| 摘要 |
An extruded foamed product of polyvinyl-aromatic resin comprises a mass of substantially parallel elongated cells enclosed by a surface skin, the cells being orientated substantially at right-angles to the surface skin. The preferred resin is polystyrene. The surface skin is normally orientated in the direction of extrusion, is of a fibrous nature and is peelable from the rest of the poduct. The blowing agent is a normally gaseous substance or a volatile liquid. Preferred blowing agents are C1-C5 aliphatic hydrocarbons, e.g. a butane. The foamable composition preferably contains a nucleating agent, e.g. finely divided silica. The product may be produced by extruding a foamable polyvinylaromatic resin composition through a die orifice into a zone of lower pressure defined by stationary surfaces that are cooled so as to solidify the resin in contact with them and are spaced progressively further apart from each other along the direction of extrusion such that foaming of the resin occurs as it moves through the zone. |
