Refrigerating machine oil and refrigerating machine working fluid composition

Abstract

One aspect of the present invention provides a refrigerator oil which contains: an ester-based base oil; at least one type of epoxy compound selected from between an alkyl glycidyl ether and an aryl glycidyl ether; and a phenol-based antioxidant. The content of the epoxy compound is 0.7 mass% or more based on the entire amount of the refrigerator oil. The refrigerator oil is used together with a refrigerant such as trifluoroiodomethane.

Description

[Technical field]

[0001] The present invention relates to a refrigerating machine oil and a working fluid composition for a refrigerating machine. [Background technology]

[0002] A freezing machine such as a refrigerator is equipped with a refrigerant circulation system having a compressor, a condenser, an expansion mechanism (expansion valve, capillary), an evaporator, etc., and heat exchange is performed by the refrigerant circulating within this refrigerant circulation system.

[0003] Refrigeration compressors include rotary compressors and piston-crank compressors. For example, in a piston-crank compressor, the rotary motion of a motor is converted into reciprocating motion by a connecting rod, and a piston connected to the connecting rod is reciprocated to compress the refrigerant. Refrigeration oil is sealed in the compressor together with the refrigerant, and lubricates sliding members such as the connecting rod and piston. For example, Patent Document 1 below discloses such a refrigeration oil that contains a predetermined ester oil and various additives. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6545337 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the study by the present inventors, when a refrigerant containing trifluoroiodomethane is used, the refrigerating machine oil is likely to be discolored and contaminants are likely to be generated, and the above-mentioned conventional refrigerating machine oils have room for improvement in this respect. Therefore, the present invention aims to provide a refrigerating machine oil that can suppress the discoloration and generation of contaminants even when a refrigerant containing trifluoroiodomethane is used, and a working fluid composition for a refrigerating machine that contains the refrigerating machine oil. [Means for solving the problem]

[0006] One aspect of the present invention provides a refrigerating machine oil that contains an ester-based base oil, at least one epoxy compound selected from alkyl glycidyl ethers and aryl glycidyl ethers, and a phenol-based antioxidant, the epoxy compound content being 0.7 mass% or more based on the total amount of the refrigerating machine oil, and that is used together with a refrigerant containing trifluoroiodomethane.

[0007] Another aspect of the present invention provides a working fluid composition for a refrigerating machine, comprising: a refrigerant containing trifluoroiodomethane; and a refrigerating machine oil containing an ester-based base oil, at least one epoxy compound selected from an alkyl glycidyl ether and an aryl glycidyl ether, and a phenol-based antioxidant, wherein the content of the epoxy compound is 0.7 mass% or more based on the total amount of the refrigerating machine oil.

[0008] In each of the above aspects, the epoxy compound may include at least one selected from the group consisting of alkyl glycidyl ethers represented by the following formula (1) and aryl glycidyl ethers represented by the following formula (3). [ka] In the formula, R 1 represents a branched alkyl group. [ka] In the formula, R 3 represents an alkyl group. The epoxy compound may include an alkyl glycidyl ether represented by formula (1). The epoxy compound may include an aryl glycidyl ether represented by formula (3). The ester-based base oil may include at least one selected from the group consisting of polyol esters and complex esters. The refrigerant may further include a saturated fluorohydrocarbon. Effect of the Invention

[0009] According to the present invention, it is possible to provide a refrigerating machine oil that can suppress the generation of coloration and impurities even when a refrigerant containing trifluoroiodomethane is used, and a working fluid composition for a refrigerating machine that contains the refrigerating machine oil. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described in detail.

[0011] The refrigerating machine oil according to the present embodiment includes an ester-based base oil, at least one epoxy compound selected from alkyl glycidyl ethers and aryl glycidyl ethers, and a phenol-based antioxidant. The content of the epoxy compound is 0.7 mass% or more based on the total amount of the refrigerating machine oil. The refrigerating machine oil is used together with a refrigerant containing trifluoroiodomethane.

[0012] The ester-based base oil contained in the refrigerating machine oil according to the present embodiment includes a monoester, a polyol ester, an aromatic ester, a dibasic acid ester, a complex ester, a carbonate ester, or a mixture thereof. The ester-based base oil preferably includes at least one selected from the group consisting of a polyol ester and a complex ester, and is more preferably a mixture of a polyol ester and a complex ester (including at least one polyol ester and at least one complex ester) from the viewpoint of being able to particularly effectively suppress the generation of impurities.

[0013] The polyol ester is, for example, an ester of a polyhydric alcohol and a fatty acid. The fatty acid may be either a saturated fatty acid or an unsaturated fatty acid. The number of carbon atoms of the fatty acid is preferably 4 to 20, more preferably 4 to 18, even more preferably 4 to 9, and particularly preferably 5 to 9. The polyol ester may be a partial ester in which some of the hydroxyl groups of the polyhydric alcohol remain as hydroxyl groups without being esterified, a complete ester in which all of the hydroxyl groups are esterified, or a mixture of a partial ester and a complete ester. The hydroxyl value of the polyol ester is preferably 10 mgKOH / g or less, more preferably 5 mgKOH / g or less, and even more preferably 3 mgKOH / g or less. The hydroxyl value in the present invention means a hydroxyl value measured in accordance with JIS K0070:1992.

[0014] The proportion of fatty acids having 4 to 20 carbon atoms in the fatty acids constituting the polyol ester is preferably 20 to 100 mol %, more preferably 50 to 100 mol %, further preferably 70 to 100 mol %, and particularly preferably 90 to 100 mol %.

[0015] Specific examples of fatty acids having 4 to 20 carbon atoms include butanoic acid, 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, and oleic acid. These fatty acids may be linear or branched. More specifically, fatty acids having branches at the α-position and / or β-position are preferred, and at least one selected from 2-methylpropanoic acid, 2-methylbutanoic acid, 2-methylpentanoic acid, 2-methylhexanoic acid, 2-ethylpentanoic acid, 2-methylheptanoic acid, 2-ethylhexanoic acid, 3,5,5-trimethylhexanoic acid, and 2-ethylhexadecanoic acid is more preferred, and 2-ethylhexanoic acid and / or 3,5,5-trimethylhexanoic acid is even more preferred.

[0016] The fatty acid may contain a fatty acid other than fatty acids having 4 to 20 carbon atoms. The fatty acid other than fatty acids having 4 to 20 carbon atoms may be, for example, a fatty acid having 21 to 24 carbon atoms. Specific examples include henicosanoic acid, docosanoic acid, tricosanoic acid, and tetracosanoic acid. These fatty acids may be linear or branched.

[0017] As the polyhydric alcohol constituting the polyol ester, a polyhydric alcohol having 2 to 6 hydroxyl groups is preferably used. The number of carbon atoms of the polyhydric alcohol is preferably 4 to 12, more preferably 5 to 10. Specifically, at least one hindered alcohol selected from neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, di-(trimethylolpropane), tri-(trimethylolpropane), pentaerythritol, and dipentaerythritol is preferred. Pentaerythritol or a mixture of pentaerythritol and dipentaerythritol is more preferred because of its excellent compatibility with the refrigerant and hydrolysis stability.

[0018] The complex ester is an ester synthesized, for example, by the following method (a) or (b). (a) A method in which the molar ratio of polyhydric alcohol to polybasic acid is adjusted to synthesize an ester intermediate in which some of the carboxyl groups of the polybasic acid remain unesterified, and then the remaining carboxyl groups are esterified with a monohydric alcohol. (b) A method in which the molar ratio of polyhydric alcohol to polybasic acid is adjusted to synthesize an ester intermediate in which some of the hydroxyl groups of the polyhydric alcohol remain unesterified, and then the remaining hydroxyl groups are esterified with a monobasic fatty acid.

[0019] The complex ester obtained by the above method (a) is unlikely to produce a relatively strong acid when hydrolyzed during use as a refrigerating machine oil, and tends to be more stable than the complex ester obtained by the above method (b). The complex ester is preferably the complex ester obtained by the above method (a), which is more stable.

[0020] The complex ester is preferably an ester synthesized from at least one selected from polyhydric alcohols having 2 to 4 hydroxyl groups, at least one selected from polybasic acids having 6 to 12 carbon atoms, and at least one selected from monohydric alcohols having 4 to 18 carbon atoms and monobasic fatty acids having 2 to 12 carbon atoms.

[0021] Examples of polyhydric alcohols having 2 to 4 hydroxyl groups include neopentyl glycol, trimethylolpropane, pentaerythritol, etc. As the polyhydric alcohols having 2 to 4 hydroxyl groups, neopentyl glycol and trimethylolpropane are preferred from the viewpoint of ensuring a suitable viscosity and obtaining good low-temperature properties when the complex ester is used as a base oil, and neopentyl glycol is more preferred from the viewpoint of being able to adjust the viscosity over a wide range.

[0022] From the viewpoint of excellent lubricity, it is preferable that the polyhydric alcohol constituting the complex ester further contains a dihydric alcohol having 2 to 10 carbon atoms other than neopentyl glycol in addition to the polyhydric alcohol having 2 to 4 hydroxyl groups. Examples of dihydric alcohols having 2 to 10 carbon atoms other than neopentyl glycol include ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, and 2,2-diethyl-1,3-pentanediol. Among these, butanediol is preferred from the viewpoint of excellent lubricating base oil properties. Examples of butanediol include 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and 2,3-butanediol. Among these, 1,3-butanediol and 1,4-butanediol are more preferred from the viewpoint of obtaining good properties. The amount of the dihydric alcohol having 2 to 10 carbon atoms other than neopentyl glycol is preferably 1.2 mol or less, more preferably 0.8 mol or less, and even more preferably 0.4 mol or less, per mol of the polyhydric alcohol having 2 to 4 hydroxyl groups.

[0023] Examples of polybasic acids having 6 to 12 carbon atoms include adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, and trimellitic acid. Among these, adipic acid and sebacic acid are preferred, and adipic acid is more preferred, from the viewpoints of excellent balance of properties of the synthesized ester and easy availability. The amount of polybasic acid having 6 to 12 carbon atoms is preferably 0.4 mol to 4 mol, more preferably 0.5 mol to 3 mol, and even more preferably 0.6 mol to 2.5 mol, relative to 1 mol of polyhydric alcohol having 2 to 4 hydroxyl groups.

[0024] Examples of the monohydric alcohol having 4 to 18 carbon atoms include aliphatic alcohols such as butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, dodecanol, and oleyl alcohol. These monohydric alcohols may be linear or branched. From the viewpoint of balance of properties, the monohydric alcohol having 4 to 18 carbon atoms is preferably a monohydric alcohol having 6 to 10 carbon atoms, and more preferably a monohydric alcohol having 8 to 10 carbon atoms. Among these, 2-ethylhexanol and 3,5,5-trimethylhexanol are more preferable from the viewpoint of improving the low-temperature properties of the synthesized complex ester.

[0025] Examples of monobasic fatty acids having 2 to 12 carbon atoms include ethanoic acid, propanoic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, and dodecanoic acid. These monobasic fatty acids may be linear or branched. The monobasic fatty acids having 2 to 12 carbon atoms are preferably monobasic fatty acids having 8 to 10 carbon atoms, and among these, 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid are more preferable from the viewpoint of low-temperature properties.

[0026] The refrigeration oil according to the present embodiment may contain a base oil other than the above-mentioned ester-based base oil. As such a base oil, a known mineral oil or synthetic oil (excluding the above-mentioned ester-based base oil) can be used.

[0027] Examples of mineral oils include paraffinic and naphthenic mineral oils, which are obtained by refining lubricating oil fractions obtained by atmospheric and reduced pressure distillation of crude oil through a single or suitable combination of two or more refining processes such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, sulfuric acid washing, and clay treatment, and paraffinic mineral oils are particularly preferred. These mineral oils may be used alone or in any combination of two or more in any ratio.

[0028] As the synthetic oil other than the ester-based base oil, it is preferable to use an ether-based base oil.As the ether-based base oil, for example, polyvinyl ether, polyalkylene glycol, polyphenyl ether, perfluoroether, and mixtures thereof can be exemplified.As the synthetic oil other than the ester-based base oil, in addition to the ether-based base oil, carbonate, ketone, silicone, polysiloxane, etc. can also be exemplified.

[0029] When the refrigeration oil contains a base oil other than the ester-based base oil, the content of the ester-based base oil may be, for example, 50 mass% or more, 70 mass% or more, 90 mass% or more, or 95 mass% or more based on the total amount of the base oil. The content of the ester-based base oil may be, for example, less than 100 mass% based on the total amount of the base oil.

[0030] The content of the base oil or ester-based base oil may be, for example, 50 mass% or more, 70 mass% or more, 90 mass% or more, or 95 mass% or more based on the total amount of the refrigerating machine oil. The content of the base oil or ester-based base oil may be, for example, less than 100 mass% based on the total amount of the refrigerating machine oil.

[0031] The kinematic viscosity of the base oil or ester-based base oil at 40°C is not particularly limited. For example, 2 / s or more, 10mm 2 / s or more, or 35 mm 2 The upper limit of the kinematic viscosity of the base oil or ester-based base oil at 40° C. is not particularly limited, but may be, for example, 500 mm 2 / s or less or 300 mm 2 The kinematic viscosity of the base oil or ester-based base oil at 100°C is not particularly limited, but may be, for example, 1 mm 2 / s or more or 2mm 2 The upper limit of the kinematic viscosity of the base oil or ester-based base oil at 100° C. is not particularly limited. 2 / s or less or 50 mm 2 The kinetic viscosity in the present invention means a kinetic viscosity measured in accordance with JIS K2283:2000.

[0032] The refrigerating machine oil according to the present embodiment contains at least one epoxy compound selected from alkyl glycidyl ethers and aryl glycidyl ethers.

[0033] The alkyl glycidyl ether is a compound represented by the following formula (1). [ka] In the formula, R 1 represents an alkyl group.

[0034] R 1 The alkyl group represented by the formula (I) may be linear or branched, and is preferably branched from the viewpoint of further suppressing the generation of contaminants. The number of carbon atoms in the alkyl group may be 5 or more, 6 or more, 7 or more, or 8 or more, and may be 18 or less, 14 or less, 10 or less, or 8 or less.

[0035] Examples of alkyl glycidyl ethers include 2-ethylhexyl glycidyl ether, decyl glycidyl ether, undecyl glycidyl ether, dodecyl glycidyl ether, tridecyl glycidyl ether, and tetradecyl glycidyl ether.

[0036] The aryl glycidyl ether is a compound represented by the following formula (2). [ka] In the formula, R 2 represents an aryl group.

[0037] R 2 The number of carbon atoms in the aryl group represented by the formula may be 6 or more, 7 or more, 8 or more, 9 or more, or 10 or more, and may be 18 or less, 16 or less, 14 or less, 12 or less, or 10 or less.

[0038] From the viewpoint of further suppressing the generation of contaminants, the aryl glycidyl ether is preferably a compound represented by the following formula (3). [ka] In the formula, R 3 represents an alkyl group.

[0039] R 3 The alkyl group represented by the formula (I) may be linear or branched, and is preferably branched from the viewpoint of further suppressing the generation of contaminants. The number of carbon atoms in the alkyl group may be 1 or more, 2 or more, 3 or more, or 4 or more, and may be 12 or less, 10 or less, 8 or less, 6 or less, or 4 or less.

[0040] Examples of aryl glycidyl ethers include phenyl glycidyl ether, 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, and decylphenyl glycidyl ether.

[0041] The content of the epoxy compound is 0.7% by mass or more, preferably 0.9% by mass or more, more preferably 1% by mass or more, and even more preferably 2% by mass or more or 2.5% by mass or more, based on the total amount of the refrigerating machine oil, from the viewpoint of suppressing coloration and generation of impurities. The upper limit of the content of the epoxy compound is not particularly limited, but is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 4% by mass or less, based on the total amount of the refrigerating machine oil.

[0042] The refrigerating machine oil according to the present embodiment includes a phenol-based antioxidant. The phenol-based antioxidant may be a hindered phenol-based antioxidant. In the present specification, the hindered phenol-based antioxidant is a compound having a structure in which a benzene ring, at least one hydroxyl group and at least one tert.-butyl group bonded to the benzene ring, and the bonding positions of the hydroxyl group and the tert.-butyl group on the benzene ring are adjacent to each other. The number of tert.-butyl groups bonded adjacent to the bonding positions of the hydroxyl group on the benzene ring is preferably two. Examples of the hindered phenol-based antioxidant include 2,6-di-tert.-butyl-p-cresol (DBPC), 2,6-di-tert.-butyl-phenol, 4,4'-methylenebis(2,6-di-tert.-butyl-phenol), and 2-tert.-butyl-4-methoxyphenol. The hindered phenol-based antioxidant preferably includes DBPC.

[0043] The phenol-based antioxidant may be an alkylated hydroxyanisole-based antioxidant (excluding antioxidants corresponding to the above-mentioned hindered phenol-based antioxidant). Specific examples of alkylated hydroxyanisole-based antioxidants include butyl hydroxyanisole (BHA), and more specific examples include alkylated hydroxyanisole compounds such as 3-tert.-butyl-4-hydroxyanisole (2-tert.-butyl-4-methoxyphenol). The phenol-based antioxidant may include a hindered phenol-based antioxidant and / or an alkylated hydroxyanisole-based antioxidant.

[0044] From the viewpoint of more effectively suppressing the generation of coloration and impurities, the content of the phenol-based antioxidant is preferably 0.1 mass% or more, more preferably 0.3 mass% or more, even more preferably 0.6 mass% or more or 0.9 mass% or more, based on the total amount of the refrigerating machine oil. The upper limit of the content of the phenol-based antioxidant is not particularly limited, but is preferably 10 mass% or less, more preferably 5 mass% or less, even more preferably 3 mass% or less, based on the total amount of the refrigerating machine oil.

[0045] In the refrigeration oil according to the present embodiment, the mass ratio of the epoxy compound content to the phenolic antioxidant content ((epoxy compound content) / (phenolic antioxidant content)) is preferably 0.05 or more, more preferably 0.3 or more, and even more preferably 0.7 or more, from the viewpoint of more effectively suppressing the generation of coloration and impurities. The upper limit of the mass ratio is preferably 100 or less, more preferably 50 or less, and even more preferably 10 or less, and may be 5 or less, 2 or less, or 1 or less, from the viewpoint of more effectively suppressing the generation of coloration and impurities.

[0046] The refrigerating machine oil according to the present embodiment may further contain other additives in addition to the above-mentioned components. Examples of the other additives include antioxidants other than phenol-based antioxidants, acid scavengers other than the above-mentioned epoxy compounds, extreme pressure agents, oiliness agents, antifoaming agents, metal deactivators, antiwear agents, viscosity index improvers, pour point depressants, detergent dispersants, etc. The total content of these additives is not particularly limited, but may be 10 mass% or less or 5 mass% or less based on the total amount of the refrigerating machine oil.

[0047] The kinetic viscosity of the refrigeration oil at 40°C is preferably 3mm 2 / s or more, more preferably 4mm 2 / s or more, more preferably 5 mm 2 The kinetic viscosity of the refrigeration oil at 40°C is preferably 500 mm 2 / s or less, preferably 400 mm 2 / s or less, more preferably 300 mm 2 The kinetic viscosity of the refrigeration oil at 100°C is preferably 1 mm 2 / s or more, preferably 2 mm 2 The kinetic viscosity of the refrigeration oil at 100°C is preferably 100mm 2 / s or less, preferably 50 mm 2 / s or less.

[0048] The refrigeration oil according to the present embodiment is usually present in a state of a refrigeration working fluid composition mixed with a refrigerant containing trifluoroiodomethane in a refrigeration machine equipped with a refrigerant circulation system having a compressor, a condenser, an expansion mechanism, and an evaporator, and lubricates the refrigeration oil. That is, the refrigeration working fluid composition according to the present embodiment contains a refrigerant containing trifluoroiodomethane and the refrigeration oil.

[0049] The content of the refrigerating machine oil in the working fluid composition for a refrigerating machine may be 1 to 500 parts by mass, or 2 to 400 parts by mass, per 100 parts by mass of the refrigerant.

[0050] The refrigerant is not particularly limited as long as it contains trifluoroiodomethane, and may contain only trifluoroiodomethane or may further contain a refrigerant other than trifluoroiodomethane. The content of trifluoroiodomethane is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, based on the total amount of the refrigerant. The content of trifluoroiodomethane is preferably 100% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less, based on the total amount of the refrigerant.

[0051] Examples of refrigerants other than trifluoroiodomethane include saturated fluorohydrocarbons, unsaturated fluorohydrocarbons, hydrocarbons, fluorine-containing ethers such as perfluoroethers, bis(trifluoromethyl)sulfide, and natural refrigerants such as ammonia and carbon dioxide, as well as mixed refrigerants of two or more types selected from these refrigerants.

[0052] The saturated fluorohydrocarbon (HFC) is preferably a saturated fluorohydrocarbon having 1 to 3 carbon atoms, more preferably a saturated fluorohydrocarbon having 1 to 2 carbon atoms. Specific examples include difluoromethane (R32), trifluoromethane (R23), pentafluoroethane (R125), 1,1,2,2-tetrafluoroethane (R134), 1,1,1,2-tetrafluoroethane (R134a), 1,1,1-trifluoroethane (R143a), 1,1-difluoroethane (R152a), fluoroethane (R161), 1,1,1,2,3, Examples of such fluorocarbons include 3,3-heptafluoropropane (R227ea), 1,1,1,2,3,3-hexafluoropropane (R236ea), 1,1,1,3,3,3-hexafluoropropane (R236fa), 1,1,1,3,3-pentafluoropropane (R245fa), and 1,1,1,3,3-pentafluorobutane (R365mfc), or a mixture of two or more of these.

[0053] The saturated fluorohydrocarbon is appropriately selected from the above depending on the application and required performance, and preferred examples thereof include R32 alone; R23 alone; R134a alone; R125 alone; a mixture of R134a / R32=60-80% by mass / 40-20% by mass; a mixture of R32 / R125=40-70% by mass / 60-30% by mass; a mixture of R125 / R143a=40-60% by mass / 60-40% by mass; a mixture of R134a / R32 / R125=60% by mass / 30% by mass / 10% by mass; a mixture of R134a / R32 / R125=40-70% by mass / 15-35% by mass / 5-40% by mass; and a mixture of R125 / R134a / R143a=35-55% by mass / 1-15% by mass / 40-60% by mass. More specifically, a mixture of R134a / R32=70 / 30% by mass; a mixture of R32 / R125=60 / 40% by mass; a mixture of R32 / R125=50 / 50% by mass (R410A); a mixture of R32 / R125=45 / 55% by mass (R410B); a mixture of R125 / R143a=50 / 50% by mass (R507C); a mixture of R32 / R125 / R134a=30 / 10 / 60% by mass; a mixture of R32 / R125 / R134a=23 / 25 / 52% by mass (R407E); a mixture of R125 / R134a / R143a=44 / 4 / 52% by mass (R404A), etc. can be used.

[0054] Preferred examples of the mixed refrigerant of trifluoroiodomethane and the above-mentioned saturated fluorohydrocarbon include R32 / R125 / trifluoroiodomethane mixed refrigerant and R32 / R410A / trifluoroiodomethane mixed refrigerant. In such mixed refrigerants, the ratio of (R32 content) / (trifluoroiodomethane content) is preferably 10 / 90 to 90 / 10, more preferably 30 / 70 to 70 / 30, even more preferably 40 / 60 to 60 / 40, and particularly preferably 50 / 50 to 60 / 40, in view of the balance between compatibility with refrigerating machine oil, low GWP, and non-flammability. Similarly, the ratio of (the total content of R32 and the content of trifluoroiodomethane) / (the content of R125) in such a mixed refrigerant is preferably 10 / 90 to 95 / 5, and from the viewpoint of low GWP, is more preferably 50 / 50 to 95 / 5, and further preferably 80 / 20 to 95 / 5.

[0055] The unsaturated fluorohydrocarbon (HFO) is preferably a fluoropropene, more preferably a fluoropropene having 3 to 5 fluorines. Specifically, the unsaturated fluorohydrocarbon is preferably one or a mixture of two or more of 1,2,3,3,3-pentafluoropropene (HFO-1225ye), 1,3,3,3-tetrafluoropropene (HFO-1234ze), 2,3,3,3-tetrafluoropropene (HFO-1234yf), 1,2,3,3-tetrafluoropropene (HFO-1234ye), and 3,3,3-trifluoropropene (HFO-1243zf). From the viewpoint of refrigerant properties, it is preferably one or more selected from HFO-1225ye, HFO-1234ze, and HFO-1234yf.

[0056] The hydrocarbon is preferably a hydrocarbon having 1 to 5 carbon atoms, more preferably a hydrocarbon having 2 to 4 carbon atoms. Specific examples of the hydrocarbon include methane, ethylene, ethane, propylene, propane (R290), cyclopropane, normal butane, isobutane, cyclobutane, methylcyclopropane, 2-methylbutane, normal pentane, or a mixture of two or more of these. Among these, those that are gaseous at 25°C and 1 atmospheric pressure are preferably used, and propane, normal butane, isobutane, 2-methylbutane, or a mixture of these are preferred.

[0057] The refrigerating machine oil and working fluid composition for a refrigerating machine according to the present embodiment can be suitably used in refrigeration machines such as air conditioners having a reciprocating or rotary hermetic compressor, refrigerators, open or hermetic car air conditioners, dehumidifiers, water heaters, freezers, refrigerated and freezer warehouses, vending machines, showcases, and chemical plants, refrigeration machines having a centrifugal compressor, and the like. EXAMPLES

[0058] The present invention will be described in more detail below based on examples, but the present invention is not limited to the following examples.

[0059] [Preparation of refrigerating machine oil] Using the components shown below, refrigeration oils having the compositions shown in Tables 1 to 3 (mass % based on the total amount of refrigeration oil) were prepared.

[0060] (Base oil) A1: Polyol ester of pentaerythritol and a mixed fatty acid of 2-ethylhexanoic acid / 3,5,5-trimethylhexanoic acid (mixing ratio (mass ratio): 37 / 63) (kinetic viscosity at 40 ° C: 75.5 mm 2 / s, kinematic viscosity at 100℃: 8.9mm 2 / s) A2: Mixed base oil of the following (a1) and (a2) (mixing ratio (mass ratio): (a1) / (a2)=60 / 40) (a1) Polyol ester of pentaerythritol and a mixed fatty acid of 2-ethylhexanoic acid / 3,5,5-trimethylhexanoic acid (molar ratio: 48:52) (a2) A complex ester obtained by reacting an ester intermediate obtained by reacting neopentyl glycol (1 mol) and 1,4-butanediol (0.2 mol) with adipic acid (1.5 mol), further reacting the ester intermediate with 3,5,5-trimethylhexanol (1.1 mol), and removing the remaining unreacted material by distillation.

[0061] (Epoxy compounds) B1: 2-Ethylhexyl glycidyl ether B2: Phenyl glycidyl ether B3: 4-tert-butylphenyl glycidyl ether B4: Glycidyl neodecanoate (glycidyl ester) B5: 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (alicyclic diepoxide)

[0062] (Antioxidants) C1: 2,6-di-tert.-butyl-p-cresol (DBPC) C2: A mixture containing 2-tert.-butyl-4-methoxyphenol and 3-tert.-butyl-4-methoxyphenol in a mass ratio of 1:1 c3: Alkyldiphenylamine (mixture of diphenylamine and 2,4,4-trimethyl-1-pentene)

[0063] [Refrigeration oil evaluation] The refrigeration oils of the Examples and Comparative Examples were subjected to the following evaluation tests.

[0064] First, a mixed refrigerant of R32 (difluoromethane) / R125 (pentafluoroethane) / trifluoroiodomethane = 49.0 / 11.5 / 39.5 (mass ratio) was prepared as a refrigerant containing trifluoroiodomethane. Specifically, R32, R410A (mixed refrigerant of R32 / R125 = 50 / 50 (mass ratio)), and trifluoroiodomethane were mixed in a mass ratio of R32 / R410A / trifluoroiodomethane = 37.5 / 23 / 39.5 to prepare a refrigerant containing trifluoroiodomethane of the above composition. The refrigerant containing trifluoroiodomethane of this composition has a GWP of 733 and is classified as a non-flammable refrigerant (A1) according to the ASHRAE category.

[0065] Next, 30 g of refrigeration oil (initial hue L0.5) with a moisture content of 10 mass ppm or less, 0.6 mmφ×50 mm catalysts (one each of copper, iron, and aluminum), and 30 g of the refrigerant containing trifluoroiodomethane prepared above were charged into a 200 ml autoclave, heated to 175° C., and held for the time shown in Table 1. The content and hue (ASTM D156) of impurities were measured for the refrigeration oil after each time. The content of impurities (mg / 100 g OIL (refrigeration oil)) was calculated from the weight of the filtrate obtained by filtering the refrigeration oil after heating through a cellulose filter with a pore size of 0.3 μm, thoroughly washing the filtrate and the filter with hexane to remove the hexane-soluble matter, and drying, with reference to JIS K2276. The results are shown in Tables 1 to 3.

[0066] [Table 1]

[0067]

Table 2

[0068]

Table 3

Claims

1. An ester base oil; an epoxy compound containing at least one selected from the group consisting of an alkyl glycidyl ether represented by the following formula (1) and an aryl glycidyl ether represented by the following formula (3); a phenolic antioxidant, The content of the epoxy compound is 0.7% by mass or more based on the total amount of the refrigerating machine oil, and the content of the phenol-based antioxidant is 0.1% by mass or more based on the total amount of the refrigerating machine oil, A refrigeration oil used with a refrigerant containing trifluoroiodomethane. 【Chemistry 1】 [In the formula, R 1 represents a branched alkyl group.] 【Chemistry 2】 [In the formula, R 3 represents an alkyl group.]

2. The refrigerating machine oil according to claim 1 , wherein the epoxy compound contains an alkyl glycidyl ether represented by the formula (1).

3. The refrigerating machine oil according to claim 1 , wherein the epoxy compound contains an aryl glycidyl ether represented by the formula (3).

4. The refrigeration oil according to any one of claims 1 to 3, wherein the ester-based base oil comprises at least one selected from the group consisting of polyol esters and complex esters.

5. The refrigeration oil according to any one of claims 1 to 4, wherein the refrigerant further contains a saturated fluorohydrocarbon.

6. a refrigerant comprising trifluoroiodomethane; A refrigerating machine oil comprising an ester-based base oil, an epoxy compound containing at least one selected from the group consisting of an alkyl glycidyl ether represented by the following formula (1) and an aryl glycidyl ether represented by the following formula (3), and a phenol-based antioxidant, the content of the epoxy compound being 0.7 mass% or more based on the total amount of the refrigerating machine oil, and the content of the phenol-based antioxidant being 0.1 mass% or more based on the total amount of the refrigerating machine oil; A working fluid composition for a refrigeration machine comprising: 【Chemistry 3】 [In the formula, R 1 represents a branched alkyl group.] 【Chemistry 4】 [In the formula, R 3 represents an alkyl group.]

7. The working fluid composition for a refrigerating machine according to claim 6, wherein the epoxy compound comprises an alkyl glycidyl ether represented by the formula (1).

8. The working fluid composition for a refrigerating machine according to claim 6, wherein the epoxy compound comprises an aryl glycidyl ether represented by the formula (3).

9. The working fluid composition for a refrigerating machine according to any one of claims 6 to 8, wherein the ester-based base oil comprises at least one selected from the group consisting of polyol esters and complex esters.

10. The working fluid composition for a refrigerating machine according to any one of claims 6 to 9, wherein the refrigerant further comprises a saturated fluorohydrocarbon.

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