JPH08134481A - Hydraulic fluid composition for refrigerator and refrigerating system using the same - Google Patents

Abstract

PURPOSE: To provide a hydraulic fluid composition for refrigerators which has high compatibility with a hydrofluorocarbon refrigerant as a substitute for hydrochlorofluorocarbon refrigerants, is excellent especially in hydrolytic resistance, and does not adversely affect organic materials used in a refrigerating system. CONSTITUTION: The composition comprises a hydrofluorocarbon and a refrigerator oil comprising as a base oil an ester of an alicyclic or aromatic hydrocarbon having at least two carboxyl groups in the same ring with a monohydric aliphatic alcohol.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a working fluid composition for a refrigerator, and more particularly to a working fluid composition for a refrigeration system having a refrigeration compressor such as an electric refrigerator or an air conditioner.

[0002]

2. Description of the Related Art Refrigerators, vending machines and compressors for air conditioners have conventionally used a large amount of hydrochlorofluorocarbon (hereinafter referred to as HCFC) containing chlorine atoms in the molecule as a refrigerant. However, this HCFC is subject to CFC regulation as a substance that destroys the ozone layer, and hydrofluorocarbon (HFC) having an ozone destruction coefficient of 0 has been developed and studied as an alternative refrigerant that replaces the HCFC. For example, as an alternative refrigerant for dichlorodifluoromethane (hereinafter R12) used in a compressor of a refrigerator, 1,1,1,2-tetrafluoroethane (hereinafter R134) is used.
a) is under consideration (for example, Japanese Patent Laid-Open No. 1-27149).
No. 1).

However, HFC including R134a
Refrigerant has a higher polarity than R12, etc., so it has poor compatibility with refrigerating machine oils such as mineral oil, poly-α-olefin, and alkylbenzene oil that have been commonly used, and separates into two layers at low temperature. Cause When two-layer separation occurs, the oil return to the refrigeration compressor (hereinafter simply referred to as the compressor) deteriorates, and a thick oil film adheres to the vicinity of the condenser or evaporator as a heat exchanger, hindering heat transfer. , Cause serious defects. Further, there is a problem in that the separated refrigerant is sucked up at the time of start-up and the lubrication failure of the compressor is caused.

Since the compatibility with HFC refrigerants is higher than that of naphthenic mineral oils and alkylbenzene oils, polyether compounds (for example, Japanese Patent Laid-Open Nos. 3-14894 and 3) are used as refrigerating machine oils used together with R134a. −
No. 33193) and polyol ester oils (Japanese Patent Laid-Open No. 4-332793). However, polyether compounds are described in US Pat. No. 4,755,531.
As described in the specification of No. 6, there are problems that the two layers are separated when the temperature rises and that the electrical insulating property is poor. The problem of electrical insulation is a fatal problem for refrigerators for electric refrigerators. Furthermore,
Due to its high hygroscopicity, there is a problem that the moisture stability in the polyether compound deteriorates the thermal stability in the presence of R134a, or the polyethylene terephthalate (PET) film used in the refrigeration system is hydrolyzed. Were present.

Further, the polyol ester type oil causes the sliding member to corrode and wear due to the fatty acid generated by hydrolysis by heat. Then, there is a problem that the abrasion powder adversely affects the organic material such as the magnet wire of the electric element of the compressor and impairs the durability of the compressor. Further, the above-mentioned generated fatty acid becomes a fatty acid salt compound and is deposited at a capillary tube portion or the like in the refrigeration system, which causes a problem that the pipe is clogged.

In order to solve such problems, various ester compounds have been developed. For example, R134a
As a refrigerating machine oil that can be used together with the oil, a mixed oil of polyether oil and ester oil (US Pat. No. 4,851,144)
JP-A No. 2-158693), ester oil (UK Patent No. 2261541, JP-A No. 3-8).
8892, JP-A-3-128991, JP-A-3-128992).

[0007]

The ester compounds are
Excellent compatibility with HFC and excellent thermal stability in the presence of HFC. Further, it has an extremely excellent electric insulation property as compared with the polyether compound and has a considerably low hygroscopic property. However, the HFC / ester system is
For example, compared with the R12 / mineral oil system, both CFCs and oils have higher polarities, so that they easily contain water. The refrigeration system is equipped with a dryer that removes water by molecular sieves, but the remaining water that cannot be removed causes the ester oil to hydrolyze, producing carboxylic acid. Then, similarly to the polyol ester type oil, there is a problem that the generated carboxylic acid corrodes the metal used in the refrigeration system, causing abrasion and generation of copper plating. In addition, since the PET film is used as an insulating material because of its high polarity, PET oligomers are eluted into the CFC / oil mixed liquid, resulting in deterioration of the PET film resulting in deterioration of the insulation properties and blockage of the eluted oligomers in the capillary tube. There was a problem.

The present invention has a high compatibility with HFC as a working fluid for a refrigerator used together with an HFC refrigerant which replaces an HCFC refrigerant, and is particularly excellent in hydrolysis resistance, and has an adverse effect on organic materials used in a refrigeration system. It is an object of the present invention to provide an excellent working fluid composition for refrigerators, which has no such problems. The present invention also aims to provide a refrigeration system using such a composition.

[0009]

Means for Solving the Problems As a result of intensive studies for achieving the above object, the present inventors have found that certain ester compounds can achieve the above object and completed the present invention. Came to. That is, the composition for a working fluid of a refrigerator of the present invention is a refrigerator oil comprising an ester of a cyclic hydrocarbon carboxylic acid having at least two carboxyl groups in the same ring and a monohydric aliphatic alcohol as a base oil, and a hydrodynamic oil. Contains fluorocarbon. Here, the cyclic hydrocarbon carboxylic acid is preferably an aliphatic cyclic hydrocarbon carboxylic acid, particularly 1,3,5-tricarboxycyclohexane or a derivative thereof. Also, other preferred cyclic hydrocarbon carboxylic acids are aromatic cyclic hydrocarbon carboxylic acids. Particularly, it is preferable that the carboxylic acid is phthalic acid or a derivative thereof, and the ester is dioctyl phthalate.

Further, the hydrofluorocarbon is preferably 1,1,1,2-tetrafluoroethane. On the other hand, the monohydric aliphatic alcohol is preferably a linear or branched saturated aliphatic alcohol having 1 to 10 carbon atoms. A branched aliphatic alcohol is more preferable from the viewpoint of hydrolysis resistance. The refrigeration system of the present invention uses the above ester as a lubricant base oil, and is configured by connecting a refrigerant flow rate control unit such as a refrigeration compressor, a condenser, a dryer, and a capillary tube and an evaporator with a pipe. It is what is done.

Specific examples of the monohydric aliphatic alcohol include methanol, ethanol, 1-propanol, and 2
-Propanol, 1-butanol, 2-butanol, 2
-Methyl-1-propanol, 2-methyl-2-propanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 3-methyl- 2-butanol, 2-
Methyl-2-butanol, 2,2-dimethyl-1-propanol, cyclopentanol, 1-hexanol, 2
-Hexanol, 3-hexanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol, 2-methyl-3-pentanol, 3-methyl-1-pentanol, 3-methyl-2-pentanol, 3-methyl-3-pentanol, 4-methyl-1-pentanol, 4-methyl-2-pentanol, 2, 3-dimethyl-1-butanol, 2,3-dimethyl-2-butanol, 3,3-dimethyl-1-butanol, 3,3-dimethyl-2-butanol, 2-ethyl-1-butanol, 2,2-dimethylbutanol, cyclohexanol, cyclopentylmethanol, methylcyclopentanol, 1 -Heptanol, 2-Heptanol, 3-Heptanol, 2-Methyl-1-hexanol, 2-Methyl-2-hexanol, 2-Methyl-3 Hexanol, 5-methyl-2-Hekisanoru, 3-ethyl-3 over pentanol, 2,2
-Dimethyl-3-pentanol, 2,3-dimethyl-3
-Pentanol, 2,4-Dimethyl-3-pentanol, 4,4-Dimethyl-2-pentanol, 3-Methyl-1-hexanol, 4-Methyl-1-hexanol,
5-methyl-1-hexanol, 2-ethylpentanol, cycloheptanol, cyclohexylmethanol,
Methylcyclohexanol, 1-octanol, 2-octanol, 3-octanol, 4-methyl-3-heptanol, 6-methyl-2-heptanol, 2-ethyl-1-hexanol, 2-propyl-1-pentanol, 2,4,4-trimethyl-1-pentanol, 3,
5-dimethyl-1-hexanol, 2-methyl-1-heptanol, 2,2-dimethyl-1-hexanol, cyclooctanol, 1-cyclohexylethanol, 2
-Cyclohexyl ethanol, dimethyl cyclohexanol, ethyl cyclohexanol, 1-nonanol, 3
-Nonanol, 3,5,5-trimethyl-1-hexanol, 2,6-dimethyl-4-heptanol, 3-ethyl-2,2-dimethyl-3-pentanol, 3-cyclohexylpropanol, 5-methyloctanol, 1 −
Decanol, 2-decanol, 4-decanol, 3,7
-Dimethyl-1-octanol, 2,4,6-trimethylheptanol, 4-cyclohexylbutanol, butylcyclohexanol, 3,3,5,5-tetramethylcyclohexanol and the like can be mentioned. The above-mentioned monohydric alcohol used when producing the ester compound of the present invention is not limited to being used alone, and a plurality of kinds may be used.

Refrigerating machine oils containing an ester compound as a base oil used in the present invention are mineral oils, poly-α-olefins, alkylbenzenes, esters and polyethers other than those mentioned above, as long as the compatibility with hydrofluorocarbons is not impaired. , Synthetic oils such as perfluoropolyether and phosphoric acid ester may be mixed. For example, as mineral oil, a lubricating oil fraction obtained by distilling crude oil under atmospheric pressure and vacuum distillation is used for solvent degassing, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, sulfuric acid washing, and clay. It is possible to use a base oil such as a paraffinic oil or a naphthenic oil that is refined by appropriately combining refining treatments such as treatment. In addition, as the synthetic oil, polybutene, 1-octene oligomer, poly-α-olefin such as 1-decene oligomer, alkylbenzene, alkylnaphthalene, or a mixture of two or more thereof can be used.

If necessary, a compound having an epoxy group for trapping water or carboxylic acid formed in the composition is added to the refrigerating machine oil of the present invention, and a metal surface is added so that the carboxylic acid does not corrode the metal. A benzotriazole and / or a benzotriazole derivative for protecting the compound, a triaryl phosphate and / or a triaryl phosphite for improving lubricity, and a thermal stability for improving the thermal stability. It is also effective to add a phenolic compound having a radical trapping ability or a metal deactivator having a chelating ability.

The above-mentioned epoxy compound used in the present invention is preferably an alicyclic epoxy compound, particularly a compound having an epoxycyclohexyl group and / or a compound having an epoxycyclopentyl group. The compound having an epoxycyclohexyl group and the compound having an epoxycyclopentyl group used in the present invention have 5 to 40 carbon atoms, specifically 1,2-epoxycyclohexane,
1,2-epoxycyclopentane, bis (3,4-epoxycyclohexylmethyl) adipate, bis (3,4
-Epoxy-6-methylcyclohexylmethyl) adipate, 3,4-epoxycyclohexylmethyl-3,4
-Epoxycyclohexanecarboxylate, exo-
2,3-epoxy norbonane, 4-epoxyethyl-
1,2-epoxycyclohexane and the like can be mentioned, but not particularly limited, but preferably 1,2-epoxycyclohexane, 1,2-epoxycyclopentane, bis (3,4-epoxycyclohexylmethyl) adipate, bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate and the like. In the present invention, these compounds having an epoxycyclohexyl group may be used alone or in combination of two or more kinds. Further, the compounds having an epoxycyclopentyl group may be used alone or in combination of two or more kinds. Further, a compound having an epoxycyclohexyl group and a compound having an epoxypentyl group may be used in combination. The amount added is 100 parts by weight of the ester compound of the present invention,
The amount is 0.05 to 2.0 parts by weight, preferably 0.1 to 1.0 parts by weight.

The above triaryl phosphate or triaryl phosphite used in the present invention has 1 carbon atom.
8 to 70, preferably 18 to 50 carbon atoms are desirable. Specifically, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, xylenyl diphenyl phosphate, tris (tribromophenyl) phosphate, tris (dibromophenyl) phosphate. Triaryl phosphates such as phosphates, tris (2,4-di-t-butylphenyl) phosphate, trinonylphenylphosphate, triphenylphosphite, tricresylphosphite, trixylenylphosphite, cresyl Examples thereof include triaryl phosphites such as diphenyl phosphite, xylenyl diphenyl phosphite, and tris (2,4-di-t-butylphenyl) phosphite, preferably triphenyl phosphite, Riku registration Le phosphate, trixylenyl phosphate, tris (2,4-di -t- butyl phenyl) phosphate,
Triphenyl phosphite, tricresyl phosphite, trixylenyl phosphite, tris (2,4
-Di-t-butylphenyl) phosphite and the like.
The amount of triaryl phosphate and / or triaryl phosphite added is the same as that of the ester compound 1 of the present invention.
It is usually 0.1 to 5.0 parts by weight, preferably 0.5 to 3.0 parts by weight, relative to 00 parts by weight.

The above-mentioned benzotriazole and / or benzotriazole derivative used in the present invention has 6 carbon atoms.
To 50, preferably 6 to 30. Specifically, benzotriazole, 5-methyl-1
H-benzotriazole, 1-dioctylaminomethyl benzotriazole, 1-dioctylaminomethyl-5
-Methylbenzotriazole, 2- (5'-methyl-2 '
-Hydroxyphenyl) benzotriazole and the like, preferably benzotriazole, 5-methyl-1H
-Benzotriazole etc. are preferred. The amount of benzotriazole and / or benzotriazole derivative added is
Usually 0.0 per 100 parts by weight of the ester compound of the present invention.
01-0.1 parts by weight, preferably 0.005-
0.03 parts by weight.

The amount of the metal deactivator used in the present invention is usually 0.001 to 2.0 parts by weight, preferably 0.001 part by weight, based on 100 parts by weight of the ester compound of the present invention.
It is 3 to 0.5 parts by weight. The metal deactivator used in the present invention preferably has a chelating ability and has a carbon number of 5
To 50, preferably 5 to 20. Specifically, N, N'-disalicylidene-1,2-
Diaminoethane, N, N'-disalicylidene-1,2-
Diaminopropane, N-salicylidene-N'-dimethyl-1,2-diaminoethane, salicylaldoxime, acetylacetone, ethyl acetoacetate, dimethyl malonate, diethyl malonate, anthranilic acid, ethylenediamine, 3-mercapto-1,2- Propanediol, alizarin, quinizarin, mercaptobenzothiazole and the like can be mentioned, preferably N, N′-disalicylidene-
1,2-diaminoethane, N, N'-disalicylidene-
1,2-diaminopropane, acetylacetone, ethyl acetoacetate, alizarin, quinizarin and the like.

The amount of the phenolic compound having a radical trapping ability used in the present invention is usually 0.05 to 100 parts by weight of the ester compound used in the present invention.
It is 2.0 parts by weight, preferably 0.05 to 0.5 parts by weight. The phenolic compound used in the present invention is
Having 6 to 100 carbon atoms, preferably 10 to 8
It is 0. Specifically, 2,6-di-t-butylphenol, 2,6-di-t-butyl-4-methylphenol, 4,4′-methylenebis (2,6-di-t-butylphenol), 4, 4'-butylidene bis (3-methyl-6-t-butylphenol), 2,2'-methylenebis (4-ethyl-6-t-butylphenol),
4,4'-isopropylidene bisphenol, 1,4-
Dihydroxyanthraquinone, 2-t-butyl-4-hydroxyanisole, 2,4-dibenzoylresorcinol, 4-t-butylcatechol, 2,4-dihydroxybenzophenone, 2,4,5-trihydroxybenzophenone and the like, Preferably 2,6-di-t-butylphenol, 2,6-di-t-butyl-4-methylphenol, 4,4′-methylenebis (2,6-di-t
-Butylphenol), 4,4'-butylidene bis (3
-Methyl-6-t-butylphenol), 2,2'-methylenebis (4-ethyl-6-t-butylphenol), 4,4'-isopropylidenebisphenol and the like.

Further, if necessary, it is possible to add a commonly used lubricating oil additive such as an antioxidant, an extreme pressure agent, an oiliness improver, and an antifoaming agent. For example, as the antioxidant, p, p-dioctylphenylamine, monooctyldiphenylamine, phenothiazine, 3,7
-Amine-based antioxidants such as dioctylphenothiazine, phenyl-1-naphthylamine, phenyl-2-naphthylamine, alkylphenyl-1-naphthylamine, and alkylphenyl-2-naphthylamine, alkyldisulfide, thiodipropionate, benzothiazole And other sulfur-based antioxidants, zinc dialkyldithiophosphates, zinc diaryldithiophosphates, and the like.

As the extreme pressure agent and oiliness improver in the present invention, for example, zinc compounds such as zinc dialkyldithiophosphate and zinc diaryldithiophosphate, thiodipropionic acid ester, dialkyl sulfide, dibenzyl sulfide, Sulfur compounds such as dialkyl polysulfide, alkyl mercaptan and dibenzothiophene, phosphorus compounds such as trialkyl phosphite and trialkyl phosphate, chlorine compounds such as chlorinated paraffin, molybdenum dithiocarbamate, molybdenum dithiophosphate, molybdenum compounds such as molybdenum disulfide. , A perfluoroalkyl polyether, a trifluorochloroethylene polymer, a fluorine compound such as fluorinated graphite, a silicon compound such as a fatty acid-modified silicone, and graphite.

Further, the defoaming agent usable in the present invention is silicone oil such as dimethylpolysiloxane and organosilicates such as diethyl silicate. It is also possible to add an additive that stabilizes the chlorofluorocarbon refrigerant including HFC such as an organic tin compound and a boron compound. The blending ratio of the HFC refrigerant and the ester compound base oil used in the present invention or the base oil to which an additive is added is usually about HFC / oil = 5/1 to 1/10 by weight, but preferably 2 by weight. It is / 1-1 / 5. The HFC refrigerant used in the present invention is difluoromethane (HFC32;
R32), 1,1-difluoroethane (HFC152
a; R152a), 1,1,1-trifluoroethane (HFC143a; R143a), 1,1,1,2-tetrafluoroethane (HFC134a; R134a),
1,1,2,2-tetrafluoroethane (HFC13
4; R134a), pentafluoroethane (HFC12
5; R125) and the like, and also includes a refrigerant obtained by mixing a plurality of these.

[0022]

The present invention has the above-mentioned structure, and thus H
The composition for a working fluid of a refrigerating machine oil has excellent compatibility with an FC refrigerant such as R134a, and also has excellent thermal decomposition stability and hydrolysis stability. That is, in the present invention, in forming an ester compound having excellent compatibility with an HFC refrigerant, in contrast to the hydrolyzability which is a defect of the ester compound, a cyclic hydrocarbon whose ester bond site causing decomposition is the center of the molecular structure And a hydrocarbon group derived from a monohydric aliphatic alcohol that is adjacent to and around the aromatic ring, forms an environment that protects this ester bond site, and thereby dissolves in the oil. It makes it difficult to react with existing water molecules. Further, in the ester compound used as a refrigerating machine oil, it is reported that the alcohol used for the ester compound synthesis is preferably a saturated aliphatic alcohol from the viewpoint of heat resistance (for example, JP-A-5-271676). Also in the synthesis, the use of a linear or branched aliphatic alcohol having 1 to 10 carbon atoms contributes to the improvement of thermal decomposition stability.

[0023]

EXAMPLES The present invention will now be described in more detail with reference to examples. However, the present invention is not limited to the examples. [Example 1] A stirrer for a 2000 ml four-necked flask,
A thermometer, dropping funnel, and condenser were attached. After adding 200 ml of anhydrous toluene to the flask, 1,3,5-tricarboxycyclohexane (Al
300 g (1.388 mol) manufactured by drich) was added. Further, with a dropping funnel, thionyl chloride 231.2
g (1.94 mol) was added dropwise at 80 ° C. over 3 hours. After further aging at 80 ° C for 2 hours, distillation is performed 1,
About 2,5-tricarboxycyclohexane acid chloride
40 g was obtained. Next, in a 500 ml four-necked flask equipped with a stirrer, a thermometer, a dropping funnel and a cooling tube, 70.4 g (0.8 mol) of 2-methyl-1-butanol and 38.71 g (0.49 mol) of pyridine were added. Then, 77.4 g (0.242 mol) of the acid chloride of 1,3,5-tricarboxycyclohexane was added dropwise from the dropping funnel at room temperature in 15 minutes. The temperature was further raised to 110 ° C. and the reaction was carried out for 4 hours. Then, after cooling to room temperature, 200 ml of hexane and 50 ml of pure water were added, the mixture was separated with a separating funnel, and the hexane layer was washed 3 times with a 10% aqueous solution of sulfuric acid, and further washed once with a saturated aqueous solution of sodium hydrogen carbonate. . After removing hexane using a rotary evaporator, the residue was distilled to remove low-boiling substances to obtain the ester compound A of the present invention.

Example 2 200 ml of anhydrous toluene was added to the same flask as in Example 1, and the mixture was stirred to 1.
3.5-tricarboxycyclohexane (Aldric
h company) 300 g (1.388 mol) was added. Further, 231.2 g (1.
94 mol) was added dropwise at 80 ° C. over 3 hours. 8 more
After aging at 0 ° C. for 2 hours, distillation was performed to obtain about 240 g of acid chloride of 1,3,5-tricarboxycyclohexane. Next, in a 500 ml four-necked flask equipped with a stirrer, a thermometer, a dropping funnel and a cooling tube, 104 g (0.8 mol) of 2-ethyl-1-hexanol and 3 parts of pyridine were added.
8.71 g (0.49 mol) was taken and the above 1, 3, 5
77.4 g of the acid chloride of tricarboxycyclohexane
(0.242 mol) was added dropwise from the dropping funnel at room temperature in 15 minutes. The temperature was further raised to 110 ° C. and the reaction was carried out for 4 hours. Then, after cooling to room temperature, 200 ml of hexane
And 50 ml of pure water were added, and the mixture was separated in a separating funnel, and the hexane layer was washed 3 times with a 10% aqueous sulfuric acid solution and further once with a saturated aqueous sodium hydrogen carbonate solution. Hexane was removed using a rotary evaporator, and the residue was distilled to obtain the ester compound B of the present invention.

[Example 3] To the same flask as in Example 1 was added 200 ml of anhydrous toluene, and 300 g (1.806 mol) of phthalic acid (manufactured by Kanto Chemical Co., Inc.) with stirring.
Was added. Further, thionyl chloride 30 with a dropping funnel
0 g (2.52 mol) was added dropwise at 80 ° C. over 3 hours. After further aging at 80 ° C. for 2 hours, distillation was performed to obtain about 250 g of phthalic acid chloride. Next, in a 500 ml four-necked flask equipped with a stirrer, a thermometer, a dropping funnel and a cooling tube, 2-ethyl-1-hexanol (Kanto Chemical Co., Inc.)
Manufactured by the company) 104 g (0.8 mol) and pyridine 38.7
1 g (0.49 mol) was taken, and 56.9 g (0.242 mol) of the chloride of phthalic acid was added dropwise from the dropping funnel at room temperature in 15 minutes. The temperature was further raised to 110 ° C. and the reaction was carried out for 4 hours. Then, after cooling to room temperature, 200 ml of hexane and 50 ml of pure water were added, the mixture was separated with a separating funnel, and the hexane layer was washed 3 times with a 10% aqueous solution of sulfuric acid, and further washed once with a saturated aqueous solution of sodium hydrogen carbonate. . Hexane was removed using a rotary evaporator, and the residue was distilled to obtain the ester compound C of the present invention.

[Example 4] To the same flask as in Example 1 was added 200 ml of anhydrous toluene, and 300 g (1.806 mol) of phthalic acid (manufactured by Kanto Chemical Co., Inc.) with stirring.
Was added. Further, thionyl chloride 30 with a dropping funnel
0 g (2.52 mol) was added dropwise at 80 ° C. over 3 hours. After further aging at 80 ° C. for 2 hours, distillation was performed to obtain about 250 g of phthalic acid chloride. Next, in a 500 ml four-necked flask equipped with a stirrer, a thermometer, a dropping funnel and a condenser, 70.52 g (0.8 mol) of 3-methyl-1-butanol (manufactured by Aldrich) and pyridine 38.
71 g (0.49 mol) was taken, and 56.9 g (0.242 mol) of the chloride of phthalic acid was added dropwise from the dropping funnel at room temperature in 15 minutes. Further raise the temperature to 110 ° C and 4
Allowed to react for hours. Then, after cooling to room temperature, 200 ml of hexane and 50 ml of pure water were added, the mixture was separated with a separating funnel, and the hexane layer was washed 3 times with a 10% sulfuric acid aqueous solution,
Further, it was washed once with a saturated aqueous solution of sodium hydrogen carbonate.
After removing hexane using a rotary evaporator, the residue was distilled to obtain the ester compound D of the present invention.

Comparative Example 1 A 1000 ml four-necked flask was equipped with a stirrer, a thermometer, a nitrogen blowing tube, and a dehydration tube equipped with a condenser. Into the above flask, 134 g (1.00 mol) of trimethylolpropane and 520 g (4.0 mol) of 2-methylhexanoic acid were placed, and under a nitrogen atmosphere,
The reaction was carried out for 2 hours while heating at 240 ° C. under normal pressure. Then, after reacting for 6 hours under reduced pressure of 150 Torr, unreacted monocarboxylic acid was removed by distillation under reduced pressure to obtain ester compound a.

[Comparative Example 2] 29.5 g (0.22 mol) of trimethylolpropane were placed in the same flask as in Example 1.
And 104.3 g (1.32 mol) of pyridine were taken, 87.5 g (0.73 mol) of pivalic acid chloride was added, and the mixture was reacted at 110 ° C. for 4 hours. After cooling the reaction solution to room temperature, 200 ml of hexane and 50 ml of pure water were added, and the mixture was separated by a separating funnel, and the hexane layer was washed with 10% sulfuric acid aqueous solution.
It was washed once and further washed once with a saturated aqueous solution of sodium hydrogen carbonate. After removing hexane using a rotary evaporator, the low boiling point substances were removed by further distilling to obtain an ester compound b.

[Comparative Example 3] 136 g (1.00 mol) of pentaerythritol was placed in the same flask as in Comparative Example 1 and 2
-Methylhexanoic acid 324.7 g (2.50 mol) and 2-ethylhexanoic acid 216.4 g (1.50 mol)
And the ester compound c was prepared in the same manner as in Comparative Example 1.
I got

TEST EXAMPLE 1 The present invention obtained by blending the ester A, B, C or D obtained in Examples 1 to 4 and 1,1,1,2-tetrafluoroethane (HFC134a; R134a). In order to examine the hydrolysis stability of the composition for a working fluid for a refrigerator (Products A, B, C, D of the present invention), a shield tube test was conducted under the following conditions. That is, 10 g of ester A, B, C or D, and 5 g of R134a, which had been prepared in advance to a water concentration of 1000 ppm or less and an acid value of 0.01 mg (mgKOH / g) or less, were placed in a glass tube, and iron / copper was used as a catalyst. -Sealed with aluminum wire. After testing at 175 ° C. for 14 days, the sealed tube was opened and R134a was removed, and then the acid value of each ester compound was measured. Further, in order to investigate the hydrolysis stability of Comparative Products a, b and c obtained by blending the ester compound a, b or c obtained in Comparative Examples 1 to 3 and R134a, under the same conditions as above. A shield tube test was conducted. After the experiment, the acid value of each ester was measured. The test results are shown in Table 1.

[0031]

[Table 1]

As is clear from Table 1, the ester bond site which causes hydrolysis is adjacent to the cyclic hydrocarbon and aromatic ring which are the center of the molecular structure, and further around the hydrocarbon derived from a monohydric aliphatic alcohol. The products A, B, C and D of the present invention having a molecular structure in which a group is present also have an acid value after the shield tube test as compared with comparative products a, b and c prepared from an aliphatic polyhydric alcohol. It can be seen that it is low and has excellent hydrolysis stability.

[Test Example 2] The ester compound A prepared in Example 1 was used as the base oil component of the lubricating oil for a refrigerator, and it was sealed in the refrigerant compressor shown in FIG. 1, and R134a (Mitsui.
Using DuPont Fluorochemicals), an operation test was performed at 25 ° C. for 1000 hours. After the operation was completed, the electric wire coating material of the motor coil, the insulating paper, and the refrigerating machine oil were examined, and it was found that all had no abnormalities such as discoloration and were in a very good condition. Further, the sliding member was not particularly markedly worn, and sludge deposited in the oil was hardly recognized.

FIG. 1 shows the compressor used in the above test. The structure of the compressor 1 will be described below. 2 is a closed shell, 3 is a stator shrink-fitted to the closed shell 2,
4 is a rotor that forms a motor unit 5 with the stator 3 as a pair,
Reference numeral 6 is a shaft that is shrink-fitted to the rotor 4. Also, 7
Is a roller incorporated in the eccentric part of the shaft 6, 8 is a cylinder for housing the roller 7, 9 is a main bearing of the shaft 6,
Reference numeral 10 is an auxiliary bearing of the shaft 6, and 11 is a suction pipe press-fitted into the auxiliary bearing 10 and welded to the closed shell 2. 12
Is a mechanical unit including a shaft 6, a roller 7, a cylinder 8, a main bearing 9, a sub bearing 10, and a vane (not shown). A manganese phosphate coating 13 is formed on the inner wall surface of the closed shell 2 as a rust preventive treatment.

[Test Example 3] The ester compound C prepared in Example 3 was used as the base oil component of the lubricating oil for the refrigerator, and was sealed in the refrigerant compressor shown in FIG. 1, and R134a (Mitsui.
Using DuPont Fluorochemicals), an operation test was performed at 25 ° C. for 1000 hours. After the operation was completed, the electric wire coating material of the motor coil, the insulating paper, and the refrigerating machine oil were examined, and it was found that all had no abnormalities such as discoloration and were in a very good condition. Further, the sliding member was not particularly markedly worn, and sludge deposited in the oil was hardly recognized.

[0036]

INDUSTRIAL APPLICABILITY As described above, the composition for a working fluid of a refrigerator using the ester compound of the present invention as a base oil is excellent in hydrolysis resistance, and even in a refrigeration system used with hydrofluorocarbon, lubricity and abrasion resistance are obtained. It is possible to use it as a composition for refrigerator working fluid which is also excellent.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a compressor used for testing a composition for a working fluid of a refrigerator according to an example of the present invention.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location C10N 40:08 40:30 (72) Inventor Narihiro Sato 1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric Industry Co., Ltd. (72) Inventor Yusuke Ozaki 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Nobuo Sonoda 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (8)

[Claims] 1. A refrigerating machine oil containing a base oil of an ester of a cyclic hydrocarbon carboxylic acid having at least two carboxyl groups in the same ring and a monovalent aliphatic alcohol, and a refrigerating machine working fluid containing hydrofluorocarbon. Composition. 2. The composition for refrigerator working fluid according to claim 1, wherein the cyclic hydrocarbon carboxylic acid is an aliphatic cyclic hydrocarbon carboxylic acid. 3. The cyclic hydrocarbon carboxylic acid is 1,
The refrigerator working fluid composition according to claim 2, which is 3,5-tricarboxycyclohexane or a derivative thereof. 4. The composition for a working fluid of a refrigerator according to claim 1, wherein the cyclic hydrocarbon carboxylic acid is an aromatic cyclic hydrocarbon carboxylic acid. 5. The aromatic cyclic hydrocarbon carboxylic acid is
The composition for a refrigerator working fluid according to claim 4, which is phthalic acid or a derivative thereof. 6. The hydrofluorocarbon is 1,
The composition for a refrigerator working fluid according to claim 1, which is 1,1,2-tetrafluoroethane. 7. The composition for a working fluid of a refrigerator according to claim 1, wherein the monohydric aliphatic alcohol is a linear or branched saturated aliphatic alcohol having 1 to 10 carbon atoms. 8. A refrigeration system comprising a refrigeration compressor and using the composition for a refrigerating machine working fluid according to claim 1.