JP7737231B2 - Diol compound and polymer thereof, and method for producing the same - Google Patents

Description

The present invention relates to a novel diol compound having a skeleton derived from 3-hydroxybutyric acid (also known as 3HB), a resin (polymer) containing this diol compound as a polymerization component, and a method for producing the same.

From the perspective of environmental conservation and the realization of a sustainable society, efforts are being made to convert some or all of plastic raw materials into biomass, and the use of bio-based or biodegradable plastics is increasing. Plastic is an essential material in human life, but plastic released into the environment drifts on the ocean and is broken down and fragmented by ultraviolet rays and other factors, producing microplastics with diameters of 5 mm or less. Furthermore, there are concerns that if these microplastics are ingested by the living organisms of birds, fish, and other animals, they may cause endocrine disruption.

In recent years, efforts have been made to address the microplastic problem, such as by adding biodegradability to garbage bags. Examples of biodegradable plastics include polylactic acid (PLA), polyhydroxyalkanoate (PHA), polybutylene succinate (PBS), and polycaprolactone (PCL). However, these biodegradable plastics have low biodegradability (or biogasification) under anaerobic conditions and low biodegradability in the ocean. Because these biodegradable plastics are highly dense and sink in the ocean, solving the microplastic problem requires the development of plastics that are highly biodegradable even in anaerobic conditions, such as those in the ocean.

H. Yagi et al., Polymer Degradation and Stability, 110, (2014), 278-283 (Non-Patent Document 1) evaluated the biodegradability of various biodegradable polyesters under anaerobic conditions, and disclosed that poly-3-hydroxybutyrate (PHB) exhibits higher biodegradability under anaerobic conditions than PLA, PCL, and PBS. However, poly-3-hydroxyalkanoates such as PHB, which are produced (biosynthesized) by microorganisms, lack the mechanical properties required for general-purpose plastic molded products and are also economically unviable, so they have not been widely used.

Meanwhile, as a biodegradable plastic into which 3HB has been introduced by chemical synthesis, Japanese Patent Laid-Open Publication No. 2017-025138 (Patent Document 1) discloses a biodegradable copolymer in which the proportion of 3-hydroxybutyric acid (3HB) units is 1 to 20 mol% relative to all constituent units. Patent Document 1 describes, among other things, that biodegradable copolymers into which 3HB units have been randomly introduced exhibit high biodegradability under both aerobic and anaerobic conditions.

JP 2017-025138 A

H. Yagi et al., Polymer Degradation and Stability, 110, (2014), 278-283 (Table 1)

In the examples of Patent Document 1, it is described that a copolyester containing 4.6 or 8.7 mol% of 3HB units was prepared by adding monomers that form PBS, PBSA, etc., and (R)-3HB all at once and polymerizing them, and that the weight-average molecular weight Mw was 5790 to 6820.

However, the biodegradable copolymer described in Patent Document 1 has low reactivity of the monomer 3HB, and is easily decomposed by intramolecular dehydration caused by heat or acid, making it difficult to increase the molecular weight and resulting in insufficient mechanical properties.

Accordingly, the object of the present invention is to provide a novel diol compound that can be used to prepare a high-molecular-weight resin having a skeleton derived from 3HB, even through chemical synthesis, a resin (polymer) that contains this diol compound as a polymerization component, and a method for producing these.

Another object of the present invention is to provide a novel diol compound that can be used to prepare a resin that has excellent mechanical properties and high moldability (or productivity), even though it has a skeleton derived from 3HB; a resin (polymer) that contains this diol compound as a polymerization component; and a method for producing these.

A further object of the present invention is to provide a novel diol compound that can be used to prepare a resin that has excellent mechanical properties and exhibits biodegradability, a resin (polymer) that contains this diol compound as a polymerization component, and a method for producing these.

3-hydroxyalkanoic acids (3HA) such as 3HB contain a highly reactive carboxyl group and a less reactive secondary alcohol hydroxyl group. Therefore, when synthesizing a resin (polymer) using 3HA as a polymerization component (resin raw material or monomer), not only is the polymerization reaction difficult to proceed due to the secondary alcohol, but intramolecular dehydration due to heating or acid is likely to occur between the hydrogen atom at the α-position of the carboxyl group and the hydroxyl group (secondary alcohol) at the β-position, leading to decomposition to unsaturated monocarboxylic acids such as crotonic acid. Therefore, synthesizing a high-molecular-weight polymer containing 3HA units has been difficult.

Therefore, the present inventors conducted extensive research to achieve the above-mentioned object, and as a result, they found that by using a diol compound (3HB skeleton-containing diol compound) having an ester bond obtained by previously reacting the carboxyl group of 3HB with a derivative of a specific diol (a diol having a residue of the group ^R1 described below) as a polymerization component, it is possible to chemically synthesize a high molecular weight resin despite containing a 3HB skeleton, and thus completed the present invention.

That is, the diol compound of the present invention is represented by the following formula (1):

(wherein R ¹ represents a divalent group, and m represents 0 or 1).

In the formula (1), ^R1 may be a residue of a diol selected from an aliphatic diol, an alicyclic diol, and an aromatic diol. Furthermore, m may be 1. In the formula (1), the structural unit derived from 3-hydroxybutyric acid may include at least a structural unit in which the steric configuration of the asymmetric carbon atom is the R configuration. The diol compound may be a polymerization component of a biodegradable resin.

The present invention includes a method for producing a diol compound represented by formula (1) above by reacting a compound represented by formula (2) below with 3-hydroxybutyric acid.

(wherein L ¹ represents a leaving group, L ² represents a leaving group or a hydroxyl group, and R ¹ is the same as in formula (1) above).

In the above method, the 3-hydroxybutyric acid may include the R-form ((R)-3-hydroxybutyric acid).

The present invention also encompasses a thermoplastic resin containing a diol component as a polymerization component, wherein the diol component contains at least a diol compound represented by formula (1). In the thermoplastic resin, the proportion of structural units derived from the diol compound represented by formula (1) may be approximately 10 to 100 mol % relative to all structural units derived from the diol component.

The polymerization components may further include at least one selected from a diisocyanate component and a dicarboxylic acid component. The diisocyanate component may include an aliphatic diisocyanate component, an alicyclic diisocyanate component, or an aromatic diisocyanate component, and the dicarboxylic acid component may include an acid halide or anhydride of at least one dicarboxylic acid selected from an aliphatic dicarboxylic acid, an alicyclic dicarboxylic acid, and an aromatic dicarboxylic acid. The weight-average molecular weight of the thermoplastic resin may be approximately 30,000 or more. The thermoplastic resin may be a biodegradable resin.

The present invention also encompasses a method for producing the thermoplastic resin by polymerizing a polymerization component containing at least a diol compound represented by formula (1). In this method, the polymerization temperature may be approximately 150°C or lower.

The present invention also encompasses a method for improving the biodegradability (or enzymatic degradability) of the resulting thermoplastic resin by polymerizing a polymerization component containing at least the diol compound represented by formula (1).

Furthermore, the present invention also encompasses a molded article containing the thermoplastic resin. The molded article may be in the form of a film.

By using the diol compound (also referred to as 3HB diol) of the present invention represented by formula (1) as a polymerization component, a resin having a 3HB-derived skeleton can be prepared with a high molecular weight, even by chemical synthesis. Moreover, such a high-molecular-weight resin can be prepared simply (easily or efficiently). Furthermore, even though the resin has a 3HB-derived skeleton, it has excellent mechanical properties and moldability (or productivity). Furthermore, the resin has excellent mechanical properties and can also exhibit biodegradability. The 3HB-derived skeleton is particularly useful because it is easily biodegradable under both aerobic and anaerobic conditions.

FIG. 1 is a ¹ H-NMR (nuclear magnetic resonance) spectrum of the CHDM-Ts obtained in Example 1. FIG. 2 is a ¹³ C-NMR spectrum of the CHDM-Ts obtained in Example 1. FIG. 3 shows the ¹ H-NMR spectrum of 3HB diol (1,4-bis(3-hydroxybutanoyloxymethyl)cyclohexane) obtained in Example 1 and represented by formula (1-1) described below. FIG. 4 shows the ¹³ C-NMR spectrum of 3HB diol (1,4-bis(3-hydroxybutanoyloxymethyl)cyclohexane) obtained in Example 1 and represented by formula (1-1) described below. FIG. 5 is a ¹ H-NMR spectrum of the polyester urethane obtained in Example 2. FIG. 6 is a ¹³ C-NMR spectrum of the polyester urethane obtained in Example 2. FIG. 7 is ^{a 1} H-NMR spectrum of 3HB diol [1,2-bis(3-hydroxybutanoyloxymethyl)ethane] represented by formula (1-2) described below, obtained in Example 3. FIG. 8 is a ¹³ C-NMR spectrum of 3HB diol [1,2-bis(3-hydroxybutanoyloxymethyl)ethane] obtained in Example 3 and represented by formula (1-2) described below. FIG. 9 shows the FT-IR spectra of 3HB polyester urethane before and after the biodegradation test of Example 4 (the solid line shows the spectrum before the test, and the dashed line shows the spectrum after the test). FIG. 10 shows the evaluation results of the biodegradation test of cyclohexanedimethanol (CHDM) in Comparative Example 2.

[3HB skeleton-containing diol compound represented by formula (1)]

(wherein R ¹ represents a divalent group, and m represents 0 or 1).

In the formula (1), the divalent group represented by R ¹ may be a residue of a diol, and examples thereof include residues of a diol selected from an aliphatic diol, an alicyclic diol, and an aromatic diol.

In this specification and claims, the term "residue of a diol" refers to a divalent group obtained by removing two hydroxyl groups (OH) from the chemical structure of a diol. In other words, the divalent group R ¹ refers to a residue of a diol represented by formula (3) HO-R ¹ -OH, which will be described later.

Examples of aliphatic diols include alkylene glycols and polyalkylene glycols.

Examples of the alkylene glycol (or alkanediol) include linear or branched C 2-20 alkylene glycols (e.g., linear or branched C _2-16 alkylene glycols), such as ethylene glycol, propylene glycol, trimethylene glycol, 1,2-butanediol, 1,3-butanediol, tetramethylene glycol (or 1,4-butanediol), 1,5-pentanediol, neopentyl glycol, _1,6 -hexanediol, 1,8-octanediol, and 1,10-decanediol.

Examples of polyalkylene glycols (or polyalkanediols) include diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, and other di- to deca-linear or branched C _2-20 alkylene glycols (e.g., di- to deca-linear or branched C _2-16 alkylene glycols), preferably di- to hexa-linear or branched C _2-12 alkylene glycols (e.g., di- to hexa-linear or branched C _2-8 alkylene glycols), and more preferably di- to tetra-linear or branched C _2-6 alkylene glycols (e.g., di- to tetra-linear or branched C _2-4 alkylene glycols).

Examples of alicyclic diols include cycloalkanediols (for example, _C3-12 cycloalkanediols such as cyclohexanediol, preferably _C4-10 cycloalkanediols, more preferably _C5-8 cycloalkanediols); bis(hydroxyalkyl)cycloalkanes [for example, bis( _hydroxyC1-6 alkyl) _{C3-12 cycloalkanes} such as cyclohexanedimethanol]; hydrogenated biphenols or bisphenols (for example, hydrogenated bisphenol A); and hydrogenated products corresponding to aromatic diols described below, such as alkylene oxide (or corresponding alkylene carbonate, haloalkanol) adducts thereof [for example, _C2-4 alkylene oxide adducts, preferably _C2-3 alkylene oxide adducts such as ethylene oxide adducts and propylene oxide adducts].

Examples of aromatic diols include dihydroxyarenes (for example, dihydroxy C _6-14 arenes such as hydroquinone and resorcinol, preferably dihydroxy C _6-10 arenes); bis(hydroxyalkyl)arenes [for example, bis(hydroxy C _1-6 alkyl) C _6-14 arenes such as benzenedimethanol, preferably bis(hydroxy C _1-4 alkyl) C _6-10 arenes]; biphenols (for example, p,p'-biphenol); bisphenols (for example, bisphenol A, bisphenol F, bisphenol AD, bisphenol C, bisphenol G, bisphenol S); and alkylene oxide (or corresponding alkylene carbonate, haloalkanol) adducts thereof [for example, C _2-4 alkylene oxide adducts, preferably C _2-3 alkylene oxide adducts such as ethylene oxide adducts and propylene oxide adducts].

Of these diol residues represented by ^R1 , aliphatic diol residues or alicyclic diol residues, especially aliphatic diol residues, are preferred from the viewpoint of biodegradability, etc. Preferred aliphatic diol residues are residues of alkylene glycols such as linear or branched _C2-12 alkylene glycol (e.g., linear or branched _C2-8 alkylene glycol), more preferably linear or branched _C2-6 alkylene glycol (e.g., linear or branched _C2-4 alkylene glycol), and particularly preferably linear or branched _C2-3 alkylene glycol residues such as ethylene glycol.

Furthermore, from the viewpoints of handleability (or productivity) and heat resistance, a residue of an alicyclic diol is preferred. Preferred examples of the residue of an alicyclic diol include a residue of a bis(hydroxyalkyl)cycloalkane, more preferably a residue of a bis( _hydroxyC1-4 alkyl) _C4-10 cycloalkane [for example, a bis( _hydroxyC1-3 alkyl)C5-8 _cycloalkane ], and particularly preferably a residue of a bis( _hydroxyC1-2 alkyl) _C5-8 cycloalkane such as benzenedimethanol.

In the formula (1), m may be either 0 (i.e., a dimer formed from 3HB and a diol corresponding to ^R1 ) or 1 (i.e., a trimer formed from two 3HBs and a diol corresponding to ^R1 ), and m is preferably 1 from the viewpoint of efficiently introducing a skeleton derived from 3HB (or a 3HB unit) into the resin.

In this specification and claims, "structural unit derived from 3-hydroxybutyric acid" or "3HB unit" refers to a unit (or divalent group) represented by the following formula, obtained by removing a hydrogen atom from the hydroxyl group of 3HB and a hydroxyl group from the carboxyl group:

The configuration of the 3HB unit in formula (1) (configuration at the asymmetric carbon atom) may be either the R configuration (R isomer) or the S configuration (S isomer), but from the viewpoint of biodegradability, it is preferable to contain at least one 3HB unit in the R configuration (R isomer). In particular, when m is 1, the configurations of the two 3HB units may be the same or different, but from the viewpoint of biodegradability, it is preferable that both are in the R configuration.

Representative examples of the diol compound represented by the formula (1) include 3HB diols in which m is 1 and R ¹ is a residue of an aliphatic diol, specifically, bis(3-hydroxybutanoyloxy)alkanes [for example, bis(3-hydroxybutanoyloxy)C _2-6 alkanes such as 1,2-bis(3-hydroxybutanoyloxy)ethane, preferably bis(3-hydroxybutanoyloxy)C _2-4 alkanes]; and 3HB diols in which m is 1 and R ¹ is a residue of an alicyclic diol, specifically, bis(3-hydroxybutanoyloxyalkyl)cycloalkanes [for example, bis(3-hydroxybutanoyloxyC _1-4 alkyl)C 5-10 cycloalkanes such as 1,4-bis(3-hydroxybutanoyloxymethyl)cyclohexane, preferably bis(3-hydroxybutanoyloxyC _1-3 alkyl)C _5-8 cycloalkanes _] .

(Method for producing diol compound represented by formula (1))
The method for producing the 3HB skeleton-containing diol compound represented by the formula (1) is not particularly limited as long as it includes at least the following reaction step (ii). For example, the compound can be produced by the following reaction steps (i) to (ii):

(wherein L ¹ represents a leaving group, L ² represents a leaving group or a hydroxyl group, and R ¹ and m are the same as defined above, including preferred embodiments).

(i) Preparation of Compound Represented by Formula (2) The compound represented by formula (2) can be prepared by converting at least one hydroxyl group of the diol represented by formula (3) into a leaving group.

Representative examples of the diol represented by the formula (3) include the aliphatic diols, alicyclic diols, and aromatic diols exemplified in the section on ^R1 , and preferred examples include aliphatic diols such as ethylene glycol and alicyclic diols such as cyclohexanedimethanol.

Examples of leaving groups represented by L ¹ and L ² include the group [—O—SO ₂ —R ² ] (wherein R ² represents a hydrocarbon group, a fluorohydrocarbon group, or a fluorine atom), and halogen atoms (for example, a chlorine atom, a bromine atom, an iodine atom, preferably a bromine atom). Of these leaving groups, the group [—O—SO ₂ —R ² ] and halogen atoms such as a bromine atom are preferred.

In the group [—O—SO ₂ —R ² ], examples of the hydrocarbon group represented by R ² include alkyl groups, cycloalkyl groups, aryl groups, and groups combining two or more of these. Examples of alkyl groups include C _1-6 alkyl groups such as methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, s-butyl, and t-butyl. Examples of cycloalkyl groups include C _5-10 cycloalkyl groups such as cyclopentyl and cyclohexyl. Examples of aryl groups include C _6-12 aryl groups such as phenyl and naphthyl. Examples of groups combining two or more of these groups include alkylaryl groups (for example, mono- to tri-C _1-6 alkyl C _6-10 aryl groups such as tolyl and xylyl), and aralkyl groups (for example, C _6-10 aryl C _1-6 alkyl groups such as benzyl and phenethyl).

In the group [-O-SO ₂ -R ² ], the fluorohydrocarbon group represented by R ² may be any group in which at least one hydrogen atom of a hydrocarbon group has been substituted with a fluorine atom, and a perfluorohydrocarbon group in which all hydrogen atoms have been substituted with fluorine atoms is particularly preferred. Therefore, examples of the fluorohydrocarbon group include groups in which at least one (preferably all) hydrogen atoms of the hydrocarbon group represented by R ² have been substituted with fluorine atoms. Specific examples of the fluorohydrocarbon group include fluorinated alkyl groups (for example, C _1-6 perfluoroalkyl groups such as trifluoromethyl and nonafluorobutyl).

Preferred examples of ^R2 include alkyl groups (C _1-4 alkyl groups such as methyl groups), aryl groups (C _6-10 aryl groups such as phenyl groups), alkylaryl groups (mono- to tri-C _1-4 alkyl C _6-10 aryl groups), perfluoroalkyl groups (C _1-6 perfluoroalkyl groups such as trifluoromethyl groups and nonafluorobutyl groups), and fluorine atoms, and more preferred are alkylaryl groups (particularly C _1-4 alkyl C _6-10 aryl groups such as p-methylphenyl groups (p-tolyl groups)).

When L ² is a leaving group, the types of the leaving groups represented by L ¹ and L ² may be different from each other, but are preferably the same.

The method for converting a hydroxyl group into a leaving group is not particularly limited, and a conventional method may be selected depending on the type of leaving group and the diol represented by formula (3). For example, when the leaving groups represented by L ¹ and L ² are halogen atoms, a method of reacting a halogenating agent corresponding to the halogen atom (for example, hydrogen halides such as hydrogen chloride, hydrogen bromide, and hydrogen iodide; thionyl halides such as thionyl chloride; phosphorus trihalides such as phosphorus trichloride and phosphorus tribromide; zinc halides such as zinc chloride) with the diol represented by formula (3) may be used; when the leaving groups represented by L ¹ and L ² are the group [—O—SO ₂ —R ² ], a sulfonylating agent [for example, a compound represented by the formula X ¹ —SO ₂ —R ² (wherein X ¹ represents a halogen atom, and R ² is the same as above, including preferred embodiments), a compound represented by the formula R ² —SO ₂ —O—SO ₂ —R ² (wherein R ² is the same as above, including preferred embodiments.) with a diol represented by formula (3). Usually, when the diol represented by formula (3) is an aliphatic diol, the former method of reacting with a halogenating agent is often used, but commercially available products can also be used. Furthermore, when the diol represented by formula (3) is an alicyclic diol, the latter method of reacting with a sulfonylating agent is often used.

Among sulfonylating agents, preferred are compounds represented by the formula X ¹ —SO ₂ —R ^2. In the compound represented by the formula X ¹ —SO ₂ —R ² , examples of the halogen atom X ¹ include a chlorine atom, a bromine atom, and an iodine atom, and preferred is a chlorine atom.

Representative compounds represented by the formula X ¹ —SO ₂ —R ² include sulfonyl chlorides corresponding to the above-mentioned preferred R ² , such as p-toluenesulfonyl chloride (or tosyl chloride) and methylsulfonyl chloride (or mesyl chloride).

The proportion of the sulfonylating agent used may be selected from the range of, for example, about 0.1 to 10 moles (e.g., 1 to 5 moles) per mole of the diol represented by formula (3), and when ^L2 in formula (2) is a leaving group, it may be preferably about 2 to 4 moles, more preferably about 2.5 to 3.5 moles. Note that when ^L2 in formula (2) is a hydroxyl group, the proportion of the sulfonylating agent may be smaller, for example, about 0.5 to 1 mole per mole of the diol represented by formula (3).

The reaction between the diol represented by formula (3) and the sulfonylating agent is usually carried out in the presence of a base. Examples of the base include organic bases such as amines; and inorganic bases such as metal hydroxides (e.g., alkali metal hydroxides such as sodium hydroxide and potassium hydroxide), metal carbonates, and metal hydrogen carbonates (e.g., alkali metal carbonates such as sodium carbonate and potassium carbonate). These bases can be used alone or in combination. Of these bases, organic bases such as amines are preferred.

Examples of amines include tertiary amines such as trialkylamines (for example, triC _1-6 alkylamines such as trimethylamine and triethylamine), N,N,N'N'-tetraalkylalkanediamines (for example, N,N,N'N'-tetraC _1-6 alkyl C _2-12 alkanediamines such as N,N,N'N'-tetramethyl-1,6-hexanediamine), and heterocyclic tertiary amines (for example, pyridine).

These amines can be used alone or in combination. Of these amines, trialkylamines such as triethylamine and N,N,N'N'-tetraalkylalkanediamines such as N,N,N'N'-tetramethyl-1,6-hexanediamine are preferred.

The proportion of amines used may be, for example, 2 to 10 moles, preferably 2.5 to 5 moles, and more preferably 3 to 3.5 moles per mole of the diol represented by formula (3).

The reaction between the diol represented by formula (3) and the sulfonylating agent may be carried out in the presence of a solvent. Examples of solvents include nitriles (e.g., acetonitrile), hydrocarbons (e.g., aromatic hydrocarbons such as toluene), and halogenated hydrocarbons (e.g., dichloromethane). These solvents can be used alone or in combination. Of these solvents, nitriles such as acetonitrile are preferred.

The proportion of the solvent is not particularly limited and may be, for example, approximately 100 to 1,000 parts by mass per 100 parts by mass of the total amount of the diol represented by formula (3), the sulfonylating agent, and the base.

In the reaction between the diol represented by formula (3) and the sulfonylating agent, the reaction temperature may be, for example, -30°C to 30°C, preferably -20°C to 10°C, and more preferably -5°C to 5°C. The reaction may usually be carried out under ice cooling. The reaction time may be, for example, 1 to 48 hours, preferably 12 to 36 hours.

The reaction between the diol represented by formula (3) and the sulfonylating agent is typically carried out in an inert atmosphere (e.g., nitrogen gas; a rare gas such as argon gas, etc.) with stirring, and may be carried out under normal pressure, elevated pressure, or reduced pressure.

The reaction between the diol represented by formula (3) and the sulfonylating agent can usually be carried out by slowly adding the sulfonylating agent (and, if necessary, the solvent) dropwise (over, for example, about 0.5 to 3 hours) to a mixture of the diol represented by formula (3) and the base (and, if necessary, the solvent) while maintaining the mixture at a low temperature (e.g., ice-cooling).

After the reaction is complete, the product may be separated and purified using conventional methods, such as neutralization, washing, dehydration, filtration, adsorption, concentration, extraction, crystallization, reprecipitation, centrifugation, column chromatography, or a combination of these methods.

(ii) Preparation of Compound Represented by Formula (1) The compound represented by formula (1) can be prepared by reacting the compound represented by formula (2) with 3HB. When ^L2 in formula (2) is a leaving group, a compound (trimer) in which m in formula (1) is 1 can be prepared, and when ^L2 is a hydroxyl group, a compound (dimer) in which m in formula (1) is 0 can be prepared.

Examples of the compound represented by formula (2) include sulfonyl compounds of the diol represented by formula (3) (e.g., derivatives corresponding to the leaving group [—O—SO ₂ —R ² ], such as tosyl compounds, mesyl compounds, and triflate compounds), and halides. Specific examples of the sulfonyl compounds include sulfonyl compounds of alicyclic diols such as 1,4-bis(p-toluenesulfonyloxymethyl)cyclohexane; and specific examples of the halides include halides of aliphatic diols such as 1,2-dibromoethane.

The 3HB used in the reaction may be an optical isomer (R or S isomer) or a racemate, but from the perspective of biodegradability, it preferably contains at least the R isomer ((R)-3-hydroxybutyric acid). The proportion of the R isomer in 3HB, i.e., the optical purity (or optical isomer excess), is, for example, about 50% e.e. or more (e.g., 80% e.e. or more), preferably 90% e.e. or more (e.g., 95 to 100% e.e.), and more preferably 98 to 100% e.e. (e.g., 99 to 100% e.e., particularly substantially 100% e.e.). If the optical purity is too low, there is a risk of significant deterioration in mechanical properties and biodegradability.

The proportion of 3HB used may be selected from the range of, for example, approximately 1 to 10 moles, and preferably approximately 2 to 3 moles, per mole of the compound represented by formula (2).

The reaction of the compound represented by formula (2) with 3HB may generally be carried out in the presence of a base. Examples of the base include the bases exemplified in section (i) Preparation of the Compound Represented by Formula (2) above. These bases can be used alone or in combination of two or more. Of these bases, inorganic bases are preferred, more preferably metal carbonates or metal hydrogen carbonates (e.g., alkali metal carbonates such as sodium carbonate and potassium carbonate), and even more preferably alkali metal carbonates such as potassium carbonate.

The ratio of the base may be, for example, about 1 to 2 moles, preferably about 1 to 1.2 moles, per mole of 3HB.

The reaction of the compound represented by formula (2) with 3HB may be carried out in the presence of a solvent. Examples of the solvent include amides (e.g., N,N-diC _1-4 alkyl C _1-3 acylamides such as N,N-dimethylformamide, N,N-diethylformamide, and N,N-dimethylacetamide, and N-C 1-4 alkyl-2- _pyrrolidones such as N-methyl-2-pyrrolidone). The solvents may be used alone or in combination of two or more. The proportion of the solvent may be, for example, about 100 to 1000 parts by mass per 100 parts by mass of the total amount of the compound represented by formula (2), 3HB, and base.

In the reaction of the compound represented by formula (2) with 3HB, the reaction conditions may be appropriately selected depending on the types of L ¹ and L ^2. When L ¹ and L ² are groups [—O—SO ₂ —R ² ], the reaction temperature may be, for example, 0 to 100° C., preferably 30 to 70° C., and more preferably 40 to 60° C., and the reaction may usually be carried out under ice-cooling, and the reaction time may be, for example, 1 to 96 hours, and preferably about 24 to 72 hours. When L ¹ and L ² are halogen atoms, the reaction temperature may be, for example, 30 to 130° C., preferably 60 to 100° C., and more preferably 70 to 90° C., and the reaction time may be, for example, 1 to 48 hours, and preferably about 12 to 24 hours.

The reaction between the compound represented by formula (2) and 3HB can usually be carried out in an inert atmosphere (e.g., nitrogen gas; a rare gas such as argon gas, etc.) with stirring, and may be carried out under normal pressure, elevated pressure, or reduced pressure.

After the reaction is complete, the product may be separated and purified using conventional methods, such as neutralization, washing, dehydration, filtration, adsorption, concentration, extraction, crystallization, reprecipitation, centrifugation, column chromatography, or a combination of these methods.

[Thermoplastic resin]
The diol compound represented by the formula (1) can be effectively used as a polymerization component (monomer) for forming a thermoplastic resin having a 3HB skeleton (or 3HB unit). By using the diol compound represented by the formula (1) as a polymerization component, decomposition of 3HB can be effectively suppressed, thereby achieving a high molecular weight.

The thermoplastic resin may contain, as a polymerization component, a diol component containing at least the diol compound represented by formula (1). For example, it may be a step-growth polymerization (polycondensation or polyaddition) thermoplastic resin such as a polyurethane resin (or a thermoplastic polyurethane resin) (e.g., polyester urethane resin), a polyester resin (polyester resin, polyester carbonate resin), or a polyether resin, with polyurethane resin and polyester resin being preferred.

Therefore, the polymerization components that form thermoplastic resins typically contain other polymerization components different from diol components, such as diisocyanate components, dicarboxylic acid components, and carbonate bond-forming components (e.g., phosgenes such as phosgene, phosgene polymers (diphosgene, triphosgene, etc.); carbonate diesters such as diphenyl carbonate). These other polymerization components can be used alone or in combination of two or more. Of these other polymerization components, diisocyanate components and dicarboxylic acid components are preferred in terms of reactivity and productivity. Below, we will discuss in detail the diisocyanate components and dicarboxylic acid components that can be the main polymerization components that form thermoplastic resins, in addition to the diol components.

(Diol component)
The diol component contains at least a diol compound represented by the formula (1) (also referred to as a first diol component), and the first diol component may be formed from a specific diol compound represented by the formula (1) alone or in combination of two or more. Preferred diol compounds as the first diol component are the same as those in the preferred embodiments described above for the formula (1).

When two or more diol compounds represented by the formula (1) are combined, for example, two or more diol compounds having different types of divalent group ^R1 or different configurations of the 3HB units in the formula (1) may be combined, or a compound in which m is 0 (dimer) and a compound in which m is 1 (trimer) may be combined (for example, when a mixture of the dimer and trimer is obtained in the production of a specific diol compound represented by the formula (1), both may be used as polymerization components without purifying either one).

The diol component may or may not contain a second diol component different from the first diol component, as necessary, taking into consideration the balance between the physical properties such as the mechanical properties of the resulting resin and biodegradability, etc. Typical examples of the second diol component include an aliphatic diol component, an alicyclic diol component, and an aromatic diol component, and specific examples of the diol include the same diol compounds corresponding to the aliphatic diols, alicyclic diols, and aromatic diols exemplified in the section on ^R1 in the formula (1).

These second diol components can be used alone or in combination of two or more. Among these second diol components, aliphatic diol components such as alkylene glycol are preferred, and linear or branched _C2-12 alkylene glycols (for example, linear or branched _C2-8 alkylene glycols) are more preferred, with linear or branched _C2-6 alkylene glycols (for example, linear or branched _C2-4 alkylene glycols) and linear or branched _C2-3 alkylene glycols such as ethylene glycol being particularly preferred.

In a thermoplastic resin, the proportion of structural units derived from a diol component (also referred to as diol units) relative to the total structural units derived from the polymerization components of the thermoplastic resin may be selected from a range of, for example, approximately 1 to 70 mol% (e.g., 10 to 60 mol%), preferably 30 to 55 mol% (e.g., 40 to 53 mol%), more preferably 45 to 52 mol%, and typically approximately 50 mol%.

Furthermore, in the thermoplastic resin, the proportion of structural units derived from the first diol component (also referred to as first diol units) relative to the total diol units may be selected from a range of, for example, approximately 1 mol% or more (10 to 100 mol%), preferably 30 mol% or more (50 to 100 mol%), more preferably 60 mol% or more (70 to 100 mol%), even more preferably 80 mol% or more (90 to 100 mol%), and particularly 95 mol% or more, or essentially 100 mol%. If the content of the first diol units is too low, the biodegradability of the resin may be reduced.

The first diol units may be formed solely from structural units derived from a dimer in which m is 0 in formula (1). However, in order to efficiently introduce 3HB units, it is preferable that they contain at least structural units derived from a trimer in which m is 1. Therefore, the proportion of structural units derived from the trimer relative to the total first diol units may be selected from a range of, for example, approximately 1 to 100 mol% (e.g., 10 to 99 mol%), preferably 30 to 100 mol% (e.g., 50 to 95 mol%), more preferably 60 to 100 mol% (e.g., 70 to 90 mol%), even more preferably 80 to 100 mol% (e.g., 90 to 100 mol%), and particularly preferably 95 to 100 mol% (substantially 100 mol%).

In addition, among the 3HB units in the thermoplastic resin, the proportion of 3HB units (or (R)-3HB units) having an R configuration (R-isomer) may be selected from a range of, for example, about 1 to 100 mol% (e.g., 10 to 99 mol%) relative to the total 3HB units, preferably 30 to 100 mol% (e.g., 50 to 95 mol%), more preferably 70 to 100 mol% (e.g., 90 to 100 mol%), even more preferably 95 to 100 mol% (e.g., 98 to 100 mol%), and particularly 99 to 100 mol% (e.g., 99.5 to 100 mol%, and particularly essentially 100 mol%). If the proportion of (R)-3HB units is too low, mechanical properties and biodegradability may be significantly reduced.

When combining a first diol component and a second diol component, the ratio of the first diol units to the structural units (second diol units) derived from the second diol component (particularly an aliphatic diol component such as alkylene glycol) can be adjusted taking into account the mechanical properties, biodegradability, and other properties of the resin. For example, the molar ratio of the former to the latter may be selected from a range of approximately 1/99 to 99/1, and from the perspective of imparting biodegradability without significantly impairing physical properties such as mechanical properties, it may preferably be approximately 1/99 to 10/90. If the amount of the first diol units is too small, the biodegradability of the resin may be reduced, and if the amount of the second diol units is too small, the mechanical properties and other properties of the resin may not be sufficiently improved.

In this specification and claims, the terms "diol unit" (including "first diol unit") or "structural unit derived from a diol component" refer to a unit (or divalent group) obtained by removing hydrogen atoms from two hydroxyl groups of the corresponding diol component, and the term "diol component" (including compounds exemplified as diol components) may be used synonymously with the corresponding "diol unit."

(Diisocyanate component)
When the polymerization component contains a diisocyanate component, it can be combined with a first diol component (a diol compound having an ester bond represented by the formula (1)) to form a polyurethane resin (such as a polyester urethane resin).

The diisocyanate component may be a diisocyanate compound or a derivative thereof that has two isocyanate groups as polymerizable groups in its chemical structure, such as an aliphatic diisocyanate component, an alicyclic diisocyanate component, an araliphatic diisocyanate component, an aromatic diisocyanate component, or a bifunctional urethane prepolymer.

In this specification and claims, the term "diisocyanate component" is used to mean not only diisocyanate compounds but also their derivatives. Examples of diisocyanate compound derivatives include multimers such as dimers (dimers or uretdione) and trimers (trimers or isocyanurates), as well as modified compounds such as biurets, allophanates, and carbodiimides.

Examples of the aliphatic diisocyanate component include linear or branched C _2-16 alkane diisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMDI), and derivatives thereof.

Examples of alicyclic diisocyanate components include 1,4-cyclohexane diisocyanate, isophorone diisocyanate (IPDI), 4,4'-methylenebis(cyclohexyl isocyanate), hydrogenated xylylene diisocyanate (hydrogenated XDI), hydrogenated diphenylmethane diisocyanate (hydrogenated MDI), norbornane diisocyanate, and derivatives thereof.

Examples of aralkyl diisocyanate components include xylylene diisocyanate (XDI), tetramethyl xylylene diisocyanate (TMXDI), and derivatives thereof.

Aromatic diisocyanate components include, for example, phenylene diisocyanate, tolylene diisocyanate (TDI), 1,5-naphthalene diisocyanate (NDI), diphenylmethane diisocyanate (MDI), toluidine diisocyanate (TODI), diphenyl ether diisocyanate, and derivatives thereof.

Examples of bifunctional urethane prepolymers include urethane prepolymers that are produced by reacting the above-mentioned diisocyanate component with a diol component (such as the second diol component) and have two free isocyanate groups.

These diisocyanate components can be used alone or in combination. Of these diisocyanate components, aliphatic diisocyanate components such as HDI are preferred from the standpoints of handleability (moldability or productivity) and biodegradability.

In a thermoplastic resin, the proportion of structural units derived from diisocyanate components (also referred to as diisocyanate units) relative to the total structural units derived from the polymerization components of the thermoplastic resin may be selected from a range of, for example, approximately 0 to 70 mol% (e.g., 10 to 60 mol%), preferably 30 to 55 mol% (e.g., 40 to 53 mol%), more preferably 45 to 52 mol%, and typically approximately 50 mol%.

Furthermore, in the thermoplastic resin, the proportion of structural units derived from aliphatic diisocyanate components (also referred to as aliphatic diisocyanate units) relative to the total diisocyanate units may be selected from a range of, for example, approximately 1 mol% or more (e.g., 10 to 100 mol%), preferably 30 mol% or more (e.g., 50 to 100 mol%), more preferably 60 mol% or more (e.g., 70 to 100 mol%), even more preferably 80 mol% or more (e.g., 90 to 100 mol%), and particularly 95 mol% or more, or essentially 100 mol%. If the aliphatic diisocyanate units are too few (if other diisocyanate units, such as aromatic diisocyanate units, are too many), the biodegradability of the resin may be reduced.

In this specification and claims, "diisocyanate unit" (including "aliphatic diisocyanate unit") or "structural unit derived from a diisocyanate component" refers to a unit (or divalent group) in which two isocyanate groups [-N=C=O] of the corresponding diisocyanate component are incorporated into the resin, i.e., the group [-NH-C(=O)-].

(Dicarboxylic acid component)
When the polymerization component contains a dicarboxylic acid component, it can be combined with a first diol component or the like to form a polyester resin or the like.

The dicarboxylic acid component may be a dicarboxylic acid compound having two carboxyl groups as polymerizable groups in its chemical structure, or an ester-forming derivative thereof, such as an aliphatic dicarboxylic acid component, an alicyclic dicarboxylic acid component, or an aromatic dicarboxylic acid component.

In this specification and claims, the term "dicarboxylic acid component" is used to mean not only dicarboxylic acid but also its ester-forming derivatives. Examples of the ester-forming derivatives include alkyl esters, acid halides, and acid anhydrides. Examples of the alkyl esters include lower alkyl esters, such as _C1-4 alkyl esters such as methyl esters, ethyl esters, and t-butyl esters. The ester-forming derivatives may be monoesters (half esters) or diesters.

Examples of the aliphatic dicarboxylic acid component include alkanedicarboxylic acids, specifically C _2-12 alkane-dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and decanedicarboxylic acid; unsaturated aliphatic dicarboxylic acids, specifically C _2-10 alkene-dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid; and ester-forming derivatives thereof.

Examples of the alicyclic dicarboxylic acid component include cycloalkane dicarboxylic acids, specifically C _5-10 cycloalkane-dicarboxylic acids such as 1,4-cyclohexane dicarboxylic acid; bridged cyclic cycloalkane dicarboxylic acids, specifically bi- or tricycloalkane dicarboxylic acids such as decalin dicarboxylic acid, norbornane dicarboxylic acid, adamantane dicarboxylic acid, tricyclodecane dicarboxylic acid; cycloalkene dicarboxylic acids, specifically C _5-10 cycloalkene-dicarboxylic acids such as cyclohexene dicarboxylic acid; bridged cyclic cycloalkene dicarboxylic acids, specifically bi- or tricycloalkene dicarboxylic acids such as norbornene dicarboxylic acid; and ester-forming derivatives thereof.

Examples of the aromatic dicarboxylic acid component include monocyclic aromatic dicarboxylic acids, polycyclic aromatic dicarboxylic acids, and ester-forming derivatives thereof. Examples of the monocyclic aromatic dicarboxylic acids include benzene dicarboxylic acids such as phthalic acid, terephthalic acid, and isophthalic acid; alkyl benzene dicarboxylic acids, specifically C _1-4 alkyl benzene dicarboxylic acids such as 4-methylisophthalic acid; and the like.

Examples of polycyclic aromatic dicarboxylic acids include condensed polycyclic aromatic dicarboxylic acids, specifically condensed polycyclic C _{10-24 arene-dicarboxylic acids such as naphthalenedicarboxylic acid, anthracenedicarboxylic acid, and phenanthrenedicarboxylic acid, preferably condensed polycyclic C 10-14} arene-dicarboxylic acids; biaryl dicarboxylic acids, specifically biC _6-10 aryl-dicarboxylic acids such as 2,2'-biphenyldicarboxylic acid, 4,4'-biphenyldicarboxylic acid, and 3,3'-dicarboxy-1,1'-binaphthyl; bis(carboxyalkoxy)biC _6-10 aryl, specifically bis(carboxyC 1-4 alkoxy)biC _6-10 aryl such as 2,2'-bis(carboxymethoxy)-1,1'-binaphthyl; and bis[(carboxyalkoxy)-C _6-10 aryl]alkanes, specifically bis[(carboxyC _1-4 alkoxy)biC _6-10 aryl]alkanes such as bis[2-(carboxymethoxy)-1-naphthyl]methane. _{diarylalkanedicarboxylic} acids, specifically, di(C _6-10 aryl)C _1-6 alkane-dicarboxylic acids such as 4,4'-diphenylmethanedicarboxylic acid; diarylketonedicarboxylic acids, specifically, di(C _6-10 aryl)ketone-dicarboxylic acids such as _4,4' -diphenylketonedicarboxylic acid; diaryletherdicarboxylic acids, specifically, di(C _6-10 aryl)ether-dicarboxylic acids such as 4,4'-diphenyletherdicarboxylic acid; diarylsulfonedicarboxylic acids, specifically, _{di(C 6-10 aryl} )sulfone-dicarboxylic acids such as 4,4'-diphenylsulfonedicarboxylic acid.

Examples of the naphthalenedicarboxylic acid include 1,2-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, and 2,6-naphthalenedicarboxylic acid, with 2,6-naphthalenedicarboxylic acid being the most common.

These dicarboxylic acid components can be used alone or in combination of two or more. Among these dicarboxylic acid components, from the viewpoint of mechanical properties, aromatic dicarboxylic acid components such as monocyclic aromatic dicarboxylic acid components (such as benzenedicarboxylic acid) and condensed polycyclic aromatic dicarboxylic acid components (such as naphthalenedicarboxylic acid) are preferred, and C _6-10 arene-dicarboxylic acid components such as terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid (particularly benzenedicarboxylic acid components such as terephthalic acid) are preferred. Furthermore, from the viewpoint of biodegradability, aliphatic dicarboxylic acid components, for example, C _2-12 alkane-dicarboxylic acids such as adipic acid are preferred.

In a thermoplastic resin, the proportion of structural units derived from dicarboxylic acid components (also referred to as dicarboxylic acid units) relative to all structural units derived from the polymerization components of the thermoplastic resin may be selected from a range of, for example, approximately 0 to 70 mol% (e.g., 10 to 60 mol%), preferably 30 to 55 mol% (e.g., 40 to 53 mol%), more preferably 45 to 52 mol%, and typically approximately 50 mol%.

In this specification and claims, the terms "dicarboxylic acid unit" or "structural unit derived from a dicarboxylic acid component" refer to a unit (or divalent group) obtained by removing OH (hydroxyl group) from the two carboxyl groups of the corresponding dicarboxylic acid.

(Method for producing thermoplastic resin)
The method for producing the thermoplastic resin is not particularly limited as long as the first diol component is polymerized as a polymerization component, and a conventional method can be used by appropriately selecting a catalyst, reaction conditions, etc. depending on the type of thermoplastic resin (or polymerization component). Furthermore, the polymerization reaction may be carried out once or multiple times depending on the type of polymerization component. For example, the thermoplastic resin may be prepared by using the oligomer (or prepolymer) obtained in the first polymerization as a polymerization component in the second polymerization.

The reaction temperature (polymerization temperature) in each polymerization may be, from the viewpoint of effectively suppressing decomposition (e.g., thermal decomposition) of the 3HB units in the first diol component and achieving high molecular weight, for example, 150°C or lower (e.g., 30 to 150°C), preferably 120°C or lower (e.g., 50 to 120°C), more preferably 100°C or lower (e.g., 60 to 100°C), and particularly 90°C or lower (e.g., 70 to 90°C, preferably 75 to 85°C). Therefore, the polymerization components preferably have excellent reactivity with the first diol component (e.g., the secondary alcohol of the 3HB units) and can be easily polymerized even at relatively low temperatures, such as a diisocyanate component and an acid halide (e.g., acid chloride) or acid anhydride of a dicarboxylic acid.

(i) When the polymerization component contains a diisocyanate component When polymerization components containing a diol component and a diisocyanate component are polymerized, the ratio of the diol component to the diisocyanate component (or the charge ratio) used may be adjusted in relation to the other polymerization components, and may be selected from a wide range, for example, from about 1/0.1 to 1/10 (e.g., 1/0.5 to 1/5) in terms of the molar ratio of the former to the latter. Typically (particularly when polymerizing polyurethane resins such as polyester urethane resins), the ratio may be about 1/0.8 to 1/1.2, preferably 1/0.9 to 1/1.1, and more preferably 1/1 to 1/1.1. It is preferable to use polymerization components such as the diol component that have been dried under reduced pressure for, for example, about 1 to 12 hours.

The reaction may be carried out in the presence of a catalyst, if necessary. Examples of catalysts include organotin compounds, organozirconium compounds, organotitanium compounds, organometallic catalysts such as metal naphthenates, and tertiary amines or their salts.

Organotin compounds include tin(II) alkanoates (or tin(II) bisalkanoates) such as tin(II) octoate (or tin(II) 2-ethylhexanoate); dialkyltin(IV) diacylates such as dibutyltin acetate and dibutyltin dilaurate (or dibutyltin(IV) dilaurate); and dialkyldialkoxytin(IV) compounds such as dibutyldimethoxytin(IV).

Examples of organic zirconium compounds include zirconium(IV) tetraalkoxides such as zirconium(IV) tetra-n-butoxide, and zirconium(IV) chelate complexes such as zirconium(IV) tetraacetylacetonate and zirconium(IV) dibutoxybis(ethylacetoacetate).

Examples of organic titanium compounds include titanium(IV) tetraalkoxides such as titanium(IV) tetra-n-butoxide and titanium(IV) tetra-2-ethylhexyloxide, and titanium(IV) chelate complexes such as titanium(IV) tetraacetylacetonate.

Examples of metal naphthenates include copper naphthenate, zinc naphthenate, and cobalt naphthenate.

Tertiary amines include linear tertiary amines (or non-heterocyclic amines), heterocyclic amines, etc.

Examples of chain tertiary amines include trialkylamines such as triethylamine; cycloalkyl-dialkylamines such as cyclohexyldimethylamine; N-alkyl-dicycloalkylamines such as N-methyldicyclohexylamine; aralkyl-dialkylamines such as benzyldimethylamine; hydroxyalkyl-dialkylamines such as 2-hydroxyethyldimethylamine and 2-hydroxyethyldiethylamine; hydroxyalkoxyalkyl-dialkylamines such as 2-(2-hydroxyethoxy)ethyldimethylamine; and N,N,N,N-tetramethyl-1,4-butanediamine and N,N,N,N-tetramethyl-1,6-hexanediamine. alkylalkanediamines; N,N-bis[(dialkylamino)alkyl]amines such as N,N-bis[3-(dimethylamino)propyl]amine; N-alkyl-N,N-bis[(dialkylamino)alkyl]amines such as N,N,N',N",N"-pentamethyldiethylenetriamine and N-methyl-N,N-bis[3-(dimethylamino)propyl]amine; bis(dialkylaminoalkyl)ethers such as bis(2-dimethylaminoethyl)ether; and N,N,N'-trialkyl-N'-(hydroxyalkyl)-bis(aminoalkyl)ethers such as N,N,N'-trimethyl-N'-(2-hydroxyethyl)-bis(2-aminoethyl)ether.

Heterocyclic tertiary amines include, for example, pyridine, N,N-dimethylpiperazine, morpholines [e.g., N-alkylmorpholines (N-methylmorpholine, N-ethylmorpholine, etc.), bis(2-morpholinoethyl)ether, etc.], triethylenediamines [e.g., triethylenediamine (DABCO), hydroxymethyltriethylenediamine, etc.], and cyclic amidines [e.g., 1,5-diazabicyclo[4.3.0]-5-nonene (DBN), 1,8-diaza-bicyclo[5.4.0]undecene-7 (DBU), etc.].

Tertiary amines (e.g., cyclic amidines) may be in the form of a salt, such as an organic acid salt such as a carboxylate (formate, octylate, etc.) or a sulfonate (p-toluenesulfonate, etc.), or a phenol salt.

These catalysts can be used alone or in combination. Of these catalysts, organometallic catalysts (such as organotin compounds such as dibutyltin(IV) dilaurate) are commonly used.

The amount of catalyst used may be, for example, about 0.00001 to 0.1 mol, preferably about 0.0001 to 0.01 mol, and more preferably about 0.0005 to 0.005 mol per 1 mol of the diisocyanate component.

The reaction may be carried out in the presence or absence of a solvent. The solvent is not particularly limited as long as it is inert or non-reactive with diisocyanates, and examples include ethers, ketones, esters, hydrocarbons, halogenated solvents, nitriles, amides, and sulfoxides.

Examples of ethers include dialkyl ethers such as diethyl ether and dipropyl ether; and cyclic ethers such as 1,4-dioxane and tetrahydrofuran.

Ketones include acetone, methyl ethyl ketone (ethyl methyl ketone), dialkyl ketones such as diisopropyl ketone and isobutyl methyl ketone.

Esters include acetate esters such as methyl acetate, ethyl acetate, and butyl acetate.

Examples of hydrocarbons include aliphatic hydrocarbons such as hexane, alicyclic hydrocarbons such as cyclohexane, and aromatic hydrocarbons such as toluene, xylene, and ethylbenzene.

Halogen-based solvents include halogenated hydrocarbons such as methylene chloride, chloroform, carbon tetrachloride, 1,2-dichloroethane, trichloroethane, and tetrachloroethane.

Examples of nitriles include acetonitrile.

Examples of amides include N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methyl-2-pyrrolidone.

Examples of sulfoxides include dimethyl sulfoxide (DMSO).

These solvents can be used alone or in combination. Of these solvents, amides such as DMF are preferred. The solvent is preferably a dehydrated solvent.

The reaction may be carried out in air or in an inert gas atmosphere. Examples of inert gases include nitrogen gas and rare gases (such as argon gas). The reaction may be carried out under reduced pressure, but is usually carried out under elevated pressure or at normal pressure. The reaction temperature is preferably within the range of the polymerization temperature mentioned above, and the reaction time may be, for example, 1 to 48 hours, preferably 12 to 36 hours.

After the reaction is complete, the product can be separated and purified using conventional separation methods, such as filtration, concentration, drying, extraction, crystallization, recrystallization, reprecipitation, column chromatography, or a combination of these.

(ii) When the polymerization component contains a dicarboxylic acid component When a polymerization component containing a diol component and a dicarboxylic acid component is polymerized, the polymerization component can be prepared by, for example, a melt polymerization method such as a transesterification method or a direct polymerization method, a solution polymerization method, an interfacial polymerization method, etc., and the solution polymerization method is preferred. The reaction may be carried out in the presence or absence of a solvent depending on the polymerization method.

The ratio (or charge ratio) of the diol component to the dicarboxylic acid component may be adjusted in relation to the other polymerization components. For example, the molar ratio (former/latter) may be selected from a wide range of approximately 1/0.1 to 1/10 (e.g., 1/0.5 to 1/5). Typically (especially when polymerizing polyester-based resins such as polyester resins), the ratio may be approximately 1/0.8 to 1/1.2, preferably 1/0.9 to 1/1.1, and more preferably 1/1 to 1/1.1. However, this range is not necessary, and at least one component selected from each diol component and each dicarboxylic acid component may be used in excess of the intended introduction ratio. For example, when the polymerization components include a diol component such as ethylene glycol that can be distilled from the reaction system, the diol component may be used in excess of the ratio (or introduction ratio) introduced into the polyester-based resin.

The reaction may be carried out in the presence of a catalyst. Conventional esterification catalysts, such as metal catalysts, can be used as the catalyst. Examples of metal catalysts include metal compounds containing alkali metals such as sodium; alkaline earth metals such as magnesium, calcium, and barium; transition metals such as titanium, manganese, and cobalt; Group 12 metals of the periodic table such as zinc and cadmium; Group 13 metals of the periodic table such as aluminum; Group 14 metals of the periodic table such as germanium and lead; and Group 15 metals such as antimony. Examples of metal compounds include alkoxides; organic acid salts such as acetates and propionates; inorganic acid salts such as borates and carbonates; metal oxides, and hydrates of these metals. Representative metal compounds include germanium compounds such as germanium dioxide, germanium hydroxide, germanium oxalate, germanium tetraethoxide, and germanium-n-butoxide; antimony compounds such as antimony trioxide, antimony acetate, and antimony ethylene glycolate; titanium compounds such as tetra-n-propyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate (titanium(IV) tetrabutoxide), titanium oxalate, and potassium titanium oxalate; manganese compounds such as manganese acetate tetrahydrate; and calcium compounds such as calcium acetate monohydrate.

These catalysts can be used alone or in combination of two or more. When using multiple catalysts, each catalyst can be added according to the progress of the reaction. Among these catalysts, manganese acetate tetrahydrate, calcium acetate monohydrate, germanium dioxide, titanium (IV) tetrabutoxide, etc. are preferred. The amount of catalyst used is, for example, 0.01×10 ⁻⁴ to 100×10 ⁻⁴ mol, preferably 0.1×10 ⁻⁴ to 40×10 ⁻⁴ mol, per 1 mol of the dicarboxylic acid component.

The reaction may be carried out in the presence of a stabilizer such as a heat stabilizer or an antioxidant, as necessary. Typically, a heat stabilizer is often used, and examples thereof include phosphorus compounds such as trimethyl phosphate, triethyl phosphate, triphenyl phosphate, dibutyl phosphate (dibutyl phosphate), phosphorous acid, trimethyl phosphite, and triethyl phosphite. These heat stabilizers can be used alone or in combination of two or more. Of these heat stabilizers, dibutyl phosphate is often used. The amount of heat stabilizer used is, for example, 0.01×10 ⁻⁴ to 100×10 ⁻⁴ mol, preferably 0.1×10 ⁻⁴ to 40×10 ⁻⁴ mol, per mol of the dicarboxylic acid component.

From the viewpoints of easily adjusting the polymerization temperature low and effectively suppressing decomposition of 3HB units, it is preferable to use an acid halide such as an acid chloride as the dicarboxylic acid component to react with the diol component. When an acid halide is used as the dicarboxylic acid component, the reaction may be carried out in the presence of a base to trap the hydrogen halide produced in the reaction. Examples of the base include inorganic bases such as metal hydroxides (such as alkali metal hydroxides or alkaline earth metal hydroxides, e.g., sodium hydroxide or calcium hydroxide) and metal carbonates (such as alkali metal carbonates or alkaline earth metal salts, e.g., sodium carbonate or sodium bicarbonate); and organic bases such as amines (such as trialkylamines, e.g., triethylamine; aromatic tertiary amines, e.g., benzyldimethylamine; and heterocyclic tertiary amines, e.g., pyridine). The base may be used alone or in combination. The amount of base used may be, for example, 0.8 to 20 moles (e.g., 1 to 10 moles), preferably 1.2 to 5 moles, and more preferably 1.5 to 3 moles per mole of acid halide.

The reaction is usually carried out in an atmosphere of an inert gas, for example, nitrogen gas or a rare gas such as helium gas or argon gas. The reaction can also be carried out under reduced pressure, for example, at about 1×10 ² to 1×10 ⁴ Pa. Usually, the transesterification reaction is often carried out under an inert gas atmosphere such as nitrogen gas, and the polycondensation reaction is often carried out under reduced pressure. The reaction temperature is preferably in the range of the polymerization temperature described above, and the reaction time may be, for example, about 1 to 48 hours, preferably about 12 to 36 hours.

After the reaction is complete, the product can be separated and purified using conventional separation methods, such as filtration, concentration, drying, extraction, crystallization, recrystallization, reprecipitation, column chromatography, or a combination of these.

(Characteristics and uses of thermoplastic resins)
Although the thermoplastic resin has a skeleton (3HB unit) derived from 3HB, the molecular weight can be surprisingly increased even when prepared by chemical synthesis, and therefore the thermoplastic resin has excellent mechanical properties and moldability (productivity).

The average molecular weight of the thermoplastic resin can be measured in polystyrene equivalent terms using gel permeation chromatography (GPC) or the like, and the weight average molecular weight Mw may be selected from a range of, for example, approximately 30,000 or more (e.g., 30,000 to 300,000), preferably 50,000 or more (e.g., 80,000 to 200,000), more preferably 100,000 or more (e.g., 110,000 to 180,000), and particularly approximately 120,000 or more (e.g., 130,000 to 150,000). The number average molecular weight Mn may be selected, for example, from a range of about 10,000 or more (e.g., 20,000 to 200,000), preferably 30,000 or more (e.g., 40,000 to 100,000), more preferably 50,000 or more (e.g., 55,000 to 80,000), and particularly 60,000 or more (e.g., 60,000 to 65,000). The polydispersity Mw/Mn may be selected, for example, from a range of about 1 to 10 (e.g., 1.2 to 5), preferably about 1.5 to 3 (e.g., 2 to 2.5).

If the average molecular weight, such as the weight average molecular weight Mw or number average molecular weight Mn, is too low, the mechanical properties and moldability (productivity) are likely to deteriorate, and it may not be possible to mold it into a film, etc.

In this specification and claims, the weight-average molecular weight Mw, number-average molecular weight Mn, and polydispersity index Mw/Mn can be measured by the method described in the examples below.

Furthermore, the thermoplastic resin containing the first diol component represented by formula (1) as a polymerization component is likely to exhibit high biodegradability derived from the 3HB units under both aerobic and anaerobic conditions (particularly under anaerobic conditions), and therefore can also be used to prepare biodegradable resins. In other words, by using the first diol component represented by formula (1) as a polymerization component, the biodegradability of the resulting resin can be improved. Furthermore, it is possible to achieve both the aforementioned mechanical properties and moldability (or productivity) and biodegradability.

As a result, molded articles containing at least the above-mentioned thermoplastic resins can be used in a variety of applications, taking advantage of their excellent mechanical properties and moldability (or productivity). They are also particularly biodegradable, making them effective for use in disposable products, etc.

The molded article may contain a thermoplastic resin other than the thermoplastic resin (a thermoplastic resin that does not contain the diol compound represented by formula (1) as a polymerization component), conventional additives, etc. Examples of additives include fillers or reinforcing agents, colorants such as dyes and pigments, conductive agents, flame retardants, plasticizers, lubricants, mold release agents, antistatic agents, dispersants, flow control agents, leveling agents, antifoaming agents, surface modifiers, hydrolysis inhibitors, carbon materials, stabilizers, and stress reducers. Examples of stabilizers include antioxidants, ultraviolet absorbers, and heat stabilizers. Examples of stress reducers include silicone oil, silicone rubber, various plastic powders, and various engineering plastic powders. These additives may be used alone or in combination.

Molded articles can be produced using, for example, injection molding, injection compression molding, extrusion molding, transfer molding, blow molding, pressure molding, casting molding, etc.

The shape of the molded product is not particularly limited, and examples include one-dimensional structures such as lines, fibers, and threads; two-dimensional structures such as films, sheets, and plates; and three-dimensional structures such as concave or convex lenses, rods, hollow (tubes), containers, or bags.

In particular, thermoplastic resins have excellent mechanical properties and moldability, making them easy to form into films, and even when thin, they have sufficient strength and are easy to handle. Therefore, the present invention also includes films (or sheets) formed from the above-mentioned thermoplastic resins.

The average thickness of such films can be selected from a range of approximately 1 to 1000 μm depending on the application, for example, 1 to 200 μm, preferably 5 to 150 μm, and more preferably 10 to 120 μm (e.g., 80 to 120 μm).

Such films can be produced by forming (or molding) the thermoplastic resin using conventional film-forming methods, such as casting (solvent casting), melt extrusion, or calendaring.

The film may be unstretched or stretched. Stretched films may be either uniaxially stretched or biaxially stretched. The stretching ratio in each direction for uniaxial or biaxial stretching is, for example, 1.1 to 10 times, preferably 1.2 to 8 times, and more preferably 1.5 to 6 times. In the case of biaxial stretching, equal stretching may be performed, for example, 1.5 to 5 times in both the longitudinal and transverse directions, or asymmetric stretching may be performed, for example, 1.1 to 4 times in the longitudinal direction and 2 to 6 times in the transverse direction. In the case of uniaxial stretching, longitudinal stretching may be performed, for example, 2.5 to 8 times in the longitudinal direction, or transverse stretching may be performed, for example, 1.2 to 5 times in the transverse direction. The average thickness of the stretched film is, for example, 1 to 150 μm, preferably 3 to 120 μm, and more preferably 5 to 100 μm.

Such stretched films can be obtained by stretching the film (or unstretched film) after film formation. The stretching method is not particularly limited; in the case of uniaxial stretching, either wet stretching or dry stretching may be used, and in the case of biaxial stretching, either the tenter method (flat method) or the tube method may be used, although the tenter method is preferred as it provides excellent uniformity in stretched thickness.

The present invention will be explained in more detail below based on examples, but the present invention is not limited to these examples. Evaluation methods are also described below.

[Evaluation method]
(NMR)
Using a nuclear magnetic resonance spectrometer (JASCO Corporation, "JNM-GSX270"), the sample was dissolved in CDCl ₃ and ¹ H-NMR spectrum (270 MHz) and ¹³ C-NMR spectrum (67.5 MHz) were measured.

(GPC (Gel Permeation Chromatography))
Using a GPC measurement device ("GL-7400 series" manufactured by JASCO Corporation), a sample was dissolved in tetrahydrofuran (THF) and measured at a flow rate of 1 mL/min by RI detection, and the number average molecular weight Mn, weight average molecular weight Mw, and polydispersity index Mw/Mn were calculated in terms of standard polystyrene.

(Biodegradation test)
Biodegradability was evaluated under anaerobic conditions according to ISO 15985.

(FT-IR)
Measurement was carried out by the ATR method (resolution 4 cm ⁻¹ , number of accumulations 64) using a Fourier transform infrared spectrophotometer ("Nicolet iS5" manufactured by Thermo Fisher Scientific Co., Ltd.).

[Example 1]
(Tosylation of cyclohexanedimethanol)

(In the formula, Ts represents a tosyl group (p-toluenesulfonyl group).)

Under an argon atmosphere, 3.51 g (24.3 mmol) of cyclohexanedimethanol represented by formula (3-1) above, 7.39 g (73.0 mmol), triethylamine, 0.84 g (4.87 mmol), and 100 mL of acetonitrile were added to a flask and cooled on ice. A mixture of 13.92 g (73.0 mmol) of p-toluenesulfonyl chloride and 100 mL of acetonitrile was added dropwise over 1 hour, and the mixture was stirred under ice cooling for 1 hour, followed by stirring at room temperature for 24 hours. 21.8 g (24.7 mmol) of N,N-dimethylethylenediamine was added, followed by 100 mL of water. The mixture was filtered, washed with 1 L of water, and dried under reduced pressure. Approximately 200 mL of a dichloromethane/methanol mixture (50/50, vol/vol) was added to the resulting reaction mixture, and the mixture was dissolved by heating. After cooling, the precipitate was filtered and dried under reduced pressure to obtain a white solid of 1,4-bis(p-toluenesulfonyloxymethyl)cyclohexane (CHDM-Ts) represented by the above formula (2-1): yield 9.89 g, isolated yield 89.9%.

^{The 1} H-NMR spectrum and ¹³ C-NMR spectrum of the resulting CHDM-Ts are shown in FIGS. 1 and 2 and below.

¹ H-NMR (270 MHz, CDCl ₃ ): δ = 0.86-1.75 (10H, -C H -C H ₂ -C H ₂ -C H -), 2.45 (s, 6H, C H ₃ -Ar-), 3.78-3.87 (d, 4H, -SO ₃ -C H ₂ -CH-), 7.35 (d,4H,Ar H ), 7.76 (d,4H, Ar H ).

^13C -NMR (67.5MHz, CDCl ₃ ): δ = 21.74, 24.61 (-CH- CH ₂ - CH ₂ -), 28.10 ( CH ₃ -Ar-), 34.46, 37.01 (-CH ₂ - CH (CH ₂ -)- _CH2- ), 127.73, 127.76, 129.71, 129.76, 132.87, 132.89, 144.58, 144.66 (ArC).

(Synthesis of 3HB diol)

(In the formula, Ts represents a tosyl group (p-toluenesulfonyl group).)

Under an argon atmosphere, 9.20 g (20.3 mmol) of CHDM-Ts represented by formula (2-1), 4.66 g (44.8 mmol) of (R)-3-hydroxybutyric acid ((R)-3HB, 99% e.e. or higher), and 150 mL of N,N-dimethylformamide (DMF) were added to a flask and dissolved. 6.18 g (44.8 mmol) of potassium carbonate was then added and stirred at 50°C for 48 hours. 500 mL of water was added, and the mixture was extracted with 500 mL of hexane/ethyl acetate (3/1, vol/vol) three times, followed by washing with 500 mL of brine. After drying over magnesium sulfate, the solvent was distilled off and column purification (hexane/ethyl acetate (volume ratio): 1/1 → 1/2) was carried out to obtain 3HB diol (1,4-bis(3-hydroxybutanoyloxymethyl)cyclohexane) represented by the above formula (1-1) as a pale yellow oil: yield 4.12 g, isolated yield 44.8%.

^{The 1} H-NMR spectrum and ¹³ C-NMR spectrum of the resulting 3HB diol represented by formula (1-1) are shown in FIGS. 3 and 4 and below.

¹ H-NMR (270 MHz, CDCl ₃ ): δ = 0.93-2.04 (10H, -C H -C H ₂ -C H ₂ -C H -), 1.23 (d, 6H, C H ₃ -CH-), 2.51 (d, 4H, -C H ₂ -C(=O)-O-), 3.10 (s, 2H, -O H ), 4.00 (d, 4H, -CH-C H ₂ -O-), 4.10-4.30 (m, 2H, CH ₃ -C H (-OH)-CH ₂ -).

¹³ C-NMR (67.5 MHz, CDCl ₃ ): δ = 22.48, 25.22 (-CH- CH ₂ - CH ₂ -), 28.75 ( CH ₃ -CH-), 34.32, 36.90 (- CH - CH ₂ -O-), 42.75 (-C H ₂ -C(=O)-O-), 60.33, 64.17 (CH ₃ - C H(-OH)-CH ₂ -), 67.22, 69.40 (-CH- C H ₂ -O-).

Since the 3HB diol represented by formula (1-1) is an isomer mixture, two types of peaks (peaks corresponding to two chemical shift values among the above assignments) of carbon were observed in the ¹³ C-NMR spectrum.

[Example 2]
(Polymerization of 3HB polyester urethane)

4.86 g (15.36 mmol) of the 3HB diol diol represented by formula (1-1) obtained in Example 1 was dried under reduced pressure at 60°C for 4 hours, after which 10.2 mg (0.016 mmol) of dibutyltin dilaurate was added and the atmosphere was replaced with argon. 15 mL of dehydrated DMF and 2.7269 g (16.21 mmol) of hexamethylene diisocyanate were added and stirred at 80°C for 24 hours to obtain a highly viscous, pale yellow solution. The resulting reaction solution was diluted with 20 mL of DMF and poured into 800 mL of water. After filtering, the solution was dried under reduced pressure at 60°C for 6 hours. 100 mL of tetrahydrofuran was added, and the mixture was heated to dissolve the solution, which was then poured into 1 L of water and reprecipitated. After filtering, the solution was dried under reduced pressure at 60°C for 8 hours to obtain the 3HB polyester urethane shown in the lower part of the formula above as a white solid.

^{The 1} H-NMR spectrum and ¹³ C-NMR spectrum of the resulting 3HB polyester urethane are shown in FIGS. 5 and 6 and below.

¹ H-NMR (270 MHz, CDCl ₃ ): δ = 0.91-1.89 (18H, -NH-CH ₂ -CH _{2 -CH 2 -} , -CH ₂ -CH ( -CH ₂ )-CH 2 _- ), 1.30 (d, 6H, CH ₃ -CH-), 2.44-2.68 (m, 4H, -CH-C H ₂ -C(=O)-O-), 3.07-3.16 (m, 4H, -NH-C H ₂ -CH ₂ -CH ₂ -), 3.85-3.98 (d, 4H, -CH-C H ₂ -O-), 4.60-5.00 (br, 2H, -N H -), 5.11-5.18 (m, 2H, CH ₃ -C H -).

In the ^C -NMR spectrum, two peaks were observed, one representing the carbon derived from the ester bond (C═O at 170.31 ppm) and the other representing the carbon derived from the urethane bond (C═O at 155.54 ppm), confirming that the desired 3HB polyesterurethane was obtained.

GPC analysis of the resulting 3HB polyesterurethane revealed a number average molecular weight Mn of 63,000, a weight average molecular weight Mw of 142,000, and a polydispersity index Mw/Mn of 2.256, indicating that a high molecular weight polyesterurethane had been obtained.

The resulting 3HB polyester urethane was then pressed for 2 minutes in a press (AH-2003, manufactured by AS ONE Corporation) at 120°C and 1 MPa, and then cooled at room temperature and 1 MPa to produce a film with an average thickness of 100 μm. The film had sufficient strength, was easy to prepare, and had high formability.

[Example 3]
(Synthesis of 3HB diol)

Under an argon stream, 8.75 g (84.05 mmol) of (R)-3-hydroxybutyric acid ((R)-3HB, 99% ee or higher), 7.17 g (38.17 mmol) of 1,2-dibromoethane represented by formula (2-2) above, and 40 mL of DMF were added and stirred at room temperature. 11.62 g (84.07 mmol) of potassium carbonate was added and stirred, resulting in the generation of _{CO2 and} gelation after approximately 30 minutes. An additional 40 mL of DMF was added, and the mixture was heated and stirred at 80°C for 18 hours, yielding a white slurry. This white slurry was filtered through Celite, and the solvent was distilled off at 60°C and 0.2 kPa to yield a pale yellow oil. The resulting pale yellow oil was purified by column chromatography (CHCl ₃ /MeOH (volume ratio) = 75:1 → 10:1) to obtain 3HB diol (1,2-bis(3-hydroxybutanoyloxymethyl)ethane: yield 5.05 g, 56.5% yield) represented by the above formula (1-2) as a pale brown oil.

^{The 1} H-NMR spectrum and ¹³ C-NMR spectrum of the resulting 3HB diol represented by formula (1-2) are shown in FIGS. 7 and 8 and below.

¹ H-NMR (270 MHz, CDCl ₃ ): δ = 1.23 (d, 6H, C H ₃ -CH-), 2.41-2.57 (dd, 4H, -C H ₂ -C(=O)-O-), 2.85-3.15 (br, 2H, -O H ), 4.16-4.27 (m, 2H, CH ₃ -C H -), 4.33 (t, 4H, -O-C H ₂ -).

¹³ C-NMR (67.5 MHz, CDCl ₃ ): δ = 22.59 ( CH ₃ -CH-), 42.91 ( -CH ₂ -C(=O)-O-), 62.17 (-O- CH ₂ -), 64.19 (CH ₃ - C H-), 172.23 (-CH ₂ - C (=O)-O-).

In addition, no isomer mixtures were confirmed in the 3HB diol represented by formula (1-2).

[Comparative Example 1]
(Polyurethane Polymerization and Its Biodegradability)

0.74 g of cyclohexanedimethanol (CHDM, vacuum dried at 60°C for 1.5 hours) and approximately 1 mg of tin ethylhexanoate were added to 5 mL of DMF and the atmosphere was purged with nitrogen. 0.91 g of hexamethylene diisocyanate was added, and the mixture was heated to 80°C and reacted for 7 hours. 10.0 mL of DMF was added to the resulting reaction solution, followed by 300.55 mL of distilled water. The precipitated white solid was filtered and dried at 60°C to obtain a polyurethane containing no 3HB units. The resulting polyurethane had an Mn of 5,500 and an Mw of 11,000.

This polyurethane, which does not contain 3HB units, was pressed for 2 minutes in a press ("AH-2003" manufactured by AS ONE Corporation) at 180°C and 1 MPa, and then cooled at room temperature and 1 MPa to produce a film with an average thickness of 100 μm. A biodegradation test was conducted using the resulting polyurethane film, and it showed no tendency to biogasify even after 77 days, and its molecular weight showed almost no change (Mn = 4900, Mw = 9800).

[Example 4]
(Biodegradability of 3HB polyester urethane)
The 3HB polyester urethane obtained in Example 2 was pressed for 2 minutes at 180°C and 1 MPa using a press ("AH-2003" manufactured by AS ONE Corporation), and then cooled at room temperature and 1 MPa to produce a film with an average thickness of 100 μm. A biodegradation test was conducted using the resulting 3HB polyester urethane film, and after 77 days, approximately 5% was converted into biogas, and the Mn decreased from 63,000 to 880 and the Mw decreased from 142,000 to 2,200.

Figure 9 shows the FT-IR spectra of 3HB polyester urethane before and after the biodegradation test. As is clear from Figure 9, when normalized by the peak top of the urethane bond, the absorption peak of the ester bond after the biodegradation test becomes relatively smaller, indicating that the ester bond between the 3HB unit and the CHDM unit has been selectively (or preferentially) cleaved.

[Comparative Example 2]
(Biodegradability of CHDM)
The results of evaluating the biodegradability of the monomer CHDM are shown in Figure 10. As is clear from Figure 10, no tendency to biogasify was observed even after 35 days, indicating that CHDM does not exhibit biodegradability.

From these results, it is believed that CHDM remains even after the biodegradation test of 3HB polyester urethane in Example 4, but due to its water solubility, it is presumed to remain dissolved in the sludge after the test. The average molecular weight value after the biodegradation test in Example 4 (Mn = 880, Mw = 2200) does not reflect the effect of CHDM dissolved in the sludge, and therefore the actual value is likely to be even lower.

The diol compounds of the present invention can be suitably used as resin raw materials (or polymerization components) [particularly as resin raw materials for biodegradable resins], and even when 3HB units are introduced into the resin by chemical synthesis, the molecular weight of the resin can be effectively increased, thereby improving mechanical properties and moldability (or productivity).

As a result, it can be used in a variety of applications, including abrasives (such as scrubbing agents in toothpaste, facial cleansers, and body washes), paints, antistatic agents, inks, adhesives, pressure-sensitive adhesives, electrical and electronic materials (such as carrier transport agents, light-emitting materials, and organic photoreceptors), electrical and electronic components or devices (such as optical lenses, optical films, optical disks, inkjet printers, digital paper, organic semiconductor lasers, and dye-sensitized solar cells), and mechanical parts or devices (such as automobiles, aerospace materials, and sensors). In particular, due to its high mechanical properties, it can be easily molded by extrusion molding, injection molding, and other methods, making it ideal for use in a variety of applications, including molded components (such as casings and housings, and tableware such as straws, cups, plates, chopsticks, spoons, and forks), containers (for food, daily necessities, electrical and electronic devices, and their components), and packaging materials such as films, sheets, and bags (such as shopping bags, Eco Bags (registered trademark), and garbage bags).

Furthermore, because it contains a skeleton derived from 3HB, it is biodegradable under aerobic and anaerobic conditions, making it suitable for use in disposable products such as tableware, containers, and bags, among other applications. This makes it useful for solving environmental issues such as microplastics, which have become increasingly important in recent years, and it can also be used in applications requiring biocompatibility and safety, such as in the medical field (e.g., medical devices, medical disposable products, etc.) and cosmetics.

Claims (15)

The following formula (1)
(In the formula, ^R1 represents a divalent group obtained by removing two hydroxyl groups from the chemical structure of a linear or branched _C2-8 alkylene glycol or bis( _hydroxyC1-6 alkyl) _C3-12 cycloalkane, and m represents 0 or 1.)
A method for producing a diol compound having a structural unit derived from 3-hydroxybutyric acid represented by the formula:
The following formula (2)
(In the formula, ^L1 represents a leaving group, ^L2 represents a leaving group or a hydroxyl group, and ^R1 is the same as in formula (1).)
and 3-hydroxybutyric acid. The method for producing a diol compound according to claim 1, wherein m is 1 in formula (1). The method for producing a diol compound according to claim 1 or 2, wherein the structural units derived from 3-hydroxybutyric acid in formula (1) contain at least a structural unit in which the asymmetric carbon atom has an R configuration. The method for producing a diol compound according to any one of claims 1 to 3, wherein the diol compound is a polymerization component of a biodegradable resin. A method for producing a diol compound according to any one of claims 1 to 4, wherein the 3-hydroxybutyric acid contains an R-isomer. A method for producing a thermoplastic resin containing a diol component as a polymerization component, the method comprising the steps of producing a diol compound by the production method described in any one of claims 1 to 5, and polymerizing the resulting polymerization component containing at least the diol compound. The method for producing a thermoplastic resin according to claim 6, wherein the proportion of structural units derived from the diol compound is 10 to 100 mol % relative to all structural units derived from the diol component. The method for producing a thermoplastic resin according to claim 6 or 7, wherein the polymerization components further include at least one selected from a diisocyanate component and a dicarboxylic acid component. the diisocyanate component includes an aliphatic diisocyanate component, an alicyclic diisocyanate component, or an aromatic diisocyanate component;
9. The method for producing a thermoplastic resin according to claim 8, wherein the dicarboxylic acid component comprises an acid halide or an acid anhydride of at least one dicarboxylic acid selected from aliphatic dicarboxylic acids, alicyclic dicarboxylic acids, and aromatic dicarboxylic acids. A method for producing a thermoplastic resin according to any one of claims 6 to 9, wherein the weight-average molecular weight of the thermoplastic resin is 30,000 or more. A method for producing a thermoplastic resin according to any one of claims 6 to 10, wherein the thermoplastic resin is a biodegradable resin. A method for producing a thermoplastic resin according to any one of claims 6 to 11, in which polymerization is carried out at 150°C or less. A method for producing a molded article containing a thermoplastic resin, comprising the steps of producing a thermoplastic resin by the manufacturing method described in any one of claims 6 to 12, and molding the obtained thermoplastic resin. The method for producing a molded article according to claim 13, wherein the molded article is in the form of a film. The following formula (1)
(In the formula, ^R1 represents a divalent group obtained by removing two hydroxyl groups from the chemical structure of a linear or branched _C2-8 alkylene glycol or bis( _hydroxyC1-6 alkyl) _C3-12 cycloalkane, and m represents 0 or 1.)
and a diisocyanate component, and a diol component containing at least a diol compound having a structural unit derived from 3-hydroxybutyric acid represented by the formula (I) above, and improving the biodegradability under anaerobic conditions of the resulting thermoplastic resin.