Patent Number: 6,169,161

Title: Method for producing polyamides

Abstract: For producing a polyamide having an unreacted caprolactam content of from 0 to 0.5% by weight and an oligomer content of from 0 to 1.25% by weight and having a relative viscosity in a 0.01 g/ml solution of sulfuric acid at 25.degree. C. of from 2.2 to 8.0, combined is a first step of polymerizing a starting material comprising caprolactam, under atmospheric pressure to prepare a polymerization product having an unreacted caprolactam content of not larger than 25% by weight and an oligomer content falling between 0 and 1.8% by weight, and a second step of heating the polymerization product prepared in the first step, at a temperature T satisfying the following formula (1) and under reduced pressure to thereby remove the unreacted caprolactam and the oligomer from it:

Inventors: Tachibana; Yasuto (Handa, JP), Okita; Shigeru (Nagoya, JP), Onishi; Koji (Kuwana, JP)

Assignee: Toray Industries, Inc.

International Classification: C08G 69/04 (20060101); C08G 69/16 (20060101); C08G 69/00 (20060101); C08G 69/18 (20060101); C08G 069/14 (); C08G 069/16 ()

Expiration Date: 01/02/2018