Refrigerating machine oil, working fluid composition, and refrigerant dissolution viscosity improver

Abstract

A refrigerating machine oil which contains a base oil and a compound represented by formula (1) [in the formula, R1 represents a hydrogen atom or a methyl group, and R2 represents an alkyl group or a group in which a part of the alkyl group is substituted. ] The average number of carbon atoms in the group represented by R2 in the polymer is 4-18. # imgabs0 #

Description

Technical Field

[0001] The present invention relates to a refrigerator oil, a working fluid composition and a refrigerant dissolving viscosity improver. Background Art

[0002] Refrigerator, such as refrigerator, car air conditioner, room air conditioner, vending machine, etc., is equipped with a compressor for circulating refrigerant in a refrigeration cycle. In addition, the compressor is filled with refrigeration oil for lubricating sliding components. Various properties are required for refrigeration oil, and suitable base oil and additives are selected according to the properties. For example, Patent Document 1 discloses a refrigeration oil containing a base oil and a specific polymer of 40% by mass or less based on the total amount of refrigeration oil as a refrigeration oil having excellent lubricity (especially wear resistance) and oil return properties.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2017 / 179687 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] According to the studies conducted by the present inventors, the refrigerating machine oil described in Patent Document 1 has room for further improvement in properties other than lubricity (particularly wear resistance) and oil return performance.

[0008] An object of one aspect of the present invention is to improve the viscosity index of refrigeration oil.

[0009] Solutions for solving problems

[0010] The present inventors have found that the viscosity index of refrigeration oil can be improved by adding a specific (meth)acrylate polymer.

[0011] The present invention includes the following aspects.

[0012] [1] A refrigerating machine oil comprising: a base oil and a polymer containing a structural unit represented by the following formula (1).

[0013]

[0014] [Where R 1 represents a hydrogen atom or a methyl group, R 2 represents an alkyl group or a group in which a part of the alkyl group is substituted.]

[0015] R in polymer 2 The groups shown have 4 to 18 carbon atoms on average.

[0016] [2] The refrigerating machine oil according to [1], which is used together with a refrigerant containing hydrocarbons.

[0017] [3] A working fluid composition comprising: the refrigeration oil described in [1], and a refrigerant.

[0018] [4] The working fluid composition according to [3], wherein the refrigerant contains a hydrocarbon.

[0019] [5] A refrigerant melt viscosity improver, which is a refrigerant melt viscosity improver of a working fluid composition comprising a refrigeration oil and a refrigerant, wherein the refrigerant melt viscosity improver contains a polymer containing a structural unit represented by the following formula (1).

[0020]

[0021] [Where R 1 represents a hydrogen atom or a methyl group, R 2 represents an alkyl group or a group in which a part of the alkyl group is substituted.]

[0022] R in polymer 2 The groups shown have 4 to 18 carbon atoms on average.

[0023] [6] The refrigerant solution viscosity improver according to [5], wherein the refrigerant contains a hydrocarbon.

[0024] Effects of the Invention

[0025] According to one aspect of the present invention, the viscosity index of refrigeration oil can be improved. According to one aspect of the present invention, the viscosity characteristics of refrigeration oil can be improved. According to another aspect of the present invention, a refrigeration oil having excellent viscosity characteristics and refrigerant compatibility can be provided. According to another aspect of the present invention, a refrigeration oil capable of improving the refrigerant dissolution viscosity can be provided. According to another aspect of the present invention, a refrigerant dissolution viscosity improver for a working fluid composition can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram showing one embodiment of a refrigerator. DETAILED DESCRIPTION

[0027] One embodiment of the present invention is a refrigerating machine oil comprising a base oil and a specific polymer (a (meth)acrylate polymer described below).

[0028] Examples of the base oil include hydrocarbon oils and oxygen-containing oils. Examples of the hydrocarbon oil include mineral oils and synthetic hydrocarbon oils. Examples of the oxygen-containing oil include esters, ethers, carbonates, ketones, silicones, and polysiloxanes.

[0029] As mineral oil, there can be mentioned: for the lubricating oil fraction obtained by atmospheric distillation and vacuum distillation of crude oil of paraffinic hydrocarbons, cycloparaffinic hydrocarbons, etc., the paraffinic hydrocarbon mineral oil or cycloparaffinic hydrocarbon mineral oil obtained by refining by methods such as solvent deasphalting, solvent refining, hydrorefining, hydrocracking, solvent dewaxing, hydrodewaxing, clay treatment, sulfuric acid cleaning, etc. The mineral oil can preferably be a hydrocracking mineral oil. The mineral oil can preferably be a paraffinic hydrocarbon oil. As a synthetic hydrocarbon oil, alkylbenzene, alkylnaphthalene, polyalphaolefin (PAO), hydrogenated product of polyalphaolefin (PAO), wax isomerized oil, polybutene, ethylene-alpha olefin copolymer, etc. can be mentioned. Among these, when mixed with (meth) acrylic acid ester polymers, from the aspect of suppressing the dissolution amount of refrigerants containing hydrocarbons such as R290 and easily further increasing the refrigerant dissolution viscosity, the base oil preferably contains at least one selected from mineral oil and wax isomerized oil.

[0030] The kinematic viscosity of hydrocarbon oil at 40°C can be 3 mm 2 / s or more, 5mm 2 / s or more, 7mm 2 / s or above, or 10mm 2 / s or more, can be 400mm 2 / s or less, 100mm 2 / s or less, 50mm 2 / s or less, or 30mm 2 From the viewpoint of obtaining a further high viscosity index improvement effect by adding the (meth)acrylate polymer, the kinematic viscosity of the hydrocarbon oil at 40° C. may be 25 mm 2 / s or less, 20mm 2 / s or less, 15mm 2 / s or less, or 13mm 2 / s or less. The kinematic viscosity of hydrocarbon oil at 100°C can be 1 mm 2 / s or more, 1.5mm 2 / s or more, 2mm 2 / s or above, or 2.5mm 2 / s or more, can be 100mm 2 / s or less, 50mm 2 / s or less, 30mm 2 / s or less, or 10mm 2 / s or less. The viscosity index of the hydrocarbon oil may be 0 or more, 50 or more, 80 or more, 100 or more, or 105 or more, and may be 200 or less, 150 or less, 130 or less, or 115 or less. The kinematic viscosity and viscosity index in this specification refer to the kinematic viscosity and viscosity index measured in accordance with JIS K2283:2000.

[0031] Examples of esters include aromatic esters, dibasic acid esters, polyol esters, complex esters, carbonates, and mixtures thereof. The ester is preferably at least one selected from polyol esters and complex esters, and more preferably polyol esters. It should be noted that the ester used as the base oil does not include the (meth)acrylate polymer described later.

[0032] Polyol esters are esters of polyols and carboxylic acids. The polyol may be a polyol having 2 to 6 hydroxyl groups. The number of carbon atoms of the polyol may be 4 or more or 5 or less than 12 or less than 10. The polyol may preferably be at least one selected from the group consisting of neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, di-(trimethylolpropane), tri-(trimethylolpropane), pentaerythritol and dipentaerythritol, and may preferably be at least one selected from the group consisting of neopentyl glycol, trimethylolpropane, pentaerythritol and dipentaerythritol.

[0033] The carboxylic acid may be a monobasic or polybasic carboxylic acid, preferably a monobasic carboxylic acid, more preferably a monobasic aliphatic carboxylic acid (fatty acid). The fatty acid may be a saturated fatty acid or an unsaturated fatty acid. The carbon number of the carboxylic acid (fatty acid) may be 4 or more, 5 or more, 8 or more, 10 or more, 12 or more, or 14 or more, and may be 20 or less, 18 or less, 16 or less, 14 or less, 10 or less, or 9 or less.

[0034] Specifically, fatty acids include butyric acid, valeric acid, caproic acid, enanthic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, hexadecenoic acid, heptadecanoic acid, octadecanoic acid, octadecenoic acid, nonadecanoic acid, and eicosanoic acid. These fatty acids may be straight-chain or branched.

[0035] In one embodiment, the base oil may contain an ester of neopentyl glycol or trimethylolpropane and a fatty acid having 4 to 10 carbon atoms. In this case, a further high viscosity index improvement effect is obtained by adding a (meth)acrylate polymer. The fatty acid may preferably be a linear or branched saturated fatty acid. In the ester of neopentyl glycol and a fatty acid having 4 to 10 carbon atoms, the carbon number of the fatty acid may be 4 to 9, 5 to 9, 6 to 9, 7 to 9, or 8 to 9, and may be 8, and the fatty acid may be branched. In the ester of trimethylolpropane and a fatty acid having 4 to 10 carbon atoms, the carbon number of the fatty acid may be 5 to 10, 6 to 10, 7 to 10, or 8 to 10, and the fatty acid may be linear.

[0036] In one embodiment, the base oil may include an ester of neopentyl glycol or trimethylolpropane and a fatty acid having 10 to 20 carbon atoms, and preferably includes an ester of trimethylolpropane and a fatty acid having 10 to 20 carbon atoms. In this case, the addition of the (meth)acrylate polymer further effectively improves the refrigerant dissolution viscosity without significantly increasing the kinematic viscosity of the refrigeration oil at 40° C. The fatty acid having 10 to 20 carbon atoms preferably includes an unsaturated fatty acid having 14 to 20 carbon atoms, and more preferably includes oleic acid.

[0037] In one embodiment, the base oil may include an ester of pentaerythritol and a fatty acid having 4 to 9 carbon atoms. The fatty acid is preferably a saturated fatty acid. The fatty acid is preferably a fatty acid having a branch at the α position and / or the β position, more preferably selected from 2-methylpropionic acid, 2-methylbutyric acid, 2-methylpentanoic acid, 2-methylhexanoic acid, 2-ethylpentanoic acid, 2-methylheptanoic acid, 2-ethylhexanoic acid, 3,5,5-trimethylhexanoic acid and 2-ethylhexadecanoic acid, and further preferably selected from 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid.

[0038] The complex ester is preferably an ester synthesized from at least one selected from polyols having 2 to 4 hydroxyl groups, at least one selected from polybasic acids having 6 to 12 carbon atoms, and at least one selected from monohydric alcohols having 4 to 18 carbon atoms and monobasic fatty acids having 2 to 12 carbon atoms.

[0039] Examples of the polyol having 2 to 4 hydroxyl groups include neopentyl glycol, trimethylolpropane, and pentaerythritol.

[0040] The polyol constituting the complex ester preferably contains a diol having 2 to 10 carbon atoms other than neopentyl glycol in addition to the polyol having 2 to 4 hydroxyl groups. Examples of the diol having 2 to 10 carbon atoms other than neopentyl glycol include ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, and 2,2-diethyl-1,3-pentanediol.

[0041] Examples of the polybasic acid having 6 to 12 carbon atoms include adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, and trimellitic acid.

[0042] Examples of the monohydric alcohol having 4 to 18 carbon atoms include aliphatic alcohols such as butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, dodecanol, and oleyl alcohol. These monohydric alcohols may be linear or branched.

[0043] Examples of the monovalent fatty acid having 2 to 12 carbon atoms include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, etc. These monovalent fatty acids may be linear or branched.

[0044] The kinematic viscosity of the ester at 40°C can be 3 mm 2 / s or more, 5mm 2 / s or more, 7mm 2 / s or above, or 10mm 2 / s or more, can be 500mm 2 / s or less, 300mm 2 / s or less, or 100mm 2 / s or less. The kinematic viscosity of the ester at 100°C can be 1 mm 2 / s or more, 1.5mm 2 / s or more, or 2mm 2 / s or more, can be 100mm 2 / s or less, 50mm 2 / s or less, or 10mm 2 The viscosity index of the ester may be 10 or more, 30 or more, or 50 or more, and may be 250 or less, 200 or less, or 150 or less.

[0045] The kinematic viscosity of the ester of neopentyl glycol or trimethylolpropane and a fatty acid having 4 to 10 carbon atoms at 40° C. may be 3 mm 2 / s or more, 5mm 2 / s or above, or 7mm 2 / s or more, can be 30mm 2 / s or less, 25mm 2 / s or less, 20mm 2 / s or less, 15mm 2 / s or less, or 10mm 2 The kinematic viscosity of the ester at 100°C may be 1 mm 2 / s or more, 1.5mm 2 / s or more, or 2mm 2 / s or more, can be 10mm 2 / s or less, 5mm 2 / s or less, or 3mm 2 The viscosity index of the ester may be 10 or more, 30 or more, or 40 or more, and may be 160 or less, 140 or less, 120 or less, 100 or less, 80 or less, 70 or less, or 60 or less.

[0046] The kinematic viscosity of the ester of neopentyl glycol or trimethylolpropane and a fatty acid having 10 to 20 carbon atoms at 40° C. may be 10 mm 2 / s or more, 15mm 2 / s or above, or 20mm 2 / s or more, can be 60mm 2 / s or less, 55mm 2 / s or less, or 50mm 2 The kinematic viscosity of the ester at 100°C may be 3 mm 2 / s or more, 4mm 2 / s or above, or 5mm 2 / s or more, can be 20mm 2 / s or less, 15mm 2 / s or less, or 10mm 2 The viscosity index of the ester may be 100 or more, 150 or more, or 170 or more, and may be 300 or less, 250 or less, or 220 or less.

[0047] The kinematic viscosity of the ester of pentaerythritol and a fatty acid having 4 to 9 carbon atoms at 40°C may be 30 mm 2 / s or more, 40mm 2 / s or above, or 50mm 2 / s or more, can be 100mm 2 / s or less, 80mm 2 / s or less, or 75mm 2 / s or less. The kinematic viscosity of the ester at 100°C may be 3 mm 2 / s or more, 4mm 2 / s or above, or 5mm 2 / s or more, can be 20mm 2 / s or less, 15mm 2 / s or less, or 10mm 2 The viscosity index of the ester may be 50 or more, 70 or more, or 80 or more, and may be 150 or less, 120 or less, or 100 or less.

[0048] Examples of the ether include polyethylene ether, polyalkylene glycol, polyphenylene ether and perfluoroether. The ether is preferably selected from polyethylene ether and polyalkylene glycol, and more preferably polyethylene ether.

[0049] The base oil preferably contains at least one selected from the group consisting of the above-mentioned hydrocarbon oils, esters and ethers, and more preferably contains at least one selected from the group consisting of mineral oils, synthetic hydrocarbon oils, esters of neopentyl glycol or trimethylolpropane and fatty acids having 4 to 10 carbon atoms, esters of neopentyl glycol or trimethylolpropane and fatty acids having 10 to 20 carbon atoms, and esters of pentaerythritol and fatty acids having 4 to 9 carbon atoms. From the viewpoint of obtaining a further high viscosity index improvement effect by adding the (meth)acrylate polymer, the base oil preferably contains at least one selected from the group consisting of mineral oil, synthetic hydrocarbon oil, esters of neopentyl glycol or trimethylolpropane and fatty acids having 4 to 10 carbon atoms, and esters of pentaerythritol and fatty acids having 4 to 9 carbon atoms. It is more preferred that the base oil contains at least one selected from the group consisting of mineral oil, synthetic hydrocarbon oil, and esters of neopentyl glycol or trimethylolpropane and fatty acids having 4 to 10 carbon atoms. It is further preferred that the base oil contains at least one selected from the group consisting of mineral oil and esters of neopentyl glycol or trimethylolpropane and fatty acids having 4 to 10 carbon atoms.

[0050] The kinematic viscosity of the base oil at 40°C can be 3 mm 2 / s or more, 4mm 2 / s or above, or 5mm 2 / s or more, can be 500mm 2 / s or less, 400mm 2 / s or less, or 300mm 2 The kinematic viscosity of the base oil at 100°C can be 1 mm 2 / s or more, 1.5mm 2 / s or more, or 2mm 2 / s or more, can be 100mm 2 / s or less, 50mm 2 / s or less, or 10mm 2 The viscosity index of the base oil may be 10 or more, 30 or more, or 50 or more, and may be 250 or less, 200 or less, or 150 or less.

[0051] The content of the 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 refrigerating machine oil.

[0052] The refrigerating machine oil contains, in addition to the base oil, a polymer including a structural unit represented by the following formula (1) (hereinafter also referred to as a "(meth)acrylate polymer").

[0053]

[0054] In formula (1), R 1represents a hydrogen atom or a methyl group, preferably represents a methyl group. 2 It represents an alkyl group or a group in which a part of the alkyl group is substituted (hereinafter also referred to as a "substituted alkyl group").

[0055] R 2 The alkyl group shown may be linear or branched. The number of carbon atoms in the alkyl group may be 1 or more and 20 or less. The substituted alkyl group may have, for example, a group containing at least one selected from a nitrogen atom and an oxygen atom. The group containing a nitrogen atom may be an amino group. The group containing an oxygen atom may be an ether group.

[0056] The (meth)acrylate polymer contains one or more structural units represented by formula (1), and preferably contains two or more structural units. The (meth)acrylate polymer preferably contains R 2 The first structural unit is a methyl group and R 2 The (meth)acrylate polymer may contain two or more of the second structural units. R in the second structural unit 2 The number of carbon atoms in the alkyl group may be 11 or more, 12 or more, or 13 or more, and may be 40 or less, 30 or less, 20 or less, 19 or less, or 18 or less.

[0057] R in the second structural unit 2 The alkyl group having 10 or more carbon atoms shown in the formula may be straight-chain or branched. When the alkyl group is branched, the alkyl group may have a methyl group or an ethyl group as a branch. The branched alkyl group having an ethyl group may be an alkyl group shown in the following formula (2a).

[0058]

[0059] In the formula, x represents an integer of 5 or more.

[0060] R in the second structural unit 2 When the alkyl group having 10 or more carbon atoms is branched, the alkyl group may be an alkyl group represented by the following formula (2b).

[0061]

[0062] In the formula, y and z are each independently an integer greater than or equal to 0, and y+z represents an integer greater than or equal to 6.

[0063] The (meth)acrylate polymer may include R 2 The first structural unit is a methyl group, R 2 One or more of the second structural units which are alkyl groups having 10 or more carbon atoms, and R 2The third structural unit is an alkyl group having 2 to 9 carbon atoms. The alkyl group having 2 to 9 carbon atoms is preferably a linear or branched alkyl group having 4 to 8 carbon atoms, and more preferably a branched alkyl group having 6 or 8 carbon atoms.

[0064] In the (meth)acrylate polymer, R 2 The average number of carbon atoms of the group shown (hereinafter also referred to as "average number of carbon atoms") is 4 to 18. The lower limit of the average number of carbon atoms may be 4.5 or more, 5 or more, 5.5 or more, or 6 or more. The upper limit of the average number of carbon atoms may be 17 or less, 16 or less, 15 or less, 14 or less, 13 or less, 12 or less, 11 or less, 10 or less, or 9.5 or less. R 2 The number of carbon atoms of the groups shown in the formula (A) is 4 or more on average, so that the (meth)acrylate polymer tends to show good compatibility with refrigeration oils and hydrocarbon refrigerants with slightly lower polarity, and tends to have a high viscosity index improvement effect. In addition, the (meth)acrylate polymer tends to have a high refrigerant dissolution viscosity improvement effect for a working fluid composition containing such a refrigeration oil and a refrigerant, and is useful as a refrigerant dissolution viscosity improver.

[0065] R in (meth)acrylate polymers 2 The carbon number of the groups shown is averaged by using 13 C-NMR analysis ( 1 H-gated decoupling method) was used to analyze the structure of (meth)acrylate polymers and analyze R 2 The ratio of the groups shown (eg, methyl group, long-chain alkyl group, branched-chain alkyl group, amino group, etc.) is calculated from the obtained ratio and the number of carbon atoms contained in each group.

[0066] The (meth)acrylate polymer may be a homopolymer composed of one of the structural units represented by formula (1), a copolymer composed of two or more of the structural units represented by formula (1), or a copolymer composed of the structural unit represented by formula (1) and other structural units. The content of the structural unit represented by formula (1) may be 50 mol% or more, 60 mol% or more, 70 mol% or more, 80 mol% or more, or 90 mol% or more, or may be 100 mol%, based on the total amount of the structural units constituting the (meth)acrylate polymer.

[0067] In one embodiment, the weight average molecular weight (Mw) of the (meth)acrylate polymer may be 500 or more, 1000 or more, 5000 or more, 10000 or more, 30000 or more, or 40000 or more, and may be 100000 or less, 80000 or less, or 60000 or less. In another embodiment, the weight average molecular weight (Mw) of the (meth)acrylate polymer may be more than 100000, 120000 or more, 150000 or more, or 200000 or more, and may be 1000000 or less, 800000 or less, 600000 or less, 500000 or less, or 400000 or less.

[0068] The weight average molecular weight (Mw) of the (meth)acrylate polymer refers to Mw (polystyrene (standard sample) conversion value) obtained by GPC analysis. Mw is measured, for example, as follows.

[0069] Tetrahydrofuran was used as a solvent for dilution to prepare a solution having a (meth)acrylate polymer concentration of 1% by mass. The solution was analyzed using a GPC device (Waters Alliance 2695). The flow rate of the solvent was 1 ml / min, and an appropriate column conforming to the molecular weight of the (meth)acrylate polymer to be analyzed was used, and the analysis was performed using a refractive index detector. It should be noted that the relationship between the column retention time and the molecular weight was obtained using a polystyrene standard with a clear molecular weight, and a standard curve was prepared separately. On this basis, the molecular weight was determined by the obtained retention time.

[0070] The content of the (meth)acrylate polymer can be 1% by mass or more, 3% by mass or more, 5% by mass or more, 10% by mass or more, 15% by mass or more, or 20% by mass or more, based on the total amount of the refrigeration oil, and can be 50% by mass or less, 40% by mass or less, 35% by mass or less, or 30% by mass or less.

[0071] The refrigerator oil may also contain other additives. As other additives, for example, acid scavengers, antioxidants, extreme pressure agents, oiliness agents, defoamers, metal deactivators, antiwear agents, viscosity index improvers, pour point depressants, clean dispersants, etc. may be cited. Based on the total amount of refrigerator oil, the total content of these additives may be 0.1% by mass or more, 1% by mass or more, or 2% by mass or less, or 10% by mass or less, 5% by mass or less, or 3% by mass or less.

[0072] The kinematic viscosity of refrigeration oil at 40°C can be 5 mm 2 / s or more, 10mm 2 / s or more, 20mm 2 / s or more, 30mm 2 / s or above, or 40mm2 / s or more, can be 500mm 2 / s or less, 400mm 2 / s or less, 300mm 2 / s or less, 200mm 2 / s or less, 100mm 2 / s or less, or 90mm 2 / s or less. The kinematic viscosity of refrigeration oil at 100°C can be 1 mm 2 / s or more, 2mm 2 / s or more, or 3mm 2 / s or more, can be 100mm 2 / s or less, 50mm 2 / s or less, or 40mm 2 / s or less. The viscosity index of the refrigeration oil can be above 80 and 100 mm 2 / s or more, 150 or more, 200 or more, or 220 or more, and may be 500 or less, 400 or less, or 300 or less.

[0073] Refrigeration oil is used together with refrigerant in refrigerators. Figure 1 Schematic diagram showing an embodiment of a refrigerator. Figure 1 As shown, the refrigerator 10 includes at least a compressor (refrigerant compressor) 1, a condenser (gas cooler) 2, an expansion mechanism 3 (capillary tube, expansion valve, etc.), and an evaporator (heat exchanger).

[0074] 4 and 5. The refrigeration cycle system 6 is connected in sequence through the flow path 5. The refrigeration cycle system 6 contains refrigeration oil and refrigerant. In order to suppress and prevent the liquid refrigerant from directly flowing into the compressor 1, the refrigeration cycle system 6 may further include a liquid accumulator 7 between the evaporator 4 and the compressor 1 (on the side of the compressor 1).

[0075] Examples of such a refrigerator 10 include automobile air conditioners, dehumidifiers, refrigerators, refrigerated warehouses, vending machines, showcases, cooling devices in chemical plants, residential air conditioners, package air conditioners, and hot water heat pumps.

[0076] In the refrigerant cycle system 6, first, the high-temperature (usually 70 to 120°C) refrigerant discharged from the compressor 1 into the flow path 5 becomes a high-density fluid (supercritical fluid, etc.) in the condenser 2. Then, the refrigerant passes through the narrow flow path of the expansion mechanism 3 and liquefies, and then vaporizes in the evaporator 4 to become a low-temperature (usually -40 to 0°C). The cooling device of the refrigerator 10 utilizes the phenomenon that the refrigerant takes away heat from the surrounding when it vaporizes in the evaporator 4.

[0077] In the compressor 1, a small amount of refrigerant and a large amount of refrigeration oil coexist under high temperature (usually 70 to 120°C). The refrigerant discharged from the compressor 1 to the flow path 5 is in the form of gas, and contains a small amount (usually 1 to 10 volume %) of refrigeration oil in the form of mist, but a small amount of refrigerant ( Figure 1 Point a).

[0078] In the condenser 2, the gaseous refrigerant is compressed to become a high-density fluid. Under relatively high temperature (usually 40 to 80°C), a large amount of refrigerant and a small amount of refrigeration oil coexist. Figure 1 In addition, a mixture of a large amount of refrigerant and a small amount of refrigeration oil is sequentially fed to the expansion mechanism 3 and the evaporator 4, and rapidly becomes a low temperature (usually -40 to 0°C) ( Figure 1 Points c, d) in the flow chart and return to compressor 1 again.

[0079] Another embodiment of the present invention can also be said to be a working fluid composition containing the above-mentioned refrigeration oil and refrigerant. The refrigerant dissolution viscosity of the working fluid composition can be improved by using the above-mentioned (meth)acrylate polymer. That is, another embodiment of the present invention can also be said to be a refrigerant dissolution viscosity improver of a working fluid composition containing the above-mentioned (meth)acrylate polymer and comprising refrigeration oil and refrigerant.

[0080] Examples of the refrigerant include saturated fluorinated hydrocarbons (also referred to as HFCs), unsaturated fluorinated hydrocarbons (also referred to as HFOs), hydrocarbons, fluorinated ethers, bis(trifluoromethyl)sulfide, trifluoromethyl iodide, ammonia, and carbon dioxide. The refrigerant may be a single refrigerant among these refrigerants or a mixed refrigerant of two or more.

[0081] The refrigerant preferably contains hydrocarbons. The content of hydrocarbons 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 refrigerant. The refrigerant may also be composed only of hydrocarbons.

[0082] As the saturated fluorinated hydrocarbon, preferably those having 1 to 3 carbon atoms, more preferably 1 to 2 carbon atoms are mentioned. Examples of the saturated fluorinated hydrocarbons 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).

[0083] As the saturated fluorinated hydrocarbon, for example, R32 alone; R23 alone; R134a alone; R125 alone; a mixture of R134a / R32=60-80 mass% / 40-20 mass%; a mixture of R32 / R125=40-70 mass% / 60-30 mass%; a mixture of R125 / R143a=40-60 mass% / 60-40 mass%; a mixture of R134a / R32 / R125=60 mass% / 30 mass% / 10 mass%; a mixture of R134a / R32 / R125=40-70 mass% / 15-35 mass% / 5-40 mass%; a mixture of R125 / R134a / R143a=35-55 mass% / 1-15 mass% / 40-60 mass%, etc. are preferred examples. More specifically, there can be mentioned a mixture of R134a / R32=70 / 30 mass %; a mixture of R32 / R125=60 / 40 mass %; a mixture of R32 / R125=50 / 50 mass % (R410A); a mixture of R32 / R125=45 / 55 mass % (R410B); a mixture of R125 / R143a=50 / 50 mass % (R507C); A mixture of R32 / R125 / R134a=30 / 10 / 60 mass %; a mixture of R32 / R125 / R134a=23 / 25 / 52 mass % (R407C); a mixture of R32 / R125 / R134a=25 / 15 / 60 mass % (R407E); a mixture of R125 / R134a / R143a=44 / 4 / 52 mass % (R404A).

[0084] Examples of the unsaturated fluorinated hydrocarbon include unsaturated fluorinated hydrocarbons having one or more carbon-carbon double bonds and having fluorine and hydrogen and having 2 to 4 carbon atoms. The unsaturated fluorinated hydrocarbon is preferably a fluoropropylene, and more preferably a fluoropropylene having 3 to 5 fluorine atoms. Examples of the unsaturated fluorinated hydrocarbon include 1,2,3,3,3-pentafluoropropylene (HFO-1225ye), 1,3,3,3-tetrafluoropropylene (HFO-1234ze), 2,3,3,3-tetrafluoropropylene (HFO-1234yf), 1,2,3,3-tetrafluoropropylene (HFO-1234ye) and 3,3,3-trifluoropropylene (HFO-1243zf). The unsaturated fluorinated hydrocarbon is preferably at least one selected from HFO-1225ye, HFO-1234ze and HFO-1234yf. The unsaturated fluorinated hydrocarbon may be vinyl fluoride having a fluorine number of 1 to 4, and may preferably be 1,1,2,3-trifluoroethylene.

[0085] The hydrocarbon is preferably a hydrocarbon having 1 to 5 carbon atoms, and more preferably a hydrocarbon having 2 to 4 carbon atoms. Examples of the hydrocarbon include methane, ethylene, ethane, propylene, propane (R290), cyclopropane, n-butane, isobutane, cyclobutane, methylcyclopropane, 2-methylbutane, and n-pentane. The hydrocarbon is preferably at least one selected from the group consisting of propane, n-butane, isobutane, and 2-methylbutane.

[0086] For example, when the oil content (amount of refrigeration oil (g) / total amount of refrigeration oil and refrigerant (g) × 100) (mass %) is 20 mass %, the low temperature side double layer separation temperature of refrigeration oil and refrigerant is preferably 10°C or less, more preferably 0°C or less, further preferably -20°C or less, and may be -30°C or less. The refrigerant exhibiting such a low temperature side double layer separation temperature may be a refrigerant containing the above-mentioned hydrocarbons, or may be a refrigerant containing propane or isobutane.

[0087] The content of the refrigeration oil in the working fluid composition may be 1 part by mass or more or 2 parts by mass or more, and may be 500 parts by mass or less or 400 parts by mass or less, based on 100 parts by mass of the refrigerant.

[0088] Example

[0089] Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited to the Examples.

[0090] Using the base oils and (meth)acrylate polymers shown below, refrigerating machine oils having the compositions (% by mass based on the total amount of the refrigerating machine oil) shown in Tables 1 to 9 were prepared. In these refrigerating machine oils, the base oils and (meth)acrylate polymers were compatible with each other.

[0091] (Base oil)

[0092] Base oil 1: Hydrocracked mineral oil (40℃ kinematic viscosity: 19.4mm 2 / s, 100℃ kinematic viscosity: 4.2mm 2 / s, viscosity index: 126)

[0093] Base oil 2: Hydrocracked mineral oil (40℃ kinematic viscosity: 11.7mm 2 / s, 100℃ kinematic viscosity: 3.0mm 2 / s, viscosity index: 106)

[0094] Base oil 3: Ester of trimethylolpropane and oleic acid (40°C kinematic viscosity: 47.6 mm 2 / s, 100℃ kinematic viscosity: 9.6mm 2 / s, viscosity index: 191)

[0095] Base oil 4: Ester of neopentyl glycol and 2-ethylhexanoic acid (40°C kinematic viscosity: 7.4 mm 2 / s, 100℃ kinematic viscosity: 2.0mm 2 / s, viscosity index: 52)

[0096] Base oil 5: Ester of pentaerythritol and 2-ethylhexanoic acid / 3,5,5-trimethylhexanoic acid (molar ratio: 50 / 50) (40°C kinematic viscosity: 68.4 mm 2 / s, 100℃ kinematic viscosity: 8.4mm 2 / s, viscosity index: 90)

[0097] Base oil 6: wax isomerized oil (40℃ kinematic viscosity: 15.7mm 2 / s, 100℃ kinematic viscosity: 3.8mm 2 / s, viscosity index: 143)

[0098] Base oil 7: Hydrogenated poly-alpha olefin (40°C kinematic viscosity: 18.4 mm 2 / s, 100℃ kinematic viscosity: 4.1mm 2 / s, viscosity index: 124)

[0099] Base oil 8: Hydrogenated poly-alpha olefin (40°C kinematic viscosity: 29.8 mm 2 / s, 100℃ kinematic viscosity: 5.8mm 2 / s, viscosity index: 143)

[0100] Base oil 9: Ester of trimethylolpropane and n-octanoic acid / n-decanoic acid (40℃ kinematic viscosity: 20.5mm 2 / s, 100℃ kinematic viscosity: 4.5mm 2 / s, viscosity index: 137)

[0101] Base oil 10: Ester of neopentyl glycol and oleic acid (40°C kinematic viscosity: 24.4 mm 2 / s, 100℃ kinematic viscosity: 5.9mm 2 / s, viscosity index: 204)

[0102] Base oil 11: Hydrorefined mineral oil (40℃ kinematic viscosity: 96.3mm 2 / s, 100℃ kinematic viscosity 8.6mm 2 / s, viscosity index: 36

[0103] Base oil 12: Alkylbenzene (40℃ kinematic viscosity: 19.3mm 2 / s, 100℃ kinematic viscosity 3.7mm 2 / s, viscosity index: 48)

[0104] ((Meth)acrylate polymer)

[0105] Polymer 1: (meth)acrylate polymer (R in formula (1) 2 Composition (molar ratio): methyl (71) / linear alkyl group having 10 or more carbon atoms (19) / branched alkyl group having 10 or more carbon atoms (10), R 2 Average number of carbon atoms: 6.4, Mw: 21000)

[0106] Polymer 2: (meth)acrylate polymer (R in formula (1) 2 Composition (molar ratio): methyl group (30) / linear alkyl group having 10 or more carbon atoms (average carbon number 13) (70), R 2 Average number of carbon atoms: 9.4, Mw: 50000)

[0107] Polymer 3: (meth)acrylate polymer (R in formula (1) 2 Composition (molar ratio): linear alkyl group having 10 or more carbon atoms (54) / branched alkyl group having 10 or more carbon atoms (46) (including branched alkyl group having ethyl group (9)), R 2 Average number of carbon atoms: 14.9, Mw: 8000)

[0108] Polymer 4: (meth)acrylate polymer (R in formula (1) 2 Composition (molar ratio): methyl (22) / linear alkyl having 10 or more carbon atoms (66) / N,N-dimethylethylamino (2) / N,N-diethylethylamino (10), R 2 Average number of carbon atoms: 8.7, Mw: 47000)

[0109] Polymer 5: (meth)acrylate polymer (R in formula (1) 2 Composition (molar ratio): methyl (70) / linear alkyl group having 10 or more carbon atoms (17) / branched alkyl group having 10 or more carbon atoms (13), R 2 Average number of carbon atoms: 6.7, Mw: 80000)

[0110] Polymer 6: (meth)acrylate polymer (R in formula (1) 2 Composition (molar ratio): methyl (38) / linear alkyl with 10 or more carbon atoms (50) / branched alkyl with 10 or more carbon atoms (5) / 2-methylpentyl (5) / 2-ethylhexyl (2), R 2 Average number of carbon atoms: 7.9, Mw: 230000)

[0111] Polymer 7: (meth)acrylate polymer (R in formula (1) 2 Composition (molar ratio): methyl (40) / linear alkyl group having 10 or more carbon atoms (51) / branched alkyl group having 10 or more carbon atoms (5) / 2-methylpentyl (3) / 2-ethylhexyl (1), R 2 Average number of carbon atoms: 8.4, Mw: 420000)

[0112] (Comparative polymer)

[0113] Ethylene alpha olefin copolymer

[0114] (Determination of physical properties of refrigeration oil)

[0115] The refrigerating machine oil of each example was measured for its kinematic viscosity at 40° C. and 100° C., and viscosity index in accordance with JIS K2283: 2000. The results are shown in Tables 1 to 9.

[0116] (Refrigeration oil refrigerant compatibility)

[0117] For the refrigeration oil of each example, according to the "Compatibility Test Method with Refrigerants" of JIS K2211:2009, 4 g of the refrigeration oil was mixed with 16 g of R290, which is a refrigerant containing hydrocarbons, and the refrigeration oil and the refrigerant were observed at 0°C to see whether they were mutually soluble. The case where the refrigeration oil and the refrigerant were mutually soluble was evaluated as "compatible", and the case where the refrigeration oil and the refrigerant were separated into two layers was evaluated as "separated". The results are shown in Tables 1 to 9.

[0118] [Table 1]

[0119]

[0120] [Table 2]

[0121]

[0122] [Table 3]

[0123]

[0124] [Table 4]

[0125]

[0126] [Table 5]

[0127]

[0128] [Table 6]

[0129]

[0130] [Table 7]

[0131]

[0132] [Table 8]

[0133]

[0134] [Table 9]

[0135]

[0136] For the refrigeration oils of the embodiments shown in Tables 10 to 13 below, the refrigerant solution viscosity, refrigerant fraction (refrigerant dissolution amount) and double-layer separation temperature were measured according to the following steps. In addition, for reference, the refrigeration oils of the reference examples shown in Tables 10 to 13 were also measured in the same manner. The results are shown in Tables 10 to 13.

[0137] (Determination of refrigerant solution viscosity)

[0138] First, in a pressure-resistant container (volume V = 400 cm) equipped with a vibration viscometer, thermometer, and pressure gauge, 3 ) is filled with 100g of refrigeration oil, the pressure container is vacuum degassed, and then filled with refrigerant (R290). The temperature of the working fluid and the pressure in the pressure container are adjusted to achieve a temperature of 80°C and an absolute pressure of 2.8MPa, to prepare a working fluid composition formed by refrigeration oil and refrigerant. When the specified conditions are not met, it is also appropriate to adjust the filling amount of refrigeration oil. Under this condition, a vibration viscometer is used to measure the absolute viscosity (mPa·s) of the working fluid composition. The refrigerant dissolution viscosity R-Vis (mm 2 / s) as the measured absolute viscosity P (mPa·s) divided by the density Dw (g / cm 3 The density Dw (g / cm 3 ) is calculated according to the following formula.

[0139] Dw=(Rf-Vv×Dv+Of) / Vmix

[0140] Dw: Density of the working fluid composition (g / cm 3 )

[0141] Rf: The amount of refrigerant filled in the pressure container (g)

[0142] Vv: The volume of the refrigerant vapor in the pressure container (cm 3 )(=Volume V of the pressure vessel-Volume Vmix of the working fluid composition)

[0143] Dv: Refrigerant vapor density (g / cm 3 )

[0144] Of: The amount of refrigeration oil filled in the pressure container (g)

[0145] Vmix: Volume of working fluid composition (cm 3 )

[0146] (Determination of refrigerant fraction (refrigerant dissolved amount))

[0147] The refrigerant fraction S (mass %) in the working fluid composition is calculated according to the following formula from the filling amounts of refrigeration oil and refrigerant, the volume of the refrigerant vapor portion in the pressure container and the refrigerant vapor density under the same conditions as the above-mentioned refrigerant dissolution viscosity measurement.

[0148] S=(Rf-Vv×Dv)×100 / ((Rf-Vv×Dv)+Of)

[0149] S: Refrigerant fraction in the working fluid composition (mass %)

[0150] Rf: The amount of refrigerant filled in the pressure container (g)

[0151] Vv: Volume of refrigerant vapor in the pressure container (cm 3 )(=Volume V of the pressure vessel-Volume Vmix of the working fluid composition)

[0152] Dv: Refrigerant vapor density (g / cm 3 )

[0153] Of: The amount of refrigeration oil filled in the pressure container (g)

[0154] (Determination of double layer separation temperature)

[0155] The low temperature side double layer separation temperature was measured when the oil content (amount of refrigeration oil (g) / total amount of refrigeration oil and refrigerant (g) × 100) (mass %) was 20 mass %. Specifically, 20 g of refrigeration oil and 80 g of refrigerant (R290) were used to measure the low temperature side double layer separation temperature.

[0156] [Table 10]

[0157]

[0158] [Table 11]

[0159]

[0160] [Table 12]

[0161]

[0162] [Table 13]

[0163]

[0164] Description of Reference Numerals

[0165] 1 ... compressor, 2 ... condenser, 3 ... expansion mechanism, 4 ... evaporator, 5 ... flow path, 6 ... refrigerant circulation system, 7 ... accumulator, 10 ... refrigerator.

Claims

1. A refrigeration oil comprising: Base oil, and A polymer comprising a structural unit represented by the following formula (1), In formula (1), R 1 represents a hydrogen atom or a methyl group, R 2 represents an alkyl group or a group in which a part of the alkyl group is substituted, The R in the polymer 2 The groups shown have 4 to 18 carbon atoms on average.

2. The refrigerating machine oil according to claim 1, which is used together with a refrigerant containing hydrocarbons.

3. A working fluid composition comprising: The refrigerating machine oil according to claim 1, and refrigerant.

4. The working fluid composition according to claim 3, wherein: The refrigerant includes a hydrocarbon.

5. A refrigerant solution viscosity improver, which is a refrigerant solution viscosity improver of a working fluid composition comprising a refrigerator oil and a refrigerant, The refrigerant melt viscosity improver contains a polymer having a structural unit represented by the following formula (1): In formula (1), R 1 represents a hydrogen atom or a methyl group, R 2 represents an alkyl group or a group in which a part of the alkyl group is substituted, The R in the polymer 2 The groups shown have 4 to 18 carbon atoms on average.

6. The refrigerant solution viscosity improver according to claim 5, wherein The refrigerant includes a hydrocarbon.

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