| 摘要 |
<p>PURPOSE:To provide the title powdery investment composed of aggregate as the skeleton of a mold and a binder, designed to improve the molding characteristics by providing aggregate granules with a water-repelling treatment and by forming a hydrophobic film on the surface of the granules. CONSTITUTION:Inorganic powder such as silica or cristoballite is used as aggregate for the skeleton of a mold, and the aggregate is provided with a water- repelling treatment using e.g. a silane coupling agent to form a hydrophobic film on the surface of the granules. The resulting aggregate is kneaded with a binder such as MgO or NH4H2PO4 in the presence of e.g. an aqueous solution of colloidal silica, thus obtaining the objective investment with good operability and high fluidity. The present investment can be used for glass ceramics having melting temperature of ca.1500 deg.C. Also, the amount of the liquid component can be reduced in the above kneading operation, leading to improvement in the heat resistance and surface roughness of the present investment. Furthermore, the binder can be protected from the moisture in air, leading to such effects as to suppress the change in the properties of the investment with the elapse of time.</p> |
