Patent Description:
Hydrogenated sugar (also known as "sugar alcohol") refers to a compound obtained by adding hydrogen to the reducing terminal group of a saccharide. Generally, it has the formula HOCH<NUM>(CHOH)nCH<NUM>OH (wherein n is an integer of <NUM> to <NUM>) and is classified into tetritol, pentitol, hexitol and heptitol (having <NUM>, <NUM>, <NUM> and <NUM> carbon atoms, respectively) depending on the number of carbon atoms. Among them, hexitol having <NUM> carbon atoms includes sorbitol, mannitol, iditol, galactitol and the like, and sorbitol and mannitol are particularly useful substances.

Anhydrosugar alcohol has a diol form with two hydroxyl groups in the molecule and can be prepared by utilizing hexitol derived from starch (for instance, <CIT> and <CIT>). Since anhydrosugar alcohol is an eco-friendly substance derived from renewable natural resources, there has been much interest for a long time, and studies on the production method have been carried out. Among these anhydrosugar alcohols, isosorbide prepared from sorbitol presently has the largest industrial application range.

Anhydrosugar alcohol is widely used in the treatment of cardiac and vascular diseases, adhesives for patches, drugs for mouthwash and the like, solvents for compositions in the cosmetics industry and emulsifiers in the food industry. In addition, it is possible to increase the glass transition temperature of a polymer such as polyester, PET, polycarbonate, polyurethane and epoxy resin, and to improve the strength of these materials, and it is also very useful in the plastics industry such as bioplastics since it is an eco-friendly material derived from natural materials. It is also known to be used as adhesives, eco-friendly plasticizers, biodegradable polymers and an eco-friendly solvent for water-soluble lacquers.

As such, anhydrosugar alcohol has attracted a great deal of attention due to its versatility, and its use in industry is increasing.

Meanwhile, efforts are being made to reduce the use of fossil resources in order to cope with their depletion, the increase of carbon dioxide in the atmosphere due to the mass consumption of petroleum resources and the global warming problem. In this regard, interest in environmentally circulating polymers is high, and studies on polyester resins using biomass raw materials such as anhydrosugar alcohol are being actively conducted.

Aliphatic polyester resins using biomass raw materials are widely used in fields such as packaging materials, molded products, and films, and are one of the eco-friendly plastics that do not contain environmental hormones. In addition, by having biodegradability, they are attracting attention as eco-friendly materials that can solve the problem of environmental pollution caused by waste plastic, which has recently become an issue.

In recent years, in polycarbonate mainly used for heat-resistant food containers, as the harmfulness of bisphenol A has been revealed, the need for a polyester resin that is environmentally friendly, has transparency and heat resistance is increasing.

In the case of a conventional homopolyester composed of terephthalic acid and ethylene glycol, mechanical properties and heat resistance can be improved to some extent through crystallization by stretching and heat fixation, but there is a limit to the application use and improvement of heat resistance. Therefore, in recent years, a method of improving the heat resistance of the polyester resin has been developed by using isosorbide, which is a biomass-derived compound derived from starch, as a comonomer of a polyester resin. Ivan S Ristic, "Synthesis and Characterisation of Polyester Based on Isosorbide and Butanedioic Acid", discloses the samples ISO-SA-DMT-<NUM>-<NUM> and <NUM> made of isosorbide, dimethyl terephthalate and butanedioic acid. However, since isosorbide is a secondary alcohol which has low reactivity, it is known that is difficult to form a polyester resin having a high viscosity used in the manufacture of sheets or bottles.

Accordingly, there is an urgent need to develop a polyester resin that is environmentally friendly, has a high molecular weight and can simultaneously exhibit excellent heat resistance and mechanical properties.

The purpose of the present invention is to provide a polyester resin having excellent heat resistance and mechanical properties as well as excellent biodegradability by copolymerizing a diester component comprising a succinic acid diester compound and a diol component comprising anhydrosugar alcohol in a specific amount and a method for preparing the same.

In order to achieve the technical purpose, in the first aspect, the present invention provides a polyester resin comprising a repeating unit derived from a diester component of a dicarboxylic acid; and a repeating unit derived from a diol component, wherein the diester component of the dicarboxylic acid comprises <NUM> to <NUM> mol% of a diester of an aliphatic dicarboxylic acid; and <NUM> to <NUM> mol% of a diester of an aromatic dicarboxylic acid, based on <NUM> mol% of the total diester component of the dicarboxylic acid, the diester of the aliphatic dicarboxylic acid comprises a succinic acid diester, the diol component comprises <NUM> to <NUM> mol% of an anhydrosugar alcohol, based on <NUM> mol% of the total diol component, and the number average molecular weight (Mn) of the polyester resin is <NUM>,<NUM>/mol or more.

In the second aspect, the present invention provides a method for preparing a polyester resin comprising (<NUM>) a step of esterification reaction or transesterification reaction of a diester component of a dicarboxylic acid comprising a diester of an aliphatic dicarboxylic acid and a diester of an aromatic dicarboxylic acid and a diol component comprising an anhydrosugar alcohol; and (<NUM>) a step of polycondensation reaction of the reaction product obtained in step (<NUM>), wherein the diester of the aliphatic dicarboxylic acid comprises a succinic acid diester, the diester component of the dicarboxylic acid comprises <NUM> to <NUM> mol% of the diester of the aliphatic dicarboxylic acid; and <NUM> to <NUM> mol% of the diester of the aromatic dicarboxylic acid, based on <NUM> mol% of the total diester component of the dicarboxylic acid, the diol component comprises <NUM> to <NUM> mol% of an anhydrosugar alcohol, based on <NUM> mol% of the total diol component, and the number average molecular weight (Mn) of the polyester resin is <NUM>,<NUM>/mol or more.

The polyester resin according to the present invention is prepared by using an anhydrosugar alcohol and a diester of an aliphatic dicarboxylic acid comprising a succinic acid diester compound which are biomass-derived compounds, so that it is environmentally friendly, can exhibit excellent heat resistance and mechanical properties (especially impact strength) at the same time and have a high molecular weight.

The present invention is explained in more detail below.

The polyester resin of the present invention comprises a repeating unit derived from a diester component of a dicarboxylic acid; and a repeating unit derived from a diol component, wherein the diester component of the dicarboxylic acid comprises <NUM> to <NUM> mol% of a diester of an aliphatic dicarboxylic acid; and <NUM> to <NUM> mol% of a diester of an aromatic dicarboxylic acid, based on <NUM> mol% of the total diester component of the dicarboxylic acid, the diester of the aliphatic dicarboxylic acid comprises a succinic acid diester, the diol component comprises <NUM> to <NUM> mol% of an anhydrosugar alcohol, based on <NUM> mol% of the total diol component, and the number average molecular weight (Mn) of the polyester resin is <NUM>,<NUM>/mol or more.

Although not particularly limited, in one embodiment, the polyester resin of the present invention may comprise a structure represented by the following Formula <NUM>:
<CHM>
in Formula <NUM>,.

The diester component used in the preparation of the polyester resin according to the present invention comprises a diester component of an aliphatic dicarboxylic acid and a diester component of an aromatic dicarboxylic acid, and the diester of the aliphatic dicarboxylic acid comprises a succinic acid diester (e.g., dimethyl succinate, diethyl succinate, etc.).

The diester component of the aliphatic dicarboxylic acid may further comprise a diester of an aliphatic dicarboxylic acid having <NUM> to <NUM> carbon atoms other than a succinic acid diester, and the diester component of the aliphatic dicarboxylic acids other than the succinic acid diester may comprise one or two or more diester components of the linear, branched or cyclic aliphatic dicarboxylic acids commonly used in the production of polyester resins, such as cyclohexanedicarboxylic acid diesters such as <NUM>,<NUM>-cyclohexanedicarboxylic acid diester and <NUM>,<NUM>-cyclohexanedicarboxylic acid diester; sebacic acid diester; isodecylsuccinic acid diester; maleic acid diester; fumaric acid diester; adipic acid diester; glutaric acid diester; azelaic acid diester; itaconic acid diester; glutamic acid diester; <NUM>,<NUM>-furandicarboxylic acid diester; tetrahydrofuran-<NUM>,<NUM>-dicarboxylic acid diester; tetrahydrofuran-<NUM>,<NUM>-dicarboxylic acid diester; undecanedioic acid diester; dodecanedioic acid diester; tridecanedioic acid diester and tetradecanedioic acid diester, etc..

In the polyester resin of the present invention, the content of the diester component of the aliphatic dicarboxylic acid may be <NUM> mol% or more, <NUM> mol% or more, <NUM> mol% or more, <NUM> mol% or more, <NUM> mol% or more, <NUM> mol% or more, <NUM> mol% or more, <NUM> mol% or more, <NUM> mol% or more, <NUM> mol% or more, or <NUM> mol% or more, and may be <NUM>. <NUM> mol% or less, <NUM> mol% or less, <NUM> mol% or less, <NUM> mol% or less, <NUM> mol% or less, <NUM> mol% or less, <NUM> mol% or less, <NUM> mol% or less, <NUM> mol% or less, or <NUM> mol% or less-for example, <NUM> to <NUM> mol%, <NUM> to <NUM> mol%, <NUM> to <NUM> mol% or <NUM> to <NUM> mol%, based on <NUM> mol% of the total diester component. If the content of the diester component of the aliphatic dicarboxylic acid is less than the above level, impact strength of the polyester resin is lowered and the biodegradability is lowered, so that it may be difficult to apply the polyester resin as an eco-friendly product, and if the content is more than the above level, the heat resistance of the polyester resin may decrease.

The diester component of the aromatic dicarboxylic acid may comprise, specifically, a diester of an aromatic dicarboxylic acid having <NUM> to <NUM> carbon atoms-for example, it may comprise one or two or more diester components of the aromatic dicarboxylic acid commonly used in the production of polyester resins, such as phthalic acid diester, terephthalic acid diester, isophthalic acid diester, <NUM>,<NUM>-naphthalenedicarboxylic acid diester, diphenic acid diester, p-phenylene diacetic acid diester and o-phenylene diacetic acid diester, preferably terephthalic acid diester (e.g., dimethyl terephthalate, diethyl terephthalate, etc.).

The content of the diester component of the aromatic dicarboxylic acid may be <NUM> mol% or more, <NUM> mol% or more, <NUM> mol% or more, <NUM> mol% or more, <NUM> mol% or more, <NUM> mol% or more, or <NUM> mol% or more, and may be <NUM> mol% or less, <NUM> mol% or less, <NUM> mol% or less, <NUM> mol% or less, <NUM> mol% or less, <NUM> mol% or less, <NUM> mol% or less, or <NUM> mol% or less-for example, <NUM> to <NUM> mol%, <NUM> to <NUM> mol%, <NUM> to <NUM> mol% or <NUM> to <NUM> mol%, based on <NUM> mol% of the total diester component. If the content of the diester component of the aromatic dicarboxylic acid is less than the above level, the heat resistance of the polyester resin is lowered, and if the content is more than the above level, the impact strength of the polyester resin is lowered and the biodegradability is lowered, so that it may be difficult to apply the polyester resin as an eco-friendly product.

The diol component used to prepare the polyester resin of the present invention may comprise <NUM> to <NUM> mol% of anhydrosugar alcohol based on <NUM> mol% of the total diol component.

The anhydrosugar alcohol is any substance obtained by removing one or more water molecules from a compound obtained by adding hydrogen to the reducing terminal group of a saccharide, generally called hydrogenated sugar or sugar alcohol.

In the present invention, as the anhydrosugar alcohol, dianhydrohexitol, which is a dehydrate of hexitol, can be preferably used, and more preferably, the anhydrosugar alcohol may be selected from the group consisting of isosorbide (<NUM>,<NUM>:<NUM>,<NUM>-dianhydroisorbitol), isomannide (<NUM>,<NUM>:<NUM>,<NUM>-dianhydromannitol), isoidide (<NUM>,<NUM>:<NUM>,<NUM>-dianhydroiditol) or mixtures thereof, and most preferably isosorbide may be used.

The content of the anhydrosugar alcohol component may be <NUM> mol% or more, <NUM> mol% or more, <NUM> mol% or more, <NUM> mol% or more, <NUM> mol% or more, <NUM> mol% or more, <NUM> mol% or more, or <NUM> mol% or more, and may be <NUM> mol% or less, <NUM> mol% or less, <NUM> mol% or less, <NUM> mol% or less, <NUM> mol% or less, <NUM> mol% or less, or <NUM> mol% or less-for example <NUM> to <NUM> mol%, <NUM> to <NUM> mol% or <NUM> to <NUM> mol%, based on <NUM> mol% of the total diol component. If the content of the anhydrosugar alcohol is less than the above level, the heat resistance of the polyester resin is lowered, and the content of the biomass-derived component is lowered, so that it may be difficult to apply the polyester resin as an eco-friendly product.

The diol component used in the present invention may further comprise an aliphatic diol component other than anhydrosugar alcohol, specifically, an aliphatic diol having <NUM> to <NUM> carbon atoms, more specifically an aliphatic diol having <NUM> to <NUM> carbon atoms-for example, it may be selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, propane diol (<NUM>,<NUM>-propane diol and <NUM>,<NUM>-propane diol, etc.), butane diol (<NUM>,<NUM>-butane diol, <NUM>,<NUM>-butane diol and <NUM>,<NUM>-butane diol, etc.), pentane diol (<NUM>,<NUM>-pentane diol, <NUM>,<NUM>-pentane diol, <NUM>,<NUM>-pentane diol and <NUM>,<NUM>-pentane diol, etc.), hexane diol (<NUM>,<NUM>-hexane diol, <NUM>,<NUM>-hexane diol, <NUM>,<NUM>-hexane diol, <NUM>,<NUM>-hexane diol and <NUM>,<NUM>-hexane diol, etc.), neopentyl glycol, cyclohexane diol (<NUM>,<NUM>-cyclohexane diol, <NUM>,<NUM>-cyclohexane diol and <NUM>,<NUM>-cyclohexane diol, etc.), cyclohexane dimethanol (<NUM>,<NUM>-cyclohexane dimethanol, <NUM>,<NUM>-cyclohexane dimethanol and <NUM>,<NUM>-cyclohexane dimethanol, etc.), tetramethylcyclobutane diol, tricyclodecane dimethanol, adamantanediol, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-propane diol, <NUM>-ethyl-<NUM>-t-butyl-<NUM>,<NUM>-propane diol, <NUM>,<NUM>,<NUM>-trimethyl-<NUM>,<NUM>-hexane diol or combinations thereof, preferably butane diol.

The content of aliphatic diols other than the anhydrosugar alcohol may be more than <NUM> mol%, <NUM> mol% or more, <NUM> mol% or more, <NUM> mol% or more, <NUM> mol% or more, <NUM> mol% or more, <NUM> mol% or more, <NUM> mol% or more, <NUM> mol% or more or <NUM> mol% or more, and may be <NUM> mol% or less, <NUM> mol% or less, <NUM> mol% or less, <NUM> mol% or less, <NUM> mol% or less, <NUM> mol% or less, or <NUM> mol% or less-for example, more than <NUM> mol% to <NUM> mol% or less, more than <NUM> mol% to <NUM> mol% or less or more than <NUM> mol% to <NUM> mol% or less, based on <NUM> mol% of the total diol component. By using aliphatic diols other than the anhydrosugar alcohol at the above level, the polyester resin can maintain excellent heat resistance, and it is easy to apply it as an eco-friendly product as the content of the biomass-derived component increases, and in particular, the impact strength can be further improved.

In the polyester resin according to the present invention, the content of the raw material component derived from biomass comprising an anhydrosugar alcohol and a diester component of an aliphatic dicarboxylic acid (e.g., succinic acid diester, etc.) may be <NUM> to <NUM>% by weight, <NUM> to <NUM>% by weight or <NUM> to <NUM>% by weight, based on the total weight of the monomers constituting the polyester resin. If the content of the raw material component derived from biomass is less than the above level, it may be difficult to apply the polyester resin as an eco-friendly product.

The polyester resin of the present invention may have a number average molecular weight (Mn: g/mol) of <NUM>,<NUM> or more, <NUM>,<NUM> or more, or <NUM>,<NUM> or more-for example, <NUM>,<NUM> to <NUM>,<NUM>, <NUM>,<NUM> to <NUM>,<NUM> or <NUM>,<NUM> to <NUM>,<NUM>, as measured by gel permeation chromatography (GPC). If the number average molecular weight is less than <NUM>,<NUM>, mechanical properties (e.g., impact strength, etc.) of the polyester resin may be poor.

In another aspect, the present invention provides a method for preparing a polyester resin comprising (<NUM>) a step of esterification reaction or transesterification reaction of a diester component of a dicarboxylic acid comprising a diester of an aliphatic dicarboxylic acid and a diester of an aromatic dicarboxylic acid and a diol component comprising an anhydrosugar alcohol; and (<NUM>) a step of polycondensation reaction of the reaction product obtained in step (<NUM>), wherein the diester of the aliphatic dicarboxylic acid comprises a succinic acid diester, the diester component of the dicarboxylic acid comprises <NUM> to <NUM> mol% of the diester of the aliphatic dicarboxylic acid; and <NUM> to <NUM> mol% of the diester of the aromatic dicarboxylic acid, based on <NUM> mol% of the total diester component of the dicarboxylic acid, the diol component comprises <NUM> to <NUM> mol% of an anhydrosugar alcohol, based on <NUM> mol% of the total diol component, and the number average molecular weight (Mn) of the polyester resin is <NUM>,<NUM>/mol or more.

The diol component comprising the anhydrosugar alcohol and the diester component of dicarboxylic acid used in the method of the present invention may be the same as those of the above-described components. In addition, the diol component may further comprise an aliphatic diol component other than anhydrosugar alcohol.

In the method for preparing a polyester resin of the present invention, (<NUM>) a step of esterification reaction or transesterification reaction of a diester component of a dicarboxylic acid comprising a diester of an aliphatic dicarboxylic acid and a diester of an aromatic dicarboxylic acid and a diol component comprising an anhydrosugar alcohol is conducted. The esterification reaction or transesterification reaction can be conducted by adding the diol component and the diester component of the dicarboxylic acid so that the reaction molar ratio of the diol component to the diester component of the dicarboxylic acid (the total number of moles of the diol component/the total number of moles of the diester component of the dicarboxylic acid) is <NUM> to <NUM> under conditions of the temperature of <NUM> to <NUM>, preferably <NUM> to <NUM>, more preferably <NUM> to <NUM>, and the pressure of <NUM> to <NUM> kgf/cm<NUM>, preferably <NUM> to <NUM> kgf/cm<NUM>.

If the reaction molar ratio of the diol component to the diester component of the dicarboxylic acid (total moles of the diol component/total moles of the diester component of the dicarboxylic acid) is less than <NUM>, the unreacted diester component during the polymerization reaction remains and there is a concern that the mechanical properties and color of the polyester resin may be deteriorated, and if the ratio exceeds <NUM>, the polymerization reaction rate is too slow, and the productivity of the polyester resin may be lowered.

The esterification reaction time or transesterification reaction time is usually <NUM> to <NUM> hours, preferably about <NUM> to <NUM> hours, and may vary depending on the reaction temperature and pressure and the reaction molar ratio of the diol component to the diester component.

In the method for preparing a polyester resin of the present invention, a catalyst is not required for the esterification reaction or the transesterification reaction (step (<NUM>)), but a catalyst may be used to shorten the reaction time. The esterification reaction or transesterification reaction (step (<NUM>)) may be conducted in a batch or continuous manner, and each reaction raw material may be added separately.

In the method for preparing a polyester resin of the present invention, step (<NUM>) of a polycondensation reaction of the reaction product obtained in step (<NUM>) may be conducted after the esterification reaction or transesterification reaction in step (<NUM>).

Prior to initiation of the polycondensation reaction, a polycondensation catalyst, a stabilizer or the like may be added to the reaction product of the esterification reaction or transesterification reaction. A polycondensation catalyst commonly used in this field may be used without limitation may be used-for example, one or a mixture of two or more selected from a titanium-based compound, a germanium-based compound, an antimony-based compound, an aluminum-based compound and a tin-based compound. As the stabilizer added to the polycondensation reaction, a phosphorus-based compound may be generally used-for example, phosphoric acid, trimethyl phosphate, triethyl phosphate or a mixture thereof.

The polycondensation reaction is conducted at a temperature of <NUM> to <NUM>, preferably <NUM> to <NUM> and more preferably <NUM> to <NUM>, and a reduced pressure condition of <NUM> to <NUM> mmHg. The reduced pressure conditions are for removing by-products of the polycondensation reaction.

In one embodiment, (a) the esterification reaction or transesterification reaction may be conducted with a polymerization reactant comprising (i) a diester component comprising a succinic acid diester compound and, if necessary, another aromatic diester component and an aliphatic diester component other than succinic acid diester; and (ii) dianhydrohexitol and, if necessary, other diol components, at a pressure of <NUM> to <NUM> kgf/cm<NUM> and a temperature of <NUM> to <NUM> for an average residence time of <NUM> to <NUM> hours. (b) Then, by conducting a polycondensation reaction of the esterification or transesterification reaction product under reduced pressure conditions of <NUM> to <NUM> mmHg and at a temperature of <NUM> to <NUM> for an average residence time of <NUM> to <NUM> hours, the polyester resin of the present invention can be prepared. Preferably, the final vacuum degree of the polycondensation reaction is less than <NUM> mmHg, and the esterification or transesterification reaction may be conducted under an inert gas atmosphere.

When the number average molecular weight of the polyester resin prepared according to the method of the present invention was measured by gel permeation chromatography (GPC) (standard: polystyrene), the number average molecular weight (Mn: g/mol) may be <NUM>,<NUM> or more, <NUM>,<NUM> or more or <NUM>,<NUM> or more, and may be <NUM>,<NUM> or less, <NUM>,<NUM> or less, or <NUM>,<NUM> or less, and specifically <NUM>,<NUM> to <NUM>,<NUM>, <NUM>,<NUM> to <NUM>,<NUM> or <NUM>,<NUM> to <NUM>,<NUM>.

Since the polyester resin of the present invention has excellent heat resistance and impact strength and excellent color, it can be molded to be useful as a film, sheet, beverage bottle, baby bottle, fiber or optical product.

The present invention is explained in more detail through the following Examples and Comparative Examples. However, the scope of the present invention is not limited thereby in any manner.

In a <NUM> <NUM>-neck flask, <NUM> (<NUM> mmol) of dimethyl succinate, <NUM> (<NUM> mmol) of dimethyl terephthalate and <NUM> (<NUM> mmol) of isosorbide were added, and <NUM> ppm of a titanium-based catalyst and <NUM> ppm of a phosphate-based stabilizer were added. Then, the temperature was raised to <NUM> to proceed with the esterification reaction. When <NUM>% of methanol, a by-product, flowed out of the system, the polycondensation reaction proceeded, and the polymerization was terminated when the viscosity increase stopped. The number average molecular weight, impact strength and heat resistance (Tg) of the prepared polyester resin were measured and shown in Table <NUM> below.

Except that the content of dimethyl succinate was changed from <NUM> (<NUM> mmol) to <NUM> (<NUM> mmol), and the content of dimethyl terephthalate was changed from <NUM> (<NUM> mmol) to <NUM> (<NUM> mmol), a polyester resin was prepared in the same manner as in Example <NUM>, and the number average molecular weight, impact strength and heat resistance (Tg) of the prepared polyester resin were measured and shown in Table <NUM> below.

Except that the content of dimethyl succinate was changed from <NUM> (<NUM> mmol) to <NUM> (<NUM> mmol), the content of dimethyl terephthalate was changed from <NUM> (<NUM> mmol) to <NUM> (<NUM> mmol), the content of isosorbide was changed from <NUM> (<NUM> mmol) to <NUM> (<NUM> mmol) and <NUM> (<NUM> mmol)of <NUM>,<NUM>-butanediol was additionally used, a polyester resin was prepared in the same manner as in Example <NUM>, and the number average molecular weight, impact strength and heat resistance (Tg) of the prepared polyester resin were measured and shown in Table <NUM> below.

Except that the content of dimethyl succinate was changed from <NUM> (<NUM> mmol) to <NUM> (<NUM> mmol), the content of dimethyl terephthalate was changed from <NUM> (<NUM> mmol) to <NUM> (<NUM> mmol), the content of isosorbide was changed from <NUM> (<NUM> mmol) to <NUM> (<NUM> mmol) and <NUM> (<NUM> mmol) of <NUM>,<NUM>-butanediol was additionally used, a polyester resin was prepared in the same manner as in Example <NUM>, and the number average molecular weight, impact strength and heat resistance (Tg) of the prepared polyester resin were measured and shown in Table <NUM> below.

Except that the content of dimethyl succinate was changed from <NUM> (<NUM> mmol) to <NUM> (<NUM> mmol) and the content of dimethyl terephthalate was changed from <NUM> (<NUM> mmol) to <NUM> (<NUM> mmol), a polyester resin was prepared in the same manner as in Example <NUM>, and the number average molecular weight, impact strength and heat resistance (Tg) of the prepared polyester resin were measured and shown in Table <NUM> below.

Except that the content of isosorbide was changed from <NUM> (<NUM> mmol) to <NUM> (<NUM> mmol), and <NUM> (<NUM> mmol) of <NUM>,<NUM>-butanediol was additionally used, a polyester resin was prepared in the same manner as in Example <NUM>, and the number average molecular weight, impact strength and heat resistance (Tg) of the prepared polyester resin were measured and shown in Table <NUM> below.

In a <NUM> <NUM>-neck flask, <NUM> (<NUM> mmol) of succinic acid and <NUM> (<NUM> mmol) of isosorbide were added, and <NUM> ppm of a titanium-based catalyst and <NUM> ppm of a phosphate-based stabilizer were added. Then, the temperature was raised to <NUM> to proceed with the esterification reaction. When <NUM>% of water, a by-product, flowed out of the system, the polycondensation reaction proceeded, and the polymerization was terminated when the viscosity increase stopped. The number average molecular weight, impact strength and heat resistance (Tg) of the prepared polyester resin were measured and shown in Table <NUM> below.

Except that <NUM> (<NUM> mmol) of dimethyl succinate was used instead of succinic acid and methanol rather than water was generated as a by-product, a polyester resin was prepared in the same manner as in Comparative Example <NUM>, and the number average molecular weight, impact strength and heat resistance (Tg) of the prepared polyester resin were measured and shown in Table <NUM> below.

Except that <NUM> (<NUM> mmol) of dimethyl terephthalate was used instead of succinic acid and methanol rather than water was generated as a by-product, a polyester resin was prepared in the same manner as in Comparative Example <NUM>, and the number average molecular weight, impact strength and heat resistance (Tg) of the prepared polyester resin were measured and shown in Table <NUM> below.

Except that the content of succinic acid was changed from <NUM> (<NUM> mmol) to <NUM> (<NUM> mmol), and <NUM> (<NUM> mmol) of terephthalic acid was additionally used, a polyester resin was prepared in the same manner as in Comparative Example <NUM>, and the number average molecular weight, impact strength and heat resistance (Tg) of the prepared polyester resin were measured and shown in Table <NUM> below.

Except that <NUM> (<NUM> mmol) of dimethyl succinate and <NUM> (<NUM> mmol) of dimethyl terephthalate were used instead of succinic acid and methanol rather than water was generated as a by-product, a polyester resin was prepared in the same manner as in Comparative Example <NUM>, and the number average molecular weight, impact strength and heat resistance (Tg) of the prepared polyester resin were measured and shown in Table <NUM> below.

Except that <NUM> (<NUM> mmol) of dimethyl succinate and <NUM> (<NUM> mmol) of dimethyl terephthalate were used instead of succinic acid, the content of isosorbide was changed from <NUM> (<NUM> mmol) to <NUM> (<NUM> mmol), <NUM> (<NUM> mmol) of <NUM>, <NUM>-butanediol was additionally used and methanol rather than water was generated as a by-product, a polyester resin was prepared in the same manner as in Comparative Example <NUM>, and the number average molecular weight, impact strength and heat resistance (Tg) of the prepared polyester resin were measured and shown in Table <NUM> below.

Except that <NUM> (<NUM> mmol) of dimethyl succinate and <NUM> (<NUM> mmol) of dimethyl terephthalate were used instead of succinic acid, the content of isosorbide was changed from <NUM> (<NUM> mmol) to <NUM> (<NUM> mmol), <NUM> (<NUM> mmol) of <NUM>,<NUM>-butanediol was additionally used and methanol rather than water was generated as a by-product, a polyester resin was prepared in the same manner as in Comparative Example <NUM>, and the number average molecular weight, impact strength and heat resistance (Tg) of the prepared polyester resin were measured and shown in Table <NUM> below.

The number average molecular weight of the polyester resin was measured under a temperature condition of <NUM> and a flow rate of <NUM>/min using a gel permeation chromatography (Waters <NUM>, PL) (standard: polystyrene ).

The polyester resin was annealed at <NUM> for <NUM> minutes, and cooled to room temperature, and then the glass transition temperature (Tg) at the time of scanning again at a heating rate of <NUM>/min was measured.

A <NUM>-thick specimen was prepared using a polyester resin, and impact strength was measured at a temperature of <NUM> using an impact tester (RESIL IMPACTOR, CEAST) according to ASTM D256.

Based on the total weight of the monomer constituting the polyester resin, the content (% by weight) of the component derived from biomass was calculated.

As shown in Table <NUM>, in Examples <NUM> to <NUM> according to the present invention, the polyester resin has a high molecular weight of a number average molecular weight (Mn) of <NUM>,<NUM>/mol or more, and can realize excellent heat resistance and impact resistance at the same time since it exhibits a glass transition temperature (Tg) of <NUM> or higher and impact resistance of <NUM> Kgεcm/cm or more, and can be applied as an eco-friendly product.

However, in Comparative Examples <NUM> and <NUM>, which did not comprise the diester component of the aromatic dicarboxylic acid, the glass transition temperature was less than <NUM> and the heat resistance was poor, and in particular, in Comparative Example <NUM>, the number average molecular weight (Mn) was less than <NUM>,<NUM>/mol and the impact strength was poor. In Comparative Example <NUM>, which did not comprise the diester component of aliphatic dicarboxylic acid, the heat resistance was excellent, but the impact strength was poor.

Claim 1:
A polyester resin comprising a repeating unit derived from a diester component of a dicarboxylic acid; and a repeating unit derived from a diol component,
wherein the diester component of the dicarboxylic acid comprises <NUM> to <NUM> mol% of a diester of an aliphatic dicarboxylic acid; and <NUM> to <NUM> mol% of a diester of an aromatic dicarboxylic acid, based on <NUM> mol% of the total diester component of the dicarboxylic acid,
the diester of the aliphatic dicarboxylic acid comprises a succinic acid diester,
the diol component comprises <NUM> to <NUM> mol% of an anhydrosugar alcohol, based on <NUM> mol% of the total diol component, and
the number average molecular weight (Mn) of the polyester resin is <NUM>,<NUM>/mol or more, determined as indicated in the specification.