Biodegradable polyester resin, and biodegradable polyester film and laminate comprising same

A process for preparing a biodegradable polyester resin, which comprises:

• a first step of mixing a diol component and an aromatic dicarboxylic acid and pretreating it to obtain a slurry;
• a second step of subjecting a mixture comprising the slurry and an aliphatic dicarboxylic acid, or a mixture of a reaction product obtained by esterification of the slurry and an aliphatic dicarboxylic acid, to an esterification reaction at least once to obtain a prepolymer;
• and
• a third step of subjecting the prepolymer to a polycondensation reaction, wherein the biodegradable polyester resin comprises a first repeat unit comprising a first diol residue and an aromatic dicarboxylic acid residue and a second repeat unit comprising a second diol residue and an aliphatic dicarboxylic acid residue, the ratio (X/Y) of the number of the first repeat unit (X) to the number of the second repeat unit (Y) is 0.2 to 1.4, and the adhesion index (AI) represented by the above Equation 1 is 8 or more:
• Adhesion
• ⁢
• index
• ⁢
• (
• AI
• )
• =
• AS
• Tm
• [
• Equation
• ⁢
• 1
• ]
• in Equation 1, AS is the adhesive strength (gf), excluding the unit, measured as the maximum stress when one side of a biodegradable polyester film specimen having a width of 15 mm and a length of 150 mm prepared from the biodegradable polyester resin and one side of a polyethylene terephthalate (PET) film are subjected to thermal adhesion with each other at 130° C. and then delaminated at a peeling angle of 180° and a peeling speed of 300 mm/minute, and
• Tm is the melting temperature (° C.), excluding the unit, of the biodegradable polyester resin measured using a differential scanning calorimeter (DSC) while the temperature is elevated from 40° C. to 180° C. at a rate of 10° C./minute and then lowered to −50° C. at a rate of 10° C./minute.