| 摘要 |
PURPOSE:To manufacture a thin cylindrical molded material whose surface is smooth, by a method wherein after a preform has been made to expand through blowing within a mold, an inside shape of which has no split part and is in a cylindrical state, in an axial and circumferential directions, a molded article is unloaded by making the same shrink by heat within the mold. CONSTITUTION:A preform 1B heated at the orientation temperature is set within a mold 7 an inside shape of which has no split part and is in a cylindrical state. The preform is stretched by a stretching rod 5 in an axial direction, and made into a cylindrical molded material 2A by blowing compressed air within the preform. After said molded material 2A has been made to shrink through heat by keeping a mold at the temperature of more than the polyester glass point, the same is unloaded through the mold 7. Polyester shall be an article having intrinsic viscosity of more than 0.5. As the molded material is unloaded after heat shrinkage has been made to perform, a scratchless and thin cylindrical material is obtained. The titled material can be used for a carrier for a high density magnetic recording material. |
