Patent ID: 7053171

Claim:
A method of producing a polyamide by a polycondensation of a diamine component comprising 70 mol % or more of m-xylylenediamine and a dicarboxylic acid component comprising 60 to 95 mol % of a straight-chain α, ω-aliphatic dicarboxylic acid and 5 to 40 mol % of an aromatic dicarboxylic acid, the method comprising: (1) a step of heating the dicarboxylic acid component to a temperature not lower than a melting point of the straight-chain α, ω-aliphatic dicarboxylic acid and not higher than 210° C., thereby obtaining a suspension of the aromatic dicarboxylic acid in a molten straight-chain α, ω-aliphatic dicarboxylic acid; (2) a step of adding the diamine component comprising 70 mol % or more of m-xylylenediamine dropwise to the suspension while maintaining a reaction system at 220° C. or lower; (3) a step of heating the reaction system to a temperature exceeding 220° C. and not higher than 270° C. while continuing or discontinuing the addition of the diamine component, thereby allowing the reaction system to change from a suspension phase into a homogeneous molten phase; (4) a step of further adding the diamine component dropwise to the reaction system at 270° C. or lower while maintaining the homogeneous molten phase; and (5) a step of maintaining the reaction system at 240 to 270° C. after completing the addition of the diamine component, thereby increasing a degree of polymerization, with the proviso that 20 to 60% by weight of a total amount of the diamine component is added while the reaction system is in the suspension phase before changing into the homogeneous molten phase.