| 摘要 |
PROBLEM TO BE SOLVED: To prepare a film having excellent oxygen barrier properties and reduced in the dependency of the properties on temperatures by performing a step of prepolymerizing a specified polyamide resin under conditions in which the reaction mixture is molten under pressure so that a specified conditions may be held between the product of the steam pressure and the polymerization time and the polymerization temperature, and starting the post- polymerization step. SOLUTION: In producing a polyamide resin containing 20mol % or above, based on the entire resin, amide repeating units such as meta-xyleneadipamide units by a polycondensation process comprising a prepolymerization step under conditions in which the reaction mixture is molten under pressure and a subsequent post-polymerization step at normal pressure or in a vacuum, the precondensation step is performed under conditions in which the polymerization temperature (T) is 170-220 deg.C, the steam pressure (P) is 3kgf/cm<2> G or above, and the relationship between Pt (t) is the polymerization time) and T is specified, the state is brought into one in which the temperature is 220 deg.C or below and the pressure is normal pressure or below, the water of condensation is removed, and the post-polymerization step is started. The water absorptivity of the amorphous part of the formed resin is 8wt.% or below (at an RH of 100% and 25 deg. and the activation energy forβrelaxation is 18kJ/mol or below (at 100Hz and a strain of 0.05%).
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