Foaming suppressant for refrigerator oil, method for suppressing foaming in refrigerator oil, use for suppressing foaming in refrigerator oil, refrigerator oil, and working fluid composition

Abstract

This foaming suppressant for a refrigerator oil contains a compound represented by a formula (1) [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 more].　In the compound represented by formula (1), the hydrogen atom / alkyl group molar ratio is 40 / 60-60 / 40 and the ethylene group / propylene group molar ratio is 10 / 90 or less.

Description

Foaming inhibitor for refrigerating machine oil, method for inhibiting foaming in refrigerating machine oil, use for inhibiting foaming in refrigerating machine oil, refrigerating machine oil, and working fluid composition

[0001] The present disclosure relates to a foam inhibitor for refrigerating machine oils, a method for inhibiting foaming in refrigerating machine oils, a use for inhibiting foaming in refrigerating machine oils, refrigerating machine oils, and working fluid compositions.

[0002] Refrigerating machine oils used in refrigerators, air conditioners, and other refrigerating machines are used together with refrigerants, and as the refrigerant is compressed and vaporized, a problem known as foaming can occur, in which bubbles form in the refrigerating machine oil. Foaming in the refrigerating machine oil can lead to increased operating noise and cavitation in the refrigerant compressor. To address this issue, it has been common practice to suppress foaming in the refrigerating machine oil by adding silicone oil as an antifoaming agent (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2005-162883

[0004] However, if a silicone-based antifoaming agent such as silicone oil is added to refrigeration oil, the antifoaming agent may settle out while the compressor is not operating, causing clogging of the piping. Therefore, it is desirable to be able to suppress foaming of refrigeration oil without adding an antifoaming agent such as a silicone-based antifoaming agent.

[0005] Therefore, one aspect of the present invention aims to suppress foaming of refrigerating machine oil without adding an antifoaming agent such as a silicone-based antifoaming agent.

[0006] The present inventors have found that by using as a base oil a polyalkylene glycol compound in which the ratio of terminal hydroxyl groups to terminal alkyl groups and the ratio of ethylene groups to propylene groups are within specific ranges, foaming of refrigerating machine oil can be suppressed without adding an antifoaming agent such as a silicone-based antifoaming agent.

[0007] The present invention includes the following aspects: [1] A foam inhibitor for refrigerating machine oil, comprising 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 foam suppressor, in which in the compound represented by formula (1), the molar ratio of hydrogen atoms / alkyl groups is 40 / 60 or greater and 60 / 40 or less, and the molar ratio of ethylene groups / propylene groups is 10 / 90 or less. [2] The foam suppressor according to [1], in which the molar ratio of ethylene groups / propylene groups is 0 / 100.

[0008] [3] A method for suppressing foaming in a refrigerating machine oil containing a polyalkylene glycol, comprising a step of selecting a compound represented by the following formula (1) as the polyalkylene glycol: [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.] The method according to [3], wherein in the compound represented by formula (1), the molar ratio of hydrogen atoms / alkyl groups is 40 / 60 or more and 60 / 40 or less, and the molar ratio of ethylene groups / propylene groups is 10 / 90 or less. [4] The method according to [3], wherein the molar ratio of ethylene groups / propylene groups is 0 / 100.

[0009] [5] Use of a compound represented by the following formula (1) for suppressing foaming in a refrigerating machine 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.] Use, wherein in the compound represented by formula (1), the molar ratio of hydrogen atoms / alkyl groups is 40 / 60 or more and 60 / 40 or less, and the molar ratio of ethylene groups / propylene groups is 10 / 90 or less. [6] Use according to [5], wherein the molar ratio of ethylene groups / propylene groups is 0 / 100.

[0010] [7] A refrigerating machine oil containing a compound represented by the following formula (1) 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.] A refrigerating machine oil, wherein in the compound represented by formula (1), the molar ratio of hydrogen atoms / alkyl groups is 40 / 60 or more and 60 / 40 or less, and the molar ratio of ethylene groups / propylene groups is 10 / 90 or less. [8] A refrigerating machine oil according to [7], wherein the molar ratio of ethylene groups / propylene groups is 0 / 100. [9] A refrigerating machine oil according to [7] or [8], which is used together with a refrigerant containing a hydrocarbon.

[10] A working fluid composition containing the refrigerating machine oil according to [7] or [8] and a refrigerant.

[11] The working fluid composition according to

[10] , wherein the refrigerant contains a hydrocarbon.

[0011] According to one aspect of the present invention, foaming of refrigerating machine oil can be suppressed without adding an antifoaming agent such as a silicone-based antifoaming agent.

[0012] One embodiment of the present invention is a foam inhibitor for refrigerating machine oils, which 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.

[0013] 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.

[0014] In the PAG compound of this embodiment, R １ and R ２ the ratio of hydrogen atoms to alkyl groups (in other words, the ratio of terminal hydroxyl groups to terminal alkyl groups) in R ３The ratio of ethylene groups to propylene groups (in other words, the ratio of ethylene oxide units (EO units) to propylene oxide units (PO units)) in the PAG compound is within a specific range. This allows the foaming of refrigerating machine oils to be suppressed when the PAG compound is used without adding an antifoaming agent.

[0015] Specifically, R １ and R ２ With respect to the above, the molar ratio of hydrogen atoms to alkyl groups (terminal hydroxyl groups to terminal alkyl groups) is 40 / 60 or more and 60 / 40 or less. The lower limit of this molar ratio may be 41 / 59 or more, 42 / 58 or more, 43 / 57 or more, 44 / 56 or more, 45 / 55 or more, 46 / 54 or more, or 47 / 53 or more. The upper limit of this molar ratio may be 59 / 41 or less, 58 / 42 or less, 57 / 43 or less, 56 / 44 or less, 55 / 45 or less, 54 / 46 or less, 53 / 47 or less, 52 / 48 or less, 51 / 49 or less, 50 / 50 or less, 49 / 51 or less, 48 / 52 or less, 47 / 53 or less, 46 / 54 or less, 45 / 55 or less, 44 / 56 or less, or 43 / 57 or less.

[0016] Also, R ３ In regard to the above, the molar ratio of ethylene groups to propylene groups (the molar ratio of EO units to PO units) is 10 / 90 or less. The molar ratio may be 9 / 91 or less, 8 / 92 or less, 7 / 93 or less, 6 / 94 or less, or 5 / 95 or less, or may be 0 / 100 or less, 1 / 99 or more, 2 / 98 or more, 3 / 97 or more, 4 / 94 or more, or 5 / 95 or more. From the viewpoint of further suppressing foaming of the refrigerating machine oil, it is preferable that the molar ratio is 0 / 100 (i.e., R ３ may be all propylene groups).

[0017] the molar ratio of hydrogen atoms / alkyl groups (terminal hydroxyl groups / terminal alkyl groups) and the molar ratio of ethylene groups / propylene groups (EO units / PO units) in the PAG compound; １３ Specifically, the molar ratio of hydrogen atoms to alkyl groups (terminal hydroxyl groups to terminal alkyl groups) is １３From the spectrum obtained by C-NMR measurement, peaks derived from carbons constituting the hydrocarbon group having a terminal hydroxyl group and peaks derived from carbons constituting the terminal alkyl group are identified, and the molar ratio of ethylene groups / propylene groups (EO units / PO units) can be appropriately determined using the integral values ​​of each peak. 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] The PAG compound is R １ and R ２ and a compound in which both R and R are hydrogen atoms (a PAG compound having hydroxyl groups at both ends), １ and R ２ and a compound in which both of R are alkyl groups (a PAG-based compound in which both terminal alkyl groups are present), １ and R ２ and the other is an alkyl group (PAG compound having a hydroxyl group at one end), and may contain two or more compounds selected from the group consisting of PAG compounds having hydroxyl groups at both ends, PAG compounds having alkyl groups at both ends, and PAG compounds having a hydroxyl group at one end so as to satisfy the above-mentioned hydrogen atom / alkyl group molar ratio.

[0019] In one molecule of a PAG compound, R ３ is an ethylene group (EO unit), and R ３ and a structural unit (PO unit) in which each structural unit is a propylene group (i.e., in which the molar ratio of ethylene group / propylene group (EO unit / PO unit) is more than 0 / 100 and 10 / 90 or less), the PAG compound may be a random copolymer or a block copolymer.

[0020] 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.

[0021] The number average molecular weight (Mn) of the PAG compound may be 500 or more, 700 or more, 900 or more, 1000 or more, or 1100 or more, and may be 5000 or less, 4500 or less, 4000 or less, 3000 or less, 2000 or less, 1800 or less, 1600 or less, or 1400 or less.

[0022] The number average molecular weight (Mn) in this specification refers to the Mn (value converted to polystyrene (standard sample)) obtained by GPC analysis. 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 (for example, 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 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 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, 40mm ２ / s or more, or 50 mm ２ / s or more, and ２ / s or less, 300mm ２ / s or less, 200mm 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, 60mm ２ / s or less, 40mm ２ / s or less, 30mm 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 foam inhibitor may consist solely of a PAG compound, or may further contain a known base oil or additive used in refrigerating machine oils. The foam inhibitor may be used in any amount in the refrigerating machine oil, thereby suppressing foaming of the refrigerating machine oil. Refrigerating machine oils may contain polyalkylene glycol as a base oil, and all of the polyalkylene glycol contained in the refrigerating machine oil may be the foam inhibitor (PAG compound), or 80% by mass or more or 90% by mass or more of the total amount of polyalkylene glycol contained in the refrigerating machine oil may be the foam inhibitor (PAG compound).

[0026] Another embodiment of the present invention can be said to be a method for suppressing foaming in a refrigerating machine oil containing a polyalkylene glycol, the method comprising a step of selecting the above-mentioned PAG compound as the polyalkylene glycol. More specifically, another embodiment of the present invention can be said to be a method for suppressing foaming in a refrigerating machine oil (improving foamability), the method comprising a step of selecting the above-mentioned PAG compound based on the relationship between the hydrogen atom / alkyl group molar ratio and the ethylene group / propylene group molar ratio in the PAG compound and the foamability of the refrigerating machine oil. Furthermore, another embodiment of the present invention can be said to be the use of the above-mentioned PAG compound for suppressing foaming in a refrigerating machine oil.

[0027] Another embodiment of the present invention can be said to be a refrigerating machine oil containing the above-mentioned PAG compound as a base oil. 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.

[0028] The refrigeration oil may further contain a base oil. Examples of the base oil include mineral oil and synthetic oil. The mineral oil may be paraffinic mineral oil, naphthenic mineral oil, etc. Examples of the synthetic oil 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.

[0029] 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.

[0030] 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.

[0031] The refrigerating machine oil preferably further contains a phosphorus-based antiwear agent. Examples of the phosphorus-based antiwear agent include phosphate esters, thiophosphate esters, acidic phosphate esters, amine salts of acidic phosphate esters, chlorinated phosphate esters, and phosphites. Examples of the phosphate esters include triaryl phosphates such as tricresyl phosphate (TCP), triphenyl phosphate (TPP), and alkylated triphenyl phosphate, and trialkyl phosphates. Examples of the 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.

[0032] 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.

[0033] Since the PAG compound has excellent antifoaming properties, the refrigerating machine oil may be substantially free of an antifoaming agent, and may be substantially free of a silicone-based antifoaming agent. Even when the refrigerating machine oil contains a silicone-based antifoaming agent, the content of the silicone-based antifoaming agent in the refrigerating machine oil may be preferably 5 ppm by mass or less, 3 ppm by mass or less, 1 ppm by mass or less, or less than 1 ppm by mass, calculated as Si atoms, based on the total amount of the refrigerating machine oil.

[0034] The Si content (Si atom content) in the refrigerating machine oil may preferably be 5 ppm by mass or less, 3 ppm by mass or less, 1 ppm by mass or less, or less than 1 ppm by mass.

[0035] The kinematic viscosity of the refrigerating oil at 40°C is 20 mm ２ / s or more, 30mm ２ / s or more, 40mm ２ / s or more, or 50 mm ２ / s or more, and ２ / s or less, 300mm ２ / s or less, 200mm 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, 60mm ２ / s or less, 40mm ２ / s or less, 30mm 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.

[0036] 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.

[0037] The refrigerant preferably contains a hydrocarbon. The refrigerating machine oil described above can suppress foaming and exhibit excellent stability even when used with a refrigerant containing a hydrocarbon.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] As explained above, by using the PAG compound, foaming of the refrigerating machine oil can be suppressed without adding an antifoaming agent such as a silicone antifoaming agent. In other words, 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 foaming properties.

[0043] 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 based on the relationship between the molar ratio of hydrogen atoms to alkyl groups and the molar ratio of ethylene groups to propylene groups in the PAG compound and the foamability of the refrigerating machine oil; and preparing a refrigerating machine oil containing the selected PAG compound as a base oil.

[0044] The present invention will be described in more detail below based on examples, but the present invention is not limited to the following examples.

[0045] Refrigerating machine oils of Examples and Comparative Examples were prepared using the following PAG compounds 1 to 8. Each refrigerating machine oil did not contain an antifoaming agent such as a silicone-based antifoaming agent, and had a Si content of less than 1 ppm by mass.

[0046] PAG compound 1: In the above formula (1), R １ and R ２ The molar ratio of hydrogen atoms to alkyl groups (n-butyl groups) is 50 / 50, and R ３ The molar ratio of ethylene groups to propylene groups is 0 / 100 (R ３ are all propylene groups) ２ / s, 100℃ kinematic viscosity: 9.079mm ２ / s, viscosity index: 186)

[0047] PAG compound 2: In the above formula (1), R １ and R ２ The molar ratio of hydrogen atoms to alkyl groups (n-butyl groups) is 50 / 50, and R ３ The molar ratio of ethylene groups to propylene groups is 0 / 100 (R ３ are all propylene groups) ２ / s, 100℃ kinematic viscosity: 11.06mm ２ / s, viscosity index: 189)

[0048] PAG compound 3: In the above formula (1), R １ and R ２The molar ratio of hydrogen atoms to alkyl groups (n-butyl groups) is 43 / 57, and R ３ The molar ratio of ethylene groups to propylene groups is 0 / 100 (R ３ are all propylene groups) ２ / s, 100℃ Kinematic viscosity: 6.275mm ２ / s, viscosity index: 167)

[0049] PAG compound 4: In the above formula (1), R １ and R ２ The molar ratio of hydrogen atoms to alkyl groups (n-butyl groups) is 42 / 58, and R ３ The molar ratio of ethylene groups to propylene groups is 0 / 100 (R ３ are all propylene groups) ２ / s, 100℃ kinematic viscosity: 10.69mm ２ / s, viscosity index: 184)

[0050] PAG compound 5: In the above formula (1), R １ and R ２ The molar ratio of hydrogen atoms to alkyl groups (n-butyl groups) is 47 / 53, and R ３ The molar ratio of ethylene groups to propylene groups is 0 / 100 (R ３ are all propylene groups) ２ / s, 100℃ kinematic viscosity: 57.92mm ２ / s, viscosity index: 230)

[0051] PAG compound 6: In the above formula (1), R １ and R ２ The molar ratio of hydrogen atoms to alkyl groups (n-butyl groups) is 50 / 50, and R ３ A compound having an ethylene group / propylene group molar ratio of 5 / 95 (Mn: 1200, kinematic viscosity at 40°C: 58.29 mm ２ / s, 100℃ kinematic viscosity: 11.33mm ２ / s, viscosity index: 192)

[0052] PAG compound 7: In the above formula (1), R１ and R ２ The molar ratio of hydrogen atoms to alkyl groups (n-butyl groups) is 50 / 50, and R ３ A compound having an ethylene group / propylene group molar ratio of 7 / 93 (Mn: 1390, kinematic viscosity at 40°C: 48.47 mm ２ / s, 100℃ kinematic viscosity: 9.676mm ２ / s, viscosity index: 190)

[0053] PAG compound 8: In the above formula (1), R １ and R ２ The molar ratio of hydrogen atoms to alkyl groups (n-butyl groups) is 37 / 63, and R ３ A compound having an ethylene group / propylene group molar ratio of 51 / 49 (Mn: 1340, kinematic viscosity at 40°C: 51.61 mm ２ / s, 100℃ kinematic viscosity: 11.09mm ２ / s, viscosity index: 214)

[0054] (Evaluation of Foaming) For each refrigeration oil, the foaming degree / foam stability (unit: mL) was measured according to Sequence I (test at 24°C), Sequence II (test at 93.5°C), and Sequence III (test at 93.5°C, followed by cooling to 24°C) as specified in JIS K2518:2003. The results are shown in Table 1.

[0055]

Claims

1. A foam inhibitor for 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 greater.] A foaming inhibitor, wherein, in the compound represented by formula (1), the molar ratio of the hydrogen atoms to the alkyl groups is 40 / 60 or greater and 60 / 40 or less, and the molar ratio of the ethylene groups to the propylene groups is 10 / 90 or less.

2. The foam suppressor according to claim 1, wherein the molar ratio of said ethylene groups to said propylene groups is 0 / 100.

3. A method for suppressing foaming in a refrigerating machine oil containing a polyalkylene glycol, comprising the step of selecting a compound represented by the following formula (1) as the polyalkylene glycol: [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.] The method of the present invention, wherein, in the compound represented by formula (1), the molar ratio of the hydrogen atoms to the alkyl groups is 40 / 60 or more and 60 / 40 or less, and the molar ratio of the ethylene groups to the propylene groups is 10 / 90 or less.

4. The method of claim 3, wherein the molar ratio of the ethylene groups to the propylene groups is 0 / 100.

5. Use of a compound represented by the following formula (1) for suppressing foaming in a refrigerating machine 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.] In the compound represented by formula (1), the molar ratio of the hydrogen atoms / the alkyl groups is 40 / 60 or more and 60 / 40 or less, and the molar ratio of the ethylene groups / the propylene groups is 10 / 90 or less.

6. The use according to claim 5, wherein the molar ratio of the ethylene groups to the propylene groups is 0 / 100.

7. 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 in the compound represented by formula (1), the molar ratio of the hydrogen atoms to the alkyl groups is 40 / 60 or more and 60 / 40 or less, and the molar ratio of the ethylene groups to the propylene groups is 10 / 90 or less.

8. The refrigerating machine oil according to claim 7, wherein the molar ratio of the ethylene group to the propylene group is 0 / 100.

9. The refrigeration oil according to claim 7 or 8, which is used together with a refrigerant containing a hydrocarbon.

10. A working fluid composition containing the refrigerating machine oil according to claim 7 or 8 and a refrigerant.

11. The working fluid composition of claim 10, wherein the refrigerant comprises a hydrocarbon.

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