Improvements in or relating to extruded foamed polystyrene

Abstract

Abstract An extruder foamed polystyrene which has an average cell size not exceeding 0,004 inch, an average cell wall thickness not exceeding 0,0004 inch and a density of from 0,75 to 8 lb/cu. ft. is produced as tube or film having a thickness of from 0,005 to 0,3 inch by extruding in a conventional extrusion apparatus using a cylinder temperature of 150 DEG to 260 DEG F. and a die temperature of 225 DEG to 290 DEG F. polystyrene in the form of particles which include from 4,5 to 9% of an aliphatic hydrocarbon (b.p. 30 DEG to 90 DEG C.) and which are homogeneously admixed with a CO2 liberating agent and an acid, the acid having at least 3,0 milli-equiv. of acetic hydrogen/gram, in sufficient amount so as to produce upon reaction a total of 5% by weight of water and CO2 based on the weight of polystyrene particles. For example, 0,5% of sodium bicarbonate and 0,4% of citric acid may be homogeneously mixed with the particles. The extrudate may be heated, e.g. by passing through a tank of hot water or a steam chamber, to expand it further, or it may be treated with a blast of cold air as it leaves the die orifice to cause the formation of a tough glazed skin.ALSO:An extruded foamed polystyrene which has an average cell size not exceeding 0,004 in., an average cell wall thickness not exceeding 0,0004 in. and a density of from 0,75 to 8 lb./cu. ft. is produced as tube or film having a thickness of from 0.005 to 0,3 in. by extruding in a conventional extrusion apparatus using a cylinder temperature of 150 DEG to 260 DEG F. and a die temperature of 225 DEG to 290 DEG F., polystyrene in the form of particles which include from 4,5 to 9% of an aliphatic hydrocarbon (b.p. 30 DEG to 90 DEG C.) and which are homogeneously admixed with a CO2 liberating agent and an acid, the acid having at least 3,0 milli-equiv. of acetic hydrogen/gram, in sufficient amount so as to produce upon reaction a total of 5% by weight of water and CO2 based on the weight of polystyrene particles. For example, 0,5% of sodium bicarbonate and 0,4% of citric acid may be homogeneously mixed with the particles. The extrudate may be heated, e.g. by passing through a tank of hot water or a steam chamber, to expand it further, or it may be treated with a blast of cold air as it leaves the die orifice to cause the formation of a tough glazed skin.

Inventors

No inventors recorded.

Bibliographic Details