material to prevent warpage in addition to shaping. The planks are then trimmed to 4-inch thickness and 10-12 inches width. Specifications 406,267 and 661,002, [Group IV(a)], are referred to.