| 摘要 |
PROBLEM TO BE SOLVED: To obtain a hollow molding of a simple shape having a uniform hollow portion and a uniform thickness by sandwich injection molding, then press injecting gas in a resin molding, and hollow injection molding it. SOLUTION: A core resin and a skin resin are filled into a mold cavity 1 so as not to completely fill the cavity 1, and sandwich molded in such a manner that a melt viscosity of the core resin when molded becomes lower than that of the skin resin. A viscosity difference between the skin resin and the core resin is decided according to a thickness of a molding, a gas injection pressure or the like, and the gas is pressure injected in the resin molding. Since the melt viscosity of the core resin is lower than that of the skin resin, the gas is selectively sufficiently impregnated and developed to a core layer 4, the gas is equivalently introduced, thereby obtaining a uniform hollow portion 2. In the case of gas injecting or after the gas is injected, the cavity 1 is enlarged, thereby obtaining a high hollow molding. Thus, a uniform hollow portion can be molded in a flat plate-like product having a uniform thickness.
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