| 摘要 |
PURPOSE:To increase the durability of a thermoplastic resin tube at high temperature by following method in which an extruded resin tube is drawn through the tube path of a sizing device, and then only the surface of the tube once having been cooled and solidified is fused by heating, and it is subsequently cooled and solidified, thereby removing the residual strain in the surface layer of the resin. CONSTITUTION:Thermoplastic resin at half fused plastic state is extruded in tubular form from a extruding head 2 and the predetermined diameter of the tube is obtained by being drawn through a sizing device 3. At sizing, the extruded tube with slightly larger diameter than that of a tube path 31 of said device is drawn through said tube path 31 with finished tube-diameter. Then, because the tube is sucked by vacuum through many holes 31a on the peripheral wall of the tube path 31, the tube is passed through the path in the state where it is closely in contact with the wall of the tube path 31. Therefore, the tube cooled and solidified in next cooling tank 4 has residual strain on its surface. Then only this surface of the tube is heated and fused in a high temperature liquid bath 6, and is again cooled and solidified in next cooling tank. Accordingly, the residual strain on its surface is removed, thereby increasing the elongation in tension remarkably and providing the durability for long period. |
