Refrigeration oil and fluid composition for refrigerator

Abstract

One aspect of the present invention is a refrigerator oil containing a base oil and a partial ester between a carboxylic acid and a polyhydric alcohol, the carboxylic acid including an unsaturated carboxylic acid.

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] Conventionally, refrigerating machine oils have been used in refrigeration machines such as room air conditioners, packaged air conditioners, home refrigerators and freezers, industrial freezers, and car air conditioners. These refrigerators are equipped with a refrigerant circulation system that includes a compressor, a condenser, an expansion mechanism (expansion valve, capillary), an evaporator, etc. Cooling is achieved by circulating the refrigerant through 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 the refrigerant is compressed by reciprocating motion of a piston connected to the connecting rod. Refrigeration oil is sealed inside the compressor together with the refrigerant and lubricates sliding parts such as the connecting rod and piston. For example, Patent Document 1 discloses a refrigeration oil containing a specific ester additive. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2015 / 182173 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of one aspect of the present invention is to provide a refrigeration oil having excellent anti-wear properties. [Means for solving the problem]

[0006] The present inventors have found that when an ester of a polyhydric alcohol and a carboxylic acid is added to a base oil, using a carboxylic acid containing an unsaturated carboxylic acid as the carboxylic acid and a partial ester as the ester results in a refrigerating machine oil with excellent anti-wear properties. Specifically, the present inventors have found that the use of a partial ester of a carboxylic acid containing an unsaturated carboxylic acid and a polyhydric alcohol (hereinafter also referred to as an "unsaturated carboxylic acid partial ester") provides superior anti-wear properties compared to the use of a partial ester of a carboxylic acid containing no unsaturated carboxylic acid (containing only a saturated carboxylic acid) and a polyhydric alcohol (hereinafter also referred to as a "saturated carboxylic acid partial ester") or the use of only a complete ester without an unsaturated carboxylic acid partial ester. It is particularly surprising that the wear resistance differs between a refrigerating machine oil containing an unsaturated carboxylic acid partial ester and a refrigerating machine oil containing no unsaturated carboxylic acid partial ester (containing only a complete ester), even when the types of polyhydric alcohol and carboxylic acid constituting the ester are the same.

[0007] One aspect of the present invention is a refrigeration oil containing a base oil and a partial ester of a carboxylic acid and a polyhydric alcohol, wherein the carboxylic acid includes an unsaturated carboxylic acid.

[0008] The unsaturated carboxylic acid may have 12 or more carbon atoms.

[0009] The polyhydric alcohol may include pentaerythritol. The partial ester may include a monoester of pentaerythritol, a diester of pentaerythritol, and a triester of pentaerythritol.

[0010] The carboxylic acid may further include a saturated carboxylic acid, which may have 12 or more carbon atoms.

[0011] Another aspect of the present invention is a working fluid composition for a refrigerating machine, comprising the refrigerating machine oil and a refrigerant. The refrigerant may contain an unsaturated fluorohydrocarbon. [Effects of the Invention]

[0012] According to one aspect of the present invention, a refrigeration oil having excellent anti-wear properties can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described in detail. A refrigerating machine oil according to one embodiment of the present invention contains a base oil and a partial ester of a carboxylic acid and a polyhydric alcohol. The partial ester (including both an unsaturated carboxylic acid partial ester and a saturated carboxylic acid partial ester; hereinafter, the term "partial ester" has the same meaning) is an ester in which some of the hydroxyl groups of a polyhydric alcohol are esterified with a carboxylic acid, and the remainder remain as hydroxyl groups without being esterified. In other words, the partial ester has an ester bond and a hydroxyl group.

[0014] The base oil includes at least one oil selected from the group consisting of mineral oils and synthetic oils (excluding unsaturated carboxylic acid partial esters).

[0015] Examples of mineral oils include paraffinic mineral oils and naphthenic mineral oils, which are obtained by refining lubricating oil fractions obtained by atmospheric distillation and vacuum distillation of crude oil through a 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 types in any ratio.

[0016] Examples of synthetic oils include esters other than unsaturated carboxylic acid partial esters, oxygen-containing synthetic oils such as ethers (polyvinyl ethers, polyalkylene glycols, etc.), carbonates, ketones, silicones, and polysiloxanes, and hydrocarbon-based synthetic oils such as alkylbenzenes, alkylnaphthalenes, polyα-olefins (PAOs), and ethylene α-olefins. The oxygen-containing synthetic oil is preferably an ester or ether other than unsaturated carboxylic acid partial esters.

[0017] Examples of other esters other than the unsaturated carboxylic acid partial esters include monobasic acid esters of monobasic acids and monohydric alcohols, dibasic acid esters of dibasic acids and monohydric alcohols, polyol esters of carboxylic acids and polyhydric alcohols, complex esters, carbonate esters, and mixtures thereof. The other esters are preferably polyol esters of carboxylic acids and polyhydric alcohols (excluding unsaturated carboxylic acid partial esters).

[0018] Examples of such polyol esters include complete esters in which all of the hydroxyl groups of a polyhydric alcohol are esterified with saturated carboxylic acids or unsaturated carboxylic acids, and partial esters in which some of the hydroxyl groups of a polyhydric alcohol are esterified only with saturated carboxylic acids (saturated carboxylic acid partial esters).

[0019] 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 in the polyhydric alcohol is preferably 4 or more, more preferably 5 or more, and preferably 12 or less, more preferably 10 or less. The polyhydric alcohol is preferably a hindered alcohol such as neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, di-(trimethylolpropane), tri-(trimethylolpropane), pentaerythritol, or dipentaerythritol. From the viewpoint of compatibility with the refrigerant, the polyhydric alcohol is preferably pentaerythritol, dipentaerythritol, or a mixture thereof.

[0020] The carboxylic acid constituting the complete ester may be either a saturated carboxylic acid or an unsaturated carboxylic acid, and may be either a linear or branched one. The number of carbon atoms in the carboxylic acid is preferably 4 or more, more preferably 6 or more, and even more preferably 8 or more, and is preferably 18 or less, more preferably 12 or less, and even more preferably 10 or less, and may be preferably 4 to 18, more preferably 6 to 12, and even more preferably 8 to 10.

[0021] Examples of saturated carboxylic acids 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, and octadecanoic acid. Examples of unsaturated carboxylic acids include pentenoic acid, hexenoic acid, heptenoic acid, octenoic acid, nonenoic acid, decenoic acid, undecenoic acid, dodecenoic acid, tridecenoic acid, tetradecenoic acid, pentadecenoic acid, hexadecenoic acid, heptadecenoic acid, and octadecenoic acid. These saturated and unsaturated carboxylic acids may be linear or branched.

[0022] The acid value of the oxygen-containing synthetic oil (preferably ester or ether) may be, for example, 0.1 mgKOH / g or less, preferably 0.05 mgKOH / g or less. The hydroxyl value of the oxygen-containing synthetic oil (preferably ester or ether) may be, for example, 10 mgKOH / g or less, preferably 5 mgKOH / g or less. When the acid value and hydroxyl value are within the above ranges, the stability of the refrigerating machine oil can be further improved when used with an unsaturated fluorohydrocarbon refrigerant. In this specification, the acid value refers to the acid value measured in accordance with JIS K2501:2003. In this specification, the hydroxyl value refers to the hydroxyl value measured in accordance with JIS K0070 "Testing methods for acid value, saponification value, ester value, iodine value, hydroxyl value and unsaponifiable matter of chemical products."

[0023] The content of the base oil may be, for example, 50% by mass or more, 70% by mass or more, or 90% by mass or more, and may be 99% by mass or less, based on the total amount of the refrigerating machine oil.

[0024] The kinematic viscosity of the base oil at 40°C is not particularly limited. 2 / s or more, 10mm 2 / s or more, or 20 mm 2 / s or more, and 2 / s or less or 300 mm 2 The kinematic viscosity of the base oil at 100°C is not particularly limited, but may be, for example, 1 mm 2 / s or more or 2 mm 2 / s or more, and 2 / s or less or 50 mm 2 The kinematic viscosity in this specification refers to the kinematic viscosity measured in accordance with JIS K2283:2000.

[0025] The carboxylic acid constituting the unsaturated carboxylic acid partial ester includes an unsaturated carboxylic acid having an unsaturated bond (carbon-carbon double bond). The number of unsaturated bonds in the unsaturated carboxylic acid may be, for example, 1 or more, 4 or less, 3 or less, or 2 or less, or may be 1.

[0026] The number of carbon atoms of the unsaturated carboxylic acid is preferably 4 or more, more preferably 8 or more, even more preferably 12 or more, and particularly preferably 16 or more, and is preferably 36 or less, more preferably 28 or less, and even more preferably 20 or less, and may be preferably 4 to 36, more preferably 8 to 28, even more preferably 12 to 20, and particularly preferably 14 to 18 or 16 to 20.

[0027] Examples of such unsaturated carboxylic acids include pentenoic acid, hexenoic acid, heptenoic acid, octenoic acid, nonenoic acid, decenoic acid, undecenoic acid, dodecenoic acid, tridecenoic acid, tetradecenoic acid, pentadecenoic acid, hexadecenoic acid, heptadecenoic acid, and octadecenoic acid. Such unsaturated carboxylic acids may be linear or branched. The unsaturated carboxylic acid particularly preferably contains oleic acid as a main component, and may also contain unsaturated fatty acids having 14 to 18 carbon atoms, such as palmitoleic acid, linoleic acid, and linolenic acid.

[0028] The polyhydric alcohol preferably has 2 to 6 hydroxyl groups. The number of carbon atoms in the polyhydric alcohol is preferably 4 to 12, and more preferably 5 to 10. Specifically, hindered alcohols such as neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, di-(trimethylolpropane), tri-(trimethylolpropane), pentaerythritol, and dipentaerythritol are preferred. The polyhydric alcohol preferably contains pentaerythritol because it has a particularly large effect of improving wear resistance (lubricity).

[0029] In the unsaturated carboxylic acid partial ester, at least a part of the hydroxyl groups of the polyhydric alcohol is esterified with the unsaturated carboxylic acid. That is, the partial ester includes the following (I) and (II): (I) A compound in which some of the hydroxyl groups of a polyhydric alcohol are esterified with an unsaturated carboxylic acid, and the remaining hydroxyl groups remain unesterified. (II) A compound in which some of the hydroxyl groups of a polyhydric alcohol are esterified with an unsaturated carboxylic acid, some of the hydroxyl groups are esterified with a saturated carboxylic acid, and the remainder remain unesterified as hydroxyl groups.

[0030] In the case of (II), in other words, the carboxylic acid constituting the unsaturated carboxylic acid partial ester further contains a saturated carboxylic acid. The number of carbon atoms in the saturated carboxylic acid is preferably 4 or more, more preferably 8 or more, and even more preferably 12 or more, and is preferably 36 or less, more preferably 28 or less, and even more preferably 20 or less, and may be preferably 4 to 36, more preferably 8 to 28, even more preferably 12 to 20, and particularly preferably 14 to 18.

[0031] Specific examples of saturated carboxylic acids 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, etc. Such saturated carboxylic acids may be linear or branched.

[0032] For example, when the polyhydric alcohol is pentaerythritol, the unsaturated carboxylic acid partial ester may be one or more selected from a monoester in which one of the four hydroxyl groups of pentaerythritol is esterified, a diester in which two of the four hydroxyl groups are esterified, and a triester in which three of the four hydroxyl groups of pentaerythritol are esterified.

[0033] The unsaturated carboxylic acid partial ester preferably includes monoesters, diesters, and triesters. In this case, the proportion of monoesters in the unsaturated carboxylic acid partial ester may be 1% by mass or more, 5% by mass or more, or 8% by mass or more, and 30% by mass or less, 20% by mass or less, or 15% by mass or less. The proportion of diesters in the unsaturated carboxylic acid partial ester may be 20% by mass or more, 30% by mass or more, or 35% by mass or more, and 60% by mass or less, 50% by mass or less, or 45% by mass or less. The proportion of triesters in the unsaturated carboxylic acid partial ester may be 20% by mass or more, 30% by mass or more, or 35% by mass or more, and 65% by mass or less, 55% by mass or less, or 50% by mass or less.

[0034] The iodine value derived from the unsaturated bond of the partial ester is preferably 20 (gI2 / 100g) or more, more preferably 40 (gI2 / 100g) or more, and even more preferably 50 (gI2 / 100g) or more. The iodine value is preferably 100 (gI2 / 100g) or less, more preferably 80 (gI2 / 100g) or less, and even more preferably 70 (gI2 / 100g) or less. The iodine value in this specification is the iodine value measured in accordance with the indicator titration method of JIS K0070 "Testing methods for acid value, saponification value, ester value, iodine value, hydroxyl value and unsaponifiable matter of chemical products," and refers to the value (gI2 / 100g) obtained by converting the amount of halogen bonded when halogen is reacted with 100g of a sample into grams of iodine.

[0035] The acid value of the unsaturated carboxylic acid partial ester is not particularly limited, but is preferably 5 mgKOH / g or less, and may be 3 mgKOH / g or less, or 2 mgKOH / g or less, or 0.1 mgKOH / g or less, or 0.1 mgKOH / g or more, 0.4 mgKOH / g or more, or 1 mgKOH / g or more.

[0036] The hydroxyl value of the unsaturated carboxylic acid partial ester is not particularly limited, but since it has a partial ester structure, it may be, for example, 10 mgKOH / g or more, preferably 20 mgKOH / g or more, 50 mgKOH / g or more, or 100 mgKOH / g or more, and may be 500 mgKOH / g or less, and preferably 300 mgKOH / g or less or 200 mgKOH / g or less.

[0037] The content of the unsaturated carboxylic acid partial ester is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, even more preferably 0.1% by mass or more or 0.5% by mass or more, based on the total amount of the refrigerating machine oil, from the viewpoint of more suitably exhibiting the effect of improving wear resistance (lubricity). The content of the unsaturated carboxylic acid partial ester is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, from the viewpoint of compatibility with the refrigerant and from the viewpoint of being able to further increase the stability of the refrigerating machine oil.

[0038] The kinematic viscosity at 40°C of the unsaturated carboxylic acid partial ester varies depending on its structure and is not particularly limited. However, in terms of excellent compatibility with the refrigerating machine oil and the refrigerant described later, it is preferably 5 mm 2 / s or more or 10 mm 2 / s or more, and 2 / s or less, 50mm 2 / s or less, or 30 mm 2 The kinematic viscosity of the unsaturated carboxylic acid partial ester at 100°C is not particularly limited, but is preferably 1 mm / s or less. 2 / s or more or 2 mm 2 / s or more, 50mm 2 / s or less, 10mm 2 / s or less, or 8 mm 2 / s or less.

[0039] The viscosity index of the unsaturated carboxylic acid partial ester is not particularly limited, and may be, for example, 80 or more, 120 or more, or 150 or more, and may be 300 or less, 250 or less, or 200 or less. In this specification, the viscosity index refers to a viscosity index measured in accordance with JIS K2283:2000.

[0040] The refrigerating machine oil may further contain additives other than the base oil and the unsaturated carboxylic acid partial ester, such as antioxidants, acid scavengers, antiwear agents, antifoaming agents, metal deactivators, viscosity index improvers, pour point depressants, detergents and dispersants.

[0041] Examples of antioxidants include phenol-based antioxidants and amine-based antioxidants. Examples of phenol-based antioxidants include 2,6-di-tert.-butyl-p-cresol (DBPC), 2,6-di-tert.-butyl-phenol, and 4,4'-methylenebis(2,6-di-tert.-butyl-phenol). Examples of amine-based antioxidants include phenyl-α-naphthylamines and dialkylated diphenylamines. These antioxidants can be used alone or in combination of two or more. The content of the antioxidant may be, for example, 0.01% by mass or more and 5% by mass or less, and preferably 0.1% by mass or more and 3% by mass or less, based on the total amount of the refrigerating machine oil.

[0042] Examples of acid scavengers include epoxy compounds (epoxy acid scavengers). Examples of epoxy compounds include glycidyl ether-type epoxy compounds, glycidyl ester-type epoxy compounds, aryl oxirane compounds, alkyl oxirane compounds, alicyclic epoxy compounds, epoxidized fatty acid monoesters, and epoxidized vegetable oils. The epoxy compound (epoxy acid scavengers) is preferably at least one selected from the group consisting of glycidyl ether-type epoxy compounds and glycidyl ester-type epoxy compounds, and more preferably a glycidyl ether-type epoxy compound, since it allows unsaturated carboxylic acid partial esters and phosphorus-based antiwear agents (described later) to function effectively even at low concentrations. These acid scavengers can be used alone or in combination of two or more. The content of the acid scavengers may be, for example, 0.01% by mass or more and 5% by mass or less, preferably 0.1% by mass or more and 3% by mass or less, based on the total amount of the refrigerating machine oil.

[0043] Examples of anti-wear agents include phosphorus-based anti-wear agents. Examples of phosphorus-based anti-wear agents include phosphate esters, acidic phosphate esters, amine salts of acidic phosphate esters, chlorinated phosphate esters, phosphites, and phosphorothioates. The phosphate esters are preferably triphenyl phosphate (TPP), tricresyl phosphate (TCP), or triphenyl phosphorothioate (TPPT). One type of anti-wear agent can be used alone, or two or more types can be used in combination. The content of the anti-wear agent is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 1% by mass or more, based on the total amount of the refrigerating machine oil, and is preferably 5% by mass or less, more preferably 3% by mass or less.

[0044] The antifoaming agent can be any compound typically used as an antifoaming agent for refrigerating machine oils, including silicones such as dimethyl silicone and fluorosilicone. The antifoaming agent can be used alone or in combination of two or more. The content of the antifoaming agent is preferably 5% by mass or less, more preferably 3% by mass or less, and is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 1% by mass or more, based on the total amount of the refrigerating machine oil.

[0045] Examples of metal deactivators include benzotriazole and benzotriazole derivatives. The metal deactivators can be used alone or in combination of two or more. The content of the metal deactivator is preferably 5% by mass or less, more preferably 3% by mass or less, and is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 1% by mass or more, based on the total amount of the refrigerating machine oil.

[0046] Examples of viscosity index improvers include non-dispersant and dispersant viscosity index improvers. Specific examples include non-dispersant and dispersant polymethacrylates, non-dispersant and dispersant ethylene-α-olefin copolymers or hydrogenated products thereof, polyisobutylene or hydrogenated products thereof, styrene-diene hydrogenated copolymers, polymethacrylate-olefin copolymers, and polyalkylstyrenes. These may be used alone or in combination of two or more. The weight-average molecular weight of these viscosity index improvers may be, for example, 10,000 or more and 1,000,000 or less. The content of the viscosity index improver is preferably 5% by mass or less, more preferably 3% by mass or less, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 1% by mass or more, based on the total amount of the refrigerating machine oil.

[0047] Examples of pour point depressants include polyalkyl(meth)acrylates different from the viscosity index improvers. The content of the pour point depressant is preferably 5% by mass or less, more preferably 3% by mass or less, and preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 1% by mass or more, based on the total amount of the refrigerating machine oil.

[0048] As the detergent-dispersant, a commonly used detergent-dispersant can be used, such as succinimide, polyalkylamine, polyetheramine, etc. These can be used alone or in combination of two or more. The content of the detergent-dispersant is preferably 5% by mass or less, more preferably 3% by mass or less, and preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 1% by mass or more, based on the total amount of the refrigerating machine oil.

[0049] The kinematic viscosity of the refrigerating machine oil at 40°C may be adjusted appropriately depending on the intended use, and is not particularly limited. 2 / s or more, 10mm 2 / s or more, or 20 mm 2 / s or more, and 2 / s or less or 300 mm 2The kinematic viscosity of the refrigerating machine oil at 100°C is not particularly limited, but may be, for example, 1 mm 2 / s or more or 2 mm 2 / s or more, and 2 / s or less or 50 mm 2 / s or less.

[0050] The viscosity index of the refrigerating machine oil is not particularly limited, but may be, for example, 10 or more, 50 or more, or 70 or more, and may be 500 or less, 300 or less, or 250 or less.

[0051] The acid value of the refrigerating machine oil may be, for example, 0.1 mgKOH / g or less, and preferably 0.05 mgKOH / g or less. The hydroxyl value of the refrigerating machine oil may be, for example, 10 mgKOH / g or less, and preferably 5 mgKOH / g or less. When the acid value and hydroxyl value are within the above ranges, the stability of the refrigerating machine oil when used with an unsaturated fluorohydrocarbon refrigerant can be further improved.

[0052] Refrigerating machine oils are usually present in the form of a working fluid composition for a refrigerating machine mixed with a refrigerant in a refrigerating machine equipped with a refrigerant circulation system having a compressor, a condenser, an expansion mechanism, and an evaporator, and serve to lubricate, for example, sliding members. That is, another embodiment of the present invention is a working fluid composition for a refrigerating machine containing the above-mentioned refrigerating machine oil and a refrigerant.

[0053] The content of the refrigerating machine oil in the working fluid composition for a refrigerating machine may be, for example, 1 part by mass or more or 2 parts by mass or more, and 500 parts by mass or less or 400 parts by mass or less, per 100 parts by mass of the refrigerant.

[0054] Examples of the refrigerant include saturated fluorohydrocarbons, unsaturated fluorohydrocarbons, hydrocarbons, fluorinated 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.

[0055] The saturated fluorohydrocarbon is preferably a saturated fluorohydrocarbon having 1 to 3 carbon atoms, more preferably 1 to 2 carbon atoms. Specific examples of saturated fluorohydrocarbon 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), and 1,1 , 1,2,3,3,3-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 thereof.

[0056] The unsaturated fluorohydrocarbon is preferably an unsaturated fluorohydrocarbon having 2 to 4 or 2 to 3 carbon atoms, more preferably a fluoropropene, and even more preferably a fluoropropene having 3 to 5 fluorine atoms. 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, the unsaturated fluorohydrocarbon is preferably one or more selected from HFO-1225ye, HFO-1234ze, and HFO-1234yf.

[0057] 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 (R600a), cyclobutane, methylcyclopropane, 2-methylbutane, normal pentane, and mixtures of two or more of these. Among these, the hydrocarbon is preferably a hydrocarbon that is gaseous at 25°C and 1 atmospheric pressure, and more preferably propane, normal butane, isobutane, 2-methylbutane, or a mixture of these.

[0058] The refrigerating machine oil is preferably used together with a refrigerant containing an unsaturated fluorohydrocarbon, more preferably with a refrigerant containing HFO-1234yf. That is, the refrigerant in the working fluid composition for a refrigerating machine preferably contains an unsaturated fluorohydrocarbon, more preferably HFO-1234yf. The content of the unsaturated fluorohydrocarbon may be preferably 20% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and particularly preferably 80% by mass or more, based on the total amount of the refrigerant.

[0059] The refrigerating machine oil and working fluid composition for a refrigerating machine can be suitably used in refrigerating machines such as air conditioners having reciprocating or rotary hermetic compressors, refrigerators, open or hermetic car air conditioners, dehumidifiers, water heaters, freezers, refrigerated and frozen warehouses, vending machines, showcases, and chemical plants, as well as refrigerating machines having centrifugal compressors.

[0060] The refrigerating machine oil and the working fluid composition for a refrigerating machine lubricate the sliding members in the compressor. The sliding members preferably contain aluminum. The refrigerating machine oil is particularly suitable for lubricating a combination of a sliding member containing iron and a sliding member containing aluminum. [Example]

[0061] The present invention will be described in more detail below based on examples, but the present invention is not limited to the following examples.

[0062] [Refrigerating machine oil] Using the components shown below, refrigerating machine oils having the compositions (mass % based on the total amount of refrigerating machine oil) shown in Table 1 were prepared. All of the refrigerating machine oils had an acid value of 0.05 mg KOH / g or less and a hydroxyl value of 5 mg KOH / g or less. (A) A base oil (kinematic viscosity at 40 ° C: 83.29 mmHg) obtained by mixing the following a1 and a2 in a mass ratio of 75 / 25: 2 / s, kinematic viscosity at 100°C: 9.63mm 2 / s, acid value: 0.05 mg KOH / g or less, hydroxyl value: 5 mg KOH / g or less) a1: Complete ester of pentaerythritol and a mixed carboxylic acid of 2-ethylhexanoic acid / 3,5,5-trimethylhexanoic acid (mixing ratio (mass ratio): 48 / 52) a2: Complete ester of dipentaerythritol and a mixed carboxylic acid of 2-ethylhexanoic acid / 3,5,5-trimethylhexanoic acid (mixing ratio (mass ratio): 50 / 50) (B) A mixture of partial esters (monoesters: 10 mass%, diesters: 37 mass%, triesters: 40 mass%) of pentaerythritol and mixed carboxylic acids having 14 to 18 carbon atoms, mainly composed of octadecenoic acid and hexadecanoic acid (octadecenoic acid: 87 mass%, hexadecanoic acid: 5 mass%, other carboxylic acids: 8 mass%), and complete esters (13 mass%) of pentaerythritol and mixed carboxylic acids having 14 to 18 carbon atoms, mainly composed of octadecenoic acid and hexadecanoic acid (octadecenoic acid: 87 mass%, hexadecanoic acid: 5 mass%, other carboxylic acids: 8 mass%) (iodine value: 66.3 (gI2 / 100 g), acid value: 1.5 mgKOH / g, hydroxyl value: 130 mgKOH / g, kinematic viscosity at 40°C: 12.5 mm 2 / s, 100℃ kinematic viscosity: 3.6mm 2 / s, viscosity index: 190) (b1) A complete ester of pentaerythritol and a mixed carboxylic acid having 14 to 18 carbon atoms, mainly composed of octadecenoic acid and hexadecanoic acid (octadecenoic acid: 88% by mass, hexadecanoic acid: 5% by mass, other carboxylic acids: 7% by mass) (iodine value: 88 (gI2 / 100g), acid value: 0.4 mgKOH / g, hydroxyl value: 6 mgKOH / g, kinematic viscosity at 40°C: 66 mm 2 / s, 100℃ kinematic viscosity: 12.5mm 2 / s, viscosity index: 188) (b2) A mixture of a partial ester of trimethylolpropane and decanoic acid (monoester: 27% by mass, diester: 46% by mass) and a complete ester of trimethylolpropane and decanoic acid (27% by mass). (C) Phosphorus-based anti-wear agent (D) Epoxy-based acid scavenger (D1) Glycidyl ester type epoxy compound (D2) Glycidyl ether type epoxy compound (E) Phenolic antioxidants

[0063] [Wear resistance evaluation] A closed-type FALEX testing machine (pin: 3135 steel (sliding component containing iron), V-block: 4032Al (sliding component containing aluminum)) was used, and the test conditions were a test load of 0.3 MPaG, a test time of 5 hours, a rotation speed of 290 rpm, and a test temperature of 25°C (room temperature). Test pieces conforming to the ASTM D2670 wear volume test were used, and a wear resistance test was conducted in an environment where 2,3,3,3-tetrafluoropropene refrigerant was blown in (refrigerant blowing rate: 10 L / h). The average block wear width (mm) after the test was measured. The results are shown in Table 1. In Table 1, the smaller the wear width, the better the wear resistance.

[0064] [Table 1]

Claims

1. A base oil, a partial ester of a carboxylic acid and a polyhydric alcohol; Contains The carboxylic acid comprises an unsaturated carboxylic acid and a saturated carboxylic acid.

2. The refrigerating machine oil according to claim 1, wherein the unsaturated carboxylic acid has 12 or more carbon atoms.

3. The refrigerating machine oil according to claim 1 or 2, wherein the polyhydric alcohol comprises pentaerythritol.

4. The refrigerator oil according to claim 3 , wherein the partial esters include a monoester of pentaerythritol, a diester of pentaerythritol, and a triester of pentaerythritol.

5. The refrigerating machine oil according to any one of claims 1 to 4, wherein the saturated carboxylic acid has 12 or more carbon atoms.

6. The refrigerating machine oil according to any one of claims 1 to 5, A refrigerant; A working fluid composition for a refrigerator comprising:

7. The working fluid composition for a refrigerating machine according to claim 6, wherein the refrigerant comprises an unsaturated fluorohydrocarbon.

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