| 摘要 |
PURPOSE:To eliminate unevenness of drying to prevent deformation by a method wherein after a ceramic molding containing a gel binder us held for a predetermined time under humidity control at a specific temperature higher than the gelling temperature of the binder, the water content of the molding is dried. CONSTITUTION:A sintering adjuvant and a polyvinyl alcohol are added to a silicon nitride powder. This is ground and mixed by an attritor with the addition of water. The obtained ground mixture is dried by a spray drier and granulated. The obtained granules are mixed with a methyl cellulose as a gel binder and a lubricating agent to be prepared. A molded item is formed by using this mixture as a molding material. The molded item is held for one hour under the environment of a humidity of 70% and a temperature of 80 deg.C which is higher than the gelling temperature of the gel binder, whereby the binder is gelled. After that, the humidity is lowered to 30% and the temperature is increased to 85 deg.C for drying the molded item. Therefore, deformation caused by shrinkage in drying is reduced, and the molded item is uniformly dried without unevenness, thus being never deformed and being enhanced in accuracy in shape. |
