| 摘要 |
PURPOSE:To obtain a beautiful and glossy heat-shrinkable tube having no foreign matter bonded to the inner surface thereof by interposing a preparatory tube between a product tube and the pin inserted therein to expand the same. CONSTITUTION:Before the expansion of the diameter of a heat-shrinkable tube, a large number of pins 3 are intersed in a tube 1a and a preparatory tube 2a and an expanding core mold 4 is moved to expand the tubes to produce a tube 1b and a preparatory tube 2b both of which are expanded in diameter. Since the abrasion powder generated by the friction of the pins 3 and the core mold 4 at the time of expansion is bonded to the inner surface of the preparatory tube 2b, it is not bonded to the inner surface of a product tube to obtain a tube having a clean inner surface. The preparatory tubes 2a, 2b are pref. composed of a material capable of being expanded in diameter and low in the adhesiveness with the product tube such as a thermoplastic resin such as polyolefin or polyvinyl chloride, an elastomer such as ethylene/propylene rubber, fluororubber or natural rubber or crosslinked matter thereof. |
