JP2007204568A - Refrigerating machine oil composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerating machine oil composition for carbon dioxide refrigerant, good in compatibility with a carbon dioxide refrigerant and slight in viscosity drop even if mixed with such a carbon dioxide refrigerant. <P>SOLUTION: The refrigerating machine oil composition for carbon dioxide refrigerant comprises (A) a base oil with dynamic viscosity of 1-300 mm<SP>2</SP>/s at 100°C and (B) an oil-soluble polymer with a weight-average molecular weight of 10,000-1,000,000. In this machine oil composition, it is preferable that the base oil A be an ether-based or ester-based synthetic oil with its SP value being 8.5-11, the oil-soluble polymer B be a vinyl polymer with its SP value being 7.5-9.5, and the absolute value of the SP value difference between the components A and B be 0.3-2.0. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a refrigerator oil composition for carbon dioxide refrigerant. Specifically, the present invention relates to a refrigerating machine oil composition having a small viscosity drop when a carbon dioxide refrigerant is dissolved.

In general, a compression refrigerator is composed of four devices: a compressor, a condenser, an expansion mechanism, and an evaporator, and cools by circulating a gas that is easily liquefied, called a refrigerant. The circulation of the refrigerant is called a refrigeration cycle, and the refrigeration action is performed with four state changes of evaporation, compression, condensation, and expansion. Conventionally, chlorofluorocarbons have been used as refrigerants.However, when these chlorofluorocarbons are released into the atmosphere, they are extremely stable, so they are not decomposed in the troposphere, but rise to the stratosphere and are decomposed for the first time by solar ultraviolet rays. It turns out to be a source of chlorine. Since then, chlorofluorocarbons have been subject to production and use regulations, and substitution has been promoted to alternative chlorofluorocarbons such as hydrofluorocarbons and fluorocarbons that do not contain chlorine. However, although this alternative chlorofluorocarbon also does not destroy the ozone layer, it is considered to be shifted to other natural refrigerants (carbon dioxide, ammonia, hydrocarbons, etc.) from the viewpoint of global warming because it has a high global warming potential. Yes.
In particular, carbon dioxide is extremely toxic and flammable and is very easy to handle, has a large heating capacity per compressor suction volume, and has a high heat transfer rate, enabling a compact system. Currently, research is actively conducted for room air conditioners.
On the other hand, the refrigerating machine oil composition is a lubricating oil for lubricating the compressor, which is the heart of the refrigerating machine, and is used for the purpose of preventing wear of the movable mechanism and reducing friction. The point that the refrigerating machine oil composition differs greatly from other lubricating oil compositions is that it is used in a refrigerant atmosphere without oxygen, and performance specific to the refrigerating machine oil composition is required. For example, since the refrigerating machine oil composition is discharged from the compressor together with the refrigerant in the refrigerant cycle, the refrigerating machine oil composition is required to have a characteristic of returning to the compressor again through the flow path together with the circulating refrigerant (referred to as liquid returnability). Therefore, the refrigerator oil composition is required to have compatibility with the refrigerant.
For refrigerating machine oil compositions used for refrigerating machines using carbon dioxide as a refrigerant, that is, refrigerating machine oil compositions for carbon dioxide refrigerant, refrigerating machine oil compositions using various base oils have been studied, for example, patents Document 1 uses a hydrocarbon base oil, Patent Document 2 and Patent Document 3 use an ether base oil such as polyalkylene glycol and polyvinyl ether, and Patent Document 4 uses an ester base oil. What was there is released.
However, among these, the refrigerating machine oil composition comprising a hydrocarbon base oil is not sufficiently compatible with the carbon dioxide refrigerant, so that sufficient liquid return cannot be obtained, and the compressor seizure due to poor lubrication or There has been a problem that the refrigeration efficiency is likely to be lowered due to staying in a refrigeration cycle such as a flow path and a heat exchanger. In addition, the refrigerating machine oil composition comprising an ether base oil or an ester base oil has no problem in liquid return properties, but because the compatibility with the carbon dioxide refrigerant is too high, the refrigerating machine oil composition is diluted with the carbon dioxide refrigerant. As a result, the viscosity is lowered, and there is a problem that a reduction in refrigeration efficiency due to a decrease in sealing performance and poor lubrication of the compressor may occur.
Japanese Patent Laid-Open No. 10-46168 Japanese Patent Laid-Open No. 2003-226887 Japanese Patent Laid-Open No. 10-46169 JP 2000-104084 A

The subject of this invention is providing the refrigerating machine oil composition for carbon dioxide refrigerants which is excellent in compatibility with a carbon dioxide refrigerant | coolant, and has little viscosity fall, even if a carbon dioxide melt | dissolves.

As a result of intensive studies to achieve the object of the present invention, the inventors have found that a refrigerating machine oil composition containing a specific base oil and a specific oil-soluble polymer exhibits excellent performance, and has reached the present invention. That is, the present invention comprises a base oil (A) having a kinematic viscosity at 100 ° C. of 1 to 300 mm ² / s and an oil-soluble polymer (B) having a weight average molecular weight of 10,000 to 1,000,000. A refrigerating machine oil composition for a carbon refrigerant.

The refrigerating machine oil composition for carbon dioxide refrigerant of the present invention has little viscosity decrease due to dissolution of the carbon dioxide refrigerant and is excellent in compatibility with the carbon dioxide refrigerant.
Therefore, the lubricity in the refrigerator is easily maintained properly and the liquid return property is excellent.

The “carbon dioxide refrigerant” in the present invention is mainly composed of carbon dioxide, and usually contains 90% by weight or more of carbon dioxide, has good liquid return properties and is dissolved when the base oil is dissolved in the refrigerant. From the viewpoint of low viscosity reduction, preferred is 100% by weight of carbon dioxide. In the case of a mixture with other refrigerants, examples of other refrigerants include hydrocarbon refrigerants such as propane and isobutane, ammonia refrigerants, 1,1,1,2-tetrafluorocarbon (R-134a). Examples thereof include fluorocarbon refrigerants such as hydrofluorocarbon and fluorocarbon.

Base oil (A) in the present invention, mineral oil is used as a base oil conventionally lubricants, among such as synthetic oil or fat, 100 ° C. kinematic viscosity refers to those 1 to 300 mm ² / s, A mixture of two or more kinds may be used.
The kinematic viscosity of the base oil (A) is preferably ² to 100 mm ² / s, more preferably 3 to 50 mm ² / s. When the kinematic viscosity at 100 ° C. is less than 1 mm ² / s, the lubricity is insufficient, and when it exceeds 300 mm ² / s, the stirring resistance increases, which is not preferable.

Among the base oils, as mineral oil, solvent degreasing, solvent extraction, hydrocracking, hydrodewaxing, and solvent dewaxing are carried out for lubricating oil fractions obtained by atmospheric and vacuum distillation of crude oil. And lubricating base oils obtained by appropriately combining one or more refining means such as hydrorefining, sulfuric acid washing, and clay treatment, and paraffinic or naphthenic oils obtained from paraffinic or naphthenic crude oils. A lubricating base oil is preferred.

Synthetic oils among the base oils include ether-based synthetic oils, ester-based synthetic oils, silicone-based synthetic oils, and hydrocarbon-based synthetic oils, all of which have a weight average molecular weight of less than 10,000.

Examples of the ether synthetic oil include compounds represented by the general formula (1).
X [-O- (AO) nR] m (1)
In the formula, X is a monool or a residue obtained by removing m hydroxyl groups from a divalent to 10-valent polyol, A is an alkylene group having 2 to 4 carbon atoms, R is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or An acyl group having 1 to 10 carbon atoms, m represents an integer of 1 to 10, n represents an integer of 2 to 100, and preferable n is a number average molecular weight of the compound represented by the general formula (1) of 500 to 3,000. Is an integer such that The monool having X as a residue is a monohydric alcohol having 1 to 24 carbon atoms, such as methanol, ethanol, n-butanol, isobutanol, sec-butanol, 2-ethylhexanol, decyl alcohol, dodecyl alcohol, and the like. Examples include octadecyl alcohol. As a polyol having X as a residue, a diol having 2 to 12 carbon atoms such as ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, hexylene glycol and dodecylene glycol; a triol having 3 to 24 carbon atoms, For example, glycerin and trimethylolpropane; tetraols having 4 to 24 carbon atoms such as pentaerythritol, diglycerin and sorbitan; pentavalent or higher (preferably 5 to 8 valent) polyols such as dipentaerythritol, triglycerin, tetra Glycerin, sorbitol and saccharides (such as sucrose).
Examples of A include an ethylene group, 1,2-propylene group, 1,3-propylene group, 1,4-butylene group and 1,2-butylene group. Examples of the alkyl group having 1 to 10 carbon atoms in R include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, pentyl group, hexyl group, heptyl group, octyl group, and nonyl. Group and decyl group. m is preferably 1 to 4 from the viewpoint of lubricity. n is preferably 10 to 100 from the viewpoint of lubricity.

Specific examples of the ether-based synthetic oil include: polyethylene glycol, polypropylene glycol, ethylene oxide-propylene oxide copolymer (block, random or a combination thereof) having a weight average molecular weight of less than 10,000, and ethylene oxide-butylene oxide copolymer ( Polyalkylene glycols such as blocks, random or combinations thereof; monoalkyl ethers of the above polyalkylene glycols: dialkyl ethers of the above polyalkylene glycols; monocarboxylic acid esters of the above polyalkylene glycols; and the above polyalkylenes A dicarboxylic acid ester of glycol.

Examples of ester synthetic oils include aromatic esters, dibasic acid esters, polyol esters, complex esters, carbonate esters, and mixtures thereof.

The aromatic ester is an ester of 1 to 6 valent, preferably 1 to 4 valent, more preferably 1 to 3 valent aromatic carboxylic acid and an aliphatic alcohol having 1 to 18 carbon atoms, preferably 1 to 12 carbon atoms. Is mentioned. Examples of 1 to 6-valent aromatic carboxylic acids 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 methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentanol, hexanol, heptanol Octanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, heptadecanol, 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 trimellitic acid, and trimethyl trimellitic acid (2- Ethylhexyl), trinonyl trimellitic acid, tridecyl trimellitic acid, tridodecyl trimellitic acid, tritridecyl trimellitic acid, and the like. 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.

Examples of the dibasic acid ester include 5 to 10 carbon atoms such as glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,2-cyclohexanedicarboxylic acid, and 4-cyclohexene-1,2-dicarboxylic acid. And an ester of a linear or branched aliphatic dibasic acid and a linear or branched aliphatic alcohol having 1 to 18 carbon atoms (such as those described above).
Specifically, ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sebacate, diester of 1,2-cyclohexanedicarboxylic acid and monohydric alcohol having 4 to 9 carbon atoms , 4-cyclohexene-1,2-dicarboxylic acid and diesters of monohydric alcohols having 4 to 9 carbon atoms, and mixtures thereof.

As the polyol ester, an ester of a polyol having 3 to 20 diols or hydroxyl groups and a fatty acid having 1 to 24 carbon atoms is preferably used. Examples of the polyol include diols exemplified as X in the general formula (1) and trivalent or higher polyols. Examples of polyols include hindered substances such as neopentyl glycol, trimethylol ethane, trimethylol propane, trimethylol butane, di- (trimethylol propane), tri- (trimethylol propane), pentaerythritol, dipentaerythritol, and tripentaerythritol. Alcohol is preferred.

Of the fatty acids used in the polyol ester, those having 3 or more carbon atoms are preferable, those having 4 or more carbon atoms are more preferable, those having 5 or more carbon atoms are more preferable, and those having 10 or more carbon atoms are particularly preferable. preferable. Moreover, from a compatibility point with a refrigerant | coolant, a C18 or less thing is preferable, a C12 or less thing is more preferable, and a C9 or less thing is further more preferable. The fatty acid may be either a linear fatty acid or a branched fatty acid, but a linear fatty acid is preferable from the viewpoint of lubricity, and a branched fatty acid is preferable from the viewpoint of hydrolysis stability. Furthermore, the fatty acid may be either a saturated fatty acid or an unsaturated fatty acid.

Fatty acids used in the polyol ester 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 and the like, and these fatty acids may be either linear fatty acids or branched fatty acids, and furthermore, fatty acids having a quaternary carbon atom (neo Acid). 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), caprin 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 5-Trimethylhexanoic acid is preferably used.

The polyol ester may be a partial ester that remains without being esterified, as long as it has two or more ester groups, and all the hydroxyl groups are esterified. It may be a complete ester, or a mixture of a partial ester and a complete ester, but is preferably a complete ester.

The complex ester is an ester of a fatty acid and a dibasic acid, and a monohydric alcohol and a polyol. As the fatty acid, dibasic acid, monohydric alcohol and polyol, in the description of the dibasic acid ester and the polyol ester, The exemplified fatty acids, dibasic acids, monohydric alcohols and polyols can be used.

The carbonate ester is a compound having a carbonate ester bond represented by the following formula (2) in the molecule.
-O-CO-O- (2)
The number of carbonate ester bonds represented by the above formula (2) may be one per molecule or two or more.

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

When an ester synthetic oil is used as the base oil in the present invention, 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 ester-based synthetic oils, dibasic acid esters, polyol esters, and carbonates are preferred because of excellent compatibility with refrigerants.

Synthetic oils further include silicone-based synthetic oils (for example, polysiloxane), hydrocarbon-based synthetic oils (for example, naphthalene compounds and alkylbenzenes), perfluoroethers, polyvinyl ethers having a weight average molecular weight of less than 10,000, and poly α- Examples include olefins.

Among the base oils (A), as fats and oils, for example, vegetable oils such as linseed oil, olive oil, rapeseed oil, corn oil, tide oil, peanut oil, sunflower oil, animal fats such as beef tallow, fish fat, milk fat or the like These hydrides are mentioned.

Of the base oils (A), ether-based synthetic oils or ester-based synthetic oils are preferable from the viewpoint of suppressing a decrease in viscosity when the carbon dioxide refrigerant is dissolved.

The SP value of the base oil (A) in the present invention is preferably 8.5 to 11 from the viewpoint of compatibility with the carbon dioxide refrigerant. More preferably, it is 9-10.5. If the base oil (A) has an SP value in this range, it is excellent in compatibility with the carbon dioxide refrigerant when combined with the oil-soluble polymer (B) described later, and has excellent liquid return properties, and carbon dioxide refrigerant. In particular, there is little decrease in viscosity.
Moreover, 2 or more types of mixtures may be sufficient as base oil (A), and when it is a 2 or more types of mixture, 1 type or more and SP value of base oil (A1) whose SP value is 7.5-9.0. Is preferably a mixture of one or more base oils (A2) of more than 9.0 and 11 or less. In addition, SP value in the case of the mixture of 2 or more types of base oil is SP value which averaged SP value of each base oil by the weight fraction.
As described above, by using a mixture of two or more kinds of base oils, the effect of suppressing the decrease in viscosity when the carbon dioxide refrigerant is mixed is further easily exhibited.

The SP value is expressed by the following formula.
SP value (δ) = (ΔH / V) ^1/2
In the formula, ΔH represents the heat of vaporization (cal), and V represents the molar volume (cm ³ ). ΔH and V are the total heat of molar evaporation (Δei) of the atomic group described in “POLYMER ENGINEERING AND FEBRUARY, 1974, Vol. 14, No. 2, ROBERT F. FEDORS. (Pages 151 to 153)”. The sum (V) of (ΔH) and molar volume (Δvi) can be used.

Specific examples of the base oil having an SP value of 8.5 to 11 include, for example, polyethylene glycol (SP value = 9.4), polypropylene glycol (SP value = 8.7), polybutylene glycol (SP value = 8.6). ), Esters of pentaerythritol and 3,5,5-trimethylhexanoic acid (SP value = 8.8), and diisodecyl adipate (SP value = 9.0).

In the present invention, “oil-soluble” in the oil-soluble polymer (B) refers to a property of being uniformly dissolved in a general liquid petroleum product, specifically, “0.1% relative to 100N solvent refined mineral oil”. The oil-soluble definition is “weight% can be uniformly dissolved at 60 ° C.” and “no precipitation when visually observed for the presence of precipitation after standing at 25 ° C. for 24 hours”.

Examples of the oil-soluble polymer (B) include polyaddition polymers, polycondensation polymers, addition condensation polymers, ring-opening polymerization polymers, and addition polymerization polymers having a weight average molecular weight of 10,000 to 1,000,000. Etc.

Polyaddition polymer as polyurethane; Polycondensation polymer as polyester, silicone resin, polyamide and polycarbonate; Addition polymerization polymer as vinyl polymer; Addition condensation polymer as phenol resin and amino resin (for example, (Urea resin and melamine resin); Examples of the ring-opening polymer include polyoxyalkylene and epoxy resin. Among these polymers, an addition polymerization polymer, particularly a vinyl polymer (B1) is preferable from the viewpoint that a decrease in viscosity of the mixture with carbon dioxide is small.

  The weight average molecular weight (hereinafter abbreviated as Mw) of the oil-soluble polymer (B) in the present invention is usually 10,000 to 1,000,000, preferably 20,000 to 900,000, and more preferably 30,000 to 800,000. (Mw is measured by gel permeation chromatography, polystyrene standard). If the Mw is less than 10,000, the effect of suppressing the viscosity decrease when mixing the carbon dioxide refrigerant is insufficient, and if it exceeds 1,000,000, it cannot withstand long-term use.

The SP value of the oil-soluble polymer (B) in the present invention is preferably 7.5 to 9.5, more preferably 7.6 to 9.4, from the viewpoint of compatibility with the carbon dioxide refrigerant.

The absolute value of the difference in SP value between the base oil (A) and the oil-soluble polymer (B) is more preferably 0.3 to 2.0. It is particularly preferable that the SP value of the base oil (A) is larger than the SP value of the oil-soluble polymer (B).
If the absolute value of the difference in SP value is 0.3 or more, it becomes easier to exert the effect of suppressing the decrease in viscosity when the carbon dioxide refrigerant is mixed, and if it is 2.0 or less, the oil is soluble in the base oil (A). It is preferable in terms of the compatibility of the polymer (B).

The SP value of the oil-soluble polymer (B) is obtained by calculating the SP value of the structural unit (repeating unit) of the polymer, and the structural unit is designed so as to be in the above preferred range.
For example, polyurethane is a repeating unit composed of an isocyanate component and a polyol, polyester is a repeating unit composed of a dicarboxylic acid and a diol, polyamide is a repeating unit composed of a dicarboxylic acid and a diamine, and is used in a vinyl polymer (B1). SP value is calculated about the vinyl monomer (a) obtained, and SP value of an oil-soluble polymer (B) can be estimated or set.

The vinyl polymer (B1) includes homopolymers and copolymers of the vinyl monomer (a).
Examples of (a) include the following (a1) to (a12), and a copolymer is preferable from the viewpoint of solubility in the base oil (A).

(A1); (meth) acrylic acid ester (meth) acrylic acid alkyl ester (a1-1), (meth) acrylic acid alkenyl ester (a1-2), (poly) alkylene glycol or mono (meta) of its monoalkyl ether ) Acrylic acid ester (a1-3), (meth) acrylic acid cycloalkyl or cycloalkylalkyl ester (a1-4), and the like.

Examples of the alkyl group constituting (a1-1) include a linear or branched alkyl group having 1 to 30 carbon atoms, preferably an alkyl group having 8 to 24 carbon atoms.
Specific examples of (a1-1) include methyl acrylate (SP value = 10.6), methyl methacrylate (SP value = 9.9), ethyl acrylate (SP value = 10.2), and ethyl methacrylate. (SP value = 9.7), n-butyl acrylate (SP value = 9.8), n-butyl methacrylate (SP value = 9.5), 2-ethylhexyl acrylate (SP value = 9.2) 2-ethylhexyl methacrylate (SP value = 9.0), decyl acrylate (SP value = 9.2), decyl methacrylate (SP value = 9.1), isodecyl (meth) acrylate, dodecyl acrylate, Dodecyl methacrylate (SP value = 9.0), tridecyl (meth) acrylate, tetradecyl methacrylate (SP value = 9.0), tetradecyl acrylate, hexadecyl methacrylate (SP value = 8.9) Hexadecyl acrylate, octadecyl methacrylate (SP value = 8.9), octadecyl acrylate, (meth) eicosyl acrylate, and (meth) acrylate, 2-decyl tetradecyl and (meth) tetracosyl acrylate.

The alkenyl group constituting (a1-2) includes a linear or branched alkenyl group having 2 to 30 carbon atoms.
Specific examples of (a1-2) include (meth) acrylic acid butenyl ester, (meth) acrylic acid octenyl ester, (meth) acrylic acid decenyl ester, (meth) acrylic acid dodecenyl ester, (meth) acrylic. And acid oleyl ester.

The (poly) alkylene glycol constituting (a1-3) or the alkylene group constituting the monoalkyl ether thereof is an alkylene group having 2 to 20 carbon atoms, such as an ethylene group, a propylene group, a butylene group, or a 2-butylene group. , Isobutylene group, 1,1-diphenylethylene group and cyclohexylene group. Preferably, it is a C2-C6 alkylene group. Moreover, as an alkyl group which comprises monoalkyl ether, a C1-C20 linear or branched alkyl group is mentioned, Preferably it is a C1-C18 alkyl group, The above-mentioned alkyl group is mentioned. The number of alkylene glycol units in the (poly) alkylene glycol is preferably 1-50, more preferably 1-20.
Specific examples of (a1-3) include polyethylene glycol (9 units of ethylene glycol) monomethacrylate, polyethylene glycol (18 units of ethylene glycol unit) monomethacrylate, polypropylene glycol (3 units of propylene glycol unit) monomethacrylate, Examples include polyethylene glycol (6 units of ethylene glycol) monomethyl ether monomethacrylate, ethylene glycol mono-2-ethylhexyl ether monomethacrylate, polypropylene glycol (3 units of propylene glycol) monobutyl ether monomethacrylate, and the like.

Specific examples of (a1-4) include cyclohexyl methacrylate, cyclohexyl acrylate, decahydronaphthyl (meth) acrylate, cyclohexylethyl (meth) acrylate, cyclohexylmethyl (meth) acrylate, cyclohexane (meth) acrylate. And heptylethyl.

(A2); an ester of an unsaturated carboxylic acid other than (meth) acrylic acid, an alkyl, cycloalkyl or aralkyl ester having 1 to 30 carbon atoms of an unsaturated monocarboxylic acid other than (meth) acrylic acid [such as crotonic acid], and C1-C24 alkyl diester [Dimethyl maleate, Dimethyl fumarate, Diethyl maleate, Dioctyl maleate, etc.] of unsaturated dicarboxylic acid [maleic acid, fumaric acid, itaconic acid, etc.] is mentioned.

(A3); Aliphatic vinyl hydrocarbon such as alkene having 2 to 30 carbon atoms [ethylene, propylene, 1-butene, isobutylene, 1-pentene, 1-heptene, 4-methylpentene-1,1-hexene, di Isobutylene, 1-octene, 1-dodecene, 1-octadecene, and other α-olefins], alkadienes having 4 to 18 carbon atoms [preferably butadiene, isoprene, and other 1,4-pentadiene having 4 to 5 carbon atoms, 1 , 6-hexadiene, 1,7-octadiene, etc.].

(A4); alkyl alkenyl ethers Alkyl vinyl ethers having a linear or branched alkyl group having 1 to 30 carbon atoms, alkyl (meth) allyl ethers, alkyl propenyl ethers, alkyl isopropenyl ethers, etc., preferably 1 to 1 carbon atoms. 24 alkyl groups. Specifically, examples of the alkyl vinyl ether include methyl vinyl ether (SP value = 8.7), ethyl vinyl ether (SP value = 8.6), and n-butyl vinyl ether. Examples of the alkyl (meth) allyl ether include methyl allyl ether. , Ethyl allyl ether, n-butyl allyl ether and the like.
Of these, preferred are methyl vinyl ether, ethyl vinyl ether, methyl allyl ether and ethyl allyl ether.

(A5); Examples of the fatty acid vinyl ester fatty acid include fatty acids having a linear, branched or alicyclic group having 1 to 30 carbon atoms, and may be either saturated or unsaturated. Moreover, two or more kinds of combinations such as linear and branched may be used. A fatty acid having an alkyl group having 1 to 24 carbon atoms, more preferably 1 to 18 carbon atoms is preferred. Specifically, vinyl acetate (SP value = 10.6), vinyl propionate (SP value = 10.2), vinyl butyrate (SP value = 10.0), vinyl hexanoate, vinyl heptanoate, 2-ethyl Examples include vinyl hexanoate, vinyl n-octanoate (SP value = 9.4), vinyl oleate, vinyl linoleate, vinyl linolenate, vinyl cyclohexane, vinyl cyclooctanoate and vinyl decahydronaphthylate.

(A6): Vinyl ketones Alkyl or aryl vinyl ketones having 1 to 8 carbon atoms [methyl vinyl ketone (SP value = 11.1), ethyl vinyl ketone, phenyl vinyl ketone, etc.].

(A7): Cyclohexene (SP value = 10.1), (di) cyclopentadiene, vinylcyclohexene (SP value = 11.5), ethylidene Bicycloheptene (SP value = 11.5), pinene, limonene, indene and the like can be mentioned.

(A8); aromatic vinyl hydrocarbon such as styrene (SP value = 10.6), other substituted styrene (substituent having 1 to 18 carbon atoms) [alkyl-substituted styrene (preferably α-methylstyrene, vinyltoluene, Others such as 2,4-dimethyl styrene, ethyl styrene, isopropyl styrene, butyl styrene), cycloalkyl-substituted styrene (such as cyclohexyl styrene), aryl-substituted styrene (such as phenyl styrene), aralkyl-substituted styrene (such as benzyl styrene), acyl group substitution Styrene (acetoxystyrene, etc.), phenoxy group-substituted styrene (phenoxystyrene, etc.)], divinyl-substituted aromatic hydrocarbons [preferably divinylbenzene, other divinyltoluene and divinylxylene, etc.], vinylnaphthalene, etc. It is.

(A9); nitrogen atom-containing monomer (a9-1); primary to tertiary amino group-containing vinyl monomer, for example, aminoalkyl (1 to 8 carbon atoms) (meth) acrylate or (meth) acrylamide [aminoethyl (meta ) Acrylate, aminopropyl (meth) acrylate, N-aminoethyl (meth) acrylamide, etc.] and their mono- and dialkyl (C 1-6) substituted products [dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate] , T-butylaminoethyl methacrylate, etc.], heterocyclic nitrogen-containing vinyl monomers [morpholinoethyl (meth) acrylate, 4-vinylpyridine, 2-vinylpyridine, vinylimidazole, N-vinylpyrrole, N-vinylthiopyrrolidone, aminocarbazole ,amino Azole, aminoindole, aminopyrrole, aminoimidazole, such as amino mercaptothiazole and their salts, such as mono- and di (meth) allylamine and the like.

(A9-2); Quaternary ammonium cation group-containing vinyl monomer, for example, dialkyl (1 to 4 carbon atoms) aminoalkyl (2 to 8 carbon atoms) quaternized product of (meth) acrylate or (meth) acrylamide [dimethylaminoethyl Quaternized products such as (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylamide, diethylaminoethyl (meth) acrylamide], and quaternized products such as diallylamine. Examples thereof include quaternization using a compound having an alkyl or aralkyl group having 1 to 12 carbon atoms such as chloride, dimethyl sulfate, benzyl chloride, dimethyl carbonate and the like.

(A9-3); amide group-containing vinyl monomer unsubstituted or monoalkyl (carbon number 1 to 4) substituted (meth) acrylamide, [acrylamide (SP value = 19.2), methacrylamide (SP value = 16.1. 3), N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, Ni-propyl (meth) acrylamide, Nn- and i-butyl (meth) acrylamide, etc.], dialkyl (1 to 1 carbon atoms) 4) Substituted (meth) acrylamide [N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-di-n-butyl (meth) acrylamide], N-vinylcarboxylic acid amide [N -Vinylformamide, N-vinylacetamide, N-vinyl-n- and i-propionylamide, N-vinylhydro Shiasetoamido] and the like.

(A9-4); Nitrile group-containing monomer, for example, acrylonitrile (SP value = 14.4), methacrylonitrile (SP value = 12.7), cyanostyrene and the like.

(A9-5); a nitro group-containing monomer such as 4-nitrostyrene.

(A10); hydroxyl group-containing vinyl monomer such as aromatic vinyl monomer [p-hydroxystyrene etc.], vinyl alcohol (formed by hydrolysis of vinyl acetate unit) (SP value = 19.1), C3-C12 alkenol [allyl alcohol (SP value = 15.8), methallyl alcohol (SP value = 13.9) crotyl alcohol, isocrotyl alcohol, 1-octenol, 1-undecenol, etc.], carbon Alkenediols of 4 to 12 [1-buten-3-ol, 2-buten-1-ol, 2-butene-1,4-diol, etc.], hydroxyalkyl (C1 to C6) alkenyl (C3 -10) Ether [2-hydroxyethylpropenyl ether and the like] and the like.

(A11); halogen-containing vinyl monomers such as vinyl chloride, vinyl bromide, vinylidene chloride, (meth) allyl chloride, halogenated styrene (mono and dichlorostyrene, tetrafluorostyrene, allyl chloride, and the like).

(A12); anionic monomer (ab12-1); carboxyl group-containing vinyl monomer monocarboxylic acid group-containing vinyl monomer, for example, unsaturated monocarboxylic acid [acrylic acid (SP value = 14.0) , Methacrylic acid (SP value = 11.2) α-methyl (meth) acrylic acid, crotonic acid, cinnamic acid, etc.], monoalkyl (carbon number 1 to 8) ester of unsaturated dicarboxylic acid [maleic acid monoalkyl ester, Fumaric acid monoalkyl esters, itaconic acid monoalkyl esters, etc.]; dicarboxylic acid group-containing vinyl monomers such as maleic acid (SP value = 16.4), fumaric acid, itaconic acid, citraconic acid and aconitic acid. Can be mentioned.

(A12-2); sulfonic acid group-containing vinyl monomer alkene sulfonic acid having 2 to 6 carbon atoms [vinyl sulfonic acid (SP value = 12.3), (meth) allyl sulfonic acid etc.], 6 to 12 carbon atoms Aromatic vinyl group-containing sulfonic acid [α-methylstyrene sulfonic acid, etc.], sulfonic acid group-containing (meth) acrylic ester monomer [sulfopropyl (meth) acrylate, 2- (meth) acryloyloxyethanesulfonic acid, etc. ], Sulfonic acid group-containing (meth) acrylamide monomers [2- (meth) acrylamide-2-methylpropanesulfonic acid, etc.], vinyl monomers containing sulfonic acid groups and hydroxyl groups [3- (meth) acrylamide 2-hydroxypropanesulfonic acid, 3-allyloxy-2-hydroxypropanesulfonic acid, 3- (meth) acryloyloxy -2-like hydroxypropane sulfonic acid, alkyl (having 3 to 18 carbon atoms) allyl sulfosuccinate [dodecyl allyl sulfosuccinate], and the like.

(A12-3); sulfate ester group-containing vinyl monomer, for example, poly (n = 2 to 30) oxyalkylene (ethylene, propylene, butylene: single, random or block) mono (meth) acrylate sulfate ester, Poly (n = 2 to 30) oxyalkylene (ethylene, propylene, butylene: single, random or block) bisphenol A mono (meth) acrylate sulfate and the like.

(A12-4); Phosphoric acid group-containing vinyl monomer, for example, (meth) acryloyloxyalkyl (2 to 6 carbon atoms) phosphoric acid monoester [(meth) acryloyloxyethyl phosphate etc.], (meth) acryloyloxyalkane (carbon) Formula 2-4) Phosphonic acid [2-acryloyloxyethanephosphonic acid etc.] etc. are mentioned.

The predicted value of the SP value of the vinyl polymer (B) 1) can be calculated from the SP value calculated as a result of polymerization of the vinyl monomer (a) and conversion of the vinyl group into a substituted ethylene group and its molar ratio.

Among the vinyl monomers (a), a viewpoint that it is easy to adjust the SP value of a copolymer containing the monomer to 7.5 to 9.5, a viewpoint that it is easy to make an oil-soluble copolymer, and From the viewpoint of copolymerizability, preferably (a1), (a2), (a3) (a7), (a8), (a9) and a combination of two or more thereof, more preferably (a1), ( a3) and a combination of two or more thereof, particularly preferably one or more selected from the group consisting of (a1-1) of (a1) and alkenes of 2 to 30 carbons of (a3) Of these, a combination of two or more of (a1-1) is particularly preferred.

A preferred combination in the case of using two or more of (a1-1) in combination is an alkyl (meth) acrylate having a linear or branched alkyl group having 8 to 24 carbon atoms, more preferably 12 to 24 carbon atoms. A combination of two or more esters.

Specific examples of the vinyl polymer having an SP value of 7.5 to 9.5 include, for example, polydodecyl methacrylate (SP value = 9.0), poly 2-decyltetradecyl methacrylate (SP value = 8.8). , Decyl polyacrylate (SP value = 9.2), poly 1-butene (SP value = 8.2), ethylene / vinyl acetate (1/1) copolymer (SP value = 9.4) and styrene / And a dodecyl methacrylate (1/9) copolymer (SP value = 9.2).

As a combination of the base oil (A) and the vinyl polymer (B1) such that the absolute value of the difference in SP value is 0.3 to 2.0, for example, polypropylene glycol (SP value = 8.7) and poly 1 -Butene (SP value = 8.2) [SP value difference = 0.5], diisodecyl adipate (SP value = 9.0) and poly 1-butene (SP value = 8.2) [SP value difference = 0.8] and the like.

The method for producing the vinyl polymer (B1) may be a conventionally known radical polymerization method, for example, solution polymerization method, emulsion polymerization method, suspension polymerization method, reverse phase suspension polymerization method, thin film polymerization method, spraying method. Examples thereof include a polymerization method. Of these, the solution polymerization method is preferred, and it can be usually produced by radical polymerization of (a) in a solvent in the presence of an initiator. As the solvent, for example, the above base oil (A) and other organic solvents can be used. Other organic solvents include, for example, hydrocarbon solvents (pentane, hexane, etc.), aromatic solvents (toluene, xylene, etc.), alcohol solvents (isopropyl alcohol, octanol, butanol, etc.), ketone solvents (methyl isobutyl ketone) , Methyl ethyl ketone, etc.), amide solvents (N, N-dimethylformamide, N-methylpyrrolidone, etc.), sulfoxide solvents (dimethyl sulfoxide, etc.), and combinations of two or more of these.
As the initiator, an initiator selected from the group consisting of known azo initiators, peroxide initiators, redox initiators, and organic halogen compound initiators can be used.
Moreover, you may add a well-known chain transfer agent to superposition | polymerization, As reaction temperature, it becomes like this. Preferably it is 30-140 degreeC, More preferably, it is 50-130 degreeC, Most preferably, it is 70-120 degreeC. In addition to the method of initiating polymerization by heat, a method of initiating polymerization by irradiating with radiation, electron beam, ultraviolet rays or the like can also be employed. Preferred is a temperature-controlled solution polymerization method.
Furthermore, the copolymerization may be either random addition polymerization or alternating copolymerization, and may be either graft copolymerization or block copolymerization.

The content weight ratio of the base oil (A) to the oil-soluble polymer (B) in the refrigerator oil composition of the present invention is preferably (A) / (B), preferably 99/1 to 75/25, more preferably 95. / 5 to 80/20. If (B) is 1% or more, the effect of suppressing the decrease in viscosity at the time of mixing the carbon dioxide refrigerant is easily exhibited.
In the refrigerator oil composition of the present invention, the weight percent of the oil-soluble polymer (B) in the total weight of the refrigerator oil composition is preferably 1 to 25%, more preferably 3 to 23%. If (B) is 1% or more, the effect of suppressing the decrease in viscosity at the time of mixing the carbon dioxide refrigerant is easily exhibited, and if it is 25% or less, it can withstand long-term use.

The refrigerating machine oil composition of the present invention is further selected from the group consisting of an acid scavenger, an extreme pressure agent, an antioxidant, a friction modifier, a copper deactivator, an antifoaming agent and an anti-emulsifier, if necessary. You may contain the additive of a seed | species or more.

As the acid scavenger, for example, phenyl glycidyl ether, alkyl glycidyl ether, alkylene glycol glycidyl ether, cyclohexene oxide, and α-olefin oxide are preferable. The blending amount is preferably 0 to 5%, particularly preferably 0.05 to 3%, based on the total weight of the refrigerator oil composition.

Examples of extreme pressure agents include metal salts of carboxylic acids and phosphoric acid compounds.

The metal salt of carboxylic acid is preferably a metal salt of carboxylic acid having 3 to 60 carbon atoms.
Carboxylic acids include aliphatic saturated monocarboxylic acids (caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid and stearic acid); aliphatic unsaturated carboxylic acids (palmitoleic acid, oleic acid, elaidic acid) , Linoleic acid and linolenic acid); aliphatic dicarboxylic acids (such as adipic acid, azelaic acid and sebacic acid); aromatic carboxylic acids (such as benzoic acid, phthalic acid, trimellitic acid and pyrometic acid); . The metal constituting the metal salt is preferably an alkali metal or alkaline earth metal.

Examples of phosphoric acid compounds include phosphorous extreme pressure agents such as phosphoric acid esters, acidic phosphoric acid esters, phosphorous acid esters, acidic phosphorous acid esters, and amine salts thereof.
Examples of the phosphate ester include triaryl phosphate (triphenyl phosphate, tricresyl phosphate, benzyldiphenyl phosphate, etc.), trialkyl phosphate, trialkylaryl phosphate, triarylalkyl phosphate, and trialkenyl phosphate.
Examples of the acidic phosphate ester include 2-ethylhexyl acid phosphate, ethyl acid phosphate, butyl acid phosphate, and oleyl acid phosphate.
Examples of the phosphite include triethyl phosphite, tributyl phosphite, triphenyl phosphite and tricresyl phosphite.

Examples of the acidic phosphite include dibutyl hydrogen phosphite, dilauryl hydrogen phosphite, dioleyl hydrogen phosphite, distearyl hydrogen phosphite, and diphenyl hydrogen phosphite.
Examples of amines constituting the amine salt of the phosphoric acid compound include mono-substituted amines (such as butylamine, hexylamine, cyclohexylamine, and laurylamine), disubstituted amines (such as dibutylamine and dicyclohexylamine), and trisubstituted amines (tributylamine, Trihexylamine and triethanolamine).

Among these phosphorus compounds, tricresyl phosphate, tri (nonylphenyl) phosphite, dioleyl hydrogen phosphite and 2-ethylhexyl diphenyl phosphite are preferable from the viewpoints of extreme pressure and friction characteristics.
Further, as extreme pressure agents other than the above, for example, sulfur-based extreme pressure agents such as sulfurized fats and oils, sulfurized fatty acids, sulfurized esters, sulfurized olefins, dihydrocarbyl polysulfides, thiocarbamates, thioterpenes, dialkylthiodipropionates and the like. Can be mentioned.

One extreme pressure agent may be used, or two or more extreme pressure agents may be used in combination. In a preferred embodiment, one or more selected from a metal salt of a carboxylic acid and a phosphorus compound, particularly a metal salt of a carboxylic acid and a phosphorus extreme pressure agent are preferably used from the viewpoint of lubricity.
The blending amount of the extreme pressure agent is preferably in the range of 0 to 5%, particularly 0.01 to 3%, based on the total weight of the refrigerator oil composition. If it exceeds 5% by weight, sludge generation may be promoted.

Antioxidants include zinc dithiophosphate, amines (phenyl-α-naphthylamine, phenyl-β-naphthylamine, N, N′-diphenyl-p-phenylenediamine, etc.), phenols (2,6-di-tert). -Butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,2'-methylenebis (such as 4-methyl-6-tert-butylphenol), zinc thiophosphate and A trialkylphenol etc. are mentioned, The addition amount is 0 to 5 weight% preferably in the total weight of a refrigerating machine oil composition, More preferably, it is 0.01 to 3%.

As friction modifiers, molybdenum dithiophosphate, molybdenum dithiocarbamate, zinc dialkyldithiophosphate, long chain fatty acid (such as oleic acid), long chain fatty acid ester (such as oleic acid ester), long chain amine (such as oleylamine), And long chain amides (oleamide and the like) and the like, and the addition amount thereof is preferably 5% or less, more preferably 0.1 to 3%, based on the total weight of the refrigerating machine oil composition.

Examples of the copper deactivator include benzotriazole and derivatives thereof such as N- [N, N′-dialkyl (C3-C12 alkyl group) aminomethyl] toltriazole.

Examples of the antifoaming agent include silicone oil, fluorinated silicone oil, metal soap, fatty acid ester and phosphate ester, and the addition amount thereof is preferably 1,000 ppm or less in the total weight of the refrigerating machine oil composition, Preferably it is 10-700 ppm.

Examples of the demulsifier include quaternary ammonium salts and sulfated oils, and the addition amount thereof is preferably 3% or less, more preferably 1% or less, based on the total weight of the refrigerating machine oil composition.

Examples of the corrosion inhibitor include benzotriazole and 1,3,4-thiodiazolyl-2,5-bisdialkyldithiocarbamate, and the addition amount thereof is preferably 3% or less based on the total weight of the refrigerator oil composition. Preferably it is 2% or less.

The total of the above additives in the refrigerating machine oil composition of the present invention is preferably 25% or less, more preferably 0.1 to 15%, based on the total weight of the refrigerating machine oil composition.

The refrigerating machine oil composition of the present invention preferably has a viscosity index of 200 or more, more preferably 200 to 250. A viscosity index of 200 or more is preferable because the stirring resistance at low temperatures is small.

The refrigerating machine oil composition of the present invention contains a specific base oil (A) and a specific oil-soluble polymer (B), so that there is little decrease in viscosity even when dissolved in carbon dioxide. Therefore, even if the refrigeration oil partially dissolves in the carbon dioxide refrigerant in the compressor of the refrigeration machine, there is little decrease in lubricity.
Furthermore, all the refrigerating machine oils are excellent in compatibility with the carbon dioxide refrigerant, and are excellent in liquid return in the refrigeration cycle.

EXAMPLES In the following, the present invention will be described with reference to examples, but the present invention is not limited thereto. In the following, parts represent parts by weight.
[Measurement method of Mw by GPC]
Apparatus: HLC-802A manufactured by Toyo Soda
Column: TSK gel GMH6 2 Measurement temperature: 40 ° C
Sample solution: 0.5% tetrahydrofuran solution Solution injection amount: 200 μl
Detector: Refractive index detector Standard: Polystyrene

Production Example 1
Production of vinyl polymer (B-1);
A reaction vessel equipped with a stirrer, heating / cooling device, thermometer, dropping funnel, and nitrogen blowing tube was charged with 30 parts of toluene, and another glass beaker with 100 parts of dodecyl methacrylate and dodecyl mercaptan as a chain transfer agent. Was added to 0.5 parts and 0.5 part of 2,2′-azobis (2,4-dimethylvaleronitrile) as a radical polymerization initiator, and stirred and mixed at 20 ° C. to prepare a monomer solution. I loaded the funnel. After carrying out nitrogen substitution of the gas phase part of the reaction vessel, the monomer solution was added dropwise at 85 ° C. for 4 hours under sealing, and after aging at 85 ° C. for 2 hours from the end of the addition, the obtained polymer was Toluene was removed under reduced pressure at 130 ° C. for 3 hours to obtain a vinyl polymer (B-1).

Production Example 2
Production of vinyl polymer (B-2);
300 parts of cyclohexane was added to an autoclave equipped with a stirrer, a heating device, a blowing line, and a dropping line, and after replacing with nitrogen, pressurized to 9 MPa with 1-butene, and then heated to 80 ° C. 1-butene was blown so that this pressure was constant during the reaction. A mixture of 6 parts of a 50% by weight cyclohexane solution of diisopropyl peroxydicarbonate [“Perroyl IPP-50” (manufactured by NOF Corporation) and 10 parts of propionaldehyde was added dropwise over 2 hours and polymerized at 80 ° C. After completion of the dropping, the reaction mixture was taken out from the autoclave, and unreacted monomers and solvent were removed by drying under reduced pressure to obtain a vinyl polymer (B-2).

Examples 1 to 3 and Comparative Example 1
As shown in Table 1, any of the following (A-1) to (A-3) as the base oil (A), (B-1) or (B-2) below as the vinyl polymer (B1), Using tricresyl phosphate as the extreme pressure agent, the refrigeration oil compositions for carbon dioxide refrigerants of Examples 1 to 3 and Comparative Example 1 of the present invention were obtained.

(A-1): Polypropylene glycol
(100 ° C. kinematic viscosity 5.3 mm ² / s, SP value = 8.7)
(A-2): Diisodecyl adipate
(100 ° C. kinematic viscosity 5.3 mm ² / s, SP value = 9.0)
(A-3): ester (tetraester) of pentaerythritol and 3,5,5-trimethylhexanoic acid (100 ° C. kinematic viscosity 14 mm ² / s, SP value = 8.8)
(B-1): Poly-2-decyltetradecyl methacrylate
(Mw 50,000, SP value = 8.8)
(B-2): Poly 1-butene
(Mw 50,000, SP value = 8.2)
TCP: tricresyl phosphate

The viscosity of the refrigerating machine oil composition was measured under the atmospheric pressure and high-pressure carbon dioxide atmosphere by the following method, and the reduction rate of the viscosity due to the coexistence of high-pressure carbon dioxide was calculated. The results are also shown in Table 1.

[Measurement method of viscosity]
A viscosity (unit: mPa · s) at 100 ° C. was measured at atmospheric pressure and in a carbon dioxide atmosphere of 10 MPa using a double cylinder rheometer (“Physica MCR300” manufactured by Nippon Sebel Hegner Co., Ltd.) having a high pressure cell.
As a measurement sample, 16 ml of a refrigerator oil composition was used and measured at a rotation speed of 500 rpm.

[Measurement method of compatibility]
In a high-pressure vessel with a peep window, 60% by weight of the refrigerating machine oil composition and 40% by weight of carbon dioxide refrigerant are sealed, gradually cooled to −40 ° C. with a low-temperature bath, and compatible with whether it becomes cloudy at −40 ° C. Evaluation criteria were used.
If the compatibility is poor, the liquid return property is deteriorated when the refrigeration oil leaks into the refrigeration cycle.
"Compatibility evaluation criteria"
○: No cloudiness ×: Cloudiness

Viscosity reduction rate (%) =
[(Viscosity under atmospheric pressure−viscosity under CO ₂ of 10 MPa) / viscosity under atmospheric pressure] × 100

The refrigerating machine oil composition for carbon dioxide refrigerant of the present invention has a low viscosity decrease due to the dissolution of the carbon dioxide refrigerant in the refrigerating machine, the lubricity is properly maintained, and the liquid return property of the refrigerating machine oil leaked into the refrigerating cycle. Therefore, it can be suitably used for a compression type refrigerator using a carbon dioxide refrigerant, for example, a refrigerator, an air conditioner, a heat pump and the like for a car air conditioner, a freezer, a refrigerator, and a heat pump.

Claims (8)

Refrigeration for carbon dioxide refrigerant containing a base oil (A) having a kinematic viscosity at 100 ° C. of 1 to 300 mm ² / s and an oil-soluble polymer (B) having a weight average molecular weight of 10,000 to 1,000,000. Machine oil composition. The SP value of the base oil (A) is 8.5 to 11, the SP value of the oil-soluble polymer (B) is 7.5 to 9.5, and the SP values of (A) and (B) The refrigerating machine oil composition according to claim 1, wherein the absolute value of the difference is 0.3 to 2.0. The base oil (A) is a mixture of a base oil (A1) having an SP value of 7.5 to 9.0 and a base oil (A2) having an SP value of more than 9.0 and 11 or less. Item 3. The refrigerator oil composition according to Item 1 or 2. The refrigerating machine oil composition according to any one of claims 1 to 3, wherein the base oil (A) is an ether synthetic oil or an ester synthetic oil. The oil-soluble polymer (B) contains one or more vinyl monomers selected from the group consisting of (meth) acrylic acid alkyl esters and alkenes having 2 to 30 carbon atoms in 50% of all constituent monomers. The refrigerating machine oil composition according to any one of claims 1 to 4, which is a vinyl polymer containing at least%. The refrigerator oil composition according to any one of claims 1 to 5, wherein a weight ratio of the base oil (A) and the oil-soluble polymer (B) in the refrigerator oil composition is 99/1 to 75/25. The refrigerating machine oil composition according to any one of claims 1 to 6, which has a viscosity index of 200 or more. Furthermore, it contains one or more additives selected from the group consisting of acid scavengers, extreme pressure agents, antioxidants, friction modifiers, copper deactivators, antifoaming agents and demulsifiers. The refrigerating machine oil composition according to any one of the above.