Refrigerator, working fluid composition, and refrigerator oil

Abstract

A refrigeration unit includes a refrigerant circulation system comprising a compressor, a condenser, an expansion mechanism, and an evaporator. The refrigerant circulation system includes a component comprising at least one selected from the group consisting of ethylene-propylene-diene terpolymer rubber and hydrogenated nitrile rubber. The refrigerant circulation system is filled with a refrigerant containing hydrocarbons and a refrigeration oil comprising a compound represented by formula (1), [where R in formula (1)]. 1 and R 2 Each is independently a hydrogen atom or an alkyl group, R 3 The molar ratio of ethylene or propylene in the compound shown in formula (1) is 85 / 15 or less.

Description

Technical Field

[0001] This invention relates to refrigeration machines, working fluid compositions, and refrigeration oils. Background Technology

[0002] Refrigeration units such as refrigerators and air conditioners contain rubber components. For example, hydrogenated nitrile rubber and ethylene-propylene-diene terpolymer rubber are known as rubbers used for sealing components in refrigeration units (see, for example, Patent Document 1). Patent Document 1 describes that hydrogenated nitrile rubber has problems with its resistance to foaming and permeability to refrigerants, while ethylene-propylene-diene terpolymer rubber, although having better resistance to foaming and permeability, has problems with its resistance to refrigeration oil.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2011-79974 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] According to the research of the inventors, in a refrigeration unit having components comprising hydrogenated nitrile butadiene rubber and ethylene-propylene-diene terpolymer rubber, when using a refrigerant containing hydrocarbons and a refrigeration oil containing polyalkylene glycol compounds, there is a concern that the acid value of the refrigeration oil may increase with use.

[0008] Therefore, one aspect of the present invention is to suppress the increase in acid value of the refrigeration oil during use in a refrigeration unit having components comprising hydrogenated nitrile butadiene rubber and ethylene-propylene-diene terpolymer rubber, when using a refrigerant containing hydrocarbons and a refrigeration oil containing polyalkylene glycol compounds.

[0009] Solution for solving the problem

[0010] The inventors have discovered that by appropriately adjusting the ratio of ethylene to propylene in the polyalkylene glycol compound, even when the refrigeration oil containing the polyalkylene glycol compound is used in a refrigeration unit having a component containing hydrogenated nitrile butadiene rubber and ethylene-propylene-diene terpolymer rubber with a refrigerant containing hydrocarbons, the increase in acid value of the refrigeration oil during use can be suppressed.

[0011] [1] A refrigeration machine comprising a refrigerant circulation system having a compressor, a condenser, an expansion mechanism and an evaporator, wherein the refrigerant circulation system has a component comprising at least one selected from the group consisting of ethylene-propylene-diene terpolymer rubber and hydrogenated nitrile rubber, and the refrigerant circulation system is filled with a refrigerant comprising hydrocarbons and refrigeration oil comprising a compound represented by the following formula (1).

[0012]

[0013] In equation (1), R 1 and R 2 Each is independently a hydrogen atom or an alkyl group, R 3 [Ethylene or propylene, where m is an integer greater than or equal to 2.]

[0014] The molar ratio of ethylidene / propyleneide in the compound shown in formula (1) is less than 85 / 15.

[0015] [2] According to the freezer described in [1], wherein the molar ratio of ethylidene / propylene in the compound represented by formula (1) is 20 / 80 or more.

[0016] [3] According to the freezer described in [1] or [2], wherein the compound represented by formula (1) contains R in formula (1). 1 and R 2 Compounds in which one atom is a hydrogen atom and the other is an alkyl group.

[0017] [4] A working fluid composition comprising a refrigerant and a refrigeration oil, wherein the refrigerant comprises a hydrocarbon and the refrigeration oil comprises a compound represented by the following formula (1).

[0018]

[0019] In equation (1), R 1 and R 2 Each is independently a hydrogen atom or an alkyl group, R 3 [Ethylene or propylene, where m is an integer greater than or equal to 2.]

[0020] The compound shown in formula (1) has a molar ratio of ethylene / propylene of 85 / 15 or less. The working fluid composition is used in a refrigeration machine having a refrigerant circulation system, the refrigerant circulation system having a compressor, a condenser, an expansion mechanism and an evaporator, the refrigerant circulation system having a component comprising at least one selected from the group consisting of ethylene-propylene-diene terpolymer rubber and hydrogenated nitrile rubber.

[0021] [5] A refrigeration oil comprising a compound represented by the following formula (1),

[0022]

[0023] In equation (1), R 1 and R 2 Each is independently a hydrogen atom or an alkyl group, R 3 [Ethylene or propylene, where m is an integer greater than or equal to 2.]

[0024] The compound shown in formula (1) has a molar ratio of ethylene / propylene of 85 / 15 or less. The refrigeration oil is used in a refrigeration unit equipped with a refrigerant containing hydrocarbons, the refrigerant circulation system having a compressor, a condenser, an expansion mechanism and an evaporator, and the refrigerant circulation system having a component comprising at least one selected from the group consisting of ethylene-propylene-diene terpolymer rubber and hydrogenated nitrile rubber.

[0025] The effects of the invention

[0026] According to one aspect of the invention, in a refrigeration unit having components comprising hydrogenated nitrile butadiene rubber and ethylene-propylene-diene terpolymer rubber, when using a refrigerant containing hydrocarbons and a refrigeration oil containing polyalkylene glycol compounds, it is possible to suppress the increase in acid value of the refrigeration oil during use. Attached Figure Description

[0027] Figure 1 This is a schematic diagram illustrating one embodiment of a refrigeration unit. Detailed Implementation

[0028] Hereinafter, embodiments of the present invention will be described in detail with appropriate reference to the accompanying drawings.

[0029] Figure 1 This is a schematic diagram illustrating one embodiment of a refrigeration unit. (For example...) Figure 1 As shown, the refrigeration unit 10 includes at least a refrigerant circulation system 6, which is connected in sequence via a flow path 5 to a compressor (refrigerant compressor) 1, a condenser (gas cooler) 2, an expansion mechanism 3 (capillary tube, expansion valve, etc.), and an evaporator (heat exchanger) 4. In one embodiment, to suppress and prevent liquid refrigerant from flowing directly into the compressor 1, the refrigerant circulation system 6 also includes a liquid receiver 7 between the evaporator 4 and the compressor 1 (on the side of the compressor 1).

[0030] The refrigerant circulation system 6 is filled with refrigerant and refrigeration oil. In the refrigerant circulation system 6, firstly, the high-temperature (typically 70~120°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 liquefies through the narrow flow path of the expansion mechanism 3, and then vaporizes in the evaporator 4 to a low temperature (typically -40~0°C). Refrigeration based on the refrigeration unit 10 utilizes the phenomenon that the refrigerant absorbs heat from its surroundings when it vaporizes in the evaporator 4.

[0031] Inside compressor 1, under high-temperature conditions (typically 70~120℃), a small amount of refrigerant and a large amount of refrigeration oil coexist. The refrigerant discharged from compressor 1 to flow path 5 is in gaseous form, containing a small amount (typically 1~10% by volume) of refrigeration oil in the form of mist, but a small amount of refrigerant is dissolved in this misty refrigeration oil. Figure 1 Point a in the middle).

[0032] Inside condenser 2, the gaseous refrigerant is compressed into a high-density fluid. Under relatively high temperature conditions (typically 40~80℃), a large amount of refrigerant and a small amount of refrigeration oil coexist. Figure 1 Point b in the text). In addition, a large amount of refrigerant mixed with a small amount of refrigeration oil is sequentially sent to the expansion unit 3 and the evaporator 4, rapidly decreasing to a low temperature (typically -40~0℃). Figure 1 Points c and d in the diagram return to compressor 1.

[0033] Examples of such a refrigeration unit 10 include refrigeration units and air conditioning units. Examples of refrigeration units include cooling devices used in refrigerators, cold storage warehouses, vending machines, and chemical plants. Examples of air conditioning units include automotive air conditioners, residential air conditioners, cabinet air conditioners, and dehumidifiers.

[0034] The refrigerant circulation system 6 has a component comprising at least one selected from the group consisting of ethylene-propylene-diene terpolymer rubber (EPDM) and hydrogenated nitrile butadiene rubber (H-NBR). Such a component may be, for example, an insulating component within the compressor 1, or a sealing component for preventing leakage of refrigerant and refrigeration oil from the compressor 1.

[0035] The refrigerant contains hydrocarbons. The hydrocarbons are preferably hydrocarbons with 1 to 5 carbon atoms, more preferably hydrocarbons with 2 to 4 carbon atoms. Examples of hydrocarbons include methane, ethylene, ethane, propylene, propane (R290), cyclopropane, n-butane, isobutane (R600a), cyclobutane, methylcyclopropane, 2-methylbutane, and n-pentane. The refrigerant may contain only one of these hydrocarbons, or it may contain two or more. The refrigerant preferably contains hydrocarbons that are gases at 25°C and 1 atmosphere, more preferably at least one selected from the group consisting of propane, n-butane, isobutane, and 2-methylbutane.

[0036] Refrigerants can consist of only hydrocarbons, or they can contain hydrocarbons and other refrigerants. Examples of other refrigerants include saturated fluorinated hydrocarbons, unsaturated fluorinated hydrocarbons, fluorinated ethers such as perfluoroethers, bis(trifluoromethyl) sulfides, trifluoroiodomethane, ammonia, and carbon dioxide.

[0037] The hydrocarbon content, based on the total amount of refrigerant, can be 50% or more by mass, 60% or more by mass, 70% or more by mass, 80% or more by mass, 90% or more by mass, or 95% or more by mass.

[0038] The refrigeration oil contains the compound shown in formula (1) below (hereinafter also referred to as "PAG compound").

[0039]

[0040] In equation (1), R 1 and R 2 Each is independently a hydrogen atom or an alkyl group, R 3 It is ethylidene or propyleneide, and m is an integer greater than or equal to 2.

[0041] R 1 and R 2 The alkyl group shown can be straight-chain or branched. The alkyl group can have 1 or more, 2 or more, or 3 or more carbon atoms, and can have 16 or less, 12 or less, 8 or less, or 5 or less, or 4 carbon atoms. The alkyl group is preferably n-butyl.

[0042] From the perspective of further suppressing the rise in acid value of refrigeration oil, PAG-based compounds preferably contain R. 1 and R 2 Compounds in which one atom is a hydrogen atom and the other is an alkyl group (PAG-type compounds with a single-terminal hydroxyl group). Besides PAG-type compounds with a single-terminal hydroxyl group, PAG-type compounds may also contain R... 1 and R 2 Both of these are compounds with hydrogen atoms (PAG-type compounds with two terminal hydroxyl groups).

[0043] The ratio of terminal hydroxyl groups to all terminal groups in PAG-based compounds (PAG-based compounds relative to all R groups) 1 and R 2 of, R 1 and R 2 The percentage of hydrogen atoms can 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, or it can be 90 mol% or less, 80 mol% or less, 70 mol% or less, 60 mol% or less, or 50 mol% or less. From the viewpoint of further suppressing the rise of acid value of refrigeration oil, it is preferably 45 mol% or less, 40 mol% or less, or 35 mol% or less.

[0044] The ratio of terminal hydroxyl groups to all terminal groups in PAG-based compounds is determined by... 13 This ratio is determined by C-NMR measurements. Specifically, this ratio can be calculated based on... 13 The spectrum obtained by C-NMR measurement is used to determine the peaks from the carbons that constitute the hydrocarbon group with the terminal hydroxyl group and the carbons that constitute the terminal hydrocarbon group (alkyl group, etc.), and the peaks are appropriately calculated using the integral values ​​of each peak.

[0045] Preferably, one molecule of a PAG-based compound contains R. 3 The structural unit is ethylene and R 3 Both are propylene oxide structural units. That is, PAG-based compounds preferably contain both ethylene oxide units (EO units) and propylene oxide units (PO units). In this case, the PAG-based compound can be a random copolymer or a block copolymer.

[0046] The molar ratio of ethylene / propylene (EO unit / PO unit) in PAG-based compounds (hereinafter also referred to as "EO / PO ratio") is 85 / 15 or less. Therefore, in refrigeration units having components containing EPDM or H-NBR, when using refrigerants containing hydrocarbons and refrigeration oils containing polyalkylene glycol compounds, the increase in the acid value of the refrigeration oil during use can be suppressed. The EO / PO ratio can be 80 / 20 or less, 75 / 25 or less, 70 / 30 or less, 65 / 35 or less, or 60 / 40 or less; it can be 3 / 97 or more, 5 / 95 or more, or 7 / 93 or more. From the viewpoint of further suppressing the increase in the acid value of the refrigeration oil, it is preferable to be 10 / 90 or more, 15 / 85 or more, 20 / 80 or more, or 25 / 75 or more; more preferably, it is 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 preferred to be 55 / 45 or less, 50 / 50 or less, 45 / 55 or less, 40 / 60 or less, or 38 / 62 or less. In addition, it is particularly preferred to be 30 / 70 or more, 33 / 67 or more, or 35 / 65 or more.

[0047] The EO / PO ratio in PAG-based compounds is obtained through... 13 This is determined by C-NMR measurement. Specifically, the EO / PO ratio can be obtained from... 13 In the C-NMR spectra obtained, the peaks from the carbon constituting the EO unit and the peaks from the carbon constituting the PO unit were determined, and appropriate values ​​were obtained using information related to the EO and PO units and the integral values ​​of each peak.

[0048] In formula (1), m can be 2 or more, 5 or more, 10 or more, or 15 or more, and can be 40 or less, 35 or less, 30 or less, or 25 or less. The PAG-based compound can be a mixture of multiple PAG-based compounds with different values ​​of m. The average value of m can be 2 or more, 5 or more, 10 or more, or 15 or more, and can be 40 or less, 35 or less, 30 or less, or 25 or less. The number-average molecular weight (Mn) of the PAG-based compound can be 500 or more, 700 or more, or 900 or more, and can be 1800 or less, 1600 or less, or 1400 or less. In other embodiments, the number-average molecular weight (Mn) of the PAG-based compound can be 1250 or less, 1100 or less, 1050 or less, or 1000 or less.

[0049] The number-average molecular weight (Mn) in this specification refers to the Mn (converted value for polypropylene glycol (standard sample)) obtained through GPC analysis. Specifically, for example, a 2% (w / w) solution is prepared by dilution using chloroform as a solvent and analyzed using a GPC apparatus (e.g., Waters Alliance 2695). The solvent flow rate is set to 1 ml / min, and an analysis is performed using a column capable of analyzing molecular weights from 100 to 10,000 using a refractive index detector. It should be noted that the relationship between column retention time and molecular weight is determined using a polypropylene glycol standard with a known molecular weight. After constructing a standard curve, the molecular weight is determined from the obtained retention time.

[0050] Based on the total volume of the refrigeration oil, the content of PAG compounds can be 50% or more by mass, 60% or more by mass, 70% or more by mass, 80% or more by mass, or 90% or more by mass.

[0051] Refrigeration oils contain PAG-based compounds as base oils and may further contain other base oils. Examples of other base oils include mineral oils and synthetic oils. Mineral oils can be paraffinic mineral oils, cycloalkane-based mineral oils, etc. Examples of synthetic oils include synthetic hydrocarbon oils such as polyalphaolefins and alkylbenzenes, as well as oxygenated oils other than the aforementioned PAG-based compounds such as polyalkylene glycols, esters, and polyvinyl ethers.

[0052] Refrigeration oils may further contain additives. Examples of additives include antioxidants, anti-wear agents, acid scavengers, oxygen scavengers, extreme pressure agents, oiliness agents, defoamers, metal passivators, viscosity index improvers, pour point depressants, and cleaning and dispersing agents. Based on the total volume of the refrigeration oil, the additive content can be 0.1% by mass or more, or 1% by mass or less, or less than 10% by mass or less than 5% by mass.

[0053] Refrigeration oil preferably also contains antioxidants. Examples of antioxidants include phenolic antioxidants. Examples of phenolic antioxidants include 2,6-di-tert-butyl-p-cresol (DBPC), 2,6-di-tert-butylphenol, and 4,4'-methylenebis(2,6-di-tert-butylphenol). Based on the total volume of the refrigeration oil, the antioxidant content can be 0.01% by mass or more, or 0.1% by mass or less, or 5% by mass or less, 3% by mass or less, or 1% by mass or less.

[0054] The refrigeration oil preferably also contains phosphorus-based anti-wear agents. Examples of phosphorus-based anti-wear agents include phosphate esters, thiophosphate esters, acid phosphate esters, amine salts of acid phosphate esters, chlorinated phosphate esters, and phosphites. Examples of phosphate esters include tricresyl phosphate (TCP), triphenyl phosphate (TPP), alkylated triphenyl phosphate (e.g., propylated triphenyl phosphate, butylated triphenyl phosphate), triaryl phosphates, and trialkyl phosphate esters. Examples of thiophosphate esters include triphenyl thiophosphate (TPPT). Based on the total volume of the refrigeration oil, the content of phosphorus-based anti-wear agents can be, for example, 0.01% by mass or more, or 0.1% by mass or more, or 5% by mass or less, or 3% by mass or less.

[0055] The refrigeration oil preferably also contains an acid scavenger. Examples of acid scavengers include, for instance, epoxy-based acid scavengers. Examples of epoxy-based acid scavengers include: glycidyl ether acid scavengers with 6 to 18 carbon groups, such as 2-ethylhexyl glycidyl ether and 4-tert-butylphenyl glycidyl ether; glycidyl ester acid scavengers with 6 to 18 carbon groups, such as neodecanoic acid glycidyl ester; α-olefin epoxide acid scavengers with 6 to 18 carbon groups, such as 1,2-epoxydodecane and 1,2-epoxytetradecane; and alicyclic epoxy-based acid scavengers. Based on the total amount of the refrigeration oil, the acid scavenger content can be 0.01% by mass or more, or 0.1% by mass or less, or 5% by mass or less, 3% by mass or less, or 1% by mass or less.

[0056] The kinematic viscosity of refrigeration oil at 40°C can be 20 mm. 2 / s or higher, 30mm 2 / s or above or 40mm 2 / s or higher, and can be up to 100mm 2 / s or less, 80mm 2 / s or less or 60mm 2 The kinematic viscosity of refrigeration oil at 100°C can be less than 1 mm² / s. 2 / s or more, 3mm 2 / s or more or 5mm 2 / s or higher, and can be up to 30mm 2 / s or less, 20mm 2 / s or less or 15mm 2 / s or less. The viscosity index of refrigeration oil can be above 100, above 120, or above 140, and below 270, below 250, or below 230. The kinematic viscosity and viscosity index in this specification refer to the kinematic viscosity and viscosity index measured according to JIS K2283:2000.

[0057] As explained above, refrigerant and refrigeration oil coexist in the refrigeration unit 10 (refrigeration circulation system 6). Therefore, another embodiment of the present invention is a working fluid composition containing the aforementioned refrigerant containing hydrocarbons and the aforementioned refrigeration oil containing PAG compounds, used in the aforementioned refrigeration unit. In another embodiment, the working fluid composition is also applicable to a refrigeration unit equipped with a refrigerant circulation system having both a component containing ethylene-propylene-diene terpolymer rubber and a component containing hydrogenated nitrile butadiene rubber. In another embodiment, the working fluid composition is also applicable to two types of refrigeration units: a refrigeration unit equipped with a refrigerant circulation system having a component containing ethylene-propylene-diene terpolymer rubber; and a refrigeration unit equipped with a refrigerant circulation system having a component containing hydrogenated nitrile butadiene rubber.

[0058] In addition, another embodiment of the present invention is the refrigeration oil containing PAG compounds, used in the aforementioned refrigeration machine with the aforementioned hydrocarbon-containing refrigerant. In another embodiment, the refrigeration oil is also applicable to refrigeration machines equipped with a refrigerant circulation system having both a component comprising ethylene-propylene-diene terpolymer rubber and a component comprising hydrogenated nitrile butadiene rubber. In another embodiment, the refrigeration oil is also applicable to two types of refrigeration machines: refrigeration machines equipped with a refrigerant circulation system having a component comprising ethylene-propylene-diene terpolymer rubber; and refrigeration machines equipped with a refrigerant circulation system having a component comprising hydrogenated nitrile butadiene rubber.

[0059] The content of refrigeration oil can be more than 1 part by weight or more than 2 parts by weight relative to 100 parts by weight of refrigerant, and can be less than 500 parts by weight or less than 400 parts by weight.

[0060] Example

[0061] The present invention will now be described in more detail with reference to embodiments, but the present invention is not limited to the following embodiments.

[0062] The following PAG compounds 1-6 were used as base oils to prepare various refrigeration oils for the examples and comparative examples. It should be noted that each refrigeration oil contained 0.5% by mass of a phenolic antioxidant (DBPC), 1.0% by mass of a phosphorus-based anti-wear agent (TCP), and 0.5% by mass of an epoxy acid scavenger (2-ethylhexyl glycidyl ether). Furthermore, the kinematic viscosity of each refrigeration oil at 40°C was approximately 44-56 mm. 2 The kinematic viscosity at 100℃ is approximately 9~11 mm / s. 2 / s, viscosity index is approximately 156~213.

[0063] PAG compound 1: R in formula (1) above 1 and R 2 For hydrogen atoms or n-butyl groups (the ratio of terminal hydroxyl groups to all terminal groups: 50 mol%), R 3 Compounds that are ethyl or propylene (EO / PO ratio: 93 / 7) with an average m value of approximately 19.8 (Mn: 1200).

[0064] PAG compound 2: R in formula (1) above 1 and R 2 For hydrogen atoms or n-butyl groups (the ratio of terminal hydroxyl groups to all terminal groups: 50 mol%), R 3 Compounds of ethyl or propylene (EO / PO ratio: 27 / 73) with an average m value of approximately 16.7 (Mn: 976).

[0065] PAG compound 3: R in formula (1) above 1 and R 2 For hydrogen atoms or n-butyl (the ratio of terminal hydroxyl to all terminal groups: 45 mol%), R 3 Compounds that are ethyl or propylene (EO / PO ratio: 35 / 65) with an average m value of approximately 18.2 (Mn: 1040).

[0066] PAG compound 4: R in formula (1) above 1 and R 2 For hydrogen atoms or n-butyl groups (the ratio of terminal hydroxyl groups to all terminal groups: 31 mol%), R 3 Compounds that are ethyl or propylene (EO / PO ratio: 60 / 40) with an average m value of approximately 23.1 (Mn: 1240).

[0067] PAG compound 5: R in formula (1) above 1 and R 2 For hydrogen atoms or n-butyl groups (the ratio of terminal hydroxyl groups to all terminal groups: 65 mol%), R 3 Compounds that are ethyl or propylene (EO / PO ratio: 75 / 25) with an average m value of approximately 20.8 (Mn: 1050).

[0068] PAG compound 6: R in formula (1) above 1 and R 2 For hydrogen atoms, R 3 Compounds of ethyl or propylene (EO / PO ratio: 92 / 8) with an average m value of approximately 17.4 (Mn: 849).

[0069] (Acid value evaluation)

[0070] A mixture of 100g of each refrigeration oil (adjusted to a moisture content of 1000ppm) and 30g of propane (R290) as refrigerant was added to a 200mL autoclave. EPDM components (dumbbell-shaped test pieces, 2.5cm long, 10.0cm wide, and 0.2cm thick) were immersed in the mixture, as were H-NBR components (dumbbell-shaped test pieces, 2.5cm long, 10.0cm wide, and 0.2cm thick) and PTFE components (dumbbell-shaped test pieces, 2.5cm long, 10.0cm wide, and 0.015cm thick). The mixture was heated at 130°C for 336 hours. After heating, the acid value of each refrigeration oil was determined according to JIS K2501:2003. The results are shown in Table 1.

[0071] [Table 1]

[0072]

[0073] As shown in Table 1, by using refrigeration oil containing PAG-based compounds with an EO / PO ratio of 85 / 15 or less in the presence of a hydrocarbon-containing refrigerant, the increase in the acid value of the refrigeration oil can be suppressed when using either components containing EPDM or H-NBR. This effect is not obtained when using components containing PTFE and is a unique effect achieved when using components containing either EPDM or H-NBR.

[0074] Furthermore, for each refrigeration oil in the examples and comparative examples, difluoromethane (R32) was used instead of propane (R290) as the refrigerant, and EPDM components were used as components. Otherwise, the acid value of the refrigeration oil was measured in the same manner as described above. The results were as follows: Example 1: 0.11 mg / 100g, Example 2: 0.03 mg / 100g, Example 3: 0.01 mg / 100g, Example 4: 0.01 mg / 100g, Example 5: 0.01 mg / 100g, and Comparative Example 1: 0.01 mg / 100g. These results indicate that the effect of suppressing the increase in acid value of refrigeration oil obtained by using PAG-based compounds with an EO / PO ratio of 85 / 15 or less is a unique effect exhibited when refrigeration oils containing this PAG-based compound are used with hydrocarbon refrigerants.

[0075] The effect of suppressing the rise in acid value of refrigeration oil described above can also be obtained by changing the content of phenolic antioxidant (DBPC) to 0.1-1% by mass, the content of phosphorus-based anti-wear agent (TCP) to 0.1-3% by mass, and the content of epoxy acid scavenger (2-ethylhexyl glycidyl ether) to 0.1-3% by mass. Furthermore, this effect is also observed when TCP is replaced with triphenyl phosphate, propyltriphenyl phosphate, or butyltriphenyl phosphate, and when 2-ethylhexyl glycidyl ether is replaced with 4-tert-butylphenyl glycidyl ether, neodecanoic acid glycidyl ether, or 1,2-epoxytetradecane. Additionally, this effect is also observed when propane (R290) is replaced with isobutane (R600a).

[0076] Explanation of reference numerals in the attached figures

[0077] 1…compressor, 2…condenser, 3…expansion mechanism, 4…evaporator, 5…flow path, 6…refrigerant circulation system, 7…liquid receiver, 10…refrigeration unit.

Claims

1. A refrigeration unit comprising a refrigerant circulation system, said refrigerant circulation system having a compressor, a condenser, an expansion mechanism, and an evaporator, wherein, The refrigerant circulation system has a component comprising at least one selected from the group consisting of ethylene-propylene-diene terpolymer rubber and hydrogenated nitrile rubber. The refrigerant circulation system is filled with a refrigerant containing hydrocarbons and refrigeration oil containing a compound represented by the following formula (1). In formula (1), R 1 and R 2 are each independently a hydrogen atom or an alkyl group, R 3 is an ethylene group or a propylene group, and m is an integer of 2 or more. The molar ratio of the ethylidene to the propyleneide in the compound represented by formula (1) is less than 85 / 15.

2. The refrigeration unit according to claim 1, wherein, The molar ratio of the ethylidene to the propyleneide in the compound represented by formula (1) is 20 / 80 or more.

3. The refrigeration unit according to claim 1 or 2, wherein, The compound represented by the formula (1) includes a compound in which one of R 1 and R 2 is the hydrogen atom and the other is the alkyl group.

4. A working fluid composition comprising a refrigerant and refrigeration oil. The refrigerant contains hydrocarbons. The refrigeration oil contains a compound represented by the following formula (1). In equation (1), R 1 and R 2 Each is independently a hydrogen atom or an alkyl group, R 3 It is ethylene or propyleneene, and m is an integer greater than or equal to 2. The molar ratio of the ethylene to the propylene in the compound represented by formula (1) is less than 85 / 15. The working fluid composition is used in a refrigeration machine having a refrigerant circulation system, the refrigerant circulation system comprising a compressor, a condenser, an expansion mechanism, and an evaporator. The refrigerant circulation system has a component comprising at least one selected from the group consisting of ethylene-propylene-diene terpolymer rubber and hydrogenated nitrile rubber.

5. A refrigeration oil comprising a compound represented by formula (1) below, In equation (1), R 1 and R 2 Each is independently a hydrogen atom or an alkyl group, R 3 It is ethylene or propyleneene, and m is an integer greater than or equal to 2. The molar ratio of the ethylene to the propylene in the compound represented by formula (1) is less than 85 / 15. The refrigeration oil is used in a refrigeration unit equipped with a refrigerant containing hydrocarbons, which includes a compressor, condenser, expander, and evaporator. The refrigerant circulation system has a component comprising at least one selected from the group consisting of ethylene-propylene-diene terpolymer rubber and hydrogenated nitrile rubber.

Images