| 摘要 |
PURPOSE:To homogenize the internal composition of a molded form by keeping in a molten state under normal pressure an injected resin and pressing the resin when the resin is cooled down to a temperature where curing is started by pressing. CONSTITUTION:When a resin such as PMMA is injected into a mold, the temperature of the resin lowers down to 145 deg.C some time after a gate is sealed. PMMA is melted completely when it is cooled to approximately 145 deg.C at the time of normal pressure, and brought to the state in which pressure is applied uniformly to each section of PMMA. When PMMA reaches 145 deg.C, a controller 56 controls a valve mechanism 50 and increases pressure applied to a port 12a for a clamping cylinder 12, and pressure such as 600bar is applied to PMMA in a mold. When PMMA is cooled to 135 deg.C, the controller 56 applies pressure of 1,000bar to PMMA in the mold. The dynamic modulus of rigidity of PMMA is further elevated by the pressing, PMMA completely passes through glass transition when it is cooled to 133 deg.C, curing is completed approximately when PMMA is cooled to 130 deg.C, and PMMA is changed into a solid perfectly when PMMA is cooled to 125 deg.C.
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