Definitions

• the present invention relates to a working medium and a refrigerant compression refrigeration/heating cycle device that uses the working medium.
• Refrigerant compression refrigeration and heating cycle devices such as car air conditioners, room air conditioners, refrigerators and other freezers, and heat pump devices that use hot water (e.g., water heaters, floor heating, washing machines), use technology that utilizes the heat and cold generated by the compression and expansion of the refrigerant.
• the refrigerant used in these refrigeration cycle devices is often hydrofluorocarbon (HFC), a hydrocarbon containing fluorine atoms.
• HFCs hydrofluorocarbon
• HFO-1234yf (2,3,3,3-tetrafluoropropane) in refrigeration cycle equipment instead of HFCs, which have an ozone depletion potential of zero and a global warming potential that is significantly smaller than that of HFCs.
• HFO-1234yf is widely used in the field of car air conditioners because it is flame-retardant.
• the refrigerating machine oil used together with the refrigerant as a working medium component is polyol ester, mineral oil, alkylbenzene, or polyalkylene glycol (see, for example, WO 2006/030490).
• HFO-1234yf's intramolecular double bonds readily decompose to produce hydrofluoric acid (HF). Therefore, when using HFO-1234yf as a refrigerant, refrigeration oils must have high stability, including acid resistance.
• mineral oil and alkylbenzene are incompatible with HFO-1234yf, posing a problem of the refrigeration oil not returning to the compressor during the refrigeration cycle.
• polyol esters are highly compatible with HFO-1234yf, they are susceptible to hydrolysis when water is mixed in, raising stability concerns. Polyalkylene glycols have poor electrical insulation properties, which can cause leakage currents in motor-integrated compressors, making them unusable. Therefore, there is a demand for refrigeration oils (e.g., refrigeration oils with high stability and/or electrical insulation) that are suitable for use with HFO-1234yf as a refrigerant.
• the refrigeration oil proposed in WO 2006/030490 dissolves the refrigerant (R744) too much, resulting in a decrease in viscosity and insufficient lubrication. Therefore, there is a need for a refrigeration oil that is suitable for use when R744 is used as the refrigerant (for example, a refrigeration oil that has appropriate compatibility with R744).
• the present invention therefore aims to provide a working fluid in which, when using 2,3,3,3-tetrafluoropropene (HFO-1234yf), 1,3,3,3-tetrafluoropropene (HFO-1234ze), or carbon dioxide (R744) as a refrigerant, the refrigerant oil achieves at least one of high stability, high electrical insulation, and suitable compatibility with the refrigerant.
• HFO-1234yf 2,3,3,3-tetrafluoropropene
• HFO-1234ze 1,3,3,3-tetrafluoropropene
• R744 carbon dioxide
• a working fluid includes 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 refrigeration oil containing an aromatic ester synthesized from benzenetricarboxylic acid and/or phthalic acid and an alcohol having from 4 to 12 carbon atoms.
• refrigerants selected from 2,3,3,3-tetrafluoropropene (HFO-1234yf), 1,3,3,3-tetrafluoropropene (HFO-1234ze), and carbon dioxide (R744)
• 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.
• One aspect 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 4 to 12 carbon atoms.
• HFO-1234yf 2,3,3,3-tetrafluoroperopene
• HFO-1234ze 1,3,3,3-tetrafluoropropene
• R744 carbon dioxide
• refrigerating machine oil containing an aromatic ester synthesized from benzenetricarboxylic acid and/or phthalic acid and an alcohol having 4 to 12 carbon atoms.
• the refrigerating machine oil achieves at least one of high stability, high electrical insulation, and suitable compatibility with the refrigerant.
• the refrigerating machine oil has at least one of high stability, high electrical insulation, and suitable compatibility with the refrigerant.
• the refrigerating machine oil has at least one of high stability, high electrical insulation properties, and suitable compatibility with the 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.
• R744 is carbon dioxide (CO 2 ) and is non-flammable and safe.
• HFO-1234yf (CF 3 CF ⁇ CH 2 ) and HFO-1234ze (CF 3 CH ⁇ CHF) are slightly flammable, but at a level that does not pose a problem in practical use.
• 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 for the refrigerating machine oil. Due to their physical properties, these HFO-1234yf, HFO-1234ze, and R744 refrigerants are suitable for use mainly in car air conditioners, water heaters, and heat pumps.
• the refrigerant may be one selected from HFO-1234yf, HFO-1234ze, and R744, or a combination of two or more selected from HFO-1234yf, HFO-1234ze, and R744.
• the refrigerant may also contain refrigerants other than HFO-1234yf, HFO-1234ze, and R744.
• the main component of the refrigerant is a component selected from HFO-1234yf, HFO-1234ze, and R744.
• the total amount is the total amount.
• "main component” means a component that accounts for more than 50% by mass (upper limit 100% by mass) of the total mass of the refrigerant (100% by mass).
• the content of the other refrigerants is preferably 1% by mass or more but less than 50% by mass, more preferably 2% by mass or more but less than 40% by mass, even more preferably 3% by mass or more but less than 35% by mass, particularly preferably 5% by mass or more but less than 25% by mass, and most preferably 10% by mass or more but less than 20% by mass, relative to the total mass (100% by mass) of HFO-1234yf, HFO-1234ze, and R744.
• the content of the other refrigerants is the total amount.
• 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). According to another embodiment, the refrigerant consists of one selected from HFO-1234yf, HFO-1234ze, and R744.
• 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.
• 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.
• the base oil in the 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.
• HFO-1234yf and HFO-1234ze easily decompose to produce hydrofluoric acid (HF), a strong acid. Therefore, when using HFO-1234yf and HFO-1234ze as refrigerants, high stability is required of the refrigeration oil.
• the inventors reasoned that an ester with low solubility in water might provide good stability even when using HFO-1234yf and/or HFO-1234ze as refrigerants.
• the aliphatic esters commonly used in refrigeration oils are too miscible with HFO-1234yf and HFO-1234ze. In this case, the refrigeration oil dissolves too much in HFO-1234yf and HFO-1234ze, resulting in a thinner oil film formed on sliding parts and reduced lubricity.
• aromatic esters which are commonly used as plasticizers, have moderate compatibility with HFO-1234yf and HFO-1234ze. While aromatic esters are known to have low compatibility with fluorinated refrigerants such as HFCs (hydrofluorocarbons), the inventors discovered that certain aromatic esters have suitable compatibility with HFO-1234yf and HFO-1234ze.
• the aromatic ester according to this embodiment has high electrical insulation properties. Therefore, refrigeration oils containing the aromatic ester according to this embodiment have high electrical insulation properties.
• Benzenetricarboxylic acid (C 6 H 3 (COOH) 3 ) is trimellitic acid (1,2,4-benzenetricarboxylic acid) or trimesic acid (1,3,4-benzenetricarboxylic acid).
• Phthalic acid (C 6 H 4 (COOH) 2 ) includes ortho-phthalic acid, meta-isophthalic acid, and para-terephthalic acid, of which ortho-phthalic acid is preferred from the viewpoints of low-temperature properties and hydrolysis stability.
• aromatic esters used in this embodiment 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 depends on the required viscosity. Two or more types may be mixed to match the viscosity.
• the conditions for reacting benzenetricarboxylic acid and/or phthalic acid with an alcohol having 4 to 12 carbon atoms to obtain the aromatic ester of this embodiment are not particularly limited, and general conditions employed by those skilled in the art for esterification can be used as appropriate.
• the kinematic viscosity of the aromatic ester according to this embodiment at 40°C is preferably 2 mm2 /s or more and 200 mm2 /s or less, more preferably 3 mm2 /s or more and 150 mm2 /s or less, preferably 5 mm2 /s or more and 150 mm2 /s or less, more preferably 10 mm2 /s or more and 120 mm2/s or less, even more preferably 15 mm2 /s or more and 100 mm2 /s or less, particularly preferably 20 mm2 /s or more and 95 mm2 /s or less, and most preferably 25 mm2 / s or more and 90 mm2 /s or less.
• the viscosity resistance of the refrigerating machine oil can be adjusted to an appropriate range, improving the efficiency of the refrigerant compression refrigeration/heating cycle device.
• the aromatic ester of this embodiment preferably has a pour point of -10°C or less, more preferably -20°C or less, even more preferably -25°C or less, and particularly preferably -30°C or less. If the pour point of the aromatic ester is -10°C or less, it can be suitably used as a liquid.
• the aromatic ester according to the present invention preferably has a volume resistivity of 0.2 ⁇ 10 ⁇ cm or more, more preferably 0.5 ⁇ 10 ⁇ cm or more, and even more preferably 1.0 ⁇ 10 ⁇ cm or more. From a practical standpoint, the upper limit of the volume resistivity of the aromatic ester according to the present invention is preferably 1000.0 ⁇ 10 ⁇ cm or less. The volume resistivity is measured by the method described in the Examples below.
• 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, per 100 parts by mass of the refrigerating machine oil.
• the content of aromatic ester in the refrigerating machine oil may be 98% by mass or more, or 99% by mass or more, per 100 parts by mass of the refrigerating machine oil.
• the refrigerating machine oil may be composed solely of aromatic ester; therefore, the upper limit of the content of aromatic ester in the refrigerating machine oil is 100% by mass, per 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 achieved.
• 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.
• 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.
• 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.
• Additives include oiliness agents, stability improvers, antioxidants, anti-wear agents, metal deactivators, and anti-foaming agents.
• oily agents examples include monohydric alcohols; higher fatty acids; esters other than aromatic esters synthesized from benzenetricarboxylic acid and/or phthalic acid and alcohols having 4 to 12 carbon atoms (hereinafter referred to as "other esters"); ethers such as polyalkylene glycols (e.g., polyethylene glycol, polypropylene glycol) and polyvinyl ether; hydrocarbon-based oils such as alkylbenzenes, polyolefins, and mineral oils; etc.
• other esters such as polyalkylene glycols (e.g., polyethylene glycol, polypropylene glycol) and polyvinyl ether
• hydrocarbon-based oils such as alkylbenzenes, polyolefins, and mineral oils
• 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 are preferred from the standpoint of hydrolytic stability, and esters of neopentyl glycol and carboxylic acids (e.g., 2-ethylhexanoic acid) are more preferred due to their small molecular weight and low viscosity.
• esters of neopentyl glycol and carboxylic acids e.g., 2-ethylhexanoic acid
• Refrigerating machine oils may further contain a stability improver as an additive to further enhance the stability of the working medium of the refrigerant and refrigerating machine oil during actual use.
• a stability improver 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.
• 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 properties 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.
• aromatic esters do not dissolve excessively in the refrigerant.
• the refrigerating machine oil of the present invention has excellent compatibility with the refrigerant (appropriate compatibility with the refrigerant), and therefore a working fluid containing the refrigerating machine oil of the present invention can exhibit good performance even with a small amount of refrigerant charged.
• 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).
• refrigerant compression refrigeration and heating cycle devices e.g., air conditioners such as car air conditioners and room air conditioners, and water heaters.
• Working fluids containing refrigerating machine oil with a good balance of properties can exhibit good performance.
• Refrigerating machine oil is typically present in the form of a working fluid mixed with the refrigerant described above in refrigerant compression refrigeration/heating cycle devices.
• 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 refrigerant.
• 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 refrigerant.
• 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 refrigerant.
• 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.
• HFO-1234yf 2,3,3,3-tetrafluoropropene
• 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.
• 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.
• the kinematic viscosity of the working fluid at 40°C is preferably 1 mm 2 /s or more and 200 mm 2 /s or less, more preferably 2 mm 2 /s or more and 150 mm 2 /s or less, even more preferably 5 mm 2 /s or more and 120 mm 2 /s or less, particularly preferably 10 mm 2 /s or more and 100 mm 2 /s or less, and most preferably 15 mm 2 /s or more and 90 mm 2 /s or less.
• the kinematic viscosity of the working fluid at 40°C is 1 mm 2 /s or more and 70 mm 2 /s or less.
• the present invention includes the following aspects and configurations.
• a working medium 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 refrigeration oil containing an aromatic ester synthesized from benzenetricarboxylic acid and/or phthalic acid and an alcohol having 4 to 12 carbon atoms.
• refrigerants selected from 2,3,3,3-tetrafluoropropene (HFO-1234yf), 1,3,3,3-tetrafluoropropene (HFO-1234ze), and carbon dioxide (R744)
• a refrigeration oil containing an aromatic ester synthesized from benzenetricarboxylic acid and/or phthalic acid and an alcohol having 4 to 12 carbon atoms.
• 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.
• Refrigerating machine oils of Examples 1 to 4 and Comparative Examples 1 to 4 were prepared.
• Aromatic esters are primarily used as plasticizers for plastics, and when used as plasticizers, they do not need to be highly purified. As a result, aromatic esters sold as general-purpose products have low purity and must be purified when used as refrigeration oils. Therefore, the aromatic esters used in Examples 1 to 4 were evaluated using reagents from Tokyo Chemical Industry Co., Ltd.
• 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).
• tributyl trimellitate an ester of trimellitic acid and butanol (an alcohol having 4 carbon atoms)
• Example 3 Refrigerant oil (without additives) containing diisononyl phthalate (an ester of phthalic acid and isononyl alcohol (an alcohol having 9 carbon atoms)) (100% by mass based on the total mass of the refrigerant oil) as a base oil.
• diisononyl phthalate an ester of phthalic acid and isononyl alcohol (an alcohol having 9 carbon atoms)
• 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 based on the total mass of the refrigerating machine oil); and 4,4'-thiobis(2-methyl-6-tert-butylphenol) (0.2% by mass based on the total mass of the refrigerating machine oil), p,p'-di-octyl-diphenylamine (0.5% by mass based on the total mass of the refrigerating machine oil), and glycerol monooleate (0.2% by mass based on the total mass of the refrigerating machine oil) as additives.
• diundecyl phthalate an ester of phthalic acid and undecyl alcohol (an alcohol having 11 carbon atoms)
• base oil 99.1% by mass based on the total mass of the refrigerating machine oil
• Refrigerant oil (without additives) containing a 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).
• a polyol ester ester of pentaerythritol (a tetrahydric alcohol having 5 carbon atoms) and 2-ethylhexanoic acid
• the viscosity grade refers to the kinematic viscosity at 40°C.
• the viscosity grade can be measured using the kinematic viscosity measurement method described below (kinematic viscosity at 40°C ( ⁇ 10%)).
• Table 1 shows that the aromatic esters of Examples 1 to 4 are well-balanced refrigeration oils with excellent electrical insulation, low-temperature fluidity (pour point), thermal and chemical stability, and phase separation temperature.
• Examples 2 and 4 which contain additives, do not show an increase in acid value and have extremely good thermal and chemical stability.
• the mineral oil and alkylbenzene of Comparative Examples 1 and 2 are incompatible with HFO-1234yf (they separate into two layers), and it is suspected that this could cause problems with oil returning to the compressor in refrigerant compression refrigeration and 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), making it unsuitable for refrigerant compression refrigeration and heating cycle equipment that is used maintenance-free (without oil changes) for long periods of time.
• the polypropylene glycol of Comparative Example 4 has a low volume resistivity, which could cause leakage current in hermetic compressors with built-in motors.
• a working fluid for a refrigerant compression type refrigeration/heating cycle device which has a good balance of high stability, suitable compatibility with the refrigerant, high electrical insulation, and low low-temperature fluidity.

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• 2024
  • 2024-03-28 WO PCT/JP2024/012723 patent/WO2025203454A1/ja active Pending

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