Working medium for refrigerant compression type refrigeration cycle device and refrigeration cycle device using said working medium

Abstract

[Problem] The present invention addresses the problem of providing a working medium for refrigerant compression-type refrigeration cycle devices, the working medium comprising a hydrocarbon-containing refrigerant and a refrigerating machine oil, wherein the refrigerating machine oil achieves at least one of the following advantages, i.e., high stability, appropriate compatibility with the refrigerant, high lubricity and high electrical insulation. [Solution] The present invention provides a working medium for refrigerant compression-type refrigeration cycle devices, the working medium comprising a refrigerant that contains a hydrocarbon having 2 to 4 carbon atoms but not having a halogen atom, and a refrigerating machine oil that contains a polyalkylene glycol and a mineral oil, wherein: the polyalkylene glycol is represented by general formula (1), and has a kinematic viscosity of 2 mm2 / s to 60 mm2 / s at 40°C; the mineral oil has an aniline point of 55°C to 105°C, a pour point of -15°C or less, and a kinematic viscosity of 2 mm2 / s to 100 mm2 / s at 40°C; the polyalkylene glycol is contained in an amount of 10% by mass to 60% by mass relative to the total mass of the refrigerating machine oil; and the mineral oil is contained in an amount of 40% by mass to 90% by mass relative to the total mass of the refrigerating machine oil.

Description

[Technical field]

[0001] The present invention relates to a working medium for a refrigerant compression type refrigeration cycle device and a refrigeration cycle device using the working medium. More specifically, the present invention relates to a working medium containing a refrigerant and a refrigerating machine oil for use in a refrigerant compression type refrigeration cycle device and a refrigeration cycle device using the working medium. [Background technology]

[0002] Hydrofluorocarbons (HFCs), which are hydrocarbons containing fluorine atoms, are used as refrigerants in refrigeration cycle devices that compress refrigerants, such as air conditioners, electric refrigerators, industrial freezers, and refrigerated or frozen warehouses. However, because HFCs have a long life in the atmosphere, they have a large greenhouse effect and are not satisfactory refrigerants in terms of preventing global warming, so there are moves to restrict their use.

[0003] Instead of the above-mentioned HFCs, halogen-free hydrocarbons (hereinafter also simply referred to as "hydrocarbon refrigerants"), which are highly flammable but have zero ozone depletion potential and a significantly smaller global warming potential than HFCs, are being used as refrigerants for refrigeration cycle devices. For example, electric refrigerators using isobutane (R600a), a hydrocarbon that does not contain halogen atoms, as a refrigerant have been put to practical use. Furthermore, the development of large-scale equipment using a hydrocarbon that does not contain halogen atoms as a refrigerant is being considered, and propane (R290) is being put to practical use in air conditioners. When using these hydrocarbon refrigerants, mineral oils, alkylbenzenes, polyol esters, polyethers, etc. are known as refrigeration oils that are used as working medium components together with the hydrocarbon refrigerants. (For example, Patent Documents 1 to 5). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2000-60031 [Patent Document 2] JP 2003-041278 A [Patent Document 3] Patent No. 3664511 [Patent Document 4] Patent No. 5086782 [Patent Document 5] Patent No. 4603117 Summary of the Invention [Problem to be solved by the invention]

[0005] The refrigeration oils containing mineral oil, alkylbenzene or polyol ester proposed in the above Patent Documents 1 to 3 have good compatibility with hydrocarbon refrigerants such as propane and isobutane, and the amount of refrigerant dissolved in the refrigeration oil is large. For this reason, in order to fully utilize the capacity of the refrigeration cycle device, it is necessary to fill the refrigeration cycle device with a large amount of hydrocarbon refrigerant. However, since hydrocarbons such as propane and isobutane are highly flammable, it is desirable from a safety standpoint that the amount of hydrocarbon refrigerant be as small as possible within a range that fully exhibits operating efficiency. In addition, the smaller the amount of hydrocarbon refrigerant dissolved in the refrigeration oil, the smaller the fluctuation in dissolution and evaporation of the hydrocarbon refrigerant in the refrigeration oil caused by fluctuations in operating conditions, and the smaller the viscosity change of the working medium, which is preferable. In addition, when the amount of hydrocarbon refrigerant dissolved in the refrigeration oil is small, a refrigeration oil with a lower viscosity can be selected, which leads to high efficiency of the refrigeration cycle device and energy saving.

[0006] In the refrigeration oil containing polyol ester and polyalkylene glycol proposed in the above Patent Document 4, both the polyol ester and the polyalkylene glycol have high polarity, so that the hygroscopicity of the refrigeration oil is high. In this case, the water content in the refrigeration oil increases, and hydrolysis of the polyol ester proceeds, which may cause deterioration of the refrigeration oil. The refrigeration oil is used for a long period of time in a refrigeration cycle device in the presence of a refrigerant and is exposed to low and high temperatures, so it is required to have high stability. If such a highly hygroscopic refrigeration oil is used in a refrigeration cycle device, there is a risk of trouble occurring due to an increase in the water content in the refrigeration cycle device or deterioration of the refrigeration oil. In addition, the refrigeration oil containing polyol ester and polyalkylene glycol has a problem that it is prone to leak current in the refrigeration cycle device because of its low electrical insulation, which is indicated by its volume resistivity.

[0007] Patent Document 5 discloses a refrigeration oil containing a polyether compound and a mineral oil. Patent Document 5 only specifies that the polyether compound is polyalkylene glycol or polyvinyl ether, and that the mineral oil has a specific sulfur content to improve lubricity. Therefore, the refrigeration oil disclosed in Patent Document 5 includes a very wide range of refrigeration oils. Here, the refrigeration oil disclosed in Patent Document 5 uses an ammonia refrigerant as a refrigerant. That is, the refrigeration oil disclosed in Patent Document 5 is a refrigeration oil suitable for a large open-type refrigeration machine using an ammonia refrigerant, that is, a non-circulation system in which the refrigerant and the refrigeration oil are mixed and do not circulate through the refrigeration cycle.

[0008] In contrast to the non-circulating system, a small-sized closed circulation system is known in which a motor is built in the compressor and a mixture of a hydrocarbon refrigerant and a refrigerating machine oil is circulated through the refrigeration cycle. In this circulation system, the motor is built in, so the refrigerating machine oil is required to have high electrical insulation. The ammonia refrigerant used in Patent Document 5 has high polarity and leaks current, so it cannot be used in the circulation system. In addition, in the circulation system, the medium is required to be a uniform liquid even at low temperatures because it is cooled to low temperatures (e.g., -25°C). Therefore, a hydrocarbon refrigerant that is liquid even at low temperatures is preferably used as the refrigerant. The refrigerating machine oil is required to be uniformly mixed with the hydrocarbon refrigerant even at low temperatures. For example, in the refrigerating machine oil disclosed in Patent Document 5, the polyether compound (particularly polyalkylene glycol) has polarity, and the mineral oil is non-polar. In this case, the polyether compound is difficult to mix with the mineral oil and the hydrocarbon refrigerant at low temperatures (e.g., -25°C) due to the difference in polarity, and separates or precipitates at low temperatures. As described above, the ammonia refrigerant and the refrigerating machine oil disclosed in Patent Document 5 are not suitable for the circulation system.

[0009] As described above, there is still room for improvement in the properties of refrigerating machine oils, i.e., stability, compatibility with hydrocarbon refrigerants, electrical insulation properties, and the like.

[0010] An object of the present invention is to provide a working fluid for a refrigerant compression type refrigeration cycle device, which contains a hydrocarbon refrigerant and a refrigerating machine oil, and which achieves at least one of high stability, appropriate solubility with the refrigerant, high lubricity, and high electrical insulation. [Means for solving the problem]

[0011] According to one embodiment of the present invention, a refrigerant containing a hydrocarbon having 2 to 4 carbon atoms and not containing a halogen atom, and a refrigeration oil containing a polyalkylene glycol and a mineral oil are included, and the polyalkylene glycol is represented by the following general formula (1):

[0012] [ka]

[0013] [In formula (1), R 1 is a linear or branched alkyl group having 1 to 25 carbon atoms, and OR 2 are the same or different and each represents an oxyalkylene group having 2 to 4 carbon atoms, and n is OR 2 represents the number of moles of oxyalkylene groups added. The kinetic viscosity at 40°C is 2mm 2 / s or more 60mm 2 The mineral oil has an aniline point of 55° C. or more and 105° C. or less, a pour point of -15° C. or less, and a kinematic viscosity at 40° C. of 2 mm 2 / s or more 100mm 2 / s or less, the polyalkylene glycol is contained in an amount of 10 mass % or more and 60 mass % or less based on the total mass of the refrigerating machine oil, and the mineral oil is contained in an amount of 40 mass % or more and 90 mass % or less based on the total mass of the refrigerating machine oil.

[0014] According to another embodiment of the present invention, a refrigerant containing a hydrocarbon having 2 to 4 carbon atoms and not containing a halogen atom, a refrigerating machine oil containing a polyalkylene glycol and a mineral oil, and a thiobisphenol compound, wherein the polyalkylene glycol is represented by the following general formula (1):

[0015] [ka]

[0016] [In formula (1), R 1 is a linear or branched alkyl group having 1 to 25 carbon atoms, and OR 2 are the same or different and each represents an oxyalkylene group having 2 to 4 carbon atoms, and n is OR 2 represents the number of moles of oxyalkylene groups added.] The kinetic viscosity at 40°C is 2mm2 / s or more 60mm 2 The mineral oil has an aniline point of 55° C. or more and 105° C. or less, a pour point of -15° C. or less, and a kinematic viscosity at 40° C. of 2 mm 2 / s or more 100mm 2 / s or less, the polyalkylene glycol is contained in an amount of 10 mass % or more and 60 mass % or less based on the total mass of the refrigerating machine oil, and the mineral oil is contained in an amount of 40 mass % or more and 90 mass % or less based on the total mass of the refrigerating machine oil. Effect of the Invention

[0017] According to the present invention, there is provided a working fluid for a refrigerant compression type refrigeration cycle device, which includes a hydrocarbon-containing refrigerant and a refrigerating machine oil, and the refrigerating machine oil achieves at least one of high stability, appropriate solubility with the refrigerant, high lubricity, and high electrical insulation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The refrigeration oil and working fluid of the present invention will be described in detail below. In this specification, unless otherwise specified, operations and measurements of physical properties are performed under conditions of room temperature (20 to 25°C) and relative humidity of 40 to 50% RH. In addition, in this specification, "X to Y" is used to mean that the numerical values ​​(X and Y) written before and after it are included as the lower and upper limits, and means "X or more and Y or less."

[0019] The working medium for a refrigerant compression type refrigeration cycle device according to the present invention (hereinafter simply referred to as the "working medium") contains a refrigerant containing a hydrocarbon having 2 to 4 carbon atoms and not containing a halogen atom, and a refrigeration oil containing a specific polyalkylene glycol and a specific mineral oil. 2 / s or more 32mm 2 / s or less is preferable, and 3 mm 2 / s or more 30mm 2 / s or less is preferable, and 5 mm 2 / s or more 25mm 2 In this specification, the kinematic viscosity is measured by the method described in the Examples.

[0020] First, the refrigerant contained in the working fluid of the present invention will be described. The refrigerant contains a hydrocarbon having 2 to 4 carbon atoms that does not contain a halogen atom (hereinafter, also simply referred to as "hydrocarbon"). Examples of the hydrocarbon having 2 to 4 carbon atoms that does not contain a halogen atom include saturated hydrocarbons such as ethane (R170), propane (R290), normal butane (R600), and isobutane (R600a), and unsaturated hydrocarbons such as ethylene and propene. The hydrocarbon preferably contains at least one selected from the saturated hydrocarbons, that is, at least one selected from the group consisting of ethane, propane, normal butane, and isobutane. As the working fluid, a combination of propane, ethane, or a mixed refrigerant thereof with a refrigerating machine oil containing a specific polyalkylene glycol and a specific mineral oil is more preferable because it has a high effect of the present invention. As the working fluid, a combination of a refrigerant containing propane with a refrigerating machine oil containing a specific polyalkylene glycol and a specific mineral oil is even more preferable because it has a high effect of the present invention. As the hydrocarbon, one type of hydrocarbon may be used alone, or two or more types of hydrocarbons may be used in combination.

[0021] In a preferred embodiment, the hydrocarbon includes propane (R290). In this case, the refrigerant may further contain other hydrocarbons than propane, such as saturated hydrocarbons such as ethane, n-butane (normal butane) (R600), and isobutane (R600a); unsaturated hydrocarbons such as ethylene and propene, in addition to propane. When the hydrocarbon including propane further includes other hydrocarbons than propane, the main component of the hydrocarbon is preferably propane. In addition, in the present invention, the "main component" means a component that is more than 50 mass% (upper limit 100 mass%) with respect to the total mass of the hydrocarbon. Therefore, when the hydrocarbon includes propane and a hydrocarbon other than propane, the content of the hydrocarbon other than propane is preferably 1 mass% or more and less than 50 mass%, more preferably 2 mass% or more and 40 mass% or less, even more preferably 3 mass% or more and 35 mass% or less, particularly preferably 5 mass% or more and 25 mass% or less, and most preferably 10 mass% or more and 20 mass% or less with respect to the total mass of the hydrocarbon. In one embodiment, the hydrocarbon consists of propane (R290) (100% by weight propane).

[0022] The working fluid of the present invention may further contain other refrigerants such as saturated hydrofluorocarbons, unsaturated hydrofluorocarbons, dimethyl ether, carbon dioxide, etc. (hereinafter referred to as "other refrigerants") In this case, the other refrigerants are preferably 1 to 100 parts by mass, more preferably 5 to 50 parts by mass, and even more preferably 10 to 30 parts by mass, per 100 parts by mass of the hydrocarbon.

[0023] In a preferred embodiment, the refrigerant contains propane in an amount of preferably more than 50 mass%, more preferably 60 mass% or more, even more preferably 75 mass% or more, particularly preferably 80 mass% or more, and most preferably 90 mass% or more, based on the total mass of the refrigerant. The refrigerant may be composed of only propane, and therefore the upper limit of the propane content in the refrigerant is 100 mass%. Thus, in one embodiment, the refrigerant is composed of propane (R290) (propane 100 mass%). That is, the refrigerant is propane (R290).

[0024] The refrigerating machine oil of the present invention contains a specific polyalkylene glycol and a specific mineral oil. In one embodiment, the refrigerating machine oil has a mixed oil containing a specific polyalkylene glycol and a specific mineral oil as a base oil. The base oil of the refrigerating machine oil refers to a component contained in the refrigerating machine oil in an amount of more than 50 mass% (up to 100 mass%), preferably 80 mass% or more, more preferably 90 mass% or more. Polyalkylene glycol can be used alone as a refrigerating machine oil, but has high hygroscopicity due to its polarity. Therefore, when polyalkylene glycol is used alone as a refrigerating machine oil, the water content in the refrigerating machine oil increases, and the water may cause trouble in the refrigeration cycle device. In addition, polyalkylene glycol has low electrical insulation, i.e., low volume resistivity, so that it is prone to current leakage in air conditioners, electric refrigerators, industrial freezers, and the like that use sealed compressors. However, on the other hand, polyalkylene glycol has an advantage that it dissolves less in refrigerants containing hydrocarbons due to its polarity.

[0025] Although mineral oil has low hygroscopicity and high electrical insulation, it dissolves in a large amount in a refrigerant containing hydrocarbons because it is made of the same hydrocarbons as the refrigerant. Therefore, when mineral oil is used alone as a refrigeration oil, there is a drawback in that the viscosity of the refrigeration oil in a refrigeration cycle device decreases, resulting in a decrease in lubricity, i.e., wear resistance.

[0026] Therefore, by mixing both polyalkylene glycol and mineral oil, it is possible to make up for the shortcomings and obtain a refrigeration oil with good balance of properties. However, it is considered that polar polyalkylene glycol and non-polar mineral oil are difficult to dissolve in each other and separate into two layers. If these polyalkylene glycol and mineral oil separate into two layers, they cannot be used as a refrigeration oil. As a result of intensive research, it was found that by containing a specific polyalkylene glycol and a specific mineral oil in a specific mass ratio as a refrigeration oil, the refrigeration oil becomes a homogeneous liquid and can exhibit suitable properties as a refrigeration oil, and the present invention was completed.

[0027] The specific polyalkylene glycol of the present invention is represented by the following general formula (1).

[0028] [ka]

[0029] [However, R 1 is a linear or branched alkyl group having 1 to 25 carbon atoms, and OR 2 represents one or more oxyalkylene groups having 2 to 4 carbon atoms, and n is OR 2 represents the number of moles of oxyalkylene groups added. In the above formula (1), R 1 represents a linear or branched alkyl group having 1 to 25 carbon atoms. As the linear or branched alkyl group, a linear or branched alkyl group having 1 to 20 carbon atoms is preferred, a linear or branched alkyl group having 1 to 10 carbon atoms is more preferred, a linear or branched alkyl group having 1 to 8 carbon atoms is even more preferred, a linear or branched alkyl group having 1 to 5 carbon atoms is particularly preferred, and a linear or branched alkyl group having 3 to 5 carbon atoms is most preferably used. Examples of the linear or branched alkyl group having 1 to 25 carbon atoms include a methyl group, an ethyl group, a linear or branched propyl group (n-propyl group, isopropyl group), a linear or branched butyl group (n-butyl group, isobutyl group, sec-butyl group, tert-butyl group), a linear or branched pentyl group (n-pentyl group, isopentyl group, sec-pentyl group, 3-pentyl group, tert-pentyl group, neopentyl group), and the like. R 1 In terms of the balance between the solubility in a refrigerant containing a hydrocarbon and the properties as a refrigerating machine oil, R is preferably an isopropyl group, an n-butyl group, or a tert-butyl group, and more preferably a linear or branched butyl group having 4 carbon atoms (n-butyl group, tert-butyl group). 1 When is a short chain alkyl group, low temperature fluidity is excellent.

[0030] In the general formula (1) above, OR 2 are the same or different and each represents an oxyalkylene group having 2 to 4 carbon atoms. That is, R 2 represents an alkylene group having 2 to 4 carbon atoms. 2 may be one type of oxyalkylene group, or may be composed of two or more types of oxyalkylene groups. Specific examples of such oxyalkylene groups include an oxyethylene group (-OCH2CH2-), an oxypropylene group (-OCH(CH3)CH2-), an oxytrimethylene group (-OCH2CH2CH2-), and an oxybutylene group (-OCH2CH2CH2CH2-). Among these oxyalkylene groups, an oxyethylene group and an oxypropylene group are preferred, and an oxypropylene group is more preferred. In this case, (OR 2 ) n In the repeating unit represented by the formula: 2 ) may be the same or different oxyalkylene groups. 2 The upper limit of the proportion of oxypropylene groups in the whole is not particularly limited, but in the polyalkylene glycol, 2 Most preferably, all of OR is oxypropylene, and therefore the upper limit is 100 mol %. For example, OR 2 When the copolymer is composed of oxyethylene groups and oxypropylene groups, the ratio of the oxypropylene groups is OR 2 It is preferably 70 mol % or more, more preferably 80 mol % or more, based on the total (i.e., the total number of moles of oxyethylene groups and oxypropylene groups added). 2 The proportion of oxyethylene groups in the whole 2 From the viewpoint of the properties as a refrigerating machine oil, that is, to reduce the moisture absorption of the refrigerating machine oil, the proportion of the carbon number 2) is preferably 30 mol % or less, and more preferably 20 mol % or less.

[0031] In one embodiment, the polyalkylene glycol is R 1 is an alkyl group having 4 carbon atoms, and OR2 is an oxypropylene group. This makes it possible to provide the refrigerating machine oil with even better low-temperature fluidity and hygroscopicity.

[0032] In the above general formula (1), n ​​is OR 2 represents the number of moles of oxyalkylene groups (degree of polymerization) represented by the formula (1). The number average molecular weight of the polyalkylene glycol represented by the formula (1) is preferably 100 to 1500, more preferably 200 to 1200, even more preferably 300 to 1000, particularly preferably 350 to 850, and most preferably 350 to 700. n is preferably a number that satisfies the above condition for the number average molecular weight of the polyalkylene glycol. When the number average molecular weight of the polyalkylene glycol is within the above range, it has good compatibility with mineral oil and can fully exhibit the lubricity of the refrigerating machine oil in the coexistence with a refrigerant containing a hydrocarbon. In this specification, the number average molecular weight is measured by GPC (gel permeation chromatography) using polystyrene as a standard substance. The number of moles of addition n in the formula (1) can be calculated based on the number average molecular weight obtained by measurement.

[0033] In the present invention, the polyalkylene glycol has a kinetic viscosity of 2 mm at 40°C. 2 / s or more 60mm 2 / s or less. The kinetic viscosity of polyalkylene glycol at 40°C is 2mm 2 If the kinematic viscosity of the polyalkylene glycol is less than 60 mm / s, the oil film formed by the polyalkylene glycol will be thin. In other words, metal-to-metal contact will occur easily in the sliding materials (sliding parts) of the compressor, which is the heart of the refrigeration cycle equipment, and the lubrication of the refrigeration oil in the presence of the refrigerant will be insufficient. 2 If the kinematic viscosity exceeds 5 mm / s, the viscous resistance of the refrigerating machine oil becomes too high, and the efficiency of the refrigeration cycle device decreases. 2 / s or more 55mm 2 / s or less, and more preferably 8 mm 2 / s or more 50mm2 / s or less, and more preferably 9 mm 2 / s or more 45mm 2 / s or less, and particularly preferably 10 mm 2 / s or more 40mm 2 / s or less, and most preferably 10 mm 2 / s or more 35mm 2 When the kinematic viscosity at 40° C. of the polyalkylene glycol is within the above range, the polyalkylene glycol can exhibit good lubricating properties as a refrigerating machine oil.

[0034] In the present invention, the kinetic viscosity of the polyalkylene glycol at 100°C is 0.1 mm 2 / s or more is preferable, and 0.25 mm 2 / s or more is preferable, and 0.3 mm 2 It is particularly preferable that the thickness is 0.4 mm / s or more. 2 More preferably, the thickness is 0.5 mm / s or more. 2 The kinematic viscosity of the polyalkylene glycol at 100°C is preferably 15 mm / s or more. 2 / s or less is preferable, and 10 mm 2 / s or less is preferable, and 5 mm 2 / s or less is particularly preferable, and 3 mm 2 More preferably, the thickness is less than 2.9 mm / s. 2 That is, the kinematic viscosity of the polyalkylene glycol at 100°C is preferably 0.1 mm / s or less. 2 / s or more 15mm 2 / s or less is preferable, and 0.25 mm 2 / s or more 10mm 2 / s or less is preferable, and 0.3 mm 2 / s or more 5mm 2 It is particularly preferable that the thickness is 0.4 mm / s or less. 2 / s or more 3mm 2 More preferably, it is less than 0.5 mm / s. 2 / s or more 2.9mm 2In one embodiment, the kinematic viscosity of the polyalkylene glycol at 100° C. is 0.1 mm / s or less. 2 / s or more 10mm 2 / s or less, 0.1mm 2 / s or more 8mm 2 / s or less, 0.1mm 2 / s or more 7.5mm 2 / s or less, 0.1mm 2 / s or more 7mm 2 / s or less, 0.1mm 2 / s or more 6mm 2 In one embodiment, the kinematic viscosity of the polyalkylene glycol at 100° C. is 0.1 mm / s or less. 2 / s or more 3mm 2 / s Less than 0.1mm 2 / s or more 2.9mm 2 The kinetic viscosity of polyalkylene glycol at 100°C is 0.1 mm 2 If the kinematic viscosity of the polyalkylene glycol at 100°C is 15 mm / s or more, the oil film formed by the polyalkylene glycol is formed with a sufficient thickness, and the lubricating properties of the refrigeration oil can be fully exhibited. 2 / s or less, the viscosity of the refrigeration oil is low, so that the efficiency of the refrigeration cycle device can be further improved.

[0035] In the present invention, the polyalkylene glycol has a kinetic viscosity of 2 mm at 40°C. 2 / s or more 60mm 2 / s or less, and the kinetic viscosity at 100°C is 0.1 mm 2 / s or more 15mm 2 The polyalkylene glycol preferably has a kinematic viscosity of 2 mm / s or less at 40° C. 2 / s or more 60mm 2 / s or less, and the kinetic viscosity at 100°C is 0.4 mm 2 / s or more 3mm 2 / s, and more preferably the kinetic viscosity at 40 °C is less than 2 mm 2 / s or more 60mm 2 / s or less, and the kinetic viscosity at 100°C is 0.5 mm2 / s or more 2.9mm 2 / s or less.

[0036] In one embodiment of the present invention, the polyalkylene glycol has a kinematic viscosity of 5 mm at 40° C. 2 / s or more 55mm 2 / s or less, and the kinetic viscosity at 100°C is 0.1 mm 2 / s or more 10mm 2 The polyalkylene glycol preferably has a kinematic viscosity of 8 mm / s or less at 40° C. 2 / s or more 50mm 2 / s or less, and the kinetic viscosity at 100°C is 0.4 mm 2 / s or more 8mm 2 More preferably, the kinetic viscosity at 40°C is 9 mm 2 / s or more 45mm 2 / s or less, and the kinetic viscosity at 100°C is 0.5 mm 2 / s or more 7.5mm 2 / s or less.

[0037] The polyalkylene glycol preferably has a pour point of −25° C. or less, more preferably −30° C. or less, and even more preferably −40° C. or less. When the pour point of the polyalkylene glycol is −25° C. or less, the fluidity of the refrigeration oil containing the polyalkylene glycol and mineral oil is high, and the polyalkylene glycol can be suitably used as a refrigeration oil.

[0038] The polyalkylene glycol according to the present invention can be synthesized by a conventional method ("Alkylene Oxide Polymer", Mitsuta Shibata et al., Kaibundo Publishing, published on November 20, 1990). For example, an alcohol (R 1 OH;R 1 is R in the above general formula (1). 1It is obtained by addition polymerization of one or more specific alkylene oxides to a polyalkylene glycol having the same definition as that of the alkylene oxide having the same structure as ...

[0039] Examples of the polyalkylene glycol represented by the general formula (1) include polypropylene glycol monomethyl ether, polypropylene glycol monoethyl ether, polypropylene glycol monopropyl ether (polypropylene glycol mono n-propyl ether, polypropylene glycol monoisopropyl ether), polypropylene glycol monobutyl ether (polypropylene glycol mono n-butyl ether), polypropylene glycol mono tert-butyl ether, polypropylene glycol monohexyl ether (polypropylene glycol mono n-hexyl ether), polypropylene glycol monooctyl ether (polypropylene glycol mono n-octyl ether); monomethyl ether of polyethylene glycol-polypropylene glycol copolymer (polyethylene glycol polypropylene glycol monomethyl ether), monoethyl ether of polyethylene glycol-polypropylene glycol copolymer (polyethylene glycol polypropylene glycol monoethyl ether), polyethylene mono n-propyl ether of polyethylene glycol-polypropylene glycol copolymer (polyethylene glycol polypropylene glycol mono n-propyl ether), monoisopropyl ether of polyethylene glycol-polypropylene glycol copolymer (polyethylene glycol polypropylene glycol monoisopropyl ether), mono n-butyl ether of polyethylene glycol-polypropylene glycol copolymer (polyethylene glycol polypropylene glycol mono n-butyl ether), mono tert-butyl ether of polyethylene glycol-polypropylene glycol copolymer (polyethylene glycol polypropylene glycol mono tert-butyl ether), monohexyl ether of polyethylene glycol-polypropylene glycol copolymer (polyethylene glycol polypropylene glycol mono n-hexyl ether), monooctyl ether of polyethylene glycol-polypropylene glycol copolymer (polyethylene glycol polypropylene glycol mono n-octyl ether);

[0040] Of these polyalkylene glycols, polypropylene glycol monoalkyl ethers such as polypropylene glycol monomethyl ether, polypropylene glycol monoethyl ether, polypropylene glycol monopropyl ether, polypropylene glycol monobutyl ether, polypropylene glycol monohexyl ether and polypropylene glycol monooctyl ether, which have high electrical insulation properties, are preferred, and polypropylene glycol mono-n-propyl ether, polypropylene glycol mono-n-butyl ether, polypropylene glycol mono-tert-butyl ether, polypropylene glycol monohexyl ether and polypropylene glycol monooctyl ether, which have higher electrical insulation properties and lower hygroscopicity, are more preferred.

[0041] Since the polyalkylene glycol of the present invention has a hydroxyl group with high polarity at one end, it is considered that it has low affinity with non-polar hydrocarbons contained in the refrigerant and can reduce the amount of dissolution in the refrigerant. Therefore, the amount of refrigerant filled in the working medium can be reduced. In addition, since the hydroxyl group has a high adsorption power to metal materials, the polyalkylene glycol easily forms an oil film on the sliding material of the compressor, which is the heart of the refrigeration cycle device, and shows good lubricity (wear resistance). From this, it is presumed that the use of a specific polyalkylene glycol in the present invention can reduce the viscosity of the refrigeration oil, leading to high efficiency of the refrigeration cycle device. However, it has disadvantages in that it is highly hygroscopic and has low electrical insulation. It should be noted that the present invention is not limited by the above reasoning.

[0042] The mineral oil used in the present invention has an aniline point of 55°C or more and 105°C or less, a pour point of -15°C or less, and a kinematic viscosity of 2mm at 40°C. 2 / s or more 100mm 2 / s or less. In the present invention, the mineral oil is soluble in the polyalkylene glycol, and the aniline point of the mineral oil is a guide to the solubility with the polyalkylene glycol. If the aniline point of the mineral oil is less than 55°C, the viscosity characteristics as a refrigerating machine oil, such as the viscosity index, become insufficient, and the refrigerating machine oil cannot exhibit good performance (for example, the formation of a sufficiently thick oil film at high temperatures). If the aniline point of the mineral oil is more than 105°C, the mineral oil and the polyalkylene glycol become difficult to dissolve in each other, and are easily separated into two layers, and the stability as a refrigerating machine oil cannot be maintained. The aniline point of the mineral oil is preferably 65°C or more and 100°C or less, more preferably 75°C or more and 95°C or less. If the aniline point of the mineral oil is within the above range, the compatibility between the mineral oil and the polyalkylene glycol is good, and the advantages of each component as a refrigerating machine oil can be further exhibited.

[0043] The mineral oil used in the present invention has a pour point of -15°C or less. If the pour point of the mineral oil exceeds -15°C, the fluidity of the refrigeration oil containing polyalkylene glycol and mineral oil is low, and the refrigeration oil cannot exhibit good performance (e.g., formation of a sufficiently thick oil film at high temperatures). The pour point of the mineral oil is preferably -25°C or less, more preferably -30°C or less, and particularly preferably -35°C or less.

[0044] In the present invention, the kinetic viscosity of the mineral oil at 40°C is 2mm 2 / s or more 100mm 2 / s or less. The kinetic viscosity of mineral oil at 40°C is 2mm 2 If the kinematic viscosity of mineral oil at 40°C is less than 100mm / s, the oil film formed on the sliding material of the compressor becomes thin, the properties associated with viscosity become insufficient, and the oil cannot exhibit good lubrication and sealing properties as a refrigeration oil. 2 If the kinematic viscosity exceeds 3 mm / s, the mineral oil will not dissolve in the polyalkylene glycol, and will separate into two layers, making it impossible to maintain stability as a refrigeration oil. 2 / s or more 95mm 2 / s or less, and more preferably 3 mm 2 / s or more 90mm 2 / s or less, and more preferably 5 mm 2 / s or more 80mm 2 In one embodiment, the mineral oil preferably has a kinematic viscosity of 3 mm / s or less at 40° C. 2 / s or more 65mm 2 / s or less, and more preferably 3 mm 2 / s or more 50mm 2 / s or less, and more preferably 5 mm 2 / s or more 45mm 2 According to one embodiment of the present invention, the mineral oil has a kinematic viscosity of 8 mm / s or less at 40° C. 2 / s exceeds 70mm 2 / s or less.

[0045] The refrigerating machine oil is required to be a homogeneous liquid at −25° C. The refrigerating machine oil of the present invention is a homogeneous liquid at −25° C. by containing a specific polyalkylene glycol and a specific mineral oil in a specific mass ratio.

[0046] In the present invention, the kinetic viscosity of the mineral oil at 100°C is 0.1 mm 2 / s or more is preferable, and 0.25 mm 2 / s or more is preferable, and 0.3 mm 2 / s or more is particularly preferable, and 0.5 mm 2 The kinematic viscosity of mineral oil at 100°C is preferably 30 mm / s or more. 2 / s or less is preferable, and 15 mm 2 / s or less is preferable, and 10 mm 2 / s or less is particularly preferable, and 8 mm 2 It is most preferable that the kinematic viscosity of the mineral oil at 100°C is 0.1 mm / s or less. 2 If the kinetic viscosity of mineral oil at 100°C is 30mm / s or more, the properties associated with viscosity can be fully imparted and the oil can exhibit good lubrication properties as a refrigeration oil. 2 In one embodiment, the kinetic viscosity of the mineral oil at 100° C. is 0.5 mm / s or less, and therefore the viscosity of the refrigerating machine oil is low, so that the efficiency of the refrigeration cycle device can be further improved. 2 / s or more 15mm 2 / s or less, 1mm 2 / s or more 12mm 2 / s or less, or 1.5 mm 2 / s or more 10mm 2 / s or less.

[0047] Examples of mineral oils include refined oils obtained by atmospheric distillation of paraffin-based crude oil (paraffinic mineral oil), intermediate-based crude oil or naphthenic crude oil (naphthenic mineral oil) or by vacuum distillation of the residual oil from atmospheric distillation and refining the distillate in a conventional manner, such as solvent refined oil, hydrogenated refined oil, dewaxed oil, and clay-treated oil. Among these, from the viewpoint of stability at low temperatures (homogeneity of liquid) when mixed with polyalkylene glycol, the mineral oil is preferably a paraffinic mineral oil or naphthenic mineral oil having a low aniline point and a pour point of -25°C or less; more preferably a naphthenic mineral oil having an aniline point of 55°C to 95°C and a pour point of -30°C or less; still more preferably a naphthenic mineral oil having an aniline point of 55°C to 90°C and a pour point of -35°C or less; and particularly preferably a naphthenic mineral oil having an aniline point of 55°C to 85°C and a pour point of -35°C or less. Here, when the mineral oil is naphthenic, the kinetic viscosity of the mineral oil at 40°C is preferably 3mm 2 / s or more 100mm 2 / s or less, and more preferably 3 mm 2 / s or more 95mm 2 / s or less, and more preferably 5 mm 2 / s or more 90mm 2 If the mineral oil is paraffinic, the kinetic viscosity of the mineral oil at 40°C is preferably 3 mm 2 / s or more 65mm 2 / s or less, and more preferably 3 mm 2 / s or more 50mm 2 / s or less, and more preferably 5 mm 2 / s or more 45mm 2 / s or less.

[0048] The refrigerating machine oil of the present invention contains 10 to 60 mass % of polyalkylene glycol and 40 to 90 mass % of mineral oil. In the refrigerating machine oil of the present invention, the specific polyalkylene glycol and the specific mineral oil are contained in the above mass ratio, so that the polyalkylene glycol and the mineral oil can be well mixed with each other. In addition, the refrigerating machine oil contains the specific polyalkylene glycol and the specific mineral oil in a specific mass ratio, so that the refrigerating machine oil of the present invention has high electrical insulation properties. In one embodiment, the volume resistivity of the refrigerating machine oil at 25° C. is 1×10 11 Ω·cm or more. If the mass ratio of polyalkylene glycol exceeds 60% by mass (i.e., if the mass ratio of mineral oil is less than 40% by mass), the hygroscopicity of the refrigeration oil becomes too high, and the electrical insulation property decreases. If the mass ratio of mineral oil exceeds 90% by mass (i.e., if the mass ratio of polyalkylene glycol is less than 10% by mass), the amount of polyalkylene glycol dissolved in the hydrocarbon contained in the refrigerant increases, and the viscosity of the refrigeration oil decreases. In other words, wear is likely to occur in the refrigeration cycle device due to the decrease in the lubricity of the refrigeration oil. In the refrigeration oil, the polyalkylene glycol is preferably contained at 10 to 40% by mass, and the mineral oil is preferably contained at 60 to 90% by mass. If the mass ratio of polyalkylene glycol and mineral oil is within the above range, the two are well mixed and can exhibit good lubricity.

[0049] In the refrigeration oil of the present invention, the polyalkylene glycol and the mineral oil are preferably contained in a mass ratio of 1:9 to 6:4, more preferably 2:8 to 6:4, even more preferably 2:8 to 5:5, and particularly preferably 2:8 to 4.6:5.4.

[0050] The refrigerating machine oil contains a specific polyalkylene glycol and a specific mineral oil in a specific mass ratio, so that the moisture content of the refrigerating machine oil can be reduced. In one embodiment, the refrigerating machine oil of the present invention has a saturated moisture content of 1 mass% or less at 25°C and a humidity of 50%. This makes the polyalkylene glycol and mineral oil contained in the refrigerating machine oil less susceptible to chemical changes such as hydrolysis, and increases the stability of the refrigerating machine oil.

[0051] Refrigeration oil is required to have various characteristics as mentioned above, but the most important characteristic is lubrication, that is, wear resistance and seizure resistance. If a machine such as a refrigeration compressor becomes unable to operate due to wear or seizure, the factory or other facility will be unable to operate.

[0052] Refrigeration oil is a lubricant for the compressor in the refrigeration cycle, and unlike general lubricants, it is used in air, i.e. in an environment with almost no oxygen. General lubricants are used in air, so the surface of the metal material in the sliding part becomes an oxide film, and anti-wear additives that are effective against this oxide film are applied. On the other hand, in the case of refrigeration oil, after the initial oxide film on the surface of the sliding material is scraped off, the amount of oxygen in the refrigeration cycle is small, making it difficult to repair the oxide film, and lubrication is provided to the newly formed surface of the metal base material, so the anti-wear additives used in general lubricants are less effective, and improving lubricity has been a challenge.

[0053] Improving the lubricity of the refrigeration oil prevents wear and seizure, and allows the use of oil with low viscosity in the compressor, which reduces resistance during operation and improves the efficiency of the compressor, ultimately resulting in power saving in the refrigeration system. Therefore, another object of the present invention is to provide a working fluid for a refrigerant compression type refrigeration cycle device containing a hydrocarbon refrigerant and a refrigeration oil, in which the refrigeration oil achieves at least one of high stability, appropriate solubility with the refrigerant, high lubricity, and high electrical insulation, as well as high wear resistance.

[0054] Therefore, the present inventors have conducted extensive research into additives to improve the lubricity of refrigeration oils. As a result, the present inventors have found that by blending a thiobisphenol compound, which is generally known as a stabilizer (antioxidant), with the base oil combination of the present invention, the lubricity is improved significantly compared to phosphate esters and the like that have been used in refrigeration oils up to now. The present inventors speculate that the mechanism by which such an effect is obtained by the present invention is as follows. However, the following mechanism is merely speculation, and the scope of the present invention is not limited thereby.

[0055] The thiobisphenol compound is an electron-donating compound, and after the initial oxide film on the surface of the sliding material is scraped away, the new surface of the metal base material becomes an electron-deficient Lewis acid. However, a reaction film is formed with the surface, creating a lubricating state that prevents metal-to-metal contact. As a result, it has been found that by incorporating a thiobisphenol compound into the refrigerating machine oil of the present invention, wear resistance can be imparted to the refrigerating machine oil.

[0056] Thus, one embodiment of the present invention includes a refrigerant comprising propane as a refrigerant, a refrigeration oil containing a polyalkylene glycol and a mineral oil, and a thiobisphenol compound, wherein the polyalkylene glycol is represented by the following general formula (1):

[0057] [ka]

[0058] [In formula (1), R 1 is a linear or branched alkyl group having 1 to 25 carbon atoms, and OR 2 are the same or different and each represents an oxyalkylene group having 2 to 4 carbon atoms, and n is OR 2 represents the number of moles of oxyalkylene groups added.] The kinetic viscosity at 40°C is 2mm 2 / s or more 60mm 2 The mineral oil has an aniline point of 55° C. or more and 105° C. or less, a pour point of -15° C. or less, and a kinematic viscosity at 40° C. of 2 mm2 / s or more 100mm 2 / s or less, the polyalkylene glycol is contained in an amount of 10 mass % or more and 60 mass % or less based on the total mass of the refrigerating machine oil, and the mineral oil is contained in an amount of 40 mass % or more and 90 mass % or less based on the total mass of the refrigerating machine oil.

[0059] Here, according to one embodiment of the present invention, the thiobisphenol compound contained in the refrigerating machine oil imparts wear resistance. That is, according to one embodiment of the present invention, a working fluid for a refrigerant compression type refrigeration cycle device is provided in which a thiobisphenol compound is used as an wear-resistant material. Furthermore, the refrigerating machine oil containing the thiobisphenol compound also imparts wear resistance to the working fluid containing the refrigerating machine oil. Thus, according to one embodiment of the present invention, a working fluid is provided which contains a refrigerant containing a hydrocarbon having 2 to 4 carbon atoms and not containing a halogen atom, a refrigerating machine oil containing a polyalkylene glycol and a mineral oil, and a thiobisphenol compound; The polyalkylene glycol is represented by the following general formula (1):

[0060] [ka]

[0061] [In formula (1), R 1 is a linear or branched alkyl group having 1 to 25 carbon atoms, and OR 2 are the same or different and each represents an oxyalkylene group having 2 to 4 carbon atoms, and n is OR 2 represents the number of moles of oxyalkylene groups added.] The kinetic viscosity at 40°C is 2mm 2 / s or more 60mm 2 / s or less, The mineral oil has an aniline point of 55° C. or more and 105° C. or less, a pour point of −15° C. or less, and a kinematic viscosity of 2 mm at 40° C. 2 / s or more 100mm 2 / s or less, the polyalkylene glycol is contained in an amount of 10 mass % or more and 60 mass % or less based on the total mass of the refrigerating machine oil, and the mineral oil is contained in an amount of 40 mass % or more and 90 mass % or less based on the total mass of the refrigerating machine oil.

[0062] Suitable thiobisphenol compounds include 4,4'-thiobis(2,6-di-tert-butylphenol), 4,4'-thiobis(2-methyl-6-tert-butylphenol), 4,4'-thiobis(3-methyl-6-tert-butylphenol), etc. The content of the thiobisphenol compound is 0.05 to 3.0 mass% based on the total mass of the refrigerating machine oil, preferably 0.05 to 1.0 mass%, and more preferably 0.1 to 0.5 mass%.

[0063] In one embodiment, the working fluid according to the present invention is substantially free of polyphosphate ester compounds. When the working fluid contains a polyphosphate ester compound, the polyphosphate ester compound deteriorates and generates highly active phosphoric acid, which may cause corrosion and wear, and reduce the stability of the oil. In this specification, "substantially free of" preferably means that the amount of the polyphosphate ester compound in the working fluid is 1 mass % or less, more preferably 0.5 mass % or less, and even more preferably 0.1 mass % or less. It is particularly preferable that the working fluid according to the present invention is free of polyphosphate ester compounds. Here, the polyphosphate ester compound is a compound represented by the following formula (2):

[0064] [ka]

[0065] [In formula (2), m represents an integer of 1 to 10, and R a ~R h each independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms; R i represents a divalent hydrocarbon group having 2 to 20 carbon atoms. Examples include:

[0066] Whether polyalkylene glycol and mineral oil become a homogeneous liquid without being separated into two layers at -25°C depends largely on the molecular weight of both, that is, the kinetic viscosity, and the smaller the molecular weight of both, the easier it is to become a homogeneous liquid. In the case of refrigeration oil, the viscosity required varies depending on the model. For example, in the case of a refrigeration oil with high viscosity, stability is improved by blending 0.1 mass% to 20 mass% of an ester compound with respect to the total mass of the refrigeration oil, and even higher stability can be exhibited over the long term. Examples of the ester compound include polyol ester, monoester, diester, and phosphate ester (excluding polyphosphate ester compounds). Thus, in one embodiment, the refrigeration oil is a mixed oil containing a specific polyalkylene glycol, a specific mineral oil, and a specific ester compound as a base oil. Since the ester compound may be hydrolyzed, the blending ratio is preferably low from the viewpoint of stability, and is preferably 0.1 mass% to 15 mass%, more preferably 0.1 mass% to 12 mass%, and even more preferably 0.5 mass% to 10 mass%.

[0067] According to one embodiment, the refrigerating machine oil of the present invention contains 10% by mass to 40% by mass of polyalkylene glycol, 60% by mass to 90% by mass of mineral oil, and 0.1% by mass to 15% by mass of ester compound, based on the total mass of the refrigerating machine oil. Here, the total mass of the refrigerating machine oil refers to the total mass (100% by mass) of the components contained in the refrigerating machine oil.

[0068] Examples of polyol esters include esters of alcohols such as neopentyl glycol, trimethylolpropane, and pentaerythritol with carboxylic acids such as octyl acid, nonanoic acid, and oleic acid. Examples of monoesters include alkyl esters of various carboxylic acids such as octyl oleate, butyl octanoate, and hexyl 2-ethylhexanoate. Examples of diesters include esters of dibasic acids and alcohols such as dioctyl sebacate, dioctyl adipate, and dioleate adipate. Examples of phosphoric acid esters include trialkyl phosphate, triphenyl phosphate, and tricresyl phosphate. Among these, polyol esters are preferred from the viewpoint of hydrolysis stability, and esters of neopentyl glycol and carboxylic acids (e.g., 2-ethylhexanoic acid) are more preferred because of their small molecular weight and low viscosity.

[0069] In addition, components other than the above components (polyalkylene glycol, mineral oil, and ester compound) may be contained within a range that satisfies the function as a refrigerating machine oil. The components other than the above components may be contained as a base oil or as an additive. Other components that may be contained in the refrigerating machine oil according to this embodiment include polyalkylene glycols with both ends etherified, polyalkylene glycols with both ends or one end esterified, ethers such as polyvinyl ethers, alkylbenzenes that are hydrocarbons, and polyolefins.

[0070] In addition, the refrigerating machine oil according to the present embodiment may further contain a stability improver as an additive in order to further increase the stability of the working medium of the refrigerant and the refrigerating machine oil in actual use. Preferred examples of the stability improver include one or more selected from the group consisting of thiobisphenol compounds, aromatic amine compounds, phenol compounds, and benzotriazole compounds. Here, when a thiobisphenol compound is added, it is more preferable to use it in combination with an aromatic amine compound. In addition, the refrigerating machine oil according to the present embodiment may further contain an oiliness agent as an additive. Preferred examples of the oiliness agent include partial esters of polyhydric alcohols such as glycerol monooleate (glycerin monooleate) and sorbitan monooleate (excluding ester compounds contained as the base oil of the refrigerating machine oil). The total content of the stability improver and the oiliness agent is preferably 0.1 mass% or more and 3.0 mass% or less based on the total mass of the refrigerating machine oil. In one embodiment, the refrigerating machine oil preferably contains one or more additives selected from the group consisting of aromatic amine compounds, phenol compounds, and benzotriazole compounds in an amount of 0.1 mass % or more and 3.0 mass % or less based on the total mass of the refrigerating machine oil.

[0071] According to one embodiment, the refrigerating machine oil of the present invention contains, relative to the total mass of the refrigerating machine oil, 10% by mass to 40% by mass of polyalkylene glycol, 60% by mass to 90% by mass of mineral oil, and 0.1% by mass to 3.0% by mass of one or more additives selected from the group consisting of thiobisphenol compounds, aromatic amine compounds, phenol compounds, and benzotriazole compounds. The total mass of the refrigerating machine oil refers to the total mass (100% by mass) of the components contained in the refrigerating machine oil.

[0072] According to one embodiment, the refrigerating machine oil of the present invention contains, relative to the total mass of the refrigerating machine oil, 10% by mass to 40% by mass of polyalkylene glycol, 60% by mass to 90% by mass of mineral oil, 0.1% by mass to 15% by mass of ester compound, and 0.1% by mass to 3.0% by mass of one or more additives selected from the group consisting of thiobisphenol compounds, aromatic amine compounds, phenol compounds, and benzotriazole compounds. Here, the total mass of the refrigerating machine oil refers to the total mass (100% by mass) of the components contained in the refrigerating machine oil.

[0073] The thiobisphenol compound may be the same as that described above. For example, among the stability improvers, the thiobisphenol compound is preferably 4,4'-thiobis(2,6-di-tert-butylphenol), 4,4'-thiobis(2-methyl-6-tert-butylphenol), 4,4'-thiobis(3-methyl-6-tert-butylphenol), etc. The content of the thiobisphenol compound is preferably 0.05 to 1.0 mass%, more preferably 0.1 to 0.5 mass%, based on the total mass of the refrigerating machine oil.

[0074] Examples of the aromatic amine compound include α-naphthylamine and N-phenyl-1-naphthylamine, and di(alkylphenyl)amines having an alkyl group with 4 to 12 carbon atoms (e.g., p,p'-di-octyl-diphenylamine), alkylated phenyl-α-naphthylamine, and alkylated phenyl-β-naphthylamine are preferred. The content of the aromatic amine compound is preferably 0.05 to 1.0 mass%, more preferably 0.1 to 0.5 mass%, based on the total mass of the refrigerating machine oil.

[0075] Suitable phenol compounds are 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, etc. The content of the phenol compound is preferably 0.05 to 1.0 mass%, more preferably 0.1 to 0.5 mass%, based on the total mass of the refrigerating machine oil.

[0076] The benzotriazole compound includes benzotriazole and 1-[bis(alkyl)aminomethyl]-alkyl-1H-benzotriazole having various alkyl groups, such as 1-[bis(2-ethylhexyl)aminomethyl]-4-methyl-1H-benzotriazole. The content of the benzotriazole compound is preferably 0.05 to 1.0 mass%, more preferably 0.1 to 0.5 mass%, based on the total mass of the refrigerating machine oil.

[0077] The refrigerating machine oil according to the present embodiment may be appropriately supplemented with additives such as antioxidants such as hindered phenols, anti-wear agents such as phosphoric esters and organic sulfur compounds, oiliness agents such as monohydric alcohols and higher fatty acids, metal deactivators such as benzotriazole derivatives, and antifoaming agents such as silicone oils. Furthermore, a pour point depressant such as polymethacrylate may be added to lower the pour point of the refrigerating machine oil, and the amount of the pour point depressant added is 0.05 to 1.0 mass %, preferably 0.1 to 0.5 mass %, based on the total mass of the refrigerating machine oil.

[0078] According to one embodiment, the refrigerating machine oil of the present invention contains, relative to the total mass of the refrigerating machine oil, 10% by mass to 40% by mass of polyalkylene glycol, 60% by mass to 90% by mass of mineral oil, 0.05% by mass to 3.0% by mass of a thiobisphenol compound, and 0.1% by mass to 3.0% by mass of one or more additives selected from the group consisting of aromatic amine compounds, phenol compounds, and benzotriazole compounds. Here, the total of the polyalkylene glycol, mineral oil, thiobisphenol compound, and additives is 100% by mass.

[0079] According to one embodiment, the refrigerating machine oil of the present invention contains, relative to the total mass of the refrigerating machine oil, 10% by mass to 40% by mass of polyalkylene glycol, 60% by mass to 90% by mass of mineral oil, 0.1% by mass to 15% by mass of ester compound, and 0.1% by mass to 3.0% by mass of one or more additives selected from the group consisting of aromatic amine compounds, phenol compounds, and benzotriazole compounds. Here, the total of the polyalkylene glycol, mineral oil, ester compound, and additives is 100% by mass.

[0080] According to one embodiment, the refrigerating machine oil of the present invention contains, relative to the total mass of the refrigerating machine oil, 10% by mass to 40% by mass of polyalkylene glycol, 60% by mass to 90% by mass of mineral oil, 0.05% by mass to 3.0% by mass of thiobisphenol compound, 0.1% by mass to 15% by mass of ester compound, and 0.1% by mass to 3.0% by mass of one or more additives selected from the group consisting of aromatic amine compounds, phenol compounds, and benzotriazole compounds. Here, the total of the polyalkylene glycol, mineral oil, thiobisphenol compound, ester compound, and additives is 100% by mass.

[0081] From the viewpoint of efficiency of the refrigeration cycle device, the kinetic viscosity of the refrigeration oil of the present invention at 40°C is preferably 0.1 mm 2 / s or more 65mm 2 / s or less, and more preferably 0.5 mm 2 / s or more 60mm 2 / s or less, and more preferably 1 mm 2 / s or more 50mm 2 / s or less, and particularly preferably 1 mm 2 / s or more 45mm 2 / s or less, and most preferably 5 mm 2 / s or more 40mm 2 In one embodiment, the upper limit of the kinematic viscosity of the refrigerating machine oil at 40° C. is 40 mm 2 / s or less is preferable, and 39 mm 2 / s or less is more preferable, and 35 mm 2 / s or less is more preferable, and 30 mm 2 / s or less, and even more preferably 28 mm 2 In one embodiment, the lower limit of the kinematic viscosity of the refrigeration oil at 40° C. is 0.1 mm / s or less. 2 More preferably, the ratio is 0.2 mm / s or more. 2 / s or more, and even more preferably 0.5 mm 2 / s or more, particularly preferably 1 mm 2 / s or more, most preferably 1.5 mm 2 When the kinetic viscosity of the refrigeration oil is in the above range, the effects of the present invention are more pronounced. In one embodiment, the kinetic viscosity of the refrigeration oil at 40° C. is 0.1 mm / s or more. 2 / s or more 30mm 2 / s or less.

[0082] The refrigerating machine oil of the present invention is usually present in the form of a working medium mixed with the above-mentioned refrigerant containing a hydrocarbon in a refrigeration cycle device. The blending ratio of the refrigerating machine oil and the refrigerant containing a hydrocarbon in this working medium is not particularly limited, but the refrigerating machine oil is preferably 1 to 500 parts by mass, more preferably 2 to 400 parts by mass, per 100 parts by mass of the refrigerant containing a hydrocarbon.

[0083] In the present invention, "having excellent compatibility with the refrigerant (having appropriate compatibility with the refrigerant)" means that the two-layer separation temperature is low and does not dissolve too much in the refrigerant. In the present invention, the two-layer separation temperature between the refrigerant and the refrigerating machine oil is preferably -30°C or lower, more preferably -35°C or lower, even more preferably -40°C or lower, and even more preferably -45°C or lower. The lower limit of the two-layer separation temperature is determined by the balance between the return of the refrigerating machine oil from the evaporator to the compressor in the refrigeration cycle and the lubrication of the refrigerating machine oil, and depends on the design of the refrigeration system. The two-layer separation temperature is measured by the method described in the examples below. In addition, polyalkylene glycol has a higher polarity than mineral oil and polyol ester, and does not dissolve too much in the refrigerant containing hydrocarbon. Therefore, the refrigerating machine oil according to the present invention does not dissolve too much in the refrigerant by containing polyalkylene glycol in addition to mineral oil. As described above, the refrigerating machine oil according to the present invention has excellent compatibility with refrigerants (has appropriate compatibility with refrigerants), so that a working medium containing the refrigerating machine oil according to the present invention can exhibit good performance even if the amount of refrigerant containing highly flammable hydrocarbons charged is small.

[0084] In the present invention, the high stability of a refrigeration oil means that the refrigeration oil has at least one of the following: an acid value of 0.01 to 0.05 mgKOH / g; and a hue of L0.5 to L1.0 before and after a thermal and chemical stability test (the method is described in detail in the Examples below). When the acid value is within the above range before and after the thermal and chemical stability test, it can be said that the stability is high (excellent thermal stability). When the hue of a refrigeration oil is within the above range before and after the thermal and chemical stability test, it can be said that the stability is high (excellent thermal stability).

[0085] In the present invention, the lubricity of the refrigeration oil is evaluated by the seizure load. Specifically, the seizure load is preferably less than 3000 N, and more preferably less than 2950 N. The seizure load is measured by the method described in the examples below.

[0086] In the present invention, the refrigerating machine oil preferably has low hygroscopicity, and for example, the saturated moisture content of the refrigerating machine oil is preferably less than 1%, more preferably 0.9% or less, even more preferably 0.7% by mass or less, and particularly preferably 0.6% by mass or less. The saturated moisture content is measured by the method described in the Examples below.

[0087] In the present invention, the electrical insulating property of the refrigeration oil is evaluated by the volume resistivity. 11 It is preferable that the resistance is 5.0×10 Ω·cm or more. 11 More preferably, it is 1.0×10 12 It is more preferable that the volume resistivity is Ω·cm or more. The volume resistivity is measured by the method described in the Examples below.

[0088] The working fluid of the present invention can be suitably used in refrigeration cycle devices, for example, air conditioners, electric refrigerators, and industrial freezers having a reciprocating or rotary hermetic compressor. The working fluid of the present invention can also be suitably used in cooling devices such as dehumidifiers, water heaters, freezers, refrigerated and frozen warehouses, showcases, vending machines, and chemical plants. It can also be suitably used in devices having a centrifugal compressor. The working fluid of the present invention can be suitably used in hermetic refrigeration cycle devices. Thus, the present invention also provides a hermetic refrigeration cycle device using the working fluid.

[0089] Although the embodiments of the present invention have been described in detail, it is apparent that the same are illustrative and exemplary, not restrictive, and the scope of the present invention should be interpreted by the appended claims.

[0090] The present invention encompasses the following aspects and configurations.

[0091] [1] A refrigerant containing a hydrocarbon having 2 to 4 carbon atoms and not containing a halogen atom, and a refrigeration oil containing a polyalkylene glycol and a mineral oil, wherein the polyalkylene glycol is represented by the following general formula (1):

[0092] [ka]

[0093] [In formula (1), R 1 is a linear or branched alkyl group having 1 to 25 carbon atoms, and OR 2 are the same or different and each represents an oxyalkylene group having 2 to 4 carbon atoms, and n is OR 2 represents the number of moles of oxyalkylene groups added.] The kinetic viscosity at 40°C is 2mm 2 / s or more 60mm 2 The mineral oil has an aniline point of 55° C. or more and 105° C. or less, a pour point of -15° C. or less, and a kinematic viscosity at 40° C. of 2 mm 2 / s or more 100mm 2 / s or less, the polyalkylene glycol is contained in an amount of 10 mass % or more and 60 mass % or less based on the total mass of the refrigerating machine oil, and the mineral oil is contained in an amount of 40 mass % or more and 90 mass % or less based on the total mass of the refrigerating machine oil.

[0094] [2] A refrigerant comprising a hydrocarbon having 2 to 4 carbon atoms and not containing a halogen atom, a refrigerating machine oil comprising a polyalkylene glycol and a mineral oil, and a thiobisphenol compound, wherein the polyalkylene glycol is represented by the following general formula (1):

[0095] [ka]

[0096] [In formula (1), R 1 is a linear or branched alkyl group having 1 to 25 carbon atoms, and OR 2 are the same or different and each represents an oxyalkylene group having 2 to 4 carbon atoms, and n is OR 2 represents the number of moles of oxyalkylene groups added.] The kinetic viscosity at 40°C is 2mm 2 / s or more 60mm2 The mineral oil has an aniline point of 55° C. or more and 105° C. or less, a pour point of -15° C. or less, and a kinematic viscosity at 40° C. of 2 mm 2 / s or more 100mm 2 / s or less, the polyalkylene glycol is contained in an amount of 10 mass % or more and 60 mass % or less based on the total mass of the refrigerating machine oil, and the mineral oil is contained in an amount of 40 mass % or more and 90 mass % or less based on the total mass of the refrigerating machine oil.

[0097] [3] The working fluid for a refrigerant compression type refrigeration cycle apparatus according to the above [2], wherein the thiobisphenol compound is contained in an amount of 0.05 mass % or more and 3.0 mass % or less based on the total mass of the refrigerating machine oil.

[0098] [4] The working medium for a refrigerant compression type refrigeration cycle apparatus according to any one of claims [1] to [3], wherein the refrigeration oil further contains 0.1 mass % or more and 20 mass % or less of an ester compound.

[0099] [5] The working fluid for a refrigerant compression type refrigeration cycle apparatus according to any one of the above [1] to [4], wherein the mineral oil is a naphthenic mineral oil having an aniline point of 55°C or higher and 95°C or lower and a pour point of -30°C or lower.

[0100] [6] The refrigeration oil has a volume resistivity of 1×10 at 25°C. 11 The working fluid for a refrigerant compression type refrigeration cycle apparatus according to any one of the above [1] to [5], having a resistance of Ω·cm or more.

[0101] [7] The working medium for a refrigerant compression type refrigeration cycle apparatus according to any one of the above [1] to [6], wherein the refrigeration oil has a saturated moisture content of 1 mass% or less at 25°C and a humidity of 50%, and is a homogeneous liquid at -10°C.

[0102] [8] The working medium for a refrigerant compression type refrigeration cycle apparatus according to any one of the above [1] to [7], wherein the refrigerant is propane.

[0103] [9] The working medium for a refrigerant compression type refrigeration cycle apparatus according to any one of the above [1] to [8], wherein the refrigerant is propane.

[0104]

[10] The polyalkylene glycol is R 1 is an alkyl group having 4 carbon atoms, and OR 2 The working fluid for a refrigerant compression type refrigeration cycle apparatus according to any one of the above [1] to [8], wherein is an oxypropylene group.

[0105]

[11] The working medium for a refrigerant compression type refrigeration cycle apparatus according to any one of the above [1] to [9], wherein the refrigerating machine oil contains one or more additives selected from the group consisting of an amine compound, a phenol compound, and a benzotriazole compound in an amount of 0.1 mass % or more and 3.0 mass % or less, based on the total mass of the refrigerating machine oil.

[0106]

[12] The working medium for a refrigerant compression type refrigeration cycle apparatus according to [4] above, wherein the refrigeration oil contains, relative to a total mass of the refrigeration oil, 10 mass % or more and 40 mass % or less of the polyalkylene glycol, 60 mass % or more and 90 mass % or less of the mineral oil, and 0.1 mass % or more and 15 mass % or less of the ester compound.

[0107]

[13] A refrigerant comprising a hydrocarbon having 2 to 4 carbon atoms and not containing a halogen atom, a refrigerating machine oil comprising a polyalkylene glycol and a mineral oil, and a thiobisphenol compound, wherein the polyalkylene glycol is represented by the following general formula (1):

[0108] [ka]

[0109] [In formula (1), R 1 is a linear or branched alkyl group having 1 to 25 carbon atoms, and OR 2 are the same or different and each represents an oxyalkylene group having 2 to 4 carbon atoms, and n is OR 2 represents the number of moles of oxyalkylene groups added.] The kinetic viscosity at 40°C is 2mm 2 / s or more 60mm 2 The mineral oil has an aniline point of 55° C. or more and 105° C. or less, a pour point of -15° C. or less, and a kinematic viscosity at 40° C. of 2 mm 2 / s or more 100mm 2 / s or less, the polyalkylene glycol is contained in an amount of 10 mass % or more and 60 mass % or less based on the total mass of the refrigerating machine oil, and the mineral oil is contained in an amount of 40 mass % or more and 90 mass % or less based on the total mass of the refrigerating machine oil.

[0110]

[14] A sealed refrigeration cycle device using the working medium according to any one of the above [1] to

[13] . EXAMPLES

[0111] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. In the examples, unless otherwise specified, operations and measurements of physical properties are performed under conditions of room temperature (20 to 25°C) and relative humidity of 40 to 50% RH.

[0112] In the following examples, pentane may be used instead of propane as a refrigerant. From the viewpoint of polarity or dielectric constant, pentane is considered to have the same compatibility with refrigerating machine oil as propane as a refrigerant. It has also been confirmed that the two-layer separation temperature described below is the same as that when propane is used as a refrigerant, even when pentane is used as a refrigerant. Therefore, the examples using pentane as a refrigerant in the following examples are considered to satisfy the constituent elements of the present invention.

[0113] The components shown below were mixed and stirred at 40° C. for 10 minutes to obtain refrigerating machine oils of Examples 1 to 8 and Comparative Examples 1 to 8.

[0114] Example 1 R 1 (Terminal) is n-butyl group, OR 2is an oxypropylene group, and its kinetic viscosity is 10.5 mm at 40°C. 2 / s, 2.8 mm at 100°C 2 / s, polypropylene glycol with a pour point of -50°C (40.0% by mass relative to the total mass of the refrigeration oil); kinematic viscosity of 7.1 mm at 40°C 2 / s, 2.2 mm at 100°C 2 / s, paraffinic mineral oil (60.0 mass% based on the total mass of the refrigerating oil) having a pour point of -35°C and an aniline point of 90°C; and a refrigerating oil (without additives).

[0115] Example 2 Polypropylene glycol of Example 1 (40.0% by mass relative to the total mass of the refrigerating machine oil); 2 / s, 2.5 mm at 100°C 2 / s, a naphthenic mineral oil (60.0 mass% based on the total mass of the refrigerating oil) having a pour point of -45°C and an aniline point of 65°C; and a refrigerating oil (without additives).

[0116] Example 3 Polypropylene glycol of Example 1 (40.0% by mass relative to the total mass of the refrigerating machine oil); kinematic viscosity of 45.4 mm at 40°C 2 / s, 5.5 mm at 100°C 2 / s, a naphthenic mineral oil (60.0 mass% based on the total mass of the refrigerating oil) having a pour point of -40°C and an aniline point of 77°C; and a refrigerating oil (without additives).

[0117] Comparative Example 1 Polypropylene glycol of Example 1 (40.0% by mass relative to the total mass of the refrigerating machine oil); kinematic viscosity of 45.0 mm at 40°C 2 / s, 6.7 mm at 100°C 2 / s, paraffinic mineral oil (60.0 mass% of the total mass of the refrigerating oil) having a pour point of -15°C and an aniline point of 106°C; and refrigerating oil (without additives).

[0118] Comparative Example 2 Polypropylene glycol of Example 1 (40.0% by mass relative to the total mass of the refrigerating machine oil); kinematic viscosity of 97.0 mm at 40°C 2 / s, 10.9 mm at 100°C 2 / s, paraffinic mineral oil (60.0 mass% based on the total mass of the refrigerating oil) having a pour point of -15°C and an aniline point of 115°C; and a refrigerating oil (without additives).

[0119] Comparative Example 3 R 1 (Terminal) is n-butyl group, OR 2 is an oxypropylene group, and its kinetic viscosity is 108 mm at 40°C. 2 / s, 19.3 mm at 100°C 2 / s, polypropylene glycol with a pour point of -45°C (40.0% by mass relative to the total mass of the refrigeration oil); kinematic viscosity of 10.5 mm at 40°C 2 / s, 2.5 mm at 100°C 2 / s, a naphthenic mineral oil (60.0 mass% based on the total mass of the refrigerating oil) having a pour point of -45°C and an aniline point of 65°C; and

[0120] Comparative Example 4 R 1 (Terminal) is n-butyl group, OR 2 is an oxypropylene group, and its kinetic viscosity is 108 mm at 40°C. 2 / s, 19.3 mm at 100°C 2 / s, polypropylene glycol with a pour point of -45°C (40.0% by mass relative to the total mass of the refrigeration oil); kinematic viscosity of 45.4 mm at 40°C 2 / s, 5.5 mm at 100°C 2 / s, a naphthenic mineral oil (60.0 mass% based on the total mass of the refrigerating oil) having a pour point of -40°C and an aniline point of 77°C; and

[0121] Example 4 R 1 (Terminal) is n-butyl group, OR 2 is an oxypropylene group, and its kinetic viscosity is 10.5 mm at 40°C. 2 / s, 2.7 mm at 100°C 2 / s, and polypropylene glycol with a pour point of -50°C (30.0% by mass relative to the total mass of the refrigeration oil); 2 / s, 5.4 mm at 100°C 2 / s, a naphthenic mineral oil (70.0 mass% based on the total mass of the refrigerating oil) having a pour point of -35°C and an aniline point of 78°C; and a refrigerating oil (without additives).

[0122] Example 5 R 1 (Terminal) is ethyl group, OR 2 is an oxypropylene group, and its kinetic viscosity is 22.1 mm at 40°C. 2 / s, 5.1 mm at 100°C 2 / s, and polypropylene glycol with a pour point of -50°C (29.9% by mass relative to the total mass of the refrigeration oil); kinematic viscosity of 22.2 mm at 40°C 2 / s, 3.7 mm at 100°C 2 A refrigerating machine oil comprising: a naphthenic mineral oil (69.9% by mass based on the total mass of the refrigerating machine oil) having a pour point of -45°C and an aniline point of 72°C, and 4,4'-thiobis(2-methyl-6-tert-butylphenol) (0.2% by mass based on the total mass of the refrigerating machine oil) as an additive.

[0123] Example 6 R 1 (Terminal) is tert-butyl group, OR 2 is an oxyethylene group and an oxypropylene group, and the kinetic viscosity is 32.7 mm at 40°C. 2 / s, 7.3 mm at 100°C 2 / s and a pour point of -40°C (the molar ratio of oxyethylene groups to oxypropylene groups is 1:9, 19.8% by mass based on the total mass of the refrigeration oil); 2 / s, 2.5 mm at 100°C 2a naphthenic mineral oil (79.3% by mass based on the total mass of the refrigerating machine oil) having a pour point of -45°C and an aniline point of 65°C, and 4,4'-thiobis(2-methyl-6-tert-butylphenol) (0.2% by mass based on the total mass of the refrigerating machine oil) and p,p'-di-octyl-diphenylamine (0.5% by mass based on the total mass of the refrigerating machine oil) as additives; and glycerol monooleate (0.2% by mass based on the total mass of the refrigerating machine oil) as an oiliness agent.

[0124] Example 7 R 1 (Terminal) is n-butyl group, OR 2 is an oxypropylene group, and its kinetic viscosity is 32.5 mm at 40°C. 2 / s, 7.1 mm at 100°C 2 / s, and polypropylene glycol (40% by mass relative to the total mass of the refrigeration oil) with a pour point of -50°C; and a kinetic viscosity of 7.1 mm at 40°C. 2 / s, 2.2 mm at 100°C 2 / s, a pour point of -35°C, and an aniline point of 90°C (50% by mass based on the total mass of the refrigerating oil), and dioctyl sebacate (10% by mass based on the total mass of the refrigerating oil) as an ester compound.

[0125] Example 8 Polypropylene glycol of Example 1 (30.0% by mass based on the total mass of the refrigerating machine oil); kinematic viscosity of 95.8 mm at 40°C 2 / s, 8.4 mm at 100°C 2 / s, a naphthenic mineral oil (70.0 mass% based on the total mass of the refrigerating oil) having a pour point of -30°C and an aniline point of 82°C; and a refrigerating oil (without additives).

[0126] Comparative Example 5 R 1 (Terminal) is n-butyl group, OR 2 is an oxypropylene group, and its kinetic viscosity is 32.5 mm at 40°C. 2 / s, 7.1 mm at 100°C 2 / s, and polypropylene glycol (40% by mass relative to the total mass of the refrigeration oil) with a pour point of -50°C; and a kinetic viscosity of 136 mm at 40°C. 2 / s, 13.7 mm at 100°C 2 / s, a paraffinic mineral oil (60 mass% based on the total mass of the refrigerating oil), having a pour point of -15°C and an aniline point of 118°C; and a refrigerating oil (without additives).

[0127] Comparative Example 6 R 1 (Terminal) is n-butyl group, OR 2 is an oxypropylene group, and its kinetic viscosity is 32.5 mm at 40°C. 2 / s, 7.1 mm at 100°C 2 / s, and polypropylene glycol (40% by mass relative to the total mass of the refrigeration oil) with a pour point of -50°C; and a kinetic viscosity of 9.8 mm at 40°C. 2 / s, 2.6 mm at 100°C 2 / s, a paraffinic mineral oil (60 mass% of the total mass of the refrigerating oil) having a pour point of -5°C and an aniline point of 85°C; and a refrigerating oil (without additives).

[0128] Comparative Example 7 R 1 (Terminal) is n-butyl group, OR 2 is an oxypropylene group, and its kinetic viscosity is 32.5 mm at 40°C. 2 / s, 7.1 mm at 100°C 2 / s, and a pour point of -50°C. A refrigeration oil containing polypropylene glycol (100% by mass based on the total mass of the refrigeration oil) (without additives).

[0129] Comparative Example 8 Kinematic viscosity is 22.2 mm at 40°C 2 / s, 3.7 mm at 100°C 2 / s, a pour point of -45°C, and an aniline point of 72°C. A paraffinic mineral oil (100% by mass of the total mass of the refrigerating oil) with no additives.

[0130] [evaluation] The polyalkylene glycols and mineral oils used in the Examples and Comparative Examples were evaluated for kinematic viscosity, aniline point, and pour point according to the following methods. In addition, the refrigeration oils obtained in the Examples and Comparative Examples were subjected to evaluation tests for separation with an ammonia refrigerant, viscosity (measurement of kinematic viscosity), low-temperature properties (measurement of pour point), electrical insulation (measurement of volume resistivity), hygroscopicity (measurement of saturated moisture), lubricity (measurement of seizure load), compatibility (measurement of two-phase separation temperature when mixed with a hydrocarbon refrigerant), and thermal and chemical stability (measurement of color and acid value).

[0131] <Kinematic viscosity, aniline point, pour point> The kinematic viscosity was measured in accordance with JIS K2283 (2000); the aniline point was measured in accordance with JIS K2256 (2013); and the pour point was measured in accordance with JIS K2269 (1987).

[0132] <Volume resistivity> The volume resistivity was measured in accordance with JIS C2101 (2010).

[0133] <Stability test at -25℃> The state of the refrigeration oil at -25°C was observed visually. 0.1 L of each of the refrigeration oils of the Examples and Comparative Examples was placed in a glass container (0.3 L), sealed, and left to stand for 5 hours at a specified temperature (-10°C and -25°C), and the liquid state was observed. It is essential that refrigeration oils used with hydrocarbon refrigerants are homogeneous liquids at -25°C. Therefore, in the stability test at -25°C, it is necessary that they are homogeneous liquids (do not separate).

[0134] <Separation test with ammonia refrigerant> 10% by mass of refrigeration oil and 90% by mass of ammonia were sealed in a glass tube and the condition was observed after standing at room temperature (25°C) for 30 minutes. If the ammonia refrigerant and the refrigeration oil separate, it means that the refrigeration oil cannot be used in a sealed refrigeration cycle.

[0135] <Saturated moisture> The moisture content was measured after 48 hours (50 g of refrigeration oil was left to stand in a 100 ml beaker) at a temperature of 30°C and a humidity of 80%. The moisture content was measured in accordance with JIS K2275-2 (2015 edition).

[0136] <Evaluation of thermal and chemical stability> 30g of each refrigeration oil, 30g of isobutane (R600a), and catalysts (iron, copper, and aluminum wires) were placed in an autoclave, then heated to 175°C and held for 7 days for testing. After the test, the color and acid value of the refrigeration oil were evaluated. The color was measured in accordance with ASTM D156. The acid value was measured in accordance with JIS K2501 (2003). In addition, the evaluation of thermal and chemical stability was performed using isobutane as a refrigerant, but it was confirmed that similar results for thermal and chemical stability were obtained when propane was used.

[0137] <Seizure load> Compliant with ASTM D-3233-19 method. Rotation speed: 290 rpm, temperature: room temperature.

[0138] <Two-phase separation temperature with hydrocarbon refrigerant> As a compatibility test between refrigeration oil and hydrocarbon refrigerant, the two-phase separation temperature was measured in accordance with the JIS method (refrigeration oil: K2211 (2009)). The compatibility test was performed using pentane instead of propane as the refrigerant, with 7.5 g of refrigeration oil per 42.5 g of refrigerant. In this example, the measurements were performed in a temperature range from room temperature (25°C) to -50°C. Therefore, in a sample containing refrigeration oil and refrigerant, if separation did not occur even at -50°C, the two-phase separation temperature was evaluated as "-50°C or lower" (indicated as "<-50°C" in the table).

[0139] The results are shown in Tables 1 and 2. In Tables 1 and 2, "PAG" indicates polyalkylene glycol, and "-" indicates that the corresponding component was not used. Furthermore, for samples in which the refrigeration oil was allowed to stand at 25°C for 30 minutes and separated into two layers, various evaluations could not be measured (in the tables, this is indicated as "separated into two layers" or "NA").

[0140] In addition, the evaluation of the two-phase separation temperature was performed using pentane as the refrigerant, but as mentioned above, similar results were obtained when propane was used.

[0141] [Table 1]

[0142] [Table 2]

[0143] From Tables 1 and 2, it is understood that only the combination of a specific polyalkylene glycol and a specific mineral oil is a homogeneous liquid even at a low temperature of −25° C. and can be used as a refrigeration oil. Note that, since all of the refrigeration oils of the Examples and Comparative Examples separate into cloudy white form when mixed with ammonia, it is understood that the refrigeration oils of Examples 1 to 8 cannot be used as refrigeration oils for a closed refrigeration cycle in which a refrigerant and a refrigeration oil are mixed and circulated.

[0144] From Tables 1 and 2, it can be seen that the refrigerating machine oils of Examples 1 to 8 are refrigerating machine oils with a good balance of properties. In other words, the refrigerating machine oils of Examples 1 to 8 have sufficiently low pour points, are homogeneous liquids even at low temperatures, and have good electrical insulation properties (volume resistivity), lubricity (seizure load), and thermal and chemical stability, as well as good two-phase separation temperature with a hydrocarbon refrigerant and hygroscopicity (water content). Comparative Example 5 has a kinetic viscosity of 60 mm 2 / s and a combination of a mineral oil having an aniline point exceeding 105°C with a specific polyalkylene glycol, but it was found that the mixture was not suitable for use as a refrigerating oil because it separated into two layers and did not become a homogeneous liquid. Comparative Example 6 is a refrigerating oil that combines a mineral oil having a viscosity pour point of -15°C or higher with a specific polyalkylene glycol, but it was found that the pour point of the refrigerating oil was high, the lubricity was insufficient, and it was not suitable for use as a refrigerating oil.

[0145] The refrigeration oil of Comparative Example 7 is a refrigeration oil containing a specific polyalkylene glycol alone, and although it has good lubricity (seizure load), it has low electrical insulation (volume resistivity) and high hygroscopicity (high saturated water content). The refrigeration oils of Examples 5 and 6, due to the addition of additives, are comparable in lubricity to the refrigeration oil of Comparative Example 7, and have significantly higher lubricity than the refrigeration oil of Comparative Example 8, which is a refrigeration oil containing mineral oil alone. The refrigeration oil of Comparative Example 8 is inferior in lubricity, and coloring of the oil is observed in terms of thermal and chemical stability, indicating that it is inferior in terms of stability. In addition, since mineral oil is a hydrocarbon, there is a problem that it dissolves too much with the same hydrocarbon refrigerant.

[0146] Next, refrigeration oils containing thiobisphenol compounds were prepared, and the effects of the thiobisphenol compounds were evaluated. First, the components shown below were mixed and stirred at 40°C for 10 minutes to obtain refrigeration oils of Examples 9 to 13. Using the obtained refrigeration oils, lubricity tests were performed according to the methods shown below.

[0147] Example 9 The refrigeration oil (base oil) of Example 1 contains 0.3 mass % of 4,4'-thiobis(2,6-di-tert-butylphenol).

[0148] Example 10 Refrigeration oil containing the base oil of Example 1 and 0.2 mass of 4,4'-thiobis(2-methyl-6-tert-butylphenol).

[0149] Example 11 Refrigeration oil containing 0.1 mass% of 4,4'-thiobis(3-methyl-6-tert-butylphenol) in the base oil of Example 1 Example 12 Refrigeration oil of Example 1 (base oil only).

[0150] (Example 13) A refrigeration oil containing the base oil of Example 1 and 0.5 mass % of tricresyl phosphate (TCP), a typical anti-wear agent for refrigeration oils.

[0151] <Lubricity test> The effect of thiobisphenol compounds was evaluated in a lubricity test. The evaluation test was performed using a Stribeck curve to evaluate each lubrication region (hydrodynamic lubrication region, mixed lubrication region, boundary lubrication region), We used an MTM (Mini Traction Machine) test machine manufactured by PCS Instruments in the UK, which is said to have a correlation with actual machines.

[0152] The test was carried out in two atmospheres: in normal air and under nitrogen gas blowing conditions (100ml / min) to create an oxygen-free atmosphere more closely related to refrigeration oil, and friction characteristics were measured in a friction test (rolling / sliding contact) between a steel ball (diameter 3 / 4 inch) and a steel disk (diameter 46mm). The test conditions were oil temperature: 40°C, load: 10N, slip ratio: 30%, and peripheral speed: 10-2500mm / s.

[0153] In this test, the slower the peripheral speed, the more severe the conditions. The friction coefficient obtained from the test is evaluated from A to C based on the following evaluation criteria. (Evaluation Criteria) A: Friction coefficient less than 0.03: Fluid lubrication region. There is no wear because there is no contact between metals. B: Friction coefficient 0.03 to 0.05: Mixed lubrication region. Slight wear. C: Friction coefficient over 0.05: boundary lubrication region. The higher the coefficient, the more wear there is.

[0154] In addition, the evaluation results in Table 3 are shown as A to C for the friction coefficients at peripheral speeds of 500 mm / s and 50 mm / s based on the above evaluation, with the numerical values ​​of the friction coefficients shown in parentheses.

[0155] [Table 3]

[0156] From the results in Table 3, it can be seen that when the refrigeration oil according to the present invention contains thiobisphenol, the friction coefficient is low and the lubricity is excellent even in an oxygen-free nitrogen atmosphere. Moreover, TCP, a phosphate ester generally used as an anti-wear additive in refrigeration oils, is effective in air, but its effect is reduced in an oxygen-free nitrogen atmosphere (Example 13).

[0157] As described above, according to the present invention, a working fluid capable of exhibiting good performance when a refrigerant containing a hydrocarbon such as ethane, propane, normal butane, or isobutane is used in a refrigeration cycle device can be provided.

[0158] This application is based on International Patent Application PCT / JP2021 / 039624 filed on October 27, 2021, the disclosure of which is incorporated by reference in its entirety into this specification.

Claims

1. The refrigerant contains a hydrocarbon having 2 to 4 carbon atoms and no halogen atom, a refrigerating machine oil contains a polyalkylene glycol monoalkyl ether and a mineral oil, and a thiobisphenol compound, The polyalkylene glycol monoalkyl ether is represented by the following general formula (1): 【Chemistry 2】 [In formula (1), R １ is a linear or branched alkyl group having 1 to 5 carbon atoms; OR ２ are the same or different and each represents an oxyalkylene group having 2 to 4 carbon atoms; n is OR ２ represents the number of moles of oxyalkylene groups added. The number average molecular weight is 100 to 1500, and the kinetic viscosity at 40°C is 2 mm ２ / s or more 40mm ２ / s or less, The mineral oil has an aniline point of 55° C. or higher and 105° C. or lower, a pour point of −15° C. or lower, and a kinematic viscosity of 8 mm at 40° C. ２ / s exceeds 100 mm ２ / s or less, The polyalkylene glycol monoalkyl ether is contained in an amount of 10 mass% or more and 60 mass% or less, based on the total mass of the refrigerating machine oil, and the mineral oil is contained in an amount of 40 mass% or more and 90 mass% or less, based on the total mass of the refrigerating machine oil.

2. The working medium for a refrigerant compression type refrigeration cycle apparatus according to claim 1, wherein the thiobisphenol compound is contained in an amount of 0.05 mass % or more and 3.0 mass % or less based on a total mass of the refrigerating machine oil.

3. The working medium for a refrigerant compression type refrigeration cycle apparatus according to claim 1 or 2, wherein the refrigerating machine oil further contains 0.1 mass % to 20 mass % of an ester compound.

4. 3. The working medium for a refrigerant compression type refrigeration cycle apparatus according to claim 1, wherein the mineral oil is a naphthenic mineral oil having an aniline point of 55° C. or higher and 95° C. or lower and a pour point of −30° C. or lower.

5. The refrigerating machine oil has a volume resistivity of 1×10 at 25° C. １１ The working fluid for a refrigerant compression type refrigeration cycle apparatus according to claim 1 or 2, having a resistance of Ω·cm or more.

6. The working medium for a refrigerant compression type refrigeration cycle apparatus according to claim 1 or 2, wherein the refrigeration oil has a saturated moisture content of 1 mass % or less at 25°C and a humidity of 50%, and is a homogeneous liquid at -10°C.

7. The working medium for a refrigerant compression type refrigeration cycle apparatus according to claim 1 or 2, wherein the refrigerant is propane.

8. The polyalkylene glycol monoalkyl ether is R １ is an alkyl group having 4 carbon atoms, and OR ２ The working fluid for a refrigerant compression type refrigeration cycle apparatus according to claim 1 or 2, wherein is an oxypropylene group.

9. 3. The working medium for a refrigerant compression type refrigeration cycle apparatus according to claim 1 or 2, wherein the refrigerating machine oil contains one or more additives selected from the group consisting of an amine compound, a phenol compound, and a benzotriazole compound in an amount of 0.1 mass % or more and 3.0 mass % or less based on a total mass of the refrigerating machine oil.

10. 4. The working medium for a refrigerant compression type refrigeration cycle apparatus according to claim 3, wherein the refrigerating machine oil contains, with respect to a total mass of the refrigerating machine oil, 10 mass% or more and 40 mass% or less of the polyalkylene glycol monoalkyl ether, 60 mass% or more and 90 mass% or less of the mineral oil, and 0.1 mass% or more and 15 mass% or less of the ester compound.

11. The refrigerant contains a hydrocarbon having 2 to 4 carbon atoms and no halogen atom, a refrigerating machine oil contains a polyalkylene glycol monoalkyl ether and a mineral oil, and a thiobisphenol compound, The polyalkylene glycol monoalkyl ether is represented by the following general formula (1): 【Chemistry 3】 [In formula (1), R １ is a linear or branched alkyl group having 1 to 5 carbon atoms; OR ２ are the same or different and each represents an oxyalkylene group having 2 to 4 carbon atoms; n is OR ２ represents the number of moles of oxyalkylene groups added. The number average molecular weight is 100 to 1500, and the kinetic viscosity at 40°C is 2 mm ２ / s or more 40mm ２ / s or less, The mineral oil has an aniline point of 55° C. or higher and 105° C. or lower, a pour point of −15° C. or lower, and a kinematic viscosity of 8 mm at 40° C. ２ / s exceeds 100 mm ２ / s or less, The polyalkylene glycol monoalkyl ether is contained in an amount of 10 mass% or more and 60 mass% or less, based on the total mass of the refrigerating machine oil, and the mineral oil is contained in an amount of 40 mass% or more and 90 mass% or less, based on the total mass of the refrigerating machine oil.

12. A sealed refrigeration cycle device using the working medium according to claim 1 or 2.

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