JPH06293893A - Composition for hydraulic fluid of refrigerator - Google Patents

Abstract

PURPOSE:To obtain the subject composition having excellent lubricating properties, thermal stability and electric insulating properties, comprising a refrigerator oil prepared by adding an epoxycycloalkyl compound to a branched aliphatic monocarboxylic acid ester of neopentylpolyol and a fluorinated hydrocarbon. CONSTITUTION:An ester obtained from a neopentylpolyol (e.g. trimethylolpropane) and a 7-9C saturated branched aliphatic monocarboxylic acid (e.g. 2-methylhexaenoic acid) is mixed with 0.05-2.0 pts.wt. of an epoxycyclohexyl group-containing compound and/or an epoxycyclopentyl group- containing compound (e.g. 1,2-epoxycyclopentane) based on 100 pts.wt. of the ester to give a refrigerator oil, which is mixed with a hydrofluorocarbon to give the objective composition for hydraulic fluid of refrigerator having excellent compatibility, lubricating properties, thermal stability and electrical insulating properties.

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 refrigerators, and more particularly to a working fluid composition for compression refrigerators such as electric refrigerators.

[0002]

2. Description of the Related Art Recently, the problems to be solved by the invention
The use of dichlorodifluoromethane (CFC12), which is used in refrigerators and car coolers to protect the ozone layer, is regulated, and it is about to be prohibited in the future. Therefore, as an alternative to this CFC12, a hydrofluorocarbon that does not destroy the ozone layer, such as 1,
1,1,2-Tetrafluoroethane (HFC134a)
Is being developed.

However, hydrofluorocarbons are CF
Since the polarity thereof is higher than that of C12, if a lubricating oil such as naphthene-based mineral oil, poly α-olefin, or alkylbenzene which has been generally used as a refrigerating machine oil is used, the compatibility between these lubricating oil and hydrofluorocarbon is poor. , Two-phase separation occurs at low temperature. When two-layer separation occurs, oil return deteriorates, a thick oil film adheres to the vicinity of the condenser or evaporator as a heat exchanger to prevent heat transfer, and poor lubrication or foaming at startup may occur. It causes a serious defect. Therefore, the conventional refrigerating machine oil cannot be used as the refrigerating machine oil under these new refrigerant atmospheres.

Also, regarding the lubricity, in CFC12, it is partially decomposed to generate hydrogen chloride, and this hydrogen chloride reacts with the friction surface to form a chloride film to improve lubricity. was there. However, since such effects cannot be expected for hydrofluorocarbons that do not contain chlorine atoms, refrigerating machine oils used with hydrofluorocarbons are required to have even better lubricity than conventional ones.

Further, the refrigerating machine oil used together with the hydrofluorocarbon must have good thermal stability in the presence of the hydrofluorocarbon. In addition, in addition to this, in compression refrigerators of electric refrigerators, there are organic materials used for motors such as insulating materials and enameled wires, so as a working fluid consisting of hydrofluorocarbon and refrigerator oil, these organic materials are used. It is necessary that the material is not adversely affected and that the electrical insulation is good.

Hydrofluorocarbons such as HFC
As refrigerating machine oil that can be used together with 134a, U.S. Pat. No. 4,755,316 and JP-A-1-198.
694, JP-A-1-256594, JP-A 1-25
No. 9093, Japanese Patent Application Laid-Open Nos. 1-259094, 1-2
59095, JP-A-2-84491, JP-A2-1.
02296, JP-A-2-129294, JP-A-2-
132176, JP-A-2-132177, JP-A-2
Polyether compounds are disclosed in JP-A-132178, JP-A-2-132179, JP-A-2-173195, JP-A-2-180986, JP-A-2-180987, JP-A-2-182780 and the like.

Since the polyether compound has a higher polarity than naphthenic mineral oil, the compatibility with HFC134a at low temperature is certainly good. However, US Pat.
As described in the specification of No. 55316, the polyether compound has a problem of causing two-layer separation when the temperature rises, and therefore cannot be used as a refrigerating machine oil without anxiety. Further, the polyether compound has some other problems. One is that it has poor electrical insulation. This is a very big problem and cannot be used in refrigerators for electric refrigerators. Another problem is that it is highly hygroscopic. Due to the water content in the polyether compound, the thermal stability in the coexistence with HFC134a is deteriorated, or the PET film or the like which is an organic material is hydrolyzed. Further, regarding the lubricity, it cannot be said that the polyether compound is sufficiently good.
The hydrofluorocarbon refrigerant-polyether compound system such as HFC134a is inferior to the 12-naphthene mineral oil system.

On the other hand, some methods of using an ester together with fluoromethane have been proposed in the field of refrigerators, for example, JP-A-56-131548 and JP-A-SHO-5.
No. 6-133241, JP-A-61-181895 and JP-A-62-592. Also,
JP-A-56-125494, JP-A-56-12549
No. 5, JP-A No. 61-62596, there is described an example in which an ester is mixed with another lubricating oil. Further, an example of use in which an additive is added to an ester is disclosed in JP-A-55-55.
150993, JP-A-56-36570, JP-A-5
6-125494, JP-A-58-15592, JP-A-58-103594, JP-A-61-171799.
And JP-A-62-292895.

However, these are all intended for systems used with dichlorodifluoromethane (CFC12) or monochlorodifluoromethane (HCFC22) type refrigerants, and no mention is made of hydrofluorocarbon refrigerants. Further, its purpose is also to improve the thermal stability in an atmosphere of CFC12 or HCFC22. In addition, JP-A-53-14
3609 and JP-A-59-164393 describe compatibility with chlorofluorocarbon as well as improvement in thermal stability in a chlorofluorocarbon atmosphere, but the former is CF.
In C12, the latter is aimed at not being too soluble in HCFC22, and there is no description about improving the compatibility with the hydrofluorocarbon refrigerant.

Hydrofluorocarbons such as HFC
A method of using both 134a and an ester is described in US Pat.
It is described in Japanese Patent No. 851144 and Japanese Patent Application Laid-Open No. 2-158693. However, in all of these, HFC134a is obtained by partially mixing a polyether compound with an ester.
The use of the ester alone is not mentioned. Also, the purpose of adding the ester is not mentioned.

As described above, in the prior art, compositions such as hydrofluorocarbons and oils used in refrigerators for electric refrigerators and the like have properties such as compatibility, lubricity, thermal stability, and electrical insulation. The current situation is that nothing satisfying the above has been found. Therefore, an object of the present invention is to provide a composition for a working fluid of a refrigerator used in an electric refrigerator or the like which has excellent properties such as compatibility, lubricity, thermal stability and electric insulation.

[0012]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventor has added a compound having an epoxycyclohexyl group or an epoxycyclopentyl group to certain ester compounds and ester compounds. It was found that the above-mentioned objects can achieve the above-mentioned objects, and the present invention has been completed.

That is, the gist of the present invention is (1) an ester obtained from neopentyl polyol and a saturated branched chain aliphatic monocarboxylic acid having 7 to 9 carbon atoms, and the ester 100
Refrigerating machine oil containing 0.05 to 2.0 parts by weight of a compound having an epoxycyclohexyl group and / or a compound having an epoxycyclopentyl group, and a composition for a refrigerator working fluid containing hydrofluorocarbon And (2) an ester obtained from neopentyl polyol and a saturated branched aliphatic monocarboxylic acid having 7 to 9 carbon atoms, and a compound having an epoxycyclohexyl group and / or an epoxycyclopentyl group based on 100 parts by weight of the ester. 0.05 to 2.0 parts by weight of a compound having the formula (1) and 0.1 to 5.0 parts by weight of triaryl phosphate and / or triaryl phosphite, and benzotriazole, relative to 100 parts by weight of the ester. And / or benzotriazole derivative 0.001-
0.1 parts by weight and a metal deactivator having a chelating ability.
The present invention relates to a refrigerator working fluid composition containing hydrofluorocarbon and a refrigerator oil prepared by blending at least one selected from the group consisting of 001 to 2.0 parts by weight.

The alcohol portion of the ester used in the present invention is neopentyl polyol, for example, neopentyl glycol, 2,2-diethyl-1,3-propanediol, 2-n-butyl-2-ethyl-1,3. -Propanediol, trimethylolethane, trimethylolpropane, trimethylolnonane, pentaerythritol, dipentaerythritol and the like, preferably neopentyl glycol, trimethylolpropane,
It is pentaerythritol. These neopentyl polyols are superior in heat resistance to polyhydric alcohols having hydrogen at the β-position.

The carboxylic acid moiety of the ester used in the present invention is a saturated branched chain aliphatic monocarboxylic acid having 7 to 9 carbon atoms, specifically, 2,2-dimethylpentanoic acid and 2
-Ethylpentanoic acid, 3-ethylpentanoic acid, 2-methylhexanoic acid, 3-methylhexanoic acid, 4-methylhexanoic acid, 5-methylhexanoic acid, cyclohexanecarboxylic acid, cyclopentylacetic acid, 2-ethylhexanoic acid,
3,5-dimethylhexanoic acid, 2,2-dimethylhexanoic acid, 2-methylheptanoic acid, 3-methylheptanoic acid,
4-methylheptanoic acid, 2-propylpentanoic acid, 3,
4-dimethylhexanoic acid, cyclohexylacetic acid, 3-cyclopentylpropionic acid, 2,2-dimethylheptanoic acid, 3,5,5-trimethylhexanoic acid, 2-methyloctanoic acid, 2-ethylheptanoic acid, 3-methyloctanoic acid , 2-ethyl-2,3,3-trimethylbutyric acid, 2,
2,4,4-tetramethylpentanoic acid, 2,2-diisopropylpropionic acid and the like can be mentioned, preferably 2-methylhexanoic acid, 2-ethylhexanoic acid, 3,5-dimethylhexanoic acid, 3,5,5. -Trimethylhexanoic acid.

An ester of a monocarboxylic acid having a carbon number of more than 9 may have poor compatibility with hydrofluorocarbon, and an ester of a monocarboxylic acid having a carbon number of less than 7 may have a high corrosiveness to a metal. Not preferable. Further, from the viewpoint of hydrolysis resistance and corrosion to metals, esters of branched monocarboxylic acids are preferable to esters of linear monocarboxylic acids, and,
From the viewpoint of compatibility with hydrofluorocarbons, esters of branched-chain monocarboxylic acids are superior. For example,
The critical dissolution temperature with HFC134a is as low as trimethylolpropane triheptanate: -20 ° C, trimethylolpropane tri2-methylhexanate: -60 ° C, and trimethylolpropane trioctanoate: 30 ° C.
On the other hand, trimethylolpropane tri-2-ethylhexanate: -33 ° C, trimethylolpropane tri 3,5
-Dimethylhexanate: low at -27 ° C. Further, pentaerythritol tetranonanate: 30 ° C or higher, pentaerythritol tetra (3,5,5-
Trimethylhexanate): as low as -25 ° C, and esters of branched-chain monocarboxylic acid are superior.

From the viewpoint of thermal stability, saturated monocarboxylic acid ester is preferable to unsaturated monocarboxylic acid ester. In addition, among the above-mentioned four branched chain monocarboxylic acid esters, in terms of compatibility with HFC134a, 2-methylhexanoic acid ester> 3,5,5-trimethylhexane as seen from the following data. Acid ester> 2-ethylhexanoic acid ester> 3,5-
The compatibility is excellent in the order of dimethylhexanoic acid ester, and 2-methylhexanoic acid ester is the most excellent.

Neopentyl glycol di2-methylhexanate (critical melting temperature with HFC134a: -70 ° C)
The following), neopentyl glycol di3,5,5-trimethylhexanate (critical solution temperature with HFC134a:
-69 ° C), neopentyl glycol di2-ethylhexanate (critical solution temperature with HFC134a: -64
C), neopentyl glycol di3,5-dimethylhexanate (critical melting temperature with HFC134a: -60
), Trimethylolpropane tri-2-methylhexanate (critical melting temperature with HFC134a: -60 ° C),
Trimethylolpropane tri 3,5,5-trimethylhexanate (critical solution temperature with HFC134a: -40
), Trimethylolpropane tri-2-ethylhexanate (critical dissolution temperature with HFC134a: -33 ° C),
Trimethylolpropane tri 3,5-dimethylhexanate (critical solution temperature with HFC134a: -27 ° C),
Pentaerythritol tetra-2-methylhexanate (critical melting temperature with HFC134a: -40 ° C), pentaerythritol tetra 3,5,5-trimethylhexanate (critical melting temperature with HFC134a: -25
C.), pentaerythritol tetra-2-ethylhexanate (critical melting temperature with HFC134a: −9 ° C.), pentaerythritol tetra3,5-dimethylhexanate (critical melting temperature with HFC134a: 0 ° C.),

From the viewpoint of hydrolysis resistance, 2-methylhexanoic acid ester and 2-ethylhexanoic acid ester having a branched chain at the α-position of the carbonyl group do not have a branched chain at the α-position. 3,5-dimethylhexanoic acid ester,
Superior to 3,5,5-trimethylhexanoic acid ester. Therefore, considering the compatibility with HFC134a and the hydrolysis resistance, 2-methylhexanoic acid ester is the most excellent.

Therefore, it is desirable that the ester used in the present invention contains 2-methylhexanoic acid in the carboxylic acid portion thereof, and particularly in the case of a divalent neopentyl polyol ester, 70% by weight or more and a trivalent with respect to the total amount of the carboxylic acid. In the above neopentyl polyol ester, it is very desirable to contain 25% by weight or more with respect to the total amount of carboxylic acid.
In this case, a carboxylic acid containing a saturated branched chain aliphatic monocarboxylic acid having 7 to 9 carbon atoms in an amount of 70% by weight or more based on the total amount of the carboxylic acid, wherein the saturated branched chain aliphatic monocarboxylic acid is at least 2-methylhexanoic acid. It is highly desirable that the carboxylic acid contains 25% by weight or more with respect to the total amount of carboxylic acid. Here, the saturated branched-chain aliphatic monocarboxylic acid having 7 to 9 carbon atoms is composed of only 2-methylhexanoic acid, or 2-ethylhexanoic acid, 3,5-dimethylhexanoic acid and 3,5,5 A mixed acid composed of at least one selected from the group consisting of trimethylhexanoic acid and 2-methylhexanoic acid is particularly preferable. Although such a mixed acid is not particularly limited, a preferable example is a mixed acid of 2-methylhexanoic acid and 3,5,5-trimethylhexanoic acid.

In the divalent neopentyl polyol ester, if 2-methylhexanoic acid is less than 70% by weight based on the total amount of carboxylic acid, the performances such as compatibility with hydrofluorocarbon, hydrolysis resistance and viscosity index are well balanced. I can't be satisfied. Further, in the trivalent or higher valent neopentyl polyol ester, 2-methylhexanoic acid is less than 25% by weight with respect to the total amount of carboxylic acid, or 2-methylhexanoic acid is 25% with respect to the total amount of carboxylic acid.
If the saturated branched-chain aliphatic monocarboxylic acid having 7 to 9 carbon atoms is less than 70% by weight based on the total amount of carboxylic acid, the compatibility with hydrofluorocarbon, hydrolysis resistance, viscosity index, and low temperature fluidity It is not possible to achieve a good balance of performance such as sex.

As described above, in the di- or tri- or higher-valent neopentyl polyol ester, the carboxylic acid component is 2
-It is desirable to contain a predetermined amount or more of methylhexanoic acid, but 2-methylhexanoic acid may be the total amount of the carboxylic acid component. Examples thereof include an ester composed of neopentyl glycol and 2-methylhexanoic acid, or an ester composed of trimethylolpropane and / or pentaerythritol and 2-methylhexanoic acid. Further, the total carboxylic acid component may be composed only of a mixed acid composed of a saturated branched chain aliphatic monocarboxylic acid having 7 to 9 carbon atoms including 2-methylhexanoic acid.
As such a mixed acid, a mixed acid of a saturated branched-chain aliphatic monocarboxylic acid having 7 carbon atoms and a saturated branched-chain aliphatic monocarboxylic acid having 8 carbon atoms, or similarly, having 7 carbon atoms and 9 carbon atoms A mixed acid of C2, C7, C8 and C7, and a mixture of two or more C7 and C8 mixed two or more. An acid is mentioned. However, as described above, in any case, it is preferable that at least 2-methylhexanoic acid is contained in a predetermined amount or more. Specifically, 2-methylhexanoic acid and 2-ethylhexanoic acid, 2-methylhexanoic acid and 3,
5-dimethylhexanoic acid, 2-methylhexanoic acid and 3,
Two kinds of mixed acids such as 5,5-trimethylhexanoic acid, or 2-methylhexanoic acid and 2-ethylhexanoic acid,
An example is a mixed acid of three kinds composed of 3,5-dimethylhexanoic acid.

On the other hand, when the saturated branched-chain aliphatic monocarboxylic acid having 7 to 9 carbon atoms including these 2-methylhexanoic acid is not used as the total amount of the carboxylic acid component, the remaining carboxylic acid moiety is the monocarboxylic acid. It may be a carboxylic acid, a linear monocarboxylic acid or a branched monocarboxylic acid. However, it is preferably a branched monocarboxylic acid, and the entire carboxylic acid preferably has a branched structure. When a linear monocarboxylic acid is used, it is preferably 20% by weight or less, more preferably 10% by weight or less, based on the total amount of carboxylic acid. If it is used in an amount of more than 20% by weight, the compatibility with hydrofluorocarbon is poor and the hydrolysis resistance is remarkably poor. The carbon number of the monocarboxylic acid used for the remaining carboxylic acid moiety other than 2-methylhexanoic acid and the saturated branched-chain aliphatic monocarboxylic acid having 7 to 9 carbon atoms is preferably 5 to 12, and more preferably 7 ~
It is 9. When a monocarboxylic acid having a carbon number of more than 12 is used, compatibility with hydrofluorocarbon is deteriorated, and when a monocarboxylic acid having a carbon number of less than 5 is used, corrosiveness to a metal may be increased, which is not preferable.

The viscosity range of the ester obtained from the above alcohol and acid is such that the kinematic viscosity at 40 ° C. is usually 5 cst to 1
It is 15 cst, and preferably 5 cst to 56 cst. If the kinematic viscosity at 40 ° C. is less than 5 cst, the lubricity deteriorates, and if it exceeds 115 cst, the compatibility deteriorates, which is not preferable. In order to obtain an ester in this viscosity range, two or more kinds of these esters may be mixed, or two or more kinds of acids may be reacted with an alcohol to obtain an ester having a desired viscosity grade.

For example, VG5 (viscosity at 40 ° C. is 5 cs
Examples of the ester of t) include neopentyl glycol di (2-methylhexanate).

The ester of VG8 is prepared by mixing neopentyl glycol di2-ethylhexanate or neopentyl glycol di2-methylhexanate / trimethylolpropane tri-2-methylhexanate at a weight ratio of about 60/40. Or 2-methylhexanoic acid / 3,5,5-trimethylhexanoic acid = about 60/40
It is obtained by reacting a mixed carboxylic acid in a weight ratio with neopentyl glycol.

The ester of VG15 is trimethylolpropane tri-2-methylhexanate, or neopentyl glycol di3,5,5-trimethylhexanate / pentaerythritol tetra3,5,5-trimethylhexanate at about 90%. / 10 weight ratio, or neopentyl glycol di 3,5-
Dimethylhexanate / trimethylolpropane tri 3,5-dimethylhexanate is mixed at a ratio of about 50/50 by weight, or neopentyl glycol di2-methylhexanate / trimethylolpropane tri 3,5,5-trimethylhexanate. It is obtained by mixing nates in a weight ratio of about 55/45.

As the ester of VG22, trimethylolpropane tri-2-methylhexanate / pentaerythritol tetra-2-methylhexanate is about 40/6.
0 weight ratio or neopentyl glycol di3,5,5-trimethylhexanate / pentaerythritol tetra 3,5,5-trimethylhexanate at about 75/25 weight ratio or neopentyl Glycol di 3,5,5-trimethylhexanate / trimethylolpropane tri 3,5,5
-By mixing trimethylhexanate in a weight ratio of about 65/35 or 2-methylhexanoic acid / 3,3
5,5-trimethylhexanoic acid = about 70/30 (weight ratio) by reacting a mixed carboxylic acid with trimethylolpropane, or trimethylolpropane tri2-methylhexanate / pentaerythritol tetra 3,5,5- About 80/20 trimethylhexanate
By mixing in a weight ratio, or 2-methylhexanoic acid / 2-ethylhexanoic acid = about 20/80 (weight ratio)
Of 2-methylhexanoic acid / 3,5 by reacting mixed carboxylic acid of
It is obtained by reacting trimethylolpropane with a mixed carboxylic acid of dimethylhexanoic acid = about 45/55 (weight ratio).

The ester of VG32 is neopentyl glycol di3,5,5-trimethylhexanate / pentaerythritol tetra3,5,5-trimethylhexanate in a mixture of about 60/40 weight ratio, or neopentyl glycol. Di 3,5,5-trimethylhexanate / trimethylolpropane tri 3,5,5-
By mixing trimethylhexanate in a ratio of about 35/65 by weight, or by mixing 2-methylhexanoic acid / 3,5,5
5-trimethylhexanoic acid = about 35/65 weight ratio mixed carboxylic acid is reacted with trimethylolpropane, or 2-methylhexanoic acid / 3,5-dimethylhexanoic acid = about 80/20 weight ratio mixed carboxylic acid. By reacting an acid with pentaerythritol, or by reacting pentaerythritol with a mixed carboxylic acid of 2-methylhexanoic acid / 3,5,5-trimethylhexanoic acid = about 90/10 weight ratio, or 2
By reacting a mixed carboxylic acid of -ethylhexanoic acid / 3,5,5-trimethylhexanoic acid = about 65/35 (weight ratio) with trimethylolpropane, or 2
-Methylhexanoic acid / 2-ethylhexanoic acid = about 60 /
By reacting 40 (weight ratio) of mixed carboxylic acid and pentaerythritol, or by reacting mixed carboxylic acid of 2-methylhexanoic acid / 3,5-dimethylhexanoic acid = about 80/20 (weight ratio) with pentaerythritol Or from trimethylolpropane tri3,5-dimethylhexanate.

The ester of VG56 is trimethylolpropane tri 3,5,5-trimethyl hexanate, or neopentyl glycol di 3,5,5-trimethyl hexanate / pentaerythritol tetra 3,5,5-trimethyl hexanate. By mixing the carboxylic acid at a ratio of 35/65 by weight, or by reacting a mixed carboxylic acid of 2-methylhexanoic acid / 3,5,5-trimethylhexanoic acid = about 50/50 by weight with pentaerythritol, or 2-ethylhexanoic acid / 3,
It is obtained by reacting trimethylolpropane with a mixed carboxylic acid of 5,5-trimethylhexanoic acid = about 75/25 (weight ratio). However, the ester used in the present invention is not limited to the above.

As described above, various types of esters of various viscosity grades can be obtained. Considering the compatibility with HFC134a and the hydrolysis resistance as mentioned above, (A) neopentyl glycol, trimethylolpropane or pentapentane is used. Ester obtained from erythritol and 2-methylhexanoic acid and / or a mixture of these esters, or (B) a mixed acid of 2-methylhexanoic acid and 3,5,5-trimethylhexanoic acid and trimethylolpropane or pentaerythritol The ester obtained from is the best. From the (A) type, esters of VG5 to VG22 are obtained, and from the (B) type, esters of VG22 to VG56 are obtained.

The ester used in the present invention includes at least one neopentyl polyol described above and at least one saturated saturated aliphatic monocarboxylic acid or lower alkyl ester thereof, an acid anhydride and the like described above. Thus, it can be obtained by a usual esterification reaction or transesterification reaction. In this case, the lower the acid value of the obtained ester is, the more preferable it is usually 0.1 mgKOH / g or less, particularly 0.05 mgKOH / g or less. If the acid value is larger than 0.1 mgKOH / g, the corrosiveness to metal may be increased, which is not preferable. The hydroxyl value of the ester used in the present invention is usually 1
More than mgKOH / g and less than 50mgKOH / g, preferably 1mg
KOH / g or more and 30 mg KOH / g or less. More preferably, it is 2 mgKOH / g or more and 20 mgKOH / g or less. Hydroxyl value is 5
If it is greater than 0 mgKOH / g, the hygroscopicity will increase and 1 mgKOH / g will
If it is smaller than g, abrasion resistance is deteriorated, which is not preferable.

A working fluid comprising a composition containing hydrofluorocarbon and the above-mentioned ester sufficiently satisfies the object of the present invention. However, compared with CFC12-mineral oil system, which is a conventional working fluid, hydrofluorocarbon-ester system has higher polarities of both freon and oil and tends to contain water. Although the refrigerator is equipped with a dryer that removes water by molecular sieves, the ester may be hydrolyzed by the remaining water that cannot be sufficiently removed to form a carboxylic acid. It is feared that the generated carboxylic acid corrodes the metal and causes wear and copper plating. Therefore, it is desirable to add a certain epoxy compound so that the produced carboxylic acid does not have a bad influence.

CFC12 and HCFC22 containing chlorine atoms
In this system, hydrochloric acid is generated by the decomposition of freon, so in order to trap it, epoxy compounds such as phenylglycidyl ether type epoxy compounds, epoxidized fatty acid monoesters, and epoxidized vegetable oils are widely added to oils such as naphthenic oil. ing. As disclosed in JP-A-57-63395, there is also an example in which a compound having an epoxycycloalkyl group such as epoxycyclooctane is added to a polyether compound to prevent the deterioration of the polyether compound due to hydrochloric acid. .

However, the acid generated in the composition of the hydrofluorocarbon and the ester in the present invention is not a strong acid such as hydrochloric acid but is a saturated branched chain aliphatic monocarboxylic acid mainly having 7 to 9 carbon atoms. It has been found that the addition of the compound having an epoxycyclohexyl group and / or the compound having an epoxycyclopentyl group is very effective in the present invention.

The compound having an epoxycyclohexyl group and the compound having an epoxycyclopentyl group used in the present invention have 5 to 40 carbon atoms, preferably 5 to 2 carbon atoms.
No. 5, 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-epoxynorbornane, 2- (7
-Oxabicyclo [4.1.0] hept-3-yl)-
Spiro (1,3-dioxane-5,3 '-[7] oxabicyclo [4.1.0] heptane), 4-epoxyethyl-1,2-epoxycyclohexane, 4- (1'-methylepoxyethyl) -1,2-epoxy-2-methylcyclohexane 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, 2- (7
-Oxabicyclo [4.1.0] hept-3-yl)-
It is spiro (1,3-dioxane-5,3 '-[7] oxabicyclo [4.1.0] heptane). In the present invention, these compounds having an epoxycyclohexyl group may be used alone or in combination of two or more, and the compounds having an epoxycyclopentyl group may be used alone or in combination of two or more. Further, a compound having an epoxycyclohexyl group and a compound having an epoxycyclopentyl group may be used in combination. The amount added is usually 0.05 to 2.0 parts by weight, preferably 0.1 to 1.5 parts by weight, and more preferably 0.1 to 1.0 parts by weight, relative to 100 parts by weight of the ester used in the present invention. It is a department.

Further, triaryl phosphate and / or triaryl phosphite may be added to improve the lubricity, protect the metal surface from carboxylic acid corrosion, and prevent copper plating from occurring. It is also effective to add a benzotriazole and / or a benzotriazole derivative, or to add a metal deactivator having a chelating ability in order to improve thermal stability.

The triaryl phosphate and triaryl phosphite used in the present invention have 18 to 18 carbon atoms.
70, more preferably 18 to 50 carbon atoms
belongs to. 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 Diphenyl phosphite, xylenyl diphenyl phosphite, tris (2,4-di-t-butylphenyl) phosphite, trinonylphenyl phosphite, tris (tribromophenyl) phosphite, Examples thereof include triaryl phosphites such as lis (dibromophenyl) phosphite, preferably triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, tris (2,4-di-t-butylphenyl) phosphite. These are fate, triphenyl phosphite, tricresyl phosphite, trixylenyl phosphite, and tris (2,4-di-t-butylphenyl) phosphite. Triaryl phosphate and /
Alternatively, the amount of triaryl phosphite added is usually 0.1 to 5.0 with respect to 100 parts by weight of the ester used in the present invention.
Parts by weight, preferably 0.5 to 2.0 parts by weight.

The amount of benzotriazole and / or benzotriazole derivative used in the present invention is usually 0.001 with respect to 100 parts by weight of the ester used in the present invention.
To 0.1 part by weight, preferably 0.003 to 0.0
3 parts by weight. The benzotriazole and benzotriazole derivative used in the present invention have 6 to 50 carbon atoms.
And preferably from 6 to 30. Specifically, benzotriazole, 5-methyl-1H-benzotriazole, 1-dioctylaminomethylbenzotriazole, 1-dioctylaminomethyl-5-methylbenzotriazole, 2- (5'-methyl-2'-hydroxyphenyl) ) Benzotriazole, 2- [2'-hydroxy-3 ', 5'-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2-
(3 ', 5'-di-t-butyl-2'-hydroxyphenyl) benzotriazole, 2- (3'-t-butyl-
5'-methyl-2'-hydroxyphenyl) -5-chlorobenzotriazole, 2- (3 ', 5'-di-t-butyl-2'-hydroxyphenyl) -5-chlorobenzotriazole, 2- (3 ', 5'-di-t-amyl-
2'-hydroxyphenyl) benzotriazole, 2-
(5'-t-butyl-2'-hydroxyphenyl) benzotriazole, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-5'-t-octylphenyl) Benzotriazole, 2- [2'-hydroxy-3 '-(3 ", 4",
5 ", 6" -tetrahydrophthalimidomethyl) -5'-
Methylphenyl] benzotriazole etc. are mentioned, Preferably it is benzotriazole, 5-methyl-1H-benzotriazole etc.

The amount of the metal deactivator used in the present invention is usually 0.001 to 2.0 parts by weight, and preferably 0.00, to 100 parts by weight of the ester used in the present invention.
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 5.
It is 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, N, N'-salicylidenehydrazine,
N, N'-bis (α, 5-dimethylsalicylidene)-
1,2-diaminoethane, N, N′-bis (α, 5-dimethylsalicylidene) -1,3-propanediamine,
N, N'-bis (α, 5-dimethylsalicylidene)-
1,6-hexanediamine, N, N'-bis (α, 5-
Dimethylsalicylidene) -1,10-decanediamine,
N, N'-bis (α, 5-dimethylsalicylidene) ethylenetetraamine, salicylaldoxime, 2-hydroxy-5-methylacetophenooxime, acetylacetone, ethyl acetoacetate, 2-ethylhexyl acetoacetate, dimethyl malonate , Diethyl malonate, malonic acid 2
-Ethylhexyl, anthranilic acid, nitronilotriacetic acid,
Examples thereof include dihydroxyethylglycine, hydroxyethylethylenediamine triacetic acid, hydroxyethyliminodiacetic acid, ethylenediamine, 3-mercapto-1,2-propanediol, alizarin, quinizarine, mercaptobenzothiazole, and the like, preferably N, N′-disalicylidene- 1,2-diaminoethane, N, N′-disalicylidene-1,2-diaminopropane, acetylacetone, acetoacetic acid ester, alizarin, quinizarin and the like.

Further, if necessary, a lubricating oil additive such as a normally used extreme pressure agent, oiliness improver, defoaming agent and the like other than those shown above may be added. Extreme pressure agents, those usable as oiliness improvers include, for example, zinc compounds such as zinc dialkyldithiophosphate, zinc diaryldithiophosphate, thiodipropionate, dialkyl sulfide, dibenzyl sulfide, dialkyl polysulfide, alkyl mercaptan, Dibenzothiophene,
Sulfur compounds such as 2,2′-dithiobis (benzothiazole), phosphorus compounds such as trialkyl phosphite and trialkyl phosphate, chlorine compounds such as chlorinated paraffin, molybdenum dithiocarbamate, molybdenum dithiophosphate, molybdenum disulfide and the like Examples thereof include molybdenum compounds, perfluoroalkyl polyethers, trifluoroethylene chloride polymers, fluorine compounds such as graphite fluoride, silicon compounds such as fatty acid-modified silicone, and graphite. What is used as an antifoaming agent is a silicone oil such as dimethylpolysiloxane or an organosilicate such as diethyl silicate. Also, an organic tin compound,
An additive that stabilizes the chlorofluorocarbon refrigerant such as a boron compound may be added.

The composition for a working fluid for a refrigerator of the present invention can be easily prepared by blending a hydrofluorocarbon and the above-mentioned ester used in the present invention or an oil obtained by adding an additive to the ester by a conventional method. You can The compounding ratio is usually HFC134a / oil = 5/1 to 1 /
10 (weight ratio), preferably 2/1 to 1/5 (weight ratio)
Is.

The hydrofluorocarbon used in the present invention means 1,1,1,2-tetrafluoroethane (H
FC134a), 1,1,2,2-tetrafluoroethane (HFC134), 1,1-difluoroethane (HF
C152a), 1,1,1-trifluoroethane (HF
C143a), pentafluoroethane (HFC12
5), difluoromethane (HFC32) and the like, with 1,1,1,2-tetrafluoroethane being particularly preferable.

[0044]

EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. Example 1 A 1-liter four-necked flask was equipped with a stirrer, a thermometer, a nitrogen blowing tube, and a dehydration tube with a condenser. 104 g (1.0 mol) of neopentyl glycol and 260 g (2.0 mol) of 2-methylhexanoic acid were placed in the flask, and the esterification reaction was carried out at 240 ° C. for 10 hours under a nitrogen stream to obtain ester A.
Got Further, using alcohols and carboxylic acids shown in Table 1 and Table 2, the same reaction is performed below to obtain the ester B to
T and esters ad were obtained.

[0045]

[Table 1]

[0046]

[Table 2]

The esters A to T and the mixture of these esters gave the oils 1 to 21 used in the present invention as shown in Tables 3 and 4. Table 4 also shows oils 1 to 8 used in Comparative Examples, which consist of esters a to d and other oil types. Oils 1 to 21 used in these products of the present invention and oils 1 to 8 used in comparative products
Kinematic viscosity and viscosity index (JI
S K-2283) was measured. The pour point (JIS K-2269) was also measured. The results are shown in Tables 3 and 4. Among the esters of the present invention, the esters of 2-ethylhexanoic acid (oils 2 and 19 used in the present invention) are significantly inferior in viscosity index and fluidity at low temperature as compared with the others.

[0048]

[Table 3]

[0049]

[Table 4]

The compositions of oils 22 to 35 used in the products of the present invention and oils 9 to 10 used in the comparative products prepared by adding additives to these esters are shown in Table 5. The amount (parts by weight) of the additive is shown relative to 100 parts by weight, and the additives (1) to (11) are shown below. (1) 1,2-epoxycyclopentane (2) 1,2-epoxycyclohexane (3) 2- (7-oxabicyclo [4.1.0] hept-3-yl) -spiro (1,3-dioxane -5,3 '
-[7] oxabicyclo [4.1.0] heptane) (4) bis (3,4-epoxycyclohexylmethyl)
Adipate (5) Phenyl glycidyl ether (6) 2-Ethylhexyl glycidyl ether (7) Tricresyl phosphate (8) Trixylenyl phosphate (9) Tricresyl phosphite (10) Benzotriazole (11) Acetylacetone

[0051]

[Table 5]

Example 2 The oils obtained in Example 1 (oils 1 to 35 used in the present invention and oils 1 to 8 used in comparative products) and 1,1,1,2-tetrafluoroethane (HFC134a), respectively. In order to examine the compatibility of the products of the present invention 1 to 35 and the comparative products 1 to 8 which are the compositions of
The two-phase separation temperatures at low and high temperatures were measured at various sample concentrations of 10 vol% for 1,1,1,2-tetrafluoroethane. In the comparative product, the measurement of the high temperature separation temperature was omitted for the low temperature two-phase separation temperature higher than 0 ° C. The results are shown in Table 6, Table 7 and Table 8. As is clear from Tables 6, 7, and 8, the products of the present invention have a higher compatibility than Comparative Products 1 to 3 which are compositions of an ester of a linear monocarboxylic acid and HFC134a (for example, the present invention). Product 2 and comparative product 1, invention product 11 and comparative product 2, invention product 9 and comparative product 3), and comparative product 4 which is a composition of a carboxylic acid ester having a branched chain and a long carbon number and HFC134a.
Was poorly compatible. Further, the conventional oils such as naphthene oil and Comparative Products 5 and 6 which are compositions of poly α-olefin and HFC134a also had poor compatibility. Further, the products 22 to 35 of the present invention to which the additives are added have excellent compatibility. In addition, among the products of the present invention, 2-methylhexanoic acid is less than 25% by weight with respect to the total amount of carboxylic acid in the tri- or higher-valent neopentyl polyol ester, (Products of the present invention 16, 19),
Even if 2-methylhexanoic acid is 25% by weight or more based on the total amount of carboxylic acid, saturated branched chain aliphatic monocarboxylic acid having 7 to 9 carbon atoms is less than 70% by weight based on the total amount of carboxylic acid (the present invention product 15, In 17), the compatibility with HFC134a is poor. In addition, for all esters of branched monocarboxylic acids, some linear monocarboxylic acids were used (invention product 2
0,21) has a poor compatibility with HFC134a, especially 20
Those used in excess of wt% (invention product 21) are significantly inferior.

[0053]

[Table 6]

[0054]

[Table 7]

[0055]

[Table 8]

Example 3 Inventive products 1 to 35 and comparative products 1 to 3, 9, and 10 were subjected to a shield tube test under the following conditions in order to examine hydrolysis resistance. That is, oil 10 in a glass tube.
g, HFC134a (5 g) was added, water was added to the oil in an amount of 3000 ppm, and iron, copper and aluminum were added as catalysts, and the tube was sealed. 175
After testing at 14 ° C for 14 days, the sealed tube was opened, and the acid value of the oil after removing the freon was examined. The results are shown in Table 9. As is clear from Table 9, the products 1 to 21 of the present invention are remarkably excellent in hydrolysis resistance as compared with the comparative products 1 to 3 using the ester of the linear carboxylic acid. Further, among the products of the present invention, the divalent neopentyl polyol ester contains 2-methylhexanoic acid in an amount of 70% by weight or more based on the total amount of the carboxylic acid (Products 1 and 3 of the present invention), or a trivalent or more neopentyl polyol ester. The ester contains 2-methylhexanoic acid in an amount of 25% by weight or more based on the total amount of the carboxylic acid, and contains 70% by weight or more of the saturated branched chain aliphatic monocarboxylic acid having 7 to 9 carbon atoms in the total amount of the carboxylic acid (the present invention. Items 4, 6, 7, 9,
12, 14, 18) were particularly good. In addition, all of the esters of branched monocarboxylic acids, in which some linear monocarboxylic acids were used (invention products 20 and 21) were inferior in hydrolysis resistance, and particularly those in which the amount was more than 20% by weight ( Invention product 21)
Is significantly inferior. Further, the composition using the oil added with the compound having the epoxycyclopentyl group or the epoxycyclohexyl group (the products 22 to 35 of the present invention) is a composition using the oil added with phenylglycidyl ether or 2-ethylhexylglycidyl ether ( The acid value was significantly lower than that of Comparative Products 9 and 10), and it was effective in preventing carboxylic acid formation.

[0057]

[Table 9]

Example 4 In order to examine the wear resistance of the oils 1 to 21, 28 to 31 used in the products of the present invention and the oils 5 to 8 used in the comparative products, those having a hydroxyl value of less than 1 mgKOH / g and 1 mgKOH respectively. / G or more was prepared and Falex test was conducted. Here, the ester having a hydroxyl value of 1 mgKOH / g or more was prepared by reducing the equivalent of carboxylic acid to alcohol. For example, hydroxyl value 10.5mg
KOH / g ester A is neopentyl glycol 1
04 g (1.0 mol) and 2-methylhexanoic acid 252.
2 g (1.94 mol) was taken in a flask, and the reaction was carried out in the same manner as in Example 1 to obtain. The test is 1,
1,1,2-Tetrafluoroethane (HFC134a) was blown into the oil at a rate of 150 cc / min, and it was rotated for 10 minutes with no load, followed by preliminary rotation for 5 minutes at 200 1b, and then for 60 minutes at 350 1b. The wear amount of the V block and the pin after the operation was examined. The results are shown in Table 10. As is clear from Table 10, the products of the present invention are compositions with conventional oils such as naphthene oil and poly α-olefins (Comparative products 5 and 6) and compositions with polyether compounds (Comparative products 7 and 8). Wear resistance was better than Among the esters of the present invention, the hydroxyl value is 1 mg.
Hydroxyl value is 1m compared to ester smaller than KOH / g
The ester having gKOH / g or more had excellent abrasion resistance. In addition, those to which triaryl phosphate or triaryl phosphite is added (invention products 28 to 31) are
The wear resistance was remarkably improved. In addition, the above-mentioned Example 1
In each evaluation of the ester in Examples 3 to 3 and Examples 5 to 7 described later, there is no difference in effect between the ester having a hydroxyl value of less than 1 mgKOH / g and the ester having a hydroxyl value of 1 mgKOH / g or more, and only the abrasion resistance is different. Admitted.

[0059]

[Table 10]

Example 5 Using the products 22, 24, 30, 32, 33 and 34 of the present invention, the effect of preventing benzotriazole from copper plating was examined. That is,
Take 10 g of oil and 5 g of HFC134a in a glass tube, add 1% of 2-methylhexanoic acid copper salt to the oil, and use iron as a catalyst.
Copper and aluminum were added and the tube was sealed. After testing at 175 ° C for 14 days, the presence or absence of copper plating was visually confirmed. The results are shown in Table 11. As is clear from Table 11, the addition of benzotriazole was able to prevent the occurrence of copper plating.

[0061]

[Table 11]

Example 6 A shielded tube test was conducted to examine the thermal stability of the products 1 to 35 of the present invention. That is, oil 10g, H in the glass tube
FC134a (5 g) was taken, and iron, copper, and aluminum were added as a catalyst and the tube was sealed. After testing at 175 ° C. for 14 days, the appearance of the HFC134a and oil composition and the presence or absence of deposits were examined. The results are shown in Table 12. As is clear from Table 12, all the products of the present invention had a good appearance, no precipitates, and good thermal stability.

[0063]

[Table 12]

Example 7 The volume resistivity (25 ° C.) at 25 ° C. was examined in order to examine the electrical insulation properties of the oils used in the invention products 3, 4, 6, 7, 9, 10 and the oils used in the comparative products 7, 8. JIS C210 1) was measured. The results are shown in Table 13. As is clear from Table 13, the ester of the present invention has a larger volume resistivity and is superior in electrical insulation as compared with the polyether compound.

[0065]

[Table 13]

[0066]

EFFECTS OF THE INVENTION The composition for a working fluid for a refrigerator of the present invention containing hydrofluorocarbon and an ester or an oil to which an additive is added to an ester has compatibility, lubricity, thermal stability,
It has excellent electrical insulation.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C10M 133: 38 129: 18 129: 10) C10N 40:30

Claims (10)

[Claims] 1. A neopentyl polyol and a carbon number of 7 to 9
0.05 to 2.0 parts by weight of a compound having an epoxycyclohexyl group and / or a compound having an epoxycyclopentyl group is added to 100 parts by weight of the ester, in an ester obtained from the saturated branched aliphatic monocarboxylic acid. A composition for refrigerating machine working fluid containing the refrigerating machine oil and hydrofluorocarbon. 2. A neopentyl polyol and a carbon number of 7 to 9
0.05 to 2.0 parts by weight of a compound having an epoxycyclohexyl group and / or a compound having an epoxycyclopentyl group is added to 100 parts by weight of the ester, in an ester obtained from the saturated branched aliphatic monocarboxylic acid. 0.1 to 5.0 parts by weight of triaryl phosphate and / or triaryl phosphite, and 0.001 to 0.1 part of benzotriazole and / or benzotriazole derivative relative to 100 parts by weight of the ester.
Part by weight and metal deactivator having chelating ability 0.001
The composition for refrigerating machine working fluids containing refrigerating machine oil and hydrofluorocarbon which mix | blend at least 1 sort (s) or more selected from the group which consists of -2.0 weight part. 3. A carboxylic acid containing a saturated branched chain aliphatic monocarboxylic acid having 7 to 9 carbon atoms in an amount of 70% by weight or more based on the total amount of the carboxylic acid, wherein the saturated branched chain aliphatic monocarboxylic acid is at least 2-methyl. The composition for a working fluid of a refrigerator according to claim 1 or 2, which is an ester obtained from a carboxylic acid containing 25% by weight or more of hexanoic acid based on the total amount of the carboxylic acid and a trivalent or higher neopentyl polyol. 4. An ester obtained from a carboxylic acid containing 2-methylhexanoic acid in an amount of 70% by weight or more based on the total amount of the carboxylic acid and a divalent neopentyl polyol.
Or the composition for a working fluid of a refrigerator described in 2. 5. The saturated branched-chain aliphatic monocarboxylic acid having 7 to 9 carbon atoms consists only of 2-methylhexanoic acid, or 2-ethylhexanoic acid, 3,5-dimethylhexanoic acid and 3,5,5- The composition for a refrigerator working fluid according to claim 3, which is a mixed acid containing at least one selected from the group consisting of trimethylhexanoic acid and 2-methylhexanoic acid. 6. The composition for refrigerator working fluid according to claim 3, wherein the tri- or higher valent neopentyl polyol is trimethylolpropane and / or pentaerythritol. 7. The refrigerator working fluid composition according to claim 4, wherein the divalent neopentyl polyol is neopentyl glycol. 8. The composition for a working fluid of a refrigerator according to claim 1, which is an ester composed of trimethylolpropane and / or pentaerythritol and 2-methylhexanoic acid. 9. The composition for a working fluid of a refrigerator according to claim 1, which is an ester composed of neopentyl glycol and 2-methylhexanoic acid. 10. The hydroxyl value of the ester is 1 to 50 mgK.
The composition for refrigerator working fluid according to claim 1 or 2, which is OH / g.