WO2020226200A1

WO2020226200A1 - Biodegradable copolyester resin produced by esterification and polycondensation of biomass-derived aliphatic dicarboxylic acid and aromatic dicarboxylic acid with diol and production method thereof

Info

Publication number: WO2020226200A1
Application number: PCT/KR2019/005440
Authority: WO
Inventors: Heon-Young LIM; Seung-Lyul Choi; Yoon Cho
Original assignee: Tlc Korea Co., Ltd.
Priority date: 2019-05-07
Filing date: 2019-05-07
Publication date: 2020-11-12

Abstract

The present invention relates to a biodegradable copolyester resin produced by esterification and polycondensation of biomass-derived aliphatic dicarboxylic acid and aromatic dicarboxylic acid with diol, and a production method thereof. The aliphatic dicarboxylic acid or diol used as the raw material comprises biomass-derived succinic acid or 1,4-butanediol so as to reduce the use of fossil-derived raw materials, thus making the copolyester resin more environmentally friendly. In addition, the copolyester resin is produced using a multifunctional diphenyl compound that increases reaction rate, thus allowing the copolyester resin to have excellent economic efficiency and mechanical properties.

Description

BIODEGRADABLE COPOLYESTER RESIN PRODUCED BY ESTERIFICATION AND POLYCONDENSATION OF BIOMASS-DERIVED ALIPHATIC DICARBOXYLIC ACID AND AROMATIC DICARBOXYLIC ACID WITH DIOL AND PRODUCTION METHOD THEREOF

The present invention relates to a biodegradable copolyester resin produced by esterification and polycondensation of biomass-derived aliphatic dicarboxylic acid and aromatic dicarboxylic acid with diol, and a production method thereof, and more particularly to a biodegradable copolyester resin produced by the esterification and polycondensation of aliphatic dicarboxylic acid and aromatic dicarboxylic acid with diol, wherein the aliphatic dicarboxylic acid or diol used as the raw material comprises biomass-derived succinic acid or 1,4-butanediol so as to reduce the use of fossil-derived raw materials, thus making the copolyester resin more environmentally friendly, and the copolyester resin is produced using a multifunctional diphenyl compound that increases reaction rate, thus allowing the polyester resin to have excellent economic efficiency and mechanical properties, and a method for producing the biodegradable polyester resin.

In modern society, plastics can be produced in large amounts by various methods, and are also excellent in lightweight, durability, price competitiveness, chemical resistance and mechanical properties. Thus, these plastics are widely used in food packaging, medicine packaging, agricultural packaging, and industrial packaging, as well as human life in modern society.

However, these plastic materials, when disposed of by landfill after use, remain non-degraded in in the soil, and when incinerated, generate toxic gases such as dioxin.

Environmental pollution caused by such plastics is now reaching a level of concern in the world. As one of solutions to this problem, application and development of biodegradable resins for disposable products have been actively carried out.

Biodegradable resins are resins which are finally decomposed into water and carbon dioxide by soil or aquatic microorganisms. Biodegradable resins developed to date include polylactic acid (PLA) synthesized by the ring-opening reaction of lactic acid or lactide in the presence of a chemical catalyst or an enzyme, polycaprolactone chemically synthesized from an ε-caprolactone monomer as a starting material, aliphatic polyesters based on diol-dicarboxylic acid, and polyhydroxybutyrate (PHB) synthesized in vivo by microorganisms. The most representative of these materials are polylactic acid (PLA) and an aliphatic (or aliphatic/aromatic) polyester obtained by the polymerization of diol and dicarboxylic acid, which are dividing the world market.

Among them, polylactic acid is the most environmentally friendly product derived from biomass resources, but its application is limited due to insufficient physical properties, such as low heat resistance temperature, strong brittleness and the like, as well as slow biodegradation rate.

Unlike this, aliphatic (or aliphatic/aromatic) polyesters produced from diol and dicarboxylic acid have properties similar to those of polyethylene, polypropylene and the like. However, it is difficult to control the degradation rate thereof. Therefore, most commercialized polyester products are synthesized from raw materials derived from fossil resources.

Looking at conventional arts related to the aliphatic/aromatic copolyester resin, Korean Patent No. 10-0722516 (May 21, 2007) discloses a method for producing a biodegradable and water-dispersible aliphatic/aromatic copolyester resin, comprising the steps of: (i) reacting 3-(4-hydroxyphenyl)propionic acid (or its derivative) with an aliphatic polyol having a molecular weight of 200 to 1,000, thereby preparing a chain-extended aliphatic/aromatic polyol having a molecular weight of 500 to 10,000; (ii) subjecting aliphatic (or cyclic aliphatic) glycol to esterification or transesterification in the presence of dimethyl terephthalate (or its acid anhydride), which is an aromatic dicarboxylic acid, dimethyl isophthalate (or its acid anhydride), which is an isomer thereof, and dimethyl 5-sulfoisophthalate sodium salt, thereby obtaining a first reaction product; (iii) subjecting aliphatic (or cyclic aliphatic) dicarboxylic acid (or its acid anhydride) and aliphatic (or cyclic aliphatic) glycol to esterification and transesterification in the presence of the first reaction product of step (ii) and the aliphatic/aromatic polyol of step (i), thereby obtaining a second reaction product; and (iv) subjecting the reaction product of step (iii) to polycondensation.

In addition, Korean Patent Application Publication No. 10-2013-0118221 (October 29, 2013) discloses an aliphatic-aromatic copolyester comprising the following repeat units, which comprise a dicarboxylic component and a dihydroxylic component:

-[-O-(R11)-O-C(O)-(R13)-C(O)-]-

-[-O-(R12)-O-C(O)-(R14)-C(O)-]-

wherein the dihydroxylic component comprises units -O-(R11)-O- and -O-(R12)-O- deriving from diols, wherein R11 and R12 are the same or different and are selected from the group comprising C2-C14 alkylene, C5-C10 cycloalkylene, C2-C12 oxyalylene, heterocycles, and mixtures thereof, wherein the dicarboxylic component comprises units -C(O)-(R13)-C(O)- deriving from aliphatic diacids and units -C(O)-(R14)-C(O)- deriving from aromatic diacids, wherein R13 is selected from the group comprising C0-C20 alkylene and mixtures thereof, wherein the aromatic diacids comprise at least one heterocyclic aromatic diacid of renewable origin and wherein the molar percentage of said aromatic diacids is higher than 90% and lower than 100%　of the dicarboxylic component.

However, the above-described aliphatic-aromatic copolyester resins problems in that they cannot help solve the problem of exhaustion of petroleum resources, which are finite resources, and the problem of global warming, and are not environmentally friendly.

In an attempt to solve the above-described problems, studies have recently been actively conducted to use biomass-derived raw materials due to the occurrence of problems, including environmental pollution caused by carbon dioxide emissions and the exhaustion of fossil fuels.

For example, a technology was developed in which adipic acid and succinic acid among dicarboxylic acids which are used as raw materials for biodegradable aliphatic (or aliphatic/aromatic) polyesters are produced by fermentation of biomass-derived polysaccharides, such as glucose, cellulose, and the like, which are photosynthesized by plants. However, the dicarboxylic acids obtained by this production method need to be extracted, neutralized and purified according to their intended use due to impurities, including nitrogen, ammonia, metal cations and the like, which come from the fermentation process.

Methods of producing polyesters using the biomass-derived dicarboxylic acids obtained by the above-described method are disclosed in the following documents: Future Materials, Vol. 1, No. 11, page 31 (2001); Japanese Unexamined Patent Application Publication No. 2005-27533; Biotechnology and Bioengineering Symp. No.17(1986) 355-363; Journal of the American Chemical Society No.116 (1994) 399-400; Appl. Microbiol Biotechnol No.51 (1999) 545-552; and Japanese Unexamined Patent Application Publication No. 2005-139287. However, unlike dicarboxylic acids derived from fossil resources, the biomass-derived dicarboxylic acids subjected to the purification process contain a nitrogen atom, or ammonia used in the purification process and a nitrogen atom contained therein, organic acid, inorganic acid, or metal cations. Hence, they have insufficient reactivity. This makes it difficult to obtain a sufficient molecular weight, resulting in reduced moldability/processability and making it difficult to obtain sufficient mechanical properties, and also results in a significant increase in the reaction time, resulting in an economic disadvantage. In addition, these biomass-derived dicarboxylic acids disadvantageously have insufficient hydrolysis resistance, and hence change over time.

As one solution to the above-described problems, Korean Patent No. 10-1276100 (June 12, 2013) discloses a biodegradable copolyester resin produced from biomass raw materials, which comprises: as a first comonomer component, a dicarboxylic acid component comprising (a) an aromatic dicarboxylic acid, an acid anhydride thereof, or a mixture thereof, and (b) an aliphatic dicarboxylic acid including glutaric acid, an acid anhydride thereof, or a mixture thereof; and as a second comonomer component, a glycol component comprising biomass-derived ethylene glycol, isosorbide, and neopentyl glycol, wherein the dicarboxylic acid component comprises 60 to 95 mol% of the aromatic dicarboxylic acid, or the acid anhydride thereof or the a mixture thereof, (a) and 5 to 40 mol% of the aliphatic dicarboxylic acid including glutaric acid, the acid anhydride thereof, or the mixture thereof (b), and the glycol component comprises 80 to 99.8 mole% of the biomass-derived ethylene glycol, 0.1 to 10 mol% of the isosorbide, and 0.1 to 10 mol% of the neopentyl glycol.

Korean Patent No. 10-1502051 (March 6, 2015) discloses a biodegradable copolyester resin produced by polycondensation between a dicarboxylic acid component, which comprises aromatic dicarboxylic acid and petroleum- or biomass-derived aliphatic dicarboxylic acid, and at least one aliphatic glycol component selected from the group consisting of petroleum- or biomass-derived 1,4-butanediol, ethylene glycol, 1,2-propanediol, neopentyl glycol, and polyol, wherein the petroleum- or biomass-derived aliphatic dicarboxylic acid is contained in an amount of more than 15 mol% and not more than 30 mol% based on 100 mol% of the dicarboxylic acid component, and the petroleum- or biomass-derived polyol is contained in an amount of 10 to 30 mol% based on 100 mol% of the aliphatic glycol component, and wherein the biodegradable copolyester resin has a Shore D hardness of 30 to 50 and a limiting viscosity of 1.1 to 1.6 dL/g.

In addition, Korean Patent No. 10-1514786 (April 17, 2015) discloses a polyester resin comprising a reaction product between a diol component, which comprises 1 mol% to 30 mol% of 2,5-bis(hydroxymethylfuran) derived from biomass and the balance of an aromatic diol compound (excluding 2,5-bis(hydroxymethylfuran)) and an aliphatic diol compound, and a dicarboxylic acid component, wherein the molar ratio between the dicarboxylic acid component and the diol component is 1:1.05 to 1: 3.0, and wherein the polyester resin has a glass transition temperature of 80°C to 100°C and an intrinsic viscosity of 0.5 to 1.5 dl/g.

However, the above-described biodegradable polyester resins produced using biomass-derived raw materials have an sufficient degree of completion of reaction due to the impurities contained in the biomass-derived raw materials, and hence are more easily hydrolyzed than polyesters produced using fossil-derived raw materials, and thus pose a problem in terms of durability.

The present invention has been made in order to solve the above-described problems, and it is an object of the present invention to provide a biodegradable copolyester resin produced by the esterification and polycondensation of aliphatic dicarboxylic acid and aromatic dicarboxylic acid with diol, wherein the aliphatic dicarboxylic acid or diol used as the raw material comprises biomass-derived succinic acid or 1,4-butanediol so as to reduce the use of fossil-derived raw materials, thus making the copolyester resin more environmentally friendly, and the copolyester resin is produced using a multifunctional diphenyl compound that increases reaction rate, thus allowing the polyester resin to have excellent economic efficiency and mechanical properties, and a method for producing the biodegradable polyester resin.

To achieve the above object, the present invention provides a biodegradable copolyester resin produced by esterification and polycondensation of a mixture comprising: (1) biomass-derived succinic acid alone, or a mixture of biomass-derived succinic acid and fossil-derived aliphatic (including cyclic aliphatic) dicarboxylic acid(or its anhydride), or fossil-derived aliphatic (including cyclic aliphatic) dicarboxylic acid (or its anhydride) alone; (2) aromatic dicarboxylic acid (or its anhydride); (3) biomass-derived 1,4-butanediol alone, or a mixture of biomass-derived 1,4-butanediol and fossil-derived aliphatic (including cyclic aliphatic) diol, or fossil-derived aliphatic (including cyclic aliphatic) diol alone; and (4) a multifunctional compound represented by the following formula 1, which is obtained by esterification of 4,4-bis(4-hydroxyphenyl)valeric acid with polyethylene glycol:

Formula 1

wherein n is 8 to 10.

The fossil-derived aliphatic (including cyclic aliphatic) dicarboxylic acid (or its anhydride) may be any one or a mixture of two or more selected from among oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid.

The aromatic dicarboxylic acid (or its anhydride) may be any one or a mixture of two or more selected from among dimethyl terephthalate, terephthalic acid, isophthalic acid, and 2,6-naphthoic acid.

The fossil-derived aliphatic (including cyclic aliphatic) diol may be any one or a mixture of two or more selected from among ethylene glycol, 1,3-propanediol, neopentyl glycol, propylene glycol, 1,2-butanediol, 1,4-butanediol, and 1,6-hexanediol.

The biodegradable copolyester may have a number-average molecular weight of 25,000 to 70,000, a molecular weight distribution of 2.2 to 3.0, a melt flow index of 1 g/10 min to 20 g/10 min, as measured at 190℃ and 2,160 kg, and a melting point of 95℃ to 170°C.

The biodegradable copolyester resin may be a compound represented by the following formula 2:

Formula 2

wherein n is 2 to 6, m is 0 to 8, x, y and z are values representing the degree of polymerization of the copolyester resin, and the molar ratio of x to y is 70: 30 to 5: 95.

The present invention also provides a method for producing a biodegradable copolyester resin, comprising the steps of:

(i) performing an esterification reaction between 4,4-bis(4-hydroxyphenyl)valeric acid and a polyethylene glycol having an average molecular weight of 400 at 210℃ for 2 hours in the presence of a catalyst, thereby producing a multifunctional compound represented by the following formula 1:

Formula 1

wherein n is 8 to 10;

(ii) performing an esterification reaction and transesterification reaction between an aromatic dicarboxylic acid (or its anhydride) and biomass-derived 1,4-butanediol alone, or a mixture of biomass-derived 1,4-butanediol and fossil-derived aliphatic (including cyclic aliphatic) diol, or fossil-derived aliphatic (including cyclic aliphatic) diol alone, at 200℃ for 2 hours, thereby obtaining a reaction product;

(iii) adding, to the reaction product of step (ii), biomass-derived succinic acid alone, or a mixture of biomass-derived succinic acid and fossil-derived aliphatic (including cyclic aliphatic) dicarboxylic acid (or its anhydride), or fossil-derived aliphatic (including cyclic aliphatic) dicarboxylic acid (or its anhydride) alone, and the multifunctional compound produced in step (i), followed by an esterification reaction and transesterification reaction at a temperature of 190℃ to 210℃, thereby obtaining a reaction product; and

(iv) subjecting the reaction product of step (iii) to a polycondensation reaction at a temperature of 235℃ to 255℃ under a vacuum of less than 3 Torr for 120 to 200 minutes, thereby obtaining a biodegradable copolyester represented by the following formula 2:

Formula 2

The aromatic dicarboxylic acid (or its anhydride) that is used in step (ii) may be any one or a mixture of two or more selected from among dimethyl terephthalate, terephthalic acid, isophthalic acid, and 2,6-naphthoic acid.

The fossil-derived aliphatic (including cyclic aliphatic) diol that is used in step (ii) may be any one or a mixture of two or more selected from among ethylene glycol, 1,3-propanediol, neopentyl glycol, propylene glycol, 1,2-butanediol, 1,4-butanediol, and 1,6-hexanediol.

The fossil-derived aliphatic (including cyclic aliphatic) dicarboxylic acid (or its anhydride) that is used in step (iii) may be any one or a mixture of two or more selected from among oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid.

As described above, the biodegradable copolyester resin produced by esterification and polycondensation of biomass-derived aliphatic dicarboxylic acid and aromatic dicarboxylic acid with diol according to the present invention has excellent processability, moldability, tearing tensile and tensile strength compared to a biodegradable polyester produced according to a conventional art. In addition, it has excellent hydrolysis resistance, and thus does not easily change over time.

Furthermore, the biodegradable copolyester resin produced by esterification and polycondensation of biomass-derived aliphatic dicarboxylic acid and aromatic dicarboxylic acid with diol according to the present invention shows substantially the same productivity and yield as those of a conventional resin composition having the same molecular structure, produced using fossil-derived raw materials, and thus has excellent economic efficiency. In addition, since it is produced using a biomass-derived product as succinic acid among raw materials thereof, it has environmentally friendly effects, including reduced use of fossil-derived materials and reduced emissions of carbon dioxide.

In addition, according to the present invention, the multifunctional diphenyl compound is used as a reaction aid in esterification and polycondensation of biomass-derived aliphatic dicarboxylic acid and aromatic dicarboxylic acid with diol, thereby increasing reaction rate, thereby allowing the copolyester resin to have excellent economic efficiency and mechanical properties.

The present invention provides a biodegradable copolyester resin produced by esterification and polycondensation of a mixture comprising: (1) biomass-derived succinic acid alone, or a mixture of biomass-derived succinic acid and fossil-derived aliphatic (including cyclic aliphatic) dicarboxylic acid (or its anhydride), or fossil-derived aliphatic (including cyclic aliphatic) dicarboxylic acid (or its anhydride) alone; (2) aromatic dicarboxylic acid (or its anhydride); (3) biomass-derived 1,4-butanediol alone, or a mixture of biomass-derived 1,4-butanediol and fossil-derived aliphatic (including cyclic aliphatic) diol, or fossil-derived aliphatic (including cyclic aliphatic) diol alone; and (4) a multifunctional compound represented by the following formula 1, which is obtained by esterification of 4,4-bis(4-hydroxyphenyl)valeric acid with polyethylene glycol:

Formula 1

wherein n is 8 to 10.

The biodegradable copolyester may have a number-average molecular weight of 25,000 to 70,000, a molecular weight distribution of 2.2 to 3.0, a melt flow index of 1 g/10 min to 20 g/10 min, as measured at 190°C and 2,160 kg, and a melting point of 95℃ to 170℃.

Formula 2

Formula 1

wherein n is 8 to 10;

Formula 2

The biodegradable copolyester resin of the present invention is produced by esterification and polycondensation of a mixture comprising: (1) biomass-derived succinic acid alone, or a mixture of biomass-derived succinic acid and fossil-derived aliphatic (including cyclic aliphatic) dicarboxylic acid (or its anhydride), or fossil-derived aliphatic (including cyclic aliphatic) dicarboxylic acid (or its anhydride) alone; (2) aromatic dicarboxylic acid (or its anhydride); (3) biomass-derived 1,4-butanediol alone, or a mixture of biomass-derived 1,4-butanediol and fossil-derived aliphatic (including cyclic aliphatic) diol, or fossil-derived aliphatic (including cyclic aliphatic) diol alone; and (4) a multifunctional compound represented by formula 1, which is obtained by esterification of 4,4-bis(4-hydroxyphenyl)valeric acid with polyethylene glycol. The esterification and the polycondensation are performed in the presence of a catalyst.

The biomass-derived succinic acid that is used as an essential component in the present invention is used to enhance the environmentally friendly nature of aliphatic and aromatic copolyesters which are produced from conventional fossil-derived raw materials, and it is obtained by fermentation, extraction, purification and the like from materials, including starch and cellulose, which are obtained by plant photosynthesis. In the present invention, commercialized succinic acid products derived from plant resources as described above may be used without any particular post-treatment.

In addition, as the characteristic constitution of the present invention, the multifunctional compound represented by formula 1, which is obtained by esterification of 4,4-bis(4-hydroxyphenyl)valeric acid with polyethylene glycol, is used as a reaction aid in order to solve problems, including long reaction time, weak mechanical properties and rapid time-dependent changes, which are caused by the impurities contained in the biomass-derived succinic acid.

The biodegradable copolyester produced according to the present invention has a number-average molecular weight of 25,000 to 70,000, a molecular weight distribution of 2.2 to 3.0, a melt flow index of 1 g/10 min to 20 g/10 min, as measured at 190℃ and 2,160 kg, and a melting point of 95℃ to 170℃.

The fossil-derived aliphatic (including cyclic aliphatic) dicarboxylic acid (or its anhydride) that is used in the present invention preferably has 0 to 8 carbon atoms, and may be, for example, any one or a mixture of two or more selected from among oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and anhydride derivatives thereof.

The aromatic dicarboxylic acid (or its anhydride) that is used in the present invention is selected from among dimethyl terephthalate, terephthalic acid, isophthalic acid, 2,6-naphthoic acid, and ester-forming derivatives thereof. In particular, dimethyl terephthalate which is terephthalic acid (or a ester-forming derivative thereof) is most preferable. These components may be used alone or as a mixture of two or more thereof.

In addition, the aliphatic (including cyclic aliphatic) diol preferably has 2 to 6 carbon atoms. In the present invention, a diol having a hydroxyl group at both ends is used as the aliphatic (including cyclic aliphatic) diol. It may be, for example, any one or a mixture of two or more selected from the group consisting of ethylene glycol, 1,3-propanediol, neopentyl glycol, propylene glycol, 1,2-butanediol, 1,4-butanediol, and 1,6-hexanediol.

Meanwhile, the multifunctional compound that is used in the present invention is produced by esterifying 4,4-bis(4-hydroxyphenyl)valeric acid with a polyethylene glycol having an average molecular weight of 400, as shown in the following reaction scheme:

Reaction Scheme

wherein n is 8 to 10.

The multifunctional compound is introduced in the step of performing an esterification reaction between aliphatic dicarboxylic acid and aliphatic diol during synthesis of the aliphatic/aromatic copolyester which is a product. It functions to enhance the reactivity between the biomass-derived succinic acid having reduced reactivity due to impurities contained therein and the aliphatic diol, thereby increasing reaction rate and molecular weight. This improves productivity and allows the copolyester to have excellent physical properties. In addition, the multifunctional compound allows the synthesized polymer chain structure to have a fine network structure, thereby improving the hydrolysis resistance and durability of the copolyester.

In one embodiment, the biodegradable aliphatic/aromatic copolyester of the present invention is a compound represented by the following formula 2:

Formula 2

The compound represented by formula 2 may be produced by a method comprising the steps of:

Formula 1

wherein n is 8 to 10;

Formula 2

The aromatic dicarboxylic acid (or its anhydride) that is used in step (ii) is preferably any one or a mixture of two or more selected from among dimethyl terephthalate, terephthalic acid, isophthalic acid, 2,6-naphthoic acid, and anhydrides thereof.

The fossil-derived aliphatic (including cyclic aliphatic) diol that is used in step (ii) is preferably any one or a mixture of two or more selected from among ethylene glycol, 1,3-propanediol, neopentyl glycol, propylene glycol, 1,2-butanediol, 1,4-butanediol, and 1,6-hexanediol.

The fossil-derived aliphatic (including cyclic aliphatic) dicarboxylic acid (or its anhydride) that is used in step (iii) is preferably any one or a mixture of two or more selected from among oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and mixtures thereof.

Hereinafter, the present invention will be described in detail with reference to examples so that it can be easily carried out by those skilled in the technical field to the present invention pertains. However, the present invention may be embodied in various different forms and is not limited to the examples described herein.

Example 1

Production of Multifunctional Compound of the Present Invention

A 1-L round bottom flask was charged with nitrogen, and 286.33 g of 4,4-bis(4-hydroxyphenyl)valeric acid, 440 g of a polyethylene glycol having an average molecular weight of 400, and 0.01 g of monobutyltin oxide as a catalyst, were introduced into the flask, and then subjected to an esterification reaction at 210℃ for 2 hours. Then, water as a by-product of the reaction was sufficiently removed, thereby obtaining a multifunctional compound.

Production of Biodegradable Resin of the Present Invention

A 100-L reactor was charged with nitrogen, and 1.942 kg of dimethyl terephthalate and 23.43 kg of 1,4-butanediol were introduced into the reactor and subjected to an esterification reaction at a temperature of 200℃ for 2 hours, followed by removal of methanol. At this time, 10 g of tetrabutyl titanate as a catalyst and 10 g of trimethyl phosphate as a stabilizer were added. After a theoretical amount of methanol was removed, 22.44 kg of biomass-derived succinic acid (Biosuccinium, Reverdia, Netherlands) and 15 g of the multifunctional compound produced as described above were introduced and allowed to react at a temperature of 200℃, followed by removal of water. At this time, 10 g of dibutyltin oxide and 10 g of tetrabutyl titanate were added as a catalyst, and 20 g of trimethyl phosphate was added as a stabilizer. Subsequently to removal of a theoretical amount of water, the temperature was increased and a polycondensation reaction was performed at a temperature of 243℃ under a vacuum of 1.5 Torr for 130 minutes in the presence of 10 g of antimony trioxide as a catalyst, thereby obtaining a polybutylene succinate-co-butylene terephthalate resin.

Example 2

Production of Biodegradable Resin of the Present Invention

A 100-L reactor was charged with nitrogen, and 18.64 kg of dimethyl terephthalate and 23.43 kg of 1,4-butanediol were introduced into the reactor and subjected to an esterification reaction at a temperature of 200℃ for 2 hours, followed by removal of methanol. At this time, 10 g of tetrabutyl titanate as a catalyst and 10 g of trimethyl phosphate as a stabilizer were added. After a theoretical amount of methanol was removed, 12.28 kg of biomass-derived succinic acid (Biosuccinium, Reverdia, Netherlands) and 10 g of the multifunctional compound produced as described above were introduced and allowed to react at a temperature of 200℃, followed by removal of water. At this time, 10 g of dibutyltin oxide and 10 g of tetrabutyl titanate were added as a catalyst, and 20 g of trimethyl phosphate was added as a stabilizer. Subsequently to removal of a theoretical amount of water, the temperature was increased and a polycondensation reaction was performed at a temperature of 243℃ under a vacuum of 1.5 Torr for 162 minutes in the presence of 10 g of antimony trioxide as a catalyst, thereby obtaining a polybutylene succinate-co-butylene terephthalate resin.

Example 3

Production of Biodegradable Resin of the Present Invention

A 100-L reactor was charged with nitrogen, and 18.64 kg of dimethyl terephthalate and 23.43 kg of biomass-derived 1,4-butanediol (Myriant Bio-BDO, USA) were introduced into the reactor and subjected to an esterification reaction at a temperature of 200℃ for 2 hours, followed by removal of methanol. At this time, 10 g of tetrabutyl titanate as a catalyst and 10 g of trimethyl phosphate as a stabilizer were added. After a theoretical amount of methanol was removed, 15.2 kg of adipic acid (BSAF, Germany) and 18 g of the multifunctional compound produced as described above were introduced and allowed to react at a temperature of 200℃, followed by removal of water. At this time, 5 g of dibutyltin oxide and 15 g of tetrabutyl titanate were added as a catalyst, and 15 g of trimethyl phosphate was added as a stabilizer. Subsequently to removal of a theoretical amount of water, the temperature was increased and a polycondensation reaction was performed at a temperature of 243℃ under a vacuum of 1.5 Torr for 170 minutes in the presence of 15 g of antimony trioxide as a catalyst, thereby obtaining a polybutylene adipate-co-butylene terephthalate resin.

Example 4

Production of Biodegradable Resin of the Present Invention

A 100-L reactor was charged with nitrogen, and 23.3 kg of dimethyl terephthalate and 22.53 kg of biomass-derived 1,4-butanediol (Myriant Bio-BDO, USA) were introduced into the reactor and subjected to an esterification reaction at a temperature of 200℃ for 2 hours, followed by removal of methanol. At this time, 12 g of tetrabutyl titanate as a catalyst and 10 g of trimethyl phosphate as a stabilizer were added. After a theoretical amount of methanol was removed, 11.69 kg of adipic acid (BSAF, Germany) and 20 g of the multifunctional compound produced as described above were introduced and allowed to react at a temperature of 200℃, followed by removal of water. At this time, 12 g of dibutyltin oxide and 8 g of tetrabutyl titanate were added as a catalyst, and 15 g of trimethyl phosphate was added as a stabilizer. Subsequently to removal of a theoretical amount of water, the temperature was increased and a polycondensation reaction was performed at a temperature of 243℃ under a vacuum of 1.5 Torr for 147 minutes in the presence of 15 g of antimony trioxide as a catalyst, thereby obtaining a polybutylene adipate-co-butylene terephthalate resin.

Comparative Example 1

Production of Conventional Biodegradable Resin

A 100-L reactor was charged with nitrogen, and 18.64 kg of dimethyl terephthalate and 23.43 kg of 1,4-butanediol were introduced into the reactor and subjected to an esterification reaction at a temperature of 200℃ for 2 hours, followed by removal of methanol. At this time, 10 g of tetrabutyl titanate as a catalyst and 10 g of trimethyl phosphate as a stabilizer were added. After a theoretical amount of methanol was removed, 12.28 kg of biomass-derived succinic acid (Biosuccinium, Reverdia, Netherlands) was introduced and allowed to react at a temperature of 200℃, followed by removal of water. At this time, 10 g of dibutyltin oxide and 10 g of tetrabutyl titanate were added as a catalyst, and 20 g of trimethyl phosphate was added as a stabilizer. Subsequently to removal of a theoretical amount of water, the temperature was increased and a polycondensation reaction was performed at a temperature of 243℃ under a vacuum of 1.5 Torr for 320 minutes in the presence of 10 g of antimony trioxide as a catalyst, thereby obtaining a polybutylene succinate-co-butylene terephthalate resin.

Comparative Example 2

Production of Conventional Biodegradable Resin

A 100-L reactor was charged with nitrogen, and 1.942 kg of dimethyl terephthalate and 23.43 kg of 1,4-butanediol were introduced into the reactor and subjected to an esterification reaction at a temperature of 200℃ for 2 hours, followed by removal of methanol. At this time, 10 g of tetrabutyl titanate as a catalyst and 10 g of trimethyl phosphate as a stabilizer were added. After a theoretical amount of methanol was removed, 22.44 kg of succinic acid was introduced and allowed to react at a temperature of 200℃, followed by removal of water. At this time, 10 g of dibutyltin oxide and 10 g of tetrabutyl titanate were added as a catalyst, and 20 g of trimethyl phosphate was added as a stabilizer. Subsequently to removal of a theoretical amount of water, the temperature was increased and a polycondensation reaction was performed at a temperature of 243℃ under a vacuum of 1.5 Torr for 200 minutes in the presence of 10 g of antimony trioxide as a catalyst, thereby obtaining a polybutylene succinate-co-butylene terephthalate resin.

Comparative Example 3

Production of Conventional Biodegradable Resin

A 100-L reactor was charged with nitrogen, and 18.64 kg of dimethyl terephthalate and 23.43 kg of 1,4-butanediol were introduced into the reactor and subjected to an esterification reaction at a temperature of 200℃ for 2 hours, followed by removal of methanol. At this time, 10 g of tetrabutyl titanate as a catalyst and 10 g of trimethyl phosphate as a stabilizer were added. After a theoretical amount of methanol was removed, 12.28 kg of succinic acid was introduced and allowed to react at a temperature of 200℃, followed by removal of water. At this time, 10 g of dibutyltin oxide and 10 g of tetrabutyl titanate were added as a catalyst, and 20 g of trimethyl phosphate was added as a stabilizer. Subsequently to removal of a theoretical amount of water, the temperature was increased and a polycondensation reaction was performed at a temperature of 243℃ under a vacuum of 1.5 Torr for 192 minutes in the presence of 10 g of antimony trioxide as a catalyst, thereby obtaining a polybutylene succinate-co-butylene terephthalate resin.

Comparative Example 4

Production of Conventional Biodegradable Resin

A 100-L reactor was charged with nitrogen, and 18.64 kg of dimethyl terephthalate and 23.43 kg of 1,4-butanediol were introduced into the reactor and subjected to an esterification reaction at a temperature of 200℃ for 2 hours, followed by removal of methanol. At this time, 10 g of tetrabutyl titanate as a catalyst and 10 g of trimethyl phosphate as a stabilizer were added. After a theoretical amount of methanol was removed, 15.2 kg of adipic acid (BASF, Germany) was introduced and allowed to react at a temperature of 200℃, followed by removal of water. At this time, 5 g of dibutyltin oxide and 15 g of tetrabutyl titanate were added as a catalyst, and 15 g of trimethyl phosphate was added as a stabilizer. Subsequently to removal of a theoretical amount of water, the temperature was increased and a polycondensation reaction was performed at a temperature of 243℃ under a vacuum of 1.5 Torr for 220 minutes in the presence of 15 g of antimony trioxide as a catalyst, thereby obtaining a polybutylene adipate-co-butylene terephthalate resin.

Comparative Example 5

Production of Conventional Biodegradable Resin

A 100-L reactor was charged with nitrogen, and 23.3 kg of dimethyl terephthalate and 22.53 kg of 1,4-butanediol were introduced into the reactor and subjected to an esterification reaction at a temperature of 200℃ for 2 hours, followed by removal of methanol. At this time, 12 g of tetrabutyl titanate as a catalyst and 10 g of trimethyl phosphate as a stabilizer were added. After a theoretical amount of methanol was removed, 11.69 kg of adipic acid (BASF, Germany) was introduced and allowed to react at a temperature of 200℃, followed by removal of water. At this time, 12 g of dibutyltin oxide and 8 g of tetrabutyl titanate were added as a catalyst, and 15 g of trimethyl phosphate was added as a stabilizer. Subsequently to removal of a theoretical amount of water, the temperature was increased and a polycondensation reaction was performed at a temperature of 243℃ under a vacuum of 1.5 Torr for 196 minutes in the presence of 15 g of antimony trioxide as a catalyst, thereby obtaining a polybutylene adipate-co-butylene terephthalate resin.

Test Example 1

Tests for Physical Performance and Biodegradability of Resin Compositions

From each of the resin compositions produced in Examples 1, 2, 3 and 4 and the resin compositions produced in Comparative Examples 1 to 5 according to conventional methods, film samples having a thickness of 100 μm were manufactured using a hot press. The tensile strength and elongation of each of the film samples were measured using a universal testing machine in accordance with ASTM D638 standards. For evaluation of biodegradability, each of the film samples manufactured as described above was cut to a size of 10 cm (W) x 10 cm (L), and the cut film samples were buried 30 cm below the soil surface and then collected after 12 months, and the biodegradability of the collected film samples was measured by the weight loss method. The results of measurement of the mechanical properties and the elongation are shown in Table 1 below.

Items	Tensile strength (kgf/cm²)	Elongation (%)	Biodegradability (%)
Example 1	382	150	80.9
Example 2	336	625	77.2
Example 3	315	575	78.8
Example 4	359	450	58.9
Comparative Example 1	168	75	93.1
Comparative Example 2	378	125	82.7
Comparative Example 3	322	575	80.5
Comparative Example 4	309	450	80.2
Comparative Example 5	367	400	57.3

Test Example 2

Test for Chemical Performance of Resin Compositions

The number-average molecular weights and molecular weight distributions of the resin compositions produced in Examples 1, 2, 3 and 4 and the resin compositions produced in Comparative Examples 1 to 5 according to conventional methods were measured by gel permeation chromatography at a temperature of 35°C by means of a system equipped with a polystyrene-packed column. The chromatography was performed using chloroform as a developing solvent at a sample concentration of 5 mg/mL and a solvent flow rate of 1.0 mL/min.

The melting points of the resin compositions prepared in Examples 1, 2, 3 and 4 and the resin compositions prepared in Comparative Examples 1 to 5 according to conventional methods were measured using a differential scanning calorimeter under a nitrogen atmosphere over a temperature ranging from 20℃ to 200℃ at a heating rate of 10℃/min, and the melt flow indices of the resin compositions were measured in accordance with ASTM D1238 standards under the conditions of 190℃ and 2,160 g. The results of measurement of the number-average molecular weight, the molecular weight distribution, the melting point and the melt flow index are shown in Table 2 below.

Items	Number-average molecular weight	Molecular weight distribution	Melting point(℃)	Melt flow index (g/10 min)
Example 1	52,368	2.58	108	2.4
Example 2	51,213	2.61	120	3.8
Example 3	49,142	2.77	125	4.6
Example 4	58,203	2.44	165	4.1
Comparative Example 1	28,345	3.02	118	38
Comparative Example 2	53,112	2.47	108.2	2.5
Comparative Example 3	48,032	2.52	118	5.3
Comparative Example 4	53,312	2.64	126	3.4
Comparative Example 5	57,228	2.42	166	3.9

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed herein are intended to illustrate rather than limit the technical spirit of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed by the appended claims, and all technical ideas within the scope of equivalents thereof should be construed as falling within the scope of the present invention.

Claims

A biodegradable copolyester resin produced by esterification and polycondensation of a mixture comprising: (1) biomass-derived succinic acid alone, or a mixture of biomass-derived succinic acid and fossil-derived aliphatic (including cyclic aliphatic) dicarboxylic acid (or its anhydride), or fossil-derived aliphatic (including cyclic aliphatic) dicarboxylic acid (or its anhydride) alone; (2) aromatic dicarboxylic acid (or its anhydride); (3) biomass-derived 1,4-butanediol alone, or a mixture of biomass-derived 1,4-butanediol and fossil-derived aliphatic (including cyclic aliphatic) diol, or fossil-derived aliphatic (including cyclic aliphatic) diol alone; and (4) a multifunctional compound represented by the following formula 1, which is obtained by esterification of 4,4-bis(4-hydroxyphenyl)valeric acid with polyethylene glycol:

Formula 1

wherein n is 8 to 10.
The biodegradable copolyester resin of claim 1, wherein the fossil-derived aliphatic (including cyclic aliphatic) dicarboxylic acid (or its anhydride) is any one or a mixture of two or more selected from among oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and anhydrides thereof.
The biodegradable copolyester resin of claim 1, wherein the aromatic dicarboxylic acid (or its anhydride) is any one or a mixture of two or more selected from among dimethyl terephthalate, terephthalic acid, isophthalic acid, 2,6-naphthoic acid, and anhydrides thereof.
The biodegradable copolyester resin of claim 1, wherein the fossil-derived aliphatic (including cyclic aliphatic) diol is any one or a mixture of two or more selected from among ethylene glycol, 1,3-propanediol, neopentyl glycol, propylene glycol, 1,2-butanediol, 1,4-butanediol, and 1,6-hexanediol.
The biodegradable copolyester resin of claim 1, wherein the biodegradable copolyester has a number-average molecular weight of 25,000 to 70,000, a molecular weight distribution of 2.2 to 3.0, a melt flow index of 1 g/10 min to 20 g/10 min, as measured at 190℃ and 2,160 kg, and a melting point of 95℃ to 170℃.
The biodegradable copolyester resin of claim 1, wherein the biodegradable copolyester resin is a compound represented by the following formula 2:

Formula 2

wherein n is 2 to 6, m is 0 to 8, x, y and z are values representing the degree of polymerization of the copolyester resin, and the molar ratio of x to y is 70: 30 to 5: 95.
A method for producing a biodegradable copolyester resin, comprising the steps of:

(i) performing an esterification reaction between 4,4-bis(4-hydroxyphenyl)valeric acid and a polyethylene glycol having an average molecular weight of 400 at 210℃ for 2 hours in the presence of a catalyst, thereby producing a multifunctional compound represented by the following formula 1:

Formula 1

wherein n is 8 to 10;

(ii) performing an esterification reaction and transesterification reaction between an aromatic dicarboxylic acid (or its anhydride) and biomass-derived 1,4-butanediol alone, or a mixture of biomass-derived 1,4-butanediol and fossil-derived aliphatic (including cyclic aliphatic) diol, or fossil-derived aliphatic (including cyclic aliphatic) diol alone, at 200℃ for 2 hours, thereby obtaining a reaction product;

(iii) adding, to the reaction product of step (ii), biomass-derived succinic acid alone, or a mixture of biomass-derived succinic acid and fossil-derived aliphatic (including cyclic aliphatic) dicarboxylic acid (or its anhydride), or fossil-derived aliphatic (including cyclic aliphatic) dicarboxylic acid (or its anhydride) alone, and the multifunctional compound produced in step (i), followed by an esterification reaction and transesterification reaction at a temperature of 190℃ to 210℃, thereby obtaining a reaction product; and

(iv) subjecting the reaction product of step (iii) to a polycondensation reaction at a temperature of 235℃ to 255℃ under a vacuum of less than 3 Torr for 120 minutes to 200 minutes, thereby obtaining a biodegradable copolyester represented by the following formula 2:

Formula 2

wherein n is 2 to 6, m is 0 to 8, x, y and z are values representing the degree of polymerization of the copolyester resin, and the molar ratio of x to y is 70: 30 to 5: 95.
The method of claim 7, wherein the aromatic dicarboxylic acid (or its anhydride) that is used in step (ii) is any one or a mixture of two or more selected from among dimethyl terephthalate, terephthalic acid, isophthalic acid, 2,6-naphthoic acid, and anhydrides thereof.
The method of claim 7, wherein the fossil-derived aliphatic (including cyclic aliphatic) diol that is used in step (ii) is any one or a mixture of two or more selected from among ethylene glycol, 1,3-propanediol, neopentyl glycol, propylene glycol, 1,2-butanediol, 1,4-butanediol, and 1,6-hexanediol.
The method of claim 7, wherein the fossil-derived aliphatic (including cyclic aliphatic) dicarboxylic acid (or its anhydride) that is used in step (iii) is any one or a mixture of two or more selected from among oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and anhydrides thereof.