Patent ID: 6657037
Filing Date: 2003-12-02
Classification: B01J,C08G

Abstract:
A process for producing a polyamide by melt-polycondensing a diamine with a dicarboxylic acid in the absence of a solvent, comprising:(1) a step of melting the dicarboxylic acid; (2) a step of continuously or intermittently adding the diamine into the dicarboxylic acid kept in a molten state in a batch-wise first polymerizer equipped with a partial condenser to subject the diamine and the dicarboxylic acid to polycondensation at a predetermined molar ratio to produce a middle-stage polyamide having a relative viscosity of 1.4 to 2.7, the diamine having a boiling point higher than a melting point of the middle-stage polyamide under an inner pressure of the first polymerizer; (3) a step of feeding the middle-stage polyamide from the first polymerizer to a melt retention tank, where the middle-stage polyamide is fed into a continuous second polymerizer while controlling a change of relative viscosity of the middle-stage polyamide during the retention in the melt retention tank within Â±0.2 by maintaining a vapor phase portion of the melt retention tank at a predetermined pressure by saturated steam; and (4) a step of subjecting the middle-stage polyamide in the second polymerizer to a further polycondensation while removing water from a molten reaction system under reduced pressure, thereby producing a later-stage polyamide.