JP2000104085A - Lubricating oil for refrigerator using dimetyl ether as refrigerant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a lubricating oil which exhibits excellent lubricity, compatibility with a refrigerant, stability, etc., when used together with a dimethyl ether refrigerant by incorporating an oxygen-contg. synthetic oil into a lube base oil. SOLUTION: An ester, a polyoxyalkylene glycol, a polyvinyl ether, a ketone, a polyphenyl ether, a silicone, a polysiloxane, a perfluoro ether, etc., are listed as the oxygen-contg. synthetic oil used for a lubricating oil. Among above-listed synthetic oils, an ester, a polyoxyalkylene glycol, a polyvinyl ether, and mixtures of these synthetic oils are pref. The lubricating oil may cotain only one oil or two or more oils selected from among various oxygen-contg. synthetic oils. The content of the oxygen-contg. synthetic oil in the lubricating oil is not specifically limited, though it is pref. 50 mass % or higher based on the total amt. of the lubricating oil. In addition to the oxygen-contg. synthetic oil, the lubrication oil may further contain a hydrocarbon oil such as a mineral oil, an olefin polymer, or an alkylbenzene.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a lubricating oil for a refrigerator, and more particularly to a lubricating oil useful for a refrigerator using dimethyl ether (DME) as a refrigerant.

[0002]

2. Description of the Related Art Due to the recent problem of depletion of the ozone layer, CFC (chlorofluorocarbon) and HCFC (hydrochlorofluorocarbon) which have been conventionally used as refrigerants for refrigeration equipment are subject to regulation.
FC (hydrofluorocarbon) is being used as a refrigerant. However, such HFC refrigerants also have problems such as high global warming ability, and the search for alternative refrigerants in place of these CFC-based refrigerants is being promoted. Among them, harmlessness to the environment, safety, from the viewpoint of availability, dimethyl ether (DME: CH ₃ -O
-CH ₃ ) has attracted attention. With the replacement of refrigerants with DME, development of refrigeration oils for DME refrigerants is underway.

[0003] Performances required for refrigerating machine oil include lubricity, refrigerant compatibility, stability, and the like, and these characteristics greatly vary depending on the type of coexisting refrigerant.
Since DME has a different chemical property from conventional chlorofluorocarbon-based refrigerants, refrigeration oil used in conventional chlorofluorocarbon-based refrigerants cannot be applied as it is, and there is still no DME refrigerant having excellent performance as a refrigeration oil for refrigerants. Not developed.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and when used with a DME refrigerant, has excellent lubricity, refrigerant compatibility, and stability. The purpose is to provide oil.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, by containing oxygen-containing synthetic oil, refrigeration using DME excellent in the above various performances as a refrigerant. It has been found that lubricating oil for machinery can be obtained.

That is, the present invention is a lubricating oil for a refrigerator using dimethyl ether (DME) as a refrigerant, characterized by containing an oxygen-containing synthetic oil.

[0007]

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

Examples of the oxygen-containing synthetic oil used in the lubricating oil of the present invention include esters, polyoxyalkylene glycols, polyvinyl ethers, ketones, polyphenyl ethers, silicones, polysiloxanes and perfluoroethers. Among them, esters, polyoxyalkylene glycols, polyvinyl ethers and mixtures thereof are preferably used.

The esters used in the lubricating oil of the present invention include, for example, aromatic esters, dibasic acid esters, polyol esters, complex esters, carbonate esters, and mixtures thereof.

As the aromatic ester, 1 to 6, preferably 1 to 4, more preferably 1 to 3 aromatic carboxylic acids and C 1 to C 18, preferably C 1 to C 12 aliphatic alcohols are used. And the like. Specific examples of the monovalent to hexavalent aromatic carboxylic acid include benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, and mixtures thereof. The aliphatic alcohol having 1 to 18 carbon atoms may be linear or branched, and specifically, for example, methanol, ethanol, linear or branched propanol , Straight or branched butanol, straight or branched pentanol, straight or branched hexanol, straight or branched heptanol, straight or branched Octanol, linear or branched nonanol, linear or branched decanol, linear or branched undecanol, linear or branched dodecanol, linear or branched Tridecanol, linear or branched tetradecanol, linear or branched pentadecanol, linear or branched hexadecanol, linear or branched heptadecanol, Straight chain It is like branched octadecanol, and mixtures thereof. Specific examples of the aromatic ester include dibutyl phthalate, di (2-ethylhexyl) phthalate, dinonyl phthalate, didecyl phthalate, didodecyl phthalate, ditridecyl phthalate, tributyl trimellitate, tributyl trimellitate. (2-ethylhexyl), trinonyl trimellitate, tridecyl trimellitate, tridodecyl trimellitate, tritridecyl trimellitate, and the like. Of course, when a divalent or higher aromatic carboxylic acid is used, it may be a simple ester composed of one kind of aliphatic alcohol or a complex ester composed of two or more kinds of aliphatic alcohols. You may.

As the dibasic acid ester, glutaric acid,
Adipic acid, pimelic acid, suberic acid, azelaic acid,
C5-10 dibasic acids such as sebacic acid and methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol,
1 carbon atom having a linear or branched alkyl group such as nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol, etc.
~ 15 esters with monohydric alcohols and mixtures thereof are preferably used, and more specifically, for example, ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di 2-ethylhexyl sebacate, And mixtures thereof.

The polyol ester includes a diol or a polyol having 3 to 20 hydroxyl groups.
Esters with fatty acids having 6 to 20 carbon atoms are preferably used. Here, as the diol, specifically, for example,
Ethylene glycol, 1,3-propanediol, propylene glycol, 1,4-butanediol, 1,2-
Butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 2-ethyl-2-methyl-1,3-propanediol, 1,7- Heptanediol, 2-methyl-2-propyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decane Diol, 1,11-undecanediol, 1,12-dodecanediol and the like. As the polyol, specifically, for example, trimethylolethane, trimethylolpropane, trimethylolbutane, di- (trimethylolpropane), tri-
(Trimethylolpropane), pentaerythritol,
Di- (pentaerythritol), tri- (pentaerythritol), glycerin, polyglycerin (2-20 mer of glycerin), 1,3,5-pentanetriol,
Sorbitol, sorbitan, sorbitol glycerin condensate, polyhydric alcohols such as adonitol, arabitol, xylitol, mannitol, xylose, arabinose, ribose, rhamnose, glucose, fructose, galactose, mannose, sorbose, cellobiose, maltose, isomaltose, trehalose,
Saccharides such as sucrose, raffinose, gentianose, and melezitose, as well as partially etherified products thereof, and methylglucoside (glycoside). Among them, polyols include neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, di- (trimethylolpropane), tri- (trimethylolpropane), pentaerythritol, di- (pentaerythritol), Hindered alcohols such as-(pentaerythritol) are preferred.

The fatty acid is not particularly limited in the number of carbon atoms, but usually has 1 to 24 carbon atoms. Among fatty acids having 1 to 24 carbon atoms, those having 3 or more carbon atoms are preferable from the viewpoint of lubricity, those having 4 or more carbon atoms are more preferable, those having 5 or more carbon atoms are even more preferable, and those having 10 or more carbon atoms are more preferable. Are most preferred. Further, from the viewpoint of compatibility with the refrigerant, those having 18 or less carbon atoms are preferable,
Those having 2 or less are more preferred, and those having 9 or less carbon atoms are even more preferred.

Further, any of a linear fatty acid and a branched fatty acid may be used. A linear fatty acid is preferred from the viewpoint of lubricity, and a branched fatty acid is preferred from the viewpoint of hydrolysis stability. Further, any of saturated fatty acids and unsaturated fatty acids may be used.

Examples of the fatty acid include, for example, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecane Acid, octadecanoic acid, nonadecanoic acid,
Straight or branched ones such as icosanoic acid and oleic acid,
Alternatively, a so-called neo acid having a quaternary α carbon atom may be used. More specifically, valeric acid (n-pentanoic acid), caproic acid (n-hexanoic acid), and enanthic acid (n
-Heptanoic acid), caprylic acid (n-octanoic acid), pelargonic acid (n-nonanoic acid), capric acid (n-decanoic acid), oleic acid (cis-9-octadecenoic acid), isopentanoic acid (3-methylbutanoic acid) ), 2-methylhexanoic acid, 2-ethylpentanoic acid, 2-ethylhexanoic acid, and 3,5,5-trimethylhexanoic acid.

The polyol ester may be a partial ester in which all of the hydroxyl groups of the polyol remain without being esterified, or may be a complete ester in which all of the hydroxyl groups have been esterified. And a complete ester, but preferably a complete ester.

The complex ester is an ester of a fatty acid and a dibasic acid with a monohydric alcohol and a polyol. The fatty acid, the dibasic acid, the monohydric alcohol and the polyol include a dibasic ester and a polyol. The same ones as exemplified in the description of the ester can be used.

The carbonic acid ester has the following carbonic acid ester structure in the molecule:

Embedded image It has. Note that one or more carbonic acid ester structures may be present in one molecule.

As the alcohol constituting the carbonate ester, the above-mentioned aliphatic alcohols and polyols can be used, and polyglycols and those obtained by adding polyglycol to polyols can also be used. Further, those using carbonic acid and fatty acids and / or dibasic acids may be used.

As a matter of course, the ester referred to in the present invention may be a single ester having a single structure, or a mixture of two or more esters having different structures.

Among these various esters, polyol esters and carbonate esters are preferred because of their excellent compatibility with the refrigerant.

Among the polyol esters, neopentyl glycol, which is more excellent in hydrolytic stability,
Trimethylolethane, trimethylolpropane, trimethylolbutane, di- (trimethylolpropane),
Esters of hindered alcohols such as tri- (trimethylolpropane), pentaerythritol, di- (pentaerythritol) and tri- (pentaerythritol) are more preferred, and neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane And pentaerythritol esters are even more preferable, and pentaerythritol esters are most preferable because they are particularly excellent in compatibility with a refrigerant and hydrolysis stability.

Specific examples of preferred polyol esters include neopentyl glycol and valeric acid, caproic acid,
Enanthic acid, caprylic acid, pelargonic acid, capric acid,
Oleic acid, isopentanoic acid, 2-methylhexanoic acid,
2-ethylpentanoic acid, 2-ethylhexanoic acid, 3,
Diester of one or more fatty acids selected from 5,5-trimethylhexanoic acid, trimethylolethane and valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, oleic acid, isopentane Triester with one or more fatty acids selected from acids, 2-methylhexanoic acid, 2-ethylpentanoic acid, 2-ethylhexanoic acid, 3,5,5-trimethylhexanoic acid, and trimethylolpropane And valeric acid,
Caproic acid, enanthic acid, caprylic acid, pelargonic acid,
One or more fatty acids selected from capric acid, oleic acid, isopentanoic acid, 2-methylhexanoic acid, 2-ethylpentanoic acid, 2-ethylhexanoic acid, and 3,5,5-trimethylhexanoic acid; Triesters, trimethylol butane and valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, oleic acid, isopentanoic acid, 2-methylhexanoic acid, 2-ethylpentanoic acid, 2-ethylhexanoic acid, Triester with one or more fatty acids selected from 3,5,5-trimethylhexanoic acid, pentaerythritol and valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, oleic acid , Isopentanoic acid, 2
And tetraesters with one or more fatty acids selected from -methylhexanoic acid, 2-ethylpentanoic acid, 2-ethylhexanoic acid, and 3,5,5-trimethylhexanoic acid.

The ester of two or more fatty acids may be a mixture of two or more esters of one fatty acid and a polyol, or an ester of a mixture of two or more fatty acids and a polyol. Esters of two or more fatty acids, particularly esters of a mixed fatty acid and a polyol, are excellent in low-temperature characteristics and compatibility with a refrigerant.

Further, among the carbonate esters, the following general formula (1):

Embedded image Ｘ In the above formula (1), X ¹ is a hydrogen atom, an alkyl group, a cycloalkyl group or the following general formula (2): Y ² — (OA ³ ) _e − (2) (In the above formula (2), Y ² Represents a hydrogen atom, an alkyl group or a cycloalkyl group, A ³ represents an alkylene group having 2 to 4 carbon atoms, e represents an integer of 1 to 50), A ¹ and A ² may be the same or different, each represent an alkylene group having 2 to 4 carbon atoms, Y ¹
Represents a hydrogen atom, an alkyl group or a cycloalkyl group; B represents a residue of a compound having 3 to 20 hydroxyl groups;
Represents an integer of 1 to 20, b represents an integer of 0 to 19 and a + b = 3 to 20, c represents an integer of 0 to 50, and d represents an integer of 1 to 50.
The structure represented by the following formula is preferred.

In the above formula (1), X ¹ is a hydrogen atom,
It represents an alkyl group, a cycloalkyl group or a group represented by the above formula (2). The number of carbon atoms in the alkyl group is not particularly limited, but is usually 1 to 24, preferably 1 to 1
8, more preferably 1 to 12. Further, it may be straight-chain or branched.

Examples of the alkyl group having 1 to 24 carbon atoms include, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s
an ec-butyl group, a tert-butyl group, a linear or branched pentyl group, a linear or branched hexyl group, a linear or branched heptyl group, a linear or branched octyl group, a linear or branched nonyl group, Straight or branched decyl group, straight or branched undecyl group, straight or branched dodecyl group, straight or branched tridecyl group, straight or branched tetradecyl group,
Linear or branched pentadecyl, linear or branched hexadecyl, linear or branched heptadecyl, linear or branched octadecyl, linear or branched nonadecyl, linear or branched icosyl, linear Or a branched henicosyl group, a straight or branched docosyl group, a straight or branched tricosyl group, a straight or branched tetracosyl group, and the like.

Specific examples of the cycloalkyl group include a cyclopentyl group, a cyclohexyl group and a cycloheptyl group.

In the above formula (2), the alkylene group having 2 to 4 carbon atoms represented by A ³ includes ethylene, propylene, trimethylene, butylene, tetramethylene, 1-methyltrimethylene, 2 -Methyltrimethylene group, 1,1-dimethylethylene group, 1,2-dimethylethylene group and the like.

Y ² in the above formula (2) is a hydrogen atom, an alkyl group or a cycloalkylalkyl group.
Although the number of carbon atoms of the alkyl group referred to herein is not particularly limited,
Usually 1 to 24, preferably 1 to 18, more preferably 1
~ 12. Further, it may be straight-chain or branched. Specific examples of the alkyl group having 1 to 24 carbon atoms include the groups listed in the description of X ¹ .

Specific examples of the cycloalkyl group include a cyclopentyl group, a cyclohexyl group and a cycloheptyl group.

Among them, Y ² is preferably a hydrogen atom or an alkyl group having 1 to 12 carbon atoms.
Hydrogen atom, methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group,
tert-butyl group, n-pentyl group, iso-pentyl group, neo-
Pentyl, n-hexyl, iso-hexyl, n-heptyl, iso-heptyl, n-octyl, iso-octyl, n-nonyl, iso-nonyl, n-decyl, iso- More preferably, it is any one of a decyl group, an n-undecyl group, an iso-undecyl group, an n-dodecyl group and an iso-dodecyl group. E represents an integer of 1 to 50.

X ¹ is a hydrogen atom, carbon number 1
To 12 or a group represented by the general formula (2), and is preferably a hydrogen atom, a methyl group, an ethyl group,
n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, i
so-pentyl group, neo-pentyl group, n-hexyl group, iso-
Hexyl group, n-heptyl group, iso-heptyl group, n-octyl group, iso-octyl group, n-nonyl group, iso-nonyl group,
More preferably, it is any one of an n-decyl group, an iso-decyl group, an n-undecyl group, an iso-undecyl group, an n-dodecyl group, an iso-dodecyl group and a group represented by the general formula (2).

Specific examples of the compound having 3 to 20 hydroxyl groups having B as a residue include the polyols described above.

A ¹ and A ² may be the same or different and each represents an alkylene group having 2 to 4 carbon atoms.
Specifically, for example, ethylene group, propylene group, trimethylene group, butylene group, tetramethylene group, 1-methyltrimethylene group, 2-methyltrimethylene group, 1,1-dimethylethylene group, 1,2-dimethylethylene And the like.

Y ¹ is a hydrogen atom, an alkyl group or a cycloalkylalkyl group. The number of carbon atoms in the alkyl group is not particularly limited, but is usually 1 to 24, preferably 1 to 18, and more preferably 1 to 12. Also,
It may be linear or branched. As the alkyl group having 1 to 24 carbon atoms, specifically, for example,
The groups listed in the description of X ¹ can be mentioned.

Specific examples of the cycloalkyl group include a cyclopentyl group, a cyclohexyl group and a cycloheptyl group.

Among them, Y ¹ is preferably a hydrogen atom or an alkyl group having 1 to 12 carbon atoms.
Hydrogen atom, methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group,
tert-butyl group, n-pentyl group, iso-pentyl group, neo-
Pentyl, n-hexyl, iso-hexyl, n-heptyl, iso-heptyl, n-octyl, iso-octyl, n-nonyl, iso-nonyl, n-decyl, iso- More preferably, it is any one of a decyl group, an n-undecyl group, an iso-undecyl group, an n-dodecyl group and an iso-dodecyl group.

In the above formulas (1) and (2), c, d and e represent the degree of polymerization of the polyoxyalkylene moiety, which may be the same or different in the molecule. When it has a plurality of different polyoxyalkylene moieties, the polymerization form of the oxyalkylene group is not particularly limited, and may be random copolymerization or block copolymerization.

The method for producing the carbonic ester used in the present invention is optional. For example, a polyalkylene glycol polyol ether is produced by adding an alkylene oxide to a polyol compound, and this is mixed with sodium hydroxide, It is obtained by reacting at 0 to 30 ° C. in the presence of an alkali metal hydroxide such as potassium hydroxide, an alkali metal alkoxide such as sodium methoxide or sodium ethoxide, or an alkali such as sodium metal. Alternatively, a polyalkylene glycol polyol ether may be added to a source of carbonic acid such as diester carbonate or phosgene and an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide, an alkali metal alkoxide such as sodium methoxide or sodium ethoxide, or a metal sodium. It is obtained by reacting at 80 to 150 ° C. in the presence of an alkali such as Thereafter, free hydroxyl groups are etherified as required.

The products obtained from the above-mentioned raw materials may be purified to remove by-products and unreacted products, but a small amount of by-products and unreacted products are used in the lubricating oil of the present invention. As long as excellent performance is not impaired, there is no problem even if present.

In the present invention, the carbonate may be used in the form of a mixture or as a single product. The molecular weight of the carbonate according to the present invention is not particularly limited,
From the viewpoint of further improving the hermeticity of the compressor, those having a number average molecular weight of 200 to 4000 are preferably used, and those having a number average molecular weight of 300 to 3000 are more preferably used. Furthermore, the preferred kinematic viscosity of the carbonate according to the present invention is 10
At 0 ° C., preferably 2-150 mm ² / s, more preferably 4
100100 mm ² / s.

The polyoxyalkylene glycol used in the lubricating oil of the present invention includes, for example, a compound represented by the following general formula (I): R ¹ -[(OR ² ) _f -OR ³ ] _g (I) )), R ¹ represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an acyl group or a hydroxyl group having 2 to 10 carbon atoms,
R ² is an alkylene group having 2 to 4 carbon atoms, R 3 is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms or an acyl group having 2 to 10 carbon atoms, f is an integer of 1 to 80, g
Represents an integer of 1 to 8).

In the general formula (I), the alkyl group for R ¹ and R ³ may be linear, branched or cyclic. Specific examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a linear or branched butyl group, a linear or branched pentyl group, a linear or branched Hexyl group, linear or branched heptyl group, linear or branched octyl group,
Examples thereof include a linear or branched nonyl group, a linear or branched decyl group, a cyclopentyl group, and a cyclohexyl group. If the carbon number of the alkyl group exceeds 10, the compatibility with the refrigerant is reduced, and phase separation may occur. The preferred alkyl group has 1 to 6 carbon atoms.

The alkyl group of the acyl group in R ¹ and R ³ may be linear, branched or cyclic. As specific examples of the alkyl group portion of the acyl group, various groups having 1 to 9 carbon atoms mentioned above as specific examples of the alkyl group can be similarly mentioned. If the acyl group has more than 10 carbon atoms, the compatibility with the refrigerant may be reduced, and phase separation may occur. Preferred acyl groups have 2 to 6 carbon atoms.

When R ¹ and R ³ are both an alkyl group or an acyl group, R ¹ and R ³ may be the same or different from each other. When g is 2 or more, a plurality of R ^{3 in} one molecule may be the same,
It may be different.

When R ¹ is a residue of a compound having 2 to 8 hydroxyl groups, this compound may be a chain or a cyclic compound. Examples of the compound having two hydroxyl groups include ethylene glycol, 1,3-
Propanediol, propylene glycol, 1,4-butanediol, 1,2-butanediol, 2-methyl-
1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 2-ethyl-2-methyl-1,3-propanediol, 1,7-heptanediol, 2-methyl -2-propyl-1,3-propanediol, 2,2-diethyl-
Examples thereof include 1,3-propanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, and 1,12-dodecanediol.

Compounds having 3 to 8 hydroxyl groups include:
For example, trimethylolethane, trimethylolpropane, trimethylolbutane, di- (trimethylolpropane), tri- (trimethylolpropane), pentaerythritol, di- (pentaerythritol), tri-
(Pentaerythritol), glycerin, polyglycerin (glycerin dimer to hexamer), 1,3,5-pentanetriol, sorbitol, sorbitan, sorbitol glycerin condensate, polyhydric alcohols such as adonitol, arabitol, xylitol, mannitol, Saccharides such as xylose, arabinose, ribose, rhamnose, glucose, fructose, galactose, mannose, sorbose, cellobiose, maltose, isomaltose, trehalose, sucrose, raffinose, gentianose, melezitose and the like, and partially etherified products thereof, and methylglucoside ( Glycosides).

In the present invention, the residue of the compound having a hydroxyl group means a residue excluding the hydroxyl group.

In the present invention, at least one of R ¹ and R ³ is preferably an alkyl group, particularly an alkyl group having 1 to 4 carbon atoms, and particularly preferably a methyl group from the viewpoint of viscosity characteristics. Further, for the same reasons as described above, both R ¹ and R ³ are alkyl groups, particularly those having 1 to 1 carbon atoms.
It is preferably an alkyl group of No. 4 and particularly preferably a methyl group.

R ² in the general formula (I) has 2 to 4 carbon atoms.
And an ethylene group, a propylene group, a butylene group and the like. Examples of the oxyalkylene group of the repeating unit represented by (OR ² ) include an oxyethylene group, an oxypropylene group, and an oxybutylene group. The oxyalkylene groups in one molecule may be the same, or may contain two or more oxyalkylene groups.

From the viewpoint of refrigerant compatibility and hygroscopicity, oxyethylene groups (EO) and oxypropylene groups (PO)
Is preferable. In such a case, the value of EO / (PO + EO) is 0.1 in view of the seizure load and the viscosity characteristics.
It is preferably in the range of 0.8 to 0.8, and more preferably in the range of 0.3 to 0.6.

In terms of hygroscopicity and thermal oxidation stability, EO
The value of / (PO + EO) is preferably in the range of 0 to 0.5, more preferably 0 to 0.2, and most preferably a PO homopolymer.

F in the general formula (I) is an integer of 1 to 80. G in the general formula (I) is an integer of 1 to 8. For example, when R ¹ is an alkyl group or an acyl group, g
Is 1. When R ¹ is a residue of a compound having 2 to 8 hydroxyl groups, g is the number of the hydroxyl groups.

Although f × g is not particularly limited, the average value of f × g should be 6 to 80 in order to satisfy the above-mentioned required performance as a lubricating oil for refrigerators in a well-balanced manner. Is preferred.

The polyoxyalkylene glycol represented by the general formula (I) includes a polyoxyalkylene glycol having a hydroxyl group at a terminal, and has a hydroxyl group content of 50 mol% or less based on all terminal groups. If it is such a ratio, it can be suitably used even if it is contained. If the content of the hydroxyl group exceeds 50 mol%, the hygroscopicity increases and the viscosity index decreases, which is not preferable.

The polyoxyalkylene glycol according to the present invention is represented by the general formula: CH ₃ O— (C ₃ H ₆ O) _h —CH ₃ (where h is a number from 6 to 80). Polyoxypropylene glycol dimethyl ether, general formula: CH ₃ O— (C ₃ H ₆ O) _i — (C ₂ H ₄ O) _j —CH ₃ (wherein i and j are each 1 or more, and total polyoxyethylene polyoxypropylene glycol dimethyl ether represented by indicating the number of the 6 to 80) are preferable from the viewpoint of economy and effect and the general _{formula: C 4 H 9 O- (C} 3 H 6 O) _k- H ( _{where k} represents a number from 6 to 80), such as polyoxypropylene glycol monobutyl ether, and further polyoxypropylene glycol diacetate.
It is suitable in terms of economy and the like.

In the present invention, the above polyoxyalkylene glycol is represented by the following general formula (II):

Embedded image 中 In the formula (II), R ^{4 to} R ⁷ each represent a hydrogen atom and a carbon atom 1
A monovalent hydrocarbon group or a general formula (III):

Embedded image (In the formula (III), R ⁸ and R ⁹ each represent a hydrogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms or an alkoxyalkyl group having 2 to 20 carbon atoms, and R ¹⁰ has 2 to 5 carbon atoms. Total number of carbon atoms having an alkylene group or an alkyl group as a substituent of 2 to 5
Represents a substituted alkylene group having a total of 4 to 10 carbon atoms having a substituted alkylene group or an alkoxyalkyl group as a substituent, p represents an integer of 0 to 20, and R ¹¹ represents a monovalent hydrocarbon group having 1 to 10 carbon atoms. Wherein at least one of R ^{4 to} R ⁷ is a group represented by the general formula (III), and a polyoxyalkylene glycol derivative having at least one structural unit represented by｝ is used. be able to.

Here, in the formula (II), R ^{4 to} R ⁷ are each a hydrogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms or one represented by the above general formula (III). 1 to 1
Specific examples of the monovalent hydrocarbon group 0 include, for example, a linear or branched alkyl group having 1 to 10 carbon atoms, a linear or branched alkenyl group having 2 to 10 carbon atoms, Examples thereof include a cycloalkyl group or an alkylcycloalkyl group having 5 to 10 carbon atoms, an aryl group or an alkylaryl group having 6 to 10 carbon atoms, and an arylalkyl group having 7 to 10 carbon atoms. Among them, a monovalent hydrocarbon group having 6 or less carbon atoms can be preferably used, and in particular, an alkyl group having 3 or less carbon atoms, specifically, a methyl group, an ethyl group, an n-propyl group,
An isopropyl group is optimal.

In the general formula (III), R ⁸ and R ⁹
Represents a hydrogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms or an alkoxyalkyl group having 2 to 20 carbon atoms, and among these, an alkyl group having 3 or less carbon atoms or an alkoxyalkyl having 6 or less carbon atoms is preferable. Groups are preferred. Carbon number 3
Specific examples of the following alkyl groups include a methyl group, an ethyl group, an n-propyl group, and an isopropyl group.
Examples of the alkoxyalkyl group having 2 to 6 carbon atoms include a methoxymethyl group, an ethoxymethyl group, an n-propoxymethyl group, an isopropoxymethyl group, an n-butoxymethyl group, an isobutoxymethyl group, and a sec-butoxymethyl group. Group, tert-butoxymethyl group, pentoxymethyl group (including all isomers), methoxyethyl group (including all isomers), ethoxyethyl group (including all isomers), propoxyethyl group (all Butoxyethyl group (including all isomers),
Methoxypropyl group (including all isomers), ethoxypropyl group (including all isomers), propoxypropyl group (including all isomers), methoxybutyl group (including all isomers), ethoxybutyl Groups (including all isomers), methoxypentyl groups (including all isomers), and the like.

R ¹⁰ is an alkylene group having 2 to 5 carbon atoms, a substituted alkylene group having 2 to 5 carbon atoms having an alkyl group as a substituent or a substituted alkylene group having 4 to 10 carbon atoms having an alkoxyalkyl group as a substituent. The group is preferably an alkylene group having 2 to 4 carbon atoms or a substituted ethylene group having 6 or less total carbon atoms. Specific examples of the alkylene group having 2 to 4 carbon atoms include an ethylene group, a propylene group, and a butylene group. Examples of the substituted ethylene group having a total carbon number of 6 or less include a 1- (methoxymethyl) ethylene group, a 2- (methoxymethyl) ethylene group, and a 1- (methoxymethyl) ethylene group.
(Methoxyethyl) ethylene group, 2- (methoxyethyl) ethylene group, 1- (ethoxymethyl) ethylene group,
2- (ethoxymethyl) ethylene group, 1-methoxymethyl-2-methylethylene group, 1,1-bis (methoxymethyl) ethylene group, 2,2-bis (methoxymethyl) ethylene group, 1,2-bis ( Methoxymethyl) ethylene group, 1-methyl-2-methoxymethylethylene group, 1-
Methoxymethyl-2-methylethylene group, 1-ethyl-
2-methoxymethylethylene group, 1-methoxymethyl-
2-ethylethylene group, 1-methyl-2-ethoxymethylethylene group, 1-ethoxymethyl-2-methylethylene group, 1-methyl-2-methoxyethylethylene group, 1
-Methoxyethyl-2-methylethylene group and the like.

R ¹¹ represents a monovalent hydrocarbon group having 1 to 10 carbon atoms, specifically, for example, a linear or branched alkyl group having 1 to 10 carbon atoms, A linear or branched alkenyl group, a cycloalkyl group or an alkylcycloalkyl group having 5 to 10 carbon atoms,
10 aryl or alkylaryl groups, 7 carbon atoms
And 10 to 10 arylalkyl groups. Among these, a monovalent hydrocarbon group having 6 or less carbon atoms can be preferably used, and an alkyl group having 3 or less carbon atoms, specifically, a methyl group, an ethyl group, an n-propyl group, and an isopropyl group are most suitable.

Incidentally, R ^{4 to} R ⁷ in the aforementioned general formula (II)
At least one of them is a group represented by the general formula (III). In particular, any one of R ⁴ and R ⁶ is a group represented by the general formula (III), and the other one of R ⁴ and R ⁶ and R ⁵ and R ⁷ are each a hydrogen atom or a group having 1 to 10 carbon atoms. It is preferably a monovalent hydrocarbon group.

The polyoxyalkylene glycol derivative contains at least one structural unit represented by the general formula (II). More specifically, the polyoxyalkylene glycol derivative comprises a single polymer comprising the structural unit represented by the general formula (II). Coalesce, a copolymer comprising two or more different structural units contained in the general formula (II), and a structural unit of the general formula (II) and another structural unit, for example, a general formula
(IV):

Embedded image (In the formula (IV), each of R ^{12 to} R ¹⁵ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms). Preferred examples of the homopolymer include 1 to 200 structural units A represented by the general formula (II), and each of the terminal groups is a hydroxyl group, an acyloxy group having 1 to 10 carbon atoms, and a 1 to 10 carbon atoms.
And those comprising an alkoxy group or an aryloxy group. On the other hand, preferred examples of the copolymer include two types of structural units A and B represented by the general formula (II) each having 1
Having from 200 to 200 or from 1 to 200 structural units A represented by the general formula (II) and from 1 to 200 structural units C represented by the general formula (IV), and the terminal groups each having a hydroxyl group An acyloxy group having 1 to 10 carbon atoms, 1 to 1 carbon atoms
And 10 alkoxy groups or aryloxy groups. These copolymers are obtained by alternate copolymerization of the structural unit A and the structural unit B (or the structural unit C), random copolymerization, block copolymer or graft in which the structural unit B is graft-bonded to the main chain of the structural unit A. There are various things such as copolymers.

The polyvinyl ether used in the lubricating oil of the present invention includes, for example, the general formula (V):

Embedded image (In the formula (V), R ¹⁶ , R ¹⁷ and R ¹⁸ each represent a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, which may be the same or different, and R ¹⁹ has 1 carbon atom. -10
A divalent hydrocarbon group or a divalent ether-bonded oxygen-containing hydrocarbon group having 2 to ²⁰ carbon atoms, R ²⁰ is a hydrocarbon group having 1 to ²⁰ carbon atoms, and q is a number having an average value of 0 to 10. Shows, R ¹⁶
To R ²⁰ may be the same or different for each structural unit, and when there are a plurality of R ¹⁹ O,
⁽ 19O may be the same or different).

Further, the structural unit represented by the above general formula (V) and the general formula (VI):

Embedded image (In the formula (VI), R ²¹ ~R ²⁴ each represent a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms and may be the same with or different from each other, also R ²¹ to R ²⁴ are configured A polyvinyl ether-based compound comprising a block or a random copolymer having a structural unit represented by the formula (1) may be the same or different for each unit) can also be used.

R ¹⁶ , R ¹⁷ and R ¹⁸ in the above formula (V) each represent a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms. Is also good. Here, the hydrocarbon group specifically refers to a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group,
Alkyl groups such as tert-butyl group, various pentyl groups, various hexyl groups, various heptyl groups, various octyl groups, cycloalkyl groups such as cyclopentyl group, cyclohexyl group, various methylcyclohexyl groups, various ethylcyclohexyl groups, various dimethylcyclohexyl groups, and the like. Phenyl group, various methylphenyl groups, various ethylphenyl groups, various dimethylphenyl groups and the like, and arylalkyl groups such as benzyl group, various phenylethyl groups and various methylbenzyl groups. These R ¹⁶ ,
As R ¹⁷ and R ¹⁸ , a hydrogen atom is particularly preferable.

On the other hand, R ¹⁹ in the general formula (V) has 1 carbon atom.
A divalent hydrocarbon group having 10 to 10, preferably 2 to 10 or a divalent ether-bonded oxygen-containing hydrocarbon group having 2 to 20 carbon atoms, wherein a divalent hydrocarbon group having 1 to 10 carbon atoms Are specifically a methylene group, an ethylene group, a phenylethylene group, a 1,2-propylene group, a 2-phenyl-1,2
-Divalent aliphatic groups such as propylene group, 1,3-propylene group, various butylene groups, various pentylene groups, various hexylene groups, various heptylene groups, various octylene groups, various nonylene groups, various decylene groups, cyclohexane, methyl Alicyclic groups having two binding sites on alicyclic hydrocarbons such as cyclohexane, ethylcyclohexane, dimethylcyclohexane, propylcyclohexane, various phenylene groups, various methylphenylene groups, various ethylphenylene groups, various dimethylphenylene groups, various Divalent aromatic hydrocarbon groups such as naphthylene groups, alkyl aromatic groups such as toluene, xylene, and ethylbenzene, and alkyl aromatic groups each having a monovalent binding site in the aromatic portion, xylene, and diethylbenzene Such as polyalkyl aromatic Is an alkyl aromatic group having an alkyl group moiety binding site of hydrogen. Of these, aliphatic groups having 2 to 4 carbon atoms are particularly preferred.

Specific examples of the divalent ether-bonded oxygen-containing hydrocarbon group having 2 to 20 carbon atoms include a methoxymethylene group, a methoxyethylene group, a methoxymethylethylene group, a 1,1-bismethoxymethylethylene group, 1,2-
Bismethoxymethylethylene group, ethoxymethylethylene group, (2-methoxyethoxy) methylethylene group,
A (1-methyl-2-methoxy) methylethylene group can be preferably exemplified. In the general formula (V), q represents the number of repetitions of R ¹⁹ O, and the average value thereof is 0 to
It is a number in the range of 10, preferably 0-5. When the R ¹⁹ O is plural, plural R ¹⁹ O may be the same or different.

Further, R ²⁰ in the general formula (V) represents a hydrocarbon group having 1 to ²⁰ carbon atoms, preferably 1 to 10 carbon atoms, specifically, a methyl group, an ethyl group, n-propyl group, isopropyl group, n-butyl group,
Isobutyl group, sec-butyl group, tert-butyl group, various pentyl groups, various hexyl groups, various heptyl groups, various octyl groups, various nonyl groups, alkyl groups such as various decyl groups, cyclopentyl groups, cyclohexyl groups,
Various methylcyclohexyl groups, various ethylcyclohexyl groups, various propylcyclohexyl groups, cycloalkyl groups such as various dimethylcyclohexyl groups, phenyl groups,
Various methylphenyl groups, various ethylphenyl groups, various dimethylphenyl groups, various propylphenyl groups, various trimethylphenyl groups, various butylphenyl groups, various aryl groups such as naphthyl groups, benzyl groups, various phenylethyl groups, various methylbenzyl groups And arylalkyl groups such as various phenylpropyl groups and various phenylbutyl groups. Note that R ^{16 to} R ²⁰ may be the same or different for each structural unit.

The polyvinyl ether compound (1) represented by the general formula (V) has a carbon / oxygen molar ratio of 4.2.
Those in the range of ~ 7.0 are preferred. If the molar ratio is less than 4.2, the hygroscopicity is high, and if it exceeds 7.0, the compatibility with the refrigerant may be reduced. In the above general formula (VI), R ^{21 to} R ²⁴ each represent a hydrogen atom or a carbon atom having 1 to 2 carbon atoms.
It represents 0 hydrocarbon radicals, which may be identical or different. Examples of the hydrocarbon group having 1 to 20 carbon atoms may include the same as those exemplified in the description of R ²⁰ in formula (V). R ^{21 to} R ²⁴ may be the same or different for each structural unit.

The polyvinyl ether compound (2) comprising a block or a random copolymer having the structural unit represented by the general formula (V) and the structural unit represented by the general formula (VI) has a carbon / oxygen Those having a molar ratio in the range of 4.2 to 7.0 are preferably used. If the molar ratio is less than 4.2, the hygroscopicity is high, and if it exceeds 7.0, the compatibility with the refrigerant may decrease. Furthermore, in the present invention, a mixture of the polyvinyl ether compound (1) and the polyvinyl ether compound (2) can also be used. The polyvinyl ether compounds (1) and (2) used in the present invention are obtained by polymerizing the corresponding vinyl ether monomers and copolymerizing the corresponding hydrocarbon monomers having an olefinic double bond with the corresponding vinyl ether monomers. Can be manufactured. As the polyvinyl ether compound used in the present invention,
Those having the following terminal structure, that is, one terminal of which has the general formula (VII) or (VIII):

Embedded image (In the formulas (VII) and (VIII), R ²⁵ , R ²⁶ and R ²⁷ each represent a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms,
R ^25, R ²⁶ and R ²⁷ may be the same with or different from each ^{other, R 30, R 31, R} 32 and R ³³ each represent a hydrogen atom or a hydrocarbon group having a carbon number of 1 to 20, R ³⁰ , R ³¹ ,
R ³² and R ³³ may be the same or different.
R ²⁸ is a divalent hydrocarbon group having 1 to 10 carbon atoms or 2 carbon atoms;
To 20 divalent ether-linked oxygen-containing hydrocarbon groups, R ²⁹
Is a hydrocarbon group having 1 to 20 carbon atoms, and r has an average value of 0 to
10 indicates a number, and when there are a plurality of R ²⁸ O,
²⁸ O may be the same or different), and the remaining terminal is represented by the general formula (IX) or (X):

Embedded image (In the formulas (IX) and (X), R ³⁴ , R ³⁵ and R ³⁶ each represent a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms,
R ^34, R ³⁵ and R ³⁶ may be the same with or different from each ^{other, R 39, R 40, R} 41 and R ⁴² each represent a hydrogen atom or a hydrocarbon group having a carbon number of 1 to 20, R ³⁹ , R ⁴⁰ ,
R ⁴¹ and R ⁴² may be the same or different.
R ³⁷ is a divalent hydrocarbon group having 1 to 10 carbon atoms or 2 carbon atoms;
To 20 divalent ether-linked oxygen-containing hydrocarbon groups, R ³⁸
Is a hydrocarbon group having 1 to 20 carbon atoms, and s is an average of 0 to 0.
10 indicates a number, and when there are a plurality of R ³⁷ O,
³⁷ O may have the same or different structures, and one end thereof has the general formula (VI
(I) or (VIII), and the remaining terminal is represented by the general formula (X
I):

Embedded image (In the formula (XI), R ⁴³ , R ⁴⁴ and R ⁴⁵ each represent a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, which may be the same or different.) Are preferred. Among such polyvinyl ether compounds, the following compounds are particularly preferred in the present invention.

(1) One terminal of which has a structure represented by the general formula (VII) or (VIII) and the other terminal has a structure represented by the general formula (IX) or (X), R ¹⁶ , R ¹⁷ and R ¹⁸ in V) are all hydrogen atoms, q is a number of 0 to 4,
R ¹⁹ is a divalent hydrocarbon group having 2 to 4 carbon atoms and R ²⁰ is a hydrocarbon group having 1 to ²⁰ carbon atoms.

(2) It has only a structural unit represented by the general formula (V), and one terminal thereof has the general formula (VI)
Represented by the formula (IX), and the remaining terminal has a structure represented by the formula (IX), and R ¹⁶ , R ¹⁷ and R in the formula (V)
¹⁸ are both hydrogen atoms, q is a number of 0 to 4, and R ¹⁹ is 2 to 2 carbon atoms.
A divalent hydrocarbon group of 4 and R ²⁰ being a hydrocarbon group having 1 to ²⁰ carbon atoms.

(3) One of the terminals has a structure represented by the general formula (VII) or (VIII), and the other terminal has a structure represented by the general formula (XI). ¹⁶ , R ¹⁷
And R ¹⁸ are both hydrogen atoms, q is a number of 0 to 4, R ¹⁹ is a divalent hydrocarbon group having 2 to 4 carbon atoms, and R ²⁰ is a 1 to ²⁰ carbon atom.
Which are hydrocarbon groups.

(4) It has only a structural unit represented by the general formula (V), and one of its terminals is represented by the general formula (VI)
Represented by I), and has a structure in which the other terminal is represented by the general formula (X), R ¹⁶ in the general formula (V), R ¹⁷ and R
¹⁸ are both hydrogen atoms, q is a number of 0 to 4, and R ¹⁹ is 2 to 2 carbon atoms.
A divalent hydrocarbon group of 4 and R ²⁰ being a hydrocarbon group having 1 to ²⁰ carbon atoms.

Further, the present invention has a structural unit represented by the general formula (V), one end of which is represented by the general formula (VII), and the other end is represented by the general formula (XI)
I):

Embedded image (In the formula ^{(XII), R 46, R} 47 and R ⁴⁸ each represent a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, they may be different even identical to each other, R ⁴⁹ And R
⁵¹ represents a divalent hydrocarbon group having 2 to 10 carbon atoms, which may be the same or different, and R ⁵⁰ and R ⁵² each represent a hydrocarbon group having 1 to 10 carbon atoms. May be the same or different from each other, t and u each represent an average number of 0 to 10, they may be the same or different from each other, and a plurality of R ^{When 49} O is present, a plurality of R ⁴⁹ Os may be the same or different. When there are a plurality of R ⁵¹ Os, a plurality of R ⁵¹ Os may be the same or different. Good) can also be used.

Further, in the present invention, the compound represented by the general formula (XII)
I) or (XIV):

Embedded image (In the formulas (XIII) and (XIV), R ⁵³ and R ⁵⁴ each represent a hydrocarbon group having 1 to 8 carbon atoms) and have a weight average molecular weight of 300 to 5,000. And one end has the general formula (XV) or (XVI):

Embedded image (In the formulas (XV) and (XVI), R ⁵⁵ represents an alkyl group having 1 to 3 carbon atoms, and R ⁵⁶ and R ⁵⁷ each represent a hydrocarbon group having 1 to 8 carbon atoms.) A polyvinyl ether compound composed of a homopolymer or a copolymer of vinyl ether can also be used.

The lubricating oil of the present invention may contain only one kind selected from the above-mentioned various oxygen-containing synthetic oils, or may contain two or more kinds of oxygen-containing synthetic oils. Is also good.

The content of the oxygen-containing synthetic oil in the lubricating oil of the present invention is not particularly limited.
The oxygen-containing synthetic oil is preferably contained in an amount of 50% by mass or more, more preferably 70% by mass or more, and more preferably 80% by mass, based on the total amount of the lubricating oil, from the viewpoint of superiority in various performances such as chemical stability and electric insulation. More preferably, the content is more preferably 90% by mass or more.

The lubricating oil of the present invention contains the above-described oxygen-containing synthetic oil. In addition to this, a hydrocarbon oil such as a mineral oil, an olefin polymer, a naphthalene compound, or an alkylbenzene is used in combination. Is also good.

The lubricating oil of the present invention contains an oxygen-containing synthetic oil and, if necessary, a hydrocarbon-based oil, and these are mainly used as a base oil. The lubricating oil of the present invention can be suitably used in a state where no additives are added, but can be used in a form in which various additives are blended as required.

In order to further improve the wear resistance and load bearing capacity of the lubricating oil of the present invention, phosphate esters, acidic phosphate esters, amine salts of acidic phosphate esters, chlorinated phosphate esters and phosphite esters At least one phosphorus compound selected from the group consisting of:
These phosphorus compounds are esters of phosphoric acid or phosphorous acid with alkanols or polyether-type alcohols or derivatives thereof.

Specifically, for example, phosphate esters include tributyl phosphate, tripentyl phosphate, trihexyl phosphate, triheptyl phosphate, trioctyl phosphate, trinonyl phosphate, tridecyl phosphate, triundecyl phosphate, and 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, xylendiphenyl phosphate and the like. Examples of the acidic phosphate include monobutyl acid phosphate, monopentyl acid phosphate, monohexyl acid phosphate, monoheptyl acid phosphate, monooctyl acid phosphate,
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
Examples thereof include dipentadecyl acid phosphate, dihexadecyl acid phosphate, diheptadecyl acid phosphate, dioctadecyl acid phosphate, and dioleyl acid phosphate. Examples of the amine salt of the acidic phosphoric acid ester include the acidic phosphoric acid ester methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, Dipentylamine, dihexylamine, diheptylamine, dioctylamine, trimethylamine, triethylamine,
Examples thereof include salts with amines such as tripropylamine, tributylamine, tripentylamine, trihexylamine, triheptylamine, and trioctylamine. As chlorinated phosphates, tris-dichloropropyl phosphate, tris-chloroethyl phosphate,
Tris chlorophenyl phosphate, polyoxyalkylene bis [di (chloroalkyl)] phosphate and the like can be mentioned. As the phosphite, 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. Also, a mixture of these can be used.

When these phosphorus compounds are blended in the lubricating oil of the present invention, the blending amount is not particularly limited, but usually,
An amount such that its content is 0.01 to 5.0% by mass, more preferably 0.02 to 3.0% by mass, based on the total amount of the lubricating oil (based on the total amount of the base oil and all the blending additives). It is desirable to add a phosphorus compound.

In the lubricating oil of the present invention, in order to further improve the stability, (1) phenylglycidyl ether type epoxy compound (2) alkyl glycidyl ether type epoxy compound (3) glycidyl ester type epoxy compound (4 ) Allyl oxirane compound (5) alkyl oxirane compound (6) alicyclic epoxy compound (7) epoxidized fatty acid monoester (8) epoxidized vegetable oil At least one epoxy compound selected from the group consisting of .

(1) Specific examples of the 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.

(2) 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,
Examples thereof include 1,6-hexanediol diglycidyl ether, sorbitol polyglycidyl ether, polyalkylene glycol monoglycidyl ether, and polyalkylene glycol diglycidyl ether.

(3) As the glycidyl ester type epoxy compound, specifically, phenyl glycidyl ester,
Examples thereof include an alkyl glycidyl ester and an alkenyl glycidyl ester, and preferred examples include glycidyl-2,2-dimethyloctanoate, glycidyl benzoate, glycidyl acrylate, and glycidyl methacrylate.

(4) Specific examples of the allyloxirane compound include 1,2-epoxystyrene, alkyl-1,
Examples thereof include 2-epoxystyrene.

(5) As the alkyloxirane compound,
Specifically, 1,2-epoxybutane, 1,2-epoxypentane, 1,2-epoxyhexane, 1,2-epoxyheptane, 1,2-epoxyoctane, 1,2-epoxynonane, 1,2 -Epoxydecane, 1,2-epoxyundecane, 1,2-epoxidedodecane, 1,2-
Epoxy tridecane, 1,2-epoxytetradecane,
1,2-epoxypentadecane, 1,2-epoxyhexadecane, 1,2-epoxyheptadecane, 1,1,2
-Epoxy octadecane, 2-epoxynonadecane,
Examples thereof include 1,2-epoxyicosane.

(6) Specific examples of the alicyclic epoxy compound include 1,2-epoxycyclohexane, 1,2-epoxycyclopentane, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate. , 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) -1,2-epoxy-2-methylcyclohexane,
4-epoxyethyl-1,2-epoxycyclohexane and the like can be exemplified.

(7) Examples of the epoxidized fatty acid monoester include epoxidized fatty acids having 12 to 20 carbon atoms and alcohols or phenols having 1 to 8 carbon atoms,
Examples thereof include esters with alkylphenol. Particularly, butyl, hexyl, benzyl, cyclohexyl, methoxyethyl, octyl, phenyl and butylphenyl esters of epoxystearic acid are preferably used.

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

Preferred among these epoxy compounds are phenylglycidyl ether type epoxy compounds, glycidyl ester type epoxy compounds, alicyclic epoxy compounds and epoxidized fatty acid monoesters. Among them, a phenyl glycidyl ether type epoxy compound and a glycidyl ester type epoxy compound are more preferable, and phenyl glycidyl ether, butyl phenyl glycidyl ether, alkyl glycidyl ester and a mixture thereof are particularly preferable.

When these epoxy compounds are blended with the lubricating oil of the present invention, the amount of the compound is not particularly limited, but the content is usually based on the total amount of the lubricating oil (based on the total amount of the base oil and all the additives). Of the epoxy compound is desirably 0.1 to 5.0% 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.

In order to further enhance the performance of the lubricating oil of the present invention, if necessary, a conventionally known refrigerating machine oil additive such as di-tert-butyl-p-
Phenolic antioxidants such as cresol and bisphenol A; amine antioxidants such as phenyl-α-naphthylamine and N, N-di (2-naphthyl) -p-phenylenediamine; and wear prevention such as zinc dithiophosphate. Agent,
Chlorinated paraffins, extreme pressure agents such as sulfur compounds, oil agents such as fatty acids, silicone-based defoamers, metal deactivators such as benzotriazole, viscosity index improvers, pour point depressants,
Additives such as detergents and dispersants may be used alone or in combination of several types. The total 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 lubricating oil (based on the total amount of the base oil and all the additives).

The kinematic viscosity of the lubricating oil of the present invention is not particularly limited, but the kinematic viscosity at 40 ° C. is preferably 3 to 100 m
m ² / s, more preferably 4~50mm ² / s, and most preferably, to 5 to 40 mm ² / s. Also,
The kinematic viscosity at 100 ° C. is preferably 1 to ²⁰ mm ² /
s, more preferably ² to 10 mm ² / s.

The volume resistivity of the lubricating oil of the present invention is not particularly limited, but is preferably 1.0 × 10 ¹² Ω · cm or more, more preferably 1.0 × 10 ¹³ Ω · cm or more, and most preferably. It can be 1.0 × 10 ¹⁴ Ω · cm or more. In particular, when used for hermetic refrigerators, high electrical insulation tends to be required. In the present invention, the volume resistivity represents a value at 25 ° C. measured according to JIS C 2101 “Testing method for electric insulating oil”.

The water content of the lubricating oil of the present invention is not particularly limited, but can be preferably 200 ppm or less, more preferably 100 ppm or less, most preferably 50 ppm or less based on the total amount of the lubricating oil. In particular, when used for hermetic refrigerators, the water content is required to be low from the viewpoint of the effect on oil stability and electrical insulation.

Further, the total acid value of the lubricating oil of the present invention is not particularly limited. However, when the ester is used as an oxygen-containing oil to prevent corrosion of metals used in refrigerators or pipes, In order to prevent the decomposition of, preferably 0.1 mgKOH / g or less, more preferably 0.0 mgKOH / g
It can be 5 mgKOH / g or less. In addition, in this invention, the total acid value represents the value of the total acid value measured based on JISK2501 "Petroleum products and lubricating oils-neutralization number test method".

The ash content of the lubricating oil of the present invention is not particularly limited, but is preferably 100 ppm or less, more preferably 50 ppm or less, in order to enhance the stability of the lubricating oil of the present invention and suppress the generation of sludge. Can be. In the present invention, ash is defined by JIS K2272.
Shows the value of ash measured according to "Test method for ash content and sulfated ash content of crude oil and petroleum products".

The refrigerant used in the refrigerator using the lubricating oil of the present invention is dimethyl ether (DME).
Or a mixture with other refrigerants. Other refrigerants include hydrofluorocarbons, hydrocarbons, carbon dioxide, ammonia and the like.

As the hydrofluorocarbon refrigerant,
Hydrofluorocarbons having 1 to 3 carbon atoms, preferably 1 to 2 carbon atoms, are mentioned. Specifically, for example, difluoromethane (HFC-32), trifluoromethane (HFC-32)
23), pentafluoroethane (HFC-125),
1,1,2,2-tetrafluoroethane (HFC-13
4), 1,1,1,2-tetrafluoroethane (HFC
-134a), 1,1,1-trifluoroethane (HF
C-143a), 1,1-difluoroethane (HFC-
152a) or a mixture of two or more thereof. These refrigerants are appropriately selected depending on the application and required performance, for example, HFC-32 alone;
HFC-23 alone; HFC-134a alone; HFC-1
25 alone; HFC-134a / HFC-32 = 60 to 8
0% by mass / 40 to 20% by mass of a mixture; HFC-32 /
HFC-125 = 40 to 70% by mass / 60 to 30% by mass
HFC-125 / HFC-143a = 40 to
60% by mass / 60 to 40% by mass of a mixture; HFC-13
4a / HFC-32 / HFC-125 = 60% by mass / 3
0% by mass / 10% by mass mixture; HFC-134a / H
FC-32 / HFC-125 = 40 to 70% by mass / 15
-35% by weight / 5-40% by weight mixture; HFC-12
5 / HFC-134a / HFC-143a = 35-55
A preferable example is a mixture of mass% / 1 to 15 mass% / 40 to 60 mass%. More specifically,
HFC-134a / HFC-32 = 70/30% by weight mixture; HFC-32 / HFC-125 = 60/40% by weight mixture; HFC-32 / HFC-125 = 50 /
50% by weight mixture (R410A); HFC-32 / H
FC-125 = 45/55% by weight mixture (R410
B); HFC-125 / HFC-143a = 50/50
% By weight mixture (R507C); HFC-32 / HFC
-125 / HFC-134a = 30/10/60% by mass
HFC-32 / HFC-125 / HFC-1
34a = 23/25/52% by mass of a mixture (R407
C); HFC-32 / HFC-125 / HFC-134
a = 25/15/60% by weight mixture (R407E);
HFC-125 / HFC-134a / HFC-143a
= 44/4/52% by mass (R404A).

Further, as the hydrocarbon refrigerant, 25 ° C., 1
A gas at atmospheric pressure is preferably used. Specifically, it is an alkane, cycloalkane, alkene or a mixture thereof having 1 to 5, preferably 1 to 4 carbon atoms. Specific examples include methane, ethylene, ethane, propylene, propane, cyclopropane, butane, isobutane, cyclobutane, methylcyclopropane, and a mixture of two or more of these. Among these, propane, butane, isobutane or a mixture thereof is preferred.

The lubricating oil of the present invention is usually present in the refrigerator in the form of a fluid composition for a refrigerator as described above alone or mixed with DME and other refrigerants. The mixing ratio of the lubricating oil and the refrigerant in this composition is not particularly limited, but the lubricating oil is preferably 1 to 500 parts by weight, more preferably 2 to 100 parts by weight of the refrigerant.
400 parts by weight.

The lubricating oil of the present invention is preferably used for an air conditioner or a refrigerator having a reciprocating or rotary hermetic compressor. The lubricating oil of the present invention is preferably used for air conditioners for automobiles, dehumidifiers, freezers, freezing and refrigerated warehouses, vending machines, showcases, cooling devices for chemical plants, and the like. Further, the lubricating oil of the present invention is preferably used for those having a centrifugal compressor.

[0109]

EXAMPLES Hereinafter, the content of the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

Examples 1 to 15 The polyols (base oils) and additives shown in Table 1 were blended as shown in Tables 2 to 4 to prepare sample oils of Examples 1 to 15. Properties of each obtained sample oil (40 ° C and 10 ° C)
(Kinematic viscosity at 0 ° C., total acid value) are shown in Tables 2 to 4.

[0111]

[Table 1] Next, the following tests were performed on each of the above sample oils.

(Compatibility test with refrigerant) JIS-K-22
11 According to the “refrigerant oil” “Test method for compatibility with refrigerant”, 27 g of each sample oil is blended with 3 g of DME refrigerant, and whether the refrigerant and the sample oil are mutually dissolved at 0 ° C. It was observed whether it had separated or clouded. Tables 2 to 4 show the obtained results.

(Insulation Characteristics Test) JIS-C-2101
The volume resistivity of each sample oil at 25 ° C. was measured according to “Electrical Insulating Oil Test Method”. Table 2 shows the obtained results.
It is shown in FIG.

(Thermal Stability Test) In an autoclave, 90 g of each sample oil, 10 g of DME refrigerant and a catalyst (each wire of iron, copper and aluminum) were sealed, and then heated to 175 ° C. Appearance, appearance of catalyst, volume resistivity of sample oil,
The total acid number of the sample oil was measured. Tables 2 to 4 show the obtained results.

(Lubricity test) ASTM D 2670
In accordance with the “FALEX WEAR TEST”, the running-in operation was performed at 150 lb under the condition of the temperature of the sample oil of 100 ° C.
After one minute under load, the tester was operated under 250 lb load for 2 hours. The wear amount of the test journal (pin) after the test was measured for each sample oil. Tables 2 to 4 show the obtained results.

(Hydrolysis Stability Test) 90 g of a sample oil, 0.1 g of water and 10 g of a DME refrigerant were placed in a 300 ml glass test tube, and copper, iron and aluminum wires were put as a deterioration promoting catalyst, and a stainless steel autoclave was used.
Degradation by heating at 75 ° C. for 168 hours. The total acid value of each sample oil after the test was measured. The obtained results are shown in Tables 2 to 4 together with the total acid value before the test.

[0117]

[Table 2]

[0118]

[Table 3]

[0119]

[Table 4]

As is clear from the results shown in Tables 2 to 4, the sample oils of Examples 1 to 15 which are lubricating oils for refrigerators of the present invention using a polyol ester as an oxygen-containing synthetic oil were mixed with dimethyl ether refrigerant. When used, all the properties of lubricity, refrigerant compatibility, thermal stability, electrical insulation, hydrolysis resistance and kinematic viscosity were excellent in a well-balanced manner.

Examples 16 to 22 The sample oils used in Examples 16 to 22 are as follows. Table 5 shows the properties (kinematic viscosity at 100 ° C.) of these sample oils.

Embodiment 16:

Embedded image [Wherein (PO) _m and (PO) _n each represent a polyoxypropylene group] and a carbonate ester having an average molecular weight of 1,000.

Example 17:

Embedded image [Wherein, (PO) _l- (EO) _m is a random copolymer of a polyoxypropylene group and a polyoxyethylene group, and the weight ratio of the polyoxypropylene group to the polyoxyethylene group is 90: 1.
0; and (PO) _n represents a polyoxypropylene group].

Embodiment 18:

Embedded image [Wherein, (PO) _l- (EO) _m is a random copolymer of a polyoxypropylene group and a polyoxyethylene group, and the weight ratio of the polyoxypropylene group to the polyoxyethylene group is 90: 1.
0; and (PO) _n represents a polyoxypropylene group].

Example 19:

Embedded image [Wherein, (PO) _l- (EO) _m is a random copolymer of a polyoxypropylene group and a polyoxyethylene group, and the weight ratio of the polyoxypropylene group to the polyoxyethylene group is 90: 1.
0; and (PO) _n represents a polyoxypropylene group].

Example 20:

Embedded image [Wherein (PO) _m and (PO) _n each represent a polyoxypropylene group], a carbonate ester having an average molecular weight of 1,000.

Example 21:

Embedded image [Wherein, (PO) _l- (EO) _m is a random copolymer of a polyoxypropylene group and a polyoxyethylene group, and the weight ratio of the polyoxypropylene group to the polyoxyethylene group is 90: 1.
0; and (PO) _n represents a polyoxypropylene group].

Embodiment 22:

Embedded image [Wherein, (PO) _l- (EO) _m is a random copolymer of a polyoxypropylene group and a polyoxyethylene group, and the weight ratio of the polyoxypropylene group to the polyoxyethylene group is 90: 1.
0; and (PO) _n represents a polyoxypropylene group].

Next, the following tests were performed on the above sample oils.

(Compatibility test with refrigerant) JIS-K-22
11 In accordance with “Method of testing compatibility with refrigerant” of “Refrigeration oil”, 0.5 g of each sample oil was blended with 4.5 g of DME refrigerant, and the refrigerant and the sample oil were mutually dissolved at 0 ° C. And whether it was separated or cloudy. Table 5 shows the obtained results.

(Insulation Characteristics Test) JIS-C-2101
The volume resistivity of each sample oil at 25 ° C. was measured according to “Electrical Insulating Oil Test Method”. Table 5 shows the obtained results.

(Thermal Stability Test) In an autoclave, 90 g of each sample oil, 10 g of DME refrigerant and a catalyst (each wire of iron, copper and aluminum) were sealed, and then heated to 175 ° C. The appearance, the appearance of the catalyst, the volume resistivity of the sample oil, and the total acid value of the sample oil were measured. Table 5 shows the obtained results.

[0133]

[Table 5] As is clear from the results shown in Table 5, the sample oils of Examples 16 to 22, which are lubricating oils for refrigerators of the present invention using carbonate esters as oxygen-containing synthetic oils, when used with dimethyl ether refrigerant, All the performances of the refrigerant compatibility, thermal stability, electric insulation and kinematic viscosity were excellent in a well-balanced manner.

Examples 23 to 35 Polyoxyalkylene glycols (PAG:
Base oil) or polyvinyl ether (PVE: base oil) and additives were blended as shown in Tables 7 to 9, and Examples 23 to 3 were mixed.
Five sample oils were prepared. Properties of each sample oil obtained (40
Kinematic viscosity at 100 ° C and 100 ° C, total acid number) in Tables 7-9.
Shown in

[0135]

[Table 6] Next, the following tests were performed on each of the above sample oils.

(Compatibility test with refrigerant) JIS-K-22
11 According to the “refrigerant oil” “Test method for compatibility with refrigerant”, 27 g of each sample oil is blended with 3 g of DME refrigerant, and whether the refrigerant and the sample oil are mutually dissolved at 0 ° C. It was observed whether it had separated or clouded. Tables 7 to 9 show the obtained results.

(Insulation Characteristics Test) JIS-C-2101
The volume resistivity of each sample oil at 25 ° C. was measured according to “Electrical Insulating Oil Test Method”. Table 7-
It is shown in FIG.

(Thermal Stability Test) 90 g of each sample oil, 30 g of DME refrigerant and a catalyst (each wire of iron, copper and aluminum) were sealed in an autoclave, heated to 175 ° C. Appearance, appearance of catalyst, volume resistivity of sample oil,
The total acid number of the sample oil was measured. Tables 7 to 9 show the obtained results.

(Lubricity test) ASTM D 2670
In accordance with the “FALEX WEAR TEST”, the running-in operation was performed at 150 lb under the condition of the temperature of the sample oil of 100 ° C.
After one minute under load, the tester was operated under 250 lb load for 2 hours. The wear amount of the test journal (pin) after the test was measured for each sample oil. Tables 7 to 9 show the obtained results.

[0140]

[Table 7]

[0141]

[Table 8]

[0142]

[Table 9]

As is clear from the results shown in Tables 7 to 9, the sample oils of Examples 23 to 35 which are lubricating oils for refrigerators of the present invention using polyoxyalkylene glycol or polyvinyl ether as the oxygen-containing synthetic oil. Is, when used with dimethyl ether refrigerant, lubricity, refrigerant compatibility,
All the properties of thermal stability, electrical insulation and kinematic viscosity were excellent in a well-balanced manner.

[0144]

As described above, according to the lubricating oil for refrigerators of the present invention, when used with a dimethyl ether refrigerant, the lubricating oil, the compatibility with the refrigerant, and the required performance such as the stability are high. Performance can be achieved.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Satoshi Suda 8 Chidori-cho, Naka-ku, Yokohama-shi, Kanagawa Prefecture Nippon Petroleum Oil Co., Ltd. F-term (reference) 4H104 BB32A BB33A BB34A BB36A BB37A BB45A BB46A BC09A CB02A CB14A LA04 LA20 PA20

Claims (1)

[Claims] A lubricating oil for a refrigerator using dimethyl ether as a refrigerant, characterized by containing an oxygen-containing synthetic oil.