Polyester resin composition containing amino-triazine derivative

A method for crystallizing a polyester resin, comprising:

• heating the polyester resin in the presence of a crystal nucleating agent containing 0.01 to 10 parts by mass of a 2-amino-1,3,5-triazine derivative of formula [1] relative to 100 parts by mass of the polyester resin to crystallize the polyester resin:
• where:
• each of R1 and R2 is independently —C(═O)R10, —C(═O)OR6, —C(═O)NR7R8, or —SO2R9, and
• each of R3 and R4 is independently a hydrogen atom, a C1-6 alkyl group, —C(═O)R5, —C(═O)OR6, —C(═O)NR7R8, or —SO2R9,
• each of R5, R6, R9, and R10 is independently a C1-20 alkyl group or a phenyl group optionally substituted with a C1-6 alkyl group, and
• each of R7 and R8 is independently a hydrogen atom, a C1-20 alkyl group, or a phenyl group optionally substituted with a C1-6 alkyl group.