Refrigerator oil and working fluid composition

Abstract

This refrigerator oil contains a compound represented by formula (I) as a base oil. [In the formula, R1 and R2 are each independently a hydrogen atom or an alkyl group, R3 is an ethylene group or a propylene group, and m is an integer of 2 or greater.] The compound represented by formula (1) has an ethylene group / propylene group molar ratio of 5 / 95 to 65 / 35.

Description

Refrigerating machine oil and working fluid composition

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

[0002] Lubricating oils (refrigeration oils) used to lubricate sliding parts in refrigerators, air conditioners, and other refrigeration systems are sometimes used with refrigerants (e.g., hydrocarbon refrigerants) that are highly soluble in the refrigeration oil. In this case, the viscosity of the lubricating oil decreases as the refrigerant dissolves, making it difficult to maintain a film of the lubricating oil on the sliding parts, which can lead to harsh lubrication conditions. Under such harsh lubrication conditions, the lubricating oil is susceptible to shear stress, which can further reduce the viscosity of the lubricating oil as the shear stress increases.

[0003] In contrast to this, for example, Patent Document 1 discloses that a lubricating oil composition obtained by blending a small amount (0.2 to 15 mass%) of polyalkylene glycol as a viscosity index improver with a specific base oil has excellent shear stability.

[0004] Japanese Patent Application Laid-Open No. 2016-113521

[0005] As disclosed in the above-mentioned Patent Document 1, it is known that when a small amount of polyalkylene glycol is used as a viscosity index improver, better shear stability can be obtained than when a polymethacrylate-based viscosity index improver is used. However, according to the study by the present inventors, when a polypropylene glycol-based compound is used as the base oil, which is the main component of the lubricating oil, sufficient shear stability cannot necessarily be obtained, and there is still room for improvement.

[0006] Therefore, one aspect of the present invention aims to improve the shear stability of a refrigerating machine oil when a polyalkylene glycol compound is used as a base oil.

[0007] The present inventors have found that when a polyalkylene glycol compound is used as a base oil in a refrigerating machine oil, the shear stability is improved when the ratio of ethylene groups to propylene groups in the polyalkylene glycol compound is within a specific range.

[0008] The present invention includes the following aspects: [1] A refrigerating machine oil containing a compound represented by the following formula (1) as a base oil, [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 in which the molar ratio of ethylene groups / propylene groups in the compound represented by formula (1) is 5 / 95 or more and 65 / 35 or less. [2] A refrigerating machine oil according to [1], further containing a phenolic antioxidant, a phosphorus-based antiwear agent, and an epoxy-based acid scavenger. [3] A refrigerating machine oil according to [2], in which the content of the phenolic antioxidant is 0.1 mass% or more, the content of the phosphorus-based antiwear agent is 0.1 mass% or more, and the content of the epoxy-based acid scavenger is 0.1 mass% or more, based on the total amount of the refrigerating machine oil. [4] A refrigerating machine oil according to any one of [1] to [3], in which the weight-average molecular weight of the compound represented by formula (1) is 1,000 or more. [5] A refrigerating machine oil according to any one of [1] to [4], in which the ratio of weight-average molecular weight / number-average molecular weight of the compound represented by formula (1) is 1.15 or more. [6] The refrigerating machine oil according to any one of [1] to [5], wherein the molar ratio of ethylene groups to propylene groups is 5 / 95 or more and 50 / 50 or less, and the ratio of weight average molecular weight to number average molecular weight of the compound represented by formula (1) is 1.6 or less. [7] The refrigerating machine oil according to any one of [1] to [6], which is used together with a refrigerant consisting solely of hydrocarbons. [8] A working fluid composition containing the refrigerating machine oil according to any one of [1] to [7] and a refrigerant. [9] The working fluid composition according to [8], wherein the refrigerant consists solely of hydrocarbons.

[0009] According to one aspect of the present invention, it is possible to improve the shear stability of a refrigerating machine oil when a polyalkylene glycol compound is used as a base oil.

[0010] One embodiment of the present invention is a refrigeration oil containing a compound represented by the following formula (1) (hereinafter also referred to as a "PAG compound") as a base oil. 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 more.

[0011] 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.

[0012] From the viewpoint of further improving shear stability, the PAG compound is preferably R １ and R ２ The PAG compounds include compounds in which one of the groups is a hydrogen atom and the other is an alkyl group (PAG compounds with a hydroxyl group at one end). 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).

[0013] The ratio of terminal hydroxyl groups to all terminal groups of a PAG compound (R １ and R ２ R for all of １ , R ２ are hydrogen atoms) may be 10 mol% or more, 20 mol% or more, 30 mol% or more, 40 mol% or more, or 45 mol% or more, and may be 90 mol% or less, 80 mol% or less, 70 mol% or less, 60 mol% or less, or 55 mol% or less.

[0014] 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.

[0015] The PAG compound of this embodiment includes R ３is an ethylene group, and R ３ The PAG compound may contain both structural units in which the EO unit is a propylene group and structural units in which the PO unit is a propylene group. That is, the PAG compound is a copolymer containing ethylene oxide units (EO units) and propylene oxide units (PO units). The PAG compound may be a random copolymer or a block copolymer.

[0016] The molar ratio of ethylene groups to propylene groups (EO units to PO units) in the PAG compound (hereinafter also referred to as "EO / PO ratio") is 5 / 95 or more and 65 / 35 or less. This allows the shear stability of the base oil (PAG compound) to be improved. The lower limit of the EO / PO ratio may be 7 / 93 or more, 10 / 90 or more, 15 / 85 or more, 17 / 83 or more, 20 / 80 or more, or 25 / 75 or more, from the viewpoint of further improving the shear stability of the base oil (PAG compound). The upper limit of the EO / PO ratio may be 60 / 40 or less, 56 / 44 or less, 55 / 45 or less, 50 / 50 or less, 45 / 65 or less, 40 / 60 or less, 35 / 65 or less, or 30 / 70 or less, from the viewpoint of further improving the shear stability of the base oil (PAG compound).

[0017] The EO / PO ratio in the PAG-based 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.

[0018] 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.

[0019] The weight-average molecular weight (Mw) of the PAG compound may be 1,000 or more, 1,100 or more, 1,200 or more, or 1,300 or more. Generally, when the Mw of a polymer is large, viscosity reduction due to shear is likely to occur. However, in the PAG compound of this embodiment, the EO / PO ratio is within a specific range, so that viscosity reduction due to shear can be suppressed even when the Mw is relatively large. The Mw of the PAG compound may be 5,000 or less, 3,000 or less, 2,000 or less, 1,800 or less, 1,600 or less, or 1,500 or less.

[0020] 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 5000 or less, 3000 or less, 2000 or less, 1500 or less, 1300 or less, or 1100 or less.

[0021] The ratio of weight average molecular weight to number average molecular weight (Mw / Mn) of the PAG compound may be 1.05 or more, 1.08 or more, 1.1 or more, 1.12 or more, or 1.13 or more. From the viewpoint of further improving the shear stability of the base oil (PAG compound), it may be 1.15 or more, 1.2 or more, 1.22 or more, 1.25 or more, 1.3 or more, 1.35 or more, or 1.38 or more, or may be 1.6 or less, 1.5 or less, 1.45 or less, 1.42 or less, or 1.40 or less.

[0022] The weight-average molecular weight (Mw), number-average molecular weight (Mn), and weight-average molecular weight / number-average molecular weight (Mw / Mn) in this specification refer to values ​​obtained by GPC analysis (values ​​converted to polystyrene (standard sample)). Specifically, for example, a solution is prepared using tetrahydrofuran as a solvent, diluted to a sample concentration of 1% by mass, and analyzed using a GPC device (e.g., an ACQUITY APC UV RI system manufactured by Waters). The solvent flow rate is set to 0.7 ml / min, the temperature is set to 40°C, and a column with an analytical 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 polystyrene standards with clear molecular weights, and a calibration curve is separately prepared, and the molecular weight is determined from the obtained retention time.

[0023] The kinematic viscosity of the PAG compound at 40°C is 20 mm ２ / s or more, 30mm ２ / s or more, or 40 mm ２ / s or more, and ２ / s or less, 100mm ２ / s or less, 80mm ２ / s or less, or 60 mm ２ The kinematic viscosity of the PAG compound at 100°C may be 1 mm / s or less. ２ / s or more, 3mm ２ / s or more, or 5 mm ２ / s or more, and ２ / s or less, 20mm ２ / s or less, or 15 mm ２ / s or less.

[0024] The viscosity index of the PAG compound may be 100 or more, 120 or more, 140 or more, or 160 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.

[0025] 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.

[0026] The refrigeration oil may further contain other base oils. Examples of the other base oils include mineral oils and synthetic oils. The mineral oils may be paraffinic mineral oils, naphthenic mineral oils, etc. Examples of the synthetic oils include synthetic hydrocarbon oils such as poly-α-olefins and alkylbenzenes, and oxygenated oils such as polyalkylene glycol compounds other than the above-mentioned PAG compounds, esters, and polyvinyl ethers.

[0027] 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.

[0028] The refrigerating machine oil preferably further contains an antioxidant. The antioxidant preferably includes a phenolic antioxidant. Examples of phenolic antioxidants 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 (preferably a phenolic 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, 1% by mass or less, 0.7% by mass or less, or 0.5% by mass or less, based on the total amount of the refrigerating machine oil.

[0029] The refrigerating machine oil preferably further contains a phosphorus-based antiwear agent. Examples of phosphorus-based antiwear 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 triaryl phosphates such as tricresyl phosphate (TCP), triphenyl phosphate (TPP), and alkylated triphenyl phosphate, and trialkyl phosphates (e.g., propylated triphenyl phosphate, butylated triphenyl phosphate). 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, 0.1% by mass or more, 0.3% by mass or more, or 0.5% by mass or more, based on the total amount of the refrigerating machine oil, and may be 5% by mass or less, 3% by mass or less, 2% by mass or less, or 1% by mass or less.

[0030] The refrigerating machine oil preferably further contains an acid scavenger. The acid scavenger preferably includes an epoxy-based acid scavenger. Examples of epoxy-based acid scavengers include glycidyl ether-based acid scavengers having a hydrocarbon group (preferably an alkyl group or an aryl group) having 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 (preferably an alkyl group) having 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 (preferably an epoxy-based acid scavenger) may be 0.01% by mass or more, 0.1% by mass or more, 0.3% by mass or more, or 0.5% 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.

[0031] The refrigerating machine oil may preferably contain one or more selected from the group consisting of an antioxidant, an antiwear agent, and an acid scavenger, more preferably two or more selected from the group consisting of an antioxidant, an antiwear agent, and an acid scavenger, and even more preferably all of the antioxidant, the antiwear agent, and the acid scavenger. The refrigerating machine oil may also preferably contain one or more selected from the group consisting of a phenolic antioxidant, a phosphorus-based antiwear agent, and an epoxy-based acid scavenger, more preferably two or more selected from the group consisting of a phenolic antioxidant, a phosphorus-based antiwear agent, and an epoxy-based acid scavenger, and even more preferably all of the phenolic antioxidant, the phosphorus-based antiwear agent, and the epoxy-based acid scavenger.

[0032] In this embodiment, a PAG compound having an EO / PO ratio of 5 / 95 or more and 65 / 35 or less is used as the base oil, so that the PAG compound (base oil) itself has high shear stability, and the shear stability is maintained at the same level even when a phenolic antioxidant, a phosphorus-based antiwear agent, and an epoxy-based acid scavenger are added. Therefore, in the refrigerating machine oil according to this embodiment, by adding a phenolic antioxidant, a phosphorus-based antiwear agent, and an epoxy-based acid scavenger, the functions of these additives can be imparted to the refrigerating machine oil without impairing shear stability.

[0033] On the other hand, when a PAG compound having an EO / PO ratio outside the range of 5 / 95 to 65 / 35 is used as a base oil, not only is the shear stability of the PAG compound (base oil) itself low, but the shear stability is further reduced when a phenolic antioxidant, a phosphorus-based antiwear agent, and an epoxy-based acid scavenger are added. Thus, it is surprising that the behavior of shear stability when a phenolic antioxidant, a phosphorus-based antiwear agent, and an epoxy-based acid scavenger are added varies depending on the EO / PO ratio of the PAG compound.

[0034] 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 ２ / s or less, 100mm 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, 3mm ２ / 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, 140 or more, or 160 or more, and may be 270 or less, 250 or less, or 230 or less.

[0035] The refrigerating machine oil described above is used together with a refrigerant in a refrigerator. Another embodiment of the present invention is a working fluid composition containing the refrigerating machine oil described above and a refrigerant. 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.

[0036] The refrigerant preferably 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.

[0037] 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.

[0038] 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.

[0039] Examples of the refrigeration machine include refrigeration devices, air conditioners, etc. Examples of the refrigeration device include refrigerators, refrigerated and frozen warehouses, vending machines, cooling devices in chemical plants, etc. Examples of the air conditioner include automotive air conditioners, residential air conditioners, packaged air conditioners, dehumidifiers, etc.

[0040] As described above, the use of the PAG compound as a base oil can improve shear stability. That is, another embodiment of the present invention can be said to be a refrigerating machine oil containing the PAG compound as a base oil and having improved shear stability. Another embodiment of the present invention can be said to be a refrigerating machine oil containing the PAG compound as a base oil and further containing one or more selected from the group consisting of an antioxidant, an antiwear agent, and an acid scavenger and having improved shear stability.

[0041] Another embodiment of the present invention can also be described as a method for improving the shear stability of a refrigerating machine oil (base oil), comprising the steps of selecting the PAG compound as a base oil for the refrigerating machine oil based on the relationship between the molar ratio of ethylene groups / propylene groups in the compound represented by formula (1) and the shear stability of the refrigerating machine oil (base oil). Another embodiment of the present invention can also be described as a method for improving the shear stability of a refrigerating machine oil (base oil), comprising the steps of selecting the PAG compound as a base oil for the refrigerating machine oil based on the relationship between the molar ratio of ethylene groups / propylene groups in the compound represented by formula (1) and the shear stability of the refrigerating machine oil (base oil), and blending the selected base oil (PAG compound) with one or more selected from the group consisting of antioxidants, antiwear agents, and acid scavengers.

[0042] Another embodiment of the present invention can also be described as a method for producing a refrigerating machine oil, comprising the steps of: selecting a PAG compound as a base oil for the refrigerating machine oil based on the relationship between the molar ratio of ethylene groups / propylene groups in the compound represented by formula (1) above and the shear stability of the refrigerating machine oil (base oil), and preparing a refrigerating machine oil containing the selected PAG compound as a base oil. Another embodiment of the present invention can also be described as a method for producing a refrigerating machine oil, comprising the steps of selecting a PAG compound as a base oil for the refrigerating machine oil based on the relationship between the molar ratio of ethylene groups / propylene groups in the compound represented by formula (1) above and the shear stability of the refrigerating machine oil (base oil), and blending the selected base oil (PAG compound) with one or more selected from the group consisting of antioxidants, antiwear agents, and acid scavengers (preferably a phenolic antioxidant, a phosphorus-based antiwear agent, and an epoxy-based acid scavenger) to prepare a refrigerating machine oil.

[0043] The present invention will be described in more detail below based on examples, but the present invention is not limited to the following examples.

[0044] In the examples and comparative examples, the following PAG compounds 1 to 5 were used as base oils, respectively.

[0045] 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: 31 mol%), R ３ is an ethylene group or a propylene group (EO / PO ratio: 60 / 40) (Mw: 1400, Mw / Mn: 1.13, kinematic viscosity at 40°C: 45.6 mm ２ / s, 100℃ kinematic viscosity: 9.72mm ２ / s, viscosity index: 206)

[0046] 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 ３is an ethylene group or a propylene group (EO / PO ratio: 36 / 64) (Mw: 824, Mw / Mn: 1.33, kinematic viscosity at 40°C: 19.7 mm ２ / s, 100℃ kinematic viscosity: 4.7mm ２ / s, viscosity index: 167)

[0047] 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: 49 mol%), R ３ is an ethylene group or a propylene group (EO / PO ratio: 26 / 74) (Mw: 1230, Mw / Mn: 1.25, kinematic viscosity at 40°C: 36.1 mm ２ / s, 100℃ kinematic viscosity: 7.8mm ２ / s, viscosity index: 194)

[0048] 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: 50 mol%), R ３ is an ethylene group or a propylene group (EO / PO ratio: 7 / 93) (Mw: 1360, Mw / Mn: 1.13, kinematic viscosity at 40°C: 48.5 mm ２ / s, 100℃ kinematic viscosity: 9.7mm ２ / s, viscosity index: 190)

[0049] 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: 42 mol%), R ３ is an ethylene group or a propylene group (EO / PO ratio: 0 / 100) (Mw: 1370, Mw / Mn: 1.06, kinematic viscosity at 40°C: 56.3 mm ２ / s, 100℃ kinematic viscosity: 10.7mm ２ / s, viscosity index: 184)

[0050] Examples 1 to 4 and Comparative Example 1 Each of the above PAG compounds 1 to 5 was used as a base oil to prepare a refrigerating machine oil consisting solely of the base oil. The shear viscosity reduction rate of each refrigerating machine oil was evaluated using the following procedure. The results are shown in Table 1.

[0051] (Evaluation of Shear Viscosity Reduction Rate) The viscosity reduction rate of the 40 ° C. kinematic viscosity of the refrigerating machine oil due to shear (shear viscosity reduction rate) was measured using a method in accordance with JPI-5S-29-2006 "Lubricant Shear Stability Test Method." Specifically, first, the 40 ° C. kinematic viscosity of the refrigerating machine oil (new oil) was measured before the test. Next, the ultrasonic output was set to high output conditions (adjusted using ASTM standard oil A), and then the refrigerating machine oil was irradiated with ultrasonic waves for 30 minutes, and the 40 ° C. kinematic viscosity of the refrigerating machine oil after ultrasonic irradiation (after the test) was measured. Using the measured 40 ° C. kinematic viscosity of the refrigerating machine oil before and after the test, the shear viscosity reduction rate (%) was calculated by the following formula: Shear viscosity reduction rate (%) = (40 ° C. kinematic viscosity of the refrigerating machine oil before the test - 40 ° C. kinematic viscosity of the refrigerating machine oil after the test) / 40 ° C. kinematic viscosity of the refrigerating machine oil before the test × 100. A smaller value of the shear viscosity reduction rate indicates better shear stability.

[0052]

[0053] (Examples 5 to 10 and Comparative Example 2) Each of the above PAG compounds 1 to 5 was used as a base oil, and 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 acid scavenger (2-ethylhexyl glycidyl ether) were blended with each base oil to prepare refrigerating machine oils. The 40°C kinematic viscosity, 100°C kinematic viscosity, and viscosity index of each refrigerating machine oil were equivalent to the 40°C kinematic viscosity, 100°C kinematic viscosity, and viscosity index of each base oil (PAG compound), respectively. The shear viscosity reduction rate of each refrigerating machine oil was evaluated using the above procedure. The results are shown in Table 2.

[0054]

[0055] When a PAG compound having an EO / PO ratio of less than 5 / 95 is used as a base oil, the addition of a phenolic antioxidant, a phosphorus-based antiwear agent, and an epoxy-based acid scavenger significantly reduces shear stability (the shear viscosity reduction rate increases), whereas when a PAG compound having an EO / PO ratio of 5 / 95 or more and 65 / 35 or less is used as a base oil, the addition of a phenolic antioxidant, a phosphorus-based antiwear agent, and an epoxy-based acid scavenger maintains the same shear stability (the shear viscosity reduction rate remains the same). Thus, in a refrigerating machine oil containing a PAG compound having an EO / PO ratio of 5 / 95 or more and 65 / 35 or less as a base oil, the addition of a phenolic antioxidant, a phosphorus-based antiwear agent, and an epoxy-based acid scavenger can impart the functions of each additive to the refrigerating machine oil without impairing shear stability.

[0056] The above-described effects are also obtained when the content of the epoxy acid scavenger (2-ethylhexyl glycidyl ether) is changed to 0.6 to 1.5 mass %. Similar effects are also obtained 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.

Claims

1. A refrigeration oil containing a compound represented by the following formula (1) as a base oil, [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 5 / 95 or more and 65 / 35 or less.

2. The refrigeration oil according to claim 1, further comprising a phenolic antioxidant, a phosphorus-based antiwear agent, and an epoxy-based acid scavenger.

3. The refrigerating machine oil according to claim 2, wherein the content of the phenolic antioxidant is 0.1 mass% or more, the content of the phosphorus-based anti-wear agent is 0.1 mass% or more, and the content of the epoxy-based acid scavenger is 0.1 mass% or more, based on the total amount of the refrigerating machine oil.

4. The refrigerating machine oil according to claim 1, wherein the weight-average molecular weight of the compound represented by formula (1) is 1,000 or more.

5. A refrigerating machine oil according to claim 1, wherein the ratio of weight average molecular weight to number average molecular weight of the compound represented by formula (1) is 1.15 or more.

6. The refrigerating machine oil according to claim 1, wherein the molar ratio of the ethylene groups to the propylene groups is 5 / 95 or more and 50 / 50 or less, and the ratio of the weight average molecular weight to the number average molecular weight of the compound represented by formula (1) is 1.6 or less.

7. The refrigeration oil according to any one of claims 1 to 6, which is used together with a refrigerant consisting solely of hydrocarbons.

8. A working fluid composition comprising the refrigerating machine oil according to any one of claims 1 to 7 and a refrigerant.

9. The working fluid composition of claim 8, wherein the refrigerant consists solely of hydrocarbons.

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