Polyester raw material composition and method for producing polyester

Abstract

To provide a polyester raw material composition that has a high reaction rate at a start of polymerization reaction, does not require a long necessary time at a polymerization end, and can suppress yellow tone of an obtained polyester.SOLUTION: A polyester raw material composition obtained by mixing monomer diol with dicarboxylic acid or dicarboxylic acid dialkyl, where the a / b value obtained by the measurement method described below is 0.970 or more and less than 1.000. <Measurement Method>Step 1: Weigh the monomer diol and dicarboxylic acid or dicarboxylic acid dialkyl, and obtain the content ratio of monomer diol (parts by mass) in 100 parts by mass of the mixture. Step 2: Mix the monomer diol with dicarboxylic acid or dicarboxylic acid dialkyl to obtain a polyester raw material composition. Step 3: Obtain the theoretical value b of the hydroxyl amount from the content ratio of monomer diol. Step 4: Obtain the measured value a of the hydroxyl amount through NMR measurement. Step 5: Divide the measured value a of the hydroxyl amount by the theoretical value b of the hydroxyl amount to obtain the value (a / b).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyester raw material composition. More specifically, the present invention relates to a polyester raw material composition comprising a monomer diol and a dicarboxylic acid or a dialkyl dicarboxylate. The present invention also relates to a method for producing a polyester using the polyester raw material composition. [Background technology]

[0002] Polyesters are produced by esterification or transesterification of a monomer diol with a dicarboxylic acid or dialkyl dicarboxylate, followed by a polycondensation reaction. Therefore, a polyester raw material composition containing a monomer diol and a dicarboxylic acid or dialkyl dicarboxylate is used as a raw material for producing polyesters. Conventionally, the monomer diol, dicarboxylic acid, or dialkyl dicarboxylate used in producing polyester raw material compositions have been produced using petroleum (fossil fuel) as a raw material. For example, butanediol produced from butadiene produced from fossil fuels, and terephthalic acid and dimethyl terephthalate produced from paraxylene produced from fossil fuels have been used.

[0003] However, with the growing demand for building a recycling-oriented (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 derived from biomass resources such as plants, rather than from fossil fuels, 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 hydrogen reduction after producing succinic acid from biomass resources have been proposed (Patent Document 2). In addition, chemically recycled butanediol produced by depolymerizing polybutylene terephthalate using a chemical recycling method has also been proposed (for example, Patent Document 3). Furthermore, various methods have been proposed for producing terephthalic acid and dialkyl terephthalate derived from recycled resources such as waste materials such as PET bottles (Patent Document 4). [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 [Patent Document 4] Japanese Patent Application Laid-Open No. 2001-151934 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the polyester polymerization reaction using the polyester raw material composition containing a biomass resource-derived monomer diol disclosed in Patent Document 1 and Patent Document 2, or the polyester raw material composition containing recycled resource-derived terephthalic acid or dialkyl terephthalate disclosed in Patent Document 4, the reaction rate was low in the early stages of the polymerization reaction and the time required in the later stages of the polymerization reaction was long, 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 butanediol as disclosed in Patent Document 3.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a polyester raw material composition which, when used in polymerization, gives a high reaction rate in the early stage of the polymerization reaction, does not prolong the time required in the later stage of the polymerization reaction, and keeps the yellowness of the obtained polyester low; and a method for producing a polyester using the polyester raw material composition. [Means for solving the problem]

[0007] As a result of intensive investigations into solving the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by using a polyester raw material composition 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 polyester raw material composition comprising a mixture of a dicarboxylic acid or a dialkyl dicarboxylate and a monomer diol, the polyester raw material composition being a composition used as a raw material for producing a polyester, and 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: The monomer diol and the dicarboxylic acid or dialkyl dicarboxylate to be mixed are each weighed, and the content ratio of the monomer diol is determined in parts by mass when the mixture of the monomer diol and the dicarboxylic acid or dialkyl dicarboxylate is taken as 100 parts by mass. Step 2: The monomer diol and the dicarboxylic acid or dialkyl dicarboxylate in step 1 are mixed to obtain the polyester raw material composition. Step 3: Using the content ratio of the monomer diol obtained in step 1, the theoretical value b of the hydroxyl group amount of the polyester raw material composition obtained in step 2 is obtained. Step 4: The polyester raw material composition obtained in step 2 is subjected to NMR measurement to obtain a measured value a of the amount of hydroxyl groups in the polyester raw material 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 polyester raw material composition according to [1], wherein the monomer diol is an alkanediol.

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

[0011] [4] The polyester raw material composition according to [3], wherein the alkanediol is an alkanediol produced by fermentation.

[0012] [5] The polyester raw material composition according to [4], wherein the alkanediol is produced by direct fermentation of sugar.

[0013] [6] The polyester raw material composition according to [4], wherein the alkanediol is an alkanediol produced by hydrogen reduction of succinic acid or a succinic acid derivative produced using biomass resources.

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

[0015] [8] The polyester raw material composition according to [7], wherein the depolymerization of the polyester is depolymerization of polyethylene terephthalate and / or polybutylene terephthalate.

[0016] [9] The polyester raw material composition according to any one of [1] to [8], wherein the dicarboxylic acid or dialkyl dicarboxylate is produced by chemical recycling of polyester.

[0017]

[10] The polyester raw material composition according to [9], wherein the chemical recycling of the polyester is chemical recycling of polyethylene terephthalate.

[0018]

[11] The polyester raw material composition according to [9], wherein the chemical recycling of the polyester is chemical recycling of polybutylene terephthalate.

[0019]

[12] A method for producing a polyester, using the polyester raw material composition according to any one of [1] to

[11] . [Effects of the Invention]

[0020] When the polyester raw material composition of the present invention is subjected to a polymerization reaction, 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 polyester raw material composition of the present invention, high-quality polyester with little yellowing can be produced with excellent production efficiency. DETAILED DESCRIPTION OF THE INVENTION

[0021] 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.

[0022] [Polyester raw material composition] The polyester raw material composition of the present invention is characterized by being a mixture of a monomer diol and a dicarboxylic acid or a dialkyl dicarboxylate. In the present invention, "dicarboxylic acid or dialkyl dicarboxylate" is not limited to "dicarboxylic acid" or "dialkyl dicarboxylate", but includes "dicarboxylic acid and dialkyl dicarboxylate".

[0023] The polyester raw material composition of the present invention may be in the form of a slurry of a mixture of solid and liquid, but is preferably a liquid.

[0024] [Monomer diol] Examples of the monomer diol include one or more of a linear alkanediol, an alkanediol having a cyclic structure, and a bisphenol (including bisphenol).

[0025] 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.

[0026] 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.

[0027] 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, 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.

[0028] The monomer diol may be any of 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, or a mixture thereof. All of these monomer diols have the object of the present invention, and the object is solved by the present invention, 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.

[0029] The monomer diol in the polyester raw material composition of the present invention 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 one produced from a biomass resource.Also preferred as the alkanediol is an alkanediol produced by depolymerization of waste polyester.

[0030] The alkanediol such as 1,4-butanediol produced using biomass resources as raw materials is preferably an alkanediol produced by fermentation, and examples thereof include alkanediols produced by direct fermentation of sugars, and biomass-derived alkanediols such as 1,4-butanediol produced by hydrogenating succinic acid or succinic acid derivatives produced using biomass resources, such as succinic anhydride and succinic acid esters such as dialkyl succinates (more specifically, dialkyl succinates having an alkyl group with 1 to 4 carbon atoms, preferably 1 to 3, more preferably 1 to 2, and most preferably a methyl group with 1 carbon atom). Other examples include chemically recycled 1,4-butanediol obtained by depolymerizing polybutylene terephthalate and chemically recycled ethylene glycol obtained by depolymerizing polyethylene terephthalate, as described in Patent Document 3 above.

[0031] <Dicarboxylic acid or dialkyl dicarboxylate> The dicarboxylic acid is not particularly limited, and examples thereof include aromatic dicarboxylic acids such as terephthalic acid, 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. Examples of dialkyl dicarboxylates include dialkyl esters of these dicarboxylic acids in which the alkyl group has 1 to 6 carbon atoms.

[0032] These dicarboxylic acids or dialkyl dicarboxylates may be used alone or in combination of two or more.

[0033] Examples of these dicarboxylic acids or dialkyl dicarboxylates include dicarboxylic acids or dialkyl dicarboxylates produced using fossil fuels as raw materials, dicarboxylic acids or dialkyl dicarboxylates produced using biomass resources as raw materials, and dicarboxylic acids or dialkyl dicarboxylates produced by recycling waste products or defective products. All of these dicarboxylic acids or dialkyl dicarboxylates have the problems that the present invention solves, but among these, dicarboxylic acids or dialkyl dicarboxylates produced using biomass resources as raw materials and dicarboxylic acids or dialkyl dicarboxylates produced by recycling waste products or defective products are preferred. For example, the dicarboxylic acid or dialkyl dicarboxylate used in the present invention is preferably a chemically recycled polyester such as polyethylene terephthalate or polybutylene terephthalate.

[0034] [Method of producing polyester raw material composition] The method for producing the polyester raw material composition of the present invention is not particularly limited, and it can be produced by a conventional method. For example, a method can be used in which a monomer diol and a dicarboxylic acid or a dialkyl dicarboxylate are supplied to a mixing vessel equipped with a heater and a stirrer, and the mixture is heated and mixed to form a homogeneous solution, thereby obtaining the polyester raw material composition of the present invention. The heating and stirring conditions are preferably those suitable for [Procedure 1] when determining the a / b value described below.

[0035] In the polyester raw material composition of the present invention, since the composition is used as a raw material for producing a polyester, the molar ratio of the monomer diol to the dicarboxylic acid or dialkyl dicarboxylate is preferably 0.80 or more and 10 or less, more preferably 0.9 or more and 9 or less, and even more preferably 1.0 or more and 8 or less.

[0036] [value (a / b) obtained by dividing the measured value a of the hydroxyl group content of the polyester raw material composition by the theoretical value b of the hydroxyl group content of the polyester raw material composition] The polyester raw material 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: The monomer diol and the dicarboxylic acid or dialkyl dicarboxylate to be mixed are each weighed, and the content ratio of the monomer diol is determined in parts by mass when the mixture of the monomer diol and the dicarboxylic acid or dialkyl dicarboxylate is taken as 100 parts by mass. Step 2: The monomer diol and the dicarboxylic acid or dialkyl dicarboxylate in step 1 are mixed to obtain the polyester raw material composition. Step 3: Using the content ratio of the monomer diol obtained in step 1, the theoretical value b of the hydroxyl group amount of the polyester raw material composition obtained in step 2 is obtained. Step 4: The polyester raw material composition obtained in step 2 is subjected to NMR measurement to obtain a measured value a of the amount of hydroxyl groups in the polyester raw material 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).

[0037] If the a / b value of the polyester raw material composition of the present invention is small, the polymerization reaction rate decreases when this polyester raw material composition is used to produce a polyester. On the other hand, a polyester raw material composition with a large a / b value contains a polyhydric alcohol such as a triol in the polyester raw material composition, and polyesters obtained using such polyester raw material compositions form gels with a chemically crosslinked structure and are significantly thickened. From this perspective, the a / b value of the polyester raw material 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.

[0038] The a / b value of the polyester raw material composition of the present invention can be determined by the following procedure, for example, in the case of a polyester raw material composition comprising a monomer diol and a dialkyl dicarboxylate. [Step 1] After precisely weighing out the monomer diol and dialkyl dicarboxylate to mass c and mass d, respectively, these are mixed and stirred at a temperature above 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 or the dialkyl dicarboxylate, 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 ease of melting the polyester raw material composition 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 and dialkyl dicarboxylate in step 1 are set to the same ratio as the mixing ratio of the monomer diol and dialkyl dicarboxylate in the polyester raw material composition 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 integral value of the peak derived from the hydroxyl groups of the monomer diol and the integral value of the internal standard are calculated, and the integral value ratio h (=integral value of the peak derived from the hydroxyl groups of the monomer diol / 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

[0039] The method for measuring and calculating the measured value of the hydroxyl group amount has been described above for a polyester raw material composition obtained by mixing a monomer diol and a dialkyl dicarboxylate, but the same method can be used for a polyester raw material composition obtained by mixing two or more types of monomer diols and a dicarboxylic acid and / or a dialkyl dicarboxylate. Furthermore, when the monomer diol, dicarboxylic acid and / or dialkyl dicarboxylate contain unknown impurities, the measured value a of the hydroxyl group amount in the polyester raw material composition may be corrected, or the theoretical value a may be calculated without correction. When correction is performed, for example, when the monomer diol contains unknown impurities, the content of the pure monomer diol in the monomer diol is calculated using chromatography or the like, and after correction, the a / b value of the mixed solution C can be calculated.

[0040] [Polyester manufacturing method] Examples of the production method of the polyester of the present invention for producing a polyester using the polyester raw material composition of the present invention include a method in which the polyester raw material composition of the present invention is subjected to an esterification or transesterification reaction in the presence of an esterification catalyst or a transesterification catalyst.

[0041] Hereinafter, the polyester production method of the present invention will be described mainly focusing on a method for producing polybutylene terephthalate (PBT) as a polyester, when the polyester raw material composition of the present invention is a polyester raw material composition containing 1,4-butanediol (hereinafter sometimes abbreviated as "BDO") and dimethyl terephthalate. However, according to the polyester production method of the present invention, polyesters other than PBT can be produced using polyester raw material compositions other than the polyester raw material composition comprising 1,4-butanediol and dimethyl terephthalate, in the same manner as the method described below.

[0042] 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".

[0043] PBT refers to a polymer having a structure in which a dicarboxylic acid component (i.e., dicarboxylic acid and / or dialkyl dicarboxylate) and a diol component are ester-bonded, in which 50 mol % or more of the dicarboxylic acid component is a terephthalic acid component (i.e., terephthalic acid and / or dialkyl terephthalate), 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 of PBT may be difficult. The speed will decrease, resulting in deterioration of formability.

[0044] <Terephthalic acid component and diol component> In the method for producing a polyester of the present invention, the polyester raw material composition of the present invention is used as the raw material terephthalic acid component and diol component.

[0045] <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.

[0046] 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 the polyester raw material composition of the present invention, which comprises a dicarboxylic acid component mainly composed of a terephthalic acid component and a monomer diol mainly composed of BDO, and further, if necessary, other components to an esterification reaction and / or an ester exchange reaction, followed by a polycondensation reaction, and preferably further a solid-state polycondensation reaction.

[0047] 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 1 mass%, more preferably 3 mass%, and even more preferably 5 mass%, and the upper limit is preferably 50 mass%, more preferably 45 mass%, and even more preferably 40 mass%.

[0048] 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.

[0049] <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, by a step of using the polyester raw material composition of the present invention as an ester raw material liquid and heating the ester raw material liquid under normal pressure or reduced pressure to cause an ester exchange reaction to form a polyester oligomer, followed by a melt polycondensation step of gradually reducing the pressure and heating the obtained oligomer to cause a melt polycondensation reaction to obtain the 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 transesterification reaction step and polycondensation reaction step.

[0050] (Transesterification reaction process) An example of a process for subjecting the polyester raw material composition of the present invention to a transesterification reaction to produce an oligomer is a method in which a single transesterification reaction tank or a multistage reaction apparatus in which multiple transesterification reaction tanks are connected in series is used to perform the transesterification reaction under normal or reduced pressure with or without a catalyst until the transesterification reaction rate (the proportion of ester groups in the raw material dicarboxylic acid component that have reacted with the diol component and undergone a transesterification reaction) reaches typically 90% or more, while removing the alcohol produced in the reaction and excess diol component from the system, to obtain an oligomer. Generally, the temperature of the transesterification 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.

[0051] (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.

[0052] 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.

[0053] 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).

[0054] <Polycondensation catalyst> When the oligomer obtained by the above esterification reaction or transesterification reaction is polycondensed, 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 esterification or transesterification reaction and then directly subjected to the polycondensation reaction. Alternatively, they may not be used in the esterification or transesterification 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 esterification or transesterification reaction, and then appropriately added as the polycondensation reaction proceeds. In any case, in the present invention, the polyester finally obtained necessarily contains titanium and preferably also a metal of Group 2A of the Periodic Table. The content thereof will be described later.

[0055] (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.

[0056] (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.

[0057] (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.

[0058] 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.

[0059] 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.

[0060] (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.

[0061] 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.

[0062] (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.

[0063] (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.

[0064] (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.

[0065] [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.

[0066] 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.

[0067] [Compound] The polyester of the present invention is produced with excellent polymerization reaction efficiency and good productivity using the polyester raw material 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]

[0068] 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.

[0069] [Raw materials and reagents] Dimethyl terephthalate 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.

[0070] [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] 1,4-butanediol and dimethyl terephthalate were weighed out 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 was measured, and the integral value of the peak derived from the hydroxyl groups of 1,4-butanediol and the integral value of the internal standard triphenylmethane (PhC-H) were calculated, and the integral value ratio h (integral value of the peak derived from the hydroxyl groups of 1,4-butanediol / 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

[0071] <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.

[0072] <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

[0073] <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, ηsp = η / η0 - 1, where η is the number of seconds for the sample solution to drop, η0 is the number of seconds for the solvent to drop, C is the PBT concentration (g / dL) of the sample solution, and KH is the Huggins constant. KH = 0.33 was adopted.)

[0074] <PBT Color Tone> The color 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 color is preferred. However, when the b value is lower than -2.0, although the yellowish color is less, the bluish color increases and the color tone is not preferred. The evaluation criteria for the b value are 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

[0075] [Production Example of 1,4-Butanediol] <Production Example 1: 1,4-Butanediol by Hydrogenation of Succinic Acid Derived from Biomass Resources>[[]] 1,4-Butanediol manufactured by Yuanli Chemical Group Co., Ltd. and 1,4-Butanediol manufactured by Zhejiang Boju New Materials Co., Ltd., which were produced by hydrogenation of succinic acid derived from biomass resources, were mixed to obtain a mixed solution. The obtained mixed solution was distilled under reduced pressure, and from the order of distillate, a first fraction, main fraction A, main fraction B, main fraction C, main fraction D, and a post-fraction were obtained. When a part was extracted from each of the main fraction A, main fraction B, main fraction C, main fraction D, and the post-fraction and analyzed by gas chromatography, the 1,4-butanediol content in each was 99% by mass or more.)

[0076] <Production Example 2: 1,4-Butanediol by Depolymerization of PBT>[[]] Following Example 3 of JP-A-2004-323378, chemically recycled 1,4-butanediol was produced.) An autoclave equipped with a stirring blade was charged with 1,030 parts by mass of polybutylene terephthalate, 3,200 parts by mass of methanol, and 13 parts by mass of sodium carbonate. The autoclave was immersed in an oil bath at 200°C, and the mixture was reacted for 8 hours with stirring at a pressure of 1.3 MPa. The autoclave was removed from the oil bath and cooled to below 10°C with ice water to obtain a slurry. 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. Methanol and tetrahydrofuran were recovered as light-boiling fractions by atmospheric distillation, and then vacuum distillation was carried out to obtain, in 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. Portions of the obtained main fractions A to D were extracted and analyzed by gas chromatography, and it was found that the 1,4-butanediol content in each was 99% by mass or more.

[0077] [Example of chemically recycled dimethyl terephthalate production] <Production Example 3: Chemically Recycled Dimethyl Terephthalate A> Chemically recycled dimethyl terephthalate was obtained with reference to the method described in JP-A-2001-151934. A flask equipped with a fraction recovery receiver, a stirrer, and a thermometer was charged with 100 parts by mass of polyethylene terephthalate waste fiber, 400 parts by mass of ethylene glycol, and 1.5 parts by mass of sodium carbonate. The flask was immersed in an oil bath at 210°C, and the mixture was reacted for 10 hours while removing low-boiling components, yielding a depolymerization reaction solution 1. The resulting depolymerization reaction solution 1 was filtered while hot using a glass filter, yielding a filtrate 1. The obtained filtrate 1 was cooled to 25°C to obtain a slurry. The obtained slurry was subjected to solid-liquid separation using a centrifuge to obtain a crude wet cake. The obtained wet cake was washed by sprinkling ethylene glycol, and then subjected to solid-liquid separation using a centrifuge to obtain a purified wet cake. A portion of the obtained purified wet cake was extracted and analyzed by gas chromatography, and the content of bis(2-hydroxyethyl) terephthalate was found to be 90 mass% or more. 90 parts by mass of the purified wet cake containing the obtained bis(2-hydroxyethyl) terephthalate, 200 parts by mass of methanol, and 0.5 parts by mass of sodium carbonate were added to a flask equipped with a fraction recovery receiver, a stirrer, and a thermometer, and the mixture was reacted at 65°C for 1 hour to obtain reaction liquid 1. The resulting reaction liquid 1 was placed in a vacuum distillation apparatus equipped with a fraction collection receiver, a Liebig condenser, a stirrer, a thermometer, and a pressure controller. The distillation apparatus was immersed in an oil bath, and the temperature and pressure of the oil bath were controlled while monitoring the distillate. The initial fraction, main fraction, and bottoms were obtained in the order of distillation. The resulting main fraction and xylene were placed in an eggplant flask and heated to form a homogeneous solution. The solution was then cooled to room temperature for crystallization, yielding Slurry 1. The resulting Slurry 1 was filtered through a glass filter to obtain a cake. The resulting cake was placed in an eggplant flask and attached to an evaporator equipped with an oil bath. The xylene was distilled off from the cake under reduced pressure, yielding a white solid (chemically recycled dimethyl terephthalate A). A portion of the resulting white solid was extracted and analyzed by gas chromatography. The dimethyl terephthalate content was found to be 99% by mass or more.

[0078] <Production Example 4: Chemically Recycled Dimethyl Terephthalate B> Chemically recycled dimethyl terephthalate B was obtained with reference to the method described in JP-A-2004-323378. An autoclave equipped with a stirrer and a thermometer was charged with 100 parts by mass of polyethylene terephthalate waste fiber, 300 parts by mass of methanol, and 1.5 parts by mass of sodium carbonate. The autoclave was immersed in an oil bath at 150°C, and the reaction was carried out at 1.3 MPa for 10 hours. Thereafter, a distillation tube was attached to the autoclave, and the pressure was slowly reduced to normal pressure to distill off low-boiling components, thereby obtaining depolymerization reaction solution 1. After the temperature of the obtained depolymerization reaction liquid 1 was lowered to room temperature, xylene was added, and the mixture was immersed in an oil bath at 120°C to obtain slurry 1. The obtained slurry 1 was filtered through a glass filter, cooled to room temperature, and crystallized to obtain slurry 2. The obtained slurry 2 was subjected to solid-liquid separation using a centrifuge to obtain a cake. The obtained cake was placed in a flask equipped with a fraction collection receiver, a stirrer, and a thermometer, and then immersed in an oil bath. The temperature and pressure of the oil bath were controlled while monitoring the distillate, and the initial fraction, main fraction, and bottoms were obtained in the order of distillation. A portion of the obtained main fraction (chemically recycled dimethyl terephthalate B) was extracted and analyzed by gas chromatography, and the dimethyl terephthalate content was found to be 99% by mass or more.

[0079] <Production Example 5: Chemically Recycled Dimethyl Terephthalate C> Chemically recycled dimethyl terephthalate C was obtained with reference to the method described in JP-A-2001-151934. An autoclave equipped with a stirrer and thermometer was charged with 100 parts by weight of glass filler-containing polybutylene terephthalate and 200 parts by weight of methanol. The autoclave was immersed in an oil bath at 170°C and reacted at 5.5 MPa for 5 hours. The autoclave was then removed from the oil bath and cooled to room temperature to obtain depolymerization reaction solution 1. The resulting depolymerization reaction solution 1 was filtered through a glass filter to obtain a solid fraction. Tetrahydrofuran was added to the resulting solid fraction to dissolve the white solid contained in the solid fraction. The glass filler was removed as a filtrate by filtration to obtain solution 1. The resulting solution 1 was placed in a flask equipped with a fraction collection receiver, a stirrer, and a thermometer and then immersed in an oil bath. The temperature and pressure of the oil bath were controlled while monitoring the distillate, and the following fractions were obtained in the order of distillation: light-boiling components containing tetrahydrofuran, main fraction A, main fraction B, main fraction C, main fraction D, and bottoms. A portion of the obtained main fractions A to D (chemically recycled dimethyl terephthalate C) was extracted and analyzed by gas chromatography, and it was found that the content of dimethyl terephthalate in each fraction was 99 mass % or more.

[0080] [Example 1] 108.7 g (mass c) of the main fraction B obtained in Production Example 1 as the monomer diol and 191.3 g of dimethyl terephthalate as a reagent were placed in a recovery flask equipped with a stirrer. The recovery flask was then immersed in an oil bath heated to 150°C and stirred for 1 hour to obtain mixed solution C-1. The theoretical value e of the amount of hydroxyl groups per unit mass of this mixed solution C-1 was 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) =(108.7 / 90.12)×2 / (108.7+191.3) A portion of the resulting mixed solution C-1 was extracted, and 10.1 mg (mass f) was placed in an NMR tube. In addition, 10.5 mg (mass g) of triphenylmethane 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 / Ph3C-H of triphenylmethane) was found to be 1.858. 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 =(1.858×10.5×10 -3 ) / 244.33 =7.985×10 -5 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 =(108.7 / 90.12)×2 / (108.7+191.3)×(10.1×10 -3 ) =8.122×10 -5 Therefore, the a / b value is calculated as follows: a / b value = measured amount of hydroxyl groups a / theoretical amount of hydroxyl groups b =7.985×10 -5 / 8.122×10 -5 =0.983

[0081] <Conversion rate of dimethyl terephthalate> A 0.354% by mass tetrabutoxy titanate solution was prepared using the main fraction B and tetrabutoxy titanate obtained in Production Example 1. 19.2 g of the mixed solution C-1 was placed in a test tube with a stirrer and a sidearm, and the atmosphere was replaced with nitrogen. The tube was then immersed in a 150°C oil bath and melted to obtain a homogeneous solution. 1 g of a 0.354% by mass tetrabutoxy titanate solution was added thereto, and the reaction was allowed to proceed 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 was estimated to be 9.3%.

[0082] <Transesterification reaction> 207 g of the mixture C-1 was supplied to 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 butanediol mixture containing 94 mass% of the main fraction B obtained in Production Example 1 and 6 mass% of tetrabutyl titanate was supplied so that the titanium atom content was 33 mass ppm relative to the polybutylene terephthalate obtained. Thereafter, the temperature of the oil bath was raised from 150°C to 210°C over 105 minutes to obtain a transesterification reaction liquid.

[0083] <Polycondensation reaction> A butanediol mixture containing 90% by mass of the main fraction B obtained in Production Example 1 and 10% by mass of magnesium acetate tetrahydrate was supplied to the obtained transesterification reaction liquid so as to give a magnesium atom concentration of 48 ppm by mass relative to the polybutylene terephthalate obtained. A butanediol mixture containing 94% by mass of the main fraction B obtained in Production Example 1 and 6% by mass of ADK STAB AO-60 was also supplied to give a magnesium atom concentration of 530 ppm by mass relative to the polybutylene terephthalate obtained. A butanediol mixture containing 94% by mass of the main fraction B obtained in Production Example 1 and 6% by mass of tetrabutyl titanate was also supplied to give a titanium atom concentration of 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.

[0084] [Example 2] 108.5 g of the main fraction C obtained in Production Example 1 as the monomer diol and 191.4 g of dimethyl terephthalate as a reagent were placed in a recovery flask equipped with a stirrer. The recovery flask was then immersed in an oil bath heated to 150°C and stirred for 1 hour to obtain a mixed solution C-2. 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-2 and 10.6 mg of triphenylmethane as an internal standard were used, resulting in an integral value ratio h of 1.887. 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 = 1.887 × 10.6 × 10 -3 / 244.33 =8.187×10 -5 Theoretical value of hydroxyl group amount b = (108.5 / 90.12) × 2 / (108.5 + 191.3) × (10.4 × 10 -3 ) =8.353×10 -5 Therefore, the a / b value is calculated as follows: a / b value = 8.187 × 10 -5 / 8.353×10 -5 =0.980

[0085] <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 liquid C-2 was used instead of the mixed liquid C-1, and the main fraction C obtained in Production Example 1 was used instead of the main fraction B obtained in Production Example 1. As a result, the residual rate of dimethyl terephthalate was found to be 89.8% by high performance liquid chromatography, and the conversion rate of dimethyl terephthalate was estimated to be 10.2%.

[0086] <Transesterification reaction / polycondensation reaction> Polybutylene terephthalate was produced by carrying out a transesterification reaction and a polycondensation reaction in the same manner as in Example 1, except that the mixed liquid C-2 was used instead of the mixed liquid C-1 and the main fraction C obtained in Production Example 1 was used instead of the main fraction B obtained in Production Example 1. In the polycondensation reaction, the polycondensation time until the predetermined stirring power was reached was 169 minutes. The intrinsic viscosity of the obtained pelletized polybutylene terephthalate was 0.978 dL / g, and the color tone was evaluated as S with a b value of -0.2.

[0087] [Comparative Example 1] 108.8 g of the main fraction A obtained in Production Example 1 as the monomer diol and 191.5 g of dimethyl terephthalate as a reagent were placed in a recovery flask equipped with a stirrer. The recovery flask was then immersed in an oil bath heated to 150°C and stirred for 1 hour to obtain a mixed solution C-3. NMR measurement was carried out in the same manner as in Example 1, except that 10.3 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 1.912. 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 = 1.912 × 10.2 × 10 -3 / 244.33 =7.982×10 -5 Theoretical value of hydroxyl group amount b = (108.8 / 90.12) × 2 / (108.8 + 191.5) × (10.3 × 10 -3 )​ =8.282×10 -5 Therefore, the a / b value is calculated as follows: a / b value = 7.982 × 10 -5 / 8.282×10 -5 =0.964

[0088] <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, and the main fraction A obtained in Production Example 1 was used instead of the main fraction B obtained in Production Example 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%.

[0089] <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, and the main fraction A obtained in Production 1 was used instead of the main fraction B obtained in Production Example 1. In the polycondensation reaction, the polycondensation time until the predetermined stirring power was reached was 201 minutes. The intrinsic viscosity of the obtained pelletized polybutylene terephthalate was 0.981 dL / g, and the color tone was evaluated as C in terms of b value, with a b value of 3.0.

[0090] Comparative Example 2 108.5 g of the main fraction D obtained in Production Example 1 as the monomer diol and 191.6 g of dimethyl terephthalate as a reagent were placed in a recovery flask equipped with a stirrer. The recovery flask was then immersed in an oil bath heated to 150°C and stirred for 1 hour to obtain a mixed solution C-4. 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 2.131.​ 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 = 2.131 × 10.4 × 10 -3 / 244.33 =9.071×10 -5 Theoretical value of hydroxyl group amount b = (108.5 / 90.12) × 2 / (108.5 + 191.6) × (10.5 × 10 -3 ) =8.425×10 -5 Therefore, the a / b value is calculated as follows: a / b value = 9.071 x 10 -5 / 8.425×10 -5 =1.077

[0091] <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, and the main fraction D obtained in Production Example 1 was used instead of the main fraction B obtained in Production Example 1. As a result, the residual rate of dimethyl terephthalate was found to be 99.0% by high performance liquid chromatography, and the conversion rate of dimethyl terephthalate was estimated to be 1.0%.

[0092] <Transesterification reaction / polycondensation reaction> Polybutylene terephthalate was produced by carrying out a transesterification reaction and a polycondensation reaction in the same manner as in Example 1, except that the mixed liquid C-4 was used instead of the mixed liquid C-1, and the main fraction D obtained in Production Example 1 was used instead of the main fraction B obtained in Production Example 1. In the polycondensation reaction, the polycondensation time until the predetermined stirring power was reached was 222 minutes. The intrinsic viscosity of the obtained pelletized polybutylene terephthalate was 0.985 dL / g, and the color tone was evaluated as C in terms of b value, with a b value of 3.3.

[0093] Table 1 shows the a / b values, DMT (dimethyl terephthalate) conversion rates, polycondensation times, and PBT color tone evaluations of the polyester raw material compositions in Examples 1 and 2 and Comparative Examples 1 and 2. Table 1 shows that when hydrogenated BDO of biosuccinic acid is used, when the a / b value of the polyester raw material composition 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.

[0094] [Table 1]

[0095] [Example 3] 108.2 g of the main fraction B obtained in Production Example 2 as the monomer diol and 191.5 g of dimethyl terephthalate as a reagent were placed in a recovery flask equipped with a stirrer. The recovery flask was then immersed in an oil bath heated to 150°C and stirred for 1 hour to obtain a mixed solution C-5. 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 10.8 mg of triphenylmethane as an internal standard were used, and the integral value ratio h was found to be 1.834. 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 = 1.834 × 10.8 × 10 -3 / 244.33 =8.107×10 -5 Theoretical value of hydroxyl group amount b = (108.1 / 90.12) × 2 / (108.1 + 191.5) × (10.2 × 10 -3 ) =8.168×10 -5 Therefore, the a / b value is calculated as follows: a / b value = 8.107 x 10 -5 / 8.168×10 -5 =0.993

[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-5 was used instead of the mixed solution C-1, and the main fraction B obtained in Production Example 2 was used instead of the main fraction B obtained in Production Example 1. As a result, the residual rate of dimethyl terephthalate was found to be 90.5% by high performance liquid chromatography, and the conversion rate of dimethyl terephthalate was estimated to be 9.5%.

[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 liquid C-5 was used instead of the mixed liquid C-1, and the main fraction B obtained in Production Example 2 was used instead of the main fraction B obtained in Production Example 1. In the polycondensation reaction, the polycondensation time until the predetermined stirring power was reached was 172 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.

[0098] [Example 4] 108.3 g of the main fraction C obtained in Production Example 2 as the monomer diol and 190.7 g of dimethyl terephthalate as a reagent were placed in a recovery flask equipped with a stirrer. The recovery flask was then immersed in an oil bath heated to 150°C and stirred for 1 hour to obtain a mixed solution C-6. 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 10.8 mg of triphenylmethane as an internal standard were used, and the integral value ratio h=1.9651 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 = 1.911 × 10.8 × 10 -3 / 244.33 =8.447×10 -5 ​Theoretical value of hydroxyl group amount b = (108.3 / 90.12) × 2 / (108.3 + 190.7) × (10.6 × 10 -3 ) =8.521×10 -5 Therefore, the a / b value is calculated as follows: a / b value = 8.447 × 10 -5 / 8.521×10 -5 =0.991

[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, and the main fraction C obtained in Production Example 2 was used instead of the main fraction B obtained in Production Example 1. As a result, the residual rate of dimethyl terephthalate was found to be 90.8% by high performance liquid chromatography, and the conversion rate of dimethyl terephthalate was estimated to be 9.2%.

[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 liquid C-6 was used instead of the mixed liquid C-1 and the main fraction C obtained in Production Example 2 was used instead of the main fraction B obtained in Production Example 1. In the polycondensation reaction, the polycondensation time until the predetermined stirring power was reached was 178 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.

[0101] Comparative Example 3 108.1 g of the main fraction A obtained in Production Example 2 as the monomer diol and 191.3 g of dimethyl terephthalate as a reagent were placed in a recovery flask equipped with a stirrer. The recovery flask was then immersed in an oil bath heated to 150°C and stirred for 1 hour to obtain mixed solution C-7. ​NMR measurement was carried out in the same manner as in Example 1, except that 10.3 mg of a portion of the obtained mixed solution C-7 and 10.2 mg of triphenylmethane as an internal standard were used, and the integral value ratio h was found to be 1.842. 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 = 1.842 × 10.2 × 10 -3 / 244.33 =7.690×10 -5 Theoretical value of hydroxyl group amount b = (108.1 / 90.12) × 2 / (108.1 + 191.3) × (10.3 × 10 -3 ) =8.253×10 -5 Therefore, the a / b value is calculated as follows: a / b value = 7.690 x 10 -5 / 8.253×10 -5 =0.932

[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, and the main fraction A obtained in Production Example 2 was used instead of the main fraction B obtained in Production Example 1. As a result, the residual rate of dimethyl terephthalate was found to be 95.4% by high performance liquid chromatography, and the conversion rate of dimethyl terephthalate was estimated to be 4.6%.

[0103] <Transesterification reaction / polycondensation reaction> Polybutylene terephthalate was produced by carrying out transesterification and polycondensation reactions in the same manner as in Example 1, except that mixed liquid C-7 was used instead of mixed liquid C-1 and main fraction A obtained in Production Example 2 was used instead of main fraction B obtained in Production Example 1. In the polycondensation reaction, the polycondensation time until the predetermined stirring power was reached was 212 minutes. The intrinsic viscosity of the obtained pelletized polybutylene terephthalate was 0.978 dL / g, and the color tone was evaluated as C in terms of b value, with a b value of 4.2.

[0104] Comparative Example 4 108.7 g of the main fraction D obtained in Production Example 2 as the monomer diol and 191.6 g of dimethyl terephthalate as a reagent were placed in a recovery flask equipped with a stirrer. The recovery flask was then immersed in an oil bath heated to 150°C and stirred for 1 hour to obtain a mixed solution C-8. NMR measurement was carried out in the same manner as in Example 1, except that 10.8 mg of a portion of the obtained mixed solution C-8 and 10.9 mg of triphenylmethane as an internal standard were used, resulting in an integral value ratio h of 2.089. 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 = 2.089 × 10.9 × 10 -3 / 244.33 =9.319×10 -5 Theoretical value of hydroxyl group amount b = (108.7 / 90.12) × 2 / (108.7 + 191.6) × (10.8 × 10 -3 ) =8.676×10 -5 Therefore, the a / b value is calculated as follows: a / b value = 9.319 × 10 -5 / 8.676×10 -5 =1.074

[0105] <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, and the main fraction D obtained in Production Example 2 was used instead of the main fraction B obtained in Production Example 1. As a result, the residual rate of dimethyl terephthalate was found to be 96.9% by high performance liquid chromatography, and the conversion rate of dimethyl terephthalate was estimated to be 3.1%.

[0106] <Transesterification reaction / polycondensation reaction> ​Polybutylene terephthalate was produced by carrying out transesterification and polycondensation reactions in the same manner as in Example 1, except that mixed liquid C-8 was used instead of mixed liquid C-1, and main fraction D obtained in Production Example 2 was used instead of main fraction B obtained in Production Example 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 0.981 dL / g, and the color tone was evaluated as C in terms of b value, with a b value of 4.5.

[0107] Table 2 shows the a / b values, DMT (dimethyl terephthalate) conversion rates, polycondensation times, and PBT color tone evaluations of the polyester raw material compositions in Examples 3 and 4 and Comparative Examples 3 and 4. Table 2 shows that even when chemically recycled BDO obtained by depolymerizing PBT is used, when the a / b value of the polyester raw material composition 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.

[0108] [Table 2]

[0109] [Example 5] 108.3 g of petroleum-derived 1,4-butanediol as the monomer diol and 191.6 g of the main fraction B obtained in Production Example 5 as the dialkyl dicarboxylate were placed in a recovery flask equipped with a stirrer. The recovery flask was then immersed in an oil bath heated to 150°C and stirred for 1 hour to obtain mixed liquid C-9. NMR measurement was carried out in the same manner as in Example 1, except that 10.7 mg of a portion of the obtained mixed solution C-9 and 10.2 mg of triphenylmethane as an internal standard were used, resulting in an integral value ratio h of 2.033. 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 = 2.033 × 10.2 × 10 -3 ​ / 244.33 =8.4875×10 -5 Theoretical value of hydroxyl group amount b = (108.3 / 90.12) × 2 / (108.3 + 191.6) × (10.7 × 10 -3 ) =8.5752×10 -5 Therefore, the a / b value is calculated as follows: a / b value = 8.4875 x 10 -5 / 8.5752×10 -5 =0.990

[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 and petroleum-derived 1,4-butanediol was used instead of the main fraction B obtained in Production Example 1. As a result, the residual rate of dimethyl terephthalate was found to be 88.9% by high performance liquid chromatography, and the conversion rate of dimethyl terephthalate was estimated to be 11.1%.

[0111] <Transesterification reaction / polycondensation reaction> Polybutylene terephthalate was produced by carrying out a transesterification reaction and a polycondensation reaction in the same manner as in Example 1, except that mixed solution C-9 was used instead of mixed solution C-1 and petroleum-derived 1,4-butanediol was used instead of the main fraction B obtained in Production Example 1. In the polycondensation reaction, the polycondensation time until the predetermined stirring power was reached was 174 minutes. The intrinsic viscosity of the obtained pelletized polybutylene terephthalate was 0.985 dL / g, and the color tone was evaluated as S in terms of b value, with a b value of 0.6.

[0112] [Example 6] ​108.2 g of petroleum-derived 1,4-butanediol as the monomer diol and 191.7 g of the main fraction C obtained in Production Example 5 as the dialkyl dicarboxylate were placed in a recovery flask equipped with a stirrer. The recovery flask was then immersed in an oil bath heated to 150°C and stirred for 1 hour to obtain mixed liquid C-10. NMR measurement was carried out in the same manner as in Example 1, except that 10.8 mg of a portion of the obtained mixed solution C-10 and 10.1 mg of triphenylmethane as an internal standard were used, and the integral value ratio h was found to be 2.062. 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 = 2.062 × 10.1 × 10 -3 / 244.33 =8.524×10 -5 Theoretical value of hydroxyl group amount b = (108.2 / 90.12) × 2 / (108.2 + 191.7) × (10.8 × 10 -3 ) =8.647×10 -5 Therefore, the a / b value is calculated as follows: a / b value = 8.524 × 10 -5 / 8.647×10 -5 =0.986

[0113] <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 and petroleum-derived 1,4-butanediol was used instead of the main fraction B obtained in Production Example 1. As a result, the residual rate of dimethyl terephthalate was found to be 87.8% by high performance liquid chromatography, and the conversion rate of dimethyl terephthalate was estimated to be 12.2%.

[0114] <Transesterification reaction / polycondensation reaction> Polybutylene terephthalate was produced by carrying out a transesterification reaction and a 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 and petroleum-derived 1,4-butanediol was used instead of the main fraction B obtained in Production Example 1. In the polycondensation reaction, the polycondensation time until the predetermined stirring power was reached was 181 minutes. The resulting pelletized polybutylene terephthalate had an intrinsic viscosity of 0.989 dL / g, and the color tone was evaluated as S with a b value of 1.0.

[0115] Comparative Example 5 108.2 g of petroleum-derived 1,4-butanediol as the monomer diol and 191.6 g of the main fraction A obtained in Production Example 5 as the dialkyl dicarboxylate were placed in a recovery flask equipped with a stirrer. The recovery flask was then immersed in an oil bath heated to 150°C and stirred for 1 hour to obtain mixed liquid C-11. 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-11 and 10.3 mg of triphenylmethane as an internal standard were used, and the integral value ratio h was found to be 1.831. 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 = 1.831 × 10.3 × 10 -3 / 244.33 =7.719×10 -5 Theoretical value of hydroxyl group amount b = (108.2 / 90.12) × 2 / (108.2 + 191.6) × (10.1 × 10 -3 ) =8.090×10 -5 Therefore, the a / b value is calculated as follows: a / b value = 7.719 × 10 -5 / 8.090×10 -4 =0.954

[0116] <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 liquid C-11 was used instead of the mixed liquid C-1 and petroleum-derived 1,4-butanediol was used instead of the main fraction B obtained in Production Example 1. As a result, the residual rate of dimethyl terephthalate was found to be 93.8% by high performance liquid chromatography, and the conversion rate of dimethyl terephthalate was estimated to be 6.2%.

[0117] <Transesterification reaction / polycondensation reaction> Polybutylene terephthalate was produced by carrying out a transesterification reaction and a polycondensation reaction in the same manner as in Example 1, except that the mixed solution C-11 was used instead of the mixed solution C-1 and petroleum-derived 1,4-butanediol was used instead of the main fraction B obtained in Production Example 1. In the polycondensation reaction, the polycondensation time until the predetermined stirring power was reached was 216 minutes. The intrinsic viscosity of the obtained pelletized polybutylene terephthalate was 0.981 dL / g, and the color tone was evaluated as C in terms of b value, with a b value of 3.5.

[0118] Comparative Example 6 108.5 g of petroleum-derived 1,4-butanediol as the monomer diol and 191.2 g of the main fraction D obtained in Production Example 5 as the dialkyl dicarboxylate were placed in a recovery flask equipped with a stirrer. The recovery flask was then immersed in an oil bath heated to 150°C and stirred for 1 hour to obtain mixed liquid C-12. 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-11 and 10.2 mg of triphenylmethane as an internal standard were used, and the integral value ratio h was found to be 2.082. 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 = 2.082 × 10.2 × 10 -3 / 244.33 =8.692×10 -5 ​Theoretical value of hydroxyl group amount b = (108.5 / 90.12) × 2 / (108.5 + 191.2) × (10.2 × 10 -3 ) =8.195×10 -5 Therefore, the a / b value is calculated as follows: a / b value = 8.692 × 10 -5 / 8.195×10 -5 =1.061

[0119] <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 liquid C-12 was used instead of the mixed liquid C-1 and petroleum-derived 1,4-butanediol was used instead of the main fraction B obtained in Production Example 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%.

[0120] <Transesterification reaction / polycondensation reaction> Polybutylene terephthalate was produced by carrying out a transesterification reaction and a polycondensation reaction in the same manner as in Example 1, except that the mixed solution C-12 was used instead of the mixed solution C-1 and petroleum-derived 1,4-butanediol was used instead of the main fraction B obtained in Production Example 1. In the polycondensation reaction, the polycondensation time until the predetermined stirring power was reached was 204 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 4.2.

[0121] Table 3 shows the a / b values, DMT (dimethyl terephthalate) conversion rates, polycondensation times, and PBT color tone evaluations of the polyester raw material compositions in Examples 5 and 6 and Comparative Examples 5 and 6. Table 3 shows that even when chemically recycled dimethyl terephthalate is used, when the a / b value of the polyester raw material composition 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.

[0122] [Table 3]

[0123] [Example 7] 108.1 g of the main fraction B obtained in Production Example 1 as the monomer diol and 191.4 g of the main fraction B obtained in Production Example 5 as the dialkyl dicarboxylate were placed in a recovery flask equipped with a stirrer. The recovery flask was then immersed in an oil bath heated to 150°C and stirred for 1 hour to obtain mixed solution C-13. 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-13 and 10.1 mg of triphenylmethane as an internal standard were used, resulting in an integral value ratio h of 2.015. 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 = 2.015 × 10.1 × 10 -3 / 244.33 =8.330×10 -5 Theoretical value of hydroxyl group amount b = (108.1 / 90.12) × 2 / (108.1 + 191.4) × (10.5 × 10 -3 ) =8.411×10 -5 Therefore, the a / b value is calculated as follows: a / b value = 8.330 x 10 -5 / 8.411×10 -5 =0.990

[0124] <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-13 was used instead of the mixed solution C-1. As a result, the residual rate of dimethyl terephthalate was found to be 90.5% by high performance liquid chromatography, and the conversion rate of dimethyl terephthalate was estimated to be 9.5%.

[0125] <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-13 was used instead of the mixed solution C-1. In the polycondensation reaction, the polycondensation time until the predetermined stirring power was reached was 174 minutes. The resulting pelletized polybutylene terephthalate had an intrinsic viscosity of 0.987 dL / g, and the color tone had a b value of 0.1, with the b value being evaluated as S.

[0126] [Example 8] 108.2 g of the main fraction B obtained in Production Example 1 as the monomer diol and 191.7 g of the main fraction C obtained in Production Example 5 as the dialkyl dicarboxylate were placed in a recovery flask equipped with a stirrer. The recovery flask was then immersed in an oil bath heated to 150°C and stirred for 1 hour to obtain mixed liquid C-14. 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-14 and 10.5 mg of triphenylmethane as an internal standard were used, and the integral value ratio h was found to be 1.872. 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 = 1.872 × 10.5 × 10 -3 / 244.33 =8.045×10 -5 Theoretical value of hydroxyl group amount b = (108.2 / 90.12) × 2 / (108.2 + 191.7) × (10.1 × 10 -3 ) =8.087×10 -5 ​Therefore, the a / b value is calculated as follows: a / b value = 8.045 × 10 -5 / 8.087×10 -5 =0.995

[0127] <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-14 was used instead of the mixed solution C-1. As a result, the residual rate of dimethyl terephthalate was found to be 90.4% by high performance liquid chromatography, and the conversion rate of dimethyl terephthalate was estimated to be 9.6%.

[0128] <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-14 was used instead of the mixed solution C-1. In the polycondensation reaction, the polycondensation time until the predetermined stirring power was reached was 173 minutes. The intrinsic viscosity of the obtained pelletized polybutylene terephthalate was 0.992 dL / g, and the color tone was evaluated as S with a b value of 0.4.

[0129] Comparative Example 7 108.5 g of the main fraction B obtained in Production Example 1 as the monomer diol and 191.5 g of the main fraction A obtained in Production Example 5 as the dialkyl dicarboxylate were placed in a recovery flask equipped with a stirrer. The recovery flask was then immersed in an oil bath heated to 150°C and stirred for 1 hour to obtain a mixed solution C-15. 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-15 and 10.2 mg of triphenylmethane as an internal standard were used, and the integral value ratio h was found to be 1.871. 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 = 1.871 × 10.2 × 10 -3 / 244.33​ =7.811×10 -5 Theoretical value of hydroxyl group amount b = (108.2 / 90.12) × 2 / (108.2 + 191.7) × (10.1 × 10 -3 ) =8.087×10 -5 Therefore, the a / b value is calculated as follows: a / b value = 7.811 x 10 -5 / 8.087×10 -5 =0.966

[0130] <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-15 was used instead of the mixed solution C-1. As a result, the residual rate of dimethyl terephthalate was found to be 96.5% by high performance liquid chromatography, and the conversion rate of dimethyl terephthalate was estimated to be 3.5%.

[0131] <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-15 was used instead of the mixed solution C-1. In the polycondensation reaction, the polycondensation time until the predetermined stirring power was reached was 222 minutes. The intrinsic viscosity of the obtained pelletized polybutylene terephthalate was 0.996 dL / g, and the color tone was evaluated as C in terms of b value, with a b value of 4.5.

[0132] [Comparative Example 8] 108.2 g of the main fraction B obtained in Production Example 2 as the monomer diol and 191.2 g of the main fraction D obtained in Production Example 5 as the dialkyl dicarboxylate were placed in a recovery flask equipped with a stirrer. The recovery flask was then immersed in an oil bath heated to 150°C and stirred for 1 hour to obtain a mixed solution C-16. ​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-16 and 10.4 mg of triphenylmethane as an internal standard were used, resulting in an integral value ratio h of 1.991. 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 = 1.991 × 10.4 × 10 -3 / 244.33 =8.475×10 -5 Theoretical value of hydroxyl group amount b = (108.2 / 90.12) × 2 / (108.2 + 191.2) × (10.1 × 10 -3 ) =8.100×10 -5 Therefore, the a / b value is calculated as follows: a / b value = 8.475 x 10 -5 / 8.100×10 -5 =1.046

[0133] <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-16 was used instead of the mixed solution C-1. As a result, the residual rate of dimethyl terephthalate was found to be 96.8% by high performance liquid chromatography, and the conversion rate of dimethyl terephthalate was estimated to be 3.2%.

[0134] <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-16 was used instead of the mixed solution C-1. In the polycondensation reaction, the polycondensation time until the predetermined stirring power was reached was 232 minutes. The intrinsic viscosity of the obtained pelletized polybutylene terephthalate was 0.991 dL / g, and the color tone was evaluated as C in terms of b value, with a b value of 4.8.

[0135] Table 4 shows the a / b values, DMT (dimethyl terephthalate) conversion rates, polycondensation times, and PBT color tone evaluations of the polyester raw material compositions in Examples 7 to 8 and Comparative Examples 7 to 8. Table 4 shows that even when BDO obtained by hydrogenating succinic acid derived from biomass resources and chemically recycled dimethyl terephthalate are used, when the a / b value of the polyester raw material composition 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.

[0136] [Table 4]

[0137] [Example 9] 108.6 g of the main fraction B obtained in Production Example 2 as the monomer diol and 191.7 g of the main fraction B obtained in Production Example 5 as the dialkyl dicarboxylate were placed in a recovery flask equipped with a stirrer. The recovery flask was then immersed in an oil bath heated to 150°C and stirred for 1 hour to obtain mixed liquid C-17. 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-17 and 10.3 mg of triphenylmethane as an internal standard were used, and the integral value ratio h=1.981 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 = 1.981 × 10.3 × 10 -3 / 244.33 =8.351×10 -5 Theoretical value of hydroxyl group amount b = (108.6 / 90.12) × 2 / (108.6 + 191.7) × (10.5 × 10 -3 ) =8.427×10 -5 Therefore, the a / b value is calculated as follows: a / b value = 8.107 x 10 -5 / 8.168×10 -5 ​=0.991

[0138] <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-17 was used instead of the mixed solution C-1, and the main fraction B obtained in Production Example 2 was used instead of the main fraction B obtained in Production Example 1. As a result, the residual rate of dimethyl terephthalate was found to be 91.1% by high performance liquid chromatography, and the conversion rate of dimethyl terephthalate was estimated to be 8.9%.

[0139] <Transesterification reaction / polycondensation reaction> Polybutylene terephthalate was produced by carrying out transesterification and polycondensation reactions in the same manner as in Example 1, except that mixed liquid C-17 was used instead of mixed liquid C-1 and main fraction B obtained in Production Example 2 was used instead of main fraction B obtained in Production Example 1. In the polycondensation reaction, the polycondensation time until the predetermined stirring power was reached was 181 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.

[0140] [Example 10] 108.1 g of the main fraction B obtained in Production Example 2 as the monomer diol and 191.2 g of the main fraction C obtained in Production Example 5 as the dialkyl dicarboxylate were placed in a recovery flask equipped with a stirrer. The recovery flask was then immersed in an oil bath heated to 150°C and stirred for 1 hour to obtain a mixed liquid C-18. NMR measurement was carried out in the same manner as in Example 1, except that 10.3 mg of a portion of the obtained mixed solution C-18 and 10.5 mg of triphenylmethane as an internal standard were used, and the integral value ratio h=1.911 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 = 1.911 × 10.5 × 10 -3 / 244.33 =8.212×10​-5 Theoretical value of hydroxyl group amount b = (108.1 / 90.12) × 2 / (108.1 + 191.2) × (10.3 × 10 -3 ) =8.256×10 -5 Therefore, the a / b value is calculated as follows: a / b value = 8.212 × 10 -5 / 8.256×10 -5 =0.995

[0141] <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-18 was used instead of the mixed solution C-1, and the main fraction B obtained in Production Example 2 was used instead of the main fraction B obtained in Production Example 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%.

[0142] <Transesterification reaction / polycondensation reaction> Polybutylene terephthalate was produced by carrying out transesterification and polycondensation reactions in the same manner as in Example 1, except that mixed solution C-18 was used instead of mixed solution C-1, and main fraction B obtained in Production Example 2 was used instead of main fraction B obtained in Production Example 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 0.982 dL / g, and the color tone was evaluated as b value of 0.9 and S.

[0143] Comparative Example 9 108.7 g of the main fraction B obtained in Production Example 2 as the monomer diol and 191.5 g of the main fraction A obtained in Production Example 5 as the dialkyl dicarboxylate were placed in a recovery flask equipped with a stirrer. The recovery flask was then immersed in an oil bath heated to 150°C and stirred for 1 hour to obtain a mixed liquid C-19.​ 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-19 and 10.6 mg of triphenylmethane as an internal standard were used, and the integral value ratio h=1.828 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 = 1.828 × 10.6 × 10 -3 / 244.33 =7.931×10 -5 Theoretical value of hydroxyl group amount b = (108.7 / 90.12) × 2 / (108.7 + 191.5) × (10.2 × 10 -3 ) =8.196×10 -5 Therefore, the a / b value is calculated as follows: a / b value = 7.931 x 10 -5 / 8.196×10 -5 =0.968

[0144] <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-19 was used instead of the mixed solution C-1, and the main fraction B obtained in Production Example 2 was used instead of the main fraction B obtained in Production Example 1. As a result, the residual rate of dimethyl terephthalate was found to be 97.7% by high performance liquid chromatography, and the conversion rate of dimethyl terephthalate was estimated to be 2.3%.

[0145] <Transesterification reaction / polycondensation reaction> Polybutylene terephthalate was produced by carrying out transesterification and polycondensation reactions in the same manner as in Example 1, except that mixed liquid C-19 was used instead of mixed liquid C-1 and main fraction B obtained in Production Example 2 was used instead of main fraction B obtained in Production Example 1. In the polycondensation reaction, the polycondensation time until the predetermined stirring power was reached was 212 minutes. The intrinsic viscosity of the obtained pelletized polybutylene terephthalate was 0.979 dL / g, and the color tone was evaluated as C in terms of b value, with a b value of 5.1.

[0146] [Comparative Example 10] 108.5 g of the main fraction B obtained in Production Example 2 as the monomer diol and 191.3 g of the main fraction D obtained in Production Example 5 as the dialkyl dicarboxylate were placed in a recovery flask equipped with a stirrer. The recovery flask was then immersed in an oil bath heated to 150°C and stirred for 1 hour to obtain mixed solution C-20. NMR measurement was carried out in the same manner as in Example 1, except that 10.9 mg of a portion of the obtained mixed solution C-20 and 10.8 mg of triphenylmethane as an internal standard were used, resulting in an integral value ratio h of 2.047. 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 = 2.047 × 10.8 × 10 -3 / 244.33 =9.048×10 -5 Theoretical value of hydroxyl group amount b = (108.5 / 90.12) × 2 / (108.5 + 191.3) × (10.9 × 10 -3 ) =8.755×10 -5 Therefore, the a / b value is calculated as follows: a / b value = 9.048 x 10 -5 / 8.755×10 -5 =1.033

[0147] <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-20 was used instead of the mixed solution C-1, and the main fraction B obtained in Production Example 2 was used instead of the main fraction B obtained in Production Example 1. As a result, the residual rate of dimethyl terephthalate was found to be 97.2% by high performance liquid chromatography, and the conversion rate of dimethyl terephthalate was estimated to be 2.8%. ​

[0148] <Transesterification reaction / polycondensation reaction> Polybutylene terephthalate was produced by carrying out transesterification and polycondensation reactions in the same manner as in Example 1, except that mixed liquid C-20 was used instead of mixed liquid C-1, and main fraction B obtained in Production Example 2 was used instead of main fraction B obtained in Production Example 1. In the polycondensation reaction, the polycondensation time until the predetermined stirring power was reached was 218 minutes. The intrinsic viscosity of the obtained pelletized polybutylene terephthalate was 0.988 dL / g, and the color tone was evaluated as C in terms of b value, with a b value of 5.2.

[0149] Table 5 shows the a / b values, DMT (dimethyl terephthalate) conversion rates, polycondensation times, and PBT color tone evaluations of the polyester raw material compositions in Examples 9 to 10 and Comparative Examples 9 to 10. Table 5 shows that even when chemically recycled BDO and chemically recycled dimethyl terephthalate obtained by depolymerization of PBT are used, when the a / b value of the polyester raw material composition 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.

[0150] [Table 5]

[0151] [Example 11] 108.4 g of the main fraction B obtained in Production Example 1 as the monomer diol and 191.6 g of chemically recycled dimethyl terephthalate A obtained in Production Example 3 were placed in a recovery flask equipped with a stirrer. The recovery flask was then immersed in an oil bath heated to 150°C and stirred for 1 hour to obtain mixed solution C-21. NMR measurement was carried out in the same manner as in Example 1, except that 10.3 mg of a portion of the obtained mixed solution C-21 and 10.2 mg of triphenylmethane as an internal standard were used, and the integral value ratio h was found to be 1.967. ​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 = 1.967 × 10.2 × 10 -3 / 244.33 =8.212×10 -5 Theoretical value of hydroxyl group amount b = (108.4 / 90.12) × 2 / (108.4 + 191.6) × (10.3 × 10 -3 ) =8.260×10 -5 Therefore, the a / b value is calculated as follows: a / b value = 8.212 × 10 -5 / 8.260×10 -5 =0.994

[0152] <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-21 was used instead of the mixed solution C-1. As a result, the residual rate of dimethyl terephthalate was found to be 90.5% by high performance liquid chromatography, and the conversion rate of dimethyl terephthalate was estimated to be 9.5%.

[0153] <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-21 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 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 0.3.

[0154] [Example 12] ​108.1 g of the main fraction B obtained in Production Example 1 as the monomer diol and 191.3 g of chemically recycled dimethyl terephthalate B obtained in Production Example 4 as the dialkyl dicarboxylate were placed in a recovery flask equipped with a stirrer. The recovery flask was then immersed in an oil bath heated to 150°C and stirred for 1 hour to obtain mixed solution C-22. 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-22 and 10.1 mg of triphenylmethane as an internal standard were used, and the integral value ratio h was found to be 1.956. 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 = 1.956 × 10.1 × 10 -3 / 244.33 =8.086×10 -5 Theoretical value of hydroxyl group amount b = (108.1 / 90.12) × 2 / (108.1 + 191.3) × (10.2 × 10 -3 ) =8.173×10 -5 Therefore, the a / b value is calculated as follows: a / b value = 8.086 x 10 -5 / 8.173×10 -5 =0.989

[0155] <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-22 was used instead of the mixed solution C-1. As a result, the residual rate of dimethyl terephthalate was found to be 90.7% by high performance liquid chromatography, and the conversion rate of dimethyl terephthalate was estimated to be 9.3%.

[0156] <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-22 was used instead of the mixed solution C-1. In the polycondensation reaction, the polycondensation time until the predetermined stirring power was reached was 181 minutes. The intrinsic viscosity of the obtained pelletized polybutylene terephthalate was 0.985 dL / g, and the color tone was evaluated as S with a b value of 0.2.

[0157] Table 6 shows the a / b values, DMT (dimethyl terephthalate) conversion rates, polycondensation times, and PBT color tone evaluations of the polyester raw material compositions in Examples 11 and 12. Table 6 shows that even when BDO obtained by hydrogenating succinic acid derived from biomass resources and chemically recycled dimethyl terephthalate obtained by depolymerizing polyethylene terephthalate are used, when the a / b value of the polyester raw material composition 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.

[0158] [Table 6]

Claims

1. A polyester raw material composition comprising a mixture of a dicarboxylic acid or a dialkyl dicarboxylate and a monomer diol, The polyester raw material composition is a composition used as a raw material for producing a polyester, and A polyester raw material composition, wherein a / b, the ratio of a measured value of a hydroxyl group amount measured by the following measurement method, divided by a theoretical value of a hydroxyl group amount, is 0.970 or more and less than 1.

000. <Measurement method> Step 1: The monomer diol and the dicarboxylic acid or dialkyl dicarboxylate to be mixed are each weighed, and the content ratio of the monomer diol is determined in parts by mass relative to 100 parts by mass of the mixture of the monomer diol and the dicarboxylic acid or dialkyl dicarboxylate. Step 2: The monomer diol and the dicarboxylic acid or dialkyl dicarboxylate in Step 1 are mixed to obtain the polyester raw material composition. Step 3: Using the content ratio of the monomer diol obtained in Step 1, the theoretical value b of the hydroxyl group amount of the polyester raw material composition obtained in Step 2 is calculated. Step 4: The polyester raw material composition obtained in step 2 is subjected to NMR measurement to obtain a measured value a of the amount of hydroxyl groups in the polyester raw material 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. 2. The polyester raw material composition according to claim 1, wherein the monomer diol is an alkane diol.

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

4. 4. The polyester raw material composition according to claim 3, wherein the alkanediol is produced by fermentation.

5. 5. The polyester raw material composition according to claim 4, wherein the alkanediol is produced by direct fermentation of sugar.

6. 5. The polyester raw material composition according to claim 4, wherein the alkanediol is produced by hydrogen reduction of succinic acid or a succinic acid derivative produced using a biomass resource.

7. 3. The polyester raw material composition according to claim 2, wherein the alkanediol is produced by depolymerization of a polyester.

8. 8. The polyester raw material composition according to claim 7, wherein the depolymerization of the polyester is depolymerization of polyethylene terephthalate and / or polybutylene terephthalate.

9. 2. The polyester raw material composition according to claim 1, wherein the dicarboxylic acid or dialkyl dicarboxylate is produced by chemical recycling of polyester.

10. 10. The polyester raw material composition according to claim 9, wherein the chemical recycling of the polyester is chemical recycling of polyethylene terephthalate.

11. The polyester raw material composition according to claim 9, wherein the chemical recycling of the polyester is chemical recycling of polybutylene terephthalate.

12. A method for producing a polyester, using the polyester raw material composition according to any one of claims 1 to 11.

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