Patent ID: 7138482

Claim:
A production method of polyamide by batch melt polymerization which comprises: (1) a step of developing at least one estimating equation selected from the group consisting of (a) an estimating equation for calculating a mole balance (diamine unit/carboxylic acid unit) of polyamide under melt polymerization from a melt viscosity of polyamide measured at a set point during the melt polymerization, (b) an estimating equation for calculating a molecular weight of polyamide under melt polymerization from the melt viscosity, and (c) an estimating equation for calculating a relative viscosity of polyamide under melt polymerization from the melt viscosity; (2) a step of estimating, so as to provide an estimation, using said at least one estimating equation, at least one property selected from the group consisting of a mole balance, a molecular weight and a relative viscosity of polyamide under melt polymerization from a melt viscosity of polyamide measured at a set point during melt polymerization in next and subsequent; and (3) a step of continuing the melt polymerization in the next and subsequent batches under conditions determined by results of the estimation.