Refrigeration cycle working medium and refrigeration cycle system

Abstract

The refrigeration cycle working medium comprises: as a refrigerant component, a fluoroolefin in which a disproportionation reaction occurs; and, as a disproportionation inhibitor that inhibits the disproportionation reaction of the fluoroolefin, a haloalkene in which at least one of the hydrogen atoms of the alkene is substituted by another halogen atom excluding fluorine. This haloalkene may be a C2 haloethene (haloethylene) or a C3 halopropene.

Description

Refrigeration cycle working medium and refrigeration cycle system

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

[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, particularly hydrofluoroolefins (HFOs), which have a lower global warming potential (GWP), has recently been proposed.

[0003] Known 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 due to the low stability of HFOs, they are prone to undergo a self-polymerization reaction known as a disproportionation reaction (hereinafter referred to as a disproportionation reaction).

[0004] It is known that the disproportionation reaction is likely to occur due to heat generated during use of the working fluid for the refrigeration cycle, and that the disproportionation reaction is accompanied by a large heat release, leading to a chain reaction of disproportionation reactions, which may result 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 1,1,2-trifluoroethylene, for example, is used as a refrigerant component of a working fluid for a refrigeration cycle, the applicant has proposed the following as a component (disproportionation inhibitor) for inhibiting the disproportionation reaction of 1,1,2-trifluoroethylene: halomethane (Patent Document 1), saturated hydrocarbon (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, Refrigerating 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.

[0007] JP 2017-145380 A JP 2018-048271 A JP 2018-104565 A JP 2018-104566 A JP 2019-034983 A JP 2021-161316 A

[0008] The disproportionation inhibitors described above 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 disproportionation inhibitors described above 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.

[0011] As a result of extensive research aimed at solving the above-mentioned problems, the present inventors have independently discovered that haloalkenes such as hydrochlorofluoroolefins (HCFOs), which have been considered as refrigerant components up to now, can effectively inhibit or mitigate the disproportionation reaction of fluoroolefins and can also 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, a haloalkene in which at least one hydrogen atom of an alkene is substituted with a halogen atom other than fluorine.

[0013] According to the above configuration, the working fluid for a refrigeration cycle containing a fluoroolefin that undergoes a disproportionation reaction contains, as a disproportionation inhibitor, a haloalkene in which at least one hydrogen atom of an alkene has been substituted with a halogen atom other than fluorine, which can effectively inhibit or mitigate the disproportionation reaction of the fluoroolefin.

[0014] Moreover, many of these haloalkenes are compounds that 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.

[0015] Furthermore, like fluoroolefins, which are refrigerant components, haloalkenes contain carbon-carbon double bonds in their molecular structures, and therefore are easily decomposed in the natural environment, resulting in a short atmospheric lifetime and a relatively small environmental impact.

[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 further reduced.

[0017] The present disclosure also includes a refrigeration cycle system configured using the working fluid for a refrigeration cycle having the above configuration.

[0018] The above and other objects, features, and advantages of the present invention will become apparent from the following detailed description of preferred embodiments, which proceeds with reference to the accompanying drawings.

[0019] The present invention has the above-mentioned constitution, and has the 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.

[0020] 1A and 1B are schematic block diagrams illustrating an example of a refrigeration cycle system according to an embodiment of the present disclosure.

[0021] 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, as a disproportionation inhibitor that suppresses the disproportionation reaction of the fluoroolefin, a haloalkene in which at least one hydrogen atom of an alkene has been substituted with a halogen atom other than fluorine.

[0022] According to the above configuration, the working fluid for a refrigeration cycle containing a fluoroolefin that undergoes a disproportionation reaction contains, as a disproportionation inhibitor, a haloalkene in which at least one hydrogen atom of an alkene has been substituted with a halogen atom other than fluorine, which can effectively inhibit or mitigate the disproportionation reaction of the fluoroolefin.

[0023] Moreover, many of these haloalkenes are compounds that 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.

[0024] Furthermore, like fluoroolefins, which are refrigerant components, haloalkenes contain carbon-carbon double bonds in their molecular structures, and therefore are easily decomposed in the natural environment, resulting in a short atmospheric lifetime and a relatively small environmental impact.

[0025] 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 further reduced.

[0026] In the working fluid for a refrigeration cycle having the above-described configuration, the haloalkene is represented by the following formula (1): k F m X n ...(1) (wherein X in formula (1) is any halogen atom selected from the group consisting of Cl, Br, and I, k and m are each an integer of 0 or more, n is an integer of 1 or more, the sum of k, m, and n is 4, and when n is 2 or more, X are the same or different halogen atoms).

[0027] In the working fluid for a refrigeration cycle having the above-described configuration, the haloalkene is represented by the following formula (2): p F q X r ...(2) (wherein X in formula (2) is any halogen atom selected from the group consisting of Cl, Br, and I, p and q are each an integer of 0 or more, r is an integer of 1 or more, the sum of p, q, and r is 6, and when r is 2 or more, X are the same or different halogen atoms).

[0028] In the working fluid for a refrigeration cycle having the above configuration, the haloalkene may be 1-chloro-2,2-difluoroethene (HCFO-1122, CF═CHCl), 1-chloro-1,2-difluoroethene (HCFO-1122a, CFH═CFCl), 3-chloro-2,3,3-trifluoro-1-propene (HCFO-1233yf, CH═CF-CF═Cl), 1,1,2-trifluoro-2-bromoethene (CF═CFBr), 1,1,2-trifluoro-2-iodoethene (iodotrifluoroethene, CF═CFI), or 3-iodopentafluoropropene (CF═CFCF═I).

[0029] 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.

[0030] The working fluid for a refrigeration cycle having the above-described configuration may further contain difluoromethane (R32) as a refrigerant component.

[0031] Furthermore, 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 less, and (iii) saturated hydrocarbons having 2 to 5 carbon atoms.

[0032] In the working fluid for a refrigeration cycle having the above configuration, the content of the haloalkene 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 the working fluid for a refrigeration cycle having the above configuration, the content of difluoromethane 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.

[0034] In the working fluid for a refrigeration cycle having the above configuration, the content of the secondary disproportionation inhibitor may be 10% by mass or less when the total amount of the refrigerant components and the disproportionation inhibitor is taken as 100% by mass.

[0035] The present disclosure also includes a refrigeration cycle system configured using a working fluid for a refrigeration cycle having any of the above configurations.

[0036] Representative embodiments of the working fluid for a refrigeration cycle according to the present disclosure, as well as representative modes of use thereof, will be specifically described below.

[0037] [Refrigerant Component] The working fluid for a refrigeration cycle according to the present disclosure uses, as a refrigerant component, at least a fluoroolefin (fluoroalkene) that undergoes a disproportionation reaction.

[0038] Specific examples of fluoroolefins that undergo such a disproportionation reaction include, but are not limited to, 1,1,2-trifluoroethylene (CF2=CHF, HFO1123), trans-1,2-difluoroethylene (CHF=CHF(E), HFO1132(E)), cis-1,2-difluoroethylene (CHF=CHF(Z), HFO1132(Z)), 1,1-difluoroethylene (CF2=CH2, HFO1132a), and tetrafluoroethylene (CF2=CF2, FO1114). These fluoroolefins may be used alone or in combination as a refrigerant component.

[0039] 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 substituted with a fluorine atom, or at least one of the two hydrogen atoms bonded to both carbon atoms is substituted with a fluorine atom. Note that in fluoroolefins, some of the hydrogen atoms may be substituted with other atoms or other substituents.

[0040] For example, 1,1,2-trifluoroethylene has a structure in which both of the two hydrogen atoms bonded to one carbon atom (the carbon atom at position 1) of the ethylene structure are substituted with fluorine atoms, and one of the two hydrogen atoms bonded to the other carbon atom (the carbon atom at position 2) is substituted with a fluorine atom.

[0041] 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 at the position opposite to the carbon atom at position 1 across the double bond, rather than the hydrogen atom adjacent to the carbon atom at position 1, is substituted with a fluorine atom.

[0042] 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, atmospheric ozone generates hydroxyl radicals (OH radicals) through photochemical reactions, and these hydroxyl radicals can undergo addition reactions with double bonds, making fluoroolefins easily decomposed. Therefore, fluoroolefins have little impact on ozone layer depletion and global warming.

[0043] The working fluid for a refrigeration cycle according to the present disclosure may contain, as a refrigerant component, difluoromethane (HFC32, R32, chemical formula: CHF) in addition to the fluoroolefin. In this case, if the fluoroolefin is considered to be the "main component" of the refrigerant component in the working fluid for a refrigeration cycle according to the present disclosure, the difluoromethane is considered to be the "secondary component" of the refrigerant component in the working fluid for a refrigeration cycle according to the present disclosure.

[0044] 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 to now.

[0045] Furthermore, the working fluid for a refrigeration cycle according to the present disclosure may contain, as refrigerant components, "other refrigerant components" in addition to the fluoroolefin as the main refrigerant component and the difluoromethane as the secondary refrigerant component. Representative other refrigerant components include, but are not limited to, hydrofluorocarbons (HFCs) such as difluoroethane, trifluoroethane, tetrafluoroethane, pentafluoroethane, pentafluoropropane, hexafluoropropane, heptafluoropropane, pentafluorobutane, and heptafluorocyclopentane; and hydrofluoroolefins (HFOs) such as monofluoropropene, trifluoropropene, tetrafluoropropene, pentafluoropropene, and hexafluorobutene.

[0046] These HFCs or HFOs are known to have little impact on ozone layer 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.

[0047] Here, fluoroolefins are also known to cause rapid disproportionation reactions due to the aforementioned good decomposition properties. Taking 1,1,2-trifluoroethylene as a typical example of fluoroolefins, this disproportionation reaction involves an autolysis reaction in which 1,1,2-trifluoroethylene molecules decompose, and subsequent to this autolysis reaction, a polymerization reaction occurs in which carbon produced by the decomposition polymerizes to form soot. When active radicals are generated due to heat generation or the like under high temperature and pressure conditions, these active radicals react with 1,1,2-trifluoroethylene to cause the aforementioned disproportionation reaction. Since this disproportionation reaction is accompanied by heat generation, active radicals are generated by this heat generation, and further, these active radicals induce the disproportionation reaction. In this way, the generation of active radicals and the occurrence of the disproportionation reaction are linked together, causing the disproportionation reaction to progress rapidly.

[0048] As a result of previous intensive studies by the present applicant, it has become clear that the active radicals that induce the disproportionation reaction of 1,1,2-trifluoroethylene are mainly fluorine radicals (F radicals), as well as radicals such as trifluoromethyl radicals (CF3 radicals) and difluoromethylene radicals (CF2 radicals).

[0049] Therefore, the present applicants attempted to suppress or mitigate the rapid disproportionation reaction by adding a substance (disproportionation inhibitor) capable of efficiently capturing F radicals, CF3 radicals, CF2 radicals, etc. to a working fluid for a refrigeration cycle under conditions where difluoromethane is used in combination with a fluoroolefin such as 1,1,2-trifluoroethylene, which undergoes a disproportionation reaction, as a refrigerant component. As a result, they independently found that the addition of the disproportionation inhibitors disclosed in Patent Documents 1 to 6 can serve as suitable disproportionation inhibitors.

[0050] Furthermore, as a result of extensive research, the present inventors have newly discovered that the disproportionation reaction of fluoroolefins can be effectively suppressed if the haloalkene is a haloalkene in which at least one hydrogen atom of the alkene is substituted with a halogen atom other than fluorine.

[0051] [Disproportionation Inhibitor] 1. Main Disproportionation Inhibitor The working fluid for a refrigeration cycle according to the present disclosure contains, as a disproportionation inhibitor for suppressing the disproportionation reaction of the fluoroolefin, which is the main refrigerant component, a haloalkene in which at least one hydrogen atom of an alkene is substituted with a halogen atom other than fluorine.

[0052] The haloalkene used as the disproportionation inhibitor may have at least one hydrogen atom substituted with a halogen atom other than fluorine, and the other hydrogen atoms may be substituted with fluorine. In this case, the fluoroolefins that are the main refrigerant components described above also contain compounds that can be classified as haloalkenes used as disproportionation inhibitors. Therefore, in this embodiment, the haloalkene used as the disproportionation inhibitor will be referred to as a "disproportionation-inhibited haloalkene" for ease of explanation.

[0053] As will be described later, the working fluid for a refrigeration cycle according to the present disclosure may contain other disproportionation inhibitors in addition to the disproportionation-inhibited haloalkene. Therefore, in this embodiment, for convenience of explanation, the disproportionation-inhibited haloalkene is referred to as the "main component (main disproportionation inhibitor)" of the disproportionation inhibitor, and the other disproportionation inhibitors other than the disproportionation-inhibited haloalkene are referred to as the "secondary components (secondary disproportionation inhibitors)" of the disproportionation inhibitor.

[0054] As described above, the disproportionation-inhibited haloalkene used as the main disproportionation inhibitor in the working fluid for a refrigeration cycle according to the present disclosure may be any alkene having at least one “substituted halogen atom” in which a hydrogen atom is substituted with a halogen atom other than fluorine, but may also include a “substituted fluorine atom” in which a hydrogen atom is substituted with a fluorine atom.

[0055] The halogen atom other than the fluorine atom constituting the substituting halogen atom may be at least one of chlorine (Cl), bromine (Br), and iodine (I), and among these, a chlorine atom is a typical example.

[0056] In general, among organic compounds having chlorine atoms, saturated compounds that do not have a carbon-carbon double bond in their molecular structure are difficult to decompose in the natural environment, and as a result, are prone to depletion of the ozone layer. On the other hand, unsaturated compounds that have a chlorine atom and a double bond in their molecular structure are prone to decomposition in the natural environment. Therefore, a representative example of the halogen atom (excluding fluorine atoms) contained in the disproportionation-inhibiting haloalkene is a chlorine atom.

[0057] Furthermore, if the disproportionation-inhibiting haloalkene contains at least a chlorine atom, it will decompose to produce a decomposition product containing a chlorine atom. This decomposition product is likely to react with active radicals. Therefore, the disproportionation reaction caused by active radicals can be inhibited, and the chain reaction between the generation of active radicals and the disproportionation reaction can be stopped.

[0058] Furthermore, disproportionation-inhibited haloalkenes inherently contain double bonds in their molecular structures, and therefore are easily decomposed in the natural environment regardless of the presence or absence of chlorine atoms, resulting in a short atmospheric lifetime and a relatively small environmental impact.

[0059] In addition, many disproportionation-inhibited haloalkenes are compounds that can be used as refrigerant components. In particular, hydrochlorofluoroolefins (HCFOs), which have substituted chlorine atoms and fluorine atoms in their molecular structures, are known as fluorocarbons with low environmental impact. Therefore, they 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.

[0060] The specific type of disproportionation inhibiting haloalkene that is the main disproportionation inhibitor is not particularly limited, but representative examples include haloalkenes having two carbon atoms, i.e., haloethenes (haloethylenes), and haloalkenes having three carbon atoms, i.e., halopropenes. Of these, the haloethenes having two carbon atoms may be compounds having the structure of formula (1) shown below. CH k F m X n ...(1)

[0061] In formula (1), X is any halogen atom selected from the group consisting of Cl, Br, and I, k and m are each an integer of 0 or more, n is an integer of 1 or more, the sum of k, m, and n is 4, and when n is 2 or more, X is the same or different halogen atom.

[0062] That is, the haloethene having two carbon atoms shown in formula (1) becomes a fluorohaloethene having two carbon atoms when k is 0 and m is an integer of 1 or more, and becomes a hydrohaloethene having two carbon atoms when k is an integer of 1 or more and m is 0. Furthermore, when both k and m are integers other than 0, it becomes a hydrofluorohaloethene having two carbon atoms.

[0063] The halopropene having three carbon atoms may be a compound having the structure of formula (2) shown below: p F q X r ... (2)

[0064] In formula (2), X is any halogen atom selected from the group consisting of Cl, Br, and I, p and q are each an integer of 0 or more, r is an integer of 1 or more, the sum of p, q, and r is 6, and when r is 2 or more, X is the same or different halogen atom.

[0065] That is, when p is 0 and q is an integer of 1 or greater, the halopropene having 3 carbon atoms shown in formula (2) becomes a fluorohalopropene having 3 carbon atoms, and when p is an integer of 1 or greater and q is 0, the halopropene becomes a hydrohalopropene having 3 carbon atoms. When both p and q are integers other than 0, the halopropene becomes a hydrofluorohalopropene having 3 carbon atoms.

[0066] Specific compounds corresponding to such haloethenes or halopropenes include, for example, hydrochlorofluorocarbons such as 1-chloro-2,2-difluoroethene (HCFO1122, CF₂=CHCl), 1-chloro-1,2-difluoroethene (HCFO1122a, CFH₂=CFCl), 3-chloro-1,1,2,3,3-pentafluoro-1-propene (3-chloropentafluoro-1-propene, (HCFO1214yc, CF₂=CF-CF₂Cl), and 3-chloro-2,3,3-trifluoro-1-propene (HCFO1233yf, CH₂=CF-CF₂Cl). Examples of the main disproportionation inhibitor include, but are not limited to, iodofluoroolefin (HCFO) compounds; iodofluoroolefin compounds such as 1,1,2-trifluoro-2-ethene (iodotrifluoroethene, CF═CFI) and 3-iodopentafluoropropene (CF═CFCF═I); and bromofluoroolefin compounds such as 1,1,2-trifluoro-2-bromoethene (bromotrifluoroethene, CF═CFBr). These compounds may be used alone or in combination of two or more as the main disproportionation inhibitor.

[0067] Among these compounds, 1-chloro-2,2-difluoroethene (HCFO-1122), 1-chloro-1,2-difluoroethene (HCFO-1122a), 3-chloro-2,3,3-trifluoro-1-propene (HCFO-1233yf), 1,1,2-trifluoro-2-bromoethene (bromotrifluoroethene), 1,1,2-trifluoro-2-iodoethene (iodotrifluoroethene), 3-iodopentafluoropropene, and the like can be more preferably used as the main disproportionation inhibitor.

[0068] The working fluid for a refrigeration cycle according to the present disclosure contains at least the disproportionation-inhibited haloalkene as a primary disproportionation inhibitor, and the disproportionation-inhibited haloalkene effectively inhibits or moderates the disproportionation reaction of the fluoroolefin.

[0069] Furthermore, many of these disproportionation-inhibited haloalkenes are compounds that can be used as refrigerant components, and therefore have good heat capacities comparable to those of fluoroolefins and are easily blended with fluoroolefins, making them suitable as blend components for working fluids for refrigeration cycles.

[0070] Furthermore, such disproportionation-inhibited haloalkenes contain carbon-carbon double bonds in their molecular structures, similar to the fluoroolefins used as refrigerant components, and therefore are easily decomposed in the natural environment, resulting in a short atmospheric lifetime and a relatively small environmental impact.

[0071] Therefore, even if the working fluid for a refrigeration cycle according to the present disclosure contains a fluoroolefin, which undergoes a disproportionation reaction, as a refrigerant component, the disproportionation reaction can be suppressed or alleviated, and the energy efficiency can be improved, and further environmental load can be reduced.

[0072] 2. Minor 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 in which all the halogen atoms are fluorine (fluoroalkanes) can be used. For ease of explanation, "haloalkanes other than those having 1 or 2 carbon atoms and in which all the halogen atoms are fluorine (fluoroalkanes)" will be simply referred to as "(i) haloalkanes." In this way, by using a disproportionation-inhibiting haloalkene as the main disproportionation inhibitor in combination with (i) haloalkane as the minor disproportionation inhibitor, it is possible to suppress or moderate the progress of the disproportionation reaction even in smaller amounts.

[0073] 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 of the halogen atoms are fluorine (fluoroalkanes). More specifically, examples include haloalkanes having two carbon atoms, i.e., haloethanes (halogenated ethanes), and haloalkanes having one carbon atom, i.e., halomethanes (halogenated methanes). As the disproportionation inhibitor, either haloethane or halomethane may be used in combination with the saturated hydrocarbon described above, but both haloethane and halomethane may also be used in combination.

[0074] The haloethane among the haloalkanes (i) used as the secondary disproportionation inhibitor may specifically be one having the structure of the following formula (3): CH s X t ... (3)

[0075] In formula (3), X is a halogen atom selected from the group consisting of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I), s is an integer of 0 or greater, t is an integer of 1 or greater, the sum of s and t is 6, and when t is 2 or greater, X is the same or different halogen atom.

[0076] That is, the haloethane shown in formula (3) may be at least one of a monohaloethane shown in the following formula (31), a dihaloethane shown in the following formula (32), a trihaloethane shown in the following formula (33), a tetrahaloethane shown in the following formula (34), a pentahaloethane shown in the following formula (35), and a hexahaloethane shown in the following formula (36).

[0077] 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. 1 ~X 6 may be different types of halogen atoms, or at least two may be the same type and the others may be different types of halogen atoms, or all may be the same type of halogen atom. 1 CH3... (31) CHX 1 X 2 CH3... (32) CX 1 X 2 X 3 CH3... (33) CX 1 X 2 X 3 CH2X 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)

[0078] However, haloethanes represented by the formula (3) above exclude those in which X is composed only of F. This is because haloethanes 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 secondary disproportionation inhibitor (ii) described below.

[0079] In the haloethane represented by formula (3), the halogen atom X may be at least one of F, Cl, Br, and I, as described above (except when only F is present), but it is preferable that the halogen atom X is F and I, or that the halogen atom X is I. When the haloethane represented by formula (3) contains Cl and / or Br, the ozone depletion potential (ODP) tends to be high, which may limit availability or handling. Furthermore, regardless of the type of halogen atom X, the haloethane represented by formula (3) also includes compounds with relatively high ozone depletion potential (ODP) and / or global warming potential (GWP).

[0080] However, in the working fluid for a refrigeration cycle according to the present disclosure, because the primary disproportionation inhibitor is a disproportionation-inhibited haloalkene, the amount of haloethane added as a secondary disproportionation inhibitor is relatively small, as will be described later. 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 a haloethane with a relatively high ODP or GWP is used, there is no significant impact on the environment.

[0081] The specific haloethane represented by formula (3) is not particularly limited, and examples thereof include 1,1,1-trifluoro-2-iodoethane (CFCHI), monoiodoethane (CHCHI), monobromoethane (CHCHBr), and 1,1,1-triiodoethane (CHCI). These haloethanes may be used alone or in appropriate combination of two or more. Among these, 1,1,1-trifluoro-2-iodoethane (CFCHI) is particularly preferred, taking into consideration availability, ODP value, ease of handling, and the like.

[0082] Among the (i) haloalkanes used as the secondary disproportionation inhibitor, the halomethane may specifically be one having the structure of the following formula (4): CH v X w ... (4)

[0083] In 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.

[0084] 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 these halomethanes shown in formulas (41) to (44) 1 , X 2 , X 3 , and X 4 Each independently represents one halogen atom, as in the case of haloethane. 1 ~X 4 may be different types of halogen atoms, or at least two may be the same type and the others may be different types of halogen atoms, or all may be the same type of halogen atom. 1 ... (41) CH2X 1 X 2 ... (42) CHX 1 X 2 X 3 ... (43) CX 1 X 2 X 3 X 4 ... (44)

[0085] However, halomethanes represented by the 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 secondary disproportionation inhibitor (ii) described below.

[0086] Specific examples of the halomethane represented by formula (4) include, but are not limited to, (mono)iodomethane (CH3I), diiodomethane (CH2I2), dibromomethane (CH2Br2), bromomethane (CH3Br), dichloromethane (CH2Cl2), chloroiodomethane (CH2ClI), dibromochloromethane (CHBr2Cl), tetraiodomethane (CI4), carbon tetrabromide (CBr4), bromotrichloromethane (CBrCl3), dibromodichloromethane (CBr2Cl2), tribromofluoromethane (CBr3F), difluoroiodomethane (CHF2I), fluorodiiodomethane (CHFI2), difluorodiiodomethane (CF2I2), dibromodifluoromethane (CBr2F2), and trifluoroiodomethane (CF3I). These halomethanes may be used alone or in combination of two or more.

[0087] Among these, more preferred halomethanes include those containing bromine as the halogen atom X, and more preferred halomethanes include dibromomethane (CHBr), bromomethane (CHBr), dibromodichloromethane (CBrCl), difluoroiodomethane (CHF1), and trifluoroiodomethane (CF1), and particularly preferred halomethane is difluoroiodomethane (CHF1).

[0088] 3. Minor Disproportionation Inhibitor (ii) In the present disclosure, the minor 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 can be defined as an alkane having 1 to 3 carbon atoms in which at least one hydrogen atom has been substituted with fluorine.

[0089] For ease of explanation, "a fluoroalkane having 1 to 3 carbon atoms and a boiling point of 0°C or less (excluding difluoromethane)" will be simply referred to as "(ii) fluoroalkane." In this way, by using a disproportionation-inhibiting haloalkene as the primary disproportionation inhibitor in combination with a (ii) fluoroalkane as the secondary disproportionation inhibitor, it is possible to suppress or moderate the progress of the disproportionation reaction even with a smaller amount.

[0090] 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 fluoroalkane include fluoroethanes such as 1,1,1,2,2-pentafluoroethane (boiling point: -48.5°C); and fluoropropanes such as 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). One of these (ii) fluoroalkanes may be used alone as the minor disproportionation inhibitor, or two or more of them may be used in combination as the minor disproportionation inhibitor.

[0091] 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).Of these, particularly representative (ii) fluoroalkanes include fluoropropane.

[0092] In the present disclosure, fluoroethane usable as a minor disproportionation inhibitor is ethane, an alkane having two carbon atoms, in which one or more hydrogen atoms have been substituted with fluorine atoms, and has a boiling point of 0° C. or lower. Similarly, in the present disclosure, fluoropropane usable as a minor disproportionation inhibitor is propane, an alkane having three carbon atoms, in which one or more hydrogen atoms have been substituted with fluorine atoms, and has a boiling point of 0° C. or lower.

[0093] Furthermore, in the present disclosure, only fluoroethane may be used as the (ii) fluoroalkane that is the side disproportionation inhibitor, or 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 types of fluoroethane or two or more types of fluoropropane may be used. Similarly, when fluoroethane or fluoropropane is used in combination, only one type of each may be used, 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.

[0094] In the present disclosure, the (ii) fluoroalkane as a secondary disproportionation inhibitor is used as a working fluid for a refrigeration cycle together with a fluoroolefin as a primary refrigerant component and a disproportionation-inhibited haloalkene as a primary 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.

[0095] 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.

[0096] Furthermore, in the present disclosure, difluoromethane is not included in the (ii) fluoroalkane serving as the minor disproportionation inhibitor. 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. Therefore, in the present disclosure, difluoromethane is excluded from the (ii) fluoroalkane serving as the minor disproportionation inhibitor.

[0097] In addition, as is clear from the results of the comparative examples in Patent Documents 4 and 5, for example, it is believed that difluoromethane, a secondary refrigerant component, does not have the effect of suppressing the disproportionation reaction in fluoroolefins such as 1,1,2-trifluoroethylene.From this perspective, difluoromethane is excluded from (ii) fluoroalkanes as secondary disproportionation suppressors.

[0098] 4. Minor Disproportionation Inhibitor (iii) In the present disclosure, (iii) saturated hydrocarbons having 2 to 5 carbon atoms can be used as the minor disproportionation inhibitor. For ease of explanation, the "saturated hydrocarbons having 2 to 5 carbon atoms" will be simply referred to as "(iii) alkane." In this way, by using a disproportionation-inhibiting haloalkene as the primary disproportionation inhibitor in combination with (iii) an alkane as the minor disproportionation inhibitor, it is possible to suppress or moderate the progress of the disproportionation reaction even with smaller amounts.

[0099] 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 appropriate combination of two or more. Of these (iii) alkanes, n-propane is a representative example.

[0100] These (iii) alkanes are all gases at room temperature (n-pentane and methylcyclobutane have the highest boiling points of approximately 36°C, while the boiling points of other hydrocarbons are less than 36°C), and can be well mixed as components of a working fluid for a refrigeration cycle. Saturated hydrocarbons with six or more carbon atoms are liquid at room temperature and are difficult to mix as components of a working fluid for a refrigeration cycle, and are therefore not preferred as (iii) alkanes as minor disproportionation inhibitors. Furthermore, saturated hydrocarbons with one carbon atom, i.e., methane, are not preferred because of their high global warming potential (GWP). Among the saturated hydrocarbons that fall under the category of (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.

[0101] In the present disclosure, the minor disproportionation inhibitor may be (i) a haloalkane, (ii) a fluoroalkane, or (iii) an alkane, or may be used alone or in combination as appropriate. 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) a haloalkane, (ii) a fluoroalkane, and (iii) an alkane may be used as the minor disproportionation inhibitor in combination with the disproportionation-inhibited haloalkene, which is the main disproportionation inhibitor.

[0102] Therefore, in the working fluid for a refrigeration cycle according to the present disclosure, the minor disproportionation inhibitor may be a single compound selected from the group consisting of (i) haloalkanes, (ii) fluoroalkanes, and (iii) alkanes; a combination of two or more compounds selected from the group consisting of (i) haloalkanes, (ii) fluoroalkanes, and (iii) alkanes; or a combination of two or three compounds selected from the group consisting of (i) haloalkanes, (ii) fluoroalkanes, and (iii) alkanes. Alternatively, a combination of two or three compounds selected from (i) haloalkanes, (ii) fluoroalkanes, and (iii) alkanes may be used as the minor disproportionation inhibitor. Alternatively, a combination of only one compound selected from any one or two compounds selected from (i) haloalkanes, (ii) fluoroalkanes, and (iii) alkanes, or a combination of two or three compounds selected from any one compound selected from any one compound, may be used as the minor disproportionation inhibitor.

[0103] [Content of Disproportionation Inhibitor] 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, a disproportionation-inhibiting haloalkene is used as the primary disproportionation inhibitor, and at least one compound selected from the group consisting of (i) a haloalkane, (ii) a fluoroalkane, and (iii) an alkane can be used in combination as the secondary disproportionation inhibitor.

[0104] Here, for convenience, the total amount of the refrigerant components and the 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% by mass, the upper limit of the amount (content) of the disproportionation inhibitor to be added is not particularly limited, but may be 40% by mass or less of the total amount of the refrigerant-related components, or may be 30% by mass or less, 20% by mass or less, or 15% by mass or less.

[0105] 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 working 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, the disproportionation inhibitor may be added in an amount of 40% by mass or more of the total amount of the refrigerant-related components.

[0106] When only a disproportionation-inhibited haloalkene, which is the primary disproportionation inhibitor, is used as the disproportionation inhibitor (including cases where only one type of disproportionation-inhibited haloalkene is used or where two or more types of disproportionation-inhibited haloalkene are used in combination), the content thereof is not particularly limited, but may be 30% by mass or less, 20% by mass or less, or 10% by mass or less of the total amount of refrigerant-related components.

[0107] Basically, the higher the content of the disproportionation-inhibiting haloalkene, the easier it is to obtain the effect of inhibiting the disproportionation reaction of fluoroolefins. However, as mentioned above, if the content of the disproportionation inhibitor is too high, the working fluid for a refrigeration cycle may not be able to exhibit good physical properties as a "refrigerant." On the other hand, if the content of the disproportionation-inhibiting haloalkene is 30 mass%, it is possible to satisfactorily achieve both the effect of inhibiting the disproportionation reaction of fluoroolefins and good physical properties of the working fluid for a refrigeration cycle (performance as a refrigerant).

[0108] Although it depends on various conditions, when the content of the disproportionation-inhibited haloalkene is 20% by mass or less or 15% 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, when the content is 20% by mass or less or 15% by mass or less, the overall content of the disproportionation inhibitor can be reduced, thereby improving the performance of the working fluid for a refrigeration cycle as a refrigerant.

[0109] Furthermore, although it depends on various conditions, when the content of the disproportionation-inhibiting haloalkene is 10 mass% or less, the disproportionation reaction of the fluoroolefin can be effectively inhibited with a smaller amount, 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 reduced.

[0110] When the disproportionation inhibitor is a disproportionation-inhibiting haloalkene, which is the primary disproportionation inhibitor, and at least one of (i) a haloalkane, (ii) a fluoroalkane, and (iii) an alkane, which is a secondary disproportionation inhibitor, is used in combination, the content thereof is not particularly limited, but the total amount of these secondary disproportionation inhibitors may be 10% by mass or less, 5% by mass or less, 3% by mass or less, or 1% by mass or less of the total amount of the refrigerant-related components.

[0111] As with the disproportionation-inhibited haloalkene, the greater the content of the secondary disproportionation inhibitor, the more effectively it is possible to inhibit the disproportionation reaction of the fluoroolefin. However, as mentioned above, if the content of the disproportionation inhibitor is too high, the working fluid for a refrigeration cycle may not be able to exhibit good physical properties as a "refrigerant."

[0112] Although it depends on various conditions, when 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, when the content is 5% by mass or less or 3% by mass or less, the overall content of the disproportionation inhibitor can be reduced, thereby improving the performance of the working fluid for a refrigeration cycle as a refrigerant.

[0113] Although it depends on various conditions, when the content of the secondary disproportionation inhibitor is 1% by mass or less, the disproportionation reaction of fluoroolefins can be effectively inhibited with a relatively small amount, particularly when combined with a disproportionation-inhibited haloalkene, 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, thereby improving the performance of the working fluid for a refrigeration cycle as a refrigerant.

[0114] When a disproportionation inhibitor containing a disproportionation-inhibiting haloalkene as the primary disproportionation inhibitor is used in combination with a secondary disproportionation inhibitor (at least one of (i) a haloalkane, (ii) a fluoroalkane, and (iii) an alkane), the mixing ratio between these is not particularly limited, and the upper limit of the content described above can be applied. As described above, when the total amount of refrigerant-related components is taken as 100% by mass, a preferred total content of disproportionation inhibitors among these is 40% by mass or less. Therefore, it is sufficient that the disproportionation-inhibiting haloalkene and secondary disproportionation inhibitor are used in combination at an appropriate mixing ratio within this range.

[0115] Furthermore, the lower limit of the content of the disproportionation inhibitor is not particularly limited, but a typical 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, it is assumed that the haloalkane is used in combination with a disproportionation-inhibiting haloalkene, so the lower limit of the total content of disproportionation inhibitors (the total content of the disproportionation-inhibiting haloalkene, which is the primary disproportionation inhibitor, and the secondary disproportionation inhibitor) may be 1.2 mass% or more.

[0116] Depending on various conditions, it is possible to obtain the effect of inhibiting the disproportionation reaction even if the total amount (total content) of the disproportionation inhibitor is less than 1.2 mass%. 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 achieved. 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.

[0117] Generally, in working fluids for refrigeration cycles, the impurities contained in the refrigerant components are often 2 to 3% by mass or less. For example, commercially available products of 1,1,2-trifluoroethylene, a typical fluoroolefin, are known to have a purity of about 97% by mass. Impurities contained in such commercially available products include residues of synthetic raw materials or by-products, and these impurities are contained in amounts 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 impurity content of the commercially available product, i.e., 3% by mass or more.

[0118] Here, the upper limit of the content of (iii) alkane among the secondary disproportionation inhibitors may be 10% by mass or less, as described above, and may be 5% by mass or less or 3% by mass or less. However, when (iii) alkane is n-propane, the upper limit may be 8.5% by mass or less, or may be 7.5% by mass or less.

[0119] On the other hand, although the lower limit of (iii) the alkane is not particularly limited, when (iii) the 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.

[0120] (iii) Alkane can also be used as a refrigerant component, but when used as a secondary disproportionation inhibitor together with a primary disproportionation inhibitor (disproportionation-inhibited haloalkene) rather than as a refrigerant component, it can exhibit the effect of inhibiting the disproportionation reaction at a relatively smaller amount than the content as a refrigerant component in the working fluid for a refrigeration cycle. Although it depends on various conditions, when the (iii) alkane is n-propane, a good disproportionation reaction inhibition effect can be exhibited by selecting a combination of the above upper and lower limit values.

[0121] The amount of the disproportionation inhibitor added can be adjusted depending on various conditions and is therefore not necessarily specified. Therefore, the upper and lower limits of the content of the disproportionation inhibitor described above are merely representative and preferred examples.

[0122] The content of difluoromethane as 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 fluoroolefins are the main refrigerant components, it is sufficient that the content of fluoroolefins in the working fluid for a refrigeration cycle according to the present disclosure is greater than the content of difluoromethane.

[0123] 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 fluoroolefin and difluoromethane in combination as refrigerant components, the upper limit of the difluoromethane content may be 30% by mass or less, 25% by mass or less, or 20% by mass or less of the total amount of refrigerant-related components.

[0124] 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. The lower limit of difluoromethane is not particularly limited. The working fluid for a refrigeration cycle according to the present disclosure does not need to contain difluoromethane, so the difluoromethane content may be 0% by mass or more.

[0125] [Other Components 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 (refrigerating machine oil) that lubricates a compressor included in the refrigeration cycle system.

[0126] As described above, the working fluid for a refrigeration cycle according to the present disclosure uses, as the main refrigerant component, a fluoroolefin (e.g., 1,1,2-trifluoroethylene) that undergoes a disproportionation reaction, optionally in combination with difluoromethane as a secondary refrigerant component, and at least a disproportionation-inhibited haloalkene (main disproportionation inhibitor) as a disproportionation inhibitor. However, 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 also be mixed with the lubricating oil component depending on the circumstances.

[0127] The lubricating oil component contained in the working fluid-containing composition (used in combination with the working fluid for a refrigeration cycle) can be any of various lubricating oils known in refrigeration cycle systems. Specific examples of lubricating oils 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. These lubricating oils may be used alone or in combination of two or more.

[0128] In addition, various known additives other than the disproportionation inhibitor may be added to the working fluid-containing composition. Specific additives include, but are not limited to, antioxidants, moisture scavengers, metal deactivators, antiwear agents, and antifoaming agents. Antioxidants are used to improve the thermal stability, oxidation resistance, chemical stability, etc. of refrigerant components or lubricating oils. Moisture scavengers are used to remove moisture when moisture enters the refrigeration cycle system, and are particularly used to suppress changes in the properties of lubricating oils. Metal deactivators are used to suppress or prevent chemical reactions caused by the catalytic action of metal components. Antiwear agents are used to reduce wear on sliding parts in compressors, especially during high-pressure operation. Antifoaming agents are used, particularly, to suppress the generation of bubbles in lubricating oils.

[0129] The specific types of these additives are not particularly limited, and known compounds can be suitably used depending on various conditions. Furthermore, as these additives, only one type of compound or an appropriate combination of two or more types of compounds can be used. Furthermore, the amount of these additives added is also not particularly limited, and they can be added within known ranges as long as the properties of the working fluid for a refrigeration cycle according to the present disclosure or the working fluid-containing composition containing the same are not impaired.

[0130] The working fluid for a refrigeration cycle according to the present disclosure may contain no other components. For example, a working fluid for a refrigeration cycle using 1,1,2-trifluoroethylene, a fluoroolefin, as the refrigerant component and using only a disproportionation-inhibited haloalkene as the disproportionation inhibitor may be mentioned. Alternatively, a working fluid for a refrigeration cycle using 1,1,2-trifluoroethylene and difluoromethane as the refrigerant components and using only a disproportionation-inhibited haloalkene as the disproportionation inhibitor may be mentioned.

[0131] Alternatively, the working fluid for a refrigeration cycle according to the present disclosure may contain, as the refrigerant component, only a fluoroolefin as the main refrigerant component, while containing, as the disproportionation inhibitor, a disproportionation-inhibiting haloalkene as the main disproportionation inhibitor and at least one of (i) a haloalkane, (ii) a fluoroalkane, and (iii) an alkane as the secondary disproportionation inhibitor. Alternatively, the working fluid for a refrigeration cycle may contain, as the refrigerant component, a fluoroolefin as the main refrigerant component and difluoromethane as the secondary refrigerant component, while containing, as the disproportionation inhibitor, a disproportionation-inhibiting haloalkene as the main disproportionation inhibitor and at least one of (i) a haloalkane, (ii) a fluoroalkane, and (iii) an alkane as the secondary disproportionation inhibitor.

[0132] [Configuration Example of Refrigeration Cycle System] Next, an example of a refrigeration cycle system configured using a working fluid for a refrigeration cycle according to the present disclosure will be described with reference to FIGS. 1A and 1B.

[0133] The specific configuration of the refrigeration cycle system according to the present disclosure is not particularly limited as long as 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 include air conditioners, refrigerators (for home and commercial use), dehumidifiers, showcases, ice makers, heat pump water heaters, heat pump washer-dryers, and vending machines.

[0134] 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 Figure 1A, an air conditioner 10 according to this embodiment includes an indoor unit 11, an outdoor unit 12, and piping 13 connecting these. 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.

[0135] 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 this order by piping 13 in a ring shape. The piping 13 connecting the heat exchanger 14, compressor 16, and heat exchanger 15 is provided with a four-way valve 18 for switching between heating and cooling. The indoor unit 11 is equipped with a blower fan, a temperature sensor, an operating unit, etc. (not shown), and the outdoor unit 12 is equipped with a blower, an accumulator, etc. (not shown). The piping 13 is also provided with various valve devices (including the four-way valve 18), a strainer, etc. (not shown).

[0136] 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 heated by heat exchange into the room, and during cooling, it 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.

[0137] 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.

[0138] An example of the operation of the air conditioner 10 shown in FIG. 1A will be described in detail. First, during cooling or dehumidifying operation, the compressor 16 of the outdoor unit 12 compresses and discharges gas refrigerant, which is then 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, causing the gas refrigerant to condense and liquefy. 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 into gas refrigerant through heat exchange with the indoor air. 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.

[0139] Furthermore, during heating operation, the compressor 16 of the outdoor unit 12 compresses and discharges 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 through heat exchange with the indoor air. The liquefied liquid refrigerant is decompressed by the pressure reducing device 17 to become a two-phase gas-liquid refrigerant and is sent to the heat exchanger 15 of the outdoor unit 12. As 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 gas refrigerant, which returns to the compressor 16. The compressor 16 compresses the gas refrigerant and discharges it again via the four-way valve 18 to the heat exchanger 14 of the indoor unit 11.

[0140] 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. 1B , refrigerator 20 according to the present embodiment includes compressor 21, condenser 22, pressure reducing device 23, evaporator 24, and piping 25. Refrigerator 20 also includes a housing, a blower, an operating unit, a control unit, and the like, which are not shown.

[0141] The compressor 21 compresses refrigerant gas to produce a high-temperature, high-pressure gas refrigerant. The condenser 22 cools the refrigerant to liquefy it. The pressure reducing device 23, which is formed, for example, by a capillary tube, 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.

[0142] The configurations of compressor 21, condenser 22, pressure reducing device 23, evaporator 24, piping 25, main body housing, blower, operation unit, control unit, etc. are not particularly limited, and known configurations can be suitably used. Furthermore, refrigerator 20 may have known configurations other than those described above.

[0143] An example of the operation of refrigerator 20 shown in Fig. 1B will be described in detail. Compressor 21 compresses gas refrigerant and discharges it to condenser 22. Condenser 22 cools the gas refrigerant to liquid refrigerant. The liquid refrigerant is reduced in pressure by passing through pressure reducing device 23 and sent to evaporator 24. In evaporator 24, the liquid refrigerant absorbs heat from the surroundings and is vaporized as gas refrigerant, which returns to compressor 21. Compressor 21 compresses the gas refrigerant and discharges it again to condenser 22.

[0144] Such an air conditioner 10 or 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 favorable 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 disproportionation-inhibited haloalkene as a disproportionation inhibitor.

[0145] 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, thereby realizing a refrigeration cycle system that has a reduced impact on the environment, is efficient, and has excellent practicality.

[0146] The present invention is not limited to the description of the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments or multiple modified examples are also included in the technical scope of the present invention.

[0147] Furthermore, many modifications and other embodiments of the present invention will be apparent to those skilled in the art from the above description. Therefore, the above description should be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode for carrying out the present invention. Details of the structure and / or function thereof may be substantially changed without departing from the spirit of the present invention.

[0148] (Additional Notes) Based on the descriptions of the above embodiments, the present specification discloses the following technologies: (Technology 1) A working fluid for a refrigeration cycle, which 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, a haloalkene in which at least one hydrogen atom of an alkene has been substituted with a halogen atom other than fluorine.

[0149] (Technique 2) The haloalkene is represented by the following formula (1): CH k F m X n ...(1) (wherein X in formula (1) is any halogen atom selected from the group consisting of Cl, Br, and I, k and m are each an integer of 0 or more, n is an integer of 1 or more, the sum of k, m, and n is 4, and when n is 2 or more, X are the same or different halogen atoms).

[0150] (Technique 3) The haloalkene is represented by the following formula (2): C3H p F q X r...(2) (wherein X in formula (2) is any halogen atom selected from the group consisting of Cl, Br, and I, p and q are each an integer of 0 or more, r is an integer of 1 or more, the sum of p, q, and r is 6, and when r is 2 or more, X are the same or different halogen atoms).

[0151] (Technology 4) The working fluid for a refrigeration cycle according to any one of Technology 1 to Technology 3, wherein the haloalkene is 1-chloro-2,2-difluoroethene (HCFO-1122, CF₂=CHCl), 1-chloro-1,2-difluoroethene (HCFO-1122a, CFH₂=CFCl), 3-chloro-2,3,3-trifluoro-1-propene (HCFO-1233yf, CH₂=CF-CF₂Cl), 1,1,2-trifluoro-2-bromoethene (CF₂=CFBr), 1,1,2-trifluoro-2-iodoethene (iodotrifluoroethene, CF₂=CFI), or 3-iodopentafluoropropene (CF₂=CFCF₂I).

[0152] (Technology 5) The working fluid 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.

[0153] (Technology 6) The working fluid for a refrigeration cycle according to any one of Technology 1 to Technology 6, further containing difluoromethane (R32) as a refrigerant component.

[0154] (Technology 7) The working fluid 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 less, and (iii) saturated hydrocarbons having 2 to 5 carbon atoms.

[0155] (Technology 8) The working fluid for a refrigeration cycle according to any one of Technology 1 to Technology 7, wherein the content of the haloalkene is 30% by mass or less when the total amount of the refrigerant components and the disproportionation inhibitor is 100% by mass.

[0156] (Technology 9) The working fluid for a refrigeration cycle according to Technology 6 (or Technology 7 or Technology 8 dependent only on Technology 6), wherein the content of the difluoromethane is 30 mass% or less when the total amount of the refrigerant components and the disproportionation inhibitor is 100 mass%.

[0157] (Technology 10) The working fluid 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%.

[0158] (Technology 11) A refrigeration cycle system configured using the working medium for a refrigeration cycle according to any one of Technology 1 to Technology 10.

[0159] 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.

[0160] 10: Air conditioner (refrigeration cycle system) 11: Indoor unit 12: Outdoor unit 13: Piping 14: Heat exchanger 15: Heat exchanger 16: Compressor 17: Pressure reducing device 18: Four-way valve 20: Refrigerator (refrigeration cycle system) 21: Compressor 22: Condenser 23: Pressure reducing device 24: Evaporator 25: Piping

Claims

1. A working fluid for a refrigeration cycle, comprising as a refrigerant component a fluoroolefin which undergoes a disproportionation reaction, and as a disproportionation inhibitor which inhibits the disproportionation reaction of the fluoroolefin, a haloalkene in which at least one hydrogen atom of an alkene is substituted with a halogen atom other than fluorine.

2. The haloalkene is represented by the following formula (1): k F m X n 2. The working fluid for a refrigeration cycle according to claim 1, which is a haloethene (haloethylene) having the structure represented by the following formula (1): (wherein X in formula (1) is any halogen atom selected from the group consisting of Cl, Br and I, k and m are each an integer of 0 or more, n is an integer of 1 or more, the sum of k, m and n is 4, and when n is 2 or more, X is the same or different halogen atoms).

3. The haloalkene is represented by the following formula (2): C3H p F q X r .theta.-(2) (wherein X in formula (2) is any halogen atom selected from the group consisting of Cl, Br and I, p and q are each an integer of 0 or more, r is an integer of 1 or more, the sum of p, q and r is 6, and when r is 2 or more, X is the same or different halogen atom). the working fluid for a refrigeration cycle according to claim 1, 4. The working medium for a refrigeration cycle according to any one of claims 1 to 3, wherein the haloalkene is 1-chloro-2,2-difluoroethene (HCFO-1122, CF2=CHCl), 1-chloro-1,2-difluoroethene (HCFO-1122a, CFH=CFCl), 3-chloro-2,3,3-trifluoro-1-propene (HCFO-1233yf, CH2=CF-CF2Cl), 1,1,2-trifluoro-2-bromoethene (CF2=CFBr), 1,1,2-trifluoro-2-iodoethene (iodotrifluoroethene, CF2=CFI), or 3-iodopentafluoropropene (CF2=CFCF2I).

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

6. The working fluid for a refrigeration cycle according to any one of claims 1 to 3, further comprising difluoromethane (R32) as a refrigerant component.

7. The working medium for a refrigeration cycle according to any one of claims 1 to 3, wherein when the hydrofluoroolefin is used as the 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 less, and (iii) saturated hydrocarbons having 2 to 5 carbon atoms.

8. The working fluid for a refrigeration cycle according to any one of claims 1 to 3, wherein the content of said haloalkene is 30 mass% or less when the total amount of said refrigerant components and said disproportionation inhibitor is 100 mass%.

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

10. The working fluid for a refrigeration cycle according to claim 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 %.

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

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