Copolymer and production method of copolymer

Abstract

To provide a copolymer excellent in biodegradability, heat resistance and water resistance, and to provide a production method of the same.SOLUTION: A copolymer is a polycondensation product of an aliphatic polyester (A) and a polyester (B) having a xylose structure, a polycondensation product of an aliphatic polyester diol and a polycarboxylic acid ester having a xylose structure, or a ring-opening polymer of a cyclic ester compound and the polyester (B) having a xylose structure. A production method of the copolymer includes the steps of producing an aliphatic polyester (A), producing a polyester (B) having a xylose structure, and polycondensing the aliphatic polyester (A) and the polyester (B), or the step of polycondensing an aliphatic polyester diol and a polycarboxylic acid ester having a xylose structure, or the steps of producing the polyester (B) having a xylose structure, and carrying out a ring-opening polymerization of a cyclic ester compound and the polyester (B).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a copolymer and a method for producing the copolymer. [Background technology]

[0002] In recent years, biomass-derived polymers have been attracting attention, and products using biodegradable polymers have been proposed. For example, Patent Document 1 discloses a chewing gum containing a biodegradable polymer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2008-523826 Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventional biodegradable polymers do not necessarily satisfy the requirements for heat resistance and water resistance. An object of the present invention is to provide a copolymer having excellent biodegradability, heat resistance, and water resistance, and a method for producing the same. [Means for solving the problem]

[0005] The present invention has the following aspects. [1] A copolymer that is a polycondensation product of an aliphatic polyester (A) and a polyester (B) having a xylose structure. [2] The copolymer according to [1], wherein the aliphatic polyester (A) is a lactic acid oligomer, and the polyester (B) has a structural unit derived from xylose dimethylglyoxylate. [3] A copolymer that is a polycondensation product of an aliphatic polyester diol and a polycarboxylic acid ester having a xylose structure. [4] The copolymer according to [3], wherein the aliphatic polyester diol is polylactic acid diol and the polycarboxylic acid ester is xylose dimethylglyoxylate. [5] A copolymer that is a ring-opening polymerization product of a cyclic ester compound and a polyester (B) having a xylose structure. [6] The copolymer according to [5] above, wherein the cyclic ester compound is L-lactide, and the polyester (B) has a structural unit derived from xylose dimethylglyoxylate. [7] The copolymer according to any one of the above [1] to [6], which has a glass transition temperature of 55°C or higher. [8] The copolymer according to any one of the above [1] to [7], which has a thermal decomposition temperature of 370°C or higher. [9] The copolymer according to any one of [1] to [8] above, wherein when the copolymer is formed into a film under the following conditions, the maximum stress of the film is 50 MPa or more. Film molding conditions: Heat press molding using a 0.1 mm thick mold under conditions of 20 MPa, 10 minutes, and 180°C.

[10] The copolymer according to any one of [1] to [9] above, wherein when the copolymer is formed into a film under the following conditions, the film has a breaking elongation of 3% or more. Film molding conditions: Heat press molding using a 0.1 mm thick mold under conditions of 20 MPa, 10 minutes, and 180°C.

[11] A step of producing an aliphatic polyester (A); a step of producing a polyester (B) having a xylose structure; a step of polycondensing the aliphatic polyester (A) and the polyester (B); A method for producing a copolymer, comprising:

[12] The aliphatic polyester (A) is produced by polycondensing at least one of L-lactic acid and D-lactic acid, The method for producing a copolymer according to

[11] above, wherein the polyester (B) is produced by polycondensing xylose dimethylglyoxylate and an aliphatic diol.

[13] A method for producing a copolymer, comprising a step of polycondensing an aliphatic polyester diol and a polycarboxylic acid ester having a xylose structure.

[14] The method for producing a copolymer according to

[13] above, wherein the aliphatic polyester diol is polylactic acid diol, and the polycarboxylic acid ester is xylose dimethylglyoxylate.

[15] A step of producing a polyester (B) having a xylose structure; a step of ring-opening polymerizing a cyclic ester compound and the polyester (B); A method for producing a copolymer, comprising:

[16] The cyclic ester compound is L-lactide, The method for producing a copolymer according to

[15] above, wherein the polyester (B) is produced by polycondensing xylose dimethylglyoxylate and an aliphatic diol. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide a copolymer having excellent biodegradability, heat resistance, and water resistance, and a method for producing the same. [Brief explanation of the drawings]

[0007] [Figure 1] 1 shows 1H-NMR spectra of the copolymer (C1-1) obtained in Example 1, and the lactic acid oligomer and compound (2) used in the production of the copolymer. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments within the scope of the object. The following definitions of terms are used herein: The term "structural unit" refers to a structural unit derived from a compound that constitutes a copolymer such as a monomer, i.e., a structural unit formed by polymerization of the compound, or a structural unit in which a portion of the structural unit is converted into a different structure by treating the polymer. A numerical range indicated by "to" means a numerical range that includes the numbers before and after "to" as the lower and upper limits. The numerical ranges of the contents, various physical property values, and property values ​​disclosed in this specification can be arbitrarily combined with the lower and upper limits to form new numerical ranges.

[0009] [Copolymer] First Embodiment The copolymer (C1) according to the first embodiment of the present invention is a polycondensate of the aliphatic polyester (A) shown below and the polyester (B) having a xylose structure. That is, the copolymer (C1) has a structural unit derived from the aliphatic polyester (A) and a structural unit derived from the polyester (B).

[0010] (Aliphatic polyester (A)) Examples of the aliphatic polyester (A) include polylactic acid, lactic acid oligomer, polyglycolic acid, poly-ε-caprolactone, polyhydroxybutyric acid, polybutylene succinate, etc. Among these, lactic acid oligomer is preferred because it is derived from biomass, can be synthesized directly from lactic acid easily and at low cost, and is highly biodegradable. The aliphatic polyester (A) may be used alone or in combination of two or more kinds.

[0011] The lactic acid oligomer has structural units derived from at least one of L-lactic acid and D-lactic acid (hereinafter, these are also collectively referred to as "structural units derived from lactic acid.") When the total of all structural units constituting the lactic acid oligomer is taken as 100 mol%, the proportion of structural units derived from lactic acid is preferably 80 to 100 mol%, more preferably 90 to 100 mol%, even more preferably 95 to 100 mol%, and particularly preferably 100 mol%. Lactic acid oligomers can be obtained, for example, by polycondensing at least one of L-lactic acid and D-lactic acid. In addition, since polylactic acid is obtained by depolymerizing a lactic acid oligomer to obtain lactide and then ring-opening polymerizing the obtained lactide, the lactic acid oligomer is an intermediate obtained in the process of producing polylactic acid using at least one of L-lactic acid and D-lactic acid.

[0012] The number average molecular weight (Mn) of the lactic acid oligomer is preferably from 90 to 10000, more preferably from 160 to 8000, and even more preferably from 230 to 5000. When the Mn of the lactic acid oligomer is equal to or greater than the above lower limit, it can be easily synthesized directly from lactic acid.

[0013] The weight average molecular weight (Mw) of the lactic acid oligomer is preferably from 90 to 10000, more preferably from 160 to 8000, and even more preferably from 230 to 5000. When the Mw of the lactic acid oligomer is equal to or greater than the above lower limit, it can be easily synthesized directly from lactic acid.

[0014] The Mn and Mw of the lactic acid oligomer are polystyrene equivalent values ​​measured by gel permeation chromatography (GPC). The detailed measurement conditions are as described in the Examples below.

[0015] When the total of all structural units constituting the copolymer (C1) is taken as 100 mol%, the proportion of structural units derived from the aliphatic polyester (A) is preferably 1 to 99 mol%, more preferably 2 to 80 mol%, and even more preferably 3 to 50 mol%. When the proportion of structural units derived from the aliphatic polyester (A) is at least the above lower limit, water resistance and hydrophobicity are improved. When the proportion of structural units derived from the aliphatic polyester (A) is at most the above upper limit, heat resistance is further improved. In addition, mechanical properties are improved.

[0016] (Polyester (B)) The polyester (B) has a xylose structure. Examples of such polyester (B) include polycondensates of a polycarboxylic acid ester having a xylose structure (hereinafter also referred to as "polycarboxylic acid ester (b1)") and a polyhydric alcohol. That is, the polyester (B) preferably has a structural unit derived from the polycarboxylic acid ester (b1) and a structural unit derived from the polyhydric alcohol.

[0017] The polycarboxylic acid ester (b1) is preferably a xylose derivative derived from wood, and examples thereof include dicarboxylic acid esters such as dimethylglyoxylate xylose (hereinafter also referred to as "DMGX" or "compound (1)"), which is a compound represented by the following formula (1), xylose diglyoxylate, and xylose diethylglyoxylate; and compounds that may have structural units derived from monomers in which any substituent, such as an alkyl chain, is bonded to any carbon atom of these dicarboxylic acid esters. Among these, dicarboxylic acid esters are preferred from the viewpoint of compound stability, and DMGX is particularly preferred from the viewpoint of ease of production, as it can be produced from wood-derived xylose. In other words, polyester (B) preferably has structural units derived from DMGX. The polycarboxylic acid ester (b1) may be used alone or in combination of two or more kinds.

[0018] [ka]

[0019] Examples of polyhydric alcohols include ethylene glycol, propylene glycol (1,2-propanediol), 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,3-hexanediol, 1,4-hexanediol, 1,5-hexanediol, 1,6-hexanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, pentamethylene glycol, and hexamethylene glycol. Examples of the alcohol include aliphatic diols such as cholesteryl alcohol, octamethylene glycol, decamethylene glycol, dodecamethylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, and polyethylene glycols having a molecular weight of 1,000 or less; and tri- or higher hydric aliphatic alcohols such as trimethylolpropane, sorbitol, 1,4-sorbitan, erythritol, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, 2-methyl-1,2,3-propanetriol, 2-methyl-1,2,4-butanetriol, and glycerin. Among these, compounds that are inexpensive and that easily improve the degree of polymerization are preferred, aliphatic diols are more preferred, aliphatic diols having 2 to 6 carbon atoms are even more preferred, ethylene glycol, propylene glycol (1,2-propanediol), 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,3-hexanediol, 1,4-hexanediol, 1,5-hexanediol, and 1,6-hexanediol are even more preferred, and ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol are particularly preferred.Among these, 1,6-hexanediol is most preferred from the viewpoints that it is solid at room temperature and easy to handle, and that it increases the molecular weight of the copolymer (C1) and improves the thermal and mechanical properties. The polyhydric alcohols may be used alone or in combination of two or more.

[0020] When the total of all structural units constituting the polyester (B) is taken as 100 mol%, the proportion of structural units derived from the polycarboxylic acid ester (b1) is preferably 10 to 90 mol%, more preferably 20 to 80 mol%, and even more preferably 30 to 70 mol%, while the proportion of structural units derived from the polyhydric alcohol is preferably 10 to 90 mol%, more preferably 20 to 80 mol%, and even more preferably 30 to 70 mol%. When the proportion of the structural units derived from the polycarboxylic acid ester (b1) and the proportion of the structural units derived from the polyhydric alcohol are within the above ranges, the molecular weight of the copolymer (C1) tends to be high.

[0021] The polyester (B) is preferably a polycondensation product of DMGX and an aliphatic diol, more preferably a polycondensation product of DMGX and an aliphatic diol having 2 to 6 carbon atoms, and more preferably a polycondensation product of DMGX and an aliphatic diol having 2 to 6 carbon atoms, such as a polycondensation product of DMGX and ethylene glycol, propylene glycol (1,2-propanediol), 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol, 1,2-hexanediol, or a polycondensation product of DMGX and an aliphatic diol having 2 to 6 carbon atoms. Polycondensation products of DMGX and one or more aliphatic diols selected from ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol and 1,6-hexanediol are more preferred, polycondensation products of DMGX and one or more aliphatic diols selected from ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol and 1,6-hexanediol are particularly preferred, and polycondensation products of DMGX and 1,6-hexanediol are most preferred.

[0022] An example of the chemical structural formula of the polyester (B) is shown below as formula (2). The polyester (B) represented by the chemical structural formula shown below is polyhexylenexylose diglyoxylic acid (hereinafter also referred to as "PHX" or "compound (2)"), which is a polycondensation product of DMGX and 1,6-hexanediol.

[0023] [ka]

[0024] In formula (2), p is an integer of 1 or more. p is not particularly limited as long as it is an integer of 1 or more. For example, an integer of 1 to 1000 is preferable, an integer of 1 to 500 is more preferable, and an integer of 1 to 100 is even more preferable.

[0025] When the total of all structural units constituting copolymer (C1) is taken as 100 mol%, the proportion of structural units derived from polyester (B) is preferably 1 to 99 mol%, more preferably 20 to 98 mol%, and even more preferably 50 to 97 mol%. When the proportion of structural units derived from polyester (B) is at least the above lower limit, heat resistance is further improved. In addition, mechanical properties are improved. When the proportion of structural units derived from polyester (B) is at most the above upper limit, water resistance and hydrophobicity are improved.

[0026] Furthermore, the ratio of the structural units derived from the aliphatic polyester (A) to the structural units derived from the polyester (B) (hereinafter also referred to as the "A / B ratio") is preferably 1 / 99 to 99 / 1, more preferably 2 / 98 to 80 / 20, and even more preferably 3 / 97 to 50 / 50, in molar ratio. When the A / B ratio is equal to or greater than the above lower limit, heat resistance is further improved. In addition, mechanical properties are improved. When the A / B ratio is equal to or less than the above upper limit, water resistance and hydrophobicity are improved.

[0027] (chemical structure) The copolymer (C1) is preferably a polycondensation product of a lactic acid oligomer and a polyester (B) having structural units derived from a polycarboxylic acid ester, more preferably a polycondensation product of a lactic acid oligomer and a polyester (B) having structural units derived from a dicarboxylic acid ester, and even more preferably a polycondensation product of a lactic acid oligomer and a polyester (B) having structural units derived from DMGX. Such a copolymer (C1) has lactic acid units and polycarboxylic acid ester units such as DMGX.

[0028] An example of the chemical structural formula of the copolymer (C1) is shown below as formula (3). The copolymer (C1) represented by the chemical structural formula shown below is a polycondensate of a lactic acid oligomer and a compound (2) (hereinafter also referred to as "compound (3)").

[0029] [ka]

[0030] In formula (3), m1 is an integer of 1 or greater, m2 is an integer of 1 or greater, n is an integer of 1 or greater, and z is an integer of 1 or greater. m1 is not particularly limited as long as it is an integer of 1 or more, but for example, it is preferably an integer of 1 to 1000, more preferably an integer of 1 to 500, and even more preferably an integer of 1 to 300. In particular, when m1 is equal to or greater than the above lower limit, heat resistance is further improved. In addition, mechanical properties are improved. m2 is not particularly limited as long as it is an integer of 1 or more, but for example, it is preferably an integer of 1 to 1000, more preferably an integer of 1 to 500, and even more preferably an integer of 1 to 300. In particular, when m2 is equal to or greater than the above lower limit, heat resistance is further improved. In addition, mechanical properties are improved. Although n is not particularly limited as long as it is an integer of 1 or more, for example, it is preferably an integer of 1 to 1000, more preferably an integer of 1 to 500, and even more preferably an integer of 1 to 300. In particular, when n is equal to or greater than the above lower limit, water resistance and hydrophobicity are improved. Although z is not particularly limited as long as it is an integer of 1 or more, for example, it is preferably an integer of 1 to 300, more preferably an integer of 1 to 200, and even more preferably an integer of 1 to 100. In particular, when z is equal to or greater than the above lower limit, moldability is improved.

[0031] (Properties) The number average molecular weight (Mn) of the copolymer (C1) is preferably from 1000 to 300000, more preferably from 5000 to 200000, and even more preferably from 10000 to 150000. When the Mn of the copolymer (C1) is at least the above lower limit, mechanical properties such as toughness tend to be improved.

[0032] The weight average molecular weight (Mw) of the copolymer (C1) is preferably from 3,000 to 400,000, more preferably from 5,000 to 300,000, and even more preferably from 10,000 to 200,000. When the Mw of the copolymer (C1) is at least the above lower limit, mechanical properties such as toughness tend to be improved.

[0033] The Mn and Mw of the copolymer (C1) can be controlled by the types of aliphatic polyester (A) and polyester (B), the type of catalyst used in polycondensing them, etc. For example, when a lactic acid oligomer is used as the aliphatic polyester (A), a polycondensation product of DMGX and 1,6-hexanediol is used as the polyester (B), or a titanium-based catalyst described below is used as the catalyst, the Mn and Mw of the copolymer (C1) tend to be high. The Mn and Mw of the copolymer (C1) are polystyrene-equivalent values ​​measured by gel permeation chromatography (GPC), under the detailed measurement conditions described in the Examples below.

[0034] The glass transition temperature (Tg) of the copolymer (C1) is preferably 55°C or higher, more preferably 60°C or higher, even more preferably 65°C or higher, and particularly preferably 70°C or higher. When the Tg of the copolymer (C1) is equal to or higher than the above lower limit, sufficient heat resistance can be obtained. There is no particular limitation on the upper limit of the Tg of the copolymer (C1). The Tg of the copolymer (C1) is a value measured using a differential scanning calorimeter (DSC). The detailed measurement conditions are as described in the examples below.

[0035] The thermal decomposition temperature (Td) of the copolymer (C1) is preferably 370°C or higher, more preferably 373°C or higher, even more preferably 375°C or higher, and particularly preferably 380°C or higher. If the Td of the copolymer (C1) is equal to or higher than the above lower limit, sufficient heat resistance can be obtained. There is no particular upper limit to the Td of the copolymer (C1). The Td of the copolymer (C1) is a value measured using a thermogravimetric and differential thermal analyzer (TG-DTA). The detailed measurement conditions are as described in the examples below.

[0036] When copolymer (C1) is hot-press molded using a 0.1 mm thick mold at 20 MPa, 180°C for 10 minutes to form a film (hereinafter also referred to as "film (F1)"), the maximum stress of film (F1) is preferably 50 MPa or more, more preferably 51 MPa or more, and even more preferably 53 MPa or more. If the maximum stress of film (F1) is equal to or greater than the above lower limit, the mechanical properties will be even more excellent. There is no particular limitation on the upper limit of the maximum stress of film (F1). The maximum stress of the film (F1) and the elongation at break and toughness described below are values ​​measured in accordance with JIS K 7127: 1999. Detailed measurement conditions are as described in the examples below.

[0037] The breaking elongation of the film (F1) is preferably 3% or more, more preferably 10% or more, and even more preferably 50% or more. When the breaking elongation of the film (F1) is equal to or more than the above lower limit, the mechanical properties are further improved. There is no particular limitation on the upper limit of the breaking elongation of the film (F1).

[0038] The toughness of film (F1) is 1MJ / m 3 is preferred, and 5MJ / m 3 More preferably, 10MJ / m or more 3The above is more preferable. If the toughness of the film (F1) is equal to or greater than the above lower limit, the mechanical properties will be even more excellent. There is no particular limitation on the upper limit of the toughness of the film (F1).

[0039] (Manufacturing method) The copolymer (C1) can be obtained by polycondensing the aliphatic polyester (A) and the polyester (B). An example of a method for producing the copolymer (C1) will be described below. The method for producing the copolymer (C1) of this embodiment includes the following steps. Step (11): Step of producing aliphatic polyester (A) Step (12): Step of producing polyester (B) having a xylose structure Step (13): Polycondensation of the aliphatic polyester (A) and the polyester (B)

[0040] Step (11) is a step for producing an aliphatic polyester (A). When a lactic acid oligomer is produced as the aliphatic polyester (A), the lactic acid oligomer can be obtained, for example, by polycondensing at least one of L-lactic acid and D-lactic acid. Specifically, the lactic acid oligomer can be obtained by heating at least one of L-lactic acid and D-lactic acid and reducing the pressure to carry out a polycondensation reaction. The heating temperature is preferably from 100 to 300°C, more preferably from 120 to 250°C, and even more preferably from 140 to 200°C. The reaction time is preferably 0.5 to 36 hours, more preferably 1 to 24 hours, and even more preferably 2 to 12 hours. The reduced pressure is preferably 0.01 to 100 kPa, more preferably 0.1 to 50 kPa, and even more preferably 1 to 20 kPa.

[0041] Step (12) is a step for producing a polyester (B) having a xylose structure. The polyester (B) can be obtained, for example, by polycondensing the polycarboxylic acid ester (b1) and a polyhydric alcohol. In particular, it is preferable to produce the polyester (B) by polycondensing DMGX and an aliphatic diol.

[0042] The molar ratio of polyhydric alcohol to polycarboxylic acid ester (b1) (hereinafter also referred to as "alcohol / carboxylic acid ester ratio") is preferably 1 to 3, more preferably 1.1 to 2.5, and even more preferably 1.2 to 2.3. When the alcohol / carboxylic acid ester ratio is equal to or greater than the above lower limit, the terminal groups are likely to be capped with hydroxyl groups. When the alcohol / carboxylic acid ester ratio is equal to or less than the above upper limit, the degree of polymerization is likely to be improved.

[0043] The reaction temperature is preferably 100 to 300°C, more preferably 110 to 250°C, and even more preferably 120 to 230°C. The reaction time is preferably 1 to 30 hours, more preferably 2 to 20 hours, and even more preferably 3 to 10 hours.

[0044] The polycondensation of the polycarboxylic acid ester (b1) and the polyhydric alcohol is preferably carried out in the presence of a catalyst. The catalyst is not particularly limited, but examples thereof include tin-based catalysts such as tin(II) 2-ethylhexanoate, dibutyltin oxide, and tin(II) chloride; antimony-based catalysts such as antimony trioxide; and zinc-based catalysts such as zinc acetate. The catalyst may be used alone or in combination of two or more kinds.

[0045] The amount of the catalyst used is preferably 0.01 to 0.5 parts by mol, more preferably 0.03 to 0.3 parts by mol, and even more preferably 0.05 to 0.1 parts by mol, when the total amount of the polycarboxylic acid ester (b1) and the polyhydric alcohol is 100 parts by mol.

[0046] Step (13) is a step of polycondensing the aliphatic polyester (A) and the polyester (B). By polycondensing the aliphatic polyester (A) and the polyester (B), a copolymer (C1) is obtained. The molar ratio of aliphatic polyester (A) / polyester (B) (hereinafter also referred to as "A / B ratio") is preferably 1 / 99 to 99 / 1, more preferably 2 / 98 to 80 / 20, and even more preferably 3 / 97 to 50 / 50. When the A / B ratio is equal to or greater than the lower limit, water resistance and hydrophobicity are improved. When the A / B ratio is equal to or less than the upper limit, heat resistance is further improved. In addition, mechanical properties are improved.

[0047] The amount of the aliphatic polyester (A) used is preferably such that, when the total of the aliphatic polyester (A) and the polycarboxylic acid ester (b1) used in step (12) is taken as 100% by mass, the proportion of the aliphatic polyester (A) is 1 to 99% by mass, more preferably 2 to 80% by mass, and even more preferably 3 to 50% by mass. When the proportion of the aliphatic polyester (A) is equal to or greater than the lower limit, water resistance and hydrophobicity are improved. When the proportion of the aliphatic polyester (A) is equal to or less than the upper limit, heat resistance is further improved. In addition, mechanical properties are improved.

[0048] The reaction temperature is preferably 100 to 300°C, more preferably 130 to 250°C, and even more preferably 160 to 230°C. The reaction time is preferably 1 to 36 hours, more preferably 2 to 24 hours, and even more preferably 3 to 12 hours. The reaction is preferably carried out under reduced pressure, and the pressure at this time is preferably 3 to 2000 Pa, more preferably 5 to 500 Pa, and even more preferably 10 to 100 Pa.

[0049] The polycondensation of the aliphatic polyester (A) and the polyester (B) is preferably carried out in the presence of a catalyst. The catalyst is not particularly limited, and examples thereof include titanium-based catalysts such as titanium(IV) tetrabutoxide and titanium(IV) oxide; tin-based catalysts such as tin(II) 2-ethylhexanoate, dibutyltin oxide and tin(II) chloride; antimony-based catalysts such as antimony trioxide; and zinc-based catalysts such as zinc acetate. Among these, titanium-based catalysts are preferred, and titanium(IV) tetrabutoxide is more preferred, from the viewpoint of increasing the molecular weight of the copolymer (C1) and improving the mechanical properties. The catalyst may be used alone or in combination of two or more kinds.

[0050] The amount of the catalyst used is preferably 0.01 to 0.5 parts by mass, more preferably 0.03 to 0.2 parts by mass, and even more preferably 0.05 to 0.1 parts by mass, relative to 100 parts by mass of the total of the aliphatic polyester (A) and the polyester (B).

[0051] (Mechanism of action) The copolymer (C1) of this embodiment is a polycondensation product of the aliphatic polyester (A) and the polyester (B) described above. Since the polyester (B) has a xylose structure, the copolymer (C1) has excellent biodegradability, a high glass transition temperature and a high thermal decomposition temperature, and excellent heat resistance.

[0052] Furthermore, polylactic acid and the like are known as biodegradable polymers, but polylactic acid tends to be brittle and have poor mechanical properties. However, the copolymer (C1) of the present embodiment has structural units derived from the stronger polyester (B), and therefore tends to have higher toughness, making it easier to improve mechanical properties. Although the polyester (B) alone does not have sufficient hydrophobicity and water resistance, the combined use of the aliphatic polyester (A) and the polyester (B) tends to improve the hydrophobicity and water resistance.

[0053] Furthermore, terephthalic acid, which is used as a raw material for polyethylene terephthalate, commonly known as polyester, is usually produced from fossil or edible resources, which could lead to resource shortages. However, the polycarboxylic acid ester (b1), which is the raw material for the polyester (B), can be produced from xylose, which can be obtained directly from wood, a sustainable inedible resource.

[0054] Furthermore, polylactic acid is usually obtained by ring-opening polymerization of lactide, so copolymerizing polylactic acid with other compounds requires a large number of steps, which increases the labor and production costs. However, in the case of lactic acid oligomer, an intermediate obtained in the process of producing polylactic acid can be used, so the ring-opening polymerization step is not necessary, and the copolymer (C1) can be produced simply and at low cost. In particular, if a titanium-based catalyst is used during polycondensation of the aliphatic polyester (A) and the polyester (B), a high molecular weight copolymer (C1) can be easily produced, and the mechanical properties tend to be further improved.

[0055] The copolymer (C1) of this embodiment has excellent versatility, is useful as a biodegradable polymer, and can be applied to a variety of uses.

[0056] (Application) The uses of copolymer (C1) are not particularly limited. For example, it can be used as a material for various articles such as films, sheets, injection-molded products, fibers, containers, medical products, and toys. Fibers can be applied to textile products such as nonwoven fabrics and woven fabrics. Films and containers can be used in various fields such as the food industry, clothing industry, medical products industry, and pharmaceutical industry. Potential applications in the medical and pharmaceutical fields include sutures, artificial bones, artificial skin, wound dressings, microcapsules and other DDS applications, and scaffolding materials for tissue and organ regeneration. In addition, copolymer (C1) can be used as a binder in toners and thermal transfer inks, but the applications are not limited to these.

[0057] The copolymer (C1) may be used alone or in the form of a composition in combination with additives, etc. The additives are not particularly limited and can be appropriately selected depending on the application and molding method. The copolymer (C1) can be applied to various molding methods. The molding method is not particularly limited. For example, various molding methods such as heat press molding, injection molding, solvent casting, and extrusion molding can be applied. Specific forms of the molded product include, but are not limited to, sheets, films, containers, petri dishes, plates, casings, fibers, and nonwoven fabrics.

[0058] Second Embodiment The copolymer (C2) according to the second embodiment of the present invention is a polycondensate of the following aliphatic polyester diol and a polycarboxylic acid ester having a xylose structure. That is, the copolymer (C1) has a constitutional unit derived from the aliphatic polyester diol and a constitutional unit derived from the polycarboxylic acid ester having a xylose structure.

[0059] (Aliphatic polyester diol) Examples of aliphatic polyester diols include polylactic acid diol, polycaprolactone diol, polycarbonate diol, and polyethylene glycol. Among these, polylactic acid diol is preferred from the viewpoints of easy availability, biomass origin, and excellent biodegradability. That is, it is preferred that the copolymer (C2) has a structural unit derived from polylactic acid diol. The aliphatic polyester diols may be used alone or in combination of two or more.

[0060] Polylactic acid diol can be produced, for example, by a method of ring-opening addition polymerization of lactide monomers using a diol compound as an initiator, or by a method of reacting a lactic acid oligomer with a diol compound. Examples of the diol compound include aliphatic diols such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 1,5-pentanediol, 1,6-hexanediol, 2-methyl-1,3-propylene glycol, and neopentyl glycol; and alicyclic diols such as 1,3-bis(hydroxymethyl)cyclohexane, 1,4-bis(hydroxymethyl)cyclohexane, 2,2-bis(4-hydroxymethoxycyclohexyl)propane, 2,2-bis(4-hydroxyethoxycyclohexyl)propane, bis(4-hydroxycyclohexyl)methane, and 2,2-bis(4-hydroxycyclohexyl)propane. The diol compounds may be used alone or in combination of two or more.

[0061] The number average molecular weight (Mn) of the aliphatic polyester diol is preferably from 300 to 20000, more preferably from 500 to 10000, and even more preferably from 1000 to 5000. When Mn of the copolymer (C1) is at least the above lower limit, water resistance and hydrophobicity are improved. The Mn of the aliphatic polyester diol is a polystyrene-equivalent value measured by gel permeation chromatography (GPC). Detailed measurement conditions are as described in the examples below.

[0062] When the total of all structural units constituting the copolymer (C2) is taken as 100 mol%, the proportion of structural units derived from aliphatic polyester diol is preferably 1 to 90 mol%, more preferably 10 to 80 mol%, and even more preferably 20 to 70 mol%. When the proportion of structural units derived from aliphatic polyester diol is at least the above lower limit, water resistance and hydrophobicity are improved. When the proportion of structural units derived from aliphatic polyester diol is at most the above upper limit, heat resistance is further improved.

[0063] (polycarboxylic acid ester having a xylose structure) Examples of polycarboxylic acid esters having a xylose structure include the polycarboxylic acid esters (b1) exemplified above in the description of the polyester (B) of the first embodiment. Dicarboxylic acids are particularly preferred, and DMGX is more preferred. That is, the copolymer (C2) preferably has a structural unit derived from DMGX. The polycarboxylic acid ester (b1) may be used alone or in combination of two or more kinds.

[0064] When the total of all structural units constituting copolymer (C2) is taken as 100 mol%, the proportion of structural units derived from polycarboxylic acid ester (b1) is preferably 10 to 99 mol%, more preferably 20 to 90 mol%, and even more preferably 30 to 80 mol%. When the proportion of structural units derived from polycarboxylic acid ester (b1) is at least the above lower limit, heat resistance is further improved. When the proportion of structural units derived from polycarboxylic acid ester (b1) is at most the above upper limit, water resistance and hydrophobicity are improved.

[0065] Furthermore, the ratio of the structural units derived from the aliphatic polyester diol to the structural units derived from the polycarboxylic acid ester (b1) (hereinafter also referred to as the "diol / carboxylic acid ester ratio") is preferably 1 / 99 to 90 / 10, more preferably 10 / 90 to 80 / 20, and even more preferably 20 / 80 to 70 / 30, in terms of molar ratio. When the diol / carboxylic acid ester ratio is equal to or greater than the above lower limit, heat resistance is further improved. When the diol / carboxylic acid ester ratio is equal to or less than the above upper limit, water resistance and hydrophobicity are improved.

[0066] (chemical structure) The copolymer (C2) is preferably a polycondensation product of a polylactic diol and a polycarboxylic acid ester (b1), more preferably a polycondensation product of a polylactic diol and a dicarboxylic acid ester, and even more preferably a polycondensation product of a polylactic diol and DMGX. Such a copolymer (C2) has lactic acid units and polycarboxylic acid ester units such as DMGX.

[0067] (Properties) The number average molecular weight (Mn), weight average molecular weight (Mw), glass transition temperature (Tg), melting point (Tm) and thermal decomposition temperature (Td) of copolymer (C2) are the same as the number average molecular weight (Mn), weight average molecular weight (Mw), glass transition temperature (Tg), melting point (Tm) and thermal decomposition temperature (Td) of copolymer (C1) described above, respectively.

[0068] Furthermore, copolymer (C2) was hot-press molded using a 0.1 mm thick mold at 20 MPa for 10 minutes at 180°C to form a film (hereinafter also referred to as "film (F2)"), which had the same maximum stress, breaking elongation and toughness as those of the above-mentioned film (F1), respectively.

[0069] (Manufacturing method) The copolymer (C2) can be obtained by polycondensation of an aliphatic polyester diol and a polycarboxylic acid ester (b1). An example of a method for producing the copolymer (C2) will be described below. The method for producing the copolymer (C2) of this embodiment includes the following steps. Step (21): A step of polycondensing an aliphatic polyester diol with a polycarboxylic acid ester (b1)

[0070] Step (21) is a step of polycondensing an aliphatic polyester diol with a polycarboxylic acid ester (b1). By polycondensing an aliphatic polyester diol with a polycarboxylic acid ester (b1), a copolymer (C2) is obtained. The aliphatic polyester diol is preferably polylactic acid diol. The polycarboxylic acid ester (b1) is preferably DMGX.

[0071] The molar ratio of aliphatic polyester diol to polycarboxylic acid ester (b1) (hereinafter also referred to as "diol / carboxylic acid ester ratio") is preferably 1 / 99 to 90 / 10, more preferably 10 / 90 to 80 / 20, and even more preferably 20 / 80 to 70 / 30. When the diol / carboxylic acid ester ratio is equal to or greater than the above lower limit, heat resistance is further improved. When the diol / carboxylic acid ester ratio is equal to or less than the above upper limit, water resistance and hydrophobicity are improved.

[0072] The reaction temperature is preferably 100 to 300°C, more preferably 110 to 250°C, and even more preferably 120 to 230°C. The reaction time is preferably 1 to 30 hours, more preferably 2 to 20 hours, and even more preferably 3 to 10 hours. The reaction is preferably carried out under reduced pressure, and the pressure at that time is preferably 1 to 100,000 Pa, more preferably 5 to 10,000 Pa, and even more preferably 10 to 1,000 Pa.

[0073] The polycondensation of the polycarboxylic acid ester (b1) and the aliphatic polyester diol is preferably carried out in the presence of a catalyst. The catalyst is not particularly limited, and examples thereof include tin-based catalysts such as tin(II) 2-ethylhexanoate, dibutyltin oxide, and tin(II) chloride; titanium-based catalysts such as titanium(IV) tetrabutoxide and titanium(IV) oxide; antimony-based catalysts such as antimony trioxide; and zinc-based catalysts such as zinc acetate. Among these, tin-based catalysts are preferred from the viewpoint of workability, and tin(II) 2-ethylhexanoate is more preferred. The catalyst may be used alone or in combination of two or more kinds.

[0074] The amount of the catalyst used is preferably 0.01 to 0.5 parts by mol, more preferably 0.03 to 0.3 parts by mol, and even more preferably 0.05 to 0.1 parts by mol, relative to 100 parts by mol of the total of the aliphatic polyester diol and the polyvalent carboxylic acid ester (b1).

[0075] (Mechanism of action) The copolymer (C2) of this embodiment is a polycondensate of the above-mentioned polycarboxylic acid ester (b1) and an aliphatic polyester diol. Since the polycarboxylic acid ester (b1) has a xylose structure, the copolymer (C2) has excellent biodegradability, a high glass transition temperature and a high thermal decomposition temperature, and excellent heat resistance. Furthermore, the above-mentioned method for producing the copolymer (C2) allows the copolymer (C2) to be produced simply and at low cost.

[0076] Furthermore, since the copolymer (C2) of this embodiment has structural units derived from the polycarboxylic acid ester (b1), it is easy to improve heat resistance. In addition, since the copolymer (C2) of this embodiment has a structural unit derived from an aliphatic polyester diol, it is easy to improve hydrophobicity and water resistance. Furthermore, the polycarboxylic acid ester (b1) can be produced from xylose, which can be obtained directly from wood, a sustainable inedible resource.

[0077] The copolymer (C2) of this embodiment has excellent versatility, is useful as a biodegradable polymer, and can be applied to a variety of uses. The uses of the copolymer (C2) are the same as those of the copolymer (C1) according to the first embodiment.

[0078] <Third embodiment> The copolymer (C3) according to the third embodiment of the present invention is a ring-opening polymer of the following cyclic ester compound and a polyester (B) having a xylose structure. That is, the copolymer (C3) has a structural unit derived from the cyclic ester compound and a structural unit derived from the polyester (B).

[0079] (cyclic ester compound) A cyclic ester compound is a compound having a lactone structure within its molecular structure. The lactone structure is a cyclic structure formed by atoms constituting an ester group, and is a structure formed by dehydration condensation of a hydroxy group and a carboxy group. Examples of cyclic ester compounds include α-lactone, β-lactone, γ-lactone, δ-lactone, and ε-lactone. More specifically, α-acetolactone, α-angelicalactone, ε-caprolactone, δ-valerolactone, β-propiolactone, γ-butyrolactone, γ-crotonolactone, γ-pentanolactone, γ-dodecanolactone, γ-hexanolactone, L-lactide, D-lactide, D-mannonic acid δ-lactone, 2-furanone, and pentano-4-lactone are listed. Among these, L-lactide and D-lactide are preferred, and L-lactide is more preferred, from the viewpoints of being derived from biomass, inexpensive, and having excellent biodegradability. That is, it is preferable that the copolymer (C3) has at least one of a structural unit derived from L-lactide and a structural unit derived from D-lactide. The cyclic ester compounds may be used alone or in combination of two or more.

[0080] When the total of all structural units constituting copolymer (C3) is taken as 100 mol%, the proportion of structural units derived from cyclic ester compounds is preferably 1 to 99 mol%, more preferably 20 to 90 mol%, and even more preferably 40 to 80 mol%. When the proportion of structural units derived from cyclic ester compounds is at least the above lower limit, water resistance and hydrophobicity are improved. When the proportion of structural units derived from cyclic ester compounds is at most the above upper limit, heat resistance is further improved.

[0081] (Polyester (B)) Examples of the polyester (B) include the polyester (B) exemplified above in the description of the first embodiment. When the total of all structural units constituting copolymer (C3) is taken as 100 mol%, the proportion of structural units derived from polyester (B) is preferably 1 to 99 mol%, more preferably 10 to 80 mol%, and even more preferably 20 to 60 mol%. When the proportion of structural units derived from polyester (B) is at least the above lower limit, heat resistance is further improved. When the proportion of structural units derived from polyester (B) is at most the above upper limit, water resistance and hydrophobicity are improved.

[0082] Furthermore, the ratio of the structural units derived from the cyclic ester compound to the structural units derived from the polyester (B) (hereinafter also referred to as the "ester / B ratio") is preferably 1 / 99 to 99 / 1, more preferably 20 / 80 to 90 / 10, and even more preferably 40 / 60 to 80 / 20, in terms of molar ratio. When the ester / B ratio is equal to or greater than the above lower limit, heat resistance is further improved. When the ester / B ratio is equal to or less than the above upper limit, water resistance and hydrophobicity are improved.

[0083] (chemical structure) The copolymer (C3) is preferably a ring-opening polymer of at least one of L-lactide and D-lactide with a polyester (B) having structural units derived from a polycarboxylic acid ester, more preferably a ring-opening polymer of at least one of L-lactide and D-lactide with a polyester (B) having structural units derived from a dicarboxylic acid ester, and even more preferably a ring-opening polymer of at least one of L-lactide and D-lactide with a polyester (B) having structural units derived from DMGX. Such a copolymer (C3) has lactic acid units and polycarboxylic acid ester units such as DMGX.

[0084] (Properties) The number average molecular weight (Mn), weight average molecular weight (Mw), glass transition temperature (Tg), melting point (Tm) and thermal decomposition temperature (Td) of copolymer (C3) are the same as the number average molecular weight (Mn), weight average molecular weight (Mw), glass transition temperature (Tg), melting point (Tm) and thermal decomposition temperature (Td) of copolymer (C1) described above, respectively.

[0085] Furthermore, copolymer (C3) was hot-press molded using a 0.1 mm thick mold at 20 MPa for 10 minutes at 180°C to form a film (hereinafter also referred to as "film (F3)"), which had the same maximum stress, breaking elongation and toughness as those of the above-mentioned film (F1), respectively.

[0086] (Manufacturing method) The copolymer (C3) can be obtained by ring-opening polymerization of a cyclic ester compound and the polyester (B). An example of a method for producing the copolymer (C3) will be described below. The method for producing the copolymer (C3) of this embodiment includes the following steps. Step (31): A step of producing polyester (B) having a xylose structure Step (32): Ring-opening polymerization of the cyclic ester compound and the polyester (B)

[0087] Step (31) is a step for producing a polyester (B) having a xylose structure. The various conditions in step (31) are the same as those in step (12) described above in the first embodiment. In particular, it is preferable to produce polyester (B) by polycondensing DMGX and an aliphatic diol.

[0088] Step (32) is a step of ring-opening polymerization of a cyclic ester compound and a polyester (B). By ring-opening polymerization of a cyclic ester compound and a polyester (B), a copolymer (C3) is obtained. As the cyclic ester compound, L-lactide and D-lactide are preferred, and L-lactide is more preferred.

[0089] When the total of the cyclic ester compound and the polyester (B) is taken as 100% by mass, the proportion of the cyclic ester compound is preferably 1 to 99% by mass, more preferably 20 to 90% by mass, and even more preferably 40 to 80% by mass. When the proportion of the cyclic ester compound is equal to or greater than the lower limit, hydrophobicity and water resistance are improved. When the proportion of the cyclic ester compound is equal to or less than the upper limit, heat resistance is further improved.

[0090] The reaction temperature is preferably 100 to 300°C, more preferably 110 to 250°C, and even more preferably 120 to 230°C. The reaction time is preferably 1 to 30 hours, more preferably 2 to 20 hours, and even more preferably 3 to 10 hours.

[0091] The ring-opening polymerization of the cyclic ester compound and the polyester (B) is preferably carried out in the presence of a catalyst. The catalyst is not particularly limited, and examples thereof include tin-based catalysts such as tin(II) 2-ethylhexanoate, dibutyltin oxide, and tin(II) chloride; titanium-based catalysts such as titanium(IV) tetrabutoxide and titanium(IV) oxide; antimony-based catalysts such as antimony trioxide; and zinc-based catalysts such as zinc acetate. Among these, tin-based catalysts are preferred from the viewpoint of workability, and tin(II) 2-ethylhexanoate is more preferred. The catalyst may be used alone or in combination of two or more kinds.

[0092] The amount of the catalyst used is preferably 0.03 to 0.2 mol parts, more preferably 0.05 to 0.15 mol parts, and even more preferably 0.08 to 0.12 mol parts, per mol part of the terminal hydroxyl groups of the polyester (B).

[0093] (Mechanism of action) The copolymer (C3) of this embodiment is a ring-opening polymerization product of the above-mentioned cyclic ester compound and polyester (B). Since polyester (B) has a xylose structure, it has excellent biodegradability, a high glass transition temperature and a high thermal decomposition temperature, and excellent heat resistance. Furthermore, the above-mentioned method for producing the copolymer (C3) allows the copolymer (C3) to be produced simply and at low cost.

[0094] Furthermore, the copolymer (C3) of this embodiment has structural units derived from the stronger polyester (B), and therefore tends to have higher toughness, making it easier to improve mechanical properties. In addition, the copolymer (C3) of this embodiment has a structural unit derived from a cyclic ester compound, and therefore tends to have high hydrophobicity and water resistance. Furthermore, the polycarboxylic acid ester (b1), which is the raw material for the polyester (B), can be produced from xylose, which can be obtained directly from wood, a sustainable inedible resource.

[0095] The copolymer (C3) of this embodiment has excellent versatility, is useful as a biodegradable polymer, and can be applied to a variety of uses. The uses of the copolymer (C3) are the same as those of the copolymer (C1) according to the first embodiment. [Example]

[0096] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The embodiments of the present invention can be modified in various ways as long as the gist of the present invention is not changed.

[0097] [Measurement and evaluation] <Molecular weight measurement> The molecular weights (number average molecular weight (Mn) and weight average molecular weight (Mw)) of the lactic acid oligomer, polylactic acid diol, and copolymer were measured by gel permeation chromatography (GPC) molecular weight analysis. Specifically, a GPC (manufactured by Tosoh Corporation, product name "HLC-8420") was used and the measurements were performed with an RI detector. The column used was a TSKgel GMHHR-M (manufactured by Tosoh Corporation). The GPC eluent was chloroform (CHCl3). The column temperature was 40°C, and the flow rate was 1.0 ml / min. The standard sample used in the measurements was polystyrene (manufactured by Tosoh Corporation, product name "Standard Polystyrene Kit PStQuick"). A calibration curve was created in polystyrene equivalent, and the molecular weights (Mw, Mn) of each compound were calculated.

[0098] < 1 H-NMR analysis> Using a nuclear magnetic resonance device (manufactured by JEOL Ltd., product name "JNM-EC400") 1 H-NMR analysis was performed using 32 cycles of accumulation and chloroform-d (CDCl3) as the deuterated solvent. 1In the H-NMR spectrum, the area (a) of the peak (near 5.1 ppm) attributable to the lactic acid unit and the area (b) of the peaks (near 6.1 ppm and 6.2 ppm) attributable to the DMGX unit were determined. The ratio represented by area (a) / area (b) was considered to be the ratio (molar ratio) of "structural units derived from aliphatic polyester (A) / structural units derived from polyester (B)," "structural units derived from aliphatic polyester diol / structural units derived from polycarboxylic acid ester (b1)," or "structural units derived from a cyclic ester compound / structural units derived from polyester (B)."

[0099] <Evaluation of heat resistance> (Measurement of glass transition temperature and melting point) The glass transition temperature (Tg [°C]) and melting point (Tm [°C]) of the copolymer were measured using a differential scanning calorimeter (DSC, Hitachi High-Tech Science Corporation, product name "NEXTA DSC200") in the temperature range of -80 to 200°C, with a heating rate of 10°C / min.

[0100] (Measurement of thermal decomposition temperature) The thermal decomposition temperature (Td [°C]) of the copolymer was measured using a thermogravimetric differential thermal analyzer (TG-DTA, Hitachi High-Tech Science Corporation, product name "NEXTA STA200RV") in the temperature range of 50 to 530°C, with a heating rate of 10°C / min.

[0101] <Evaluation of mechanical properties> The copolymer was heat-pressed using a 0.1 mm thick mold at 20 MPa for 10 minutes at 180°C to obtain a 0.1 mm thick film. From the obtained film, a dumbbell-shaped tensile test piece with a balance part length of 20 mm and width of 4 mm was cut out, and a tensile test was carried out in accordance with JIS K 7127:1999 using a tensile tester (Shimadzu Corporation, product name "Desktop Precision Universal Testing Machine AGS-X"), and the maximum stress [Pa], breaking elongation [%] and toughness [MJ / m 3 The crosshead speed was 10 mm / min and the distance between the grippers was 20 mm.

[0102] <Biodegradability evaluation 1: Compost environment> 60 g of compost inoculum (manufactured by Yawata Bussan Co., Ltd., product name "Inoculum No. YK-12") was weighed as the total dry solids, and water was added to the mixture until the moisture content reached 65% by mass. After thorough mixing, the mixture was left to stand at room temperature for 24 hours to cure. Next, the cured compost inoculum was thoroughly mixed with 320 g of dry sea sand, which had previously been adjusted to a moisture content of 15% by mass by adding water, to prepare compost.

[0103] Separately, a film having a thickness of 0.1 mm was produced in the same manner as in the evaluation of mechanical properties. The obtained film was cut into pieces 20 mm long and 20 mm wide, and the cut film was sandwiched between nylon meshes. The previously prepared compost was kept at 58°C in a thermo-hygrostat (Tokyo Rikakikai Co., Ltd., product name "KCL-2000A") and cured for one week while maintaining a constant moisture content. Next, the film sandwiched between nylon mesh was buried in the compost and left to stand for 10 and 20 days. Changes in the film after 10 and 20 days were visually confirmed. The weight of the film was also measured to confirm the weight change before and after burial. Biodegradability in the compost environment was evaluated using the following evaluation criteria. (As of the 10th) Good: After 10 days, the film was visually unable to retain its shape and had lost more than 50% of its weight. △: The film visually retains its shape after 10 days, and the weight has not decreased by 50% or more. (As of the 20th) 〇: As of the 20th day, the film had visually lost its shape and had lost more than 50% of its weight. △: The film visually retains its shape after 20 days, and the weight has not decreased by 50% or more.

[0104] <Biodegradability evaluation 2: Seawater environment> The seawater used was collected from Tokyo Bay (Odaiba Seaside Park) in the morning of January 18, 2024. The test device used was Respirometric Sensor System 6 for Plastic Biodegradability (VELP Scientifica).

[0105] A film having a thickness of 0.1 mm was produced in the same manner as in the evaluation of mechanical properties. The resulting film was cut into pieces 20 mm long and 20 mm wide, and the cut pieces were immersed in 250 mL of seawater and stirred at 150 rpm in the dark at 30°C for 30 days. The changes in the film after 30 days were visually confirmed. The biodegradability was also measured. Biodegradability in a seawater environment was evaluated according to the following criteria. The biodegradability was measured by a method for measuring oxygen consumption using a closed respiratory system in accordance with ASTM D6691-17. The biodegradability was calculated using the following formula (S). Biodegradation degree (%)=(BOD0-BOD B ) / ThOD×100 (S) (In formula (S), "BOD0" is the biochemical oxygen demand of the object to be measured (measured value: mg), and "BOD B " is the average biochemical oxygen demand (measured value: mg) of the blank test, and "ThOD" is the theoretical oxygen demand (calculated value: mg) required when the test material or target material is completely oxidized.

[0106] (Evaluation criteria) ○: After 30 days, the film has visually lost its shape and the biodegradability is 10% or more. ×: The film shows no visible change in shape after 30 days, and the biodegradability is less than 10%.

[0107] <Water resistance evaluation 1: degree of swelling> A film having a thickness of 0.1 mm was produced in the same manner as in the evaluation of mechanical properties. The resulting film was cut into pieces 20 mm long and 20 mm wide, and the cut pieces were immersed in 50 mL of pure water for 5 days. After that, the film was removed from the pure water, the pure water on the film surface was wiped off, and the weight was measured to confirm the change in weight before and after immersion. Water resistance was evaluated according to the following criteria. (Evaluation criteria) ○: No weight change of 3% or more was observed after 5 days. ×: The film swelled after 5 days, and the weight increased by 3% or more.

[0108] <Water resistance evaluation 2: Contact angle> A film having a thickness of 0.1 mm was produced in the same manner as in the evaluation of mechanical properties. A water droplet was dropped onto the obtained film in accordance with JIS R 3257:1999, and the contact angle between the water droplet and the film was measured using an automatic contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., product name "Drop Master DM300").

[0109] [Manufacturing example] <Production Example 1: Production of lactic acid oligomer (OLLA)> 100 g of L-lactic acid was placed in a 200 mL three-neck flask and stirred at 150 °C under atmospheric pressure for 2 hours. The mixture was then dehydrated for 2 hours. The pressure was reduced to 13.3 kPa while still at 150 °C and maintained for 2 hours. The pressure was further reduced to 4.0 kPa and maintained for 1 hour. The pressure was then reduced to 2.7 kPa and maintained for 2 hours to obtain a reaction product. The resulting reaction product was dissolved in a small amount of chloroform and poured into an excess amount of cold diethyl ether to obtain a precipitate. The precipitate was filtered, washed with diethyl ether, and dried in vacuo to recover a white powdery lactic acid oligomer, which was aliphatic polyester (A), in a 22% yield. The Mn of the lactic acid oligomer was 800 and the Mw was 1400. The obtained lactic acid oligomer 1 H-NMR measurement results ( 1 The H-NMR spectrum is shown in Figure 1. Note that (b) in Figure 1 is the lactic acid oligomer. 1 This is the H-NMR spectrum. A peak (around 5.1 ppm) due to the lactic acid unit was confirmed. As used herein, "cold diethyl ether" refers to diethyl ether at a temperature of 4°C.

[0110] <Production Example 2: Production of dimethylglyoxylic xylose (DMGX)> 100 g of xylose and an excess amount of glyoxylic acid were placed in a 1 L flask, melted, heated in the presence of sulfuric acid, and maintained at 90 °C under reduced pressure for 3 hours. The reaction mixture was then refluxed with methanol at 85 °C for 2 hours and neutralized with sodium bicarbonate to a pH of 4-5. The resulting neutralized salt was filtered, and the filtrate was concentrated under reduced pressure and dissolved in chloroform. Using a separatory funnel, the chloroform phase was washed three times with deionized water to remove water-soluble impurities, and then concentrated under reduced pressure. For purification, the concentrate was gradually heated to 180 °C under reduced pressure and fractionated. After removing the distillate (first fraction) containing methyl glyoxylate and residual solvent, the second fraction of the reaction product was recovered by holding the temperature at 180 °C. This was then dissolved in chloroform and decolorized with activated carbon. After filtering off the activated carbon and drying, an oily DMGX (corresponding to the dicarboxylic acid ester, i.e., polycarboxylic acid ester (b1)) was obtained.

[0111] [Example 1] A 100 mL three-neck flask was charged with 3.2839 g of DMGX (molar ratio: approximately 0.011 mol, 290 g / mol) and 2.676 g of 1,6-hexanediol (molar ratio: approximately 0.023 mol, 118.17 g / mol), and the mixture was dried under reduced pressure to remove water. 0.881 μL of tin(II) 2-ethylhexanoate (approximately 0.008 mol%, 405.12 g / mol) was added dropwise, followed by repeated nitrogen substitution to create a nitrogen atmosphere inside the flask. The mixture was stirred at 140°C for 4 hours under a nitrogen atmosphere to undergo transesterification, yielding compound (2) represented by the general formula (2), a relatively low molecular weight polyester (B). The obtained compound (2) 1 H-NMR measurement results ( 1 The H-NMR spectrum is shown in Figure 1. Note that (c) in Figure 1 is the compound (2). 1 1H-NMR spectrum. Peaks attributable to DMGX units (around 6.1 ppm and 6.2 ppm) were confirmed.

[0112] To the obtained compound (2), 0.173 g of lactic acid oligomer (DMGX:OLLA = 95:5 (mass ratio)) was added, and then 3.067 μl (approximately 0.05 mass%) of titanium (IV) tetrabutoxide was added dropwise. The temperature was gradually increased under reduced pressure at 150 °C for 2 hours, 170 °C for 1 hour, and 190 °C for 4 hours to cause a reaction. The obtained reaction product was then dissolved in chloroform and reprecipitated with methanol, and copolymer (C1-1) was recovered in a yield of 57%. The molecular weight of the copolymer (C1-1) obtained was measured, and the heat resistance and mechanical properties were evaluated. The results are shown in Table 2. Also, regarding copolymer (C1-1) 1 H-NMR analysis was performed. Measurement results ( 1 The H-NMR spectrum is shown in Figure 1. Note that (a) in Figure 1 is the copolymer (C1-1). 1 1H-NMR spectrum. 1 The area (a) / area (b) was calculated from the H-NMR spectrum, and the results are shown in Table 2. The copolymer (C1-1) was also evaluated for biodegradability and water resistance, and the results are shown in Table 3.

[0113] [Example 2] A 100 mL three-neck flask was charged with 4.377 g of DMGX (molar ratio: approximately 0.015 mol, 290 g / mol) and 3.567 g of 1,6-hexanediol (molar ratio: approximately 0.030 mol, 118.17 g / mol), and the mixture was dried under reduced pressure to remove water. 1.174 μL of tin(II) 2-ethylhexanoate (approximately 0.008 mol%, 405.12 g / mol) was added dropwise, followed by repeated nitrogen substitution to create a nitrogen atmosphere inside the flask. The mixture was stirred at 140°C for 4 hours under a nitrogen atmosphere to undergo transesterification, yielding compound (2) represented by the general formula (2), a relatively low molecular weight polyester (B). To the obtained compound (2), 0.486 g of lactic acid oligomer (DMGX:OLLA = 90:10 (mass ratio)) was added, and then 4.215 μl (approximately 0.05 mass%) of titanium (IV) tetrabutoxide was added dropwise. The temperature was gradually increased under reduced pressure at 150 °C for 2 hours, 170 °C for 1 hour, and 190 °C for 4 hours to cause a reaction. The obtained reaction product was then dissolved in chloroform and reprecipitated with methanol, and copolymer (C1-2) was recovered in a yield of 59%. The molecular weight of the copolymer (C1-2) was measured, and the heat resistance and mechanical properties were evaluated. The results are shown in Table 2. Also, regarding copolymer (C1-2) 1 H-NMR analysis was performed. 1 The area (a) / area (b) was calculated from the H-NMR spectrum, and the results are shown in Table 2. The copolymer (C1-2) was also evaluated for biodegradability and water resistance, and the results are shown in Table 3.

[0114] [Example 3] A 100 mL three-neck flask was charged with 3.850 g of DMGX (molar ratio: approximately 0.013 mol, 290 g / mol) and 3.138 g of 1,6-hexanediol (molar ratio: approximately 0.027 mol, 118.17 g / mol), and the mixture was dried under reduced pressure to remove water. 1.033 μL of tin(II) 2-ethylhexanoate (approximately 0.008 mol%, 405.12 g / mol) was added dropwise, followed by repeated nitrogen substitution to create a nitrogen atmosphere inside the flask. The mixture was stirred at 140°C for 4 hours under a nitrogen atmosphere to undergo transesterification, yielding compound (2) represented by the general formula (2), a relatively low molecular weight polyester (B). To the obtained compound (2), 0.963 g of lactic acid oligomer (DMGX:OLLA = 80:20 (mass ratio)) was added, and then 3.975 μl (approximately 0.05 mass%) of titanium (IV) tetrabutoxide was added dropwise. The temperature was gradually increased under reduced pressure at 150 °C for 2 hours, 170 °C for 1 hour, and 190 °C for 4 hours to cause a reaction. The obtained reaction product was then dissolved in chloroform and reprecipitated with methanol, and copolymer (C1-3) was recovered in a yield of 70%. The molecular weight of the copolymer (C1-3) was measured, and the heat resistance and mechanical properties were evaluated. The results are shown in Table 2. Also, regarding copolymer (C1-3) 1 H-NMR analysis was performed. 1 The area (a) / area (b) was calculated from the H-NMR spectrum, and the results are shown in Table 2. The copolymer (C1-3) was also evaluated for biodegradability and water resistance, and the results are shown in Table 3.

[0115] [Example 4] A 100 mL three-neck flask was charged with 3.850 g of DMGX (molar ratio: approximately 0.013 mol, 290 g / mol) and 3.138 g of 1,6-hexanediol (molar ratio: approximately 0.027 mol, 118.17 g / mol), and the mixture was dried under reduced pressure to remove water. 1.033 μL of tin(II) 2-ethylhexanoate (approximately 0.008 mol%, 405.12 g / mol) was added dropwise, followed by repeated nitrogen substitution to create a nitrogen atmosphere inside the flask. The mixture was stirred at 140°C for 4 hours under a nitrogen atmosphere to undergo transesterification, yielding compound (2) represented by the general formula (2), a relatively low molecular weight polyester (B). To the obtained compound (2), 2.567 g of lactic acid oligomer (DMGX:OLLA = 60:40 (mass ratio)) was added, and then 4.777 μl (approximately 0.05 mass%) of titanium (IV) tetrabutoxide was added dropwise. The temperature was gradually increased under reduced pressure at 150 °C for 2 hours, 170 °C for 1 hour, and 190 °C for 4 hours to cause a reaction. The obtained reaction product was then dissolved in chloroform and reprecipitated with methanol, and copolymer (C1-4) was recovered in a yield of 67%. The molecular weight of the copolymer (C1-4) was measured, and the heat resistance and mechanical properties were evaluated. The results are shown in Table 2. Also, regarding copolymer (C1-4) 1 H-NMR analysis was performed. 1 The area (a) / area (b) was calculated from the H-NMR spectrum, and the results are shown in Table 2. The copolymer (C1-4) was also evaluated for biodegradability and water resistance, and the results are shown in Table 3.

[0116] [Example 5] A 100 mL three-neck flask was charged with 4.377 g of DMGX (molar ratio: approximately 0.015 mol, 290 g / mol) and 1.874 g of ethylene glycol (molar ratio: approximately 0.030 mol, 62.07 g / mol), and the mixture was dried under reduced pressure to remove water. 1.174 μL of tin(II) 2-ethylhexanoate (approximately 0.008 mol%, 405.12 g / mol) was added dropwise, followed by repeated nitrogen substitution to create a nitrogen atmosphere inside the flask. The mixture was stirred at 140°C for 4 hours under a nitrogen atmosphere to transesterify, yielding a polycondensate of DMGX and ethylene glycol, a relatively low molecular weight polyester (B). To the resulting polycondensate, 0.486 g of lactic acid oligomer (DMGX:OLLA = 90:10 (mass ratio)) was added, and then 3.368 μl (approximately 0.05 mass%) of titanium (IV) tetrabutoxide was added dropwise. The temperature was gradually increased under reduced pressure at 150 °C for 2 hours, 170 °C for 1 hour, and 190 °C for 4 hours to cause the reaction. The resulting reaction product was then dissolved in chloroform and reprecipitated with cold diethyl ether, and copolymer (C1-5) was recovered in a yield of 51%. The molecular weight of the copolymer (C1-5) obtained was measured, and the heat resistance was evaluated. The results are shown in Table 2. Also, regarding copolymer (C1-5) 1 H-NMR analysis was performed. 1 The area (a) / area (b) was calculated from the H-NMR spectrum, and the results are shown in Table 2. The copolymer (C1-5) was also evaluated for biodegradability and water resistance, and the results are shown in Table 3.

[0117] [Example 6] A 100 mL three-neck flask was charged with 4.26 g of DMGX (molar ratio: approximately 0.015 mol, 290 g / mol) and 2.235 g of 1,3-propanediol (molar ratio: approximately 0.030 mol, 76.09 g / mol), and the mixture was dried under reduced pressure to remove water. 1.143 μL of tin(II) 2-ethylhexanoate (approximately 0.008 mol%, 405.12 g / mol) was added dropwise, followed by repeated nitrogen substitution to create a nitrogen atmosphere inside the flask. The mixture was stirred at 140°C for 4 hours under a nitrogen atmosphere to transesterify, yielding a polycondensate of DMGX and 1,3-propanediol, a relatively low molecular weight polyester (B). To the resulting polycondensate, 0.473 g of lactic acid oligomer (DMGX:OLLA = 90:10 (mass ratio)) was added, and then 3.484 μl (approximately 0.05 mass%) of titanium (IV) tetrabutoxide was added dropwise. The temperature was gradually increased under reduced pressure at 150 °C for 2 hours, 170 °C for 1 hour, and 190 °C for 4 hours to cause the reaction. The resulting reaction product was then dissolved in chloroform and reprecipitated with methanol, and copolymer (C1-6) was recovered in a yield of 53%. The molecular weight of the copolymer (C1-6) obtained was measured, and the heat resistance was evaluated. The results are shown in Table 2. Also, regarding copolymer (C1-6) 1 H-NMR analysis was performed. 1 The area (a) / area (b) was calculated from the H-NMR spectrum, and the results are shown in Table 2. The copolymer (C1-6) was also evaluated for biodegradability and water resistance, and the results are shown in Table 3.

[0118] [Example 7] A 100 mL three-neck flask was charged with 4.377 g of DMGX (molar ratio: approximately 0.015 mol, 290 g / mol) and 2.72 g of 1,4-butanediol (molar ratio: approximately 0.030 mol, 90.121 g / mol), and the mixture was dried under reduced pressure to remove water. After adding 1.174 μL of tin(II) 2-ethylhexanoate (approximately 0.008 mol%, 405.12 g / mol), the atmosphere in the flask was repeatedly replaced with nitrogen, creating a nitrogen atmosphere. The mixture was stirred at 140°C for 4 hours under a nitrogen atmosphere, resulting in transesterification and the production of a relatively low molecular weight polyester (B), a polycondensate of DMGX and 1,4-butanediol. To the resulting polycondensate, 0.486 g of lactic acid oligomer (DMGX:OLLA = 90:10 (mass ratio)) was added, and then 3.792 μl (approximately 0.05 mass%) of titanium (IV) tetrabutoxide was added dropwise. The temperature was gradually increased under reduced pressure at 150 °C for 2 hours, 170 °C for 1 hour, and 190 °C for 4 hours to cause a reaction. The resulting reaction product was then dissolved in chloroform and reprecipitated with methanol, and copolymer (C1-7) was recovered in a yield of 55%. The molecular weight of the copolymer (C1-7) was measured, and the heat resistance and mechanical properties were evaluated. The results are shown in Table 2. Also, regarding copolymer (C1-7) 1 H-NMR analysis was performed. 1 The area (a) / area (b) was calculated from the H-NMR spectrum, and the results are shown in Table 2. The copolymer (C1-7) was also evaluated for biodegradability and water resistance, and the results are shown in Table 3.

[0119] [Example 8] A 100 mL three-neck flask was charged with 4.377 g of DMGX (molar ratio: approximately 0.015 mol, 290 g / mol) and 3.144 g of 1,5-pentanediol (molar ratio: approximately 0.030 mol, 104.15 g / mol), and the mixture was dried under reduced pressure to remove water. 1.174 μL of tin(II) 2-ethylhexanoate (approximately 0.008 mol%, 405.12 g / mol) was added dropwise, followed by repeated nitrogen substitution to create a nitrogen atmosphere inside the flask. The mixture was stirred under a nitrogen atmosphere at 140°C for 4 hours to transesterify, yielding a polycondensate of DMGX and 1,5-pentanediol, a relatively low molecular weight polyester (B). To the resulting polycondensate, 0.486 g of lactic acid oligomer (DMGX:OLLA = 90:10 (mass ratio)) was added, and then 4.004 μl (approximately 0.05 mass%) of titanium (IV) tetrabutoxide was added dropwise. The temperature was gradually increased under reduced pressure at 150 °C for 2 hours, 170 °C for 1 hour, and 190 °C for 4 hours to cause a reaction. The resulting reaction product was then dissolved in chloroform and reprecipitated with methanol, and copolymer (C1-8) was recovered in a yield of 51%. The molecular weight of the copolymer (C1-8) was measured, and the heat resistance and mechanical properties were evaluated. The results are shown in Table 2. Also, regarding copolymer (C1-8) 1 H-NMR analysis was performed. 1 The area (a) / area (b) was calculated from the H-NMR spectrum, and the results are shown in Table 2. The copolymer (C1-8) was also evaluated for biodegradability and water resistance, and the results are shown in Table 3.

[0120] [Example 9] A 100 mL three-neck flask was charged with 4.377 g of DMGX (molar ratio: approximately 0.015 mol, 290 g / mol) and 3.567 g of 1,6-hexanediol (molar ratio: approximately 0.030 mol, 118.17 g / mol), and the mixture was dried under reduced pressure to remove water. 1.174 μL of tin(II) 2-ethylhexanoate (approximately 0.008 mol%, 405.12 g / mol) was added dropwise, followed by repeated nitrogen substitution to create a nitrogen atmosphere inside the flask. The mixture was stirred at 140°C for 4 hours under a nitrogen atmosphere to undergo transesterification, yielding compound (2) represented by the general formula (2), a relatively low molecular weight polyester (B). 2.918 g of lactic acid oligomer (DMGX:OLLA = 60:40 (mass ratio)) was added to the obtained compound (2), and the mixture was reacted under reduced pressure at 150°C for 2 hours, at 170°C for 1 hour, and at 190°C for 4 hours while gradually increasing the temperature. The obtained reaction product was then dissolved in chloroform and reprecipitated with methanol, and copolymer (C1-9) was recovered in a yield of 44%. The molecular weight of the copolymer (C1-9) obtained was measured, and the heat resistance was evaluated. The results are shown in Table 2. Also, for copolymer (C1-9) 1 H-NMR analysis was performed. 1 The area (a) / area (b) was calculated from the H-NMR spectrum, and the results are shown in Table 2. The copolymer (C1-9) was also evaluated for biodegradability and water resistance, and the results are shown in Table 3.

[0121] [Example 10] A 100 mL three-neck flask was charged with 4.377 g of DMGX (molar ratio: approximately 0.015 mol, 290 g / mol) and 3.567 g of 1,6-hexanediol (molar ratio: approximately 0.030 mol, 118.17 g / mol), and the mixture was dried under reduced pressure to remove water. 1.174 μL of tin(II) 2-ethylhexanoate (approximately 0.008 mol%, 405.12 g / mol) was added dropwise, followed by repeated nitrogen substitution to create a nitrogen atmosphere inside the flask. The mixture was stirred at 140°C for 4 hours under a nitrogen atmosphere to undergo transesterification, yielding compound (2) represented by the general formula (2), a relatively low molecular weight polyester (B). 2.918 g of lactic acid oligomer (DMGX:OLLA = 60:40 (mass ratio)) was added to the obtained compound (2), and the mixture was reacted under reduced pressure at 150°C for 2 hours, at 170°C for 1 hour, and at 190°C for 7 hours while gradually increasing the temperature. The obtained reaction product was then dissolved in chloroform and reprecipitated with methanol, and copolymer (C1-10) was recovered in a yield of 48%. The molecular weight of the copolymer (C1-10) obtained was measured, and the heat resistance was evaluated. The results are shown in Table 2. Also, regarding copolymer (C1-10) 1 H-NMR analysis was performed. 1 The area (a) / area (b) was calculated from the H-NMR spectrum, and the results are shown in Table 2. The copolymer (C1-10) was also evaluated for biodegradability and water resistance, and the results are shown in Table 3.

[0122] [Example 11] A 100 mL three-neck flask was charged with 4.377 g of DMGX (molar ratio: approximately 0.015 mol, 290 g / mol) and 3.567 g of 1,6-hexanediol (molar ratio: approximately 0.030 mol, 118.17 g / mol), and the mixture was dried under reduced pressure to remove water. After adding 0.601 μL of dibutyltin oxide (approximately 0.008 mol%, 248.94 g / mol), the atmosphere in the flask was repeatedly purged with nitrogen to create a nitrogen atmosphere. The mixture was stirred at 140°C for 4 hours under a nitrogen atmosphere to undergo transesterification, yielding compound (2) represented by the general formula (2), a relatively low molecular weight polyester (B). 2.918 g of lactic acid oligomer (DMGX:OLLA = 60:40 (mass ratio)) was added to the obtained compound (2), and the mixture was reacted under reduced pressure at 150°C for 2 hours, at 170°C for 1 hour, and at 190°C for 4 hours while gradually increasing the temperature. The obtained reaction product was then dissolved in chloroform and reprecipitated with cold diethyl ether, and copolymer (C1-11) was recovered in a yield of 10%. The molecular weight of the copolymer (C1-11) obtained was measured, and the heat resistance was evaluated. The results are shown in Table 2. Also, regarding copolymer (C1-11) 1 H-NMR analysis was performed. 1The area (a) / area (b) was calculated from the H-NMR spectrum, and the results are shown in Table 2. The copolymer (C1-11) was also evaluated for biodegradability and water resistance, and the results are shown in Table 3.

[0123] [Example 12] A 100 mL three-neck flask was charged with 1.45 g of DMGX (molar ratio: approximately 0.005 mol, 290 g / mol) and 10 g of polylactic acid diol (molar ratio: approximately 0.005 mol, Mn = 2000), which was then dried under reduced pressure and dehydrated. 0.259 μL of tin(II) 2-ethylhexanoate (approximately 0.008 mol%, 405.12 g / mol) was added dropwise, followed by repeated nitrogen substitution to create a nitrogen atmosphere inside the flask. The mixture was stirred under a nitrogen atmosphere at 140°C for 4 hours to transesterify. The reaction mixture was gradually heated under reduced pressure to 150°C for 2 hours, 170°C for 1 hour, and 190°C for 4 hours. The resulting reaction product was then dissolved in chloroform and reprecipitated with methanol, yielding copolymer (C2-1) in a 12% yield. The molecular weight of the copolymer (C2-1) obtained was measured, and the heat resistance was evaluated. The results are shown in Table 2. Also, regarding copolymer (C2-1) 1 H-NMR analysis was performed. 1 The area (a) / area (b) was calculated from the H-NMR spectrum, and the results are shown in Table 2. The copolymer (C2-1) was also evaluated for biodegradability and water resistance, and the results are shown in Table 3.

[0124] [Example 13] A 100 mL three-neck flask was charged with 4.377 g of DMGX (molar ratio: approximately 0.015 mol, 290 g / mol) and 3.567 g of 1,6-hexanediol (molar ratio: approximately 0.030 mol, 118.17 g / mol), and the mixture was dried under reduced pressure to remove water. 1.174 μL of tin(II) 2-ethylhexanoate (approximately 0.008 mol%, 405.12 g / mol) was added dropwise, followed by repeated nitrogen substitution to create a nitrogen atmosphere inside the flask. The mixture was stirred at 140°C for 4 hours under a nitrogen atmosphere to undergo transesterification, yielding compound (2) represented by the general formula (2), a relatively low molecular weight polyester (B). The resulting compound (2) was reacted under reduced pressure at 150°C for 2 hours, 170°C for 1 hour, and 190°C for 4 hours, gradually increasing the temperature. The resulting reaction product was then dissolved in chloroform and reprecipitated with diethyl ether to recover the polymer. After drying, the polymer (6 g, Mn = 11900) and L-lactide (3 g) were placed in a 100 mL three-neck flask and dried under reduced pressure to dehydrate. Tin(II) 2-ethylhexanoate (0.01 mol per 1 mol of terminal hydroxyl group in compound (2), Mn: 405.12 g / mol) was added dropwise, followed by repeated nitrogen substitution and stirring at 150°C for 5 hours under a nitrogen atmosphere. The resulting reaction product was then dissolved in chloroform and reprecipitated with cold diethyl ether to recover copolymer (C3-1) in a 10% yield. The molecular weight of the copolymer (C3-1) obtained was measured, and the heat resistance was evaluated. The results are shown in Table 2. Also, regarding copolymer (C3-1) 1 H-NMR analysis was performed. 1 The area (a) / area (b) was calculated from the H-NMR spectrum, and the results are shown in Table 2. The copolymer (C3-1) was also evaluated for biodegradability and water resistance, and the results are shown in Table 3.

[0125] [Comparative Example 1] The heat resistance of commercially available polylactic acid (Sigma Aldrich, Mn=10,000, Mw=11,000) was evaluated. The results are shown in Table 2. In addition, the polylactic acid used in Comparative Example 1 1 H-NMR analysis was performed.1 The area (a) / area (b) was calculated from the H-NMR spectrum, and the results are shown in Table 2. The polylactic acid used in Comparative Example 1 was also evaluated for biodegradability and water resistance. The results are shown in Table 3.

[0126] Comparative Example 2 The heat resistance and mechanical properties of commercially available polylactic acid (Sigma Aldrich, Mn=40,000, Mw=44,000) were evaluated. The results are shown in Table 2. In addition, the polylactic acid used in Comparative Example 2 1 H-NMR analysis was performed. 1 The area (a) / area (b) was calculated from the H-NMR spectrum, and the results are shown in Table 2. The polylactic acid used in Comparative Example 2 was also evaluated for biodegradability and water resistance. The results are shown in Table 3.

[0127] Comparative Example 3 A 100 mL three-neck flask was charged with 4.377 g of DMGX (molar ratio: approximately 0.015 mol, 290 g / mol) and 3.567 g of 1,6-hexanediol (molar ratio: approximately 0.030 mol, 118.17 g / mol), and the mixture was dried under reduced pressure to remove water. 1.174 μL of tin(II) 2-ethylhexanoate (approximately 0.008 mol%, 405.12 g / mol) was added dropwise, followed by repeated nitrogen substitution to create a nitrogen atmosphere inside the flask. The mixture was stirred at 140°C for 4 hours under a nitrogen atmosphere to undergo transesterification, yielding compound (2) represented by the general formula (2), a relatively low molecular weight polyester (B). The resulting compound (2) was reacted under reduced pressure at 150°C for 2 hours, 170°C for 1 hour, and 190°C for 7 hours while gradually increasing the temperature. The resulting reaction product was then dissolved in chloroform and reprecipitated with diethyl ether, and the precipitate was collected. The collected precipitate was then redissolved in chloroform and reprecipitated with cold diethyl ether, and polyhexylene xylose diglyoxylate (PHX) was collected in a 60% yield. The biodegradability and water resistance of the obtained PHX were evaluated, and the results are shown in Table 3.

[0128] [Table 1]

[0129] [Table 2]

[0130] [Table 3]

[0131] The abbreviations in Table 1 are as follows: In addition, "lactic acid oligomer [mass %]" in Table 1 is the amount (mass %) of lactic acid oligomer when the total of the lactic acid oligomer and dicarboxylic acid ester is taken as 100 mass %. · Sn(Oct)2: Tin(II) 2-ethylhexanoate. · Ti(OBu)4: Titanium(IV) tetrabutoxide. · DBTO: Dibutyltin oxide.

[0132] As is clear from the results in Tables 1 and 2, the copolymers obtained in each example were superior in heat resistance to polylactic acid, and also had excellent mechanical properties.

[0133] As is clear from the results in Table 3, the copolymers obtained in each example were highly biodegradable in both compost and seawater environments. In addition, they were resistant to swelling even after immersion in pure water for 5 days, and were also highly water-resistant. On the other hand, polylactic acid has poor biodegradability in seawater environments. PHX, a polymer that does not have a structural unit derived from the aliphatic polyester (A), was inferior in biodegradability in a compost environment compared to the copolymers obtained in each example. Furthermore, it was prone to swelling when immersed in pure water for 5 days and had poor water resistance. [Industrial Applicability]

[0134] According to the present invention, a copolymer having excellent biodegradability, heat resistance and water resistance is provided.

Claims

1. A copolymer which is a polycondensation product of an aliphatic polyester (A) and a polyester (B) having a xylose structure.

2. The copolymer according to claim 1, wherein the aliphatic polyester (A) is a lactic acid oligomer, and the polyester (B) has a structural unit derived from xylose dimethylglyoxylate.

3. A copolymer that is a polycondensation product of an aliphatic polyester diol and a polycarboxylic acid ester having a xylose structure.

4. The copolymer according to claim 3, wherein the aliphatic polyester diol is polylactic acid diol and the polycarboxylic acid ester is xylose dimethylglyoxylate.

5. A copolymer which is a ring-opening polymerization product of a cyclic ester compound and a polyester (B) having a xylose structure.

6. 6. The copolymer according to claim 5, wherein the cyclic ester compound is L-lactide, and the polyester (B) has a structural unit derived from xylose dimethylglyoxylate.

7. The copolymer according to any one of claims 1 to 6, which has a glass transition temperature of 55°C or higher.

8. The copolymer according to any one of claims 1 to 6, which has a thermal decomposition temperature of 370°C or higher.

9. The copolymer according to any one of claims 1 to 6, wherein when the copolymer is formed into a film under the following conditions, the maximum stress of the film is 50 MPa or more. Film molding conditions: Heat press molding was performed using a mold with a thickness of 0.1 mm under conditions of 20 MPa, 10 minutes, and 180°C.

10. The copolymer according to any one of claims 1 to 6, wherein when the copolymer is formed into a film under the following conditions, the film has a breaking elongation of 3% or more. Film molding conditions: Heat press molding was performed using a mold with a thickness of 0.1 mm under conditions of 20 MPa, 10 minutes, and 180°C.

11. a step of producing an aliphatic polyester (A); a step of producing a polyester (B) having a xylose structure; a step of polycondensing the aliphatic polyester (A) and the polyester (B); A method for producing a copolymer, comprising:

12. The aliphatic polyester (A) is produced by polycondensing at least one of L-lactic acid and D-lactic acid, The method for producing a copolymer according to claim 11, wherein the polyester (B) is produced by polycondensation of xylose dimethylglyoxylate and an aliphatic diol.

13. A method for producing a copolymer, comprising a step of polycondensing an aliphatic polyester diol and a polycarboxylic acid ester having a xylose structure.

14. The method for producing a copolymer according to claim 13, wherein the aliphatic polyester diol is polylactic acid diol, and the polycarboxylic acid ester is xylose dimethylglyoxylate.

15. a step of producing a polyester (B) having a xylose structure; a step of ring-opening polymerizing a cyclic ester compound and the polyester (B); A method for producing a copolymer, comprising:

16. the cyclic ester compound is L-lactide, The method for producing a copolymer according to claim 15, wherein the polyester (B) is produced by polycondensation of xylose dimethylglyoxylate and an aliphatic diol.

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