Refrigeration cycle working medium and refrigeration cycle system

Abstract

The present invention includes, as a refrigerant component, a fluoroalkene that undergoes a disproportionation reaction, such as 1,1,2-trifluoroethylene, and difluoromethane, and as a disproportionation inhibitor that inhibits the disproportionation reaction of the fluoroalkene, at least difluoroiodomethane (CF₂HI). The present invention may further include, n·propane, may further include 1,1,1-trifluoro-2-iodoethane, or may further included trifluoroiodomethane (CF₃I) as the disproportionation inhibitor.

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 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 layer 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 hydrofluoroolefins (HFOs), which have a smaller global warming potential (GWP), has recently been proposed.

[0003] A typical HFO is known to be, for example, 1,1,2-trifluoroethylene (HFO1123). 1,1,2-trifluoroethylene is less stable than conventional HFCs and is therefore less likely to remain in the atmosphere, and therefore has low ODP and GWP. However, it is also known that due to the low stability of 1,1,2-trifluoroethylene, it is 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, the present applicant has proposed the use of halomethanes (Patent Document 1), saturated hydrocarbons (Patent Document 2), haloethanes (Patent Document 3), or combinations of these (Patent Document 4 or Patent Document 5) as components (disproportionation inhibitors) for inhibiting the disproportionation reaction of 1,1,2-trifluoroethylene when 1,1,2-trifluoroethylene is used as a refrigerant component of a working fluid for a refrigeration cycle. It is also known that difluoromethane (HFC32, R32) can be used in combination with 1,1,2-trifluoroethylene (R32 is the refrigerant number based on Standard 34 of the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE)).

[0006] JP 2017-145380 A JP 2018-048271 A JP 2018-104565 A JP 2018-104566 A JP 2019-034983 A

[0007] The disproportionation inhibitor described above can effectively inhibit or mitigate the disproportionation reaction of 1,1,2-trifluoroethylene. Even when difluoromethane is used in combination as a refrigerant component, the disproportionation inhibitor described above can effectively inhibit or mitigate the disproportionation reaction of 1,1,2-trifluoroethylene.

[0008] Here, the present inventors have conducted extensive studies based on specific conditions of use of a working fluid for a refrigeration cycle containing 1,1,2-trifluoroethylene, and have found that in an actual refrigeration cycle system, 1,1,2-trifluoroethylene may be exposed to conditions of higher temperature and pressure than expected.

[0009] For example, as described in Patent Document 5, the above-mentioned disproportionation inhibitor can effectively inhibit or mitigate the disproportionation reaction by setting the content of haloalkane having 1 to 4 carbon atoms within a predetermined range even under temperature conditions of 150° C. or higher. However, a working fluid for a refrigeration cycle that can effectively inhibit or mitigate the disproportionation reaction not only under high-temperature conditions but also under high-pressure conditions has not been clarified.

[0010] The present invention has been made to solve the above problems, and an object of the present invention is to provide a working fluid for a refrigeration cycle that can more effectively suppress or mitigate the disproportionation reaction of fluoroalkene even under high-temperature and high-pressure conditions when difluoromethane is used in combination with a fluoroalkene that undergoes a disproportionation reaction, such as 1,1,2-trifluoroethylene, as a refrigerant component, and a refrigeration cycle system using the same.

[0011] In order to solve the above-mentioned problems, the working fluid for a refrigeration cycle according to the present invention contains, as refrigerant components, a fluoroalkene and difluoromethane, which undergo a disproportionation reaction, and also contains at least difluoroiodomethane (CHF2I) as a disproportionation inhibitor for suppressing the disproportionation reaction of the fluoroalkene.

[0012] According to the above configuration, at least difluoroiodomethane is added as a disproportionation inhibitor to a refrigerant component mainly composed of fluoroalkene, which undergoes a disproportionation reaction. In the disproportionation reaction of fluoroalkene, radicals such as fluorine radicals, fluoromethyl radicals, and fluoromethylene radicals cause chain branching reactions. Difluoroiodomethane can effectively capture these radicals. Therefore, even under high-temperature and high-pressure conditions, the disproportionation reaction of fluoroalkene can be effectively suppressed and the rapid progression of the disproportionation reaction can be alleviated. As a result, the reliability of a working fluid for a refrigeration cycle and a refrigeration cycle system using the same can be improved.

[0013] 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.

[0014] The present invention, with the above-described configuration, has the effect of providing a working fluid for a refrigeration cycle that can more effectively suppress or mitigate the disproportionation reaction of fluoroalkene even under high-temperature and high-pressure conditions when difluoromethane is used in combination with a fluoroalkene that undergoes a disproportionation reaction, such as 1,1,2-trifluoroethylene, as a refrigerant component, and a refrigeration cycle system using the working fluid.

[0015] 1A and 1B are schematic block diagrams illustrating an example of a refrigeration cycle system according to an embodiment of the present disclosure.

[0016] The working fluid for a refrigeration cycle according to the present disclosure contains, as refrigerant components, a fluoroalkene and difluoromethane, which undergo a disproportionation reaction, and also contains at least difluoroiodomethane (CHF2I) as a disproportionation inhibitor for suppressing the disproportionation reaction of the fluoroalkene.

[0017] According to the above configuration, at least difluoroiodomethane is added as a disproportionation inhibitor to a refrigerant component mainly composed of fluoroalkene, which undergoes a disproportionation reaction. In the disproportionation reaction of fluoroalkene, radicals such as fluorine radicals, fluoromethyl radicals, and fluoromethylene radicals cause chain branching reactions. Difluoroiodomethane can effectively capture these radicals. Therefore, even under high-temperature and high-pressure conditions, the disproportionation reaction of fluoroalkene can be effectively suppressed and the rapid progression of the disproportionation reaction can be alleviated. As a result, the reliability of a working fluid for a refrigeration cycle and a refrigeration cycle system using the same can be improved.

[0018] In the working fluid for a refrigeration cycle having the above configuration, the fluoroalkene that undergoes the disproportionation reaction may be 1,1,2-trifluoroethylene.

[0019] According to the above configuration, at least difluoroiodomethane is added as a disproportionation inhibitor to a refrigerant component primarily composed of 1,1,2-trifluoroethylene (HFO1123). In the disproportionation reaction of 1,1,2-trifluoroethylene, radicals such as fluorine radicals, fluoromethyl radicals, and fluoromethylene radicals cause chain branching reactions. Difluoroiodomethane can effectively capture these radicals. Therefore, even under high-temperature and high-pressure conditions, the disproportionation reaction of 1,1,2-trifluoroethylene can be effectively suppressed and the rapid progression of the disproportionation reaction can be mitigated. As a result, the reliability of a working fluid for a refrigeration cycle and a refrigeration cycle system using the same can be improved.

[0020] The working fluid for a refrigeration cycle having the above configuration may further contain n-propane as the disproportionation inhibitor.

[0021] According to the above-described configuration, n-propane is used in combination with difluoroiodomethane as a disproportionation inhibitor, which makes it possible to more effectively suppress or moderate the progress of the disproportionation reaction even under high-temperature and high-pressure conditions.

[0022] The working fluid for a refrigeration cycle having the above-described configuration may further contain 1,1,1-trifluoro-2-iodoethane (CF3CH2I) or trifluoroiodomethane (CF3I) as the disproportionation inhibitor.

[0023] According to the above-described configuration, 1,1,1-trifluoro-2-iodoethane or trifluoroiodomethane is used in combination with difluoroiodomethane as a disproportionation inhibitor, thereby making it possible to more effectively suppress or moderate the progress of the disproportionation reaction even under high-temperature and high-pressure conditions.

[0024] In the working fluid for a refrigeration cycle having the above configuration, the content of difluoromethane in the total amount of the refrigerant components and the disproportionation inhibitor may be 30 mass % or less.

[0025] According to the above-mentioned configuration, the content of difluoromethane used together with 1,1,2-trifluoroethylene as a refrigerant component is not more than the above-mentioned upper limit value, so that an increase in the global warming potential (GWP) of the working fluid for a refrigeration cycle can be effectively suppressed.

[0026] In addition, in the working fluid for a refrigeration cycle having the above configuration, the content of the difluoroiodomethane may be 15% by mass or less when the total amount of the refrigerant components and the disproportionation inhibitor is taken as 100% by mass.

[0027] According to the above-mentioned configuration, the content of difluoroiodomethane as a disproportionation inhibitor is not more than the above-mentioned upper limit, so that the disproportionation reaction can be more effectively inhibited or its progress can be more effectively slowed down even under high-temperature and high-pressure conditions.

[0028] In the working fluid for a refrigeration cycle having the above configuration, the content of n-propane 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.

[0029] According to the above-mentioned configuration, the content of n-propane used together with difluoroiodomethane as a disproportionation inhibitor is not more than the above-mentioned upper limit, so that the disproportionation reaction can be more effectively inhibited or its progress can be more effectively alleviated even under high-temperature and high-pressure conditions.

[0030] Furthermore, the present disclosure also includes a refrigeration cycle system configured using the working fluid for a refrigeration cycle having the above configuration.

[0031] Representative embodiments of the present disclosure will be described in detail below. A working fluid for a refrigeration cycle according to the present disclosure contains, as refrigerant components, (A) a fluoroalkene that undergoes a disproportionation reaction and (B) difluoromethane, and also contains (C-1) at least difluoroiodomethane (CHF2I or CF2HI) as a (C) disproportionation inhibitor that suppresses the disproportionation reaction of the (A) fluoroalkene.

[0032] In the present disclosure, the (C) disproportionation inhibitor may contain (C-2) n-propane in addition to (C-1) difluoroiodomethane, or may further contain (C-3) 1,1,1-trifluoro-2-iodoethane (CF3CH2I) or (C-4) trifluoroiodomethane (CF3I) in addition to (C-1) difluoroiodomethane. Needless to say, the working fluid for a refrigeration cycle according to the present disclosure may contain components other than the components (A) to (C).

[0033] Furthermore, the high-temperature, high-pressure conditions in the present disclosure refer to conditions under which a working fluid for a refrigeration cycle, in which (A) a fluoroalkene is used in combination with (B) difluoromethane as a refrigerant component, is exposed to a temperature of 60°C or higher and a pressure of 4.2 MPa or higher. These high-temperature, high-pressure conditions are conditions that take into consideration the temperatures and pressures that may actually occur in a compressor provided in a refrigeration cycle system such as an air conditioner, which will be described later.

[0034] [Refrigerant Components] The working fluid for a refrigeration cycle according to the present disclosure uses at least two refrigerant components: (A) a fluoroalkene that undergoes a disproportionation reaction, and (B) difluoromethane (HFC32, R32, chemical formula: CH2F2). (A) Examples of the fluoroalkene that undergoes a disproportionation reaction include 1,1,2-trifluoroethylene (HFO1123), trans-1,2-difluoroethylene (HFO1132(E)), and tetrafluoroethylene (CF2=CF2, HFO1114).

[0035] Of these, (A-1) 1,1,2-trifluoroethylene has a structure represented by the following formula (2), in which two hydrogen atoms (H) bonded to the carbon atom at position 1 of ethylene (C [element symbol]) are substituted with fluorine (F), and one of the two hydrogen atoms bonded to the carbon atom at position 2 is substituted with fluorine.

[0036] (A-1) 1,1,2-trifluoroethylene contains a carbon-carbon double bond. Ozone in the atmosphere generates hydroxyl radicals (OH radicals) through photochemical reactions, and these hydroxyl radicals easily decompose the double bond. Therefore, (1) 1,1,2-trifluoroethylene has little impact on ozone layer depletion and global warming.

[0037] If component (A) is considered to be the "main component" of the refrigerant components in the working fluid for a refrigeration cycle according to the present disclosure, then (B) difluoromethane is considered to be the "secondary component" of the refrigerant components in the working fluid for a refrigeration cycle according to the present disclosure. As described above, (B) difluoromethane has an ozone depletion potential (ODP) of 0 and exhibits good refrigerant performance compared to the HCFCs (hydrochlorofluorocarbons) that have been used until now.

[0038] Furthermore, the working fluid for a refrigeration cycle according to the present disclosure may contain, as a refrigerant component, "other refrigerant components" other than component (A) and component (B). Typical examples of the 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.

[0039] These HFCs or HFOs are known to have little impact on ozone depletion and global warming, and can therefore be used in combination with component (A) as a refrigerant component. The other refrigerant components described above may be used alone or in appropriate combination of two or more.

[0040] Here, it is also known that component (A) causes a rapid disproportionation reaction due to the aforementioned good decomposition property. Taking (A-1) 1,1,2-trifluoroethylene as a representative example of component (A), this disproportionation reaction involves an autolysis reaction in which the molecules of 1,1,2-trifluoroethylene (A-1) decompose, and following this autolysis reaction, a polymerization reaction occurs in which the 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 high-pressure conditions, these active radicals react with 1,1,2-trifluoroethylene (A-1), causing 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 proceed rapidly.

[0041] As a result of previous intensive studies by the applicant of the present application, it has become clear that (A-1) 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).

[0042] 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 the conditions where (A) a fluoroalkene such as (A-1) 1,1,2-trifluoroethylene, which undergoes a disproportionation reaction, and (B) difluoromethane are used in combination as refrigerant components. As a result, they independently found that the addition of the disproportionation inhibitors disclosed in Patent Documents 1 to 5 can serve as suitable disproportionation inhibitors.

[0043] As a result of further intensive studies by the present inventors, it has become clear that there is a possibility that a working fluid for a refrigeration cycle will be exposed to higher temperature and pressure conditions (the aforementioned conditions of 60°C or higher and 4.2 MPa or higher). As a result of further intensive studies by the present inventors, they have independently found that, under conditions in which (A) a fluoroalkene that undergoes a disproportionation reaction, such as (A-1) 1,1,2-trifluoroethylene, is used in combination with (B) difluoromethane, by using at least (C-1) difluoroiodomethane (CHF2I) as the disproportionation inhibitor (C), the disproportionation reaction of (A) the fluoroalkene can be more effectively inhibited even under conditions of higher temperature and pressure than previously assumed.

[0044] [Disproportionation Inhibitor] The working fluid for a refrigeration cycle according to the present disclosure contains at least (C-1) difluoroiodomethane (CHF2I) as the disproportionation inhibitor (C) that inhibits the disproportionation reaction of (A) fluoroalkene such as (A-1) 1,1,2-trifluoroethylene.

[0045] In Patent Documents 1 to 5, examples of halomethanes used as disproportionation inhibitors include (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), fluorodiiodomethane (CHFI2), difluorodiiodomethane (CF2I2), dibromodifluoromethane (CBr2F2), and trifluoroiodomethane (CF3I), but difluoroiodomethane is not mentioned.

[0046] As is clear from the results of the Examples described later, difluoroiodomethane, even when used alone, can effectively suppress or mitigate the disproportionation reaction of (A) a fluoroalkene such as (A-1) 1,1,2-trifluoroethylene.

[0047] Furthermore, in the working fluid for a refrigeration cycle according to the present disclosure, (C-1) difluoroiodomethane and (C-2) n-propane can be used in combination as the disproportionation inhibitor (C). That is, the working fluid for a refrigeration cycle according to the present disclosure may use a fluoroalkene (A) such as (A-1) 1,1,2-trifluoroethylene and (B) difluoromethane in combination as the refrigerant components, and (C-1) difluoroiodomethane alone as the disproportionation inhibitor (C), or may use a fluoroalkene (A) such as (A-1) 1,1,2-trifluoroethylene and (B) difluoromethane in combination as the refrigerant components, and (C-1) difluoroiodomethane and (C-2) n-propane in combination as the disproportionation inhibitor.

[0048] Alternatively, in the working fluid for a refrigeration cycle according to the present disclosure, (C-3) 1,1,1-trifluoro-2-iodoethane (CFCHI) may be used in combination with (C-1) difluoroiodomethane as the disproportionation inhibitor (C), or (C-4) trifluoroiodomethane (CFI) may be used in combination with (C-1) difluoroiodomethane as the disproportionation inhibitor (C).

[0049] Furthermore, in the working fluid for a refrigeration cycle according to the present disclosure, as the disproportionation inhibitor (C), two or more of (C-2) n-propane, (C-3) 1,1,1-trifluoro-2-iodoethane, and (C-4) trifluoroiodomethane may be used in combination with (C-1) difluoroiodomethane. That is, when (C-1) difluoroiodomethane is defined as the "main component of the disproportionation inhibitor," any one of (C-2) n-propane, (C-3) 1,1,1-trifluoro-2-iodoethane, and (C-4) trifluoroiodomethane may be used as the "minor component of the disproportionation inhibitor." Alternatively, any two of these three "minor components of the disproportionation inhibitor" may be used in appropriate combination, or all three may be used as the "minor component of the disproportionation inhibitor."

[0050] [Composition of Working Fluid for Refrigeration Cycle] Next, a typical composition of the working fluid for a refrigeration cycle according to the present disclosure will be specifically described. First, the content of (A) the fluoroalkene that undergoes a disproportionation reaction in the working fluid for a refrigeration cycle is not particularly limited, but when the total amount of the refrigerant components and disproportionation inhibitor among the components constituting the working fluid for a refrigeration cycle (for convenience of explanation, referred to as the "total amount of refrigerant-related components") is taken as 100 mass%, the lower limit of the content of (A) the fluoroalkene such as (A-1) 1,1,2-trifluoroethylene may be 40 mass% or more, or may be 50 mass% or more, or may be 60 mass% or more.

[0051] If the content of the (A) fluoroalkene is less than 40% by mass of the total amount of refrigerant-related components, the content of the (A) fluoroalkene in the working fluid for a refrigeration cycle will be too low, resulting in the inclusion of a large amount of other refrigerant components such as (B) difluoromethane, etc. As a result, the advantage of using the (A) fluoroalkene such as (A-1) 1,1,2-trifluoroethylene, which has a small global warming potential (GWP), in the working fluid for a refrigeration cycle cannot be fully obtained.

[0052] On the other hand, the upper limit of the content of (A) fluoroalkene is not particularly limited and can be set as appropriate depending on the contents of other essential components in the working fluid for a refrigeration cycle according to the present disclosure (i.e., (B) difluoromethane and (C) disproportionation inhibitor) and other components added other than the essential components.

[0053] Next, the content of (B) difluoromethane in the working fluid for a refrigeration cycle is not particularly limited. As described above, (A) fluoroalkene such as (A-1) 1,1,2-trifluoroethylene is the "major component (main refrigerant component)" of the refrigerant component, and (B) difluoromethane is the "minor component (secondary refrigerant component)" of the refrigerant component. Therefore, in the working fluid for a refrigeration cycle according to the present disclosure, it is sufficient that the content of (A) fluoroalkene such as (A-1) 1,1,2-trifluoroethylene is greater than the content of (B) difluoromethane.

[0054] 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). From the viewpoint of using a fluoroalkene (A) such as (A-1) 1,1,2-trifluoroethylene and difluoromethane (B) in combination as refrigerant components, the upper limit of the content of difluoromethane (B) may be 30% by mass or less, or may be 25% by mass or less, of the total amount of refrigerant-related components.

[0055] Next, the content of the disproportionation inhibitor (C) in the working fluid for a refrigeration cycle is not particularly limited, but the upper limit of the content of the disproportionation inhibitor (C) may be 15 mass% or less of the total amount of refrigerant-related components, or may be 12 mass% or less, or may be 10 mass% or less. If the content of the disproportionation inhibitor exceeds 15 mass% of the total amount of 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 15 mass% or more of the total amount of refrigerant-related components.

[0056] Therefore, even when only the essential component (C-1) difluoroiodomethane is used as the disproportionation inhibitor (C), the upper limit of its content may be 15% by mass or less, 12% by mass or less, or 10% by mass or less of the total amount of refrigerant-related components. However, under the high-temperature, high-pressure conditions described above, the content of (C-1) difluoroiodomethane may be 10% by mass or less, 8% by mass or less, or 5% by mass or less of the total amount of refrigerant-related components. In particular, under pressure conditions lower than those under high-temperature, high-pressure conditions (less than 4.2 MPa), even if the content of (C-1) difluoroiodomethane is 2% by mass or less of the total amount of refrigerant-related components, it is possible to effectively inhibit or mitigate the disproportionation reaction of (A) fluoroalkene such as (A-1) 1,1,2-trifluoroethylene.

[0057] Next, when at least one of (C-2) n-propane, (C-3) 1,1,1-trifluoro-2-iodoethane, and (C-4) trifluoroiodomethane is used in combination with (C-1) difluoroiodomethane as the (C) disproportionation inhibitor, the content can be appropriately set depending on the type of (C) disproportionation inhibitor as these "secondary components."

[0058] For example, (C-2) n-propane can be used as (C) a disproportionation inhibitor and can also be used as another refrigerant component other than (A) a fluoroalkene and (B) difluoromethane. Therefore, the content of (C-2) n-propane can be appropriately adjusted depending on the use conditions of the working fluid for a refrigeration cycle, etc. Typically, the upper limit of the content of (C-2) n-propane may be 10% by mass or less, or may be 8% by mass or less, of the total amount of refrigerant-related components. Furthermore, the upper limit of the content of (C-2) n-propane may be 4% by mass or more, or may be 5% by mass or more, of the total amount of refrigerant-related components.

[0059] If the content of (C-2) n-propane exceeds 10% by mass, the flammability of the working fluid for a refrigeration cycle may increase, and the effect of inhibiting or mitigating the disproportionation reaction commensurate with the amount added may not be obtained when viewed as (C) a disproportionation inhibitor. Furthermore, if the content of (C-2) n-propane is less than 4% by mass, depending on various conditions, there is a possibility that the adjusting effect due to the addition of (C-2) n-propane, which serves as both (C) a disproportionation inhibitor and a refrigerant component, may not be fully exerted.

[0060] Furthermore, the lower limit of the content of the (C) 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. Even if the content of the (C) disproportionation inhibitor is less than 1.2 mass%, it is possible to obtain the effect of inhibiting or mitigating the disproportionation reaction. However, if the content is 1.2 mass% or more, it is expected that the effect of inhibiting or mitigating the disproportionation reaction will be more suitably achieved. Therefore, in the present disclosure, a preferred lower limit of the content of the disproportionation inhibitor can be 1.2 mass% or more of the total amount of refrigerant-related components.

[0061] In general, impurities contained in refrigerant components of working fluids for refrigeration cycles are often 2 to 3% by mass or less. For example, commercially available (A-1) 1,1,2-trifluoroethylene, a typical example of a fluoroalkene that undergoes the disproportionation reaction (A), is known to have a purity of approximately 97% by mass, and contains less than 3% by mass of remaining synthetic raw materials or by-products as impurities. In the present disclosure, (C-1) difluoroiodomethane, an essential component of the disproportionation inhibitor (C), can effectively inhibit or slow the progress of the disproportionation reaction even when added to 1,1,2-trifluoroethylene at an impurity level (3% by mass or less). Therefore, the amount of disproportionation inhibitor to be added cannot necessarily be specified, and the upper and lower limits of each component described above are merely representative preferred examples.

[0062] [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 provided in the refrigeration cycle system.

[0063] As described above, the working fluid for a refrigeration cycle according to the present disclosure may comprise (A) a fluoroalkene such as 1,1,2-trifluoroethylene that undergoes a disproportionation reaction, and (B) difluoromethane as refrigerant components, in combination with at least (C-1) difluoroiodomethane as a disproportionation inhibitor (C). 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 constituted by 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 (C) may be mixed with the refrigerant component or the lubricating oil component.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] The working fluid for a refrigeration cycle according to the present disclosure may not contain any other components. For example, when (A-1) 1,1,2-trifluoroethylene is used as the fluoroalkene (A) undergoing the disproportionation reaction, the working fluid for a refrigeration cycle according to the present disclosure may be composed of three components: (A-1) 1,1,2-trifluoroethylene, (B) difluoromethane, and (C-1) difluoroiodomethane, or may be composed of four components: (A-1) 1,1,2-trifluoroethylene, (B) difluoromethane, (C-1) difluoroiodomethane, and (C-2) n-propane, or may be composed of four components: (A-1) 1,1,2-trifluoroethylene, (B) difluoromethane, (C-1) difluoroiodomethane, and (C-2) n-propane. It may be composed of four components: (A-1) 1,1,2-trifluoroethylene, (B) difluoromethane, (C-1) difluoroiodomethane, and (C-4) trifluoroiodomethane; or it may be composed of five or six components: (A-1) 1,1,2-trifluoroethylene, (B) difluoromethane, and (C-1) difluoroiodomethane, and at least two of (C-2) n-propane, (C-3) 1,1,1-trifluoro-2-iodoethane, and (C-4) trifluoroiodomethane. When the fluoroalkene (A) is a refrigerant component different from the fluoroalkene (A-1) 1,1,2-trifluoroethylene, the fluoroalkene (A-1) may be replaced with another refrigerant component.

[0068] [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. FIG.

[0069] 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.

[0070] 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.

[0071] 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).

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] Such an air conditioner 10 or refrigerator 20 is a refrigeration cycle system configured using the above-mentioned working fluid for the refrigeration cycle. 1,1,2-trifluoroethylene used as the working fluid for the refrigeration cycle has good properties as a refrigerant component and has low ODP and GWP. Therefore, an efficient refrigeration cycle system can be realized while minimizing the impact on the environment.

[0081] Furthermore, the working fluid for a refrigeration cycle according to the present disclosure uses, as refrigerant components, (A) a fluoroalkene such as (A-1) 1,1,2-trifluoroethylene that undergoes a disproportionation reaction, and (B) difluoromethane, and uses at least (C-1) difluoroiodomethane as a (C) disproportionation inhibitor. Preferably, as disproportionation inhibitors, (C-1) difluoroiodomethane may be used in combination with (C-2) n-propane, (C-1) difluoroiodomethane may be used in combination with (C-3) 1,1,1-trifluoro-2-iodoethane, or (C-1) difluoroiodomethane may be used in combination with (C-4) trifluoroiodomethane.

[0082] If the working fluid for a refrigeration cycle has such a configuration, it is possible to avoid, suppress, or mitigate the occurrence of a chain reaction of disproportionation of 1,1,2-trifluoroethylene even if heat is generated during operation of the refrigeration cycle. In particular, it is possible to effectively avoid, suppress, or mitigate the occurrence of a disproportionation reaction of 1,1,2-trifluoroethylene under high-temperature and high-pressure conditions (60°C or higher and 4.2 MPa or higher) that simulate the actual use environment of the working fluid for a refrigeration cycle. As a result, it is possible to effectively avoid the generation of soot due to a chain reaction of disproportionation, thereby improving the reliability of the working fluid for a refrigeration cycle and a refrigeration cycle system using the same.

[0083] The present disclosure will be described in more detail based on examples, comparative examples, and reference examples, but the present disclosure is not limited thereto. Those skilled in the art may make various changes, modifications, and alterations without departing from the scope of the present disclosure.

[0084] (Experimental system for disproportionation reaction) A sealed pressure-resistant vessel (stainless steel sealed vessel TVS-N2 [product name] manufactured by Taiatsu Glass Kogyo Co., Ltd., internal volume 50 mL) was equipped with a pressure sensor (VESVM10-2m [product name] manufactured by Valcom Co., Ltd.) for measuring the internal pressure in the pressure-resistant vessel, a thermocouple (PL thermocouple gland PL-18-K-A 4-T [product name] manufactured by Conax Technologies) for measuring the internal temperature in the pressure-resistant vessel, and a discharge device (UH-1 series mini mini welder [product name] manufactured by AS ONE Corporation) for generating a discharge in the pressure-resistant vessel.

[0085] Furthermore, a gas cylinder containing (A-1) 1,1,2-trifluoroethylene (manufactured by SynQuest Laboratories, sold by Hydras Chemical Co., Ltd., containing 5% (liquid phase) limonene as a stabilizer) as the fluoroalkene (A) that undergoes a disproportionation reaction and is the main component of the refrigerant component, and a gas cylinder containing (B) difluoromethane (manufactured by Daikin Industries, Ltd.), a secondary component of the refrigerant component, were connected so as to enable pressure adjustment. Two mantle heaters (Tokyo Glass Instruments Co., Ltd., pipe-type mantle heaters P-31 and P-51 [both trade names]) were installed to heat the entire pressure vessel, and a ribbon heater (Tokyo Technical Research Institute, Inc., flexible ribbon heater, 1 m, 200 W) was also installed to heat the piping. This constructed an experimental system for the disproportionation reaction.

[0086] Comparative Example 1 In the experimental system, (A-1) 1,1,2-trifluoroethylene and (B) difluoromethane were introduced into the pressure vessel from gas cylinders, and the amounts introduced were adjusted so that the content of (B) difluoromethane was 22 mass %.

[0087] Therefore, the content of (A-1) 1,1,2-trifluoroethylene in the working fluid for the refrigeration cycle in the pressure vessel is 78 mass %.

[0088] (A-1) In order to induce the disproportionation reaction of 1,1,2-trifluoroethylene, a discharge was generated by a discharge device under high-temperature and high-pressure conditions of an internal temperature of 150° C. and an internal pressure of 6 MPa at a discharge voltage of 300 V. After that, when the inside of the pressure vessel was checked after the internal pressure and internal temperature had sufficiently decreased, the generation of a considerable amount of soot was confirmed, indicating that the disproportionation reaction had occurred.

[0089] Comparative Example 2 In the experimental system described above, 1,1,2-trifluoroethylene (A-1) and difluoromethane (B) were introduced into a pressure vessel in the same manner as in Comparative Example 1, except that 1,1,1-trifluoro-2-iodoethane was added as the disproportionation inhibitor (C) so that the content was 7.5 mass %.

[0090] Therefore, in the working fluid for a refrigeration cycle in the pressure-resistant vessel, the content of (A-1) 1,1,2-trifluoroethylene is 71.5% by mass, the content of (B) difluoromethane is 22% by mass, and the content of 1,1,1-trifluoro-2-iodoethane is 7.5% by mass.

[0091] Then, in the same manner as in Comparative Example 1, the occurrence of a disproportionation reaction of (A-1) 1,1,2-trifluoroethylene was confirmed, and similarly to Comparative Example 1, the generation of a considerable amount of soot was confirmed, indicating that a disproportionation reaction had occurred.

[0092] Example 1 In the experimental system described above, 1,1,2-trifluoroethylene (A-1) and difluoromethane (B) were introduced into a pressure vessel in the same manner as in Comparative Example 1, except that difluoroiodomethane (C-1) was added as the disproportionation inhibitor (C) so that the content was 7.5 mass %.

[0093] Therefore, in the working fluid for a refrigeration cycle in the pressure-resistant vessel, the content of (A-1) 1,1,2-trifluoroethylene is 71.5% by mass, the content of (B) difluoromethane is 22% by mass, and the content of (C-1) difluoroiodomethane is 7.5% by mass.

[0094] Then, in the same manner as in Comparative Example 1, the occurrence of disproportionation reaction of (A-1) 1,1,2-trifluoroethylene was confirmed, but no disproportionation reaction was confirmed.

[0095] Example 2 In the experimental system, (A-1) 1,1,2-trifluoroethylene and (B) difluoromethane were introduced into the pressure-resistant vessel in the same manner as in Comparative Example 1, except that (C) difluoroiodomethane was added as a disproportionation inhibitor (C) to give a content of 1 mass %, a gas cylinder of (C-2) n-propane was connected to the pressure-resistant vessel so as to be pressure-adjustable, and the amount of (C-2) n-propane introduced was adjusted so that the content was 7.5 mass %.

[0096] Therefore, in the working fluid for a refrigeration cycle in the pressure-resistant vessel, the content of (A-1) 1,1,2-trifluoroethylene was 69.5% by mass, the content of (B) difluoromethane was 22% by mass, the content of (C-1) difluoroiodomethane was 1.0% by mass, and the content of (C-2) n-propane was 7.5% by mass.

[0097] Then, in the same manner as in Comparative Example 1, the occurrence of disproportionation reaction of (A-1) 1,1,2-trifluoroethylene was confirmed, but no disproportionation reaction was confirmed.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] REFRIGERATION CYCLE SYSTEM 10 AIR CONDITIONER (REFRIGERATION CYCLE SYSTEM) 11 INDOOR UNIT 12 OUTDOOR UNIT 13 PIPE 14 HEAT EXCHANGER 15 HEAT EXCHANGER 16 COMPRESSOR 17 PRESSURE RESPONSE DEVICE 18 FOUR-WAY VALVE 20 REFRIGERATOR (REFRIGERATION CYCLE SYSTEM) 21 COMPRESSOR 22 CONDENSER 23 PRESSURE RESPONSE DEVICE 24 EVAPORATOR 25 PIPE

Claims

1. A refrigerant containing fluoroalkene and difluoromethane, which undergo a disproportionation reaction, as components thereof, and containing at least difluoroiodomethane (CHF) as a disproportionation inhibitor for suppressing the disproportionation reaction of the fluoroalkene. 2 I).

2. The working fluid for a refrigeration cycle according to claim 1, characterized in that the fluoroalkene in which the disproportionation reaction occurs is 1,1,2-trifluoroethylene.

3. The working fluid for a refrigeration cycle according to claim 1 or 2, further comprising n-propane as the disproportionation inhibitor.

4. The disproportionation inhibitor may further include 1,1,1-trifluoro-2-iodoethane (CF 3 CH 2 I), or trifluoroiodomethane (CF 3 The working fluid for a refrigeration cycle according to claim 1 , further comprising:

5. A working medium for a refrigeration cycle according to any one of claims 1 to 4, characterized in that a content of said difluoromethane in the total amount of said refrigerant components and said disproportionation inhibitor is 30 mass% or less.

6. A working medium for a refrigeration cycle according to any one of claims 1 to 5, characterized in that when the total amount of the refrigerant components and the disproportionation inhibitor is 100 mass%, the content of the difluoroiodomethane is 15 mass% or less.

7. The working fluid for a refrigeration cycle according to claim 3, characterized in that the content of said n-propane is 10 mass % or less when the total amount of said refrigerant components and said disproportionation inhibitor is 100 mass %.

8. A refrigeration cycle system constructed using the working medium for a refrigeration cycle according to any one of claims 1 to 7.