JPWO2013027428A1 - Pentaerythritol tetraester - Google Patents

Abstract

The present invention is a mixed ester of pentaerythritol and carboxylic acid, and the carboxylic acid is 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid or 3-methylbutyric acid and 3,5,5-trimethylhexane An acid and any one kind of carboxylic acid selected from isobutyric acid, pentanoic acid, 2-methylbutanoic acid and 2-methylpentanoic acid, while ensuring a viscosity range necessary as a refrigerating machine oil, and against difluoromethane refrigerant Provided is a tetraester of pentaerythritol used for refrigerating machine oil or the like having excellent compatibility.

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. The difluoromethane refrigerant (HFC-32) is a refrigerant in which GWP is currently used [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).

  In the refrigerant circulation cycle of the refrigerator, the refrigerant oil is circulated in the cycle together with the refrigerant that normally lubricates the refrigerant compressor. Therefore, the refrigerating machine oil is required to have compatibility with the refrigerant, and since it is used for the purpose of lubricating the operating part of the refrigerating machine, the lubricating performance is naturally important. When the refrigeration oil undergoes phase separation with the refrigerant, the refrigeration oil discharged from the refrigerant compressor is likely to stay in the cycle, resulting in a decrease in the amount of refrigeration oil in the refrigerant compressor, resulting in poor lubrication, capillaries, etc. This causes a problem of closing the expansion mechanism. For lubrication performance in the refrigerator, it is particularly important to maintain the oil film in the compressor at a high temperature, and the viscosity of the refrigerator oil is important for maintaining the oil film. When the viscosity is low, the oil film is thin and lubrication is liable to occur, and when the viscosity is high, the efficiency of heat exchange decreases (Patent Document 1 and Patent Document 2).

  Patent Document 2 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.

  Patent Document 3 includes a 2-9 valent hindered alcohol having 5 to 15 carbon atoms and a saturated aliphatic monovalent carboxylic acid having 3 to 20 carbon atoms or a derivative thereof used in a composition for a refrigerator working fluid. Although the resulting ester compound is disclosed, the compatibility of the ester with a difluoromethane refrigerant is not mentioned.

Japanese Patent No. 3429031 JP 2002-129177 A International Publication No. 97/11933 Pamphlet

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

  An object of the present invention is to provide a tetraester of pentaerythritol used in a refrigerator oil or the like having an excellent compatibility with a difluoromethane refrigerant while ensuring a viscosity range necessary for the refrigerator oil.

The present invention provides the following [1] to [4].
[1] A mixed ester of pentaerythritol and carboxylic acid, wherein the carboxylic acid is 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid, or 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid And a tetraester of pentaerythritol comprising any one carboxylic acid selected from isobutyric acid, pentanoic acid, 2-methylbutanoic acid and 2-methylpentanoic acid.
[2] The pentaester of pentaerythritol according to [1], wherein the carboxylic acid is composed of 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid.
[3] The carboxylic acid is any one carboxylic acid selected from 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid, isobutyric acid, pentanoic acid, 2-methylbutyric acid, and 2-methylpentanoic acid The tetraester of pentaerythritol as described in [1] consisting of:
[4] The tetraester of pentaerythritol according to any one of [1] to [3], wherein the kinematic viscosity at 100 ° C. is in the range of 5.5 to 9.0 mm ² / sec.

  INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide pentaerythritol tetraester used in refrigerator oil and the like having excellent compatibility with a difluoromethane refrigerant while ensuring a viscosity range necessary for the refrigerator oil.

  The tetraester of pentaerythritol of the present invention is pentaerythritol and 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid, or pentaerythritol, 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid, and isobutyric acid. , Pentanoic acid, 2-methylbutanoic acid, and 2-methylpentanoic acid, a mixed ester composed of any one carboxylic acid. 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.

Further, the “mixed ester composed of pentaerythritol, 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid” in the present invention includes the following (i) to (iii):
(I) the tetraester of pentaerythritol in which the constituent carboxylic acids in the same molecule are both 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid (ii) the tetraester of pentaerythritol and 3-methylbutyric acid, and Mixtures of tetraesters of pentaerythritol and 3,5,5-trimethylhexanoic acid (iii) The embodiments of the above mixtures (i) and (ii) are included.

In the present invention, “pentaerythritol, 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid, any one selected from isobutyric acid, pentanoic acid, 2-methylbutyric acid and 2-methylpentanoic acid” The “mixed ester comprising carboxylic acid” includes the following (iv) to (ix):
(Iv) The constituent carboxylic acid in the same molecule is any one selected from 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid, isobutyric acid, pentanoic acid, 2-methylbutyric acid and 2-methylpentanoic acid Tetraester of pentaerythritol consisting of carboxylic acid (v) Constituent carboxylic acid in the same molecule is 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid, isobutyric acid, pentanoic acid, 2-methylbutyric acid and 2-methyl Any one carboxylic acid selected from pentanoic acid, and two tetraesters of pentaerythritol selected from (vi) pentaerythritol and 3-methylbutyric acid tetraester (vii) pentaerythritol and 3,5,5 Tetraester (viii) pentaerythrito consisting of 5-trimethylhexanoic acid And tetraester consisting of any one carboxylic acid selected from isobutyric acid, pentanoic acid, 2-methylbutanoic acid and 2-methylpentanoic acid (ix) 2 selected from the group of (iv) to (viii) above Embodiments of a mixture of two or more tetraesters are included (however, the carboxylic acid constituting the mixed ester is 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid, isobutyric acid, pentanoic acid, 2-methyl It consists of any one carboxylic acid selected from butyric acid and 2-methylpentanoic acid).
The pentaerythritol tetraester of the present invention may contain a pentaerythritol triester as an impurity.

  When the carboxylic acid constituting the tetraester of pentaerythritol of the present invention comprises 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid, the molar ratio of 3-methylbutyric acid to 3,5,5-trimethylhexanoic acid The (3-methylbutyric acid / 3,5,5-trimethylhexanoic acid ratio) is preferably in the range of 20/80 to 95/5, and more preferably in the range of 45/55 to 85/15.

  The carboxylic acid constituting the tetraester of pentaerythritol of the present invention is selected from 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid, isobutyric acid, pentanoic acid, 2-methylbutyric acid and 2-methylpentanoic acid When any one kind of carboxylic acid is used, any one kind of carboxylic acid selected from isobutyric acid, pentanoic acid, 2-methylbutanoic acid and 2-methylpentanoic acid is isobutyric acid or pentanoic acid. Is preferred.

  The carboxylic acid constituting the tetraester of pentaerythritol of the present invention is any one selected from 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid, isobutyric acid, 2-methylbutyric acid and 2-methylpentanoic acid 3-methylbutyric acid with respect to the sum of 3,5,5-trimethylhexanoic acid and any one carboxylic acid selected from isobutyric acid, 2-methylbutyric acid and 2-methylpentanoic acid Molar ratio [3-methylbutyric acid / (sum of 3,5,5-trimethylhexanoic acid and any one carboxylic acid selected from isobutyric acid, 2-methylbutyric acid and 2-methylpentanoic acid)] Is preferably in the range of 5/95 to 95/5, and more preferably in the range of 20/80 to 65/35.

  When the carboxylic acid constituting the tetraester of pentaerythritol of the present invention comprises 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid and pentanoic acid, The molar ratio of 3-methylbutyric acid to the sum [3-methylbutyric acid / (sum of 3,5,5-trimethylhexanoic acid and pentanoic acid) ratio] is preferably in the range of 5/95 to 95/5. 30/70 to 50/50 is more preferable.

  Any of the carboxylic acids constituting the tetraester of pentaerythritol of the present invention is selected from 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid, isobutyric acid, pentanoic acid, 2-methylbutyric acid and 2-methylpentanoic acid 3 or 5 for the sum of 3-methylbutyric acid and any one carboxylic acid selected from isobutyric acid, pentanoic acid, 2-methylbutyric acid and 2-methylpentanoic acid. , 5-trimethylhexanoic acid molar ratio [3,5,5-trimethylhexanoic acid / (3-methylbutyric acid and any one selected from isobutyric acid, pentanoic acid, 2-methylbutyric acid and 2-methylpentanoic acid Of the carboxylic acid) is preferably in the range of 5/95 to 80/20, and more preferably in the range of 15/85 to 60/40.

  The tetraester of pentaerythritol of the present invention is, for example, pentaerythritol and 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid, or pentaerythritol, 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid. And any one carboxylic acid selected from isobutyric acid, pentanoic acid, 2-methylbutanoic acid and 2-methylpentanoic acid at 120 to 300 ° C. 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.

  In the tetraester of pentaerythritol according to the present invention, when a tetraester comprising 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid is produced, the amount of 3-methylbutyric acid used and 3,5 It is preferable that the sum with the usage-amount of 1,5-trimethylhexanoic acid is 1.1-1.4 times mole with respect to the hydroxyl group of the pentaerythritol to be used.

  In the tetraester of pentaerythritol of the present invention, the constituent carboxylic acid is selected from 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid, isobutyric acid, pentanoic acid, 2-methylbutyric acid and 2-methylpentanoic acid When producing a tetraester comprising any one carboxylic acid, the amount of 3-methylbutyric acid used, the amount of 3,5,5-trimethylhexanoic acid, isobutyric acid, pentanoic acid, 2-methylbutyric acid and It is preferable that the sum with the usage-amount of any 1 type carboxylic acid chosen from 2-methylpentanoic acid is 1.1-1.4 times mole with respect to the hydroxyl group of the pentaerythritol to be used.

  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 produced by the reaction is removed from the reaction mixture, 3-methylbutyric acid and / or isobutyric acid and / or pentanoic acid and / or 2-methylbutyric acid may be removed from the reaction mixture at the same time.

  Also, the difference in reactivity between 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid with respect to pentaerythritol, or 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid, isobutyric acid, pentanoic acid, 2 From the difference in reactivity with any one carboxylic acid selected from 2-methylbutyric acid and 2-methylpentanoic acid, 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid constituting the resulting tetraester Or a molar ratio of 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid and any one carboxylic acid selected from isobutyric acid, pentanoic acid, 2-methylbutyric acid and 2-methylpentanoic acid The ratio may differ from that in the amount used to make 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. Further, when the tetraester of the present invention is used as a refrigerating machine oil, lubricity such as friction reduction and wear reduction of the tetraester is important. Generally, the lubricity is affected by the viscosity of the tetraester. 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 too high. And the friction coefficient tends to increase and the energy efficiency tends to decrease. Tetraesters are required to have a viscosity range necessary for refrigerating machine oil. However, conventional tetraesters tend to have poor compatibility with difluoromethane refrigerant when the viscosity is in the range required for refrigerating machine oil from the viewpoint of lubricity.
Since the tetraester of the present invention contains 3-methylbutyric acid as one component of the carboxylic acid constituting the tetraester, it has excellent compatibility with the difluoromethane refrigerant while ensuring the necessary viscosity range as a refrigerating machine oil. Have. In addition, the pentaerythritol tetraester of the present invention has excellent oxidation / hydrolysis stability, excellent low temperature characteristics, sufficient low temperature fluidity, sufficient lubricity, sufficient oxidation stability, sufficient thermal stability, etc. Have.

  Compatibility with difluoromethane refrigerant is generally expressed using the 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.

When the tetraester of pentaerythritol of the present invention is used for refrigerating machine oil, the kinematic viscosity at 100 ° C. of the tetraester is preferably in the range of 5.5 to 9.0 mm ² / sec. more preferably in the range of 7 mm ² / s, still more preferably in the range of 6.0~6.7mm ² / sec.

  When the tetraester of pentaerythritol of the present invention is used in refrigerating machine oil, if the residual amount of hydroxyl groups in 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.

  Oxidation / hydrolysis stability refers to stability against oxidation and hydrolysis. It is known that the oxidation stability of a carboxylic acid ester is superior to that of a carboxylic acid ester having a branched structure. In addition, it is known that the hydrolysis stability of the ester of a carboxylic acid having a branched structure is superior to that of a carboxylic acid having a linear structure [for example, Synthetics, Mineral Oils, and Bio-Based Lubricants Chemistry and Technology, by Leslie R. Rudnick, p. 47].

  The low temperature fluidity is a property that the liquid becomes difficult to flow as the temperature becomes low, and is expressed by a pour point, a freezing point, a channel point, or 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 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.

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

  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 2 (Example 2 described later), which is the tetraester of pentaerythritol of the present invention, is 0.024 g / g or more, and tetraester 5 (described later). The solubility of benzotriazole (25 ° C.) in Example 5) is 0.026 g / g or more, and the solubility of benzotriazole (25 ° C.) in tetraester 6 (Example 6 described later) is 0.022 g / g. As described above, any pentaerythritol tetraester exhibits high solubility of benzotriazole. The pentaerythritol tetraester of the present invention has sufficient low-temperature fluidity and sufficient 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 tetraesters of pentaerythritol produced in Examples 1 to 3 below, a nuclear magnetic resonance spectrum was measured, and the moles of 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid in the tetraester of pentaerythritol were measured. The ratio was calculated by the following formula.
3-methylbutyric acid / 3,5,5-trimethylhexanoic acid = (integral value of peak X / 2) / (integral value of peak U / 2)
Here, the peak X corresponds to the peak of the hydrogen atom on the methylene group at the α-position of the carbonyl group in 3-methylbutyric acid, and the peak U is on the methylene group at the γ-position of the carbonyl group in 3,5,5-trimethylhexanoic acid. Corresponds to the peak of hydrogen atoms.

For each of the tetraesters of pentaerythritol produced in Examples 4 to 6 below, the nuclear magnetic resonance spectrum was measured, and 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid and isobutyric acid in the tetraester of pentaerythritol were measured. The molar ratio was calculated by the following formula.
3-methylbutyric acid / 3,5,5-trimethylhexanoic acid / isobutyric acid = (integrated value of peak X / 2) / (integrated value of peak Y / 2) / integrated value of peak T where peak X is Peak Y corresponds to the peak of the hydrogen atom on the methylene group at the α-position of the carbonyl group in 3,5,5-trimethylhexanoic acid, and peak T corresponds to the peak of the hydrogen atom on the methine group in isobutyric acid. Equivalent to.

For the tetraesters of pentaerythritol produced in Examples 7 to 9 below, the nuclear magnetic resonance spectrum was measured, and 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid and pentanoic acid in the tetraester of pentaerythritol were measured. The molar ratio was calculated by the following formula.
3-methylbutyric acid / 3,5,5-trimethylhexanoic acid / pentanoic acid = (integrated value of peak X / 2) / (integrated value of peak U / 2) / (integrated value of peak V / 2)
Here, the peak X and the peak U have the same meaning as described above, and the peak V corresponds to the peak of the hydrogen atom on the methylene group at the β-position of the carbonyl group in pentanoic acid.

Nuclear magnetic resonance spectra were measured for the tetraesters of pentaerythritol produced in Examples 10 and 11 below, and 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid and 2-methylbutyric acid in the tetraester of pentaerythritol were measured. The molar ratio was calculated by the following formula.
3-methylbutyric acid / 3,5,5-trimethylhexanoic acid / 2-methylbutyric acid = (integrated value of peak X / 2) / (integrated value of peak Y / 2) / (integrated value of peak W / 2)
Here, the peak X and the peak Y have the same meaning as described above, and the peak W corresponds to the peak of a hydrogen atom on the β-position methylene group of the carbonyl group in 2-methylbutyric acid.

For the tetraester of pentaerythritol produced in Example 12 below, the nuclear magnetic resonance spectrum was measured, and 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid and 2-methylpentanoic acid in the tetraester of pentaerythritol Was calculated by the following formula.
3-methylbutyric acid / 3,5,5-trimethylhexanoic acid / 2-methylpentanoic acid = (integrated value of peak X / 2) / (integrated value of peak Y / 2) / integrated value of peak S where peak X And peak Y has the same meaning as described above, and peak S corresponds to the peak of a hydrogen atom on the methine group in 2-methylpentanoic acid.

For the tetraester of pentaerythritol produced in Comparative Example 1 below, the nuclear magnetic resonance spectrum was measured, and the molar ratio of 3,5,5-trimethylhexanoic acid to pentanoic acid in the tetraester of pentaerythritol was determined by the following formula: Calculated.
3,5,5-trimethylhexanoic acid / pentanoic acid = (integral value of peak Y / 2) / (integral value of peak V / 2)
Here, peak Y and peak V have the same meanings as described above.

For the pentaester of pentaerythritol produced in Comparative Example 2 below, the nuclear magnetic resonance spectrum was measured, and the molar ratio of pentanoic acid, 3,5,5-trimethylhexanoic acid and 2-methylbutyric acid in the tetraester of pentaerythritol was determined. The following formula was used for calculation.
Pentanoic acid / 3,5,5-trimethylhexanoic acid / 2-methylbutyric acid = (integrated value of peak V / 2) / (integrated value of peak Y / 2) / (integrated value of peak W / 2)
Here, the peak V, the peak Y, and the peak W are as defined above.

[Example 1]
[Tetraester of pentaerythritol having a molar ratio of 3-methylbutyric acid to 3,5,5-trimethylhexanoic acid (ratio of 3-methylbutyric acid / 3,5,5-trimethylhexanoic acid) of 81/19 (tetraester 1 )Manufacturing of]
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, 123 g of pentaerythritol (0.9 mol, manufactured by Guangei Perstorp), 353 g of 3-methylbutyric acid (3.5 mol, manufactured by Wako Pure Chemical Industries, Ltd.) and 3,5,5-trimethylhexane 137 g of acid (0.9 mol, manufactured by Kyowa Hakko Chemical Co., Ltd.) was charged, and the mixture was degassed by bubbling nitrogen at room temperature for 20 minutes while stirring the mixture.
The mixture was then stirred at 156-225 ° C. for 15.5 hours with nitrogen bubbling. After the reaction, the reaction product was stirred at 200 ° C. under a reduced pressure of 1.0 kPa for 1 hour to distill off unreacted carboxylic acid in the reaction product. The reaction product was washed with 200 mL of an alkaline aqueous solution containing sodium hydroxide twice as much as the acid value of the reaction product at 80 ° C. for 1 hour. The reaction product was then washed 3 times with 200 mL of water at 75 ° C. for 30 minutes. Subsequently, the reaction product was dried by stirring at 113 ° C. for 30 minutes under a reduced pressure of 1.0 kPa while performing nitrogen bubbling.
Add 1.4 g of adsorbent (corresponding to 0.3% of reaction product weight) and 1.4 g of activated carbon (corresponding to 0.3% of reaction product weight) to the reaction product, and perform nitrogen bubbling. The reaction product was stirred at 100 ° C. for 1 hour under a reduced pressure of 1.0 kPa, and then filtered using a filter aid to obtain 397 g of tetraester 1.

[Example 2]
[Tetraester of pentaerythritol having a molar ratio of 3-methylbutyric acid to 3,5,5-trimethylhexanoic acid (ratio of 3-methylbutyric acid / 3,5,5-trimethylhexanoic acid) of 59/41 (tetraester 2 )Manufacturing of]
The molar ratio of pentaerythritol, 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid used (pentaerythritol / 3-methylbutyric acid / 3,5,5-trimethylhexanoic acid ratio) is 1 / 2.74 / The tetraester 2 was obtained in the same manner as in Example 1 except that it was changed to 2.06.

[Example 3]
[Tetraester of pentaerythritol with a molar ratio of 3-methylbutyric acid to 3,5,5-trimethylhexanoic acid (ratio of 3-methylbutyric acid / 3,5,5-trimethylhexanoic acid) of 50/50 (tetraester 3 )Manufacturing of]
The molar ratio of pentaerythritol, 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid used (pentaerythritol / 3-methylbutyric acid / 3,5,5-trimethylhexanoic acid ratio) is 1 / 2.16 / The tetraester 3 was obtained in the same manner as in Example 1 except that the amount was 2.64.

[Example 4]
[A pentane having a molar ratio of 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid and isobutyric acid (ratio of 3-methylbutyric acid / 3,5,5-trimethylhexanoic acid / isobutyric acid) of 50/36/14 Production of tetraester of erythritol (tetraester 4)]
Instead of 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid, 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid and isobutyric acid were used. Pentaerythritol, 3-methylbutyric acid, 3,5,5 The molar ratio of the amounts of 5-trimethylhexanoic acid and isobutyric acid used (pentaerythritol / 3-methylbutyric acid / 3,5,5-trimethylhexanoic acid / isobutyric acid ratio) was set to 1 / 2.40 / 1.68 / 0. The tetraester 4 was obtained in the same manner as in Example 1 except that the amount was 72.

[Example 5]
[Pentane having a molar ratio of 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid and isobutyric acid (ratio of 3-methylbutyric acid / 3,5,5-trimethylhexanoic acid / isobutyric acid) of 31/41/28 Production of tetraester of erythritol (tetraester 5)]
Instead of 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid, 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid and isobutyric acid were used. Pentaerythritol, 3-methylbutyric acid, 3,5,5 The molar ratio of 5-trimethylhexanoic acid and isobutyric acid used (pentaerythritol / 3-methylbutyric acid / 3,5,5-trimethylhexanoic acid / isobutyric acid ratio) was changed to 1 / 1.46 / 2.04 / 1. The tetraester 5 was obtained in the same manner as in Example 1 except that 30 was used.

[Example 6]
[A pentane having a molar ratio of 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid and isobutyric acid (ratio of 3-methylbutyric acid / 3,5,5-trimethylhexanoic acid / isobutyric acid) of 25/54/21 Production of tetraester of erythritol (tetraester 6)]
Instead of 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid, 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid and isobutyric acid were used. Pentaerythritol, 3-methylbutyric acid, 3,5,5 The molar ratio of the amounts of 5-trimethylhexanoic acid and isobutyric acid used (pentaerythritol / 3-methylbutyric acid / 3,5,5-trimethylhexanoic acid / isobutyric acid ratio) was 1 / 1.20 / 2.64 / 0.0. The tetraester 6 was obtained in the same manner as in Example 1 except that it was changed to 96.

[Example 7]
[A pentane having a molar ratio of 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid and pentanoic acid (ratio of 3-methylbutyric acid / 3,5,5-trimethylhexanoic acid / pentanoic acid) of 46/35/19 Production of tetraester of erythritol (tetraester 7)]
Instead of 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid, 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid and pentanoic acid were used. Pentaerythritol, 3-methylbutyric acid, 3,5,5 The molar ratio of the amounts of 5-trimethylhexanoic acid and pentanoic acid used (pentaerythritol / 3-methylbutyric acid / 3,5,5-trimethylhexanoic acid / pentanoic acid ratio) was set to 1 / 2.16 / 1.80 / 0. The tetraester 7 was obtained in the same manner as in Example 1 except that it was changed to 84.

[Example 8]
[Pentane having a molar ratio of 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid and pentanoic acid (ratio of 3-methylbutyric acid / 3,5,5-trimethylhexanoic acid / pentanoic acid) of 37/40/23 Production of tetraester of erythritol (tetraester 8)]
Instead of 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid, 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid and pentanoic acid were used. Pentaerythritol, 3-methylbutyric acid, 3,5,5 The molar ratio of the amounts of 5-trimethylhexanoic acid and pentanoic acid used (pentaerythritol / 3-methylbutyric acid / 3,5,5-trimethylhexanoic acid / pentanoic acid ratio) was changed to 1 / 1.75 / 2.03 / 1. The tetraester 8 was obtained by operating in the same manner as in Example 1 except that it was changed to 02.

[Example 9]
[A pentane having a molar ratio of 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid and pentanoic acid (ratio of 3-methylbutyric acid / 3,5,5-trimethylhexanoic acid / pentanoic acid) of 33/58/9 Production of tetraester of erythritol (tetraester 9)]
Instead of 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid, 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid and pentanoic acid were used. Pentaerythritol, 3-methylbutyric acid, 3,5,5 The molar ratio of the amounts of 5-trimethylhexanoic acid and pentanoic acid used (pentaerythritol / 3-methylbutyric acid / 3,5,5-trimethylhexanoic acid / pentanoic acid ratio) was changed to 1 / 1.73 / 2.59 / 0. The tetraester 9 was obtained in the same manner as in Example 1 except that it was changed to 48.

[Example 10]
[Mole ratio of 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid and 2-methylbutyric acid (ratio of 3-methylbutyric acid / 3,5,5-trimethylhexanoic acid / 2-methylbutyric acid) is 22/20 / Production of tetraester of pentaerythritol (tetraester 10) which is 58]
Instead of 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid, 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid and 2-methylbutyric acid were used, pentaerythritol, 3-methylbutyric acid, 3, The molar ratio of the amounts of 5,5-trimethylhexanoic acid and 2-methylbutyric acid used (pentaerythritol / 3-methylbutyric acid / 3,5,5-trimethylhexanoic acid / 2-methylbutyric acid ratio) is 1 / 0.96 / The tetraester 10 was obtained in the same manner as in Example 1 except that the ratio was 0.96 / 2.88.

[Example 11]
[Mole ratio of 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid and 2-methylbutyric acid (ratio of 3-methylbutyric acid / 3,5,5-trimethylhexanoic acid / 2-methylbutyric acid) is 62/18 / Production of Tetraester of Pentaerythritol (Tetraester 11) which is 20]
Instead of 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid, 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid and 2-methylbutyric acid were used, pentaerythritol, 3-methylbutyric acid, 3, The molar ratio of the amounts of 5,5-trimethylhexanoic acid and 2-methylbutyric acid used (pentaerythritol / 3-methylbutyric acid / 3,5,5-trimethylhexanoic acid / 2-methylbutyric acid ratio) is 1 / 2.88 / The tetraester 11 was obtained in the same manner as in Example 1 except that the ratio was 0.96 / 0.96.

[Example 12]
[The molar ratio of 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid and 2-methylpentanoic acid (ratio of 3-methylbutyric acid / 3,5,5-trimethylhexanoic acid / 2-methylpentanoic acid) is 40 / Production of tetraester of pentaerythritol which is 22/38 (tetraester 12)]
Instead of 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid, 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid and 2-methylpentanoic acid were used, and pentaerythritol, 3-methylbutyric acid, 3 , 5,5-trimethylhexanoic acid and 2-methylpentanoic acid molar ratio (pentaerythritol / 3-methylbutyric acid / 3,5,5-trimethylhexanoic acid / 2-methylpentanoic acid ratio) 1/1 The tetraester 12 was obtained in the same manner as in Example 1 except that the ratio was .92 / 0.96 / 1.92.

[Comparative Example 1]
[Production of tetraester of pentaerythritol (tetraester A) having a molar ratio of 3,5,5-trimethylhexanoic acid to pentanoic acid (ratio of 3,5,5-trimethylhexanoic acid / pentanoic acid) of 60/40]
Instead of 3-methylbutyric acid, pentanoic acid is used, and the molar ratio of pentaerythritol, 3,5,5-trimethylhexanoic acid, pentanoic acid used (pentaerythritol / 3,5,5-trimethylhexanoic acid / pentanoic acid) The tetraester A was obtained in the same manner as in Example 1 except that the ratio was 1 / 3.00 / 1.80.

[Comparative Example 2]
[Pentarate with a molar ratio of pentanoic acid, 3,5,5-trimethylhexanoic acid and 2-methylbutyric acid (pentanoic acid / 3,5,5-trimethylhexanoic acid / 2-methylbutyric acid ratio) of 61/20/19 Production of tetraester of erythritol (tetraester B)]
Instead of 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid, pentanoic acid, 3,5,5-trimethylhexanoic acid and 2-methylbutyric acid are used. Pentaerythritol, pentanoic acid, 3,5,5-trimethyl The molar ratio of hexanoic acid and 2-methylbutyric acid used (pentaerythritol / pentanoic acid / 3,5,5-trimethylhexanoic acid / 2-methylbutyric acid ratio) was 1 / 2.68 / 1.04 / 1.08. The tetraester B was obtained in the same manner as in Example 1 except that.

(Test Example 1) Measurement of kinematic viscosity Using a Canon-Fenske viscometer, the kinematic viscosities of tetraesters 1 to 12, A and B at 40 ° C and 100 ° C were measured according to the method of JIS K2283: 2000. The results are shown in Tables 1-3.

(Test Example 2) Measurement of two-layer separation temperature According to the method of JIS K2211: 2009, two-layer separation temperatures of tetraesters 1 to 12, A and B were measured. Tetraester 1-12, 0.28 g of each of A and B and 2.52 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 separation or white turbidity occurred was defined as the two-layer separation temperature. The results are shown in Tables 1-3.

(Test Example 3) Measurement of pour point The pour point of tetraesters 1 to 12 was 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 below.

(Test Example 4) Measurement of pour point of tetraester solution 0.90 g of benzotriazole was mixed with 44.10 g of each of tetraester 2, tetraester 5, tetraester 6, tetraester 10 and tetraester 12 at 60 ° C. To prepare a 2 wt% tetraester solution of benzotriazole. In the same manner as in Test Example 3, the pour point of each 2 wt% tetraester solution was measured. The results are shown below.

(Test Example 5) Solidification at −20 ° C., confirmation of presence or absence of precipitates (evaluation of low temperature characteristics)
Each of tetraesters 1 to 12 was put in a 1.0 g glass container and allowed to stand for 24 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 Kosei Co., Ltd.). 49.50 g of each of tetraesters 1 to 12, A and B, 0.25 g of 4,4′-methylenebis (2,6-di-tert-butylphenol) (manufactured by Tokyo Chemical Industry Co., Ltd.), IRGANOX L57 (Ciba 0.25 g (manufactured by Specialty Chemicals), 5 mL of water, and electrolytic copper wire (diameter 1.6 mm, length 3 m) polished with sandpaper # 400 were placed in a pressure-resistant container. 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 in Tables 1-3.

"Condition 2"
4,4′-methylenebis (2,6-di-tert-butylphenol), IRGANOX L57 and water were not put in a pressure vessel, and the other operations were performed in the same manner as in condition 1 except that tetraester 4 and tetraester 9 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 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 12 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 3, the tetraesters 1 to 12 have a kinematic viscosity at 100 ° C. of 5.9 to 8.7 mm ² / sec and a two-layer separation temperature of −19 ° C. or less and an excellent phase for difluoromethane refrigerant. It turns out that it has solubility.

From Tables 1 to 3, the tetraesters 1 to 12 have a kinematic viscosity at 100 ° C. of 5.9 to 8.7 mm ² / sec, and an RBOT life of 1 at least 1348 minutes, which is excellent in oxidation and hydrolysis stability. It turns out that it has sex.

  In Test Example 3, the pour points of tetraesters 1 to 12 were −40.0 ° C. or lower. It turns out that the tetraester of this invention has sufficient low-temperature fluidity | liquidity.

  In Test Example 4, the pour point when tetraester 2 was used as the solvent was −37.5 ° C., the pour point when tetraester 5 was used as the solvent was −40.0 ° C., and tetraester 6 was the solvent. The pour point is −37.5 ° C., the pour point when the tetraester 10 solvent is −42.5 ° C., and the pour point when the tetraester 12 is the solvent is −50.0. ° C. It can be seen that the tetraester of the present invention has sufficient low-temperature fluidity even when benzotriazole is dissolved.

  In Test Example 5, the tetraesters 1 to 12 were not solidified and no precipitate was confirmed. 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 2” of Test Example 6, the RBOT life of tetraester 4 was 364 minutes, and the RBOT life of tetraester 9 was 337 minutes. It can be seen that the tetraester of the present invention has sufficient oxidative stability.

  In Test Example 7, the 5% weight loss temperature of tetraesters 1 to 12 was 214.4 ° C. or higher. It can be seen that the tetraester of the present invention has sufficient thermal stability.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide pentaerythritol tetraester used in refrigerator oil and the like having excellent compatibility with a difluoromethane refrigerant while ensuring a viscosity range necessary for the refrigerator oil.

Claims (4)

  A mixed ester of pentaerythritol and carboxylic acid, wherein the carboxylic acid is 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid, or 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid, A tetraester of pentaerythritol comprising any one carboxylic acid selected from butyric acid, pentanoic acid, 2-methylbutanoic acid and 2-methylpentanoic acid.   The tetraester of pentaerythritol according to claim 1, wherein the carboxylic acid comprises 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid.   The carboxylic acid comprises 3-methylbutyric acid, 3,5,5-trimethylhexanoic acid, and any one carboxylic acid selected from isobutyric acid, pentanoic acid, 2-methylbutyric acid, and 2-methylpentanoic acid. The tetraester of pentaerythritol according to claim 1. The tetraester of pentaerythritol according to any one of claims 1 to 3, wherein the kinematic viscosity at 100 ° C is in the range of 5.5 to 9.0 mm ² / sec.