POLYESTER HAVING TERMINAL CARBOXYL GROUP CAPPED WITH POLYCARBONATE, FIBROUS MATERIAL MADE FROM THIS POLYESTER, AND PREPARATION OF THIS POLYESTER

摘要

The polyester has improved resistance to hydrolysis and aminolysis, has good adhesion to rubber and comprises at least 85 mol% of polyethylene terephthalate units, contains from 5 to 15 mmol/kg of polycarbonate-blocked carboxyl terminal groups and a maximum of 4.5 mol of free carboxyl terminal groups, and has a tear strength of 70 cN/tex, a residual strength after hydrolysis of 50% and after aminolysis of 70% of the initial strength, and a rubber adhesion of 95%. A process is also described for preparation of this polyester in which the polyester preparation is carried out in the presence of an alkali metal salt or alkaline earth metal salt as blocking catalyst and in the presence of a polycarbonate, but otherwise in a known manner. The polyester described is preferably used for the production of tyre cord.