| 摘要 |
PURPOSE:To obtain the titled foamed particles having good moldability, by applying pressure with an inorganic gas to particles of a noncrosslinked polypropylene resin in a liquid dispersion medium, and releasing them from the pressurized zone, in a specified temperature range, into a lower-pressure zone. CONSTITUTION:Particles of a noncrosslinked polypropylene resin are dispersed in a liquid dispersion medium, and pressure is applied to this dispersion with an inorganic gas. Then, the particles of the secondarily crystallized, noncrosslinked polypropylene resin containing the inorganic gas, together with the liquid dispersion medium, are released, in the temperature range in which the secondary crystals will exist, from the pressurized zone into a lower-pressure zone, causing to foam. The examples of the noncrosslinked polypropylene resins to be used are a propylene-ethylene random copolymer and propylene-butene random copolymer, preferably a propylene-ethylene random copolymer containing 1-10wt% ethylene. As the inorganic gas, preferably a nitrogen-containing gas such as nitrogen or air is used.
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