PURPOSE: To manufacture the captioned tube having a large thermal shrinkability in the diametrical direction by a method wherein a thermally shrinkable film provided with thermal shrinkability obliquely to a length direction is coiled spirally about a heat resisting core body and heated.
CONSTITUTION: Thermoplastic resin such as PE, PP, etc. with which additives such as ageing resistor, filler, coloring agent, etc. are mixed is molded in a tube form and stretched in a diametrical direction at 80W200°C to give thermal shrinkability and then cut in a spiral direction to obtain a thermally shrinkable film 7 having thicknesses 0.05W1mm, thermal shrinking ratios 30W80% and a thermal shrinkability oblique to a length direction. Then, this film 7 is wound spirally on the heat resisting core body 6 at angles 70W85° so that its thermal shrinking direction is nearly parallel to the diametrical direction of the core body 6 and the films are laminated in a width direction. Then, it is heated at temperatures higher than the melting point and laminated parts 8 of the film 7 are welded and cooled to remove the core body 6.
YAMASHITA NOBORU
SUZUKI KOUJI
