Patent ID: 6610816
Filing Date: 2003-08-26
Classification: C08G

Abstract:
A process for producing a polyamide constituted of a dicarboxylic acid unit comprising 80% by mol or more of an aliphatic dicarboxylic acid unit having 6 to 12 carbon atoms and a diamine unit comprising 80% by mol or more of xylylenediamine unit or bisaminomethylcyclohexane unit, the process comprising:(1) performing a melt-polymerization in batch-wise manner by adding a diamine monomer directly into a molten dicarboxylic acid monomer, thereby producing a polyamide; (2) measuring, in the absence of bubbles, (A) a molar ratio of a diamine component and a dicarboxylic acid component in a reaction mixture, and (B) at least one property selected from the group consisting of a water content of the reaction mixture, and a carboxyl end group concentration, an amino end group concentration, a molecular weight, a relative viscosity and a melt viscosity of the polyamide obtained in the step (1) using a near-infrared spectrometer when a number average molecular weight of the polyamide obtained in the step (1) reaches 6000 to 20,000, the diamine component including the diamine monomer remaining in the reaction mixture not polymerized and the diamine monomer polymerized to constitute the polyamide obtained in the step (1), and the dicarboxylic acid component including the dicarboxylic acid monomer remaining in the reaction mixture not polymerized and the dicarboxylic acid monomer polymerized to constitute the polyamide obtained in the step (1); and (3) regulating the molar ratio to a desired level and determining a time for further continuing the melt-polymerization and the timing for changing the polymerization conditions on the basis of measured values (A) and (B), while continuing the melt-polymerization.