Abstract: A polylactic acid resin composition includes: 0.005 parts by weight to 1.2 parts by weight of a metal phosphate represented by Formula (1): MxHyPOz??(1) (in Formula (1), M is an alkali metal atom or an alkaline earth metal atom, and x, y, and z are integers satisfying 1?x?2, 1?y?4, and 2?z?8, respectively) with respect to 100 parts by weight of a polylactic acid resin including a poly-L-lactic acid component and a poly-D-lactic acid component, wherein a crystallization enthalpy of crystals in the polylactic acid resin is not less than 5 J/g when a temperature of the polylactic acid resin composition is increased to 250° C., and the temperature is kept constant for 3 minutes, followed by decreasing the temperature at a cooling rate of 20° C./min in differential scanning calorimetry.

Abstract: A polylactic acid resin composition includes: 0.005 parts by weight to 1.2 parts by weight of a metal phosphate represented by Formula (1): MxHyPOz??(1) (in Formula (1), M is an alkali metal atom or an alkaline earth metal atom, and x, y, and z are integers satisfying 1?x?2, 1?y?4, and 2?z?8, respectively) with respect to 100 parts by weight of a polylactic acid resin including a poly-L-lactic acid component and a poly-D-lactic acid component, wherein a crystallization enthalpy of crystals in the polylactic acid resin is not less than 5 J/g when a temperature of the polylactic acid resin composition is increased to 250° C., and the temperature is kept constant for 3 minutes, followed by decreasing the temperature at a cooling rate of 20° C./min in differential scanning calorimetry.

Abstract: A method for producing a polyamide prepolymer including heating an aqueous solution of caprolactam having a water content of from 2 to 20% by weight, under pressure at a temperature of from 200 to 330° C. for 1 to 30 minutes, to produce polyamide prepolymer having an amino end group content of at least 0.1 mmol/g and a cyclic oligomer content of at most 0.6% by weight, and a conversion at most 40% by weight.

Abstract: A mixture substantially comprising caprolactam and water is heated for at most 30 minutes to obtain a polyamide prepolymer having an amino end group content of at least 0.1 mmol/g and a cyclic oligomer content of at most 0.6% by weight. An aqueous solution of caprolactam having a water content of from 2 to 20% by weight is heated under pressure at a temperature of from 200 to 330° C. for 1 to 30 minutes to obtain a polyamide prepolymer having an amino group content of at least 0.1 mmol/g and a cyclic oligomer content of at most 0.6% by weight.

Abstract: For producing a polyamide having an unreacted caprolactam content of from 0 to 0.5% by weight and an oligomer content of from 0 to 1.25% by weight and having a relative viscosity in a 0.01 g/ml solution of sulfuric acid at 25° C. of from 2.2 to 8.0, combined is a first step of polymerizing a starting material comprising caprolactam, under atmospheric pressure to prepare a polymerization product having an unreacted caprolactam content of not larger than 25% by weight and an oligomer content falling between 0 and 1.8% by weight, and a second step of heating the polymerization product prepared in the first step, at a temperature T satisfying the following formula (1) and under reduced pressure to thereby remove the unreacted caprolactam and the oligomer from it: Glass transition point of polyamide<T<melting point of polyamide+150° C.