| 摘要 |
PURPOSE:To prevent strength from being deteriorated by preventing cracks attributed to internal stress of a partly-thick parts, by a method wherein, in an injection molding method for molding a product having a nonuniform thickness, an inorganic foaming agent having a specific weight ratio to thermoplastic resin is added to the thermoplastic resin. CONSTITUTION:In an injection molding method for molding a product having a nonuniform thickness, a 0.05-0.001wt.% inorganic foaming agent is added to the thermoplastic resin. The same is applied to a thermoplastic plastic molded product wherein cracks are produced because of internal stress in thick parts of intersections of ribs. In, for example, a vessel for carrying foodstuffs, the thick parts are intersections 3 of bottom ribs 1 and intersections 4 of the side ribs 2. Consequently, the internal stress is mitigated without spoiling not only the external appearance due to, e.g. swirl marks of the surface of the product through foaming but also the physical properties. Polyethylene or polypropylene or polystyrene are available as the thermoplastic resin. Then sodium bicarbonate is available as a kind of the foaming agent. |
