Polyester polyol, urethane prepolymer and polyurethane

Abstract

The present invention provides: a polyester polyol which has excellent hydrolysis resistance, while being capable of suppressing the viscosity low if used as a prepolymer; a urethane prepolymer which uses this polyester polyol; and a polyurethane.　A polyester polyol which is obtained by reacting (A) a dicarboxylic acid component and (B) a diol component with each other, and which is characterized in that: the dicarboxylic acid component (A) contains a dicarboxylic acid (a1) represented by genera formula (I) and a dicarboxylic acid (a2) represented by genera formula (II); and the content of the dicarboxylic acid (a2) in a total of 100% by mass of the dicarboxylic acid component (A) is 0.02%-3.00% by mass. (In general formulae (I) and (II), each of R1, R2, R4 and R5 independently represents a divalent hydrocarbon group having 1 to 3 carbon atoms; and each of R3 and R6 independently represents a monovalent hydrocarbon group having 1 to 3 carbon atoms.)

Description

[Technical Field]

[0001] The present invention relates to a polyester polyol that has excellent hydrolysis resistance and can reduce the viscosity of a prepolymer when used in the prepolymer, and also to a urethane prepolymer and a polyurethane using the polyester polyol. [Background technology]

[0002] Polyester polyols having hydroxyl groups at the molecular terminals have been used as polyol components for use as raw materials in paints, adhesives, foams, polyurethanes, etc. However, because polyester polyols have poor hydrolysis resistance, products using them have had the problem of their surfaces becoming sticky or cracking in a relatively short period of time.

[0003] One method for solving this problem is to use a glycol with a large number of carbon atoms and a dicarboxylic acid with a large number of carbon atoms to reduce the concentration of ester groups in the polyester polyol. However, the polyester polyol obtained by this method has a high tendency to crystallize and tends to become a highly viscous liquid or solid, which reduces workability, and also has problems such as poor flex resistance, flexibility, and low-temperature adhesiveness when used in a low-temperature atmosphere of about -20°C.

[0004] One method for solving the above-mentioned problems and achieving both viscosity and hydrolysis resistance is to introduce a branched structure into the molecule. Specifically, Patent Document 1 proposes a polyester polyol using 2-methyl-1,8-octanediol and 1,9-nonanediol as diol components. Furthermore, Patent Document 2 proposes a polyester polyol using 3-methylpentanedioic acid having a branched structure. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 182330 / 1983 [Patent Document 2] Japanese Patent Application Publication No. 60-26018 Summary of the Invention [Problem to be solved by the invention]

[0006] Although the polyester polyols described in Patent Documents 1 and 2 have excellent hydrolysis resistance, the viscosity of the urethane prepolymers using these polyols is not sufficiently low, and further improvement has been desired.

[0007] The present invention has been made in view of the above-mentioned problems in the prior art, and an object of the present invention is to provide a polyester polyol that has excellent hydrolysis resistance and that can keep the viscosity low when used in a urethane prepolymer, and a urethane prepolymer and polyurethane using the same. [Means for solving the problem]

[0008] The present inventors conducted extensive research into improving the hydrolysis resistance of polyester polyols and reducing the viscosity of urethane prepolymers made using these polyester polyols. As a result, they discovered that by adopting an unprecedented combination of a dicarboxylic acid as the main raw material, specifically 3-methylpentanedioic acid (3-methylglutaric acid) having a branched chain, in combination with a specific dicarboxylic acid, it is possible to reduce the viscosity of urethane prepolymers made using polyester polyols while maintaining the hydrolysis resistance of the polyester polyols. After further research, they completed the present invention.

[0009] That is, the present invention provides the following [1] to [5]. [1] A polyester polyol obtained by reacting a dicarboxylic acid component (A) with a diol component (B), wherein the dicarboxylic acid component (A) contains a dicarboxylic acid (a1) represented by the following general formula (I) and a dicarboxylic acid (a2) represented by the following general formula (II), A polyester polyol characterized in that the content of the dicarboxylic acid (a2) is 0.02 to 3.00% by mass relative to 100% by mass of the total amount of the dicarboxylic acid component (A).

[0010] [ka] (In the general formulas (I) and (II), R 1 , R 2 , R 4 and R 5 each independently represents a divalent hydrocarbon group having 1 to 3 carbon atoms, and R 3 and R 6 each independently represents a monovalent hydrocarbon group having 1 to 3 carbon atoms.

[0011] [2] The polyester polyol according to [1] above, wherein the content of the dicarboxylic acid component (a2) is 3.00 parts by mass or less per 100 parts by mass of the dicarboxylic acid component (a1). [3] R in the general formulas (I) and (II) 1 , R 2 , R 4 and R 5 are both methylene groups. [4] A urethane prepolymer obtained by reacting the polyester polyol according to any one of [1] to [3] above with a polyisocyanate compound. [5] A polyurethane using the polyester polyol described in any one of [1] to [3] above or the urethane prepolymer described in [4] above. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a polyester polyol that has excellent hydrolysis resistance and that can keep the viscosity low when used in a urethane prepolymer, and a urethane prepolymer and polyurethane using the same. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a graph showing the area ratio of the contents of dicarboxylic acids (a1) and (a2) contained in the dicarboxylic acid component (A) obtained in Production Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0014] [Polyester polyol] The polyester polyol of the present invention is a polyester polyol obtained by reacting a dicarboxylic acid component (A) with a diol component (B), characterized in that the dicarboxylic acid component (A) contains a dicarboxylic acid (a1) represented by the following general formula (I) and a dicarboxylic acid (a2) represented by the following general formula (II), and the content of the dicarboxylic acid (a2) in 100% by mass of the total amount of the dicarboxylic acid component (A) is 0.02 to 3.00% by mass.

[0015] [ka] (In the general formulas (I) and (II), R 1 , R 2 , R 4 and R 5 each independently represents a divalent hydrocarbon group having 1 to 3 carbon atoms, and R 3 and R 6 each independently represents a monovalent hydrocarbon group having 1 to 3 carbon atoms.

[0016] As described above, the present invention is characterized by the use of a dicarboxylic acid (a1) represented by the general formula (I) and a dicarboxylic acid (a2) represented by the general formula (II) in combination as the dicarboxylic acid component (A). In the production of typical polyester polyols, a single highly purified dicarboxylic acid is typically used as the dicarboxylic acid component. However, the present inventors attempted an unusual combination of the dicarboxylic acid (a1) and a specific amount of the dicarboxylic acid (a2). They found that this combination maintained a high level of hydrolysis resistance in the resulting polyester polyol while also reducing the viscosity of the urethane prepolymer using this polyester polyol, thereby completing the present invention. The present invention will be described in detail below.

[0017] <Dicarboxylic acid component (A)> In the present invention, the dicarboxylic acid component (A) contains a dicarboxylic acid (a1) represented by the general formula (I) above and a dicarboxylic acid (a2) represented by the general formula (II) above. [Dicarboxylic acid (a1)] The dicarboxylic acid (a1) is a dicarboxylic acid represented by the following general formula (I).

[0018] [ka]

[0019] R in general formula (I) 1 and R 2 R each independently represents a divalent hydrocarbon group having 1 to 3 carbon atoms. 1 and R 2 The hydrocarbon groups represented by R may be different from each other, but from the viewpoint of ease of production, 1 and R 2 It is preferable that R are the same hydrocarbon group. 1 and R 2 As the alkyl group, a divalent hydrocarbon group having 1 to 2 carbon atoms is preferred, and a divalent hydrocarbon group having 1 carbon atom is more preferred. In addition, R 1 and R 2may be linear or branched, and may have a substituent such as a halogen atom or a hydroxyl group.

[0020] On the other hand, R in general formula (I) 3 represents a monovalent hydrocarbon group having 1 to 3 carbon atoms, and specifically, a monovalent hydrocarbon group having 1 to 2 carbon atoms is preferred, and a methyl group, which is a monovalent hydrocarbon group having 1 carbon atom, is more preferred. In addition, R 3 may be linear or branched, and may have a substituent such as a halogen atom or a hydroxyl group. Among these, the dicarboxylic acid (a1) represented by the general formula (I) is R 1 and R 2 are all methylene groups, and R 3 is a methyl group, 3-methylglutaric acid is preferred.

[0021] 3-Methylglutaric acid can be produced, for example, by the method described in Japanese Patent Laid-Open No. 7-258148. Specifically, 3-methylglutaric acid can be produced by oxidizing one compound selected from the group consisting of β-methyl-δ-valerolactone, 2-hydroxy-4-methyltetrahydropyran, and 3-methyl-1,5-pentanediol with oxygen in the presence of an oxidation catalyst and water.

[0022] The content of dicarboxylic acid (a1) in 100% by mass of the total amount of dicarboxylic acid component (A) is preferably 97.00 to 99.98% by mass. When the content of dicarboxylic acid (a1) is 97.00% by mass or more, various physical properties of products made from polyester polyol as a raw material can be improved. On the other hand, when the content is 99.98% by mass or less, the viscosity of prepolymers using polyester polyol can be reduced. From these viewpoints, the content of the dicarboxylic acid (a1) in the total amount (100% by mass) of the dicarboxylic acid component (A) is preferably 97.50 to 99.97% by mass, more preferably 98.00 to 99.96% by mass, and even more preferably 98.50 to 99.95% by mass.

[0023] [Dicarboxylic acid (a2)] The dicarboxylic acid (a2) is a dicarboxylic acid represented by the following general formula (II). [ka]

[0024] R in general formula (II) 4 and R 5 R each independently represents a divalent hydrocarbon group having 1 to 3 carbon atoms. 4 and R 5 The hydrocarbon groups represented by R may be different from each other, but from the viewpoint of ease of production, 4 and R 5 It is preferable that R are the same hydrocarbon group. 4 and R 5 As the alkyl group, a divalent hydrocarbon group having 1 to 2 carbon atoms is preferred, and a divalent hydrocarbon group having 1 carbon atom is more preferred. In addition, R 4 and R 5 may be linear or branched, and may have a substituent such as a halogen atom or a hydroxyl group.

[0025] On the other hand, R in general formula (II) 6 represents a monovalent hydrocarbon group having 1 to 3 carbon atoms, and specifically, a monovalent hydrocarbon group having 1 to 2 carbon atoms is preferred, and a methyl group, which is a monovalent hydrocarbon group having 1 carbon atom, is more preferred. In addition, R 6 may be linear or branched, and may have a substituent such as a halogen atom or a hydroxyl group. Among these, the dicarboxylic acid (a2) represented by the general formula (II) is R 4 and R 5 are all methylene groups, and R 6 is a methyl group, 3-hydroxy-3-methylglutaric acid is preferred.

[0026] As a method for producing 3-hydroxy-3-methylglutaric acid, for example, the method described in Japanese Patent Application Laid-Open No. 60-190735 can be mentioned.

[0027] In the present invention, from the viewpoint of suppressing the viscosity of the urethane prepolymer while maintaining the hydrolysis resistance of the polyester polyol, it is preferable that the dicarboxylic acid (a1) is 3-methylglutaric acid and the dicarboxylic acid (a2) is 3-hydroxy-3-methylglutaric acid. When the dicarboxylic acid (a1) and the dicarboxylic acid (a2) are in this combination, a mixture of the dicarboxylic acid (a1) and the dicarboxylic acid (a2) is obtained by producing the dicarboxylic acid (a1) using the dicarboxylic acid (a2) as a raw material (for example, producing 3-methylglutaric acid by dehydration hydrogenation of 3-hydroxy-3-methylglutaric acid), and by purifying this mixture, it becomes possible to adjust the quantitative ratio of the dicarboxylic acid (a1) and the dicarboxylic acid (a2), facilitating the preparation of the dicarboxylic acid component (A).

[0028] The content of dicarboxylic acid (a2) in the total amount (100% by mass) of the dicarboxylic acid component (A) is 0.02 to 3.00% by mass. If the content of dicarboxylic acid (a2) is less than 0.02% by mass, the viscosity of the urethane prepolymer obtained by reacting the polyester polyol with the polyisocyanate compound cannot be reduced. On the other hand, if the content exceeds 3.00% by mass, yellowing of the obtained polyester polyol occurs. From these viewpoints, the content of the dicarboxylic acid (a2) in the total amount (100% by mass) of the dicarboxylic acid component (A) is preferably 0.03 to 2.50% by mass, more preferably 0.04 to 2.00% by mass, and even more preferably 0.05 to 1.50% by mass.

[0029] [Other dicarboxylic acids] The dicarboxylic acid component (A) used in the present invention may contain other dicarboxylic acids in addition to the dicarboxylic acid (a1) and dicarboxylic acid (a2). The other dicarboxylic acids are not particularly limited, but low molecular weight dicarboxylic acids are more preferred. Examples of low molecular weight dicarboxylic acids include aliphatic dicarboxylic acids such as succinic acid, methylsuccinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; and aromatic dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid. These dicarboxylic acids may be used alone or in combination of two or more. In the present invention, a polycarboxylic acid having three or more functional groups may be used, and when a polycarboxylic acid having three or more functional groups is used, it is treated as a dicarboxylic acid component (A).

[0030] The content of the other dicarboxylic acids contained in the total amount (100% by mass) of the dicarboxylic acid component (A) is preferably 20.0% by mass or less, more preferably 10.0% by mass or less, and even more preferably 5.0% by mass or less. When the content of the other dicarboxylic acids is the above upper limit or less, the effects based on the dicarboxylic acid component (a1) can be easily obtained. In the present invention, whether or not other dicarboxylic acids are contained, the content of the dicarboxylic acid component (a2) relative to 100 parts by mass of the dicarboxylic acid component (a1) is preferably 3.00 parts by mass or less, more preferably 2.00 parts by mass or less. The closer the content of the dicarboxylic acid component (a2) is to the upper limit, the more easily the effects based on the dicarboxylic acid component (a2) can be obtained.

[0031] <Diol component (B)> Examples of the diol component (B) used in the present invention include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 2-methyl-1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 2-methyl-1,8-octanediol, and 2,7-dimethyl-1,8-octanediol. aliphatic diols such as 1,9-nonanediol, 2-methyl-1,9-nonanediol, 2,8-dimethyl-1,9-nonanediol, 1,10-decanediol, 2,2-diethyl-1,3-propanediol, and 2-butyl-2-ethyl-1,3-propanediol; and alicyclic diols such as 1,4-cyclohexanediol, cyclohexanedimethanol, and 3 (or 4), 8 (or 9)-dihydroxytricyclo[5.2.1.02,6]decane. Among these, aliphatic diols are preferred. These diols may be used alone or in combination of two or more.

[0032] The polyester polyol of the present invention may contain an aromatic ring-containing diol such as 1,4-bis(β-hydroxyethoxy)benzene or bis(β-hydroxyethoxy)terephthalate, as long as the gist of the invention is not impaired. Also, it may contain a polyol with three or more functionalities such as trimethylolpropane, trimethylolethane, glycerin, 1,2,6-hexanetriol, or 1,2,4-butanetriol.

[0033] <Number average molecular weight of polyester polyol> The number-average molecular weight of the polyester polyol of the present invention is preferably 300 to 30,000. When the number-average molecular weight of the polyester polyol is 300 or more, the mechanical properties such as strength of the polyurethane produced using the polyester polyol are improved. On the other hand, when the number-average molecular weight of the polyester polyol is 30,000 or less, the low-temperature properties and flexibility of the polyurethane produced using the polyester polyol are improved. From these viewpoints, the number-average molecular weight of the polyester polyol is more preferably 700 to 20,000, and even more preferably 1,000 to 10,000. In the present invention, the number average molecular weight of the polyester polyol refers to a value determined by the method described in the examples.

[0034] <Number of hydroxyl groups in one polyester polyol molecule> In the present invention, the number of hydroxyl groups in one polyester polyol molecule varies depending on the application, but is preferably 2 or more per molecule. If the number is in the range of 2 to 3, the polyester can be used in the widest range of applications and is versatile.

[0035] <Method of producing polyester polyol> There is no particular limitation on the method for producing the polyester polyol of the present invention, and it can be produced by a known polycondensation method. For example, the dicarboxylic acid component (A) containing the dicarboxylic acid (a1) and the dicarboxylic acid (a2) and the diol component (B) are charged in a predetermined ratio, and subjected to an esterification or transesterification reaction. The resulting reaction product is then subjected to a polycondensation reaction at high temperature under vacuum in the presence of a polycondensation catalyst, whereby the polycarboxylic acid component (A) can be produced. The polycondensation catalyst used in the production of polyester polyol may be a known catalyst, and examples thereof include titanium compounds such as tetramethoxytitanium, tetraethoxytitanium, tetra-n-propoxytitanium, tetraisopropoxytitanium, and tetrabutoxytitanium; tin compounds such as di-n-butyltin oxide, di-n-butyltin dilaurate, and dibutyltin diacetate; and combinations of acetates of magnesium, calcium, zinc, or the like with antimony oxide or the above-mentioned titanium compounds. The amount of these polycondensation catalysts is preferably 5 to 500 ppm based on the total amount of the dicarboxylic acid component (A) and the diol component (B).

[0036] [Urethane prepolymer and polyurethane] The urethane prepolymer of the present invention is obtained by reacting the polyester polyol of the present invention with a polyisocyanate compound, and can have a lower viscosity than urethane prepolymers produced from similar raw materials. This allows for greater flexibility in subsequent formulation, and allows for, for example, better dispersibility of pigments. Furthermore, the low viscosity of the urethane prepolymer improves workability in applications such as paints, adhesives, and foams. Furthermore, the polyurethane of the present invention uses the polyester polyol or urethane prepolymer of the present invention, and is excellent in hydrolysis resistance due to the properties of the polyester polyol.

[0037] <Polyisocyanate compounds> The polyisocyanate compound used in the present invention is not particularly limited as long as it has two or more isocyanate groups in one molecule, and examples thereof include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, 1,4-phenylene diisocyanate, polymethylene polyphenylene polyisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, tolidine diisocyanate, 1,5-naphthalene diisocyanate, and triphenylmethane triisocyanate; Examples of the polyisocyanate include aliphatic polyisocyanates such as diisocyanate, trimethylhexamethylene diisocyanate, lysine diisocyanate, and norbornane diisocyanate methyl; alicyclic polyisocyanates such as transcyclohexane-1,4-diisocyanate, isophorone diisocyanate, bis(isocyanatemethyl)cyclohexane, and dicyclohexylmethane diisocyanate; carbodiimide-modified isocyanate compounds and isocyanurate-modified isocyanate compounds of these isocyanate compounds; etc. These polyisocyanate compounds may be used alone or in combination of two or more.

[0038] Among these polyisocyanate compounds, aromatic polyisocyanates and alicyclic polyisocyanates are preferred from the viewpoint of improving various physical properties such as strength of the resulting polyurethane, and liquid tolylene diisocyanate (TDI) and isophorone diisocyanate (IPDI) are more preferred from the viewpoint of reducing viscosity.

[0039] <Viscosity of urethane prepolymer> The urethane prepolymer of the present invention is obtained by reacting the polyester polyol of the present invention with a polyisocyanate compound, and can have a lower viscosity than urethane prepolymers produced from similar raw materials, specifically, a viscosity at 60°C of preferably 4,000 mPa s or less, more preferably 3,500 mPa s or less, and even more preferably 1,500 mPa s or less. When the viscosity of the urethane prepolymer at 60°C is the above upper limit or less, workability is improved in applications such as paints, adhesives, and foams. The viscosity of the urethane prepolymer at 60°C can be measured by the method described in the examples.

[0040] <Method of manufacturing urethane prepolymer> The urethane prepolymer can be produced by mixing the polyester polyol of the present invention, the polyisocyanate compound, and optional components such as a plasticizer, which are used as needed. The mixing device is not particularly limited, and examples thereof include a roll, a kneader, a pressure kneader, a Banbury mixer, a horizontal mixer (such as a Loedige mixer), a vertical mixer (such as a planetary mixer), an extruder, and a universal mixer.

[0041] Examples of the optional components include additives such as plasticizers, crosslinking agents, fillers, crosslinking accelerators, crosslinking aids, tackifiers, antioxidants, foaming agents, processing aids, adhesion imparting agents, inorganic fillers, organic fillers, crystal nucleating agents, heat stabilizers, weathering stabilizers, antistatic agents, colorants, lubricants, flame retardants, flame retardant aids (antimony oxide, etc.), anti-blooming agents, release agents, thickeners, antioxidants, and conductive agents. There are no particular restrictions on the content of optional components in the urethane prepolymer, but it is preferably 50% by mass or less, more preferably 20% by mass or less, and even more preferably 5% by mass or less.

[0042] <Polyurethane manufacturing method> There are no particular limitations on the method for producing the polyurethane of the present invention, but it is preferable to obtain it by polymerizing the above-mentioned raw materials through a urethane reaction using a known prepolymer method or one-shot method. More specifically, examples of the method include a method in which the above-mentioned components are blended in a predetermined ratio in substantially the absence of a solvent and melt-mixed using a single-screw or multi-screw extruder, followed by melt polymerization, and a method in which the components are polymerized by a prepolymer method in the presence of a solvent. The melt polymerization may be carried out continuously. The polyurethane obtained may be pelletized and then molded into a sheet-like molded article by various molding methods such as extrusion molding, injection molding, blow molding, and calendar molding. [Example]

[0043] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples. In the examples and comparative examples, the contents of the dicarboxylic acids (a1) and (a2) in the total amount of the dicarboxylic acid component (A) and the number average molecular weight of the polyester polyol were measured by the following methods. The hydrolysis resistance of the polyester polyol and the viscosity of the prepolymer were evaluated by the following methods.

[0044] <Contents of the Dicarboxylic Acids (a1) and (a2) in the Total Amount of the Dicarboxylic Acid Component (A)> The contents of the dicarboxylic acids (a1) and (a2) in the total amount of the dicarboxylic acid component (A) were calculated from the following formula using the peak areas (%) of the dicarboxylic acids (a1) and (a2) obtained by the following LC measurement. Dicarboxylic acid (a1) content (mass%)= Peak area (%) of dicarboxylic acid (a1) × 100 / (peak area (%) of dicarboxylic acid (a1) + peak area (%) of dicarboxylic acid (a2)) Dicarboxylic acid (a2) content (mass%)= Peak area (%) of dicarboxylic acid (a2) × 100 / (peak area (%) of dicarboxylic acid (a1) + peak area (%) of dicarboxylic acid (a2)) The area values ​​were measured using HPLC Prominence manufactured by Shimadzu Corporation under the following conditions. Column: L-column ODS (Chemicals Evaluation Institute, Japan (CERI), 4.6 x 150 mm) Flow rate: 1.0mL / min Injection volume: 5 μL (sample concentration: 12 mg / mL, solvent: acetonitrile) Detector: UV (220 nm) Column temperature: 40℃ Eluent A: 0.1% by mass phosphoric acid aqueous solution Eluent B: Acetonitrile Gradient: Conditions in Table 1 below Retention time (HMGA): 2.3min Retention time (MGA): 3.6min

[0045] [Table 1]

[0046] <Number average molecular weight of polyester polyol> The hydroxyl value was calculated based on the hydroxyl value of the polyester polyol obtained in the examples and comparative examples, and was measured by the phthalation method described in JIS K1557-1.

[0047] <Evaluation of Hydrolysis Resistance of Polyester Polyol> 0.5 g of the polyester polyol obtained in each of the examples and comparative examples was left in 10 ml of hot water at 100°C for 7 days. The acid values ​​of the water and polyester polyol were then measured according to JIS K1557-5:2007, and the sum of these values ​​was used as the acidity value, which was used as an index of hydrolysis resistance. A smaller acidity value indicates better hydrolysis resistance.

[0048] <Viscosity of urethane prepolymer> The viscosity at 60°C of the urethane prepolymers obtained in the examples and comparative examples was measured using a Brookfield B-type viscometer LVDV-II.

[0049] [Manufacturing example] <Production Example 1: Synthesis of 3-methylglutaric acid> According to the following method, 3-hydroxy-3-methylglutaric acid was produced, which was then used as a raw material to produce 4-methyl-3,6-dihydro-2H-pyran-2,6-dione, which was then used as a raw material to produce 3-methylglutaric acid. First, 3-hydroxy-3-methylglutaric acid was produced according to the method described in JP-A-60-190735. 300 g of the resulting 3-hydroxy-3-methylglutaric acid was placed in a three-neck flask equipped with a condenser, and 600 mL of acetyl chloride was added. The mixture was then heated to 60°C and subjected to an acetylation reaction for 5 hours. After cooling, the recovered reaction product was filtered and washed with xylene. The reaction product was then placed again in the three-neck flask, 600 mL of xylene was added, and the mixture was heated to 150°C and subjected to a deacetylation reaction under reflux for 5 hours, producing 4-methyl-3,6-dihydro-2H-pyran-2,6-dione. The reaction product was separated and obtained by crystallization upon cooling the reaction solution.

[0050] Next, 200 g of the obtained 4-methyl-3,6-dihydro-2H-pyran-2,6-dione was dissolved in 500 mL of ethanol and placed in a pressure-resistant vessel equipped with a stirrer. 2 g of commercially available 10% Pd / C was added, and the mixture was purged with nitrogen three times. The mixture was then pressurized with hydrogen to 0.3 MPa and hydrogenated for 12 hours. The catalyst was removed from the reaction mixture by filtration, and the solvent was then removed using a rotary evaporator to obtain 3-methylglutaric anhydride. Furthermore, 128 g of the obtained 3-methylglutaric anhydride was placed in a three-neck flask equipped with a condenser together with 18 g of water and 500 mL of toluene. This was heated to 70°C and stirred for 5 hours to obtain 3-methylglutaric acid by hydrolysis in the solvent. The resulting reaction product was separated by crystallization upon cooling the reaction solution. The content of 3-hydroxy-3-methylglutaric acid [dicarboxylic acid (a2)] in the obtained dicarboxylic acid component (A) was 1.28 mass%. The results of LC measurement of the obtained dicarboxylic acid component (A) are shown in Figure 1. In Figure 1, HMGA represents 3-hydroxy-3-methylglutaric acid (dicarboxylic acid (a2)), and MGA represents 3-methylglutaric acid (dicarboxylic acid (a1)).

[0051] [Examples and Comparative Examples] Example 1 [Synthesis of polyester polyol] As the dicarboxylic acid component (A) [1 mole], 146 g of the 3-methylglutaric acid obtained in Production Example 1 was prepared. The content of 3-methylglutaric acid [dicarboxylic acid (a1)] in the dicarboxylic acid component (A) was 98.72 mass%, and the content of 3-hydroxy-3-methylglutaric acid [dicarboxylic acid (a2)] was 1.28 mass%. Furthermore, 177 g (1.5 mol) of 3-methyl-1,5-pentanediol was prepared as diol component (B) and charged into a reactor. Then, the mixture was heated to 200°C under normal pressure in a nitrogen atmosphere, and an esterification reaction was carried out while distilling off the generated water from the system. When the amount of water distilled decreased, 5 mg of tetraisopropoxytitanium was added, and the reaction was continued while reducing the pressure to 200 to 100 mmHg using a vacuum pump, yielding a polyester polyol with a hydroxyl value of 56.5 KOH mg / g, an acid value of 0.05 KOH mg / g, and a number average molecular weight of 1,986. The hydrolysis resistance of the resulting polyester polyol was measured according to the method described above, and the results are shown in Table 2.

[0052] [Synthesis of prepolymer] 50 g (0.025 mol) of the obtained polyester polyol was weighed into a three-necked flask, which was then equipped with a vacuum stirrer and a mechanical stirrer, and immersed in an oil bath at 80°C. The polyester polyol was dehydrated while reducing the pressure with a vacuum pump. After dehydration for 1 hour, 8.77 g (0.05 mol) of tolylene diisocyanate ("Coronate T-65" manufactured by Tosoh Corporation) was added under a nitrogen atmosphere and mixed with stirring for 10 minutes at 80°C. The temperature was then lowered to 60°C and stirring was continued for 2 hours under a nitrogen atmosphere. The viscosity of the resulting urethane prepolymer was evaluated by measuring it using the method described above, and the results are shown in Table 2.

[0053] <Examples 2 to 5, Comparative Examples 1 to 5> Polyester polyols were produced using the dicarboxylic acid component (A) and diol component (B) shown in Table 2 in the same manner as in Example 1, and the number average molecular weights were calculated and the hydrolysis resistance was evaluated. The results are shown in Table 2. The ratio of the dicarboxylic acid (a1) to the dicarboxylic acid (a2) in the dicarboxylic acid component (A) was adjusted by the number of purifications shown in Table 2 (specifically, the number of recrystallizations from heated toluene). In addition, a urethane prepolymer was produced in the same manner as in Example 1 by using a polyisocyanate compound in the formulation shown in Table 2, and the viscosity was measured. The results are shown in Table 2. The polyester polyols obtained in Examples 1 to 5 were low-viscosity liquids at 20°C.

[0054] [Table 2] *1) Number of times dicarboxylic acid component (A) is purified

[0055] In Table 2, each component is represented by the following abbreviations. MGA: 3-methylglutaric acid HMGA: 3-hydroxy-3-methylglutaric acid MPD: 3-methyl-1,5-pentanediol TDI: Tolylene diisocyanate IPDI: Isophorone diisocyanate BD: 1,4-butanediol ADA: Adipic acid

[0056] As is clear from the results in Table 2, the polyester polyols of the examples synthesized using a dicarboxylic acid component (A) containing both dicarboxylic acid (a1) and dicarboxylic acid (a2) and containing a specific amount of dicarboxylic acid (a2) have hydrolysis resistance comparable to that of polyester polyols having a similar structure, and can also reduce the viscosity of the urethane prepolymer.

Claims

1. A polyester polyol obtained by reacting a dicarboxylic acid component (A) with a diol component (B), wherein the dicarboxylic acid component (A) contains a dicarboxylic acid (a1) represented by the following general formula (I) and a dicarboxylic acid (a2) represented by the following general formula (II): A polyester polyol characterized in that the content of the dicarboxylic acid (a2) is 0.02 to 3.00 mass% based on 100 mass% of the total amount of the dicarboxylic acid component (A). 【Chemical 1】 (In the general formulas (I) and (II), R 1 , R 2 , R 4 and R 5 each independently represents a divalent hydrocarbon group having 1 to 3 carbon atoms; R 3 and R 6 each independently represents a monovalent hydrocarbon group having 1 to 3 carbon atoms.

2. The polyester polyol according to claim 1, wherein the content of the dicarboxylic acid component (a2) relative to 100 parts by mass of the dicarboxylic acid component (a1) is 3.00 parts by mass or less.

3. R in the general formulas (I) and (II) 1 , R 2 , R 4 and R 5 The polyester polyol according to claim 1 or 2, wherein each of the is a methylene group.

4. A urethane prepolymer obtained by reacting the polyester polyol according to any one of claims 1 to 3 with a polyisocyanate compound.

5. A polyurethane using the polyester polyol according to any one of claims 1 to 3 or the urethane prepolymer according to claim 4.

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