Block copolymer

Abstract

To provide block copolymers with excellent biodegradability and heat resistance. [Solution] A block copolymer comprising a polyol unit (A) having a constituent unit derived from a dicarboxylic acid having 4 or more carbon atoms, and a polylactic acid unit (B). Preferably, the block copolymer has a plurality of triblock structures in which the polylactic acid unit (B) is bonded to both ends of the polyol unit (A) by ester bonds, and the plurality of the triblock structures are bonded to each other.

Description

[Technical Field]

[0001] This invention relates to block copolymers. [Background technology]

[0002] In recent years, biomass-derived polymers have attracted attention, and products using biodegradable polymers are being proposed. As a biodegradable polymer, a polymer has been proposed that has multiple triblock structures in which polycaprolactone units are bonded to both ends by polylactic acid units via ester bonds, and these multiple triblock structures are linked to each other by units containing urethane bonds (for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2024-80378 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, while biodegradable polymers containing polylactic acid have excellent heat resistance, there is room for improvement in terms of biodegradability. The present invention aims to provide a block copolymer that exhibits excellent biodegradability and heat resistance. [Means for solving the problem]

[0005] The present invention has the following aspects. [1] A block copolymer comprising a polyol unit (A) having a dicarboxylic acid-derived structural unit having 4 or more carbon atoms, and a polylactic acid unit (B). [2] The block copolymer according to [1], wherein the polyol unit (A) and the polylactic acid unit (B) are linked by an ester bond. [3] The block copolymer according to [1] or [2], wherein the block copolymer has a plurality of triblock structures in which polylactic acid units (B) are bonded to both ends of the polyol unit (A) by ester bonds, and the plurality of the triblock structures are bonded to each other. [4] The block copolymer according to [3], wherein a plurality of the aforementioned triblock structures are bonded together by units including urethane bonds. [5] The block copolymer according to [3] or [4], wherein at least one of the glass transition temperature and melting point, as measured by differential scanning calorimeter, is one. [6] The block copolymer according to any one of [1] to [5], wherein the dicarboxylic acid comprises at least one of sebadic acid and adipic acid. [7] The block copolymer according to any one of [1] to [6], wherein the content of the polylactic acid unit (B) is 40 to 90% by mass with respect to the total mass of the block copolymer. [8] The block copolymer according to any one of [1] to [7], wherein the glass transition temperature is 50°C or less. [9] A block copolymer according to any of [1] to [8], wherein the weight-average molecular weight is 50,000 to 500,000.

[10] The block copolymer according to any one of [1] to [9], wherein when the block copolymer is formed into a film under the following conditions, the total light transmittance of the film is 90% or more. Film forming conditions: Hot press forming is performed using a 0.1 mm thick mold under conditions of 20 MPa, 10 minutes, and 180°C.

[11] The block copolymer according to any one of [1] to

[10] , wherein when the block copolymer is formed into a film under the following conditions, the elongation at break of the film is 2% or more. Film forming conditions: Hot press forming is performed using a 0.1 mm thick mold under conditions of 20 MPa, 10 minutes, and 180°C. [Effects of the Invention]

[0006] According to the present invention, a block copolymer excellent in biodegradability and heat resistance can be provided.

Brief Description of the Drawings

[0007] [Figure 1] It is a diagram schematically showing an example of the chemical structure of the block copolymer of the present invention. [Figure 2] It is a diagram schematically showing another example of the chemical structure of the block copolymer of the present invention.

Modes for Carrying Out the Invention

[0008] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments without departing from the object. In this specification, the following definitions of terms are adopted. The “structural unit” means a structural unit derived from a compound (such as a monomer) constituting a unit, that is, a structural unit formed by polymerization of the compound, or a structural unit in which a part of the structural unit is converted into another structure by treating the polymer. The numerical range represented by “~” means a numerical range including the numerical values before and after “~” as the lower limit value and the upper limit value. The numerical ranges of the contents, various physical property values, and property values disclosed in this specification can be combined arbitrarily with their lower limit values and upper limit values to form new numerical ranges.

[0009] [Block Copolymer] The block copolymer (X) of the present invention contains the following polyol unit (A) and polylactic acid unit (B). In addition to the polyol unit (A) and the polylactic acid unit (B), the block copolymer (X) may further contain units other than the polyol unit (A) and the polylactic acid unit (B) (hereinafter also referred to as “other units (C)”) as long as the effects of the present invention are not impaired.

[0010] <Polyol Unit (A)> The polyol unit (A) is a unit composed of a polyol having a structural unit derived from a dicarboxylic acid having 4 or more carbon atoms. Since the polyol unit (A) has a structural unit derived from a dicarboxylic acid having 4 or more carbon atoms, it has high resolution and the polymer chain is easily cleaved, so the biodegradability of the block copolymer (X) is improved. The dicarboxylic acid has 4 or more carbon atoms, preferably 5 or more carbon atoms, and more preferably 6 or more carbon atoms. In one aspect, the dicarboxylic acid preferably has 10 or more carbon atoms. If the dicarboxylic acid has the above lower limit or more of carbon atoms, it has excellent resolution. The upper limit of the number of carbon atoms of the dicarboxylic acid is not particularly limited. For example, the dicarboxylic acid preferably has 20 or less carbon atoms, more preferably 16 or less carbon atoms, and further preferably 12 or less carbon atoms. In another aspect, the dicarboxylic acid particularly preferably has 10 or less carbon atoms.

[0011] Examples of the dicarboxylic acid include aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, fumaric acid, maleic acid, and itaconic acid; and aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid. Among these, from the viewpoint of further improving biodegradability, aliphatic dicarboxylic acids are preferred. Among them, particularly from the viewpoint of being available as a dicarboxylic acid derived from biomass, adipic acid, sebacic acid, succinic acid, fumaric acid, maleic acid, and itaconic acid are more preferred, adipic acid and sebacic acid are further preferred, and sebacic acid is particularly preferred. The polyol unit (A) may have a structural unit derived from one type of dicarboxylic acid, or may have structural units derived from two or more types of dicarboxylic acids. In particular, the polyol unit (A) is preferably a polyol unit derived from biomass and having a structural unit derived from a dicarboxylic acid having 4 or more carbon atoms, and more preferably a polyol unit having at least one of a structural unit derived from adipic acid and a structural unit derived from sebacic acid. Furthermore, from the viewpoint of improving biodegradability, it is preferable that the dicarboxylic acid does not contain aromatic dicarboxylic acids. That is, it is preferable that the polyol unit (A) substantially does not contain any constituent units derived from aromatic dicarboxylic acids. Here, "substantially free of constituent units derived from aromatic dicarboxylic acids" means that the content of constituent units derived from aromatic dicarboxylic acids is 0.1% by mass or less relative to the total mass of all constituent units constituting the polyol unit (A). Preferably, the content of constituent units derived from aromatic dicarboxylic acids is 0.01% by mass or less, and more preferably below the detection limit.

[0012] Examples of polyols that constitute the polyol unit (A) include polyester polyols, polyether polyols, polycarbonate polyols, and acrylic polyols. Among these, polyester polyols are preferred from the viewpoint of further improving biodegradability.

[0013] Examples of polyester polyols include condensed polyester polyols. Condensed polyester polyols are condensed polymers obtained by the condensation reaction of a dibasic acid and a diol compound. Examples of dibasic acids include the dicarboxylic acids having four or more carbon atoms or their anhydrides mentioned above. Furthermore, within limits that do not impair the effects of the present invention, other dibasic acids (hereinafter also referred to as "other dibasic acids") may be used in combination with dicarboxylic acids having four or more carbon atoms, as needed. Examples of other dibasic acids include malonic acid. Examples of diol compounds include ethylene glycol, propylene glycol, diethylene glycol, neopentyl glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,9-nonanediol, 1,4-hexanedimethanol, dimer acid diol, polyethylene glycol, and the like. These dibasic acids and diol compounds may be used individually or in combination of two or more.

[0014] There are no particular restrictions on the combination of dibasic acid and diol compound, but examples of polyester polyols include condensation polymers obtained by the condensation reaction of at least one of adipic acid and sebacic acid with 3-methyl-1,5-pentanediol. More specifically, examples include poly3-methyl-1,5-pentanesebacate diol and poly3-methyl-1,5-pentaneadipate diol. Furthermore, polyester polyols, which are condensation polymers of biomass-derived dicarboxylic acids (e.g., adipic acid, sebacic acid, succinic acid, etc.) as dibasic acids and diol compounds, are also specifically called "biomass polyester polyols."

[0015] The content of polyol units (A) is preferably 10 to 60% by mass, more preferably 20 to 55% by mass, and even more preferably 32 to 50% by mass, relative to the total mass of the block copolymer (X). If the content of polyol units (A) is above the lower limit, biodegradability is further improved. In addition, mechanical properties are also excellent. If the content of polyol units (A) is below the upper limit, heat resistance can be maintained more effectively. The content of polyol units (A) is measured using a differential thermogravimetric simultaneous thermogravimetric analyzer (TG-DTA). The detailed measurement conditions are as described in the examples below.

[0016] <Polylactic acid unit (B)> Polylactic acid unit (B) is typically a polymer unit obtained by polymerizing lactide. In typical examples, polylactic acid unit (B) has constituent units based on lactide. However, polylactic acid unit (B) may have constituent units based on monomers in which any side chain, such as an alkyl chain, is bonded to any carbon atom of lactide, in place of or in addition to the lactide-based constituent units. Furthermore, polylactic acid unit (B) may have constituent units based on polylactic acid diols obtained by polymerizing lactide and diol compounds. In one example, polylactic acid units (B) are formed by the bonding of units based on each monomer through ester bonds.

[0017] The number-average molecular weight of the polylactic acid unit (B) is preferably 300 to 30,000, more preferably 2,000 to 15,000, and even more preferably 4,000 to 10,000. If the number-average molecular weight of the polylactic acid unit (B) is above the lower limit, the heat resistance tends to improve further. Also, it is easier to produce block copolymer (X). If the number-average molecular weight of the polylactic acid unit (B) is below the upper limit, the biodegradability tends to improve further.

[0018] The content of polylactic acid units (B) is preferably 40 to 90% by mass, more preferably 45 to 80% by mass, and even more preferably 50 to 68% by mass, relative to the total mass of the block copolymer (X). If the content of polylactic acid units (B) is above the lower limit, the heat resistance is further improved. If the content of polylactic acid units (B) is below the upper limit, the biodegradability can be maintained more effectively. The polylactic acid unit (B) content is a value measured using TG-DTA. The detailed measurement conditions are as described in the examples below.

[0019] Furthermore, the total content of polyol units (A) and polylactic acid units (B) is preferably 50% by mass or more, more preferably 75% by mass or more, even more preferably 95% by mass or more, and may also be 100% by mass, relative to the total mass of the block copolymer (X). The block copolymer (X) is particularly preferably composed only of polyol units (A) and polylactic acid units (B).

[0020] Furthermore, the mass ratio (A:B) of the polyol unit (A) and the polylactic acid unit (B) is preferably 10:90 to 60:40, more preferably 20:80 to 55:45, and even more preferably 32:68 to 50:50.

[0021] <Other Units (C)> Other units (C) include, for example, polycaprolactone units, polycarbonate units, polyhydroxyalkanoate units, polyethylene glycol units, polyethylene terephthalate units, polytrimethylene terephthalate units, and polyglycolic acid units. The other units (C) may be one type or two or more types. Note that other units (C) do not include units that connect each unit (for example, units that include urethane bonding).

[0022] The content of other units (C) is preferably 50% by mass or less, more preferably 25% by mass or less, and even more preferably 5% by mass or less, relative to the total mass of the block copolymer (X), and it is particularly preferable that the block copolymer (X) is substantially free of other units (C). Here, "substantially free of other units (C)" means that the content of other units (C) is below the detection limit. The content of other units (C) is measured using TG-DTA. The detailed measurement conditions are as described in the examples below.

[0023] <Chemical structure> Preferably, the polyol unit (A) and the polylactic acid unit (B) are linked by an ester bond. The block copolymer (X) may be an alternating multiblock copolymer (X1) in which polyol units (A) and polylactic acid units (B) are arranged regularly, or a random multiblock copolymer (X2) in which polyol units (A) and polylactic acid units (B) are arranged randomly. Among these, the alternating multiblock copolymer (X1) is preferred from the viewpoint of improving mechanical properties.

[0024] Whether a block copolymer (X) is an alternating multiblock copolymer (X1) or a random multiblock copolymer (X2) can be determined, for example, by measuring the glass transition temperature and melting point of the block copolymer (X). In the case of an alternating multiblock copolymer (X1), at least one of the glass transition temperature and melting point of the block copolymer (X) measured by differential scanning calorimeter (DSC) tends to be one (one point). In particular, the melting point measured by DSC tends to be one (one point) in the case of an alternating multiblock copolymer (X1), and two or more (two or more points) in the case of a random multiblock copolymer (X2).

[0025] (Alternating multiblock copolymer (X1)) The alternating multiblock copolymer (X1) is a block copolymer in which polyol units (A) and polylactic acid units (B) are arranged in a regular pattern. The alternating multiblock copolymer (X1) preferably has multiple triblock structures in which polylactic acid units (B) are bonded to both ends of a polyol unit (A) by ester bonds. Furthermore, it is preferable that the multiple triblock structures are bonded to each other. In particular, it is more preferable that the multiple triblock structures are bonded to each other by units containing urethane bonds. Hereinafter, the alternating multiblock copolymer (X1) in which the multiple triblock structures are bonded to each other by units containing urethane bonds will also be specifically referred to as "alternating multiblock copolymer (X1-1)".

[0026] Figure 1 schematically shows an example of the chemical structure of an alternating multiblock copolymer (X1). In the alternating multiblock copolymer (X1) 1A shown in Figure 1, multiple triblock structures 4 are formed in which polylactic acid units (B) 3 are bonded to both ends of a polyol unit (A) 2. These multiple triblock structures 4 are repeatedly bonded together by units 5 containing urethane bonds.

[0027] As shown in the example of alternating multiblock copolymer (X1) 1A, the triblock structures are bonded together by units containing urethane bonds, which further improves heat resistance and biodegradability. In addition, it also exhibits excellent mechanical properties.

[0028] In the triblock structure, polylactic acid units (B) are bonded to both ends of a polyol unit (A). The polyol unit (A) and the polylactic acid unit (B) are bonded by ester bonds. Specifically, the polylactic acid unit (B) is bonded to both ends of the polyol unit (A) by ester bonds containing each oxygen atom at each end of the polyol unit (A). The number of repeats and monomer unit composition of the two polylactic acid units (B) bonded to both ends of the polyol unit (A) may be different from or the same from each other.

[0029] When triblock structures are bonded together by units containing urethane bonds, for the alternating multiblock copolymer (X1), 1 When 1H-NMR measurements are performed, a peak originating from the "-CH2-" group adjacent to the "-NH-" group of the urethane bond may be detected at around 3.1 ppm. Units containing urethane bonds are typically based on aliphatic diisocyanates. Examples of aliphatic diisocyanates include tetramethylene diisocyanate, dodecamethylene diisocyanate, hexamethylene diisocyanate (HDI), 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2-methylpentane-1,5-diisocyanate, and 3-methylpentane-1,5-diisocyanate. However, compounds that can be conferred units containing urethane bonds are not limited to these aliphatic diisocyanates.

[0030] When the triblock structures are bonded together by units containing urethane bonds, the alternating multiblock copolymer (X1) can also be described as a thermoplastic polyurethane polymer. Alternatively, the alternating multiblock copolymer (X1) can be described as a copolymer in which a polyol having a triblock structure is used as one constituent unit, and multiple such constituent units are bonded together via units containing urethane bonds.

[0031] Preferably, at least one of the glass transition temperature and melting point of the alternating multiblock copolymer (X1), as measured by DSC, is one; more preferably, at least one melting point is one; and even more preferably, both the glass transition temperature and melting point are one. The glass transition temperature and melting point will be discussed later.

[0032] (Random multiblock copolymer (X2)) Random multiblock copolymer (X2) is a block copolymer in which polyol units (A) and polylactic acid units (B) are arranged randomly. In the random multiblock copolymer (X2), it is preferable that the polyol units (A) and polylactic acid units (B) are bonded together by units containing urethane bonds. Alternatively, the polyol units (A) may be bonded together by units containing urethane bonds, or the polylactic acid units (B) may be bonded together by units containing urethane bonds.

[0033] Figure 2 schematically shows an example of the chemical structure of a random multiblock copolymer (X2). In the random multiblock copolymer (X2) 1B shown in Figure 2, polyol units (A) 2 and polylactic acid units (B) 3 are linked by units 5 containing urethane bonds. Furthermore, polyol units (A) 2 are linked to each other, and polylactic acid units (B) 3 are linked to each other, also by units 5 containing urethane bonds.

[0034] As shown in the example of random multiblock copolymer (X2) 1B, the polyol unit (A) and polylactic acid unit (B) are bonded by units including urethane bonds, which further improves heat resistance and biodegradability.

[0035] When the polyol unit (A) and the polylactic acid unit (B) are bonded by a unit containing a urethane bond, for the random multiblock copolymer (X2), 1 When 1H-NMR measurements are performed, a peak originating from the "-CH2-" group adjacent to the "-NH-" group of the urethane bond may be detected at around 3.1 ppm. The same applies when polyol units (A) are bonded together by units containing urethane bonds, and when polylactic acid units (B) are bonded together by units containing urethane bonds. Units containing urethane bonds are typically based on aliphatic diisocyanates. Examples of aliphatic diisocyanates include those previously exemplified in the description of the alternating multiblock copolymer (X1). However, compounds that can be given units containing urethane bonds are not limited to these examples of aliphatic diisocyanates.

[0036] If one or more of the polyol units (A) and polylactic acid units (B), polyol units (A) to each other, and polylactic acid units (B) to each other are linked by units containing urethane bonds, then the random multiblock copolymer (X2) can also be said to be a thermoplastic polyurethane polymer.

[0037] Preferably, at least one of the glass transition temperature and melting point of the random multiblock copolymer (X2), as measured by DSC, is two or more; more preferably, at least two melting points; even more preferably, two melting points; and particularly preferably, one glass transition temperature and two melting points. The glass transition temperature and melting point will be discussed later.

[0038] <Properties> (Glass transition temperature) The glass transition temperature of the block copolymer (X) is preferably 50°C or lower, more preferably 40°C or lower, even more preferably 30°C or lower, and particularly preferably 10°C or lower. There is no particular limit on the lower limit, but for example, the glass transition temperature of the block copolymer (X) is preferably -60°C or higher, more preferably -40°C or higher, even more preferably -20°C or higher, and particularly preferably 0°C or higher. If the glass transition temperature of the block copolymer (X) is below the above upper limit, hydrolysis of the block copolymer (X) is easily induced, and the polymer chains are easily cleaved, thus further improving biodegradability.

[0039] When the block copolymer (X) is an alternating multiblock copolymer (X1), the glass transition temperature of the alternating multiblock copolymer (X1) is preferably 50°C or lower, more preferably 40°C or lower, even more preferably 30°C or lower, and particularly preferably 10°C or lower. There is no particular limit on the lower limit, but for example, the glass transition temperature of the alternating multiblock copolymer (X1) is preferably -60°C or higher, more preferably -40°C or higher, even more preferably -20°C or higher, and particularly preferably 0°C or higher. The glass transition temperature of the alternating multiblock copolymer (X1) is preferably one in the region of 50°C or below, and more preferably one in the region of -60 to 50°C.

[0040] When the block copolymer (X) is a random multiblock copolymer (X2), the glass transition temperature of the random multiblock copolymer (X2) is preferably 50°C or lower, more preferably 45°C or lower, even more preferably 40°C or lower, and particularly preferably 20°C or lower. There is no particular limit on the lower limit, but for example, the glass transition temperature of the random multiblock copolymer (X2) is preferably -60°C or higher, more preferably -40°C or higher, even more preferably -20°C or higher, and particularly preferably 0°C or higher. If there are two or more glass transition temperatures for the random multiblock copolymer (X2), the highest value among the observed glass transition temperatures is taken as the glass transition temperature of the random multiblock copolymer (X2). The glass transition temperature of the random multiblock copolymer (X2) is preferably one in the region of 50°C or below, and more preferably one in the region of -60 to 50°C.

[0041] The glass transition temperature of a block copolymer (X) can be controlled by the content of polyol units (A) and polylactic acid units (B) in the block copolymer (X). For example, the lower the content of polylactic acid units (B), the lower the glass transition temperature tends to be. The glass transition temperature of the block copolymer (X) is measured using DSC. The detailed measurement conditions are as described in the examples below.

[0042] (Melting point) The melting point of the block copolymer (X) is preferably 100°C or higher. There is no particular upper limit, but for example, the melting point of the block copolymer (X) is preferably 200°C or lower. If the melting point of the block copolymer (X) is above the lower limit, the heat resistance will be further improved.

[0043] When the block copolymer (X) is an alternating multiblock copolymer (X1), the melting point of the alternating multiblock copolymer (X1) is preferably 100°C or higher, more preferably 110°C or higher, even more preferably 120°C or higher, and particularly preferably 130°C or higher. There is no particular upper limit, but for example, the melting point of the alternating multiblock copolymer (X1) is preferably 200°C or lower, more preferably 180°C or lower, even more preferably 160°C or lower, and particularly preferably 140°C or lower. The alternating multiblock copolymer (X1) preferably has one melting point in the region of 100°C or higher, and more preferably has one melting point in the region of 100 to 200°C.

[0044] When the block copolymer (X) is a random multiblock copolymer (X2), the melting point of the random multiblock copolymer (X2) is preferably 100°C or higher, more preferably 110°C or higher, even more preferably 120°C or higher, and particularly preferably 130°C or higher. There is no particular upper limit, but for example, the melting point of the random multiblock copolymer (X2) is preferably 200°C or lower, more preferably 180°C or lower, even more preferably 160°C or lower, and particularly preferably 140°C or lower. If a random multiblock copolymer (X2) has two or more melting points, the highest value among the observed melting points is taken as the melting point of the random multiblock copolymer (X2). If there are two or more melting points, the lower melting point is preferably -60 to 0°C, more preferably -40 to -20°C, and even more preferably -40 to -30°C. The melting point of the random multiblock copolymer (X2) is preferably one in the region of 100°C or higher, more preferably one in the region of 0°C or lower and one in the region of 100°C or higher, and even more preferably one in the region of -60 to 0°C and one in the region of 100 to 200°C.

[0045] The melting point of a block copolymer (X) can be controlled by the content of polyol units (A) and polylactic acid units (B) in the block copolymer (X). For example, the melting point tends to increase as the content of polylactic acid units (B) increases. The melting point of the block copolymer (X) is measured using DSC. The detailed measurement conditions are as described in the examples below.

[0046] The weight-average molecular weight of the block copolymer (X) is not particularly limited, but is preferably between 50,000 and 500,000. If the weight-average molecular weight of the block copolymer (X) is above the lower limit mentioned above, mechanical properties such as toughness tend to improve. The number-average molecular weight of the block copolymer (X) is not particularly limited, but 20,000 to 200,000 is preferred. If the number-average molecular weight of the block copolymer (X) is above the lower limit mentioned above, mechanical properties such as toughness tend to improve.

[0047] When the block copolymer (X) is an alternating multiblock copolymer (X1), the weight-average molecular weight of the alternating multiblock copolymer (X1) is not particularly limited, but is preferably 50,000 to 500,000, more preferably 80,000 to 200,000, even more preferably 110,000 to 180,000, and particularly preferably 130,000 to 140,000. The number-average molecular weight of the alternating multiblock copolymer (X1) is not particularly limited, but is preferably 20,000 to 200,000, more preferably 30,000 to 80,000, even more preferably 40,000 to 70,000, and particularly preferably 50,000 to 60,000.

[0048] When the block copolymer (X) is a random multiblock copolymer (X2), the weight-average molecular weight of the random multiblock copolymer (X2) is not particularly limited, but is preferably 50,000 to 400,000, more preferably 55,000 to 100,000, even more preferably 60,000 to 800,000, and particularly preferably 65,000 to 70,000. The number-average molecular weight of the random multiblock copolymer (X2) is not particularly limited, but is preferably 20,000 to 200,000, more preferably 25,000 to 50,000, and even more preferably 29,000 to 35,000.

[0049] The weight-average molecular weight and number-average molecular weight of the alternating multiblock copolymer (X1) can be controlled by the number of bonds between the triblock structures. The weight-average molecular weight and number-average molecular weight of the alternating multiblock copolymer (X1) tend to increase as the number of bonds between the triblock structures increases. The weight-average molecular weight and number-average molecular weight of the random multiblock copolymer (X2) can be controlled by the number of bonds between polyol units (A) and polylactic acid units (B), the number of bonds between polyol units (A) themselves, and the number of bonds between polylactic acid units (B) themselves. As the number of these bonds increases, the weight-average molecular weight and number-average molecular weight of the random multiblock copolymer (X2) tend to increase. The weight-average molecular weight and number-average molecular weight of the block copolymer (X) are polystyrene-equivalent values ​​measured by gel permeation chromatography (GPC). The detailed measurement conditions are as described in the examples below.

[0050] When a film (hereinafter also referred to as "film (F)") is formed by hot-press molding of a block copolymer (X) using a 0.1 mm thick mold under the conditions of 20 MPa for 10 minutes at 180°C, the total light transmittance of film (F) is preferably 90% or higher, more preferably 91% or higher, and even more preferably 92% or higher. If the total light transmittance of film (F) is above the above lower limit, the transparency and visibility of the block copolymer (X) are excellent. There is no particular limit to the upper limit of the total light transmittance of the film (F), and it may be, for example, 100%. The total light transmittance of film (F) is a value measured in accordance with JIS K 7361:1997. The detailed measurement conditions are as described in the examples below.

[0051] The haze of film (F) is preferably 50% or less, more preferably 45% or less, and even more preferably 40% or less. If the haze of film (F) is below the above upper limit, the transparency and visibility of the block copolymer (X) are excellent. There is no particular limit to the lower limit of the haze of the film (F); for example, it may be around 25%. The haze of film (F) is measured according to JIS K 7136:2000. The detailed measurement conditions are as described in the examples below.

[0052] The elongation at break of the film (F) is preferably 2% or more, more preferably 5% or more, even more preferably 50% or more, particularly preferably 100% or more, and most preferably 200% or more. If the elongation at break of the film (F) is above the above lower limit, it has excellent mechanical properties. There is no particular limit to the upper limit of the elongation at break of the film (F), and it may be, for example, around 550%. The elongation at break of the film (F1), and the maximum stress and toughness described later, are values ​​measured in accordance with JIS K 7127:1999. The detailed measurement conditions are as described in the examples below.

[0053] The maximum stress of the film (F) is preferably 4 MPa or higher, more preferably 10 MPa or higher, and even more preferably 20 MPa or higher. If the maximum stress of the film (F) is above the lower limit, it exhibits excellent mechanical properties. There is no particular upper limit to the maximum stress of the film (F), and it may be, for example, around 50 MPa.

[0054] The toughness of film (F) is 0.2 MJ / m 3 The above is preferable, 1 MJ / m 3 The above is more preferable: 5 MJ / m 3 The above is even more preferable, 30 MJ / m 3 The above is particularly preferable. If the toughness of the film (F) is above the lower limit value mentioned above, it will have excellent mechanical properties. There is no particular limit to the upper limit of the toughness of the film (F), for example, 70 MJ / m 3It can be to a certain extent.

[0055] When film (F) is treated at 90°C for 12 hours, the degree of crystallinity is preferably 10-90%, more preferably 15-80%, even more preferably 20-70%, and particularly preferably 30-50%. If the degree of crystallinity of film (F) is within the above range, it will have appropriate mechanical strength and flexibility and can be suitably used for specific applications such as packaging materials. The degree of crystallinity is determined by X-ray analysis. The detailed measurement conditions are as described in the examples below.

[0056] <Manufacturing method> The method for producing the block copolymer (X) is not particularly limited, as long as the desired chemical structure can be obtained. For example, an alternating multiblock copolymer (X1-1) having multiple triblock structures in which polylactic acid units (B) are bonded to both ends of a polyol unit (A) by ester bonds, and in which multiple triblock structures are linked to each other by units containing urethane bonds, can be obtained as follows. That is, after synthesizing a triblock structure by adding polylactic acid units (B) to both ends of a polyol unit (A), an alternating multiblock copolymer (X1-1) is produced by carrying out a urethane reaction to link the triblock structures to each other by units containing urethane bonds. In this case, after synthesizing the triblock structure, the triblock structure may be purified and recovered before carrying out the urethane reaction.

[0057] When the polyol constituting the polyol unit (A) is a polyester polyol, the polyol unit (A) can be produced, for example, by condensation polymerization of a monomer component (1) containing a dibasic acid and a diol compound, as previously exemplified in the description of polyester polyols. The monomer component (1) typically contains a dicarboxylic acid or its anhydride having four or more carbon atoms and a diol compound. However, in one example, the monomer component (1) may contain, in place of the dibasic acid, or in addition to the dibasic acid, a monomer in which any side chain, such as an alkyl chain, is bonded to any carbon atom of the dibasic acid. Also, in one example, the monomer component (1) may contain, in place of the diol compound, or in addition to the diol compound, a monomer in which any side chain, such as an alkyl chain, is bonded to any carbon atom of the diol compound. Alternatively, a commercially available polyol such as polyester polyol may be used as the polyol unit (A). The molecular weight of the polyol unit (A) may be controlled by the composition of the monomer component (1), the polymerization reaction, and the polymerization conditions. Commercially available products with a molecular weight within the desired range may also be used.

[0058] In the synthesis of the triblock structure, for example, a monomer component (2) containing lactide can be added to both ends of the polyol unit (A) through addition polymerization. In one example, the addition reaction of monomer component (2) to the hydroxyl groups (-OH) at both ends of the polyol unit (A) results in the extension of the polylactic acid unit (B), thereby synthesizing the triblock structure.

[0059] Monomer component (2) typically includes lactide. However, in one example, monomer component (2) may include, in place of or in addition to lactide, monomers in which any side chain, such as an alkyl chain, is bonded to any carbon atom of lactide. The molecular weight of the polylactic acid unit (B) can be controlled by the composition of the monomer component (2), the polymerization reaction, and the polymerization conditions.

[0060] In a typical urethane reaction, a triblock structure is reacted with an aliphatic diisocyanate, and the triblock structures are linked together by units containing urethane bonds. The urethane reaction produces an alternating multiblock copolymer (X1-1).

[0061] A random multiblock copolymer (X2-1) in which polyol units (A) and polylactic acid units (B) are randomly arranged and the polyol units (A) and polylactic acid units (B) are linked by units containing urethane bonds is obtained as follows. Specifically, a random multiblock copolymer (X2-1) is produced by carrying out a urethane reaction to link polylactic acid diol and polyol units (A) by units containing urethane bonds.

[0062] Polylactic acid diols can be produced, for example, by ring-opening polymerization of monomer component (3) containing lactide and a diol compound. Monomer component (3) typically contains lactide and a diol compound. Examples of diol compounds include those previously exemplified in the description of polyester polyols. However, in one example, monomer component (3) may contain, in place of or in addition to lactide, a monomer in which any side chain, such as an alkyl chain, is bonded to any carbon atom of lactide. Also, in one example, monomer component (3) may contain, in place of or in addition to the diol compound, a monomer in which any side chain, such as an alkyl chain, is bonded to any carbon atom of the diol compound. Alternatively, commercially available polylactic acid diols may be used as the polylactic acid diol. The molecular weight of polylactic acid diol can be controlled by the composition of monomer component (2), the polymerization reaction, and the polymerization conditions.

[0063] When the polyol constituting the polyol unit (A) is a polyester polyol, the polyol unit (A) can be produced, for example, by condensation polymerization of the monomer component (1) described above. Alternatively, a commercially available polyol such as a polyester polyol may be used as the polyol unit (A). The molecular weight of the polyol unit (A) may be controlled by the composition of the monomer component (1), the polymerization reaction, and the polymerization conditions. Commercially available products with a molecular weight within the desired range may also be used.

[0064] In a typical urethane reaction, polylactic acid diol, a polyol unit (A), and an aliphatic diisocyanate are reacted to bond the polylactic acid diol and the polyol unit (A) with a unit containing a urethane bond. The urethane reaction produces a random multiblock copolymer (X2-1).

[0065] <Mechanism of Action> The block copolymer (X) of this embodiment contains the polyol unit (A) described above. Since the polyol unit (A) has constituent units derived from dicarboxylic acid having 4 or more carbon atoms, it has high decomposition and the polymer chain is easily cleaved, so the block copolymer (X) has excellent biodegradability. Furthermore, since the block copolymer (X) contains polylactic acid unit (B), it also has excellent heat resistance. In particular, when the block copolymer (X) is an alternating multiblock copolymer (X1), toughness, or ductility, is imparted to the alternating multiblock copolymer (X1). As a result, the elongation at break increases, and the mechanical properties are improved. The block copolymer (X) of this embodiment is highly versatile, useful as a biodegradable polymer, and can be applied to a variety of uses.

[0066] <Application> The applications of the block copolymer (X) are not particularly limited. For example, it can be used as a material for various articles such as films, sheets, injection molded articles, fibers, containers, medical products, and toys. Fibers can be applied to textile products such as nonwovens and woven fabrics. Films and containers can be used in various fields such as the food industry, clothing industry, medical product industry, and pharmaceutical industry. In the medical and pharmaceutical fields, it can be applied to sutures, artificial bones, artificial skin, wound dressings, applications in the DDS field such as microcapsules, and applications to scaffolds for tissue and organ regeneration, etc. In addition, it can also be used as a binder in toner and thermal transfer ink, but the uses of the block copolymer (X) are not limited to these.

[0067] The block copolymer (X) may be used alone or in combination with additives and the like in the form of a composition. The additives are not particularly limited and can be appropriately selected according to the use and molding method. The block copolymer (X) can be applied to various molding methods. The molding method is not particularly limited. For example, various molding methods such as hot press molding, injection molding, solvent casting, and extrusion molding can be applied. Specific forms of the molded article include, for example, sheets, films, containers, petri dishes, plates, housings, fibers, and non-woven fabrics, but are not limited thereto.

Examples

[0068] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto. The embodiments of the present invention can be variously modified without departing from the gist of the present invention.

[0069] [Measurement and Evaluation] < 1 1H-NMR analysis> 1H-NMR was analyzed using a nuclear magnetic resonance apparatus (manufactured by JEOL Ltd., product name “JNM-EC400”). The number of integrations was 32 times, and chloroform-d (CDCl3) was used as the heavy solvent. 1 1H-NMR was analyzed. The number of integrations was 32 times, and chloroform-d (CDCl3) was used as the heavy solvent.

[0070] <Measurement of molecular weight> The molecular weight (number-average molecular weight (Mn) and weight-average molecular weight (Mw)) of the block copolymer was measured by gel permeation chromatography (GPC) molecular weight analysis. Specifically, GPC (manufactured by Tosoh Corporation, product name "HLC-8420") was used, and the measurement was performed with an RI detector. The column used was TSKgel GMHHR-M (manufactured by Tosoh Corporation). Chloroform (CHCl3) was used as the eluent for GPC. The column temperature was set to 40°C, and the flow rate was set to 1.0 ml / min. The standard sample used for the measurement was polystyrene (manufactured by Tosoh Corporation, product name "Standard Polystyrene Kit PStQuick"). A calibration curve was created using polystyrene equivalents, and the molecular weight (Mn, Mw) of the block copolymer was calculated.

[0071] <Heat resistance evaluation> (Measurement of thermal decomposition temperature) Using a differential thermogravimetric analyzer (TG-DTA, manufactured by Hitachi High-Tech Science Corporation, product name "NEXTA STA200RV"), the thermal decomposition temperature (Td) of the block copolymer was determined. A , Td B The thermal decomposition temperature (Td) was measured. The measurement temperature range was 50 to 530°C, and the heating rate was 10°C / min. A ) is the temperature at which the decomposition of the polyol unit (A) proceeds most rapidly during thermal decomposition, i.e., the temperature at which the weight loss rate is maximum. Thermal decomposition temperature (Td B ) is the temperature at which the decomposition of the polylactic acid unit (B) proceeds most rapidly during thermal decomposition, i.e., the temperature at which the weight loss rate is maximum. Furthermore, the content of polylactic acid units (B) (hereinafter also referred to as "PLA content") was determined from the weight loss of the block copolymer. Specifically, it was determined as follows. First, the amount of weight loss in the temperature range corresponding to the decomposition of polylactic acid units (B) was identified from the weight loss curve obtained by TG-DTA measurement. Next, this weight loss was calculated as a percentage of the total weight loss, and this was defined as the PLA content.

[0072] (Measurement of glass transition temperature and melting point) The glass transition temperature (Tg [°C]) and melting point (Tm [°C]) of block copolymers were measured using a differential scanning calorimeter (DSC, manufactured by Hitachi High-Tech Science Corporation, product name "NEXTA DSC200"). The measurement temperature range was -80 to 200°C, and the heating rate was 10°C / min.

[0073] <Measurement of crystallinity> A block copolymer was hot-press molded using a 0.1 mm thick mold at 20 MPa for 10 minutes at 180°C to obtain a 0.1 mm thick film. The obtained films were treated at 90°C for 12 hours, and then measured using an X-ray diffractometer (Rigaku Corporation, product name "RINT-UltimateIII") with a tube voltage of 40kW, tube current of 40mA, measurement range of diffraction angle 2θ = 5~40°, and scan speed of 1.0° / min. The degree of crystallinity [%] of the films was determined using the following formula. Crystallinity [%] = (Crystalline peak area / (Crystalline peak area + Amorphous peak area)) × 100

[0074] <Evaluation of Mechanical Properties> A block copolymer was hot-press molded using a 0.1 mm thick mold at 20 MPa for 10 minutes at 180°C to obtain a 0.1 mm thick film. From the obtained film, a dumbbell-shaped tensile test specimen with a length of 20 mm and a width of 4 mm at the equilibrium section was cut out. Tensile testing was performed using a tensile testing machine (Shimadzu Corporation, product name "Benchtop Precision Universal Testing Machine AGS-X") in accordance with JIS K 7127:1999, and the tensile modulus of elasticity [MPa], maximum stress [MPa], elongation at break [%], and toughness [MJ / m] of the tensile test specimen were determined. 3 The following was measured: The crosshead speed was set to 10 mm / min, and the distance between grips was set to 20 mm.

[0075] <Measurement of total light transmittance and haze> A block copolymer was hot-press molded using a 0.1 mm thick mold at 20 MPa for 10 minutes at 180°C to obtain a 0.1 mm thick film. The total light transmittance and haze of the obtained films were measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "NDH-4000"). Total light transmittance was measured in accordance with JIS K 7361-1:1997. Haze was measured in accordance with JIS K 7136:2000.

[0076] <Biodegradability Assessment 1: Compost Environment> 60g of compost seed source (manufactured by Yawata Bussan Co., Ltd., product name "Seed Source No. YK-12") was weighed as total dry solids, water was added until the moisture content reached 65% by mass, and the mixture was thoroughly mixed. The mixture was then left to stand at room temperature for 24 hours to cure. Next, 320g of dried sea sand, which had been pre-mixed with water to adjust the moisture content to 15% by mass, was thoroughly mixed with the cured compost seed source to prepare the compost.

[0077] Separately, a 0.1 mm thick mold was used to hot-press the block copolymer at 20 MPa for 10 minutes at 180°C to obtain a 0.1 mm thick film. The obtained film was cut into pieces measuring 20 mm vertically and 20 mm horizontally, and the cut film pieces were sandwiched between nylon mesh. The previously prepared compost was kept at 58°C in a constant temperature and humidity chamber (Tokyo Rikakikai Co., Ltd., product name "KCL-2000A") and cured for one week while maintaining a constant moisture content. Next, the film, sandwiched between nylon mesh, was buried in the compost and left undisturbed for two and four weeks. The changes in the film were visually observed at the two-week and four-week marks. The weight of the film was also measured to confirm the weight change before and after burial. The biodegradability in the compost environment was evaluated according to the following evaluation criteria. (Evaluation Criteria) ◎: The weight of the film after 2 weeks is lower than that of the film obtained in Comparative Example 2. ○: The weight of the film at the 4-week mark is lower than that of the film obtained in Comparative Example 2. ×: The weight of the film at the 4-week mark is similar to or less than that of the film obtained in Comparative Example 2.

[0078] <Biodegradability Assessment 2: Marine Environment> The seawater used was collected from Tokyo Bay (Odaiba Seaside Park) on the morning of July 16, 2024. The Respirometric Sensor System 6 for Plastic Biodegradability (VELP Scientifica) was used as the test apparatus.

[0079] A block copolymer was hot-press molded using a 0.1 mm thick mold at 20 MPa for 10 minutes at 180°C to obtain a 0.1 mm thick film. The obtained film was cut into pieces measuring 20 mm vertically and 20 mm horizontally. The cut film pieces were immersed in 250 mL of seawater and stirred at 150 rpm in the dark at 30°C for 3 months. The changes in the film after 3 months were visually observed. The degree of biodegradation was also measured. The biodegradability in the seawater environment was evaluated according to the following evaluation criteria. For measuring biodegradability, we adopted a method for measuring oxygen consumption using a closed respiratory system in accordance with ASTM D6691-17. The degree of biodegradation was calculated using the following formula. Biodegradation degree [%]=(BOD0-BOD B ) / ThOD×100 (In the formula, "BOD0" is the biochemical oxygen demand of the target (measured value: mg), and "BOD B " is the average biochemical oxygen demand (measured value: mg) in a blank test, and "ThOD" is the theoretical oxygen demand (calculated value: mg) required when the test material or target material is completely oxidized.

[0080] (Evaluation Criteria) ◎: The film's weight decreased by 15% or more after 3 months, and its biodegradability is 15% or more. ○: The film's weight decreased by 2% or more after 3 months, and its biodegradability was 2% or more. ×: No decrease in film weight was observed after 3 months, indicating a biodegradability of less than 2%.

[0081] [Example 1] In a 200 mL three-necked flask, approximately 5 g of lactide (moles: approximately 0.035 mol, molar mass: 144.13 g / mol) and approximately 5 g of poly-3-methyl-1,5-pentanebacate diol (manufactured by Kuraray Co., Ltd., product name "Kuraray Polyol P-2050") (moles: approximately 0.0025 mol, molar mass: 2000 g / mol) were placed, dried under reduced pressure, and dehydrated. Approximately 20.3 mg of 2-ethylhexanoate tin(II) (moles: approximately 0.05 mmol, molar mass: 405.12 g / mol) was added dropwise, and the flask was repeatedly purged with nitrogen to create a nitrogen atmosphere. Subsequently, the mixture was stirred at 170 °C for 3 hours under a nitrogen atmosphere to synthesize an oligomer having a triblock structure. To calculate the charging ratio, a portion of the sample was separated and analyzed. Then, approximately 631 mg of hexamethylene diisocyanate (moles: approximately 3.75 mmol, molar mass: 168.2 g / mol) was added dropwise to the oligomer having a triblock structure in a molten state so that NCO / OH = 1.5 / 1 (mol), and the reaction was carried out at 170°C for 30 minutes under a nitrogen atmosphere. After that, the reaction product was dissolved in chloroform, reprecipitated with methanol, and the block copolymer was recovered. The obtained block copolymer is an alternating multiblock copolymer. Various measurements and evaluations were performed using the obtained block copolymer. The results are shown in Tables 1-3.

[0082] [Example 2] In a 200 mL three-necked flask, approximately 6 g of lactide (moles: approximately 0.042 mol, molar mass: 144.13 g / mol) and approximately 3 g of poly-3-methyl-1,5-pentanebacate diol (manufactured by Kuraray Co., Ltd., product name "Kuraray Polyol P-2050") (moles: approximately 0.0015 mol, molar mass: 2000 g / mol) were placed, dried under reduced pressure, and dehydrated. Approximately 12.2 mg of 2-ethylhexanoate tin(II) (moles: approximately 0.03 mol, molar mass: 405.12 g / mol) was added dropwise, and the flask was repeatedly purged with nitrogen to create a nitrogen atmosphere. Subsequently, the mixture was stirred at 170 °C for 3 hours under a nitrogen atmosphere to synthesize an oligomer having a triblock structure. To calculate the charging ratio, a portion of the sample was separated and analyzed. Then, approximately 378 mg of hexamethylene diisocyanate (moles: approximately 2.25 mmol, molar mass: 168.2 g / mol) was added dropwise to the oligomer having a triblock structure in a molten state so that NCO / OH = 1.5 / 1 (mol), and the reaction was carried out at 170°C for 30 minutes under a nitrogen atmosphere. After that, the reaction product was dissolved in chloroform, reprecipitated with methanol, and the block copolymer was recovered. The obtained block copolymer is an alternating multiblock copolymer. Various measurements and evaluations were performed using the obtained block copolymer. The results are shown in Tables 1-3.

[0083] [Example 3] In a 200 mL three-necked flask, approximately 8 g of lactide (moles: approximately 0.06 mol, molar mass: 144.13 g / mol) and approximately 2 g of poly-3-methyl-1,5-pentanebacate diol (manufactured by Kuraray Co., Ltd., product name "Kuraray Polyol P-2050") (moles: approximately 0.001 mol, molar mass: 2000 g / mol) were placed, dried under reduced pressure, and dehydrated. Approximately 8.1 mg of 2-ethylhexanoate tin(II) (moles: approximately 0.02 mmol, molar mass: 405.12 g / mol) was added dropwise, and the flask was repeatedly purged with nitrogen to create a nitrogen atmosphere. Subsequently, the mixture was stirred at 170 °C for 3 hours under a nitrogen atmosphere to synthesize an oligomer having a triblock structure. To calculate the charging ratio, a portion of the sample was separated and analyzed. Then, approximately 252 mg of hexamethylene diisocyanate (moles: approximately 1.5 mmol, molar mass: 168.2 g / mol) was added dropwise to the oligomer having a triblock structure in a molten state so that NCO / OH = 1.5 / 1 (mol), and the reaction was carried out at 170°C for 30 minutes under a nitrogen atmosphere. After that, the reaction product was dissolved in chloroform, reprecipitated with methanol, and the block copolymer was recovered. The obtained block copolymer is an alternating multiblock copolymer. Various measurements and evaluations were performed using the obtained block copolymer. The results are shown in Tables 1-3.

[0084] [Example 4] In a 200 mL three-necked flask, approximately 8 g of lactide (moles: 0.056 mol, molar mass: 144.13 g / mol) and approximately 1 g of poly-3-methyl-1,5-pentanebacate diol (manufactured by Kuraray Co., Ltd., product name "Kuraray Polyol P-2050") (moles: 0.0005 mol, molar mass: 2000 g / mol) were placed, dried under reduced pressure, and dehydrated. Approximately 4.1 mg of 2-ethylhexanoate tin(II) (moles: approximately 0.01 mmol, molar mass: 405.12 g / mol) was added dropwise, and the flask was repeatedly purged with nitrogen to create a nitrogen atmosphere. Subsequently, the mixture was stirred at 170 °C for 3 hours under a nitrogen atmosphere to synthesize an oligomer having a triblock structure. To calculate the charging ratio, a portion of the sample was separated and analyzed. Then, approximately 126 mg of hexamethylene diisocyanate (moles: approximately 0.75 mmol, molar mass: 168.2 g / mol) was added dropwise to the oligomer having a triblock structure in a molten state so that NCO / OH = 1.5 / 1 (mol), and the reaction was carried out at 170°C for 30 minutes under a nitrogen atmosphere. After that, the reaction product was dissolved in chloroform, reprecipitated with methanol, and the block copolymer was recovered. The obtained block copolymer is an alternating multiblock copolymer. Various measurements and evaluations were performed using the obtained block copolymer. The results are shown in Tables 1-3.

[0085] [Example 5] In a 200 mL three-necked flask, approximately 8 g of lactide (moles: approximately 0.06 mol, molar mass: 144.13 g / mol) and approximately 2 g of poly-3-methyl-1,5-pentaneadipate diol (manufactured by Kuraray Co., Ltd., product name "Kuraray Polyol P-2010") (moles: approximately 0.001 mol, molar mass: 2000 g / mol) were placed, dried under reduced pressure, and dehydrated. Approximately 8.1 mg of 2-ethylhexanoate tin(II) (moles: approximately 0.02 mmol, molar mass: 405.12 g / mol) was added dropwise, and the flask was repeatedly purged with nitrogen to create a nitrogen atmosphere. Subsequently, the mixture was stirred at 170 °C for 3 hours under a nitrogen atmosphere to synthesize an oligomer having a triblock structure. To calculate the charging ratio, a portion of the sample was separated and analyzed. Then, approximately 252 mg of hexamethylene diisocyanate (moles: approximately 1.5 mmol, molar mass: 168.2 g / mol) was added dropwise to the oligomer having a triblock structure in a molten state so that NCO / OH = 1.5 / 1 (mol), and the reaction was carried out at 170°C for 30 minutes under a nitrogen atmosphere. After that, the reaction product was dissolved in chloroform, reprecipitated with methanol, and the block copolymer was recovered. The obtained block copolymer is an alternating multiblock copolymer. Various measurements and evaluations were performed using the obtained block copolymer. The results are shown in Tables 1-3.

[0086] [Example 6] Approximately 14 g of lactide (moles: approximately 0.097 mol, molar mass: 144.13 g / mol) and approximately 0.32 g of 1,4-butanediol (moles: approximately 0.0035 mol, molar mass: 90.121 g / mol) were placed in a 200 mL three-necked flask, dried under reduced pressure, and dehydrated. Approximately 28 mg of 2-ethylhexanoate tin(II) (moles: approximately 0.07 mmol, molar mass: 405.12 g / mol) was added dropwise, and the flask was repeatedly purged with nitrogen to create a nitrogen atmosphere. Subsequently, the mixture was stirred at 170 °C for 3 hours under a nitrogen atmosphere to synthesize polylactic acid diol. After that, the reaction product was dissolved in chloroform, reprecipitation with methanol, and the polylactic acid diol was recovered. A portion of the recovered polylactic acid diol was separated and analyzed for calculation of the charging ratio. Approximately 5 g of recovered polylactic acid diol and approximately 2.38 g of poly-3-methyl-1,5-pentanesebacate diol (manufactured by Kuraray Co., Ltd., trade name "Kuraray Polyol P-2050") (moles: approximately 1.29 mmol, molar mass: 2000 g / mol) were placed in a separate flask and melted at 170°C. Approximately 601 mg of hexamethylene diisocyanate (moles: approximately 3.57 mmol, molar mass: 168.2 g / mol) was added dropwise to the molten polylactic acid diol and poly-3-methyl-1,5-pentanesebacate diol so that NCO / OH = 1.5 / 1 (mol), and the reaction was carried out under a nitrogen atmosphere at 170°C for 30 minutes. Subsequently, the reaction product was dissolved in chloroform, reprecipitation with methanol, and the block copolymer was recovered. Thus, in Example 6, instead of synthesizing a triblock structure, polylactic acid diol was synthesized, and then the polylactic acid diol and poly3-methyl-1,5-pentanesebacate diol were subjected to a urethane reaction. The block copolymer obtained in Example 6 is a random multiblock copolymer formed by urethane bonding between polylactic acid diol and poly3-methyl-1,5-pentanesebacate diol. Example 6 relates to a copolymerization method that does not involve a triblock structure. Various measurements and evaluations were performed using the obtained block copolymer. The results are shown in Tables 1-3.

[0087] [Example 7] Approximately 20 g of lactide (moles: approximately 0.14 mol, molar mass: 144.13 g / mol) and approximately 0.23 g of 1,4-butanediol (moles: approximately 0.0025 mol, molar mass: 90.121 g / mol) were placed in a 200 mL three-necked flask, dried under reduced pressure, and dehydrated. Approximately 20 mg of 2-ethylhexanoate tin(II) (moles: approximately 0.05 mmol, molar mass: 405.12 g / mol) was added dropwise, and the flask was repeatedly purged with nitrogen to create a nitrogen atmosphere. Subsequently, the mixture was stirred at 170 °C for 3 hours under a nitrogen atmosphere to synthesize polylactic acid diol. After that, the reaction product was dissolved in chloroform, reprecipitation with methanol, and the polylactic acid diol was recovered. A portion of the recovered polylactic acid diol was separated and analyzed for calculation of the charging ratio. Approximately 6 g of recovered polylactic acid diol and approximately 1.62 g of poly-3-methyl-1,5-pentanesebacate diol (manufactured by Kuraray Co., Ltd., product name "Kuraray Polyol P-2050") (moles: approximately 0.81 mmol, molar mass: 2000 g / mol) were placed in a separate flask and melted at 170°C. To the molten polylactic acid diol and poly-3-methyl-1,5-pentanesebacate diol, approximately 409 mg of hexamethylene diisocyanate (moles: approximately 2.43 mmol, molar mass: 168.2 g / mol) was added dropwise to achieve NCO / OH = 1.5 / 1 (mol), and the mixture was reacted under a nitrogen atmosphere at 170°C for 30 minutes. Subsequently, the reaction product was dissolved in chloroform, reprecipitation with methanol, and the block copolymer was recovered. Thus, in Example 7, instead of synthesizing a triblock structure, polylactic acid diol was synthesized, and then the polylactic acid diol and poly3-methyl-1,5-pentanesebacate diol were subjected to a urethane reaction. The block copolymer obtained in Example 7 is a random multiblock copolymer formed by urethane bonding between polylactic acid diol and poly3-methyl-1,5-pentanesebacate diol. Example 7 relates to a copolymerization method that does not involve a triblock structure. Various measurements and evaluations were performed using the obtained block copolymer. The results are shown in Tables 1-3.

[0088] [Comparative Example 1] Approximately 5 g (moles: approximately 0.0025 mol, molar mass: 2000 g / mol) of poly-3-methyl-1,5-pentanesebacate diol (manufactured by Kuraray Co., Ltd., trade name "Kuraray Polyol P-2050") was placed in a 200 mL three-necked flask and melted at 170°C. To the molten poly-3-methyl-1,5-pentanesebacate diol, approximately 630 mg (moles: approximately 3.75 mmol, molar mass: 168.2 g / mol) of hexamethylene diisocyanate was added dropwise to achieve a ratio of NCO / OH = 1.5 / 1 (mol), and the reaction was carried out under a nitrogen atmosphere at 170°C for 30 minutes. Subsequently, the reaction product was dissolved in chloroform, reprecipitation with methanol, and the polymer was recovered. Various measurements and evaluations were performed using the recovered polymer. The results are shown in Tables 1-3. When we attempted to fabricate a film using the obtained polymer, an oily product was produced, and it was not possible to form a film. Therefore, crystallinity, total light transmittance, and haze could not be measured, and mechanical properties and biodegradability could not be evaluated.

[0089] [Comparative Example 2] Approximately 20 g of lactide (moles: approximately 0.14 mol, molar mass: 144.13 g / mol) and approximately 0.23 g of 1,4-butanediol (moles: approximately 0.0025 mol, molar mass: 90.121 g / mol) were placed in a 200 mL three-necked flask, dried under reduced pressure, and dehydrated. Approximately 20 mg of 2-ethylhexanoate tin(II) (moles: approximately 0.05 mmol, molar mass: 405.12 g / mol) was added dropwise, and the flask was repeatedly purged with nitrogen to create a nitrogen atmosphere. Subsequently, the mixture was stirred at 170 °C for 3 hours under a nitrogen atmosphere to synthesize polylactic acid diol. After that, the reaction product was dissolved in chloroform, reprecipitation with methanol, and the polylactic acid diol was recovered. A portion of the recovered polylactic acid diol was separated and analyzed for calculation of the charging ratio. Approximately 5 g of the recovered polylactic acid diol was placed in a separate three-necked flask and melted at 170°C. To the molten polylactic acid diol, approximately 170 mg of hexamethylene diisocyanate (moles: approximately 1.01 mmol, molar mass: 168.2 g / mol) was added dropwise to achieve a ratio of NCO / OH = 1.5 / 1 (mol), and the reaction was carried out at 170°C for 30 minutes under a nitrogen atmosphere. Subsequently, the reaction product was dissolved in chloroform, reprecipitation with methanol, and the polymer was recovered. Various measurements and evaluations were performed using the obtained polymer. The results are shown in Tables 1-3.

[0090] [Table 1]

[0091] [Table 2]

[0092] [Table 3]

[0093] Note that the "PLA content" in Table 2 is the content of polylactic acid units (B) [mass%] when the total of polyol units (A) and polylactic acid units (B) obtained from TG-DTA is set to 100 mass%.

[0094] As is clear from the results in Tables 1-3, the block copolymers obtained in each example exhibited excellent biodegradability and heat resistance. Furthermore, the block copolymers obtained in each example showed good appearance, transparency, and visibility when formed into films. In particular, the block copolymers obtained in Examples 1-5, which were alternating multi-block copolymers, also exhibited excellent mechanical properties. In contrast, the polymer obtained in Comparative Example 1 had poor heat resistance. The polymer obtained in Comparative Example 2 had poor biodegradability. [Industrial applicability]

[0095] According to the present invention, a block copolymer with excellent biodegradability and heat resistance is provided. [Explanation of symbols]

[0096] 1A Alternating multiblock copolymer (X1) 1B Random multiblock copolymer (X2) 2 Polyol Unit (A) 3. Polylactic acid unit (B) 4 Triblock structure 5. Units containing urethane bonds

Claims

1. A block copolymer comprising a polyol unit (A) having a constituent unit derived from a dicarboxylic acid having four or more carbon atoms, and a polylactic acid unit (B).

2. The block copolymer according to claim 1, wherein the polyol unit (A) and the polylactic acid unit (B) are linked by an ester bond.

3. The block copolymer according to claim 1, wherein the block copolymer has a plurality of triblock structures in which polylactic acid units (B) are bonded to both ends of the polyol unit (A) by ester bonds, and the plurality of triblock structures are bonded to each other.

4. The block copolymer according to claim 3, wherein multiple of the aforementioned triblock structures are linked together by units including urethane bonds.

5. The block copolymer according to claim 3, wherein at least one of the glass transition temperature and melting point, as measured by differential scanning calorimeter, is one.

6. The block copolymer according to claim 1, wherein the dicarboxylic acid comprises at least one of sebadic acid and adipic acid.

7. The block copolymer according to claim 1, wherein the content of the polylactic acid unit (B) is 40 to 90% by mass relative to the total mass of the block copolymer.

8. The block copolymer according to claim 1, wherein the glass transition temperature is 50°C or lower.

9. The block copolymer according to claim 1, wherein the weight-average molecular weight is 50,000 to 500,000.

10. The block copolymer according to any one of claims 1 to 9, wherein when the block copolymer is formed into a film under the following conditions, the total light transmittance of the film is 90% or more. Film forming conditions: Hot press forming is performed using a 0.1 mm thick mold under the conditions of 20 MPa, 10 minutes, and 180°C.

11. The block copolymer according to any one of claims 1 to 9, wherein when the block copolymer is formed into a film under the following conditions, the elongation at break of the film is 2% or more. Film forming conditions: Hot press forming is performed using a 0.1 mm thick mold under the conditions of 20 MPa, 10 minutes, and 180°C.

Images