Method for suppressing disproportionation reaction of refrigeration cycle working medium, refrigeration cycle working medium, and refrigeration cycle device

Abstract

In a refrigeration cycle in which a refrigeration cycle working medium containing a refrigerant component that causes a disproportionation reaction, for example, fluoroolefin is circulated, carbene is produced in accordance with the disproportionation reaction of the fluoroolefin. At this time, the refrigeration cycle working medium contains, as a carbene scavenger, a compound having a chemical structure including an X-H bond (X is O, S, or Si) that is a bond of an oxygen atom (O), a sulfur atom (S), or a silicon atom (Si), which reacts with the carbene, to a hydrogen atom, for example, an organic hetero compound or a silane compound. Capturing the produced carbene by means of the carbene scavenger suppresses an increase in the carbene in the refrigeration cycle and satisfactorily suppresses or alleviates the disproportionation reaction of the fluoroolefin.

Description

Method for inhibiting disproportionation reaction of working fluid for refrigeration cycle, working fluid for refrigeration cycle, and refrigeration cycle device

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

[0002] Recently, the use of fluoroolefins, particularly hydrofluoroolefins (HFOs), which have an ozone depletion potential (ODP) of zero and a smaller global warming potential (GWP), has been proposed as working fluids (refrigerants or heat transfer media) for refrigeration cycles. Typical HFOs include 1,1,2-trifluoroethylene (HFO1123) and difluoroethylene (HFO1132). HFOs are less stable than conventional HFCs (hydrofluorocarbons) and are therefore less likely to remain in the atmosphere.

[0003] However, it is also known that HFOs are prone to self-polymerization reactions known as disproportionation reactions (hereinafter referred to as disproportionation reactions) due to their low stability. Disproportionation reactions are likely to occur due to heat generated during use of the working fluid for a refrigeration cycle, and since the occurrence of a disproportionation reaction is accompanied by a large heat release, it is also known that disproportionation reactions can occur in a chain reaction. As a result, a large amount of soot is generated, which may reduce the reliability of the refrigeration cycle system or the compressors that constitute the system.

[0004] 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.

[0005] JP 2017-145380 A JP 2018-048271 A JP 2018-104565 A JP 2018-104566 A JP 2019-034983 A JP 2021-161316 A

[0006] Patent Documents 1 to 6 propose various disproportionation inhibitors or combinations thereof, taking into consideration various conditions that may affect the occurrence of disproportionation reactions in a refrigeration cycle. These disproportionation inhibitors can effectively inhibit or mitigate the disproportionation reactions of fluoroolefins such as 1,1,2-trifluoroethylene.

[0007] However, much remains unknown about the disproportionation reaction of fluoroolefins, and therefore, in addition to the disproportionation inhibitors proposed in Patent Documents 1 to 6, there is a need to investigate new methods that can effectively inhibit or mitigate the disproportionation reaction.

[0008] The present invention has been made to solve the above problems, and an object of the present invention is to provide a novel method for effectively suppressing or mitigating the disproportionation reaction of a refrigerant component in a working fluid for a refrigeration cycle containing the refrigerant component that undergoes the disproportionation reaction.

[0009] In order to solve the above-mentioned problems, the method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to the present disclosure is configured so that, when carbene is generated in association with the disproportionation reaction of a refrigeration cycle component in which a working fluid for a refrigeration cycle containing a refrigerant component that undergoes a disproportionation reaction circulates in a refrigeration cycle, the working fluid for a refrigeration cycle further contains, as a carbene scavenger, a compound having in its chemical structure an X—H bond (X is O, S, or Si) that is a bond between an oxygen atom (O), a sulfur atom (S), or a silicon atom (Si) and a hydrogen atom (H), and the carbene reacts with the carbene, and the carbene scavenger suppresses an increase of the carbene in the refrigeration cycle, thereby suppressing the disproportionation reaction of the refrigerant component.

[0010] According to the above configuration, a compound having an X—H bond in its chemical structure, which is a bond between a heteroatom (X) of O, S, or Si and a hydrogen atom (H), captures the carbene by reacting with the X—H bond. Because organic hetero compounds or silane compounds having an X—H bond are substantially non-self-decomposing, working fluids containing such compounds as carbene traps are stable. Although the activation energy of the carbene trapping reaction is relatively high, the working fluid is stable, and therefore the carbene trap can effectively capture the carbene while avoiding situations in which the carbene trap promotes the disproportionation reaction of the refrigerant components. Therefore, the disproportionation reaction of the refrigerant components can be more effectively suppressed.

[0011] The present disclosure also includes a working fluid for a refrigeration cycle that contains a refrigerant component that undergoes a disproportionation reaction, and contains, as a carbene scavenger that captures carbene generated in conjunction with the disproportionation reaction of the refrigerant component, a compound having in its chemical structure an X—H bond (X is O, S, or Si) that is a bond between an oxygen atom (O), a sulfur atom (S), or a silicon atom (Si) and a hydrogen atom (H), and that reacts with the carbene.

[0012] The present disclosure also includes a carbene scavenger for refrigerants that contains a compound having, in its chemical structure, an X—H bond (X is O, S, or Si), which is a bond between an oxygen atom (O), a sulfur atom (S), or a silicon atom (Si) and a hydrogen atom (H).

[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 an effect of providing a new method for effectively suppressing or mitigating the disproportionation reaction of a refrigerant component in a working fluid for a refrigeration cycle containing the refrigerant component that undergoes the disproportionation reaction.

[0015] 3A and 3B are schematic block diagrams showing an example of a refrigeration cycle system to which a refrigeration cycle according to an embodiment of the present disclosure is applied.

[0016] (Findings, etc. that form the basis of the present disclosure) As a result of intensive research to solve the above-mentioned problems, the present inventors independently discovered that an organic hetero compound or a silane compound having in its chemical structure an X-H bond (X is O, S, or Si) that is a bond between an oxygen atom (O), a sulfur atom (S), or a silicon atom (Si) and a hydrogen atom, which had not previously been considered in the field of suppression of disproportionation reactions, can contribute to suppressing or mitigating disproportionation reactions, and further that such an organic hetero compound or a silane compound acts on carbenes rather than on active radicals generated in the self-decomposition of fluoroolefins, and have completed the present invention.

[0017] Through extensive research by the present inventors, it has become clear that in the disproportionation reaction of fluoroolefins, carbene generated during autolysis contributes to the chain reaction of the disproportionation reaction. In the above-described configuration, the carbene is captured by a carbene capture agent, an organic hetero compound or a silane compound. This effectively suppresses the increase of carbene in the refrigeration cycle, thereby making it possible to suppress or alleviate the disproportionation reaction of fluoroolefins.

[0018] Furthermore, while fluoroolefins have self-decomposition properties, organic hetero compounds or silane compounds, which are carbene scavengers, do not have self-decomposition properties. Therefore, when such organic hetero compounds or silane compounds are contained in a working fluid for a refrigeration cycle, the stability of the working fluid can be relatively increased.

[0019] Hereinafter, a representative embodiment of the method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to the present disclosure and a representative application thereof will be specifically described.

[0020] [Fluoroolefin] The working fluid for a refrigeration cycle according to the present disclosure, which is the target of the method for suppressing a disproportionation reaction according to the present disclosure, uses, as a refrigerant component, at least a fluoroolefin (fluoroalkene) in which a disproportionation reaction occurs.

[0021] 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.

[0022] 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 four 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.

[0023] 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.

[0024] 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 fluorine atom bonded to the carbon atom at position 1 across the double bond, rather than the hydrogen atom adjacent to it, is substituted with a fluorine atom.

[0025] 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.

[0026] 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 active radicals or carbenes (hereinafter collectively referred to as active species) produced by the decomposition react with surrounding 1,1,2-trifluoroethylene, or a sooting reaction occurs in which carbon fragments produced by dissociation polymerize to form soot. When active species are generated due to heat generation or the like under high temperature and high pressure conditions, these active species and 1,1,2-trifluoroethylene undergo a polymerization reaction or a sooting reaction, or both, repeatedly, resulting in a disproportionation reaction. Since this disproportionation reaction is exothermic, active radicals are generated by this heat generation, and these active radicals further induce the disproportionation reaction. In this way, the generation of active radicals and the occurrence of disproportionation reactions are linked together, and the spontaneous self-decomposition reaction propagates to other 1,1,2-trifluoroolefins, causing the disproportionation reaction to rapidly proceed.

[0027] 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 radicals such as fluorine radicals (F radicals), difluoromethyl radicals (CF radicals), and trifluoromethyl radicals (CF radicals).

[0028] 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.

[0029] Furthermore, the present inventors have newly discovered that the disproportionation reaction of fluoroolefins can be effectively inhibited or alleviated by adding an organic hetero compound or a silane compound having in its chemical structure an X-H bond, which is a bond between a hetero atom (X) and a hydrogen atom (H), to a working fluid for a refrigeration cycle containing fluoroolefins. Furthermore, it has been newly discovered that this organic hetero compound or silane compound does not capture radicals like the disproportionation inhibitors previously proposed by the present applicant, but rather captures carbenes, and that in the disproportionation reaction of fluoroolefins, carbenes can be involved in the rapid progress of the reaction.

[0030] [Organic Hetero Compound or Silane Compound as Carbene Scavenger] In the method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to the present disclosure, when carbene is generated in association with the disproportionation reaction of a fluoroolefin in a refrigeration cycle in which a working fluid for a refrigeration cycle containing a fluoroolefin circulates, the working fluid for a refrigeration cycle contains, as a carbene scavenger, an organic hetero compound or a silane compound having in its chemical structure an X—H bond, which is a bond between a hetero atom (X) and a hydrogen atom (H), that reacts with carbene. That is, the working fluid for a refrigeration cycle according to the present disclosure contains a fluoroolefin as a refrigerant component, and also contains the organic hetero compound or the silane compound as a carbene scavenger.

[0031] In the present disclosure, the organic hetero compound used as a carbene scavenger may be any organic compound having an X-H bond in its chemical structure, where the heteroatom (X) is an oxygen atom (O), a sulfur atom (S), or a silicon atom (Si). While the specific type of such an organic hetero compound is not particularly limited, representative examples include organic compounds having 4 or fewer carbon atoms or derivatives thereof. More specific examples of such organic hetero compounds include alcohols, thiols, or organosilanes having 4 or fewer carbon atoms, or derivatives thereof.

[0032] In the present disclosure, the silane compound used as the carbene scavenger may be silane (SiH4) or a derivative thereof. However, if the silane compound is a silane derivative containing a carbon atom (C), it is included in the organic hetero compound, organosilanes or derivatives thereof.

[0033] In the present disclosure, the specific type of alcohol, thiol, or organosilane having 4 or less carbon atoms, or silane compound, or derivative thereof used as a carbene scavenger is not particularly limited, but representative examples include an alcohol or thiol or derivative thereof shown in the following formula (1), and a silane compound or derivative thereof shown in the following formula (2):

[0034]

[0035] In formula (1), if the heteroatom (X) is an oxygen atom (O), the compound represented by formula (1) is an alcohol, and if the heteroatom (X) is a sulfur atom (S), the compound represented by formula (1) is a thiol. 1 ~R 3 are each independently an atom or an atomic group selected from the group consisting of a hydrogen atom (H), a fluorine atom (F), a chlorine atom (Cl), a bromine atom (Br), an iodine atom (I), a methyl group (CH), a trifluoromethyl group (CF), an ethyl group (C2H5), a pentafluoroethyl group (C2F5), a propyl group (C3H7), and a heptafluoromethyl group (C3F7).

[0036] When the organic hetero compound represented by formula (1) is an alcohol (X is O), specific examples of alcohols having 4 or less carbon atoms include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, and 2-methyl-2-propanol (tert-butanol). Derivatives of these alcohols include compounds in which the hydrogen atoms (H) contained in these alcohols are substituted with substituents other than alkyl groups. Representative examples include halogenated alcohols in which H is substituted with a halogen atom such as F, Cl, Br, or I, as described above.

[0037] In Examples 1 and 2 described below, hexafluoro-2-propanol (hexafluoroisopropyl alcohol) is used as a specific example of a carbene scavenger. Hexafluoro-2-propanol is a compound in which the hydrogen atoms of the alcohol represented by formula (1) are substituted with fluorine atoms, i.e., a halogen derivative (halogenated alcohol) of an organic hetero compound. In Example 3 described below, methanol and nonafluoro-tert-butanol (nonafluoro-tert-butyl alcohol) are given as other examples of carbene scavenger that are alcohols (X is O).

[0038] When the organic hetero compound represented by formula (1) is a thiol (X is S), specific examples of thiols having 4 or less carbon atoms include methanethiol, ethanethiol, 1-propanethiol, 2-propanethiol, 1-butanethiol, 2-butanethiol, 2-methylpropane-1-thiol, and 2-methylpropane-2-thiol (tert-butylthiol). Derivatives of these thiols include compounds in which the hydrogen atoms (H) contained in these thiols are substituted with substituents other than alkyl groups. Representative examples include halogenated thiols in which H is substituted with a halogen atom such as F, Cl, Br, or I, as described above. In Example 3 described below, methanethiol, hexafluoro-2-propanethiol, and 2-propanethiol are given as examples of carbene traps that are thiols (X is S).

[0039] Examples of silane compounds represented by formula (2) include silane (SiH4) having one silicon atom, i.e., monosilane (0 carbon atoms), monomethylsilane (1 carbon atom), dimethylsilane (2 carbon atoms), monoethylsilane (2 carbon atoms), monopropylsilane (3 carbon atoms), ethylmethylsilane (3 carbon atoms), trimethylsilane (3 carbon atoms), diethylsilane (4 carbon atoms), monoethyldimethylsilane (4 carbon atoms), etc. Of these compounds, all except for monosilane having 0 carbon atoms are organic silanes, and therefore all of them are monosilane derivatives as well as organic hetero compounds.

[0040] Furthermore, examples of derivatives of these silane compounds include compounds in which the hydrogen atoms (H) contained in these silane compounds are substituted with substituents other than alkyl groups. As mentioned above, representative examples include halogenated silanes in which H is substituted with halogen atoms such as F, Cl, Br, and I. While monosilane halides are derivatives of monosilane, the aforementioned organosilane halides are derivatives of monosilane and also of organosilane. In Example 3 described below, hexafluorodimethylsilane, dichlorosilane, and dimethylsilane are given as examples of carbene scavengers that are silane compounds (X is Si).

[0041] Here, in the present disclosure, derivatives of monosilane may be defined as excluding organosilanes. In the present disclosure, monosilane or its derivatives are silane compounds having an X-H bond (X is Si), but do not contain an organic group and therefore are not considered organic hetero compounds. On the other hand, organosilanes are silane compounds having an X-H bond and also organic hetero compounds having an X-H bond (X is Si). Therefore, organosilanes can be said to be both silane compounds and organic hetero compounds, but when clearly distinguishing between them, organosilanes can be defined as organic hetero compounds, and only derivatives of monosilanes that do not have an organic group can be defined as silane compounds.

[0042] In addition, R in formula (1) or formula (2) 1 ~R 3 As described above, each of R can be independently substituted with any substituent (including a substituted atom) selected from the group (substituent group) consisting of H, F, Cl, Br, I, CH, CF, CH, CF, CH, and CF. 1 ~R 3 When two or more of the above are substituents other than hydrogen atoms, they may all be the same substituent, only some of them may be the same substituent, or all of them may be different substituents.

[0043] In the organic hetero compound exemplified by formula (1) or the silane compound (or organic hetero compound) exemplified by formula (2), R 1 ~R 3 is not limited to the substituents (atoms or atomic groups) constituting the above-mentioned substituent group, and may be a derivative substituted with another substituent. In addition, the organic hetero compound exemplified by formula (1) or the silane compound exemplified by formula (2) may have more than 4 carbon atoms.

[0044] For example, when the organic hetero compound represented by formula (1) is an alcohol (X is O), R 1 ~R 3are all CH, CF, C2H, C2F, C3H, or C3F, the number of carbon atoms in the alcohol may be 5 or more. However, as long as an alcohol having 5 or more carbon atoms has the reactivity to capture a carbene, it is included in the carbene trapping agent of the present disclosure.

[0045] Furthermore, in the organic hetero compound exemplified by formula (1) or the silane compound (or organic hetero compound) exemplified by formula (2), CH, CF, CH, CF, CH, and CF are exemplified as substituents, and halogen atoms (F, Cl, Br, and I) are exemplified as substituting atoms, but the substituents (including substituting atoms) are not limited to these. That is, the olefin derivatives in the present disclosure are not limited to halogen compounds, etc., but may also be derivatives into which other atoms or atomic groups have been introduced. Therefore, the carbene scavenger in the present disclosure is not limited to the organic hetero compound shown in formula (1) or a derivative thereof, or the silane compound (or organic hetero compound) shown in formula (2) or a derivative thereof.

[0046] In the method for suppressing a disproportionation reaction according to the present disclosure, the carbene to be captured by the carbene scavenger is not particularly limited, but typically includes at least one selected from the group consisting of CF, CHF, and CH. When one or more carbenes belonging to these groups are generated by the self-decomposition of a fluoroolefin, these carbenes can be effectively captured by the organic hetero compound or silane compound described above.

[0047] In the case of an organic hetero compound or silane compound serving as a carbene trap, the X-H bond contained in the compound reacts with carbene to convert the carbene to a methyl group or a fluoromethyl group. If the carbene to be trapped is at least one selected from the group consisting of CF, CHF, and CH, the compound produced (converted) will have five or fewer carbon atoms and a carbene-derived difluoromethyl group (CHF-), monofluoromethyl group (CHF-), or methyl group (CH-) in its molecular structure. Unless otherwise specified, the term "fluoromethyl group" used in this embodiment is a generic term encompassing both difluoromethyl and monofluoromethyl groups.

[0048] In this disclosure, the chemical reaction (carbene trapping reaction) in which the unsaturated compound described above traps carbene and is converted into a compound having a methyl group, a monofluoromethyl group, or a difluoromethyl group, and the suppression of the disproportionation reaction of fluoroolefins as a result, will be specifically described with reference to Fig. 1. In Fig. 1, alcohol or thiol or a derivative thereof shown in formula (1) is exemplified as an organic hetero compound serving as a carbene trap, and CF2 is exemplified as a carbene.

[0049] First, the process in which the disproportionation reaction of fluoroolefins progresses rapidly can be divided into an initial stage, an induction stage, and a chain reaction stage. In the initial stage, for example, the occurrence of discharge in the compressor 16 is triggered, and the initial self-decomposition of the fluoroolefin occurs. At this time, active radicals are likely to be generated. The induction stage occurs immediately after the initial stage and immediately before the chain reaction stage, i.e., immediately before the self-decomposition of the fluoroolefin progresses explosively, and in this stage, carbenes are gradually generated and accumulate. It is believed that if the concentration of carbene exceeds an upper limit in this induction stage, the self-decomposition reaction of the fluoroolefin progresses rapidly.

[0050] Therefore, even if the active radicals are captured and eliminated by a radical scavenger in the initial stage, the carbene will slowly accumulate in the induction stage, and if its concentration exceeds a certain value (critical condition), the process will transition to a chain reaction stage, and the self-decomposition of the fluoroolefin will proceed explosively.

[0051] Here, the method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to the present disclosure is schematically shown, for example, as shown in Fig. 1. In Fig. 1, the compressor 16 is schematically shown as a large circle, and the location where discharge occurs, which is one of the triggers for the disproportionation reaction (autolysis reaction of fluoroolefins) within the compressor 16, is schematically shown as a discharge region 201 located in the center of the schematic compressor 16.

[0052] The temperature of the discharge region 201 is expected to be approximately 3,000 K to 10,000 K, and a region 201a, shown by the shaded area in FIG. 1 , is generated around the discharge region 201, where the temperature is approximately 400 K to 1,000 K. In this region 201a, products generated by the autolysis of the fluoroolefin accumulate. These products can be considered "intermediates" rather than the final products of the autolysis reaction. For ease of explanation, this region 201a is referred to as the reaction intermediate accumulation region 201a. In FIG. 1 , CF is illustrated as an example of carbene 31, and this carbene 31 (CF) gradually accumulates in this reaction intermediate accumulation region 201a.

[0053] According to the studies of the present inventors, as described above, it has been revealed that in the initial stage of the self-decomposition of fluoroolefins, the generation of active radicals is dominant, and in the subsequent induction stage, carbenes are gradually generated. Therefore, in the present disclosure, the present inventors have uniquely found that in order to suppress the chain reaction of the self-decomposition of fluoroolefins, it is important to keep the amount of carbenes remaining in the induction stage at or below a predetermined value.

[0054] Therefore, in the present disclosure, the working fluid for a refrigeration cycle contains, for example, an organic hetero compound 32 (alcohol, thiol, or a derivative thereof) represented by the above formula (1) as a carbene scavenger. The organic hetero compound 32 is highly reactive with carbene 31 (CF), but is relatively less reactive with other substances present in the refrigeration cycle, including the reaction intermediate retention region 201a. Therefore, the organic hetero compound 32 reacts to capture carbene 31 by cleaving its carbon-carbon double bond, thereby producing a compound 33 having a fluoromethyl group.

[0055] In the example shown in FIG. 1 R 2 R 3 If the group is simply an alkyl group and the heteroatom (X) is an oxygen atom (O), compound 33 having a fluoromethyl group will be an alkyl difluoromethyl ether (alkoxydifluoromethane). Alternatively, if the heteroatom (X) is a sulfur atom (S), compound 33 having a fluoromethyl group will be an alkyl difluoromethyl sulfide (alkoxysulfanyldifluoromethane). Note that if carbene 31 is CHF, compound 33 having a fluoromethyl group will have a monofluoromethyl group rather than a difluoromethyl group, and if carbene is CH, compound 33 will be a compound having a methyl group rather than a fluoromethyl group.

[0056] Such a compound 33 having a fluoromethyl group is a singlet ground state molecule having no unpaired electron. This effectively suppresses the increase in carbene 31, thereby suppressing or avoiding the progression of chain-like autolysis of the fluoroolefin. As a result, the disproportionation reaction can be effectively suppressed or alleviated.

[0057] As a result of extensive investigations, the inventors of the present invention have determined the intrinsic reaction coordinate of an organic hetero compound or a silane compound used as a carbene trap by quantum chemical calculations, calculated the activation energy of the carbene trapping reaction, and calculated the reaction rate using transition state theory to confirm its effectiveness. As a result, it is believed that the carbene trapping reaction via the X-H bond has a relatively high activation energy, but the organic hetero compound or silane compound itself is a relatively stable compound that does not exhibit self-decomposition. Therefore, in the method for suppressing the disproportionation reaction of a working fluid for a refrigeration cycle according to the present disclosure, the organic hetero compound or silane compound is less likely to promote the disproportionation reaction, making it possible to more effectively suppress the disproportionation reaction of fluoroolefins.

[0058] Furthermore, the inventors' intensive studies have revealed that carbenes are likely to be generated not only in the discharge region 201 but also in regions where sliding parts exist within the compressor. The "sliding parts" herein refer to areas where multiple sliding members slide against each other with their sliding surfaces in contact with each other.

[0059] When the likelihood of carbene generation is evaluated over time, as mentioned above, carbene is likely to be generated immediately after the occurrence of discharge that triggers self-decomposition, after the disappearance of radicals generated by self-decomposition, or immediately before the progression of chain reaction self-decomposition. Furthermore, when the likelihood of carbene generation is evaluated in regions within the compressor, carbene is naturally likely to be generated in regions where discharge that triggers self-decomposition may occur, i.e., the discharge region (see Figure 1). Furthermore, it was revealed that carbene is likely to be generated in and near areas that are subject to high temperatures and pressures within the compressor, such as sliding parts.

[0060] In the present disclosure, the region in the compressor where such a sliding part exists is referred to as the “sliding region.” In the method for suppressing a disproportionation reaction according to the present disclosure, it is sufficient if the increase of carbene is suppressed in at least one of the discharge region and the sliding region, or in both the discharge region and the sliding region.

[0061] A typical example of a discharge region and a sliding region in a compressor will be specifically described with reference to Fig. 2. Fig. 2 illustrates a rotary (or scroll) compressor. For the sake of convenience in explaining the discharge region and the sliding region, Fig. 2 illustrates only the essential components related to these regions, and does not illustrate all of the main components of a typical compressor.

[0062] Furthermore, the refrigeration cycle to which the method for suppressing a disproportionation reaction according to the present disclosure is applicable is not limited to a configuration including a rotary (or scroll) compressor as shown in Fig. 2. It goes without saying that the refrigeration cycle to which the present disclosure is applicable may include a reciprocating compressor or any other known type.

[0063] Similarly, in the present disclosure, regardless of whether the compressor is of a rotary type (or scroll type), the components of the compressor are not limited to the essential configuration schematically shown in Fig. 2. In various known types of compressors, the area where discharge can occur and its surroundings may be referred to as the "discharge area," and the area where high temperature and high pressure occur and its surroundings may be referred to as the "sliding area" (or high temperature and high pressure area).

[0064] 2 includes an electric motor unit 162 and a compression mechanism unit 163 housed within a sealed container 161. The electric motor unit 162 and the compression mechanism unit 163 are connected by a shaft 166. The electric motor unit 162 is composed of at least a stator 164 fixed to the inner surface of the sealed container 161 and a rotor 165 that rotates within the stator 164.

[0065] An airtight power supply terminal 173 is hermetically welded to the sealed container 161. The airtight power supply terminal 173 is electrically connected to an external power supply, and is also electrically connected to the stator 164 of the electric motor unit 162 via wiring 174 inside the sealed container 161. This allows power to be supplied from the external power supply to the electric motor unit 162.

[0066] The compressor 16 includes a compression mechanism 163, which includes a first compression mechanism 163A and a second compression mechanism 163B. The first compression mechanism 163A includes a first piston 169A disposed within a first cylinder and a vane that divides the first cylinder. The first piston 169A revolves within the first cylinder, thereby drawing in and compressing low-pressure refrigerant gas (a working medium for the refrigeration cycle). The first piston 169A is disposed within the first cylinder so as to be capable of revolving, thereby forming a first compression chamber 172A.

[0067] Similar to the first compression mechanism 163A, the second compression mechanism 163B also includes a second piston 169B disposed within a second cylinder and a vane that divides the second cylinder. The second piston 169B revolves within the second cylinder, thereby drawing in and compressing low-pressure refrigerant gas (a working medium for the refrigeration cycle). The second piston 169B is disposed within the second cylinder so as to be capable of revolving, thereby forming a second compression chamber 172B.

[0068] The shaft 166 has the rotor 165 fixed thereto, and is rotatably supported by a main bearing 167 and a sub-bearing 168. A first piston 169A and a second piston 169B are also fixed to the shaft 166 with a phase difference of 180 degrees from each other.

[0069] Lubricating oil is stored at the bottom of the sealed container 161, and this lubricating oil is passed through an oil supply passage formed in the shaft 166 to lubricate the sliding part formed by the shaft 166 and the main bearing 167, or the sliding part formed by the shaft 166 and the auxiliary bearing 168.

[0070] A first suction pipe 171A and a second suction pipe 171B are connected to the side of the sealed container 161. The first suction pipe 171A is connected to the first compression chamber 172A, and the second suction pipe 171B is connected to the second compression chamber 172B. An accumulator 170 is provided upstream of the first suction pipe 171A and the second suction pipe 171B. The accumulator 170 separates the refrigerant in a gas-liquid mixed state that has returned from the refrigeration cycle into liquid refrigerant and gas refrigerant. Gas refrigerant flows through the first suction pipe 171A and the second suction pipe 171B.

[0071] As the shaft 166 rotates, the first piston 169A and the second piston 169B revolve within the first compression chamber 172A and the second compression chamber 172B. The gas refrigerant is drawn into the first compression chamber 172A and the second compression chamber 172B from the first suction pipe 171A and the second suction pipe 171B by the orbital motion of the first piston 169A and the second piston 169B, is compressed in the first compression chamber 172A and the second compression chamber 172B, and then discharged into the sealed container 161. The gas refrigerant separates from the lubricating oil while passing through the electric motor unit 162 and rising, and is then discharged out of the sealed container 161 from the discharge pipe.

[0072] 2, discharge regions 201A and 201B are areas surrounded by dashed lines, and the sliding region is an area surrounded by a dotted line within compressor 16. Of these, discharge region 201A is the winding portion of stator 164 constituting motor unit 162 and its surroundings, and discharge region 201B is airtight power supply terminal 173 and its surroundings.

[0073] On the other hand, in the configuration example shown in FIG. 2 , examples of sliding parts (parts where multiple sliding members are combined and slide with their sliding surfaces in contact with each other) that are prone to high temperature and pressure within the compressor 16 include the space between the first piston 169A or the second piston 169B and the vane, the space between the main bearing 167 and the shaft 166, and the space between the rotor 165 and the main bearing 167.

[0074] 2, for example, the area between and around the first piston 169A and the vane, and the area between and around the second piston 169B and the vane are defined as sliding areas 202A surrounded by dotted lines. Similarly, the area between and around the main bearing 167 and the shaft 166 is defined as sliding area 202B (area surrounded by dotted lines), and the area between and around the rotor 165 and the main bearing 167 is defined as sliding area 202C (area surrounded by dotted lines).

[0075] In the present disclosure, it is sufficient that an increase in carbene can be suppressed by an organic hetero compound or a silane compound, which is a carbene scavenger, in a refrigeration cycle including the compressor 16. Furthermore, it is sufficient that an increase in carbene can be suppressed by a carbene scavenger (an organic hetero compound or a silane compound) in at least one of the discharge regions 201A and 201B and the sliding regions 202A to 202C in the compressor 16 of the refrigeration cycle.

[0076] In particular, if the increase in carbenes in the discharge regions 201A and 201B can be suppressed by using a carbene scavenger (an organic hetero compound or a silane compound), the allowable discharge energy value, i.e., the discharge energy value at which the self-decomposition of fluoroolefins does not proceed in a chain reaction, becomes higher, and the disproportionation reaction can be more effectively suppressed or alleviated.

[0077] Note that, although the example shown in FIG. 2 illustrates two discharge regions and three sliding regions in compressor 16, the number of discharge regions and sliding regions in the present disclosure is not limited to the example shown in FIG. 2. There may be multiple discharge regions in compressor 16, or there may be only one sliding region. In the present disclosure, "at least one of a discharge region and a sliding region" means at least one region when there are multiple discharge regions and multiple sliding regions in compressor 16. Furthermore, "at least one of a discharge region and a sliding region" includes cases where there is only one or multiple discharge regions, cases where there are one or multiple sliding regions, and also includes all discharge regions and sliding regions.

[0078] In the method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to the present disclosure, the increase of carbenes in the refrigeration cycle can be suppressed by the carbene scavenger, and as a result, the disproportionation reaction of the fluoroolefin contained in the working fluid for a refrigeration cycle can be suppressed or alleviated. Therefore, in the present disclosure, to suppress the increase of carbenes, an upper limit of the carbene concentration in the refrigeration cycle is set in advance, and when the carbene concentration falls below the upper limit due to the carbene scavenger, it can be determined that the increase of carbenes has been suppressed.

[0079] Alternatively, in the present disclosure, it may be determined that an increase in carbene has been suppressed when it is confirmed that the carbene concentration in the refrigeration cycle is substantially 0. That is, when the carbene concentration in the refrigeration cycle has decreased to a level that can be regarded as an impurity in the working fluid for the refrigeration cycle and the working fluid is in a state in which it does not substantially contain carbene, it may be determined that the carbene concentration has become substantially 0 and that the carbene concentration has been suppressed.

[0080] The upper limit of the carbene concentration is appropriately set depending on various conditions including the specific configuration of the refrigeration cycle or the compressor, and is not particularly limited. A typical upper limit may be set such that the molar fraction of carbene is 0.35 (mol / mol) or less in at least one of the discharge region and the sliding region.

[0081] According to a study using simulations by the present inventors, it has become clear that the disproportionation reaction can be suppressed if the molar fraction of carbene is 0.35 or less. As described above, since carbenes are likely to be generated in the discharge region or the sliding region, by setting the upper limit of the carbene concentration in at least one of the discharge region and the sliding region to 0.35 or less in molar fraction and adding a carbene scavenger so that the concentration is below this upper limit, it is possible to effectively suppress or alleviate the disproportionation reaction of fluoroolefins.

[0082] Furthermore, in the present disclosure, the increase of carbenes can be suppressed not only by lowering the upper limit of the carbene concentration but also by lowering the temperature or pressure at which carbene is likely to be generated by self-decomposition of the fluoroolefin.

[0083] For example, in the present disclosure, the increase in carbene may be suppressed by controlling the temperature in at least one of the discharge region and the sliding region to 700 K or less. Alternatively, the increase in carbene may be suppressed by controlling the pressure in at least one of the discharge region and the sliding region from a high-temperature, high-pressure state to 2 MPa or less.

[0084] If the upper temperature limit in the discharge region or the sliding region is set to 700 K or less, or if the upper pressure limit is set to 2 MPa or less, either of the high-temperature and high-pressure conditions for the occurrence of the fluoroolefin self-decomposition reaction and the propagation of the spontaneous self-decomposition reaction will not be fully satisfied. As a result, even if the fluoroolefin self-decomposes, the generation of carbene will be significantly suppressed. As a result, the increase of carbene can be effectively suppressed in the discharge region or the sliding region.

[0085] The present disclosure includes not only a method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle, but also a method for capturing carbenes present in the refrigeration cycle. Specifically, the carbene capturing method according to the present disclosure may be configured such that, in a refrigeration cycle containing a composition for a refrigeration cycle, the composition for a refrigeration cycle contains a compound having in its chemical structure an X-H bond (X is O, S, or Si) that reacts with carbene and is a bond between an oxygen atom (O), a sulfur atom (S), or a silicon atom (Si) and a hydrogen atom (H), and the compound reacts with the carbene present in the refrigeration cycle to capture the carbene present in the refrigeration cycle.

[0086] In the working fluid for a refrigeration cycle according to the present disclosure, the content of the organic hetero compound or the silane compound as a carbene scavenger is not particularly limited. The organic hetero compound or the silane compound can be contained in any proportion depending on various conditions such as the specific composition of the working fluid for a refrigeration cycle, the specific configuration of the refrigeration cycle (including the compressor) to which the working fluid for a refrigeration cycle is applied, and the conditions of use of the refrigeration cycle, as long as the function of the working fluid for a refrigeration cycle or the refrigeration cycle is not impaired.

[0087] Typically, the organic hetero compound or silane compound (carbene scavenger) may be contained in the working fluid for a refrigeration cycle so that the content of the organic hetero compound or silane compound (carbene scavenger) is 30 mass% or less per 100 parts by mass of the fluoroolefin, based on the content of the fluoroolefin contained in the working fluid for a refrigeration cycle. If the content of the organic hetero compound or silane compound is not more than this upper limit, it will be possible to effectively suppress or mitigate the disproportionation reaction of the fluoroolefin in the working fluid for a refrigeration cycle, although this will depend on various conditions.

[0088] On the other hand, the lower limit of the content of the organic hetero compound or silane compound (carbene scavenger) in the working fluid for a refrigeration cycle is not particularly limited, but typically, the content of the organic hetero compound or silane compound (carbene scavenger) may be 1 mass% or more relative to 100 parts by mass of the fluoroolefin contained in the working fluid for a refrigeration cycle. If the content of the organic hetero compound or silane compound (carbene scavenger) is 1 mass% or more, the effect of suppressing the disproportionation reaction can be even better. The lower limit of the content of the organic hetero compound or silane compound (carbene scavenger) may be 5 mass% or more, or 10 mass% or more.

[0089] In addition, the composition of the working fluid for a refrigeration cycle according to the present disclosure other than the content of the carbene scavenger, i.e., the content of the fluoroolefin as a refrigerant component, or the components and contents other than the refrigerant component and the carbene scavenger, will be described later.

[0090] As described above, in the working fluid for a refrigeration cycle or the method for suppressing a disproportionation reaction according to the present disclosure, an organic hetero compound or a silane compound having in its chemical structure an X—H bond (X is O, S, or Si) between a hetero atom (X) and a hydrogen atom (H), which reacts with carbene, is added as a carbene scavenger to a refrigerant component mainly composed of a fluoroolefin, as described above.

[0091] As described above, the inventors' intensive studies have revealed that in the disproportionation reaction of fluoroolefins, carbene generated by autolysis is involved in the chain reaction of the disproportionation reaction. Therefore, by capturing this carbene with an organic hetero compound or a silane compound, which is a carbene capture agent, the increase of carbene in the refrigeration cycle can be effectively suppressed. Therefore, it is possible to suppress or alleviate the disproportionation reaction of fluoroolefins.

[0092] In the working fluid for a refrigeration cycle or the method for suppressing a disproportionation reaction according to the present disclosure, the fluoroolefin has self-decomposition properties, whereas the organic hetero compound or silane compound serving as a carbene scavenger does not have self-decomposition properties. Therefore, when the organic hetero compound or silane compound is contained in a working fluid for a refrigeration cycle, the stability of the working fluid can be relatively increased.

[0093] [Configuration Example of Refrigeration Cycle System] Next, a refrigeration cycle to which the method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to the present disclosure is applied will be described with reference to a representative "refrigeration cycle system (refrigeration cycle device)" shown in Figs. 3A and 3B .

[0094] 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.

[0095] An air conditioner will be described as a typical application example of the refrigeration cycle system according to the present disclosure. Specifically, as shown in the block diagram of Fig. 3A, 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.

[0096] 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 according to the present disclosure. 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, the compressor 16, and the heat exchanger 15 is provided with a four-way valve 18 for switching between heating and cooling. The indoor unit 11 is 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).

[0097] 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.

[0098] 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.

[0099] An example of the operation of the air conditioner 10 shown in Figure 3A 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.

[0100] 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.

[0101] Furthermore, a refrigerator will be described as another typical application example of the refrigeration cycle system (refrigeration cycle device) according to the present disclosure. Specifically, as shown in the block diagram of Fig. 3B, refrigerator 20 according to the present embodiment includes compressor 21, condenser 22, pressure reducing device 23, evaporator 24, and piping 25, etc., as shown in Fig. 3. Refrigerator 20 also includes a housing, a blower, an operation unit, a control unit, etc., which are not shown.

[0102] 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.

[0103] 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.

[0104] An example of the operation of refrigerator 20 shown in Fig. 3B 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.

[0105] Such an air conditioner 10 or refrigerator 20 is equipped with a refrigeration cycle (refrigeration cycle system) configured using the working fluid for the refrigeration cycle described above. The fluoroolefin used in the working fluid for the refrigeration cycle has good properties as a refrigerant component and has low ODP and GWP. Moreover, as described above, the working fluid for the refrigeration cycle contains the organic hetero compound or silane compound described above as a carbene scavenger.

[0106] Therefore, the carbene generated in the self-decomposition of the fluoroolefin is captured by the carbene scavenger. This effectively suppresses the increase of the carbene in the refrigeration cycle, thereby suppressing or avoiding the chain reaction of the self-decomposition of the fluoroolefin. This makes it possible to suppress or alleviate the disproportionation reaction of the fluoroolefin.

[0107] [Working Fluid for Refrigeration Cycle and Composition for Refrigeration Cycle] The present disclosure also includes a working fluid for a refrigeration cycle containing the above-described carbene scavenger. Specifically, the working fluid for a refrigeration cycle according to the present disclosure may contain, as a refrigerant component, a fluoroolefin that undergoes a disproportionation reaction, as described above, and may also contain, as a carbene scavenger, the above-described organic hetero compound or silane compound, for capturing the carbene generated as a result of the disproportionation reaction. Specific examples of the carbene scavenger may include, as described above, any carbene scavenger having, in its chemical structure, an X—H bond (X is O, S, or Si) between a heteroatom (X) and a hydrogen atom (H), which reacts with carbene. Representative examples include organic compounds having 4 or less carbon atoms and having an X—H bond, or derivatives thereof, or monosilane or derivatives thereof.

[0108] Furthermore, the working fluid for a refrigeration cycle according to the present disclosure may contain at least a refrigerant component that undergoes a disproportionation reaction. As mentioned above, examples of the refrigerant component that undergoes a disproportionation reaction include, but are not limited to, fluoroolefins. In the present disclosure, the working fluid for a refrigeration cycle may contain a refrigerant component that undergoes a disproportionation reaction (a compound that can be used as a refrigerant).

[0109] The working fluid for a refrigeration cycle according to the present disclosure may contain, as an example of a specific 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. Compared to the HCFCs (hydrochlorofluorocarbons) that have been used until now, difluoromethane has an ozone depletion potential (ODP) of 0 and exhibits good refrigerant performance.

[0110] Furthermore, the working fluid for a refrigeration cycle according to the present disclosure is sufficient as long as it contains at least a fluoroolefin as a main refrigerant component, but may contain a refrigerant component other than difluoromethane as a secondary refrigerant component. Representative secondary refrigerant components include 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, but are not particularly limited thereto.

[0111] 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.

[0112] The content of the secondary refrigerant component is not particularly limited. In the present disclosure, it is sufficient that the refrigerant component contains at least a fluoroolefin (main refrigerant component). Therefore, in the working fluid for a refrigeration cycle according to the present disclosure, when a secondary refrigerant component is contained, it is sufficient that the content of the fluoroolefin is greater than the content of the secondary refrigerant component.

[0113] It is important to minimize the GWP of the working fluid for a refrigeration cycle according to the present disclosure. Specifically, the GWP is preferably 200 or less (GWP≦200), and more preferably 150 or less (GWP≦150). When a fluoroolefin, which is the main refrigerant component, is used in combination with, for example, difluoromethane as a secondary refrigerant component, 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 the refrigerant components.

[0114] When the difluoromethane content is 30% by mass or less, the GWP of the working fluid for a refrigeration cycle can be set to 200 or less, and when it is 20% by mass or less, the GWP of the working fluid for a refrigeration cycle can be set to 150 or less. There is no particular limitation on the lower limit of difluoromethane. The working fluid for a refrigeration cycle according to the present disclosure does not need to contain a secondary refrigerant component, and therefore, when a secondary refrigerant component is used in combination with the fluoroolefin that is the main refrigerant component, the content of the secondary refrigerant component only needs to be 0% by mass or more.

[0115] 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.

[0116] As described above, the working fluid for a refrigeration cycle according to the present disclosure may contain, as refrigerant components, a fluoroolefin (e.g., 1,1,2-trifluoroethylene) that undergoes a disproportionation reaction and difluoromethane in combination, and may further contain a carbene scavenger. Furthermore, in the present disclosure, when the working fluid for a refrigeration cycle is used in combination with a lubricating oil, the refrigeration cycle composition (or working fluid-containing composition) can be considered to be composed of the refrigerant component, the carbene scavenger, the lubricating oil component, and other components. In the working fluid for a refrigeration cycle according to the present disclosure, the carbene scavenger may be mixed with the refrigerant component, but may also be mixed with the lubricating oil component depending on the circumstances.

[0117] The lubricating oil component contained in the refrigeration cycle composition (used together with the working fluid for the refrigeration cycle) can suitably be any of various lubricating oils known in refrigeration cycle systems. Specific examples of the lubricating oil include, but are not limited to, ester-based lubricating oils, ether-based lubricating oils, glycol-based lubricating oils, alkylbenzene-based lubricating oils, fluorine-based lubricating oils, mineral oils, and hydrocarbon-based synthetic oils. These lubricating oils may be used alone or in combination of two or more.

[0118] In addition, various known additives other than disproportionation inhibitors may be added to the refrigeration cycle composition. Specific additives include, but are not limited to, various stabilizers, antioxidants, moisture scavengers, metal deactivators, anti-wear agents, antifoaming agents, and leak detection substances. 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 it enters the refrigeration cycle system, particularly 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. Anti-wear 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.

[0119] 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 amounts of these additives added are not particularly limited, and they can be added within known ranges as long as they do not impair the properties of the working fluid for a refrigeration cycle according to the present disclosure or the composition for a refrigeration cycle containing the same.

[0120] As described above, in the method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to the present disclosure, the working fluid for a refrigeration cycle contains, as a carbene scavenger, an organic hetero compound or a silane compound having, in its chemical structure, an X—H bond, which is a bond between a hetero atom (X) of O, S, or Si and a hydrogen atom (H).

[0121] These organic hetero compounds or silane compounds capture carbene by reacting with the X-H bond. Because organic hetero compounds or silane compounds having an X-H bond are substantially non-self-decomposing, working fluids containing them as carbene scavengers are stable. Although the activation energy of the carbene capture reaction is relatively high, the working fluid is stable, and thus the carbene scavengers can effectively capture carbenes while avoiding situations in which the carbene scavengers promote the disproportionation reaction of fluoroolefins. Therefore, according to the present disclosure, it is possible to more effectively suppress the disproportionation reaction of fluoroolefins.

[0122] The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited thereto. Those skilled in the art may make various changes, modifications, and alterations without departing from the scope of the present invention.

[0123] (Experimental System for Disproportionation Reaction) A sealed pressure-resistant vessel (stainless steel sealed vessel, internal volume 50 mL) was equipped with a pressure sensor (GC61 manufactured by Nagano Keiki Co., Ltd.) to measure the internal pressure within the pressure-resistant vessel, a thermocouple (PL Thermocouple Grand PL-18-K-A4-T manufactured by Conax Technologies) to measure the internal temperature within the pressure-resistant vessel, and a discharge device to generate a discharge within the pressure-resistant vessel. Furthermore, a gas cylinder of 1,1,2-trifluoroethylene was connected so that the pressure could be adjusted. A mantle heater was installed to heat the entire pressure-resistant vessel, and a ribbon heater (flexible ribbon heater, 1 m, 200 W manufactured by Tokyo Institute of Technology Co., Ltd.) was also installed to heat the piping. Thus, an experimental system for the disproportionation reaction was constructed.

[0124] (Comparative Example 1) In the experimental system, 1,1,2-trifluoroethylene was introduced into the pressure vessel from an HFO1123 gas cylinder. Therefore, the content of 1,1,2-trifluoroethylene in the working fluid for the refrigeration cycle in the pressure vessel was 100 mass %. The stored energy of the discharge device was set to 0.035 J, and a discharge was generated in the experimental system. The results are shown in Table 1.

[0125] Example 1 In the experimental system, 1,1,2-trifluoroethylene was introduced into a pressure-resistant vessel from an HFO1123 gas cylinder, and hexafluoro-2-propanol (hexafluoroisopropyl alcohol; see formula (1) above) was used as a carbene scavenger. 1 and R 3 are both CF groups, and R 2 is H.) was added to a content of 10 mass %. The stored energy of the discharge device was set to 0.035 J, and a discharge was generated in the above-mentioned experimental system. The results are shown in Table 1.

[0126] Example 2 A discharge was generated in the experimental system in the same manner as in Example 1, except that the stored energy of the discharge device was set to 0.396 J. The results are shown in Table 1.

[0127]

[0128] In Table 1, the temperature [°C] is the internal temperature inside the pressure vessel. The pressure [MPa] is the internal pressure inside the pressure vessel. The stored energy [J] is the electrostatic energy stored in the capacitor section installed inside the discharge device. The number of consecutive discharges is the number of consecutive discharges at regular intervals under the conditions in question. If a disproportionation reaction was observed after the number of consecutive discharges, the presence or absence of the disproportionation reaction was recorded as "Yes," and if no disproportionation reaction was observed, the presence or absence of the disproportionation reaction was recorded as "No."

[0129] From the results in Table 1, a disproportionation reaction was observed in Comparative Example 1, but no disproportionation reaction was observed in either Example 1 or Example 2. Furthermore, from the results of Example 1 and Example 2, no disproportionation reaction was observed even when the amount of carbene scavenger (hexafluoro-2-propanol) added was the same and the stored energy was higher. Therefore, it was confirmed that the introduction of a carbene scavenger can effectively suppress the disproportionation reaction of fluoroolefins.

[0130] Example 3 As shown in Table 2, a total of six compounds, including hexafluoro-2-propanol, which was used as the carbene trap in Examples 1 and 2, were selected as compounds having an X-H bond (X is O, S, or Si) in their chemical structure. The equilibrium structures of the reactants and products obtained when these compounds were reacted with CF2 carbene were calculated using density functional theory. The reaction paths with carbene and the intrinsic reaction paths were calculated using the global reaction route mapping (GRRM) method. From the calculated intrinsic reaction paths, the activation energy was calculated from the energy difference between the reactant and the transition state. The results are shown in Table 2. A lower activation energy indicates that the reactant more easily reaches the transition state and the reaction proceeds more easily thermodynamically.

[0131]

[0132] As shown in Table 2, the activation energy in the reaction between hexafluoro-2-propanol, the carbene trap in Examples 1 and 2, and CF carbene was 0.92 eV. Similarly, the activation energies in the reaction with CF carbene were lower than 0.92 eV for the other eight compounds exemplified in Table 2. Therefore, it is determined that all of the nine compounds shown in Table 2 (including hexafluoro-2-propanol) thermodynamically react easily with CF carbene and are capable of effectively trapping CF carbene. Therefore, it is believed that the organic hetero compounds or silane compounds having an X—H bond in their chemical structures according to the present disclosure are capable of suppressing disproportionation reactions by trapping carbene.

[0133] (Additional Notes) Based on the descriptions of the above embodiments, the present specification discloses the following technologies: (Technology 1) A method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle, in which a working fluid for a refrigeration cycle containing a refrigerant component that undergoes a disproportionation reaction circulates, the working fluid for a refrigeration cycle containing a compound having in its chemical structure an X-H bond (X is O, S, or Si) that reacts with the carbene and is a bond between an oxygen atom (O), a sulfur atom (S), or a silicon atom (Si) and a hydrogen atom (H), as a carbene scavenger, and the carbene produced by the disproportionation reaction of the refrigerant component is captured by the carbene scavenger, thereby suppressing the disproportionation reaction of the refrigerant component.

[0134] (Technology 2) The method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to Technology 1, wherein the refrigerant component causing the disproportionation reaction is a fluoroolefin.

[0135] (Technology 3) The method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to Technology 1 or Technology 2, wherein the compound having an X—H bond in its chemical structure is an organic hetero compound or a silane compound.

[0136] (Technology 4) The method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to any one of Technology 1 to Technology 3, wherein the carbene includes at least one selected from the group consisting of CF2, CHF, and CH2.

[0137] (Technology 5) The method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to Technology 4, wherein the carbene scavenger suppresses an increase of the carbene by reacting with the X—H bond to convert the carbene to a methyl group or a fluoromethyl group.

[0138] (Technology 6) The method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to Technology 5, wherein the suppression of an increase in the carbene includes reducing the carbene concentration below a predetermined upper limit value or making the carbene concentration substantially zero.

[0139] (Technology 7) The method for suppressing a disproportionation reaction of a working medium for a refrigeration cycle according to any one of Technology 1 to Technology 6, wherein the refrigeration cycle includes a compressor, the compressor including a discharge region where discharge can occur and a sliding region having sliding parts where a plurality of sliding members slide on each other with their sliding surfaces in contact with each other, and the method suppresses an increase of the carbene present in at least one of the discharge region and the sliding region.

[0140] (Technology 8) A composition for a refrigeration cycle, which contains a refrigerant component that undergoes a disproportionation reaction, and which contains, as a carbene scavenger that captures carbene generated in conjunction with the disproportionation reaction of the refrigerant component, a compound having in its chemical structure an X-H bond (X is O, S, or Si) that is a bond between an oxygen atom (O), a sulfur atom (S), or a silicon atom (Si) and a hydrogen atom (H), and which reacts with the carbene.

[0141] (Technology 9) The composition for a refrigeration cycle according to Technology 8, wherein the refrigerant component in which the disproportionation reaction occurs is a fluoroolefin.

[0142] (Technology 10) The composition for a refrigeration cycle according to Technology 8 or Technology 9, wherein the compound having an X—H bond in its chemical structure is an organic hetero compound or a silane compound.

[0143] (Technology 11) The composition for a refrigeration cycle according to Technology 10, wherein the organic hetero compound is an organic compound having 4 or less carbon atoms or a derivative thereof, and the silane compound is monosilane (SiH4) or a derivative thereof.

[0144] (Technology 12) The composition for a refrigeration cycle according to Technology 11, wherein the organic hetero compound is an alcohol, a thiol, or an organic silane, or a derivative thereof.

[0145] (Technology 13) A refrigeration cycle device comprising the composition for a refrigeration cycle according to any one of Technology 8 to Technology 12.

[0146] (Technology 14) A method for capturing carbene present in a refrigeration cycle, wherein the refrigeration cycle composition contains a compound having in its chemical structure an X-H bond (X is O, S, or Si) which is a bond between an oxygen atom (O), a sulfur atom (S), or a silicon atom (Si) and a hydrogen atom (H), and the compound reacts with the carbene present in the refrigeration cycle to capture the carbene present in the refrigeration cycle.

[0147] (Technology 15) A carbene scavenger for refrigerants, containing a compound having in its chemical structure an X-H bond (X is O, S, or Si), which is a bond between an oxygen atom (O), a sulfur atom (S), or a silicon atom (Si) and a hydrogen atom (H).

[0148] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Therefore, embodiments obtained by appropriately combining the technical means disclosed in different embodiments or multiple modifications are also included in the technical scope of the present invention.

[0149] 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.

[0150] The present disclosure 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, vending machines, etc.

[0151] DESCRIPTION OF SYMBOLS 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 31: Carbene (CF2) 32: Organic hetero compound (carbene scavenger) 33: Compound having a fluoromethyl group (singlet ground state molecule) 161: Sealed container 162: Motor section 163: Compression mechanism section 163A: First compression mechanism section 163B: Second compression mechanism section 164: Stator 165: Rotor 166: Shaft 167: Main bearing 168: Auxiliary bearing 169A: First piston 169B: Second piston 170: Accumulator 171A: First suction pipe 171B: Second suction pipe 172A: First compression chamber 172B: Second compression chamber 173: Airtight power supply terminal 174: Wiring 201: Discharge area 201a: Reaction intermediate retention area 201A: Discharge area 201B: Discharge area 202A: Sliding area 202B: Sliding area 202C: Sliding area

Claims

1. A method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle, wherein the working fluid for a refrigeration cycle circulates within the refrigeration cycle and contains a refrigerant component that undergoes a disproportionation reaction, the working fluid for the refrigeration cycle containing a compound having in its chemical structure an X-H bond (X is O, S, or Si) that reacts with the carbene, the X-H bond being a bond between an oxygen atom (O), a sulfur atom (S), or a silicon atom (Si) and a hydrogen atom (H), and the carbene generated by the disproportionation reaction of the refrigerant component is captured by the carbene scavenger, thereby suppressing the disproportionation reaction of the refrigerant component.

2. The method for inhibiting a disproportionation reaction in a working fluid for a refrigeration cycle according to claim 1, wherein the refrigerant component in which the disproportionation reaction occurs is a fluoroolefin.

3. The method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to claim 1, wherein the compound having an X-H bond in its chemical structure is an organic hetero compound or a silane compound.

4. The method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to claim 1, wherein the carbene includes at least one selected from the group consisting of CF2, CHF, and CH2.

5. The method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to claim 4, wherein the carbene scavenger suppresses an increase of the carbene by reacting the carbene with the X-H bond to convert the carbene to a methyl group, a monofluoromethyl group, or a dimethylfluoromethyl group.

6. The method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to claim 5, wherein the suppression of the increase in carbene includes reducing the carbene concentration below a predetermined upper limit value or making the carbene concentration substantially zero.

7. The refrigeration cycle includes a compressor, the compressor including a discharge region where discharge can occur, and a sliding region having sliding parts where a plurality of sliding members slide with their sliding surfaces in contact with each other, and a method for suppressing a disproportionation reaction of a working medium for a refrigeration cycle according to any one of claims 1 to 6, wherein an increase of the carbene present in at least one of the discharge region and the sliding region is suppressed.

8. A composition for a refrigeration cycle comprising a refrigerant component that undergoes a disproportionation reaction, and a compound having in its chemical structure an X-H bond (X is O, S, or Si) that is a bond between an oxygen atom (O), a sulfur atom (S), or a silicon atom (Si) and a hydrogen atom (H), as a carbene scavenger that captures carbene generated in the disproportionation reaction of the refrigerant component, and that reacts with the carbene.

9. The composition for a refrigeration cycle according to claim 8, wherein the refrigerant component in which the disproportionation reaction occurs is a fluoroolefin.

10. The composition for a refrigeration cycle according to claim 8, wherein the compound having an X-H bond in its chemical structure is an organic hetero compound or a silane compound.

11. The composition for a refrigeration cycle according to claim 10, wherein the organic hetero compound is an organic compound having four or less carbon atoms or a derivative thereof, and the silane compound is monosilane (SiH4) or a derivative thereof.

12. The composition for a refrigeration cycle according to claim 11, wherein the organic hetero compound is an alcohol, a thiol, or an organic silane, or a derivative thereof.

13. A refrigeration cycle device comprising the refrigeration cycle composition according to claim 8.

14. A method for capturing carbene present in a refrigeration cycle comprising: a refrigeration cycle composition; the composition for a refrigeration cycle contains a compound having in its chemical structure an X-H bond (X is O, S, or Si) which is a bond between an oxygen atom (O), a sulfur atom (S), or a silicon atom (Si) and a hydrogen atom (H), and which reacts with carbene; and the compound captures the carbene present in the refrigeration cycle by reacting with the carbene present in the refrigeration cycle.

15. A carbene scavenger for refrigerants, characterized by containing a compound having in its chemical structure an X-H bond (X is O, S, or Si), which is a bond between an oxygen atom (O), a sulfur atom (S), or a silicon atom (Si) and a hydrogen atom (H).

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