Monomer diol composition and method for producing polyester

Abstract

To provide a monomer diol composition that enables a high reaction rate in the early stage of polymerization when used as a polyester feedstock, does not lengthen the required duration in the later stage of polymerization, and ensures suppression of the yellow tint in the produced polyester.SOLUTION: A monomer diol composition comprising a mixture of two or more monomer diols, wherein the a / b value determined by the following measurement method is 0.970 or more and less than 1.000. [Measurement Method] Step 1: Weigh two or more monomer diols to determine the mass of each monomer diol. Step 2: Mix the two or more monomer diols to produce the monomer diol composition. Step 3: Determine a theoretical value b of the hydroxyl group content of the monomer diol composition based on the mass of each monomer diol. Step 4: Determine a measured value a of the hydroxyl group content of the monomer diol composition by NMR measurement. Step 5: Divide the measured value a of the hydroxyl group content by the theoretical value b of the hydroxyl group content to determine the value (a / b).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a monomer diol composition. More specifically, the present invention relates to a monomer diol composition containing two or more types of monomer diols, which is also useful as a raw material for polyesters, polyurethanes, polycarbonates, etc. The present invention also relates to a method for producing polyesters using the monomer diol composition. [Background technology]

[0002] Conventionally, the monomer diols used to make polyesters have been produced from petroleum (fossil fuels). For example, butanediol can be produced from butadiene, which is produced from fossil fuels.

[0003] However, with the growing demand for a circular (sustainable) society, there is a desire to move away from raw materials derived from fossil fuels such as petroleum, and in recent years, various methods for producing butanediol from biomass resources such as plants, which do not use fossil fuels as raw materials, have been proposed. For example, a method for producing butanediol by direct fermentation of sugar (Patent Document 1) and a method for producing butanediol by producing succinic acid from biomass resources and then reducing it with hydrogen have been proposed (Patent Document 2). In recent years, a method has also been proposed in which butanediol is recovered by depolymerizing waste polyester using a chemical recycling method (Patent Document 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2021-505539 [Patent Document 2] Chinese Patent Application Publication No. 114773153 [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-323378 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when a monomer diol composition containing two or more types of monomer diols, including a biomass resource-derived monomer diol, as disclosed in Patent Documents 1 and 2 was used as a polyester raw material, the polymerization reaction had a low reaction rate in the early stages of the polymerization reaction and required a long time in the later stages of the polymerization reaction, making it impossible to efficiently produce polyester. Furthermore, the resulting polyester had a strong yellowish tint and was of unsatisfactory quality. It was estimated that this problem could also occur with chemically recycled monomer diols.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a monomer diol composition which, when used as a polyester raw material in polymerization, results in a high reaction rate in the early stage of the polymerization reaction, does not require a long time in the later stage of the polymerization reaction, and enables the obtained polyester to have a low yellow tinge, and a method for producing a polyester using the monomer diol composition. [Means for solving the problem]

[0007] As a result of extensive research into solving the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by using a monomer diol composition obtained by mixing two or more types of monomer diols, in which the value obtained by dividing the measured hydroxyl group amount by the theoretical hydroxyl group amount falls within a specific range, and have thus completed the present invention. That is, the present invention relates to the following inventions.

[0008] [1] A monomer diol composition comprising a mixture of two or more monomer diols, A monomer diol composition, wherein the value (a / b) obtained by dividing the measured value (a) of the amount of hydroxyl groups measured by the following measurement method by the theoretical value (b) of the amount of hydroxyl groups is 0.970 or more and less than 1.000. <Measurement method> Step 1: Two or more types of monomer diols to be mixed are weighed to obtain the mass of each monomer diol. Step 2: The two or more monomer diols in step 1 are mixed to obtain a monomer diol composition. Step 3: From the mass of each monomer diol obtained in step 1, the theoretical value b of the hydroxyl group amount of the monomer diol composition obtained in step 2 is obtained. Step 4: The monomer diol composition obtained in step 2 is subjected to NMR measurement to obtain a measured value a of the amount of hydroxyl groups in the monomer diol composition. Step 5: The measured value a of the amount of hydroxyl groups obtained in step 4 is divided by the theoretical value b of the amount of hydroxyl groups obtained in step 3 to obtain a value (a / b).

[0009] [2] The monomer diol composition according to [1], wherein at least one of the two or more monomer diols is an alkanediol.

[0010] [3] The monomer diol composition according to [2], wherein the alkanediol is produced using a biomass resource as a raw material.

[0011] [4] The monomer diol composition according to [3], wherein the alkanediol is an alkanediol produced by fermentation.

[0012] [5] The monomer diol composition according to [4], wherein the alkanediol is an alkanediol produced by direct fermentation of sugar.

[0013] [6] The monomer diol composition according to [3], wherein the alkanediol is an alkanediol produced by hydrogen reduction of succinic acid or a succinic acid derivative produced using a biomass resource.

[0014] [7] The monomer diol composition according to [2], wherein the alkanediol is an alkanediol produced by depolymerization of a polyester.

[0015] [8] The monomer diol composition according to [7], wherein the polyester is polyethylene terephthalate and / or polybutylene terephthalate.

[0016] [9] A method for producing a polyester, using the monomer diol composition according to any one of [1] to [8]. [Effects of the Invention]

[0017] When the monomer diol composition of the present invention is subjected to a polymerization reaction as a polyester raw material, the reaction rate is high in the early stage of the polymerization reaction, the time required for the later stage of the polymerization reaction is not prolonged, and the yellowness of the resulting polyester can be kept low. Therefore, by using the monomer diol composition of the present invention, high-quality polyesters with little yellowing can be produced with excellent production efficiency. DETAILED DESCRIPTION OF THE INVENTION

[0018] The following describes in detail an embodiment of the present invention. However, the description of the constituent elements described below is an example of an embodiment of the present invention, and the present invention is not limited to the following description as long as it does not go beyond the gist of the present invention. In this specification, when the expression "to" is used, it is intended to be used as an expression that includes the numerical values or physical property values before and after it. In this specification, "parts by weight" and "parts by mass" are synonymous, and "% by weight" and "% by mass" are synonymous. In the present invention, the "main component" of a dicarboxylic acid component refers to a component that accounts for 50 mol % or more of the dicarboxylic acid component. The same applies to the "main component" of a diol component. Furthermore, "ppm" refers to "ppm by mass" except for the unit of NMR chemical shift, which will be described later.

[0019] [Monomer diol composition] The monomer diol composition of the present invention is characterized by containing two or more types of monomer diols. The two or more types of monomer diols may be two or more types of monomer diols having different chemical structures, or two or more types of monomer diols having the same chemical structure but obtained by different production methods, or may include two or more types of monomer diols having different chemical structures and production methods. The monomer diol composition of the present invention may contain two or more types of monomer diols, and may also contain two or three or more types of monomer diols. However, from the viewpoint of the required mechanical properties and biomass conversion rate of the resulting polyester, the number of types of monomer diols is usually two to three, and preferably two.

[0020] The monomer diol composition of the present invention may be in the form of a slurry of a mixture of solids and liquids, but is preferably a liquid.

[0021] [Monomer diol] Examples of the monomer diol include linear alkanediols, alkanediols having a cyclic structure, and bisphenols (including bisphenol).

[0022] Examples of the linear alkanediol include linear alkanediols having 2 to 12 carbon atoms, such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, pentanediol, 1,2-hexanediol, 1,3-hexanediol, 1,4-hexanediol, 1,5-hexanediol, 1,6-hexanediol, heptanediol, octanediol, nonanediol, decanediol, undecanediol, and dodecanediol. All of these linear alkanediols have the object of the present invention, and the object can be solved by the present invention. Among them, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-hexanediol, 1,3-hexanediol, 1,4-hexanediol, 1,5-hexanediol, and 1,6-hexanediol are preferred.

[0023] Examples of alkanediols having a cyclic structure include cyclohexanedimethanol, cyclopentanediol, cyclohexanediol, bicyclohexanol, hydroxymethylcyclohexanol, hydroxyethylcyclohexanol, tetramethylcyclobutanediol, adamantanediol, 3-hydroxymethyl-1-adamantanol, 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane, 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane, 2,2-bis[4-(2-hydroxyethoxy)-3-methylphenyl]propane, 9,9'-bis[4-(2-hydroxyethoxy)phenyl]fluorene, and 9,9'-bis[4-(2-hydroxyethoxy)-3-methylphenyl]fluorene.

[0024] Examples of bisphenols include 2,2'-biphenol, 4,4'-biphenol, 1,5-naphthalenediol, 2,7-naphthalenediol, bis(4-hydroxyphenyl)methane (i.e., bisphenol F), bis{(4-hydroxy-3,5-dimethyl)phenyl}methane, 1,1-bis(4-hydroxyphenyl)ethane (i.e., bisphenol E), 1,1-bis(4-hydroxyphenyl)-1-phenylethane (i.e., bisphenol AP), 2,2-bis(4-hydroxyphenyl)hexafluoropropanediol, bis(4-hydroxyphenyl)-1-phenylethane ... propane (i.e., bisphenol AF), 2,2-bis(4-hydroxyphenyl)propane (i.e., bisphenol A), 2,2-bis{(4-hydroxy-3-methyl)phenyl}propane (i.e., bisphenol C), 2,2-bis{(4-hydroxy-3,5-dimethyl)phenyl}propane, 2,2-bis{(3,5-dibromo-4-hydroxy)phenyl}propane, 2,2-bis{(3-isopropyl-4-hydroxy)phenyl}propane, 2,2-bis{(4-hydroxy-3-phenyl)phenyl}propane, 2 -(4-hydroxyphenyl)-2-(3-carboxy-4-hydroxyphenyl)propane, 2-(2-hydroxyphenyl)-2-(4-hydroxyphenyl)propane, 1-(4-hydroxyphenyl)-1,3,3-trimethyl-5-hydroxyindan, 2-(4-hydroxyphenyl)-[3-{2-(4-hydroxyphenyl)propan-2-yl}-4-hydroxyphenyl]propane, 2,2-bis(4-hydroxyphenyl)butane (i.e., bisphenol B), 1,1-bis(4-hydroxyphenyl)-1,1-di Phenylmethane (i.e., bisphenol BP), 2,2-bis(4-hydroxy-3-isopropylphenyl)propane (i.e., bisphenol G), 2,2-bis(4-hydroxyphenyl)-3-methylbutane, 2,2-bis(4-hydroxyphenyl)-3,3-dimethylbutane, 2,4-bis(4-hydroxyphenyl)-2-methylbutane, 2,2-bis(4-hydroxyphenyl)pentane, 2,2-bis(4-hydroxyphenyl)-4-methylpentane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,Examples of such hydroxydiphenyl compounds include 1-bis(4-hydroxyphenyl)-4-isopropylcyclohexane, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 9,9-bis(4-hydroxyphenyl)fluorene, 9,9-bis{(4-hydroxy-3-methyl)phenyl}fluorene, α,α'-bis(4-hydroxyphenyl)-o-diisopropylbenzene, α,α'-bis(4-hydroxyphenyl)-m-diisopropylbenzene, α,α'-bis(4-hydroxyphenyl)-p-diisopropylbenzene, 1,3-bis(4-hydroxyphenyl)-5,7-dimethyladamantane, 4,4'-dihydroxydiphenyl sulfone (i.e., bisphenol S), 4,4'-dihydroxydiphenyl sulfoxide, 4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxydiphenyl ketone, 4,4'-dihydroxydiphenyl ether, and 4,4'-dihydroxydiphenyl ester.

[0025] Examples of monomer diols that have the same chemical structure but are obtained by different production methods include monomer diols produced using fossil fuels as raw materials, monomer diols produced using biomass resources as raw materials, and monomer diols produced by recycling waste products or defective products. All of these monomer diols have the problems that the present invention solves, but among them, monomer diols produced using biomass resources as raw materials and monomer diols produced by recycling waste products or defective products are preferred.

[0026] Of the two or more monomer diols in the monomer diol composition of the present invention, at least one is preferably an alkanediol from the viewpoints of the efficiency of the polymerization-condensation reaction of the polyester and the required mechanical properties of the resulting polyester, and the alkanediol is preferably produced using biomass resources as raw materials.

[0027] There are no particular restrictions on the combination of two or more monomer diols contained in the monomer diol composition of the present invention. For example, in the case of a monomer diol composition containing two types of monomer diols, the following combinations are preferred. (1) A combination of alkanediols such as 1,4-butanediol produced from biomass resources and alkanediols such as 1,4-butanediol, ethylene glycol, and 1,6-hexanediol produced from petroleum (fossil fuel) (2) A combination of ethylene glycol produced from biomass resources and ethylene glycol produced from petroleum (fossil fuel) as well as alkanediols such as 1,4-butanediol and 1,6-hexanediol produced from petroleum (fossil fuel) as raw materials. (3) Combinations of 1,2-propylene glycol produced from biomass resources with alkanediols such as ethylene glycol produced from petroleum (fossil fuel), ethylene glycol produced from biomass resources, 1,4-butanediol produced from petroleum (fossil fuel), 1,4-butanediol produced from biomass resources, and 1,6-hexanediol. (4) Combinations of 1,3-propylene glycol produced from biomass resources with alkanediols such as ethylene glycol produced from petroleum (fossil fuel), ethylene glycol produced from biomass resources, 1,4-butanediol produced from petroleum (fossil fuel), 1,4-butanediol produced from biomass resources, and 1,6-hexanediol. (5) A combination of an alkanediol such as 1,4-butanediol produced by depolymerization of polyester with an alkanediol such as ethylene glycol produced from petroleum (fossil fuel), ethylene glycol produced from biomass resources, 1,4-butanediol produced from petroleum (fossil fuel), 1,4-butanediol produced from biomass resources, or 1,6-hexanediol.

[0028] Alkanediols such as 1,4-butanediol produced using biomass resources as raw materials are preferably alkanediols produced by fermentation, and examples thereof include alkanediols produced by direct fermentation of sugars and alkanediols produced by hydrogen reduction of succinic acid or a succinic acid derivative produced using biomass resources. Examples of alkanediols such as 1,4-butanediol produced by depolymerization of polyester include 1,4-butanediol obtained by depolymerization of polybutylene terephthalate and ethylene glycol obtained by depolymerization of polyethylene terephthalate. Specifically, examples of methods for obtaining 1,4-butanediol include those described in JP 2007-197654 A, which involve hydrogenating succinic acid or a succinic acid derivative obtained by fermentation of sugar, such as succinic anhydride or a succinate ester such as a dialkyl succinate (more specifically, a dialkyl succinate having a methyl group with an alkyl group having 1 to 4 carbon atoms, preferably 1 to 3, more preferably 1 to 2, and most preferably 1 carbon atom), and the like. Furthermore, examples of methods for directly obtaining 1,4-butanediol by fermenting a biomass resource such as sugar include those described in WO 2015 / 158716 A, and methods for producing 1,4-butanediol by depolymerizing polybutylene terephthalate include those described in JP 2004-323378 A, which are also examples.

[0029] [Method of producing a monomer diol composition] The method for producing the monomer diol composition of the present invention is not particularly limited, and it can be produced by a conventional method. For example, there is a method in which two or more types of monomer diols are supplied to a mixing vessel equipped with a heater and a stirrer, heated to the melting points of the monomer diols or higher, and then stirred and mixed to form a homogeneous solution, thereby obtaining the monomer diol composition. The heating and stirring conditions are preferably the conditions suitable for [Procedure 1] when determining the a / b value described below.

[0030] The mixing ratio of two or more monomer diol compositions of the present invention is not particularly limited, as it is determined by the required physical properties and required biocontent of the resulting polyester. For example, in a monomer diol composition consisting of two types of monomer diol, monomer diol A and monomer diol B, the mass ratio of monomer diol B to monomer diol A is preferably 0.001 or more, more preferably 0.005 or more, and particularly preferably 0.01 or more. On the other hand, it is preferably 1000 or less, more preferably 200 or less, and particularly preferably 100 or less.

[0031] [value (a / b) obtained by dividing the measured value a of the hydroxyl group amount of the monomer diol composition by the theoretical value b of the hydroxyl group amount of the monomer diol composition] The monomer diol composition of the present invention is characterized in that the value (a / b) (hereinafter sometimes simply referred to as the "a / b value") obtained by dividing the measured value a of the hydroxyl group amount measured by the following measurement method by the theoretical value b of the hydroxyl group amount is 0.970 or more and less than 1.000. <Measurement method> Step 1: Two or more types of monomer diols to be mixed are weighed to obtain the mass of each monomer diol. Step 2: The two or more monomer diols in step 1 are mixed to obtain a monomer diol composition. Step 3: From the mass of each monomer diol obtained in step 1, the theoretical value b of the hydroxyl group amount of the monomer diol composition obtained in step 2 is obtained. Step 4: The monomer diol composition obtained in step 2 is subjected to NMR measurement to obtain a measured value a of the amount of hydroxyl groups in the monomer diol composition. Step 5: The measured value a of the amount of hydroxyl groups obtained in step 4 is divided by the theoretical value b of the amount of hydroxyl groups obtained in step 3 to obtain a value (a / b).

[0032] If the a / b value of the monomer diol composition of the present invention is small, the polymerization reaction rate will decrease when this monomer diol composition is used to produce a polyester. On the other hand, a monomer diol composition with a large a / b value contains a polyhydric alcohol such as a triol in the monomer diol composition, and polyesters obtained using such monomer diol compositions as raw materials will form gels with chemically crosslinked structures and will be significantly thickened. From this perspective, the a / b value of the monomer diol composition of the present invention is 0.970 or more and less than 1.000, preferably 0.975 or more and 0.997 or less, and more preferably 0.980 or more and 0.995 or less.

[0033] The a / b value of the monomer diol composition of the present invention can be determined by the following procedure, for example, in the case of a monomer diol composition consisting of two kinds of monomer diols, monomer diol A and monomer diol B. [Step 1] After weighing out the monomer diol A and the monomer diol B to have masses c and d, respectively, they are mixed and stirred at a temperature equal to or higher than the melting point to obtain a uniform mixed solution C. The temperature during mixing is preferably equal to or higher than the melting point of the monomer diol A or the monomer diol B, whichever has the higher melting point, and is preferably at least 50°C higher than the melting point and at least 20°C lower than the boiling point, from the viewpoint of facilitating the monomer diol composition melting to form a homogeneous solution C. The stirring time is preferably about 1 to 30 hours, for example, 1 hour. The weighed amounts of the monomer diol A and the monomer diol B in step 1 are set to the same ratio as the mixing ratio of the monomer diol A and the monomer diol B in the monomer diol composition to be actually produced. [Step 2] Calculate the theoretical value e (mol / g) of the amount of hydroxyl groups per unit mass of the mixed solution C obtained in Step 1. [Step 3] The mixed solution C obtained in Step 1 and an internal standard substance (e.g., triphenylmethane (molecular weight: 244.33)) are weighed to mass f and mass g, respectively, in an NMR tube, and a deuterated solvent (e.g., deuterated chloroform) is added to obtain an NMR measurement solution. [Step 4] NMR of the NMR measurement solution obtained in Step 3 is measured, and the sum of the integral values of the peaks derived from the hydroxyl groups of the monomer diol A and the monomer diol B and the integral value of the internal standard are calculated, and the integral value ratio h (= the sum of the integral values of the peaks derived from the hydroxyl groups of the monomer diol A and the monomer diol B / the integral value of the internal standard) is calculated. [Step 5] Using the formula below, calculate the measured value a of the hydroxyl group amount and the theoretical value b of the hydroxyl group amount, and calculate the a / b value by dividing the measured value a of the hydroxyl group amount by the theoretical value b of the hydroxyl group amount. a = (integral value ratio h × mass g) / molecular weight of internal standard substance b = theoretical value of the amount of hydroxyl groups per unit mass of mixed solution C e × mass f a / b value = measured amount of hydroxyl groups a / theoretical amount of hydroxyl groups b

[0034] The method for measuring and calculating the measured value of the hydroxyl group amount has been described above for a monomer diol composition obtained by mixing two types of monomer diols, but the same method can be used for a monomer diol composition obtained by mixing three or more types of monomer diols. Furthermore, when the monomer diol A and / or the monomer diol B contain unknown impurities, the measured value a of the hydroxyl group amount of the monomer diol composition may be corrected, or the theoretical value a may be calculated without correction. When correction is performed, for example, when the monomer diol A contains unknown impurities, the content of the pure monomer diol A in the monomer diol A is calculated using chromatography or the like, and after correction, the a / b value of the mixed solution C can be calculated.

[0035] [Polyester manufacturing method] Examples of a method for producing a polyester of the present invention using the monomer diol composition of the present invention include a method in which the monomer diol composition of the present invention and a dicarboxylic acid component are subjected to an esterification or transesterification reaction in the presence of an esterification catalyst or a transesterification catalyst.

[0036] Hereinafter, the method for producing a polyester of the present invention will be described mainly with reference to a method for producing polybutylene terephthalate (hereinafter sometimes abbreviated as "PBT") as a polyester, when the monomer diol composition of the present invention is a 1,4-butanediol composition containing 1,4-butanediol (hereinafter sometimes abbreviated as "BDO"). However, according to the method for producing a polyester of the present invention, a polyester other than PBT can be produced in the same manner as the method described below, using a monomer diol composition of the present invention other than a 1,4-butanediol composition.

[0037] Hereinafter, the polyester produced by the polyester production method of the present invention may be referred to as "the polyester of the present invention", and the PBT produced by the polyester production method of the present invention may be referred to as "the PBT of the present invention".

[0038] PBT refers to a polymer having a structure in which a dicarboxylic acid component and a diol component are ester-bonded, in which 50 mol % or more of the dicarboxylic acid component is a terephthalic acid component, and 50 mol % or more of the diol component is BDO. The proportion of the terephthalic acid component in all dicarboxylic acid components is preferably 70 mol % or more, more preferably 80 mol % or more, and even more preferably 95 mol % or more, and the proportion of BDO in all diol components is preferably 70 mol % or more, more preferably 80 mol % or more, and even more preferably 95 mol % or more. If the terephthalic acid component or BDO is less than 50 mol %, the crystallization acceleration of the PBT decreases, resulting in poor moldability.

[0039] <Dicarboxylic acid component> In the present invention, the dicarboxylic acid component includes dicarboxylic acids and dicarboxylic acid derivatives.

[0040] Examples of the terephthalic acid derivative include esters of terephthalic acid such as dimethyl terephthalate, and ester-forming derivatives such as terephthalic acid halide.

[0041] Dicarboxylic acids other than terephthalic acid that can be used as raw materials for producing PBT are not particularly limited, and examples include aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-benzophenonedicarboxylic acid, 4,4'-diphenoxyethanedicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid, and 2,6-naphthalenedicarboxylic acid; alicyclic dicarboxylic acids such as 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid; and aliphatic dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. Dicarboxylic acid derivatives include esters of these dicarboxylic acids and ester-forming derivatives such as dicarboxylic acid halides.

[0042] These dicarboxylic acid components other than the terephthalic acid component may be used alone or in combination of two or more.

[0043] The terephthalic acid used as a raw material for producing PBT can be terephthalic acid synthesized by oxidizing the petrochemical product paraxylene (petrochemical-derived terephthalic acid), chemically recycled terephthalic acid obtained by recovering waste polyester and depolymerizing the recovered polyester, or biomass-derived terephthalic acid obtained using paraxylene produced from isobutanol or ethanol produced from plant-derived raw materials such as corn or sugarcane (for example, JP 2013-506717 A, etc.). From the perspective of aiming for a sustainable society for the global environment and future generations, the terephthalic acid used as a raw material for producing PBT is preferably chemically recycled terephthalic acid. From the same viewpoint, the terephthalic acid used as a raw material for producing PBT is preferably biomass-derived terephthalic acid.

[0044] Furthermore, with regard to dimethyl terephthalate, a raw material for producing PBT, the raw material can be terephthalic acid synthesized by oxidizing paraxylene, a petrochemical product (petrochemical-derived terephthalic acid), as well as chemically recycled terephthalic acid obtained by recovering waste polyester and depolymerizing the recovered polyester, or biomass-derived terephthalic acid obtained using paraxylene produced from isobutanol or ethanol produced from plant-derived raw materials such as corn or sugarcane (for example, JP 2013-506717 A, etc.). From the perspective of striving for a sustainable society for the global environment and future generations, it is preferable that the terephthalic acid that is the raw material for dimethyl terephthalate used in the production of PBT is terephthalic acid derived from chemical recycling. From the same viewpoint, it is preferable that the terephthalic acid that is the raw material for dimethyl terephthalate, which is the raw material for producing PBT, is biomass-derived terephthalic acid. These terephthalic acids can be esterified with methanol under high temperature and pressure conditions, and the esterification reaction mixture can be separated and purified to give dimethyl terephthalate. The dimethyl terephthalate may also be dimethyl terephthalate produced directly by chemical recycling through the depolymerization of polyesters such as polyethylene terephthalate or polybutylene terephthalate.

[0045] Dicarboxylic acid components such as succinic acid may also be derived from biomass.

[0046] <Diol component> In the method for producing a polyester of the present invention, the monomer diol composition of the present invention is used as the diol component.

[0047] <Other ingredients> In the present invention, one or more of the following copolymerization components can be used in the production of PBT: hydroxycarboxylic acids such as lactic acid, glycolic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid, 6-hydroxy-2-naphthalenecarboxylic acid, and p-β-hydroxyethoxybenzoic acid; monofunctional components such as stearyl alcohol, benzyl alcohol, stearic acid, benzoic acid, t-butylbenzoic acid, and benzoylbenzoic acid; and trifunctional or higher polyfunctional components such as tricarballylic acid, trimellitic acid, trimesic acid, pyromellitic acid, gallic acid, trimethylolethane, trimethylolpropane, glycerol, and pentaerythritol.

[0048] The polyester of the present invention may also be a PTMG copolymerized PBT in which crystalline PBT is used as a hard segment and polytetramethylene ether glycol (hereinafter, sometimes referred to as "PTMG") is used as a soft segment. The PTMG copolymerized PBT can be obtained by subjecting a dicarboxylic acid component containing terephthalic acid as the main component, a diol component containing the butanediol composition of the present invention and PTMG, and further other components used as necessary, to an esterification reaction and / or an ester exchange reaction, followed by a polycondensation reaction, and preferably further a solid-state polycondensation reaction.

[0049] In this case, the number average molecular weight of the PTMG used is preferably 650 to 2000, more preferably 800 to 1500. When the molecular weight is within this range, the reactivity during production of the PTMG copolymerized PBT is good, the degree of melting point depression due to copolymerization is small, and a PTMG copolymerized PBT with good mechanical properties can be obtained. The molecular weight of the PTMG is controlled by the reaction temperature, reaction time, catalyst amount, etc. during production of the PTMG. Furthermore, the lower limit of the copolymerization amount of the PTMG component in the PTMG copolymerized PBT is preferably 8 mass%, more preferably 10 mass%, and even more preferably 15 mass%, and the upper limit is preferably 35 mass%, more preferably 30 mass%, and even more preferably 25 mass%.

[0050] Here, the copolymerization amount (content) of PTMG refers to the proportion of PTMG units as a diol component in the PTMG-copolymerized PBT, i.e., the proportion of the amount of the component obtained by subtracting the amount of water molecules resulting from ester bond formation from PTMG, relative to the PTMG-copolymerized PBT, expressed in mass %. By ensuring that the copolymerization ratio of PTMG is within this range, a PTMG copolymerized PBT with a good balance of flexibility and impact strength can be obtained. The amount of PTMG copolymerized can be controlled by the amount of PTMG charged during the production of the copolymerized PBT.

[0051] <Polyester manufacturing method> The method for producing the polyester of the present invention is not particularly limited, and the production method may be a continuous method or a batch method. The polyester of the present invention can be produced by a conventional method, for example, through a step of mixing, under stirring, a dicarboxylic acid component mainly composed of terephthalic acid or a terephthalic acid diester and a diol component mainly composed of the monomer diol composition of the present invention in a predetermined ratio to obtain an ester raw material liquid, a step of heating the ester raw material liquid under normal pressure or reduced pressure to cause an esterification reaction or an ester exchange reaction (hereinafter, sometimes referred to as an "ester (exchange) reaction") to obtain a polyester oligomer, and a melt polycondensation step of gradually reducing the pressure and heating the obtained oligomer to cause a melt polycondensation reaction to obtain a polyester. As described above, the method for producing the polyester of the present invention is not limited, but an example thereof includes a production method via the following ester (transfer) reaction step and polycondensation reaction step.

[0052] (Transesterification reaction step) An example of a process for first subjecting a starting material terephthalic acid or terephthalic acid diester and the monomer diol composition of the present invention to an ester (exchange) reaction to produce an oligomer is a method in which, using a single ester (exchange) reaction tank or a multistage reaction apparatus in which a plurality of ester (exchange) reaction tanks are connected in series, the ester (exchange) reaction is carried out under normal or reduced pressure with or without a catalyst until the ester (exchange) reaction rate (the proportion of all carboxyl groups or all ester groups in the starting dicarboxylic acid component that have reacted with the diol component and undergone an ester (exchange) reaction) reaches typically 90% or more, while removing water or alcohol produced in the reaction and excess diol component from the system, to obtain an oligomer. Typically, the temperature of the ester (transfer) reaction is about 210 to 230°C, the pressure is about 10 to 133 kPa, and the residence time in the reaction tank, which corresponds to the reaction time, is about 1 to 4 hours.

[0053] (Polycondensation reaction step) An example of the polycondensation reaction step is a method in which a single melt polycondensation tank or a multistage reaction apparatus in which a plurality of melt polycondensation tanks are connected in series, for example, a first-stage reactor is a complete mixing type reactor equipped with stirring blades, and second-stage and third-stage reactors are horizontal plug flow type reactors equipped with stirring blades, is used, and the diol produced is distilled out of the system while heating under reduced pressure in the presence of a catalyst. Generally, the polycondensation reaction is carried out at a temperature of 210 to 280°C, preferably about 220 to 250°C, under reduced pressure of 27 kPa or less, preferably 13 kPa or less.

[0054] The reaction tank may be a single tank or multiple tanks. However, in order to prevent coloration and deterioration and to suppress an increase in terminal groups such as vinyl groups, it is advisable to carry out the reaction in at least one reaction tank under a high vacuum of usually 1.3 kPa or less, preferably 0.3 kPa or less.

[0055] The polyester obtained by the polycondensation reaction is usually withdrawn in the form of a strand or sheet from a withdrawal port provided at the bottom of the polycondensation reaction tank, and then cut with a cutter while or after water cooling to form granular bodies such as pellets or chips (for example, lengths of about 3 to 10 mm). Alternatively, the molten resin is released from the polycondensation reaction tank through a pipe into cold water adjusted to a predetermined temperature, and then cut with a cutter to form spheres (diameters of about 2 to 10 mm).

[0056] <Polycondensation catalyst> When polycondensing an oligomer obtained by an ester (exchange) reaction between a diol component and a dicarboxylic acid component, a titanium compound and preferably a compound of a metal of Group 2A of the Periodic Table are usually used as catalysts. These catalyst components may be used in the ester (exchange) reaction and then directly subjected to the polycondensation reaction, or they may not be used in the ester (exchange) reaction, or only the titanium catalyst may be used, with the remaining catalyst components added at the polycondensation stage. Furthermore, a portion of the catalyst amount ultimately used may be used in the ester (exchange) reaction, and then appropriately added as the polycondensation reaction proceeds. In any case, in the present invention, titanium and preferably also a metal of Group 2A of the Periodic Table are inevitably contained in the polyester finally obtained. The content thereof will be described later.

[0057] (Example of titanium compound) Specific examples of titanium compounds used as catalysts include inorganic titanium compounds such as titanium oxide and titanium tetrachloride, tetraalkyl titanates such as tetramethyl titanate, tetraisopropyl titanate and tetrabutyl titanate, and tetraaryl titanates such as tetraphenyl titanate. These may be used alone or in combination of two or more. Of these, tetraalkyl titanates are preferred, and among these, tetrabutyl titanate is preferred.

[0058] (titanium catalyst amount) The content of the titanium catalyst in the polyester of the present invention is preferably 5 to 200 ppm by mass of titanium atoms relative to the polyester. This amount is more preferably 10 ppm or more, even more preferably 20 ppm or more, and most preferably 25 ppm or more. This amount is more preferably 190 ppm or less, even more preferably 180 ppm or less, particularly preferably 170 ppm or less, particularly preferably 160 ppm or less, and most preferably 150 ppm or less. If the titanium content is too high, problems arise such as deterioration in color tone, hydrolysis resistance, and solution haze, and an increase in fish eyes in the resulting molded product, while if the titanium content is too low, polymerization properties deteriorate.

[0059] (Group 2A metal compound) Specific examples of the Group 2A metal compound of the periodic table used as a catalyst include various compounds of beryllium, magnesium, calcium, strontium, and barium. From the viewpoints of ease of handling and availability, and catalytic effect, magnesium compounds and / or calcium compounds are preferred, and magnesium compounds, which have excellent catalytic effect, are particularly preferred.

[0060] Specific examples of magnesium compounds include magnesium acetate, magnesium hydroxide, magnesium carbonate, magnesium oxide, magnesium alkoxide, magnesium hydrogen phosphate, and the like. Specific examples of calcium compounds include calcium acetate, calcium hydroxide, calcium carbonate, calcium oxide, calcium alkoxide, and calcium hydrogen phosphate.

[0061] These Group 2A metal compounds of the periodic table may be used alone or in combination of two or more. Of these, magnesium acetate is preferred.

[0062] (Group 2A metal catalyst amount) The content of the Group 2A metal catalyst in the polyester of the present invention is not particularly limited, but is preferably 3 to 150 ppm by mass relative to the polyester in terms of Group 2A metal atoms. This amount is more preferably 5 ppm or more, and even more preferably 10 ppm or more. This amount is more preferably 140 ppm or less, even more preferably 130 ppm or less, and particularly preferably 100 ppm or less. If the content of the Group 2A metal is too high, color tone and hydrolysis resistance will deteriorate, while if it is too low, polymerization will deteriorate.

[0063] When an acetate of a metal of Group 2A of the Periodic Table is used, the amount of the metal of Group 2A of the Periodic Table in the polyester is preferably 100 ppm or less, since the acetic acid source enters the reaction system.

[0064] (M / Ti ratio) The molar ratio of titanium atoms to Group 2A metal atoms of the periodic table (Group 2A metal atoms of the periodic table / titanium) contained in the polyester of the present invention is usually 0.01 to 100, preferably 0.1 to 10, more preferably 0.3 to 3, and even more preferably 0.3 to 1.5.

[0065] (Metal analysis method) The content of metals such as titanium atoms in polyester can be measured using methods such as atomic emission, atomic absorption, and ICP emission after recovering the metals in the polymer by a method such as wet ashing.

[0066] (Other catalysts) In producing the polyester of the present invention, in addition to the titanium compound and the compound of a metal of Group 2A of the Periodic Table, reaction aids such as antimony compounds such as antimony trioxide, germanium compounds such as germanium dioxide and germanium tetroxide, manganese compounds, zinc compounds, zirconium compounds, cobalt compounds, phosphorus compounds such as orthophosphoric acid, phosphorous acid, hypophosphorous acid, polyphosphoric acid, esters or metal salts thereof, sodium hydroxide, sodium benzoate, etc. may be used.

[0067] [Intrinsic viscosity of PBT] When the PBT of the present invention is used for compounding or injection molding, the intrinsic viscosity of the PBT is preferably 0.6 to 1.3 dL / g. If the intrinsic viscosity is less than 0.6 dL / g, the mechanical strength of the molded product tends to be insufficient, while if it exceeds 1.3 dL / g, the melt viscosity tends to be high, which deteriorates the flowability and moldability. The intrinsic viscosity of the PBT of the present invention is more preferably 0.65 to 1.26 dL / g, and even more preferably 0.7 to 1.2 dL / g.

[0068] Furthermore, when the PBT pellets of the present invention are used for extrusion applications such as film, sheet, or filament, the intrinsic viscosity of the PBT is usually 1.00 to 1.60 dL / g, preferably 1.03 to 1.50 dL / g, more preferably 1.05 to 1.55 dL / g, particularly preferably 1.10 to 1.50 dL / g, and particularly preferably 1.15 to 1.35 dL / g. If the intrinsic viscosity is less than 1.00 dL / g, extrusion moldability deteriorates, leading to drawdown of the resin and molding defects, resulting in insufficient mechanical strength of extrusion-molded products such as films, or the melt viscosity decreases, resulting in excessively high fluidity and thus poor extrusion moldability. On the other hand, if the intrinsic viscosity exceeds 1.60 dL / g, the melt viscosity increases, resulting in poor fluidity and thus poor extrusion moldability.

[0069] [Compound] The polyester of the present invention is produced with excellent polymerization reaction efficiency and good productivity using the monomer all composition of the present invention, and is excellent in color tone with suppressed yellowing. The polyester of the present invention can be compounded into a compound product by adding various additives or compounding materials as required during or after the polyester production stage. [Example]

[0070] The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention.

[0071] [Raw materials and reagents] Dimethyl terephthalate, ethylene glycol, 1,6-hexanediol, and tetrabutyl titanate were reagents manufactured by Tokyo Chemical Industry Co., Ltd. The deuterated chloroform used was a reagent manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., which was prepared by immersing molecular sieves 4A manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., which had been previously dehydrated under reduced pressure in an oil bath at 200°C for 3 hours, and then drying the chloroform. The internal standard substance for NMR, triphenylmethane, was a reagent manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. The petroleum-derived 1,4-butanediol used was a product of Mitsubishi Chemical Corporation. Furthermore, "ADEKA STAB AO-60" manufactured by ADEKA Corporation was used as a phenolic antioxidant. Terephthalic acid (high-purity terephthalic acid, hereinafter referred to as "PTA") is a refined TPA produced through the following two steps. Step 1: Paraxylene is mixed with acetic acid and a catalyst, and air is blown into it under high temperature and pressure conditions to obtain crude TPA. Step 2: The crude "TPA" obtained in Step 1 is purified to obtain purified TPA. Terephthalic acid (single-step oxidation method, hereinafter referred to as "QTA") is the crude TPA obtained in step 1 above.

[0072] [Evaluation method] The a / b value was calculated by determining the measured value a of the hydroxyl group amount and the theoretical value b of the hydroxyl group amount according to the following procedures 1 to 5, and dividing the measured value a of the hydroxyl group amount by the theoretical value b of the hydroxyl group amount. [Step 1] Monomer diol A and monomer diol B were weighed to masses c and d, respectively, and then mixed. The mixture was stirred for 1 hour at a temperature equal to or higher than the melting point described below, to obtain a homogeneous mixed solution C. [Step 2] The theoretical value e (mol / g) of the amount of hydroxyl groups per unit mass of the mixed solution C obtained in Step 1 was calculated. [Step 3] The mixed solution C obtained in Step 1 and the internal standard triphenylmethane (molecular weight: 244.33) were weighed to mass f and mass g, respectively, in an NMR tube, and deuterated chloroform was added to obtain an NMR measurement solution. ​[Step 4] NMR of the NMR measurement solution obtained in Step 3 is measured, and the sum of the integral values of the peaks derived from the hydroxyl groups of the monomer diol A and the monomer diol B and the integral value of the peaks derived from the internal standard triphenylmethane (Ph3C- H ) was calculated, and the integral ratio h (total integrals of the peaks derived from the hydroxyl groups of monomer diol A and monomer diol B / integral value of triphenylmethane) was calculated. In addition, nuclear magnetic resonance ( 1 1 H NMR measurements were carried out using a Bruker Advance NEO600 spectrometer under the following conditions: (NMR measurement conditions) Flip angle: 45° Data acquisition time: 3 seconds Pulse repetition time: 10 seconds Accumulation count: 512 ·Temperature: 25℃ [Step 5] The measured hydroxyl group amount a and the theoretical hydroxyl group amount b were calculated using the following formula, and the measured hydroxyl group amount a was divided by the theoretical hydroxyl group amount b to calculate the a / b value. a = (integral value ratio h × mass g) / molecular weight of internal standard substance (244.33) b = theoretical value of the amount of hydroxyl groups per unit mass of mixed solution C e × mass f a / b value = measured amount of hydroxyl groups a / theoretical amount of hydroxyl groups b

[0073] <Analysis of 1,4-butanediol> Analysis of 1,4-butanediol was carried out by gas chromatography using the following equipment and conditions. Equipment: Shimadzu GC-2014 Column: Agilent Technologies "DB-1" (inner diameter 0.53 mm, column length 30 m, film thickness 1 μm) Carrier gas: Helium Carrier gas flow rate: 5.58 cm per minute 3 Linear speed: 47.4 cm per second ·Inlet temperature: 250℃ Detector temperature: 280℃ Column temperature rise pattern: First, hold at 150°C for 5 minutes, then raise the temperature at 13°C per minute to 295°C, and hold at 295°C for 15 minutes for analysis.

[0074] <Residual rate of dimethyl terephthalate> The residual rate of dimethyl terephthalate was measured by high performance liquid chromatography using the following apparatus and conditions. Apparatus: Shimadzu high performance liquid chromatography Pump: LC-20AD Column oven: CTO-20AC Detector: SPD-20A Column: CAPCELL PAK C18, TYPE MGII 5 μm, 4.6 mm ID x 150 mm Method: Low-pressure gradient method ·Analysis temperature: 40℃ ·Eluent composition: I liquid: water Solution II: Acetonitrile For analysis times of 0 to 10 minutes, the eluent composition was I:II = 50:50 (volume ratio, same below), gradually changed to I:II = 100:0 for analysis times of 10 to 20 minutes, and then I:II = 100:0 for analysis times of 20 to 30 minutes. ·Flow rate: 0.8mL / min Detection wavelength: 254nm

[0075] <Intrinsic viscosity> The viscosity was measured using a fully automatic viscosity measuring device (model DT553, capillary type) manufactured by Sentec Co., Ltd. in the following manner. A mixed solution of phenol and 1,1,2,2-tetrachloroethane (1 / 1 mass ratio mixture) was used as the solvent. The number of seconds it took for a 1.0 g / dL PBT sample solution and the solvent alone to fall at 30°C was measured and calculated using the following formula. Intrinsic viscosity (dL / g)=((1+4KHη sp ) 0.5 -1) / (2K H C) (However, η sp =η / η0-1, where η is the time it takes for the sample solution to fall, η0 is the time it takes for the solvent to fall, C is the PBT concentration of the sample solution (g / dL), and KH is Hagins' constant. K H Adopted 0.33.)

[0076] <Tone of PBT> The tone of PBT was evaluated in the Lab color system using a color difference meter "Z-300A type" manufactured by Nippon Denshoku Industries Co., Ltd. The lower the b value, the less yellowish and more preferable. However, when the b value is lower than -2.0, although the yellow tint is less, the blue tint increases and the tone is not preferable. The evaluation criteria for the b value were as follows. S: -1.0 ≤ b value ≤ 1.0 A: -2.0 ≤ b value < -1.0 or 1.0 < b value ≤ 2.0 B: b value < -2.0 or 2.0 < b value ≤ 2.5 C: 2.5 < b value

[0077] [Production Example of BDO] [Production Example 1: BDO by Hydrogenation of Succinic Acid Derived from Biomass Resources] BDO manufactured by Yuanli Chemical Group and BDO manufactured by Zhejiang Boju New Materials Co., Ltd., both produced by hydrogenation of succinic acid derived from biomass resources, were mixed to obtain a mixed solution. The obtained mixed solution was subjected to vacuum distillation to obtain, in the order of distillation, a first fraction, a main fraction A, a main fraction B, a main fraction C, a main fraction D, and a tail fraction. When a part was extracted from each of the main fraction A, the main fraction B, the main fraction C, the main fraction D, and the tail fraction and analyzed by gas chromatography, the 1,4-butanediol content in each was 99% by mass or more.

[0078] [Production Example 2: BDO by Depolymerization of PBT] Following Example 3 of JP-A-2004-323378, chemically recycled 1,4-butanediol was produced. Into an autoclave equipped with a stirring blade, 1030 parts by mass of polybutylene terephthalate, 3200 parts by mass of methanol, and 13 parts by mass of sodium carbonate were supplied. The autoclave was immersed in an oil bath at 200 °C and reacted with stirring at a pressure of 1.3 MPa for 8 hours. The autoclave was taken out of the oil bath and cooled to 10 °C or lower with ice water to obtain a slurry liquid. The resulting slurry was subjected to solid-liquid separation using a centrifuge to obtain a filtrate. The filtrate was placed in a distillation apparatus equipped with a thermometer, a pressure reduction controller, a stirring blade, a condenser, and a distillate receiver. After recovering methanol and tetrahydrofuran as initial fractions, the mixture was distilled under reduced pressure to obtain the initial fraction, main fraction A, main fraction B, main fraction C, and subsequent fractions in the order of distillation. A portion of the obtained main fractions A to C was extracted and analyzed by gas chromatography, and it was found that the 1,4-butanediol content was 99% by mass or more.

[0079] [Example 1] 11.52 g (mass c) of the main fraction B obtained in Production Example 1 as monomer diol A and 12.75 g (mass d) of petroleum-derived 1,4-butanediol (a product of Mitsubishi Chemical Corporation) as monomer diol B were placed in an eggplant flask equipped with a stirrer. The eggplant flask was then immersed in an oil bath heated to 150°C and stirred for 1 hour to obtain mixed liquid C-1. The theoretical value e of the amount of hydroxyl groups per unit mass of this mixed solution C-1 is calculated as follows, since the molecular weight of butanediol is 90.12 and the number of hydroxyl groups per molecule is "2". Theoretical value of the amount of hydroxyl groups per unit mass e (mol / g) ={(11.52+12.75) / 90.12}×2 / (11.52+12.15) A portion of the resulting mixture C-1 was extracted, and 10.5 mg (= mass f) was placed in an NMR tube. In addition, 10.4 mg (= mass g) of triphenylmethane (molecular weight: 244.33) was placed in the NMR tube as an internal standard substance, and then a deuterated chloroform solution was added to obtain an NMR measurement solution. The obtained NMR measurement solution was subjected to NMR measurement, and the integral value ratio h (integral value of OH of 1,4-butanediol / triphenylmethane Ph3C- H The integral value of 5.403 was obtained. Here, the measured value a of the amount of hydroxyl groups is calculated as follows. Measured amount of hydroxyl groups a = (integral value ratio h × mass g) / 244.33 =(5.403×10.4×10​-3 ) / 244.33 =2.2998×10 -4 On the other hand, the theoretical value b of the amount of hydroxyl groups is calculated as follows: Theoretical value of the amount of hydroxyl groups b = Theoretical value of the amount of hydroxyl groups per unit mass e × mass f ={(11.52+12.75) / 90.12}×2 / (11.52+12.75)×(10.5×10 -3 ) =2.3302×10 -4 Therefore, the a / b value is calculated as follows: a / b value = measured amount of hydroxyl groups a / theoretical amount of hydroxyl groups b =2.2998×10 -4 / 2.3302×10 -4 =0.987

[0080] <Conversion rate of dimethyl terephthalate> A 0.354% by mass tetrabutoxy titanate solution was prepared using the mixed solution C-1 and tetrabutoxy titanate. 13.2 g of dimethyl terephthalate and 6.0 g of the mixed solution C-1 were placed in a side-arm test tube equipped with a stirrer and purged with nitrogen. The tube was then immersed in a 150°C oil bath to melt and obtain a homogeneous solution. 1 g of a 0.354% by mass tetrabutoxy titanate solution was added thereto and allowed to react for 30 minutes from the time of addition to obtain a reaction solution. A portion of the resulting reaction solution was extracted, and high-performance liquid chromatography revealed that the residual rate of dimethyl terephthalate was 90.7%, and the conversion rate of dimethyl terephthalate (referred to as "DMT" in Table 1) was estimated to be 9.3%.

[0081] <Transesterification reaction> 132 g of dimethyl terephthalate and 175 g of the mixed solution C- were fed into a glass reactor equipped with a stirrer and a distillation tube. The pressure in the glass reactor was reduced to approximately 100 Pa, and then the pressure was returned to atmospheric pressure with nitrogen. This operation was repeated three times to replace the inside of the reactor with nitrogen. The reactor was then immersed in an oil bath at 150°C. After confirming that the contents had dissolved, the rotation speed was increased to 150 rpm. Subsequently, a tetrabutyl titanate solution containing 94% by mass of the mixed solution C-1 and 6% by mass of tetrabutyl titanate was added so that the titanium atom content was 33 ppm by mass relative to the polybutylene terephthalate obtained. The oil bath temperature was then raised from 150°C to 210°C over 105 minutes to obtain a transesterification reaction solution.

[0082] <Polycondensation reaction> A magnesium acetate solution containing 90% by mass of the mixture C-1 and 10% by mass of magnesium acetate tetrahydrate was supplied to the resulting transesterification reaction liquid so that the magnesium atom content was 48 ppm by mass relative to the polybutylene terephthalate obtained. An antioxidant solution containing 94% by mass of the mixture C-1 and 6% by mass of ADK STAB AO-60 was supplied to the resulting polybutylene terephthalate so that the ADK STAB AO-60 content was 530 ppm by mass relative to the polybutylene terephthalate obtained. Furthermore, a tetrabutyl titanate solution containing 94% by mass of the mixture C-1 and 6% by mass of tetrabutyl titanate was supplied to the resulting polybutylene terephthalate so that the titanium atom content was 61 ppm by mass relative to the polybutylene terephthalate obtained. The oil bath was heated from 210°C to 240°C over 45 minutes, and the internal pressure of the glass reactor was reduced from 760 Torr to 1 Torr over 85 minutes to carry out the polycondensation reaction. The internal pressure was then fully evacuated, and the polymerization reaction was terminated when the reactor's agitator reached a predetermined stirring power. The time when the oil bath was heated from 210°C was set to zero, and the polycondensation time until the predetermined stirring power was reached was 175 minutes. The reactor was then returned to a pressure of 760 Torr with nitrogen, and then the gauge pressure was increased to 1500 Torr, and polybutylene terephthalate was extracted in a strand form from the bottom of the reactor, and the strand-like polybutylene terephthalate was then pelletized using a rotary cutter to obtain pellet-like polybutylene terephthalate. The resulting pelletized polybutylene terephthalate had an intrinsic viscosity of 0.988 dL / g, and the color b value was 0.5, giving it an S rating.

[0083] [Example 2] Mixture C-2 was obtained in the same manner as in Example 1, except that 11.64 g of the main fraction C obtained in Production Example 1 was used as monomer diol A and 11.62 g of petroleum-derived 1,4-butanediol (a product of Mitsubishi Chemical Corporation) was used as monomer diol B. NMR measurement was carried out in the same manner as in Example 1, except that 10.1 mg of a portion of the obtained mixed solution C-2 and 10.6 mg of triphenylmethane as an internal standard were used, and the integral value ratio h was found to be 5.142. Here, the measured value a of the amount of hydroxyl groups and the theoretical value b of the amount of hydroxyl groups are calculated as follows. Measured amount of hydroxyl groups a = 5.142 × 10.6 × 10 -3 / 244.33 =2.2308×10 -4 Theoretical value of hydroxyl group amount b = {(11.64 + 11.62) / 90.12} × 2 / (11.64 + 11.62) × (10.1 × 10 -3 ) =2.2415×10 -4 Therefore, the a / b value is calculated as follows: a / b value = 2.2308 x 10 -4 / 2.2415×10 -4 =0.995

[0084] <Conversion rate of dimethyl terephthalate> The conversion rate of dimethyl terephthalate was measured in the same manner as in Example 1 except that the mixed solution C-2 was used instead of the mixed solution C-1. As a result, the residual rate of dimethyl terephthalate was found to be 88.6% by high performance liquid chromatography, and the conversion rate of dimethyl terephthalate was estimated to be 11.4%.

[0085] <Transesterification reaction / polycondensation reaction> ​Polybutylene terephthalate was produced by carrying out the transesterification reaction and polycondensation reaction in the same manner as in Example 1, except that the mixed solution C-2 was used instead of the mixed solution C-1. In the polycondensation reaction, the polycondensation time until the predetermined stirring power was reached was 179 minutes. The intrinsic viscosity of the obtained pelletized polybutylene terephthalate was 0.971 dL / g, and the color tone was evaluated as S with a b value of -0.3.

[0086] [Example 3] Mixture C-3 was obtained in the same manner as in Example 1, except that 11.54 g of the main fraction D obtained in Production Example 1 was used as monomer diol A and 11.51 g of petroleum-derived 1,4-butanediol (a product of Mitsubishi Chemical Corporation) was used as monomer diol B. NMR measurement was carried out in the same manner as in Example 1, except that 10.5 mg of a portion of the obtained mixed solution C-3 and 10.2 mg of triphenylmethane as an internal standard were used, and the integral value ratio h was found to be 5.521. Here, the measured value a of the amount of hydroxyl groups and the theoretical value b of the amount of hydroxyl groups are calculated as follows. Measured amount of hydroxyl groups a = 5.521 × 10.2 × 10 -3 / 244.33 =2.3048×10 -4 Theoretical value of hydroxyl group amount b = {(11.54 + 11.51) / 90.12} × 2 / (11.54 + 11.51) × (10.5 × 10 -3 ) =2.3302×10 -4 Therefore, the a / b value is calculated as follows: a / b value = 2.3048 × 10 -4 / 2.3202×10 -4 =0.993

[0087] <Conversion rate of dimethyl terephthalate> ​The conversion rate of dimethyl terephthalate was measured in the same manner as in Example 1 except that the mixed solution C-3 was used instead of the mixed solution C-1. As a result, the residual rate of dimethyl terephthalate was found to be 89.7% by high performance liquid chromatography, and the conversion rate of dimethyl terephthalate was estimated to be 10.3%.

[0088] <Transesterification reaction / polycondensation reaction> Polybutylene terephthalate was produced by carrying out the transesterification reaction and polycondensation reaction in the same manner as in Example 1, except that the mixed solution C-3 was used instead of the mixed solution C-1. In the polycondensation reaction, the polycondensation time until the predetermined stirring power was reached was 172 minutes. The intrinsic viscosity of the obtained pelletized polybutylene terephthalate was 0.981 dL / g, and the color tone was evaluated as S with a b value of 0.8.

[0089] [Example 4] A mixed solution C-4 was obtained in the same manner as in Example 1, except that 11.74 g of the main fraction B obtained in Production Example 2 was used as the monomer diol A and 11.52 g of petroleum-derived 1,4-butanediol (a product of Mitsubishi Chemical Corporation) was used as the monomer diol B. NMR measurement was carried out in the same manner as in Example 1, except that 10.5 mg of a portion of the obtained mixed solution C-4 and 10.4 mg of triphenylmethane as an internal standard were used, and the integral value ratio h was found to be 5.313. Here, the measured value a of the amount of hydroxyl groups and the theoretical value b of the amount of hydroxyl groups are calculated as follows. Measured amount of hydroxyl groups a = 5.413 × 10.4 × 10 -3 / 244.33 =2.3041×10 -4 Theoretical value of hydroxyl group amount b = {(11.74 + 11.52) / 90.12} × 2 / (11.74 + 11.52) × (10.5 × 10 -3 ) =2.3302×10 -4 Therefore, the a / b value is calculated as follows:​ a / b value = 2.3041 × 10 -4 / 2.3302×10 -4 =0.989

[0090] <Conversion rate of dimethyl terephthalate> The conversion rate of dimethyl terephthalate was measured in the same manner as in Example 1 except that the mixed solution C-4 was used instead of the mixed solution C-1. As a result, the residual rate of dimethyl terephthalate was found to be 91.2% by high performance liquid chromatography, and the conversion rate of dimethyl terephthalate was estimated to be 8.8%.

[0091] <Transesterification reaction / polycondensation reaction> Polybutylene terephthalate was produced by carrying out the transesterification reaction and polycondensation reaction in the same manner as in Example 1, except that the mixed solution C-4 was used instead of the mixed solution C-1. In the polycondensation reaction, the polycondensation time until the predetermined stirring power was reached was 186 minutes. The resulting pelletized polybutylene terephthalate had an intrinsic viscosity of 0.988 dL / g, and the color tone was evaluated as b value of 0.9 and S.

[0092] [Example 5] Mixture C-5 was obtained in the same manner as in Example 1, except that 10.88 g of the main fraction C obtained in Production Example 2 was used as monomer diol A and 11.54 g of petroleum-derived 1,4-butanediol (a product of Mitsubishi Chemical Corporation) was used as monomer diol B. NMR measurement was carried out in the same manner as in Example 1, except that 10.2 mg of a portion of the obtained mixed solution C-5 and 10.1 mg of triphenylmethane as an internal standard were used, and the integral value ratio h was found to be 5.378. Here, the measured value a of the amount of hydroxyl groups and the theoretical value b of the amount of hydroxyl groups are calculated as follows. Measured amount of hydroxyl groups a = 5.378 × 10.1 × 10 -3 / 244.33 =2.2231×10 -4 ​Theoretical value of hydroxyl group amount b = {(10.88 + 11.54) / 90.12} × 2 / (10.88 + 11.54) × (10.2 × 10 -3 ) =2.2636×10 -4 Therefore, the a / b value is calculated as follows: a / b value = 2.2231 x 10 -4 / 2.2636×10 -4 =0.982

[0093] <Conversion rate of dimethyl terephthalate> The conversion rate of dimethyl terephthalate was measured in the same manner as in Example 1 except that the mixed solution C-5 was used instead of the mixed solution C-1. As a result, the residual rate of dimethyl terephthalate was found to be 92.2% by high performance liquid chromatography, and the conversion rate of dimethyl terephthalate was estimated to be 7.8%.

[0094] <Transesterification reaction / polycondensation reaction> Polybutylene terephthalate was produced by carrying out the transesterification reaction and polycondensation reaction in the same manner as in Example 1, except that the mixed solution C-5 was used instead of the mixed solution C-1. In the polycondensation reaction, the polycondensation time until the predetermined stirring power was reached was 180 minutes. The resulting pelletized polybutylene terephthalate had an intrinsic viscosity of 0.985 dL / g, and the color tone was evaluated as S with a b value of 0.8.

[0095] [Example 6] A mixed solution C-10 was obtained in the same manner as in Example 1, except that 11.27 g of the main fraction B obtained in Production Example 1 was used as the monomer diol A and 12.10 g of the main fraction obtained in Production Example 2 was used as the monomer diol B. NMR measurement was carried out in the same manner as in Example 1, except that 9.8 mg of a portion of the obtained mixed solution C-10 and 9.7 mg of triphenylmethane as an internal standard were used, and the integral value ratio h=5.421 was obtained. ​Here, the measured value a of the amount of hydroxyl groups and the theoretical value b of the amount of hydroxyl groups are calculated as follows. Measured amount of hydroxyl groups a = 5.421 × 9.7 × 10 -3 / 244.33 =2.1522×10 -4 Theoretical value of hydroxyl group amount b = {(11.27 + 12.10) / 90.12} × 2 / (11.27 + 12.10) × (9.8 × 10 -3 ) =2.1749×10 -4 Therefore, the a / b value is calculated as follows: a / b value = 2.1522 × 10 -4 / 2.1749×10 -4 =0.990

[0096] <Conversion rate of dimethyl terephthalate> The conversion rate of dimethyl terephthalate was measured in the same manner as in Example 1 except that the mixed solution C-10 was used instead of the mixed solution C-1. As a result, the residual rate of dimethyl terephthalate was found to be 92.5% by high performance liquid chromatography, and the conversion rate of dimethyl terephthalate was estimated to be 7.5%.

[0097] <Transesterification reaction / polycondensation reaction> Polybutylene terephthalate was produced by carrying out the transesterification reaction and polycondensation reaction in the same manner as in Example 1, except that the mixed solution C-10 was used instead of the mixed solution C-1. In the polycondensation reaction, the polycondensation time until the predetermined stirring power was reached was 182 minutes. The resulting pelletized polybutylene terephthalate had an intrinsic viscosity of 0.988 dL / g, and the color tone had a b value of 0.7, with the b value being evaluated as S.

[0098] [Comparative Example 1] ​Mixed solution C-6 was obtained in the same manner as in Example 1, except that 11.42 g of the main fraction A obtained in Production Example 1 was used as monomer diol A and 11.76 g of petroleum-derived 1,4-butanediol (a product of Mitsubishi Chemical Corporation) was used as monomer diol B. NMR measurement was carried out in the same manner as in Example 1, except that 10.6 mg of a portion of the obtained mixed solution C-6 and 10.7 mg of triphenylmethane as an internal standard were used, resulting in an integral value ratio h of 5.144. Here, the measured value a of the amount of hydroxyl groups and the theoretical value b of the amount of hydroxyl groups are calculated as follows. Measured amount of hydroxyl groups a = 5.144 × 10.7 × 10 -3 / 244.33 =2.2527×10 -4 Theoretical value of hydroxyl group amount b = {(11.42 + 11.76) / 90.12} × 2 / (11.42 + 11.76) × (10.6 × 10 -3 ) =2.3524×10 -4 Therefore, the a / b value is calculated as follows: a / b value = 2.2527 × 10 -4 / 2.3524×10 -4 =0.958

[0099] <Conversion rate of dimethyl terephthalate> The conversion rate of dimethyl terephthalate was measured in the same manner as in Example 1 except that the mixed solution C-6 was used instead of the mixed solution C-1. As a result, the residual rate of dimethyl terephthalate was found to be 95.5% by high performance liquid chromatography, and the conversion rate of dimethyl terephthalate was estimated to be 4.5%.

[0100] <Transesterification reaction / polycondensation reaction> Polybutylene terephthalate was produced by carrying out the transesterification reaction and polycondensation reaction in the same manner as in Example 1, except that the mixed solution C-6 was used instead of the mixed solution C-1. In the polycondensation reaction, the polycondensation time until the predetermined stirring power was reached was 210 minutes. The intrinsic viscosity of the obtained pelletized polybutylene terephthalate was 0.984 dL / g, and the color tone was evaluated as C in terms of b value, with a b value of 3.1.

[0101] Comparative Example 2 Mixture C-7 was obtained in the same manner as in Example 1, except that 11.27 g of the main fraction A obtained in Production Example 1 was used as monomer diol A and 11.12 g of petroleum-derived 1,4-butanediol (a product of Mitsubishi Chemical Corporation) was used as monomer diol B. NMR measurement was carried out in the same manner as in Example 1, except that 10.2 mg of a portion of the obtained mixed solution C-7 and 10.3 mg of triphenylmethane as an internal standard were used, resulting in an integral value ratio h of 5.725. Here, the measured value a of the amount of hydroxyl groups and the theoretical value b of the amount of hydroxyl groups are calculated as follows. Measured amount of hydroxyl groups a = 5.725 × 10.3 × 10 -3 / 244.33 =2.4134×10 -4 Theoretical value of hydroxyl group amount b = {(11.27 + 11.12) / 90.12} × 2 / (11.27 + 11.12) × (10.2 × 10 -3 ) =2.2636×10 -4 Therefore, the a / b value is calculated as follows: a / b value = 2.4134 × 10 -4 / 2.2636×10 -4 =1.066

[0102] <Conversion rate of dimethyl terephthalate> The conversion rate of dimethyl terephthalate was measured in the same manner as in Example 1 except that the mixed solution C-7 was used instead of the mixed solution C-1. As a result, the residual rate of dimethyl terephthalate was found to be 94.4% by high performance liquid chromatography, and the conversion rate of dimethyl terephthalate was estimated to be 5.6%.

[0103] <Transesterification reaction / polycondensation reaction> ​Polybutylene terephthalate was produced by carrying out the transesterification reaction and polycondensation reaction in the same manner as in Example 1, except that the mixed solution C-7 was used instead of the mixed solution C-1. In the polycondensation reaction, the polycondensation time until the predetermined stirring power was reached was 215 minutes. The intrinsic viscosity of the obtained pelletized polybutylene terephthalate was 0.992 dL / g, and the color tone was evaluated as C in terms of b value, with a b value of 3.5.

[0104] Table 1 shows the a / b values, DMT conversion rates, polycondensation times, and PBT color tone evaluations for Examples 1 to 6 and Comparative Examples 1 and 2. From Table 1, it can be seen that when the a / b value is 0.970 or more and less than 1.000, the DMT conversion rate is high, the polycondensation time is short, and the PBT color tone evaluation is good.

[0105] [Table 1]

[0106] [Example 7] A mixed solution C-8 was obtained in the same manner as in Example 1, except that 11.62 g of the main fraction C obtained in Production Example 1 was used as the monomer diol A and 10.57 g of petroleum-derived ethylene glycol (a product of Tokyo Chemical Industry Co., Ltd.) was used as the monomer diol B. NMR measurement was carried out in the same manner as in Example 1, except that 10.4 mg of a portion of the obtained mixed solution C-8 and 10.2 mg of triphenylmethane as an internal standard were used. The integral value ratio h = (total integral value of OH of 1,4-butanediol and integral value of OH of ethylene glycol) / triphenylmethane PhC- H The integral value of (x) was obtained as 6.645. Here, the measured value a of the hydroxyl group amount and the theoretical value b of the hydroxyl group amount are calculated as follows (molecular weight of butanediol: 90.12, molecular weight of ethylene glycol: 62.07). Measured amount of hydroxyl groups a = 6.645 × 10.2 × 10 -3 / 244.33 ​=2.7741×10 -4 Theoretical value of hydroxyl group amount b = (11.62 / 90.12 + 10.57 / 62.07) × 2 / (11.62 + 10.57) × (10.4 × 10 -3 ) =2.8049×10 -4 Therefore, the a / b value is calculated as follows: a / b value = 2.7741 × 10 -4 / 2.8049×10 -4 =0.989

[0107] <Conversion rate of dimethyl terephthalate> The conversion rate of dimethyl terephthalate was measured in the same manner as in Example 1 except that the mixed solution C-8 was used instead of the mixed solution C-1. As a result, the residual rate of dimethyl terephthalate was found to be 91.4% by high performance liquid chromatography, and the conversion rate of dimethyl terephthalate was estimated to be 8.6%.

[0108] <Transesterification reaction / polycondensation reaction> Polybutylene terephthalate was produced by carrying out the transesterification reaction and polycondensation reaction in the same manner as in Example 1, except that the mixed solution C-8 was used instead of the mixed solution C-1. In the polycondensation reaction, the polycondensation time until the predetermined stirring power was reached was 178 minutes. The resulting pelletized polybutylene terephthalate had an intrinsic viscosity of 0.986 dL / g, and the color tone was evaluated as S with a b value of 0.8.

[0109] [Example 8] A mixed solution C-9 was obtained in the same manner as in Example 1, except that 11.43 g of the main fraction C obtained in Production Example 1 was used as the monomer diol A and 16.21 g of petroleum-derived 1,6-hexanediol (a product of Tokyo Chemical Industry Co., Ltd.) was used as the monomer diol B. ​NMR measurement was carried out in the same manner as in Example 1, except that 10.6 mg of a portion of the obtained mixed solution C-9 and 10.8 mg of triphenylmethane as an internal standard were used. The integral value ratio h = (the sum of the integral value of OH of 1,4-butanediol and the integral value of OH of 1,6-hexanediol) / triphenylmethane PhC- H The integral value of (x) was obtained as 4.551. Here, the measured value a of the hydroxyl group amount and the theoretical value b of the hydroxyl group amount are calculated as follows (molecular weight of butanediol: 90.12, molecular weight of 1,6-hexanediol: 118.17). Measured amount of hydroxyl groups a = 4.551 × 10.8 × 10 -3 / 244.33 =2.0117×10 -4 Theoretical value of hydroxyl group amount b = (11.43 / 90.12 + 16.21 / 118.17) × 2 / (11.43 + 16.21) × (10.6 × 10 -3 ) =2.0249×10 -4 Therefore, the a / b value is calculated as follows: a / b value = 2.0117 × 10 -4 / 2.0249×10 -4 =0.993

[0110] <Conversion rate of dimethyl terephthalate> The conversion rate of dimethyl terephthalate was measured in the same manner as in Example 1 except that the mixed solution C-9 was used instead of the mixed solution C-1. As a result, the residual rate of dimethyl terephthalate was found to be 92.5% by high performance liquid chromatography, and the conversion rate of dimethyl terephthalate was estimated to be 7.5%.

[0111] <Transesterification reaction / polycondensation reaction> Polybutylene terephthalate was produced by carrying out the transesterification reaction and polycondensation reaction in the same manner as in Example 1, except that the mixed solution C-9 was used instead of the mixed solution C-1. In the polycondensation reaction, the polycondensation time until the predetermined stirring power was reached was 175 minutes. The resulting pelletized polybutylene terephthalate had an intrinsic viscosity of 0.988 dL / g, and the color tone had a b value of 1.0, with the b value being evaluated as S.

[0112] In Examples 7 and 8, the types of monomer diol A and monomer diol B, the a / b value, the DMT conversion rate, the polycondensation time, and the PBT color tone evaluation are summarized in Table 2. Table 2 shows that even when a glycol other than 1,4-butanediol is used as monomer diol B, when the a / b value is 0.970 or more and less than 1.000, the DMT conversion rate is high, the polycondensation time is short, and the PBT color tone evaluation is good.

[0113] [Table 2]

[0114] [Example 9] <Esterification reaction> A glass reactor equipped with a stirrer and a distillation tube was charged with 113 parts by mass of terephthalic acid (PTA) and 184 parts by mass of the mixed solution C-1 obtained in Example 1. The pressure in the glass reactor was reduced to approximately 100 Pa, and then the pressure was returned to atmospheric pressure with nitrogen. This operation was repeated three times to replace the atmosphere inside the reactor with nitrogen. The reactor was then immersed in an oil bath at 150°C. After confirming dissolution of the contents, the rotation speed was increased to 150 rpm. Next, a butanediol mixture containing 94% by mass of the mixed solution C-1 obtained in Example 1 and 6% by mass of tetrabutyl titanate was charged so that the titanium atom concentration relative to the resulting polybutylene terephthalate was 40 ppm by mass. The temperature of the oil bath was then increased from 150°C to 210°C over 90 minutes and maintained at 210°C for 60 minutes to obtain an ester reaction solution. 61 parts by mass of a fraction was obtained in a receiver at the end of the distillation tube.

[0115] <Polycondensation reaction> A butanediol mixture containing 90% by mass of the mixture C-1 obtained in Example 1 and 10% by mass of magnesium acetate tetrahydrate was added to the resulting esterification reaction solution so that the magnesium atom content was 12 ppm by mass relative to the resulting polybutylene terephthalate. The oil bath was heated from 210°C to 240°C over 45 minutes, and the internal pressure of the glass reaction vessel was reduced from 760 Torr to 0.5 Torr over 90 minutes to carry out a polycondensation reaction. The internal pressure was then fully evacuated, and the polycondensation reaction was terminated when the reaction vessel's agitator reached a predetermined stirring power. The reactor was then returned to a pressure of 760 Torr with nitrogen, and then the gauge pressure was increased to 1500 Torr, and polybutylene terephthalate was extracted in a strand form from the bottom of the reactor, and the strand-like polybutylene terephthalate was then pelletized using a rotary cutter to obtain pellet-like polybutylene terephthalate. The resulting pelletized polybutylene terephthalate had an intrinsic viscosity of 0.991 dL / g, and the color tone was evaluated as S with a b value of -0.5.

[0116] [Example 10] The same procedure as in Example 9 was carried out, except that 113 parts by mass of terephthalic acid (QTA) was used instead of 113 parts by mass of terephthalic acid (PTA). The resulting pelletized polybutylene terephthalate had an intrinsic viscosity of 0.995 dL / g, and the color tone was evaluated as S with a b value of 0.9.

[0117] From Examples 9 and 10, it is clear that polybutylene terephthalate having excellent color tone can be obtained according to the present invention even in the production of polybutylene terephthalate by esterification reaction using terephthalic acid.

Claims

1. A monomer diol composition comprising a mixture of two or more monomer diols, A monomer diol composition, wherein the value (a / b) obtained by dividing the measured value (a) of the amount of hydroxyl groups measured by the following measurement method by the theoretical value (b) of the amount of hydroxyl groups is 0.970 or more and less than 1.

000. <Measurement method> Step 1: Two or more types of monomer diols to be mixed are weighed to obtain the mass of each monomer diol. Step 2: The two or more monomer diols in step 1 are mixed to obtain the monomer diol composition. Step 3: From the mass of each monomer diol obtained in step 1, the theoretical value b of the hydroxyl group content of the monomer diol composition obtained in step 2 is calculated. Step 4: The monomer diol composition obtained in step 2 is subjected to NMR measurement to obtain a measured value a of the amount of hydroxyl groups in the monomer diol composition. Step 5: The measured value a of the amount of hydroxyl groups obtained in step 4 is divided by the theoretical value b of the amount of hydroxyl groups obtained in step 3 to obtain a value (a / b).

2. The monomer diol composition of claim 1 , wherein at least one of the two or more monomer diols is an alkane diol.

3. The monomer diol composition according to claim 2 , wherein the alkanediol is produced using a biomass resource as a raw material.

4. 4. The monomer diol composition of claim 3, wherein the alkanediol is an alkanediol produced by fermentation.

5. 5. The monomer diol composition of claim 4, wherein the alkanediol is an alkanediol produced by direct fermentation of sugars.

6. 4. The monomer diol composition according to claim 3, wherein the alkanediol is an alkanediol produced by hydrogen reduction of succinic acid or a succinic acid derivative produced using a biomass resource.

7. 3. The monomer diol composition of claim 2, wherein the alkanediol is an alkanediol produced by depolymerization of a polyester.

8. 8. The monomer diol composition of claim 7, wherein the polyester is polyethylene terephthalate and / or polybutylene terephthalate.

9. A method for producing a polyester, using the monomer diol composition according to any one of claims 1 to 8.

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