Abstract: There are described polyester fibers and filaments which, following reaction with carbodiimides, have capped carboxyl end groups, the carboxyl end groups being predominantly capped by reaction with mono- and/or biscarbodiimides which are present in the fibers and filaments in an amount of from 30 to 200 ppm, based on the weight of the polyester, the free carboxyl end group content being less than 3 meq/kg of polyester, and the fibers and filaments additionally containing at least 0.02 percent by weight of at least one free polycarbodiimide or of a reaction product containing still reactive carbodiimide groups, and also a process for the preparation thereof.The filaments described are suitable in particular for producing papermaker's machine wire-cloths.

Abstract: A process for the production of hydrolysis resistant polyester fibers and filaments (preferably monofilaments for use in paper making machine sieves) comprises feeding a masterbatch of a polymeric carrier and an end group blocking agent to a spinneret together with a thread-forming polyester material, wherein the polymeric carrier has practically no end groups which react with the end group blocking agents. In addition to the process and the masterbatch, the polyester fibers or filaments of increased resistance to hydrolysis, in which the agents for blocking the end groups are distributed inhomogeneously over the cross-section of the monofilament, comprise a content of end group blocking agent that increases continuously from the core to the jacket of the fiber.

Abstract: Solutions are described containing polyarylene sulfide and, as solvent, quinoline and/or isoquinoline and/or substituted derivatives thereof, the solvent being liquid at 25.degree. C. These solutions are processed at temperatures above 170.degree. C. and are used to produce shaped objects, such as films or fibers, or coatings. In addition they are used to determine the molecular weight of polyarylene sulfides or to purify polyarylene sulfides, or to clean apparatuses which were used in the production or processing of polyarylene sulfides.

Abstract: Polyester fibers and filaments which contain carboxyl end groups closed off by reaction with carbodiimides, whereinthe closing off of the carboxyl end groups has predominantly been carried out by reaction with mono- and/or biscarbodiimides which the fibers and filaments still contain in the free form, however in as little an amount as less than 30 ppm (by weight) of the polyester,the content of free carboxyl end groups is less than 3 meq/kg of polyester andthe fibers and filaments still contain at least 0.05% by weight of at least one free polycarbodiimide or a reaction product which still contains reactive carbodiimide groups, and a process for their preparation are described.The filaments described are particularly suitable for the production of paper making machinery screens.