Refrigerator, working fluid composition, and refrigerator oil

Abstract

Provided is a refrigerator equipped with a refrigerant circulation system having a compressor, a condenser, an expansion mechanism, and an evaporator, wherein the refrigerant circulation system has a member containing at least one selected from the group consisting of ethylene propylene diene rubber and hydrogenated nitrile butadiene rubber, the refrigerant circulation system is filled with a refrigerant containing a hydrocarbon and a refrigerator oil containing a compound represented by formula (1) [in the formula, R1 and R2 each independently are a hydrogen atom or an alkyl group, R3 is an ethylene group or a propylene group, and m is an integer of 2 or more.], and the molar ratio of ethylene groups / propylene groups in the compound represented by formula (1) is 85 / 15 or less.

Description

Refrigerating machines, working fluid compositions, and refrigeration oils

[0001] The present invention relates to a refrigerator, a working fluid composition, and a refrigerating machine oil.

[0002] Refrigerators, air conditioners, and other such freezers contain rubber components. For example, hydrogenated nitrile rubber and ethylene propylene diene rubber are known rubbers used in seal members for freezers (see, for example, Patent Document 1). Patent Document 1 describes that hydrogenated nitrile rubber has problems with blister resistance and permeability to refrigerants, while ethylene propylene diene rubber has relatively good blister resistance and permeability but has problems with resistance to refrigerating machine oil.

[0003] JP 2011-79974 A

[0004] According to the investigations of the present inventors, when a refrigerant containing a hydrocarbon and a refrigerating machine oil containing a polyalkylene glycol compound are used in a refrigerating machine having a component containing hydrogenated nitrile or ethylene propylene diene rubber, the acid value of the refrigerating machine oil may increase with use.

[0005] Therefore, one aspect of the present invention aims to suppress an increase in the acid value of a refrigerating machine oil that occurs during use when a refrigerant containing a hydrocarbon and a refrigerating machine oil containing a polyalkylene glycol compound are used in a refrigerating machine having a component containing hydrogenated nitrile or ethylene propylene diene rubber.

[0006] The present inventors have found that by appropriately adjusting the ratio of ethylene groups to propylene groups in a polyalkylene glycol-based compound, it is possible to suppress an increase in the acid value of a refrigerating machine oil that occurs during use, even when the refrigerating machine oil containing the polyalkylene glycol-based compound is used together with a refrigerant that contains a hydrocarbon in a refrigerator having components that contain hydrogenated nitrile or ethylene propylene diene rubber.

[0007] [1] A refrigerator equipped with a refrigerant circulation system having a compressor, a condenser, an expansion mechanism, and an evaporator, wherein the refrigerant circulation system has a member containing at least one selected from the group consisting of ethylene propylene diene rubber and hydrogenated nitrile butadiene rubber, and the refrigerant circulation system is filled with a refrigerant containing a hydrocarbon and a refrigerating machine oil containing a compound represented by the following formula (1): [In the formula, R １ and R ２ are each independently a hydrogen atom or an alkyl group, and R ３ is an ethylene group or a propylene group, and m is an integer of 2 or more.] A refrigerator in which the molar ratio of ethylene groups / propylene groups in the compound represented by formula (1) is 85 / 15 or less. [2] The refrigerator according to [1], in which the molar ratio of ethylene groups / propylene groups in the compound represented by formula (1) is 20 / 80 or more. [3] The refrigerator according to [1], in which the compound represented by formula (1) is １ and R ２ The refrigerator according to [1] or [2], containing a compound in which one of the groups is a hydrogen atom and the other is an alkyl group.

[0008] [4] A working fluid composition containing a refrigerant and a refrigerating machine oil, wherein the refrigerant contains a hydrocarbon, and the refrigerating machine oil contains a compound represented by the following formula (1): [In the formula, R １ and R ２ are each independently a hydrogen atom or an alkyl group, and R ３ is an ethylene group or a propylene group, and m is an integer of 2 or more.] A working fluid composition, wherein the molar ratio of ethylene groups / propylene groups in the compound represented by formula (1) is 85 / 15 or less, and the working fluid composition is used in a refrigerator equipped with a refrigerant circulation system having a compressor, a condenser, an expansion mechanism, and an evaporator, the refrigerant circulation system having a member containing at least one member selected from the group consisting of ethylene propylene diene rubber and hydrogenated nitrile butadiene rubber.

[0009] [5] A refrigerating machine oil containing a compound represented by the following formula (1): [In the formula, R １ and R ２are each independently a hydrogen atom or an alkyl group, and R ３ is an ethylene group or a propylene group, and m is an integer of 2 or greater.] A refrigerating machine oil, wherein the molar ratio of ethylene groups / propylene groups in the compound represented by formula (1) is 85 / 15 or less, and the refrigerating machine oil is used together with a refrigerant containing a hydrocarbon in a refrigerating machine equipped with a refrigerant circulation system having a compressor, a condenser, an expansion mechanism, and an evaporator, and the refrigerant circulation system has a member containing at least one selected from the group consisting of ethylene propylene diene rubber and hydrogenated nitrile butadiene rubber.

[0010] According to one aspect of the present invention, in a refrigerator having a component containing hydrogenated nitrile or ethylene propylene diene rubber, when a refrigerant containing a hydrocarbon and a refrigerating machine oil containing a polyalkylene glycol-based compound are used, an increase in the acid value of the refrigerating machine oil due to use can be suppressed.

[0011] FIG. 1 is a schematic diagram illustrating an embodiment of a refrigerator.

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

[0013] Fig. 1 is a schematic diagram showing one embodiment of a refrigerator. As shown in Fig. 1, the refrigerator 10 includes at least a refrigerant circulation system 6 in which a compressor (refrigerant compressor) 1, a condenser (gas cooler) 2, an expansion mechanism 3 (capillary, expansion valve, etc.), and an evaporator (heat exchanger) 4 are sequentially connected by a flow path 5. In one embodiment, the refrigerant circulation system 6 further includes an accumulator 7 between the evaporator 4 and the compressor 1 (on a side of the compressor 1) to suppress or prevent liquid refrigerant from flowing directly into the compressor 1.

[0014] The refrigerant circulation system 6 is filled with a refrigerant and refrigeration oil. In the refrigerant circulation system 6, first, a high-temperature (usually 70 to 120°C) refrigerant discharged from the compressor 1 into the flow path 5 becomes a high-density fluid (such as a supercritical fluid) in the condenser 2. Next, the refrigerant is liquefied by passing through a narrow flow path in the expansion mechanism 3, and then vaporizes in the evaporator 4 to become a low temperature (usually -40 to 0°C). Cooling by the refrigerator 10 utilizes the phenomenon in which the refrigerant absorbs heat from the surroundings when vaporizing in the evaporator 4.

[0015] A small amount of refrigerant and a large amount of refrigerating machine oil coexist under high temperature conditions (usually 70 to 120°C) inside the compressor 1. The refrigerant discharged from the compressor 1 to the flow path 5 is in a gaseous state and contains a small amount (usually 1 to 10% by volume) of refrigerating machine oil as a mist, and a small amount of refrigerant is dissolved in this mist-like refrigerating machine oil (point a in Figure 1).

[0016] In the condenser 2, the gaseous refrigerant is compressed to become a high-density fluid, and a large amount of refrigerant and a small amount of refrigerating machine oil coexist under relatively high temperature conditions (usually 40 to 80°C) (point b in Figure 1). Furthermore, the mixture of a large amount of refrigerant and a small amount of refrigerating machine oil is sent sequentially to the expansion mechanism 3 and the evaporator 4, where it is rapidly cooled (usually -40 to 0°C) (points c and d in Figure 1), and then returned to the compressor 1.

[0017] Examples of such a chiller 10 include refrigeration devices, air conditioners, etc. Examples of refrigeration devices include refrigerators, refrigerated and frozen warehouses, vending machines, cooling devices used in chemical plants, etc. Examples of air conditioners include automotive air conditioners, residential air conditioners, packaged air conditioners, dehumidifiers, etc.

[0018] The refrigerant circulation system 6 includes a member containing at least one selected from the group consisting of ethylene propylene diene rubber (EPDM) and hydrogenated nitrile butadiene rubber (H-NBR). Such a member may be, for example, an insulating member in the compressor 1, or a sealing member for preventing leakage of the refrigerant and refrigerating machine oil from the compressor 1.

[0019] The refrigerant contains a hydrocarbon. The hydrocarbon is preferably a hydrocarbon having 1 to 5 carbon atoms, more preferably a hydrocarbon having 2 to 4 carbon atoms. Examples of hydrocarbons include methane, ethylene, ethane, propylene, propane (R290), cyclopropane, normal butane, isobutane (R600a), cyclobutane, methylcyclopropane, 2-methylbutane, and normal pentane. The refrigerant may contain only one of these hydrocarbons, or may contain two or more of them. The refrigerant preferably contains a hydrocarbon that is gaseous at 25°C and 1 atmosphere, and more preferably contains at least one selected from the group consisting of propane, normal butane, isobutane, and 2-methylbutane.

[0020] The refrigerant may consist solely of hydrocarbons, or may contain hydrocarbons and other refrigerants, such as saturated fluorohydrocarbons, unsaturated fluorohydrocarbons, fluorinated ethers such as perfluoroethers, bis(trifluoromethyl)sulfide, trifluoroiodomethane, ammonia, and carbon dioxide.

[0021] The hydrocarbon content may be 50 mass % or more, 60 mass % or more, 70 mass % or more, 80 mass % or more, 90 mass % or more, or 95 mass % or more based on the total amount of the refrigerant.

[0022] The refrigerating machine oil contains a compound represented by the following formula (1) (hereinafter also referred to as a "PAG compound"). In the formula, R １ and R ２ are each independently a hydrogen atom or an alkyl group, and R ３ is an ethylene group or a propylene group, and m is an integer of 2 or more.

[0023] R １ and R ２ The alkyl group represented by the formula (I) may be linear or branched. The number of carbon atoms in the alkyl group may be 1 or more, 2 or more, or 3 or more, and may be 16 or less, 12 or less, 8 or less, or 5 or less, or may be 4. The alkyl group may preferably be an n-butyl group.

[0024] From the viewpoint of further suppressing an increase in the acid value of the refrigerating machine oil, the PAG compound is preferably R １ and R ２ In addition to the PAG compounds having a hydroxyl group at one end, the PAG compounds include compounds having a hydroxyl group at one end, in which R １ and R ２ and (b) may further include a compound in which both of the groups are hydrogen atoms (a PAG compound having hydroxyl groups at both ends).

[0025] The ratio of terminal hydroxyl groups to all terminal groups of a PAG compound (R １ and R ２ R for all of １ and R ２ are hydrogen atoms) may be 10 mol% or more, 20 mol% or more, 30 mol% or more, 40 mol% or more, 50 mol% or more, 60 mol% or more, or 70 mol% or more, and may be 90 mol% or less, 80 mol% or less, 70 mol% or less, 60 mol% or less, or 50 mol% or less, and from the viewpoint of being able to further suppress an increase in the acid value of the refrigerating machine oil, may be preferably 45 mol% or less, 40 mol% or less, or 35 mol% or less.

[0026] The ratio of terminal hydroxyl groups to all terminal groups of the PAG compound is １３ It is determined by C-NMR measurement. Specifically, the ratio is １３ From the spectrum obtained by C-NMR measurement, a peak derived from the carbon constituting the hydrocarbon group having a terminal hydroxyl group and a peak derived from the carbon constituting the terminal hydrocarbon group (such as an alkyl group) can be identified, and the integral value of each peak can be used to appropriately determine the molecular weight.

[0027] In one molecule of a PAG compound, R ３ is an ethylene group, and R ３ is a propylene group. That is, the PAG compound preferably contains both ethylene oxide units (EO units) and propylene oxide units (PO units). In this case, the PAG compound may be a random copolymer or a block copolymer.

[0028] The PAG compound has a molar ratio of ethylene groups to propylene groups (EO units to PO units) (hereinafter also referred to as "EO / PO ratio") of 85 / 15 or less. This makes it possible to suppress an increase in the acid value of a refrigerating machine oil that is caused by use in a refrigerating machine having a component that contains EPDM or H-NBR, when the refrigerant contains a hydrocarbon and the refrigerating machine oil contains a polyalkylene glycol compound. The EO / PO ratio may be 80 / 20 or less, 75 / 25 or less, 70 / 30 or less, 65 / 35 or less, or 60 / 40 or less, or may be 3 / 97 or more, 5 / 95 or more, or 7 / 93 or more. From the viewpoint of further suppressing an increase in the acid value of the refrigerating machine oil, it may be preferably 10 / 90 or more, 15 / 85 or more, 20 / 80 or more, or 25 / 75 or more, more preferably 30 / 70 or more, 35 / 45 or more, 40 / 60 or more, 45 / 55 or more, 50 / 50 or more, or 55 / 45 or more. The EO / PO ratio is particularly preferably 55 / 45 or less, 50 / 50 or less, 45 / 55 or less, 40 / 60 or less, or 38 / 62 or less, and particularly preferably 30 / 70 or more, 33 / 67 or more, or 35 / 65 or more.

[0029] The EO / PO ratio in the PAG compound is １３ Specifically, the EO / PO ratio is determined by C-NMR measurement. １３ From the spectrum obtained by C-NMR measurement, peaks derived from carbons constituting EO units and peaks derived from carbons constituting PO units can be identified, and the amount of each peak can be appropriately determined using information on EO units and PO units and the integral values ​​of each peak.

[0030] In formula (1), m may be 2 or more, 5 or more, 10 or more, or 15 or more, and may be 40 or less, 35 or less, 30 or less, or 25 or less. The PAG compound may be a mixture of multiple types of PAG compounds each having a different m value. The average value of m may be 2 or more, 5 or more, 10 or more, or 15 or more, and may be 40 or less, 35 or less, 30 or less, or 25 or less. The number average molecular weight (Mn) of the PAG compound may be 500 or more, 700 or more, or 900 or more, and may be 1800 or less, 1600 or less, or 1400 or less. In other embodiments, the number average molecular weight (Mn) of the PAG compound may be 1250 or less or less than 1250, 1100 or less or less than 1100, 1050 or less or less than 1050, or 1000 or less.

[0031] The number average molecular weight (Mn) in this specification refers to the Mn (value converted to polypropylene glycol (standard sample)) obtained by GPC analysis. Specifically, for example, chloroform is used as a solvent, and a solution with a sample concentration of 2% by mass is prepared by dilution, and analysis is performed using a GPC device (for example, Alliance 2695, manufactured by Waters). The solvent flow rate is set to 1 ml / min, and a column with an analyzable molecular weight of 100 to 10,000 is used, and the analysis is performed using a refractive index detector. Note that the relationship between column retention time and molecular weight is determined using a polypropylene glycol standard with a clear molecular weight, and a calibration curve is separately created, and the molecular weight is determined from the obtained retention time.

[0032] The content of the PAG compound 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.

[0033] The refrigeration oil contains a PAG compound as a base oil and may further contain other base oils. Examples of other base oils include mineral oils and synthetic oils. The mineral oil may be paraffinic mineral oil, naphthenic mineral oil, etc. Examples of synthetic oils include synthetic hydrocarbon oils such as poly-α-olefins and alkylbenzenes, and oxygenated oils such as polyalkylene glycol compounds, esters, and polyvinyl ethers other than the PAG compounds.

[0034] The refrigerating machine oil may further contain additives. Examples of the additives include antioxidants, antiwear agents, acid scavengers, oxygen scavengers, extreme pressure agents, oiliness agents, antifoaming agents, metal deactivators, viscosity index improvers, pour point depressants, and detergent dispersants. The content of the additives may be 0.1% by mass or more or 1% by mass or more, and 10% by mass or less or 5% by mass or less, based on the total amount of the refrigerating machine oil.

[0035] The refrigerating machine oil preferably further contains an antioxidant. Examples of the antioxidant include phenol-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). The content of the antioxidant may be 0.01% by mass or more or 0.1% by mass or more, and may be 5% by mass or less, 3% by mass or less, or 1% by mass or less, based on the total amount of the refrigerating machine oil.

[0036] The refrigerating machine oil preferably further contains a phosphorus-based antiwear agent. Examples of phosphorus-based antiwear agents include phosphate esters, thiophosphate esters, acidic phosphate esters, amine salts of acidic phosphate esters, chlorinated phosphate esters, and phosphites. Examples of phosphate esters include triaryl phosphates such as tricresyl phosphate (TCP), triphenyl phosphate (TPP), and alkylated triphenyl phosphates (e.g., propylated triphenyl phosphate, butylated triphenyl phosphate), and trialkyl phosphates. Examples of thiophosphate esters include triphenylphosphorothionate (TPPT). The content of the phosphorus-based antiwear agent may be, for example, 0.01% by mass or more or 0.1% by mass or more, and 5% by mass or less or 3% by mass or less, based on the total amount of the refrigerating machine oil.

[0037] The refrigerating machine oil preferably further contains an acid scavenger. Examples of the acid scavenger include epoxy-based acid scavengers. Examples of epoxy-based acid scavengers include glycidyl ether-based acid scavengers having a hydrocarbon group with 6 to 18 carbon atoms, such as 2-ethylhexyl glycidyl ether and 4-tert-butylphenyl glycidyl ether; glycidyl ester-based acid scavengers having a hydrocarbon group with 6 to 18 carbon atoms, such as glycidyl neodecanoate; α-olefin oxide-based acid scavengers having 6 to 18 carbon atoms, such as 1,2-epoxydodecane and 1,2-epoxytetradecane; and alicyclic epoxy-based acid scavengers. The content of the acid scavenger may be 0.01% by mass or more or 0.1% by mass or more, and may be 5% by mass or less, 3% by mass or less, or 1% by mass or less, based on the total amount of the refrigerating machine oil.

[0038] The kinematic viscosity of the refrigerating oil at 40°C is 20 mm ２ / s or more, 30mm ２ / s or more, or 40 mm ２ / s or more, and 100 mm ２ / s or less, 80mm ２ / s or less, or 60 mm ２ The kinematic viscosity of the refrigerating machine oil at 100°C may be 1 mm / s or less. ２ / s or more, 3mm２ / s or more, or 5 mm ２ / s or more, and ２ / s or less, 20mm ２ / s or less, or 15 mm ２ The viscosity index of the refrigerating machine oil may be 100 or more, 120 or more, or 140 or more, and may be 270 or less, 250 or less, or 230 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.

[0039] As described above, since a refrigerant and a refrigerating machine oil coexist in the refrigerator 10 (refrigerant circulation system 6), another embodiment of the present invention is a working fluid composition containing the above-mentioned hydrocarbon-containing refrigerant and the above-mentioned PAG-based compound-containing refrigerating machine oil, and is also a working fluid composition used in the above-mentioned refrigerator. In another embodiment, the working fluid composition is also a working fluid composition that can be applied to a refrigerator equipped with a refrigerant circulation system having both a component containing ethylene propylene diene rubber and a component containing hydrogenated nitrile butadiene rubber. In another embodiment, the working fluid composition is also a working fluid composition that can be applied to both a refrigerator equipped with a refrigerant circulation system having a component containing ethylene propylene diene rubber and a refrigerator equipped with a refrigerant circulation system having a component containing hydrogenated nitrile butadiene rubber.

[0040] Another embodiment of the present invention is a refrigerating machine oil containing the PAG compound, which is used in the refrigerating machine together with the refrigerant containing the hydrocarbon. In another embodiment, the refrigerating machine oil is applicable to a refrigerating machine equipped with a refrigerant circulation system having both a component containing ethylene propylene diene rubber and a component containing hydrogenated nitrile butadiene rubber. In another embodiment, the refrigerating machine oil is applicable to both a refrigerating machine equipped with a refrigerant circulation system having a component containing ethylene propylene diene rubber and a refrigerating machine equipped with a refrigerant circulation system having a component containing hydrogenated nitrile butadiene rubber.

[0041] The content of the refrigerating machine oil 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, per 100 parts by mass of the refrigerant.

[0042] The present invention will be described in more detail below based on examples, but the present invention is not limited to the following examples.

[0043] The following PAG compounds 1 to 6 were used as base oils to prepare refrigerating machine oils for Examples and Comparative Examples. Each refrigerating machine oil contained 0.5 mass% of a phenolic antioxidant (DBPC), 1.0 mass% of a phosphorus-based antiwear agent (TCP), and 0.5 mass% of an epoxy-based acid scavenger (2-ethylhexyl glycidyl ether). The kinematic viscosity of each refrigerating machine oil at 40°C was approximately 44 to 56 mmHg. ２ / s, kinematic viscosity at 100°C is approximately 9 to 11 mm ２ / s, and the viscosity index was about 156 to 213.

[0044] PAG compound 1: In the above formula (1), R １ and R ２ is a hydrogen atom or an n-butyl group (ratio of terminal hydroxyl groups to all terminal groups: 50 mol%), R ３ is an ethylene group or a propylene group (EO / PO ratio: 93 / 7), and the average value of m is about 19.8 (Mn: 1200).

[0045] PAG compound 2: In the above formula (1), R １ and R ２ is a hydrogen atom or an n-butyl group (ratio of terminal hydroxyl groups to all terminal groups: 50 mol%), R ３ is an ethylene group or a propylene group (EO / PO ratio: 27 / 73), and the average value of m is about 16.7 (Mn: 976).

[0046] PAG compound 3: In the above formula (1), R １ and R ２ is a hydrogen atom or an n-butyl group (ratio of terminal hydroxyl groups to all terminal groups: 45 mol%), R ３ is an ethylene group or a propylene group (EO / PO ratio: 35 / 65), and the average value of m is about 18.2 (Mn: 1040).

[0047] PAG compound 4: In the above formula (1), R １ and R ２ is a hydrogen atom or an n-butyl group (ratio of terminal hydroxyl groups to all terminal groups: 31 mol%), R ３ is an ethylene group or a propylene group (EO / PO ratio: 60 / 40), and the average value of m is about 23.1 (Mn: 1240).

[0048] PAG compound 5: In the above formula (1), R １ and R ２ is a hydrogen atom or an n-butyl group (ratio of terminal hydroxyl groups to all terminal groups: 65 mol%), R ３ is an ethylene group or a propylene group (EO / PO ratio: 75 / 25), and the average value of m is about 20.8 (Mn: 1050).

[0049] PAG compound 6: In the above formula (1), R １ and R ２ is a hydrogen atom, and R ３ is an ethylene group or a propylene group (EO / PO ratio: 92 / 8), and the average value of m is about 17.4 (Mn: 849).

[0050] (Evaluation of Acid Value) A mixture of 100 g of each refrigerating machine oil, the water content of which had been adjusted to 1000 ppm, and 30 g of propane (R290) as a refrigerant was placed in a 200 mL autoclave. An EPDM member (dumbbell-shaped test piece, length 2.5 cm, width 10.0 cm, thickness 0.2 cm), an H-NBR member (dumbbell-shaped test piece, length 2.5 cm, width 10.0 cm, thickness 0.2 cm), and a PTFE member (dumbbell-shaped test piece, length 2.5 cm, width 10.0 cm, thickness 0.015 cm) were immersed in the mixture and heated at 130°C for 336 hours. After heating, the acid value of each refrigerating machine oil was measured in accordance with JIS K2501:2003. The results are shown in Table 1.

[0051]

[0052] As can be seen from Table 1, by using a refrigerating machine oil containing a PAG compound with an EO / PO ratio of 85 / 15 or less in the presence of a hydrocarbon-containing refrigerant, it is possible to suppress an increase in the acid value of the refrigerating machine oil, regardless of whether a component containing EPDM or a component containing H-NBR is used. This effect cannot be obtained when a component containing PTFE is used, but is a unique effect achieved when a component containing EPDM or a component containing H-NBR is used.

[0053] The acid values ​​of the refrigerating machine oils of the Examples and Comparative Examples were measured in the same manner as above, except that difluoromethane (R32) was used instead of propane (R290) as the refrigerant and EPDM components were used as the components. The results were: Example 1: 0.11 mg / 100 g, Example 2: 0.03 mg / 100 g, Example 3: 0.01 mg / 100 g, Example 4: 0.01 mg / 100 g, Example 5: 0.01 mg / 100 g, and Comparative Example 1: 0.01 mg / 100 g. As can be seen from these results, the effect of suppressing an increase in the acid value of refrigerating machine oil, which is obtained by using a PAG compound having an EO / PO ratio of 85 / 15 or less, is a unique effect achieved when refrigerating machine oils containing such PAG compounds are used together with hydrocarbon refrigerants.

[0054] The effect of suppressing the increase in the acid value of refrigerating machine oils shown above can also be achieved when the content of the phenolic antioxidant (DBPC) is changed to 0.1 to 1 mass%, when the content of the phosphorus-based antiwear agent (TCP) is changed to 0.1 to 3 mass%, and when the content of the epoxy acid scavenger (2-ethylhexyl glycidyl ether) is changed to 0.1 to 3 mass%. Furthermore, similar trends can be achieved when TCP is changed to triphenyl phosphate, propylated triphenyl phosphate, or butylated triphenyl phosphate, and when 2-ethylhexyl glycidyl ether is changed to 4-t-butylphenyl glycidyl ether, glycidyl neodecanoate, or 1,2-epoxytetradecane. Furthermore, similar trends can be achieved when propane (R290) is changed to isobutane (R600a).

[0055] REFRIGERATION SYSTEM 7 ACCUMULATOR 10 REFRIGERATOR 2 CONDENSER 3 EXPANSION MECHANISM 4 EVAPORATOR

Claims

1. A refrigerator equipped with a refrigerant circulation system having a compressor, a condenser, an expansion mechanism, and an evaporator, wherein the refrigerant circulation system has a member containing at least one selected from the group consisting of ethylene propylene diene rubber and hydrogenated nitrile butadiene rubber, and the refrigerant circulation system is filled with a refrigerant containing a hydrocarbon and a refrigerating machine oil containing a compound represented by the following formula (1): [In the formula, R １ and R ２ are each independently a hydrogen atom or an alkyl group, and R ３ represents an ethylene group or a propylene group, and m is an integer of 2 or more.] A refrigerator, wherein the molar ratio of the ethylene group / the propylene group in the compound represented by formula (1) is 85 / 15 or less.

2. The refrigerator according to claim 1, wherein the molar ratio of the ethylene group to the propylene group in the compound represented by formula (1) is 20 / 80 or more.

3. The compound represented by the formula (1) is １ and R ２ 3. The refrigerator according to claim 1, further comprising a compound in which one of said groups is the hydrogen atom and the other is the alkyl group.

4. A working fluid composition containing a refrigerant and a refrigerating machine oil, wherein the refrigerant contains a hydrocarbon, and the refrigerating machine oil contains a compound represented by the following formula (1): [In the formula, R １ and R ２ are each independently a hydrogen atom or an alkyl group, and R ３ is an ethylene group or a propylene group, and m is an integer of 2 or more.] A working fluid composition, wherein a molar ratio of the ethylene group / the propylene group in the compound represented by formula (1) is 85 / 15 or less, the working fluid composition is used in a refrigerator equipped with a refrigerant circulation system having a compressor, a condenser, an expansion mechanism, and an evaporator, and the refrigerant circulation system has a member containing at least one member selected from the group consisting of ethylene propylene diene rubber and hydrogenated nitrile butadiene rubber.

5. A refrigerating machine oil containing a compound represented by the following formula (1): [In the formula, R １ and R ２ are each independently a hydrogen atom or an alkyl group, and R ３ is an ethylene group or a propylene group, and m is an integer of 2 or more.] A refrigerating machine oil, wherein the molar ratio of the ethylene group / the propylene group in the compound represented by formula (1) is 85 / 15 or less, the refrigerating machine oil is used together with a refrigerant containing a hydrocarbon in a refrigerating machine equipped with a refrigerant circulation system having a compressor, a condenser, an expansion mechanism, and an evaporator, and the refrigerant circulation system has a member containing at least one selected from the group consisting of ethylene propylene diene rubber and hydrogenated nitrile butadiene rubber.

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