| 摘要 |
PROBLEM TO BE SOLVED: To provide a molding method capable of inexpensively manufacturing a lightweight foamed resin magnet having small cells and high strength. SOLUTION: An injection material comprising a thermoplastic resin containing a predetermined amount of a magnetic powder is plasticized in a plasticizing injection apparatus. At this time, a physical foaming agent such as carbon dioxide or nitrogen is injected in the screw cylinder corresponding to the reduced pressure part of a screw to be dissolved in the plasticized molten resin in a supercritical state to obtain a foamable molten resin. This resin is injected in the cavities (C2, C2) of molds (31,35) to which counter pressure (40) is applied by gas such as nitrogen gas, carbon dioxide or air so as to leave predetermined spaces (SP2, SP2) in the cavities (C2, C2) and the counter pressure (40) is relieved at a stroke to foam the molten resin to obtain the foamed resin magnet low in specific gravity.
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