JP6035240B2 - Pentaerythritol tetraester - Google Patents

Description

  The present invention relates to a tetraester of pentaerythritol used for industrial lubricating oil such as refrigerator oil.

  In recent years, hydrofluorocarbons (HFCs) having zero ozone depletion coefficient and lower global warming potential (GWP) have been used as refrigerants for refrigerators. Difluoromethane refrigerant (HFC-32) is a refrigerant that currently uses GWP [R-410A (mixture of difluoromethane and pentafluoroethane), R-407C (difluoromethane, pentafluoroethane, 1,1,1 , 2-tetrafluoroethane, etc.)] and the coefficient of performance (COP) is improved by about 5 to 13% relative to R-410A, R-407C, etc. It is a preferable refrigerant from the viewpoint of energy saving (Non-Patent Document 1).

  Patent Document 1 discloses an ester of pentaerythritol and a fatty acid used in a refrigerating machine oil for a difluoromethane refrigerant, but the compatibility of the ester with the difluoromethane refrigerant is not sufficient.

JP 2002-129177 A

“Lubrication Economy”, June 2004 (No. 460), p. 17

  An object of the present invention is to provide a pentaester of pentaerythritol used for refrigerating machine oil or the like having excellent compatibility with a difluoromethane refrigerant.

The present invention provides the following [1] to [9].
[1] A mixed ester of pentaerythritol and carboxylic acid, wherein the carboxylic acid contains butaric acid, 3,5,5-trimethylhexanoic acid, and an aliphatic carboxylic acid having 5 to 7 carbon atoms. ester.
[2] The tetraester of pentaerythritol according to [1], wherein the carboxylic acid comprises butyric acid, 3,5,5-trimethylhexanoic acid, and an aliphatic carboxylic acid having 5 to 7 carbon atoms.
[3] The tetraester of pentaerythritol according to [1] or [2], wherein the aliphatic carboxylic acid having 5 to 7 carbon atoms is a branched aliphatic carboxylic acid having 5 or 6 carbon atoms.
[4] The tetraester of pentaerythritol according to any one of [1] to [3], wherein the aliphatic carboxylic acid having 5 to 7 carbon atoms is 2-methylbutyric acid.
[5] The tetraester of pentaerythritol according to any one of [1] to [3], wherein the aliphatic carboxylic acid having 5 to 7 carbon atoms is 3-methylbutyric acid.
[6] The tetraester of pentaerythritol according to any one of [1] to [3], wherein the aliphatic carboxylic acid having 5 to 7 carbon atoms is 2-methylpentanoic acid.
[7] The tetraester of pentaerythritol according to [1] or [2], wherein the aliphatic carboxylic acid having 5 to 7 carbon atoms is a linear aliphatic carboxylic acid having 5 to 7 carbon atoms.
[8] The tetraester of pentaerythritol according to any one of [1], [2], and [7], wherein the aliphatic carboxylic acid having 5 to 7 carbon atoms is pentanoic acid.
[9] The tetraester of pentaerythritol according to any of [1] to [8], wherein the kinematic viscosity at 100 ° C. is in the range of 4.6 to 8.2 mm ² / sec.

  According to the present invention, it is possible to provide a pentaerythritol tetraester used for refrigerating machine oil or the like having excellent compatibility with a difluoromethane refrigerant.

  The tetraester of pentaerythritol of the present invention is a mixed ester of pentaerythritol and a carboxylic acid containing butyric acid, 3,5,5-trimethylhexanoic acid, and an aliphatic carboxylic acid having 5 to 7 carbon atoms. Here, the tetraester of pentaerythritol means a compound obtained by esterification using a plurality of carboxylic acids that form an ester with respect to pentaerythritol.

The “mixed ester” as used in the present invention includes the following (i) to (vi):
(I) Tetraester of pentaerythritol whose constituent carboxylic acid in the same molecule contains butyric acid, 3,5,5-trimethylhexanoic acid, and aliphatic carboxylic acid having 5 to 7 carbon atoms (ii) The constituent carboxylic acid in the same molecule Tetraester of pentaerythritol containing two selected from the group of butyric acid, 3,5,5-trimethylhexanoic acid, and aliphatic carboxylic acids having 5 to 7 carbon atoms (iii) carboxylic acid containing pentaerythritol and butyric acid (Iv) Tetraester of pentaerythritol and carboxylic acid containing 3,5,5-trimethylhexanoic acid (v) of pentaerythritol and carboxylic acid containing an aliphatic carboxylic acid having 5 to 7 carbon atoms Tetraester (vi) two or more tetra selected from the group of (i) to (v) above Each aspect of the mixture of ester and the like (except carboxylic acid constituting the mixed ester, butyric acid, 3,5,5-trimethyl hexanoic acid, and the aliphatic carboxylic acids having 5 to 7 carbon atoms).
The pentaerythritol tetraester of the present invention may contain a pentaerythritol triester as an impurity.

  In the present invention, by using butyric acid, 3,5,5-trimethylhexanoic acid and an aliphatic carboxylic acid having 5 to 7 carbon atoms as the carboxylic acid, compatibility with the difluoromethane refrigerant is improved, and a wide range of temperatures can be obtained. The viscosity change in the range can be reduced.

  The carboxylic acid constituting the mixed ester may contain other carboxylic acids other than butyric acid, 3,5,5-trimethylhexanoic acid, and aliphatic carboxylic acids having 5 to 7 carbon atoms. Examples of other carboxylic acids include acetic acid, propionic acid, octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid and other linear aliphatic carboxylic acids, 2-methylheptanoic acid, Branched fats such as 2-ethylhexanoic acid, 3-ethylhexanoic acid, 2-ethyl-2-methylpentanoic acid, 2-methyloctanoic acid, 2,2-dimethylheptanoic acid, isodecanoic acid, isotridecanoic acid and isostearic acid Group carboxylic acid and the like.

  The content of other carboxylic acids in the carboxylic acid containing butyric acid, 3,5,5-trimethylhexanoic acid, and aliphatic carboxylic acid having 5 to 7 carbon atoms is such that the tetraester of pentaerythritol of the present invention has a low temperature. It may be in a range that does not impair excellent characteristics such as fluidity and compatibility with a difluoromethane refrigerant. Molar ratio of other carboxylic acid to the sum of butyric acid, 3,5,5-trimethylhexanoic acid and aliphatic carboxylic acid having 5 to 7 carbon atoms [other carboxylic acid / (butyric acid, 3,5,5-trimethylhexane Acid and aliphatic carboxylic acid having 5 to 7 carbon atoms) ratio] is preferably in the range of 0/100 to 5/100.

  In the present invention, the carboxylic acid constituting the mixed ester is more preferably composed of butyric acid, 3,5,5-trimethylhexanoic acid, and an aliphatic carboxylic acid having 5 to 7 carbon atoms.

  Examples of the aliphatic carboxylic acid having 5 to 7 carbon atoms constituting the tetraester of pentaerythritol of the present invention include a linear aliphatic carboxylic acid having 5 to 7 carbon atoms or a branched aliphatic carboxylic acid having 5 to 7 carbon atoms. It is done. Specific examples of the linear aliphatic carboxylic acid having 5 to 7 carbon atoms include pentanoic acid, hexanoic acid and heptanoic acid. Among them, pentanoic acid or hexanoic acid is preferable, and pentanoic acid is more preferable. Examples of the branched aliphatic carboxylic acid having 5 to 7 carbon atoms include 2-methylbutyric acid, 3-methylbutyric acid, a mixture of 2-methylbutyric acid and 3-methylbutyric acid, 2,2-dimethylpropionic acid, 2-methylpentanoic acid, Examples include 2-ethylbutyric acid, 2-methylhexanoic acid, 3-methylhexanoic acid, and neoheptanoic acid. Among them, 2-methylbutyric acid, 3-methylbutyric acid, a mixture of 2-methylbutyric acid and 3-methylbutyric acid, or 2-methyl Pentanoic acid is preferred, and 2-methylbutyric acid or 3-methylbutyric acid is more preferred.

  The aliphatic carboxylic acid having 5 to 7 carbon atoms constituting the tetraester of pentaerythritol of the present invention is one aliphatic carboxylic acid selected from aliphatic carboxylic acids having 5 to 7 carbon atoms, or 5 to 5 carbon atoms. It is a mixture of two or more carboxylic acids selected from 7 aliphatic carboxylic acids. Among them, one aliphatic carboxylic acid selected from aliphatic carboxylic acids having 5 to 7 carbon atoms is preferable.

  The aliphatic carboxylic acid having 5 to 7 carbon atoms may be a branched aliphatic carboxylic acid having 5 or 6 carbon atoms. Examples of the branched aliphatic carboxylic acid having 5 or 6 carbon atoms include branched aliphatic carboxylic acids having 5 or 6 carbon atoms among the branched aliphatic carboxylic acids having 5 to 7 carbon atoms.

  When the aliphatic carboxylic acid having 5 to 7 carbon atoms is pentanoic acid, hexanoic acid, heptanoic acid, 2-methylbutyric acid, 3-methylbutyric acid, 2-methylpentanoic acid or 2-ethylbutyric acid, the pentaerythritol of the present invention Tetraesters have a good balance of compatibility with difluoromethane refrigerant in a wide range of concentrations, excellent properties such as viscosity-temperature characteristics, low-temperature fluidity, low-temperature characteristics, and sufficient stability.

  When the aliphatic carboxylic acid having 5 to 7 carbon atoms constituting the tetraester of pentaerythritol of the present invention is pentanoic acid, 2-methylbutyric acid, 3-methylbutyric acid or 2-methylpentanoic acid, butyric acid and 3,5,5 Molar ratio of pentanoic acid, 2-methylbutyric acid, 3-methylbutyric acid or 2-methylpentanoic acid to the sum of 5-trimethylhexanoic acid [(pentanoic acid, 2-methylbutyric acid, 3-methylbutyric acid or 2-methylpentanoic acid ) / (Butyric acid and 3,5,5-trimethylhexanoic acid) ratio] is preferably in the range of 5/100 to 250/100.

  When the tetraester of the present invention is used as a lubricating oil, if the viscosity of the tetraester is too low, wear tends to increase and the life of equipment using the lubricating oil tends to be shortened, while the viscosity of the tetraester is high. If the amount is too high, the coefficient of friction tends to increase and the energy efficiency tends to decrease. Therefore, the tetraester is required to have an appropriate viscosity range. The tetraester of the present invention is a 3,5,5-trimethylhexanoic acid with respect to the sum of butyric acid, 3,5,5-trimethylhexanoic acid and an aliphatic carboxylic acid having 5 to 7 carbon atoms from the viewpoint of an appropriate viscosity range. The molar ratio [3,5,5-trimethylhexanoic acid / (butyric acid, 3,5,5-trimethylhexanoic acid and aliphatic carboxylic acid having 5 to 7 carbon atoms)] of 15/100 to 65/100 A range is preferred.

  The tetraester of pentaerythritol of the present invention includes, for example, pentaerythritol, butyric acid, 3,5,5-trimethylhexanoic acid, an aliphatic carboxylic acid having 5 to 7 carbon atoms, and optionally other carboxylic acid. It can manufacture by making it react at 120-250 degreeC for 5 to 60 hours.

  A catalyst may be used in the reaction, and examples of the catalyst include mineral acids, organic acids, Lewis acids, organic metals, solid acids and the like. Specific examples of the mineral acid include hydrochloric acid, hydrofluoric acid, sulfuric acid, phosphoric acid, nitric acid and the like. Specific examples of the organic acid include p-toluenesulfonic acid, benzenesulfonic acid, butanesulfonic acid, propanesulfonic acid, ethanesulfonic acid, methanesulfonic acid and the like. Specific examples of the Lewis acid include boron trifluoride, aluminum chloride, tin tetrachloride, titanium tetrachloride and the like. Specific examples of the organic metal include tetrapropoxy titanium, tetrabutoxy titanium, tetrakis (2-ethylhexyloxy) titanium, and the like. Specific examples of the solid acid include a cation exchange resin.

  The sum of the amount of butyric acid used, the amount of 3,5,5-trimethylhexanoic acid, the amount of aliphatic carboxylic acid having 5 to 7 carbon atoms and the amount of other carboxylic acid used is the hydroxyl group of pentaerythritol used. The amount is preferably 1.1 to 1.4 times mol.

  A solvent may be used in the reaction, and examples of the solvent include hydrocarbon solvents such as benzene, toluene, xylene, hexane, heptane, isohexane, isooctane, isononane, and decane.

  It is preferable to carry out the reaction while removing water produced by the reaction from the reaction mixture. When water generated by the reaction is removed from the reaction mixture, butyric acid and / or an aliphatic carboxylic acid having 5 to 7 carbon atoms may be removed from the reaction mixture at the same time.

  Further, from the reactivity difference between butyric acid, 3,5,5-trimethylhexanoic acid and aliphatic carboxylic acid having 5 to 7 carbon atoms with respect to pentaerythritol, butyric acid constituting the obtained tetraester and 3,5,5 The molar ratio of 5-trimethylhexanoic acid to an aliphatic carboxylic acid having 5 to 7 carbon atoms may differ from that in the amount used to produce the tetraester.

  After the reaction, the pentaerythritol tetraester of the present invention is a method usually used in organic synthetic chemistry (washing with water and / or alkaline aqueous solution, treatment with activated carbon, adsorbent, etc., various chromatographic methods, if necessary) It may be purified by a distillation method or the like.

  The tetraester of pentaerythritol of the present invention is excellent in compatibility with not only a conventional difluoromethane mixed solvent (R-410A, R-407C) but also a difluoromethane refrigerant alone. Further, it has excellent low temperature fluidity, excellent low temperature characteristics, sufficient viscosity-temperature characteristics, excellent lubricity, sufficient stability, and the like.

  Moreover, the compatibility with a difluoromethane refrigerant is generally expressed using a two-layer separation temperature. It can be said that the lower the two-layer separation temperature, the better the compatibility on the low temperature side. When the tetraester is used in refrigerating machine oil, for example, when the tetraester is added to the refrigerant at 10%, the two-layer separation temperature is preferably −10 ° C. or lower, more preferably −20 ° C. or lower. preferable. The compatibility of the ester with the refrigerant has a correlation with the property of the ester.

The viscosity-temperature characteristic is a change in kinematic viscosity with respect to a temperature change of an oil agent such as a lubricating oil. Good viscosity-temperature characteristics means that the viscosity change is small with respect to temperature changes, while poor ones mean that the viscosity increases rapidly in the low temperature range and the kinematic viscosity becomes lower than expected in the high temperature range. It is a thing. Generally, this characteristic is expressed as a viscosity index, and it can be said that the higher the numerical value, the better the viscosity-temperature characteristic. When used in an oil agent such as a lubricating oil, the viscosity index is preferably 80 or more, and more preferably 90 or more.
The viscosity characteristic in a low temperature region is also called low temperature fluidity, and is expressed by a pour point, a freezing point, a channel point, and the like.

  The pour point refers to the lowest temperature at which the oil agent flows when the oil agent such as lubricating oil is cooled according to the method of Japanese Industrial Standard (JIS) K2269. An oil agent with a low pour point does not deteriorate its fluidity even in low temperature environments such as in winter or in cold regions, or when operating as an evaporator in a refrigerator at low temperatures when used as refrigeration oil. It is preferable in that it does not cause malfunction of the equipment using the device.

  In addition, when storing or using an oil agent such as lubricating oil for a long period of time in a place where the temperature difference is large, an oil agent that has no volatility in the high temperature range and does not solidify or precipitate in the low temperature range is preferable. Although there is no restriction | limiting in particular as a temperature range, The oil agent which can be used stably at about -20 degreeC at about 150 degreeC in a high temperature side and a low temperature side is preferable. The characteristic that solidification and precipitation do not occur in the low temperature range is defined as the low temperature characteristic.

  Stability includes, for example, thermal stability, oxidation stability, oxidation / hydrolysis stability, shear stability and the like in lubricating oil applications.

  Examples of lubricity include friction reduction, wear reduction, extreme pressure, and the like.

When the tetraester of pentaerythritol of the present invention is used in a refrigerating machine oil, the kinematic viscosity at 100 ° C. of the tetraester is preferably in the range of 4.6 to 8.2 mm ² / sec, 5.6 to 8.2 mm. More preferably, it is in the range of ² / sec.

  When the tetraester of pentaerythritol of the present invention is used in refrigerating machine oil, if the residual amount of hydroxyl groups of the tetraester is large, the refrigerating machine oil becomes cloudy at a low temperature and undesired phenomena occur such as blocking the refrigeration cycle capillary device. Therefore, the hydroxyl value of the mixed ester is preferably 10 mgKOH / g or less, and more preferably 5 mgKOH / g or less.

  The pentaerythritol tetraester of the present invention is used for refrigeration machine oils, engine oils, gear oils, motor oils used in hybrid cars and electric cars, grease, metal parts cleaning agents, plasticizers, etc. Can do.

  Examples of the refrigerating machine oil using the pentaerythritol tetraester of the present invention include a refrigerating machine oil containing a pentaerythritol tetraester and an additive for lubricating oil. In the refrigerating machine oil using the tetraester of pentaerythritol of the present invention, the tetraester is used as a lubricating oil base oil.

  Examples of additives for lubricating oil include antioxidants, wear reducing agents (antiwear agents, anti-seizure agents, extreme pressure agents, etc.), friction modifiers, acid scavengers, metal deactivators, and antifoaming agents. And the like which are usually used as lubricating oil additives. The content of these additives is preferably 0.001 to 5% by weight in the refrigerating machine oil.

  You may use together the tetraester of the pentaerythritol of this invention, and another lubricating base oil. Examples of other lubricating base oils include mineral oils and synthetic base oils.

  Examples of the mineral oil include paraffinic crude oil, intermediate crude oil, and naphthenic crude oil. Further, refined oils obtained by refining them by distillation or the like can also be used.

  Synthetic base oils include, for example, poly-α-olefins (polybutene, polypropylene, α-olefin oligomers having 8 to 14 carbon atoms, etc.), aliphatic esters (fatty acid monoesters, polyhydric alcohols) other than the tetraesters of the present invention. Fatty acid ester, aliphatic polybasic acid ester, etc.), aromatic ester (aromatic monoester, aromatic ester of polyhydric alcohol, aromatic polybasic acid ester, etc.), polyalkylene glycol, polyvinyl ether, polyphenyl ether, alkylbenzene , Carbonate, synthetic naphthene and the like.

  The tetraester of pentaerythritol of the present invention is excellent in the ability to dissolve additives for lubricating oil such as metal deactivators such as benzotriazole and silicone antifoaming agents. The additive for lubricating oil is used by being dissolved in the lubricating oil, for example, in order to extend the life of the lubricating oil, equipment using the lubricating oil, and the like. The lubricating oil additive generally has low solubility in pentaerythritol ester (Japanese Patent Laid-Open No. 10-259394). Benzotriazole has low solubility in mineral oil and / or synthetic oil (Japanese Patent Laid-Open No. 59-189195). However, for example, the solubility (25 ° C.) of benzotriazole in tetraester 4 (Example 4 described later) which is a tetraester of pentaerythritol of the present invention is 0.030 g / g or more. Also exhibits high solubility of benzotriazole. On the other hand, the solubility (25 ° C.) of benzotriazole in tetraester A (Comparative Example 1 described later) was 0.021 g / g. The pentaerythritol tetraester of the present invention has excellent low-temperature fluidity and excellent wear resistance when benzotriazole is dissolved.

EXAMPLES Hereinafter, although an Example, a comparative example, and a test example demonstrate this invention further more concretely, it is not limited to a following example.
The nuclear magnetic resonance spectrum was measured by the following measuring instrument and measuring method.
Measuring instrument: GSX-400 (400 MHz) manufactured by JEOL Ltd.
Measurement method: ¹ H-NMR, standard (tetramethylsilane), solvent (CDCl ₃ )

For each of the pentaesters of pentaerythritol produced in Examples 1 to 9 and Comparative Example 1 below, nuclear magnetic resonance spectra were measured, butyric acid, 3,5,5-trimethylhexanoic acid and 2 in the tetraester of pentaerythritol. -The molar ratio with methylbutyric acid was calculated by the following formula.
Butyric acid / 3,5,5-trimethylhexanoic acid / 2-methylbutyric acid = (integrated value of peak X / 2) / integrated value of peak Y / (integrated value of peak Q / 2)
Here, the peak X corresponds to the peak of the hydrogen atom on the methylene group at the β-position of the carbonyl group in butyric acid, the peak Y corresponds to the hydrogen atom on the methine group in 3,5,5-trimethylhexanoic acid, and the peak Q Corresponds to the peak of a hydrogen atom on the methylene group at the β-position of the carbonyl group in 2-methylbutyric acid.

For each of the tetraesters of pentaerythritol produced in Examples 10 and 11 below, the nuclear magnetic resonance spectrum was measured, butyric acid, 3,5,5-trimethylhexanoic acid and 3-methylbutyric acid in the tetraester of pentaerythritol Was calculated by the following formula.
Butyric acid / 3,5,5-trimethylhexanoic acid / 3-methylbutyric acid = (integrated value of peak X / 2) / (integrated value of peak Z / 2) / (integrated value of peak R / 2)
Here, peak X has the same meaning as above, peak Z corresponds to the peak of the hydrogen atom on the methylene group at the γ position of the carbonyl group in 3,5,5-trimethylhexanoic acid, and peak R in 3-methylbutyric acid. This corresponds to the peak of the hydrogen atom on the methylene group at the α-position of the carbonyl group.

For the pentaesters of pentaerythritol produced in Examples 12 to 15 below, the nuclear magnetic resonance spectrum was measured, and the molar ratio of butyric acid, 3,5,5-trimethylhexanoic acid and pentanoic acid in the tetraester of pentaerythritol was determined. The following formula was used for calculation.
Butyric acid / 3,5,5-trimethylhexanoic acid / pentanoic acid = (integrated value of peak X / 2) / integrated value of peak Y / (integrated value of peak S / 2)
Here, the peak X and the peak Y have the same meanings as described above, and the peak S corresponds to a hydrogen atom peak on the methylene group at the γ-position of the carbonyl group in pentanoic acid.

For each of the tetraesters of pentaerythritol produced in Examples 16 to 22 below, the nuclear magnetic resonance spectrum was measured, butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylpentanoic acid in the tetraester of pentaerythritol were measured. The molar ratio was calculated by the following formula.
Butyric acid / 3,5,5-trimethylhexanoic acid / 2-methylpentanoic acid = (integrated value of peak X / 2) / integrated value of peak Y / integrated value of peak T Here, peak X and peak Y are as defined above. And peak T corresponds to the peak of the hydrogen atom on the methine group in 2-methylpentanoic acid.

About the pentaester of pentaerythritol produced in the following Example 23, a nuclear magnetic resonance spectrum was measured, and the molar ratio of butyric acid, 3,5,5-trimethylhexanoic acid and 2-ethylbutyric acid in the tetraester of pentaerythritol was determined. The following formula was used for calculation.
Butyric acid / 3,5,5-trimethylhexanoic acid / 2-ethylbutyric acid = (integrated value of peak X / 2) / integrated value of peak Y / (integrated value of peak U / 4)
Here, the peak X and the peak Y have the same meaning as described above, and the peak U corresponds to the peak of a hydrogen atom on the β-position methylene group of the carbonyl group in 2-ethylbutyric acid.

For the tetraester of pentaerythritol produced in Example 24 below, the nuclear magnetic resonance spectrum was measured, and the molar ratio of butyric acid, 3,5,5-trimethylhexanoic acid and hexanoic acid in the tetraester of pentaerythritol was as follows: Calculated by the formula.
Butyric acid / 3,5,5-trimethylhexanoic acid / hexanoic acid = (integrated value of peak X / 2) / integrated value of peak Y / (integrated value of peak V / 4)
Here, the peak X and the peak Y have the same meaning as described above, and the peak V corresponds to the peak of the hydrogen atom on the γ-position and δ-position methylene group of hexanoic acid.

For the tetraester of pentaerythritol produced in Example 25 below, the nuclear magnetic resonance spectrum was measured, and the molar ratio of butyric acid, 3,5,5-trimethylhexanoic acid and heptanoic acid in the tetraester of pentaerythritol was as follows: Calculated by the formula.
Butyric acid / 3,5,5-trimethylhexanoic acid / heptanoic acid = (integrated value of peak X / 2) / integrated value of peak Y / (integrated value of peak W / 6)
Here, the peak X and the peak Y have the same meaning as described above, and the peak W corresponds to the peak of the hydrogen atom on the γ-position, δ-position and ε-position methylene group of heptanoic acid.

[Example 1]
[Pentaerythritol with a molar ratio of butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylbutyric acid (butyric acid / 3,5,5-trimethylhexanoic acid / 2-methylbutyric acid ratio) of 80/20/7 Production of tetraester (tetraester 1)]
As an adsorbent, Kyoward 500 manufactured by Kyowa Chemical Industry Co., Ltd. was used.
As activated carbon, Shirahige P manufactured by Nippon Enviro Chemicals was used.
In a reactor equipped with a Dean-Stark trap, 325 g of pentaerythritol (2.4 mol, manufactured by Guangei Perstorp), 727 g of butyric acid (8.3 mol, manufactured by Tokyo Kasei Co., Ltd.), 362 g of 3,5,5-trimethylhexanoic acid (2 3 mol, manufactured by Kyowa Hakko Chemical Co., Ltd.) and 94 g of 2-methylbutyric acid (0.9 mol, manufactured by Wako Pure Chemical Industries, Ltd.), and the mixture was removed by bubbling nitrogen at room temperature for 30 minutes while stirring the mixture. I worried.
The mixture was then stirred at 151-225 ° C. for 23 hours with nitrogen bubbling. After the reaction, the reaction product was stirred at 207 ° C. for 1 hour under a reduced pressure of 0.1 kPa to distill off unreacted carboxylic acid in the reaction product. The reaction product was washed for 2 hours at 88 ° C. with 400 mL of an aqueous alkaline solution containing sodium hydroxide twice as much as the acid value of the reaction product. The reaction product was then washed 3 times with 400 mL of water at 61 ° C. for 1 hour. Subsequently, the reaction product was dried at 116 ° C. for 2 hours under a reduced pressure of 0.1 kPa while performing nitrogen bubbling to dry the reaction product.
8.0 g of adsorbent (corresponding to 0.7% of the reaction product) and 5.7 g of activated carbon (corresponding to 0.5% of the reaction product) are added to the reaction product, and nitrogen bubbling is performed. The reaction product was stirred at 111 ° C. for 2 hours under a reduced pressure of 0.1 kPa, and then filtered using a filter aid to obtain 938 g of tetraester 1.

[Example 2]
[Pentaerythritol whose molar ratio of butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylbutyric acid (butyric acid / 3,5,5-trimethylhexanoic acid / 2-methylbutyric acid ratio) is 69/31/59 Production of tetraester (tetraester 2)]
The molar ratio of pentaerythritol, butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylbutyric acid used (pentaerythritol / butyric acid / 3,5,5-trimethylhexanoic acid / 2-methylbutyric acid ratio) is 1 / The tetraester 2 was obtained in the same manner as in Example 1 except that the ratio was changed to 1.92 / 0.96 / 1.92.

[Example 3]
[Pentaerythritol whose molar ratio of butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylbutyric acid (butyric acid / 3,5,5-trimethylhexanoic acid / 2-methylbutyric acid ratio) is 38/62/224 Production of tetraester (tetraester 3)]
The molar ratio of pentaerythritol, butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylbutyric acid used (pentaerythritol / butyric acid / 3,5,5-trimethylhexanoic acid / 2-methylbutyric acid ratio) is 1 / The tetraester 3 was obtained in the same manner as in Example 1 except that the ratio was changed to 0.38 / 0.96 / 3.46.

[Example 4]
[Pentaerythritol with a molar ratio of butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylbutyric acid (butyric acid / 3,5,5-trimethylhexanoic acid / 2-methylbutyric acid ratio) of 25/75/138 Production of tetraester (tetraester 4)]
The molar ratio of pentaerythritol, butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylbutyric acid used (pentaerythritol / butyric acid / 3,5,5-trimethylhexanoic acid / 2-methylbutyric acid ratio) is 1 / The tetraester 4 was obtained in the same manner as in Example 1 except that the ratio was 0.45 / 1.35 / 3.00.

[Example 5]
[Pentaerythritol whose molar ratio of butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylbutyric acid (butyric acid / 3,5,5-trimethylhexanoic acid / 2-methylbutyric acid ratio) is 46/54/33 Production of tetraester (tetraester 5)]
The molar ratio of pentaerythritol, butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylbutyric acid used (pentaerythritol / butyric acid / 3,5,5-trimethylhexanoic acid / 2-methylbutyric acid ratio) is 1 / The tetraester 5 was obtained in the same manner as in Example 1 except that the ratio was 1.44 / 1.92 / 1.44.

[Example 6]
[Pentaerythritol with a molar ratio of butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylbutyric acid (butyric acid / 3,5,5-trimethylhexanoic acid / 2-methylbutyric acid ratio) of 32/68/92 Production of tetraester (tetraester 6)]
The molar ratio of pentaerythritol, butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylbutyric acid used (pentaerythritol / butyric acid / 3,5,5-trimethylhexanoic acid / 2-methylbutyric acid ratio) is 1 / The tetraester 6 was obtained in the same manner as in Example 1 except that the ratio was 0.72 / 1.68 / 2.40.

[Example 7]
[Pentaerythritol with a molar ratio of butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylbutyric acid (butyric acid / 3,5,5-trimethylhexanoic acid / 2-methylbutyric acid ratio) of 41/59/8 Production of tetraester (tetraester 7)]
The molar ratio of pentaerythritol, butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylbutyric acid used (pentaerythritol / butyric acid / 3,5,5-trimethylhexanoic acid / 2-methylbutyric acid ratio) is 1 / The tetraester 7 was obtained in the same manner as in Example 1 except that the ratio was 1.62 / 3.00 / 0.18.

[Example 8]
[Pentaerythritol whose molar ratio of butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylbutyric acid (butyric acid / 3,5,5-trimethylhexanoic acid / 2-methylbutyric acid ratio) is 25/75/33 Production of tetraester (tetraester 8)]
The molar ratio of pentaerythritol, butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylbutyric acid used (pentaerythritol / butyric acid / 3,5,5-trimethylhexanoic acid / 2-methylbutyric acid ratio) is 1 / The tetraester 8 was obtained in the same manner as in Example 1 except that the ratio was 0.90 / 3.00 / 0.90.

[Example 9]
[Pentaerythritol with a molar ratio of butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylbutyric acid (butyric acid / 3,5,5-trimethylhexanoic acid / 2-methylbutyric acid ratio) of 23/77/54 Production of tetraester (tetraester 9)]
The molar ratio of pentaerythritol, butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylbutyric acid used (pentaerythritol / butyric acid / 3,5,5-trimethylhexanoic acid / 2-methylbutyric acid ratio) is 1 / The tetraester 9 was obtained in the same manner as in Example 1 except that the ratio was 0.72 / 2.40 / 1.68.

[Example 10]
[Pentaerythritol with a molar ratio of butyric acid, 3,5,5-trimethylhexanoic acid and 3-methylbutyric acid (butyric acid / 3,5,5-trimethylhexanoic acid / 3-methylbutyric acid ratio) of 62/38/37 Production of tetraester (tetraester 10)]
Instead of 2-methylbutyric acid, 3-methylbutyric acid was used, and the molar ratio of pentaerythritol, butyric acid, 3,5,5-trimethylhexanoic acid and 3-methylbutyric acid used (pentaerythritol / butyric acid / 3,5,5) The tetraester 10 was obtained in the same manner as in Example 1 except that -trimethylhexanoic acid / 3-methylbutyric acid ratio) was 1 / 2.16 / 1.20 / 1.44.

[Example 11]
[Pentaerythritol in which the molar ratio of butyric acid, 3,5,5-trimethylhexanoic acid and 3-methylbutyric acid (butyric acid / 3,5,5-trimethylhexanoic acid / 3-methylbutyric acid ratio) is 36/64/76 Production of tetraester (tetraester 11)]
Instead of 2-methylbutyric acid, 3-methylbutyric acid was used, and the molar ratio of pentaerythritol, butyric acid, 3,5,5-trimethylhexanoic acid and 3-methylbutyric acid used (pentaerythritol / butyric acid / 3,5,5) The tetraester 11 was obtained in the same manner as in Example 1 except that -trimethylhexanoic acid / 3-methylbutyric acid ratio) was changed to 1 / 0.72 / 1.68 / 2.40.

[Example 12]
[Tetraester of pentaerythritol with a molar ratio of butyric acid, 3,5,5-trimethylhexanoic acid and pentanoic acid (butyric acid / 3,5,5-trimethylhexanoic acid / pentanoic acid ratio) of 63/37/65 (tetra Production of ester 12)]
Using pentanoic acid instead of 2-methylbutyric acid, the molar ratio of pentaerythritol, butyric acid, 3,5,5-trimethylhexanoic acid and pentanoic acid used (pentaerythritol / butyric acid / 3,5,5-trimethylhexanoic acid) The tetraester 12 was obtained in the same manner as in Example 1 except that the ratio (pentanoic acid ratio) was changed to 1 / 1.92 / 0.96 / 1.92.

[Example 13]
[Tetraester of pentaerythritol with a molar ratio of butyric acid, 3,5,5-trimethylhexanoic acid and pentanoic acid (butyric acid / 3,5,5-trimethylhexanoic acid / pentanoic acid ratio) of 56/44/57 (tetra Production of ester 13)]
Using pentanoic acid instead of 2-methylbutyric acid, the molar ratio of pentaerythritol, butyric acid, 3,5,5-trimethylhexanoic acid and pentanoic acid used (pentaerythritol / butyric acid / 3,5,5-trimethylhexanoic acid) The tetraester 13 was obtained in the same manner as in Example 1 except that the ratio / pentanoic acid ratio was 1 / 1.63 / 1.54 / 1.63.

[Example 14]
[Tetraester of pentaerythritol with a molar ratio of butyric acid, 3,5,5-trimethylhexanoic acid and pentanoic acid (butyric acid / 3,5,5-trimethylhexanoic acid / pentanoic acid ratio) of 49/51/41 (tetra Production of ester 14)]
Using pentanoic acid instead of 2-methylbutyric acid, the molar ratio of pentaerythritol, butyric acid, 3,5,5-trimethylhexanoic acid and pentanoic acid used (pentaerythritol / butyric acid / 3,5,5-trimethylhexanoic acid) The tetraester 14 was obtained in the same manner as in Example 1 except that the ratio of / pentanoic acid was changed to 1 / 1.39 / 2.02 / 1.39.

[Example 15]
[Tetraester of pentaerythritol with a molar ratio of butyric acid, 3,5,5-trimethylhexanoic acid and pentanoic acid (butyric acid / 3,5,5-trimethylhexanoic acid / pentanoic acid ratio) of 33/67/32 (tetra Production of ester 15)]
Using pentanoic acid instead of 2-methylbutyric acid, the molar ratio of pentaerythritol, butyric acid, 3,5,5-trimethylhexanoic acid and pentanoic acid used (pentaerythritol / butyric acid / 3,5,5-trimethylhexanoic acid) The tetraester 15 was obtained in the same manner as in Example 1 except that the ratio (pentanoic acid ratio) was 1 / 1.08 / 2.64 / 1.08.

[Example 16]
[Pentas having a molar ratio of butyric acid to 3,5,5-trimethylhexanoic acid to 2-methylpentanoic acid (ratio of butyric acid / 3,5,5-trimethylhexanoic acid / 2-methylpentanoic acid) of 81/19/6 Production of tetraester of erythritol (tetraester 16)]
Using 2-methylpentanoic acid instead of 2-methylbutyric acid, the molar ratio of pentaerythritol, butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylpentanoic acid used (pentaerythritol / butyric acid / 3,5 , 5-trimethylhexanoic acid / 2-methylpentanoic acid ratio) was changed to 1 / 3.46 / 0.96 / 0.38, and was operated in the same manner as in Example 1 to obtain the tetraester 16.

[Example 17]
[Pentas having a molar ratio of butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylpentanoic acid (butyric acid / 3,5,5-trimethylhexanoic acid / 2-methylpentanoic acid ratio) of 71/29/53 Production of tetraester of erythritol (tetraester 17)]
Using 2-methylpentanoic acid instead of 2-methylbutyric acid, the molar ratio of pentaerythritol, butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylpentanoic acid used (pentaerythritol / butyric acid / 3,5 , 5-trimethylhexanoic acid / 2-methylpentanoic acid ratio) was changed to 1 / 1.92 / 0.96 / 1.92 to give tetraester 17 in the same manner as in Example 1.

[Example 18]
[Pentarate in which the molar ratio of butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylpentanoic acid (ratio of butyric acid / 3,5,5-trimethylhexanoic acid / 2-methylpentanoic acid) is 33/67/237 Production of tetraester of erythritol (tetraester 18)]
Using 2-methylpentanoic acid instead of 2-methylbutyric acid, the molar ratio of pentaerythritol, butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylpentanoic acid used (pentaerythritol / butyric acid / 3,5 , 5-trimethylhexanoic acid / 2-methylpentanoic acid ratio) was changed to 1 / 0.38 / 0.96 / 3.46 in the same manner as in Example 1 to obtain tetraester 18.

[Example 19]
[Pentarate having a molar ratio of butyric acid, 3,5,5-trimethylhexanoic acid to 2-methylpentanoic acid (ratio of butyric acid / 3,5,5-trimethylhexanoic acid / 2-methylpentanoic acid) of 31/69/105 Production of tetraester of erythritol (tetraester 19)]
Using 2-methylpentanoic acid instead of 2-methylbutyric acid, the molar ratio of pentaerythritol, butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylpentanoic acid used (pentaerythritol / butyric acid / 3,5 , 5-trimethylhexanoic acid / 2-methylpentanoic acid ratio) was changed to 1 / 0.72 / 1.68 / 2.40, and was operated in the same manner as in Example 1 to obtain tetraester 19.

[Example 20]
[Pentarate having a molar ratio of butyric acid to 3,5,5-trimethylhexanoic acid to 2-methylpentanoic acid (ratio of butyric acid / 3,5,5-trimethylhexanoic acid / 2-methylpentanoic acid) of 43/57/32 Production of tetraester of erythritol (tetraester 20)]
Using 2-methylpentanoic acid instead of 2-methylbutyric acid, the molar ratio of pentaerythritol, butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylpentanoic acid used (pentaerythritol / butyric acid / 3,5 , 5-trimethylhexanoic acid / 2-methylpentanoic acid ratio) was changed to 1 / 1.44 / 1.92 / 1.44 to give tetraester 20 in the same manner as in Example 1.

[Example 21]
[Pentarate whose molar ratio of butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylpentanoic acid (butyric acid / 3,5,5-trimethylhexanoic acid / 2-methylpentanoic acid ratio) is 36/64/6 Production of tetraester of erythritol (tetraester 21)]
Using 2-methylpentanoic acid instead of 2-methylbutyric acid, the molar ratio of pentaerythritol, butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylpentanoic acid used (pentaerythritol / butyric acid / 3,5 , 5-trimethylhexanoic acid / 2-methylpentanoic acid ratio) was changed to 1 / 1.62 / 3.00 / 0.18, and was operated in the same manner as in Example 1 to obtain the tetraester 21.

[Example 22]
[Pentarate in which the molar ratio of butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylpentanoic acid (butyric acid / 3,5,5-trimethylhexanoic acid / 2-methylpentanoic acid ratio) is 26/74/19 Production of tetraester of erythritol (tetraester 22)]
Using 2-methylpentanoic acid instead of 2-methylbutyric acid, the molar ratio of pentaerythritol, butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylpentanoic acid used (pentaerythritol / butyric acid / 3,5 , 5-trimethylhexanoic acid / 2-methylpentanoic acid ratio) was changed to 1 / 0.90 / 3.00 / 0.90, and was operated in the same manner as in Example 1 to obtain the tetraester 22.

[Example 23]
[Pentaerythritol whose molar ratio of butyric acid, 3,5,5-trimethylhexanoic acid and 2-ethylbutyric acid (butyric acid / 3,5,5-trimethylhexanoic acid / 2-ethylbutyric acid ratio) is 35/65/40 Production of tetraester (tetraester 23)]
2-ethylbutyric acid is used instead of 2-methylbutyric acid, and the molar ratio of pentaerythritol, butyric acid, 3,5,5-trimethylhexanoic acid and 2-ethylbutyric acid used (pentaerythritol / butyric acid / 3,5,5) The tetraester 23 was obtained in the same manner as in Example 1 except that -trimethylhexanoic acid / 2-ethylbutyric acid ratio) was changed to 1 / 1.20 / 2.00 / 1.60.

[Example 24]
[Tetraester of pentaerythritol whose molar ratio of butyric acid, 3,5,5-trimethylhexanoic acid and hexanoic acid (ratio of butyric acid / 3,5,5-trimethylhexanoic acid / hexanoic acid) is 73/27/76 (tetra Production of ester 24)]
Using hexanoic acid instead of 2-methylbutyric acid, the molar ratio of pentaerythritol, butyric acid, 3,5,5-trimethylhexanoic acid and hexanoic acid used (pentaerythritol / butyric acid / 3,5,5-trimethylhexanoic acid) The tetraester 24 was obtained in the same manner as in Example 1 except that the ratio of / hexanoic acid was changed to 1 / 1.92 / 0.96 / 1.92.

[Example 25]
[Tetraester of pentaerythritol having a molar ratio of butyric acid, 3,5,5-trimethylhexanoic acid to heptanoic acid (butyric acid / 3,5,5-trimethylhexanoic acid / heptanoic acid ratio) of 71/29/70 (tetra Production of ester 25)]
Using heptanoic acid instead of 2-methylbutyric acid, the molar ratio of pentaerythritol, butyric acid, 3,5,5-trimethylhexanoic acid and heptanoic acid used (pentaerythritol / butyric acid / 3,5,5-trimethylhexanoic acid) The tetraester 25 was obtained in the same manner as in Example 1 except that the ratio (1 / heptanoic acid ratio) was changed to 1 / 1.92 / 0.96 / 1.92.

[Comparative Example 1]
[Production of pentaerythritol tetraester (tetraester A) having a molar ratio of butyric acid to 3,5,5-trimethylhexanoic acid (butyric acid / 3,5,5-trimethylhexanoic acid ratio) of 25/75]
The molar ratio of pentaerythritol, butyric acid, 3,5,5-trimethylhexanoic acid and 2-methylbutyric acid used (pentaerythritol / butyric acid / 3,5,5-trimethylhexanoic acid / 2-methylbutyric acid ratio) is 1 / The tetraester A was obtained in the same manner as in Example 1 except that it was changed to 1.20 / 3.60 / 0.

(Test Example 1) Measurement of pour point The pour points of tetraesters 1 to 25 and A were measured according to the method of JIS K2269-1987 using an automatic pour point measuring device RPC-01CML (manufactured by Rouai Co., Ltd.). The results are shown in Tables 1-5.

(Test Example 2) Measurement of pour point of tetraester solution 1.35 g of benzotriazole was mixed with 43.65 g of each of tetraesters 1 to 25 and A, heated at 60 ° C., and 3 wt. An ester solution was prepared. In the same manner as in Test Example 1, the pour point of each 3 wt% tetraester solution was measured. The results are shown in Tables 1-5. In Tables 1 to 5, BZT represents benzotriazole.

(Test Example 3) Measurement of kinematic viscosity Using a Canon-Fenske viscometer, the kinematic viscosities of tetraesters 1 to 25 and A at 40 ° C and 100 ° C were measured according to the method of JIS K2283: 2000. The viscosity index was calculated according to the same method. The results are shown in Tables 1-5.

(Test Example 4) Measurement of two-layer separation temperature The two-layer separation temperatures of tetraesters 1 to 25 and A were measured according to the method of JIS K2211: 2009. Each 0.4 g of tetraesters 1 to 25 and A and 3.6 g of difluoromethane refrigerant are sealed in a pressure-resistant glass tube, and the mixture is cooled from 30 ° C. at a rate of 0.5 ° C. per minute. The temperature at which white turbidity occurred was defined as the two-layer separation temperature. The results are shown in Tables 1-5.

(Test Example 5) Solidification at −20 ° C., confirmation of presence or absence of precipitates (evaluation of low temperature characteristics)
Each of tetraesters 1 to 25 was put in a 1.0 g glass container and allowed to stand for 96 hours in a thermostat set to −20 ° C. Solidification after standing and presence / absence of precipitates were visually confirmed. The results are shown below.

(Test Example 6) Measurement of RBOT life (evaluation of oxidation / hydrolysis stability and oxidation stability)
"Condition 1"
An oxidation stability test was performed according to the method of JIS K2514-1996, using a rotary cylinder type oxidation stability tester RBOT-02 (manufactured by Rouai Co., Ltd.). 49.50 g of each of tetraesters 1 to 25, 0.25 g of 4,4′-methylenebis (2,6-di-tert-butylphenol) (manufactured by Tokyo Chemical Industry Co., Ltd.), IRGANOX L57 (Ciba Specialty Chemicals) 0.25g, water (5mL), and electrolytic copper wire (diameter 1.6mm, length 3m) polished with sandpaper # 400 were placed in a pressure vessel. Next, oxygen was injected into the pressure vessel up to 620 kPa, and the pressure vessel was placed in a thermostatic bath at 150 ° C. and rotated at 100 revolutions per minute. The time required for the pressure drop of 175 kPa from the time when the pressure in the pressure vessel reached the maximum (RBOT life) was measured. Here, the longer the RBOT life, the better the oxidation / hydrolysis stability of the tetraester. The results are shown below.

"Condition 2"
4,4'-methylenebis (2,6-di-tert-butylphenol), IRGANOX L57, and water are not put into the pressure vessel, and the other operations are performed in the same manner as in condition 1 above, and the pressure in the pressure vessel is maximized. The time required for the pressure drop of 175 kPa (RBOT life) was measured. Here, the longer the RBOT lifetime, the better the oxidation stability of the tetraester. The results are shown below.

(Test Example 7) Measurement of weight loss temperature (evaluation of thermal stability)
Using a thermogravimetric / differential calorimeter Tg-DTA6200 (manufactured by Seiko Instruments Inc.), the 5% weight loss temperature of tetraesters 1 to 25 was measured under the following conditions. The results are shown below.
Measurement temperature: 40 to 420 ° C., rate of temperature increase: 10 ° C./min, atmosphere: nitrogen aeration (300 mL / min), sample container: aluminum 15 μl (open), sample amount: 3 mg

From Tables 1 to 5, the tetraesters 1 to 25 have a kinematic viscosity at 100 ° C. of 4.6 to 8.2 mm ² / sec and a viscosity index of 83 or more and sufficient viscosity-temperature characteristics. It can be seen that the point has excellent low temperature fluidity of −40.0 ° C. or lower. Moreover, it turns out that it has the outstanding compatibility with a difluoromethane refrigerant | coolant with a two-layer separation temperature of -10 degrees C or less. Furthermore, it can be seen that the pour point of a 3% by weight tetraester solution of benzotriazole is −32.5 ° C. or less, and even when benzotriazole is dissolved, it has excellent low-temperature fluidity.

  In Test Example 5, tetraesters 1 to 25 were not solidified and no precipitate was observed. It can be seen that the tetraester of the present invention can be preferably used even when stored or used for a long time in a low temperature range.

  In “Condition 1” of Test Example 6, tetraesters 1 to 25 have an RBOT lifetime of 716 minutes or longer, among which tetraester 4 is 1546 minutes, tetraester 6 is 1510 minutes, and tetraester 9 is 1440. Minutes, tetraester 10 was 996 minutes, tetraester 11 was 1355 minutes, tetraester 14 was 912 minutes, tetraester 15 was 1140 minutes, and tetraester 22 was 1500 minutes. It can be seen that the tetraester of the present invention has sufficient oxidation / hydrolysis stability.

  The RBOT lifetime in “Condition 2” of Test Example 6 is 180 minutes for tetraester 4, 218 minutes for tetraester 6, 421 minutes for tetraester 11, 401 minutes for tetraester 12, Ester 22 was 195 minutes, tetraester 24 was 282 minutes, and tetraester 25 was 180 minutes. It can be seen that the tetraester of the present invention has sufficient oxidative stability.

  In Test Example 7, tetraesters 1 to 25 had a 5% weight loss temperature of 209.5 ° C. or higher in the measurement of Tg-DTA. It can be seen that the tetraester of the present invention has sufficient thermal stability.

  According to the present invention, it is possible to provide a pentaerythritol tetraester used for refrigerating machine oil or the like having excellent compatibility with a difluoromethane refrigerant.

Claims (8)

A mixed ester of pentaerythritol and a carboxylic acid, wherein the carboxylic acid is a butyric acid, 3,5,5-trimethyl hexanoic acid, and tetra-esters of aliphatic carboxylic acids Tona Ru pentaerythritol having 5 to 7 carbon atoms Molar ratio of 3,5,5-trimethylhexanoic acid to the sum of butyric acid, 3,5,5-trimethylhexanoic acid and aliphatic carboxylic acid having 5 to 7 carbon atoms [3,5,5-trimethylhexanoic acid / (Butyric acid, 3,5,5-trimethylhexanoic acid and aliphatic carboxylic acid having 5 to 7 carbon atoms) ratio] is a tetraester of pentaerythritol having a range of 15/100 to 65/100. The tetraester of pentaerythritol according to claim 1 , wherein the aliphatic carboxylic acid having 5 to 7 carbon atoms is a branched aliphatic carboxylic acid having 5 or 6 carbon atoms. The tetraester of pentaerythritol according to claim 1 or 2 , wherein the aliphatic carboxylic acid having 5 to 7 carbon atoms is 2-methylbutyric acid. The tetraester of pentaerythritol according to claim 1 or 2 , wherein the aliphatic carboxylic acid having 5 to 7 carbon atoms is 3-methylbutyric acid. The tetraester of pentaerythritol according to claim 1 or 2 , wherein the aliphatic carboxylic acid having 5 to 7 carbon atoms is 2-methylpentanoic acid. The tetraester of pentaerythritol according to claim 1 , wherein the aliphatic carboxylic acid having 5 to 7 carbon atoms is a linear aliphatic carboxylic acid having 5 to 7 carbon atoms. The tetraester of pentaerythritol according to claim 1 or 6 , wherein the aliphatic carboxylic acid having 5 to 7 carbon atoms is pentanoic acid. Pentaerythritol tetraester according to any one of claims 1 to 7, a kinematic viscosity of 100 ° C. is in the range of 4.6~8.2mm ² / sec.