POLYESTER WITH POLYCARBONATE-CAPPED CARBOXYLIC ENDGROUPS, FIBRE MATERIAL MADE THEREFROM AND PROCESS FOR ITS PREPARATION

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.