Preparation method of copolyester for metal powder coating

The invention relates to a preparation method of a copolyester for a metal powder coating, mainly comprising the following steps of: (1) carrying out transesterification reaction between terephthalic acid, isophthalic acid, hydroxyethyl bisphenol A and C2-C6 dihydric alcohol under the action of a tetrabutyl titanate/butylhydroxyoxo-stannane catalyst; and (2) adding a stabilizer triphenyl phosphite into the product obtained from Step (1) at atmospheric pressure and carrying out decompressing copolycondensation at 230-250 DEG C and at 80-130 Pa to obtain the copolyester. The obtained copolyester has advantages of steaming and boiling resistance, acid and alkali resistance and strong adhesive force. The coating provided by the invention can be applied in the field of metal can coating.