USE OF POLYESTER INSTEAD OF LEAD FOR USE AS FACING SUBSTANCE FOR HARDENING OF LONG SIZE HOSE

摘要

PURPOSE: To cure a hose without using lead, by a method wherein unoriented polyethylene terephthalate provided around a tubular article is changed to a crystalline state and heated to a vulcanized state. CONSTITUTION: A tubular article is passed through a die of a crosshead extruder to which unoriented polyethylene terephthalate is applied, and by quenching then the article, a sheathing material is brought into an amorphous state. The sheathing material is wound on a drum for vulcanization and it is put in a vulcanizing device such as an autoclave and subjected to heat and pressure. The amorphous polyethylene terephthalate is crystallized at about 130 deg.C and shrinks on the tubular article due to an increase in density. Since the cooled sheathing material is in the crystalline state and fragile, it can be broken down by making a bending radius small. The sheathing material can be cooled down quickly to the amorphous state so as to prevent a raw tubular article from being strained before a process of vulcanization.