METHOD AND APPARATUS FOR MOLDING FOAM RESIN MAGNET

摘要

PURPOSE:To mold a foam resin magnet having specific gravity smaller than 1 by the use of one wherein resin is added with a foaming agent of being 0.2-2% in volume ratio and magnetic powder of being 10-30% in volume ratio and by applying a pressure of 65-400kg/cm<2> to molten resin being in a measuring process. CONSTITUTION:Foamable resin containing magnetic powder within a plasticizing cylinder 10 is transferred to the outlet side through revolution of a screw 12 while being kneaded and melted, and then stored in a resin reservoir chamber A. Resin used herein is of the kind that is blended with a foaming agent of 0.2-2% in volume ratio and a magnetic powder of 10-30 in volume ratio. Accompanying this measuring process, the screw 12 is made to withdraw by resin pressure, and oil is pushed out of the Infection side oil chamber 42 of an injection cylinder 32 while being exerted with back pressure and is then returned to a tank 54 through a check valve 48 and a control valve 52. During the withdrawal period of the screw 12, the back pressure is so controlled that a pressure of the molten resin becomes 65-400kg/cm<2>. Molten resin within the mold cavity D is injected and then the resin is foamed so as to mold a magnet.