| 摘要 |
A process for producing a foamed thermoplastic polymer comprises mixing finely divided solid particles of a thermoplastic polymer and a nucleating agent with a volatile blowing agent, increasing the pressure and heating the particles to melt them while maintaining the blowing agent in intimate contact with the polymer and then extruding the molten mixture through a die, thereby releasing the pressure of the mixture to foam the polymer. The polymer may be a polymer or copolymer of monomers such as ethylene, propylene, butylene, styrene, a -methylstyrene, methyl methacrylate, ethyl- or butyl acrylate, vinyl acetate, vinylidene chloride and vinyl chloride. The nucleating agent may be a silicate or finely divided silica powders or bentonites. In an example, powdered isotactic polypropylene, finely divided silica powder and isopentane are used to produce a foam having a density of 45 g./l. and a homogenous cell size below 0.3 mm.
|
