Working medium for refrigeration cycle and refrigeration cycle system

Abstract

To achieve further reduction of environmental impact in a working medium for a refrigeration cycle that contains a fluoroolefin as a refrigerant component and also contains a disproportionation inhibitor.SOLUTION: This working medium for a refrigeration cycle contains, as a refrigerant component, a fluoroolefin in which a disproportionation reaction occurs, and also contains an ether compound, which is a hydrohaloether, a haloether, or a hydroether, as a disproportionation inhibitor that suppresses the disproportionation reaction in the fluoroolefin. The ether compound can be, for example, an ether having 2 or 3 carbons.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a working fluid for a refrigeration cycle capable of effectively suppressing or mitigating the disproportionation reaction of fluoroolefins (fluoroalkenes) such as 1,1,2-trifluoroethylene, and a refrigeration cycle system using the same. [Background technology]

[0002] HCFCs (hydrochlorofluorocarbons) were previously used as working fluids (refrigerants or heat transfer media) for refrigeration cycles, but HCFCs have a significant impact on ozone depletion. Therefore, in recent years, HFCs (hydrofluorocarbons), which have an ozone depletion potential (ODP) of zero, have been used. Among these HFCs, the use of fluoroolefins, especially hydrofluoroolefins (HFOs), which have a smaller global warming potential (GWP), has been proposed in recent years.

[0003] Representative HFOs include, for example, 1,1,2-trifluoroethylene (HFO1123) and difluoroethylene (HFO1132). These HFOs are less stable than conventional HFCs and are therefore less likely to remain in the atmosphere, and therefore have low ODP and GWP. However, it is also known that the low stability of HFOs makes them prone to self-polymerization reactions known as disproportionation reactions (hereinafter referred to as disproportionation reactions).

[0004] It is known that the disproportionation reaction is likely to occur due to the heat generated during the use of the working fluid for the refrigeration cycle, and since the disproportionation reaction is accompanied by a large heat release, the disproportionation reaction may occur in a chain reaction, resulting in the generation of a large amount of soot, which may reduce the reliability of the refrigeration cycle system or the compressor constituting the system.

[0005] Therefore, when, for example, 1,1,2-trifluoroethylene is used as a refrigerant component of a working fluid for a refrigeration cycle, the applicant has proposed, as a component (disproportionation inhibitor) for suppressing the disproportionation reaction of 1,1,2-trifluoroethylene, halomethane (Patent Document 1), saturated hydrocarbons (Patent Document 2), haloethane (Patent Document 3), a combination of these (Patent Document 4 or Patent Document 5), or difluoroiodomethane (Patent Document 6) as a representative example of a particularly suitable disproportionation inhibitor.

[0006] It is also known that difluoromethane (HFC32, R32) can be used in combination with 1,1,2-trifluoroethylene as a refrigerant component (R32 is a refrigerant number based on Standard 34 of the American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE)). For example, Patent Documents 1 to 4 disclose that the main refrigerant component is 1,1,2-trifluoroethylene, but that difluoromethane can also be used in combination, and Patent Documents 5 and 6 disclose the use of 1,1,2-trifluoroethylene (or a fluoroolefin) and difluoromethane in combination as refrigerant components. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2017-145380 A [Patent Document 2] JP 2018-048271 A [Patent Document 3] JP 2018-104565 A [Patent Document 4] JP 2018-104566 A [Patent Document 5] JP 2019-034983 A [Patent Document 6] JP 2021-161316 A Summary of the Invention [Problem to be solved by the invention]

[0008] The above-mentioned disproportionation inhibitor can effectively inhibit or mitigate the disproportionation reaction of fluoroolefins such as 1,1,2-trifluoroethylene. Even when difluoromethane is used in combination as a refrigerant component, the above-mentioned disproportionation inhibitor can effectively inhibit or mitigate the disproportionation reaction of fluoroolefins.

[0009] In recent years, there has been a trend toward requiring such working fluids for refrigeration cycles to not only effectively inhibit or mitigate the disproportionation reaction of fluoroolefins, but also to further reduce the environmental load.

[0010] The present invention has been made to solve the above problems, and an object of the present invention is to further reduce the environmental load in a working fluid for a refrigeration cycle which contains a fluoroolefin as a refrigerant component and also contains a disproportionation inhibitor. [Means for solving the problem]

[0011] Means for Solving the Problems The present inventors have conducted intensive research to solve the above problems and have independently discovered that hydrohaloethers or hydroethers, which have been considered as refrigerant components up to now, can effectively inhibit or mitigate the disproportionation reaction of fluoroolefins and can further reduce the environmental load, thereby completing the present invention.

[0012] In order to solve the above-mentioned problems, the working fluid for a refrigeration cycle according to the present disclosure contains, as a refrigerant component, a fluoroolefin that undergoes a disproportionation reaction, and also contains, as a disproportionation inhibitor that suppresses the disproportionation reaction of the fluoroolefin, an ether compound which is a hydrohaloether, a haloether or a hydroether.

[0013] According to the above-mentioned configuration, the working fluid for a refrigeration cycle containing a fluoroolefin in which a disproportionation reaction occurs contains a hydrohaloether, a haloether or a hydroether as a disproportionation inhibitor. These ether compounds can effectively inhibit or mitigate the disproportionation reaction of the fluoroolefin.

[0014] Moreover, many of these ether compounds can be used as refrigerant components, and therefore, since they have good heat capacities comparable to those of fluoroolefins and can be easily mixed with fluoroolefins, they are suitable as mixing components for working fluids for refrigeration cycles.

[0015] Furthermore, these ether compounds have a relatively low global warming potential (GWP) and an ozone depletion potential (ODP) of almost zero, so that their environmental impact is relatively small.

[0016] Therefore, according to the above-mentioned configuration, the disproportionation reaction of fluoroolefins can be effectively suppressed or alleviated, the energy efficiency of the working fluid for a refrigeration cycle can be improved, and further the environmental load can be reduced.

[0017] The present disclosure also includes a refrigeration cycle system configured using the working medium for a refrigeration cycle having the above-described configuration. Effect of the Invention

[0018] The present invention has the above-mentioned configuration, and has an effect of further reducing the environmental load in a working fluid for a refrigeration cycle that contains a fluoroolefin as a refrigerant component and also contains a disproportionation inhibitor. [Brief description of the drawings]

[0019]

Figure 1

[0020] The working fluid for a refrigeration cycle according to the present disclosure contains, as a refrigerant component, a fluoroolefin that undergoes a disproportionation reaction, and contains, as a disproportionation inhibitor that suppresses the disproportionation reaction of the fluoroolefin, an ether compound which is a hydrohaloether, a haloether or a hydroether.

[0021] According to the above-mentioned configuration, the working fluid for a refrigeration cycle containing a fluoroolefin in which a disproportionation reaction occurs contains a hydrohaloether, a haloether or a hydroether as a disproportionation inhibitor. These ether compounds can effectively inhibit or mitigate the disproportionation reaction of the fluoroolefin.

[0022] Moreover, many of these ether compounds can be used as refrigerant components, and therefore, since they have good heat capacities comparable to those of fluoroolefins and can be easily mixed with fluoroolefins, they are suitable as mixing components for working fluids for refrigeration cycles.

[0023] Furthermore, these ether compounds have a relatively low global warming potential (GWP) and an ozone depletion potential (ODP) of almost zero, so that their environmental impact is relatively small.

[0024] Therefore, according to the above-mentioned configuration, the disproportionation reaction of fluoroolefins can be effectively suppressed or alleviated, the energy efficiency of the working fluid for a refrigeration cycle can be improved, and further the environmental load can be reduced.

[0025] In the working fluid for a refrigeration cycle having the above-described configuration, the ether compound is represented by the following formula (1): C 2 H m X n O (1) (In the formula (1), the oxygen atom (O) constitutes an ether bond (-O-), X is any halogen atom selected from the group consisting of F, Cl, Br, and I, m and n are each an integer of 0 or more, the sum of m and n is 6, and further, when n is 2 or more, X is the same or different halogen atom.) The compound may be an ether having two carbon atoms and having the structure shown in the following formula:

[0026] In the working fluid for a refrigeration cycle having the above-mentioned configuration, the ether compound is represented by the following formula (2): C 3 H p X q O (2) (In the formula (2), the oxygen atom (O) constitutes an ether bond (-O-), X is any halogen atom selected from the group consisting of F, Cl, Br, and I, p and q are each an integer of 0 or more, the sum of p and q is 6 or 8, when the sum of p and q is 6, one carbon-carbon double bond is contained, and further, when q is 2 or more, X is the same or different halogen atom.) The compound may be an ether having three carbon atoms and having the structure shown in the following formula:

[0027] In the working fluid for a refrigeration cycle having the above-mentioned configuration, the hydrohaloether is 1,2,2,2-tetrafluoroethyl trifluoromethyl ether (HFE227ea, CF 3 -O-CFH-CF 3 ) or iodomethyl methyl ether (CH 2 IO-CH 3 ), and the haloether is trifluorovinyl trifluoromethyl ether (HFE216, CF 3 -O-CF=CF 2 ), and the hydroether is dimethyl ether (CH 3 -O-CH 3 ) or ethyl methyl ether (CH 3 -OC 2 H 5 ) may be used.

[0028] In the working fluid for a refrigeration cycle having the above configuration, the fluoroolefin in which the disproportionation reaction occurs may be 1,1,2-trifluoroethylene or difluoroethylene.

[0029] The working fluid for a refrigeration cycle having the above-mentioned configuration may further contain difluoromethane (R32) as a refrigerant component.

[0030] In addition, in the working fluid for a refrigeration cycle having the above configuration, when the hydrofluoroolefin is used as the main disproportionation inhibitor, the disproportionation inhibitor may further contain at least one secondary disproportionation inhibitor selected from the group consisting of (i) haloalkanes having 1 or 2 carbon atoms excluding those in which all of the halogen atoms are fluorine, (ii) fluoroalkanes having 1 to 3 carbon atoms (excluding difluoromethane) and having a boiling point of 0°C or lower, and (iii) saturated hydrocarbons having 2 to 5 carbon atoms.

[0031] In the working fluid for a refrigeration cycle having the above configuration, the content of the ether compound may be 30% by mass or less when the total amount of the refrigerant components and the disproportionation inhibitor is taken as 100% by mass.

[0032] In the working fluid for a refrigeration cycle having the above configuration, the difluoromethane content may be 30% by mass or less when the total amount of the refrigerant components and the disproportionation inhibitor is taken as 100% by mass.

[0033] In addition, in the working fluid for a refrigeration cycle having the above configuration, the content of the secondary disproportionation inhibitor may be 10 mass% or less when the total amount of the refrigerant components and the disproportionation inhibitor is 100 mass%.

[0034] The present disclosure also includes a refrigeration cycle system configured using a working medium for a refrigeration cycle having any of the above configurations.

[0035] Representative embodiments of the working fluid for a refrigeration cycle according to the present disclosure and representative applications thereof will be specifically described below.

[0036] [Refrigerant components] The working fluid for a refrigeration cycle according to the present disclosure uses, as a refrigerant component, at least a fluoroolefin (fluoroalkene) capable of causing a disproportionation reaction.

[0037] Specific examples of fluoroolefins that undergo disproportionation include 1,1,2-trifluoroethylene (CF 2 =CHF,HFO1123), trans-1,2-difluoroethylene (CHF=CHF(E),HFO1132(E)), cis-1,2-difluoroethylene (CHF=CHF(Z),HFO1132(Z)), 1,1-difluoroethylene (CF 2 =CH 2 ,HFO1132a), tetrafluoroethylene (CF 2 =CF 2 , FO1114), etc. These fluoroolefins may be used as the refrigerant component either alone or in combination of two or more.

[0038] These fluoroolefins have a backbone ethylene structure, i.e., a double bond between carbon atoms, and have a chemical structure in which at least one of the two hydrogen atoms bonded to one carbon atom is replaced by a fluorine atom, or at least one of the two hydrogen atoms bonded to both carbon atoms is replaced by a fluorine atom. Note that in the fluoroolefins, some of the hydrogen atoms may be replaced by other atoms or other substituents.

[0039] For example, 1,1,2-trifluoroethylene has a structure in which both of the two hydrogen atoms bonded to one carbon atom of the ethylene structure (the carbon atom at position 1) are replaced by fluorine atoms, and one of the two hydrogen atoms bonded to the other carbon atom (the carbon atom at position 2) is replaced by a fluorine atom.

[0040] Alternatively, trans-1,2-difluoroethylene has a structure in which one of the two hydrogen atoms bonded to the carbon atom at position 1 of the ethylene structure is substituted with a fluorine atom, and of the two hydrogen atoms bonded to the carbon atom at position 2, only the hydrogen atom facing the carbon atom at position 1 across the double bond, not the hydrogen atom adjacent to the carbon atom at position 2, is substituted with a fluorine atom.

[0041] As mentioned above, such fluoroolefins contain an ethylene skeleton, i.e., a carbon-carbon double bond, and this double bond is easily decomposed. That is, ozone in the atmosphere generates hydroxyl radicals (OH radicals) through photochemical reactions, and these hydroxyl radicals can cause addition reactions with double bonds, making fluoroolefins easily decomposed. Therefore, fluoroolefins have little impact on ozone layer destruction and global warming.

[0042] The working fluid for a refrigeration cycle according to the present disclosure contains, as a refrigerant component, difluoromethane (HFC32, R32, chemical formula: CH) in addition to fluoroolefins. 2 F 2 In this case, if the fluoroolefin is considered to be the "main component (principal refrigerant component)" of the refrigerant components in the working fluid for a refrigeration cycle according to the present disclosure, the difluoromethane is considered to be the "secondary component (secondary refrigerant component)" of the refrigerant components in the working fluid for a refrigeration cycle according to the present disclosure.

[0043] As mentioned above, difluoromethane has an ozone depletion potential (ODP) of 0 and has good refrigerant performance compared to the HCFCs (hydrochlorofluorocarbons) that have been used up until now.

[0044] In addition, the working fluid for a refrigeration cycle according to the present disclosure may contain, as a refrigerant component, "other refrigerant components" in addition to the fluoroolefin as the main refrigerant component and difluoromethane as the secondary refrigerant component. Representative examples of the other refrigerant components include hydrofluorocarbons (HFCs) such as difluoroethane, trifluoroethane, tetrafluoroethane, pentafluoroethane, pentafluoropropane, hexafluoropropane, heptafluoropropane, pentafluorobutane, and heptafluorocyclopentane; hydrofluoroolefins (HFOs) such as monofluoropropene, trifluoropropene, tetrafluoropropene, pentafluoropropene, and hexafluorobutene, but are not particularly limited thereto.

[0045] These HFCs or HFOs are known to have little impact on ozone depletion and global warming, and can therefore be used together with fluoroolefins, or fluoroolefins and difluoromethane, as refrigerant components. The other refrigerant components mentioned above may be used alone or in appropriate combination of two or more.

[0046] Here, it is also known that fluoroolefins cause rapid disproportionation reactions due to the good decomposability described above. Taking 1,1,2-trifluoroethylene as a representative example of fluoroolefins, in this disproportionation reaction, an auto-decomposition reaction occurs in which the molecules of 1,1,2-trifluoroethylene decompose, and following this auto-decomposition reaction, a polymerization reaction occurs in which the carbon generated by the decomposition polymerizes to become soot. When active radicals are generated due to heat generation or the like in a high-temperature and high-pressure state, the active radicals react with 1,1,2-trifluoroethylene to cause the above-mentioned disproportionation reaction. Since this disproportionation reaction is accompanied by heat generation, active radicals are generated by the heat generation, and further, the active radicals induce the disproportionation reaction. In this way, the generation of active radicals and the generation of the disproportionation reaction are linked together, and the disproportionation reaction progresses rapidly.

[0047] The applicant's previous intensive research has revealed that the active radicals that induce the disproportionation reaction of 1,1,2-trifluoroethylene are mainly fluorine radicals (F radicals) and trifluoromethyl radicals (CF 3 radical), difluoromethylene radical (CF 2 It was revealed that the radicals were aryl radicals.

[0048] Therefore, the applicants have demonstrated that, under conditions in which difluoromethane is used in combination with a fluoroolefin such as 1,1,2-trifluoroethylene, which undergoes a disproportionation reaction, as a refrigerant component, F radicals, CF 3 Radical, CF 2 We attempted to suppress or mitigate the rapid disproportionation reaction by adding a substance (disproportionation inhibitor) capable of efficiently capturing radicals, etc., to a working fluid for a refrigeration cycle. As a result, we independently found that the addition of the disproportionation inhibitors disclosed in Patent Documents 1 to 6 can be suitable disproportionation inhibitors.

[0049] As a result of further intensive research by the present inventors, it has been newly discovered that an ether compound which is a hydrohaloether, a haloether or a hydroether can effectively inhibit the disproportionation reaction of a fluoroolefin.

[0050] [Disproportionation inhibitor] 1. Main disproportionation inhibitor The working fluid for a refrigeration cycle according to the present disclosure contains an ether compound which is a hydrohaloether, a haloether or a hydroether as a disproportionation inhibitor for suppressing the disproportionation reaction of the fluoroolefin which is the main refrigerant component. In the present embodiment, unless otherwise specified, the ether compound refers to the hydrohaloether, the haloether or the hydroether as the disproportionation inhibitor.

[0051] As described later, the working fluid for a refrigeration cycle according to the present disclosure may contain other disproportionation inhibitors in addition to the ether compounds. Therefore, in this embodiment, for the sake of convenience, the disproportionation inhibitor HFO is referred to as the "main component (main disproportionation inhibitor)" of the disproportionation inhibitor, and the other disproportionation inhibitors other than the ether compounds are referred to as the "secondary component (secondary disproportionation inhibitor)" of the disproportionation inhibitor.

[0052] The main disproportionation inhibitor used in the working fluid for a refrigeration cycle according to the present disclosure may be a hydrohaloether, a fluoroether or a hydroether.

[0053] In the present disclosure, a hydrohaloether is a compound that is a divalent aryl group consisting of two organic groups ("R 1 -OR 2 "R in 1 and R 2 ) in which at least one hydrogen atom is substituted with a halogen atom and all hydrogen atoms are not substituted with halogen atoms. In other words, the hydrohaloether may be a compound in which a hydrogen atom bonded to a carbon atom and a halogen atom bonded to a carbon atom coexist in two organic groups bonded to each other by an ether bond. In addition, the haloether in the present disclosure may be a compound in which all hydrogen atoms are substituted with halogen atoms in two organic groups bonded to each other by an ether bond.

[0054] On the other hand, a hydroether is a compound in which none of the hydrogen atoms in two organic groups bonded together via an ether bond is replaced with another substituting element such as a halogen atom, i.e., a general "ether compound." In the present disclosure, for the convenience of clarifying the distinction from hydrohaloethers or haloethers, a general "ether compound" is referred to as a "hydroether."

[0055] The specific type of the ether compound that is the main disproportionation inhibitor is not particularly limited, but representative examples include ethers having a carbon number of 2 or ethers having a carbon number of 3. Of these, the ethers having a carbon number of 2 may be compounds having the structure of the following formula (1). C 2 H m X n O (1)

[0056] In the formula (1), the oxygen atom (O) forms an ether bond (-O-), X is a halogen atom selected from the group consisting of F, Cl, Br, and I, m and n are each an integer of 0 or more, the sum of m and n is 6, and further, when n is 2 or more, X is the same or different halogen atom.

[0057] In other words, the ether having two carbon atoms shown in formula (1) becomes a haloether having two carbon atoms when m is 0, becomes a hydroether having two carbon atoms when n is 0, and becomes a hydrohaloether having two carbon atoms when both m and n are integers other than 0.

[0058] The ether having 3 carbon atoms may be a compound having the structure of formula (2) shown below. C 3 H p X q O (2)

[0059] In the formula (2), the oxygen atom (O) forms an ether bond (-O-), X is any halogen atom selected from the group consisting of F, Cl, Br, and I, p and q are each an integer of 0 or more, the sum of p and q is 6 or 8, when the sum of p and q is 6, one carbon-carbon double bond is contained, and further, when q is 2 or more, X is the same or different halogen atom.

[0060] In other words, the ether having three carbon atoms shown in formula (2) becomes a haloether having three carbon atoms when p is 0, becomes a hydroether having three carbon atoms when q is 0, and becomes a hydrohaloether having three carbon atoms when both p and q are integers other than 0.

[0061] Specific examples of compounds corresponding to the ether having 2 or 3 carbon atoms include trifluoromethyl difluoromethyl ether (HFE125, CF 3 -O-CF 2 H), bis(difluoromethyl)ether (HFE134a,CF 2 HO-CF 2 H), trifluoromethyl methyl ether (HFE143a, CF 3 -O-CH 3 ), trifluorovinyl trifluoromethyl ether (HFE216, CF 3 -O-CF=CF 2 ), 1,2,2,2-tetrafluoroethyl trifluoroether (HFE227ea,CF 3 -O-CFH-CF 3 ), 2,2,2-trifluoroethyl trifluoromethyl ether (HFE236fa, CF 3 -O-CH 2 -CF 3 ), hydrofluoroether (HFE) compounds; 3 -O-CH 3 ), ethyl methyl ether (CH 3 -OC 2 H 5 ) and other hydroether (HE) compounds; iodomethyl methyl ether (CH 3 -O-CH 2 I), bromomethyl methyl ether (CH 3 -O-CH 2 Hydrohaloether compounds such as, but not limited to, Br. Only one of these compounds may be used as the main disproportionation inhibitor, or two or more of them may be used in combination as the main disproportionation inhibitor.

[0062] Among these compounds, 1,2,2,2-tetrafluoroethyl trifluoromethyl ether (HFE227ea), iodomethyl methyl ether, trifluorovinyl trifluoromethyl ether (HFE216), dimethyl ether, ethyl methyl ether, and the like can be more preferably used as the main disproportionation inhibitor.

[0063] In addition, 1,2,2,2-tetrafluoroethyl trifluoromethyl ether (HFE227ea) and iodomethyl methyl ether are classified as hydrohaloethers because hydrogen atoms bonded to carbon atoms and halogen atoms (substitution of hydrogen atoms) bonded to carbon atoms coexist in the molecular structure. In addition, dimethyl ether and ethyl methyl ether are classified as hydroethers because none of the hydrogen atoms bonded to carbon atoms are replaced by other substitution elements such as halogen atoms.

[0064] On the other hand, trifluorovinyl trifluoromethyl ether (HFE216) corresponds to a haloether because all hydrogen atoms bonded to carbon atoms are replaced with fluorine atoms and unsubstituted hydrogen atoms and substituted fluorine atoms do not coexist. However, as a refrigerant component, trifluorovinyl trifluoromethyl ether (HFE216) is classified as a hydrofluoroether (HFE) type, as described above.

[0065] The working fluid for a refrigeration cycle according to the present disclosure contains at least the above-mentioned ether compound as a main disproportionation inhibitor in a fluoroolefin-containing working fluid for a refrigeration cycle that undergoes a disproportionation reaction. Such an ether compound can effectively inhibit or mitigate the disproportionation reaction of the fluoroolefin.

[0066] In particular, in the above-mentioned ether compounds, the oxygen atom constituting the ether bond attracts electrons due to the induction effect of the organic group, making it electron-rich. Therefore, it is expected to have an effect of effectively capturing active radicals that induce disproportionation reactions. In addition, the decomposition products generated by the dissociation of the carbon-oxygen bond (CO) in the ether bond are likely to react with active radicals. Therefore, it is expected to have an effect of suppressing the induction of disproportionation reactions by active radicals, thereby stopping the chain reaction between the generation of active radicals and the occurrence of disproportionation reactions.

[0067] Furthermore, ethers generally have a higher ignition energy than alkanes (saturated hydrocarbons) with the same carbon number. Therefore, by including an ether compound as a primary disproportionation inhibitor, the flammability of the working fluid for the refrigeration cycle can be effectively suppressed. In addition, by adjusting the content of the ether compound according to the type of secondary disproportionation inhibitor used in combination, it is also possible to adjust the ignition energy so as to suppress the flammability of the working fluid for the refrigeration cycle.

[0068] Moreover, many of these ether compounds can be used as refrigerant components, and therefore have good heat capacities comparable to those of fluoroolefins and are easily mixed with fluoroolefins, making them suitable as mixing components for working fluids for refrigeration cycles.

[0069] Furthermore, such ether compounds have a relatively low global warming potential (GWP) and an ozone depletion potential (ODP) of almost zero, and therefore pose a relatively small environmental burden.

[0070] Therefore, even if the working fluid for a refrigeration cycle according to the present disclosure contains, as a refrigerant component, a fluoroolefin which undergoes a disproportionation reaction, the disproportionation reaction can be suppressed or mitigated, the energy efficiency can be improved, and further the environmental load can be reduced.

[0071] 2. Sub - disproportionation inhibitor (i) In the present disclosure, as the minor disproportionation inhibitor, first, (i) haloalkanes other than those having 1 or 2 carbon atoms and all halogen atoms being fluorine (fluoroalkanes) can be used. For convenience of explanation, "haloalkanes other than those having 1 or 2 carbon atoms and all halogen atoms being fluorine (fluoroalkanes)" will be simply referred to as "(i) haloalkane." In this way, by using an ether compound as the main disproportionation inhibitor in combination with (i) haloalkane as the minor disproportionation inhibitor, it is possible to suppress or mitigate the progress of the disproportionation reaction even with a smaller amount.

[0072] The (i) haloalkane used as the secondary disproportionation inhibitor in the present disclosure may be any haloalkane having one or two carbon atoms, excluding those in which all halogen atoms are fluorine (fluoroalkanes). More specifically, examples include haloalkanes having two carbon atoms, i.e., haloethane (halogenated ethane), and haloalkanes having one carbon atom, i.e., halomethane (halogenated methane). As the disproportionation inhibitor, either haloethane or halomethane may be used in combination with the above-mentioned saturated hydrocarbon, but both haloethane and halomethane may also be used in combination.

[0073] The haloethane among the haloalkanes (i) used as the secondary disproportionation inhibitor may specifically be any haloethane having the structure of the following formula (3). C 2 H r X s ... (3)

[0074] In the formula (3), X is a halogen atom selected from the group consisting of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I); r is an integer of 0 or more and s is an integer of 1 or more; the sum of r and s is 6; and when s is 2 or more, X is the same or different halogen atom.

[0075] In other words, the haloethane shown in formula (3) may be at least one of a monohaloethane shown in formula (31) below, a dihaloethane shown in formula (32) below, a trihaloethane shown in formula (33) below, a tetrahaloethane shown in formula (34) below, a pentahaloethane shown in formula (35) below, and a hexahaloethane shown in formula (36) below.

[0076] X in the haloethanes shown in formulas (31) to (36) 1 ,X 2 ,X 3 ,X 4 ,X 5 , and X 6 Each independently represents one halogen atom. Therefore, X 1 ~X 6 may be different types of halogen atoms, at least two of them may be the same type and the others may be different types of halogen atoms, or all of them may be the same type of halogen atoms. CH 2 X 1 CH 3 (31) CHX 1 X 2 CH 3 ... (32) CX 1 X 2 X 3 CH 3 ... (33) CX 1 X 2 X 3 CH 2 X 4 ... (34) CX 1 X 2 X 3 CHX 4 X 5 ... (35) CX 1 X 2 X 3 CX 4 X 5 X 6 ... (36)

[0077] However, the haloethane represented by the formula (3) does not include those in which X is composed only of F. This is because haloethane in which X is composed only of F corresponds to a fluoroalkane having 1 to 3 carbon atoms (a fluoroalkane having 2 carbon atoms, i.e., fluoroethane) used as the minor disproportionation inhibitor (ii) described later.

[0078] In the haloethane shown in formula (3), the halogen atom X may be at least one of F, Cl, Br, and I as described above (except for the case of only F), and among them, it is preferable that the halogen atom X is F and I, or the halogen atom X is I. When the haloethane shown in formula (3) contains Cl and / or Br, the ozone depletion potential (ODP) tends to be high, so that the availability or handling may be restricted. In addition, regardless of the type of the halogen atom X, the haloethane shown in formula (3) also includes compounds with relatively high ozone depletion potential (ODP) and / or global warming potential (GWP).

[0079] However, in the working fluid for a refrigeration cycle according to the present disclosure, since the main disproportionation inhibitor is an ether compound, the amount of haloethane added as a secondary disproportionation inhibitor is relatively small, as described below. Even when multiple types of disproportionation inhibitors are used in combination, the total amount of disproportionation inhibitors added is sufficiently small compared with the refrigerant components. Therefore, even if haloethane with a relatively large ODP or GWP is used, there is no significant impact on the environment.

[0080] The specific haloethane shown in formula (3) is not particularly limited, but for example, 1,1,1-trifluoro-2-iodoethane (CF 3 CH 2 I), monoiodoethane (CH 3 CH 2 I), monobromoethane (CH 3 CH 2 Br), 1,1,1-triiodoethane (CH 3 CI 3) and the like. These haloethanes may be used alone or in combination of two or more. Among these, 1,1,1-trifluoro-2-iodoethane (CF 3 CH 2 I) can be particularly preferably used.

[0081] Of the (i) haloalkanes used as the minor disproportionation inhibitor, the halomethane may specifically be one having the structure of the following formula (4). CH v X w (4)

[0082] In the formula (4), X is a halogen atom selected from the group consisting of F, Cl, Br, and I, v is an integer of 0 or more and w is an integer of 1 or more, the sum of v and w is 4, and when w is 2 or more, X is the same or different halogen atom.

[0083] That is, the halomethane shown in formula (4) may be at least one of the monohalomethane shown in formula (41), the dihalomethane shown in formula (42), the trihalomethane shown in formula (43), and the tetrahalomethane shown in formula (44). X in the halomethanes shown in formulas (41) to (44) 1 ,X 2 ,X 3 , and X 4 Each independently represents one halogen atom, just like the haloethane mentioned above. Therefore, X 1 ~X 4 may be different types of halogen atoms, at least two of them may be the same type and the others may be different types of halogen atoms, or all of them may be the same type of halogen atoms. CH 3 X 1 ... (41) CH 2 X 1 X 2 ... (42) CHX1 X 2 X 3 ... (43) CX 1 X 2 X 3 X 4 ... (44)

[0084] However, the halomethanes shown in formula (4) above exclude those in which X is composed only of F. This is because halomethanes in which X is composed only of F correspond to fluoroalkanes having 1 to 3 carbon atoms (fluoroalkanes having 2 carbon atoms, i.e., fluoroethane) used as the minor disproportionation inhibitor (ii) described below.

[0085] Specific examples of the halomethane represented by formula (4) include (mono)iodomethane (CH 3 I ), diiodomethane (CH 2 I 2 ), dibromomethane (CH 2 Br 2 ), bromomethane (CH 3 Br), dichloromethane (CH 2 Cl 2 ), chloroiodomethane (CH 2 ClI), dibromochloromethane (CHBr 2 Cl), tetraiodomethane (Cl 4 ), carbon tetrabromide (CBr 4 ), bromotrichloromethane (CBrCl 3 ), dibromodichloromethane (CBr 2 Cl 2 ), tribromofluoromethane (CBr 3 F), difluoroiodomethane (CHF 2 I), fluorodiiodomethane (CHFI 2 ), difluorodiiodomethane (CF 2 I 2 ), dibromodifluoromethane (CBr 2 F 2 ), trifluoroiodomethane (CF 3I) and the like can be mentioned, but are not particularly limited to these. These halomethanes may be used alone or in appropriate combination of two or more kinds.

[0086] Among these, more preferred halomethanes include those containing bromine as the halogen atom X, and more preferred halomethanes include dibromomethane (CH 2 Br 2 ), bromomethane (CH 3 Br), dibromodichloromethane (CBr 2 Cl 2 ), difluoroiodomethane (CHF 2 I ), or trifluoroiodomethane (CF 3 I ), and particularly preferred halomethanes include difluoroiodomethane (CHF 2 I) can be mentioned.

[0087] 3. Sub - disproportionation inhibitor (ii) In the present disclosure, the secondary disproportionation inhibitor may be (ii) a fluoroalkane having 1 to 3 carbon atoms (excluding difluoromethane) having a boiling point of 0° C. or less. The term "fluoroalkane having 1 to 3 carbon atoms" used herein refers to an alkane having 1 to 3 carbon atoms in which at least one hydrogen atom has been substituted with fluorine.

[0088] For ease of explanation, "a fluoroalkane having 1 to 3 carbon atoms and a boiling point of 0° C. or less (excluding difluoromethane)" is simply referred to as "(ii) fluoroalkane." In this way, by using an ether compound as the main disproportionation inhibitor in combination with (ii) a fluoroalkane as the secondary disproportionation inhibitor, it is possible to suppress the disproportionation reaction or slow down its progress even with a smaller amount.

[0089] Specific examples of such (ii) fluoroalkanes include fluoromethane (boiling point -78.2°C), difluoromethane (boiling point -51.6°C), trifluoromethane (boiling point -84.4°C), and tetrafluoromethane (boiling point -127.8°C); fluoroethane (boiling point -37.1°C), 1,1-difluoroethane (boiling point -24.7°C), 1,1,1-trifluoroethane (boiling point -47.2°C), and 1,1,1,2-tetrafluoroethane (boiling point -26.3°C); Examples of the fluoroethanes include 1,1,1,2,2-pentafluoroethane (boiling point: -48.5°C); fluoropropanes include 1-fluoropropane (boiling point: -2.5°C), 2-fluoropropane (boiling point: -10.0°C), 2,2-difluoropropane (boiling point: -1.0°C), 1,1,1-trifluoropropane (boiling point: -12.0°C), 1,1,2,2-tetrafluoropropane (boiling point: -0.8°C), and 1,1,1,3,3,3-hexafluoropropane (boiling point: -1.4°C). Only one of these (ii) fluoroalkanes may be used as the secondary disproportionation inhibitor, or two or more of them may be used in combination as the secondary disproportionation inhibitor.

[0090] Among these (ii) fluoroalkanes, particularly representative compounds include fluoroalkanes having 2 or 3 carbon atoms, i.e., fluoroethane (having 2 carbon atoms) or fluoropropane (having 3 carbon atoms). Among these, particularly representative (ii) fluoroalkanes include fluoropropane.

[0091] In the present disclosure, a fluoroethane that can be used as a minor disproportionation inhibitor is one in which one or more hydrogen atoms of ethane, an alkane having two carbon atoms, are substituted with fluorine atoms, and has a boiling point of 0° C. or lower. Similarly, a fluoropropane that can be used as a minor disproportionation inhibitor is one in which one or more hydrogen atoms of propane, an alkane having three carbon atoms, are substituted with fluorine atoms, and has a boiling point of 0° C. or lower.

[0092] In addition, in the present disclosure, only fluoroethane may be used as the (ii) fluoroalkane that is the side disproportionation inhibitor, only fluoropropane may be used as the (ii) fluoroalkane that is the side disproportionation inhibitor, or fluoroethane and fluoropropane may be combined and used as the (ii) fluoroalkane. When only fluoroethane or fluoropropane is used as the side disproportionation inhibitor, for example, two or more kinds of fluoroethane or two or more kinds of fluoropropane may be used. Similarly, when fluoroethane or fluoropropane is used in combination, each of them may be only one type, or at least one of them may be two or more types. The same applies when fluoromethane having one carbon atom is used in combination as a side disproportionation inhibitor.

[0093] In the present disclosure, the (ii) fluoroalkane as the secondary disproportionation inhibitor is used as a working fluid for a refrigeration cycle together with a fluoroolefin as the main refrigerant component and an ether compound as the main disproportionation inhibitor. The working fluid for a refrigeration cycle containing the refrigerant component and the disproportionation inhibitor is basically a gas in the normal temperature range, and therefore, its boiling point must be 0°C or lower.

[0094] For example, 1,2-difluoroethane (boiling point 31°C), 1,1,2-trifluoroethane (boiling point 5°C), 1,3-difluoropropane (boiling point 40 to 42°C), 1,1,1,3,3-pentafluoropropane (boiling point 15.3°C), 1,1,2,2,3-pentafluoropropane (boiling point 25 to 26°C) and the like all have boiling points above 0°C and therefore cannot be used as the secondary disproportionation inhibitor in the working fluid for a refrigeration cycle according to the present disclosure.

[0095] Furthermore, in the present disclosure, the (ii) fluoroalkane serving as the minor disproportionation inhibitor does not include difluoromethane. Difluoromethane has a boiling point of -51.7°C and corresponds to a fluoroalkane having one carbon atom, i.e., fluoromethane. However, as described above, difluoromethane is a minor refrigerant component used in combination with a fluoroolefin, which is a main refrigerant component, and therefore in the present disclosure, difluoromethane is excluded from the (ii) fluoroalkane serving as the minor disproportionation inhibitor.

[0096] In addition, as is clear from the results of the comparative examples in Patent Documents 4 and 5, for example, difluoromethane, which is a secondary refrigerant component, is considered to have no effect of suppressing the disproportionation reaction in fluoroolefins such as 1,1,2-trifluoroethylene.From this viewpoint as well, difluoromethane is excluded from (ii) fluoroalkanes as secondary disproportionation suppressors.

[0097] 4. Sub - disproportionation inhibitor (iii) In the present disclosure, as the secondary disproportionation inhibitor, (iii) a saturated hydrocarbon having 2 to 5 carbon atoms can be used. For convenience of explanation, the "saturated hydrocarbon having 2 to 5 carbon atoms" is simply referred to as "(iii) an alkane." In this way, by using an ether compound as the primary disproportionation inhibitor in combination with (iii) an alkane as the secondary disproportionation inhibitor, it is possible to suppress or moderate the progress of the disproportionation reaction even with a smaller amount.

[0098] Specific examples of (iii) alkanes include ethane, n-propane, cyclopropane, n-butane, cyclobutane, isobutane (2-methylpropane), methylcyclopropane, n-pentane, isopentane (2-methylbutane), neopentane (2,2-dimethylpropane), and methylcyclobutane. These (iii) alkanes may be used alone or in combination of two or more. Among these (iii) alkanes, a representative example is n-propane.

[0099] These (iii) alkanes are all gases at room temperature (n-pentane and methylcyclobutane have the highest boiling points of about 36°C, and the boiling points of the other hydrocarbons are less than 36°C), and can be mixed well as components of the working fluid for the refrigeration cycle. Saturated hydrocarbons with six or more carbon atoms are liquid at room temperature, and are difficult to mix as components of the working fluid for the refrigeration cycle, so they are not preferable as (iii) alkanes as the minor disproportionation inhibitor. In addition, saturated hydrocarbons with one carbon atom, i.e., methane, are not preferable because of their large global warming potential (GWP). Among the saturated hydrocarbons that fall under (iii) alkanes, cyclopentane has a boiling point of 49°C and is liquid at room temperature, but can be used as a minor disproportionation inhibitor under certain conditions.

[0100] In the present disclosure, as the minor disproportionation inhibitor, only (i) haloalkane, (ii) fluoroalkane, or (iii) alkane may be used, or an appropriate combination of these may be used. That is, in the working fluid for a refrigeration cycle according to the present disclosure, at least one compound selected from the group consisting of (i) haloalkane, (ii) fluoroalkane, and (iii) alkane may be used as the minor disproportionation inhibitor in combination with an ether compound as the main disproportionation inhibitor.

[0101] Therefore, in the working fluid for a refrigeration cycle according to the present disclosure, the minor disproportionation inhibitor may be a single compound corresponding to any one of (i) haloalkanes, (ii) fluoroalkanes, and (iii) alkanes, or a combination of two or more compounds corresponding to any one of (i) haloalkanes, (ii) fluoroalkanes, and (iii) alkanes, or a combination of two or three compounds corresponding to two or three of (i) haloalkanes, (ii) fluoroalkanes, and (iii) alkanes. Alternatively, a combination of multiple types of compounds corresponding to two or three of (i) haloalkanes, (ii) fluoroalkanes, and (iii) alkanes may be used as the minor disproportionation inhibitor. Alternatively, a combination of only one type of compound corresponding to any one or two of (i) haloalkanes, (ii) fluoroalkanes, and (iii) alkanes, or a combination of multiple types of compounds corresponding to any two or one of (i) haloalkanes, (ii) fluoroalkanes, and (iii) alkanes may be used as the minor disproportionation inhibitor.

[0102] [Disproportionation inhibitor content] Next, the content (addition amount) of the disproportionation inhibitor will be specifically described. As described above, in the working fluid for a refrigeration cycle according to the present disclosure, an ether compound is used as the main disproportionation inhibitor, and at least one compound selected from the group consisting of (i) haloalkanes, (ii) fluoroalkanes, and (iii) alkanes can be used in combination as the secondary disproportionation inhibitor.

[0103] Here, for convenience, the total amount of refrigerant components and disproportionation inhibitor is referred to as the "total amount of refrigerant-related components", and when this total amount of refrigerant-related components is taken as 100 mass%, the upper limit of the amount (content) of the disproportionation inhibitor added is not particularly limited, but may be 40 mass% or less of the total amount of refrigerant-related components, or may be 30 mass% or less, 20 mass% or less, or 15 mass% or less.

[0104] This is because if the content of the disproportionation inhibitor exceeds 40% by mass of the total amount of the refrigerant-related components, the content of the disproportionation inhibitor becomes too high when viewed as a working fluid for a refrigeration cycle, and there is a possibility that the fluid will not be able to exhibit good physical properties as a "refrigerant." Of course, it goes without saying that, depending on the composition of the working fluid for a refrigeration cycle, more than 40% by mass of the total amount of the refrigerant-related components may be added.

[0105] When only an ether compound, which is the main disproportionation inhibitor, is used as the disproportionation inhibitor (including the use of only one type of ether compound or a combination of two or more types of ether compounds), the content is not particularly limited as long as it is 30 mass % or less of the total amount of refrigerant-related components, or may be 20 mass % or less, or may be 10 mass % or less.

[0106] Basically, the higher the content of the ether compound, the easier it is to obtain the effect of suppressing the disproportionation reaction of fluoroolefins. However, as mentioned above, if the content of the disproportionation inhibitor is too high, the working fluid for the refrigeration cycle may not be able to exhibit good physical properties as a "refrigerant". On the other hand, if the content of the ether compound is 30 mass%, it is possible to satisfactorily achieve both the effect of suppressing the disproportionation reaction of fluoroolefins and the good physical properties (performance as a refrigerant) of the working fluid for the refrigeration cycle.

[0107] Although it depends on various conditions, if the content of the ether compound is 20% by mass or less or 15% by mass or less, the disproportionation reaction of fluoroolefins can be suppressed well with a relatively small amount even when the working fluid for a refrigeration cycle is exposed to high temperature and high pressure conditions. Moreover, if the content is 20% by mass or less or 15% by mass or less, the overall content of the disproportionation inhibitor can be reduced, so that the performance of the working fluid for a refrigeration cycle as a refrigerant can be improved.

[0108] Furthermore, although depending on various conditions, when the content of the ether compound is 10 mass% or less, the disproportionation reaction of the fluoroolefin can be effectively suppressed with a smaller amount of the ether compound, the performance of the working fluid for a refrigeration cycle as a refrigerant can be further improved, and the flammability of the working fluid for a refrigeration cycle can be further suppressed.

[0109] When an ether compound, which is the main disproportionation inhibitor, is used in combination with at least one of (i) a haloalkane, (ii) a fluoroalkane, and (iii) an alkane, which is a secondary disproportionation inhibitor, the content thereof is not particularly limited, but the total amount of these secondary disproportionation inhibitors may be 10 mass% or less of the total amount of the refrigerant-related components, and may be 5 mass% or less, 3 mass% or less, or 1 mass% or less.

[0110] As with the ether compound, the greater the content of the secondary disproportionation inhibitor, the easier it is to obtain the effect of inhibiting the disproportionation reaction of the fluoroolefin. However, as described above, if the content of the secondary disproportionation inhibitor is too high, the working fluid for the refrigeration cycle may not be able to exhibit good physical properties as a "refrigerant."

[0111] Although it depends on various conditions, if the content of the secondary disproportionation inhibitor is 5% by mass or less or 3% by mass or less, the disproportionation reaction of fluoroolefins can be effectively inhibited with a relatively small amount even when the working fluid for a refrigeration cycle is exposed to high temperature and high pressure conditions. Moreover, if the content is 5% by mass or less or 3% by mass or less, the overall content of the disproportionation inhibitor can be reduced, so that the performance of the working fluid for a refrigeration cycle as a refrigerant can be improved.

[0112] Although it depends on various conditions, when the content of the secondary disproportionation inhibitor is 1% by mass or less, the disproportionation reaction of the fluoroolefin can be suppressed satisfactorily with a relatively small amount, especially when combined with an ether compound, even when the working fluid for a refrigeration cycle is exposed to high temperature and high pressure conditions. Furthermore, when the content is 1% by mass or less, the overall content of the disproportionation inhibitor can be reduced, so that the performance of the working fluid for a refrigeration cycle as a refrigerant can be improved.

[0113] When the disproportionation inhibitor is a primary disproportionation inhibitor, ether compounds, and secondary disproportionation inhibitors (at least one of (i) haloalkanes, (ii) fluoroalkanes, and (iii) alkanes) used in combination, the mixing ratio is not particularly limited, and the upper limit of the content described above can be applied. As described above, when the total amount of the refrigerant-related components is taken as 100% by mass, a preferred total content of the disproportionation inhibitors among them is 40% by mass or less. Therefore, it is sufficient that the ether compounds and secondary disproportionation inhibitors are used in combination at an appropriate mixing ratio within this range.

[0114] In addition, the lower limit of the content of the disproportionation inhibitor is not particularly limited, but a representative lower limit can be 1.2 mass% or more of the total amount of refrigerant-related components. Although 1 mass% is given as the upper limit when a secondary disproportionation inhibitor is used as the disproportionation inhibitor, in the present disclosure, since it is assumed that the haloalkane is used in combination with an ether compound, it is sufficient that the lower limit of the total content of the disproportionation inhibitor (the total content of the ether compound as the primary disproportionation inhibitor and the secondary disproportionation inhibitor) is 1.2 mass% or more.

[0115] Depending on various conditions, even if the total amount (total content) of the disproportionation inhibitor is less than 1.2 mass%, it is possible to obtain the effect of inhibiting the disproportionation reaction. However, if the total amount of the disproportionation inhibitor is 1.2 mass% or more, the effect of inhibiting the disproportionation reaction can be more suitably realized. Therefore, in the present disclosure, a more preferable range for the content of the disproportionation inhibitor is 1.2 mass% or more and 40 mass% or less of the total amount of the refrigerant-related components.

[0116] In general, impurities contained in the refrigerant components of a working fluid for a refrigeration cycle are often 2 to 3% by mass or less. For example, a commercially available product of 1,1,2-trifluoroethylene, a representative fluoroolefin, is known to have a purity of about 97% by mass. Examples of impurities contained in the commercially available product include residues of synthetic raw materials or by-products, and these impurities are contained in an amount of less than 3% by mass. In the present disclosure, the lower limit of the content of the disproportionation inhibitor may be equal to or greater than the content of impurities in the commercially available product, that is, 3% by mass or more.

[0117] Here, the content of the (iii) alkane among the secondary disproportionation inhibitors may have an upper limit of 10% by mass or less, as described above, and may also be 5% by mass or less or 3% by mass or less. However, when the (iii) alkane is n-propane, the upper limit may be 8.5% by mass or less, or 7.5% by mass or less.

[0118] On the other hand, although the lower limit of the (iii) alkane is not particularly limited, when the (iii) alkane is n-propane, the lower limit may be 5.0 mass% or more, 2.0 mass% or more, 1.0 mass% or more, or 0.6 mass% or more.

[0119] (iii) Alkane can also be used as a refrigerant component, but when it is used as a secondary disproportionation inhibitor together with a primary disproportionation inhibitor (ether compound) rather than as a refrigerant component, it can exert a disproportionation reaction suppressing effect in a relatively small amount compared to the content as a refrigerant component in the working fluid for the refrigeration cycle. Although it depends on various conditions, when the (iii) alkane is n-propane, a good disproportionation reaction suppressing effect can be exerted by selecting a combination of the above upper and lower limit values.

[0120] The amount of the disproportionation inhibitor added is not necessarily specified because it can be adjusted depending on various conditions. Therefore, the upper and lower limits of the content of the disproportionation inhibitor described above are merely representative and preferred examples.

[0121] The content of difluoromethane, which is a secondary refrigerant component in the working fluid for a refrigeration cycle, is also not particularly limited. As described above, in the present disclosure, since fluoroolefin is the main refrigerant component, it is sufficient that the content of fluoroolefin is higher than the content of difluoromethane in the working fluid for a refrigeration cycle according to the present disclosure.

[0122] However, in the working fluid for a refrigeration cycle according to the present disclosure, it is important to make the GWP as small as possible. Specifically, the GWP is desirably 200 or less (GWP≦200), and more desirably 150 or less (GWP≦150). From the viewpoint of using a combination of fluoroolefin and difluoromethane as refrigerant components, the upper limit of the difluoromethane content may be 30% by mass or less, or may be 25% by mass or less, or may be 20% by mass or less, of the total amount of refrigerant-related components.

[0123] When the difluoromethane content is 30% by mass or less, the GWP of the working fluid for a refrigeration cycle can be set to 200 or less, and when it is 20% by mass or less, the GWP of the working fluid for a refrigeration cycle can be set to 150 or less. There is no particular limitation on the lower limit of difluoromethane. The working fluid for a refrigeration cycle according to the present disclosure does not need to contain difluoromethane, so the content thereof may be 0% by mass or more.

[0124] [Other ingredients that can be used in combination] The working fluid for a refrigeration cycle according to the present disclosure is used in a refrigeration cycle system, and therefore can be used in combination with a lubricating oil (refrigeration oil) that lubricates a compressor provided in the refrigeration cycle system.

[0125] As described above, the working fluid for a refrigeration cycle according to the present disclosure uses a fluoroolefin (e.g., 1,1,2-trifluoroethylene, etc.) in which a disproportionation reaction occurs as a main refrigerant component, and optionally uses difluoromethane as a secondary refrigerant component, and at least an ether compound (main disproportionation inhibitor) as a disproportionation inhibitor, but when the working fluid for a refrigeration cycle is used in combination with a lubricating oil, the working fluid-containing composition can be considered to be composed of the refrigerant component, the disproportionation inhibitor, the lubricating oil component, and other components. In the working fluid for a refrigeration cycle according to the present disclosure, the disproportionation inhibitor is usually mixed with the refrigerant component, but may be mixed with the lubricating oil component depending on the situation.

[0126] The lubricating oil component contained in the working fluid-containing composition (used together with the working fluid for the refrigeration cycle) can be suitably selected from various lubricating oils known in the refrigeration cycle system. Specific examples of the lubricating oil include, but are not limited to, ester-based lubricating oils, ether-based lubricating oils, glycol-based lubricating oils, alkylbenzene-based lubricating oils, fluorine-based lubricating oils, mineral oils, and hydrocarbon-based synthetic oils. Only one type of these lubricating oils may be used, or two or more types may be used in appropriate combination.

[0127] In addition, various known additives other than the disproportionation inhibitor may be added to the working medium-containing composition. Specific additives include, but are not limited to, antioxidants, moisture scavengers, metal deactivators, antiwear agents, and antifoamers. The antioxidants are used to improve the thermal stability, oxidation resistance, chemical stability, and the like of refrigerant components or lubricating oils. The moisture scavengers are used to remove moisture when moisture infiltrates into the refrigeration cycle system, and are particularly used to suppress changes in the properties of the lubricating oil. The metal deactivators are used to suppress or prevent chemical reactions caused by the catalytic action of metal components. The antiwear agents are used to reduce wear in the sliding parts of the compressor, especially wear during high-pressure operation. The antifoamers are used to suppress the generation of bubbles in the lubricating oil.

[0128] The specific types of these additives are not particularly limited, and known compounds can be suitably used depending on various conditions. In addition, as these additives, only one type of compound may be used, or two or more types of compounds may be used in appropriate combination. Furthermore, the amount of these additives added is not particularly limited, and they can be added within a known range as long as it does not impair the properties of the working fluid for a refrigeration cycle according to the present disclosure or the working fluid-containing composition containing the same.

[0129] The working fluid for a refrigeration cycle according to the present disclosure may not contain other components. For example, a working fluid for a refrigeration cycle using 1,1,2-trifluoroethylene among fluoroolefins as a refrigerant component and using only an ether compound as a disproportionation inhibitor may be used. Alternatively, a working fluid for a refrigeration cycle using 1,1,2-trifluoroethylene and difluoromethane as refrigerant components and using only an ether compound as a disproportionation inhibitor may be used.

[0130] Alternatively, the working fluid for a refrigeration cycle according to the present disclosure may be configured to contain only a fluoroolefin as a main refrigerant component, while containing, as a disproportionation inhibitor, an ether compound as a main disproportionation inhibitor and at least one of (i) a haloalkane, (ii) a fluoroalkane, and (iii) an alkane as a secondary disproportionation inhibitor. Alternatively, the working fluid for a refrigeration cycle may be configured to contain, as a main refrigerant component, a fluoroolefin, and as a secondary refrigerant component, difluoromethane, while containing, as a disproportionation inhibitor, an ether compound as a main disproportionation inhibitor and at least one of (i) a haloalkane, (ii) a fluoroalkane, and (iii) an alkane.

[0131] [Example of refrigeration cycle system configuration] Next, an example of a refrigeration cycle system configured using the working fluid for a refrigeration cycle according to the present disclosure will be described with reference to FIGS. 1(A) and 1(B).

[0132] The specific configuration of the refrigeration cycle system according to the present disclosure is not particularly limited, and may be any configuration in which components such as a compressor, a condenser, an expansion means, and an evaporator are connected by piping. Specific application examples of the refrigeration cycle system according to the present disclosure are also not particularly limited, and examples thereof include air conditioners (air conditioners), refrigerators (for home and commercial use), dehumidifiers, showcases, ice makers, heat pump water heaters, heat pump washing and drying machines, and vending machines.

[0133] An air conditioner will be described as a typical application example of the refrigeration cycle system according to the present disclosure. Specifically, as shown in the block diagram of Fig. 1(A), an air conditioner 10 according to this embodiment includes an indoor unit 11 and an outdoor unit 12, and piping 13 connecting them. The indoor unit 11 includes a heat exchanger 14, and the outdoor unit 12 includes a heat exchanger 15, a compressor 16, and a pressure reducing device 17.

[0134] The heat exchanger 14 of the indoor unit 11 and the heat exchanger 15 of the outdoor unit 12 are connected in a ring shape by piping 13, thereby forming a refrigeration cycle. Specifically, the heat exchanger 14 of the indoor unit 11, the compressor 16, the heat exchanger 15 of the outdoor unit 12, and the pressure reducing device 17 are connected in a ring shape by piping 13 in this order. In addition, the piping 13 connecting the heat exchanger 14, the compressor 16, and the heat exchanger 15 is provided with a four-way valve 18 for switching between heating and cooling. The indoor unit 11 is provided with a blower fan, a temperature sensor, an operation unit, etc., not shown, and the outdoor unit 12 is provided with a blower, an accumulator, etc., not shown. Furthermore, the piping 13 is provided with various valve devices (including the four-way valve 18), a strainer, etc., not shown.

[0135] The heat exchanger 14 provided in the indoor unit 11 exchanges heat between indoor air drawn into the indoor unit 11 by the blower fan and the refrigerant flowing inside the heat exchanger 14. During heating, the indoor unit 11 blows air warmed by heat exchange into the room, and during cooling, blows air cooled by heat exchange into the room. The heat exchanger 15 provided in the outdoor unit 12 exchanges heat between outside air drawn into the outdoor unit 12 by the blower and the refrigerant flowing inside the heat exchanger 15.

[0136] The specific configurations of the indoor unit 11 and the outdoor unit 12, or the specific configurations of the heat exchanger 14 or heat exchanger 15, compressor 16, pressure reducing device 17, four-way valve 18, blower fan, temperature sensor, operating unit, blower, accumulator, other valve devices, strainer, etc. are not particularly limited, and known configurations can be suitably used.

[0137] An example of the operation of the air conditioner 10 shown in FIG. 1(A) will be specifically described. First, in cooling operation or dehumidification operation, the compressor 16 of the outdoor unit 12 compresses and discharges the gas refrigerant, and the gas refrigerant is sent to the heat exchanger 15 of the outdoor unit 12 via the four-way valve 18. The heat exchanger 15 exchanges heat between the outside air and the gas refrigerant, so that the gas refrigerant condenses and becomes liquid. The liquefied liquid refrigerant is depressurized by the pressure reducing device 17 and sent to the heat exchanger 14 of the indoor unit 11. In the heat exchanger 14, the liquid refrigerant evaporates due to heat exchange with the indoor air, and becomes a gas refrigerant. This gas refrigerant returns to the compressor 16 of the outdoor unit 12 via the four-way valve 18. The compressor 16 compresses the gas refrigerant and discharges it again to the heat exchanger 15 via the four-way valve 18.

[0138] During heating operation, the compressor 16 of the outdoor unit 12 compresses and discharges the gas refrigerant, which is then sent to the heat exchanger 14 of the indoor unit 11 via the four-way valve 18. In the heat exchanger 14, the gas refrigerant condenses and liquefies due to heat exchange with the indoor air. The liquefied liquid refrigerant is depressurized by the decompression device 17 to become a two-phase gas-liquid refrigerant, and is sent to the heat exchanger 15 of the outdoor unit 12. Since the heat exchanger 15 exchanges heat between the outside air and the two-phase gas-liquid refrigerant, the two-phase gas-liquid refrigerant evaporates and becomes a gas refrigerant, which returns to the compressor 16. The compressor 16 compresses the gas refrigerant and discharges it again to the heat exchanger 14 of the indoor unit 11 via the four-way valve 18.

[0139] A refrigerator will be described as another typical application example of the refrigeration cycle system according to the present disclosure. Specifically, as shown in the block diagram of Fig. 1(B), a refrigerator 20 according to the present embodiment includes a compressor 21, a condenser 22, a pressure reducing device 23, an evaporator 24, and piping 25, etc., as shown in Fig. 1. Although not shown, the refrigerator 20 also includes a housing, a blower, an operation unit, a control unit, etc., which are the main body of the refrigerator.

[0140] The compressor 21 compresses the refrigerant gas to produce a high-temperature, high-pressure gas refrigerant. The condenser 22 cools and liquefies the refrigerant. The pressure reducing device 23 is formed, for example, of a capillary tube, and reduces the pressure of the liquefied refrigerant (liquid refrigerant). The evaporator 24 evaporates the refrigerant to produce a low-temperature, low-pressure gas refrigerant. The compressor 21, condenser 22, pressure reducing device 23, and evaporator 24 are connected in this order in a ring shape by piping 25 that circulates the refrigerant gas, thereby forming a refrigeration cycle.

[0141] The configurations of the compressor 21, the condenser 22, the pressure reducing device 23, the evaporator 24, the piping 25, the main body housing, the blower, the operation unit, the control unit, etc. are not particularly limited, and known configurations can be suitably used. The refrigerator 20 may also have known configurations other than those.

[0142] An example of the operation of the refrigerator 20 shown in Fig. 1(B) will be specifically described. The compressor 21 compresses the gas refrigerant and discharges it to the condenser 22. The condenser 22 cools the gas refrigerant to liquid refrigerant. The liquid refrigerant is reduced in pressure by passing through the pressure reducing device 23 and sent to the evaporator 24. In the evaporator 24, the liquid refrigerant is evaporated by removing heat from the surroundings, and returns to the compressor 21 as gas refrigerant. The compressor 21 compresses the gas refrigerant and discharges it again to the condenser 22.

[0143] Such an air conditioner 10 or a refrigerator 20 is a refrigeration cycle system configured using the above-mentioned working fluid for the refrigeration cycle. The fluoroolefin used in the working fluid for the refrigeration cycle has good properties as a refrigerant component and has low ODP and GWP. Moreover, the working fluid for the refrigeration cycle contains at least the above-mentioned ether compound as a disproportionation inhibitor.

[0144] Therefore, the disproportionation reaction of fluoroolefins can be effectively suppressed or alleviated, the energy efficiency can be improved, and the environmental load can be further reduced, so that the refrigeration cycle system can be made to have a small impact on the environment, is efficient, and has good practicality. EXAMPLES

[0145] The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited thereto. Those skilled in the art can make various changes, modifications, and alterations without departing from the scope of the present invention.

[0146] (Experimental system for disproportionation reaction) A pressure sensor for measuring the internal pressure in a sealed pressure-resistant vessel (internal volume 50 mL), a thermocouple for measuring the internal temperature in the pressure-resistant vessel, and a discharge device for generating a discharge in the pressure-resistant vessel were attached to the vessel.

[0147] In addition, a gas cylinder (HFO1123 gas cylinder) of the refrigerant component 1,1,2-trifluoroethylene (containing 5% limonene (liquid phase) as a stabilizer) was connected to the pressure-resistant container so that the pressure could be adjusted. The pressure sensor and thermometer attached to the pressure-resistant container were connected to a data logger. This created an experimental system for the disproportionation reaction.

[0148] (Comparative Example) In the experimental system, 1,1,2-trifluoroethylene was introduced into the pressure vessel from the HFO1123 gas cylinder. Therefore, the content of 1,1,2-trifluoroethylene in the working fluid for the refrigeration cycle in the pressure vessel was 100% by mass.

[0149] In order to induce the disproportionation reaction of 1,1,2-trifluoroethylene, a discharge was generated by a discharge device under conditions of an internal pressure of 1.3 MPa at room temperature with a discharge voltage of 100 V. When the inside of the pressure vessel was then checked after the internal pressure and temperature had sufficiently decreased, a considerable amount of soot was found to have been generated, confirming the occurrence of the disproportionation reaction of 1,1,2-trifluoroethylene.

[0150] (Example) In the experimental system, 1,1,2-trifluoroethylene was introduced into a pressure-resistant vessel from an HFO1123 gas cylinder, and 1,2,2,2-tetrafluoroethyl trifluoromethyl ether (HFE227ea) was added as a disproportionation inhibitor to a content of 20 mass %.

[0151] Except for this, discharge was generated three times in the pressure vessel in the same manner as in the comparative example, but no significant increase in pressure or temperature was observed. After that, the inside of the pressure vessel was checked, but no occurrence of a disproportionation reaction of 1,1,2-trifluoroethylene was confirmed.

[0152] The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the claims. The technical scope of the present invention also includes embodiments obtained by appropriately combining the technical means disclosed in different embodiments or multiple modified examples.

[0153] (Additional Note) Based on the above description of the embodiments, the following techniques are disclosed in this specification. (Technology 1) A working fluid for a refrigeration cycle, comprising, as a refrigerant component, a fluoroolefin that undergoes a disproportionation reaction, and an ether compound that is a hydrohaloether, a haloether, or a hydroether, as a disproportionation inhibitor that suppresses the disproportionation reaction of the fluoroolefin.

[0154] (Technology 2) The ether compound is represented by the following formula (1) C 2 H m X n O (1) (In the formula (1), the oxygen atom (O) constitutes an ether bond (-O-), X is any halogen atom selected from the group consisting of F, Cl, Br, and I, m and n are each an integer of 0 or more, the sum of m and n is 6, and further, when n is 2 or more, X is the same or different halogen atom.) The working medium for a refrigeration cycle according to Technical 1, wherein the working medium is an ether having two carbon atoms and having a structure shown in

[0155] (Technology 3) The ether compound is represented by the following formula (2) C 3 H p X q O (2) (In the formula (2), the oxygen atom (O) constitutes an ether bond (-O-), X is any halogen atom selected from the group consisting of F, Cl, Br, and I, p and q are each an integer of 0 or more, the sum of p and q is 6 or 8, when the sum of p and q is 6, one carbon-carbon double bond is contained, and further, when q is 2 or more, X is the same or different halogen atom.) The working medium for a refrigeration cycle according to Technical 1, wherein the working medium is an ether having three carbon atoms and having a structure shown in

[0156] (Technology 4) The hydrohaloether is 1,2,2,2-tetrafluoroethyl trifluoromethyl ether (HFE227ea, CF 3 -O-CFH-CF 3 ) or iodomethyl methyl ether (CH2 IO-CH 3 ), and the haloether is trifluorovinyl trifluoromethyl ether (HFE216, CF 3 -O-CF=CF 2 ), and the hydroether is dimethyl ether (CH 3 -O-CH 3 ) or ethyl methyl ether (CH 3 -OC 2 H 5 4. The working medium for a refrigeration cycle according to any one of Techniques 1 to 3,

[0157] (Technology 5) The working medium for a refrigeration cycle according to any one of Technology 1 to Technology 4, wherein the fluoroolefin in which the disproportionation reaction occurs is 1,1,2-trifluoroethylene or difluoroethylene.

[0158] (Technology 6) The working medium for a refrigeration cycle according to any one of Techniques 1 to 5, further containing difluoromethane (R32) as a refrigerant component.

[0159] (Technology 7) The working medium for a refrigeration cycle according to any one of Techniques 1 to 6, wherein when the hydrofluoroolefin is used as a main disproportionation inhibitor, the disproportionation inhibitor further contains at least one secondary disproportionation inhibitor selected from the group consisting of (i) haloalkanes having 1 or 2 carbon atoms excluding those in which all of the halogen atoms are fluorine, (ii) fluoroalkanes having 1 to 3 carbon atoms (excluding difluoromethane) and having a boiling point of 0°C or lower, and (iii) saturated hydrocarbons having 2 to 5 carbon atoms.

[0160] (Technology 8) The working fluid for a refrigeration cycle according to any one of Technology 1 to Technology 7, wherein the content of the ether compound is 30 mass% or less when the total amount of the refrigerant components and the disproportionation inhibitor is 100 mass%.

[0161] (Technology 9) The working medium for a refrigeration cycle according to Technology 6 (or Technology 7 or Technology 8 dependent only on Technology 6), wherein the content of difluoromethane is 30 mass% or less when the total amount of the refrigerant components and the disproportionation inhibitor is 100 mass%.

[0162] (Technology 10) The working medium for a refrigeration cycle according to Technology 7 (or Technology 8 or Technology 9 dependent only on Technology 7), wherein the content of the secondary disproportionation inhibitor is 10 mass% or less when the total amount of the refrigerant components and the disproportionation inhibitor is 100 mass%.

[0163] (Technology 11) A refrigeration cycle system configured using a working medium for a refrigeration cycle according to any one of Technologies 1 to 10. [Industrial Applicability]

[0164] The present invention can be suitably used in the field of working fluids used in refrigeration cycles, and can also be suitably used widely in the field of refrigeration cycle systems, such as air conditioners, refrigerators (for home and commercial use), dehumidifiers, showcases, ice makers, heat pump water heaters, heat pump washer-dryers, and vending machines. [Explanation of symbols]

[0165] 10: Air conditioning equipment (refrigeration cycle system) 11: Indoor unit 12:Outdoor unit 13:Plumbing 14:Heat exchanger 15: Heat exchanger 16: Compressor 17: Pressure reducing device 18: Four-way valve 20: Refrigerator (freezing cycle system) 21: Compressor 22: Condenser 23: Pressure reducing device 24: Evaporator 25:Plumbing

Claims

1. The refrigerant component contains a fluoroolefin that undergoes a disproportionation reaction, The present invention is characterized in that the disproportionation inhibitor for suppressing the disproportionation reaction of the fluoroolefin contains an ether compound which is a hydrohaloether, a haloether or a hydroether. Working medium for refrigeration cycle.

2. The ether compound is represented by the following formula (1): C 2 H m X n O ・・・(1) (In the formula (1), the oxygen atom (O) constitutes an ether bond (-O-), X is any halogen atom selected from the group consisting of F, Cl, Br, and I, m and n are each an integer of 0 or more, the sum of m and n is 6, and further, when n is 2 or more, X is the same or different halogen atom.) It is an ether having two carbon atoms and having the structure shown in The working medium for a refrigeration cycle according to claim 1.

3. The ether compound is represented by the following formula (2): C 3 H p X q O ・・・(2) (In the formula (2), the oxygen atom (O) constitutes an ether bond (-O-), X is any halogen atom selected from the group consisting of F, Cl, Br, and I, p and q are each an integer of 0 or more, the sum of p and q is 6 or 8, when the sum of p and q is 6, one carbon-carbon double bond is contained, and further, when q is 2 or more, X is the same or different halogen atom.) It is a carbon number 3 ether having the structure shown in The working medium for a refrigeration cycle according to claim 1.

4. The hydrohaloether is 1,2,2,2-tetrafluoroethyl trifluoromethyl ether (HFE227ea, CF 3 -O-CFH-CF 3 ) or iodomethyl methyl ether (CH 2 I-O-CH 3 ) and The haloether is trifluorovinyl trifluoromethyl ether (HFE216, CF 3 -O-CF=CF 2 ) and The hydroether is dimethyl ether (CH 3 -O-CH 3 ) or ethyl methyl ether (CH 3 -O-C 2 H 5 ) The working medium for a refrigeration cycle according to any one of claims 1 to 3.

5. The fluoroolefin in which the disproportionation reaction occurs is 1,1,2-trifluoroethylene or difluoroethylene. The working medium for a refrigeration cycle according to any one of claims 1 to 3.

6. The refrigerant component further contains difluoromethane (R32). The working medium for a refrigeration cycle according to any one of claims 1 to 3.

7. When the hydrofluoroolefin is used as the main disproportionation inhibitor, the disproportionation inhibitor further includes (i) haloalkanes having 1 or 2 carbon atoms, except for those in which all halogen atoms are fluorine; (ii) Fluoroalkanes having 1 to 3 carbon atoms (excluding difluoromethane) having a boiling point of 0° C. or less, and (iii) Saturated hydrocarbons having 2 to 5 carbon atoms At least one secondary disproportionation inhibitor selected from the group consisting of: The working medium for a refrigeration cycle according to any one of claims 1 to 3.

8. When the total amount of the refrigerant components and the disproportionation inhibitor is 100 mass%, the content of the ether compound is 30 mass% or less. The working medium for a refrigeration cycle according to any one of claims 1 to 3.

9. the content of difluoromethane is 30% by mass or less when the total amount of the refrigerant components and the disproportionation inhibitor is 100% by mass; The working medium for a refrigeration cycle according to claim 6.

10. When the total amount of the refrigerant components and the disproportionation inhibitor is 100 mass%, the content of the secondary disproportionation inhibitor is 10 mass% or less. The working medium for a refrigeration cycle according to claim 7.

11. A refrigeration cycle system constructed by using the working fluid for a refrigeration cycle according to any one of claims 1 to 3.

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