Abstract: The present invention relates to a process for preparing an aromatic polyamide which comprises:(A) a dicarboxylic acid component unit comprising 30 to 100 mol % of a terephthalic acid component unit, and, as required, 0 to 70 mol % of a cyclic dicarboxylic acid component unit other than the terephthalic acid and, as required, 0 to 15 mol % of an aliphatic dicarboxylic acid having 7 to 20 carbon atoms; and(B) a diamine unit comprising 50 to 100 mol % of a component unit derived from an aliphatic alkylene diamine having 4 to 25 carbon atoms, and 0 to 50 mol % of a component unit derived from an alicyclic diamine having 3 to 25 carbon atoms; said process comprising:a step (i) of preparing a solid low-degree condensation product having an intrinsic viscosity [.eta.].sub.1 of from 0.05 to 0.2 dl/g is prepared by the polycondensation reaction of the dicarboxylic acid with the diamine;a step (ii) of solid-phase polymerizing said low-degree condensation product at a temperature of not higher than 195.degree. C.

Abstract: A process for producing an aromatic polyamide which comprises:(a) a dicarboxylic acid component which consists of 30-100 mol % of terephthalic acid and optionally 0-70 mol % of at least one dicarboxylic acid other than terephthalic acid, and(b) a diamine component which consists of 50-100 mol % of an aliphatic alkylenediamine of 4-25 carbons and optionally 0-50 mol % of at least one alicyclic diamine of 3-25 carbons, said process comprising a first step of performing melt reaction of said dicarboxylic acid with said diamine, thereby giving a low molecular weight condensate having an intrinsic viscosity [.eta.] of 0.05-0.6 dl/g, a second step of subjecting it to solid phase polymerization, thereby giving an aromatic polyamide precursor having an intrinsic viscosity [.eta.] of 0.5-1.0 dl/g, and a third step of subjecting it to melt polymerization, thereby giving an aromatic polyamide having a desired intrinsic viscosity [.eta.] of 0.8-2.5 dl/g.

Abstract: The semiaromatic polyamide of the invention comprises 40 to 90% by mol of (A) recurring units derived from terephthalic acid and an aliphatic diamine of 4 to 12 carbon atoms, 0 to 50% by mol of (B) recurring units derived from isophthalic acid and an aliphatic diamine of 4 to 12 carbon atoms, 0 to 60% by mol of (C) recurring units derived from an aliphatic dicarboxylic acid of 4 to 18 carbon atoms and an aliphatic diamine of 4 to 12 carbon atoms and 0 to 50% by mol of (D) recurring units derived from a lactam or an aminocarboxylic acid of 6 to 20 carbon atoms, and has a content of boiling water-soluble components (MO components) of not more than 0.25% by weight. The semiaromatic polyamide has a low content of the MO components, so that mold contamination hardly brought about in the molding process, and also molded articles of good heat resistance can be produced.

Abstract: Disclosed is a process for preparing cycloolefin random copolymer pellets, comprising adding an organic polar solvent to a solution of a copolymer obtained by copolymerizing ethylene and a specific cycloolefin and if desired an .alpha.-olefin other than ethylene, in an amount exceeding such an amount that the liquid mixture exhibits the cloud point, separating the copolymer solution utilizing phase separation phenomenon into a concentrated phase containing the cycloolefin random copolymer in a high concentration and a dilute phase containing said copolymer in a low concentration, feeding the obtained concentrated phase to an extruder where the solvents are removed and the copolymer is melted during extrusion processing, followed by pelletizing the copolymer.

Abstract: In accordance with the present invention, there are provided cycloolefin random copolymers composed of ethylene and cycloolefin and containing substantially no polyethylene, and processes for preparing the same. Optical disc substrates prepared from the above-mentioned copolymers are excellent in transparency and also capable of minimizing the occurence of errors in reading of the discs due to quality of the substrates used therefor.