| 摘要 |
PROBLEM TO BE SOLVED: To smooth the surface of a hollow part by a method in which thermoplastic resin granules having a part of high additive content, a part of low additive content, and a part containing no additive are kneaded/plasticated and injected into a mold cavity as a molten resin, and pressurized fluid is injected into the molten resin to form a hollow part. SOLUTION: A crystalline thermoplastic resin such as polypropylene or an amorphous thermoplastic resin having no clear melting point is added with additives of glass fibers which are opened in granules, etc., and pigment, etc., to make the granules having nonuniform additive distribution. The granules are supplied into a heating cylinder 15, kneaded/plasticated, and injected into the cavity 13 of a mold 10. After the end of injection, pressurized fluid of gaseous or liquid inert gas such as nitrogen and helium is injected from a pressurized fluid injection part 16 into the molten resin in the cavity 13 at ordinary temperature and pressure to form a hollow part in the resin so that a good molding having good surface smoothness in which fuzzing on the surface of the hollow part is reduced, and the hollow part has no abnormally uneven wall-thickness part is obtained. |
