Biodegradable polyester resin, biodegradable polyester resin composition, and molded bodies thereof

Abstract

Provided are: a biodegradable polyester resin having excellent biodegradability and excellent hydrolysis resistance; a biodegradable polyester resin composition; and molded bodies thereof. The biodegradable polyester resin, the biodegradable polyester resin composition, and the molded bodies thereof include a structural unit derived from a dicarboxylic acid component (A) and a structural unit derived from an aliphatic diol component (B) and satisfy at least one of the following conditions (alpha) and (beta). Condition (alpha): The dicarboxylic acid component (A) contains a first dicarboxylic acid component (A1) comprising at least one compound selected from the group consisting of aliphatic dicarboxylic acids (a1) represented by formula (I) and derivatives thereof. Condition (beta): The aliphatic diol component (B) contains a first aliphatic diol (B1) comprising at least one compound selected from aliphatic diols (b1) represented by formula (II). (The symbols in formulae (I) and (II) are as defined in the description of the present application.)

Description

Biodegradable polyester resin, biodegradable polyester resin composition, and molded body thereof

[0001] The present invention relates to a biodegradable polyester resin, a biodegradable polyester resin composition, and a molded article thereof.

[0002] In recent years, environmental issues, including the problem of microplastics, have been in the spotlight. When ordinary synthetic resins are left in the environment, they weather and break down into fine powder due to exposure to ultraviolet rays and other factors, but they do not completely decompose and turn into microplastics, causing problems with marine pollution. In recent years, biodegradable plastics known as GreenPla have been developed. Known synthetic resins include polyesters, polyvinyl alcohol resins, and polyamino acids, but currently, only polyesters can be practically melt-molded.

[0003] Known biodegradable polyesters include aliphatic polyester resins such as polybutylene succinate and polybutylene succinate adipate, aliphatic oxycarboxylic acid resins such as polylactic acid, and aromatic-aliphatic copolymer polyester resins such as polybutylene adipate terephthalate. While these biodegradable polyester resins have excellent biodegradability, their high degradability leads to poor storage stability and the resins decompose during storage. Since this decomposition is primarily due to hydrolysis of the polyester resin, they are often used in combination with a hydrolysis stabilizer. For example, Patent Document 1 proposes a configuration for improving hydrolysis resistance by combining a hydrolysis stabilizer with a polyester resin. Patent Document 2 also proposes a method for improving hydrolysis resistance by introducing a special structure into a polyester resin.

[0004] On the other hand, in recent years, there has been an increasing demand for environmental compatibility of synthetic resins, and proposals have been made to further enhance the biodegradability of conventional polyester resins. For example, Patent Document 3 shows that the biodegradation rate at room temperature can be increased by compounding an aliphatic polyester resin with a polyhydroxyalkanoate.

[0005] Patent No. 5279352 Publication JP 10-130377 Publication International Publication No. 2019 / 189367

[0006] However, according to the inventors' investigations, it has been found that the proposals for improving hydrolysis resistance as shown in Patent Documents 1 and 2 result in a deterioration in the biodegradation rate, and that a sufficient biodegradation rate cannot be obtained depending on the environment. Furthermore, it has been found that the proposal for improving the biodegradation rate as shown in Patent Document 3 still has problems, such as the inability to ensure the storage stability of the resin due to a significant deterioration in hydrolysis resistance.

[0007] The present invention aims to solve the above problems, and its object is to provide a biodegradable polyester resin, a biodegradable polyester resin composition, and molded articles thereof, which have excellent biodegradability and excellent hydrolysis resistance.

[0008] As a result of intensive research aimed at solving the above-mentioned problems, the present inventors have conceived the following invention and found that it is possible to solve the above-mentioned problems. That is, the present invention encompasses the following inventions. [1] A biodegradable polyester resin containing structural units derived from a dicarboxylic acid component (A) and structural units derived from an aliphatic diol component (B), which satisfies at least one of the following conditions (α) and (β): - Condition (α): The dicarboxylic acid component (A) contains a first dicarboxylic acid component (A1) consisting of at least one compound selected from the group consisting of aliphatic dicarboxylic acids (a1) represented by the following formula (I) and derivatives thereof. - Condition (β): The aliphatic diol component (B) contains a first aliphatic diol component (B1) consisting of at least one compound selected from aliphatic diols (b1) represented by the following formula (II). [In formulas (I) and (II), R １ , R ２ , R ５ , R ６ each independently represents a divalent hydrocarbon group having 1 to 3 carbon atoms; R ３ , R ７ each independently represents a monovalent hydrocarbon group having 1 to 3 carbon atoms; R ４ , R８ each independently represent a hydrogen atom or a monovalent hydrocarbon group having 1 to 3 carbon atoms, and m, n, x, and y each independently represent 0 or 1.] [2] The biodegradable polyester resin according to the above [1], wherein the dicarboxylic acid component (A) comprises the first dicarboxylic acid component (A1) and a second dicarboxylic acid component (A2) consisting of one compound selected from the group consisting of a second dicarboxylic acid (a2) different from the aliphatic dicarboxylic acid (a1) and derivatives thereof, and wherein the biodegradable polyester resin satisfies the following condition (i) or (ii): - Condition (i): The number of carbon atoms of the dicarboxylic acid contained in the second dicarboxylic acid component (A2) and the number of carbon atoms of the aliphatic diol contained in the aliphatic diol component (B) are both 4 or less. - Condition (ii): The second dicarboxylic acid component (A2) contains an aromatic dicarboxylic acid. [3] The biodegradable polyester resin according to the above [2], wherein the second dicarboxylic acid component (A2) contains an aromatic dicarboxylic acid. [4] The biodegradable polyester resin according to any one of [1] to [3] above, wherein the content of the aliphatic dicarboxylic acid (a1) in the dicarboxylic acid component (A) is 2 to 60 mol %. [5] R in formula (I) １ , R ２ [6] The biodegradable polyester resin according to any one of the above [1] to [4], wherein R in formula (I) are both methylene groups. ３ is a methyl group, and R ４ [7] The biodegradable polyester resin according to any one of the above [1] to [6], wherein the content of the first aliphatic diol component (B1) in the aliphatic diol component (B) is 2 to 50 mol %. [8] The biodegradable polyester resin according to any one of the above [1] to [6], wherein R in formula (II) is a hydrogen atom. ５ and R ６ [9] The biodegradable polyester resin according to any one of the above [1] to [7], wherein R in formula (II) is a methylene group. ７ is a methyl group, and R ８

[10] The biodegradable polyester resin according to any one of the above [1] to [9], wherein the dicarboxylic acid component (A) does not contain an aliphatic dicarboxylic acid (a2X) having an alkylene group having a branch and a hydroxyl group, or the content of the aliphatic dicarboxylic acid (a2X) in the dicarboxylic acid component (A) is more than 0 mol % and 3 mol % or less.

[11] The biodegradable polyester resin according to any one of [1] to

[10] above, wherein the dicarboxylic acid component (A) comprises the first dicarboxylic acid component (A1), a second dicarboxylic acid component (A2) consisting of one compound selected from the group consisting of a second dicarboxylic acid (a2) different from the aliphatic dicarboxylic acid (a1) and derivatives thereof, and a third dicarboxylic acid component (A3) consisting of one compound selected from the group consisting of a third dicarboxylic acid (a3) ​​different from the aliphatic dicarboxylic acid (a1) and the second dicarboxylic acid (a2) and derivatives thereof.

[12] The biodegradable polyester resin according to

[11] above, wherein the third dicarboxylic acid (a3) ​​is methylsuccinic acid.

[13] A biodegradable polyester resin composition comprising the biodegradable polyester resin according to any one of [1] to

[12] above and a hydrolysis stabilizer (C).

[14] The biodegradable polyester resin composition according to

[13] above, wherein the hydrolysis stabilizer (C) is a carbodiimide compound.

[15] The biodegradable polyester resin composition according to

[13] or

[14] above, wherein the content of the hydrolysis stabilizer (C) is 0.15 to 2 parts by mass per 100 parts by mass of the biodegradable polyester resin.

[16] A molded article comprising the biodegradable polyester resin according to any one of [1] to

[12] above, or the biodegradable polyester resin composition according to any one of

[13] to

[15] above.

[17] A film comprising the biodegradable polyester resin according to any one of [1] to

[12] above, or the biodegradable polyester resin composition according to any one of

[13] to

[15] above.

[18] A sheet comprising the biodegradable polyester resin according to any one of [1] to

[12] above, or the biodegradable polyester resin composition according to any one of

[13] to

[15] above.

[19] A food utensil comprising the biodegradable polyester resin according to any one of [1] to

[12] above, or the biodegradable polyester resin composition according to any one of

[13] to

[15] above.

[20] A plastic modifier comprising the biodegradable polyester resin according to any one of [1] to

[12] above, or the biodegradable polyester resin composition according to any one of

[13] to

[15] above.

[21] A coating agent comprising the biodegradable polyester resin according to any one of [1] to

[12] above, or the biodegradable polyester resin composition according to any one of

[13] to

[15] above.

[0009] According to the present invention, it is possible to provide a biodegradable polyester resin, a biodegradable polyester resin composition, and a molded article thereof, which have excellent biodegradability and excellent hydrolysis resistance.

[0010] 1 is an example of a photograph of the appearance of a polyester resin film after evaluation of compostability; FIG. 2 is an example of a photograph of the appearance of another polyester resin film after evaluation of compostability; FIG. 3 is an example of a photograph of the appearance of a polyester resin film after evaluation of hydrolysis resistance; FIG. 4 is an example of a photograph of the appearance of another polyester resin film after evaluation of hydrolysis resistance.

[0011] The following is a description based on one example of an embodiment of the present invention. However, the embodiment shown below is an example for embodying the technical idea of ​​the present invention, and the present invention is not limited to the following description. Furthermore, although preferred embodiments are shown in this specification, a combination of two or more of the individual preferred embodiments is also a preferred embodiment. For matters shown as numerical ranges, when there are several numerical ranges, the lower limit and upper limit can be selectively combined to form a preferred embodiment. Furthermore, in this specification, when a numerical range is described as "XX to YY," it means "XX or more and YY or less."

[0012] [Biodegradable Polyester Resin] A biodegradable polyester resin according to an embodiment of the present invention is a biodegradable polyester resin containing structural units derived from a dicarboxylic acid component (A) and structural units derived from an aliphatic diol component (B), and satisfies at least one of the following conditions (α) and (β): - Condition (α): The dicarboxylic acid component (A) contains a first dicarboxylic acid component (A1) consisting of at least one compound selected from the group consisting of aliphatic dicarboxylic acids (a1) represented by the following formula (I) and derivatives thereof. - Condition (β): The aliphatic diol component (B) contains a first aliphatic diol component (B1) consisting of at least one compound selected from aliphatic diols (b1) represented by the following formula (II). [In formulas (I) and (II), R １ , R ２ , R ５ , R ６ each independently represents a divalent hydrocarbon group having 1 to 3 carbon atoms; R ３ , R ７ each independently represents a monovalent hydrocarbon group having 1 to 3 carbon atoms; R ４ , R ８ each independently represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 3 carbon atoms, and m, n, x, and y each independently represent 0 or 1.

[0013] The aliphatic dicarboxylic acid (a1) represented by the formula (I) and the aliphatic diol (b1) represented by the formula (II) have a branched structure. Therefore, when the dicarboxylic acid component (A) contains a first dicarboxylic acid component (A1) consisting of at least one compound selected from the group consisting of the aliphatic dicarboxylic acid (a1) and its derivatives, or, in addition, when the aliphatic diol component (B) contains a first aliphatic diol component (B1) consisting of at least one compound selected from the aliphatic diol (b1), the crystallinity of the resulting biodegradable polyester resin is thought to be reduced, making it easier to improve biodegradability. On the other hand, due to the branched structure of the aliphatic dicarboxylic acid (a1) and its derivatives, the branched structure of the aliphatic diol (b1), or both, the decomposition reaction of the biodegradable polyester resin is suppressed by steric hindrance, and it is thought that the biodegradable polyester resin can have improved hydrolysis resistance while maintaining biodegradability. As a result, it is presumed that the biodegradable polyester resin can achieve both excellent biodegradability and excellent hydrolysis resistance. The biodegradable polyester resin has good biodegradability and hydrolysis resistance, and therefore has high environmental compatibility and storage stability.

[0014] As used herein, "biodegradable" refers to the ability to ultimately be decomposed into water and carbon dioxide by microorganisms or the like, and includes, for example, a material that exhibits a decrease in mass when stored in a composting environment for a certain period of time. Therefore, in this specification, "biodegradable" may also be referred to as "compostability." From the perspective of exhibiting good biodegradability, the biodegradable polyester resin according to an embodiment of the present invention is subjected to a composting test in accordance with JIS K6954:2008. The weight of the resin or resin composition is measured before and after 30 days, and the weight retention after the test is preferably 85% or less, more preferably 70% or less, even more preferably 50% or less, and even more preferably 40% or less. The ideal lower limit for weight retention is 0%, but even a weight retention of 20% or more sufficiently satisfies the required performance. In other words, the weight retention of the biodegradable polyester resin after the composting test is preferably 0 to 85%, and may be 20 to 85%.

[0015] A biodegradable polyester resin according to a preferred embodiment of the present invention is a biodegradable polyester resin in which the dicarboxylic acid component (A) comprises the first dicarboxylic acid component (A1) and a second dicarboxylic acid component (A2) consisting of one compound selected from the group consisting of a second dicarboxylic acid (a2) different from the aliphatic dicarboxylic acid (a1) and derivatives thereof, and which satisfies the following condition (i) or (ii): Condition (i): The number of carbon atoms of the dicarboxylic acid contained in the second dicarboxylic acid component (A2) and the number of carbon atoms of the aliphatic diol contained in the aliphatic diol component (B) are both 4 or less. Condition (ii): The second dicarboxylic acid component (A2) comprises an aromatic dicarboxylic acid. In the biodegradable polyester resin according to the above embodiment, the dicarboxylic acid component (A) further comprises the second dicarboxylic acid component (A2), which makes it easier to impart other necessary properties, such as mechanical properties, to the biodegradable polyester resin.

[0016] In addition, compared to the case where the dicarboxylic acid component (A) is only the second dicarboxylic acid component (A2) as in the above embodiment, at least a portion of the second dicarboxylic acid component (A2) can be considered to be replaced with the first dicarboxylic acid component (A1). Therefore, the biodegradable polyester resin of this embodiment may be described as "a dicarboxylic acid component (A) modified with the first dicarboxylic acid component (A1)." Below, details of each component for obtaining the biodegradable polyester resin, the biodegradable polyester resin and biodegradable polyester resin composition, and molded articles thereof will be described. In the following, to avoid redundant repetition of component names, for example, "dicarboxylic acid component (A)" may be abbreviated to simply "component (A)."

[0017] <Dicarboxylic Acid Component (A)> The dicarboxylic acid component (A) includes a first dicarboxylic acid component (A1) consisting of an aliphatic dicarboxylic acid (a1) represented by the above-mentioned formula (I). Preferably, the dicarboxylic acid component (A) includes the first dicarboxylic acid component (A1) and a second dicarboxylic acid component (A2) consisting of one compound selected from the group consisting of a second dicarboxylic acid (a2) different from the aliphatic dicarboxylic acid (a1) and derivatives thereof.

[0018] (First dicarboxylic acid component (A1)) The first dicarboxylic acid component (A1) comprises at least one compound selected from the group consisting of aliphatic dicarboxylic acids (a1) represented by the following formula (I) and derivatives thereof. In the following description, the aliphatic dicarboxylic acid (a1) represented by formula (I) may be simply referred to as "aliphatic dicarboxylic acid (a1)."

[0019] In formula (I), R １ , R ２ R each independently represents a divalent hydrocarbon group having 1 to 3 carbon atoms. １ and R ２ Examples of the divalent hydrocarbon group having 1 to 3 carbon atoms represented by include a methylene group, an ethylene group, a trimethylene group, and a methylethylene group.

[0020] In formula (I), m and n each independently represent 0 or 1. From the viewpoint of achieving both biodegradation rate and hydrolysis resistance, it is preferable that both m and n are 1 and R １ , R ２ are preferably all methylene groups.

[0021] In formula (I), R ３ represents a monovalent hydrocarbon group having 1 to 3 carbon atoms. ４ represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 3 carbon atoms. ３ , R ４ Examples of the monovalent hydrocarbon group having 1 to 3 carbon atoms represented by include a methyl group, an ethyl group, a 1-propyl group, and a 2-propyl group. Among these, a methyl group is preferred from the viewpoint of providing an appropriate degree of steric hindrance. In one embodiment, R ３ is a methyl group, and R ４ is a hydrogen atom. In this case, the aliphatic dicarboxylic acid (a1) and its derivatives tend to exhibit a moderate steric hindrance.

[0022] Examples of the aliphatic dicarboxylic acid (a1) include 3-methylpentanedioic acid (also known as 3-methylglutaric acid), methylsuccinic acid, methylmalonic acid, 2-methylglutaric acid, propylsuccinic acid, 3-ethylglutaric acid, 2-ethylglutaric acid, 3-propylglutaric acid, 2-propylglutaric acid, propylpropanedioic acid (also known as propylmalonic acid), ethylpropanedioic acid (also known as ethylmalonic acid), 2-methyladipic acid, and 3-methyladipic acid. Of these, 3-methylpentanedioic acid is preferred from the viewpoints of reduced crystallinity and steric hindrance.

[0023] Examples of derivatives of aliphatic dicarboxylic acid (a1) include acid anhydrides of the above aliphatic dicarboxylic acid (a1), ester compounds of the above aliphatic dicarboxylic acid (a1), and acid halides of the above aliphatic dicarboxylic acid (a1). Examples of acid anhydrides of the above aliphatic dicarboxylic acid (a1) include 3-methylpentanedioic anhydride, 2-methylglutaric anhydride, and methylsuccinic anhydride. Examples of ester compounds of the above aliphatic dicarboxylic acid (a1) include dialkyl esters of the above aliphatic dicarboxylic acid (a1). Examples of the dialkyl esters include dimethyl esters and diethyl esters of the above aliphatic dicarboxylic acid (a1). Examples of acid halides of the above aliphatic dicarboxylic acid (a1) include dihalides of the above aliphatic dicarboxylic acid (a1). Examples of halogen atoms constituting the above acid halides include chlorine atoms and bromine atoms.

[0024] The aliphatic dicarboxylic acid (a1) and its derivatives may be used alone or in combination of two or more, but it is preferred to use one alone from the viewpoint of making it easier to exhibit the desired properties.

[0025] (Second Dicarboxylic Acid Component (A2)) As described above, the dicarboxylic acid component (A) used to obtain a biodegradable polyester resin according to a preferred embodiment of the present invention comprises the first dicarboxylic acid component (A1) and a second dicarboxylic acid component (A2) consisting of one compound selected from the group consisting of a second dicarboxylic acid (a2) different from the aliphatic dicarboxylic acid (a1) and derivatives thereof.

[0026] The second dicarboxylic acid (a2) may be an aliphatic dicarboxylic acid, an alicyclic dicarboxylic acid, or an aromatic dicarboxylic acid. An aliphatic dicarboxylic acid or an aromatic dicarboxylic acid is more preferable. Examples of the second dicarboxylic acid (a2) include aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; and aromatic dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid. Among these, succinic acid, adipic acid, and terephthalic acid are preferred. The derivatives of the second dicarboxylic acid (a2) include the acid anhydrides of the above-mentioned aliphatic dicarboxylic acids, the ester compounds of the above-mentioned aliphatic dicarboxylic acids, the acid halides of the above-mentioned aliphatic dicarboxylic acids, the acid anhydrides of the above-mentioned alicyclic dicarboxylic acids, the ester compounds of the above-mentioned alicyclic dicarboxylic acids, the acid halides of the above-mentioned alicyclic dicarboxylic acids, the acid anhydrides of the above-mentioned aromatic dicarboxylic acids, the ester compounds of the above-mentioned aromatic dicarboxylic acids, and the acid halides of the above-mentioned aromatic dicarboxylic acids.From the viewpoint of easily increasing the flexibility of the biodegradable polyester resin, it is preferred that the second dicarboxylic acid component (A2) contains an aromatic dicarboxylic acid.These may be used alone or in combination of two or more.

[0027] When the dicarboxylic acid component (A) contains a second dicarboxylic acid component (A2), it is preferred that the number of carbon atoms of the dicarboxylic acid contained in the second dicarboxylic acid component (A2) and the number of carbon atoms of the aliphatic diol contained in the aliphatic diol component (B) are both 4 or less as specified in the above condition (i), or that the second dicarboxylic acid component (A2) contains an aromatic dicarboxylic acid as specified in the above condition (ii).

[0028] Examples of the dicarboxylic acid having 4 or less carbon atoms specified in the above condition (i) include succinic acid, malonic acid, and oxalic acid, with succinic acid being preferred.

[0029] The total mass of the first dicarboxylic acid component (A1) and the second dicarboxylic acid component (A2) in the dicarboxylic acid component (A) is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more, when the total mass of the dicarboxylic acid component (A) is 100% by mass. There is no particular upper limit, and it may be 100% by mass or less, 98% by mass or less, or 95% by mass or less. In other words, the total mass of the first dicarboxylic acid component (A1) and the second dicarboxylic acid component (A2) in the dicarboxylic acid component (A) is preferably 80 to 100% by mass.

[0030] The content (or modification rate) of the aliphatic dicarboxylic acid (a1) in the dicarboxylic acid component (A), in other words, the content (or modification rate) of the first dicarboxylic acid component (A1) in the dicarboxylic acid component (A), is preferably 2 to 80 mol %, more preferably 2 to 70 mol %, even more preferably 2 to 60 mol %, still more preferably 3 to 60 mol %, and particularly preferably 3 to 58 mol %, from the viewpoint of easily enhancing biodegradability and hydrolysis resistance.

[0031] From the viewpoint of making it easier for the biodegradable polyester resin to have an appropriate molecular weight, it is preferable that the dicarboxylic acid component (A) does not contain an aliphatic dicarboxylic acid having a branched alkylene group and a hydroxyl group (aliphatic dicarboxylic acid (a2X)) as the second dicarboxylic acid component (A2), or that the content of the aliphatic dicarboxylic acid (a2X) in the dicarboxylic acid component (A) is more than 0 mol % and not more than 3 mol %. Examples of the aliphatic dicarboxylic acid (a2X) include 3-hydroxy-3-methylglutaric acid.

[0032] In a preferred embodiment of the biodegradable polyester resin of the present invention, the dicarboxylic acid component (A) may include the first dicarboxylic acid component (A1), the second dicarboxylic acid component (A2), and a third dicarboxylic acid (a3) ​​different from the aliphatic dicarboxylic acid (a1) and the second dicarboxylic acid (a2) and a third dicarboxylic acid component (A3) composed of one compound selected from the group consisting of a third dicarboxylic acid component (A3) and a derivative thereof. Examples of the third dicarboxylic acid (a3) ​​include 2-methylsuccinic acid.

[0033] <Aliphatic Diol Component (B)> The aliphatic diol component (B) includes a first aliphatic diol component (B1) consisting of at least one compound selected from aliphatic diols (b1) represented by formula (I). Preferably, the aliphatic diol component (B) includes the first aliphatic diol component (B1) and a second diol component (B2) consisting of one compound selected from a second diol (b2) different from the aliphatic diol (b1).

[0034] (First Aliphatic Diol Component (B1)) The first aliphatic diol component (B1) comprises at least one compound selected from aliphatic diols (b1) represented by the following formula (II): In the following description, the aliphatic diol (b1) represented by formula (II) may be simply referred to as "aliphatic diol (b1)."

[0035] In formula (I), R ５ , R ６ R each independently represents a divalent hydrocarbon group having 1 to 3 carbon atoms. ５ and R ６ Examples of the divalent hydrocarbon group having 1 to 3 carbon atoms represented by R include a methylene group, an ethylene group, a trimethylene group, and a methylethylene group. ５ and R ６ is a methylene group.

[0036] In formula (II), x and y each independently represent 0 or 1. From the viewpoint of achieving both biodegradation rate and hydrolysis resistance, it is preferable that both x and y are 1 and R in formula (I) is 0 or 1. ５ , R ６are preferably all methylene groups.

[0037] In formula (II), R ７ represents a monovalent hydrocarbon group having 1 to 3 carbon atoms. ８ represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 3 carbon atoms. ７ , R ８ Examples of the monovalent hydrocarbon group having 1 to 3 carbon atoms represented by include a methyl group, an ethyl group, a 1-propyl group, and a 2-propyl group. Among these, a methyl group is preferred from the viewpoint of easily providing an appropriate degree of steric hindrance. In one embodiment, R ７ is a methyl group, and R ８ is a hydrogen atom. In this case, the aliphatic diol (b1) tends to exhibit a moderate steric hindrance.

[0038] Examples of the aliphatic diol (b1) include propylene glycol, 2-methyl-1,3-propanediol, 1,3-butylene glycol, 2-methyl-1,4-butanediol, 2-isopropyl-1,4-butanediol, 3-methyl-1,5-pentanediol, 2-methyl-1,8-octanediol, 2,7-dimethyl-1,8-octanediol, 2-methyl-1,9-nonanediol, 2,8-dimethyl-1,9-nonanediol, 2,2-diethyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, neopentyl glycol, etc. Of these, 3-methyl-1,5-pentanediol is preferred from the viewpoints of reduced crystallinity and steric hindrance.

[0039] The aliphatic diol (b1) may be used alone or in combination of two or more kinds, but it is preferred to use one kind alone from the viewpoint of making it easier to exhibit the desired properties.

[0040] (Second Diol Component (B2)) As described above, the aliphatic diol component (B) used to obtain a biodegradable polyester resin according to a preferred embodiment of the present invention comprises the first aliphatic diol component (B1) and a second diol component (B2) consisting of one compound selected from the group consisting of a second diol (b2) different from the aliphatic diol (b1).

[0041] The second diol (b2) may be an aliphatic diol or an alicyclic diol. Examples of the second diol (b2) include aliphatic diols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol; and alicyclic diols such as cyclohexanedimethanol. Of these, ethylene glycol and 1,4-butanediol are preferred. These may be used alone or in combination of two or more.

[0042] When the aliphatic diol component (B) contains a second diol component (B2), the number of carbon atoms of the aliphatic diol (b1) that is the first aliphatic diol component (B1) and the number of carbon atoms of the second diol (b2) that is the second diol component (B2) are preferably 6 or less. Furthermore, when the aliphatic diol component (B) contains the second diol component (B2) and the dicarboxylic acid component (A) contains the second dicarboxylic acid component (A2), it is preferable that the number of carbon atoms of the dicarboxylic acid contained in the second dicarboxylic acid component (A2) is 4 or less, as specified in the above condition (i), or that the number of carbon atoms of the dicarboxylic acid contained in the second dicarboxylic acid component (A2) is 6 or less, as specified in the above condition (ii).

[0043] Examples of diols having 4 or less carbon atoms include ethylene glycol, 1,3-propanediol, and 1,4-butanediol, with butanediol being preferred.

[0044] The total mass of the first aliphatic diol component (B1) and the second diol component (B2) in the aliphatic diol component (B) is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more, based on 100% by mass of the entire aliphatic diol component (B). There is no particular upper limit, and the total mass may be 100% by mass or less, 98% by mass or less, or 95% by mass or less. In other words, the total mass of the first aliphatic diol component (B1) and the second diol component (B2) in the aliphatic diol component (B) is preferably 80 to 100% by mass.

[0045] From the viewpoint of easily enhancing biodegradability and hydrolysis resistance, the content (or modification rate) of the aliphatic diol (b1) in the aliphatic diol component (B), in other words, the content (or modification rate) of the first aliphatic diol component (B1) in the aliphatic diol component (B), is preferably 2 to 80 mol %, more preferably 2 to 70 mol %, even more preferably 2 to 60 mol %, still more preferably 3 to 60 mol %, and particularly preferably 2 to 50 mol %.

[0046] <Content of structural units derived from components (A) and (B) in the resin> In the biodegradable polyester resin according to this embodiment, the total content of the structural units derived from the dicarboxylic acid component (A) and the structural units derived from the aliphatic diol component (B) is preferably 70% by mass or more, more preferably 75% by mass or more, and even more preferably 80% by mass or more, when the mass of the biodegradable polyester resin is taken as 100% by mass, from the viewpoint of easily ensuring good biodegradability and hydrolysis resistance. There is no particular upper limit, and it may be 100% by mass or less, 95% by mass or less, or 90% by mass or less. In other words, in the biodegradable polyester resin according to this embodiment, the total proportion of the mass of the structural units derived from the dicarboxylic acid component (A) and the mass of the structural units derived from the aliphatic diol component (B) is preferably 70 to 100% by mass.

[0047] (Other Components) The biodegradable polyester resin according to this embodiment may contain other components. Examples of the other components include inorganic fillers, softeners, heat aging inhibitors, antioxidants, light stabilizers, antistatic agents, release agents, flame retardants, foaming agents, pigments, dyes, brighteners, UV absorbers, lubricants, plasticizers, crosslinking agents, fillers, crosslinking accelerators, crosslinking aids, tackifiers, adhesion promoters, organic fillers, crystal nucleating agents, heat stabilizers, colorants, flame retardant aids, blooming inhibitors, thickeners, conductive aids, and flowability improvers. However, the other components that may be contained in the biodegradable polyester resin do not include the hydrolysis stabilizer (C) described below. These may be used alone or in combination of two or more. The content of the other components may be appropriately determined depending on the desired physical properties of the biodegradable polyester resin. However, from the viewpoint of making it easier for the biodegradable polyester resin to exhibit its intended performance, the content is preferably 0.001 to 30% by mass, more preferably 0.005 to 25% by mass, even more preferably 0.07 to 20% by mass, still more preferably 0.01 to 15% by mass, even more preferably 0.01 to 10% by mass, and particularly preferably 0.01 to 5% by mass, when the biodegradable polyester resin is taken as 100% by mass.

[0048] <Physical Properties of Biodegradable Polyester Resin> (Biodegradability) As described above, when a compost test is carried out with reference to JIS K6954:2008, the biodegradable polyester resin preferably has a weight retention rate of 0 to 85% or less after measuring the weight of the resin or resin composition before and after the test.

[0049] (Number Average Molecular Weight (Mn)) From the viewpoints of strength and handleability, the Mn of the biodegradable polyester resin is preferably 2,000 to 100,000, more preferably 3,000 to 80,000, even more preferably 4,000 to 60,000, and still more preferably 5,000 to 50,000. In this specification, the Mn of the biodegradable polyester resin is the number average molecular weight calculated as a standard polymethyl methacrylate resin (PMMA) determined by size exclusion high performance liquid chromatography measurement, and is measured in detail by the method described in the Examples.

[0050] (Weight-average molecular weight (Mw)) From the viewpoint of strength and handleability, the Mw of the biodegradable polyester resin is preferably 5,000 to 200,000, more preferably 10,000 to 150,000, even more preferably 15,000 to 120,000, and still more preferably 20,000 to 100,000. In this specification, the Mw of the biodegradable polyester resin is the number-average molecular weight calculated as a standard polymethyl methacrylate resin (PMMA) determined by size-exclusion high-performance liquid chromatography measurement, and is measured in detail by the method described in the examples.

[0051] (Solution Intrinsic Viscosity (IV)) The solution intrinsic viscosity (IV) of the biodegradable polyester resin at 30°C is preferably 0.90 to 1.05 dl / g, more preferably 0.91 to 1.04 dl / g, and even more preferably 0.92 to 1.03 dl / g, from the viewpoint of easily obtaining an appropriate molecular weight. The IV is measured by the method described in the examples.

[0052] (Elongation at break) From the viewpoint of ensuring good flexibility, the elongation at break of the biodegradable polyester resin is desirably high, preferably 200% or more, more preferably 300% or more, even more preferably 400% or more, and even more preferably 500% or more. There is no particular upper limit to the elongation at break, but from the viewpoint of strength, it is, for example, 1,000% or less, 900% or less, or 800% or less. In other words, the elongation at break of the biodegradable polyester resin is preferably 200 to 1,000%. When high flexibility is not required for the biodegradable polyester resin depending on the application, the elongation at break of the biodegradable polyester resin is, for example, 10 to 100%, 12 to 70%, or 13 to 50%. The elongation at break is measured by the method described in the examples.

[0053] (Hydrolysis Resistance) From the viewpoint of easily improving storage stability, it is desirable for the biodegradable polyester resin to have as high a hydrolysis resistance as possible, as defined by the molecular weight retention rate after immersing the biodegradable polyester resin having a predetermined shape in hot water for a predetermined time. More specifically, when the biodegradable polyester resin is processed into a film shape of a predetermined size and immersed in hot water at 80°C, the molecular weight retention rate after 4 days is preferably 76% or more, more preferably 78% or more, and even more preferably 80% or more, and the molecular weight retention rate after 7 days is preferably 55% or more, more preferably 58% or more, and even more preferably 60% or more. The upper limits of the molecular weight retention rates after 4 days and 7 days may be 100%, 95%, or 90%. In other words, the hydrolysis resistance of the biodegradable polyester resin (after 4 days) is preferably 80 to 100%, and the hydrolysis resistance (after 7 days) is preferably 60 to 100%. Hydrolysis resistance is measured by the method described in the Examples.

[0054] <Method for Producing Biodegradable Polyester Resin> There are no particular limitations on the method for producing the polyester of the present invention, and known polyester polycondensation methods can be applied. For example, 3-methylpentanedioic acid or a derivative thereof and a diol component are charged in a predetermined ratio, and an esterification or transesterification reaction is carried out. The resulting reaction product is then subjected to a further polycondensation reaction at high temperature under vacuum in the presence of a polycondensation catalyst, thereby producing a polyester of the desired molecular weight. A wide range of polycondensation catalysts can be used in producing the polyester. Examples of such polycondensation catalysts include titanium compounds such as tetramethoxytitanium, tetraethoxytitanium, tetra-n-propoxytitanium, tetraisopropoxytitanium, and tetrabutoxytitanium; tin compounds such as di-n-butyltin oxide, di-n-butyltin dilaurate, and dibutyltin diacetate; and combinations of acetates of magnesium, calcium, zinc, or the like with antimony oxide or the above-mentioned titanium compounds. These polycondensation catalysts are preferably used in an amount of 5 to 500 ppm by mass relative to the total polyester produced. The ratio MA:MB of the molar amount MA of the dicarboxylic acid component (A) to the molar amount MB of the aliphatic diol component (B) used in the polycondensation reaction is preferably 0.8:1.0 to 1.0:0.8, more preferably 0.9:1.0 to 1.0:0.9, and even more preferably 0.95:1.0 to 1.0:0.95. When the dicarboxylic acid component (A) and the aliphatic diol component (B) each consist of multiple compounds, the molar amount is the arithmetic average of the molar amounts of the multiple compounds.

[0055] [Biodegradable polyester resin composition] The biodegradable polyester resin composition according to an embodiment of the present invention comprises the biodegradable polyester resin and a hydrolysis stabilizer (C). By including the hydrolysis stabilizer (C), the hydrolysis reaction of the biodegradable polyester resin composition is suppressed, making it easier to obtain good durability. The content of the biodegradable polyester resin in the biodegradable polyester resin composition is preferably 35 to 99.8% by mass, more preferably 45 to 99.5% by mass, and even more preferably 50 to 99% by mass, relative to 100% by mass of the total mass of the biodegradable polyester resin composition.

[0056] <Hydrolysis Stabilizer (C)> The hydrolysis stabilizer (C) is not particularly limited as long as it is a component that has the property of preventing hydrolysis, and known hydrolysis stabilizers can be used. Examples of the hydrolysis stabilizer (C) include oxazoline group-containing compounds (oxazoline compounds), epoxy group-containing compounds (epoxy compounds), and carbodiimide group-containing compounds (carbodiimide compounds). Among these, from the viewpoints of hydrolysis resistance and moldability, carbodiimide compounds are preferred as the hydrolysis stabilizer (C).

[0057] Examples of the carbodiimide compound include dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide, di-β-naphthylcarbodiimide, polycarbodiimide, and cyclic carbodiimides. The polycarbodiimide is a compound in which two or more carbodiimide groups are bonded together via a linking group composed of an aliphatic group, an alicyclic group, an aromatic group, or a combination thereof. The cyclic carbodiimide is a compound in which one or more carbodiimide groups are bonded together within the molecular structure to form a ring structure by bonding the first and second nitrogen atoms of the carbodiimide groups together via a linking group composed of an aliphatic group, an alicyclic group, an aromatic group, or a combination thereof. The linking group may have a heteroatom or a substituent. The hydrolysis stabilizer (C) may be used singly or in combination of two or more.

[0058] The content of the hydrolysis stabilizer (C) is preferably 0.15 to 2 parts by mass, more preferably 0.15 to 1.8 parts by mass, even more preferably 0.18 to 1.5 parts by mass, and still more preferably 0.18 to 1.2 parts by mass, per 100 parts by mass of the biodegradable polyester resin, from the viewpoint of easily increasing hydrolysis resistance while maintaining good biodegradability.

[0059] <Other Resins> The biodegradable polyester resin composition according to an embodiment of the present invention may contain a resin other than the biodegradable polyester resin described above, for example, a biomass resin or a biodegradable resin. Examples of such biomass resins or biodegradable resins include polylactic acid (PLA), polycaprolactone (PCL), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), polybutylene adipate terephthalate (PBAT), polyglycolic acid (PGA), polyethylene furanoate (PEF), polyhydroxyalkanoates (PHAs) (e.g., polyhydroxybutyrate valerate (PHBV), 3-hydroxybutyric acid-3-hydroxyhexanoic acid copolymer polyester, etc.), cellulose acetate (CA), starch, and other polysaccharides. The composition may also contain biodegradable polymers such as 3-hydroxybutanoic acid-based polymers and β-methyl-δ-valerolactone-based polymers.

[0060] From the viewpoint of effectively obtaining the effects of the present invention, the content of the other resin in the biodegradable polyester resin composition is preferably less than 50 parts by mass, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less, per 100 parts by mass of the total of the biodegradable polyester resin and the other resin. There is no particular restriction on the lower limit, but it is, for example, 5 parts by mass or more. In other words, the content of the other resin is preferably 5 parts by mass or more and less than 50 parts by mass, per 100 parts by mass of the total of the biodegradable polyester resin and the other resin.

[0061] <Other Additives> As additives other than the hydrolysis stabilizer (C) that can be contained in the biodegradable polyester resin composition according to an embodiment of the present invention (hereinafter referred to as "other additives"), those listed above as other components that can be contained in the biodegradable polyester resin can be used. The content of the additives other than the hydrolysis stabilizer (C) in the biodegradable polyester resin composition can be determined appropriately depending on the desired physical properties of the biodegradable polyester resin composition. From the viewpoint of making it easier for the biodegradable polyester resin composition to exhibit its intended performance, the content is preferably 0.001 to 30 mass%, more preferably 0.005 to 25 mass%, even more preferably 0.007 to 20 mass%, still more preferably 0.01 to 15 mass%, even more preferably 0.01 to 10 mass%, and particularly preferably 0.01 to 5 mass%, relative to 100 mass% of the biodegradable polyester resin composition.

[0062] <Physical Properties of Biodegradable Polyester Resin Composition> The "biodegradability," "elongation at break," and "hydrolysis resistance" of the biodegradable polyester resin composition are the same as those described for the respective physical properties of the biodegradable polyester resin. That is, with regard to the biodegradability of the biodegradable polyester resin composition, when a compost test is conducted with reference to JIS K6954:2008, the weight retention after the test, when the weight of the resin or resin composition is measured before and after the test, is preferably 0 to 85% or less. Furthermore, the elongation at break of the biodegradable polyester resin composition is preferably 200 to 1,000% when high flexibility is required, and, for example, 10 to 100% when high flexibility is not required. Furthermore, the hydrolysis resistance of the biodegradable polyester resin composition, as defined by the molecular weight retention after immersing the biodegradable polyester resin having a predetermined shape in hot water for a predetermined time, is preferably 80 to 100% (after 4 days), and preferably 60 to 100% (after 7 days).

[0063] <Method for Producing Biodegradable Polyester Resin Composition> The method for producing the biodegradable polyester resin composition according to this embodiment is not particularly limited, and it is sufficient to uniformly mix the biodegradable polyester resin, the hydrolysis stabilizer (C), and, if necessary, additives. Examples of mixing methods include melt-kneading using a single-screw extruder, a multi-screw extruder, a Banbury mixer, a heated roll, a Brabender, various kneaders, or the like, or melt-kneading by feeding each component through separate inlets. Pre-blending may also be performed before melt-kneading. Examples of pre-blending methods include using a mixer such as a Henschel mixer, a high-speed mixer, a V-blender, a ribbon blender, a tumbler blender, or a conical blender. The temperature during melt-kneading can be selected arbitrarily, preferably within the range of 130 to 200°C, taking into account the melting point and decomposition temperature of the biodegradable polyester resin.

[0064] [Molded Article] A molded article according to an embodiment of the present invention comprises the biodegradable polyester resin or the biodegradable polyester resin composition. The shape of the molded article may be any molded article that can be produced using the biodegradable polyester resin or the biodegradable polyester resin composition. Examples of molded articles include pellets, films, sheets, plates, pipes, tubes, bottles, fibers, rods, microparticles, particles, and foams. The method for producing the molded article is not particularly limited, and it can be molded by various known methods such as injection molding, blow molding, press molding, extrusion molding, calendar molding, and molding using a 3D printer. When the molded article is a film, its thickness is, for example, 5 to 500 μm, 25 to 300 μm, or 50 to 200 μm.

[0065] [Uses] The biodegradable polyester resin, biodegradable polyester resin composition, and molded articles thereof according to this embodiment can be used in a variety of applications. Examples of uses for the biodegradable polyester resin, biodegradable polyester resin composition, and molded articles thereof include: Food utensils, such as disposable or reusable food bags, food caps, food trays, straws, cutlery, food containers, coffee capsules, and bottles; Stoppers and cap liners for containers for storing food, beverages, medicines, and the like; Food packaging materials, such as electronic component packaging materials, pharmaceutical packaging materials, and food packaging films; Agricultural materials, such as agricultural mulch films and compost bags; Civil engineering and construction materials; Single-layer or multi-layer films and sheets for industrial materials; Daily commodities, such as seedling pots, cosmetic containers, detergent containers, bleach containers, shopping bags, and garbage bags; Laminated films, plates, stretched sheets, sanitary cover stock materials, outdoor leisure products, water-retaining sheets, insulated boxes, cushioning films, and synthetic paper; and Industrial materials, such as: Fibers such as fishing line, fishing nets, vegetation nets, monofilaments, flat yarns, staples, crimped fibers, creased tape, split yarns, ropes, binding materials, composite fibers, woven fabrics, and nonwoven fabrics; adhesives and bonding agents such as solvent-based, hot-melt-based, and heat-stretched types; coating agents such as water-based, solution-based, emulsion-based, and dispersion-based types; medical materials such as surgical thread, sutures, artificial bones, artificial skin, DDS such as microcapsules, and wound dressings; filaments for 3D printers; developing toners; support materials for hydraulic fracturing and agents for preventing water loss during excavation; various vibration-isolating and vibration-damping materials such as vibration-isolating rubber, mats, sheets, cushions, dampers, pads, and mounting rubber; components for home appliances such as televisions, stereos, vacuum cleaners, refrigerators, and housings for mobile phones; automotive interior and exterior parts such as bumper parts, body panels, weatherstrips, grommets, skins for instrument panels, and airbag covers; Various grips for scissors, screwdrivers, toothbrushes, ski poles, etc.; plastic modifiers; etc.

[0066] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0067] [Calculation of Content] Using a nuclear magnetic resonance spectrometer "Avance 600" manufactured by JEOL Ltd., the content of polyester resin was measured at 323 K in trifluoroacetic acid solvent. １ H-NMR was measured, and the content of aliphatic dicarboxylic acid (a1) and its derivatives was calculated according to the following formula (F1): Ratio (mol %) of aliphatic dicarboxylic acid (a1) and its derivatives = (integral value of aliphatic dicarboxylic acid (a1) / number of protons) × 100 / [(integral value of aliphatic dicarboxylic acid (a1) / number of protons) + (integral value of second dicarboxylic acid (a2) / number of protons)] ... formula (F1) Note that in the above formula (F1), the integral value of the aliphatic dicarboxylic acid (a1) and the integral value of the second dicarboxylic acid (a2) (i.e., a dicarboxylic acid different from the aliphatic dicarboxylic acid (a1)) are the integral values ​​of signals in the following ranges. Furthermore, when multiple second dicarboxylic acids (a2) are used, the integral value is the sum of their integral values. When the aliphatic dicarboxylic acid (a1) is 3-methylpentanedioic acid (also known as 3-methylglutaric acid): integral value of the 3H signal of the methyl group from δ 1.1 to 1.2 ppm When the aliphatic dicarboxylic acid (a1) is methylsuccinic acid: integral value of the 3H signal of the methyl group from δ 1.4 to 1.5 ppm When the second dicarboxylic acid (a2) is adipic acid: integral value of the 4H signal of the methylene from δ 2.5 to 2.6 ppm When the second dicarboxylic acid (a2) is terephthalic acid: integral value of the 4H signal of the aromatic ring from δ 8.0 to 8.5 ppm When the second dicarboxylic acid (a2) is succinic acid: integral value of the 4H signal of the methylene from δ 2.8 to 3.0 ppm The content of the second dicarboxylic acid (a2) was also calculated in the same manner as above, except that the second dicarboxylic acid (a2) (when a plurality of second dicarboxylic acids (a2) are used, the sum of their integrated values) was used as the numerator.

[0068] The content of aliphatic diol (b1) was calculated in the same manner as above according to the following formula (F2): Ratio of aliphatic diol (b1) (mol %) = (integral value of aliphatic diol (b1) / number of protons) x 100 / [(integral value of aliphatic diol (b1) / number of protons) + (integral value of second diol (b2) / number of protons)] ... formula (F2) In the above formula (F2), the integral value of the aliphatic diol (b1) and the integral value of the second diol (b2) (i.e., a diol different from the aliphatic diol (b1)) are the integral values ​​of signals in the following ranges: When multiple second diols (b2) are used, the integral value is the sum of their integral values. When the aliphatic diol (b1) is 3-methyl-1,5-pentanediol: integral value of the 3H signal of the methyl group at δ 1.0 to 1.2 ppm When the second diol (b2) is butanediol: integral value of the 4H signal of the methylene at δ 4.5 to 4.7 ppm

[0069] [Measurement of number average molecular weight (Mn) and weight average molecular weight (Mw)] The number average molecular weight (Mn) and weight average molecular weight (Mw) were measured using a size exclusion high performance liquid chromatography system manufactured by Shimadzu Corporation. The measurement conditions were as follows: Column: Two HFIP-based columns "GMHHR-H(S)" manufactured by Tosoh Corporation connected in series Standard sample: Polymethyl methacrylate resin (PMMA) Solvent and mobile phase: 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) Flow rate: 0.35 mL / min Temperature: 40°C Sample solution concentration: 0.1 wt% (filtered through a filter with an opening diameter of 0.45 μm) Injection volume: 10 μL Detector: LC-20AD (RI detector)

[0070] [Measurement of Solution Intrinsic Viscosity (IV)] (Measurement Method) 0.200 g of polyester resin was dissolved in 20 mL of a 50 / 50 mass% phenol / 1,1,2,2-tetrachloroethane solution (hereinafter simply referred to as "solvent") (hereinafter referred to as "sample solution"). 10 mL of the solvent was weighed into a dilution-type Ubbelohde viscometer IC manufactured by Asahi Seisakusho Co., Ltd. using a volumetric pipette, and the viscometer was immersed in a 30°C water bath. The time until the solvent level naturally dropped from the upper marked line to the lower marked line was measured (t0). After measuring t0, the instrument was dried, and 10 mL of the sample solution was similarly weighed into a viscosity tube and measured (t1). After measuring t1, 10 mL of solvent was added to the viscometer, and measurement was performed in the same manner (t2). After measuring t2, another 10 mL of solvent was added to the viscometer, and measurement was performed in the same manner (t3). (Calculation Method) η was calculated according to the following formulas (F3) and (F4). ｓｐｘ (x = 1, 2, 3) was calculated. ｒｘ =tx / t0...Formula (F3) η ｓｐｘ =η ｒｘ -1...Equation (F4) For x = 1, 2, 3, the horizontal axis represents the sample solution concentration Co ｘ (g / dL), and the vertical axis shows η at each concentration. ｓｐｘ was plotted, and the intercept with the vertical axis was taken as the intrinsic viscosity (IV) of the solution.

[0071] [Preparation of Pressed Films] The polyester resins or resin compositions of the Examples and Comparative Examples were press-molded at 180 to 190° C. for 60 seconds to prepare pressed films with a thickness of 120 to 150 μm. The thickness of each pressed film was measured with a micrometer.

[0072] [Evaluation of Compostability] The compostability of the polyester resins and resin compositions of the Examples and Comparative Examples was evaluated by conducting tests in the same manner as in JIS K6954: 2008, except that a test cup (external dimensions: φ96 × 110 mm, material: PP) was used. Simulated compost (synthetic solid waste) was prepared with the composition shown in Table 1 below.

[0073]

[0074] Test pieces were prepared by cutting 15 mm x 15 mm from the press film. 90 g of simulated compost was weighed into a cup, and one test piece was buried in the center of the simulated compost both horizontally and in the depth direction. The cup was then capped. The cup was placed in a thermostatic chamber at 58°C. The cup was periodically removed and water was added to the initial weight until the end of the test after 30 days, and the compost was stirred. At the end of the test, the compost was sieved through 4.75 mm and 2.0 mm sieves. The test pieces were collected from the residue, dried, and weighed. The weight before the test was calculated as 100. A weight retention of 30% or less was designated "A," a weight retention of 30-85% was designated "B," and a weight retention of 85% or more was designated "C." For reference, photographs of the appearance of the polyester resins of Example 2 and Comparative Example 1 after the compostability evaluation are shown in Figure 1 (Example 2) and Figure 2 (Comparative Example 1).

[0075] [Evaluation of Hydrolysis Resistance] The film prepared by the method described in the "Preparation of Pressed Film" section above was cut into 20 mm x 60 mm strips and immersed in hot water at 80°C and allowed to stand. After 7 days, the film was removed, a portion cut out, and dried in a dryer at 40°C and 1.3 Pa for 20 hours. The weight-average molecular weight was then measured according to the method described above. The molecular weight retention rate was calculated relative to the weight-average molecular weight before testing, which was defined as 100. A molecular weight retention rate of 71% or more was assigned an "A," a molecular weight retention rate of 61 to 70% was assigned a "B," and a molecular weight retention rate of 60% or less was assigned a "C." For reference, photographs of the appearance of the polyester resins of Example 5 and Comparative Example 1 after 14 days of hydrolysis resistance evaluation are shown in Figure 3 (Example 5) and Figure 4 (Comparative Example 1).

[0076] [Overall evaluation of biodegradability and hydrolysis resistance] When the evaluation of biodegradability and the evaluation of hydrolysis resistance were "A" and "A," "A" and "B," or "B" and "A," it was determined that the balance between the two was good. When either evaluation was "C," or when both evaluations were "B," it was determined that the balance between these performances was not good.

[0077] [Evaluation of Mechanical Properties] The films prepared by the method described in the above "Preparation of Press Film" section were cut into 10 mm wide dumbbell shapes and conditioned for one week in a storage environment of 23°C and 50% RH. After that, the breaking elongation was measured using an autograph (AG-5000B manufactured by Shimadzu Corporation) (load cell 1 kN, tensile speed 500 mm / min (Examples 4, 5, 6, Comparative Example 3), tensile speed 5 mm / min (Examples 1 to 3, 7, Comparative Examples 1 and 2), chuck distance 70 mm). The breaking elongation values ​​shown in Table 3 below were the average of three measurements.

[0078] [Example 1] 5.6 parts by mass of 3-methylpentanedioic anhydride as the aliphatic dicarboxylic acid (a1), 46.7 parts by mass of succinic acid as the second dicarboxylic acid (a2)-1, 47.6 parts by mass of 1,4-butanediol as the aliphatic diol component (B), and 0.06 parts by mass of tetrabutoxytitanium as the catalyst were prepared and charged into a reactor. Next, the mixture was heated to 190°C under normal pressure in a nitrogen atmosphere, and an esterification reaction was carried out while distilling off the water produced outside the system. When the amount of water distilled off decreased, the pressure was reduced to 0.15 mmHg using a vacuum pump, and the reaction was carried out at 200°C. Stirring was terminated when the torque reached 90 mA when stirring at 230°C and 180 rpm. The molten resin was then removed with a metal spatula and allowed to cool to obtain polyester resin "PES-1."

[0079] [Example 2] A reaction was carried out in the same manner as in Example 1, except that the amounts of 3-methylpentanedioic anhydride, succinic acid, and 1,4-butanediol were changed to 11.2 parts by mass, 41.3 parts by mass, and 47.4 parts by mass, respectively, to obtain a polyester resin "PES-2."

[0080] [Example 3] A reaction was carried out in the same manner as in Example 1, except that the amounts of 3-methylpentanedioic anhydride, succinic acid, and 1,4-butanediol were changed to 2.8 parts by mass, 49.4 parts by mass, and 47.7 parts by mass, respectively, to obtain a polyester resin "PES-3."

[0081] Example 4 A polyester resin "PES-4" was obtained by carrying out a reaction in the same manner as in Example 1, except that 29.2 parts by mass of 3-methylpentanedioic anhydride was used as the aliphatic dicarboxylic acid (a1), 29.5 parts by mass of dimethyl terephthalate was used as the second dicarboxylic acid (a2)-1, and 41.3 parts by mass of 1,4-butanediol was used.

[0082] Example 5 A polyester resin "PES-5" was obtained by carrying out a reaction in the same manner as in Example 1, except that 34.9 parts by mass of 3-methylpentanedioic anhydride was used as the aliphatic dicarboxylic acid (a1), 22.7 parts by mass of dimethyl terephthalate was used as the second dicarboxylic acid (a2)-1, and 42.4 parts by mass of 1,4-butanediol was used.

[0083] Example 6 A polyester resin "PES-6" was obtained by carrying out a reaction in the same manner as in Example 1, except that 11.5 parts by mass of methylsuccinic acid was used as the aliphatic dicarboxylic acid (a1), 41.2 parts by mass of succinic acid was used as the second dicarboxylic acid (a2)-1, and 47.2 parts by mass of 1,4-butanediol was used.

[0084] Example 7 100 parts by mass of the above PES-2 and 0.2 parts by mass of Carbodilite HMV-5CA-LC (trade name) manufactured by Nisshinbo Chemical Inc. were filled into a Laboplastomill (registered trademark) manufactured by Toyo Seiki Seisaku-sho, Ltd. for 3 minutes, and the resin was kneaded at 190°C for 5 minutes. The molten material was then cooled and solidified to obtain a resin composition.

[0085] Example 8 100 parts by mass of the above PES-4 and 0.2 parts by mass of Carbodilite HMV-5CA-LC (trade name) manufactured by Nisshinbo Chemical Inc. were kneaded and solidified in the same manner as in Example 7 to obtain a resin composition.

[0086] Comparative Example 1 A polyester resin "PES-7" was obtained by carrying out a reaction in the same manner as in Example 1, except that the aliphatic dicarboxylic acid (a1) was not used and 52.1 parts by mass of succinic acid and 47.8 parts by mass of 1,4-butanediol were used as the second dicarboxylic acid (a2)-1.

[0087] Comparative Example 2 A polyester resin "PES-8" was obtained by carrying out a reaction in the same manner as in Example 1, except that no aliphatic dicarboxylic acid (a1) was used, and 40.7 parts by mass of succinic acid was used as the second dicarboxylic acid (a2)-1, and 12.6 parts by mass of adipic acid and 46.7 parts by mass of 1,4-butanediol were used as the second dicarboxylic acid (a2)-2.

[0088] Comparative Example 3 A polyester resin "PES-9" was obtained by carrying out a reaction in the same manner as in Example 1, except that no aliphatic dicarboxylic acid (a1) was used, and 34.8 parts by mass of terephthalic acid was used as the second dicarboxylic acid (a2)-1, and 26.2 parts by mass of adipic acid and 38.9 parts by mass of 1,4-butanediol were used as the second dicarboxylic acid (a2)-2.

[0089] Comparative Example 4 100 parts by mass of PES-7 and 1 part by mass of Carbodilite HMV-5CA-LC (trade name) manufactured by Nisshinbo Chemical Inc. were kneaded and solidified in the same manner as in Example 7 to obtain a resin composition.

[0090] Comparative Example 5 100 parts by mass of PES-9 and 1 part by mass of Carbodilite HMV-5CA-LC (trade name) manufactured by Nisshinbo Chemical Inc. were kneaded and solidified in the same manner as in Example 7 to obtain a resin composition.

[0091] [Example A1] A polyester resin "PES-10" was obtained by carrying out a reaction in the same manner as in Example 1, except that no aliphatic dicarboxylic acid (a1) was used, 33.9 parts by mass of dimethyl terephthalate was used as the second dicarboxylic acid (a2)-1, 25.5 parts by mass of adipic acid was used as the second dicarboxylic acid (a2)-2, 12.4 parts by mass of 3-methyl-1,5-pentanediol was used as the aliphatic diol (b1), and 28.2 parts by mass of 1,4-butanediol was used as the second diol (b2).

[0092] [Example A2] A polyester resin "PES-11" was obtained by carrying out a reaction in the same manner as in Example 1, except that no aliphatic dicarboxylic acid (a1) was used, 33.2 parts by mass of dimethyl terephthalate was used as the second dicarboxylic acid (a2)-1, 25.0 parts by mass of adipic acid was used as the second dicarboxylic acid (a2)-2, 20.2 parts by mass of 3-methyl-1,5-pentanediol was used as the aliphatic diol (b1), and 21.6 parts by mass of 1,4-butanediol was used as the second diol (b2).

[0093] [Example A3] A polyester resin "PES-12" was obtained by carrying out a reaction in the same manner as in Example 1, except that 11.2 parts by mass of 3-methylpentanedioic anhydride was used as the aliphatic dicarboxylic acid (a1)-1, 0.06 parts by mass of methylsuccinic acid was used as the aliphatic dicarboxylic acid (a1)-2, 41.3 parts by mass of succinic acid was used as the second dicarboxylic acid (a2), and 47.4 parts by mass of 1,4-butanediol was used as the second diol (b2).

[0094] Example A4 100 parts by mass of the above PES-10 and 0.6 parts by mass of Carbodilite HMV-5CA-LC (trade name) manufactured by Nisshinbo Chemical Inc. were kneaded and solidified in the same manner as in Example 7 to obtain a resin composition.

[0095]

[0096]

[0097] As shown in Tables 2 and 3, the polyester resins of Examples 1 to 6 and A1 to A3, and the resin compositions of Examples 7 to 8 and A4, exhibited good hydrolysis resistance and compostability. On the other hand, as shown in Comparative Example 1, PES-7, a polybutylene succinate, exhibited insufficient compostability. Furthermore, as shown in Comparative Example 2, PES-8, a polybutylene succinate containing a structure derived from adipic acid, exhibited good compostability but poor hydrolysis resistance. Furthermore, as shown in Comparative Example 3, PES-9, a polybutylene terephthalate adipate, exhibited poor compostability and hydrolysis resistance. Furthermore, as shown in Comparative Examples 4 and 5, resin compositions using PES-7 or PES-9 in combination with carbodilite exhibited insufficient compostability.

[0098] The present invention provides a biodegradable polyester resin, a biodegradable polyester resin composition, and a molded article thereof, which have excellent biodegradability and hydrolysis resistance. The biodegradable polyester resin, the biodegradable polyester resin composition, and a molded article thereof are useful for applications such as agricultural mulch films, compost bags, food packaging films, and disposable cutlery.

Claims

1. A biodegradable polyester resin comprising structural units derived from a dicarboxylic acid component (A) and structural units derived from an aliphatic diol component (B), The dicarboxylic acid component (A) includes a first dicarboxylic acid component (A1) which is selected from the group consisting of aliphatic dicarboxylic acids (a1) represented by the following formula (I) and their derivatives, The aliphatic diol component (B) includes a diol with 4 or fewer carbon atoms. A biodegradable polyester resin with a number-average molecular weight of 5,000 to 50,000. 【Chemistry 1】 [In formula (I), R １ R2 independently represents a divalent hydrocarbon group having 1 to 3 carbon atoms, R3 represents a monovalent hydrocarbon group having 1 to 3 carbon atoms, R4 represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 3 carbon atoms, and m and n independently represent 0 or 1.

2. The dicarboxylic acid component (A) comprises the first dicarboxylic acid component (A1) and a second dicarboxylic acid component (A2) which is a compound selected from the group consisting of a second dicarboxylic acid (a2) and its derivatives, which is different from the aliphatic dicarboxylic acid (a1). A biodegradable polyester resin according to claim 1, satisfying either condition (i) or (ii) below. Condition (i): The number of carbon atoms in the dicarboxylic acid contained in the second dicarboxylic acid component (A2) and the number of carbon atoms in the aliphatic diol contained in the aliphatic diol component (B) are both 4 or less. Condition (ii): The second dicarboxylic acid component (A2) contains an aromatic dicarboxylic acid.

3. The biodegradable polyester resin according to claim 2, wherein the second dicarboxylic acid component (A2) comprises an aromatic dicarboxylic acid.

4. A biodegradable polyester resin comprising structural units derived from a dicarboxylic acid component (A) and structural units derived from an aliphatic diol component (B), The aliphatic diol component (B) includes a first aliphatic diol component (B1) which consists of at least one compound selected from aliphatic diols (b1) represented by the following formula (II). The aliphatic diol component (B) includes a second diol component (B2) having four or fewer carbon atoms. A biodegradable polyester resin in which the dicarboxylic acid component (A) contains an aromatic dicarboxylic acid. 【Chemistry 2】 [In formula (II), R5 and R6 each independently represent a divalent hydrocarbon group having 1 to 3 carbon atoms, R7 represents a monovalent hydrocarbon group having 1 to 3 carbon atoms, R8 represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 3 carbon atoms, and x and y each independently represent 0 or 1.]

5. The biodegradable polyester resin according to claim 1 or 4, wherein the content of the aliphatic dicarboxylic acid (a1) in the dicarboxylic acid component (A) is 2 to 60 mol%.

6. R in equation (I) １ , R ２ The biodegradable polyester resin according to claim 1 or 4, wherein all of them are methylene groups.

7. R in equation (I) ３ is a methyl group, R ４ The biodegradable polyester resin according to claim 1 or 4, wherein is a hydrogen atom.

8. The biodegradable polyester resin according to claim 1 or 4, wherein the content of the first aliphatic diol component (B1) in the aliphatic diol component (B) is 2 to 50 mol%.

9. R in equation (II) ５ and R ６ The biodegradable polyester resin according to claim 1 or 4, wherein the group is a methylene group.

10. R in formula (II) ７ is a methyl group, and R ８ is a hydrogen atom, the biodegradable polyester resin according to claim 1 or 4.

11. The biodegradable polyester resin according to claim 1 or 4, wherein the dicarboxylic acid component (A) does not contain an aliphatic dicarboxylic acid (a2X) having a branched and hydroxyl group-containing alkylene group, or the content of the aliphatic dicarboxylic acid (a2X) in the dicarboxylic acid component (A) is greater than 0 mol% and 3 mol% or less.

12. The aforementioned dicarboxylic acid component (A) The first dicarboxylic acid component (A1) and, A second dicarboxylic acid component (A2) is a compound selected from the group consisting of a second dicarboxylic acid (a2) and derivatives thereof, which is different from the aliphatic dicarboxylic acid (a1), The biodegradable polyester resin according to claim 1 or 4, comprising a third dicarboxylic acid component (A3) selected from the group consisting of a third dicarboxylic acid (a3) ​​and derivatives thereof, which is different from the aliphatic dicarboxylic acid (a1) and the second dicarboxylic acid (a2).

13. The biodegradable polyester resin according to claim 12, wherein the third dicarboxylic acid (a3) ​​is methyl succinic acid.

14. A biodegradable polyester resin composition comprising the biodegradable polyester resin according to claim 1 or 4 and a hydrolysis-resistant agent (C).

15. The biodegradable polyester resin composition according to claim 14, wherein the hydrolysis-resistant agent (C) is a carbodiimide compound.

16. The biodegradable polyester resin composition according to claim 14, wherein the content of the hydrolysis-resistant agent (C) is 0.15 to 2 parts by mass per 100 parts by mass of the biodegradable polyester resin.

17. A molded article comprising the biodegradable polyester resin described in claim 1 or 4.

18. A film comprising the biodegradable polyester resin described in claim 1 or 4.

19. A sheet comprising the biodegradable polyester resin described in claim 1 or 4.

20. A food utensil comprising the biodegradable polyester resin described in Claim 1 or 4.

21. A plastic modifier comprising the biodegradable polyester resin described in claim 1 or 4.

22. A coating agent comprising the biodegradable polyester resin described in claim 1 or 4.

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