Refrigerating machine oil, working fluid composition for refrigerating machine, lubrication method, and method for producing refrigerating machine oil

Abstract

To a provide a refrigerating machine oil that exhibits an excellent friction property in a lubrication region in which a friction coefficient increases sharply as a sliding speed decreases (an elastohydrodynamic lubrication region or a mixed lubrication region).SOLUTION: The refrigerating machine oil comprises a lubricant base oil and a polymer additive, and has a residual carbon content of 0.05 mass% or more in its 10% residual oil.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a refrigeration oil, a working fluid composition for a refrigerator, a lubrication method, and a method for producing a refrigeration oil.

Background Art

[0002] Refrigerators and the like have a refrigerant circulation system having a compressor, a condenser, an expansion mechanism (expansion valve, capillary tube), an evaporator, etc., and heat exchange is performed by circulating the refrigerant in this refrigerant circulation system.

[0003] Compressors for refrigerators include rotary compressors, piston-crank compressors, etc. For example, in a piston-crank compressor, the rotational motion of a motor is converted into a reciprocating motion by a connecting rod, and the piston connected to the connecting rod is reciprocated to compress the refrigerant. Refrigeration oil is enclosed in the compressor together with the refrigerant, and lubricates sliding members such as connecting rods and pistons. As such a refrigeration oil, for example, Patent Document 1 below discloses a refrigeration oil containing a predetermined base oil, a phosphorus-based extreme pressure agent, and an ester-based additive.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When the viscosity of conventional refrigeration oils is reduced, for example, it is effective for reducing friction in the hydrodynamic lubrication regime. However, in regions with low sliding speeds, such as the elastohydrodynamic lubrication regime, the mixed lubrication regime, or the boundary lubrication regime, the effect of reducing friction cannot be fully achieved, and there is still room for improvement in this regard. The present invention has been made in view of the above circumstances, and its object is to provide a refrigeration oil having excellent friction characteristics, a refrigeration machine working fluid composition containing the refrigeration oil, a lubrication method using the refrigeration oil, and a production method of the refrigeration oil in a lubrication regime (elastohydrodynamic lubrication regime or mixed lubrication regime) where the friction coefficient rapidly increases as the sliding speed decreases.

Means for Solving the Problems

[0006] To solve the above problems, the present inventors first found that in a refrigeration oil containing a polymer additive, the residual carbon content of 10% residual oil serves as an index of friction characteristics. Then, as a result of further studies based on such findings, the present inventors found that the friction characteristics of the refrigeration oil can be improved by adjusting the residual carbon content of 10% residual oil of the refrigeration oil, and thus completed the present invention.

[0007] That is, the present invention provides a refrigeration oil containing a lubricating oil base oil and a polymer additive, wherein the residual carbon content of 10% residual oil is 0.05% by mass or more.

[0008] In the present invention, the residual carbon content of 10% residual oil means a value measured by the micro method in accordance with JIS K2270-2:2009.

[0009] The lubricating oil base oil may contain mineral oil.

[0010] The polymer additive may be a (co)polymer derived from an unsaturated carboxylic acid ester.

[0011] The residual carbon content of the polymer additive may be 0.2% by mass or more.

[0012] The present invention also provides a refrigerant working fluid composition containing a refrigerant and the refrigerant oil according to the present invention.

[0013] The present invention further provides a lubrication method characterized by using the refrigerant oil according to the present invention in a refrigerant circulation system having a compressor, a condenser, an expansion mechanism, and an evaporator.

[0014] The present invention further provides a method for producing a refrigerant oil, which comprises mixing a polymer additive with a lubricating base oil so that the residual carbon content of 10% residual oil of the refrigerant oil is 0.05% by mass or more.

Advantages of the Invention

[0015] According to the present invention, it is possible to provide a refrigerant oil having excellent friction characteristics, a refrigerant working fluid composition containing the refrigerant oil, a lubrication method using the refrigerant oil, and a method for producing the refrigerant oil in a lubrication region (such as a mixed lubrication region) where the friction coefficient rapidly increases as the sliding speed decreases.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present invention will be described in detail.

[0017] The refrigerant oil according to this embodiment includes a lubricating base oil and a polymer additive. The residual carbon content of 10% residual oil of this refrigerant oil is 0.05% by mass or more.

[0018] The lubricating base oil may be any of mineral oil, synthetic oil, or a mixture of both, but preferably contains mineral oil from the viewpoint of exhibiting more excellent friction characteristics in a region where the sliding speed is low.

[0019] As the mineral oil, there are mentioned mineral oils such as paraffinic mineral oils and naphthenic mineral oils obtained by subjecting the lubricating oil fraction obtained by atmospheric distillation and vacuum distillation of crude oil to purification treatments such as solvent dewaxing, solvent extraction, hydrocracking, solvent deoiling, catalytic deoiling, hydrorefining, sulfuric acid washing, and clay treatment, alone or in appropriate combination of two or more. In particular, paraffinic mineral oils are preferably used. These mineral oils may be used alone or in combination of two or more in any ratio.

[0020] %C of the mineral oil P and %C N The ratio of (%C P / %C N ) may be, for example, 0.2 or more, preferably 0.5 or more, more preferably 1 or more, and still more preferably 1.1 or more.

[0021] %C of the paraffinic mineral oil P and %C N The ratio of (%C P / %C N ) may preferably be greater than 1, more preferably 1.1 or more, and still more preferably 1.5 or more. When the %C P / %C N of the paraffinic mineral oil is greater than 1, the flash point (COC) is improved (for example, 100°C or higher, preferably 120°C or higher), and a refrigerating machine oil with more excellent friction characteristics can be obtained. %C P and %C N in the present invention each mean the values measured by the method (n-d-M ring analysis) conforming to ASTM D3238-95(2010). Also, the flash point (COC) means the flash point by the Cleveland open cup method measured conforming to JIS K2265-4:2007.

[0022] When the lubricating base oil contains mineral oil, the lubricating base oil may consist only of mineral oil (i.e., the content of mineral oil is 100% by mass based on the total amount of the lubricating base oil), or may further contain base oil components other than mineral oil. Examples of base oil components other than mineral oil include synthetic oils such as synthetic hydrocarbon oils and oxygen-containing oils. In this case, the content of mineral oil may be 50% by mass or more, 70% by mass or more, or 90% by mass or more based on the total amount of the lubricating base oil.

[0023] Examples of synthetic hydrocarbon oils include alkylbenzenes, alkylnaphthalenes, polyalpha-olefins (PAO), polybutenes, ethylene-alpha-olefin copolymers, and the like.

[0024] Examples of oxygen-containing oils include esters, ethers (e.g., polyalkylene glycols (PAG), polyvinyl ethers (PVE)), carbonates, ketones, silicones, polysiloxanes, and the like. Examples of esters include monoesters, polyol esters, aromatic esters, dibasic acid esters, complex esters, carbonic acid esters, and mixtures thereof. Among them, it is preferable to use a monoester of a monohydric aliphatic alcohol and a monohydric fatty acid, and if necessary, it is desirable to use a mixture of the monoester and a polyol ester of a di- to hexavalent alcohol and a monohydric fatty acid. Examples of such monohydric aliphatic alcohols constituting such esters include monohydric aliphatic alcohols having 1 to 20 carbon atoms, preferably 4 to 18 carbon atoms, and more preferably 4 to 12 carbon atoms. Examples of such monohydric fatty acids constituting such esters include monohydric fatty acids having 1 to 20 carbon atoms, preferably 4 to 18 carbon atoms, and more preferably 4 to 12 carbon atoms. Examples of such di- to hexavalent alcohols constituting such esters preferably include neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol, and the like. Examples of ethers include polyvinyl ethers, polyalkylene glycols, polyphenyl ethers, perfluoroethers, and mixtures thereof.

[0025] The kinematic viscosity of the lubricating base oil at 40 °C is not particularly limited, but from the viewpoint of effectively reducing the friction coefficient in the region of low sliding speed, it is preferably 50 mm 2 / s or less, more preferably 20 mm 2 / s or less, and from the viewpoint of significantly reducing the frictional resistance in the fluid lubrication region, it is still more preferably 10 mm 2 / s or less, particularly preferably 5 mm 2 / s or less, very preferably 4 mm 2 / s or less. The kinematic viscosity of the lubricating base oil at 40 °C is not particularly limited, but may be, for example, 1 mm 2 / s or more. The kinematic viscosity of the lubricating base oil at 100 °C is preferably 0.5 mm 2 / s or more, more preferably 0.8 mm 2 / s or more, still more preferably 1 mm 2 / s or more. The kinematic viscosity of the lubricating base oil at 100 °C is preferably 10 mm 2 / s or less, more preferably 5 mm 2 / s or less, still more preferably 3 mm 2 / s or less, particularly preferably 2 mm 2 / s or less or less than 2.0 mm 2 / s may be. The kinematic viscosity in the present invention means the kinematic viscosity measured in accordance with JIS K2283:2000.

[0026] The content of the lubricating base oil may be 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more based on the total amount of the refrigerant oil.

[0027] The refrigerant oil according to the present embodiment contains a polymer additive. By containing the polymer additive, the residual carbon content of 10% residual oil of the refrigerant oil described later can be efficiently adjusted, and the friction characteristics of the refrigerant oil can be effectively improved. As described above, the lubricating base oil may contain base oil components such as PAO, PAG, and PVE. In that case, the polymer additive is a polymer different from these base oil components. The polymer additive may consist of a polymer alone, or may contain a diluent oil or the like having a different structure from the polymer.

[0028] Examples of the polymer additive specifically include at least one selected from (co)polymers of unsaturated carboxylic acid esters and (co)polymers of other polymerizable unsaturated compounds.

[0029] The (co)polymer of an unsaturated carboxylic acid ester is a (co)polymer having an unsaturated carboxylic acid ester as an essential monomer, and is not particularly limited as long as it is such a (co)polymer. It may be a polymer of one kind of unsaturated carboxylic acid ester, a copolymer of two or more kinds of unsaturated carboxylic acid esters, or a copolymer of one kind or two or more kinds of unsaturated carboxylic acid esters and other polymerizable unsaturated compounds. Examples of the unsaturated carboxylic acid constituting the unsaturated carboxylic acid ester include unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, and unsaturated dicarboxylic acids such as maleic acid, fumaric acid, citraconic acid, mesaconic acid, and itaconic acid. Examples of the alcohol constituting the unsaturated carboxylic acid ester include alcohols having 1 to 20 carbon atoms, which are usually monohydric alcohols having 1 to 20 carbon atoms, preferably monohydric alcohols having 1 to 8 carbon atoms, more preferably monohydric alcohols having 4 to 8 carbon atoms, but may also be polyhydric alcohols.

[0030] The other polymerizable unsaturated compounds are not particularly limited, but include the unsaturated carboxylic acids or their anhydrides exemplified as the unsaturated carboxylic acids constituting the above-described unsaturated carboxylic acid esters, and unsaturated hydrocarbon compounds having 2 to 20 carbon atoms. Among them, α-olefins having 2 to 20 carbon atoms, styrene, and the like are included. Examples of the copolymer of an unsaturated carboxylic acid ester and other polymerizable unsaturated compounds include, for example, a copolymer of an unsaturated carboxylic acid ester and an α-olefin having 2 to 20 carbon atoms as a preferred example.

[0031] Specific examples of the (co)polymer of an unsaturated carboxylic acid ester in the present invention include, for example, a (co)polymer of an unsaturated carboxylic acid ester having a structural unit represented by the general formula (1).

Chemical formula

[0032] In general formula (1), R 1 , R 2 is hydrogen or a methyl group, and at least one of R 3 , R 4 represents a group represented by C(=O)OR 5 , and the other of R 3 , R 4 represents hydrogen, a hydrocarbon group or a group represented by C(=O)OR 5 . Here, R 5 is a hydrocarbon group or a group represented by -(R 6 )a-E or (R 7 )b-R 8 , R 6 is an alkylene group, preferably an alkylene group having 1 to 30 carbon atoms, E represents an amine residue or a heterocyclic residue preferably containing 1 to 2 nitrogen atoms and preferably 0 to 2 oxygen atoms, a is an integer, preferably an integer of 0 or 1, R 7 is an oxyalkylene group, preferably an oxyalkylene group having 1 to 4 carbon atoms, b is an integer, preferably an integer of 1 to 10, and R 8 represents a hydrogen atom or a hydrocarbon group, preferably a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.

[0033] The hydrocarbon group in the above general formula (1) is preferably a hydrocarbon group having 1 to 30 carbon atoms, more preferably an alkyl group, such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, an icosyl group, a docosyl group, a tetracosyl group, a hexacosyl group, an octacosyl group, etc. (these alkyl groups may be linear or branched). etc. can be exemplified.

[0034] The alkylene group in the general formula (1) is preferably an alkylene group having 1 to 30 carbon atoms, and examples thereof include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group, an undecylene group, a dodecylene group, a tridecylene group, a tetradecylene group, a pentadecylene group, a hexadecylene group, a heptadecylene group, an octadecylene group, etc. (these alkylene groups may be linear or branched).

[0035] When E is an amine residue, specific examples thereof include a dimethylamino group, a diethylamino group, a dipropylamino group, a dibutylamino group, an anilino group, a toluidino group, a xylylidino group, an acetylamino group, a benzoylamino group, etc. When it is a heterocyclic residue, specific examples thereof include a morpholino group, a pyrrolyl group, a pyrrolino group, a pyridyl group, a methylpyridyl group, a pyrrolidinyl group, a piperidinyl group, a quinonyl group, a pyrrolidonyl group, a pyrrolidono group, an imidazolinyl group, a pyrazino group, etc.

[0036] More specifically, as the (co)polymer of the unsaturated carboxylic acid ester, a (co)polymer of a (meth)acrylic acid ester or a copolymer of an unsaturated carboxylic acid ester and an α-olefin is preferably exemplified, and a copolymer of an unsaturated carboxylic acid ester and an α-olefin is particularly preferred.

[0037] The (co)polymer of the (meth)acrylic acid ester is a (co)polymer having a structural unit represented by the general formula (1), and R 1 is hydrogen, R 2 is hydrogen or a methyl group, R 3 is hydrogen, R 4 is a group represented by C(=O)OR 5 Here, R 5 is a hydrocarbon group, -(R 6 )a-E or -(R 7 )b-R 8 represents a group represented by, and R 6is an alkylene group, preferably an alkylene group having 1 to 30 carbon atoms, E represents an amine residue or a heterocyclic residue containing preferably 1 to 2 nitrogen atoms and preferably 0 to 2 oxygen atoms, a is an integer, preferably an integer of 0 or 1, R 7 is an oxyalkylene group, preferably an oxyalkylene group having 1 to 4 carbon atoms, b is an integer, preferably an integer of 1 to 10, R 8 represents a hydrogen atom or a hydrocarbon group, preferably a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. Further, as the (co)polymer of (meth)acrylic acid ester, R 1 is hydrogen, R 2 is hydrogen or a methyl group, R 3 is hydrogen, R 4 is C(=O)OR 5 and R 5 is preferably a copolymer selected from two or more (meth)acrylic acid esters in which R is a hydrocarbon group.

[0038] As the copolymer of an unsaturated carboxylic acid ester and an α-olefin, a copolymer having a structural unit represented by the general formula (1) and a structural unit represented by the general formula (2) is mentioned as a more preferable example.

Chemical formula

[0039] Here, R 1 and R 2 in the general formula (1) are hydrogen or a methyl group, at least one of R 3 and R 4 represents a group represented by C(=O)OR 5 , and the other of R 3 and R 4 represents hydrogen, a hydrocarbon group or a group represented by C(=O)OR 5 . Here, R 5 is a hydrocarbon group, preferably a hydrocarbon group having 1 to 30 carbon atoms, -(R 6 )a-E or -(R 7 )c-R 8 represents a group represented by, and R 6represents an alkylene group, E represents an amine residue or a heterocyclic residue containing preferably 1 to 2 nitrogen atoms and preferably 0 to 2 oxygen atoms, a is an integer, preferably an integer of 0 or 1, R 7 represents an oxyalkylene group, preferably an oxyalkylene group having 1 to 4 carbon atoms, b is an integer, preferably an integer of 1 to 10, R 8 represents hydrogen or a hydrocarbon group, preferably hydrogen or an alkyl group having 1 to 8 carbon atoms. Also, R 5 is preferably a hydrocarbon group having 1 to 20 carbon atoms, more preferably a hydrocarbon group having 3 to 8 carbon atoms.

[0040] The copolymer of an unsaturated carboxylic acid ester and an α-olefin in the present invention is preferably at least one selected from a copolymer of a (meth)acrylic acid ester and an α-olefin and a copolymer of an unsaturated dicarboxylic acid ester and an α-olefin, and any of them may be used, but a copolymer of an unsaturated dicarboxylic acid ester and an α-olefin is more preferred.

[0041] Specific examples of this unsaturated dicarboxylic acid include maleic acid, fumaric acid, citraconic acid, mesaconic acid, itaconic acid, and the like.

[0042] Preferred examples of this unsaturated dicarboxylic acid ester include, for example, diesters of these unsaturated dicarboxylic acids such as maleic acid, fumaric acid, citraconic acid, mesaconic acid, itaconic acid, and aliphatic alcohols having 3 to 8 carbon atoms such as propanol, butanol, pentanol, hexanol, heptanol, and octanol. In the case of maleic acid ester, dimethyl maleate, diethyl maleate, dipropyl maleate, dibutyl maleate, dipentyl maleate, dihexyl maleate, diheptyl maleate, dioctyl maleate, etc. are cited as preferred examples.

[0043] Also, R in the general formula (2) 9It is preferably hydrogen or a hydrocarbon group having 1 to 18 carbon atoms, more preferably an alkyl group having 1 to 18 carbon atoms, and still more preferably an alkyl group having 4 to 16 carbon atoms. The structural unit of the general formula (2) is derived from an α-olefin. Specific examples of this α-olefin include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene and the like.

[0044] In addition, the molar ratio of the α-olefin to the carboxylic acid ester when producing the copolymer of the unsaturated carboxylic acid ester and the α-olefin is not particularly limited, but is preferably 1:9 to 9:1, more preferably 3:7 to 7:3.

[0045] The number average molecular weight (Mn) of the polymer additive is preferably 300 or more, more preferably 1000 or more, still more preferably 1500 or more, preferably 500000 or less, more preferably 50000 or less, still more preferably 30000 or less, and may be 20000 or less or 15000 or less.

[0046] Also, the weight average molecular weight (Mw) of the polymer additive is preferably 400 or more, more preferably 2000 or more, more preferably 3000 or more, preferably 1000000 or less, more preferably 100000 or less, still more preferably 50000 or less, and may be 30000 or less, 20000 or less or 15000 or less.

[0047] Also, the value of Mw / Mn of the polymer additive is preferably 1.2 or more, more preferably 1.5 or more, still more preferably 1.7 or more, particularly preferably 2 or more, preferably 5 or less, more preferably 3.5 or less, and may be 3 or less.

[0048] In addition, the "number average molecular weight (Mn)" and "weight average molecular weight (Mw)" in this specification refer to the number average molecular weight and weight average molecular weight in terms of polystyrene determined by gel permeation chromatography (GPC) (standard substance: polystyrene) using an APC XT column manufactured by Waters Corporation for the column and tetrahydrofuran for the mobile phase. In the measurement of these average molecular weights, when the polymer additive contains a third component such as a diluent oil with a different structure from the polymer, these average molecular weights indicate the values measured after excluding the third component.

[0049] Also, the kinematic viscosity of the polymer additive at 100°C is preferably 10 mm 2 / s or more, more preferably 20 mm 2 / s or more, still more preferably 100 mm 2 / s or more, and preferably 10000 mm 2 / s or less, more preferably 1000 mm 2 / s or less, still more preferably 800 mm 2 / s or less, and may be 500 mm 2 / s or less.

[0050] Also, the kinematic viscosity of the polymer additive at 40°C is preferably 100 mm 2 / s or more, more preferably 200 mm 2 / s or more, still more preferably 400 mm 2 / s or 400 mm 2 / s exceeding, and may be 500 mm 2 / s or more or 1000 mm 2 / s or more, and preferably 100000 mm 2 / s or less, more preferably 20000 mm 2 / s or less, still more preferably 15000 mm 2 / s or less, and may be 10000 mm 2 / s or less or 5000 mm 2 / s or less.

[0051] The viscosity index of the polymer additive is preferably 80 or more, more preferably 140 or more, may be 180 or more or 200 or more, preferably 400 or less, more preferably 300 or less, and may be 250 or less.

[0052] The polymer additive preferably has a residual carbon content within a predetermined range when evaporated and thermally decomposed. Although the reason is unclear, it is presumed that the precursor can reduce the friction coefficient in a predetermined sliding speed range. The residual carbon content of the polymer additive is, for example, 0.2% by mass or more, preferably 0.5% by mass or more, more preferably 1% by mass or more, still more preferably 1.5% by mass or more, may be 2% by mass or more or 2.5% by mass or more, preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 4% by mass or less, and may be 3.5% by mass or less.

[0053] Note that the residual carbon content of the polymer additive in this specification means the residual carbon content measured by the micro method in accordance with JIS K2270-2:2009.

[0054] The ratio of the value of the residual carbon content (% by mass) to the value of the kinematic viscosity (mm 2 / s) of the polymer additive at 100°C is preferably 0.001 or more, more preferably 0.002 or more, preferably 0.1 or less, and more preferably 0.05 or less. By setting this ratio within the above range, thickening of the refrigeration oil can be suppressed by adding a small amount of the polymer additive, and the friction coefficient reduction effect can be effectively exerted.

[0055] By applying the polymer additive within the above range, the friction coefficient at each sliding speed of the refrigeration oil of the present invention and the friction coefficient in a predetermined sliding speed range, particularly in the elastohydrodynamic lubrication region or the mixed lubrication region where the friction coefficient increases rapidly, can be effectively reduced.

[0056] The content of the above-mentioned polymer additive is not particularly limited. However, from the perspective of further improving the friction characteristics of the refrigeration oil, based on the total amount of the refrigeration oil, it is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, still more preferably 0.8% by mass or more. From the perspective of suppressing an increase in the viscosity of the refrigeration oil and maintaining a low friction coefficient even in a region with a relatively high sliding speed, it is preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 3% by mass or less, particularly preferably 2% by mass or less, may be 1.5% by mass or less, and may be 1% by mass or less or less than 1% by mass. The polymer additive may be a polymer alone or may contain a third component such as a diluent oil having a structure different from that of the polymer. In this case, the preferred range of the content of the above-mentioned polymer additive can be read as the preferred range of the content of the polymer.

[0057] The refrigeration oil according to this embodiment may further contain other additives in addition to the above-mentioned components as long as the effects of the present invention are not significantly impaired. Examples of the additives include antioxidants, acid scavengers, extreme pressure agents, metal deactivators, antiwear agents, pour point depressants, and detergent dispersants. The content of these additives may be 10% by mass or less or 5% by mass or less based on the total amount of the refrigeration oil.

[0058] Examples of the antioxidant include phenolic antioxidants and amine antioxidants. Examples of the phenolic 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), etc. Examples of the amine antioxidant 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 is, for example, 0.01 to 5% by mass, preferably 0.1 to 3% by mass based on the total amount of the refrigeration oil.

[0059] Examples of the acid scavenger include epoxy compounds (epoxy-based acid scavengers). Examples of the epoxy compounds include glycidyl ether type epoxy compounds, glycidyl ester type epoxy compounds, aryloxirane compounds, alkyloxirane compounds, alicyclic epoxy compounds, epoxidized fatty acid monoesters, epoxidized vegetable oils, and the like. These acid scavengers can be used alone or in combination of two or more. The content of the acid scavenger is, for example, 0.01 to 5% by mass, preferably 0.1 to 3% by mass based on the total amount of the refrigeration oil.

[0060] Examples of the extreme pressure agent include phosphorus-based extreme pressure agents. Examples of the phosphorus-based extreme pressure agents include phosphate esters, acidic phosphate esters, amine salts of acidic phosphate esters, chlorinated phosphate esters, phosphite esters, phosphorothioates, and the like. The phosphate ester is preferably triphenyl phosphate (TPP), tricresyl phosphate (TCP), or triphenyl phosphorothionate (TPPT). These extreme pressure agents can be used alone or in combination of two or more. The content of the extreme pressure agent is, for example, 0.01 to 5% by mass, preferably 0.1 to 3% by mass based on the total amount of the refrigeration oil.

[0061] The residual carbon content of 10% residual oil of the refrigeration oil is 0.05% by mass or more, preferably 0.10% by mass or more, more preferably 0.15% by mass or more, and may be 0.20% by mass or more or exceed 0.20% by mass from the viewpoint of reducing the friction coefficient. The upper limit of the residual carbon content of 10% residual oil of the refrigeration oil may be, for example, 0.6% by mass or less or 0.4% by mass or less from the viewpoint of the balance between the friction reduction effect by the polymer additive and the viscosity reduction. The residual carbon content of 10% residual oil in the present invention means the residual carbon content of 10% residual oil measured by the micro method in accordance with JIS K2270-2:2009.

[0062] The kinematic viscosity of the refrigeration oil at 40 °C is not particularly limited, but is preferably 50 mm 2 / s or less, more preferably 20 mm 2 / s or less, and from the viewpoint of more effectively reducing the friction coefficient, preferably 10 mm 2 / s or less, more preferably 5 mm 2 / s or less, still more preferably 4 mm 2 / s or less. The lower limit of the kinematic viscosity of the refrigeration machine oil at 40 °C is not particularly limited, but for example, it may be 1 mm 2 / s or more or 2 mm 2 / s or more. The kinematic viscosity of the refrigeration machine oil at 100 °C is preferably 0.5 mm 2 / s or more, more preferably 0.8 mm 2 / s or more, still more preferably 1 mm 2 / s or more. The kinematic viscosity of the refrigeration machine oil at 100 °C is preferably 10 mm 2 / s or less, more preferably 5 mm 2 / s or less, still more preferably 3 mm 2 / s or less or 2 mm 2 / s or less.

[0063] As a method for producing the refrigeration machine oil according to the present embodiment, a polymer additive may be mixed with a lubricating base oil so that the residual carbon content of 10% residual oil of the refrigeration machine oil is 0.05% by mass or more. In the refrigeration machine oil according to the present embodiment, the ratio of the kinematic viscosity of the refrigeration machine oil at 40 °C before and after blending the polymer additive (kinematic viscosity at 40 °C after blending the polymer additive (Va) / kinematic viscosity at 40 °C before blending the polymer additive (Vb)) is preferably 1.01 or more, more preferably 1.02 or more, preferably 1.5 or less, more preferably 1.2 or less, still more preferably 1.1 or less, and particularly preferably 1.08 or less. By suppressing the thickening by the polymer additive to a low level, it is possible to obtain a refrigeration machine oil capable of reducing the friction coefficient in the elastohydrodynamic lubrication region or the mixed lubrication region while maintaining a relatively low friction coefficient even in the fluid lubrication region.

[0064] Incidentally, the kinematic viscosity (Vb) at 40°C before adding the polymer additive can be read as the kinematic viscosity at 40°C of the lubricating base oil described above, and the kinematic viscosity (Va) at 40°C after adding the polymer additive can be read as the kinematic viscosity at 40°C of the refrigeration machine oil described above. In the present embodiment, it is particularly preferable that the Va is 1 mm 2 / s or more and 4 mm 2 / s or less and the Va / Vb ratio is 1.01 or more and 1.2 or less.

[0065] The viscosity index of the refrigeration machine oil may be -50 or more, preferably 0 or more, more preferably 50 or more, and may be 200 or less. The viscosity index in the present invention means the viscosity index measured in accordance with JIS K2283:2000.

[0066] The pour point of the refrigeration machine oil is preferably -10°C or lower, more preferably -20°C or lower. The pour point in the present invention means the pour point measured in accordance with JIS K2269:1987.

[0067] The volume resistivity of the refrigeration machine oil is preferably 1.0×10 9 Ω·m or more, more preferably 1.0×10 10 Ω·m or more, still more preferably 1.0×10 11 Ω·m or more. The volume resistivity in the present invention means the volume resistivity at 25°C measured in accordance with JIS C2101:1999.

[0068] The water content of the refrigeration machine oil may be preferably 200 ppm or less, more preferably 100 ppm or less, still more preferably 50 ppm or less based on the total amount of the refrigeration machine oil.

[0069] The acid value of the refrigeration machine oil is preferably 1.0 mgKOH / g or less, more preferably 0.1 mgKOH / g or less. The hydroxyl value of the refrigeration machine oil is, for example, 10 mgKOH / g or less, preferably 5 mgKOH / g or less, more preferably 2 mgKOH / g or less.

[0070] The ash content of the refrigeration oil is preferably 100 ppm or less, more preferably 50 ppm or less. The ash content in the present invention means the ash content measured in accordance with JIS K2272:1998.

[0071] The low-temperature two-layer separation temperature of the refrigeration oil and the refrigerant is, for example, when the oil rate (the amount of refrigeration oil collected (g) / the total amount of refrigeration oil and refrigerant collected (g)×100) (%) is 20%, preferably 10°C or less, more preferably 0°C or less, still more preferably -20°C or less, and may be -30°C or less. Examples of such refrigerants include hydrocarbon refrigerants such as propane and isobutane.

[0072] The refrigeration oil according to the present embodiment usually exists in the form of a refrigeration machine working fluid composition mixed with a refrigerant and lubricates in a refrigeration machine equipped with a refrigerant circulation system having a compressor, a condenser, an expansion mechanism, and an evaporator. That is, the refrigeration machine working fluid composition according to the present embodiment contains the above refrigeration oil and the refrigerant, and the lubrication method according to the present embodiment lubricates the above refrigeration oil in the above refrigerant circulation system. The content of the refrigeration oil in the refrigeration machine working fluid composition may be 1 to 500 parts by mass, or 2 to 400 parts by mass with respect to 100 parts by mass of the refrigerant.

[0073] Examples of refrigerants include hydrocarbon refrigerants, saturated fluorinated hydrocarbon refrigerants, unsaturated fluorinated hydrocarbon refrigerants, fluorine-containing ether-based refrigerants such as perfluoroethers, bis(trifluoromethyl)sulfide refrigerant, trifluoroiodomethane refrigerant, and natural refrigerants such as ammonia and carbon dioxide.

[0074] The hydrocarbon refrigerant 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, or a mixture of two or more of these. Among these, the hydrocarbon refrigerant is preferably a gaseous hydrocarbon refrigerant at 25°C and 1 atm, and more preferably propane, normal butane, isobutane, 2-methylbutane, or a mixture of these.

[0075] The saturated fluorinated hydrocarbon refrigerant is preferably a saturated fluorinated hydrocarbon having 1 to 3 carbon atoms, more preferably 1 to 2 carbon atoms. Specific examples of the saturated fluorinated hydrocarbon refrigerant 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), 1,1,1,2,3,3,3-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.

[0076] The saturated hydrofluorocarbon refrigerant is appropriately selected from the above according to the application and required performance. The saturated hydrofluorocarbon refrigerant is, for example, R32 alone; R23 alone; R134a alone; R125 alone; a mixture of R134a / R32 = 60 to 80% by mass / 40 to 20% by mass; a mixture of R32 / R125 = 40 to 70% by mass / 60 to 30% by mass; a mixture of R125 / R143a = 40 to 60% by mass / 60 to 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 to 70% by mass / 15 to 35% by mass / 5 to 40% by mass; a mixture of R125 / R134a / R143a = 35 to 55% by mass / 1 to 15% by mass / 40 to 60% by mass, etc. More specifically, the saturated hydrofluorocarbon refrigerant may be 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 (R407C); a mixture of R32 / R125 / R134a = 25 / 15 / 60% by mass (R407E); a mixture of R125 / R134a / R143a = 44 / 4 / 52% by mass (R404A), etc.

[0077] Unsaturated fluorinated hydrocarbon (HFO) refrigerants are preferably unsaturated fluorinated hydrocarbons having 2 to 3 carbon atoms, more preferably fluoropropenes, and even more preferably fluoropropenes having 3 to 5 fluorine atoms. The unsaturated fluorinated hydrocarbon refrigerant 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 perspective of refrigerant physical properties, the unsaturated fluorinated hydrocarbon refrigerant is preferably one or two or more selected from HFO-1225ye, HFO-1234ze, and HFO-1234yf. The unsaturated fluorinated hydrocarbon refrigerant may be fluoroethylene, preferably 1,1,2,3-tetrafluoroethylene.

Examples

[0078] Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to the following examples.

[0079] [Lubricating oil base oil] As the lubricating oil base oil, base oil A shown below was used. A: Paraffinic mineral oil-based base oil (kinematic viscosity at 40 °C: 3.2 mm 2 / s, kinematic viscosity at 100 °C: 1.3 mm 2 / s, pour point: -30 °C, flash point (COC): 130 °C, %C P / %C N = 1.2)

[0080] [Refrigeration oil] In the examples and comparative examples, refrigeration oils having the compositions (mass% based on the total amount of refrigeration oil) shown in Tables 1, 2, and 3 were prepared using the above lubricating oil base oil and the following polymer additives as additives. These polymer additives contained, for example, 5 to 20 mass% of diluent oil.

[0081] Polymer Additive 1: Copolymer of maleic acid ester and α-olefin (kinematic viscosity at 40°C: 1980 mm 2 / s, kinematic viscosity at 100°C: 200 mm 2 / s, viscosity index 227, Mn of polymer: 4500, Mw / Mn: 2.2, residual carbon content: 3.1 mass%, value of residual carbon content (mass%) / kinematic viscosity at 100°C (mm 2 / s): 0.016) Polymer Additive 2: Copolymer of maleic acid ester and α-olefin (kinematic viscosity at 40°C: 4100 mm 2 / s, kinematic viscosity at 100°C: 260 mm 2 / s, viscosity index 190, Mn of polymer: 1800, Mw / Mn: 2.7, residual carbon content: 2.8 mass%, value of residual carbon content (mass%) / kinematic viscosity at 100°C (mm 2 / s): 0.011) Polymer Additive 3: Copolymer of maleic acid ester and α-olefin (kinematic viscosity at 40°C: 4300 mm 2 / s, kinematic viscosity at 100°C: 300 mm 2 / s, viscosity index 225, Mn of polymer: 2000, Mw / Mn: 2.5, residual carbon content: 1.7 mass%, value of residual carbon content (mass%) / kinematic viscosity at 100°C (mm 2 / s): 0.006) Polymer Additive 4: Copolymer of maleic acid ester and α-olefin (kinematic viscosity at 40°C: 7000 mm 2 / s, kinematic viscosity at 100°C: 500 mm 2 / s, viscosity index 230, Mn of polymer: 2650, Mw / Mn: 4.0, residual carbon content: 2 mass%, value of residual carbon content (mass%) / kinematic viscosity at 100°C (mm 2 / s): 0.004) Polymer Additive 5: Copolymer of maleic acid ester and α-olefin (kinematic viscosity at 40°C: 11000 mm 2 / s, kinematic viscosity at 100°C: 700 mm 2 / s, viscosity index 250, Mn of polymer: 2690, Mw / Mn: 3.1, residual carbon content: 1.5 mass%, value of residual carbon content (mass%) / kinematic viscosity at 100°C (mm2 Value of ( / s): 0.002) Polymer Additive 6: Copolymer of maleic acid ester and α-olefin (kinematic viscosity at 40°C: 400 mm 2 / s, kinematic viscosity at 100°C: 40 mm 2 / s, viscosity index 160, residual carbon content: 0.8 mass%, value of residual carbon content (mass%) / kinematic viscosity at 100°C (mm 2 / s): 0.02) Polymer Additive 7: Copolymer of (meth)acrylic acid ester (kinematic viscosity at 100°C: 600 mm 2 / s, Mn of polymer: 25000, Mw / Mn: 1.4, residual carbon content: 1.1 mass%, value of residual carbon content (mass%) / kinematic viscosity at 100°C (mm 2 / s): 0.002) Polymer Additive 8: Copolymer of (meth)acrylic acid ester (kinematic viscosity at 100°C: 370 mm 2 / s, Mn of polymer: 25900, Mw / Mn: 1.3, residual carbon content: 1.1 mass%, value of residual carbon content (mass%) / kinematic viscosity at 100°C (mm 2 / s): 0.003) Polymer Additive 9: Copolymer of (meth)acrylic acid ester (kinematic viscosity at 100°C: 180 mm 2 / s, Mn of polymer: 3620, Mw / Mn: 2.0, residual carbon content: 1.3 mass%, value of residual carbon content (mass%) / kinematic viscosity at 100°C (mm 2 / s): 0.007) Polymer Additive 10: Copolymer of (meth)acrylic acid ester (kinematic viscosity at 100°C: 360 mm 2 / s, Mn of polymer: 11000, Mw / Mn: 1.6, residual carbon content: 0.9 mass%, value of residual carbon content (mass%) / kinematic viscosity at 100°C (mm 2 / s): 0.003) Polymer Additive 11: Copolymer of (meth)acrylic acid ester (kinematic viscosity at 100°C: 380 mm 2 / s, Mn of polymer: 22500, Mw / Mn: 1.5, residual carbon content: 0.1 mass%, value of residual carbon content (mass%) / kinematic viscosity at 100°C (mm2 Value of ( / s): 0.0003)

[0082] [Evaluation of Friction Characteristics] In order to evaluate the friction characteristics of each refrigerant oil in the examples and comparative examples, the following tests were carried out. Using an MTM (Mini Traction Machine) tester (manufactured by PCS Instruments), the coefficient of friction (μ) in the lubrication region corresponding to the elastohydrodynamic lubrication region or the mixed lubrication region was measured under the following conditions. The results are shown in Tables 1, 2, and 3. The smaller the coefficient of friction, the better the friction characteristics. Ball and disk: Standard test piece (AISI52100 standard) Test temperature: 40 °C Sliding speed: 0.0006 - 0.9 m / s (partial extraction) Load: 10 N Sliding ratio: 30% Note that the sliding speed uses the value of |U D -U B |[m / s]. Here, UD is the speed of the disk [m / s] at the sliding part, and UB is the speed of the ball [m / s] at the sliding part. Also, taking Comparative Example 1 without a polymer additive as a reference sample, the change rate (%) of the coefficient of friction at each sliding speed was calculated using the following formula, and the average value (average change rate (%) of the coefficient of friction) of the change rates (%) at sliding speeds of 0.03, 0.09, 0.15, and 0.3 was calculated. The results are shown in Tables 1, 2, and 3. Change rate (%) = (Coefficient of friction of the sample - Coefficient of friction of the reference sample) / Coefficient of friction of the reference sample × 100

[0083]

Table 1

[0084]

Table 2

[0085]

Table 3

[0086] [Compatibility test] In accordance with the "Test Method for Compatibility with Refrigerant" in JIS K2211:2009 "Refrigerating Machine Oil", for R600a (isobutane) or R290 (propane) and each of the refrigerating machine oils in Examples 1 to 10, the low-temperature side two-layer separation temperature was measured when the oil rate (amount of refrigerating machine oil collected (g) / total amount of refrigerating machine oil and refrigerant collected (g) × 100) (%) was 20%. All of the two-layer separation temperatures were -30°C or lower, confirming that there is no problem with refrigerant compatibility.

Claims

1. A lubricant comprising a lubricant base oil and a polymer additive, A refrigeration oil having a residual carbon content of 0.05 mass% or more in a 10% residual oil.

2. The refrigeration oil of claim 1 , wherein the lubricating base oil comprises a mineral oil.

3. The refrigerating machine oil according to claim 1 or 2, wherein the polymer additive is a (co)polymer of an unsaturated carboxylic acid ester.

4. The refrigerating machine oil according to any one of claims 1 to 3, wherein the polymer additive has a residual carbon content of 0.2 mass% or more.

5. A working fluid composition for a refrigerating machine, comprising a refrigerant and the refrigerating machine oil according to any one of claims 1 to 4.

6. A lubrication method for a refrigerant circulation system having a compressor, a condenser, an expansion mechanism, and an evaporator, comprising using the refrigerating machine oil according to any one of claims 1 to 4.

7. A method for producing a refrigerating machine oil, comprising mixing a polymer additive with a lubricating base oil so that a residual carbon content of a 10% residual oil of the refrigerating machine oil is 0.05 mass% or more.

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