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

Abstract

One aspect of the present invention provides a refrigerating machine oil containing a mixed base oil of a first hydrocarbon base oil having a kinematic viscosity at 40°C of less than 6 mm2 / s and a second hydrocarbon base oil having a kinematic viscosity at 40°C of 6 mm2 / s or higher, wherein (A) / (B) is greater than 1 and no greater than 1.5, where (A) is the kinematic viscosity at 40°C of the mixed base oil and (B) is the kinematic viscosity at 40°C of the first hydrocarbon base oil.

Description

[Technical field]

[0001] The present invention relates to a refrigerating machine oil, a working fluid composition for a refrigerating machine, and a method for producing a refrigerating machine oil. [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 relatively low-viscosity mineral oil and a specific copolymer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-83920 A Summary of the Invention [Problem to be solved by the invention]

[0005] When the viscosity of conventional refrigeration oil is reduced, it is effective to some extent in reducing friction in the fluid lubrication region, but in the low sliding speed region such as the elastohydrodynamic lubrication region, the mixed lubrication region, or the boundary lubrication region, the metal-to-metal contact opportunities increase, and the friction coefficient tends to increase. In addition, for example, the above-mentioned conventional refrigeration oil is expected to be effective to some extent in reducing friction in the boundary lubrication region where the friction coefficient is high, but it is not necessarily sufficient to improve the efficiency of the compressor. In particular, in the lubrication region (elastohydrodynamic lubrication region or mixed lubrication region) where the friction coefficient begins to increase rapidly with the sliding speed, which is the focus of the present inventors, the effect of reducing friction cannot be fully obtained, and there is still room for improvement in this respect.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide a refrigeration oil having excellent low friction characteristics even in a lubrication range where the sliding speed is relatively high, as described above. [Means for solving the problem]

[0007] One aspect of the present invention is a kinetic viscosity of 6mm at 40°C. 2 A first hydrocarbon base oil having a kinematic viscosity of less than 6 mm / s at 40°C 2 The present invention provides a refrigeration oil comprising a mixed base oil with a second hydrocarbon base oil having a kinetic viscosity of at least 1.5 / s, in which, when the mixed base oil has a kinetic viscosity of (A) at 40°C and the first hydrocarbon base oil has a kinetic viscosity of (B) at 40°C, the ratio (A) / (B) is greater than 1 and is not greater than 1.5.

[0008] The second hydrocarbon base oil has a kinematic viscosity of 20 mm at 40°C. 2 / s or more 1000mm 2 / s or less.

[0009] The content of the second hydrocarbon base oil in the mixed base oil may be 0.5 mass % or more and 10 mass % or less.

[0010] The refrigeration oil may further contain a phosphorus-containing additive.

[0011] The refrigerating machine oil may further contain a polymer additive. The content of the polymer additive may be 5 mass % or less based on the total amount of the refrigerating machine oil.

[0012] The kinetic viscosity of refrigeration oil at 40°C is 6mm 2 / s or less.

[0013] The refrigeration oil may be used in conjunction with a hydrocarbon refrigerant.

[0014] Another aspect of the present invention provides a working fluid composition for a refrigerating machine, comprising the above refrigerating machine oil and a refrigerant. The refrigerant may include a hydrocarbon refrigerant.

[0015] Another aspect of the present invention is a method for producing a kinetic viscosity of 6mm at 40°C. 2 A first hydrocarbon base oil having a kinematic viscosity of less than 6 mm / s at 40°C 2 The present invention provides a method for producing a refrigeration oil containing a mixed base oil with a second hydrocarbon-based base oil having a kinetic viscosity of at least 1.0 / s, the method comprising a step of mixing the first hydrocarbon-based base oil with the second hydrocarbon-based base oil so that, when the mixed base oil has a kinetic viscosity of (A) at 40°C and the first hydrocarbon-based base oil has a kinetic viscosity of (B) at 40°C, the ratio (A) / (B) is greater than 1 and is not greater than 1.5. Effect of the Invention

[0016] According to the present invention, it is possible to provide a refrigeration oil having excellent low friction characteristics, particularly in a lubrication range where the sliding speed is relatively high. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described in detail.

[0018] The refrigeration oil according to the present embodiment is a lubricating base oil having a kinetic viscosity of 6 mm at 40°C. 2 A first hydrocarbon base oil having a kinematic viscosity of less than 6 mm / s at 40°C 2 / s or more of a mixed base oil with a second hydrocarbon base oil.

[0019] As the first hydrocarbon base oil, for example, a mineral hydrocarbon oil, a synthetic hydrocarbon oil, or a mixture thereof can be used. Examples of the mineral hydrocarbon oil include paraffinic mineral oil and naphthenic mineral oil, which are obtained by distilling a lubricating oil fraction obtained by distilling a crude oil such as paraffinic or naphthenic at atmospheric pressure and reduced pressure, and refining the lubricating oil fraction by methods such as solvent deasphalting, solvent refining, hydrorefining, hydrocracking, solvent dewaxing, hydrodewaxing, clay treatment, and sulfuric acid washing. These refining methods may be used alone or in combination of two or more. Examples of the synthetic hydrocarbon oil include alkylbenzene, alkylnaphthalene, polyα-olefin (PAO), polybutene, and ethylene-α-olefin copolymer.

[0020] The first hydrocarbon base oil has a kinematic viscosity of 6mm at 40°C. 2 / s, and from the viewpoint of more effectively reducing the coefficient of friction, 2 / s or less is preferable, and 4 mm 2 The lower limit of the kinematic viscosity at 40° C. of the first hydrocarbon base oil is not particularly limited, but may be, for example, 0 mm 2 / s, preferably 0.5 mm 2 / s or more, preferably 1mm 2 / s or more, more preferably 1.5 mm 2 The kinetic viscosity in this specification means a kinetic viscosity measured in accordance with JIS K2283:2000.

[0021] As the second hydrocarbon base oil, for example, a mineral hydrocarbon oil, a synthetic hydrocarbon oil, or a mixture thereof can be used. Examples of the mineral hydrocarbon oil include paraffinic mineral oil and naphthenic mineral oil, which are obtained by distilling a lubricating oil fraction obtained by distilling a crude oil such as paraffinic or naphthenic at atmospheric pressure and reduced pressure, and refining the lubricating oil fraction by methods such as solvent deasphalting, solvent refining, hydrorefining, hydrocracking, solvent dewaxing, hydrodewaxing, clay treatment, and sulfuric acid washing. These refining methods may be used alone or in combination of two or more. Examples of the synthetic hydrocarbon oil include alkylbenzene, alkylnaphthalene, polyα-olefin (PAO), polybutene, and ethylene-α-olefin copolymer.

[0022] The kinematic viscosity of the second hydrocarbon base oil at 40°C is 6mm 2 / s or more, and from the viewpoint of more effectively reducing the coefficient of friction, 2 / s or more is preferable, and 10 mm 2 More preferably, it is 20 mm / s or more. 2 More preferably, it is 50 mm / s or more. 2 / s or more is particularly preferable, and 90 mm 2 The upper limit of the kinematic viscosity at 40° C. of the second hydrocarbon base oil is not particularly limited, but is preferably 1000 mm 2 / s or less, preferably 500 mm 2 / s or less.

[0023] When the kinematic viscosity of the mixed base oil at 40 ° C. is (A) and the kinematic viscosity of the first hydrocarbon base oil at 40 ° C. is (B), (A) / (B) is more than 1 and 1.5 or less. From the viewpoint of more effectively reducing the friction coefficient, the above (A) / (B) is preferably 1.4 or less, more preferably 1.35 or less, even more preferably 1.3 or less, and particularly preferably 1.25 or less. The lower limit of (A) / (B) is not particularly limited, but from the viewpoint of more effectively reducing the friction coefficient, it may usually be more than 1, for example, 1.1 or more. In addition, when a plurality of base oil components corresponding to the first hydrocarbon base oil or the second hydrocarbon base oil are included, the above (A) means the kinematic viscosity of the mixed base oil containing all of the base oil components corresponding to the first hydrocarbon base oil or the second hydrocarbon base oil. In addition, when multiple base oil components corresponding to the first hydrocarbon base oil are included, the above (B) means the kinematic viscosity of the mixed base oil containing all of the base oil components corresponding to the first hydrocarbon base oil.

[0024] The content of the first hydrocarbon base oil may be 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more based on the total amount of the first hydrocarbon base oil and the second hydrocarbon base oil (i.e., the total amount of the mixed base oil. The same applies below.) The upper limit of the content of the first hydrocarbon base oil is not particularly limited, but may be, for example, less than 100% by mass or 99.9% by mass or less, 99.5% by mass or less, or 99% by mass or less based on the total amount of the first hydrocarbon base oil and the second hydrocarbon base oil.

[0025] The content of the first hydrocarbon base oil may be 50 mass% or more, 60 mass% or more, 70 mass% or more, 80 mass% or more, or 85 mass% or more based on the total amount of the refrigerating machine oil. The upper limit of the content of the first hydrocarbon base oil is not particularly limited, but may be, for example, 98 mass% or less, 95 mass% or less, or 90 mass% or less based on the total amount of the refrigerating machine oil.

[0026] The content of the second hydrocarbon base oil may be 0.1% by mass or more, 0.5% by mass or more, or 1% by mass or more based on the total amount of the first hydrocarbon base oil and the second hydrocarbon base oil. The upper limit of the content of the second hydrocarbon base oil may be, for example, 50% by mass or less, 40% by mass or less, 30% by mass or less, 20% by mass or less, 10% by mass or less, or 5% by mass or less based on the total amount of the first hydrocarbon base oil and the second hydrocarbon base oil.

[0027] The content of the second hydrocarbon base oil may be 0.1 mass% or more, 0.5 mass% or more, 1 mass% or more, or 3 mass% or more based on the total amount of the refrigerating machine oil. The upper limit of the content of the second hydrocarbon base oil is not particularly limited, but may be, for example, 50 mass% or less, 40 mass% or less, 30 mass% or less, 20 mass% or less, 10 mass% or less, or 5 mass% or less based on the total amount of the refrigerating machine oil.

[0028] The refrigeration oil may further contain a base oil other than the above-mentioned mixed base oil as a lubricating base oil. The total content of the first and second hydrocarbon-based base oils (i.e., the mixed base oil) is, for example, 50 mass% or more, 60 mass% or more, 70 mass% or more, 80 mass% or more, 90 mass% or more, or 100 mass% based on the total amount of the lubricating base oil.

[0029] The total content of the first hydrocarbon base oil and the second hydrocarbon base oil (i.e., the mixed base oil) may be 50 mass% or more, 60 mass% or more, 70 mass% or more, 80 mass% or more, or 90 mass% or more, based on the total amount of the refrigeration oil.

[0030] The base oil other than the first hydrocarbon base oil and the second hydrocarbon base oil is not particularly limited, and examples thereof include oxygen-containing oils such as esters, ethers, carbonates, ketones, silicones, and polysiloxanes. Examples of esters include monoesters, polyol esters, aromatic esters, dibasic acid esters, complex esters, carbonate esters, and mixtures thereof. Examples of ethers include polyvinyl ethers (PVEs), polyalkylene glycols (PAGs), polyphenyl ethers, perfluoroethers, and mixtures thereof. Among these, it is preferable to use a monoester of a monohydric aliphatic alcohol and a monohydric fatty acid, and it is desirable to use a mixture of the monoester and a polyol ester of a dihydric to hexahydric alcohol and a monohydric fatty acid, as necessary.

[0031] Examples of the monohydric aliphatic alcohol constituting such an ester include monohydric aliphatic alcohols having 1 to 20 carbon atoms, preferably 4 to 18, and more preferably 4 to 12. Examples of the monohydric fatty acid constituting such an ester include monohydric fatty acids having 1 to 20 carbon atoms, preferably 4 to 18, and more preferably 4 to 12. Examples of the dihydric to hexahydric alcohol constituting such an ester include preferably neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol, and the like.

[0032] The kinematic viscosity of the mixed base oil or the lubricating base oil at 40°C is preferably 20mm 2 / s or less, and more preferably 10 mm 2 / s or less, and more preferably 6 mm 2 / s or less, and particularly preferably 4 mm 2 / s or less, and highly preferably 3.5 mm 2 The kinematic viscosity of the mixed base oil or the lubricating base oil at 40°C is not particularly limited, but is, for example, 0.5 mm 2 / s or more, preferably 1 mm 2 / s or more, more preferably 1.5 mm 2 / s or more.

[0033] The kinematic viscosity of the mixed base oil or lubricating base oil at 100°C is preferably 0.5 mm 2 / s or more, preferably 0.8 mm 2 / s or more, more preferably 1 mm 2 The kinematic viscosity of the blend base oil or lubricating base oil at 100° C. is preferably 10 mm 2 / s or less, preferably 5 mm 2 / s or less, more preferably 3 mm 2 / s or less, particularly preferably 2 mm 2 / s or less, and very preferably 1.5 mm 2 / s or less.

[0034] The content of the lubricating base oil may be 50 mass% or more, 60 mass% or more, 70 mass% or more, 80 mass% or more, or 90 mass% or more based on the total amount of the refrigerating machine oil, and may be 99.9 mass% or less, 99.5 mass% or less, or 99 mass% or less.

[0035] The refrigeration oil according to the present embodiment may further contain a phosphorus-containing additive in addition to the above-mentioned mixed base oil (lubricant base oil). Examples of the phosphorus-containing additive include phosphorus-based extreme pressure agents. Examples of the phosphorus-based extreme pressure agents include phosphate esters, acid phosphate esters, amine salts of acid phosphate esters, chlorinated phosphate esters, phosphites, and thiophosphoric acids. These phosphorus-containing additives may be used alone or in combination of two or more. The phosphorus-containing additive is preferably at least one selected from the group consisting of phosphate esters and thiophosphoric acids, and more preferably at least one selected from the group consisting of triphenyl phosphate (TPP), tricresyl phosphate (TCP), and triphenyl phosphorothionate (TPPT).

[0036] From the viewpoint of more effectively reducing the friction coefficient, the content of the phosphorus-containing additive is, based on the total amount of the refrigerating machine oil, preferably 0.01 mass% or more, more preferably 0.1 mass% or more, even more preferably 1 mass% or more, particularly preferably 1.2 mass% or more, and is preferably 5 mass% or less, more preferably 3 mass% or less, and even more preferably 2 mass% or less.

[0037] The refrigeration oil according to the present embodiment may further contain a polymer additive in addition to the above-mentioned mixed base oil (lubricant base oil). As described above, the lubricant base oil may contain base oil components such as PAO, PAG, PVE, etc., but the polymer additive according to the present embodiment contains a polymer different from these base oil components. The polymer additive is preferably a polymer containing an unsaturated carboxylic acid ester (an ester of a carboxylic acid having a polymerizable unsaturated bond and an alcohol) as a monomer unit. In addition to such a polymer, the polymer additive may further contain other components other than the polymer, such as a diluent oil.

[0038] The polymer may further contain, as a monomer unit, a monomer other than the unsaturated carboxylate (a monomer copolymerizable with the unsaturated carboxylate). That is, the polymer may be a homopolymer of one kind of unsaturated carboxylate, a copolymer of two or more kinds of unsaturated carboxylate, or a copolymer of one or more kinds of unsaturated carboxylate and one or more kinds of other monomer.

[0039] The unsaturated carboxylic acid constituting the unsaturated carboxylate ester has at least one polymerizable unsaturated bond (polymerizable carbon-carbon double bond) and at least one carboxyl group, and may be, for example, an unsaturated monocarboxylic acid having one polymerizable unsaturated bond and one carboxyl group, or an unsaturated dicarboxylic acid having one polymerizable unsaturated bond and two carboxyl groups. Examples of the unsaturated monocarboxylic acid include (meth)acrylic acid and crotonic acid. Examples of the unsaturated dicarboxylic acid include maleic acid, fumaric acid, citraconic acid, mesaconic acid, and itaconic acid.

[0040] The alcohol constituting the unsaturated carboxylic acid ester may be, for example, an alcohol having 1 to 40 carbon atoms, preferably includes an alcohol having 1 to 18 carbon atoms, and more preferably includes an alcohol having 1 to 8 carbon atoms. These alcohols may be linear or branched. The alcohols may include alcohols having 1 to 18 carbon atoms and alcohols having 20 to 40 carbon atoms. These alcohols may be aliphatic alcohols.

[0041] The alcohol may be a monohydric alcohol or a polyhydric alcohol, for example, methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol (which may be linear or branched), etc.

[0042] The monomer other than the unsaturated carboxylate (monomer copolymerizable with the unsaturated carboxylate) is not particularly limited, and examples thereof include the unsaturated carboxylic acid or its anhydride exemplified as the unsaturated carboxylic acid constituting the unsaturated carboxylate described above, and an unsaturated hydrocarbon compound having a polymerizable unsaturated bond. The unsaturated hydrocarbon may be, for example, an unsaturated hydrocarbon compound having 2 to 20 carbon atoms, and may preferably be an α-olefin or styrene having 2 to 20 carbon atoms. Specific examples of the 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, and 1-eicosene.

[0043] More specifically, the (co)polymer of the unsaturated carboxylate ester may be a (co)polymer of a (meth)acrylic acid ester or a copolymer of an unsaturated carboxylate ester and an α-olefin, with a copolymer of an unsaturated carboxylate ester and an α-olefin being particularly preferred. The copolymer of the unsaturated carboxylate ester and an α-olefin 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 dicarboxylate ester and an α-olefin, and more preferably a copolymer of an unsaturated dicarboxylate ester and an α-olefin.

[0044] Preferable examples of the unsaturated dicarboxylic acid ester in the copolymer of the unsaturated dicarboxylic acid ester and the α-olefin include monoesters or diesters of unsaturated dicarboxylic acids such as maleic acid, fumaric acid, citraconic acid, mesaconic acid, and itaconic acid with aliphatic alcohols having 3 to 10 carbon atoms such as propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, and decanol. The unsaturated dicarboxylic acid ester is preferably a maleic acid ester. Preferable examples of the maleic acid ester include dimethyl maleate, diethyl maleate, dipropyl maleate, dibutyl maleate, dipentyl maleate, dihexyl maleate, diheptyl maleate, and dioctyl maleate.

[0045] When the polymer is a copolymer, the content of the unsaturated carboxylic acid ester may be 10 mol % or more, 30 mol % or more, or 50 mol % or more, and may be 90 mol % or less, 70 mol % or less, or 50 mol % or less, based on all monomer units constituting the copolymer.

[0046] When the polymer is a copolymer of an unsaturated carboxylic acid ester and an α-olefin, the molar ratio of the unsaturated carboxylic acid ester / α-olefin is not particularly limited, but is preferably 1 / 9 or more, more preferably 3 / 7 or more, and is preferably 9 / 1, more preferably 7 / 3 or less.

[0047] The number average molecular weight (Mn) of the polymer additive is preferably 300 or more, more preferably 1000 or more, even more preferably 1500 or more, and is preferably 500000 or less, more preferably 50000 or less, even more preferably 30000 or less, and may be 20000 or less or 15000 or less.

[0048] The weight average molecular weight (Mw) of the polymer additive is preferably 400 or more, more preferably 1000 or more, even more preferably 2000 or more, particularly preferably 3000 or more, and is preferably 10,000,000 or less, more preferably 100,000 or less, even more preferably 50,000 or less, particularly preferably 30,000 or less.

[0049] The Mw / Mn value of the polymer additive is preferably 1.2 or more, more preferably 1.5 or more, even more preferably 1.7 or more, particularly preferably 2 or more, and is preferably 5 or less, more preferably 3.5 or less, even more preferably 3 or less.

[0050] In this specification, the terms "weight average molecular weight (Mw)" and "number average molecular weight (Mn)" refer to the weight average molecular weight and number average molecular weight, respectively, calculated in terms of polystyrene, determined by gel permeation chromatography (GPC) (standard substance: polystyrene) using a Waters APC XT column as the column and tetrahydrofuran as the mobile phase. When the polymer additive contains components other than the polymer, the number average molecular weight (Mn) and weight average molecular weight (Mw) of the polymer additive indicate values ​​measured excluding the other components.

[0051] The polymer additive preferably has a kinematic viscosity of 10 mm at 100°C. 2 / s or more, preferably 20 mm 2 / s or more, more preferably 100 mm 2 / s or more, preferably 10000 mm 2 / s or less, preferably 1000 mm 2 / s or less, more preferably 800 mm 2 / s or less, and 500 mm2 / s or less.

[0052] The polymer additive preferably has a kinematic viscosity of 100 mm at 40°C. 2 / s or more, preferably 200 mm 2 / s or more, more preferably 400 mm 2 / s or 400mm 2 / s, and exceeds 500 mm 2 / s or more or 1000mm 2 / s or more, preferably 100000 mm 2 / s or less, more preferably 20000mm 2 / s or less, more preferably 15000 mm 2 / s or less, 10000mm 2 / s or less or 5000mm 2 / s or less.

[0053] The viscosity index of the polymer additive is preferably 80 or more, more preferably 140 or more, and may be 180 or more or 200 or more, and is preferably 400 or less, more preferably 300 or less, and may be 250 or less. In this specification, the viscosity index means a viscosity index measured in accordance with JIS K2283:2000.

[0054] The polymer additive is preferably one whose residual carbon content is within a predetermined range when evaporated and pyrolyzed. The reason is unclear, but it is presumed that the presence of a precursor (precursor of the polymer additive) corresponding to the residual carbon content can further reduce the friction coefficient in a predetermined sliding speed range. The residual carbon content of the polymer additive is, for example, 0.2 mass% or more, preferably 0.5 mass% or more, more preferably 1 mass% or more, and even more preferably 1.5 mass% or more, and may be 2 mass% or more or 2.5 mass% or more, and is preferably 10 mass% or less, more preferably 5 mass% or less, and even more preferably 4 mass% or less, and may be 3.5 mass% or less. The residual carbon content in this specification means the residual carbon content measured by a micro method in accordance with JIS K 2270-2:2009.

[0055] More specific examples of the polymer additives (polymers) described above include the polymer additives described in the examples described below, but other examples include the following polymer additives (polymers). Polymer additive 1: Maleic acid ester and α-olefin copolymer (dynamic viscosity at 40°C: 1980 mm 2 / s, kinetic viscosity at 100°C: 200mm 2 / s, viscosity index 227, polymer Mn: 4500, Mw / Mn: 2.2, residual carbon content: 3.1% by mass Polymer additive 2: Maleic acid ester and α-olefin copolymer (dynamic viscosity at 40°C: 4100 mm 2 / s, kinematic viscosity at 100°C: 260mm 2 / s, viscosity index 190, polymer Mn: 1800, Mw / Mn: 2.7, residual carbon content: 2.8% by mass Polymer additive 3: Maleic acid ester and α-olefin copolymer (dynamic viscosity at 40°C: 4300 mm 2 / s, kinematic viscosity at 100°C: 300mm 2 / s, viscosity index 225, polymer Mn: 2000, Mw / Mn: 2.5, residual carbon content: 1.7% by mass Polymer additive 4: Maleic acid ester and α-olefin copolymer (dynamic viscosity at 40°C: 7000 mm 2 / s, kinematic viscosity at 100°C: 500mm 2 / s, viscosity index 230, polymer Mn: 2650, Mw / Mn: 4.0, residual carbon content: 2% by mass Polymer additive 5: Maleic acid ester and α-olefin copolymer (dynamic viscosity at 40°C: 11000mm 2 / s, kinematic viscosity at 100°C: 700mm 2 / s, viscosity index 250, polymer Mn: 2690, Mw / Mn: 3.1, residual carbon content: 1.5% by mass Polymer additive 6: Maleic acid ester and α-olefin copolymer (dynamic viscosity at 40°C: 400 mm 2 / s, kinetic viscosity at 100°C: 40mm 2 / s, viscosity index 160, residual carbon content: 0.8% by mass) Polymer additive 7: (meth)acrylic acid ester copolymer (dynamic viscosity at 100°C: 600mm 2 / s, polymer Mn: 25000, Mw / Mn: 1.4, residual carbon content: 1.1% by mass Polymer additive 8: (meth)acrylic acid ester copolymer (dynamic viscosity at 100°C: 370 mm 2 / s, polymer Mn: 25900, Mw / Mn: 1.3, residual carbon content: 1.1% by mass Polymer additive 9: (meth)acrylic acid ester copolymer (dynamic viscosity at 100°C: 180 mm 2 / s, polymer Mn: 3620, Mw / Mn: 2.0, residual carbon content: 1.3% by mass Polymer additive 10: (meth)acrylic acid ester copolymer (dynamic viscosity at 100°C: 360 mm 2 / s, polymer Mn: 11000, Mw / Mn: 1.6, residual carbon content: 0.9% by mass Polymer additive 11: (meth)acrylic acid ester copolymer (dynamic viscosity at 100°C: 380 mm 2 / s, polymer Mn: 22500, Mw / Mn: 1.5, residual carbon content: 0.1% by mass

[0056] The content of the polymer additive is not particularly limited, but from the viewpoint of further improving the friction characteristics of the refrigerating machine oil, it is preferably 0.1 mass % or more, more preferably 0.5 mass % or more, and even more preferably 0.8 mass % or more, based on the total amount of the refrigerating machine oil; from the viewpoint of suppressing the viscosity of the refrigerating machine oil and achieving a lower friction coefficient even in a region where the sliding speed is relatively high, it is preferably 5 mass % or less, more preferably 2 mass % or less, even more preferably less than 2 mass %, particularly preferably 1 mass % or less, and may be less than 1 mass %.

[0057] The refrigerating machine oil according to the present embodiment may further contain additives other than the above-mentioned components. Examples of additives include antioxidants, acid scavengers, phosphorus-free extreme pressure agents, metal deactivators, antiwear agents, pour point depressants, detergent dispersants, and antifoaming agents. 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 refrigerating machine oil, unless otherwise specified below.

[0058] Examples of the antioxidant include phenol-based antioxidants and amine-based antioxidants. Examples of the phenol-based antioxidant 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 the amine-based 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 mass%, preferably 0.1 to 3 mass%, based on the total amount of the refrigerating machine oil.

[0059] Examples of the acid scavenger include epoxy compounds (epoxy acid scavenger). Examples of the 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. 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 mass%, preferably 0.1 to 3 mass%, based on the total amount of the refrigerating machine oil.

[0060] The kinetic viscosity of the refrigeration oil at 40°C is preferably 6mm. 2 / s or less, preferably 5 mm 2 / s or less, more preferably 4 mm 2 The lower limit of the kinetic viscosity of the refrigeration oil at 40°C is not particularly limited.2 / s or more or 2mm 2 The kinetic viscosity of the refrigeration oil at 100°C is preferably 0.5 mm 2 / s or more, preferably 0.8 mm 2 / s or more, more preferably 1 mm 2 The kinetic viscosity of the refrigeration oil at 100°C is preferably 10 mm 2 / s or less, preferably 5 mm 2 / s or less, more preferably 3 mm 2 / s or less, particularly preferably 2 mm 2 / s or less.

[0061] The viscosity index of the refrigerating machine oil may be −50 or more, preferably 0 or more, and more preferably 50 or more and 200 or less.

[0062] The pour point of the refrigerating machine oil may be preferably −10° C. or lower, more preferably −20° C. or lower. In this specification, the pour point means the pour point measured in accordance with JIS K2269:1987.

[0063] The volume resistivity of the refrigeration oil is preferably 1.0×10 9 Ω·m or more, preferably 1.0×10 10 Ω·m or more, more preferably 1.0×10 11 The volume resistivity in this specification means the volume resistivity at 25° C. measured in accordance with JIS C2101:1999.

[0064] The water content of the refrigerating machine oil may be preferably 200 ppm or less, more preferably 100 ppm or less, and even more preferably 50 ppm or less, based on the total amount of the refrigerating machine oil. In this specification, the water content means the water content measured in accordance with JIS K2275-2 or 3 (Karl Fischer volumetric titration method or coulometric titration method).

[0065] The acid value of the refrigeration oil may be preferably 1.0 mgKOH / g or less, more preferably 0.1 mgKOH / g or less. The hydroxyl value of the refrigeration oil is, for example, 10 mgKOH / g or less, preferably 5 mgKOH / g or less, more preferably 2 mg / KOH / g or less. The acid value in this specification means the acid value measured in accordance with JIS K2501:2003. The hydroxyl value in this specification means the hydroxyl value measured in accordance with JIS K0070:1992.

[0066] The ash content of the refrigerating machine oil may be preferably 100 ppm or less, more preferably 50 ppm or less. In this specification, the ash content means the ash content measured in accordance with JIS K2272:1998.

[0067] The method for producing a refrigerating machine oil according to this embodiment includes a step of mixing the first hydrocarbon-based base oil and the second hydrocarbon-based base oil so that the above-mentioned (A) / (B) is more than 1 and not more than 1.5. The phosphorus-containing additive, polymer additive, and other additives contained in the refrigerating machine oil may be added to one or both of the first hydrocarbon-based base oil and the second hydrocarbon-based base oil before the above step, may be added to the mixed base oil after the above step, or may be added to the first hydrocarbon-based base oil and the second hydrocarbon-based base oil simultaneously with the above step.

[0068] The refrigerating machine oil according to this embodiment is usually present in a state 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 lubricates, for example, sliding members in the compressor. 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. 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, relative to 100 parts by mass of the refrigerant.

[0069] Examples of the refrigerant include hydrocarbon refrigerants, saturated fluorohydrocarbon refrigerants, unsaturated fluorohydrocarbon refrigerants, fluorine-containing ether refrigerants such as perfluoroethers, bis(trifluoromethyl)sulfide refrigerants, trifluoroiodomethane refrigerants, and natural refrigerants such as ammonia and carbon dioxide. In particular, the refrigerating machine oil according to the present embodiment is preferably used together with a hydrocarbon refrigerant. In other words, the working fluid composition for a refrigerating machine preferably contains a refrigerating machine oil and a hydrocarbon refrigerant.

[0070] 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 hydrocarbon refrigerant that is gaseous at 25°C and 1 atmospheric pressure, more preferably propane, normal butane, isobutane, 2-methylbutane, or a mixture of these.

[0071] The saturated fluorohydrocarbon refrigerant is preferably a saturated fluorohydrocarbon having a carbon number of 1 to 3, more preferably a saturated fluorohydrocarbon having a carbon number of 1 to 2. Specific examples of the saturated fluorohydrocarbon 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, Examples of such fluorocarbons include 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.

[0072] The saturated fluorohydrocarbon refrigerant is appropriately selected from the above depending on the application and required performance. Examples of the saturated fluorohydrocarbon refrigerant 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; a mixture of R125 / R134a / R143a=35-55% by mass / 1-15% by mass / 40-60% by mass, and the like. More specifically, the saturated fluorohydrocarbon refrigerant is 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.

[0073] The unsaturated fluorohydrocarbon (HFO) refrigerant is preferably an unsaturated fluorohydrocarbon having 2 to 3 carbon atoms, more preferably a fluoropropene, and even more preferably a fluoropropene having 3 to 5 fluorines. The unsaturated fluorohydrocarbon 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 viewpoint of refrigerant physical properties, the unsaturated fluorohydrocarbon refrigerant is preferably one or more selected from HFO-1225ye, HFO-1234ze, and HFO-1234yf. The unsaturated fluorohydrocarbon refrigerant may be a fluoroethylene, preferably 1,1,2,3-trifluoroethylene. EXAMPLES

[0074] The present invention will be described in more detail below based on examples, but the present invention is not limited to the following examples.

[0075] [Lubricant base oil] Base oils 1 to 5 shown below were prepared and mixed to obtain the compositions (parts by mass) shown in Table 1 to obtain mixed base oils a to g. Base oil 1: Mineral oil (Kinematic viscosity at 40°C: 3.4 mm 2 / s) Base oil 2: Mineral oil (Kinematic viscosity at 40°C: 2.4 mm 2 / s) Base oil 3: Mineral oil (Kinematic viscosity at 40°C: 8.0 mm 2 / s) Base oil 4: Mineral oil (Kinematic viscosity at 40°C: 100mm 2 / s) Base oil 5: Ethylene-α-olefin copolymer (Kinematic viscosity at 40°C: 384 mm 2 / s) Base oil 1 and base oil 2 correspond to the above-mentioned first hydrocarbon base oil, and base oil 3, base oil 4, and base oil 5 correspond to the above-mentioned second hydrocarbon base oil.

[0076] The kinematic viscosity (A) of the resulting mixed base oil at 40°C [mm 2 / s], the kinematic viscosity (B) at 40 °C of the first hydrocarbon base oil (a mixture of base oil 1 and base oil 2 in the ratio shown in Table 1) [mm 2 / s] and the values ​​of (A) / (B) are shown in Table 1 below.

[0077] [Table 1]

[0078] [Refrigerating machine oil] In the examples and comparative examples, the lubricating base oil (mixed base oil) and the additives shown below were used to prepare refrigerating machine oils having the compositions (mass % based on the total amount of refrigerating machine oil) shown in Tables 2 to 4. Note that 5 ppm of a silicone-based defoaming agent was added to all of these refrigerating machine oils. Phosphorus-containing additives: tricresyl phosphate and triphenyl phosphorothionate (both with a purity of 98% or more) Polymer additive: Maleic acid ester and α-olefin copolymer (Kinematic viscosity at 40°C: 1980mm 2 / s, kinetic viscosity at 100°C: 200mm 2 / s, viscosity index 227, copolymer Mn: 4500, Mw / Mn: 2.2, residual carbon content: 3.1% by mass

[0079] [Evaluation of friction characteristics] In order to evaluate the friction characteristics of each of the refrigeration oils of the Examples and Comparative Examples, the following tests were carried out. Using an MTM (Mini Traction Machine) tester (manufactured by PCS Instruments), the friction coefficient (μ) was measured in each lubrication region under the following conditions. The results are shown in Tables 2 to 4. The smaller the friction coefficient, the more excellent the friction characteristics. Balls and discs: standard test pieces (AISI 52100 standard) Test temperature: 40℃ Sliding speed: 0.0006~0.9m / s (partial excerpt) Load: 10N Slip rate: 30% The slip velocity is |U D -U B |[m / s] was used. Here, U D is the speed of the disk at the sliding part [m / s], and U B is the ball's speed at the sliding part [m / s].

[0080] [Table 2]

[0081] [Table 3]

[0082] [Table 4]

Claims

1. Dynamic viscosity at 40°C is 6mm ２ A first hydrocarbon base oil having a kinematic viscosity of less than 6 mm / s at 40° C. ２ A refrigeration oil containing a mixed base oil with a second hydrocarbon base oil having a molecular weight of 100 or more; A refrigeration oil in which, when the kinetic viscosity of the mixed base oil at 40°C is (A) and the kinetic viscosity of the first hydrocarbon base oil at 40°C is (B), the ratio (A) / (B) is greater than 1 and not greater than 1.25 (however, this does not include a refrigeration oil which contains a mineral oil having a % C N of 20 to 60 in an ndM ring analysis, a pour point of -15°C or less, and a kinetic viscosity at 40°C of 1.5 to 15 mm 2 / s, and an alkylbenzene having a kinetic viscosity at 40°C of 3 to 10 mm 2 / s, in a mass ratio of said mineral oil / said alkylbenzene of 85 / 15 to 15 / 85, and which has a kinetic viscosity at 40°C of 2 to 12 mm 2 / s and a flash point of 120°C or higher).

2. A refrigeration oil comprising a mixed base oil of a first hydrocarbon base oil having a kinetic viscosity at 40°C of less than 6 mm2 / s and a second hydrocarbon base oil having a kinetic viscosity at 40°C of 6 mm2 / s or more, When the kinematic viscosity of the mixed base oil at 40°C is (A) and the kinematic viscosity of the first hydrocarbon base oil at 40°C is (B), (A) / (B) is greater than 1 and is not greater than 1.25; The second hydrocarbon base oil has a kinematic viscosity at 40° C. of 20 mm ２ / s or more 1000mm ２ / s or less.

3. A refrigeration oil comprising a mixed base oil of a first hydrocarbon base oil having a kinetic viscosity at 40°C of less than 6 mm2 / s and a second hydrocarbon base oil having a kinetic viscosity at 40°C of 6 mm2 / s or more, When the kinematic viscosity of the mixed base oil at 40°C is (A) and the kinematic viscosity of the first hydrocarbon base oil at 40°C is (B), (A) / (B) is greater than 1 and is not greater than 1.25; A refrigeration oil, wherein the content of the second hydrocarbon base oil in the mixed base oil is 0.5 mass % or more and 10 mass % or less.

4. A refrigeration oil comprising a mixed base oil of a first hydrocarbon base oil having a kinetic viscosity at 40°C of less than 6 mm2 / s and a second hydrocarbon base oil having a kinetic viscosity at 40°C of 6 mm2 / s or more, When the kinematic viscosity of the mixed base oil at 40°C is (A) and the kinematic viscosity of the first hydrocarbon base oil at 40°C is (B), (A) / (B) is greater than 1 and is not greater than 1.25; A refrigeration oil further comprising a polymer additive.

5. The refrigeration oil according to any one of claims 1 to 4, further comprising a phosphorus-containing additive.

6. The refrigerating machine oil according to claim 4, wherein the content of the polymer additive is 5 mass% or less based on the total amount of the refrigerating machine oil.

7. Dynamic viscosity at 40°C is 6mm ２ The refrigerating machine oil according to any one of claims 1 to 6, wherein the refrigerating machine oil has a viscosity of 1000:1 or less.

8. The refrigeration oil according to any one of claims 1 to 7, which is used together with a hydrocarbon refrigerant.

9. The refrigerating machine oil according to any one of claims 1 to 8, A working fluid composition for a refrigerating machine comprising a refrigerant.

10. The refrigeration fluid composition according to claim 9 , wherein the refrigerant comprises a hydrocarbon refrigerant.

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