Working medium, and refrigerant compression-type refrigerating / heating cycle device using said working medium

Abstract

The present invention provides a working medium that, when 2,3,3,3-tetrafluoropropene (HFO-1234yf), 1,3,3,3-tetrafluoropropene (HFO-1234ze), or carbon dioxide (R744) is used as a refrigerant, enables a refrigerating machine oil to achieve at least one of high stability, high electrical insulation property, and appropriate compatibility with respect to a refrigerant. The present disclosure pertains to a working medium comprising: at least one refrigerant selected from 2,3,3,3-tetrafluoropropene (HFO-1234yf), 1,3,3,3-tetrafluoropropene (HFO-1234ze), and carbon dioxide (R744); and a refrigerating machine oil containing an aromatic ester that is synthesized from an alcohol having 4-12 carbon atoms and benzenetricarboxylic acid and / or phthalic acid.

Description

Working medium and refrigerant compression type refrigeration / heating cycle device using the working medium

[0001] The present invention relates to a working medium and a refrigerant compression type refrigeration / heating cycle device using the working medium.

[0002] Refrigerant compression refrigeration and heating cycle devices, such as air conditioners (e.g., car air conditioners, room air conditioners), freezers (e.g., refrigerators), and heat pump-type devices that use hot water (e.g., water heaters, floor heating systems, and washing machines), use technology that utilizes the heat and cold generated by the compression and expansion of a refrigerant. The refrigerant used in such refrigeration cycle devices is often hydrofluorocarbon (HFC), a hydrocarbon containing fluorine atoms. However, HFCs have a long lifespan in the atmosphere, which results in a significant greenhouse effect, making them unsatisfactory refrigerants for preventing global warming, and there are moves to restrict their use.

[0003] In recent years, instead of HFCs, R744 (CO ２ It has been proposed to use fluorocarbons such as 2,3,3,3-tetrafluoropropane (HFO-1234yf) and HFO-1234yf (2,3,3,3-tetrafluoropropane) in refrigeration cycle devices. For example, HFO-1234yf is widely used in the field of car air conditioners because of its flame retardancy.

[0004] When these refrigerants are used, polyol esters, mineral oils, alkylbenzenes, and polyalkylene glycols are used as refrigerating machine oils used together with the refrigerants as a working medium component (for example, WO 2006 / 030490).

[0005] Because the double bonds present in HFO-1234yf molecules are prone to decomposition to generate hydrofluoric acid (HF), when HFO-1234yf is used as a refrigerant, the refrigerating machine oil must have high stability, such as acid resistance. However, among the refrigerating machine oils proposed in International Publication No. 2006 / 030490, mineral oil and alkylbenzene are incompatible with HFO-1234yf, posing a problem in that the refrigerating machine oil does not return to the compressor during the refrigeration cycle. Furthermore, while polyol esters are highly compatible with HFO-1234yf, they may hydrolyze when water is mixed in, raising stability concerns. Due to their low electrical insulation, polyalkylene glycols may cause leakage current in motor-integrated compressors, making them unusable. Therefore, there is a demand for refrigerating machine oils (e.g., refrigerating machine oils with high stability and / or high electrical insulation) that are suitable for use when HFO-1234yf is used as a refrigerant.

[0006] Furthermore, when R744 is used as the refrigerant, the refrigerating machine oil proposed in WO 2006 / 030490 dissolves the refrigerant (R744) too much, resulting in a decrease in viscosity and insufficient lubrication. Therefore, a refrigerating machine oil that is suitable for use when R744 is used as the refrigerant (for example, a refrigerating machine oil that has appropriate compatibility with R744) is desired.

[0007] Therefore, the present invention provides a working fluid that, when 2,3,3,3-tetrafluoroperopene (HFO-1234yf), 1,3,3,3-tetrafluoropropene (HFO-1234ze) or carbon dioxide (R744) is used as a refrigerant, provides a refrigerating machine oil that achieves at least one of high stability, high electrical insulation properties, and suitable compatibility with the refrigerant.

[0008] According to one embodiment of the present invention, there is provided a working fluid comprising: one or more refrigerants selected from 2,3,3,3-tetrafluoroperopene (HFO-1234yf), 1,3,3,3-tetrafluoropropene (HFO-1234ze), and carbon dioxide (R744); and a refrigerating machine oil containing an aromatic ester synthesized from benzenetricarboxylic acid and / or phthalic acid and an alcohol having from 4 to 12 carbon atoms.

[0009] The following describes in detail the embodiments of the present invention. The embodiments described herein are merely illustrative examples for embodying the technical concept of the present invention and are not intended to limit the present invention. Therefore, all other possible embodiments, methods of use, and operational techniques conceivable by those skilled in the art without departing from the spirit of the present invention are included within the scope and spirit of the present invention, as well as within the scope of the claims and their equivalents. The embodiments described herein can be arbitrarily combined to create other embodiments. Furthermore, in this specification, the term "X to Y" indicating a range means "X or more and Y or less," and "weight," "mass," "wt %," "mass %," and "parts by weight" and "parts by mass" are treated as synonyms. Unless otherwise specified, operations and measurements of physical properties are performed at room temperature (20-25°C) and a relative humidity of 40-60% RH.

[0010] <<Working Fluid>> One embodiment of the present invention is a working fluid comprising: one or more refrigerants selected from 2,3,3,3-tetrafluoroperopene (hereinafter referred to as "HFO-1234yf"), 1,3,3,3-tetrafluoropropene (hereinafter referred to as "HFO-1234ze"), and carbon dioxide (hereinafter referred to as "R744"); and a refrigerating machine oil containing an aromatic ester synthesized from benzenetricarboxylic acid and / or phthalic acid and an alcohol having from 4 to 12 carbon atoms. With this configuration, when HFO-1234yf, HFO-1234ze, or R744 is used as the refrigerant, the refrigerating machine oil becomes a working fluid that achieves at least one of high stability, high electrical insulation, and suitable compatibility with the refrigerant. For example, when HFO-1234yf or HFO-1234ze is used as a refrigerant, the refrigerating machine oil has at least one of high stability, high electrical insulation, and suitable compatibility with the refrigerant. Also, when R744 is used as a refrigerant, the refrigerating machine oil has at least one of high stability, high electrical insulation, and suitable compatibility with the refrigerant.

[0011] [Refrigerant] The refrigerant contained in the working fluid of this embodiment includes one or more refrigerants selected from HFO-1234yf, HFO-1234ze, and R 744. HFO-1234yf, HFO-1234ze, and R 744 have an ozone depletion potential of zero and an extremely low global warming potential.

[0012] R744 is carbon dioxide (CO ２ ), and is non-flammable and safe. ３ CF=CH ２ ) and HFO-1234ze(CF ３ Although HFO-1234yf and HFO-1234ze are slightly flammable, this is at a level that does not pose a problem in practical use. However, HFO-1234yf and HFO-1234ze are fluorinated olefins having double bonds, and are prone to decomposition to produce hydrofluoric acid (HF), a strong acid. Therefore, when HFO-1234yf and / or HFO-1234ze are used as refrigerants, high stability is required of the refrigerating machine oil. These HFO-1234yf, HFO-1234ze, and R744 refrigerants are suitable for use mainly in car air conditioners, water heaters, and heat pumps due to their physical properties.

[0013] As the refrigerant, one selected from HFO-1234yf, HFO-1234ze, and R744 may be used alone, or two or more selected from HFO-1234yf, HFO-1234ze, and R744 may be used in combination. Furthermore, the refrigerant may contain a refrigerant other than HFO-1234yf, HFO-1234ze, and R744. In this case, the main component of the refrigerant is a component selected from HFO-1234yf, HFO-1234ze, and R744. When two or more selected from HFO-1234yf, HFO-1234ze, and R744 are contained, the amount thereof is the total amount. In the present invention, the "main component" means a component that accounts for more than 50% by mass (upper limit 100% by mass) of the total mass (100% by mass) of the refrigerant.

[0014] Examples of the other refrigerant include saturated hydrofluorocarbons, unsaturated hydrofluorocarbons, dimethyl ether, hydrocarbons, etc. According to one embodiment, the content of the other refrigerant is preferably 1% by mass or more and less than 50% by mass, more preferably 2% by mass or more and 40% by mass or less, even more preferably 3% by mass or more and 35% by mass or less, particularly preferably 5% by mass or more and 25% by mass or less, and most preferably 10% by mass or more and 20% by mass or less, relative to the total mass (100% by mass) of HFO-1234yf, HFO-1234ze, and R744. When two or more other refrigerants are contained, the content of the other refrigerants is the total amount thereof.

[0015] According to one embodiment, the refrigerant consists of one or more selected from HFO-1234yf, HFO-1234ze, and R744 (the total mass of HFO-1234yf, HFO-1234ze, and R744 is 100% by mass). Also, according to one embodiment, the refrigerant consists of one selected from HFO-1234yf, HFO-1234ze, and R744.

[0016] [Refrigerating Machine Oil] Aromatic Ester The refrigerating machine oil contained in the working fluid of this embodiment contains an aromatic ester synthesized from benzenetricarboxylic acid and / or phthalic acid and an alcohol having 4 to 12 carbon atoms. According to one embodiment, the refrigerating machine oil contains, as a base oil, an aromatic ester synthesized from benzenetricarboxylic acid and / or phthalic acid and an alcohol having 4 to 12 carbon atoms. Hereinafter, the aromatic ester synthesized from benzenetricarboxylic acid and / or phthalic acid and an alcohol having 4 to 12 carbon atoms will be simply referred to as an "aromatic ester." The base oil in a refrigerating machine oil refers to a component contained in an amount greater than 50% by mass (upper limit 100% by mass) of the total mass (100% by mass) of the refrigerating machine oil, preferably 80% by mass or more, and more preferably 90% by mass or more.

[0017] As described above, HFO-1234yf and HFO-1234ze are prone to decomposition to produce hydrofluoric acid (HF), a strong acid, and therefore, when HFO-1234yf and HFO-1234ze are used as refrigerants, high stability is required of the refrigerating machine oil. The inventors believed that an ester with low solubility in water would provide good stability even when HFO-1234yf and / or HFO-1234ze are used as refrigerants. However, it was found that aliphatic esters commonly used as refrigerating machine oils are too compatible with HFO-1234yf and HFO-1234ze. In this case, the refrigerating machine oil dissolves too much in HFO-1234yf and HFO-1234ze, resulting in a thin oil film formed on the sliding parts and reduced lubricity. The present inventors have conducted extensive research into the compatibility of aromatic esters with HFO-1234yf and HFO-1234ze and have found that aromatic esters, which are generally used as plasticizers, have suitable compatibility with HFO-1234yf and HFO-1234ze. Although aromatic esters are known to have low compatibility with fluorine-based refrigerants such as HFCs (hydrofluorocarbons), the present inventors have found that certain aromatic esters have suitable compatibility with HFO-1234yf and HFO-1234ze.

[0018] Furthermore, the present inventors have also found that when a working fluid containing a refrigerant containing HFO-1234yf and / or HFO-1234ze and a refrigeration oil containing the aromatic ester according to the present embodiment is used in a refrigerant compression refrigeration / heating cycle device, the aromatic ester according to the present embodiment is not easily decomposed even when hydrofluoric acid is generated by HFO-1234yf and / or HFO-1234ze, and can be suitably used as a working fluid for a long period of time. It is believed that this is due to the structure of the aromatic ester according to the present embodiment. The aromatic ester according to the present embodiment has an aromatic ring and an alkyl group of a specific chain length derived from an alcohol. In other words, the aromatic ester according to the present embodiment has high chemical stability due to the aromatic ring, but also has high hydrophobicity due to the aromatic ring and the alkyl group of a specific chain length, which is thought to make the working fluid less susceptible to moisture. Therefore, it is believed that decomposition of both the refrigerant (HFO-1234yf and / or HFO-1234ze) and the refrigerating machine oil (aromatic ester according to the present embodiment) was significantly suppressed. As described above, the aromatic ester according to the present embodiment has high thermal and chemical stability and can be suitably used with refrigerants containing HFO-1234yf and / or HFO-1234ze.

[0019] Furthermore, the aromatic ester according to the present invention has high electrical insulation properties, and therefore, the refrigerating machine oil containing the aromatic ester according to the present invention has high electrical insulation properties.

[0020] The aromatic ester according to the present embodiment can be synthesized by a dehydration condensation reaction between a carboxylic acid and an alcohol. In the working fluid according to the present embodiment, the aromatic ester contained in the refrigerating machine oil contains benzenetricarboxylic acid (C ６ H ３ (COOH) ３ ) and / or phthalic acid (C ６ H ４ (COOH) ２ and an alcohol having 4 to 12 carbon atoms. That is, the carboxylic acid has an aromatic ring (benzene ring) and two or three carboxy groups.

[0021] Benzenetricarboxylic acid (C ６H ３ (COOH) ３ ) is trimellitic acid (1,2,4-benzenetricarboxylic acid) or trimesic acid (1,3,4-benzenetricarboxylic acid). ６ H ４ (COOH) ２ ) includes ortho-phthalic acid, meta-isophthalic acid, and para-terephthalic acid, and of these, ortho-phthalic acid is preferred from the viewpoints of low-temperature properties and hydrolysis stability.

[0022] The alcohol having 4 to 12 carbon atoms used to produce the aromatic ester according to the present embodiment may be linear or branched. The alcohol used to produce the aromatic ester preferably has 6 to 12 carbon atoms, more preferably has 7 to 12 carbon atoms, particularly preferably has 8 to 12 carbon atoms, and most preferably has 8 to 11 carbon atoms.

[0023] Examples of alcohols having 4 to 12 carbon atoms include alcohols having 4 carbon atoms such as 1-butanol and 2-butanol; alcohols having 5 carbon atoms such as 1-pentanol, 2-pentanol, and 2-methyl-1-butanol; alcohols having 6 carbon atoms such as 1-hexanol, 2-hexanol, 3-methyl-1-pentanol, and 3-methyl-2-pentanol; alcohols having 7 carbon atoms such as 1-heptanol, 2-heptanol, and 2-methyl-1-hexanol; alcohols having 7 carbon atoms such as 1-octanol, 2-octanol, 2-methyl-1-heptanol, 2-methyl-2-heptanol, 3-methyl-1-heptanol, 3-methyl-2-heptanol, 2,2-dimethyl-1-hexanol, 3,3-dimethyl-1-hexanol, 2,3-dimethyl-1-hexanol, and 2- Examples of straight-chain or branched alcohols include alcohols having 8 carbon atoms such as ethyl-1-hexanol and 3-ethyl-1-hexanol; alcohols having 9 carbon atoms such as 1-nonyl alcohol, 2-methyl-1-octanol (isononyl alcohol), 2-methyl-2-octanol, 3-methyl-1-octanol and 3-methyl-2-octanol; alcohols having 10 carbon atoms such as 1-decyl alcohol and 2-decyl alcohol; alcohols having 11 carbon atoms such as 1-undecyl alcohol, 2-undecyl alcohol, 2-ethyl-1-octanol and 3-ethyl-1-octanol; and alcohols having 12 carbon atoms such as 1-dodecyl alcohol, 2-dodecyl alcohol, 2-methyl-1-undecyl alcohol and 2-methyl-2-undecyl alcohol.

[0024] Specific examples of aromatic esters according to the present invention include tributyl trimellitate, tris(2-ethylhexyl) trimellitate, triisononyl trimellitate (triisononyl 1,2,4-benzenetricarboxylate), di(2-ethylhexyl) phthalate, diisopropyl phthalate, didecyl phthalate, and diundecyl phthalate. The selection of aromatic esters depends on the required viscosity. Two or more types may be mixed to match the viscosity.

[0025] The conditions for reacting benzenetricarboxylic acid and / or phthalic acid with an alcohol having 4 to 12 carbon atoms to obtain the aromatic ester according to the present embodiment are not particularly limited, and general conditions employed by those skilled in the art for esterification may be appropriately employed.

[0026] The kinematic viscosity of the aromatic ester according to the present invention at 40°C is 2 mm ２ / s or more 200mm ２ / s or less, and ２ / s or more 150mm ２ The kinematic viscosity of the aromatic ester at 40°C is preferably 5 mm / s or less. ２ / s or more 150mm ２ / s or less, and more preferably 10 mm ２ / s or more 120mm ２ / s or less, and more preferably 15 mm ２ / s or more 100mm ２ / s or less, and particularly preferably 20 mm ２ / s or more 95mm ２ / s or less, and most preferably 25 mm ２ / s or more 90mm ２ According to one embodiment, the kinematic viscosity of the aromatic ester at 40°C is 30 mm ２ / s or more 120mm ２ / s or less, 30mm ２ / s or more 100mm ２ / s or less, 40mm ２ / s or more 120mm ２ / s or less, 40mm ２ / s or more 100mm ２ / s or less, 50mm ２ / s or more 120mm ２ / s or less, 50mm ２ / s or more 100mm ２ / s or less or 50 mm ２ / s or more 90mm ２ The kinematic viscosity of the aromatic ester at 40°C may be 2 mm / s or less. ２When the kinematic viscosity of the aromatic ester at 40°C is 200 mm / s or more, the aromatic ester can form an oil film, reducing metal-to-metal contact at sliding parts, and allowing the refrigerating machine oil to fully exhibit its lubrication properties in the presence of a refrigerant. ２ If the viscous resistance of the refrigerating machine oil is equal to or less than 1 / s, the efficiency of the refrigerant compression type refrigeration / heating cycle device can be improved.

[0027] The aromatic ester according to the present embodiment preferably has a pour point of −10° C. or lower, more preferably −20° C. or lower, even more preferably −25° C. or lower, and particularly preferably −30° C. or lower. If the pour point of the aromatic ester is −10° C. or lower, it can be suitably used as a liquid.

[0028] The aromatic ester according to the present invention has a volume resistivity of 0.2×10 １２ It is preferable that the resistance is Ω cm or more, and 0.5×10 １２ More preferably, it is 1.0×10 Ω cm or more. １２ The upper limit of the volume resistivity of the aromatic ester according to the present invention is, in practical terms, 1000.0×10 １２ The volume resistivity is preferably Ω·cm or less. The volume resistivity is measured by the method described in the examples below.

[0029] The content of aromatic ester in the refrigerating machine oil is preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 85% by mass or more, particularly preferably 90% by mass or more, and most preferably 95% by mass or more, relative to 100 parts by mass of the refrigerating machine oil. According to one embodiment, the content of aromatic ester in the refrigerating machine oil may be 98% by mass or more, or 99% by mass or more, relative to 100 parts by mass of the refrigerating machine oil. The refrigerating machine oil may be composed only of aromatic ester, and therefore the upper limit of the content of aromatic ester in the refrigerating machine oil is 100% by mass, relative to 100 parts by mass of the refrigerating machine oil. When the aromatic ester is contained within the above range, the effects of the present invention can be more effectively exhibited.

[0030] Additives According to one embodiment, the refrigerating machine oil may consist solely of aromatic esters (i.e., the aromatic ester content may be 100% by mass), but may further contain components other than aromatic esters (hereinafter referred to as "additives") as long as the function of the refrigerating machine oil is satisfied. In this case, the content of the additives in the refrigerating machine oil is preferably 3% by mass or less, more preferably 2.5% by mass or less, even more preferably 2% by mass or less, particularly preferably 1.5% by mass or less, and most preferably 1% by mass or less, relative to the total mass (100% by mass) of the refrigerating machine oil. When an additive is contained, the lower limit of the content of the additive is preferably 0.01% by mass or more, relative to the total mass (100% by mass) of the refrigerating machine oil.

[0031] Examples of additives include oiliness agents, stability improvers, antioxidants, anti-wear agents, metal deactivators, and anti-foaming agents.

[0032] Examples of oily agents include monohydric alcohols; higher fatty acids; esters other than aromatic esters synthesized from benzenetricarboxylic acid and / or phthalic acid and alcohols having from 4 to 12 carbon atoms (hereinafter referred to as "other esters"); ethers such as polyalkylene glycols (e.g., polyethylene glycol, polypropylene glycol) and polyvinyl ethers; hydrocarbon-based oils such as alkylbenzenes, polyolefins, and mineral oils; and the like.

[0033] Other esters include, for example, monoesters, diesters, polyol esters, and phosphate esters. Monoesters include esters of monobasic acids and alcohols such as octyl oleate, butyl octanoate, and hexyl 2-ethylhexanoate. Diesters include esters of dibasic acids and alcohols such as dioctyl sebacate, dioctyl adipate, and adipate dioleate. Polyol esters include esters (partial esters and complete esters) of polyhydric alcohols such as glycerin, sorbitan, neopentyl glycol, trimethylolpropane, and pentaerythritol with carboxylic acids such as octylic acid, nonanoic acid, and oleic acid. Partial esters include partial esters of polyhydric alcohols such as glycerin monooleate (glycerol monooleate) and sorbitan monooleate. Phosphate 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 (for example, 2-ethylhexanoic acid) are more preferred because of their small molecular weight and low viscosity.

[0034] The content of the oiliness agent is preferably 0.01% by mass or more and 3.0% by mass or less, relative to the total mass (100% by mass) of the refrigerating machine oil. The content of the polyol ester is preferably 0.01% by mass or more and 1.0% by mass or less, more preferably 0.05% by mass or more and 0.5% by mass or less, relative to the total mass (100% by mass) of the refrigerating machine oil. Furthermore, when the polyol ester is a monoester (partial ester), it is susceptible to hydrolysis, so the content of the monoester is preferably 0.01% by mass or more and less than 0.5% by mass, more preferably 0.01% by mass or more and 0.3% by mass or less, relative to the total mass (100% by mass) of the refrigerating machine oil.

[0035] The refrigerating machine oil may further contain a stability improver as an additive to further enhance the stability of the working medium of the refrigerant and the refrigerating machine oil in actual use. Preferred stability improvers include one or more selected from the group consisting of thiobisphenol compounds, phenol compounds, aromatic amine compounds, and benzotriazole compounds. When a thiobisphenol compound is added, it is more preferable to use it in combination with an aromatic amine compound.

[0036] Suitable examples of the thiobisphenol compound 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 preferably 0.05% by mass or more and 1.0% by mass or less, and more preferably 0.1% by mass or more and 0.5% by mass or less, relative to the total mass (100% by mass) of the refrigerating machine oil.

[0037] Suitable phenol compounds include 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% by mass or more and 1.0% by mass or less, and more preferably 0.1% by mass or more and 0.5% by mass or less, relative to the total mass (100% by mass) of the refrigerating machine oil.

[0038] Examples of aromatic amine compounds include α-naphthylamine and N-phenyl-1-naphthylamine, and di(alkylphenyl)amines having an alkyl group having from 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 from 0.05 to 1.5% by mass, more preferably from 0.1 to 1.0% by mass, relative to the total mass (100% by mass) of the refrigerating machine oil.

[0039] The benzotriazole compound includes benzotriazole and 1-[bis(alkyl)aminomethyl]-alkyl-1H-benzotriazoles 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%, relative to the total mass (100 mass%) of the refrigerating machine oil.

[0040] According to one embodiment, the total content of the oiliness agent and the stability improver is 0.1 mass % or more and 3.0 mass % or less, relative to the total mass (100 parts by mass) of the refrigerating machine oil. According to one embodiment, the refrigerating machine oil contains one or more additives selected from the group consisting of phenol compounds, aromatic amine compounds, and partial esters of polyhydric alcohols, in an amount of 0.1 mass % or more and 3.0 mass % or less, more preferably 0.2 mass % or more and 2 mass % or less, and even more preferably 0.3 mass % or more and 1.5 mass % or less, relative to the total mass (100 parts by mass) of the refrigerating machine oil.

[0041] Examples of antioxidants include hindered phenols, examples of antiwear agents include phosphate esters and organic sulfur compounds, examples of metal deactivators include benzotriazole derivatives, and examples of antifoaming agents include silicone oils. The refrigerating machine oil contains one or more additives selected from the group consisting of antioxidants, antiwear agents, metal deactivators, and antifoaming agents in an amount of preferably 0.05% by mass or more and 1.0% by mass or less, more preferably 0.1% by mass or more and 0.5% by mass or less, relative to the total mass (100 parts by mass) of the refrigerating machine oil.

[0042] Physical Properties of Refrigerating Machine Oil The pour point of the refrigerating machine oil is preferably −10° C. or lower, more preferably −20° C. or lower, even more preferably −25° C. or lower, and particularly preferably −30° C. or lower. If the pour point of the refrigerating machine oil is −10° C. or lower, it can be suitably used as a liquid.

[0043] The kinematic viscosity of refrigerating oil at 40°C is 2 mm ２ / s or more 200mm ２ / s or less, and２ / s or more 150mm ２ The kinematic viscosity of the refrigerating machine oil at 40°C is preferably 5 mm / s or less. ２ / s or more 150mm ２ / s or less, and more preferably 10 mm ２ / s or more 120mm ２ / s or less, and more preferably 15 mm ２ / s or more 100mm ２ / s or less, and particularly preferably 20 mm ２ / s or more 95mm ２ / s or less, and most preferably 25 mm ２ / s or more 90mm ２ According to one embodiment, the kinematic viscosity of the refrigerating machine oil at 40°C is 30 mm ２ / s or more 120mm ２ / s or less, 30mm ２ / s or more 100mm ２ / s or less, 40mm ２ / s or more 120mm ２ / s or less, 40mm ２ / s or more 100mm ２ / s or less, 50mm ２ / s or more 120mm ２ / s or less, 50mm ２ / s or more 100mm ２ / s or less or 50 mm ２ / s or more 90mm ２ When the kinematic viscosity of the refrigerating machine oil at 40°C is within the above range, the refrigerating machine oil can form an oil film, reducing metal-to-metal contact at sliding parts, allowing the refrigerating machine oil to fully exhibit its lubricating properties in the presence of a refrigerant, and also allowing the viscous resistance of the refrigerating machine oil to be adjusted within an appropriate range, thereby improving the efficiency of the refrigerant compression refrigeration / heating cycle device.

[0044] In the present invention, a refrigerating machine oil having "excellent compatibility with the refrigerant (appropriate compatibility with the refrigerant)" means that the two-phase separation temperature is low and the refrigerant does not dissolve excessively in the refrigerant. In the present invention, the two-phase separation temperature between the refrigerant and the refrigerating machine oil is preferably 0°C or lower, more preferably -5°C or lower, even more preferably -10°C or lower, and even more preferably -12°C or lower. The lower limit of the two-phase 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-phase separation temperature is measured by the method described in the Examples below. In addition, aromatic esters do not dissolve excessively in the refrigerant. As described above, the refrigerating machine oil according to the present invention has excellent compatibility with the refrigerant (appropriate compatibility with the refrigerant), and therefore a working fluid containing the refrigerating machine oil according to the present invention can exhibit good performance even when the amount of refrigerant charged is small.

[0045] In the present invention, the high stability of a refrigerating machine oil means that the refrigerating machine oil has at least one of the following: an acid value of 0.01 to 0.05 mgKOH / g; and a color 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). Furthermore, when the color of a refrigerating machine 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).

[0046] 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 0.7% or less, even more preferably 0.5% by mass or less, and particularly preferably 0.2% by mass or less. The saturated moisture content is measured by the method described in the examples below.

[0047] In the present invention, the electrical insulating property of a refrigerating machine oil is evaluated by its volume resistivity. Specifically, when the volume resistivity of the refrigerating machine oil is 0.2×10 １２ It is preferable that the resistance is Ω cm or more, and 0.5×10 １２ More preferably, it is 1.0×10 Ω cm or more.１２ The upper limit of the volume resistivity of the refrigerating machine oil is, in practical terms, 1000.0×10 １２ The volume resistivity is preferably Ω·cm or less. The volume resistivity is measured by the method described in the examples below.

[0048] The refrigerating machine oil of the present invention achieves a good balance of suitable compatibility with refrigerants, high stability, high electrical insulation, and good low-temperature fluidity. The refrigerating machine oil is used together with the refrigerant as a component of the working fluid for refrigerant compression refrigeration and heating cycle devices (e.g., air conditioners such as car air conditioners and room air conditioners, and water heaters). A working fluid containing a refrigerating machine oil with a good balance of properties can exhibit good performance.

[0049] In refrigerant compression refrigeration / heating cycle systems, refrigerating machine oil is typically present in the form of a working fluid mixed with the refrigerant described above. The blending ratio of the refrigerating machine oil to the refrigerant in this working fluid is not particularly limited, but the refrigerating machine oil content is preferably 1 to 500 parts by mass, more preferably 2 to 400 parts by mass, and even more preferably 4 to 300 parts by mass per 100 parts by mass of the refrigerant. Specifically, when this working fluid is used in a car air conditioner or a room air conditioner, the refrigerating machine oil content is preferably 1 to 300 parts by mass, more preferably 2 to 200 parts by mass, and even more preferably 4 to 100 parts by mass per 100 parts by mass of the refrigerant. Furthermore, when this working fluid is used in a refrigerator, the refrigerating machine oil content is preferably 5 to 500 parts by mass, more preferably 10 to 450 parts by mass, and even more preferably 50 to 400 parts by mass per 100 parts by mass of the refrigerant.

[0050] As described above, the refrigerating machine oil according to this embodiment has excellent compatibility with specific refrigerants and can significantly improve stability. Therefore, according to another embodiment of the present invention, there is also provided a refrigerating machine oil for 2,3,3,3-tetrafluoropropene (HFO-1234yf) refrigerant, which contains an aromatic ester synthesized from benzenetricarboxylic acid and / or phthalic acid and an alcohol having 4 to 12 carbon atoms. According to yet another embodiment of the present invention, there is also provided a refrigerating machine oil for 1,3,3,3-tetrafluoropropene (HFO-1234ze) refrigerant, which contains an aromatic ester synthesized from benzenetricarboxylic acid and / or phthalic acid and an alcohol having 4 to 12 carbon atoms. Furthermore, according to another embodiment of the present invention, there is also provided a refrigerating machine oil for carbon dioxide (R744) refrigerant, which contains an aromatic ester synthesized from benzenetricarboxylic acid and / or phthalic acid and an alcohol having 4 to 12 carbon atoms.

[0051] <<Physical Properties and Applications of Working Fluid>> The working fluid of this embodiment is a combination of one or more refrigerants selected from HFO-1234yf, HFO-1234ze, and R744; and a refrigerating machine oil containing an aromatic ester synthesized from benzenetricarboxylic acid and / or phthalic acid and an alcohol having from 4 to 12 carbon atoms, and thereby has appropriate compatibility with the refrigerant while maintaining good properties as a working fluid (for example, high stability, high electrical insulation, and good low-temperature fluidity).

[0052] The kinematic viscosity of the working fluid at 40°C is 1 mm ２ / s or more 200mm ２ / s or less, and ２ / s or more 150mm ２ / s or less is more preferable, and 5 mm ２ / s or more 120mm ２ / s or less, and more preferably 10 mm ２ / s or more 100mm ２ / s or less is particularly preferable, and 15 mm ２ / s or more 90mm ２ According to one embodiment, the kinematic viscosity of the working fluid at 40°C is 1 mm / s or less. ２ / s or more 70mm ２ / s or less.

[0053] According to the present invention, there is provided a refrigerant compression refrigeration / heating cycle system using the working fluid. That is, the working fluid of this embodiment can be suitably used in refrigerant compression refrigeration / heating cycle systems. Examples of refrigerant compression refrigeration / heating cycle systems include car air conditioners, room air conditioners, packaged air conditioners, heat pumps, water heaters, showcases, commercial freezers / refrigerators, and vending machines.

[0054] Therefore, another object of the present invention is to provide a working fluid for a refrigerant compression type refrigeration / heating cycle device that exhibits good performance, and a refrigerant compression type refrigeration / heating cycle device using the same.

[0055] Although the embodiments of the present invention have been described in detail, it is clear that this is by way of illustration and example only and not of limitation, and that the scope of the present invention should be interpreted by the appended claims.

[0056] The present invention encompasses the following aspects and configurations.

[0057] [1] A working fluid comprising: one or more refrigerants selected from 2,3,3,3-tetrafluoropropene (HFO-1234yf), 1,3,3,3-tetrafluoropropene (HFO-1234ze), and carbon dioxide (R744); and a refrigerating machine oil containing an aromatic ester synthesized from benzenetricarboxylic acid and / or phthalic acid and an alcohol having from 4 to 12 carbon atoms.

[0058] [2] The kinetic viscosity of the refrigerating machine oil at 40 ° C. is 3 mm ２ / s or more 150mm ２ / s or less.

[0059] [3] The working fluid according to [1] or [2] above, wherein the refrigerant contains 2,3,3,3-tetrafluoropropane (HFO-1234yf) or carbon dioxide (R744).

[0060] [4] The working fluid according to any one of the above [1] to [3], wherein the refrigerating machine oil contains one or more additives selected from the group consisting of an amine compound, a phenol compound, a thiobisphenol compound, and a benzotriazole compound in an amount of 0.1 mass % to 3.0 mass % relative to the total mass of the refrigerating machine oil.

[0061] [5] The working fluid according to any one of [1] to [4] above, which is for a refrigerant compression type refrigeration / heating cycle device.

[0062] [6] A refrigerant compression type refrigeration / heating cycle device using the working fluid described in any one of [1] to [5] above.

[0063] [7] A refrigerating machine oil for carbon dioxide (R744) refrigerant, comprising an aromatic ester synthesized from benzenetricarboxylic acid and / or phthalic acid and an alcohol having 4 to 12 carbon atoms.

[0064] [8] A refrigerating machine oil for 2,3,3,3-tetrafluoroperopene (HFO-1234yf) refrigerant, which contains an aromatic ester synthesized from benzenetricarboxylic acid and / or phthalic acid and an alcohol having 4 to 12 carbon atoms.

[0065] [9] A refrigerating machine oil for 1,3,3,3-tetrafluoropropene (HFO-1234ze) refrigerant, containing an aromatic ester synthesized from benzenetricarboxylic acid and / or phthalic acid and an alcohol having 4 to 12 carbon atoms.

[0066] The effects of the present invention will be explained using the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples. In the following examples, unless otherwise specified, operations were performed at 25°C.

[0067] [Refrigerating Machine Oil] Refrigerating machine oils of Examples 1 to 4 and Comparative Examples 1 to 4 were prepared.

[0068] Aromatic esters are primarily used as plasticizers for plastics, and when used as plasticizers, they do not require extensive purification. Therefore, aromatic esters sold as general-purpose products have low purity and must be purified when used as refrigerating machine oils. Therefore, the aromatic esters used in Examples 1 to 4 were evaluated using reagents from Tokyo Chemical Industry Co., Ltd.

[0069] Example 1 Refrigerant oil (without additives) containing, as a base oil, tributyl trimellitate (an ester of trimellitic acid and butanol (an alcohol having 4 carbon atoms)) (100% by mass based on the total mass of the refrigerant oil).

[0070] Example 2 Refrigerating machine oil containing, as a base oil, tris(2-ethylhexyl) trimellitate (an ester of trimellitic acid and 2-ethylhexanol (an alcohol having 8 carbon atoms)) (99.8% by mass based on the total mass of the refrigerating machine oil); and, as an additive, 4,4′-thiobis(2-methyl-6-tert-butylphenol) (0.2% by mass based on the total mass of the refrigerating machine oil).

[0071] Example 3 Refrigerant oil (without additives) containing diisononyl phthalate (ester of phthalic acid and isononyl alcohol (alcohol having 9 carbon atoms)) (100% by mass based on the total mass of the refrigerant oil) as the base oil.

[0072] Example 4 A refrigerating machine oil comprising diundecyl phthalate (an ester of phthalic acid and undecyl alcohol (an alcohol having 11 carbon atoms)) as a base oil (99.1% by mass relative to the total mass of the refrigerating machine oil); and 4,4'-thiobis(2-methyl-6-tert-butylphenol) (0.2% by mass relative to the total mass of the refrigerating machine oil), p,p'-di-octyl-diphenylamine (0.5% by mass relative to the total mass of the refrigerating machine oil), and glycerol monooleate (0.2% by mass relative to the total mass of the refrigerating machine oil) as additives.

[0073] Comparative Example 1 Refrigerant oil (without additives) containing paraffinic mineral oil (viscosity grade: VG83) (100% by mass based on the total mass of the refrigerant oil).

[0074] Comparative Example 2 Refrigerant oil (without any additives) containing linear alkylbenzene (viscosity grade: VG32) (100% by mass based on the total mass of the refrigerant oil).

[0075] (Comparative Example 3) Refrigerant oil (without additives) containing polyol ester (ester of pentaerythritol (a tetrahydric alcohol having 5 carbon atoms) and 2-ethylhexanoic acid) (viscosity grade: VG46) (100% by mass based on the total mass of the refrigerant oil).

[0076] Comparative Example 4 Refrigerant oil (without any additives) containing polypropylene glycol (terminal groups: n-butoxy and hydroxyl groups) (viscosity grade: VG22) (100% by mass based on the total mass of the refrigerant oil).

[0077] The viscosity grade refers to the kinematic viscosity at 40° C. The viscosity grade can be measured by the kinematic viscosity measurement method (kinematic viscosity at 40° C. (±10%)) described below.

[0078] The properties of the refrigerating machine oils prepared in Examples 1 to 4 and Comparative Examples 1 to 4 were measured and evaluated according to the following methods. The results are shown in Tables 1 and 2.

[0079] [General Properties and Color] General properties (kinematic viscosity, volume resistivity, pour point, acid value) were measured in accordance with JIS methods (kinematic viscosity: K2283 (2000), volume resistivity: C2101 (2010), pour point: K2269 (1987), acid value: K2501 (2003)), and color was measured in accordance with ASTM D156.

[0080] [Evaluation of thermal and chemical stability] Based on Appendix C (Test method for chemical stability with refrigerants) of JIS K2211 (refrigerating machine oils), each refrigerating machine oil (30 g), the refrigerant HFO-1234yf (10 g) or R744 (10 g), which requires the greatest stability, and catalysts (iron, copper, and aluminum wires: each wire 1.6 mm in diameter x 50 mm in length) were sealed in an autoclave, and then heated to 175°C and held for 7 days for testing. After the test, the color and acid value of the sample (refrigerating machine oil) were evaluated.

[0081] [Two-phase separation temperature] As a compatibility test between a refrigerating machine oil and a refrigerant, the two-phase separation temperature was measured in accordance with the JIS method (refrigerating machine oil: K2211 (2009)). The compatibility test was carried out using HFO-1234yf as the refrigerant, with 1.0 g of refrigerating machine oil per 19.0 g of refrigerant. In this example, the measurement was carried out in a temperature range from room temperature (25°C) to -50°C. Therefore, in a sample containing a refrigerating machine oil and a 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).

[0082] [Saturated Moisture Content] The moisture content was measured after 48 hours (50 g of refrigerating machine oil was left standing 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). The saturated moisture content of the refrigerating machine oils of Examples 1 to 4 was 0.1 mass% or more and 0.15 mass% or less (1000 mass ppm or more and 1500 mass ppm or less) at 25°C.

[0083]

[0084]

[0085] From Table 1, it can be seen that the aromatic esters of Examples 1 to 4 are excellent in electrical insulation, low-temperature fluidity (pour point), thermal and chemical stability, and two-phase separation temperature, making them well-balanced refrigerating machine oils. In particular, Examples 2 and 4, which contain additives, show no increase in acid value and have extremely good thermal and chemical stability.

[0086] On the other hand, the mineral oil and alkylbenzene of Comparative Examples 1 and 2 are incompatible with HFO-1234yf (they separate into two layers), which is presumed to cause problems with oil returning to the compressor in refrigerant compression refrigeration / heating cycles. The polyol ester of Comparative Example 3 showed a significant increase in acid value in thermal and chemical stability tests with HFO-1234yf, which easily decomposes to produce hydrofluoric acid (HF), indicating that it is not suitable for refrigerant compression refrigeration / heating cycle devices that are used maintenance-free (without oil changes) for long periods of time. The polypropylene glycol of Comparative Example 4 has a low volume resistivity, which may cause leakage current in hermetic compressors with built-in motors.

[0087] As described above, according to the present invention, R744(CO ２ It has been found that in a working fluid containing a refrigerant selected from the group consisting of HFO-1234yf, HFO-1234ze, and a refrigerating machine oil, the refrigerating machine oil achieves a good balance of high stability, suitable compatibility with the refrigerant, high electrical insulation, and low low-temperature fluidity. Thus, the present invention provides a working fluid for a refrigerant compression type refrigeration / heating cycle device that has a good balance of high stability, suitable compatibility with the refrigerant, high electrical insulation, and low low-temperature fluidity.

Claims

1. A working fluid comprising: one or more refrigerants selected from 2,3,3,3-tetrafluoroperopene (HFO-1234yf), 1,3,3,3-tetrafluoropropene (HFO-1234ze), and carbon dioxide (R744); and a refrigeration oil containing an aromatic ester synthesized from benzenetricarboxylic acid and / or phthalic acid and an alcohol having from 4 to 12 carbon atoms.

2. The kinetic viscosity of the refrigerating machine oil at 40°C is 3 mm ２ / s or more 150mm ２ The working medium according to claim 1, wherein the working fluid has a viscosity of 1 / s or less.

3. The working medium according to claim 1 or 2, wherein the refrigerant comprises 2,3,3,3-tetrafluoropropane (HFO-1234yf) or carbon dioxide (R744).

4. The working medium according to claim 1 or 2, wherein the refrigerating machine oil contains one or more additives selected from the group consisting of amine compounds, phenol compounds, thiobisphenol compounds, and benzotriazole compounds in an amount of 0.1 mass % to 3.0 mass % relative to the total mass of the refrigerating machine oil.

5. The working medium according to claim 1 or 2, which is a refrigerant compression type refrigeration / heating cycle device.

6. A refrigerant compression type refrigeration / heating cycle device using the working medium according to claim 1 or 2.

7. A refrigeration oil for carbon dioxide (R744) refrigerant, containing an aromatic ester synthesized from benzenetricarboxylic acid and / or phthalic acid and an alcohol having 4 to 12 carbon atoms.

8. Refrigeration oil for 2,3,3,3-tetrafluoroperopentane (HFO-1234yf) refrigerant, containing an aromatic ester synthesized from benzenetricarboxylic acid and / or phthalic acid and an alcohol having 4 to 12 carbon atoms.

9. A refrigeration oil for 1,3,3,3-tetrafluoropropene (HFO-1234ze) refrigerant, containing an aromatic ester synthesized from benzenetricarboxylic acid and / or phthalic acid and an alcohol having 4 to 12 carbon atoms.

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