| 摘要 |
PURPOSE:To reduce the production cost of a hollow resin product by a method wherein a molding cavity is formed by a sand core, on the surface of which a resin non-permeable film is formed, and a main mold made of metallic or resinous material. CONSTITUTION:A main mold, which forms the outer surface of a product, is made of metallic or resinous material and used repeatedly. And, a core 2, which forms the inner surface of the hollow product, is produced by molding sands having the predetermined particle size with proper resin. In addition, a film 3 is formed onto the surface of the core 2 so as to prevent the resin from penetrating in the interior of the core 2. Further, the film 3 consists of inorganic material, which is represented by alumina cement, plaster, water glass or the like, or of organic material, which is represented by epoxy resin, polyester, various heat resistant paint or the like. |
