JPH08302372A - Synthetic lubricating oil and refrigerator working fluid composition - Google Patents

Abstract

PURPOSE: To obtain a synthetic lubricating oil which is excellent not only in compatibility with a nonchlorinous fluorocarbon refrigerant in a wide temp. range and but also in electrical insulating properties, hydrolysis stability, and low-temp. flowability. CONSTITUTION: This synthetic lubricating oil contains 4-18C monohydric alcohols of which 50mol% or higher is accounted for by branched alcohols, a hydroxycarboxylic acid, and 4-18C monocarboxylic acids of which 50mol% or higher is accounted for by branched carboxylic acids.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synthetic lubricating oil, and more particularly to a synthetic lubricating oil used as a refrigerating machine oil for a refrigerator using non-chlorine Freon as a refrigerant, and containing this lubricating oil and non-chlorine Freon. The present invention relates to a working fluid composition for a refrigerator.

[0002]

2. Description of the Related Art Conventionally, a compression type refrigerator has CFC-11 (CCl ₃ F) and CFC-12 (CC as refrigerants.
l ₂ F ₂ ), HCFC-22 (CHClF ₂ ), CFC
-115 (CF ₃ -CClF ₂₎ is chlorofluorocarbon refrigerants, such as have been used. Of these, CFC-12 and other chlorofluorocarbons are subject to regulation because they lead to the destruction of the ozone layer. Also, HCFC
The use of -22 is about to be regulated in the medium to long term.

As a substitute for these chlorofluorocarbons, non-chlorine CFCs are about to be used.
HFC with similar thermodynamic properties as an alternative to C-12
-134a (CH ₂ F-CF ₃ ) is the same as HCFC-
As a substitute for No. 22, a mixed refrigerant containing HFC-32 (CH ₂ F ₂ ) has been proposed.

Refrigerating machine oil has various required performances, but the compatibility with the refrigerant is extremely important in terms of the lubricating performance of the refrigerating machine and the efficiency of the system. However, HFC-134a
Non-chlorine CFC refrigerants, such as HFC-32 and HFC-32, are naphthenic mineral oils, paraffinic mineral oils, and alkylbenzene-based refrigerating machine oils that have been used as refrigerating machine oils in compression refrigeration systems. It is known that it shows almost no compatibility and causes two-layer separation at low and high temperatures. Therefore, ester synthetic oil has come to be used as a new refrigerating machine oil, but this ester synthetic oil is also sufficient for chlorine-based CFC refrigerants represented by HCFC-22, which will be regulated in the future. Does not show compatibility. In particular, it is known that two-layer separation occurs at low temperatures. When such two-layer separation occurs, the lubricating oil stays in the condenser and the expander, the refrigeration efficiency is lowered, and the lubricating oil is not satisfactorily supplied to the sliding surface of the compressor.
As a result, poor lubrication may result in inconvenience such as seizure of the compressor, which makes it unsuitable for actual use.

[0005]

Under such circumstances, various lubricating oils which are compatible with a chlorine-free CFC refrigerant have been proposed. For example, U.S. Pat. No. 4,755,316 proposes a polyoxyalkylene glycol-based lubricating oil having a specific molecular weight distribution and having hydroxyl groups (-OH) at both ends. This is HFC-134a
Indicates compatibility in the range of about -40 ° C to + 50 ° C.
However, in actual use, compatibility at a higher temperature is required.

On the other hand, HFC-134a is mainly used for household refrigerators and car air conditioners as an alternative refrigerant for CFC-12.
The mixed refrigerant containing HFC-32 is mainly targeted for room air conditioners and industrial refrigerators.
In the case of household refrigerators and room air conditioners, the motor that drives the compressor is mostly used in the refrigerant-refrigerating machine oil mixture, and the refrigerating machine oil is required to have excellent electrical insulation. However, the electrical insulating property of polyoxyalkylene glycol is remarkably inferior to the conventional naphthenic mineral oil and paraffinic mineral oil, and is also highly hygroscopic. Therefore, it is unsuitable as refrigerator oil for household refrigerators and room air conditioners.

The ester-based synthetic oils described in JP-A-3-128991 and JP-A-3-128992 have a volume resistivity of 10 ¹³ to 10 ¹⁴ Ω at 80 ° C.
・ Has a good electrical insulation that can be used as refrigerating machine oil such as refrigerators and room air conditioners.
However, this ester synthetic oil has a drawback in that it is slightly inferior in terms of lubricating performance.

Further, in JP-A-5-179267, hydroxycarboxylic acid polyol ester, polyvalent carboxylic acid and monovalent carboxylic acid are essential as raw materials,
Esters using polyhydric alcohols are described as required. However, the use of polycarboxylic acids reduces the hydrolytic stability of the ester. This is probably because industrially available polyvalent carboxylic acids are almost linear, and the sites crosslinked with the linear polycarboxylic acids are vulnerable to hydrolysis.

Further, JP-A-5-179268 discloses a hydroxycarboxylic acid monoalkylene glycol ester as a raw material and an ester containing a monovalent carboxylic acid as essential components, and JP-A-7-70577 discloses a hydroxycarboxylic acid. Esters containing an acid polymer and a monovalent carboxylic acid to which neopentylpolyol or a monovalent carboxylic acid is added as an essential component are described, respectively. But,
Both esters show high values at kinematic viscosity of 40 ° C,
In recent years, it cannot be applied to the low viscosity of refrigerating machine oil due to the energy saving of the compressor built into the refrigerator.

The present invention provides a synthetic lubricating oil having excellent compatibility with a non-chlorine-based CFC refrigerant in a wide temperature range, excellent electrical insulation and hydrolysis stability, and excellent low temperature fluidity. It is also an object of the present invention to provide a refrigerator working fluid composition comprising the synthetic lubricating oil and the non-chlorine CFC refrigerant.

[0011]

DISCLOSURE OF THE INVENTION The inventors of the present invention have made diligent studies to achieve the above object, and as a result, a specific branch 1
By using an ester prepared by synthesizing three components of a valent alcohol, a hydroxycarboxylic acid and a specific branched monovalent carboxylic acid as raw material components, all of the above-mentioned various performances desired as a refrigerating machine oil for a chlorine-free CFC refrigerant can be obtained. The present invention has been accomplished by knowing that a satisfactory synthetic lubricating oil can be obtained.

That is, the first aspect of the present invention is that a) a monovalent alcohol having 4 to 18 carbon atoms in which the branched alcohol accounts for 50 mol% or more, b) a hydroxycarboxylic acid, and c) a branched carboxylic acid. Relates to a synthetic lubricating oil characterized by containing an ester derived from a monovalent carboxylic acid having 4 to 18 carbon atoms which accounts for 50 mol% or more.

The second aspect of the present invention is that a) a branched alcohol
Monohydric alcohol having 4 to 18 carbon atoms in which 50% by mole or more, b) hydroxycarboxylic acid, and c) monovalent carboxylic acid having 4 to 18 carbon atoms in which branched carboxylic acid accounts for 50% by mole or more. It is composed of a synthetic lubricating oil consisting of an ester derived from and a non-chlorine Freon, and its weight ratio is 1: 9.
9 to 99: 1 refrigerator working fluid composition.

[0014]

The monovalent alcohol of the component a used in the present invention must have 4 to 18 carbon atoms,
It is preferably 4 to 13, and more preferably 4 to 10. Monovalent alcohols having 3 or less carbon atoms cannot be used because they adversely affect the hydrolysis stability and react with the metal constituting the refrigerator, causing corrosion.
Further, a monovalent alcohol having 19 or more carbon atoms cannot be used because the compatibility with a non-chlorine CFC refrigerant is extremely reduced.

The monovalent alcohol includes straight-chain monovalent alcohol and branched monovalent alcohol. Among them, the branched monovalent alcohol accounts for 50 mol% or more of the whole. Is necessary, preferably 70 mol% or more, more preferably 80 mol% or more, and further preferably 90 mol% or more. When the branched monovalent alcohol is less than 50 mol%, favorable results cannot be obtained in terms of hydrolysis stability and compatibility with a chlorine-free fluorocarbon refrigerant.

As the straight-chain monovalent alcohol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, 1 -Decanol, 1-dodecanol, 1-tridecanol, 1
-Tetradecanol, 1-hexadecanol, 1-octadecanol and the like.

As the branched monovalent alcohol, 2-methyl-1-propanol, 2-methyl-2-propanol,
2-methyl-1-butanol, 2-ethyl-1-propanol, 2-methyl-1-pentanol, 2,2-dimethyl-1-butanol, 2-methyl-2-ethyl- 1-
Propanol, 2-methyl-1-hexanol, 2,2
-Dimethyl-1-pentanol, 2-methyl-2-ethyl-1-butanol, 1-isoheptanol, 2-ethyl-1-hexanol, 2,2-dimethyl-1-hexanol , 2-methyl-2-ethyl-1-pentanol,
1-isooctanol, 3,5,5-trimethyl-1-
Hexanol, 1-isononanol, 1-isodecanol
And isododecanol, isotridecanol, isotetradecanol, isohexadecanol and isooctadecanol.

From the viewpoint of thermal stability and oxidative stability, the hydroxyl group of the monovalent alcohol is preferably a primary hydroxyl group, more preferably the hydrogen atom is not bonded to the carbon atom at the 2-position as seen from the hydroxyl group. This is the case. In addition, the presence of a branch at the carbon atom at the 2-position with respect to the hydroxyl group is preferable from the viewpoint of obtaining good hydrolysis stability. Further, from the viewpoint of compatibility with a chlorine-free CFC refrigerant, the alkyl group of the alcohol preferably has a methyl group or an ethyl group as a branched chain. From these facts, among the monovalent alcohols, the branched alcohol having two methyl groups or ethyl groups at the carbon atom at the 2-position counting from the hydroxyl group has thermal stability, oxidation stability, hydrolysis stability, It is especially excellent in terms of compatibility with non-chlorine CFC refrigerants.

Examples of the hydroxycarboxylic acid as the component b used in the present invention include 4-hydroxybutanoic acid and 4
Examples include -hydroxy-2-methylbutanoic acid, 5-hydroxypentanoic acid, 3-hydroxy-2,2-dimethylpropanoic acid, 2,2-dimethylolpropanoic acid and 2-hydroxyisobutanoic acid.

From the viewpoint of thermal stability and oxidative stability, the hydroxyl group of hydroxycarboxylic acid is preferably a primary hydroxyl group, and more preferably a hydrogen atom is not bonded to the carbon atom at the 2-position as viewed from the hydroxyl group. Further, from the viewpoint of hydrolysis stability, the hydroxycarboxylic acid preferably has an alkyl group, and more preferably has one or more alkyl groups at the 2-position carbon atom adjacent to the carboxyl group carbon. Also, in terms of compatibility with non-chlorine CFC refrigerants,
The alkyl group of hydroxycarboxylic acid is particularly preferably a methyl group or an ethyl group.

As such a hydroxycarboxylic acid, the following formula (1); (R ¹ and R ² are a hydrogen atom, a hydroxyl group, a —CH ₂ OH group or an alkyl group, and neither R ¹ nor R ² is a hydrogen atom).
¹ , R ² is a methyl group, an ethyl group, a hydroxyl group, —CH ₂ OH
Those such as groups are preferred. In particular, a hydroxycarboxylic acid having a neopentyl skeleton is the most optimal, and good results are obtained in terms of thermal stability, oxidation stability, hydrolysis stability, and compatibility with a chlorine-free CFC refrigerant.

From the viewpoint of hydrolysis stability, those having one or more branches at the 2-position carbon atom adjacent to the hydroxyl group of the hydroxycarboxylic acid are preferred. As such a hydroxycarboxylic acid, the following formula (2); (R ^3, R ⁴ is a hydrogen atom, a hydroxyl group or an alkyl group, R ³ and R ⁴ are not both be a hydrogen atom)
Among them, those in which R ³ and R ⁴ are a methyl group, an ethyl group, a hydroxyl group or the like are the most preferable, and favorable results can be obtained in terms of hydrolysis stability. For example, 2-
Hydroxybutanoic acid, 2-hydroxyisobutanoic acid, 2
-Hydroxypentanoic acid and the like.

The monovalent carboxylic acid as the component c used in the present invention is required to have 4 to 18 carbon atoms, preferably 4 to 13, and more preferably 4 to 10. When a monovalent carboxylic acid having 3 or less carbon atoms is used, it has an adverse effect on the hydrolysis stability and is highly corrosive,
Further, if a monovalent carboxylic acid having 19 or more carbon atoms is used, the compatibility with a non-chlorine CFC refrigerant decreases.

The monovalent carboxylic acid as the component c includes straight-chain 1
Carboxylic acids and branched monovalent carboxylic acids are included,
Of these, it is necessary that the branched monovalent carboxylic acid accounts for 50 mol% or more of the whole, preferably 70 mol% or more, more preferably 80 mol% or more, still more preferably 90 mol% or more. If the branched monovalent carboxylic acid is less than 50 mol%, favorable results cannot be obtained in terms of hydrolysis stability and compatibility with a chlorine-free fluorocarbon refrigerant.

Examples of the linear monovalent carboxylic acid include, for example,
Examples thereof include butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, lauric acid, tridecanoic acid, myriphosphoric acid, palmitic acid, stearic acid, and acid anhydrides thereof.

Examples of the branched monovalent carboxylic acid include 2-methylpropanoic acid, 2-methylbutanoic acid, 3-methylbutanoic acid, 2,2-dimethylpropanoic acid, 2-methylpentanoic acid, 3-methylpentanoic acid and 4-methyl. Pentanoic acid,
2,2-dimethylbutanoic acid, 2-ethylbutanoic acid, 3,
3-dimethylbutanoic acid, 2,2-dimethylpentanoic acid,
2-methyl-2-ethylbutanoic acid, 2,2,3-trimethylbutanoic acid, 2-ethylpentanoic acid, 3-ethylpentanoic acid, 2-methylhexanoic acid, 3-methylhexanoic acid, 4-methylhexanoic acid, 5 -Methylhexanoic acid, isoheptanoic acid, 2-ethylhexanoic acid, 3,5-dimethylhexanoic acid, 2,2-dimethylhexanoic acid, 2-methylheptanoic acid, 3-methylheptanoic acid, 4-methylheptanoic acid, 2- Propylpentanoic acid, isooctanoic acid,
2,2-dimethylheptanoic acid, 3,5,5-trimethylhexanoic acid, 2-methyloctanoic acid, 2-ethylheptanoic acid, 3-methyloctanoic acid, isononanoic acid, neononanoic acid, 2,2-dimethyloctanoic acid, 2-methyl-2-
Ethylheptanoic acid, 2-methyl-2-propylhexanoic acid, isodecanoic acid, neodecanoic acid, isotridecanoic acid,
Examples thereof include isomyristic acid, isopalmitic acid, isostearic acid, and acid anhydrides thereof.

Among such branched monovalent carboxylic acids,
Those having a branched alkyl group at the carbon atom at the 2-position adjacent to the carboxyl group are preferred. From the viewpoint of compatibility with a chlorine-free CFC refrigerant, the branched alkyl group of the carboxylic acid is preferably a methyl group or an ethyl group.

In the present invention, the use ratios of the above components a to c can be appropriately determined according to the type of each component depending on the required characteristics of the target synthetic lubricating oil. Generally, b component is 0.1 to 2 mol, and c is to 1 mol of component a.
The proportion of the component is preferably 0.1 to 4 mol, more preferably 0.5 to 1.5 mol of the b component and 0.3 to 3 of the c component.
Is a mole. The ester of the present invention can be obtained by reacting the above components a to c in such a ratio by a conventional method.

The ester of the present invention may be a naphthenic mineral oil, a paraffinic mineral oil, poly α-olefin, an alkylbenzene, an ester other than the ester of the present invention, a polyoxyalkylene glycol, a fluorine-containing polyester. -Used as a lubricating oil for chlorine-free CFC refrigerants by mixing with other lubricating oils such as fluorinated oils such as tell. When mixed with another lubricating oil, the proportion of the ester of the present invention in the mixture can be arbitrarily selected within a range that does not impair performance such as hydrolysis stability and compatibility with a chlorine-free CFC refrigerant, Generally, it is 10% by weight or more, preferably 30% by weight or more, more preferably 50% by weight or more.

The synthetic lubricating oil of the present invention has a kinematic viscosity at 100 ° C. of 1 to 50 cSt (10 ⁻⁶ m ² / s), preferably 1.5 to 40 cSt, more preferably 2 to 30 cSt.
Is. If the kinematic viscosity is lower than 1 cSt, the lubricating performance is insufficient, and if the kinematic viscosity is higher than 50 cSt, the compatibility with the non-chlorine CFC refrigerant decreases.
Neither is preferred.

The refrigerator working fluid composition of the present invention comprises a synthetic lubricating oil comprising the ester of the present invention and a non-chlorine CFC as a refrigerant. The weight ratio of the two is the synthetic lubricating oil. : Non-chlorine CFC is generally 1:99
˜99: 1, preferably 5:95 to 70:30.

The chlorine-free CFC used in the refrigerator working fluid composition of the present invention includes HFC-134a and HFC-3.
2, HFC-125 (1, 1, 1, 2, 2-pe
ntafluoroethane) or the like can be used. Any one of these or a mixture thereof can be appropriately selected depending on the application, cooling temperature, shape of the cooling device, and the like.

In order to further improve the performance of the synthetic lubricating oil and refrigerator working fluid composition of the present invention, conventionally known additives for refrigerator oils, such as antioxidants, extreme pressure agents, The metal deactivator and the like can be added alone or in combination of several kinds. The amount of these additives added is usually 10% by weight or less, preferably 5% by weight or less, based on the total amount of the refrigerating machine oil.

[0034]

Industrial Applicability The synthetic lubricating oil of the present invention is excellent in electric insulation, low temperature fluidity and hydrolytic stability, and in addition to this, HFC-134a, HFC-32 or HFC-1.
The refrigerating machine working fluid composition of the present invention consisting of a non-chlorine CFC represented by No. 25 shows excellent compatibility in a wide temperature range and is excellent as a refrigerating machine oil.

[0035]

EXAMPLES Next, the present invention will be specifically described with reference to Examples.

Example 1 A one-liter four-necked flask equipped with a stirrer, a nitrogen blowing tube, a thermometer and a water separator equipped with a condenser was charged with 3,
5,5-trimethyl-1-hexanol 144.2 g
(1.0 mol), 3-hydroxy-2,2-dimethylpropanoic acid 118.1 g (1.0 mol), 3,5,5-trimethylhexanoic acid 158.1 g (1.0 mol) and esterification catalyst As p-toluenesulfonic acid monohydrate, 2.9 g (0.015 mol) was added, and nitrogen gas was added to 30 g.
While blowing at a flow rate of 0 cm ³ / min, the reaction was carried out at 200 ° C. for 22 hours while removing the distilled water.

After the reaction, in order to remove unreacted acid and low-boiling substances, distillation was performed under reduced pressure (10 mmHg) at 200 ° C. for 8 hours. The product, which is the residue of distillation, was neutralized with a 10% by weight aqueous solution of potassium hydroxide, washed with water, and then under reduced pressure (1
It was dehydrated at 90 ° C for 1 hour. In addition, activated clay 4
After adding g, the mixture was stirred at 70 ° C. for 1 hour and then filtered to obtain an ester having an acid value of 0.02 mg KOH / g.

Examples 2 to 10 Monovalent alcohol, hydroxycarboxylic acid and monovalent carboxylic acid were changed as shown in Table 1 and Table 2, and Example 1
The esterification reaction and the post-treatment after the reaction were carried out in the same manner as in, to obtain each ester having an acid value shown in Table 1 and Table 2. For reference, the raw material components of Example 1 and the acid value of the ester are also shown in Table 1.

Comparative Examples 1 to 7 The alcohol component, hydroxycarboxylic acid component and carboxylic acid component shown in Table 3 were esterified at the molar ratios shown in the table. The reaction was carried out in the same manner as in Example 1, and the post-treatment was carried out in the same manner to obtain each ester having an acid value shown in Table 3.

The esters obtained in Comparative Examples 1 to 5 are different from the ester of the present invention in that polyhydric alcohol is used as the alcohol component, and further in Comparative Example 1. The obtained ester did not use hydroxycarboxylic acid, and the esters obtained in Comparative Examples 2 and 3 used polyvalent carboxylic acid as a part of the carboxylic acid component, and in Comparative Example 5. The obtained ester is also different from the ester of the present invention in that hydroxycarboxylic acid is polymerized.

Furthermore, in the ester obtained in Comparative Example 6, the number of carbon atoms of the monovalent alcohol as the alcohol component and the number of carbon atoms of the monovalent carboxylic acid as the carboxylic acid component are within the scope of the present invention. This is an example of the outside. In the ester obtained in Comparative Example 7, the proportion of the branched alcohol used in the monovalent alcohol as the alcohol component and the proportion of the branched carboxylic acid used in the monovalent carboxylic acid as the carboxylic acid component were , Are examples outside the scope of the present invention.

Furthermore, in Tables 1 to 3, Example 1 was used.
The abbreviations of the components used in Comparative Examples 1 to 10 and Comparative Examples 1 to 7 are as follows.

<Monovalent Alcohol of Component a> bC4: 2-Methyl-1-propanol bC5: 2-Methyl-1-butanol bC6: 2-Ethyl-1-butanol bC7: Isoheptanol BC8: 2-ethyl-1-hexanol bC9: 3,5,5-trimethyl-1-hexanol bC10: 1-isodecanol bC13: 1-isotridecanol bC18: isostearyl alcohol nC4: 1-butanol nC7: 1-heptanol nC8: 1-octanol

<Other alcohol components> bC20: isoaraquine alcohol NPG: neopentyl glycol TMP: trimethylol propane PE: pentaerythritol

<Hydroxycarboxylic acid as component b> HC5: 3-hydroxy-2,2-dimethylpropanoic acid DHC5: 2,2-dimethylolpropanoic acid 2HC4: 2-hydroxyisobutanoic acid

<C component monovalent carboxylic acid> bC4: 2-methylpropanoic acid bC5: 2-methylbutanoic acid bC6: 2-ethylbutanoic acid bC7: isoheptanoic acid bC8: 2-ethylhexanoic acid bC9: 3,5,5- Trimethylhexanoic acid bC10: Isodecanoic acid bC13: Isotridecanoic acid bC14: Isomyristic acid bC18: Isostearic acid nC4: Butanoic acid nC6: Hexanoic acid nC8: Octanoic acid

<Other carboxylic acid components> bC20: isoarachidic acid 2C4: succinic acid 2C6: adipic acid 2C10: sebacic acid 2C36: oleic acid dimer

[0048]

[Table 1]

[0049]

[Table 2]

[0050]

[Table 3]

The above Examples 1 to 10 and Comparative Examples 1 to 7
The performance of each of the esters obtained in 1. as a lubricating oil for a refrigerator was measured and evaluated according to the following procedure. The results are shown in Tables 4 and 5 below.

<Kinematic Viscosity> The kinematic viscosities at 40 ° C. and 100 ° C. were measured according to JIS K 2283.

<Pour point> The pour point is defined by JIS K 226.
It was measured according to 9.

<Electrical Insulation> The volume resistivity at 80 ° C. was measured according to JIS C 2101.

<Compatibility> 20 parts by weight of sample (0.6 g)
And a chlorine-free fluorocarbon refrigerant [HFC-134a and mixed refrigerant (HFC-32: HFC-125: HFC-134
a = 23: 25: 52)] 80 parts by weight (2.4 g) are enclosed in a thick-walled pyrex tube (total length 300 mm, outer diameter 10 mm, inner diameter 6 mm) cooled in an ethanol bath containing dry ice. Then, the temperature was raised and cooled at a rate of 1 ° C./min, and the two-layer separation temperature at high temperature and low temperature was visually measured in the range of −50 ° C. to + 80 ° C.

<Hydrolysis stability> Into a hard glass ampoule having a capacity of 6 ml, 5 ml of a sample having water content adjusted to 1,500 ± 300 ppm was injected. Replace the head space inside the ampoule with nitrogen and seal the tube.
Heated for 0 hours. After the test was completed, the package was opened and the acid value of the sample was measured.

<Abrasion resistance (lubricity)> ASTM D-2
According to 670, 150 HFC-134a in the sample
The Falex abrasion test was performed while blowing at a rate of ml / min. The sample temperature was set to 100 ° C., a running operation was carried out for 1 minute under a load of 150 pounds, and then an operation under a load of 250 pounds was carried out for 2 hours, and the wear amount of the pin after the operation was measured.

In Tables 4 and 5, the results obtained by measuring the following lubricating oils as commercially available refrigerating machine oils are also shown as Reference Examples 1 to 3. Reference Example 1: Polyoxyalkylene Glycol (ISO Viscosity Grade: VG56) Reference Example 2: Mineral Oil Refrigerating Machine Oil (ISO Viscosity Grade: VG32) Reference Example 3: Alkylbenzene Refrigerating Machine Oil (ISO Viscosity Grade) (Do: VG46)

[0059]

[Table 4]

[0060]

[Table 5]

From the results shown in Tables 4 and 5 above, the ester used in the synthetic lubricating oil of the present invention has a pour point of -25 ° C or lower and exhibits compatibility with HFC-134a on a low temperature side. -30 ℃ or less, + 80 ℃ or more on high temperature side, HFC
A mixed refrigerant containing -32 covers a wide temperature range of -20 ° C or lower on the low temperature side and + 80 ° C or higher on the high temperature side, and has a large volume resistivity (80 ° C) of about 10 ¹³ to 10 ¹⁴ Ω · cm, Also, the increase in the acid value of the sample after the hydrolysis stability test is small.

As described above, the synthetic lubricating oil of the present invention is excellent in electric insulation, low temperature fluidity and hydrolysis stability, and the frozen oil of the present invention comprising the synthetic lubricating oil of the present invention and non-chlorine Freon. It is understood that the machine working fluid composition exhibits good compatibility in a wide temperature range and has excellent properties as a refrigerator working fluid composition using a non-chlorine CFC refrigerant.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location C10N 40:30

Claims (4)

[Claims] 1. A) monovalent alcohol having 4 to 18 carbon atoms in which a) branched alcohol accounts for 50 mol% or more, b) hydroxycarboxylic acid, and c) branched carboxylic acid accounts for 50 mol% or more. A synthetic lubricating oil containing an ester derived from a monovalent carboxylic acid having 4 to 18 carbon atoms. 2. A hydroxycarboxylic acid has the following formula (1) or (2); (R ¹ and R ² are a hydrogen atom, a hydroxyl group, a —CH ₂ OH group or an alkyl group, and neither R ¹ nor R ² is a hydrogen atom) (R ^3, R ⁴ is a hydrogen atom, a hydroxyl group or an alkyl group, R ³ and R ⁴ are not both be a hydrogen atom)
The synthetic lubricating oil according to claim 1, which is a hydroxycarboxylic acid represented by: 3. A) monovalent alcohol having 4 to 18 carbon atoms in which a) branched alcohol accounts for 50 mol% or more, b) hydroxycarboxylic acid, and c) branched carboxylic acid accounts for 50 mol% or more. Refrigerator working fluid composition comprising a synthetic lubricating oil composed of an ester derived from a monovalent carboxylic acid having 4 to 18 carbon atoms and a non-chlorine CFC in a weight ratio of 1:99 to 99: 1 . 4. A non-chlorine Freon is HFC-134a.
(1,1,1,2-tetrafluoroethane
e), HFC-32 (difluoromethan)
e) or HFC-125 (1,1,1,2,2-pe
The refrigerator working fluid composition according to claim 3, wherein the working fluid composition is a fluorfluoroethane.