Copolymer, and method for manufacturing copolymer

Abstract

The present invention addresses the problem of providing a polymer that can be used as a tire material and is easily decomposed. The solution provided by the present invention is a copolymer characterized by containing a segment (A) derived from a butadiene-based polymer, a segment (B) derived from a biodegradable polyester, a segment (C) derived from polyethylene glycol, and a segment (D) derived from a polyisocyanate compound. The copolymer preferably furthermore contains a segment (E) derived from a diol compound having a molecular weight of 600 or lower in addition to than the segment (A) derived from a butadiene-based polymer, the segment (B) derived from a biodegradable polyester, the segment (C) derived from polyethylene glycol, and the segment (D) derived from a polyisocyanate compound.

Description

Copolymer and method for producing copolymer

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

[0002] Butadiene-based polymers, such as butadiene rubber and styrene-butadiene rubber, used in the rubber industry, primarily for tire applications, are generally difficult to decompose. For this reason, it has been pointed out that tire wear dust, for example, may exist in nature as microplastics, potentially placing a burden on the environment. Meanwhile, among chemically synthesized polymers, polycaprolactone and the like are known as biodegradable polymers that are easily decomposed in nature. For example, Japanese Patent Laid-Open Publication No. 2023-58335 (Patent Document 1) discloses a branched biodegradable polyester having a block structure containing a random copolymer segment of lactide and caprolactone and a homopolymer segment of lactide, with a trivalent or higher polyhydric alcohol bonded to the end of the block structure.

[0003] Japanese Patent Application Laid-Open No. 2023-58335

[0004] However, the branched biodegradable polyester disclosed in Patent Document 1 does not have the physical properties required for tire applications. Therefore, there is a demand for a polymer that can be used as a tire material and is easily degradable.

[0005] Therefore, an object of the present invention is to solve the above-mentioned problems of the conventional art and to provide a polymer that can be used as a tire material and is easily degradable.A further object of the present invention is to provide a method for producing a polymer that can be used as a tire material and is easily degradable.

[0006] The copolymer of the present invention, which solves the above-mentioned problems, and the method for producing the copolymer are outlined below.

[0007] [1] A copolymer comprising a segment (A) derived from a butadiene-based polymer, a segment (B) derived from a biodegradable polyester, a segment (C) derived from polyethylene glycol, and a segment (D) derived from a polyisocyanate compound.

[0008] [2] The copolymer according to [1], further comprising a segment (E) derived from a diol compound having a molecular weight of 600 or less, other than the segment (A) derived from the butadiene-based polymer, the segment (B) derived from the biodegradable polyester, the segment (C) derived from the polyethylene glycol, and the segment (D) derived from the polyisocyanate compound.

[0009] [3] The copolymer according to [1] or [2], wherein, in the total amount of the butadiene-based polymer-derived segment (A), the biodegradable polyester-derived segment (B), and the polyethylene glycol-derived segment (C), the proportion of the butadiene-based polymer-derived segment (A) is 20 to 80% by mass, the proportion of the biodegradable polyester-derived segment (B) is 10 to 40% by mass, and the proportion of the polyethylene glycol-derived segment (C) is 10 to 40% by mass.

[0010] [4] The copolymer according to any one of [1] to [3], wherein, in the total amount of the butadiene-based polymer-derived segment (A), the biodegradable polyester-derived segment (B), and the polyethylene glycol-derived segment (C), the proportion of the butadiene-based polymer-derived segment (A) is 20 to 60% by mass, the proportion of the biodegradable polyester-derived segment (B) is 20 to 40% by mass, and the proportion of the polyethylene glycol-derived segment (C) is 20 to 40% by mass.

[0011] [5] The copolymer according to any one of [1] to [4], wherein the molar ratio (NCO / OH) of isocyanate groups (NCO) to hydroxyl groups (OH) in the raw materials of the copolymer is 0.8 or more and less than 1.0.

[0012] [6] The copolymer according to any one of [2] to [5], wherein the mass ratio (SS:HS) of the soft segment (SS) composed of the segment (A) derived from the butadiene-based polymer, the segment (B) derived from the biodegradable polyester, and the segment (C) derived from the polyethylene glycol, to the hard segment (HS) composed of the segment (D) derived from the polyisocyanate compound and the segment (E) derived from the diol compound having a molecular weight of 600 or less, is 80:20 to 50:50.

[0013] [7] The copolymer according to any one of [1] to [6], wherein the butadiene-based polymer (A') serving as a raw material for the butadiene-based polymer-derived segment (A) has a number average molecular weight (Mn) of 1,000 to 30,000.

[0014] [8] A method for producing the copolymer according to any one of [2] to [7], comprising: a step of reacting a butadiene-based polymer (A'), a biodegradable polyester (B'), a polyethylene glycol (C'), and a polyisocyanate compound (D') to form a soft segment (SS)-containing portion; and a step of reacting a diol compound (E') having a molecular weight of 600 or less, other than the butadiene-based polymer (A'), the biodegradable polyester (B'), the polyethylene glycol (C'), and the polyisocyanate compound (D'), with the soft segment (SS)-containing portion to produce the copolymer.

[0015] According to the present invention, it is possible to provide a copolymer that can be used as a tire material and is easily degradable. Also, according to the present invention, it is possible to provide a method for producing a copolymer that can be used as a tire material and is easily degradable.

[0016] The copolymer of the present invention and the method for producing the copolymer will be described in detail below with reference to the embodiments.

[0017] <Definitions> The compounds described herein may be derived in whole or in part from fossil resources, from biological resources such as plant resources, from recycled resources such as used tires, or from a mixture of two or more of fossil resources, biological resources, and recycled resources.

[0018] <Copolymer> The copolymer of the present embodiment is characterized by including a segment (A) derived from a butadiene-based polymer, a segment (B) derived from a biodegradable polyester, a segment (C) derived from a polyethylene glycol, and a segment (D) derived from a polyisocyanate compound.

[0019] The copolymer of this embodiment contains a segment (A) derived from a butadiene-based polymer, which provides the copolymer with sufficient rubber elasticity for use as a tire material. The copolymer of this embodiment also contains a segment (B) derived from a biodegradable polyester, which serves as a degradable portion (hydrolyzable portion) of the copolymer. The copolymer of this embodiment also contains a segment (C) derived from a polyethylene glycol, which provides hydrophilicity to the copolymer. A copolymer having a segment (A) derived from a butadiene-based polymer and a segment (B) derived from a biodegradable polyester but no segment (C) derived from a polyethylene glycol contains the biodegradable polyester-derived segment (B), which is a degradable portion, but is hydrophobic. Therefore, the water required for hydrolysis of the biodegradable polyester-derived segment (B) is unlikely to reach the biodegradable polyester-derived segment (B), resulting in a slow hydrolysis reaction and poor decomposition. In contrast, the copolymer of this embodiment has a polyethylene glycol-derived segment (C) in addition to a butadiene-based polymer-derived segment (A) and a biodegradable polyester-derived segment (B), and is highly hydrophilic, so that water easily reaches the biodegradable polyester-derived segment (B), the hydrolysis reaction rate is fast, and the copolymer is easily decomposed. Furthermore, the copolymer of this embodiment also contains a polyisocyanate compound-derived segment (D), and by bonding the butadiene-based polymer-derived segment (A), the biodegradable polyester-derived segment (B), and the polyethylene glycol-derived segment (C), the copolymer is endowed with physical properties sufficient for use as a tire material. Therefore, the copolymer of this embodiment can be used as a tire material and is easily decomposed, particularly in nature.

[0020] —Butadiene-Based Polymer-Derived Segment (A)— The copolymer of the present embodiment contains a butadiene-based polymer-derived segment (A), and the butadiene-based polymer-derived segment (A) provides the copolymer with sufficient rubber elasticity for use as a tire material.

[0021] The butadiene-based polymer-derived segment (A) is derived from the butadiene-based polymer (A') used as a raw material. The butadiene-based polymer (A') contains 1,3-butadiene units and may be a homopolymer of 1,3-butadiene or a copolymer of 1,3-butadiene and another monomer copolymerizable with 1,3-butadiene. Examples of the other monomer copolymerizable with 1,3-butadiene include conjugated diene monomers other than 1,3-butadiene and aromatic vinyl monomers. Examples of the conjugated diene monomers other than 1,3-butadiene include 2-methyl-1,3-butadiene (also referred to as "isoprene"), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene. Examples of the aromatic vinyl monomers include styrene, p-methylstyrene, α-methylstyrene, and vinylnaphthalene. Specific examples of the butadiene polymer (A') include polybutadiene (also called "butadiene rubber"), styrene-butadiene copolymer (also called "styrene-butadiene rubber"), etc. These butadiene polymers (A') may be used singly or in combination of two or more.

[0022] The butadiene-based polymer (A') used as the raw material for the butadiene-based polymer-derived segment (A) preferably has multiple hydroxy groups (OH), more preferably two hydroxy groups (OH) (i.e., a diol), and particularly preferably has hydroxy groups (OH) at both ends (i.e., a diol at both ends). When the butadiene-based polymer (A') used as the raw material has multiple hydroxy groups (OH), it is easy to bond it to the other segments (B) and (C) using the polyisocyanate compound (D') used as the raw material for the polyisocyanate compound-derived segment (D), which will be described later, and production becomes easier. Specific examples of butadiene-based polymers having multiple hydroxy groups include polybutadiene diols.

[0023] The butadiene-based polymer (A') used as a raw material for the butadiene-based polymer-derived segment (A) preferably has a number-average molecular weight (Mn) of 1,000 to 30,000. When the butadiene-based polymer (A') has a number-average molecular weight (Mn) of 1,000 or more, the copolymer has rubber elasticity that is more suitable for use as a tire material. When the butadiene-based polymer (A') has a number-average molecular weight (Mn) of 30,000 or less, the decomposition products containing the butadiene-based polymer-derived segment (A) produced after decomposition of the copolymer are sufficiently small, thereby reducing the environmental impact. Therefore, a copolymer having a butadiene-based polymer (A') used as a raw material for the butadiene-based polymer-derived segment (A) with a number-average molecular weight (Mn) of 1,000 to 30,000 has more suitable rubber elasticity and a low environmental impact. From the viewpoint of reducing environmental impact, the number average molecular weight (Mn) of the butadiene polymer (A') is more preferably 20,000 or less, even more preferably 10,000 or less, and particularly preferably 5,000 or less.

[0024] - Biodegradable polyester-derived segment (B) - The copolymer of this embodiment contains a biodegradable polyester-derived segment (B), and the biodegradable polyester-derived segment (B) serves as a degradable portion (hydrolyzable portion) of the copolymer. The biodegradable polyester-derived segment (B) and the biodegradable polyester (B') that serves as a raw material for the biodegradable polyester-derived segment (B) are biodegradable. Here, "biodegradation" means that a substance is decomposed into carbon dioxide, water, etc. by the action of microorganisms.

[0025] As the biodegradable polyester (B') that serves as the raw material for the biodegradable polyester-derived segment (B), various biodegradable polyesters can be used, and polylactones are preferred. Examples of such polylactones include polybutyrolactone, polyvalerolactone, polycaprolactone, and polydecalactone. Among these polylactones, polycaprolactone is particularly preferred from the viewpoint of degradability. These biodegradable polyesters (B') may be used alone or in combination of two or more.

[0026] The biodegradable polyester (B') used as the raw material for the biodegradable polyester-derived segment (B) preferably has multiple hydroxy groups (OH), more preferably two hydroxy groups (OH) (i.e., a diol), and particularly preferably has hydroxy groups (OH) at both ends (i.e., a diol at both ends). When the raw material biodegradable polyester (B') has multiple hydroxy groups (OH), it is easy to bond it to the other segments (A) and (C) using the polyisocyanate compound (D') used as the raw material for the polyisocyanate compound-derived segment (D), which will be described later, making production easier. Specific examples of biodegradable polyesters having multiple hydroxy groups include polybutyrolactone diol, polyvalerolactone diol, polycaprolactone diol, and polydecalactone diol. Among these, polycaprolactone diol is preferred.

[0027] The molecular weight of the biodegradable polyester (B') that is the raw material for the biodegradable polyester-derived segment (B) is not particularly limited. In one embodiment, the number average molecular weight (Mn) of the biodegradable polyester (B') is preferably 200 to 20,000.

[0028] -Polyethylene Glycol-Derived Segment (C)- The copolymer of this embodiment contains a polyethylene glycol-derived segment (C), and the polyethylene glycol-derived segment (C) imparts hydrophilicity to the copolymer. The polyethylene glycol (C') that serves as the raw material for the polyethylene glycol-derived segment (C) is not particularly limited. Because the polyethylene glycol (C') typically has hydroxy groups (OH) at both ends, it is easily bonded to the other segments (A) and (B) using the polyisocyanate compound (D') that serves as the raw material for the polyisocyanate compound-derived segment (D), which will be described later, and this facilitates production of the copolymer.

[0029] The molecular weight of the polyethylene glycol (C') that is the raw material for the polyethylene glycol-derived segment (C) is not particularly limited. In one embodiment, the polyethylene glycol (C') preferably has a number average molecular weight (Mn) of 200 to 20,000. The polyethylene glycol (C') may be used singly by one type having the same average molecular weight, or two or more types having different average molecular weights may be used in combination.

[0030] - Proportion of Each Segment - The proportion of the butadiene-based polymer-derived segment (A) in the total amount of the butadiene-based polymer-derived segment (A), the biodegradable polyester-derived segment (B), and the polyethylene glycol-derived segment (C) is preferably 20 to 80 mass%, and more preferably 20 to 60 mass%. When the proportion of the butadiene-based polymer-derived segment (A) in the total amount of the butadiene-based polymer-derived segment (A), the biodegradable polyester-derived segment (B), and the polyethylene glycol-derived segment (C) is 20 mass% or more, the copolymer has more suitable rubber elasticity and can be more suitably used as a tire material.

[0031] The proportion of the biodegradable polyester-derived segment (B) in the total amount of the butadiene-based polymer-derived segment (A), the biodegradable polyester-derived segment (B), and the polyethylene glycol-derived segment (C) is preferably 10 to 40 mass%, more preferably 20 to 40 mass%. When the proportion of the biodegradable polyester-derived segment (B) in the total amount of the butadiene-based polymer-derived segment (A), the biodegradable polyester-derived segment (B), and the polyethylene glycol-derived segment (C) is 10 mass% or more, the degradable portion in the copolymer increases, making it more easily degradable.

[0032] The proportion of the polyethylene glycol-derived segment (C) in the total amount of the butadiene-based polymer-derived segment (A), the biodegradable polyester-derived segment (B), and the polyethylene glycol-derived segment (C) is preferably 10 to 40 mass%, more preferably 20 to 40 mass%. When the proportion of the polyethylene glycol-derived segment (C) in the total amount of the butadiene-based polymer-derived segment (A), the biodegradable polyester-derived segment (B), and the polyethylene glycol-derived segment (C) is 10 mass% or more, the hydrophilicity of the copolymer is improved, water can more easily reach the biodegradable polyester-derived segment (B), and the copolymer can be more easily decomposed.

[0033] In the copolymer of this embodiment, it is preferable that, based on the total amount of the butadiene-based polymer-derived segment (A), the biodegradable polyester-derived segment (B), and the polyethylene glycol-derived segment (C), the proportion of the butadiene-based polymer-derived segment (A) is 20 to 80 mass%, the proportion of the biodegradable polyester-derived segment (B) is 10 to 40 mass%, and the proportion of the polyethylene glycol-derived segment (C) is 10 to 40 mass%. In this case, the copolymer can be more suitably used as a tire material and is more easily degradable.

[0034] In the copolymer of this embodiment, it is more preferable that, based on the total amount of the butadiene-based polymer-derived segment (A), the biodegradable polyester-derived segment (B), and the polyethylene glycol-derived segment (C), the proportion of the butadiene-based polymer-derived segment (A) is 20 to 60 mass%, the proportion of the biodegradable polyester-derived segment (B) is 20 to 40 mass%, and the proportion of the polyethylene glycol-derived segment (C) is 20 to 40 mass%. In this case, the copolymer can be more suitably used as a tire material and is more easily decomposable.

[0035] - Segment (D) derived from a polyisocyanate compound - The copolymer of the present embodiment includes a segment (D) derived from a polyisocyanate compound. The polyisocyanate compound (D'), which is the raw material for the polyisocyanate compound-derived segment (D), is a compound having a plurality of isocyanate groups (NCO). The polyisocyanate compound (D') preferably has two isocyanate groups (NCO), that is, is preferably a diisocyanate compound. When the polyisocyanate compound (D') is a diisocyanate compound, the copolymer becomes a linear polymer without branches, and has physical properties more suitable for use as a tire material.

[0036] Examples of the polyisocyanate compound (D') that serves as a raw material for the polyisocyanate compound-derived segment (D) include 1,3-bis(isocyanatomethyl)cyclohexane (1,3-HXDI), isophorone diisocyanate (IPDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), crude diphenylmethane diisocyanate (crude MDI), hydrogenated diphenylmethane diisocyanate, hydrogenated tolylene diisocyanate, hexamethylene diisocyanate (HDI), nurate-modified hexamethylene diisocyanate, etc. These polyisocyanate compounds (D') may be used alone or in combination of two or more.

[0037] The amount of polyisocyanate compound (D') used as a raw material for the polyisocyanate compound-derived segment (D) is preferably set appropriately so that the molar ratio (NCO / OH) of isocyanate groups (NCO) to hydroxy groups (OH) in the raw materials described below falls within a desired range. In one embodiment, the proportion of the polyisocyanate compound-derived segment (D) in the copolymer is preferably 16 to 50 mass%.

[0038] —Segment (E) Derived from a Diol Compound Having a Molecular Weight of 600 or Less—The copolymer of this embodiment preferably further comprises a segment (E) derived from a diol compound having a molecular weight of 600 or less, other than the segment (A) derived from the butadiene-based polymer, the segment (B) derived from the biodegradable polyester, the segment (C) derived from the polyethylene glycol, and the segment (D) derived from the polyisocyanate compound. The diol compound (E′) having a molecular weight of 600 or less, which is used as a raw material for the segment (E) derived from the diol compound having a molecular weight of 600 or less, acts as a chain extender, increasing the chain length of the copolymer and imparting physical properties to the copolymer that are more suitable for use as a tire material. Therefore, a copolymer containing the segment (E) derived from a diol compound having a molecular weight of 600 or less has physical properties that are more suitable for use as a tire material.

[0039] Examples of the diol compound (E') having a molecular weight of 600 or less and serving as a raw material for the segment (E) derived from the diol compound having a molecular weight of 600 or less include propylene glycol (also referred to as "propane-1,2-diol"), 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 1,8-octanediol, with 1,4-butanediol being preferred. These diol compounds (E') having a molecular weight of 600 or less may be used alone or in combination of two or more.

[0040] The proportion of the segment (E) derived from the diol compound having a molecular weight of 600 or less in the copolymer is preferably 2 to 20% by mass, more preferably 3 to 10% by mass. When the proportion of the segment (E) derived from the diol compound having a molecular weight of 600 or less is 2% by mass or more, the chain length of the copolymer becomes long, and the copolymer has physical properties more suitable for use as a tire material. Furthermore, when the proportion of the segment (E) derived from the diol compound having a molecular weight of 600 or less is 20% by mass or less, the copolymer has physical properties more suitable for use as a tire material.

[0041] —Mole Ratio of “NCO” to “OH” in Raw Materials— The molar ratio (NCO / OH) of isocyanate groups (NCO) to hydroxy groups (OH) in the raw materials for the copolymer of this embodiment is preferably 0.8 or greater and less than 1.0, and more preferably 0.9 or greater and less than 1.0. When the molar ratio (NCO / OH) of isocyanate groups (NCO) to hydroxy groups (OH) in the raw materials is 0.8 or greater, the chain length of the copolymer increases and the molecular weight of the copolymer increases, resulting in the copolymer having physical properties more suitable for use as a tire material. Furthermore, when the molar ratio (NCO / OH) of isocyanate groups (NCO) to hydroxy groups (OH) in the raw materials is less than 1.0, the copolymer ends with a hydroxy group (OH), and the chain length does not become too long, resulting in a copolymer with a molecular weight that is easy to handle. Therefore, a copolymer having a molar ratio (NCO / OH) of isocyanate groups (NCO) to hydroxyl groups (OH) in the raw materials of 0.8 or more and less than 1.0 has physical properties more suitable for use as a tire material and is easy to handle.

[0042] -Soft Segment (SS) and Hard Segment (HS)- In the copolymer containing the segment (E) derived from a diol compound having a molecular weight of 600 or less, the segment (A) derived from a butadiene-based polymer, the segment (B) derived from a biodegradable polyester, and the segment (C) derived from a polyethylene glycol act as the soft segment (SS) of the copolymer. Meanwhile, the segment (D) derived from a polyisocyanate compound and the segment (E) derived from a diol compound having a molecular weight of 600 or less act as the hard segment (HS) of the copolymer. Here, the mass ratio (SS:HS) of the soft segment (SS) consisting of the segment (A) derived from a butadiene-based polymer, the segment (B) derived from a biodegradable polyester, and the segment (C) derived from a polyethylene glycol to the hard segment (HS) consisting of the segment (D) derived from a polyisocyanate compound and the segment (E) derived from a diol compound having a molecular weight of 600 or less is preferably 80:20 to 50:50. When the proportion of the soft segments (SS) in the total of the soft segments (SS) and the hard segments (HS) is 50% by mass or more and the proportion of the hard segments (HS) is 50% by mass or less, the copolymer has physical properties more suitable for use as a tire material. Furthermore, when the proportion of the soft segments (SS) in the total of the soft segments (SS) and the hard segments (HS) is 80% by mass or less and the proportion of the hard segments (HS) is 20% by mass or more, the chain length of the copolymer increases, resulting in the copolymer having physical properties more suitable for use as a tire material. Therefore, a copolymer having a mass ratio (SS:HS) of the soft segments (SS) to the hard segments (HS) of 80:20 to 50:50 has physical properties more suitable for use as a tire material.

[0043] -Molecular Weight of Copolymer- The copolymer of this embodiment is not particularly limited, but preferably has a number average molecular weight (Mn) of 10,000 to 2,000,000, and more preferably 20,000 to 1,000,000. A number average molecular weight (Mn) of 10,000 or more makes it more suitable for use as a tire material, and a number average molecular weight (Mn) of 2,000,000 or less makes it easier to knead with various tire compounding agents. The copolymer of this embodiment is not particularly limited, but preferably has a weight average molecular weight (Mw) of 20,000 to 4,000,000, and more preferably 40,000 to 2,000,000. A weight average molecular weight (Mw) of 20,000 or more makes it more suitable for use as a tire material, and a weight average molecular weight (Mw) of 4,000,000 or less makes it easier to knead with various tire compounding agents. In this specification, the number average molecular weight (Mn) and weight average molecular weight (Mw) of the copolymer and raw materials of each segment are determined by gel permeation chromatography (GPC) using polystyrene as a standard substance.

[0044] - Uses of the copolymer - The copolymer of this embodiment can be used in various rubber products. In particular, the copolymer of this embodiment is suitable as a tire material. When using the copolymer of this embodiment in a tire, the copolymer can be mixed with various compounding agents to form a rubber composition depending on the desired performance. If desired, the copolymer may also be blended with other rubber components. As described above, the copolymer of this embodiment is easily decomposed, and therefore, a rubber composition containing the copolymer of this embodiment and the other rubber components or compounding agents is also easily decomposed. Furthermore, a tire made from such a rubber composition can be easily decomposed after use and reused.

[0045] - Decomposition of Copolymer - The copolymer of this embodiment is preferably biodegradable, i.e., preferably decomposable in nature. If desired, the copolymer of this embodiment may be decomposed (hydrolyzed) in the presence of an alkali or acid to accelerate decomposition. Examples of the alkali include sodium hydroxide and potassium hydroxide. Examples of the acid include inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid, and organic acids such as formic acid, acetic acid, and propionic acid. Materials obtained by decomposition of the copolymer of this embodiment can be reused for various purposes; for example, they can be used as raw materials for producing copolymers, or as raw materials for synthesizing other chemical substances.

[0046] <Method for Producing Copolymer> The copolymer of the present embodiment can be produced by reacting the butadiene-based polymer (A'), the biodegradable polyester (B'), the polyethylene glycol (C'), and the polyisocyanate compound (D'), which are the raw materials for the above-mentioned segments (A), (B), (C), and (D).

[0047] Furthermore, when the copolymer has the segment (E) derived from the diol compound having a molecular weight of 600 or less, the copolymer can be produced by reacting the butadiene-based polymer (A'), the biodegradable polyester (B'), the polyethylene glycol (C'), the polyisocyanate compound (D'), and the diol compound (E') having a molecular weight of 600 or less.

[0048] Here, the copolymer having the segment (E) derived from a diol compound having a molecular weight of 600 or less is preferably produced through the following steps: (Step 1) reacting the butadiene-based polymer (A'), the biodegradable polyester (B'), the polyethylene glycol (C'), and the polyisocyanate compound (D') to form a soft segment (SS)-containing moiety; and (Step 2) reacting the diol compound (E') having a molecular weight of 600 or less with the soft segment (SS)-containing moiety to produce a copolymer. In this case, a copolymer having the desired physical properties can be more easily obtained.

[0049] In the first step, it is preferable that the number of isocyanate groups (NCO) contained in the polyisocyanate compound (D') is greater than the number of hydroxyl groups (OH) contained in the butadiene-based polymer (A'), the biodegradable polyester (B'), and the polyethylene glycol (C'). That is, it is preferable that there is an excess of isocyanate groups (NCO) to form soft segment (SS)-containing moieties terminated with isocyanate groups (NCO). The soft segment (SS)-containing moieties terminated with isocyanate groups (NCO) can easily undergo a urethane reaction with the diol compound (E') having a molecular weight of 600 or less in the second step, making it easier to obtain a copolymer having the desired physical properties.

[0050] - Catalyst - In one embodiment of the production of the copolymer, a urethanization reaction is utilized, and therefore a urethanization reaction catalyst is preferably used. Examples of the urethanization reaction catalyst include organic tin compounds such as dibutyltin dilaurate, dibutyltin diacetate, dibutyltin dimaleate, and tin octenate; organic lead compounds such as lead octenate; monoamines such as triethylamine and dimethylcyclohexylamine; diamines such as tetramethylethylenediamine, tetramethylpropanediamine, and tetramethylhexanediamine; triamines such as pentamethyldiethylenetriamine, pentamethyldipropylenetriamine, and tetramethylguanidine; cyclic amines such as triethylenediamine, dimethylpiperazine, methylethylpiperazine, methylmorpholine, dimethylaminoethylmorpholine, and dimethylimidazole; alcohol amines such as dimethylaminoethanol, dimethylaminoethoxyethanol, trimethylaminoethylethanolamine, methylhydroxyethylpiperazine, and hydroxyethylmorpholine; ether amines such as bis(dimethylaminoethyl)ether and ethylene glycol bis(dimethyl)aminopropyl ether. Among these catalysts, organic tin compounds are preferred. These catalysts may be used alone or in combination of two or more. The amount of the catalyst used is preferably in the range of 0.0001 to 0.1 moles per mole of the polyisocyanate compound (D').

[0051] - Solvent - The copolymer is preferably produced in a solvent. The solvent is preferably one that does not inhibit the urethanization reaction, and preferably a solvent that does not contain active hydrogen. It is also preferable to dehydrate the solvent prior to the reaction. Examples of the solvent include ether solvents such as tetrahydrofuran, methyltetrahydrofuran, 1,3-dioxane, 1,4-dioxane, 1,3-dioxolane, diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, dipentyl ether, dihexyl ether, diheptyl ether, dioctyl ether, t-butyl methyl ether, and cyclopentyl methyl ether. These solvents may be used alone or in combination of two or more.

[0052] -Reaction Conditions- The reaction temperature in producing the copolymer is not particularly limited and can be carried out at, for example, 50°C to 100°C. The reaction time is also not particularly limited and can be set appropriately depending on the reaction temperature. For example, the reaction time is preferably about 10 minutes to 3 hours. Furthermore, even when producing the copolymer via the first step and the second step, the reaction temperature and reaction time can be set appropriately, and in one embodiment, it is preferable to carry out the reaction at 50°C to 100°C for about 10 minutes to 3 hours.

[0053] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0054] <Raw materials used in the synthesis of (co)polymers> Polybutadiene diol: Krasol LBH 3000, manufactured by Cray Valley, number average molecular weight (Mn) = approximately 3,000 Polycaprolactone: Polycaprolactone diol, number average molecular weight (Mn) = approximately 2,000, CAS: 36890-68-3, manufactured by Sigma-Aldrich Polyethylene glycol: Fujifilm Wako Pure Chemical Industries, Ltd., number average molecular weight (Mn) = approximately 1,000, Wako Grade 1, CAS: 25322-68-3 1,3-bis(isocyanatomethyl)cyclohexane: cis / trans mixture, manufactured by Tokyo Chemical Industry Co., Ltd. (TCI), CAS: 38661-72-2 Dibutyltin dilaurate: Tokyo Chemical Industry Co., Ltd. (TCI), CAS: 77-58-7 Solvent: Kanto Chemical Co., Ltd., tetrahydrofuran (dehydrated), stabilizer-free, CAS: 109-99-9 1,4-butanediol: Tokyo Chemical Industry Co., Ltd. (TCI), CAS: 110-63-4

[0055] Example 1: Polybutadiene diol (11.230 g, 3.556 mmol), polyethylene glycol (11.023 g, 11.023 mmol), and polycaprolactone (9.387 g, 4.693 mmol) were added to a dry, nitrogen-purged reactor. These were then dissolved in tetrahydrofuran (THF) (80 g) to form a homogeneous solution, followed by the addition of 1,3-bis(isocyanatomethyl)cyclohexane (7.597 g, 39.114 mmol) to form a homogeneous solution. Dibutyltin dilaurate (tin-based catalyst) (0.06 g, 0.095 mmol) was added to the reactor to initiate the reaction. The reaction was allowed to proceed at 80°C for 1.5 hours to ensure complete conversion. Following this initial step, 1,4-butanediol (BDO) (1.843 g, 20.446 mmol) dissolved in THF (20 mL) was injected into the reaction mixture. The reaction was continued for an additional 2 hours at 80°C, after which time methanol (5 mL) was added to quench the reaction. Volatiles were removed in a well-ventilated fume hood, and the resulting copolymer was washed with methanol and dried in vacuo at 60°C to a constant weight.

[0056] Example 2: To a dry, nitrogen-purged reactor were added polybutadiene diol (20.5 g, 6.491 mmol), polyethylene glycol (10.39 g, 10.390 mmol), and polycaprolactone (10.39 g, 5.193 mmol). These were dissolved in tetrahydrofuran (THF) (80 g) to form a homogeneous solution, and then 1,3-bis(isocyanatomethyl)cyclohexane (9.078 g, 46.738 mmol) was added to form a homogeneous solution. Dibutyltin dilaurate (tin-based catalyst) (0.060 g, 0.095 mmol) was added to the reactor to initiate the reaction. The reaction was allowed to proceed at 80°C for 2.0 hours to ensure complete conversion. Following this initial step, 1,4-butanediol (BDO) (2.281 g, 25.316 mmol) dissolved in THF (20 mL) was injected into the reaction mixture. The reaction was continued for an additional 2 hours at 80°C, after which time methanol (5 mL) was added to quench the reaction. Volatiles were removed in a well-ventilated fume hood, and the resulting copolymer was washed with methanol and dried in vacuo at 60°C to a constant weight.

[0057] Example 3: To a dry, nitrogen-purged reactor were added polybutadiene diol (20.5 g, 6.491 mmol), polyethylene glycol (10.39 g, 10.390 mmol), and polycaprolactone (10.39 g, 5.193 mmol). These were dissolved in tetrahydrofuran (THF) (80 g) to form a homogeneous solution, and then 1,3-bis(isocyanatomethyl)cyclohexane (12.608 g, 64.913 mmol) was added to form a homogeneous solution. Dibutyltin dilaurate (tin-based catalyst) (0.060 g, 0.095 mmol) was added to the reactor to initiate the reaction. The reaction was allowed to proceed at 80°C for 2.0 hours to ensure complete conversion. Following this initial step, 1,4-butanediol (BDO) (3.919 g, 43.492 mmol) dissolved in THF (20 mL) was injected into the reaction mixture. The reaction was continued for an additional 2 hours at 80°C, after which time methanol (5 mL) was added to quench the reaction. Volatiles were removed in a well-ventilated fume hood, and the resulting copolymer was washed with methanol and dried in vacuo at 60°C to a constant weight.

[0058] Comparative Example 1: Polyethylene glycol (0.362 g, 0.362 mmol) and polycaprolactone (4.82 g, 2.41 mmol) were added to a dry, nitrogen-purged reactor. These were then dissolved in tetrahydrofuran (THF) (10 g) to form a homogeneous solution, and 1,3-bis(isocyanatomethyl)cyclohexane (1.03 g, 5.302 mmol) was added to form a homogeneous solution. Dibutyltin dilaurate (tin-based catalyst) (0.02 g, 0.032 mmol) was added to the reactor to initiate the reaction. The reaction was allowed to proceed at 80°C for 1.5 hours to ensure complete conversion. After this initial step, 1,4-butanediol (BDO) (0.239 g, 2.651 mmol) dissolved in THF (5 mL) was injected into the reaction mixture. The reaction was continued at 80°C for an additional 2 hours, after which the reaction was quenched by the addition of methanol (5 mL). Volatiles were removed in a well-ventilated fume hood, and the resulting copolymer was washed with methanol and dried in vacuo at 60° C. to constant weight.

[0059] Comparative Example 2 Polycaprolactone (polycaprolactone diol, Mn about 10,000, CAS: 36890-68-3) manufactured by Sigma-Aldrich was used.

[0060] Comparative Example 3: Polybutadiene diol (40.759 g, 12.906 mmol) was added to a dry, nitrogen-purged reactor. This was dissolved in tetrahydrofuran (THF) (100 g) to form a homogeneous solution, and then 1,3-bis(isocyanatomethyl)cyclohexane (9.526 g, 49.044 mmol) was added to form a homogeneous solution. Dibutyltin dilaurate (tin-based catalyst) (0.100 g, 0.158 mmol) was added to the reactor to initiate the reaction. The reaction was allowed to proceed at 80°C for 80 minutes to ensure complete conversion. After this initial step, 1,4-butanediol (BDO) (3.257 g, 36.138 mmol) dissolved in THF (20 mL) was injected into the reaction mixture. The reaction was continued at 80°C for an additional 2 hours, after which the reaction was quenched by the addition of methanol (5 mL). Volatiles were removed in a well-ventilated fume hood and the resulting polymer was washed with methanol and dried in vacuo at 60° C. to constant weight.

[0061] Comparative Example 4 Polycaprolactone (polycaprolactone diol, Mn about 2,000, CAS: 36890-68-3) manufactured by Sigma-Aldrich was used.

[0062] Comparative Example 5: Polyethylene glycol (13.725 g, 13.725 mmol) and polycaprolactone (3.0 g, 1.5 mmol) were added to a dry, nitrogen-purged reactor. This was then dissolved in tetrahydrofuran (THF) (20 g) to form a homogeneous solution, and 1,3-bis(isocyanatomethyl)cyclohexane (5.929 g, 30.525 mmol) was added to form a homogeneous solution. Dibutyltin dilaurate (tin-based catalyst) (0.03 g, 0.048 mmol) was added to the reactor to initiate the reaction. The reaction was allowed to proceed at 80°C for 1.5 hours to ensure complete conversion. After this initial step, 1,4-butanediol (BDO) (1.379 g, 15.3 mmol) dissolved in THF (5 mL) was injected into the reaction mixture. The reaction was continued at 80°C for an additional 2 hours, after which the reaction was quenched by the addition of methanol (5 mL). Volatiles were removed in a well-ventilated fume hood, and the resulting copolymer was washed with methanol and dried in vacuo at 60° C. to constant weight.

[0063] <Method for Analyzing Molecular Weight of (Co)polymer> The number average molecular weight (Mn), weight average molecular weight (Mw), peak top molecular weight (Mp), and polydispersity (PDI = Mw / Mn) of the (co)polymer were determined using monodisperse polystyrene as a standard by gel permeation chromatography [GPC: HLC-8321GPC / HT manufactured by Tosoh Corporation, column: HT-806M × 2 manufactured by Showa Denko K.K., detector: differential refractometer (RI)]. The measurement temperature was 40°C.

[0064] <Method for Analyzing Glass Transition Temperature (Tg1) of (Co)polymer> The glass transition temperature (Tg1) of the (co)polymer was measured using a differential scanning calorimeter (DSC).

[0065] <Method for analyzing each segment of (co)polymer> The proportion (mass%) of each segment of the (co)polymer was determined by １The ratio was calculated from the integral ratio of each peak in the H-NMR spectrum. Table 1 shows the proportion of each segment in the total of the polybutadiene diol-derived segment, the polycaprolactone-derived segment, and the polyethylene glycol-derived segment in the (co)polymer product.

[0066] <Evaluation of decomposition of (co)polymer> The (co)polymer was immersed in alkaline water adjusted to pH 14 with an aqueous NaOH solution, and subjected to a decomposition reaction at room temperature for 11 days, and classified according to the following evaluation criteria: A: When the hydrolysis rate was fast and the (co)polymer was completely decomposed B: When the hydrolysis rate was moderate and the (co)polymer was partially decomposed C: When the hydrolysis rate was slow and the (co)polymer was hardly decomposed

[0067]

[0068] It can be seen from Table 1 that the copolymers of the examples according to the present invention contain the segment (A) derived from a butadiene-based polymer, can be used as tire materials, and are easily decomposed.

[0069] The copolymer of the present invention can be used as a tire material.

Claims

1. A copolymer comprising a segment (A) derived from a butadiene polymer, a segment (B) derived from a biodegradable polyester, a segment (C) derived from a polyethylene glycol, and a segment (D) derived from a polyisocyanate compound.

2. The copolymer according to claim 1, further comprising a segment (E) derived from a diol compound having a molecular weight of 600 or less, other than the segment (A) derived from the butadiene-based polymer, the segment (B) derived from the biodegradable polyester, the segment (C) derived from the polyethylene glycol, and the segment (D) derived from the polyisocyanate compound.

3. The copolymer according to claim 1, wherein, in the total amount of the butadiene-based polymer-derived segment (A), the biodegradable polyester-derived segment (B), and the polyethylene glycol-derived segment (C), the proportion of the butadiene-based polymer-derived segment (A) is 20 to 80 mass%, the proportion of the biodegradable polyester-derived segment (B) is 10 to 40 mass%, and the proportion of the polyethylene glycol-derived segment (C) is 10 to 40 mass%.

4. The copolymer according to claim 3, wherein the proportion of the butadiene-based polymer-derived segment (A) is 20 to 60 mass%, the proportion of the biodegradable polyester-derived segment (B) is 20 to 40 mass%, and the proportion of the polyethylene glycol-derived segment (C) is 20 to 40 mass%, in the total amount of the butadiene-based polymer-derived segment (A), the biodegradable polyester-derived segment (B), and the polyethylene glycol-derived segment (C).

5. The copolymer according to claim 1 or 2, wherein the molar ratio (NCO / OH) of isocyanate groups (NCO) to hydroxyl groups (OH) in the raw materials of the copolymer is 0.8 or more and less than 1.

0.

6. The copolymer according to claim 2, wherein a mass ratio (SS:HS) of a soft segment (SS) consisting of the segment (A) derived from the butadiene-based polymer, the segment (B) derived from the biodegradable polyester, and the segment (C) derived from the polyethylene glycol, to a hard segment (HS) consisting of the segment (D) derived from the polyisocyanate compound and the segment (E) derived from the diol compound having a molecular weight of 600 or less, is 80:20 to 50:

50.

7. The copolymer according to claim 1, wherein the butadiene polymer (A') serving as a raw material for the butadiene polymer-derived segment (A) has a number average molecular weight (Mn) of 1,000 to 30,000.

8. A method for producing the copolymer according to claim 2, comprising the steps of: reacting a butadiene-based polymer (A'), a biodegradable polyester (B'), a polyethylene glycol (C') and a polyisocyanate compound (D') to form a soft segment (SS)-containing portion; and reacting a diol compound (E') having a molecular weight of 600 or less, other than the butadiene-based polymer (A'), the biodegradable polyester (B'), the polyethylene glycol (C') and the polyisocyanate compound (D'), with the soft segment (SS)-containing portion to produce the copolymer.