| 摘要 |
PURPOSE:To prevent the occurrence of voids in pellets by pelletizing thermoplastic polyimide through a melt-molding method, at the same time, performing it in specifying the cooling speed of molten resin. CONSTITUTION:The powder of thermoplastic polyimide is preferable, wherein moisture is discharged as much as possible, to be supplied in and extruded from an extruder in a state that oxygen is discharged therefrom. Upon cooling strands or pellets extruded from the extruder in a molten state, it is conducted at a cooling speed of 150 deg.C/sec. or below. In this manner, by the heat radiation from the strands or pellets, they do not come to a state wherein only the surface is cured, and the contraction following the cooling generates entirely uniformly, resulting in not generating voids in the strands or pellets. Besides, gas to be used as a cooling medium is suitable to be 0-5% in oxygen density and 0-200ppm in moisture content and, for the main component of the gas, nitrogen or inorganic gas is preferable which is low in its reaction. |
