Abstract: The invention relates to a semi-crystalline semi-aromatic polyamide comprising A-A-B-B units derived from (a) dicarboxylic acids consisting of a mixture of aromatic dicarboxylic acid and aliphatic dicarboxylic acid and (b) diamines consisting of a mixture of long chain aliphatic diamine and short chain aliphatic diamine, wherein (a-i) the aromatic dicarboxylic acid consists for at least 80 mole % of terephthalic acid, and (a-ii) the aliphatic dicarboxylic acid constitutes at least 5 mole % of the dicarboxylic acids, (b-i) the short chain aliphatic diamine constitutes at least 10 mole % of the diamines, and (c) the aromatic dicarboxylic acid and the long chain aliphatic diamine constitute 60-90 mole % of the total molar amount of dicarboxylic acids and diamines.

Abstract: The invention relates to a process for increasing the molecular weight of a polyamide via solid-state post-condensation by exposing the polyamide in the solid-state at elevated temperature to an inert gas atmosphere, that comprises a step (a) wherein the gas atmosphere to which the polyamide is exposed has a dew temperature Tdew-1, followed by a step (b) wherein the gas atmosphere to which the polyamide is exposed has a dew temperature Tdew-2, whereby Tdew-1 is higher than Tdew-2. The effect is that a high molecular weight polyamide can be obtained in a shorter production time.

Abstract: The invention relates to a semi-aromatic polyamide containing at least tetramethylene terephthalamide units and also hexamethylene terephthalamide units. The copolyamide has a melting point higher than approximately 290° C., a high crystallinity and a good stability. Preferably the copolyamide according to the invention contains approximately 30-75 mol % hexamethylene terephthalamide units and also approximately 0.01-20 mol % other units. The invention also relates to a process for the preparation of a semi-aromatic copolyamide containing at least tetramethylene terephthalamide units and hexamethylene terephthalamide units, characterized in that, successively, a first polymerization is effected in the melt phase, followed by an post-polymerization of the low molar mass polymer thus obtained in the solid phase; and to compositions and products that contain said copolyamide.

Abstract: The invention relates to a semi-aromatic polyamide containing at least tetramethylene terephthalamide units and also hexamethylene terephthalamide units.