Patent Description:
As a living environment becomes prosperous, disposable plastics are gradually increasing. Disposable plastics used in this way cause serious environmental pollution when disposed of in the natural environment.

Accordingly, in order to solve these problems, many studies have been currently conducted worldwide to solve these serious environmental problems by manufacturing disposable products with biodegradable resins.

Biodegradable compositions have been known for decades. That is, an aromatic/aliphatic copolyester resin reacts with aromatic dicarboxylic acids such as terephthalic acid and dimethyl terephthalate, aliphatic dicarboxylic acids such as adipic acid, and glycols such as <NUM>,<NUM>-butanediol to prepare polybutylene-co-adipate terephthalate, and the prepared polybutylene-co-adipate terephthalate has been currently produced worldwide by KINGFA, BASF, Novamont, Tunhe, Jinhui, S-EnPol, Xingfu and Soltech, and sold decades ago.

All these companies use almost constant contents of raw materials used and the same raw materials such as therephthalic acid, adipic acid, and <NUM>,<NUM>-butanediol. However, the physical properties of all these companies are different from each other depending on process conditions for manufacturing polybutylene-co-adipate terephthalate.

When describing existing technologies related to biodegradable resins developed currently, in <CIT>), there is disclosed a method for obtaining an aliphatic polyester resin having a number average molecular weight of about <NUM>,<NUM> to <NUM>,<NUM> in the presence of trihydric or higher polyhydric alcohol or trihydric or higher polyhydric carboxylic acid monomers as an auxiliary component of the reaction, and then obtaining an aliphatic polyester resin having a number average molecular weight of about <NUM>,<NUM> to <NUM>,<NUM> obtained by further reacting isocyanate as a coupling agent. According to this method, since the reaction time is long, the productivity is low and the use for a film is unsuitable, and isocyanate as a coupling agent used to increase the molecular weight, is extremely harmful to the human body, so that there is a problem in that work precautions are required.

In addition, in <CIT>, it is not understood by those skilled in the art that a high acid value after condensation polymerization to prepare polybutylene-co-adipate terephthalate is lowered by solid-state polymerization, Chemical Formula obtained by reacting DL-malic acid with <NUM>,<NUM>-cyclohexanedimethanol is also incorrect, unreacted <NUM>,<NUM>-cycle hexanedimethanol remains, which slows down the reaction rate, and preparation of <NUM> steps through a reaction polycondensation compound with ester and solid-state polymerization is a problem in economic feasibility, and the effectiveness is in doubt in that the preparation is completed in two steps by other manufacturers. In addition, the acid value cannot be lowered by solid-state polymerization after condensation polymerization and the heat distortion temperature of polybutylene-co-adipate terephthalate is <NUM> to <NUM>, but solid-state polymerization at <NUM> is impossible.

In addition, in <CIT>, an aliphatic/aromatic copolyester copolymer was prepared by condensation polymerization using adipic acid and succinic acid as aliphatic dicarboxylic acid, terephthalic acid as aromatic dicarboxylic acid, dimethylterephthalate and <NUM>,<NUM>-butanediol as aliphatic diol in a method of preparing aliphatic/aromatic copolyester. In order to increase the molecular weight, a trifunctional monomer, isocyanate, and sulfonate were added, but reaction time, gelation, and the like were concerned for this preparation, and even after this synthesis, a number average molecular weight (Mn) is about <NUM>,<NUM> to <NUM>,<NUM>, so that the tensile strength and quality may be deteriorated.

Further, in <CIT>), there is provided a method for preparing a biodegradable resin composition prepared by <NUM> to <NUM> parts by weight of polylactic acid with respect to <NUM> parts by weight of aliphatic polyester and aliphatic/aromatic copolyester through compounding using a twin-screw extruder. In this case, in the compounding process of polylactic acid (or its copolymer) and polybutylene succinate (or its copolymer), there is a problem that due to a high melting point of polylactic acid, the thermal stability of the prepared resin is significantly reduced when extruded at a high temperature, and the mechanical properties of the prepared resin are also reduced.

In addition, in <CIT>) and <CIT>), polybutylene-co-adipate terephthalate was prepared using terephthalic acid as aromatic dicarboxylic acid, adipic acid as aliphatic dicarboxylic acid, and <NUM>,<NUM>-butanediol as a glycol component as used raw materials.

Further, in <CIT>, an unsaturated compound and the like are used to prepare polybutylene coadipate, that is, an aromatic/aliphatic copolyester resin, which has a problem of gelation if the unsaturated compound and the like are not properly adjusted.

<CIT> discloses a thermal adhesive co-polyester manufactured by reacting dicarboxylic acid components and diol components. The dicarboxylic acid component is <NUM>-<NUM> mol% of aromatic dicarboxylic acid and/or aromatic dicarboxylic acid ester formable derivative, and <NUM>-<NUM> mol% of aliphatic dicarboxylic acid and/or aliphatic dicarboxylic ester formable derivative. The diol component consists of <NUM>-<NUM> mol% of diol of linear-structure, and <NUM>-<NUM> mol% of diol of symmetric cyclic structure. <CIT> describes a process comprising (a) processing at least <NUM> wt. % monomers or oligomers comprising at least one (hetero)aromatic <NUM>-12C dicarboxylic acid or its diesters, at least one aliphatic <NUM>-12C dicarboxylic acid or its diesters or at least one <NUM>-12C alkanol having at least two hydroxy groups, by mixing to form a paste, and adding at least one catalyst during the preparation of the paste or into the ready-made paste, (b) reacting the paste by increasing the temperature and distilling condensation products or transesterification products to obtain an esterification- or transesterification product, and (c) polycondensing or copolycondensing the esterification- or transesterification product under reduced pressure, to obtain the polyester or copolyester having a molecular weight of <NUM>-<NUM>/mole. <NPL> disclose a study of possible eco-friendly fibres for medical applications using a synthesised oligomer poly(glycerol succinate) (PGSu) as an additive for synthetic poly(L-lactic acid) (PLLA) and poly (L-lactide-co-caprolactone) (PLCL) <CIT> discloses a biodegradable polyester, with long chain branches (isometric with respect to the main chains of the polyester) and essentially gel-free, characterized by optimum adhesion to paper, and a laminate product composed of at least a backing, preferably paper, and of at least a first layer composed of polyester according to the invention. <CIT> discloses an aliphatic-aromatic copolyester in which the dicarboxylic component has aromatic diacid as more than <NUM>% and less than <NUM>% of the dicarboxylic component, and the aromatic diacid comprises at least one aromatic diacid of renewable origin, particularly <NUM>,<NUM>-furandicarboxylic acid.

As such, existing biodegradable resins (polybutylene-co-adipate terephthalate) have been already known for decades and physical properties vary depending on who prepares polybutylene-co-adipate terephthalate with good physical properties in any method. However, existing methods have problems in spreading the uses due to poor tensile strength and transparency, and the like, and there are limitations in using the biodegradable resins due to poor workability and the like as compared with existing non-biodegradable resins.

Therefore, since the raw materials used in the preparation of polybutylene-co-adipate terephthalate, that is, aromatic/aliphatic copolyester, have been already known for decades, the key is to solve environmental pollution by manufacturing biodegradable disposable products that can be completely biodegraded by improving workability, transparency and tensile strength, which are problems of existing biodegradable resins, by using a third material to improve physical properties.

Accordingly, the present inventors developed a biodegradable polyester resin with an acid value of <NUM> to <NUM>-KOH/g, a number average molecular weight of <NUM>,<NUM> or more, and a tensile strength of <NUM> MPa (<NUM> kgf/cm<NUM>) or more using an aromatic/aliphatic copolyester biodegradable polyester resin with excellent reaction rate and tensile strength, and simultaneously maximized a production and solve the problems of biodegradability such as flexibility, tensile strength and durability by freely controlling the reaction rate, that is, the condensation polymerization time compared to existing biodegradable resins, and then completed the present invention.

An object of the present invention is to provide a biodegradable polyester resin with excellent flexibility and tensile strength that is completely degraded when disposed of in the natural environment and a method for preparing the same to protect the natural environment by solving the problems of reaction rate, tensile strength and durability, which are problems of the existing biodegradable polyester resins and solving the workability, which is a disadvantage of the existing biodegradable polyester resins.

Specifically, an object of the present invention is to a biodegradable polyester resin and a method for preparing the same, in which, to obtain a biodegradable polyester resin having a reaction rate, flexibility and tensile strength which are superior to those of polybutylene-co-adipate terephthalate, which is a conventional biodegradable polyester resin, polyglycerol succinate having a number average molecular weight of <NUM>-<NUM>,<NUM>, prepared by synthesis through an esterification reaction between glycerol and succinic acid, is added as a reaction rate control agent derived from biomass to increase the reaction rate in the synthesis of a biodegradable polyester resin, and polyglycerol furanoate having a number average molecular weight of <NUM>,<NUM>-<NUM>,<NUM>, prepared by synthesis through an esterification reaction between glycerol and <NUM>,<NUM>-furandicarboxylic acid, is added as a molecular weight increasing agent derived from biomass to increase tensile strength, to thereby prepare a biodegradable polyester resin having a number average molecular weight of <NUM>,<NUM> or more, a weight average molecular weight of <NUM>,<NUM> or more, an acid value of <NUM>-<NUM>-KOH/g, and a tensile strength of <NUM> MPa (<NUM> kgf/cm<NUM>) or more.

To solve the problem, the present invention provides a biodegradable polyester resin with excellent reaction rate, tensile strength, and durability and having an acid value of <NUM> to <NUM>-KOH/g, a number average molecular weight of <NUM>,<NUM> or more, a weight average molecular weight of <NUM>,<NUM> or more, and a tensile strength of <NUM> MPa (<NUM> kgf/cm<NUM>) or more.

More specifically, the present invention provides a method for preparing a biodegradable polyester resin having excellent flexibility and durability used in disposable products and plastic products made of biodegradable resins, wherein <NUM>,<NUM>-butanediol may be used as a glycol component.

In addition, aliphatic (including cyclic aliphatic) dicarboxylic acid (or anhydride) includes succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, <NUM>,<NUM>-nonanedicarboxylic acid, <NUM>,<NUM>-decanedicarboxylic acid and their acid anhydrides, but these aliphatic (including cyclic aliphatic) dicarboxylic acids or their acid anhydrides may be used alone or as a mixture of two or more thereof.

As another preferable specific example, in an acid component used in a process of preparing an aliphatic/aromatic co-polyester polymer of the present invention, a weight ratio of aromatic dicarboxylic acid and aliphatic dicarboxylic acid is preferably <NUM>:<NUM> to <NUM>:<NUM>, and at this time, in order to have biodegradability, if the aromatic content of the total acid component exceeds <NUM> wt%, it is not biodegradable, so that the attention is required.

Further, the technical solution is to add polyglycerol succinate with a number average molecular weight of <NUM> to <NUM>,<NUM> prepared by synthesis through an esterification reaction between glycerol and succinic acid derived from biomass, as a reaction rate control agent derived from biomass in the synthesis of the biodegradable polyester resin of the present invention.

That is, as the reaction rate control agent according to the present invention, the polyglycerol succinate is used by directly synthesizing polyglycerol succinate having a molecular weight of <NUM> to <NUM>,<NUM> as the following Reaction Formula <NUM> obtained by an esterification reaction and then condensation polymerization between glycerol and succinic acid derived from biomass. <CHM>
<CHM>.

Further, the technical solution is to add polyglycerol furanoate having a number average molecular weight of <NUM>,<NUM> to <NUM>,<NUM> prepared by synthesizing glycerol and <NUM>,<NUM>-furandicarboxylic acid derived from biomass as a molecular weight increasing agent derived from biomass in the synthesis of the biodegradable polyester resin to increase the tensile strength of the biodegradable polyester resin of the present invention.

That is, as the molecular weight increasing agent according to the present invention, the polyglycerol furanoate is used by directly synthesizing polyglycerol furanoate having a molecular weight of <NUM>,<NUM> to <NUM>,<NUM> as the following Reaction Formula <NUM> obtained by an esterification reaction and then condensation polymerization between glycerol and <NUM>,<NUM>-furandicarboxylic acid derived from biomass.

In addition, as another preferred specific example, at the beginning or end of the esterification reaction, transesterification reaction and condensation polymerization reaction of the synthesis of the biodegradable polyester resin of the present invention, the catalyst to be added is used in the range of <NUM> to <NUM> wt% based on the total weight part of the reactant.

As a specific example of catalysts mentioned in already known [cited in Sax Toxi Substance Data Book Fujiyama, Maruzer. k <NUM>, <CIT>] <NPL>], the catalyst is preferably used with one or a mixture of two or more selected from the group consisting of tetrabutyl titanate, trioctyl antimony oxide, tin oxide, calcium acetate, zinc acetate, tetrapropyl titanate, etc..

As another preferred specific example, at the beginning or end of the esterification reaction, transesterification reaction and condensation polymerization reaction, the stabilizer is further added.

As stabilizers disclosed in already known <CIT> and <CIT>, the stabilizer is used in the range of <NUM> to <NUM> wt% based on the total reaction and weight, wherein the stabilizer may be used with one or a mixture of two or more selected from phosphorous acid, trimethyl phosphate, and triphenyl phosphate.

In addition, it is good that the temperature range for performing a first esterification reaction and the transesterification reaction is maintained at <NUM> to <NUM>, and it is suitable that the temperature for performing a second esterification reaction and the transesterification reaction is in the range of <NUM> to <NUM>.

In addition, as another preferred specific example, it is preferable that a molar ratio of the acid component to the glycol to be added in the first and second esterification reactions is <NUM>:<NUM> to <NUM>:<NUM> mol.

In addition, as another preferred specific example, it is preferable that the condensation polymerization reaction is performed for <NUM> minutes to <NUM> minutes under a vacuum of <NUM> to <NUM> Pa (<NUM> to <NUM> Torr) in the temperature range of <NUM> to <NUM>.

According to the present invention, there are excellent effects of solving the disadvantages of existing biodegradable resins, such as reaction time, flexibility, and tensile strength, and protecting the natural environment by being completely decomposed when discarded in the natural environment by providing the biodegradable polyester resin prepared by adding a reaction rate control agent and a molecular weight increasing agent, which are derived from biomass, in which, to obtain a biodegradable polyester resin having a reaction rate, flexibility and tensile strength which are superior to those of polybutylene-co-adipate terephthalate, which is a conventional biodegradable polyester resin, polyglycerol succinate having a number average molecular weight of <NUM>-<NUM>,<NUM>, prepared by synthesis through an esterification reaction between glycerol and succinic acid, is added as a reaction rate control agent derived from biomass to increase the reaction rate in the synthesis of a biodegradable polyester resin, and polyglycerol furanoate having a number average molecular weight of <NUM>,<NUM>-<NUM>,<NUM>, prepared by synthesis through an esterification reaction between glycerol and <NUM>,<NUM>-furandicarboxylic acid, is added as a molecular weight increasing agent derived from biomass to increase tensile strength, to thereby prepare a biodegradable polyester resin having a number average molecular weight of <NUM>,<NUM> or more, a weight average molecular weight of <NUM>,<NUM> or more, an acid value of <NUM>-<NUM>-KOH/g, and a tensile strength of <NUM> MPa (<NUM> kgf/cm<NUM>) or more.

A biodegradable polyester resin prepared by adding a reaction rate control agent and a molecular weight increasing agent which are derived from biomass is a biodegradable polyester resin with excellent reaction rate, tensile strength and durability and has an acid value of <NUM> to <NUM>-KOH/g, a number average molecular weight of <NUM>,<NUM> or more, a weight average molecular weight of <NUM>,<NUM> or more, and a tensile strength of <NUM> MPa (<NUM> kgf/cm<NUM>) or more.

In the present invention, as aromatic dicarboxylic acid, aromatic dicarboxylic acids (or acid anhydrides thereof) containing aromatics in a molecular structure such as terephthalic acid, dimethyl terephthalate, and isophthalate may be used, but it is preferable to use dimethyl terephthalate.

In addition, <NUM>,<NUM>-butanediol may be used as a glycol component used in the biodegradable polyester resin of the present invention.

Particularly, in an acid component used in a process of preparing an aliphatic/aromatic co-polyester polymer of the present invention, a weight ratio of aromatic dicarboxylic acid and aliphatic dicarboxylic acid is preferably <NUM>:<NUM> to <NUM>:<NUM>, and at this time, in order to have biodegradability, if the aromatic content of the total acid component exceeds <NUM> wt%, it is not biodegradable, so that the attention is required.

Meanwhile, as the reaction rate control agent derived from the biomass of the present invention, polyglycerol succinate having a number average molecular weight of <NUM> to <NUM>,<NUM> is synthesized by performing an esterification reaction between glycerol and succinic acid derived from the biomass at <NUM> to <NUM> by adding a catalyst and a stabilizer, completely releasing water, gradually raising the temperature to <NUM>, and then performing condensation polymerization under a high vacuum of <NUM> to <NUM> Pa (<NUM> to <NUM> Torr) for <NUM> minutes, according to Reaction Formula <NUM>.

At this time, the condensation polymerization time is preferably <NUM> minutes to <NUM> minutes, and when the condensation polymerization time is less than <NUM> minutes, excessive glycol may remain, and when the condensation polymerization time is <NUM> minutes or more, there is a risk of gelation.

In addition, in order to increase the tensile strength of the biodegradable polyester resin of the present invention, as the molecular weight increasing agent derived from the biomass in the synthesis of the biodegradable polyester resin of the present invention, polyglycerol furanoate having a number average molecular weight of <NUM>,<NUM> to <NUM>,<NUM> is synthesized as shown in Reaction Formula <NUM> by performing an esterification reaction between glycerol and <NUM>,<NUM>-furandicarboxylic acid derived from the biomass at <NUM> to <NUM> by adding a catalyst and a stabilizer, completely releasing water, gradually raising the temperature to <NUM>, and then performing condensation polymerization under <NUM> to <NUM> Pa (<NUM> to <NUM> Torr) or less for <NUM> minutes.

At this time, when the esterification reaction temperature is <NUM> or less, it is difficult to release water, and when the esterification reaction temperature is <NUM> or more, deterioration may occur. In addition, the condensation polymerization reaction time is preferably <NUM> to <NUM> minutes. When the condensation polymerization reaction time is <NUM> minutes or less, the complete reaction may not proceed, and when the condensation polymerization reaction time is <NUM> minutes or more, there is a fear of gelation.

On the other hand, in the aliphatic/aromatic co-polyester biodegradable resin of the present invention, as a one-step synthesis method, an aromatic dicarboxylic acid component, glycol, a catalyst and a stabilizer are first added, and the temperature is gradually raised to <NUM> to <NUM>, and a theoretical amount of methanol is completely released through a transesterification reaction and then the reaction is terminated, and thereafter, aliphatic dicarboxylic acid, the reaction rate control agent and the molecular weight increasing agent are added, the temperature is gradually raised to <NUM> to <NUM> again, and water is completely released through an esterification reaction and then the reaction is terminated. In this case, a weight ratio of the aromatic dicarboxylic acid and the aliphatic dicarboxylic acid in the total acid component is preferably <NUM>:<NUM> to <NUM>:<NUM>.

In addition, as another one-step synthesis method, aliphatic dicarboxylic acid, glycol, a catalyst and a stabilizer are first added, and the temperature is gradually raised to <NUM> to <NUM>, and a theoretical amount of water is completely released through an esterification reaction and then the reaction is terminated, and thereafter, aromatic dicarboxylic acid, the reaction rate control agent and the molecular weight increasing agent are added, the temperature is gradually raised to <NUM> to <NUM> again, and methanol is completely released through a transesterification reaction and then the reaction is terminated. At this time, the weight ratio of the aromatic dicarboxylic acid and the aliphatic dicarboxylic acid in the total acid component is preferably <NUM>:<NUM> to <NUM>:<NUM>.

When the acid component of the aromatic dicarboxylic acid is more than <NUM> wt%, the biodegradability is significantly lowered, so that the biodegradable resin to be obtained in the present invention cannot be obtained. In addition, when the amount of aromatic dicarboxylic acid in the acid component is <NUM> wt% or less, heat resistance may also be deteriorated.

In the present invention, in preparing the aliphatic/aromatic copolyester resin, dicarboxylic acid and glycol is preferably added in a molar ratio of <NUM>:<NUM> to <NUM>:<NUM>.

At this time, when the amount of glycol is <NUM> mol or less, there is a problem that the reaction rate may decrease and the color may deteriorate. In addition, when the amount of glycol is <NUM> mol or more, the manufacturing cost increases to reduce price competitiveness.

In addition, in the first-step synthesis, the esterification reaction or the transesterification reaction is performed by gradually raising the temperature to <NUM> to <NUM>.

At this time, when the reaction temperature is <NUM> or less, it takes a lot of time to release the theoretical amount of water. In addition, when the reaction temperature is <NUM> or more, thermal decomposition may occur, resulting in a decrease in physical properties.

In this way, after the esterification reaction or transesterification reaction is terminated, the reaction temperature is gradually raised to start the condensation polymerization reaction, which is a second reaction. When the reaction temperature is <NUM> or less, the reaction rate slows down, and when the condensation polymerization temperature is <NUM> or more, there is a risk of thermal decomposition.

Meanwhile, in the present invention, the catalyst and the stabilizer are added at the beginning of the esterification reaction in the first and second steps, transesterification reaction or condensation polymerization reaction.

At this time, the addition amount of the catalyst is <NUM> to <NUM> wt% based on the total weight of the composition. At this time, if the amount of the catalyst used is less than <NUM> wt%, the esterification reaction and the transesterification reaction may not be performed smoothly, and as a result, the reaction time may be long and the color may be deteriorated during condensation polymerization.

In addition, when the catalyst amount exceeds <NUM> wt%, the reaction rate is fast, but the color and the molecular weight distribution are increased, which may cause the deterioration of physical properties.

In addition, it is preferred that the addition amount of the stabilizer is <NUM> to <NUM> wt%, and at this time, when the addition amount of the stabilizer is less than <NUM> wt%, a factor that significantly deteriorates the color may also occur, and when the addition amount of the stabilizer is greater than <NUM> wt%, the reaction rate is significantly reduced.

On the other hand, when the reaction rate control agent (polyglycerol succinate) derived from the biomass is added in an amount of less than <NUM> wt%, the production may be reduced, and there is a limit to shortening the condensation polymerization reaction time, and when the reaction rate control agent is added in excess of <NUM> wt%, the reaction rate is fast, but there is a high risk of gelation.

When the molecular weight increasing agent (polyglycerol furanoate) derived from the biomass is added in an amount of less than <NUM> wt% of the total component, there is a limit to increasing the molecular weight within the reaction time, and when added in an amount of more than <NUM> wt%, the molecular weight distribution may increase and the tensile strength may decrease.

When manufacturing a disposable product from the biodegradable polyester resin prepared as such, which has excellent reaction time (productivity), flexibility and tensile strength, it is possible to manufacture a product with high transparency and tensile strength.

Hereinafter, to help a more detailed understanding of the present invention, while the following Example <NUM> to Example <NUM> were performed as examples of the present invention - these are to be compared with Comparative Example <NUM> to Comparative Example <NUM> not according to the present invention, and comparatively tested as set out below, and then the results thereof are shown in Table <NUM>.

In a <NUM> round bottom flask, <NUM> mol of adipic acid and <NUM> mol of <NUM>,<NUM>-butanediol were added and then added with <NUM> of polyglycerol succinate as a reaction rate control agent and <NUM> of tetrabutyl titanate as a catalyst when an internal temperature reached <NUM> while gradually raising the temperature, and an esterification reaction was performed while the temperature was gradually raised to <NUM> to completely release water. Thereafter, <NUM> mol of dimethyl terephthalate, <NUM> of polyglycerol furanoate as a molecular weight increasing agent, and <NUM> of tetrabutyl titanate as a catalyst were added, and a transesterification reaction was performed while raising the temperature to <NUM> again to release completely ethanol, and then <NUM> of antimony trioxide as a catalyst and <NUM> of trimethyl phosphate as a stabilizer were added, and then condensation polymerization was performed while gradually raising the temperature to <NUM> again.

From the copolyester resin obtained thus, a biodegradable copolyester resin was prepared with a condensation polymerization reaction time of <NUM> minutes, an acid value of <NUM>-KOH/g, a number average molecular weight of <NUM>,<NUM>, a tensile strength of <NUM> MPa (<NUM> kgf/cm<NUM>), and a weight average molecular weight of <NUM>,<NUM>.

In a <NUM> round bottom flask, <NUM> mol of dimethylderephthalate, <NUM> mol of <NUM>,<NUM>-butanediol, and <NUM> of polyglycerol succinate were added and then added with <NUM> of tetrabutyl titanate as a catalyst when an internal temperature reached <NUM> while gradually raising the temperature, and a transesterification reaction was performed while the temperature was gradually raised to <NUM> to completely release methanol. Thereafter, <NUM> mol of adipic acid and <NUM> of tetrabutyl titanate as a catalyst were added, and an esterification reaction was performed while raising the temperature to <NUM> again to release completely water, and then <NUM> of polyglycerol furanoate as a molecular weight increasing agent, <NUM> of antimony trioxide as a catalyst and <NUM> of trimethyl phosphate as a stabilizer were added, and then condensation polymerization was performed while gradually raising the temperature to <NUM>.

In a <NUM> round bottom flask, <NUM> mol of adipic acid and <NUM> mol of <NUM>,<NUM>-butanediol were added and then added with <NUM> of polyglycerol succinate and <NUM> of tetrabutyl titanate as a catalyst when an internal temperature reached <NUM> while gradually raising the temperature, and an esterification reaction was performed while the temperature was gradually raised to <NUM> to completely release methanol. Thereafter, <NUM> mol of dimethyl terephthalate, <NUM> of polyglycerol furanoate, and <NUM> of tetrabutyl titanate as a catalyst were added, and a transesterification reaction was performed while raising the temperature to <NUM> again to release completely water, and then <NUM> of zinc oxide as a catalyst and <NUM> of trimethyl phosphate as a stabilizer were added, and then condensation polymerization was performed while gradually raising the temperature to <NUM>.

In a <NUM> round bottom flask, <NUM> mol of adipic acid, <NUM> mol of <NUM>,<NUM>-butanediol and <NUM> of polyglycerol succinate were added and then added with <NUM> of tetrabutyl titanate as a catalyst when an internal temperature reached <NUM> while gradually raising the temperature, and an esterification reaction was performed while the temperature was gradually raised to <NUM> to completely release methanol. Thereafter, <NUM> mol of dimethyl terephthalate, <NUM> of polyglycerol furanoate as a molecular weight increasing agent, and <NUM> of tetrabutyl titanate as a catalyst were added, and the reaction was performed while raising the temperature to <NUM> again to release completely water, and then <NUM> of antimony trioxide as a catalyst and <NUM> of trimethyl phosphate as a stabilizer were added, and then condensation polymerization was performed while gradually raising the temperature to <NUM>.

In a <NUM> round bottom flask, <NUM> mol of dimethylderephthalate and <NUM> mol of <NUM>,<NUM>-butanediol were added and then added with <NUM> of tetrabutyl titanate as a catalyst when an internal temperature reached <NUM> while gradually raising the temperature, and a transesterification reaction was performed while the temperature was gradually raised to <NUM> to completely release methanol. Thereafter, <NUM> mol of adipic acid, <NUM> of malic acid, and <NUM> of tetrabutyl titanate as a catalyst were added, and an esterification reaction was performed while raising the temperature to <NUM> again to release completely water, and then <NUM> of antimony trioxide as a catalyst and <NUM> of trimethyl phosphate as a stabilizer were added, and then condensation polymerization was performed while gradually raising the temperature to <NUM>.

In a <NUM> round bottom flask, <NUM> mol of dimethyl terephthalate, <NUM> mol of <NUM>,<NUM>-butanediol, and <NUM> mol of ethylene glycol were added and then added with <NUM> of tetrabutyl titanate as a catalyst when an internal temperature reached <NUM> while gradually raising the temperature, and a transesterification reaction was performed while the temperature was gradually raised to <NUM> to completely release methanol. Thereafter, <NUM> mol of adipic acid and <NUM> of tetrabutyl titanate as a catalyst were added, and an esterification reaction was performed while raising the temperature to <NUM> again to release completely water, and then <NUM> of antimony trioxide as a catalyst and <NUM> of triphenyl phosphate as a stabilizer were added, and then condensation polymerization was performed while gradually raising the temperature to <NUM>.

In a <NUM> round bottom flask, <NUM> mol of dimethylderephthalate and <NUM> mol of <NUM>-butanediol were added and then added with <NUM> of tetrabutyl titanate as a catalyst when an internal temperature reached <NUM> while gradually raising the temperature, and a transesterification reaction was performed while the temperature was gradually raised to <NUM> to completely release methanol. <NUM> mol of adipic acid and <NUM> of tetrabutyl titanate as a catalyst were added, and an esterification reaction was performed while raising the temperature to <NUM> again to release completely water, and then <NUM> of antimony trioxide as a catalyst and <NUM> of triphenyl phosphate as a stabilizer were added, and then condensation polymerization was performed while gradually raising the temperature to <NUM>.

From the copolyester resin obtained thus, a biodegradable copolyester resin was prepared with a condensation polymerization reaction time of <NUM> minutes, an acid value of <NUM>-KOH/g, a number average molecular weight of <NUM>,<NUM>, a tensile strength of <NUM> (<NUM> kgf/cm<NUM>), and a weight average molecular weight of <NUM>,<NUM>.

As in the following method, the physical properties of resins were measured and shown in Table <NUM>.

Tensile strength was measured by an ISO527 test method, and a <NUM>-micron film specimen was prepared and measured at a rate of <NUM>/min.

The molecular weight was measured by using polystyrene as a reference material and using a molecular weight measuring device, GPC.

Claim 1:
A biodegradable polyester resin prepared through an esterification reaction and a condensation polymerization reaction by adding an acid component having a weight ratio of dimethyl terephthalate as aromatic dicarboxylic acid and adipic acid as aliphatic dicarboxylic acid of <NUM>:<NUM> to <NUM>:<NUM>, a glycol component of <NUM>,<NUM>-butanediol, polyglycerol succinate as a reaction rate control agent and polyglycerol furanoate as a molecular weight increasing agent, the biodegradable polyester resin thus prepared having:
- a number average molecular weight of <NUM>,<NUM> or more, and a weight average molecular weight of <NUM>,<NUM> or more, as measured by gel permeation chromatography with polystyrene as a reference material,
- an acid value of <NUM> to <NUM>-KOH/g, as measured by the method outlined in the description and
- a tensile strength of <NUM> MPa (<NUM> kgf/cm<NUM>) or more, as measured by an ISO527 test method using a <NUM>-micron film specimen at a rate of <NUM>/min.