Method for suppressing disproportionation reaction of refrigeration cycle actuation medium, and refrigeration cycle actuation medium

Abstract

To provide a novel method favorably suppressing or relaxing a disproportionation reaction of refrigerant components in a refrigeration cycle actuation medium containing refrigerant components where the disproportionation reaction occurs.SOLUTION: A carbene is generated accompanying a disproportionation reaction of a fluoroolefin in a refrigeration cycle where a refrigeration cycle actuation medium containing refrigerant components, for example the fluoroolefin, generating the disproportionation reaction, is circulated. This time, the refrigeration cycle actuation medium contains an unsaturated compound having a carbon-carbon double bond (C=C bond) reacting with the carbene as a carbene scavenger. This carbene scavenger suppresses increase in the carbene in the refrigeration cycle by capturing the generated carbene, and suppresses the disproportionation reaction of the fluoroolefin.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[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. [Background technology]

[0002] Recently, the use of fluoroolefins, particularly hydrofluoroolefins (HFOs), which have an ozone depletion potential (ODP) of zero and a lower 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 because 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 this system.

[0004] Therefore, when, for example, 1,1,2-trifluoroethylene is used as a refrigerant component of a working fluid for a refrigeration cycle, the applicant has proposed the following as components (disproportionation inhibitors) for inhibiting the disproportionation reaction of 1,1,2-trifluoroethylene: halomethane (Patent Document 1), saturated hydrocarbons (Patent Document 2), haloethane (Patent Document 3), combinations of these (Patent Document 4 or Patent Document 5), or difluoroiodomethane (Patent Document 6) as a representative example of a particularly suitable disproportionation inhibitor. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-145380 [Patent Document 2] Japanese Patent Application Publication No. 2018-048271 [Patent Document 3] Japanese Patent Application Publication No. 2018-104565 [Patent Document 4] Japanese Patent Application Publication No. 2018-104566 [Patent Document 5] Japanese Patent Application Publication No. 2019-034983 [Patent Document 6] Patent Publication No. 2021-161316 Summary of the Invention [Problem to be solved by the invention]

[0006] Patent Documents 1 to 6 propose various disproportionation inhibitors or combinations thereof in consideration of various conditions that may affect the occurrence of disproportionation reactions in refrigeration cycles. 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. [Means for solving the problem]

[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 such that, when carbene is generated as a result of 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 the refrigeration cycle, the working fluid for a refrigeration cycle further contains, as a carbene scavenger, an unsaturated compound having in its chemical structure a carbon-carbon double bond (C=C bond) that reacts with the carbene, and the carbene scavenger captures the generated carbene, thereby suppressing an increase of the carbene in the refrigeration cycle and suppressing the disproportionation reaction of the refrigerant component.

[0010] According to the above configuration, an unsaturated compound having a carbon-carbon double bond (C=C bond) in its chemical structure captures the carbene by reacting with the double bond. Because the activation energy of this carbene capture reaction is relatively low, even under conditions in which the carbene reacts with a refrigerant component to secondarily generate active species, or under conditions in which the disproportionation reaction is promoted by reaction heat, the unsaturated compound may react before the carbene reacts with the refrigerant component. This makes it possible to more effectively suppress the disproportionation reaction of the refrigerant component.

[0011] The present disclosure also includes a working fluid for a refrigeration cycle, which 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, an unsaturated compound having in its chemical structure a carbon-carbon double bond (C=C bond) that reacts with the carbene.

[0012] The present disclosure also includes a carbene scavenger for refrigerants that contains an unsaturated compound having a carbon-carbon double bond (C=C bond) in its chemical structure. [Effects of the Invention]

[0013] 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 a refrigerant component that undergoes a disproportionation reaction. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram showing an example of a state in which ethene, a representative example of a carbene trap, reacts with carbene to produce a compound that is a singlet ground state molecule in the present disclosure. [Figure 2] 1 is a schematic diagram illustrating a configuration of a main part inside a compressor included in a refrigeration cycle according to an embodiment of the present disclosure. [Figure 3] 1A and 1B 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. DETAILED DESCRIPTION OF THE INVENTION

[0015] (Findings that formed the basis of this disclosure) As a result of intensive research to solve the above-mentioned problems, the present inventors have independently discovered that unsaturated compounds having a carbon-carbon double bond (C=C bond) in their chemical structure, which had not been considered at all in the field of suppression of disproportionation reactions, can contribute to the suppression or alleviation of disproportionation reactions, and further that these unsaturated compounds act on carbenes rather than on active radicals generated in the self-decomposition of fluoroolefins, and have thus completed the present invention.

[0016] The inventors' intensive studies have revealed that in the disproportionation reaction of fluoroolefins, carbene generated during autolysis is involved in the chain reaction of the disproportionation reaction. In the above-described configuration, the carbene is captured by an unsaturated compound, which is a carbene capture agent. This effectively suppresses the increase of carbene in the refrigeration cycle, thereby making it possible to suppress or alleviate the disproportionation reaction of fluoroolefins.

[0017] Furthermore, while fluoroolefins have self-decomposition properties, unsaturated compounds that serve as carbene scavengers do not have self-decomposition properties. Therefore, when such unsaturated compounds are contained in a working fluid for a refrigeration cycle, the stability of the working fluid can be relatively increased.

[0018] 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.

[0019] [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.

[0020] Specific examples of fluoroolefins that undergo such disproportionation reactions 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), tetrafluoroethylene (CF2=CF2, F01114), etc. These fluoroolefins may be used alone or in combination as a refrigerant component.

[0021] 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.

[0022] 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.

[0023] 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 opposite the fluorine atom bonded to the carbon atom at position 1 across the double bond is substituted with a fluorine atom, not the hydrogen atom adjacent to it.

[0024] As mentioned above, these 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.

[0025] Here, fluoroolefins are also known to cause rapid disproportionation reactions due to their excellent decomposition properties. Taking 1,1,2-trifluoroethylene as a typical example of fluoroolefin, this disproportionation reaction involves an autolysis reaction in which 1,1,2-trifluoroethylene molecules decompose. Following 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 the 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 under high-temperature and high-pressure conditions due to heat generation or the like, these active species and 1,1,2-trifluoroethylene undergo a polymerization reaction, a sooting reaction, or both, repeatedly, resulting in a disproportionation reaction. Since this disproportionation reaction is exothermic, active radicals are generated by the heat generation, and these active radicals then 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 proceed rapidly.

[0026] Previous intensive studies by the present applicant have revealed 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).

[0027] 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 in which difluoromethane is used in combination with a fluoroolefin such as 1,1,2-trifluoroethylene, which undergoes a disproportionation reaction, as a refrigerant component. 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.

[0028] Furthermore, the present inventors have newly discovered that the disproportionation reaction of fluoroolefins can be effectively inhibited or alleviated by adding an unsaturated compound having a carbon-carbon double bond (C=C bond) in its chemical structure to a working fluid for a refrigeration cycle containing fluoroolefins. Furthermore, it has been newly discovered that this unsaturated compound does not capture radicals like the disproportionation inhibitors previously proposed by the present applicant, but rather captures carbene, and that in the disproportionation reaction of fluoroolefins, carbene can be involved in the rapid progress of the reaction.

[0029] [Unsaturated Compounds 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 as a result of 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 unsaturated compound having in its chemical structure a carbon-carbon double bond (C=C bond) 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 unsaturated compound as a carbene scavenger.

[0030] In the present disclosure, the unsaturated compound used as a carbene scavenger may be any organic compound having a carbon-carbon double bond in its chemical structure, and representative examples include organic compounds having 4 or less carbon atoms or derivatives thereof. A more specific example of such an unsaturated compound is an olefin (aliphatic unsaturated hydrocarbon) having 4 or less carbon atoms or a derivative thereof.

[0031] In the present disclosure, the specific type of olefin having 4 or less carbon atoms used as a carbene scavenger is not particularly limited, but representative examples include at least one olefin selected from the group consisting of ethene (ethylene), butadiene, butene (butylene), cyclobutene (cyclobutylene), and cyclopropene, or a derivative thereof, as shown in the following formulas (1) to (5).

[0032] [ka]

[0033] Formula (1) represents ethene (ethylene), an olefin having two carbon atoms, or a derivative thereof. X in Formula (1) 1 ~X 4 are each independently an atom or an atomic group selected from the group consisting of a hydrogen atom (H), a methyl group (CH), an ethyl group (CH), a methoxy group (OCH), a trifluoromethyl group (CF), a chlorine atom (Cl), a bromine atom (Br), and an iodine atom (I).

[0034] In other words, X in Eq. (1) 1 ~X 4 are both hydrogen atoms (H), the carbene trapping agent of the present disclosure is ethene. 1 ~X 4 In the present disclosure, the carbene scavenger can be said to be a derivative of ethene if it is an unsaturated compound in which at least one of the above is substituted with a substituent (including a substituted atom) selected from the group (substituent group) consisting of CH3, C2H5, OCH3, CF3, Cl, Br, and I.

[0035] Similarly, formula (2) can be expressed as follows: butadiene (X in formula (2) 1 ~X 6 are both H) or a derivative thereof (X in formula (3) 1 ~X 6 is substituted with a substituent selected from the above-mentioned group of substituents).

[0036] Formula (3) shows that 1-butene (X in formula (3) 1 ~X 8 are both H) or a derivative thereof (X in formula (3) 1 ~X 8 is substituted with a substituent selected from the above-described group of substituents). In this embodiment, 1-butene shown in formula (3) is given as a representative example of butene (butylene), but the carbene scavenger in this disclosure is not limited to 1-butene or its derivatives, and may also include 2-butene or its derivatives. In the examples described below, 1-butene is used as the carbene scavenger.

[0037] Formula (4) is a cyclobutene (X in formula (4) 1 ~X 6 are both H) or a derivative thereof (X in formula (4) 1 ~X 6 Formula (5) represents a cyclopropene (X in formula (5)) in which one or more of 1 ~X 4 are both H) or a derivative thereof (X in formula (5) 1 ~X 4 is substituted with a substituent selected from the above-mentioned group of substituents).

[0038] In this way, in formulas (1) to (5), X in each formula 1 ~X 8 If both are H, it is an example of an olefin having 4 or less carbon atoms, and X 1 ~X 8 In the formulas (1) to (5), if one or more of X is substituted with a substituent selected from the above-mentioned group of substituents, it is an example of a derivative of an olefin having 4 or less carbon atoms. 1 ~X 8 As described above, each of the groups can be independently substituted with the above-mentioned substituents. 1 ~X 8When 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.

[0039] In the olefins exemplified in formulas (1) to (5), X 1 ~X 8 is not limited to the substituents (atoms or atomic groups) constituting the above-mentioned substituent groups, and may be a derivative substituted with other substituents. Further, the olefins exemplified in formulas (1) to (5) may have more than 4 carbon atoms. For example, X of butadiene shown in formula (3) 1 ~X 6 is CH3, C2H5, OCH3, or CF3, the olefin shown in Formula 3 has more than 5 carbon atoms, but as long as the olefin has the reactivity to capture carbene, it is included in the carbene trapping agent of the present disclosure.

[0040] Furthermore, in the olefins exemplified in formulas (1) to (5), CH3, C2H5, OCH3, and CF3 are exemplified as substituents, and halogen atoms other than fluorine (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 trapping agents in the present disclosure are not limited to the olefins shown in formulas (1) to (5) or their derivatives.

[0041] 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 unsaturated compound described above.

[0042] The unsaturated compound used as a carbene trapping agent is converted into a compound having a cyclopropane structure by the reaction of the carbene with a double bond, cleaving one of the double bonds, and capturing the carbene. If the captured carbene is at least one selected from the group consisting of CF2, CHF, and CH2, the compound produced (converted) has four or less carbon atoms and has a cyclopropane structure derived from the carbene in its molecular structure.

[0043] Thus, in the present disclosure, the chemical reaction (carbene trapping reaction) in which the above-mentioned unsaturated compound traps carbene and is converted into a compound having a cyclopropane structure, and the suppression of the disproportionation reaction of fluoroolefins thereby, will be specifically described with reference to Figure 1. In Figure 1, ethene or a derivative thereof (referred to as an "ethene compound" for convenience of explanation) shown in formula (1) is exemplified as an unsaturated compound serving as a carbene trap, and CF2 is exemplified as a carbene.

[0044] 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 a 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. In this stage, carbenes are gradually generated and accumulate. If the carbene concentration exceeds an upper limit in this induction stage, the self-decomposition of the fluoroolefin is thought to progress rapidly.

[0045] 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.

[0046] 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 fluoroolefin) within the compressor 16, is schematically shown as a discharge region 201 located in the center of the schematic compressor 16.

[0047] 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 as "intermediates" rather than final products of the autolysis reaction. Therefore, for ease of explanation, this region 201a is referred to as the reaction intermediate accumulation region 201a. In FIG. 1, CF2 is illustrated as an example of carbene 31, and this carbene 31 (CF2) gradually accumulates in this reaction intermediate accumulation region 201a.

[0048] 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.

[0049] Therefore, in the present disclosure, the working fluid for a refrigeration cycle contains, for example, an ethene compound 32 (ethene or a derivative thereof) represented by the above formula (1) as a carbene trap. The ethene compound 32 is highly reactive with carbene 31 (CF2), but is relatively less reactive with other substances present in the refrigeration cycle, including the reaction intermediate retention region 201a. Therefore, the ethene compound 32 reacts to trap carbene 31 by cleaving its carbon-carbon double bond, thereby producing a compound 33 having a cyclopropane structure.

[0050] In the example shown in FIG. 1, compound 33 having a cyclopropane structure is 1,1-difluorocyclopropane (X 1 ~X 4 are both H) or its derivatives (X 1 ~X 4 (where one or more of the substituents are the above-mentioned substituents). This compound 33 is a singlet ground state molecule with no unpaired electron. This effectively suppresses the increase in carbene 31, thereby suppressing or avoiding the progression of the chain autolysis of the fluoroolefin. As a result, the disproportionation reaction can be effectively suppressed or alleviated.

[0051] As a result of extensive research, the inventors of the present invention have determined the intrinsic reaction coordinate of an unsaturated 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, the carbene trapping reaction via this carbon-carbon double bond has a relatively low activation energy. Therefore, even under conditions in which the carbene reacts with a fluoroolefin to secondarily generate active species, or under conditions in which the disproportionation reaction is promoted by reaction heat, the unsaturated compound may react before the carbene reacts with the fluoroolefin. Therefore, the method for suppressing the disproportionation reaction of a working fluid for a refrigeration cycle according to the present disclosure can more effectively suppress the disproportionation reaction of fluoroolefins.

[0052] According to the above-mentioned investigations by the present inventors, the substituent X (X in the above formulas (1) to (5)) possessed by the unsaturated compound 1 ~X 8 It is believed that the higher the electron donating ability of the unsaturated compound (see reference 1), the higher the reactivity of the carbene capture reaction. Therefore, by appropriately selecting the substituent X in consideration of the molecular structure of the unsaturated compound, it is possible to obtain a good effect of suppressing the disproportionation reaction even if the concentration of the unsaturated compound in the working fluid for the refrigeration cycle is relatively low.

[0053] 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" here refer to areas where multiple sliding members slide against each other with their sliding surfaces in contact with each other.

[0054] When evaluating the likelihood of carbene generation over time, as mentioned above, carbene is likely to be generated immediately after the occurrence of discharge that triggers self-decomposition, after the radicals generated by self-decomposition have disappeared, or immediately before the progression of chain reaction self-decomposition. Furthermore, when evaluating the likelihood of carbene generation in regions within the compressor, it was found that carbene is naturally likely to be generated in regions where discharge that triggers self-decomposition can occur, i.e., the discharge region (see Figure 1). Furthermore, it was revealed that carbene is also likely to be generated in areas of the compressor that are subject to high temperatures and pressures, such as sliding parts, and in their vicinity.

[0055] 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.

[0056] A typical example of the discharge region and sliding region in a compressor will be specifically described with reference to Fig. 2. Fig. 2 illustrates a rotary (or scroll) type compressor. For the sake of convenience in explaining the discharge region and 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.

[0057] 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.

[0058] 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 shown schematically 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).

[0059] 2 includes an electric motor unit 162 and a compression mechanism unit 163 in 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.

[0060] 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.

[0061] 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 in a first cylinder and a vane that separates 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.

[0062] 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 partitions the interior of 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.

[0063] Rotor 165 is fixed to shaft 166, and is rotatably supported by main bearing 167 and sub-bearing 168. Also, first piston 169A and second piston 169B are fixed to shaft 166 with a phase difference of 180 degrees from each other.

[0064] 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.

[0065] 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. The gas refrigerant flows through the first suction pipe 171A and the second suction pipe 171B.

[0066] Rotation of shaft 166 causes first piston 169A and second piston 169B to revolve within first compression chamber 172A and second compression chamber 172B. The gas refrigerant sucked into first compression chamber 172A and second compression chamber 172B from first suction pipe 171A and second suction pipe 171B by the orbital motion of first piston 169A and second piston 169B is compressed in first compression chamber 172A and second compression chamber 172B and then discharged into sealed container 161, separates lubricating oil while passing through electric motor unit 162 and rising, and is then discharged out of sealed container 161 from the discharge pipe.

[0067] 2, discharge regions 201A and 201B in compressor 16 are areas surrounded by dashed lines, and the sliding region is an area surrounded by a dotted line. 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 terminal 173 and its surroundings.

[0068] 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 likely to become high temperature and high pressure within compressor 16 include the area between first piston 169A or second piston 169B and the vane, the area between main bearing 167 and shaft 166, and the area between rotor 165 and main bearing 167.

[0069] 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 area 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).

[0070] In the present disclosure, it is sufficient that an increase in carbene can be suppressed by an unsaturated compound that is a carbene scavenger in a refrigeration cycle including compressor 16. Furthermore, it is sufficient that an increase in carbene can be suppressed by a carbene scavenger (unsaturated compound) in at least one of discharge regions 201A, B and sliding regions 202A to 202C in compressor 16 of the refrigeration cycle.

[0071] In particular, if the increase in carbenes in the discharge regions 201A and 201B can be suppressed by using a carbene scavenger (unsaturated 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.

[0072] Note that, although the example shown in FIG. 2 illustrates two discharge regions and three sliding regions within 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 within 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" refers to at least one region among multiple discharge regions and multiple sliding regions within 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] According to a study using simulations by the present inventors, it has become clear that disproportionation reactions 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.

[0077] Furthermore, in the present disclosure, not only the upper limit of the carbene concentration but also the temperature or pressure at which carbene is likely to be generated by the self-decomposition of the fluoroolefin can be lowered to suppress an increase in carbene.

[0078] 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.

[0079] 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 and propagation of the self-decomposition reaction of fluoroolefins will not be fully satisfied. As a result, even if the fluoroolefins self-decompose, 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.

[0080] In the working fluid for a refrigeration cycle according to the present disclosure, the content of the unsaturated compound as a carbene scavenger is not particularly limited. The unsaturated 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.

[0081] Typically, the working fluid for a refrigeration cycle may contain 30% by mass or less of the unsaturated compound (carbene scavenger) relative to 100% 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 unsaturated compound is equal to or less than this upper limit, it is possible to effectively suppress or mitigate the disproportionation reaction of the fluoroolefin in the working fluid for a refrigeration cycle, although this depends on various conditions.

[0082] On the other hand, the lower limit of the content of the unsaturated compound (carbene scavenger) in the working fluid for a refrigeration cycle is not particularly limited, but typically, the content of the unsaturated compound (carbene scavenger) may be 1% by mass or more relative to 100% by mass of the fluoroolefin contained in the working fluid for a refrigeration cycle. If the content of the unsaturated compound (carbene scavenger) is 1% by mass or more, the effect of suppressing the disproportionation reaction can be more effectively exhibited. The lower limit of the content of the unsaturated compound (carbene scavenger) may be 5% by mass or more, or 10% by mass or more.

[0083] 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.

[0084] 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 unsaturated compound having in its chemical structure a carbon-carbon double bond (C=C bond) that reacts with carbene is added as a carbene scavenger to a refrigerant component mainly composed of a fluoroolefin, as described above.

[0085] 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 unsaturated compound that is a carbene scavenger, 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.

[0086] Furthermore, in the working fluid for a refrigeration cycle or the method for suppressing a disproportionation reaction according to the present disclosure, whereas the fluoroolefin has self-decomposition properties, the unsaturated compound serving as a carbene scavenger does not. Therefore, when the unsaturated compound is contained in a working fluid for a refrigeration cycle, the stability of the working fluid can be relatively increased. Furthermore, the higher the electron-donating property of the substituent in the molecular structure of the unsaturated compound, the greater the effect of suppressing or mitigating the disproportionation reaction can be expected, even if the content of the unsaturated compound is small (even at a low concentration).

[0087] [Example of refrigeration cycle system configuration] 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" shown in FIGS. 3(A) and 3(B).

[0088] 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.

[0089] 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. 3(A), 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.

[0090] 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. Furthermore, 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). Furthermore, the piping 13 is provided with various valve devices (including the four-way valve 18), a strainer, etc. (not shown).

[0091] 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.

[0092] The specific configurations of the indoor unit 11 and the outdoor unit 12, or the specific configurations of the heat exchanger 14 or 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.

[0093] An example of the operation of the air conditioner 10 shown in Figure 3(A) 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.

[0094] Furthermore, during heating operation, the compressor 16 of the outdoor unit 12 compresses and discharges the gas refrigerant, which is then sent to the heat exchanger 14 of the indoor unit 11 via the four-way valve 18. In the heat exchanger 14, the gas refrigerant condenses and liquefies 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 a gas refrigerant, which returns to the compressor 16. The compressor 16 compresses the gas refrigerant and discharges it again to the heat exchanger 14 of the indoor unit 11 via the four-way valve 18.

[0095] Furthermore, a refrigerator will be described as another typical application example of the refrigeration cycle system according to the present disclosure. Specifically, for example, as schematically shown in the block diagram of Fig. 3(B), refrigerator 20 according to this embodiment includes compressor 21, condenser 22, pressure reducing device 23, evaporator 24, and piping 25 shown in Fig. 3. Furthermore, refrigerator 20 also includes a housing that serves as a main body, a blower, an operation unit, a control unit, and the like, which are not shown.

[0096] The compressor 21 compresses the refrigerant gas to form a high-temperature, high-pressure gas refrigerant. The condenser 22 cools the refrigerant to liquefy it. The pressure reducing device 23 is formed, for example, by a capillary tube, and reduces the pressure of the liquefied refrigerant (liquid refrigerant). The evaporator 24 evaporates the refrigerant to form 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.

[0097] 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 these.

[0098] An example of the operation of refrigerator 20 shown in Fig. 3(B) will be specifically described. Compressor 21 compresses the gas refrigerant and discharges it to condenser 22. Condenser 22 cools the gas refrigerant to liquid refrigerant. The liquid refrigerant is decompressed by passing through decompression 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.

[0099] 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 unsaturated compound described above as a carbene scavenger.

[0100] 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.

[0101] [Working fluid for refrigeration cycle] The present disclosure also includes a working fluid for a refrigeration cycle containing the above-mentioned carbene scavenger. Specifically, the working fluid for a refrigeration cycle according to the present disclosure may contain, as a refrigerant component, a fluoroolefin in which a disproportionation reaction occurs, as described above, and may contain, as a carbene scavenger, the above-mentioned unsaturated compound, for capturing the carbene generated in the disproportionation reaction. As described above, a specific carbene scavenger may be one having, in its chemical structure, a carbon-carbon double bond (C=C bond) that reacts with carbene, and representative examples thereof include organic compounds having a carbon-carbon double bond and having 4 or less carbon atoms, or derivatives thereof.

[0102] 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).

[0103] 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: CH2F2) in addition to fluoroolefins. In this case, if the fluoroolefin is considered to be the "main component (main refrigerant component)" of the refrigerant components in the working fluid for a refrigeration cycle according to the present disclosure, the difluoromethane is considered to be the "secondary component (secondary refrigerant component)" of the refrigerant components in the working fluid for a refrigeration cycle according to the present disclosure. Compared to the HCFCs (hydrochlorofluorocarbons) that have been used until now, difluoromethane has an ozone depletion potential (ODP) of 0 and has good refrigerant performance.

[0104] Furthermore, the working fluid for a refrigeration cycle according to the present disclosure may contain 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, 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.

[0105] 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.

[0106] 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.

[0107] It is important for the working fluid for a refrigeration cycle according to the present disclosure to have a GWP as small as possible. Specifically, the GWP is preferably 200 or less (GWP≦200), and more preferably 150 or less (GWP≦150). When a secondary refrigerant component, such as difluoromethane, is used in combination with a fluoroolefin, which is the primary 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.

[0108] If 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 if 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 as the main refrigerant component, the content of the secondary refrigerant component only needs to be 0% by mass or more.

[0109] The working fluid for a refrigeration cycle according to the present disclosure is used in a refrigeration cycle system, and therefore can be used in combination with a lubricating oil (refrigerating machine oil) that lubricates a compressor included in the refrigeration cycle system.

[0110] As described above, the working fluid for a refrigeration cycle according to the present disclosure may contain at least a fluoroolefin (e.g., 1,1,2-trifluoroethylene) that undergoes a disproportionation reaction as a refrigerant component, and may further contain a carbene scavenger. When the working fluid for a refrigeration cycle is used in combination with a lubricating oil, the working fluid-containing composition may 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, or may be mixed with the lubricating oil component depending on the circumstances.

[0111] 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.

[0112] 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.

[0113] 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 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.

[0114] 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 an unsaturated compound having a carbon-carbon double bond (C=C bond) in its chemical structure as a carbene scavenger.

[0115] The unsaturated compound captures the carbene by reacting with its double bond. Because the activation energy of this carbene capture reaction is relatively low, even under conditions in which the carbene reacts with a fluoroolefin to secondarily generate an active species or under conditions in which the disproportionation reaction is promoted by reaction heat, the unsaturated compound may react before the carbene reacts with the fluoroolefin. Therefore, according to the present disclosure, it is possible to more effectively suppress the disproportionation reaction of fluoroolefins. [Example]

[0116] 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.

[0117] (Experimental system for disproportionation reaction) A sealed pressure vessel (stainless steel vessel, internal volume 50 mL) was equipped with a pressure sensor (GC61, manufactured by Nagano Keiki Co., Ltd.) to measure the internal pressure of the vessel, a thermocouple (PL thermocouple gland PL-18-K-A4-T, manufactured by Conax Technologies) to measure the internal temperature of the vessel, and a discharge device to generate a discharge within the vessel. A 1,1,2-trifluoroethylene gas cylinder was also connected to the vessel so that the pressure could be adjusted. A mantle heater was installed to heat the entire pressure 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. This completed the construction of an experimental system for the disproportionation reaction.

[0118] (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.

[0119] Example 1 In the experimental system, 1,1,2-trifluoroethylene was introduced into the pressure vessel from the HFO1123 gas cylinder, and 1-butene (see the above formula (4), where X 1 ~X 8 In each case, H) was added so that the content was 7.1 mass %. The stored energy of the discharge device was set to 0.055 J, and a discharge was generated in the above-mentioned experimental system. The results are shown in Table 1.

[0120] 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 1.08 J. The results are shown in Table 1.

[0121] [Table 1]

[0122] In Table 1, temperature [°C] is the internal temperature inside the pressure vessel. Pressure [MPa] is the internal pressure inside the pressure vessel. Stored energy [J] is the electrostatic energy stored in the capacitor 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, "Yes" was recorded for the presence or absence of a disproportionation reaction, and if no disproportionation reaction was observed, "No" was recorded.

[0123] 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 (1-butene) 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.

[0124] (Addendum) Based on the description of the above embodiments, the following techniques are disclosed in this specification. (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, wherein when carbene is generated as a result of the disproportionation reaction of the refrigerant component, the working fluid for a refrigeration cycle further contains, as a carbene scavenger, an unsaturated compound having in its chemical structure a carbon-carbon double bond (C=C bond) that reacts with the carbene, and the carbene scavenger captures the generated carbene, thereby suppressing an increase of the carbene in the refrigeration cycle and suppressing the disproportionation reaction of the refrigerant component.

[0125] (Technology 2) The refrigerant component in which the disproportionation reaction occurs is a fluoroolefin. A method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to Technical 1.

[0126] (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 unsaturated compound is an organic compound having 4 or less carbon atoms or a derivative thereof.

[0127] (Technology 4) The method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to Technology 3, wherein the unsaturated compound is at least one olefin selected from the group consisting of ethene, butadiene, cyclopropene, cyclobutene, and butene, or a derivative thereof.

[0128] (Technology 5) The method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to any one of Technology 1 to Technology 4, wherein the carbene includes at least one selected from the group consisting of CF2, CHF, and CH2.

[0129] (Technology 6) The method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to any one of Technology 1 to Technology 5, wherein the carbene scavenger reacts with the double bond, cleaving one of the double bonds to incorporate the carbene, thereby forming a cyclopropane structure and suppressing an increase of the carbene.

[0130] (Technology 7) The method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to Technology 6, wherein the suppression of an increase in the carbene includes reducing the carbene concentration below a preset upper limit value or making the carbene concentration substantially zero.

[0131] (Technology 8) The method for suppressing a disproportionation reaction of a working medium for a refrigeration cycle according to any one of Technology 1 to Technology 7, wherein the refrigeration cycle includes a compressor, the compressor including a discharge region where discharge can occur, and a sliding region having a sliding portion 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.

[0132] (Technology 9) A working fluid for a refrigeration cycle, which contains a refrigerant component that undergoes a disproportionation reaction, and also contains, as a carbene scavenger that captures carbene generated in conjunction with the disproportionation reaction of the refrigerant component, an unsaturated compound having in its chemical structure a carbon-carbon double bond (C=C bond) that reacts with the carbene.

[0133] (Technology 10) The working fluid for a refrigeration cycle according to Technology 9, wherein the refrigerant component in which the disproportionation reaction occurs is a fluoroolefin.

[0134] (Technology 11) The working fluid for a refrigeration cycle according to Technology 9 or Technology 10, wherein the unsaturated compound is an organic compound having 4 or less carbon atoms or a derivative thereof.

[0135] (Technology 12) The working medium for a refrigeration cycle according to any one of Technology 9 to Technology 11, wherein the unsaturated compound is at least one olefin selected from the group consisting of ethene, butadiene, cyclopropene, cyclobutene, and butene, or a derivative thereof.

[0136] (Technology 13) A carbene scavenger for refrigerants containing an unsaturated compound having a carbon-carbon double bond (C=C bond) in its chemical structure.

[0137] 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. [Industrial Applicability]

[0138] 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. [Explanation of symbols]

[0139] 10: Air conditioning equipment (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 (freezing cycle system) 21: Compressor 22: Condenser 23: Pressure reducing device 24: Evaporator 25: Piping 31: Carbene (CF2) 32: Ethene compounds (carbene traps) 33: Compounds with cyclopropane structure (singlet ground state molecules) 161: Airtight container 162: Electric motor section 163: Compression mechanism 163A: First compression mechanism 163B: Second compression mechanism 164: Stator 165: Rotor 166: Shaft 167: Main bearing 168: Sub 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 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. In a refrigeration cycle in which a working fluid for a refrigeration cycle containing a refrigerant component that undergoes a disproportionation reaction circulates, when carbene is generated in association with the disproportionation reaction of the refrigerant component, the working fluid for a refrigeration cycle further contains, as a carbene scavenger, an unsaturated compound having in its chemical structure a carbon-carbon double bond (C=C bond) that reacts with the carbene; The carbene scavenger traps the generated carbene, thereby suppressing an increase in the carbene in the refrigeration cycle and suppressing a disproportionation reaction of the refrigerant components. A method for suppressing disproportionation reaction of a working fluid for a refrigeration cycle.

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

3. The unsaturated compound is an organic compound having 4 or less carbon atoms or a derivative thereof. A method for suppressing a disproportionation reaction of the working fluid for a refrigeration cycle according to claim 1.

4. The unsaturated compound is at least one olefin or a derivative thereof selected from the group consisting of ethene, butadiene, cyclopropene, cyclobutene, and butene. A method for suppressing a disproportionation reaction of a working fluid for a refrigeration cycle according to claim 3.

5. The carbene is CF 2 , CHF, and CH 2 At least one selected from the group consisting of: A method for suppressing a disproportionation reaction of the working fluid for a refrigeration cycle according to any one of claims 1 to 3.

6. the carbene trapping agent reacts with the double bond, cleaving one of the double bonds and incorporating the carbene, thereby forming a cyclopropane structure and suppressing an increase in the carbene; A method for suppressing a disproportionation reaction of the working fluid for a refrigeration cycle according to any one of claims 1 to 3.

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

8. The refrigeration cycle includes a compressor, Within the compressor: a discharge region in which discharge can occur; a sliding region having a sliding portion where a plurality of sliding members slide in a state of contact with each other at their sliding surfaces; Including, suppressing an increase in the carbene present in at least one of the discharge region and the sliding region; A method for suppressing a disproportionation reaction of the working fluid for a refrigeration cycle according to any one of claims 1 to 3.

9. Contains refrigerant components that undergo disproportionation reactions, the refrigerant component is characterized in that it contains, as a carbene scavenger that captures carbene generated in conjunction with the disproportionation reaction of the refrigerant component, an unsaturated compound having, in its chemical structure, a carbon-carbon double bond (C=C bond) that reacts with the carbene; Working medium for refrigeration cycle.

10. The refrigerant component in which the disproportionation reaction occurs is a fluoroolefin. The working fluid for a refrigeration cycle according to claim 9.

11. The unsaturated compound is an organic compound having 4 or less carbon atoms or a derivative thereof. The working fluid for a refrigeration cycle according to claim 9 or 10.

12. The unsaturated compound is at least one olefin or a derivative thereof selected from the group consisting of ethene, butadiene, cyclopropene, cyclobutene, and butene. The working fluid for a refrigeration cycle according to claim 10.

13. The composition is characterized by containing an unsaturated compound having a carbon-carbon double bond (C=C bond) in its chemical structure. Carbene scavenger for refrigerants.

Images