JP2007254607A - Refrigerator oil composition for carbon dioxide refrigerants - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerating machine oil composition that is highly stable when used with a carbon dioxide refrigerant and exhibits enough lubricity without increasing viscosity of a base oil. <P>SOLUTION: The refrigerating machine oil for a carbon dioxide refrigerant comprises a specific base oil and thiophosphoric acid ester. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a refrigerator oil composition, and more particularly to a refrigerator oil composition useful as a carbon dioxide (carbon dioxide, CO ₂ ) refrigerant.

  Due to the problem of ozone layer destruction in recent years, CFC (chlorofluorocarbon) and HCFC (hydrochlorofluorocarbon), which have been used as refrigerants in conventional refrigeration equipment, are subject to regulation, and HFC (hydrofluorocarbon) is used as a refrigerant instead. It is being done. However, such HFC refrigerants also have problems such as a high global warming potential, and natural refrigerants such as ammonia, propane, isobutane, or carbon dioxide are considered as alternative refrigerants to replace these fluorocarbon refrigerants. Yes. Among these, carbon dioxide is regarded as promising because of its low toxicity and flammability risks, and as its application, an air conditioner (car air conditioner) and a water heater for automobiles are being studied.

However, carbon dioxide has poor compatibility with mineral oil, alkylbenzene, or polyalkylene glycol (PAG) used as a base material for refrigerating machine oil, and a problem of oil return is pointed out. Therefore, as disclosed in, for example, Patent Document 1 below, for carbon dioxide refrigerant, it is excellent in lubricity, refrigerant compatibility, stability, electrical insulation, etc., and aromatic esters, dibasic acid esters and Refrigerating machine oils using ester base oils such as polyol esters (POE) have been proposed.
JP 2000-104084 A

  However, in the case of refrigeration oil using ester base oil, the compatibility with carbon dioxide is good, but the viscosity of the refrigeration oil is greatly reduced due to the dissolution of carbon dioxide, and the viscosity necessary for lubricating refrigeration equipment is sufficiently retained. Can not do it.

  As a method for maintaining the lubricity of the refrigerating machine oil, it is conceivable to maintain the oil film thickness by increasing the viscosity of the base oil. In this method, however, the handling property by using the high viscosity base oil is improved. Decrease and stirring efficiency are problems.

  Further, as a method for preventing wear of the refrigeration equipment, it is conceivable to add a phosphate ester-based additive such as tricresyl phosphate (TCP) to the refrigerator oil. However, the addition of a phosphate ester additive causes a decrease in the stability of the ester refrigerator oil and cannot be a fundamental solution for improving the reliability of the refrigeration equipment.

  The present invention has been made in view of such a situation, and when used together with a carbon dioxide refrigerant, the refrigerating machine oil composition is excellent in stability and exhibits sufficient lubricity without increasing the viscosity of the base oil. The purpose is to provide goods.

As a result of intensive studies to achieve the above object, the present inventors have found that the above-mentioned problems can be solved by incorporating a thiophosphate in a refrigerating machine oil for carbon dioxide refrigerant, and to complete the present invention. It came.
That is, the refrigerating machine oil composition for carbon dioxide refrigerant of the present invention is characterized by containing a predetermined lubricating base oil and a thiophosphate ester.

  In the refrigerating machine oil composition for carbon dioxide refrigerant of the present invention, the lubricating base oil is preferably an ester.

  The refrigerating machine oil composition for carbon dioxide refrigerant of the present invention preferably contains 50 mass% or more of an ester of dipentaerythritol and a fatty acid as the lubricating base oil based on the total amount of the composition.

  In the ester of dipentaerythritol and fatty acid, the proportion of branched fatty acid in the constituent fatty acid is preferably 25 mol% or more.

  In the ester of dipentaerythritol and fatty acid, the total content of 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid in the constituent fatty acids is preferably 75 mol% or more.

  Moreover, it is preferable that the refrigerating machine oil composition for carbon dioxide refrigerant of the present invention further contains an epoxy compound.

  The refrigerating machine oil composition for carbon dioxide refrigerant of the present invention preferably further contains a phosphorus-based additive other than thiophosphate.

  As described above, according to the present invention, when used together with a carbon dioxide refrigerant, it is possible to provide a refrigerating machine oil composition that is excellent in stability and exhibits sufficient lubricity without increasing the viscosity of the base oil. It becomes.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

  As the lubricating base oil used in the present invention, an oxygen-containing synthetic oil or a mixed base oil containing an oxygen-containing synthetic oil as a main component and a hydrocarbon oil as an auxiliary component is preferably used. Examples of the oxygen-containing synthetic oil include esters, polyoxyalkylene glycols, polyvinyl ethers, ketones, and polyphenyl ethers. Among these, esters are preferable. Examples of the hydrocarbon oil include alkylbenzene, olefin polymer and naphthalene compound, alkylbenzene, mineral oil and the like.

  Examples of the ester preferably used in the present invention include polyol ester, carbonate ester, aromatic ester, dibasic acid ester, complex ester, and a mixture thereof.

  As the polyol ester, an ester of a polyol having 3 to 20 diols or hydroxyl groups and a fatty acid having 6 to 20 carbon atoms is preferably used.

  Here, as the diol, specifically, 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 1,3-propanediol, 2,2-diethyl-1,3-propanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12 -Dodecanediol etc. are mentioned.

  Specific examples of the polyol include trimethylolethane, trimethylolpropane, trimethylolbutane, di- (trimethylolpropane), tri- (trimethylolpropane), pentaerythritol, di- (pentaerythritol), tri -(Pentaerythritol), glycerin, polyglycerin (2 to 20 mer of glycerin), 1,3,5-pentanetriol, sorbitol, sorbitan, sorbitol glycerin condensate, polyhydric alcohol such as adonitol, arabitol, xylitol, mannitol , Xylose, arabinose, ribose, rhamnose, glucose, fructose, galactose, mannose, sorbose, cellobiose, maltose, itmaltose, trehalose, sucrose, rafino , Gentianose, sugars and their partial etherification such as melezitose, and methyl glucoside (glycoside) and the like. Among these, as the polyol, neopentyl glycol, trimethylol ethane, trimethylol propane, trimethylol butane, di- (trimethylol propane), tri- (trimethylol propane), pentaerythritol, di- (pentaerythritol), tri Hindered alcohols such as-(pentaerythritol) are preferred.

  Moreover, the carbon number of the fatty acid constituting the polyol ester is not particularly limited, but usually a fatty acid having 1 to 24 carbon atoms is used. Among the fatty acids having 1 to 24 carbon atoms, fatty acids having 3 or more carbon atoms are preferable from the viewpoint of lubricity, fatty acids having 4 or more carbon atoms are more preferable, fatty acids having 5 or more carbon atoms are more preferable, and fatty acids having 10 or more carbon atoms. Is particularly preferred. From the viewpoint of compatibility with the refrigerant, fatty acids having 18 or less carbon atoms are preferable, fatty acids having 12 or less carbon atoms are more preferable, and fatty acids having 9 or less carbon atoms are more preferable.

  The fatty acid constituting the polyol ester may be either a linear fatty acid or a branched fatty acid, but is preferably a linear fatty acid from the viewpoint of lubricity, and branched from the viewpoint of hydrolytic stability. A fatty acid is preferred. Furthermore, the fatty acid may be either a fatty acid or an unsaturated fatty acid.

  Specific examples of fatty acids constituting the polyol include pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, Heptadecanoic acid, octadecanoic acid, nonadecanoic acid, icosanoic acid, oleic acid, etc. may be mentioned. These fatty acids may be either linear fatty acids or branched fatty acids, and the α carbon atom is a quaternary carbon. It may be a fatty acid (neoacid) that is an atom. 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 (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 is preferably used.

  In addition, as long as it has two or more ester groups, the polyol ester according to the present invention may be a partial ester in which some of the hydroxyl groups of the polyol remain without being esterified. May be an esterified complete ester, or a mixture of a partial ester and a complete ester, but is preferably a complete ester.

As a matter of course, when a polyol ester is used, a compound having a single structure may be used alone, or two or more compounds having different structures may be used in combination.

Further, the carbonate ester is a compound having a carbonate ester bond represented by the following formula (1) in the molecule. The number of carbonate ester bonds represented by the above formula (1) may be one per molecule or two or more.
-O-CO-O- (1)

  As alcohol which comprises carbonate ester, what added polyglycol to monohydric alcohol, polyol, polyglycol, and polyol can be used. Moreover, you may use the compound obtained from a carbonic acid and a fatty acid and / or a dibasic acid.

  As a matter of course, when a carbonate is used, a compound having a single structure may be used alone, or two or more compounds having different structures may be used in combination.

  Moreover, as aromatic ester, it is 1-6 valent, Preferably it is 1-4 valent, More preferably, it is 1-3 valent aromatic carboxylic acid, C1-C18, Preferably it is 1-12 aliphatic alcohol. 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. In addition, the aliphatic alcohol having 1 to 18 carbon atoms may be linear or branched, and specifically includes methanol, ethanol, linear or branched propanol, Linear or branched butanol, linear or branched pentanol, linear or branched hexanol, linear or branched heptanol, linear 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 or minute Jo octadecanol and mixtures thereof.

  Specific examples of the aromatic ester obtained by using the above aromatic carboxylic acid and aliphatic alcohol include dibutyl phthalate, di (2-ethylhexyl) phthalate, dinonyl phthalate, didecyl phthalate, and phthalic acid. Examples include didodecyl, ditridecyl phthalate, tributyl trimellitic acid, tri (2-ethylhexyl) trimellitic acid, trinonyl trimellitic acid, tridecyl trimellitic acid, tridodecyl trimellitic acid, and tritridecyl trimellitic acid. Of course, when a divalent or higher valent 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 alcohol. May be.

  Of course, when an aromatic ester is used, a compound having a single structure may be used alone, or two or more compounds having different structures may be used in combination.

  Dibasic acid esters include glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,2-cyclohexanedicarboxylic acid, and 4-cyclohexene-1,2-dicarboxylic acid. C5-C10 linear or cyclic aliphatic dibasic acids such as acids, methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetra A straight chain or branched ester such as decanol or pentadecanol with a monohydric alcohol having 1 to 15 carbon atoms and a mixture thereof are preferably used. More specifically, ditridecyl glutarate, di-2-ethylhexyl is used. Adipate, diisodecyl adipate, ditridecyl adip Di-ethylhexyl sebacate, diester of 1,2-cyclohexanedicarboxylic acid and monohydric alcohol having 4 to 9 carbon atoms, 4-cyclohexene-1,2-dicarboxylic acid and 1 of carbon atoms of 4 to 9 Examples thereof include diesters with a monohydric alcohol and mixtures thereof.

  As a matter of course, when a dibasic acid ester is used, a compound having a single structure may be used alone, or two or more compounds having different structures may be used in combination.

  Among the above esters, polyol ester, carbonic acid ester and dibasic acid ester are preferable because of excellent compatibility with the refrigerant, and polyol ester is more preferable from the viewpoint of obtaining appropriate compatibility.

  Furthermore, among the polyol esters, since it is more excellent in hydrolysis stability, neopentyl glycol, trimethylol ethane, trimethylol propane, trimethylol butane, di- (trimethylol propane), tri- (trimethylol propane), More preferred are esters of hindered alcohols such as pentaerythritol, di- (pentaerythritol), tri- (pentaerythritol), and more preferred are esters of neopentyl glycol, trimethylol ethane, trimethylol propane, trimethylol butane and pentaerythritol. Of these, esters of di- (pentaerythritol) are most preferred because they are particularly excellent in moderate compatibility with the refrigerant and hydrolytic stability.

  Specific examples of the polyol ester preferably used in the present invention include valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, oleic acid, isopentanoic acid, 2-methylhexanoic acid, 2-ethylpentanoic acid, At least one fatty acid selected from the group consisting of 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid, neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, pentaerythritol, and di And diesters, triesters, tetraesters and mixtures thereof obtained from at least one alcohol selected from the group consisting of pentaerythritol.

  Further, among these, at least one selected from the group consisting of caprylic acid (n-octanoic acid), pelargonic acid (n-nonanoic acid), 2-ethylhexanoic acid, and 3,5,5-trimethylhexanoic acid. And an ester of di- (pentaerythritol) is more preferably used.

More specifically, an ester of di- (pentaerythritol) and any one of the following acids (A1) to (A4) is exemplified. In addition, the mixing ratio of the fatty acids in (A1) to (A4) is a molar ratio.
(A1) Mixed acid of 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid (mixing ratio: 2-ethylhexanoic acid / 3,5,5-trimethylhexanoic acid = 1/1)
(A2) Mixed acid of caprylic acid (n-octanoic acid), 2-ethylhexanoic acid, pelargonic acid (n-nonanoic acid) and 3,5,5-trimethylhexanoic acid (mixing ratio: caprylic acid / 2- Ethylhexanoic acid / pelargonic acid / 3,5,5-trimethylhexanoic acid = 1/4/4) mixture (A3) caprylic acid (n-octanoic acid) and 3,5,5-trimethylhexanoic acid Mixed acid (mixing ratio: caprylic acid / 3,5,5-trimethylhexanoic acid = 1/4)
(A4) Mixed acid of pelargonic acid (n-nonanoic acid) and 3,5,5-trimethylhexanoic acid (mixing ratio: pelargonic acid / 3,5,5-trimethylhexanoic acid = 1/4).

  Such an ester preferably has a large molecular weight from the viewpoint of lubricity in a state where the refrigerant is dissolved, and preferably has a small molecular weight from the viewpoint of compatibility with the refrigerant. The fatty acid constituting the ester is preferably a linear fatty acid from the viewpoint of lubricity, while a branched fatty acid is preferable from the viewpoint of hydrolysis stability and refrigerant solubility.

  Accordingly, the refrigerating machine oil composition preferably contains 50 mass% or more, more preferably 80 mass% or more of an ester of di- (pentaerythritol) and a fatty acid based on the total amount of the composition. Further, in the ester of di- (pentaerythritol) and a fatty acid, the proportion of the branched fatty acid in the constituent fatty acid is preferably 25 mol% or more, and more preferably 50 mol% or more.

  Furthermore, in the ester of di- (pentaerythritol) and a fatty acid, the total content of 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid in the constituent fatty acids is preferably 75 mol% or more. More preferably, it is 90 mol% or more.

  In the polyol ester used in the present invention, since the low-temperature characteristics of the refrigerating machine oil composition and the compatibility with the refrigerant tend to be improved, it is preferable that the fatty acid constituting the polyol ester is two or more. The polyol ester composed of two or more fatty acids includes a mixture of two or more esters of polyol and one fatty acid, and an ester of a polyol and two or more mixed fatty acids. .

Moreover, as polyoxyalkylene glycol used by this invention, the compound represented, for example by following General formula (2) is mentioned.
R ^l - ^[(OR ₂₎ a -OR ^3] _b (2)
Wherein (2), ^{R l} represents the residue of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, compounds having 2 to 8 an acyl group or a hydroxyl group having 2 to 10 carbon atoms, ^{R 2} is the number of carbon atoms 2 to 4 alkylene group, R ³ represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms or an acyl group having 2 to 10 carbon atoms, a represents an integer of 1 to 80, and b represents 1 to 8 Represents an integer. ]

  Among the polyoxyalkylene glycols represented by the general formula (2), from the viewpoint of refrigerant compatibility and viscosity-temperature characteristics, a copolymer containing an oxyethylene group (EO) and an oxypropylene group (PO) is used. Preferably, in such a case, the ratio of the oxyethylene group to the total of the oxyethylene group and the oxypropylene group (EO / (PO + EO)) is 0.1 to 0.8 from the standpoint of baking load and viscosity-temperature characteristics. It is preferable that it exists in the range, and it is more preferable that it exists in the range of 0.3-0.6.

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

  Moreover, although it does not restrict | limit especially about the product (axb) of a and b, in order to satisfy | fill the required performance as above-mentioned lubricating oil for refrigerators with sufficient balance, the average value of axb is 6-80. It is preferable to do so.

［式（３）中、Ｒ^４〜Ｒ^６は同一でも異なっていてもよく、それぞれ水素原子または炭素数１〜８の炭化水素基を表し、Ｒ^７は炭素数１〜１０の２価の炭化水素基または炭素数２〜２０の２価のエーテル結合酸素含有炭化水素基を表し、Ｒ^８は炭素数１〜２０の炭化水素基を表し、ｃはその平均値が０〜１０の数を表し、Ｒ^４〜Ｒ^８は構成単位毎に同一であってもそれぞれ異なっていてもよく、また一般式（３）で表される構成単位が複数のＲ^７Ｏを有するとき、複数のＲ^７Ｏは同一でも異なっていてもよい。］ Moreover, as a polyvinyl ether used by this invention, the polyvinyl ether type compound which has a structural unit represented, for example by following General formula (3) is mentioned.

[In Formula (3), R ^{4 to} R ⁶ may be the same or different and each represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms; R ⁷ is a divalent carbon atom having 1 to 10 carbon atoms; Represents a hydrogen group or a divalent ether-bonded oxygen-containing hydrocarbon group having 2 to 20 carbon atoms, R ⁸ represents a hydrocarbon group having 1 to 20 carbon atoms, and c represents a number having an average value of 0 to 10. , R ^{4 to} R ⁸ may be the same or different for each structural unit, and when the structural unit represented by the general formula (3) has a plurality of R ⁷ O, a plurality of R ⁷ Os. May be the same or different. ]

  Moreover, the polyvinyl ether type compound which consists of a block copolymer or a random copolymer which has a structural unit represented by the said General formula (3) and a structural unit represented by the following General formula (4) is also used. Can do.

［式（４）中、Ｒ^９〜Ｒ^１２は同一でも異なっていてもよく、それぞれ水素原子または炭素数１〜２０の炭化水素基を表し、Ｒ^９〜Ｒ^１２は構成単位毎に同一でも異なっていてもよい。］

[In Formula (4), R ^{9 to} R ¹² may be the same or different and each represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, and R ^{9 to} R ¹² are the same or different for each structural unit. It may be. ]

As the polyvinyl ether used in the present invention, one of its ends is represented by the following general formula (5) or (6), and the other is represented by the following general formula (7) or (8). One having one of the ends represented by the general formula (5) or (6) and the other having the structure represented by the following general formula (9) preferable.

［式（５）中、Ｒ^１３〜Ｒ^１５は同一でも異なっていてもよく、それぞれ水素原子または炭素数１〜８の炭化水素基を表し、Ｒ^１６は炭素数１〜１０の２価の炭化水素基または炭素数２〜２０の２価のエーテル結合酸素含有炭化水素基を表し、Ｒ^１７は炭素数１〜２０の炭化水素基を表し、ｄはその平均値が０〜１０の数を表し、上記一般式（５）で表される末端構造が複数のＲ^１６０を有するとき、複数のＲ^１６０はそれぞれ同一でも異なっていてもよい。］

[In the formula (5), R ^{13 to} R ¹⁵ may be the same or different and each represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, and R ¹⁶ is a divalent carbon atom having 1 to 10 carbon atoms. Represents a hydrogen group or a divalent ether-bonded oxygen-containing hydrocarbon group having 2 to 20 carbon atoms, R ¹⁷ represents a hydrocarbon group having 1 to 20 carbon atoms, and d represents a number having an average value of 0 to 10. When the terminal structure represented by the general formula (5) has a plurality of R ¹⁶ 0, the plurality of R ¹⁶ 0 may be the same or different from each other. ]

［式（６）中、Ｒ^１８〜Ｒ^１９は同一でも異なっていてもよく、それぞれ水素原子または炭素数１〜２０の炭化水素基を表す。］

[In formula (6), R ^{18 to} R ¹⁹ may be the same or different and each represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. ]

［式（７）中、Ｒ^２２〜Ｒ^２４は同一でも異なっていてもよく、それぞれ水素原子または炭素数１〜８の炭化水素基を表し、Ｒ^２５は炭素数１〜１０の２価の炭化水素基または炭素数２〜２０の２価のエーテル結合酸素含有炭化水素基を表し、Ｒ^２６は炭素数１〜２０の炭化水素基を表し、ｅはその平均値が０〜１０の数を表し、上記一般式（７）で表される末端構造が複数のＲ^２５０を有するとき、複数のＲ^２５０はそれぞれ同一でも異なっていてもよい。］

[In the formula (7), R ^{22 to} R ²⁴ may be the same or different and each represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms; R ²⁵ is a divalent carbon atom having 1 to 10 carbon atoms; Represents a hydrogen group or a divalent ether-bonded oxygen-containing hydrocarbon group having 2 to 20 carbon atoms, R ²⁶ represents a hydrocarbon group having 1 to 20 carbon atoms, and e represents a number having an average value of 0 to 10. When the terminal structure represented by the general formula (7) has a plurality of R ²⁵ 0s, the plurality of R ²⁵ 0s may be the same or different. ]

［式（８）中、Ｒ^２７〜Ｒ^３０は同一でも異なっていてもよく、それぞれ水素原子または炭素数１〜２０の炭化水素基を表す。］

[In Formula (8), R < ²⁷ > -R < ³⁰ > may be same or different and represents a hydrogen atom or a C1-C20 hydrocarbon group, respectively. ]

［式（９）中、Ｒ^３１〜Ｒ^３２は同一でも異なっていてもよく、それぞれ水素原子または炭素数１〜８の炭化水素基を表す。］

[In formula (9), R ^{31 to} R ³² may be the same or different and each represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. ]

Among such polyvinyl ethers, the following are particularly suitable.
(1) One of the terminals has a structure represented by the general formula (5) or (6), and the other has the structure represented by the general formula (7) or (8), and R ⁴ in the general formula (3) to R ⁶ are both hydrogen, c is a number from 0 to 4, ^{R 7} is a divalent hydrocarbon group having 2 to 4 carbon atoms, and hydrocarbon ^{R 8} is 1 to 20 carbon atoms Being a hydrogen group;
(2) It has only the structural unit represented by the general formula (3), and one end thereof is represented by the general formula (5) and the other has a structure represented by the general formula (6). R ^{4 to} R ⁶ in the general formula (3) are all hydrogen atoms, c is a number from 0 to 4, and R ⁷ is a divalent hydrocarbon group having 2 to 4 carbon atoms. And R ⁸ is a hydrocarbon group having 1 to 20 carbon atoms;
(3) One of the terminals has a structure represented by the general formula (5) or (6) and the other is represented by the general formula (7), and R ^{4 to} R ⁶ in the general formula (3) are All are hydrogen atoms, c is a number from 0 to 4, R ⁷ is a divalent hydrocarbon group having 2 to 4 carbon atoms, and R ⁸ is a hydrocarbon group having 1 to 20 carbon atoms. thing;
(4) It has only the structural unit represented by the general formula (3), and one end thereof is represented by the general formula (5) and the other has a structure represented by the general formula (8). R ^{4 to} R ⁶ in the general formula (3) are all hydrogen atoms, c is a number from 0 to 4, and R ⁷ is a divalent hydrocarbon group having 2 to 4 carbon atoms. And R ⁸ is a hydrocarbon group having 1 to 20 carbon atoms.

  Moreover, in this invention, it has a structural unit represented by the said General formula (3), One of the terminal is represented by General formula (5), and the other is represented by following General formula (10). Polyvinyl ether compounds having a structure can also be used.

［式（１０）中、Ｒ^３４〜Ｒ^３６は同一でも異なっていてもよく、それぞれ水素原子または炭素数１〜８の炭化水素基を表し、Ｒ^３７およびＲ^３９は同一でも異なっていてもよく、それぞれ炭素数２〜１０の２価の炭化水素基を表し、Ｒ^３８およびＲ^４０は同一でも異なっていてもよく、それぞれ炭素数１〜１０の炭化水素基を表し、ｆおよびｇは同一でも異なっていてもよく、それぞれその平均値が０〜１０の数を表し、上記一般式（１０）で表される末端構造が複数のＲ^３７０またはＲ^３９０を有するとき、複数のＲ^３７０またはＲ^３９０は同一であっても異なっていてもよい］

[In the formula (10), R ^{34 to} R ³⁶ may be the same or different, each represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, and R ³⁷ and R ³⁹ may be the same or different. Each represents a divalent hydrocarbon group having 2 to 10 carbon atoms, R ³⁸ and R ⁴⁰ may be the same or different, each represents a hydrocarbon group having 1 to 10 carbon atoms, and f and g may be the same. They may be different, each having an average value of 0 to 10, and when the terminal structure represented by the general formula (10) has a plurality of R ³⁷ 0 or R ³⁹ 0, a plurality of R ³⁷ 0 Or R ³⁹⁰ may be the same or different.]

  Furthermore, in this invention, it consists of a structural unit represented by the following general formula (11) or (12), and a weight average molecular weight is 300-5,000, and one of the terminal is the following general formula (13). Alternatively, a polyvinyl ether compound composed of a homopolymer or copolymer of an alkyl vinyl ether having a structure represented by (14) can also be used.

［式（１１）中、Ｒ５３は炭素数１〜８の炭化水素基を示す。］

[In the formula (11), R53 represents a hydrocarbon group having 1 to 8 carbon atoms. ]

［式（１２）中、Ｒ^４２は炭素数１〜８の炭化水素基を示す。］

[In the formula (12), R ⁴² represents a hydrocarbon group having 1 to 8 carbon atoms. ]

［式（１３）中、Ｒ^４３は炭素数１〜３のアルキル基を表し、Ｒ^４４は炭素数１〜８の炭化水素基を示す。］

Wherein ^{(13), R 43} represents an alkyl group having 1 to 3 carbon ^{atoms, R 44} represents a hydrocarbon group having 1 to 8 carbon atoms. ]

［式（１４）中、Ｒ^４５は炭素数１〜８の炭化水素基を示す］

[In the formula (14), R ⁴⁵ represents a hydrocarbon group having 1 to 8 carbon atoms]

  In addition, the alkylbenzene used in the present invention is not particularly limited, but has 1 to 4 alkyl groups having 1 to 40 carbon atoms, and the total carbon number of the alkyl groups is 1 from the viewpoint of excellent compatibility with the refrigerant. It is preferable that the number of carbon atoms is 1 to 40, 1 to 4 alkyl groups having 1 to 30 carbon atoms, and the total number of carbon atoms in the alkyl group is 3 to 30.

  Specific examples of the alkyl group having 1 to 40 carbon atoms that the alkylbenzene has include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a linear or branched butyl group, a linear or branched group. Pentyl group, linear or branched hexyl group, linear or branched heptyl group, linear or branched octyl group, linear or branched nonyl group Linear or branched decyl group, linear or branched undecyl group, linear or branched dodecyl group, linear or branched tridecyl group, linear or branched Branched tetradecyl group, linear or branched pentadecyl group, linear or branched hexadecyl group, linear or branched heptadecyl group, linear or branched octadecyl group , Linear or branched nonadecyl group, linear or Branched icosyl group, linear or branched hencosyl group, linear or branched docosyl group, linear or branched tricosyl group, linear or branched tetracosyl group Group, linear or branched pentacosyl group, linear or branched hexacosyl group, linear or branched heptacosyl group, linear or branched octacosyl group, linear Or a branched nonacosyl group, a linear or branched triacontyl group, a linear or branched hentriacontyl group, a linear or branched dotriacontyl group, a linear or branched group Tritriacontyl group, linear or branched tetratriacontyl group, linear or branched pentatriacontyl group, linear or branched hexatriacontyl group, linear Or branched heptatriac Til group, linear or branched octatriacontyl group, linear or branched nonatriacontyl group, linear or branched tetracontyl group (including all isomers), etc. Can be mentioned.

  The alkyl group may be either linear or branched, but is preferably a linear alkyl group from the viewpoint of compatibility with the organic material used in the refrigerant circulation system. On the other hand, branched alkyl groups are preferable from the viewpoint of refrigerant compatibility, thermal stability, lubricity, etc., and branched alkyls derived from oligomers of olefins such as propylene, butene and isobutylene are particularly preferable from the viewpoint of availability. Groups are more preferred.

  In addition, when using alkylbenzene, the compound of a single structure may be used independently, and 2 or more types of the compounds from which a structure differs may be used in combination.

  Although the manufacturing method of the said alkylbenzene is arbitrary and is not limited at all, For example, it can manufacture by the synthesis method shown below.

  Specific examples of the aromatic compound used as a raw material include benzene, toluene, xylene, ethylbenzene, methylethylbenzene, diethylbenzene, and mixtures thereof. Further, as an alkylating agent, a linear or branched olefin having 6 to 40 carbon atoms obtained by polymerization of a lower monoolefin (preferably propylene) such as ethylene, propylene, butene and isobutylene; wax, heavy oil, C6-C40 linear or branched olefins obtained by pyrolysis of petroleum fractions, polyethylene, polypropylene, etc .; n-paraffins are separated from petroleum fractions such as kerosene, light oil, etc. It is possible to use a linear olefin having 9 to 40 carbon atoms, a mixture of these, and the like obtained by converting into a carbon atom.

  In addition, when the aromatic compound and the alkylating agent are reacted, Friedel-Crafts type catalysts such as aluminum chloride and zinc chloride, sulfuric acid, phosphoric acid, silicotungstic acid, hydrofluoric acid, activated clay, etc. Conventionally known alkylation catalysts such as acidic catalysts can be used.

  The mineral oil used in the present invention includes, for example, solvent removal from a lubricating oil fraction obtained by atmospheric distillation and vacuum distillation of paraffinic crude oil, intermediate crude oil, or naphthenic crude oil. , Paraffinic mineral oil or naphthenic oil obtained by applying a suitable combination of one or more purification methods such as solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, sulfuric acid washing, and clay treatment Mineral oil.

  Among these mineral oils, it is preferable to use highly refined mineral oil (hereinafter referred to as “highly refined mineral oil”) from the viewpoint of superior thermal stability. Specific examples of highly refined mineral oil include distillate oil obtained by atmospheric distillation of paraffinic crude oil, intermediate crude oil or naphthenic crude oil, or by distilling the residual oil of atmospheric distillation under reduced pressure according to a conventional method. Refined oil obtained by refining; deep dewaxed oil obtained by further deep dewaxing after refining; hydrotreated oil obtained by hydrotreating, and the like.

  The purification method in the purification step is not particularly limited, and a conventionally known method can be used. For example, (a) hydrogenation treatment, (b) dewaxing treatment (solvent dewaxing or hydrodehydration) (C) Solvent extraction treatment, (d) Alkali washing or sulfuric acid washing treatment, (e) Clay clay treatment alone or in combination of two or more in an appropriate order Can be mentioned. It is also effective to repeat any one of the processes (a) to (e) in a plurality of stages. More specifically, (i) a method of hydrotreating the distillate, or a method of performing an alkali washing or sulfuric acid washing treatment after the hydrogenation treatment; (ii) dehydrating the distillate oil after the hydrogenation treatment; A method of wax treatment; (iii) a method of subjecting the distillate to solvent extraction and then hydrotreating; (iv) subjecting the distillate to a two-stage or three-stage hydrotreatment, or subsequent alkali washing or sulfuric acid (V) A method of dewaxing again to obtain a deep dewaxed oil after the above-described treatments (i) to (iv), and the like.

  Among the highly refined mineral oils obtained by the above refining method, naphthenic mineral oils and mineral oils obtained by deep dewaxing are preferred from the viewpoints of low temperature fluidity and no wax precipitation at low temperatures. This deep dewaxing treatment is usually performed by a solvent dewaxing treatment method under severe conditions, a catalytic dewaxing treatment method using a zeolite catalyst, or the like.

  Further, the non-aromatic unsaturation (unsaturation) of such highly refined mineral oil is preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 1% by mass or less, and particularly preferably 0.1% by mass. % Or less. If the non-aromatic unsaturation exceeds 10% by mass, sludge is likely to be generated, and as a result, the expansion mechanism such as a cavity that constitutes the refrigerant circulation system tends to be easily blocked.

  In the present invention, only one kind selected from the group consisting of the above-described synthetic oil and hydrocarbon oil may be used alone, or two or more kinds may be used in combination. When the refrigeration oil composition for a carbon dioxide refrigerant of the present invention is used in a hermetic compressor such as a refrigerator or an air conditioner using the carbon dioxide refrigerant, an ester, an alkylbenzene, or a polyvinyl ether is preferable. Among them, a polyol ester is preferable because an effect of adding a thiophosphate ester is higher, and an ester of dipentaerythritol and a fatty acid is most preferable. Moreover, when using for open type compressors, such as a car air-conditioner and a water heater, polyol ester, polyoxyalkylene glycol, polyvinyl ether, and ester polyvinyl ether are preferable among the above-mentioned synthetic oils. Among them, a polyol ester is preferable because the effect of adding a thiophosphate ester is higher, and an ester of dipentaerythritol and a fatty acid is most preferable.

Further, as the thiophosphate (also referred to as “phosphorothionate”) contained in the refrigerating machine oil composition for carbon dioxide refrigerant of the present invention, a compound represented by the following general formula (15) is preferably used.

In the general formula (15), R ⁴⁶ , R ⁴⁷ and R ⁴⁸ may be the same or different and each represents a hydrocarbon group having 1 to 24 carbon atoms. Specific examples of the hydrocarbon group having 1 to 24 carbon atoms represented by R ^{46 to} R ⁴⁸ include an alkyl group, a cycloalkyl group, an alkenyl group, an alkylcycloalkyl group, an aryl group, an alkylaryl group, and an arylalkyl group. Etc.

  Examples of the alkyl group include methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, Examples thereof include alkyl groups such as a pentadecyl group, a hexadecyl group, a heptadecyl group, and an octadecyl group (these alkyl groups may be linear or branched).

  As a cycloalkyl group, C5-C7 cycloalkyl groups, such as a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, can be mentioned, for example. Examples of the alkylcycloalkyl group include a methylcyclopentyl group, a dimethylcyclopentyl group, a methylethylcyclopentyl group, a jetylcyclopentyl group, a methylcyclohexyl group, a dimethylcyclohexyl group, a methylethylcyclohexyl group, and a jetylcyclohexyl group. Alkylcycloalkyl groups having 6 to 11 carbon atoms such as methylcycloheptyl group, dimethylcycloheptyl group, methylethylcycloheptyl group, and jetylcycloheptyl group (the substitution position of the alkyl group to the cycloalkyl group is also arbitrary) There is).

  Examples of the alkenyl group include butenyl group, pentenyl group, hexenyl group, heptenyl group, octenyl group, nonenyl group, decenyl group, undecenyl group, dodecenyl group, tridecenyl group, tetradecenyl group, pentadecenyl group, hexadecenyl group, and heptadecenyl group. And alkenyl groups such as octadecenyl group (these alkenyl groups may be linear or branched, and the position of the double bond is arbitrary).

  As an aryl group, aryl groups, such as a phenyl group and a naphthyl group, can be mentioned, for example. Examples of the alkylaryl group include tolyl group, xylyl group, ethylphenyl group, propylphenyl group, butylphenyl group, pentylphenyl group, hexylphenyl group, heptylphenyl group, octylphenyl group, nonylphenyl group, and decyl. C7-C18 alkylaryl groups such as phenyl group, undecylphenyl group, and dodecylphenyl group (the alkyl group may be linear or branched, and the substitution position on the aryl group is arbitrary). It is done.

  Examples of the arylalkyl group include arylalkyl groups having 7 to 12 carbon atoms such as a benzyl group, a phenylethyl group, a phenylpropyl group, a phenylbutyl group, a phenylpentyl group, and a phenylhexyl group. It may be branched).

The hydrocarbon group having 1 to 24 carbon atoms represented by R ⁴⁶ , R ⁴⁷ and R ⁴⁸ is preferably an alkyl group, an aryl group or an alkylaryl group, and an alkyl group having 4 to 18 carbon atoms or 7 carbon atoms. The alkylaryl group of -24 and a phenyl group are more preferable.

  Specific examples of the thiophosphate represented by the general formula (15) include tributyl phosphorothioate, tripentyl phosphorothionate, trihexyl phosphorothionate, triheptyl phosphorothionate, and trioctyl. Phosphorothioate, trinonyl phosphorothionate, tridecyl phosphorothionate, triundecyl phosphorothionate, tridodecyl phosphorothionate, tritridecyl phosphorothionate, tritetradecyl phosphorothionate, tri Pentadecyl phosphorothioate, trihexadecyl phosphorothionate, triheptadecyl phosphorothionate, trioctadecyl phosphorothionate, trioleyl phosphorothionate, triphenyl phosphorothionate, triphenyl Zyl phosphorothioate, trixylenyl phosphorothioate, cresyl diphenyl phosphorothioate, xylenyl diphenyl phosphorothioate, tris (n-propylphenyl) phosphorothioate, tris (isopropylphenyl) phosphoro Thionate, tris (-n-butylphenyl) phosphorothionate, tris (isobutylphenyl) phosphorothionate, tris (s-butylphenyl) phosphorothionate, tris (t-butylphenyl) phosphorothionate, etc. . More specifically, triphenyl phosphorothioate (TPPT), tricresyl phosphorothionate (TCPT), trixylenyl phosphorothionate (TXPT), and cresyl diphenyl phosphorothionate (CPPT) are preferable. Used. More preferably, triphenyl phosphorothioate (TPPT) is used. Mixtures of these can also be used.

  The content of the thiophosphate in the refrigerating machine oil composition for carbon dioxide refrigerant of the present invention is preferably 0.01 to 5% by mass or less based on the total amount of the composition. By setting the content of the thiophosphate within the above range, the wear resistance and stability (particularly thermal / oxidative stability) of the refrigerating machine oil composition can be further improved. More specifically, the content of the thiophosphate is preferably 0.01% by mass or more, more preferably 0.1% by mass, based on the total amount of the composition, from the viewpoint of obtaining a high level of wear resistance. % Or more. Further, even if the content is further increased, the wear reduction effect corresponding to the content cannot be obtained, and on the contrary, the stability can be reduced or the occurrence of corrosion wear can be caused. The total amount is preferably 5% by mass or less, more preferably 3% by mass or less, and still more preferably 1% by mass or less.

  Moreover, the refrigerating machine oil composition for carbon dioxide refrigerant of the present invention may further contain a phosphorus-based additive (hereinafter referred to as “phosphorous-based additive”) other than the thiophosphate. The phosphorus additive is preferably at least one phosphorus compound selected from the group consisting of phosphate esters, acidic phosphate esters, amine salts of acidic phosphate esters, chlorinated phosphate esters, and phosphite esters. These phosphorus compounds are esters of phosphoric acid or phosphorous acid with alkanols and polyether type alcohols or derivatives thereof.

Phosphate esters include 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. ; As the acidic phosphate ester, monobutyl acyl phosphate, Nopentyl 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 tetraphosphate, Decyl acid phosphate, monopentadecyl acid phosphate, monohexadecyl acid phosphate, monoheptadecyl acid phosphate, monooctadecyl acid phosphate, monooleyl acid phosphate, diptyl acid phosphate, dipentyl acid phosphate, dihexyl acid phosphate disulfate Acid phosphate, dioctyl Cyd phosphate, dinonyl acid phosphate, didecyl acid phosphate, diundecyl acid phosphate, didodecyl acid phosphate, ditridecyl acid phosphate, ditetradecyl acid phosphate, dipentadecyl acid phosphate, dihexadecyl acid phosphate, dihepta Decyl acid phosphate, dioctadecyl acid phosphate, dioleyl acid phosphate, etc .; As amine salt of acidic phosphate ester, methyl phosphate, ethyl amine, propyl amine, butyl amine, pentyl amine, hexyl amine, heptyl amine of the above acidic phosphate ester , Octylamine, dimethylamishi, jetylamine, dipropylamine, diptylamine, dipentylamine, dihe Salts with amines such as xylamine, diheptylamine, dioctylamine, trimethylamine∴triethylamine, tripropylamine, triptylamine, tripentylamine, trihexylamine, triheptylamine, trioctylamine, etc .;
Examples of the chlorinated phosphate ester include tris-dichloropropyl phosphate, tris-chloroethyl phosphate, tris-chlorophenyl phosphate, polyoxyalkylene bis [di (chloroalkyl)] phosphate, and the like. Phyto, dipentyl phosphite, dihexyl phosphite, diheptyl phosphite, dioctyl phosphite, dinonyl phosphite, didecyl phosphite, diundecyl phosphite, didodecyl phosphite, dioleyl phosphite, diphenyl phosphite, Dicresyl phosphite, tryptyl phosphite, tripentyl phosphite, trihexyl phosphite, triheptyl phosphite, trioctyl phosphite, trinonyl phosphite, Li decyl phosphite, tri undecyl phosphite, tridodecyl phosphite, trioleyl phosphite, triphenyl phosphite, tricresyl phosphite, and the like. Mixtures of these can also be used.

  When the refrigerating machine oil composition for carbon dioxide refrigerant of the present invention contains a phosphorus additive, the content of the phosphorus additive is preferably 0.01 to 5% by mass or less based on the total amount of the composition. By setting the content of the phosphorus-based additive within the above range, the abrasion resistance and stability (particularly thermal / oxidation stability) can be further improved. More specifically, the addition amount of the phosphorus-based additive is preferably 0.01% by mass or more, more preferably 0.1% by mass or more based on the total amount of the composition from the viewpoint of obtaining a high level of abrasion resistance. It is at least mass%. Further, even if the content is further increased, the effect of reducing wear corresponding to the content cannot be obtained, and on the contrary, it may cause the decrease in stability or the occurrence of corrosion wear. Based on the total amount of the composition, it is preferably 5% by mass or less, more preferably 4% by mass or less, and further preferably 3% by mass or less.

  The refrigerating machine oil composition for carbon dioxide refrigerant of the present invention preferably further contains benzotriazole and / or a derivative thereof. Inclusion of benzotriazole and / or a derivative thereof can further enhance the effect of improving wear resistance and friction characteristics.

  The content of benzotriazole and / or a derivative thereof in the refrigerating machine oil composition for carbon dioxide refrigerant of the present invention is arbitrary, but is preferably 0.001% by mass or more, more preferably 0.005% by mass based on the total amount of the composition. % Or more. When the amount is less than 0.001% by mass, the effect of improving the abrasion resistance and frictional properties due to the inclusion of benzotriazole and / or its derivatives may be insufficient. In addition, the content of benzotriazole and / or its derivative is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, based on the total amount of the composition. If it exceeds 1.0% by mass, the effect of improving the wear resistance and frictional properties corresponding to the content cannot be obtained, which may be economically disadvantageous.

  Moreover, in the refrigeration oil composition for carbon dioxide refrigerant of the present invention, it is preferable to add an epoxy compound in order to further improve the heat / hydrolysis stability and friction characteristics. Preferred examples of the epoxy compound include phenyl glycidyl ether type epoxy compound, alkyl glycidyl ether type epoxy compound, glycidyl ester type epoxy compound, allyl oxirane compound, alkyl oxirane compound, alicyclic epoxy compound, epoxidized fatty acid monoester, epoxidation Vegetable oils.

  Specific examples of the phenyl glycidyl ether type epoxy compound include phenyl glycidyl ether and alkylphenyl glycidyl ether. As used herein, the alkylphenyl glycidyl ether includes those having 1 to 3 alkyl groups having 1 to 13 carbon atoms, and those having one alkyl group having 4 to 10 carbon atoms, such as n-butylphenyl glycidyl. Ether, i-butylphenyl glycidyl ether, sec-butylphenyl glycidyl ether, tert-butylphenyl glycidyl ether, pentylphenyl glycidyl ether, hexylphenyl glycidyl ether, heptylphenyl glycidyl ether, octylphenyl glycidyl ether, nonylphenyl glycidyl ether, Decylphenyl glycidyl ether and the like can be exemplified as preferable examples.

  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, neopentyl glycol Examples include diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, 1,6-hexanediol diglycidyl ether, sorbitol polyglycidyl ether, polyalkylene glycol monoglycidyl ether, polyalkylene glycol diglycidyl ether and the like.

  Among the glycidyl ester type epoxy compounds, preferred examples include glycidyl-2,2-dimethyloctanoate, glycidyl benzoate, glycidyl-tert-butylbenzoate, glycidyl acrylate, glycidyl methacrylate, and the like. .

  Specific examples of the allyloxirane compound include 1,2-epoxystyrene and alkyl-1,2-epoxystyrene.

  Specific examples of the alkyl oxirane compound include 1,2-epoxybutane, 1,2-epoxypentane, 1,2-epoxyhexane, 1,2-epoxyheptane, 1,2-epoxyoctane, 1,2- Epoxy nonane, 1,2-epoxydecane, 1,2-epoxyundecane, 1,2-epoxydodecane, 1,2-epoxytridecane, 1,2-epoxytetradecane, 1,2-epoxypentadecane, 1,2- Examples include epoxy hexadecane, 1,2-epoxy heptadecane, 1,1,2-epoxy octadecane, 2-epoxy nonadecane, 1,2-epoxy icosane and the like.

  Examples of the alicyclic epoxy compound include compounds in which the carbon atom constituting the epoxy group directly constitutes the alicyclic ring. Specifically, 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 etc. can be illustrated.

  Specific examples of the epoxidized fatty acid monoester include esters of an epoxidized fatty acid having 12 to 20 carbon atoms with an alcohol or phenol having 1 to 8 carbon atoms or an alkylphenol. In particular, butyl, hexyl, benzyl, cyclohexyl, methoxyethyl, octyl, phenyl and butylphenyl esters of epoxy stearate are preferably used.

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

  As an epoxy compound, one of the above may be used alone, or two or more may be used in combination. In the present invention, phenyl glycidyl ether type epoxy compound, glycidyl ester type epoxy compound, alicyclic epoxy compound, and epoxidized fatty acid monoester are preferable because they can further improve the heat / hydrolysis stability and friction characteristics. A glycidyl ester type epoxy compound and an alicyclic epoxy compound are more preferable.

  When the refrigerating machine oil composition for carbon dioxide refrigerant of the present invention contains an epoxy compound, the content of the epoxy compound is not particularly limited, but is preferably 0.1 to 5.0% by mass based on the total amount of the composition. 0.2 to 2.0% by mass is more preferable.

  Furthermore, the refrigerating machine oil composition for carbon dioxide refrigerant of the present invention may further contain an oily agent. Preferable examples of the oil agent include monohydric alcohol oil agents and carboxylic acid oil agents.

  As the monohydric alcohol oily agent, those having 1 to 24 carbon atoms, preferably 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms are usually used. Such alcohols may be linear or branched, Moreover, it may be saturated or unsaturated. Specific examples of the monohydric alcohol having 1 to 24 carbon atoms include methanol, ethanol, linear or branched propanol, linear or branched butanol, linear or branched pentanol, Linear or branched hexanol, linear or branched heptanol, linear 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, linear or branched octadecanol, linear or branched Decanol, straight-chain or branched Ikosanoru, straight or branched of the N'ikosanoru, linear or branched Torikosanoru, such as straight-chain or branched tetracosanol, and mixtures thereof.

  The number of carbon atoms of the monohydric alcohol oil-based agent is preferably 6 or more, more preferably 8 or more, and particularly preferably 10 or more, from the viewpoint of improving frictional characteristics and wear characteristics. Moreover, since there exists a possibility that it may become easy to precipitate in a refrigerant | coolant atmosphere when there are too many carbon numbers, 20 or less are preferable, 18 or less are more preferable, and 16 or less are especially preferable.

  The carboxylic acid oily agent may be a monobasic acid or a polybasic acid. Examples of such carboxylic acids include monobasic acids and polybasic acids exemplified in the description of the ester oil-based agent. Among these, monobasic acids are preferable from the viewpoint of improving frictional characteristics and wear characteristics.

  The number of carbon atoms in the carboxylic acid oil-based agent is preferably 6 or more, more preferably 8 or more, and particularly preferably 10 or more, from the viewpoint of improving frictional characteristics and wear characteristics. Moreover, since there exists a possibility that it may become easy to precipitate in a refrigerant | coolant atmosphere when carbon number of a carboxylic acid oiliness agent is too large, 20 or less are preferable, 18 or less are more preferable, and 16 or less are especially preferable.

  In the refrigerating machine oil composition for carbon dioxide refrigerant of the present invention, as the oil agent, one of a monohydric alcohol oil agent and a carboxylic acid oil agent may be used alone, or two or more of them may be used in combination. May be.

  When the refrigerating machine oil composition for carbon dioxide refrigerant of the present invention contains an oily agent, the content of the oily agent is arbitrary, but from the viewpoint of excellent effect of improving wear resistance and friction properties, based on the total amount of the composition, Preferably it is 0.01 mass% or more, More preferably, it is 0.05 mass% or more, More preferably, it is 0.1 mass% or more. In addition, the content is preferably 10% by mass or less, based on the total amount of the composition, from the viewpoint of excellent precipitation prevention property under a refrigerant atmosphere and low temperature, and heat / oxidation stability of the refrigerator oil composition. Preferably it is 7.5 mass% or less, More preferably, it is 5 mass% or less.

  Furthermore, the refrigerating machine oil composition for carbon dioxide refrigerant of the present invention may further contain a conventionally known refrigerating machine oil additive as necessary in order to further enhance its performance. Examples of such additives include phenolic antioxidants such as di-tert-butyl-P-cresol and bisphenol A, phenyl-α-naphthylamine, N, N-di (2-naphthyl) -P-phenylenediamine. Amine-based antioxidants such as zinc dithiophosphate, anti-wear agents such as zinc dithiophosphate, extreme pressure agents such as chlorinated paraffin and sulfur compounds, silicone-based antifoaming agents, viscosity index improvers, pour point depressants, clean dispersion Agents and the like. These additives can be blended alone or in combination of several kinds. The content of these additives is not particularly limited, but the total amount of additives is preferably 10% by mass or less, more preferably 5% by mass or less, based on the total amount of the composition.

Although the volume resistivity of the refrigerating machine oil composition for carbon dioxide refrigerant of the present invention is not particularly limited, it is preferably 1.0 × 10 ⁹ Ω · cm or more. In particular, high electrical insulation tends to be required when used in a closed refrigerator. Here, the volume resistivity means a value [Ω · cm] at 25 ° C. measured in accordance with JIS C 2101 “Electrical Insulating Oil Test Method”.

  Furthermore, the water content of the refrigerating machine oil composition for carbon dioxide refrigerant of the present invention is not particularly limited. it can. In particular, when used for a closed type refrigerator, the water content is required to be low from the viewpoint of the influence on the heat and hydrolysis stability of oil and electrical insulation.

  Furthermore, the acid value of the refrigerating machine oil composition for carbon dioxide refrigerant of the present invention is not particularly limited, but is preferably 0.1 mgKOH / g or less in order to prevent corrosion to the metal used in the refrigerator or piping. More preferably, it can be 0.05 mgKOH / g or less. The acid value here means a value [mg KOH / g] measured in accordance with JIS K 2501 “Petroleum products and lubricating oil mono-neutralization test method”.

  Furthermore, the ash content of the refrigerating machine oil composition for carbon dioxide refrigerant of the present invention is not particularly limited. , Preferably 100 ppm or less, more preferably 50 ppm or less. In the present invention, ash means a value [ppm] measured in accordance with JIS K 2272 “Testing method for ash and sulfated ash of crude oil and petroleum products”.

  The carbon dioxide refrigerant refrigerating machine oil composition of the present invention exhibits its excellent effect when used together with a carbon dioxide refrigerant, but the refrigerant used may be a carbon dioxide refrigerant alone, or A mixed refrigerant of a carbon dioxide refrigerant and another refrigerant may be used. Examples of other refrigerants include HFC refrigerants, fluorine-containing ether refrigerants such as bar fluoroethers, non-fluorine-containing ether refrigerants such as dimethyl ether, and natural refrigerants such as ammonia and hydrocarbons.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.

[Examples 1 to 24, Comparative Examples 1 to 11]
In Examples 1 to 24 and Comparative Examples 1 to 11, refrigerating machine oil compositions having the compositions shown in Tables 1 to 6 were prepared using the lubricant base oils and additives shown below, respectively.
(Lubricant base oil)
Base oil 1: Mixed acid of dipentaerythritol, 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid (mixing ratio: 2-ethylhexanoic acid / 3,5,5-trimethylhexanoic acid = 1/1 ( Molar ratio)) and ester (kinematic viscosity at 40 ° C .: 220 mm ² / s)
Base oil 2: Mixed acid of dipentaerythritol and caprylic acid, 2-ethylhexanoic acid, pelargonic acid and 3,5,5-trimethylhexanoic acid (mixing ratio: caprylic acid / 2-ethylhexanoic acid / pelargonic acid / 3 , 5,5-trimethylhexanoic acid = 1/4/1/4 (molar ratio)) and an ester (kinematic viscosity at 40 ° C .: 180 mm ² / s)
Base oil 3: Mixed acid of dipentaerythritol, caprylic acid and 3,5,5-trimethylhexanoic acid (mixing ratio: caprylic acid / 3,5,5-trimethylhexanoic acid = 1/4 (molar ratio)) Esters (kinematic viscosity at 40 ° C .: 320 mm ² / s)
Base oil 4: Mixed acid of dipentaerythritol, pelargonic acid and 3,5,5-trimethylhexanoic acid (mixing ratio: pelargonic acid / 3,5,5-trimethylhexanoic acid = 1/4 (molar ratio)) Ester (kinematic viscosity at 40 ° C .: 400 mm ² / s)
Base oil 5: Mixed acid of pentaerythritol, 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid (mixing ratio: 2-ethylhexanoic acid / 3,5,5-trimethylhexanoic acid = 1/1 (mol Ratio)) and esters (kinematic viscosity at 40 ° C .: 68 mm ² / s)
Base oil 6: Polypropylene glycol monobutyl ether (number average molecular weight: 1300, kinematic viscosity at 40 ° C .: 100 mm ² / s)
Base oil 7: Copolymer of ethyl vinyl ether and isobutyl vinyl ether (ethyl vinyl ether / isobutyl vinyl ether = 9/1 (molar ratio), kinematic viscosity at 40 ° C .: 68 mm ² / s)
Base oil 8: branched alkylbenzene (kinematic viscosity at 40 ° C .: 68 mm ² / s)
Base oil 9: Naphthenic mineral oil (kinematic viscosity at 40 ° C .: 56 mm ² / s)
(Additive)
Additive 1: Triphenyl phosphorothioate additive 2: Glycidyl-2,2'-dimethyloctanoate additive 3: Tricresyl phosphate additive 4: Butyl stearate.

  Next, the following tests were conducted on the refrigerator oil compositions of Examples 1 to 24 and Comparative Examples 1 to 11.

(Lubricity test)
In accordance with ASTM D 2670 “FALEX WEAR TEST”, after running-in for 1 minute under a load of 150 lb under the condition of a sample oil temperature of 100 ° C., a carbon dioxide refrigerant of 10 L / h is blown and a load of 250 lb is applied. The tester was operated for 2 hours. The amount of wear of the test journal (pin) after the test was measured, and the lubricity of each sample oil was evaluated. The obtained results are shown in Tables 1-6.

(Thermal stability test)
90 g of sample oil, 10 g of carbon dioxide refrigerant, and catalyst (iron, copper, and aluminum wires) were sealed in an autoclave, heated to 175 ° C. and held for 1 week. The acid value of the sample oil after one week was measured to evaluate the thermal stability. The obtained results are shown in Tables 1-6.

Claims (7)

  A refrigerating machine oil composition for carbon dioxide refrigerant characterized by containing a predetermined lubricating base oil and a thiophosphate.   The refrigerating machine oil composition for carbon dioxide refrigerant according to claim 1, wherein the lubricating base oil is an ester.   The refrigerating machine oil composition for carbon dioxide refrigerant according to claim 1 or 2, wherein an ester of dipentaerythritol and a fatty acid is contained as the lubricating base oil in an amount of 50 mass% or more based on the total amount of the composition. .   The refrigerating machine oil composition for carbon dioxide according to claim 3, wherein in the ester of dipentaerythritol and a fatty acid, the proportion of the branched fatty acid in the constituent fatty acid is 25 mol% or more.   In the ester of dipentaerythritol and a fatty acid, the total content of 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid in the constituent fatty acid is 75 mol% or more, Item 5. The refrigerant oil composition for carbon dioxide refrigerant according to Item 3 or 4.   The refrigeration oil composition for carbon dioxide refrigerant according to any one of claims 1 to 5, further comprising an epoxy compound.   The refrigerating machine oil composition for carbon dioxide refrigerant according to any one of claims 1 to 6, further comprising a phosphorus-based additive other than the thiophosphate ester.