Aliphatic polyester, resin composition, molded object, method for producing aliphatic polyester, block copolymer, resin composition, and molded object

Abstract

The present invention relates to: an aliphatic polyester that contains a structural unit (a1) derived from an aliphatic diol which has an alkyl group as a branch chain and in which the number of main-chain carbon atoms is 3 or larger and a structural unit (a2) derived from an aliphatic dicarboxylic acid and that satisfies specific requirements; a resin composition including the aliphatic polyester and a molded object thereof; a method for producing an aliphatic polyester satisfying specific structures and requirements; a block copolymer satisfying specific structures and requirements; a resin composition containing the block copolymer and a molded object thereof; and a method for producing a block copolymer satisfying specific structures and requirements. (The specific structures and the requirements are as described in the specification.)

Description

Aliphatic polyester, resin composition, molded article, method for producing aliphatic polyester, block copolymer, resin composition, and molded article

[0001] The present invention relates to an aliphatic polyester, a resin composition, a molded article, a method for producing an aliphatic polyester, a block copolymer, a resin composition, and a molded article.

[0002] Patent Documents 1 to 4 disclose block copolymers containing aliphatic polyesters or blocks derived from aliphatic polyesters.

[0003] Specifically, Patent Document 1 describes a method for producing a polyester in which an aliphatic dicarboxylic acid and / or an aliphatic dicarboxylic acid anhydride is reacted with a diol compound and / or a cyclic ether compound under specific conditions to obtain a low-molecular-weight polyester, and the obtained low-molecular-weight polyester is heated under reduced pressure to increase the molecular weight (claim 1).

[0004] Patent Document 2 discloses a polyester resin that is a block copolymer mainly composed of polylactic acid units and polyester units and is characterized by being a stereocomplex (Claim 1). From the viewpoint of achieving both the heat resistance and mechanical properties of polylactic acid (paragraph

[0008] ), the document discloses that, in the examples, soft segments with theoretical molecular weights of 10,000 (10k) to 22,000 (22k) (Table 1) are used as soft segments used in stereocomplexing polylactic acid and copolymerizing with polylactic acid.

[0005] Patent Document 3 discloses a block copolymer having a specific polylactic acid segment and a polyester segment other than the polylactic acid segment as a resin for toner (Claim 1) for the purpose of providing a toner having excellent low-temperature fixing ability and heat-resistant storage stability (paragraph

[0003] ). Patent Document 3 also discloses that the polyester constituting the polyester segment is obtained by reacting a polyhydric alcohol component with a polycarboxylic acid component such as a polycarboxylic acid, a polycarboxylic acid anhydride, or a polycarboxylic acid ester (paragraphs

[0016] and

[0021] ).

[0006] Patent Document 4 relates to a method for producing a low-branched, high-molecular-weight aliphatic polyester, and describes using a twin-screw continuous polymerization reactor to perform an esterification reaction in a first step followed by a polycondensation reaction (deglycolization reaction) at a reaction temperature of 220 to 250°C in a second step to increase the molecular weight (claim 2 and paragraph

[0043] ).

[0007] JP 2004-300200 A JP 2011-153275 A JP 2015-169881 A JP 2006-274253 A

[0008] The technology described in Patent Document 1 explains that a high molecular weight is achieved for an aliphatic polyester resin by satisfying specific manufacturing conditions. However, Patent Document 1 does not specifically disclose whether a high molecular weight can be achieved when an aliphatic diol having an alkyl group as a branched chain is used. Furthermore, the number average molecular weight is not confirmed.

[0009] Although Patent Document 2 describes copolymerization of polylactic acid (paragraph

[0012] ), it does not describe increasing the molecular weight of the soft segment used in copolymerization of polylactic acid. Furthermore, since Patent Document 2 describes that the molecular weight of the aliphatic polyester (the soft segment) used in the examples is at most 22,000, the technology described in Patent Document 2 does not teach or suggest further increasing the molecular weight of the aliphatic polyester.

[0010] Patent Document 3 merely introduces a polyester segment into a toner resin from the viewpoint of the toner's low-temperature fixability and heat-resistant storage stability, and merely discloses that the polyester constituting such a polyester segment is obtained by a known method. Patent Document 3 also cites the necessity of obtaining a block copolymer by ring-opening polymerization of lactide because the molecular weight is limited when amorphous polylactic acid is obtained by dehydration condensation of lactic acid (paragraph

[0010] ). Therefore, it can be said that the technology described in Patent Document 4 is sufficient with a molecular weight obtained by ring-opening polymerization of lactide. Therefore, the technology described in Patent Document 3 does not require further increase in molecular weight of the polyester constituting the polyester segment. Furthermore, Patent Document 3 explains that using a branched saturated aliphatic diol as a raw material for the polyester segment is undesirable because it may reduce the crystallinity of the aliphatic crystalline polyester and lower the melting point (paragraph

[0017] ).

[0011] Furthermore, the technology described in Patent Document 4 was developed in consideration of the problem that using a coupling agent (chain extender) that is a diisocyanate to increase the molecular weight makes the manufacturing process complicated (paragraph

[0005] ). Therefore, Patent Document 4 proposes a technology that is different from the technology that uses a coupling agent (chain extender). Therefore, it cannot be said that the technology proposed in Patent Document 4 is one in which sufficient consideration has been given to the technology that uses a coupling agent (chain extender).

[0012] Incidentally, if further molecular weight increase could be achieved in relation to the aliphatic polyester resins described above, it is expected that further modification of resins such as polylactic acid could be realized, more specifically, that impact resistance derived from soft segments could be imparted. However, it is not easy to provide an alternative technology different from the technology described in Patent Document 4. For example, even with the technology using a coupling agent (chain extender), as taught in Patent Document 4, there is a possibility of side reactions occurring, so it is not possible to provide an alternative technology simply by trial and error. Furthermore, in the past, there has been a tendency for increasing the molecular weight of an aliphatic polyester and increasing the proportion of OH terminal groups in the aliphatic polyester to be in a trade-off relationship, making it difficult to obtain an aliphatic polyester with a high proportion of OH terminal groups and a high molecular weight.

[0013] Therefore, a first object of the present invention has been made in view of the above-mentioned problems, and is to provide an aliphatic polyester having a high proportion of OH terminal groups and a high molecular weight, a method for producing the same, and a resin composition containing the aliphatic polyester and a molded article thereof.

[0014] A second object of the present invention is to provide a block copolymer having properties derived from a high-molecular-weight aliphatic polyester with a high proportion of OH terminal groups, as well as a resin composition containing such a block copolymer and a molded article thereof. The properties derived from a high-molecular-weight aliphatic polyester with a high proportion of OH terminal groups refer specifically to the ability to provide a resin composition and a molded article thereof that are imparted with impact resistance while suppressing a decrease in the heat resistance of any polyester resin (excluding the aliphatic polyester and the block copolymer) by adding the aliphatic polyester or the block copolymer to the polyester resin.

[0015] To solve the above-mentioned problems, the present inventors conducted extensive research into the relationship between the OH terminal group proportion and number average molecular weight of aliphatic polyesters. As a result, they discovered that by satisfying certain conditions, it is possible to provide an aliphatic polyester with a high OH terminal group proportion and a high molecular weight, and a method for producing the same, thereby arriving at the present invention. Furthermore, by providing an aliphatic polyester with a high OH terminal group proportion and a high molecular weight, and a method for producing the same, it is possible to provide a resin composition containing the aliphatic polyester and a molded article thereof. Furthermore, it is possible to provide a block copolymer having a block derived from the aliphatic polyester, a resin composition containing the block copolymer, and a molded article thereof.

[0016] That is, the present invention provides the following: [1] An aliphatic polyester containing a structural unit (a1) derived from an aliphatic diol having 3 or more carbon atoms in its main chain and having an alkyl group as a branched chain, and a structural unit (a2) derived from an aliphatic dicarboxylic acid, which satisfies the following three conditions: Condition 1 (PE), Condition 2 (PE), and Condition 3 (PE). Condition 1 (PE): α(PE) and β(PE) below satisfy the following relational formula (I): α(PE) / (150-β(PE))≧500 (I) (In the relational formula (I), α(PE) is the number average molecular weight of the aliphatic polyester, and β(PE) is the OH terminal group proportion [mol %] of the aliphatic polyester, which indicates the proportion (percentage) of the number of OH terminal groups when the total number of terminal groups of the aliphatic polyester is 100 mol %).) Condition 2 (PE): In the aliphatic polyester, the sum (M(a)) of the average formula weight (M(a1)) of the structural unit (a1) portion and the average formula weight (M(a2)) of the structural unit (a2) portion is in the range of 25,000 to 75,000. Condition 3 (PE): β(PE)≧25 [2] The aliphatic polyester according to [1] above, wherein the aliphatic diol has a main chain carbon number of 3 or more and 10 or less. [3] The aliphatic polyester according to [1] or [2] above, wherein the branched chain in the aliphatic diol is a methyl group. [4] The aliphatic polyester according to any one of [1] to [3] above, wherein the aliphatic dicarboxylic acid has 4 to 12 carbon atoms. [5] A resin composition containing the aliphatic polyester according to any one of [1] to [4] above. [6] The resin composition according to [5] above, further containing a polyester resin (D) different from the aliphatic polyester. [7] A molded product of the resin composition according to [5] or [6] above.

[0017] [8] A method for producing an aliphatic polyester, comprising reacting a first aliphatic polyester containing a structural unit (a1) derived from an aliphatic diol having 3 or more carbon atoms in its main chain and having an alkyl group as a branched chain, and a structural unit (a2) derived from a first aliphatic dicarboxylic acid, with at least one member selected from the group consisting of a second aliphatic dicarboxylic acid (z1), an aliphatic dicarboxylic acid alkyl ester (z2), and an aliphatic dicarboxylic acid anhydride (z3), to produce a second aliphatic polyester satisfying the following three conditions: Condition 1 (PE2), Condition 2 (PE2), and Condition 3 (PE2): Condition 1 (PE2): α(PE2) and β(PE2) below satisfy the following relational formula (II): α(PE2) / (150-β(PE2))≧500 (II) (In the relational formula (II), α(PE2) is the number average molecular weight of the second aliphatic polyester, and β(PE2) is the OH terminal group proportion [mol %] of the second aliphatic polyester, which indicates the proportion (percentage) of the number of OH terminal groups when the total number of terminal groups of the aliphatic polyester is 100 mol %).) Condition 2 (PE2): In the second aliphatic polyester, the sum (M(a)) of the average formula weight (M(a1)) of the structural unit (a1) portion and the average formula weight (M(a2)) of the structural unit (a2) portion is 25,000 to 75,000. Condition 3 (PE2): β(PE2)≧25 [9] A method for producing an aliphatic polyester according to the above item [8], comprising: a first step of producing a first aliphatic polyester by reacting an aliphatic diol having 3 or more carbon atoms in its main chain and having an alkyl group as a branched chain with a first aliphatic dicarboxylic acid; and a second step of reacting the first aliphatic polyester with at least one selected from the group consisting of a second aliphatic dicarboxylic acid (z1), an aliphatic dicarboxylic acid alkyl ester (z2), and an aliphatic dicarboxylic acid anhydride (z3).

[0018]

[10] A block copolymer having a first block (A) derived from an aliphatic polyester containing structural units (a1) derived from an aliphatic diol having 3 or more carbon atoms in its main chain and having an alkyl group as a branched chain and structural units (a2) derived from an aliphatic dicarboxylic acid, and a second block (B) derived from a polylactic acid containing structural units derived from lactic acid, the block copolymer satisfying the following three conditions: Condition 1 (BCP), Condition 2 (BCP), and Condition 3 (BCP): Condition 1 (BCP): α(BCP) and β(BCP) below satisfy the following relational formula (III): α(BCP) / (150-β(BCP))≧575 (III) (In the relational formula (III), α(BCP) is the number average molecular weight of the block copolymer, and β(BCP) is the OH terminal group proportion [mol %] of the block copolymer, which indicates the proportion (percentage) of the number of OH terminal groups when the total number of terminal groups of the block copolymer is 100 mol %). Condition 2 (BCP): In the block copolymer, the sum (M(a)) of the average formula weight (M(a1)) of the structural unit (a1) portion and the average formula weight (M(a2)) of the structural unit (a2) portion is in the range of 25,000 to 75,000. Condition 3 (BCP): β(BCP)≧25

[11] The block copolymer according to item

[10] , wherein the aliphatic diol has a main chain carbon number of 3 or more and 10 or less.

[12] The block copolymer according to

[10] or

[11] above, wherein the branched chain in the aliphatic diol is a methyl group.

[13] The block copolymer according to any one of

[10] to

[12] above, wherein the aliphatic dicarboxylic acid has 4 to 12 carbon atoms.

[14] The block copolymer according to any one of

[10] to

[13] above, wherein the number average molecular weight of the block copolymer is 28,750 to 400,000.

[15] The block copolymer according to any one of

[10] to

[14] above, wherein the content of the block (B) is 5 to 95 mass% when the total of the block (A) and the block (B) is 100 mass%.

[16] A resin composition containing the block copolymer according to any one of

[10] to

[15] above.

[17] The resin composition according to

[16] above, further containing a polyester resin (D).

[18] A molded article of the resin composition according to

[16] or

[17] .

[0019]

[19] A method for producing a block copolymer having a first block (A) derived from an aliphatic polyester containing structural units (a1) derived from an aliphatic diol having 3 or more carbon atoms in its main chain and having an alkyl group as a branched chain and structural units (a2) derived from an aliphatic dicarboxylic acid, and a second block (B) derived from polylactic acid containing structural units derived from lactic acid, and which satisfies the following three conditions 1 (BCP), 2 (BCP), and 3 (BCP): Condition 1 (BCP): The following α(BCP) and β(BCP) satisfy the following relational formula (III): α(BCP) / (150-β(BCP))≧575 (III) (In the relational formula (III), α(BCP) is the number average molecular weight of the block copolymer, and β(BCP) is the OH terminal group proportion [mol %] of the block copolymer, which indicates the proportion (percentage) of the number of OH terminal groups when the total number of terminal groups of the block copolymer is 100 mol %). Condition 2 (BCP): In the block copolymer, the sum (M(a)) of the average formula weight (M(a1)) of the structural unit (a1) portion and the average formula weight (M(a2)) of the structural unit (a2) portion is in the range of 25,000 to 75,000. Condition 3 (BCP): β(BCP)≧25

[0020] According to one aspect of the present invention, there are provided an aliphatic polyester having a high proportion of OH terminal groups and a high molecular weight, a method for producing the same, a resin composition containing the aliphatic polyester, and a molded article thereof. Furthermore, according to another aspect of the present invention, there are provided a block copolymer having properties derived from the aliphatic polyester having a high proportion of OH terminal groups and a high molecular weight, and a resin composition containing the block copolymer, and a molded article thereof. The properties derived from the aliphatic polyester having a high proportion of OH terminal groups and a high molecular weight, more specifically, refer to the properties that can be obtained by adding the aliphatic polyester or the block copolymer to any polyester resin (excluding the aliphatic polyester and the block copolymer) to provide a resin composition and a molded article thereof that are imparted with impact resistance while suppressing a decrease in the heat resistance of the polyester resin.

[0021] FIG. 1 is a graph schematically showing the relationship between the total formula weight α(PE) of an aliphatic polyester and the OH terminal group proportion β(PE).

[0022] The following describes an embodiment of the present invention. However, the embodiment described below is merely an example for embodying the technical concept of the present invention, and the present invention is not limited to the following description. In this specification, preferred embodiments are shown, but 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, when a numerical range is described as "XX to YY," it means "XX or more and YY or less." Furthermore, in this specification, the "main chain" of a polymer means the longest molecular chain in the polymer molecule, unless otherwise specified.

[0023] [Aliphatic Polyester] The aliphatic polyester according to an embodiment of the present invention is an aliphatic polyester containing a structural unit (a1) derived from an aliphatic diol having three or more carbon atoms in its main chain and having an alkyl group as a branched chain, and a structural unit (a2) derived from an aliphatic dicarboxylic acid, and satisfies the following three conditions: Condition 1 (PE), Condition 2 (PE), and Condition 3 (PE). In this specification, the aliphatic polyester is also referred to as "PE." In this specification, the term "OH terminal group" refers to a hydroxyl group at the end of the molecular chain of the molecular structure of the polymer, preferably at the end of the main chain of the polymer. In this specification, the term "COOH terminal group" refers to a carboxyl group at the end of the molecular chain of the molecular structure of the polymer, preferably at the end of the main chain of the polymer. In this specification, the term "terminal group" (when used as the term "terminal group" or "total terminal groups" rather than the terms "OH terminal group" or "COOH terminal group") refers to both the functional group in the polymer, determined as the acid value measured by the method described in the Examples, and the OH terminal groups. In one aspect of the present invention, the functional group determined as the acid value measured by the method described in the Examples is preferably a COOH terminal group. Furthermore, in this specification, unless otherwise specified, the explanation "the effect of being able to impart impact resistance while suppressing a decrease in heat resistance of any polyester resin" specifically refers to the effect of being able to impart impact resistance while suppressing a decrease in heat resistance of the resulting resin composition by adding an aliphatic polyester (PE) which is one embodiment of the present invention or a block copolymer (BCP) which is another embodiment of the present invention described below to any polyester resin. Furthermore, the arbitrary polyester resin refers to a resin other than an aliphatic polyester (PE) and a block copolymer (BCP).

[0024] Condition 1 (PE): The following α(PE) and β(PE) satisfy the following relational formula (I): α(PE) / (150-β(PE))≧500 (I) (In the relational formula (I), α(PE) is the number average molecular weight of the aliphatic polyester, and β(PE) is the OH terminal group proportion [mol %] of the aliphatic polyester, which indicates the proportion (percentage) of the number of OH terminal groups when the total number of terminal groups of the aliphatic polyester is 100 mol %). Condition 2 (PE): In the aliphatic polyester, the sum (M(a)) of the average formula weight (M(a1)) of the structural unit (a1) portion and the average formula weight (M(a2)) of the structural unit (a2) portion is in the range of 25,000 to 75,000. Condition 3 (PE): β(PE)≧25

[0025] A value of 500 or more in the relational formula (I) indicates that the aliphatic polyester tends to have a relatively high proportion of OH terminal groups [mol %] relative to the size of its number-average molecular weight α(PE). Generally, when attempting to increase the number-average molecular weight of the polymer obtained in a polymerization reaction, the possibility of side reactions also increases, resulting in a decrease in the proportion of OH terminal groups in the obtained polymer, and the value of the relational formula (I) tends to be less than 500. In contrast, the aliphatic polyester according to this embodiment has a high molecular weight while maintaining a high proportion of OH terminal groups. Such an aliphatic polyester can be produced, for example, by the method for producing an aliphatic polyester described below.

[0026] According to this embodiment, an aliphatic polyester having a high OH terminal group proportion and a high molecular weight can be provided, which is expected to result in excellent properties when a block copolymer is produced, particularly contributing to the production of a high-molecular-weight block copolymer. Furthermore, the aliphatic polyester according to this embodiment contributes to the production of a high-molecular-weight block copolymer, thereby improving the heat resistance of the block copolymer. Furthermore, the aliphatic polyester according to this embodiment forms soft blocks in the block copolymer, which can impart, for example, impact resistance. Furthermore, according to this embodiment, an aliphatic polyester having a high OH terminal group proportion and a high molecular weight can be provided, so that when a resin composition containing any polyester resin is prepared, the properties of the aliphatic polyester according to this embodiment can be imparted, such as heat resistance and impact resistance. More specifically, impact resistance can be imparted to any polyester resin while suppressing a decrease in heat resistance.

[0027] (Structural Unit (a1)) The structural unit (a1) contained in the aliphatic polyester according to this embodiment is a structural unit derived from an aliphatic diol (a1-1) having an alkyl group as a branched chain and having 3 or more carbon atoms in its main chain. The aliphatic diol (a1-1) constituting the structural unit (a1) may be one type, or two or more types.

[0028] (Aliphatic Diol (a1-1)) The aliphatic diol (a1-1) is an aliphatic diol having 3 or more carbon atoms in the main chain and having an alkyl group as a branched chain. The aliphatic diol has two hydroxyl groups. Preferably, the two hydroxyl groups in the aliphatic diol (a1-1) are primary hydroxyl groups. The "primary hydroxyl group" refers to a hydroxyl group bonded to a primary atom, preferably a primary carbon atom. Preferably, the aliphatic diol (a1-1) does not have a hydroxyl group bonded to the end of the branched chain.

[0029] The "main chain" of the aliphatic diol (a1-1) refers to a partial structure that is a molecular chain composed of two hydroxyl groups (preferably two primary hydroxyl groups) in the molecule at both ends and a plurality of atoms, preferably carbon atoms, connecting the two primary hydroxyl groups. Therefore, it is preferable that the two primary hydroxyl groups in the aliphatic diol (a1-1) are located at both ends of the "main chain" of the aliphatic diol (a1-1). In other words, it is preferable that the aliphatic diol (a1-1) has hydroxyl groups at both ends of the main chain. This makes it easier to react with a dicarboxylic acid.

[0030] When the total number of carbon atoms in the main chain and the branched chains of the aliphatic diol (a1-1) is 4 or more, the hydrolysis resistance of the aliphatic polyester tends to be excellent. From the viewpoint of even better hydrolysis resistance, the total number of carbon atoms in the main chain and the branched chains of the aliphatic diol (a1-1) is preferably 5 or more, more preferably 6 or more. From the viewpoint of the biodegradability of the aliphatic polyester, the total number of carbon atoms in the main chain and the branched chains of the aliphatic diol (a1-1) is preferably 30 or less, more preferably 25 or less, even more preferably 10 or less, and even more preferably 9 or less. As described above, these stepwise lower and upper limits can be independently combined. For example, in one embodiment of the present invention, the total number of carbon atoms in the main chain and the branched chains of the aliphatic diol (a1-1) is preferably 4 to 30, more preferably 4 to 25, even more preferably 5 to 10, even more preferably 5 to 9, and even more preferably 6 to 9.

[0031] The number of carbon atoms in the main chain of the aliphatic diol (a1-1) is preferably 4 or more, even more preferably 5 or more, and preferably 10 or less, more preferably 9 or less, and even more preferably 8 or less. As described above, these stepwise lower and upper limits can be independently combined. For example, in one embodiment of the present invention, the number of carbon atoms in the main chain of the aliphatic diol (a1-1) is preferably 3 to 10, more preferably 3 to 9, even more preferably 4 to 9, still more preferably 4 to 8, and even more preferably 5 to 8.

[0032] As described above, the aliphatic diol (a1-1) has an alkyl group as a branched chain. This allows the aliphatic polyester to have both biodegradability and hydrolysis resistance, compared to when an aliphatic diol without an alkyl group as a branched chain is used. Furthermore, the number of branched chains in one molecule of the aliphatic diol (a1-1) is preferably one or two, more preferably one. The number of carbon atoms in the branched chain is preferably 1 to 6, more preferably 1 to 3, and even more preferably 1 to 2. In one aspect, the number of carbon atoms in the branched chain is preferably the same as or less than the number of carbon atoms in the main chain, more preferably less than the number of carbon atoms in the main chain. The branched chain is preferably at least one type selected from the group consisting of a methyl group, an ethyl group, and a propyl group, more preferably at least one type selected from a methyl group and an ethyl group, and even more preferably a methyl group. Furthermore, when the aliphatic diol (a1-1) has multiple branched chains, the respective branched chains may be the same or different.

[0033] Examples of the aliphatic diol (a1-1) include 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2-ethyl-1,3-propanediol, 2-ethyl-2-methyl-1,3-propanediol, 2-methyl-1,4-butanediol, 1,2-pentanediol, 1,3-pentanediol, 2,3-pentanediol, 2,4-pentanediol, 2-methyl-2,4-pentanediol, 1,4-pentanediol, and 2-methyl-1,5-pentanediol. Examples of the aliphatic diol (a1-1) include hexanediol, 3-methyl-1,5-pentanediol (hereinafter also referred to as "MPD"), 2-methyl-2,4-pentanediol, 2-ethyl-1,5-pentanediol, 2,4-dimethyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,2-hexanediol, 1,3-hexanediol, 1,4-hexanediol, 1,5-hexanediol, 2-ethyl-1,6-hexanediol, and 2-methyl-1,8-octanediol. The aliphatic diol (a1-1) is preferably at least one selected from the group consisting of 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, and 2,4-diethyl-1,5-pentanediol, and more preferably 3-methyl-1,5-pentanediol.

[0034] (Structural Unit (a2)) The structural unit (a2) contained in the aliphatic polyester according to this embodiment is a structural unit derived from an aliphatic dicarboxylic acid (a2-1). The aliphatic dicarboxylic acid (a2-1) constituting the structural unit (a2) may be one type, or two or more types.

[0035] (Aliphatic Dicarboxylic Acid (a2-1)) The number of carbon atoms in the aliphatic dicarboxylic acid (a2-1) is not limited as long as the effects of the present invention are not impaired. On the other hand, from the viewpoint of the hydrolysis resistance of the aliphatic polyester, the number of carbon atoms in the aliphatic dicarboxylic acid (a2-1) is preferably 4 or more, more preferably 5 or more, and even more preferably 6 or more. Furthermore, from the viewpoint of the biodegradability of the aliphatic polyester, the number of carbon atoms in the aliphatic dicarboxylic acid (a2-1) is preferably 12 or less, more preferably 10 or less, and even more preferably 8 or less. Furthermore, as described above, these stepwise stated lower limit values ​​and upper limit values ​​can be independently combined. For example, in one aspect of the present invention, the number of carbon atoms in the aliphatic dicarboxylic acid (a2-1) is preferably 4 to 12, more preferably 5 to 10, and even more preferably 6 to 8.

[0036] Examples of the aliphatic dicarboxylic acid (a2-1) include succinic acid, glutaric acid, adipic acid (hereinafter also referred to as "AA"), pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, and decanedicarboxylic acid. The aliphatic dicarboxylic acid (a2-1) is preferably at least one selected from the group consisting of succinic acid, adipic acid, and sebacic acid, and more preferably adipic acid.

[0037] (Preferred Combinations of Aliphatic Diol (a1-1) and Aliphatic Dicarboxylic Acid (a2-1)) From the viewpoint that the aliphatic polyester can exhibit even better biodegradability and hydrolysis resistance, preferred combinations include a combination of 2-methyl-1,3-propanediol and succinic acid, a combination of 3-methyl-1,5-pentanediol and succinic acid, a combination of 2,4-diethyl-1,5-pentanediol and succinic acid, a combination of 2-methyl-1,3-propanediol and adipic acid, a combination of 3-methyl-1,5-pentanediol (MPD) and adipic acid (AA), and a combination of 2,4-diethyl-1,5-pentanediol and adipic acid. A combination of one selected from the group consisting of a combination of 3-methyl-1,5-pentanediol and succinic acid, a combination of 2,4-diethyl-1,5-pentanediol and succinic acid, a combination of 3-methyl-1,5-pentanediol and adipic acid, and a combination of 2,4-diethyl-1,5-pentanediol and adipic acid is a more preferred embodiment, and a combination of 3-methyl-1,5-pentanediol and adipic acid is a further preferred embodiment.

[0038] (Other Structural Units (a')) The aliphatic polyester according to this embodiment may or may not contain a structural unit (a') other than the structural unit (a1) and the structural unit (a2). The monomer capable of forming the structural unit (a') is not particularly limited as long as the effects of the present invention are not impaired. Examples include aliphatic diols having 3 or more carbon atoms in their main chains and not having an alkyl group as a branched chain, aliphatic diols having 2 or less carbon atoms in their main chains, aromatic diols, aromatic dicarboxylic acids, hydroxycarboxylic acids, dicarboxylic acid anhydrides, and cyclic ester compounds. Among these, at least one selected from the group consisting of ethylene glycol, propylene glycol, L-lactide, D-lactide, DL-lactide, and meso-lactide is preferred. The content of the structural unit (a') in the aliphatic polyester is preferably 50% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, still more preferably 15% by mass or less, and even more preferably 10% by mass or less. The content of the structural unit (a') may be, for example, 0% by mass or more, or 0.1% by mass or more. These stepwise lower and upper limits can be independently combined. For example, in one embodiment of the present invention, the content of the structural unit (a') in the aliphatic polyester may be preferably 0 to 50% by mass, more preferably 0 to 30% by mass, even more preferably 0 to 20% by mass, still more preferably 0 to 15% by mass, and even more preferably 0 to 10% by mass. When the aliphatic polyester contains the structural unit (a'), the content of the structural unit (a') in the aliphatic polyester may be preferably 0.1 to 50% by mass, more preferably 0.1 to 30% by mass, even more preferably 0.1 to 20% by mass, still more preferably 0.1 to 15% by mass, and even more preferably 0.1 to 10% by mass.

[0039] (Ratio of Aliphatic Diol (a1-1) to Aliphatic Dicarboxylic Acid (a2-1)) When reacting the aliphatic diol (a1-1) with the aliphatic dicarboxylic acid (a2-1), the charge molar ratio [aliphatic diol (a1-1) / aliphatic dicarboxylic acid (a2-1)] is preferably 1.4 / 1.0 to 1.0 / 1.4, more preferably 1.2 / 1.0 to 1.0 / 1.2, and even more preferably 1.2 / 1.0 to 1.0 / 1.0. When the molar ratio of the aliphatic diol (a1-1) is lower than that of the aliphatic dicarboxylic acid (a2-1), from the viewpoint of obtaining an aliphatic polyester having a high proportion of OH terminal groups, it is preferable to charge a monomer capable of forming the structural unit (a') so that the OH group equivalent is greater than the COOH group equivalent.

[0040] (Structure of Aliphatic Polyester) The aliphatic polyester according to this embodiment preferably has a polyester structure in which the structural unit (a1) and the structural unit (a2) are alternately bonded. When such a polyester structure is used, the sum (M(a)) of the average formula weight (M(a1)) of the structural unit (a1) portion in the aliphatic polyester and the average formula weight (M(a2)) of the structural unit (a2) portion can generally be regarded as the number-average molecular weight Mn(PE) of the aliphatic polyester. In this embodiment, such a polyester structure is preferably a structure having OH groups at both ends, from the viewpoint of easily achieving the effect of imparting impact resistance while suppressing a decrease in heat resistance of any polyester resin. The term "structure having OH groups at both ends" refers to a structure in which both ends of the polyester structure are OH groups derived from an aliphatic diol or a monomer capable of forming the structural unit (a'), and preferably refers to a structure in which both ends of the polyester structure are OH groups derived from an aliphatic diol. However, the polyester structure is not necessarily a structure having OH groups at both ends; one or both ends may be a COOH group structure. A first example of a case where a terminal COOH group structure is formed is a case where the terminal of the polyester structure is a COOH group derived from an aliphatic carboxylic acid, and a second example is a case where the terminal is a COOH group derived from a side reaction. In one aspect of this embodiment, for example, when the number of moles of the terminals of the polyester structure is 200, the number of moles of the OH group structures at both ends is 50 moles or more, and preferably the number of moles of the OH group structures at both ends is greater than the total number of moles of the terminal COOH structures according to the first example and the terminal COOH structures according to the second example.

[0041] (Condition 1 (PE), Condition 2 (PE), and Condition 3 (PE)) FIG. 1 is a graph schematically showing the relationship between the total formula weight α(PE) of an aliphatic polyester and the proportion of OH terminal groups β(PE). As a result of investigations by the present inventors, it was found that increasing the molecular weight of an aliphatic polyester (for example, a number average molecular weight of 25,000 or more) tends to reduce the proportion of structures with OH groups at both ends of the polyester structure, while maintaining a high proportion of structures with OH groups at both ends tends to result in a trade-off relationship in which increasing the molecular weight of the aliphatic polyester cannot be achieved. This relationship is shown in the graph of FIG. 1 by the straight line (double-dashed line) representing α(PE) / (150-β(PE))=500.

[0042] In the aliphatic polyester according to this embodiment, the value of the relational expression α(PE) / (150−β(PE)) in the above-mentioned condition 1 (PE) is not less than 500. That is, the aliphatic polyester according to this embodiment belongs to a region on the higher molecular weight side of the straight line indicated by α(PE) / (150−β(PE))=500 in the graph of FIG.

[0043] From the viewpoint of more significantly achieving the effect of imparting impact resistance while suppressing a decrease in the heat resistance of any polyester resin, the value of such relational formula (I) is preferably 520 or more, more preferably 540 or more, even more preferably 560 or more, even more preferably 580 or more, and even more preferably 600 or more. Furthermore, in one embodiment of the present invention, the value of the relational formula (I) is preferably 520 to 1,500, more preferably 540 to 1,500, even more preferably 560 to 1,500, still more preferably 580 to 1,500, and even more preferably 600 to 1,500. Furthermore, in one embodiment of the present invention, the value of the relational formula (I) is preferably 520 to 1,400, more preferably 540 to 1,400, even more preferably 560 to 1,400, still more preferably 580 to 1,400, and even more preferably 600 to 1,400. In one embodiment of the present invention, the value of the relational formula (I) is preferably 520 to 1,300, more preferably 540 to 1,300, even more preferably 560 to 1,300, still more preferably 580 to 1,300, and even more preferably 600 to 1,300. In one embodiment of the present invention, the value of the relational formula (I) is preferably 520 to 1,297, more preferably 540 to 1,297, even more preferably 560 to 1,297, still more preferably 580 to 1,297, and even more preferably 600 to 1,297. In one embodiment of the present invention, the value of the relational formula (I) is preferably 520 to 1,000, more preferably 540 to 1,000, even more preferably 560 to 1,000, still more preferably 580 to 1,000, and even more preferably 600 to 1,000.

[0044] The above-mentioned conditions 2 (PE) and 3 (PE) limit the range expressed by the relational expression (I) of condition 1 (PE).

[0045] Specifically, the lower limit of 25,000 for the total formula weight (M(a)) under condition 2 (PE) corresponds to the lower limit of the number average molecular weight at which the above-mentioned trade-off relationship was recognized when considering increasing the molecular weight. The upper limit of the total formula weight (M(a)) under condition 2 (PE) indicates the upper limit of the number average molecular weight at which increasing the molecular weight is industrially feasible. This upper limit is set because, as the increase in molecular weight progresses, molecular motion decreases, and therefore, industrially, energy costs such as shearing for stirring the reaction solution are required.

[0046] The total formula weight (M(a)) in condition 2 (PE) is preferably 26,000 or more, more preferably 27,000 or more, even more preferably 28,000 or more, even more preferably 29,000 or more, even more preferably 30,000 or more, and even more preferably 32,000 or more, from the viewpoint of more significantly exhibiting the effect of imparting impact resistance while suppressing a decrease in the heat resistance of any polyester resin. In particular, from the viewpoint of achieving both suitable impact resistance and heat resistance in a composition with polyester resin (D), the total formula weight (M(a)) in condition 2 (PE) is preferably 26,000 or more, more preferably 27,000 or more, even more preferably 28,000 or more, and even more preferably 29,000 or more. From the viewpoint of moldability and processability, the total formula weight (M(a)) is preferably 70,000 or less, and more preferably 65,000 or less. As described above, these stepwise lower and upper limits can be independently combined. For example, in one embodiment of the present invention, the total formula weight (M(a)) under condition 2 (PE) is preferably 26,000 to 75,000, more preferably 27,000 to 70,000, even more preferably 28,000 to 70,000, even more preferably 28,000 to 65,000, even more preferably 29,000 to 65,000, even more preferably 30,000 to 65,000, and even more preferably 32,000 to 65,000. As described above, the total formula weight (M(a)) can be regarded as the number average molecular weight of the aliphatic polyester. The number average molecular weight of the polymer can be measured, for example, by GPC. Specifically, it can be measured according to the method described in the Examples section below.

[0047] (Glass Transition Temperature Tg(PE) of Aliphatic Polyester) The glass transition temperature Tg(PE) of the aliphatic polyester according to the present embodiment is not particularly limited, but is preferably −80° C. or higher and −15° C. or lower. Within this numerical range, a resin composition containing the aliphatic polyester and a molded article of the resin composition containing the aliphatic polyester tend to have excellent impact resistance. From the viewpoint that the resin composition containing the aliphatic polyester and a molded article of the resin composition containing the aliphatic polyester tend to have good low-temperature properties such as low-temperature impact resistance, the glass transition temperature Tg(PE) of the aliphatic polyester is more preferably −20° C. or lower, even more preferably −25° C. or lower, and may be −30° C. or lower, or may be −35° C. or lower. The glass transition temperature Tg(PE) of the aliphatic polyester is preferably lower from the viewpoint that the resin composition containing the aliphatic polyester and a molded article of the resin composition containing the aliphatic polyester tend to have good low-temperature impact resistance. On the other hand, the glass transition temperature Tg(PE) of the aliphatic polyester may be, for example, −75°C or higher, −70°C or higher, or −65°C or higher. Furthermore, as described above, these stepwise lower and upper limits can be independently combined. For example, in one embodiment of the present invention, the glass transition temperature Tg(PE) of the aliphatic polyester is preferably −80°C to −15°C, more preferably −80°C to −20°C, even more preferably −80°C to −25°C, still more preferably −80°C to −30°C, and even more preferably −80°C to −35°C, and may be, for example, −75°C to −35°C, −70°C to −35°C, or −65°C to −35°C. The glass transition temperature of the aliphatic polyester can be determined, for example, by differential scanning calorimetry.

[0048] The OH terminal group ratio β(PE) in Condition 3 (PE) is 25 mol% or more from the viewpoint of achieving the desired effects of the present invention. The upper limit of β(PE) is 100 mol%. The upper limit of β(PE) may be, for example, 99.9 mol%. From the viewpoint of more significantly achieving the desired effects of the present invention, β(PE) is preferably 30 mol% or more, more preferably 35 mol% or more, even more preferably 40 mol% or more, even more preferably 45 mol% or more, even more preferably 50 mol% or more, and even more preferably 60 mol% or more. β(PE) may be 65 mol% or more or 70 mol% or more. As described above, these stepwise lower limit and upper limit values ​​can be independently combined. For example, in one embodiment of the present invention, the OH terminal group proportion β(PE) in the condition 3 (PE) is preferably 25 to 100 mol%, more preferably 30 to 100 mol%, even more preferably 35 to 100 mol%, still more preferably 40 to 100 mol%, still more preferably 45 to 100 mol%, still more preferably 50 to 100 mol%, still more preferably 60 to 100 mol%, and may also be, for example, 65 to 100 mol% or 70 to 100 mol%. In one embodiment of the present invention, the OH terminal group ratio β(PE) under the condition 3(PE) is preferably 25 to 99.9 mol%, more preferably 30 to 99.9 mol%, even more preferably 35 to 99.9 mol%, still more preferably 40 to 99.9 mol%, even more preferably 45 to 99.9 mol%, still more preferably 50 to 99.9 mol%, and even more preferably 60 to 99.9 mol%, and may also be, for example, 65 to 99.9 mol% or 70 to 99.9 mol%. The OH terminal group ratio β(PE) under the condition 3(PE) can be measured by the method described in the Examples section below.

[0049] (COOH End Group Ratio of Aliphatic Polyester) The COOH end group ratio (mol %) of the aliphatic polyester according to this embodiment is the ratio (percentage) of the number of COOH end groups when the total number of end groups of the aliphatic polyester is taken as 100 mol %. COOH end groups are generated when the end of the polyester structure is derived from an aliphatic dicarboxylic acid. COOH end groups can also be generated as a result of a side reaction during polymerization to obtain the aliphatic polyester. From the viewpoint of easily achieving the desired effects of the present invention, the COOH end group ratio of the aliphatic polyester according to this embodiment is preferably 75 mol % or less, more preferably 70 mol % or less, even more preferably 65 mol % or less, even more preferably 60 mol % or less, even more preferably 55 mol % or less, even more preferably 50 mol % or less, and even more preferably 40 mol % or less. It may also be, for example, 35 mol % or less or 30 mol % or less. The lower limit of the COOH end group ratio of the aliphatic polyester may be 0 mol % or 0.1 mol %. For example, in one embodiment of the present invention, the COOH terminal group ratio of the aliphatic polyester is preferably 0 to 75 mol%, more preferably 0 to 70 mol%, even more preferably 0 to 65 mol%, still more preferably 0 to 60 mol%, still more preferably 0 to 55 mol%, still more preferably 0 to 50 mol%, and still more preferably 0 to 40 mol%, and may also be, for example, 0 to 35 mol% or 0 to 30 mol%. In one embodiment of the present invention, the COOH terminal group ratio of the aliphatic polyester is preferably 0.1 to 75 mol%, more preferably 0.1 to 70 mol%, even more preferably 0.1 to 65 mol%, still more preferably 0.1 to 60 mol%, still more preferably 0.1 to 55 mol%, still more preferably 0.1 to 50 mol%, and even more preferably 0.1 to 40 mol%, and may be, for example, 0.1 to 35 mol% or 0.1 to 30 mol%. The COOH terminal group ratio of the aliphatic polyester can be measured by the method described in the Examples section below.The sum of the OH terminal group proportion β(PE) (mol %) and the COOH terminal group proportion (mol %) of the aliphatic polyester is 100 mol % or less, may be 25 to 100 mol %, or may be 25 to 99.9 mol %.

[0050] (Total Content of Structural Unit (a1) and Structural Unit (a2)) In the aliphatic polyester according to this embodiment, the total content of the structural unit (a1) and the structural unit (a2) is preferably 50% by mass or more, more preferably 75% by mass or more, even more preferably 85% by mass or more, and even more preferably 90% by mass or more, from the viewpoint of easily achieving the effect of imparting impact resistance while suppressing a decrease in the heat resistance of any polyester resin. Alternatively, it may be, for example, 92% by mass or more, or 95% by mass or more, or even 100% by mass in one aspect. Furthermore, as described above, these stepwise lower limit values ​​and upper limit values ​​can be independently combined. For example, in one embodiment of the present invention, the total content of the structural unit (a1) and the structural unit (a2) in the aliphatic polyester is preferably 50 to 100 mass%, more preferably 75 to 100 mass%, even more preferably 85 to 100 mass%, and still more preferably 90 to 100 mass%, and may also be, for example, 92 to 100 mass%, or 95 to 100 mass%.

[0051] (Imparting Properties) (Imparting Properties to Block Copolymers) When the aliphatic polyester according to this embodiment is used as a block copolymer, it can impart the properties of the aliphatic polyester to the block copolymer or to a molded article of a resin composition containing the block copolymer. For example, the aliphatic polyester according to this embodiment has a high molecular weight, which allows the resulting block copolymer to have a high molecular weight, thereby imparting heat resistance to a molded article of the block copolymer. In addition, the aliphatic polyester according to this embodiment has a high proportion of OH terminal groups despite its high molecular weight, which allows a high triblock ratio to be achieved when used as a block copolymer. Combined with the high molecular weight, the resulting block copolymer has excellent mechanical properties, and molded articles of resin compositions containing such block copolymers have high impact resistance. Here, the triblock ratio refers to the ratio (percentage) of the number of triblock units in which a second block is bonded to both ends of a first block when the aliphatic polyester according to this embodiment is used as a first block, to the total number of diblock units in which a second block is bonded to only one end of the first block and not to the other end. Furthermore, the aliphatic polyester according to this embodiment can form soft segments derived from the aliphatic polyester in the resulting block copolymer, thereby imparting impact resistance to a molded article of the block copolymer, for example.

[0052] (Imparting Properties to Resin Composition) When the aliphatic polyester according to this embodiment is made into a resin composition, it can impart the properties of the aliphatic polyester to a molded article of the resin composition. For example, since the aliphatic polyester according to this embodiment has a high molecular weight, it can impart heat resistance to a molded article of the resin composition. Furthermore, since the aliphatic polyester according to this embodiment contains an amorphous flexible molecular chain derived from an aliphatic diol having a specific branched structure in the main chain of the molecular structure, it can impart impact resistance to a molded article of the resin composition, for example.

[0053] [Method for Producing Aliphatic Polyester] The method for producing an aliphatic polyester according to an embodiment of the present invention is a method for producing an aliphatic polyester, which comprises reacting a first aliphatic polyester containing a structural unit (a1) derived from an aliphatic diol having 3 or more carbon atoms in its main chain and having an alkyl group as a branched chain and a structural unit (a2) derived from a first aliphatic dicarboxylic acid with at least one selected from the group consisting of a second aliphatic dicarboxylic acid (z1), an aliphatic dicarboxylic acid alkyl ester (z2), and an aliphatic dicarboxylic acid anhydride (z3), to produce a second aliphatic polyester that satisfies the following three conditions: Condition 1 (PE2), Condition 2 (PE2), and Condition 3 (PE2).

[0054] Condition 1 (PE2): The following α(PE2) and β(PE2) satisfy the following relational formula (II): α(PE2) / (150-β(PE2))≧500 (II) (In the relational formula (II), α(PE2) is the number average molecular weight of the second aliphatic polyester, and β(PE2) is the OH terminal group proportion [mol %] of the second aliphatic polyester, which indicates the proportion (percentage) of the number of OH terminal groups when the total number of terminal groups of the aliphatic polyester is 100 mol %). Condition 2 (PE2): In the second aliphatic polyester, the sum (M(a)) of the average formula weight (M(a1)) of the structural unit (a1) portion and the average formula weight (M(a2)) of the structural unit (a2) portion is 25,000 to 75,000. Condition 3 (PE2): β(PE2)≧25

[0055] In this embodiment, the structural unit (a1) and the structural unit (a2) are the same as those described in the embodiment of the aliphatic polyester, and preferred embodiments thereof are also the same. Accordingly, the aliphatic diol having 3 or more carbon atoms in its main chain and having an alkyl group as a branched chain is the same as the aliphatic diol described above in the section on aliphatic diol (a1-1), and preferred embodiments thereof are also the same. Furthermore, the first aliphatic dicarboxylic acid is the same as the aliphatic dicarboxylic acid described above in the section on aliphatic dicarboxylic acid (a2-1), and preferred embodiments thereof are also the same. The first aliphatic polyester is a precursor (raw material) of the second aliphatic polyester. The second aliphatic polyester is the same as that described in the section on the aliphatic polyester according to one embodiment of the present invention, and preferred embodiments thereof are also the same. Therefore, the above-mentioned Condition 1 (PE2), α(PE2), and β(PE2), Condition 2 (PE2), and Condition 3 (PE2) are respectively similar to Condition 1 (PE), α(PE), and β(PE), Condition 2 (PE), and Condition 3 (PE) described in the embodiment of the aliphatic polyester, and the preferred embodiments thereof are also similar.

[0056] According to the production method of this embodiment, an aliphatic polyester having a high OH terminal group ratio and a high molecular weight can be provided, and therefore, the same effects as those described in the embodiment of the aliphatic polyester can be achieved.

[0057] (Second Aliphatic Dicarboxylic Acid (z1), Aliphatic Dicarboxylic Acid Alkyl Ester (z2), and Aliphatic Dicarboxylic Acid Anhydride (z3)) The second aliphatic dicarboxylic acid (z1), aliphatic dicarboxylic acid alkyl ester (z2), and aliphatic dicarboxylic acid anhydride (z3) described above may function as a coupling agent or a chain extender during the reaction. The second aliphatic dicarboxylic acid (z1), aliphatic dicarboxylic acid alkyl ester (z2), and aliphatic dicarboxylic acid anhydride (z3) may form the same structural unit as the structural unit (a2) as a result of the reaction. In this case, a structural unit derived from one or more selected from the group consisting of the second aliphatic dicarboxylic acid (z1), aliphatic dicarboxylic acid alkyl ester (z2), and aliphatic dicarboxylic acid anhydride (z3) is also considered to be the structural unit (a2) derived from the first aliphatic dicarboxylic acid. When the second aliphatic dicarboxylic acid (z1), the aliphatic dicarboxylic acid alkyl ester (z2), and the aliphatic dicarboxylic acid anhydride (z3) form the same structural unit as the structural unit (a2), a high molecular weight can be achieved without complicating the structural units of the first aliphatic polyester. The second aliphatic dicarboxylic acid (z1), the aliphatic dicarboxylic acid alkyl ester (z2), and the aliphatic dicarboxylic acid anhydride (z3) may form a structural unit different from the structural unit (a2) as a result of the reaction. In this case, the second aliphatic polyester can be endowed with properties derived from the structural unit different from the structural unit (a2).

[0058] (Second Aliphatic Dicarboxylic Acid (z1)) Examples of the second aliphatic dicarboxylic acid (z1) include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, and decanedicarboxylic acid. The second aliphatic dicarboxylic acid (z1) is preferably at least one selected from the group consisting of succinic acid, adipic acid, and sebacic acid, and more preferably adipic acid.

[0059] (Aliphatic Dicarboxylic Acid Alkyl Ester (z2)) Examples of the aliphatic dicarboxylic acid alkyl ester (z2) include succinic acid diester, glutaric acid diester, adipic acid diester, pimelic acid diester, suberic acid diester, azelaic acid diester, sebacic acid diester, undecanedioic acid diester, and decanedicarboxylic acid diester. The aliphatic dicarboxylic acid alkyl ester (z2) is preferably at least one selected from the group consisting of dimethyl adipate, diethyl adipate, dipropyl adipate, diisopropyl adipate, dibutyl adipate, diisobutyl adipate, bis(2-ethylhexyl) adipate, dioctyl adipate, heptylnonyl adipate, diisononyl adipate, diisodecyl adipate, and bis(2-butoxyethyl) adipate, and more preferably dimethyl adipate or bis(2-ethylhexyl) adipate.

[0060] (Aliphatic Dicarboxylic Acid Anhydride (z3)) Examples of the aliphatic dicarboxylic acid anhydride (z3) include succinic anhydride, glutaric anhydride, adipic anhydride, pimelic anhydride, suberic anhydride, azelaic anhydride, sebacic anhydride, undecanedioic anhydride, and decanedicarboxylic anhydride.

[0061] The method for producing an aliphatic polyester according to an embodiment of the present invention preferably includes two steps. Specifically, the method for producing an aliphatic polyester according to an embodiment of the present invention includes: a first step of reacting an aliphatic diol having 3 or more carbon atoms in its main chain and having an alkyl group as a branched chain with a first aliphatic dicarboxylic acid to produce a first aliphatic polyester containing the structural units (a1) and (a2), and a second step of reacting the first aliphatic polyester with at least one selected from the group consisting of a second aliphatic dicarboxylic acid (z1), an aliphatic dicarboxylic acid alkyl ester (z2), and an aliphatic dicarboxylic acid anhydride (z3).

[0062] (Catalyst Used in Step 1) In Step 1, a catalyst is preferably used, more preferably an esterification catalyst. Examples of the esterification catalyst include titanium catalysts, tin octoate, tin chloride, and tin oxide. Examples of the titanium catalyst include at least one selected from tetraisopropyl orthotitanate and potassium titanium oxalate dihydrate. In one embodiment, tin octoate is used in Step 1. From the viewpoint of increasing the polymerization rate, one selected from tetraisopropyl orthotitanate and potassium titanium oxalate dihydrate may be used in Step 1.

[0063] (Reaction Conditions in the First Step) The reaction conditions in the first step, specifically the polycondensation temperature and polycondensation pressure, can be the same as those in known esterification reactions. Examples of the reaction conditions in the first step include a polycondensation temperature in the range of preferably 140 to 230°C, and a polycondensation pressure in the range of preferably FV (Full Vacuum) to 2,000 Pa, more preferably FV to 1,000 Pa, even more preferably FV to 500 Pa, still more preferably FV to 300 Pa, and still more preferably FV to 200 Pa. The polycondensation pressure may be, for example, 5 to 2,000 Pa, 5 to 1,000 Pa, 5 to 500 Pa, 5 to 300 Pa, 5 to 200 Pa, 40 to 2,000 Pa, 40 to 1,000 Pa, 40 to 500 Pa, 40 to 300 Pa, or 40 to 200 Pa.

[0064] (Catalyst Used in Step 2) In Step 2, a catalyst is preferably used, more preferably an esterification catalyst. Examples of the esterification catalyst include titanium catalysts, tin octoate, tin chloride, and tin oxide. Examples of the titanium catalyst include at least one selected from tetraisopropyl orthotitanate and potassium titanium oxalate dihydrate. For example, from the viewpoint of increasing the polymerization rate, one selected from tetraisopropyl orthotitanate and potassium titanium oxalate dihydrate may be used in Step 2.

[0065] (Reaction conditions in Step 2) Reaction conditions that can be employed in Step 2 are preferably similar to those in Step 1. From the viewpoint of reducing production costs and suppressing side reactions during the reaction, reaction conditions that can be employed in Step 2 may be lower reaction temperatures and higher polycondensation pressures than conventional polycondensation conditions for performing polycondensation in one stage.

[0066] Specific examples of reaction conditions include a polycondensation temperature in the second step of preferably 140 to 230°C, and a polycondensation pressure in the second step of preferably FV (Full Vacuum) to 500 Pa. From the viewpoint of suppressing side reactions other than the condensation reaction, the polycondensation temperature in the second step is more preferably 220°C or less, and even more preferably 200°C or less. These stepwise ranges can be independently combined. For example, in one embodiment of the present invention, the polycondensation temperature in the second step is preferably 140 to 230°C, more preferably 140 to 220°C, and even more preferably 140 to 200°C. From the viewpoint of shortening the reaction time and obtaining a polymer, the polycondensation pressure in the second step of preferably 300 Pa or less, even more preferably 200 Pa or less, and even more preferably 100 Pa or less. In one embodiment of the present invention, the polycondensation pressure in the second step is preferably FV to 500 Pa, more preferably FV to 300 Pa, even more preferably FV to 200 Pa, and still more preferably FV to 100 Pa. The polycondensation pressure may be, for example, 5 to 500 Pa, 5 to 300 Pa, 5 to 200 Pa, or 5 to 100 Pa.

[0067] [Resin Composition (Aliphatic Polyester-Containing Resin Composition)] The aliphatic polyester-containing resin composition according to one embodiment of the present invention contains the aliphatic polyester (PE) according to the embodiment described above (in this specification, "aliphatic polyester (PE)" refers to at least one selected from the aliphatic polyester described in the section on the aliphatic polyester according to one embodiment of the present invention and the second aliphatic polyester produced by the production method described in the section on the production method of the aliphatic polyester according to one embodiment of the present invention). Preferably, the resin composition contains the aliphatic polyester (PE) and a polyester resin (hereinafter, for convenience, also referred to as polyester resin (D)) that is different from the aliphatic polyester (PE) and different from the block copolymer (BCP) which is one aspect of the present invention described below. The aliphatic polyester (PE) may be the second aliphatic polyester obtained by the production method of the aliphatic polyester according to the embodiment described above. The polyester resin (D) may be used alone or in combination of two or more. According to this embodiment, since the resin composition contains the aliphatic polyester (PE), the properties of the aliphatic polyester (PE) can be imparted to a molded article of the resin composition. Specifically, it can contribute to the modification of the polyester resin (D). Furthermore, the resin composition containing the aliphatic polyester (PE) according to one embodiment of the present invention may or may not contain the block copolymer (BCP) according to one embodiment of the present invention described later.

[0068] (Polyester Resin (D)) Any polyester resin can be used as the polyester resin (D) contained in the aliphatic polyester-containing resin composition according to this embodiment. However, in this embodiment, the polyester resin (D) excludes the aliphatic polyester (PE) according to the embodiment described above and the block copolymer which is an aspect of the present invention described below. As the polyester resin (D), for example, a polyester resin which requires improvement in one or both of heat resistance and impact resistance may be used. Furthermore, in this embodiment, from the viewpoint of biodegradability, the polyester resin (D) is preferably at least one selected from the group consisting of biomass resins and biodegradable resins.

[0069] Examples of the polyester resin (D) include polylactic acid (PLA), polycaprolactone (PCL), poly(caprolactone / butylene succinate) (PCLBS), polybutylene succinate (PBS), poly(butylene succinate / adipate) (PBSA), poly(butylene succinate / carbonate) (PEC), poly(ethylene terephthalate / succinate) (PETS), poly(butylene adipate / terephthalate) (PBAT), poly(tetramethylene adipate / terephthalate) (PTMT), polyethylene succinate (PES), polyglycolic acid (PGA), polyethylene furanoate (PEF), polyhydroxyalkanoate (PHA) [e.g., polyhydroxybutyrate (PHB), polyhydroxybutyrate valerate (PHBV), etc.], and copolymers containing these.

[0070] From the viewpoint of exhibiting even better hydrolysis resistance, heat resistance, impact resistance, and biodegradability, the polyester resin (D) is preferably at least one selected from the group consisting of PLA, PBS, PBSA, and PBAT, and more preferably at least one polylactic acid resin selected from the group consisting of PLA and copolymers thereof.

[0071] When the polylactic acid resin is used as the polyester resin (D), examples of the polylactic acid resin include at least one selected from the group consisting of a homopolymer of L-lactic acid, a homopolymer of D-lactic acid, a copolymer of L-lactic acid and D-lactic acid, a homopolymer of DL-lactic acid, a copolymer of DL-lactic acid and L-lactic acid, a copolymer of DL-lactic acid and D-lactic acid, and a polymer of L-lactide, D-lactide, DL-lactide, and meso-lactide, which are cyclic dimers of lactic acid.

[0072] The polylactic acid resin may also be a copolymer of lactic acid and at least one selected from aliphatic hydroxycarboxylic acids other than lactic acid, aliphatic dicarboxylic acids, aliphatic diols, and aromatic dicarboxylic acids. The content of structural units derived from lactic acid in the copolymer is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, and may be 99 mol% or less, based on 100 mol% of the total structural units constituting the copolymer, which is the polylactic acid resin. As described above, these stepwise lower and upper limits can be independently combined. For example, in one embodiment of the present invention, the content of structural units derived from lactic acid in the copolymer is preferably 70 to 99 mol%, more preferably 80 to 99 mol%, and even more preferably 90 to 99 mol%, based on 100 mol% of the total structural units constituting the copolymer, which is the polylactic acid resin.

[0073] Among the above-mentioned polymers, the polylactic acid resin is preferably a homopolymer of L-lactic acid, a homopolymer of D-lactic acid, or a copolymer of L-lactic acid and D-lactic acid, and more preferably a homopolymer of L-lactic acid.

[0074] The polylactic acid resin may be used alone or in combination of two or more kinds.

[0075] Commercially available polylactic acid resins may be used, such as the "INGEO (registered trademark) series" manufactured by NatureWorks, Inc., the "Luminy (registered trademark) series" manufactured by Total Energies Corbion, the "Revode (registered trademark)" series manufactured by Zhejiang Hisun Biomaterials Co., Ltd., and the "SUPLA" series manufactured by SUPLA Material Technology Co., Ltd.

[0076] The weight average molecular weight (Mw) of the polyester resin (D) is preferably 50,000 or more, more preferably 100,000 or more, and even more preferably 150,000 or more, from the viewpoints of impact resistance and heat resistance. From the viewpoints of moldability and compatibility with aliphatic polyesters, it is preferably 600,000 or less, more preferably 550,000 or less, and even more preferably 500,000 or less. That is, the weight average molecular weight (Mw) of the polylactic acid resin (D) is preferably 50,000 to 600,000, more preferably 100,000 to 550,000, and even more preferably 150,000 to 500,000. The weight average molecular weight (Mw) of the polylactic acid resin can be determined in terms of standard polystyrene by gel permeation chromatography (GPC). When using commercially available products, catalog values ​​may be used.

[0077] (Content of Polyester Resin (D)) The aliphatic polyester-containing resin composition of the present embodiment contains the polyester resin (D) in an amount of preferably 50.0 to 99.5 mass%, more preferably 60.0 to 99.0 mass%, even more preferably 70.0 to 98.5 mass%, and still more preferably 80.0 to 98.0 mass%, relative to 100 mass% of the total of the aliphatic polyester (PE) and the polyester resin (D). This content ratio allows the properties of the aliphatic polyester (PE) to be imparted to a molded article of the resin composition containing the aliphatic polyester (PE) without significantly impairing the properties of the polyester resin (D).

[0078] (Aliphatic polyester (PE) content) In one embodiment of the aliphatic polyester-containing resin composition, the content of the aliphatic polyester (PE) is preferably 0.5 to 50.0 mass%, more preferably 1.0 to 40.0 mass%, even more preferably 1.5 to 30.0 mass%, still more preferably 2.0 to 20.0 mass%, still more preferably 2.0 to 15.0 mass%, and still more preferably 2.0 to 10.0 mass%, relative to 100 mass% of the total amount of the aliphatic polyester-containing resin composition. In one embodiment of the aliphatic polyester-containing resin composition, the aliphatic polyester-containing resin composition preferably contains 0.5 to 50.0 mass% of the aliphatic polyester (PE), more preferably 1.0 to 40.0 mass%, even more preferably 1.5 to 30.0 mass%, still more preferably 2.0 to 20.0 mass%, even more preferably 2.0 to 15.0 mass%, and still more preferably 2.0 to 10.0 mass%, relative to 100 mass% of the total of the aliphatic polyester (PE) and the polyester resin (D). This content ratio is preferable because it makes it easier to fully exhibit the effect of imparting impact resistance while suppressing a decrease in the heat resistance of any polyester resin.

[0079] In the aliphatic polyester-containing resin composition of this embodiment, the total content of the aliphatic polyester (PE) and the polyester resin (D) is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, still more preferably 95% by mass or more, and even more preferably 98% by mass or more, based on 100% by mass of the total amount of the aliphatic polyester-containing resin composition. In the resin composition of this embodiment, the total content of the aliphatic polyester (PE) and the polyester resin (D) may be 100% by mass or less, based on 100% by mass of the total amount of the aliphatic polyester-containing resin composition. Furthermore, as described above, these stepwise lower limit values ​​and upper limit values ​​can be independently combined. For example, in one embodiment of the present invention, the total content of the aliphatic polyester (PE) and the polyester resin (D) is preferably 80 to 100 mass%, more preferably 85 to 100 mass%, even more preferably 90 to 100 mass%, still more preferably 95 to 100 mass%, and even more preferably 98 to 100 mass%, based on 100 mass% of the total amount of the aliphatic polyester-containing resin composition. This content ratio is preferable because the effects of the present invention are more significantly exhibited.

[0080] (Other Components) The aliphatic polyester-containing resin composition of the present embodiment may contain at least one other component selected from the group consisting of a plasticizer other than the aliphatic polyester (PE), the block copolymer (BCP) according to one embodiment of the present invention described later, and the polyester resin (D); a resin other than the polyester resin (D); and other additives.

[0081] (Plasticizer) A plasticizer may be added to the aliphatic polyester-containing resin composition for the purpose of adjusting the viscosity to a level suitable for molding or for the purpose of obtaining a molded product with the desired hardness. There are no particular limitations on the plasticizer, but it may be a plasticizer that is biodegradable in any of industrial compost, household compost, soil, and marine environments. Suitable examples of biodegradable plasticizers include plant esters such as rapeseed oil and castor oil; synthetic esters such as triacetin, diethyl phthalate, and triethyl citrate; polyols and derivatives thereof such as ethylene glycol and trimethylolpropane; and sugars such as sorbitol. These may be used alone or in combination of two or more.

[0082] (Resins Other Than Polyester Resin (D)) The resins other than polyester resin (D) are not particularly limited, and may be resins that are biodegradable in any of the following environments: industrial compost, household compost, soil, and marine. Suitable examples of biodegradable resins include cellulose resins such as polyvinyl alcohol and cellulose acetate; starch and its esters; 4-nylon; and a block copolymer (BCP) according to one embodiment of the present invention described below. These may be used alone or in combination of two or more.

[0083] (Additives) Examples of additives include inorganic fillers, softeners, heat aging inhibitors, antioxidants, hydrolysis inhibitors, light stabilizers, antistatic agents, release agents, flame retardants, foaming agents, pigments, dyes, brighteners, UV absorbers, lubricants, and solvents. These may be used alone or in combination of two or more. When using the additives, the content of the additives in the aliphatic polyester-containing resin composition may be appropriately determined depending on the desired physical properties of the aliphatic polyester-containing resin composition.

[0084] (Method for Producing Aliphatic Polyester-Containing Resin Composition) The method for producing the aliphatic polyester-containing resin composition of this embodiment is not particularly limited. It is sufficient to uniformly mix the aliphatic polyester (PE), the polyester resin (D), and, if necessary, at least one selected from the group consisting of a plasticizer other than the polyester resin (D), a resin other than the polyester resin (D), and an additive. Examples of methods for mixing these components include melt-kneading using a single-screw extruder, a multi-screw extruder, a Banbury mixer, a heated roll, a Brabender, various kneaders, etc. Furthermore, when using the above-mentioned equipment, the components may be melt-kneaded by supplying them all at once through a single inlet, or by supplying different components or mixtures through separate inlets. Before being charged into the inlet, some or all of the components may be pre-blended as described below, and then charged into the inlet as a mixture.

[0085] Alternatively, preblending may be carried out before melt-kneading. Examples of preblending methods include methods 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 the melt-kneading can be arbitrarily selected, preferably within the range of 140 to 220°C, taking into consideration the melting points and decomposition temperatures of the aliphatic polyester (PE) and the polyester resin (D).

[0086] (Characteristics of Aliphatic Polyester-Containing Resin Composition) (Impact Resistance) When the aliphatic polyester-containing resin composition according to the present embodiment is prepared into, for example, a resin composition containing a polyester resin, preferably a resin composition (D) containing a polyester resin, the molded article tends to exhibit excellent impact resistance. For example, the impact resistance value (kJ / m ) measured in the Examples section described later can be used to ２ ) preferably exhibits a value higher than the impact resistance value of the polyester resin.

[0087] (Heat resistance) When the aliphatic polyester-containing resin composition according to this embodiment is prepared, for example, into a resin composition containing a polyester resin, preferably into a resin composition (D) containing a polyester resin, the molded article tends to exhibit excellent heat resistance.

[0088] A resin composition according to another embodiment of the present invention may contain the aliphatic polyester (PE) according to the above-described embodiment, but may not contain a polyester resin (D) different from the aliphatic polyester (PE). According to this embodiment, the properties of the aliphatic polyester (PE) can be exhibited in the resin composition containing the aliphatic polyester (PE) or in a molded article thereof.

[0089] [Molded article] A molded article according to one embodiment of the present invention is a molded article of the aliphatic polyester-containing resin composition according to the above-described embodiment. A molded article according to another embodiment is a molded article of the resin composition according to the above-described other embodiment (an aliphatic polyester-containing resin composition not containing polyester resin (D)). According to these embodiments, the properties of the aliphatic polyester (PE) can be exhibited.

[0090] [Block Copolymer] The block copolymer according to an embodiment of the present invention has a first block (A) derived from an aliphatic polyester containing structural units (a1) derived from an aliphatic diol having 3 or more carbon atoms in its main chain and having an alkyl group as a branched chain and structural units (a2) derived from an aliphatic dicarboxylic acid, and a second block (B) derived from a polylactic acid containing structural units derived from lactic acid, and satisfies the following three conditions: Condition 1 (BCP), Condition 2 (BCP), and Condition 3 (BCP). In this specification, the block copolymer is also referred to as "BCP."

[0091] Condition 1 (BCP): The following α(BCP) and β(BCP) satisfy the following relational formula (III): α(BCP) / (150-β(BCP))≧575 (III) (In the relational formula (III), α(BCP) is the number average molecular weight of the block copolymer, and β(BCP) is the OH terminal group proportion [mol %] of the block copolymer, which indicates the proportion (percentage) of the number of OH terminal groups when the total number of terminal groups of the block copolymer is 100 mol %). Condition 2 (BCP): In the block copolymer, the sum (M(a)) of the average formula weight (M(a1)) of the structural unit (a1) portion and the average formula weight (M(a2)) of the structural unit (a2) portion is in the range of 25,000 to 75,000. Condition 3 (BCP): β(BCP)≧25

[0092] When the value of the relational formula (III) is 575 or greater, a block copolymer can be provided in which the properties of the first block (A) derived from the aliphatic polyester are fully reflected. Specifically, in order for the value of the relational formula (III) to be 575 or greater, the aliphatic polyester forming the first block (A) must have a sufficiently high molecular weight, as represented by the condition 2 (BCP). Examples of such high-molecular-weight aliphatic polyesters include the aliphatic polyesters according to the above-described embodiments or aliphatic polyesters produced by the above-described methods for producing aliphatic polyesters. Therefore, it can be said that the block copolymer according to this embodiment is endowed with properties corresponding to the high molecular weight of the aliphatic polyester.

[0093] According to this embodiment, since the block copolymer includes a first block (A) derived from a high-molecular-weight aliphatic polyester that satisfies the above-mentioned condition 2 (BCP), a block copolymer with a high molecular weight can be provided regardless of the formula weight of the second block (B). Furthermore, since the block copolymer according to this embodiment has a high molecular weight, the heat resistance of the block copolymer can be improved. Furthermore, in the block copolymer according to this embodiment, the first block (A) forms a soft block, which can impart, for example, impact resistance. In addition, the block copolymer according to this embodiment has a high proportion of OH terminal groups, i.e., a high proportion of triblock copolymers having second blocks at both ends of the first block (A). This, combined with the high molecular weight described above, allows the block copolymer to have excellent mechanical properties, and resin compositions containing such block copolymers have high impact resistance. Furthermore, from the viewpoint of achieving a better impact resistance improvement effect, the OH terminal group proportion is 25% or more. Furthermore, according to this embodiment, a high-molecular-weight block copolymer can be provided. Therefore, when a resin composition containing this block copolymer and an arbitrary polyester resin is prepared, the properties of the block copolymer according to this embodiment, such as heat resistance and impact resistance, can be imparted. More specifically, it is possible to improve the impact resistance of any polyester resin while suppressing a decrease in the heat resistance.

[0094] (Condition 1 (BCP), Condition 2 (BCP), and Condition 3 (BCP)) The above-mentioned Condition 1 (BCP), Condition 2 (BCP), and Condition 3 (BCP) are set in accordance with Condition 1 (PE), Condition 2 (PE), and Condition 3 (BCP) described in the embodiment of the aliphatic polyester. However, since the block copolymer according to this embodiment contains the second block (B), it is necessary to consider the formula weight of that portion. Therefore, 575 is set as the threshold value of the value of relational formula (III) in Condition 1 (BCP). As illustrated in the Examples section, it has been confirmed that when the value of the relational formula is 575 or more, the heat resistance and impact resistance of a resin composition containing the block copolymer or a molded article thereof are improved.

[0095] The value of relational formula (III) in condition 1 (BCP) is preferably 580 or more, more preferably 590 or more, even more preferably 600 or more, even more preferably 620 or more, even more preferably 650 or more, and even more preferably 700 or more. Furthermore, in one embodiment of the present invention, the value of relational formula (III) is preferably 575 to 8,000, more preferably 580 to 8,000, even more preferably 590 to 8,000, even more preferably 600 to 8,000, even more preferably 650 to 8,000, and even more preferably 700 to 8,000. Furthermore, in one embodiment of the present invention, the value of relational formula (III) is preferably 575 to 7,272, more preferably 580 to 7,272, even more preferably 590 to 7,272, even more preferably 600 to 7,272, even more preferably 650 to 7,272, and even more preferably 700 to 7,272. In one embodiment of the present invention, the value of the relational formula (III) is preferably 575 to 4,000, more preferably 580 to 4,000, even more preferably 590 to 4,000, still more preferably 600 to 4,000, still more preferably 650 to 4,000, and still more preferably 700 to 4,000. In one embodiment of the present invention, the value of the relational formula (III) is preferably 575 to 3,636, more preferably 580 to 3,636, even more preferably 590 to 3,636, still more preferably 600 to 1,250, still more preferably 650 to 3,636, and still more preferably 700 to 3,636. In one embodiment of the present invention, the value of the relational formula (III) is preferably 575 to 2,000, more preferably 580 to 2,000, even more preferably 590 to 2,000, still more preferably 600 to 2,000, still more preferably 650 to 2,000, and still more preferably 700 to 2,000. In one embodiment of the present invention, the value of the relational formula (III) is preferably 575 to 1,923, more preferably 580 to 1,923, even more preferably 590 to 1,923, still more preferably 600 to 1,923, still more preferably 650 to 1,923, and still more preferably 700 to 1,923.In one embodiment of the present invention, the value of the relational formula (III) is preferably 575 to 1,923, more preferably 580 to 1,667, even more preferably 590 to 1,667, still more preferably 600 to 1,667, still more preferably 650 to 1,667, and still more preferably 700 to 1,667. In one embodiment of the present invention, the value of the relational formula (III) is preferably 575 to 1,000, more preferably 580 to 1,000, even more preferably 590 to 1,000, still more preferably 600 to 1,000, still more preferably 650 to 1,000, and still more preferably 700 to 1,000.

[0096] The preferred range of the total formula weight (M(a)) under condition 2 (BCP) is the same as the preferred range of the total formula weight (M(a)) under condition 2 (PE) described above. In the block copolymer, the total formula weight (M(a)) under condition 2 (BCP) can be determined by the method described in the Examples section below. The number average molecular weight α(PE) of the aliphatic polyester used in producing the block copolymer may be used as the total formula weight (M(a)).

[0097] The preferred range of β(BCP) under condition 3 (BCP) tends to be the same as or lower than the preferred range of β(PE) under condition 3 (PE) described above. Specifically, β(BCP) is preferably 28 mol% or more, more preferably 33 mol% or more, even more preferably 38 mol% or more, even more preferably 42 mol% or more, even more preferably 45 mol% or more, and even more preferably 50 mol% or more. Furthermore, from the viewpoint of improving the impact resistance of a molded article of the block copolymer-containing resin composition, β(BCP) is preferably 50 mol% or more, more preferably 55 mol% or more, even more preferably 60 mol% or more, and even more preferably 65 mol% or more. β(BCP) may be 70 mol% or more. The upper limit of β(BCP) may be, for example, 100 mol%, 98 mol%, 95 mol%, or 90 mol%. The reason why the value of β(BCP) tends to be lower than the value of β(PE) is that side reactions may occur during the formation of the second block (B). Furthermore, as described above, these stepwise lower and upper limits can be independently combined. For example, in one embodiment of the present invention, β(BCP) is 25 to 100 mol%, preferably 28 to 100 mol%, more preferably 33 to 100 mol%, even more preferably 38 to 100 mol%, still more preferably 42 to 100 mol%, even more preferably 45 to 100 mol%, still more preferably 50 to 100 mol%, even more preferably 55 to 100 mol%, still more preferably 60 to 100 mol%, and even more preferably 65 to 100 mol%. In one embodiment of the present invention, β(BCP) is preferably 25 to 98 mol%, more preferably 28 to 98 mol%, even more preferably 33 to 98 mol%, still more preferably 38 to 98 mol%, still more preferably 42 to 98 mol%, still more preferably 45 to 98 mol%, still more preferably 50 to 98 mol%, still more preferably 55 to 98 mol%, still more preferably 60 to 98 mol%, and still more preferably 65 to 98 mol%. In one embodiment of the present invention, β(BCP) may be, for example, 60 to 95 mol%, 60 to 90 mol%, 70 to 100 mol%, 70 to 98 mol%, 70 to 95 mol%, or 70 to 90 mol%.

[0098] (COOH End Group Proportion of Block Copolymer) The COOH end group proportion (mol %) of the block copolymer according to this embodiment is the proportion (percentage) of the number of COOH end groups when the total number of end groups of the block copolymer is taken as 100 mol %. COOH end groups can be generated as a result of a side reaction when obtaining the block copolymer by polymerization. From the viewpoint of easily achieving the desired effects of the present invention, the COOH end group proportion of the block copolymer according to this embodiment is preferably 75 mol % or less, more preferably 72 mol % or less, even more preferably 67 mol % or less, even more preferably 62 mol % or less, even more preferably 58 mol % or less, even more preferably 55 mol % or less, even more preferably 50 mol % or less, even more preferably 45 mol % or less, even more preferably 40 mol % or less, even more preferably 35 mol % or less, and may even be 30 mol % or less. The lower limit of the COOH end group proportion may be 0 mol %, 2 mol %, 5 mol %, or 10 mol %. The COOH end group proportion can be measured by the method described in the Examples section below. The sum of the OH end group proportion β(BCP) (mol%) and the COOH end group proportion (mol%) of the block copolymer is 100 mol% or less, and may be 25 to 100 mol%, 25 to 98 mol%, 25 to 95 mol%, or 25 to 90 mol%. As described above, these stepwise lower and upper limits can be independently combined. For example, in one embodiment of the present invention, the COOH end group proportion of the block copolymer is preferably 0 to 75 mol%, more preferably 0 to 72 mol%, even more preferably 0 to 67 mol%, even more preferably 0 to 62 mol%, even more preferably 0 to 58 mol%, even more preferably 0 to 55 mol%, even more preferably 0 to 50 mol%, even more preferably 0 to 45 mol%, even more preferably 0 to 40 mol%, even more preferably 0 to 35 mol%, and may be, for example, 0 to 30 mol%.In one embodiment of the present invention, the COOH terminal group ratio of the block copolymer is preferably 2 to 75 mol%, more preferably 2 to 72 mol%, even more preferably 2 to 67 mol%, still more preferably 2 to 62 mol%, still more preferably 2 to 58 mol%, still more preferably 2 to 55 mol%, still more preferably 2 to 50 mol%, still more preferably 2 to 45 mol%, still more preferably 2 to 40 mol%, still more preferably 2 to 35 mol%, or may be, for example, 2 to 30 mol%. In another embodiment of the present invention, the COOH terminal group ratio of the block copolymer may be, for example, 5 to 40 mol%, 10 to 40 mol%, 5 to 30 mol%, or 10 to 30 mol%.

[0099] (First Block (A)) The structural unit (a1) and the structural unit (a2) constituting the first block (A) are the same as those described in the above-described embodiment of the aliphatic polyester or the above-described method for producing the aliphatic polyester.

[0100] (Second Block (B)) [Polylactic Acid Unit (b)] The second block (B) preferably contains, as a main component, a structural unit derived from polylactic acid (hereinafter also referred to as a "polylactic acid unit"). The "main component" refers to the structural unit that is contained in the highest proportion among the structural units of the second block (B). Preferably, the "main component" is the structural unit that is contained in the highest proportion by mass percentage among the structural units that constitute the second block (B).

[0101] The content of polylactic acid units in the second block (B) is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 85% by mass or more, and even more preferably 90% by mass or more, based on 100% by mass of the total amount of structural units constituting the second block (B). The content of polylactic acid units in the second block (B) is not limited to an upper limit, and can be, for example, 100% by mass. As described above, these stepwise lower and upper limits can be independently combined. For example, in one embodiment of the present invention, the content of polylactic acid units in the second block (B) is preferably 70 to 100% by mass, more preferably 80 to 100% by mass, even more preferably 85 to 100% by mass, and even more preferably 90 to 100% by mass, based on 100% by mass of the total amount of structural units constituting the second block (B).

[0102] The polylactic acid unit may be formed so as to be bonded to the first block (A) by a direct condensation method of lactic acid, or may be formed so as to be bonded to the first block (A) by a ring-opening polymerization method of lactide. In one aspect of the polylactic acid unit, the polylactic acid unit is formed so as to be bonded to the first block (A) by a ring-opening polymerization method of lactide. The polylactic acid constituting the polylactic acid unit may be prepared by a direct condensation method of lactic acid, or may be prepared by a ring-opening polymerization method of lactide.

[0103] The lactic acid may be, for example, at least one selected from the group consisting of L-lactic acid, D-lactic acid, and DL-lactic acid. The lactide may be, for example, at least one selected from the group consisting of L-lactide, D-lactide, DL-lactide, and meso-lactide.

[0104] The polylactic acid may be at least one selected from the group consisting of poly-L-lactic acid, poly-D-lactic acid, poly-DL-lactic acid, and stereocomplex polylactic acid obtained by mixing poly-L-lactic acid and poly-D-lactic acid. In one embodiment, the polylactic acid is at least one selected from the group consisting of poly-L-lactic acid, poly-D-lactic acid, and poly-DL-lactic acid, and is preferably at least one selected from the group consisting of poly-L-lactic acid and poly-D-lactic acid.

[0105] From the viewpoint of more easily achieving the desired effects of the present invention, the second block (B) preferably contains structural units derived from poly-L-lactic acid or structural units derived from poly-D-lactic acid in an amount of 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, based on the total amount (100% by mass) of structural units constituting the second block (B). In a preferred embodiment, the second block (B) is composed of structural units derived from poly-L-lactic acid or structural units derived from poly-D-lactic acid, i.e., the structural units derived from poly-L-lactic acid or structural units derived from poly-D-lactic acid account for 100% by mass. Furthermore, in one embodiment of the present invention, when the second block (B) contains structural units derived from polylactic acid, not all of the structural units derived from polylactic acid need to form a stereocomplex.

[0106] (Structural Units Other Than Polylactic Acid Units) The second block (B) may or may not contain structural units other than polylactic acid units. Monomers capable of forming structural units other than polylactic acid units are not particularly limited as long as they do not excessively impair the effects of the present invention. Examples include α-acetolactone, β-propiolactone, γ-butyrolactone, δ-valerolactone, and ε-caprolactone. The content of structural units other than polylactic acid units in the second block (B) is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less, and even more preferably 10% by mass or less, based on 100% by mass of the total amount of structural units constituting the second block (B). In one embodiment of the present invention, the content of structural units other than polylactic acid units in the second block (B) is preferably 0 to 30% by mass, more preferably 0 to 20% by mass, even more preferably 0 to 15% by mass, and still more preferably 0 to 10% by mass, relative to 100% by mass of the total amount of structural units constituting the second block (B).

[0107] (Number Average Molecular Weight of Second Block (B)) The number average molecular weight of the second block (B) is preferably 5,000 to 150,000, more preferably 10,000 to 100,000, and even more preferably 20,000 to 40,000, from the viewpoint of more easily achieving the effect of imparting impact resistance while suppressing a decrease in heat resistance of any polyester resin.

[0108] When the block copolymer has a plurality of second blocks (B), the number average molecular weight of the second block (B) means the total number average molecular weight of all the blocks.

[0109] The number average molecular weight of the second block (B) can be determined from the number average molecular weight of the block copolymer described below and the mass content of the second block (B).

[0110] The number average molecular weight of the second block (B) can be changed by adjusting the polymerization conditions of the polylactic acid, for example.

[0111] (Melting Point of Polylactic Acid Capable of Forming Second Block (B)) From the viewpoint of processability, such as ease of melt processing, the melting point of the polylactic acid capable of forming the second block (B) is preferably 185°C or lower, more preferably 180°C or lower, even more preferably 170°C or lower, and still more preferably 160°C or lower.

[0112] From the viewpoint of practical heat resistance, the melting point of the polylactic acid capable of forming the second block (B) is preferably 110°C or higher, more preferably 120°C or higher, and even more preferably 125°C or higher.

[0113] From the viewpoint of good processability and heat resistance, the melting point of the polylactic acid capable of forming the second block (B) is preferably 110°C or higher and 185°C or lower, more preferably 120°C or higher and 180°C or lower, even more preferably 120°C or higher and 170°C or lower, and still more preferably 125°C or higher and 160°C or lower.

[0114] The melting point of the polylactic acid capable of forming the second block (B) can be determined by a differential scanning calorimeter.

[0115] (Copolymerization Mode of Block Copolymer) The copolymerization mode of the block copolymer is not particularly limited as long as it satisfies the above-mentioned conditions, and may be, for example, any copolymerization mode such as diblock, triblock, tetrablock or higher multiblock, graft, star, dendrimer, etc., and these copolymerization modes may be present alone or in combination of two or more. Among these, from the viewpoint of improving mechanical properties such as impact resistance when blended into a resin composition containing any polyester resin, the block copolymer according to this embodiment is preferably a block copolymer containing a first block (A) and a second block (B), or a block copolymer consisting of the first block (A) and the second block (B), more preferably a multiblock copolymer having two or more second blocks (B), and even more preferably a triblock copolymer consisting of [second block (B)]-[first block (A)]-[second block (B)].

[0116] (Structural Unit Proportion in Block Copolymer) The proportion of the second block (B) is preferably 5 to 95 mass% relative to the total of 100 mass% of the first block (A) and the second block (B). In the present invention, the "proportion of the second block (B)" may also be referred to as the "hard ratio" in the block copolymer.

[0117] When the proportion of the second block (B) is 5% by mass or more, the heat resistance of the block copolymer-containing resin composition or a molded article thereof tends to be even more excellent, and when the proportion of the second block (B) is 95% by mass or less, the impact resistance and biodegradability of the block copolymer-containing resin composition or a molded article thereof tends to be even more excellent.

[0118] From the viewpoint of facilitating improvements in heat resistance and transparency of the block copolymer-containing resin composition or a molded article thereof, the proportion of the second block (B) is more preferably 7% by mass or more, even more preferably 10% by mass or more, and even more preferably 15% by mass or more. Furthermore, from the viewpoint of facilitating improvements in hydrolysis resistance, impact resistance, biodegradability, etc., the proportion of the second block (B) is more preferably 80% by mass or less, even more preferably 70% by mass or less, even more preferably 60% by mass or less, even more preferably 50% by mass or less, even more preferably 45% by mass or less, and even more preferably 40% by mass or less. Furthermore, as mentioned above, these stepwise lower and upper limits can be independently combined. For example, in one embodiment of the present invention, the proportion of the second block (B) is preferably 5 to 95 mass%, more preferably 5 to 80 mass%, even more preferably 5 to 70 mass%, still more preferably 5 to 60 mass%, even more preferably 5 to 50 mass%, and still more preferably 5 to 45 mass%, based on 100 mass% of the total of the first block (A) and the second block (B). Furthermore, for example, in one embodiment of the present invention, from the viewpoint of further improving the transparency of the block copolymer-containing resin composition or a molded article thereof, the proportion of the second block (B) is even more preferably 7 to 45 mass%, even more preferably 10 to 45 mass%, and still more preferably 15 to 45 mass%, based on 100 mass% of the total of the first block (A) and the second block (B). Furthermore, for example, in one embodiment of the present invention, from the viewpoint of making it easier to improve the impact resistance of the block copolymer-containing resin composition or a molded article thereof, the proportion of the second block (B) is even more preferably 5 to 40 mass%, even more preferably 5 to 30 mass%, and even more preferably 5 to 20 mass%, relative to 100 mass% in total of the first block (A) and the second block (B).

[0119] The proportion of the second block (B) is １ It can be determined by H-NMR, specifically by the method described in the Examples.

[0120] Furthermore, the total content of the first block (A) and the second block (B) in the block copolymer is preferably 90% by mass or more, more preferably 95% by mass or more, and may even be 100% by mass, based on 100% by mass of the total amount of structural units constituting the block copolymer. Furthermore, there is no upper limit to the total content of the first block (A) and the second block (B) in the block copolymer, and it may be, for example, 100% by mass. As described above, these stepwise lower and upper limits can be independently combined. For example, in one embodiment of the present invention, the total content of the first block (A) and the second block (B) is preferably 90 to 100% by mass, more preferably 95 to 100% by mass, based on 100% by mass of the total amount of structural units constituting the block copolymer.

[0121] The block copolymer may or may not contain a structural unit other than the first block (A) and the second block (B) (i.e., a structural unit that is neither the first block (A) nor the second block (B)). The structural unit other than the first block (A) and the second block (B) (herein, the term "structural unit that is neither the first block (A) nor the second block (B)") is not particularly limited as long as it does not excessively impair the effects of the present invention. The content of structural units other than the first block (A) and the second block (B) in the block copolymer is preferably 10% by mass or less, more preferably 5% by mass or less, and may be 0% by mass, based on 100% by mass of the total amount of structural units constituting the block copolymer. Furthermore, there is no lower limit for the content of structural units other than the first block (A) and the second block (B) in the block copolymer, and it may be, for example, 0% by mass. Furthermore, as described above, these stepwise lower and upper limits can be independently combined. For example, in one embodiment of the present invention, the content of structural units other than the first block (A) and the second block (B) is preferably 0 to 10 mass%, more preferably 0 to 5 mass%, relative to 100 mass% of the total amount of structural units constituting the block copolymer.

[0122] (Number-average molecular weight α(BCP) of block copolymer) From the viewpoint of more easily achieving the effect of imparting impact resistance while suppressing a decrease in heat resistance of any polyester resin, the number-average molecular weight α(BCP) of the block copolymer is preferably 28,750 or more, more preferably 30,000 or more, even more preferably 31,000 or more, and even more preferably 36,000 or more. From the viewpoint of ease of production and processability, the number-average molecular weight α(BCP) of the block copolymer is preferably 400,000 or less, more preferably 200,000 or less, and even more preferably 100,000 or less. Furthermore, as mentioned above, these stepwise described lower limit values ​​and upper limit values ​​can be independently combined. For example, in one embodiment of the present invention, the number average molecular weight α(BCP) of the block copolymer is preferably 28,750 to 400,000, more preferably 30,000 to 200,000, even more preferably 31,000 to 100,000, and still more preferably 36,000 to 100,000.

[0123] The number average molecular weight α(BCP) of the block copolymer can be determined by gel permeation chromatography (GPC), specifically, by the method described in the Examples.

[0124] (Glass Transition Temperature Tg(BCP) of Block Copolymer) The glass transition temperature Tg(BCP) of the block copolymer according to this embodiment is not particularly limited, but is preferably −80° C. or higher and −15° C. or lower. Within this range, the block copolymer, a resin composition containing the block copolymer, and a molded article of a resin composition containing the block copolymer tend to have excellent impact resistance. From the viewpoint of easily achieving good low-temperature properties such as low-temperature impact resistance of the block copolymer, a resin composition containing the block copolymer, and a molded article of a resin composition containing the block copolymer, the glass transition temperature Tg(BCP) of the block copolymer is more preferably −20° C. or lower, even more preferably −25° C. or lower, and may also be, for example, −30° C. or lower, or −35° C. or lower. From the viewpoint of easily achieving good low-temperature impact resistance of the block copolymer, a resin composition containing the block copolymer, and a molded article of a resin composition containing the block copolymer, the glass transition temperature Tg(BCP) of the block copolymer is preferably lower. On the other hand, the glass transition temperature Tg(BCP) of the block copolymer may be, for example, −75°C or higher, −70°C or higher, or −65°C or higher. Furthermore, as described above, these stepwise lower and upper limits can be independently combined. For example, in one embodiment of the present invention, the glass transition temperature Tg(BCP) of the block copolymer is preferably −80°C to −15°C, more preferably −80°C to −20°C, even more preferably −80°C to −25°C, still more preferably −80°C to −30°C, and even more preferably −80°C to −35°C, and may be, for example, −75°C to −35°C, −70°C to −35°C, or −65°C to −35°C. The glass transition temperature of the block copolymer can be determined, for example, by differential scanning calorimetry.

[0125] (Properties of Block Copolymer) The block copolymer according to this embodiment contains a first block derived from a high-molecular-weight aliphatic polyester that satisfies Condition 2 (BCP), and therefore, the block copolymer or a molded article of a resin composition containing the block copolymer can be provided with these properties. For example, the block copolymer according to this embodiment achieves high molecular weight due to the first block (A) derived from a high-molecular-weight aliphatic polyester. Therefore, the block copolymer according to this embodiment has excellent heat resistance in its molded article or in a molded article of a composition containing the block copolymer. Furthermore, since the first block (A) of the block copolymer according to this embodiment forms a soft segment, impact resistance can be imparted to, for example, a molded article of the block copolymer or a molded article of a composition containing the block copolymer.

[0126] (Imparting Properties to Resin Composition) When the block copolymer according to this embodiment is formed into a resin composition, it can impart the properties of the block copolymer to a molded article of the resin composition. For example, since the block copolymer according to this embodiment has a high molecular weight, it can impart heat resistance to a molded article of the resin composition. Furthermore, since the block copolymer according to this embodiment contains an amorphous, flexible molecular chain derived from an aliphatic diol having a specific branched structure in the main chain of its molecular structure, it can impart impact resistance to a molded article of the resin composition, for example.

[0127] (Method for Producing Block Copolymer) The block copolymer can be produced by, for example, a known method, such as a method of polymerizing an aliphatic polyester and a lactide.

[0128] As the aliphatic polyester, it is preferable to use the aliphatic polyester described in the above embodiment or the second aliphatic polyester obtained by the method for producing an aliphatic polyester described in the above embodiment, that is, it is preferable to use an aliphatic polyester (PE).

[0129] When the aliphatic polyester and the lactide are polymerized, it is preferable to use a ring-opening polymerization catalyst (for example, an organic carboxylic acid metal salt such as tin octoate, a metal halide such as tin chloride, or a metal oxide such as tin oxide). The polymerization reaction may be performed by solution polymerization, melt polymerization, interfacial polycondensation, or the like, and known polymerization reaction conditions can be set for each reaction.

[0130] Another known method for producing a block copolymer is, for example, a method in which polylactic acid capable of forming polylactic acid units is synthesized and the polylactic acid is reacted with the aliphatic polyester.

[0131] Polylactic acid can be synthesized by a known method, for example, by reacting lactic acid by a direct condensation method or by reacting lactide by a ring-opening polymerization method.

[0132] When polylactic acid and polyester are polymerized, it is preferable to use an esterification catalyst (for example, an organic carboxylic acid metal salt such as tin octoate, a metal halide such as tin chloride, or a metal oxide such as tin oxide). The polymerization reaction may be performed by solution polymerization, melt polymerization, interfacial polycondensation, or the like, and known polymerization reaction conditions can be set for each reaction.

[0133] One embodiment of the method for producing the block copolymer is as follows. 1. A method for producing a block copolymer, comprising: a first block (A) derived from an aliphatic polyester containing structural units (a1) derived from an aliphatic diol having 3 or more carbon atoms in its main chain and having an alkyl group as a branched chain, and structural units (a2) derived from an aliphatic dicarboxylic acid; and a second block (B) derived from polylactic acid containing structural units derived from lactic acid, the method satisfying the following three conditions 1 (BCP), 2 (BCP), and 3 (BCP): 1. The first aliphatic polyester containing the structural units (a1) and (a2) is reacted with at least one member selected from the group consisting of a second aliphatic dicarboxylic acid (z1), an aliphatic dicarboxylic acid alkyl ester (z2), and an aliphatic dicarboxylic acid anhydride (z3). 2. The method for producing a block copolymer, comprising: forming a second block (B) derived from polylactic acid containing structural units derived from lactic acid by a direct condensation method of lactic acid or a ring-opening polymerization method of lactide so that the second block (B) is bonded to the first block (A). Condition 1 (BCP): The following α(BCP) and β(BCP) satisfy the following relational formula (III): α(BCP) / (150-β(BCP))≧575 (III) (In the relational formula (III), α(BCP) is the number average molecular weight of the block copolymer, and β(BCP) is the OH terminal group proportion [mol %] of the block copolymer, which indicates the proportion (percentage) of the number of OH terminal groups when the total number of terminal groups of the block copolymer is 100 mol %). Condition 2 (BCP): In the block copolymer, the sum (M(a)) of the average formula weight (M(a1)) of the structural unit (a1) portion and the average formula weight (M(a2)) of the structural unit (a2) portion is in the range of 25,000 to 75,000. Condition 3 (BCP): β(BCP)≧25

[0134] In this embodiment, the first block (A) and the second block (B) are the same as those described in the embodiment of the block copolymer, and their preferred embodiments are also the same. Furthermore, the block copolymer obtained by the production method of this embodiment is the same as those described in the embodiment of the block copolymer, and their preferred embodiments are also the same.

[0135] [Resin Composition (Block Copolymer-Containing Resin Composition)] A block copolymer-containing resin composition according to one embodiment of the present invention contains the block copolymer (BCP) according to the embodiment described above (in this specification, "block copolymer (BCP)" refers to at least one selected from the block copolymers described in the section on the block copolymer according to one embodiment of the present invention and the block copolymers produced by the production method described in the section on the production method of the block copolymer according to one embodiment of the present invention). Preferably, the block copolymer (BCP) according to the embodiment described above and the polyester resin (D) described above are contained in the resin composition. The block copolymer (BCP) may be a block copolymer obtained by the production method of the block copolymer according to the embodiment described above. The polyester resin (D) may be used alone or in combination of two or more types. According to this embodiment, since the resin composition contains the block copolymer (BCP), the properties of the block copolymer (BCP) can be imparted to a molded article of the resin composition. Specifically, the block copolymer (BCP) can contribute to the modification of the polyester resin (D). Furthermore, the resin composition containing the block copolymer (BCP) according to one embodiment of the present invention may or may not contain the aliphatic polyester (PE) according to the embodiment described above.

[0136] (Polyester Resin (D)) The polyester resin (D) contained in the block copolymer-containing resin composition according to this embodiment can be any polyester resin. Examples of the polyester resin (D) are as described in the embodiment of the aliphatic polyester resin-containing resin composition, and preferred embodiments thereof are also the same.

[0137] (Block Copolymer (BCP) Content) In one embodiment of the block copolymer-containing resin composition, the content of the block copolymer (BCP) is preferably 0.5 to 50.0 mass%, more preferably 1.0 to 40.0 mass%, even more preferably 1.5 to 30.0 mass%, still more preferably 2.0 to 20.0 mass%, and even more preferably 2.0 to 15.0 mass%, based on 100% by mass of the total amount of the block copolymer-containing resin composition. In one embodiment of the block copolymer-containing resin composition, from the viewpoint of further improving the impact resistance of the block copolymer-containing resin composition and articles molded from the block copolymer-containing resin composition, the content of the block copolymer (BCP) may be 5 to 20.0 mass%, or may be 5 to 15.0 mass%, based on 100% by mass of the total amount of the block copolymer-containing resin composition.

[0138] In one embodiment of the block copolymer-containing resin composition, the block copolymer-containing resin composition preferably contains 0.5 to 50.0 mass%, more preferably 1.0 to 40.0 mass%, even more preferably 1.5 to 30.0 mass%, still more preferably 2.0 to 20.0 mass%, even more preferably 2.0 to 15.0 mass%, and still more preferably 2.0 to 13.0 mass%, of the total of 100 mass% of the block copolymer (BCP) and the polyester resin (D). This content ratio can sufficiently exhibit the effect of imparting impact resistance while suppressing a decrease in the heat resistance of any polyester resin. Furthermore, in one embodiment of the block copolymer-containing resin composition, from the viewpoint of making it easier to improve the impact resistance of the block copolymer-containing resin composition and a molded article of the block copolymer-containing resin composition, the content of the block copolymer (BCP) may be 5 to 20.0 mass%, 5 to 15.0 mass%, or 5 to 13.0 mass%, relative to 100 mass% in total of the block copolymer (BCP) and the polyester resin (D).

[0139] In the block copolymer-containing resin composition of this embodiment, the total content of the block copolymer (BCP) and the polyester resin (D) is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 98% by mass or more. In the block copolymer-containing resin composition of this embodiment, the total content of the block copolymer (BCP) and the polyester resin (D) may be 100% by mass or less. As described above, these stepwise lower and upper limits can be independently combined. For example, in one aspect of the present invention, the total content of the block copolymer (BCP) and the polyester resin (D) is preferably 80 to 100% by mass, more preferably 85 to 100% by mass, even more preferably 90 to 100% by mass, even more preferably 95 to 100% by mass, and even more preferably 98 to 100% by mass, based on the total amount (100% by mass) of the block copolymer-containing resin composition. This content ratio is preferred because the effects of the present invention are more pronounced.

[0140] (Other Components) The block copolymer-containing resin composition of this embodiment may contain at least one other component selected from the group consisting of a plasticizer other than the aliphatic polyester (PE), the block copolymer (BCP), and the polyester resin (D); a resin other than the polyester resin (D); and other additives. Examples of the plasticizer, resin other than the polyester resin (D), and other additives that the block copolymer-containing resin composition may contain are the same as those described in the section on embodiments of the aliphatic polyester-containing resin composition, and preferred embodiments thereof are also the same. Furthermore, the block copolymer-containing resin composition may or may not contain the aliphatic polyester (PE) according to the above-described embodiment as a resin other than the polyester resin (D).

[0141] (Method for producing block copolymer-containing resin composition) There are no particular limitations on the method for producing the block copolymer-containing resin composition of this embodiment, and examples thereof are the same as those described in the embodiment of the aliphatic polyester-containing resin composition described above.

[0142] (Characteristics of Block Copolymer-Containing Resin Composition) (Impact Resistance) When the block copolymer-containing resin composition according to this embodiment is prepared into a resin composition containing a polyester resin, preferably a resin composition (D) containing a polyester resin, the molded article tends to exhibit excellent impact resistance. For example, the impact resistance value (kJ / m) measured in the Examples section described later is ２ ) preferably exhibits a value higher than the impact resistance value of the polyester resin.

[0143] (Heat Resistance) When the block copolymer-containing resin composition according to this embodiment is prepared into a resin composition containing a polyester resin, preferably a resin composition (D) containing a polyester resin, the molded article tends to exhibit excellent heat resistance.

[0144] (Transparency) When the block copolymer-containing resin composition according to this embodiment is prepared into a resin composition containing a polyester resin, preferably a resin composition (D) containing a polyester resin, the transparency of the molded article tends to be not significantly impaired. Therefore, this embodiment is useful when a resin composition containing a polyester resin, preferably a resin composition (D) containing a polyester resin, which is required to maintain transparency, is prepared. Transparency can be evaluated, for example, by the haze value measured by the method described in the Examples section below.

[0145] A resin composition according to another embodiment of the present invention may contain the block copolymer (BCP) according to the above-described embodiment, but may not contain the polyester resin (D). According to this embodiment, the properties of the block copolymer (BCP) can be exhibited in the resin composition containing the block copolymer (BCP) or in a molded article thereof.

[0146] [Molded Article] A molded article according to one embodiment of the present invention is a molded article made from the block copolymer-containing resin composition according to the above-described embodiment. A molded article according to another embodiment is a molded article made from the resin composition according to the above-described other embodiment (a block copolymer-containing resin composition not containing polyester resin (D)). These embodiments enable the properties of the block copolymer to be exhibited. The shape of the molded article is not particularly limited, and may be a shape intended for secondary processing, such as a film, sheet, fiber, nonwoven fabric, woven fabric, foam, tube, roll, sphere, powder, or scale, or may be a shape such as a container, bag, tableware, or case. It may also be laminated with other materials such as paper, resin, metal, or ceramic. The molding method is not limited, and commonly used methods such as melt extrusion molding, blow molding, inflation molding, stretch molding, vacuum molding, injection molding, solution coating, spray coating, and solution impregnation can be used. Products can also be obtained by combining multiple molding methods. Heat treatment (annealing) of the obtained molded article under appropriate conditions may improve its crystallinity, tensile properties, heat resistance, and other properties.

[0147] Furthermore, the aliphatic polyester (PE), the block copolymer (BCP), the aliphatic polyester-containing resin composition, the block copolymer-containing resin composition, a molded article of the aliphatic polyester-containing resin composition, and a molded article of the block copolymer-containing resin composition, which are embodiments of the present invention, can each independently be suitably used as a molded article such as a sheet, a film, a tube, a hose, or a belt, or as a pressure-sensitive adhesive, taking advantage of their biodegradable properties, impact resistance, and heat resistance. Specifically, the present invention can be suitably used in footwear such as shoes and fashion sandals; components for home appliances such as televisions, stereos, vacuum cleaners, and refrigerators; building materials such as sealing packing for building doors and window frames; automotive interior and exterior parts such as bumper parts, body panels, weather strips, grommets, and instrument panel coverings, and airbag covers; grips for scissors, screwdrivers, toothbrushes, ski poles, and the like; food packaging materials such as food wrap films, sealing laminate films, and coating agents; medical tools such as infusion bags, syringes, catheters, and protective gloves; stoppers for containers for storing food, beverages, medicines, and the like; cap liners; adhesives such as hot melt adhesives, adhesive tapes, and adhesive layers of protective films; and agricultural products such as agricultural mulch films, fertilizer covering materials, sand-flying inhibitors, and soil conditioners.

[0148] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0149] [First Example (Aliphatic Polyester)] [Components] The components used in the examples and comparative examples are as follows: MPD: 3-methyl-1,5-pentanediol (manufactured by Kuraray Co., Ltd.) AA: adipic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) Sn(Oct) ２ : Tin octoate (manufactured by Tokyo Chemical Industry Co., Ltd.) (z1-1): AA ("adipic acid", manufactured by Tokyo Chemical Industry Co., Ltd.) (z2-1): Dimethyl adipate (manufactured by Tokyo Chemical Industry Co., Ltd.) (z2-2): Bis(2-ethylhexyl) adipate (manufactured by Tokyo Chemical Industry Co., Ltd.) Toluene (manufactured by Kishida Chemical Co., Ltd.) Methanol (manufactured by Fujifilm Wako Pure Chemical Industries Co., Ltd.) Ti(OiPr) ４: Tetraisopropyl orthotitanate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) K ２ TiO(C ２ O ４ ) 2H ２ O: Potassium titanium oxalate dihydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)

[0150] [Measurement and Evaluation] 1-1. Number average molecular weight (Mn) of first aliphatic polyester The number average molecular weight (Mn) of the first aliphatic polyester obtained in the first step of Examples 1-1 to 1-11 and Comparative Example 1-6 (in Tables 1 and 2, "first aliphatic polyester" is also referred to as "first PE") was determined in terms of standard polystyrene by gel permeation chromatography (GPC). <GPC measurement conditions> Apparatus: GPC apparatus "HLC-8220" manufactured by Tosoh Corporation Separation column: "TSKgel (registered trademark) SuperMultipore HZ-M (column diameter = 4.6 mm, column length = 15 cm)" manufactured by Tosoh Corporation (two columns connected in series) Eluent: tetrahydrofuran (THF) Eluent flow rate: 0.35 mL / min Column temperature: 40°C Detection method: refractive index (RI) Injection volume: 10 μL Concentration: 1 mg / 1 mL (aliphatic polyester / THF)

[0151] 1-2. OH ​​Terminal Group Ratio of First Aliphatic Polyester The first aliphatic polyester obtained in the first step of Examples 1-1 to 1-11 and Comparative Example 1-6 was used as a sample and dissolved in 200 mL of toluene, and then subjected to neutralization titration with a 0.05 N ethanol solution of potassium hydroxide, and the acid value (mol / g) was calculated according to the following formula: Acid value (mol / g) = (A - B) × 0.05 ÷ 1000 ÷ S A: Amount (mL) of 0.05 N ethanol solution of potassium hydroxide required for neutralization B: Amount (mL) of 0.05 N ethanol solution of potassium hydroxide added to a blank solution containing no sample S: Mass (g) of weighed sample

[0152] Next, １The hydroxyl value was calculated by H-NMR measurement. The hydroxyl value (mol / g) of the first aliphatic polyester resin was calculated from the area ratio of the signal at around 3.7 ppm derived from the methylene adjacent to the OH terminal group in the obtained spectrum to the signal at around 0.9 ppm derived from the main chain of the first aliphatic polyester resin. １ H-NMR measurement conditions) Apparatus: Nuclear magnetic resonance apparatus "JNM-ECX400" manufactured by JEOL Ltd. Solvent: deuterated chloroform Measurement temperature: 50°C Number of accumulations: 1024 Measurement conditions: Temperature rise rate 10°C / min

[0153] The OH terminal group ratio was calculated from the acid value and hydroxyl value of the sample obtained above according to the following formula: Total terminal group value (mol / g) = Acid value (mol / g) + Hydroxyl value (mol / g) OH terminal group ratio (mol %) = Hydroxyl value (mol / g) ÷ Total terminal group value (mol / g) × 100

[0154] 1-3. COOH Terminal Group Ratio of First Aliphatic Polyester The COOH terminal group ratio was calculated from the acid value and hydroxyl value of the sample calculated in the same manner as in 1-2 above for the OH terminal group ratio, according to the following formulas: Total terminal group value (mol / g) = Acid value (mol / g) + Hydroxyl value (mol / g) COOH terminal group ratio (mol %) = Acid value (mol / g) ÷ Total terminal group value (mol / g) × 100

[0155] 1-4. Number-Average Molecular Weight (α(PE)) of Second Aliphatic Polyester The number-average molecular weight α(PE) of the second aliphatic polyester obtained in the Examples and Comparative Examples (in Tables 1 and 2, "second aliphatic polyester" is also referred to as "second PE") was determined by GPC in the same manner as for the number-average molecular weight of the first aliphatic polyester in 1-1 above. The number-average molecular weight α(PE) refers to the sum (M(a)) of the average formula weight (M(a1)) of the structural unit (a1) portion and the average formula weight (M(a2)) of the structural unit (a2) portion in the second aliphatic polyester. In the first Example, the structural unit (a1) was a structural unit derived from 3-methyl-1,5-pentanediol (MPD) used in the Examples and Comparative Examples. The structural unit (a2) was a structural unit derived from the adipic acid (AA), (z1-1), (z2-1), and (z2-2) components used in the Examples and Comparative Examples.

[0156] 1-5. OH Terminal Group Ratio (β(PE)) of Second Aliphatic Polyester The OH terminal group ratio β(PE) of the second aliphatic polyester obtained in the Examples and Comparative Examples was determined in the same manner as in the OH terminal group ratio of the first aliphatic polyester in 1-2 above.

[0157] 1-6. COOH Terminal Group Ratio of Second Aliphatic Polyester The COOH terminal group ratio of the second aliphatic polyester obtained in the examples and comparative examples was determined in the same manner as in the COOH terminal group ratio of the first aliphatic polyester in 1-3 above.

[0158] 1-7. Evaluation of PLA block modification suitability For the second aliphatic polyesters obtained in the examples and comparative examples, the value of the following relational expression (I) was determined: α(PE) / (150-β(PE)) (I)

[0159] The value of the relational formula (I) was then evaluated for PLA block modification suitability based on the following criteria: A: The value of the relational formula (I) is 500 or more; B: The value of the relational formula (I) is 400 or more and less than 500; C: The value of the relational formula (I) is less than 400. The PLA block modification suitability refers to the expected value for producing a desired block copolymer from the perspective of increasing molecular weight when a block copolymer containing a first block derived from the second aliphatic polyester obtained in the examples and comparative examples and a second block derived from polylactic acid containing structural units derived from lactic acid is produced, with Grade A indicating a superior expected value, Grade B indicating a lower expected value, and Grade C indicating a lower expected value.

[0160] 1-8. Evaluation of biodegradability (compost) Biodegradability in compost was measured according to the method in accordance with ISO 14855-2:2018 and evaluated based on the following criteria: A: Decomposition rate after 15 days was 20% by mass or more B: 10% by mass or more but less than 20% by mass C: 5% by mass or more but less than 10% by mass D: Less than 5% by mass

[0161] Example 1-1 (First Step: Production of First Aliphatic Polyester) A 500 mL four-neck flask equipped with an apparatus capable of distilling off generated liquid and a vacuum pump was charged with 110 parts by mole (151.7 g) of 3-methyl-1,5-pentanediol and 100 parts by mole (170.7 g) of adipic acid such that the molar equivalent ratio of the number of moles of —OH groups in 3-methyl-1,5-pentanediol to the number of moles of —COOH groups in adipic acid was OH groups / COOH groups=1.1 / 1.0. Subsequently, 96.7 mg of tin octoate was added so that the amount was 0.03 phr relative to the total weight of 3-methyl-1,5-pentanediol and adipic acid. The mixture was subjected to a pre-reaction under a nitrogen atmosphere at normal pressure and 210° C. for 6 hours, and then the reduced pressure was reduced to 100 Pa and the mixture was heated for 2 hours to carry out a polycondensation reaction while distilling off water.

[0162] In this way, a dispersion of a first aliphatic polyester having a number average molecular weight Mn of 10,000 and an OH terminal group ratio of 99.9 mol % was obtained. The COOH terminal group ratio of the first aliphatic polyester was 0.1 mol %.

[0163] (Second Step: Production of Second Aliphatic Polyester) Next, 270.5 g of the first aliphatic polyester was placed in a 500 mL four-neck flask equipped with an apparatus capable of distilling off generated liquid and a vacuum pump, and 4.4 g of adipic acid as the component (z1) was added to the dispersion of the first aliphatic polyester so that the molar equivalent was 0.33 relative to the total number of terminal functional groups calculated from the total terminal functional group value of the first aliphatic polyester. Furthermore, 274.9 mg of tetraisopropyl orthotitanate as a catalyst was added so that the amount was 0.1 phr relative to the total mass of the first aliphatic polyester and the adipic acid as the component (z1).

[0164] The dispersion obtained as described above was subjected to a pre-reaction for 3 hours at a temperature of 220°C under a reduced pressure of 2,000 Pa, and then to a reaction for 11 hours under a reduced pressure of 100 Pa, while appropriately checking the reaction until the number average molecular weight reached 39,700. After completion of the reaction, the reaction system was returned to normal pressure and cooled to 80°C.

[0165] Thereafter, solid separation and washing operations were performed as follows. First, toluene was added to dilute the solid concentration to 40% by mass, and then the above toluene solution was added to methanol in an amount twice the total volume of the solution. Next, the supernatant was discarded, and an equal amount of methanol to the amount of the added toluene solution was added again for washing. Then, the supernatant was discarded to recover the insoluble matter. The insoluble matter was dried at 40°C in a vacuum dryer. This removed the organic volatile matter, leaving the solid matter. In this way, a second aliphatic polyester was obtained. The obtained second aliphatic polyester was subjected to the above-mentioned measurements and evaluations. The results are shown in Table 1.

[0166] [Examples 1-2 to 1-11] Second aliphatic polyesters were obtained by polycondensation as follows. The measurements and evaluations described above were carried out for each of the obtained second aliphatic polyesters in the same manner as in Example 1-1. The results are shown in Table 1. (First Step) A dispersion of a first aliphatic polyester was obtained under the same conditions as in the first step of Example 1-1. (Second Step) Subsequently, polycondensation was carried out in the second step in the same manner as in Example 1-1, except that the chain extender, catalyst, and polycondensation conditions were changed to those shown in Table 1. Thereafter, solid separation and washing operations similar to those in Example 1-1 were carried out to obtain second aliphatic polyesters.

[0167] Comparative Example 1-1: A 500 mL four-neck flask equipped with an apparatus capable of distilling off the generated liquid and a vacuum pump was charged with 110 molar parts (151.7 g) of 3-methyl-1,5-pentanediol and 100 molar parts (170.7 g) of adipic acid so that the molar equivalent ratio of the number of moles of -OH groups in 3-methyl-1,5-pentanediol to the number of moles of -COOH groups in adipic acid was 1.1 / 1.0. Subsequently, 322.4 mg of tin octoate was added so that the ratio was 0.1 phr relative to the total weight of 3-methyl-1,5-pentanediol and adipic acid. The mixture was subjected to a pre-reaction under a nitrogen atmosphere at normal pressure and 220°C for 6 hours, and then the reduced pressure was reduced to 100 Pa and the mixture was heated for 2 hours to carry out a polycondensation reaction while distilling off water. That is, in Comparative Example 1-1, a method of polycondensation in one stage (without using a chain extender) was adopted.

[0168] In this way, a dispersion of an aliphatic polyester having a number average molecular weight Mn of 10,000 and an OH terminal group ratio of 99 mol % was obtained. The COOH terminal group ratio of the aliphatic polyester was 1 mol %.

[0169] Thereafter, the same solid content separation and washing operations as in Example 1-1 were carried out to obtain an aliphatic polyester (for convenience, referred to as a "second aliphatic polyester resin"). The obtained second aliphatic polyester was subjected to the above measurements and evaluations in the same manner as in Example 1-1. The results are shown in Table 2.

[0170] [Comparative Examples 1-2 to 1-5] Polycondensation was carried out in the same manner as in Comparative Example 1-1, except that the catalyst and polycondensation conditions were changed as shown in Table 2. Thereafter, solid separation and washing operations similar to those in Example 1-1 were carried out to obtain aliphatic polyesters (referred to as "second aliphatic polyester resins" for convenience). For each of the obtained second aliphatic polyesters, the above measurements and evaluations were carried out in the same manner as in Example 1-1. The results are shown in Table 2.

[0171] [Comparative Example 1-6] (First Step) A dispersion of a first aliphatic polyester was obtained under the same conditions as in the first step of Example 1-1. (Second Step) Subsequently, polycondensation was carried out in the second step in the same manner as in Example 1-1, except that the chain extender, catalyst, and polycondensation conditions were changed to those shown in Table 1. Thereafter, solid separation and washing operations similar to those in Example 1-1 were carried out to obtain a second aliphatic polyester. The obtained second aliphatic polyester was subjected to the above measurements and evaluations similar to those in Example 1-1. The results are shown in Table 2.

[0172]

[0173]

[0174] Tables 1 and 2 show that the second aliphatic polyesters of Examples 1-1 to 1-11 tend to satisfy the conditions of a high molecular weight (α(PE)) and a high OH terminal group proportion (β(PE)) compared to the second aliphatic polyesters of Comparative Examples 1-1 to 1-6. In contrast, as illustrated in the comparative examples, in the prior art, increasing the molecular weight of an aliphatic polyester reduces the OH terminal group proportion, making it unsuitable for block copolymerization. On the other hand, there has been a tendency for a trade-off to be exhibited in that suppressing the decrease in the OH terminal group proportion by not excessively increasing the molecular weight of the aliphatic polyester makes it impossible to achieve a high molecular weight block copolymer. Thus, it has been found that the present invention can overcome the trade-off of the prior art. Therefore, it has been found that the second aliphatic polyesters of Examples 1-1 to 1-11 are excellent in suitability when used to produce block copolymers containing a second block derived from polylactic acid, and can be expected to particularly contribute to increasing the molecular weight of the block copolymer.

[0175] Furthermore, as can be seen from a comparison between Example 1-1 and Comparative Example 1-3, it was found that the production method of the present invention can produce a second aliphatic polyester having a high molecular weight and a high proportion of OH terminal groups even at a milder polycondensation pressure.Furthermore, as can be seen from a comparison between Example 1-4 and Comparative Example 1-2, it was found that the production method of the present invention can produce a second aliphatic polyester having a high molecular weight and a high proportion of OH terminal groups even at a milder polycondensation temperature.

[0176] [Second Example (Aliphatic Polyester-Containing Composition)] [Components] The components used in the Examples and Comparative Examples are as follows: PE: Second aliphatic polyester obtained in Examples 1-4 and Comparative Example 1-1 (D1): Polyester resin "INGEO (registered trademark) 2500HP" (polylactic acid polymer) manufactured by NatureWorks (D2): Polyester resin "trade name: ecoflex (registered trademark) F Blend C1200" manufactured by BASF (PBAT: poly(butylene adipate / terephthalate))

[0177] 2-1. Evaluation of impact resistance (Preparation of test pieces for impact strength measurement) The polyester resin (D1) of Reference Example 2-1 and each of the resin compositions obtained in Reference Example 2-2, Example 2-1, and Comparative Example 2-1 were each subjected to a pressure reduction heat press ("IMC-183B" manufactured by Imoto Machinery Co., Ltd.) using an oil rotary pump to reduce the pressure to -0.1 MPaG, preheated at 200°C for 5 minutes, and then subjected to a pressure reduction heat press of 51 kgf / cm. ２ Then, the mixture was pressed in a cooling press equipped with a water flow cooling device at 70 kgf / cm for 3 minutes. ２ The plate was pressed at 100°C for 3 minutes to produce a 3.0 mm thick pressed plate. An 80 x 10 mm rectangular piece was cut out from the obtained pressed plate and crystallized in a 110°C thermostatic chamber for 3 hours. A V-notch (remaining width 8 mm, tip radius 0.25 mm) was formed in the center of the long side to produce a notched rectangular test piece.

[0178] (Impact Strength Measurement) The notched strip test piece was stored at 23°C and a relative humidity of 49% RH for 24 hours or more, and then the impact strength (kJ / m) was measured using a Charpy impact resistance tester ("DG-CB" manufactured by Toyo Seiki Seisaku-sho, Ltd.) at 23°C and a relative humidity of 49% RH with a hammer load of 2 J. ２ The measured value was the average of five measurements.

[0179] 2-2. Evaluation of heat resistance (Preparation of test pieces for deflection temperature under load) The polyester resin (D1) of Reference Example 2-1 and each of the resin compositions obtained in Reference Example 2-2, Example 2-1, and Comparative Example 2-1 were each subjected to a pressure reduction heat press ("IMC-183B" manufactured by Imoto Machinery Co., Ltd.) using an oil rotary pump to reduce the pressure to -0.1 MPaG, preheated at 200°C for 5 minutes, and then subjected to a pressure reduction heat press of 51 kgf / cm. ２ Then, the mixture was pressed in a cooling press equipped with a water jet cooling system at 70 kgf / cm for 3 minutes. ２ The mixture was pressed at 100°C for 3 minutes to prepare a pressed plate having a thickness of 3.0 mm. A rectangular piece of 80 x 10 mm was cut out from the obtained pressed plate and subjected to crystallization treatment in a constant temperature bath at 110°C for 3 hours to prepare a rectangular test piece.

[0180] (Measurement of Deflection Temperature Under Load) The strip test pieces were stored at 23°C and a relative humidity of 49% RH for 24 hours or more, and then the deflection temperature under load (°C) was measured using a deflection temperature under load tester ("S-3M" manufactured by Toyo Seiki Seisaku-sho, Ltd.) using the flatwise method at a load of 0.45 MPa. The average value of three measurements was used.

[0181] 2-3. Evaluation of Transparency The polyester resin of Reference Example 2-1 and each of the resin compositions obtained in Reference Example 2-2, Example 2-1, and Comparative Example 2-1 were each subjected to a pressure reduction heat press ("IMC-183B" manufactured by Imoto Machinery Co., Ltd.) using an oil rotary pump to reduce the pressure to -0.1 MPaG, preheated at 200°C for 5 minutes, and then subjected to a pressure reduction of 41 kgf / cm. ２ Then, the mixture was pressed in a cooling press equipped with a water flow cooling device at 20 kgf / cm ２The mixture was pressed at 100°C for 1 minute to prepare a pressed plate having a thickness of 0.125 mm. A 50 x 50 mm square piece was cut out from the obtained pressed plate. This gave a test piece. The haze (%) of the test piece was measured using a Spectral Haze Meter SH7000 (manufactured by Nippon Denshoku Industries Co., Ltd., light source D65) according to the method of JIS-K7136:2000.

[0182] Example 2-1 Five parts by mass of the block copolymer obtained in Example 1-4 and 95 parts by mass of the polyester resin (D1), component, were added to a kneading machine, Labo Plastomill (manufactured by Toyo Seiki Seisaku-sho, Ltd., product name "3S150", roller mixer model "R60"), and melt-kneaded for 5 minutes at a cylinder temperature of 210°C and a screw rotation speed of 50 rpm to obtain a resin composition. The obtained resin composition was subjected to the above measurements and evaluations. The results are shown in Table 3.

[0183] [Comparative Example 2-1 and Reference Example 2-2] Resin compositions were obtained in the same manner as in Example 2-1, except that the formulations were changed as shown in Table 3. The above measurements and evaluations were carried out for each of the obtained resin compositions. The results are shown in Table 3.

[0184] Reference Example 2-1 For reference, the results for the polyester resin (D1) used in common in the third example are also shown in Table 3.

[0185]

[0186] From Table 3, it was found that Example 2-1 and Reference Example 2-1 showed that the second aliphatic polyester of Example 1-4, when used in a resin composition, can significantly improve the impact resistance of polylactic acid while maintaining good heat resistance. From Comparative Example 2-1, it was found that the second aliphatic polyester of Comparative Example 1-1, which does not satisfy the conditions of the present invention, improves impact resistance but reduces heat resistance when used in a resin composition.

[0187] [Third Example (Block Copolymer)] [Components] The components used in the Examples and Comparative Examples are as follows: Second PE: Second aliphatic polyesters obtained in Examples 1-1, 1-6 to 1-11, Comparative Examples 1-1 and 1-6 L-lactide: L-lactide manufactured by Tokyo Chemical Industry Co., Ltd.

[0188] [Measurement and Evaluation] 3-1. Total Formula Weight (M(a)) In the block copolymers obtained in the Examples and Comparative Examples, the value of α(PE) measured in 1-4 above was used as the sum (M(a)) of the average formula weight (M(a1)) of the structural unit (a1) portion and the average formula weight (M(a2)) of the structural unit (a2) portion. In the third example, the structural unit (a1) was a structural unit derived from 3-methyl-1,5-pentanediol (MPD) contained in the second PE (second aliphatic polyester). The structural unit (a2) was a structural unit derived from adipic acid (AA), (z1-1), (z2-1), and (z2-2) components contained in the second PE.

[0189] 3-2. Hard Ratio The hard ratio (mass%) was defined as the mass content (percentage) of the second block (B) derived from polylactic acid containing structural units derived from lactic acid in the block copolymers obtained in the Examples and Comparative Examples. In the third Example, lactic acid was defined as L-lactide. In the third Example, the first block (A) in the block copolymers obtained in the Examples and Comparative Examples was the block derived from the second aliphatic polyester used in the Examples and Comparative Examples.

[0190] The hard ratio is １ Calculated using the results of H-NMR measurement ( １(The H-NMR measurement conditions are as described below.) Specifically, first, the relative number of moles of the first block (A) and the relative number of moles of the second block (B) were calculated from the area ratio of the signal at around 5.2 ppm derived from polylactic acid to the signal at around 0.9 ppm derived from the first block (A) in the obtained spectrum. Next, each number of moles was multiplied by the molecular weight of each block to convert it to relative mass. Then, the mass content (percentage) of the second block (B) was calculated when the sum of these relative masses was adjusted to be 100, and this was defined as the hard ratio.

[0191] ( １ H-NMR measurement conditions) Apparatus: Nuclear magnetic resonance apparatus "JNM-ECX400" manufactured by JEOL Ltd. Solvent: deuterated chloroform Measurement temperature: 50°C Number of accumulations: 1024 Temperature rise rate: 10°C / min

[0192] 3-3. Number-Average Molecular Weight of Block Copolymer (α(BCP)) The number-average molecular weight α(BCP) of the block copolymer obtained in the examples and comparative examples was determined by GPC in the same manner as the number-average molecular weight of the second aliphatic polyester in 1-4 above.

[0193] 3-4. OH Terminal Group Ratio (β(BCP)) of Block Copolymer The OH terminal group ratio β(BCP) of the block copolymers obtained in the Examples and Comparative Examples was determined in the same manner as in the OH terminal group ratio of the first aliphatic polyester in 1-2 above.

[0194] 3-5. Evaluation of Suitability for Modification of Polyester Resin For the block copolymers obtained in the Examples and Comparative Examples, the value of the following relational formula (III) was determined: α(BCP) / (150-β(BCP)) (III)

[0195] The value of the relational formula (III) can be used to evaluate the suitability of polyester resin modification based on the following criteria: A: The value of the relational formula (III) is 650 or more; B: The value of the relational formula (III) is 575 or more and less than 650; C: The value of the relational formula (III) is less than 575. The polyester resin modification suitability refers to the expected value of the properties of the block copolymer when a resin composition containing a block copolymer obtained in the examples and comparative examples and a polyester resin different from the first and second aliphatic polyesters is prepared, and the resin composition containing the polyester resin is reflected in the resin composition, with evaluation A being excellent in terms of expected value, evaluation B being inferior to evaluation A but still sufficiently excellent, and evaluation C being inferior to evaluation B.

[0196] 3-6. Melting point Tm (°C) The melting points of the block copolymers obtained in the examples and comparative examples were measured by a differential scanning calorimeter according to the method described in JIS K7121:2012. When multiple peaks were observed, the melting point corresponding to the highest peak was taken as the melting point of the block copolymer. Apparatus: Mettler-Toledo K.K. Differential scanning calorimeter "DSC822" Measurement conditions: Heating rate 10°C / min

[0197] 3-7. Glass transition temperature Tg (°C) The glass transition temperatures of the block copolymers obtained in the examples and comparative examples were measured using a differential scanning calorimeter according to the method described in JIS K7121:2012. Apparatus: Mettler Toledo K.K. Differential scanning calorimeter "DSC822" Measurement conditions: Heating rate 10°C / min

[0198] 3-8. Evaluation of biodegradability (compost) Biodegradability in compost was measured according to the method in accordance with ISO 14855-2:2018 and evaluated based on the following criteria: A: Decomposition rate after 15 days was 20% by mass or more B: 10% by mass or more but less than 20% by mass C: 5% by mass or more but less than 10% by mass D: Less than 5% by mass

[0199] [Example 3-1] (Preliminary Operation (Dehydration)) First, 125 g of the second aliphatic polyester obtained in Example 1-1 and 407 g of toluene were charged into a 1 L four-neck flask equipped with a water-cooled reflux condenser, and the temperature of the dispersion was raised to 140° C. As a result, 10% by mass of the total amount of toluene was distilled off, and in this process, dehydration within the system was carried out.

[0200] (Copolymerization) Thereafter, the dispersion was cooled to 80°C, and 55 g of L-lactide was added to the dispersion so that the mass ratio of the second aliphatic polyester to L-lactide was second aliphatic polyester / L-lactide = 70 / 30. Furthermore, toluene was added to the dispersion in an amount equal to the weight of the toluene distilled off as described above. This yielded a dispersion with a solids concentration of 30 mass%.

[0201] Thereafter, the temperature of the dispersion was raised to 100° C., and tin octylate was added to the dispersion in an amount of 0.1% by mass relative to the second aliphatic polyester, followed by reaction for 4 hours.

[0202] This resulted in a toluene solution of a block copolymer having a first block (A) derived from the second aliphatic polyester and a second block (B) derived from polylactic acid containing structural units derived from L-lactide. Because the second aliphatic polyester used had a high proportion of OH terminal groups, it was estimated that the majority of the block copolymer obtained in Example 2-1 was a triblock copolymer having a polyester structure of second block-first block-second block.

[0203] (Solid Separation and Washing Operation) Thereafter, solid separation and washing operations were performed as follows. The obtained toluene solution was poured into methanol in an amount twice the total volume of the solution. This caused a solid to precipitate. Next, the supernatant methanol was discarded, and methanol in an amount equal to the amount of the poured toluene solution was added again to wash the solid. Thereafter, the methanol was discarded, and the solid was recovered. The obtained solid was dried in a vacuum dryer at 40°C to remove volatile organic compounds. In this way, a purified block copolymer was obtained. The obtained block copolymer was subjected to the above-mentioned measurements and evaluations. The results are shown in Table 4.

[0204] Examples 3-2 to 3-6 and Comparative Examples 3-1 to 3-2 As shown in Table 4 below, the second aliphatic polyester (second PE) produced in the first example was used instead of 70 parts by mass of the second aliphatic polyester in Example 1-1, and the mass ratio thereof was changed. The mass ratio of L-lactide used was also changed. Furthermore, the solids concentration of the dispersion used in the copolymerization was changed from 30% by mass to the concentration shown in Table 4. The same procedures as in Example 3-1 were then carried out to separate the solids and wash the mixture, yielding each block copolymer. The measurements and evaluations described above were carried out for each of the resulting block copolymers in the same manner as in Example 3-1. The results are shown in Table 4.

[0205] [Examples 3-7 and 3-8] As shown in Table 4 below, the second aliphatic polyester (second PE) produced in the section for the first example was used instead of 70 parts by mass of the second aliphatic polyester in Example 1-1, and the mass ratio thereof was changed. L-lactide was replaced with a mixture of L-lactide and D-lactide (L-lactide:D-lactide = 95:5 or 80:20 (mass ratio)). Furthermore, the solids concentration of the dispersion used in the copolymerization was changed from 30% by mass to the concentration shown in Table 4 below. [Examples 3-7 and 3-8] The preliminary operation and copolymerization were carried out in the same manner as in Example 3-1. Thereafter, solid separation and washing operations similar to those in Example 3-1 were carried out to obtain block copolymers. The above measurements and evaluations were carried out for each of the obtained block copolymers in the same manner as in Example 3-1. The results are shown in Table 4.

[0206]

[0207] From Table 4, it was found that the block copolymers of Examples 3-1 to 3-8, compared to the block copolymers of Comparative Examples 3-1 to 3-2, satisfy the conditions of a high number average molecular weight (α(BCP)) and a high OH terminal group ratio (β(BCP)), i.e., the ratio of high molecular weight block copolymers having a triblock structure (triblock ratio) tends to be high. Therefore, it was found that the block copolymers of Examples 3-1 to 3-8 are excellent in suitability when preparing resin compositions containing a polyester resin, and that the properties of the high molecular weight triblock copolymer (particularly the properties of the highly polymerized triblock copolymer, such as heat resistance, and the properties of the highly polymerized soft segment, such as impact resistance) can be expected to contribute to the resin composition.

[0208] [Fourth Example (Block Copolymer-Containing Resin Composition)] [Components] The components used in the examples and comparative examples are as follows. BCP: Block copolymer obtained in Examples 3-1 to 3-8, Comparative Examples 3-1 and 3-2 (D1): Polyester resin "INGEO (registered trademark) 2500HP" (polylactic acid polymer) manufactured by NatureWorks (D2): Polyester resin "trade name: ecoflex (registered trademark) F Blend C1200" manufactured by BASF (PBAT: poly(butylene adipate / terephthalate))

[0209] 4-1. Evaluation of impact resistance Test pieces for measuring impact strength (notched strip test pieces) were prepared in the same manner as in 2-1 above using the polyester resin of Reference Example 4-1 and each of the resin compositions obtained in Reference Example 4-2, each of the Examples, and each of the Comparative Examples, and the impact strength (kJ / m ２ The measured value was the average of five measurements.

[0210] 4-2. Evaluation of heat resistance Test pieces for heat deflection temperature (strip test pieces) were prepared using the polyester resin of Reference Example 4-1 and each resin composition obtained in Reference Example 4-2, each Example, and each Comparative Example in the same manner as in 2-2 above, and the heat deflection temperature (°C) was measured in the same manner as in 2-2 above. The measured value was the average of three measurements.

[0211] 4-3. Evaluation of Transparency The polyester resin of Reference Example 4-1 and the resin compositions obtained in Reference Example 4-2, each Example, and each Comparative Example were each subjected to a pressure reduction heat press using a pressure-reducing hot press machine ("IMC-183B" manufactured by Imoto Machinery Co., Ltd.) with an oil rotary pump to a pressure of -0.1 MPaG, preheated at 200°C for 5 minutes, and then subjected to a pressure reduction of 41 kgf / cm ２ Then, the mixture was pressed in a cooling press equipped with a water jet cooling system at 20 kgf / cm ２ The mixture was pressed at 100°C for 1 minute to prepare a pressed plate having a thickness of 0.125 mm. A 50 x 50 mm square piece was cut out from the obtained pressed plate. This gave a test piece. The haze (%) of the test piece was measured using a Spectral Haze Meter SH7000 (manufactured by Nippon Denshoku Industries Co., Ltd., light source D65) according to the method of JIS-K7136:2000.

[0212] Example 4-1 7 parts by mass of the block copolymer obtained in Example 3-1 and 93 parts by mass of the polyester resin (D1), component, were added to a kneader, Labo Plastomill (manufactured by Toyo Seiki Seisaku-sho, Ltd., product name "3S150", roller mixer model "R60"), and melt-kneaded for 5 minutes at a cylinder temperature of 210°C and a screw rotation speed of 50 rpm to obtain a resin composition. The obtained resin composition was subjected to the above measurements and evaluations. The results are shown in Table 5.

[0213] [Examples 4-2 to 4-8, Comparative Examples 4-1 to 4-3, and Reference Example 4-2] Resin compositions were obtained in the same manner as in Example 4-1, except that the formulations were changed as shown in Table 5. The above measurements and evaluations were carried out for each of the obtained resin compositions. The results are shown in Table 5.

[0214] Reference Example 4-1 For reference, the results for the polyester resin (D1) used in common in the fourth example are also shown in Table 5.

[0215]

[0216] From Table 5, it can be seen that the resin compositions of Examples 4-1 to 4-8, unlike the resin compositions of Comparative Examples 4-1 to 4-3, were able to significantly improve impact resistance while maintaining good heat resistance in the molded body, and as a result of imparting the properties of the block copolymer, the polyester resin of Reference Example 4-1 was able to be sufficiently modified.

[0217] Furthermore, Table 5 shows that the resin compositions of Examples 4-1 to 4-8 suppress the degree of decrease in haze relative to the haze of the polyester resin of Reference Example 4-1 compared to the resin compositions of Comparative Examples 4-1 to 4-3. In other words, it was found that the resin compositions of Examples 4-1 to 4-8 can impart the properties of a block copolymer while suppressing the decrease in transparency that accompanies modification of the polyester resin.

Claims

1. An aliphatic polyester containing a structural unit (a1) derived from an aliphatic diol having 3 or more carbon atoms in the main chain and having an alkyl group as a branched chain, and a structural unit (a2) derived from an aliphatic dicarboxylic acid, which satisfies the following three conditions: Condition 1 (PE), Condition 2 (PE), and Condition 3 (PE). Condition 1 (PE): The following α(PE) and β(PE) satisfy the following relational formula (I). α(PE) / (150-β(PE))≧500 (I) (In the above relational formula (I), α(PE) is the number average molecular weight of the aliphatic polyester, and β(PE) is the OH terminal group proportion [mol %] of the aliphatic polyester, which indicates the proportion (percentage) of the number of OH terminal groups when the total number of terminal groups of the aliphatic polyester is taken as 100 mol %).) Condition 2 (PE): In the aliphatic polyester, the sum (M(a)) of the average formula weight (M(a1)) of the portion of the structural unit (a1) and the average formula weight (M(a2)) of the portion of the structural unit (a2) is within the range of 25,000 to 75,000. Condition 3 (PE): β(PE)≧25 2. The aliphatic polyester according to claim 1, wherein the aliphatic diol has a main chain carbon number of 3 or more and 10 or less.

3. The aliphatic polyester according to claim 1, wherein the branched chain in the aliphatic diol is a methyl group.

4. The aliphatic polyester according to claim 1, wherein the aliphatic dicarboxylic acid has 4 or more and 12 or less carbon atoms.

5. A resin composition comprising the aliphatic polyester according to any one of claims 1 to 4.

6. The resin composition according to claim 5, further comprising a polyester resin (D) different from the aliphatic polyester.

7. A molded article made from the resin composition according to claim 5.

8. A method for producing an aliphatic polyester, comprising reacting a first aliphatic polyester containing a structural unit (a1) derived from an aliphatic diol having 3 or more carbon atoms in the main chain and having an alkyl group as a branched chain, and a structural unit (a2) derived from a first aliphatic dicarboxylic acid, with at least one member selected from the group consisting of a second aliphatic dicarboxylic acid (z1), an aliphatic dicarboxylic acid alkyl ester (z2), and an aliphatic dicarboxylic acid anhydride (z3), to produce a second aliphatic polyester satisfying the following three conditions 1 (PE2), 2 (PE2), and 3 (PE2): Condition 1 (PE2): The following α(PE2) and β(PE2) satisfy the following relational formula (II). α(PE2) / (150-β(PE2))≧500 (II) (In the relational formula (II), α(PE2) is the number average molecular weight of the second aliphatic polyester, and β(PE2) is the OH terminal group proportion [mol %] of the second aliphatic polyester, which indicates the proportion (percentage) of the number of OH terminal groups when the total number of terminal groups of the aliphatic polyester is 100 mol %).) Condition 2 (PE2): In the second aliphatic polyester, the sum (M(a)) of the average formula weight (M(a1)) of the portion of the structural unit (a1) and the average formula weight (M(a2)) of the portion of the structural unit (a2) is 25,000 to 75,000. Condition 3 (PE2): β(PE2)≧25 9. A method for producing an aliphatic polyester according to claim 8, comprising: a first step of producing a first aliphatic polyester by reacting an aliphatic diol having 3 or more carbon atoms in its main chain and having an alkyl group as a branched chain with a first aliphatic dicarboxylic acid; and a second step of reacting the first aliphatic polyester with at least one selected from the group consisting of a second aliphatic dicarboxylic acid (z1), an aliphatic dicarboxylic acid alkyl ester (z2) and an aliphatic dicarboxylic acid anhydride (z3).

10. A block copolymer having a first block (A) derived from an aliphatic polyester containing a structural unit (a1) derived from an aliphatic diol having 3 or more carbon atoms in the main chain and having an alkyl group as a branched chain and a structural unit (a2) derived from an aliphatic dicarboxylic acid, and a second block (B) derived from a polylactic acid containing a structural unit derived from lactic acid, the block copolymer satisfying the following three conditions 1 (BCP), 2 (BCP), and 3 (BCP): α(BCP) and β(BCP) below satisfy the following relational formula (III). α(BCP) / (150-β(BCP))≧575 (III) (In the above relational formula (III), α(BCP) is the number average molecular weight of the block copolymer, and β(BCP) is the OH terminal group proportion [mol %] of the block copolymer, which indicates the proportion (percentage) of the number of OH terminal groups when the total number of terminal groups of the block copolymer is 100 mol %).) Condition 2 (BCP): In the block copolymer, the sum (M(a)) of the average formula weight (M(a1)) of the portion of the structural unit (a1) and the average formula weight (M(a2)) of the portion of the structural unit (a2) is in the range of 25,000 to 75,000. Condition 3 (BCP): β(BCP)≧25 11. The block copolymer according to claim 10, wherein the aliphatic diol has a main chain carbon number of 3 or more and 10 or less.

12. The block copolymer according to claim 10, wherein the branched chain in the aliphatic diol is a methyl group.

13. The block copolymer according to claim 10, wherein the aliphatic dicarboxylic acid has 4 or more and 12 or less carbon atoms.

14. The block copolymer according to claim 10, wherein the number average molecular weight of said block copolymer is 28,750 or more and 400,000 or less.

15. The block copolymer according to claim 10, wherein the content of said block (B) is 5% by mass or more and 95% by mass or less, when the total of said block (A) and said block (B) is 100% by mass.

16. A resin composition comprising the block copolymer according to any one of claims 10 to 15.

17. The resin composition according to claim 16, further comprising a polyester resin (D).

18. A molded article made from the resin composition according to claim 16.

19. A method for producing a block copolymer having a first block (A) derived from an aliphatic polyester containing a structural unit (a1) derived from an aliphatic diol having 3 or more carbon atoms in its main chain and having an alkyl group as a branched chain, and a structural unit (a2) derived from an aliphatic dicarboxylic acid, and a second block (B) derived from polylactic acid containing a structural unit derived from lactic acid, and satisfying the following three conditions 1 (BCP), 2 (BCP), and 3 (BCP): Condition 1 (BCP): The following α(BCP) and β(BCP) satisfy the following relational formula (III). α(BCP) / (150-β(BCP))≧575 (III) (In the relational formula (III), α(BCP) is the number average molecular weight of the block copolymer, and β(BCP) is the OH terminal group ratio [mol %] of the block copolymer, which indicates the ratio (percentage) of the number of OH terminal groups when the total number of terminal groups of the block copolymer is taken as 100 mol %). Condition 2 (BCP): In the block copolymer, the sum (M(a)) of the average formula weight (M(a1)) of the portion of the structural unit (a1) and the average formula weight (M(a2)) of the portion of the structural unit (a2) is within the range of 25,000 to 75,000. Condition 3 (BCP): β(BCP)≧25

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