CORE MATERIAL AND ITS USE

摘要

PURPOSE: To facilitate the precise molding of a core material for injection molding because of its heat resistance and flowability and to facilitate the removal of a core after use because of its water solubility by constituting the core material of a copolymer of polyvinyl alcohol and polyethylene oxide. CONSTITUTION: A core material is constituted of polyvinyl alcohol(PVA) and polyethylene oxide(PEO) and a molar ratio of PVA and PEO is set to 99-50:1-50 and a saponification value of PVA is set to 65-99 mol%. Because of this, the core material becomes high in water solubility. The glass transition temp. Tg of the core material is set to 40-100 deg.C and the melt index thereof is set to 0.1-50 to obtain flowability. Therefore, the flowability and water solubility of the core material can be enhanced without damaging the heat resistance thereof. This core material is used to form a core and this core is used to form an injection-molded product. As a result, the core can be formed into a fine shape and can be easily dissolved and removed after use because of its water solubility.