| 摘要 |
PROBLEM TO BE SOLVED: To reduce the material cost and the cost of pigment for whitening and to improve the physical properties by crystallization by using a bathtub pressmolded at the temperature of a die exceeding a specified value and made of polyethylene terephthalate with a crystallinity thereof exceeding a specified value. SOLUTION: Pellets made of PET is thermally melted at 250 deg.C-260 deg.C by an extruder or an injection molding machine and the melted resin is supplied to a press molding machine. The temperature of a die of the press molding machine is set above 145 deg.C, and pressing and cooling are performed under the condition of a specified molding pressure and a specified time length to mold a bathtub made of polyethylene terephthalate crystallized to a crystallinity exceeding 35%. This enabless the saving of the material cost and the cost of pigment required for whitening and moreover, eliminates any changes in the body of the bathtub as caused, for example, by a situation that hot water in the bathtub accidentally boils during the heating of the bath water thereby maintaining improved physical properties by crystallization. |
