| 摘要 |
PROBLEM TO BE SOLVED: To produce a lightweight and moderately expanded polypropylene resin foam made from a monolayer parison using a monolayer molding machine, having a skin layer consisting of an unfoamed resin layer≥0.3 mm thick on the outer surface, having a specific gravity of 0.2-0.7, good at mold transferability, design and an appearance, and having high mechanical strength, rigidity and heat resistance. SOLUTION: The method for producing the hollow foam comprises the steps of melt-extruding a polypropylene resin composition containing a foaming agent to foam a parison, nipping and fixing the parison with a pair of molds, injecting air at 0.3-1 MPa into the hollow part of the parison to expand it, pressing it against the molds for 2-30 s, and reducing the air pressure to 0.001-0.1 MPa to foam the parison; wherein the mold temperature is controlled so as to meet the relationship: Tme-50≤Tmo≤Tme-5 (Tmo is the surface temperature of the molds on the cavity side; and Tme is the crystallization temperature of the raw material polypropylene resin composition). COPYRIGHT: (C)2003,JPO |
