Abstract: Thermoplastic polyesters based on aromatic diols are flexible, possess good working properties and have a high glass transition temperature when they contain dicarboxylic acids having N,N-heterocyclic rings.

Abstract: The reaction for the manufacture of linear polyesters by polycondensing dicarboxylic acids, hydroxycarboxylic acids or the esters and diols thereof is speeded up by the addition of 1 to 25% by weight of esters of phosphoric and/or phosphorous acid.

Abstract: Polyester precondensates are catalytically polycondensed in solid phase at a constant temperature with a linear increase (during polycondensation) in intrinsic viscosity. The linear increase makes possible an accurate advance determination of reaction time required to produce thermoplastic polycondensate of the desired intrinsic viscosity.

Abstract: Linear thermoplastic polyesters based on imidazolidine-4,5-dione-dicarboxylic acids are useful moulding compounds with high glass transition temperatures and good working properties.

Abstract: Moulding materials reinforced with fiber fillers and based on copolyesters of poly-1,4-butylene terephthalate are suitable for the manufacture of mouldings, especially those having thin walls, which have low tendency to distortion.

Abstract: Dicarboxylic acids and dicarboxylic acid derivatives which contain N,N-imidazolidine-4,5-diones are useful monomers for the manufacture of polymers, in particular polyesters.

Abstract: The melt phase reaction and/or solid phase reaction for the manufacture of polyesters is accelerated by adding a polycarbonate and a phosphorus containing stabilizer to the reaction mixture before completion of the reaction.

Abstract: Linear, homo- and copolymers that contain as condensation components amidocarboxylic acid radicals, imidocarboxylic acid radicals or dicarboxylic acid radicals containing two carbocyclic rings with 4 to 6 members and diol radicals containing N,N-heterocyclic rings, and which can contain in addition terephthalic and/or isophthalic acid and/or other diols, are amorphous to faintly crystalline, have high glass transition temperatures while at the same time having low softening temperatures, and are suitable for the manufacture of mouldings of all kinds with good thermomechanical properties.

Abstract: Linear polyesters based on terephthalic acid and/or isophthalic acid and containing di-(hydroxyalkyl) compounds of oligomeric N,N-heterocyclic compounds as the diol component, have higher glass transition temperatures compared with poly-(alkylene) terephthalates. The new polyesters are thermoplastic materials suitable for the manufacture, by customary moulding processes, of mouldings having a higher heat distortion point.

Abstract: Glass fiber-reinforced thermoplastic polyester moulding compositions which contain poly(2,4,6-tribromostyrene) range from flame-resistant to flameproof and exhibit improved toughness properties. These moulding compositions can be used for the manufacture of shaped articles of all kinds, in accordance with the known processes.

Abstract: Solid phase polycondensation of thermoplastic polyester melt precondensate is effected at a temperature from 50.degree. to 5.degree.C below the melting point of the precondensate, at a vacuum below 1 torr and in contact with a streaming inert gas.