JP2002220595A - Refrigerating machine oil for carbon dioxide refrigerant and fluid composition for refrigerating machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refrigerating machine oil having sufficiently satisfactory lubricity, sealing performance, compatibility to refrigerant, thermal and chemical stability, electrical insulation, etc., in balanced state in the case of using together with carbon dioxide refrigerant and capable of sufficiently preventing the deficient lubrication of a compressor and the lowering of the refrigeration efficiency and to provide a fluid composition for refrigerating machine using the refrigerating machine oil. SOLUTION: The refrigerating machine oil for carbon dioxide refrigerant contains (a) a compound having 2-3 hydroxy groups or its derivative, (b) a compound having 2-3 carboxy groups or its derivative and (c) an ester derived from a compound having one carboxy group or its derivative and/or a compound having one hydroxy group or its derivative.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a refrigerating machine oil useful when used with a carbon dioxide refrigerant, and a refrigerating machine fluid composition using the same.

[0002]

2. Description of the Related Art Due to the problem of depletion of the ozone layer in recent years, CFC (chlorofluorocarbon) and HCFC (hydrochlorofluorocarbon), which have been conventionally used as refrigerants for refrigeration equipment, are subject to regulation. Fluorocarbons) are being used as refrigerants. However, such HFC refrigerants also have problems such as high global warming ability, and use of natural refrigerants as substitutes for these CFC-based refrigerants is being studied.

[0003] Among them, carbon dioxide (CO ₂ ) is harmless to the environment and is excellent in safety, and although it has not been mainstream so far, it has been conventionally used as a refrigerant for refrigerators and the like. It is. In recent years, its application as a refrigerant for a car air conditioner, a room air conditioner, a hot water supply heat pump, or the like using an open compressor or a closed electric compressor has been studied.

[0004] Against this background, development of refrigerating machine oils for alternative refrigerants has been promoted, and use of various refrigerating machine oils has been proposed. For example, as a refrigerating machine oil for carbon dioxide refrigerant, JP-A-10-46168 uses a hydrocarbon base oil, and JP-A-10-46169 describes an ether base oil such as polyalkylene glycol and polyvinyl ether. JP-A-2000-104084, JP-A-2000-169868, JP-A-200
Japanese Patent Application Laid-Open No. 0-169869 and the like each disclose one using an ester base oil.

[0005]

In the refrigerant circulation system, since the refrigerating machine oil is discharged from the compressor together with the refrigerant, the refrigerating machine oil returns to the compressor through the flow path together with the circulating refrigerant. Hereinafter, "oil returnability" is required.

However, among the above-mentioned conventional refrigerating machine oils for carbon dioxide refrigerant, those using a hydrocarbon base oil as a base oil are as follows:
It does not necessarily show sufficient compatibility with carbon dioxide refrigerant. Therefore, when such refrigerating machine oil is used, sufficient oil return properties cannot be obtained, and seizure of the compressor and a decrease in refrigerating efficiency due to poor lubrication are likely to occur.

[0007] On the other hand, when a conventional refrigerating machine oil for carbon dioxide using an ether or ester as a base oil is used, although the oil return property is improved, the compatibility between the carbon dioxide refrigerant and the refrigerating machine oil is improved. If the temperature is excessively high, the refrigerating machine oil is diluted by the refrigerant to lower its viscosity, and the refrigerating efficiency may be lowered due to the reduced sealing performance, and poor lubrication of the compressor may occur.
In a refrigerant circulation system including a hermetic compressor, the use of polyalkylene glycol having high hygroscopicity and low electrical insulation is not appropriate because the refrigerating machine oil also plays a role as an insulating oil.

The present invention has been made in view of the above-mentioned problems of the prior art, and when used with a carbon dioxide refrigerant, it has lubricating properties, sealing properties, refrigerant compatibility, thermal / chemical stability, and electrical insulation. To provide a refrigerating machine oil capable of sufficiently satisfying properties and the like in a well-balanced manner and capable of sufficiently preventing poor lubrication of a compressor and a decrease in refrigerating efficiency, and a fluid composition for a refrigerating machine using the refrigerating machine oil. Aim.

[0009]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have obtained a refrigerating machine oil containing an ester obtained by using a specific compound, and the refrigerating machine oil. The inventors have found that the above-mentioned problems can be solved by a refrigerator fluid composition, and have completed the present invention.

That is, the refrigerating machine oil for carbon dioxide refrigerant of the present invention comprises the following compounds (a) to (c): (a) a compound having 2 to 3 hydroxyl groups or a derivative thereof, and (b) a compound having 2 to 3 carboxyl groups. (C) a compound having one carboxyl group or a derivative thereof and / or an ester obtained by using a compound having one hydroxyl group or a derivative thereof. .

The fluid composition for a refrigerator according to the present invention is characterized by containing the refrigerant oil for a carbon dioxide refrigerant of the present invention and a carbon dioxide refrigerant.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail.

The refrigerating machine oil for carbon dioxide refrigerant of the present invention comprises the following compounds (a) to (c): (a) a compound having 2 to 3 hydroxyl groups or a derivative thereof, and (b) a compound having 2 to 3 carboxyl groups. A compound or a derivative thereof, and (c) a compound having one carboxyl group or a derivative thereof and / or an ester obtained by using a compound having one hydroxyl group or a derivative thereof. sex,
The sealability, refrigerant compatibility, thermal / chemical stability, electrical insulation, etc. are sufficiently satisfied in a well-balanced manner, and poor lubrication of the compressor and a decrease in refrigeration efficiency can be sufficiently prevented.

The compound (a) constituting the ester according to the present invention is a compound having 2 to 3 hydroxyl groups or a derivative thereof. When a compound having four or more hydroxyl groups or a derivative thereof is used as the alcohol component, the compatibility with the carbon dioxide refrigerant becomes excessively high, the viscosity decreases in the presence of the refrigerant, and the refrigerating efficiency decreases due to the decrease in sealing property. Poor lubrication tends to occur. In addition, when only a compound having one hydroxyl group or its derivative is used as the alcohol component, the obtained ester does not have a sufficient viscosity, and poor lubrication or a decrease in refrigeration efficiency is likely to occur. Insufficient low-temperature fluidity.

As the compound (a), specifically, polyhydric alcohols, polyhydric phenols, polyhydric amino alcohols and condensates thereof, and the hydroxyl groups of these compounds are esterified with a carboxylic acid such as acetic acid. Compounds and the like can be mentioned, and among them, polyhydric alcohol or a condensate thereof or a derivative thereof is preferably used because the compatibility with the refrigerant, the electrical insulation and the thermal stability tend to be further increased.

The number of carbon atoms of the polyhydric alcohol is not particularly limited, but a polyhydric alcohol having 2 to 12 carbon atoms is preferably used. Specific examples of such a polyhydric alcohol include ethylene glycol, 1,3-propanediol, propylene glycol, 1,4-butanediol, 1,2-butanediol, diethylene glycol,
Dipropylene glycol, dibutylene glycol, 2-
Methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 2-ethyl-2-methyl-1,3-propanediol, 1,7-heptanediol, -Methyl-2
-Propyl-1,3-propanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,1
Examples thereof include 2-dodecanediol, trimethylolethane, trimethylolpropane, trimethylolbutane, glycerin, and 1,3,5-pentanetriol.
Among these polyhydric alcohols, it is more preferable to use hindered alcohols such as neopentyl glycol, trimethylolethane, trimethylolpropane, and trimethylolbutane.

In the present invention, as described above, the compound (a) having a hydroxyl group esterified with a carboxylic acid can be used. As such a derivative, a compound in which a hydroxyl group is esterified with a lower carboxylic acid is preferable, and specifically, an acetic acid ester or a propionic acid ester of the compound exemplified in the above description of the polyhydric alcohol is preferably used.

The compound (b) constituting the ester according to the present invention is a compound having two carboxyl groups or a derivative thereof. When only a compound having one carboxyl group or a derivative thereof is used as the acid component, the resulting ester has insufficient viscosity, which tends to cause poor lubrication and a decrease in refrigeration efficiency, as well as thermal and chemical stability and low-temperature fluidity. Performance becomes insufficient.

As the compound (b), specifically,
Examples include trivalent carboxylic acids and carboxylic acid derivatives thereof such as acid anhydrides, esters, and acid halides.

The number of carbon atoms of the dicarboxylic acid is not particularly limited, but a dicarboxylic acid having 2 to 10 carbon atoms is preferably used. Specific examples of such a divalent to trivalent carboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, methylmalonic acid, and ethylmalon. Acid, dimethylmalonic acid, methylsuccinic acid, 2,2-dimethylsuccinic acid, 2,3-dimethylsuccinic acid, 2-ethyl-2-methylsuccinic acid, 2-methylglutaric acid, 3-methylglutaric acid, 3-methyladipin Saturated aliphatic dicarboxylic acids such as acids; unsaturated aliphatic dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, citraconic acid, and mesaconic acid; 1,2-cyclohexanedicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid Alicyclic dicarboxylic acids such as acids; aromatic dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid and trimellitic acid; But it is below,
Of these, trivalent carboxylic acids are preferred, and further,
Saturated aliphatic dicarboxylic acids are more preferred from the viewpoint of oxidation stability.

In the present invention, as described above, a derivative of a compound having two carboxyl groups can be used as the compound (b). Such derivatives include:
Examples thereof include esters, acid anhydrides, and acid halides. Among them, esters of the above divalent carboxylic acids with lower alcohols (more preferably methanol or ethanol) are preferably used.

The compound (c) constituting the ester according to the present invention is a compound having one carboxyl group or a derivative thereof and / or a compound having one hydroxyl group or a derivative thereof. In the present invention, compound (c)
Any one of a compound having one carboxyl group or a derivative thereof and a compound having one hydroxyl group or a derivative thereof may be used alone or as a mixture of both. When only a compound having two or more carboxyl groups or a derivative thereof is used as the acid component, and only a compound having two or more hydroxyl groups or the derivative thereof is used as the alcohol component, thermal and chemical stability is inferior. Will be enough.

As the compound having one carboxyl group or its derivative according to the present invention, specifically,
Trivalent fatty acids and their anhydrides, esters and acid halides. The number of carbon atoms of the monovalent fatty acid is not particularly limited, and one having 1 to 24 carbon atoms is usually used. However, the number of carbon atoms of the monovalent fatty acid is preferably 3 or more, more preferably 4 or more. Is more preferably 5 or more, and particularly preferably 8 or more. 1
When the carbon number of the trivalent fatty acid is less than 3, the resulting ester has insufficient lubricity inherently, and has excessively high compatibility with the carbon dioxide refrigerant, and is diluted by the refrigerant to lower the viscosity. As a result, there is a tendency that refrigeration efficiency is reduced and lubrication failure is apt to occur due to a reduction in sealability.

The number of carbon atoms of the monovalent fatty acid is preferably 22 or less, more preferably 20 or less, and even more preferably 18 or less. When the carbon number of the monovalent fatty acid exceeds 22, the compatibility between the obtained ester and the carbon dioxide refrigerant becomes insufficient, and poor lubrication of the compressor and a decrease in the refrigerating efficiency due to a decrease in oil return properties tend to occur. is there.

The monovalent fatty acid as the compound (c) may be linear or branched, but from the viewpoint of lubricity, a linear monovalent fatty acid is preferred. From the viewpoint of hydrolysis stability, a branched monovalent fatty acid is preferred.
Further, the monovalent fatty acid may be either a saturated fatty acid or an unsaturated fatty acid.

Specific examples of the monovalent fatty acid as the compound (c) according to the present invention include pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid and tridecanoic acid , Tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, nonadecanoic acid, icosanoic acid, oleic acid, etc., or those having an α-carbon atom of a quaternary carbon atom (neoacid) And the like,
Among these, valeric acid (n-pentanoic acid), caproic acid (n-hexanoic acid), enanthic acid (n-heptanoic acid), caprylic acid (n-octanoic acid), pelargonic acid (n-nonanoic acid), capric acid Acid (n-decanoic acid), lauric acid (n-dodecanoic acid), myristic acid (n-tetradecanoic acid), palmitic acid (n-hexadecanoic acid), stearic acid (n-octadecanoic acid), oleic acid (ci
(s-9-octadecenoic acid), isopentanoic acid (3-methylbutanoic acid), 2-methylhexanoic acid, 2-ethylpentanoic acid, 2-ethylhexanoic acid, and 3,5,5-trimethylhexanoic acid are preferably used.

The compound having one hydroxyl group or a derivative thereof according to the present invention includes, specifically, monohydric alcohol, monohydric phenol, monohydric amino alcohol,
And compounds in which the hydroxyl groups of these compounds are esterified with a carboxylic acid such as acetic acid. The number of carbon atoms of these compounds is not particularly limited, but is preferably one having 1 to 24 carbon atoms, in that both lubricity and refrigerant compatibility are further enhanced in the resulting ester.
C3-C18 linear monohydric alcohol, C3-C3
18 branched monohydric alcohols and 1 to 5 carbon atoms
Trivalent cycloalcohols are preferred.

Specific examples of the monohydric alcohol having a carbon number within the above preferred range include linear or branched propanol (including n-propanol and 1-methylethanol), linear and branched propanol. Branched butanol (including n-butanol, 1-methylpropanol, 2-methylpropanol, etc.), linear or branched pentanol (n
-Pentanol, 1-methylbutanol, 2-methylbutanol, 3-methylbutanol, etc.), linear or branched hexanol (n-hexanol, 1-methylpentanol, 2-methylpentanol, -Methylpentanol, etc.), linear or branched heptanol (n-heptanol, 1-methylhexanol, 2
-Methylhexanol, 3-methylhexanol, 4-
Methylhexanol, 5-methylhexanol, 2,4
-Including dimethylpentanol, etc.), linear or branched octanol (including n-octanol, 2-ethylhexanol, 1-methylheptanol, 2-methylheptanol, etc.), linear or branched Nonanol (n-
Nonanol, 1-methyloctanol, 3,5,5-trimethylhexanol, 1- (2′-methylpropyl)
-3-methylbutanol, etc.), linear or branched decanol (including n-decanol, iso-decanol, etc.), linear or branched undecanol (n-undecanol, iso-undecanol, etc.) ), Linear or branched dodecanol (n-dodecanol, i
so-dodecanol, etc.), linear or branched tridecanol (including n-tridecanol, iso-tridecanol, etc.), linear or branched tetradecanol (n-tetradecanol, iso- Tetradecanol, etc.), linear or branched pentadecanol (n
-Pentadecanol, iso-pentadecanol, etc.), linear or branched hexadecanol (including n-hexadecanol, iso-hexadecanol, etc.),
Linear or branched heptadecanol (including n-heptadecanol, iso-heptadecanol, etc.), and linear or branched octadecanol (n-octadecanol, iso-octadecanol) Hexyl), cyclohexanol, methylcyclohexanol, dimethylcyclohexanol and the like.

In the present invention, as the compound (c), a derivative in which a hydroxyl group is esterified with a carboxylic acid can be used. As such derivatives, acetates, propionates and the like of the compounds exemplified in the description of the monohydric alcohol are preferably used.

Among the esters according to the present invention, the following compounds (a ') to (c'): (a ') ethylene glycol, propylene glycol,
At least one selected from the group consisting of butylene glycol, glycerin, neopentyl glycol, diethylene glycol, dipropylene glycol, dibutylene glycol and dibutylene glycol; (b ') oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid , Pimelic acid, suberic acid, azelaic acid, sebacic acid, and at least one selected from the group consisting of:
Valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, isopentanoic acid, 2-methylhexanoic acid, 2-ethylpentanoic acid,
-Ethylhexanoic acid, 3,5,5-trimethylhexanoic acid, n-butanol, n-pentanol, n-hexanol, n-heptanol, n-octanol, n-nonanol, n-decanol, n-undecanol, n- Dodecanol, n-tridecanol, n-tetradecanol, n-pentadecanol, n-hexadecanol, n
-Heptadecanol, n-octadecanol, iso-
Consists of butanol, iso-pentanol, iso-hexanol, iso-heptanol, 2-ethylhexanol, 3,5,5-trimethylhexanol, iso-decanol, iso-dodecanol, iso-tetradecanol and iso-hexadecanol Esters obtained using at least one selected from the group are particularly preferred. When the ester obtained by using the above compounds (a ′) to (c ′) is contained in a refrigerating machine oil, lubricity, sealability, refrigerant compatibility, thermal / chemical stability, electric insulation, etc. are more balanced. Tends to be satisfied.

In the present invention, the compounds (a) to
Although the composition ratio of (c) is not particularly limited, lubricating properties, sealing properties, refrigerant compatibility, thermal / chemical stability, electrical insulating properties, and the like tend to be satisfied at a higher level in a well-balanced manner.
It is preferable that the total amount of the compounds (a) to (c) is within the following ranges, respectively.

Compound (a): 3 to 55 mol%, preferably 5 to 50 mol%, more preferably 10 to 45 mol%
1% Compound (b): 3 to 55 mol%, preferably 5 to 50 mol%
mol%, more preferably 10 to 45 mol% Compound (c): 3 to 90 mol%, preferably 5 to 80 mol%
mol%, more preferably 10 to 70 mol%.

The ester according to the present invention is prepared by heating the compounds (a) to (c) according to a conventional method, preferably in an atmosphere of an inert gas such as nitrogen, in the presence of an esterification catalyst or in the absence of a catalyst. It is prepared by esterification.

When the compound (a) or (c) is an acetic acid ester or propionate of alcohol, or when the compound (b) or (c) is a lower alcohol ester of carboxylic acid or the like, an ester is used. It is possible to obtain the ester according to the invention by an exchange reaction.

Examples of the esterification used in the above esterification reaction include Lewis acids such as aluminum derivatives, tin derivatives and titanium derivatives; alkali metal salts such as sodium alkoxide and potassium alkoxide; para-toluenesulfonic acid; Methanesulfonic acid,
Sulfonic acids such as sulfuric acid, etc. are exemplified, and among them, the use of Lewis acids such as aluminum derivatives, tin derivatives, and titanium derivatives is preferable because the thermal and hydrolytic stability of the obtained ester is further improved, Further, a tin derivative is particularly preferable from the viewpoint of reaction efficiency. The amount of the esterification catalyst used is, for example, about 0.1 to 1% by mass based on the total amount of the compounds (a) to (c) as the raw materials.

The reaction temperature in the above esterification reaction is, for example, 150 to 230 ° C., usually 3 to 30 ° C.
The reaction is completed in time.

After the completion of the esterification reaction, the excess raw material is distilled off under reduced pressure or normal pressure, followed by conventional purification methods such as liquid-liquid extraction, vacuum distillation, activated carbon treatment and other adsorption purification treatments. Thereby, the ester can be purified.

In the above esterification reaction, for example,
A compound having two hydroxyl groups as the compound (a), a compound having two carboxyl groups as the compound (b),
As the compound (c), a compound having one carboxyl group (hereinafter, referred to as "compound (c-1)") and a compound having one hydroxyl group (hereinafter, referred to as "compound (c-2)") are used. When the reaction product is obtained, the following reaction formulas (1) to (6) are obtained: X ² —COO—R ¹ —OCO—X ¹ —COO—R ¹ —OCO—X ² (1) R ² —OCO— X ¹ -COO-R ¹ -OCO-X ¹ -COO-R ² (2) X ² -COO-R ¹ -OCO-X ¹ -COO-R ² (3) X ² -COO-R ¹ -OCO- X ² (4) R ² —OCO—X ¹ —COO—R ² (5) R ² —OCO—X ² (6) [In the formulas (1) to (6), R ¹ is 2 from the compound (a). R ² represents a residue obtained by removing one hydroxyl group from compound (c-2), and X ¹ represents two residues obtained from compound (b). Represents a residue excluding the carboxyl group of
X ² represents a residue obtained by removing one carboxyl group from compound (c-1)] (hereinafter, for example, a compound represented by the above formula (1) is referred to as a “compound ( 1) ").

In the present invention, when the compounds obtained in the above esterification reaction are the above compounds (1) to (6), one of the above compounds (1) to (3) may be used alone or It is preferable to use a combination of at least one of the compounds (1) to (3) and at least one of the compounds (4) to (6). When the ester does not contain any of the above compounds (1) to (3) and is composed of only the above compounds (4) to (6), all of the lubricity, stability and low-temperature fluidity are balanced. It tends to be difficult to satisfy well.

Further, the ester according to the present invention comprises one or more of the compounds (1) to (3) and the compound (4) to
In the case of a mixture with one or more kinds of (6), the content of each compound is not particularly limited, but from the viewpoint of the balance between refrigerant compatibility and various performances and the ease of production, each compound is based on the total amount of the mixture. The content of the compound is preferably in the range shown below.

Compound (1): 0 to 100% by mass, preferably 1 to 99% by mass, more preferably 5 to 95% by mass Compound (2): 0 to 100% by mass, preferably 1 to 99% by mass
% By mass, more preferably 5 to 95% by mass Compound (3): 0 to 100% by mass, preferably 1 to 99% by mass
Compound (4): 0 to 90% by mass, preferably 0 to 80% by mass, more preferably 0 to 75% by mass Compound (5): 0 to 90% by mass, preferably 5 to 95% by mass Is 0 to 80% by mass, more preferably 0 to 75% by mass, compound (6): 0 to 90% by mass, preferably 0 to 80% by mass, and more preferably 0 to 75% by mass. Compounds (1) to (3) Total: 10 to 100% by mass, preferably 20 to 100% by mass, more preferably 25 to 1% by mass.
00 mass% Total of compounds (4) to (6): 0 to 90 mass%, preferably 0 to 80 mass%, more preferably 0 to 75 mass%.

Here, specific compounds (a) to (a)
Although the esterification reaction using (c) has been described, in other cases, the obtained reaction product may be a mixture. Further, the ester according to the present invention has 2
In the case of a mixture of two or more kinds of compounds, the content of the ester in which the compound (a) and the compound (b) are directly bonded is determined from the viewpoint of the balance between refrigerant compatibility and various performances and the ease of production. Is preferably from 10 to 100% by mass, more preferably from 20 to 100% by mass, and still more preferably from 25 to 100% by mass, based on

The kinematic viscosity of the ester according to the present invention is not particularly limited, but the kinematic viscosity at 40 ° C. is 3 to 500 mm.
² / s, preferably 4 to 400 mm ² / s, more preferably 5 to 300 mm ² / s. It is preferable that kinematic viscosity at 100 ° C. of the esters are 1 to 50 mm ² / s, more preferably 1.5~40mm ² / s, more preferably from 2 to 30 mm ² / s .
When the kinematic viscosity of the ester is within the above range, lubricity, sealing properties, refrigerant compatibility, and the like tend to be satisfied in a more balanced manner.

As described above, the ester according to the present invention can be obtained by using the above compounds (a) to (c). Can sufficiently prevent poor lubrication of the compressor and a decrease in refrigeration efficiency, which were very difficult to achieve.

JP-A-2000-169868 discloses an ester of a polyhydric alcohol and a monohydric fatty acid, an ester of a polyhydric alcohol and a dibasic acid, and a mixture of a polyhydric alcohol, a dibasic acid and a monohydric fatty acid. Esters and the like are disclosed, and it is described that refrigerating machine oil using these esters exhibits compatibility with a carbon dioxide refrigerant. However, those esters which do not contain at least one of the compounds (a) to (c) according to the present invention have an excessively high compatibility with carbon dioxide refrigerant, and the conventional refrigeration using such esters as base oils When the machine oil is used, the viscosity is reduced when the refrigerant is dissolved, and the refrigeration efficiency is reduced and the lubrication failure in the compressor is liable to occur due to the reduction in the sealing property.

In the refrigerating machine oil for carbon dioxide refrigerant of the present invention, the content of the ester obtained by using the above compounds (a) to (c) is not particularly limited, but is preferably 5% by mass based on the total amount of the refrigerating machine oil. Or more, more preferably 10% by mass or more, and still more preferably 30% by mass.
And more preferably 50% by mass or more. When the content of the ester according to the present invention is within the above range, excellent various properties of the ester tend to be exhibited more.

In the refrigerating machine oil for carbon dioxide refrigerant of the present invention, the ester obtained by using the above compounds (a) to (c) is mainly used as a base oil. In the present invention, the ester alone may be used alone as the base oil, and the ester and an ester other than the ester according to the present invention (polyol ester, etc.), polyglycol, polyvinyl ether, ketone, polyphenylene ether And oxygen-containing synthetic oils such as silicone, polysiloxane and perfluoroether.

In the refrigerating machine oil for carbon dioxide refrigerant of the present invention, when the ester obtained by using the above compounds (a) to (c) and other synthetic oil containing oxygen are used together, Is not particularly limited, but the amount of the other oxygen-containing synthetic oil is preferably 150 parts by weight or less, and more preferably 100 parts by weight, based on 100 parts by weight of the ester obtained using the compounds (a) to (c). Is more preferable. When the compounding amount of the synthetic oil containing oxygen other than the ester obtained using the compounds (a) to (c) exceeds the above upper limit, lubricity, sealing properties, refrigerant compatibility,
There is a tendency that thermal and chemical stability, electric insulation, etc. are not satisfied in a well-balanced manner.

In the present invention, the above compounds (a) to (a)
Esters obtained using (c) and synthetic oils containing oxygen other than the esters, which are blended as required, are mainly used as base oils. The refrigerating machine oil for carbon dioxide refrigerant of the present invention can be suitably used even in a mode that is composed of only such a base oil and is not blended with any additives, but may be blended with various additives described below as necessary. Can also.

In order to further improve the abrasion resistance and load resistance of the refrigerating machine oil for carbon dioxide refrigerant of the present invention, phosphate esters, acidic phosphate esters, amine salts of acidic phosphate esters, chlorinated phosphate esters, At least one phosphorus compound selected from the group consisting of phosphites can be blended. These phosphorus compounds are esters of phosphoric acid or phosphorous acid with alkanols or polyether alcohols or derivatives thereof. Specifically, as the phosphate ester, tributyl phosphate, tripentyl phosphate, trihexyl phosphate, triheptyl phosphate, trioctyl phosphate, trinonyl phosphate, tridecyl phosphate, triundecyl phosphate, tridodecyl phosphate,
Tritridecyl phosphate, tritetradecyl phosphate, tripentadecyl phosphate, trihexadecyl phosphate, triheptadecyl phosphate, trioctadecyl phosphate, trioleyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate , Xylenyl diphenyl phosphate, etc .; Examples of the acidic phosphate include monobutyl acid phosphate, monopentyl acid phosphate, monohexyl acid phosphate, monoheptyl acid phosphate, monooctyl acid phosphate, and the like.
Monononyl acid phosphate, monodecyl acid phosphate, monoundecyl acid phosphate,
Monododecyl acid phosphate, monotridecyl acid phosphate, monotetradecyl acid phosphate, monopentadecyl acid phosphate, monohexadecyl acid phosphate, monoheptadecyl acid phosphate, monooctadecyl acid phosphate, monooleyl acid phosphate, dibutyl acid diphosphate Acid phosphate, dihexyl acid phosphate, diheptyl acid phosphate, dioctyl acid phosphate, dinonyl acid phosphate, didecyl acid phosphate, diundecyl acid phosphate, didodecyl acid phosphate, ditridecyl acid phosphate, ditetradecyl acid
Dipentadecyl acid phosphate, dihexadecyl acid phosphate, diheptadecyl acid phosphate, dioctadecyl acid phosphate, dioleyl acid phosphate, etc .; , Propylamine, butylamine,
Pentylamine, hexylamine, heptylamine, octylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, diheptylamine, dioctylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, tripentyl Salts with amines such as amine, trihexylamine, triheptylamine and trioctylamine; chlorinated phosphates include tris-dichloropropyl phosphate, tris-chloroethyl phosphate, tris-chlorophenyl phosphate, polyoxyalkylene- Bis [di (chloroalkyl)] phosphate and the like. Examples of the phosphite include dibutyl phosphite, dipentyl phosphite, dihexyl phosphite, diheptyl phosphite, dioctyl phosphite, dinonyl phosphite, didecyl phosphite, diundecyl phosphite, didodecyl phosphite, dioleyl Phosphite, diphenyl phosphite, dicresyl phosphite, tributyl phosphite, tripentyl phosphite, trihexyl phosphite, triheptyl phosphite, trioctyl phosphite, trinonyl phosphite, tridecyl phosphite, triundecyl phosphite Phyto, tridodecyl phosphite, trioleyl phosphite, triphenyl phosphite, tricresyl phosphite and the like. One of these phosphorus compounds may be used alone, or two or more thereof may be used in combination.

When the above-mentioned phosphorus compound is blended into the refrigerating machine oil for carbon dioxide refrigerant of the present invention, the blending amount is not particularly limited, but is usually based on the total amount of the refrigerating machine oil (based on the total amount of the base oil and all the blended additives). It is desirable to add a phosphorus compound in such an amount that the content becomes 0.01 to 5.0% by mass, more preferably 0.02 to 3.0% by mass.

In the refrigerating machine oil for carbon dioxide refrigerant of the present invention, the following (i) to (viii): (i) a phenylglycidyl ether type epoxy compound (ii) in order to further improve the heat / hydrolysis stability. ) Alkyl glycidyl ether type epoxy compound (iii) glycidyl ester type epoxy compound (iv) allyl oxirane compound (v) alkyl oxirane compound (vi) alicyclic epoxy compound (vii) epoxidized fatty acid monoester (viii) epoxidized vegetable oil At least one epoxy compound selected from the group consisting of:

Specific examples of (i) phenylglycidyl ether type epoxy compound include phenylglycidyl ether and alkylphenylglycidyl ether. The alkylphenyl glycidyl ether referred to herein includes those having 1 to 3 alkyl groups having 1 to 13 carbon atoms, among which those having one alkyl group having 4 to 10 carbon atoms, for example, n-butylphenyl glycidyl Ether, i-butylphenyl glycidyl ether,
sec-butylphenyl glycidyl ether, tert
-Butylphenyl glycidyl ether, pentyl phenyl glycidyl ether, hexyl phenyl glycidyl ether, heptyl phenyl glycidyl ether, octyl phenyl glycidyl ether, nonyl phenyl glycidyl ether, decyl phenyl glycidyl ether and the like can be exemplified as preferable ones.

(Ii) Specific examples of the alkyl glycidyl ether type epoxy compound include decyl glycidyl ether, undecyl glycidyl ether, dodecyl glycidyl ether, tridecyl glycidyl ether, tetradecyl glycidyl ether, 2-ethylhexyl glycidyl ether, neoethyl Pentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, 1,6-hexanediol diglycidyl ether,
Examples thereof include sorbitol polyglycidyl ether, polyalkylene glycol monoglycidyl ether, and polyalkylene glycol diglycidyl ether.

(Iii) The glycidyl ester type epoxy compound is specifically represented by the following general formula (7):

[0056]

Embedded image [In the formula (7), R represents a hydrocarbon group having 1 to 18 carbon atoms].

In the above general formula (7), R is a group having 1 to 18 carbon atoms.
Wherein the hydrocarbon group is an alkyl group having 1 to 18 carbon atoms, an alkenyl group having 2 to 18 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or a 6 to 18 carbon atoms. An alkylcycloalkyl group having 6 to 10 carbon atoms
An aryl group, an alkylaryl group having 7 to 18 carbon atoms,
An arylalkyl group having 7 to 18 carbon atoms is exemplified.
Among them, an alkyl group having 5 to 15 carbon atoms,
Alkenyl groups having 15 alkenyl groups, phenyl groups and alkyl groups having 1 to 4 carbon atoms are preferred.

Among the glycidyl ester type epoxy compounds, preferred are, for example, glycidyl-2,2-dimethyloctanoate,
Glycidyl benzoate, glycidyl-tert-butyl benzoate, glycidyl acrylate, glycidyl methacrylate and the like can be exemplified.

(Iv) As the allyloxirane compound,
Specifically, 1,2-epoxystyrene, alkyl-
1,2-epoxystyrene and the like can be exemplified.

(V) Specific examples of the alkyloxirane compound include 1,2-epoxybutane, 1,2-epoxypentane, 1,2-epoxyhexane, and 1,2-epoxyhexane.
Epoxy heptane, 1,2-epoxyoctane, 1,2
-Epoxynonane, 1,2-epoxydecane, 1,2-
Epoxy undecane, 1,2-epoxide decan, 1,
2-epoxytridecane, 1,2-epoxytetradecane, 1,2-epoxypentadecane, 1,2-epoxyhexadecane, 1,2-epoxyheptadecane, 1,
Examples thereof include 1,2-epoxyoctadecane, 2-epoxynonadecane, and 1,2-epoxyicosane.

(Vi) As the alicyclic epoxy compound, the following general formula (8):

[0062]

Embedded image Compounds in which the carbon atom constituting the epoxy group directly constitutes an alicyclic ring, such as the compound represented by

Examples of such alicyclic epoxy compounds include, for example, 1,2-epoxycyclohexane, 1,2-epoxycyclopentane, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxy. Rate, bis (3,4-epoxycyclohexylmethyl) adipate, exo-2,3-epoxynorbornane, bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate, 2- (7-oxabicyclo [4.1] .0] hept-3-yl) -spiro (1,3-dioxane-5,3 ′-[7] oxabicyclo [4.1.0] heptane, 4- (1′-methylepoxyethyl) -1, Examples thereof include 2-epoxy-2-methylcyclohexane and 4-epoxyethyl-1,2-epoxycyclohexane.

(Vii) As the epoxidized fatty acid monoester, specifically, epoxidized C12 to C2
Examples thereof include esters of 0 fatty acids with alcohols having 1 to 8 carbon atoms or phenols and alkylphenols.
Particularly, butyl, hexyl, benzyl, cyclohexyl, methoxyethyl, octyl, phenyl and butylphenyl esters of epoxystearic acid are preferably used.

(Viii) Specific examples of epoxidized vegetable oils include epoxy compounds of vegetable oils such as soybean oil, linseed oil, and cottonseed oil.

Among the above epoxy compounds, since phenylglycidyl ether type epoxy compound, glycidyl ester type epoxy compound, alicyclic epoxy compound,
Epoxidized fatty acid monoesters are preferred, and glycidyl ester type epoxy compounds and alicyclic epoxy compounds are more preferred.

When these epoxy compounds are blended with the refrigerating machine oil for carbon dioxide refrigerant of the present invention, the blending amount is not particularly limited, but is usually based on the total amount of the refrigerating machine oil (based on the total amount of the base oil and all the blended additives). And its content is 0.1 to 5.0
It is desirable to mix the epoxy compound in such an amount that the amount becomes 0.2% by mass, more preferably 0.2 to 2.0% by mass.

Of course, two or more of the above phosphorus compounds and epoxy compounds may be used in combination.

Further, in order to further enhance the lubricity of the refrigerating machine oil for carbon dioxide refrigerant of the present invention, the following general formulas (9) to (9)
(11): R ¹ —CO—NR ² — (CH ₂ ) ₁ —COOX (9) [In the formula (9), R ¹ represents an alkyl group having 6 to 30 carbon atoms or an alkenyl group having 6 to 30 carbon atoms. R ² represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, X represents a hydrogen atom,
Represents an alkyl group or alkenyl group having 1 to 30 carbon atoms having 1 to 30 carbon atoms, l is an integer of ^{1~4] [R 3 -CO-NR} 4 - (CH 2) m -COO] m 'Y (10) [In the formula (10), R ³ represents an alkyl group having 6 to 30 carbon atoms or an alkenyl group having 6 to 30 carbon atoms, R ⁴ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, Y represents an alkali metal atom or an alkaline earth metal atom;
And m ′ represents an integer of 1 or 2.] [R ⁵ —CO—NR ⁶ — (CH ₂ ) _n —COO] _{n ′} —Z— (OH) _{n ″} (11) [Formula (11) In the formula, R ⁵ represents an alkyl group having 6 to 30 carbon atoms or an alkenyl group having 6 to 30 carbon atoms; R ⁶ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; Represents a residue obtained by removing a hydroxyl group from a polyhydric alcohol, n represents an integer of 1 to 4, n ′ represents an integer of 1 or more, and n ″
Represents an integer of 0 or more, and n ′ + n ″ is a valence of a group represented by Z].

Among the compounds represented by the formulas (9) to (11), N-oleoyl sarcosine, N-oleoyl sarcosine methyl ester, N-oleoyl sarcosine potassium salt, N-oleoyl sarcosine lyserin monoester And at least one selected from the group consisting of N-oleoylsarcosine and N-oleoylsarcosine is preferable since lubricity in a refrigerant atmosphere tends to be further enhanced.

The amount of the compounds represented by the above formulas (9) to (11) is not particularly limited, but is preferably 0.001 to 5% by mass, more preferably 0.05% by mass, based on the total amount of the refrigerating machine oil.
The content is from 03 to 2% by mass, more preferably from 0.005 to 1% by mass. If the content of the compounds represented by the above general formulas (9) to (11) exceeds 5% by mass, no further improvement in lubricity commensurate with the content is observed, and the solubility of the refrigerant is poor. Therefore, there is a tendency that precipitation from the refrigerant / refrigeration oil mixture easily occurs.

When the content of the compounds represented by the above general formulas (9) to (11) is less than 0.001% by mass,
Lubricity tends to be insufficient.

Furthermore, in order to further enhance the performance of the refrigerating machine oil for carbon dioxide refrigerant of the present invention, conventionally known refrigerating machine oil additives such as di-te
phenol-based antioxidants such as rt-butyl-p-cresol and bisphenol A; amine-based antioxidants such as phenyl-α-naphthylamine and N, N-di (2-naphthyl) -p-phenylenediamine; dithioline Anti-wear agents such as zinc oxide, extreme pressure agents such as chlorinated paraffins and sulfur compounds, oil agents such as fatty acids, defoamers such as silicones, metal deactivators such as benzotriazole, viscosity index improvers,
Additives such as pour point depressants, detergents and dispersants may be used alone or in combination of several types. The total blended amount of these additives is not particularly limited, but is preferably 10% by mass or less, more preferably 5% by mass or less based on the total amount of the refrigerating machine oil (based on the total amount of the base oil and all the blended additives).

The kinematic viscosity of the refrigerating machine oil for carbon dioxide refrigerant of the present invention is not particularly limited.
500 mm ² / s, preferably 4 to 400 m
m ² / s, more preferably 5 to 300 mm ² / s
More preferably, s. It is preferable that kinematic viscosity at 100 ° C. of the esters are 1 to 50 mm ² / s, more preferably 1.5~40mm ² / s, more preferably from 2 to 30 mm ² / s . When the kinematic viscosity of the refrigerating machine oil is within the above range, lubricity, sealing properties, refrigerant compatibility, and the like tend to be satisfied in a more balanced manner.

The refrigerating machine oil for carbon dioxide refrigerant of the present invention having the above configuration is used as a fluid composition mixed with carbon dioxide refrigerant in a refrigerant circulation system of a refrigerating machine. That is, the refrigerating machine fluid composition of the present invention contains the refrigerating machine oil for carbon dioxide refrigerant of the present invention and a carbon dioxide refrigerant. Here, the mixing ratio of the refrigerating machine oil and the refrigerant in the refrigerating machine fluid composition of the present invention is not particularly limited, but the refrigerating machine oil is preferably 1 to 500 parts by weight, more preferably 2 to 500 parts by weight, based on 100 parts by weight of the refrigerant. 400
Parts by weight.

The fluid composition for a refrigerator of the present invention contains a carbon dioxide refrigerant as described above, but further contains other refrigerants such as hydrofluorocarbon (HFC), hydrocarbon, and ammonia. You may.

Here, examples of the hydrofluorocarbon refrigerant according to the present invention include hydrofluorocarbons having 1 to 3 carbon atoms, preferably 1 to 2 carbon atoms. Specifically, for example, difluoromethane (HFC-32),
Trifluoromethane (HFC-23), pentafluoroethane (HFC-125), 1,1,2,2-tetrafluoroethane (HFC-134), 1,1,1,2-tetrafluoroethane (HFC-134a) , 1,1,1
-Trifluoroethane (HFC-143a), 1,1-
Examples thereof include difluoroethane (HFC-152a), and a mixture of two or more thereof. These refrigerants are appropriately selected according to the application and required performance.
-32 alone; HFC-23 alone; HFC-134a alone; HFC-125 alone; HFC-134a / HFC-
32 = mixture of 60-80% by mass / 40-20% by mass;
HFC-32 / HFC-125 = 40 to 70% by mass / 6
0 to 30% by mass of a mixture; HFC-125 / HFC-1
43a = a mixture of 40 to 60% by mass / 60 to 40% by mass; HFC-134a / HFC-32 / HFC-125
= 60% by weight / 30% by weight / 10% by weight mixture; HF
C-134a / HFC-32 / HFC-125 = 40 ~
70% by mass / 15 to 35% by mass / 5 to 40% by mass of a mixture; HFC-125 / HFC-134a / HFC-14
3a = 35 to 55% by mass / 1 to 15% by mass / 40 to 60%
A preferable example is a mixture by mass%. More specifically, HFC-134a / HFC-32 = 70
HFC-32 / HFC-125
= 60/40% by mass of mixture; HFC-32 / HFC-
125 = 50/50% by weight mixture (R410A); H
FC-32 / HFC-125 = 45/55% by mass mixture (R410B); HFC-125 / HFC-143a
= 50/50% by weight mixture (R507C); HFC-
32 / HFC-125 / HFC-134a = 30/10
HFC-32 / HFC-125
/ HFC-134a = 23/25/52 mass% mixture (R407C); HFC-32 / HFC-125 / HF
C-134a = mixture of 25/15/60% by mass (R4
07E); HFC-125 / HFC-134a / HFC
-143a = 44/4/52% by weight of a mixture (R404
A) and the like.

As the hydrocarbon refrigerant according to the present invention, a gaseous refrigerant at 25 ° C. and 1 atm is preferably used. Specifically, it has 1 to 5 carbon atoms, preferably 1 to 5 carbon atoms.
4, alkanes, cycloalkanes, alkenes or mixtures thereof. Specifically, for example, methane, ethylene, ethane, propylene, propane, cyclopropane,
Butane, isobutane, cyclobutane, methylcyclopropane, or a mixture of two or more thereof.
Among these, propane, butane, isobutane or a mixture of two or more thereof is preferred.

The mixing ratio of carbon dioxide to hydrofluorocarbon and / or hydrocarbon is not particularly limited, but the total amount of hydrofluorocarbon and hydrocarbon is preferably 1 to 200 parts by weight per 100 parts by weight of carbon dioxide. Parts, more preferably 10 to 100 parts by weight.

The refrigerating machine oil of the present invention sufficiently satisfies all required properties such as lubricity, refrigerant compatibility, low-temperature fluidity, and stability in a well-balanced manner. It can be suitably used for refrigeration equipment having a type compressor or a heat pump. As the refrigeration equipment, more specifically, an air conditioner for an automobile,
Examples include dehumidifiers, refrigerators, freezing and refrigerated warehouses, vending machines, showcases, cooling devices for chemical plants, etc., residential air conditioners, and hot water supply heat pumps.

[0081]

EXAMPLES Hereinafter, the present invention will be described more specifically based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Example 1 According to the present invention, trimethylolpropane as compound (a), 1 mol of adipic acid as compound (b), and octanoic acid / decanoic acid mixed acid as compound (c) (octanoic acid and decanoic acid) (Molar ratio: 50/50) was used as the sample oil of Example 1. This ester was a mixture of a plurality of compounds having different structures, and the content of the ester having a structure in which trimethylolpropane and adipic acid were directly bonded was 42% by mass based on the total amount of the mixture. Properties of the obtained sample oil (100 ° C
Are shown in Table 1.

Example 2 Trimethylolpropane as the compound (a), adipic acid as the compound (b), and an octanol / decanol mixed alcohol (molar ratio of octanol and decanol) as the compound (c) according to the present invention : 50/5
0) was used as the sample oil of Example 2. This ester was a mixture of a plurality of compounds having different structures, and the content of the ester having a structure in which trimethylolpropane and adipic acid were directly bonded was 47% by mass based on the total amount of the mixture. Table 1 shows properties (kinematic viscosity at 100 ° C., pour point) of the obtained sample oil.

Example 3 3-Methyl-1,3 as a compound (a) according to the present invention
An ester obtained using 5-pentanediol, adipic acid as the compound (b), and 3,5,5-trimethylhexanoic acid as the compound (c) was used as a sample oil of Example 3. This ester was a mixture of a plurality of compounds having different structures, and the content of the ester having a structure in which trimethylolpropane and adipic acid were directly bonded was 51% by mass based on the total amount of the mixture. Table 1 shows properties (kinematic viscosity at 100 ° C., pour point) of the obtained sample oil.
Shown in

Comparative Example 1 An ester obtained by using pentaerythritol, adipic acid and 2-ethylhexanoic acid was used as a sample oil of Example 2. This ester was a mixture of a plurality of compounds having different structures, and the content of the ester having a structure in which trimethylolpropane and adipic acid were directly bonded was 38% by mass based on the total amount of the mixture. Table 1 shows properties (kinematic viscosity at 100 ° C., pour point) of the obtained sample oil.

Comparative Examples 2 to 4 In Comparative Example 2, 2-ethylhexanoic acid / 3,5,5
5-Trimethylhexanoic acid mixed acid (molar ratio of 2-ethylhexanoic acid to 3,5,5-trimethylhexanoic acid: 5
0/50) and a complete ester of pentaerythritol,
In Comparative Example 3, ethylene oxide-propylene oxide copolymer monobutyl ether (number average molecular weight: 1000, molar ratio between ethylene oxide and propylene oxide: 50/50); in Comparative Example 4,
Each of the poly-α-olefins was used as a sample oil. Table 1 shows the properties (kinematic viscosity at 100 ° C., pour point) of each sample oil.

Next, the following tests were conducted using the sample oils of Examples 1 to 3 and Comparative Examples 1 to 4.

(Viscosity Measurement Test when Refrigerant is Dissolved) 100 g of sample oil was placed in a pressure vessel and sealed, and the vessel was evacuated. A carbon dioxide refrigerant was introduced into the container, and the viscosity of the sample oil was measured under the conditions of 40 ° C. and a carbon dioxide refrigerant pressure of 5 MPa. Table 1 shows the obtained results.

(Compatibility test with refrigerant) JIS-K-22
11 In accordance with the “refrigerant oil compatibility test method” of “Refrigeration oil”, the state of the mixture when the mixture of 1 g of the carbon dioxide refrigerant and 4 g of the sample oil was maintained at a predetermined temperature (whether or not Separation or cloudiness) was observed.

In this test, the test temperature range was -55.
-30 ° C., and the compatibility was evaluated by determining the temperature range in which each sample oil was in a state of being compatible with the carbon dioxide refrigerant. Table 1 shows the obtained results.

(Insulation Characteristics Test) JIS-C-2101
25 ° C of each sample oil according to “Electrical Insulation Oil Test Method”
Was measured for volume resistivity. Table 1 shows the obtained results.

[0092]

[Table 1] As shown in Table 1, the sample oils of Examples 1 to 3 which are the refrigerating machine oils for carbon dioxide refrigerant of the present invention sufficiently satisfy lubrication, refrigerant compatibility, low-temperature fluidity, and electrical insulation in a well-balanced manner. It was confirmed that the carbon dioxide refrigerant exhibited a sufficiently wide compatible temperature range and that the decrease in viscosity when the carbon dioxide refrigerant was dissolved was sufficiently small.

On the other hand, the sample oils of Comparative Examples 1 and 2
The decrease in viscosity when the carbon dioxide refrigerant was dissolved was large. This result suggests the occurrence of poor lubrication of the compressor and a decrease in sealing performance in the refrigerant circulation system.
In addition, the sample oil of Comparative Example 3 had insufficient electric insulation,
The sample oil of Comparative Example 4 had insufficient refrigerant compatibility.

[0094]

As described above, the refrigerating machine oil for carbon dioxide refrigerant of the present invention, when used together with carbon dioxide refrigerant, has lubricity, sealability, refrigerant compatibility, thermal and chemical stability, and electrical insulation. Etc. can be satisfied in a well-balanced manner. Therefore, by using the refrigerating machine oil for a carbon dioxide refrigerant of the present invention and the fluid composition for a refrigerating machine of the present invention using the same, it is possible to sufficiently prevent poor lubrication of the compressor and a decrease in refrigerating efficiency. Become.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C10N 40:30 C10N 40:30

Claims (2)

[Claims] 1. The following compounds (a) to (c): (a) a compound having 2 to 3 hydroxyl groups or a derivative thereof, (b) a compound having 2 to 3 carboxyl groups or a derivative thereof, and (c) A refrigerating machine oil for carbon dioxide refrigerant, comprising a compound having one carboxyl group or a derivative thereof and / or an ester obtained by using a compound having one hydroxyl group or a derivative thereof. 2. A fluid composition for a refrigerator comprising the refrigerating machine oil for a carbon dioxide refrigerant according to claim 1 and a carbon dioxide refrigerant.