JP2000309790A - Mixed working fluid which does not ignite and explode and refrigerating equipment using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mixed working fluid which exerts no influence on the stratospheric ozonosphere and little influence on global warming, has excellent stability, and does not ignite and explode even if it leaks into an apparatus having a source of ignition and to provide a refrigerating equipment using the same. SOLUTION: This fluid comprises a refrigerant comprising 0.5 to below 25 wt.% trifluoroiodomethane and above 75 to 99.5 wt.% isobutane (the total is 100 wt.%) and a refrigerator oil for use in a refrigeration cycle, being a lubricating oil selected from among a naphthene oil, a paraffin oil, an alkylbenzene oil, and a mixture of at least two of them and containing an epoxy stabilizer as an essential component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mixed working fluid having no ignition explosion and a refrigeration system using the same. More specifically, the present invention relates to a refrigerant containing trifluoroiodide methane and isobutane, and a refrigerating machine oil. The present invention relates to a mixed working fluid containing a lubricating oil containing an epoxy stabilizer and having no ignition explosion even if it leaks into a device having an ignition source, and a refrigeration system using the same.

[0002]

2. Description of the Related Art Compressors for refrigerators, vending machines and showcases conventionally use dichlorodifluoromethane (R12) as a refrigerant, and air conditioners and the like use chlorodifluoromethane (R22) as a refrigerant. I was As the refrigerating machine oil, naphthenic oil, paraffin oil, alkylbenzene oil and a mixture of two or more of these having a pour point of -15 ° C or less have been used. Since these CFC and HCFC refrigerants have chlorine groups in the molecule, the refrigerant itself acts as an extreme pressure agent, so there is no seizure due to metal adhesion on the sliding part of the compressor, the amount of wear is small, and the reliability is low. High product was offered. However, due to their high ozone depletion potential, these CFC-based refrigerants are subject to Freon regulations due to the problem of destruction of this ozone layer when they are released into the atmosphere and reach the ozone layer above the earth. .

[0003] The destruction of the ozone layer is caused by chlorine groups (Cl) in the refrigerant. Therefore, a refrigerant containing no chlorine group, for example, difluoromethane (HFC-32,
R-32), 1,1-difluoroethane (HFC-15
2a, R-152a), trifluoromethane (HFC-
23, R-23), pentafluoroethane (HFC-1
25, R-125), 1,1,1,2-tetrafluoroethane (HFC-134a, R-134a), 1,1,1
1-trifluoroethane (HFC-143a, R-14
3a), fluorocarbon-based refrigerants containing no chlorine group and hydrogen (FC-based refrigerants) and the like are considered as alternative refrigerants to the above-mentioned refrigerants. However, although the danger of destruction of the ozone layer is suppressed in HFC-based refrigerants such as R134a, there is a problem that the global warming effect is extremely high, and the mineral oils (naphthene oil, paraffin oil) and alkylbenzene oils are used. Poor compatibility with refrigerating machine oil causes problems such as deterioration of oil return to the compressor, suction of separated refrigerant at the time of start-up, and poor lubrication of the compressor.

For this reason, polyol ester-based oils have been studied as refrigerating machine oils compatible with HFC-based refrigerants such as R134a. However, when this polyol ester-based oil is used in a compressor, the polyol ester-based oil is slid inside the compressor. Moving member friction
The wear is large and the temperature is easy to rise.Heat is hydrolyzed or decomposed by the action of iron oxide, etc., and fatty acids and metal soaps are generated. Also, there is a problem that a sludge component is generated by abrasion and the capillary tube or the like is clogged.

[0005] Therefore, methane, ethane, propane, which have no risk of destruction of the ozone layer and have a reduced global warming effect,
The use of hydrocarbon-based refrigerants such as butane, pentane and hexane has been studied. However, the biggest disadvantage of hydrocarbon-based refrigerants is that they have high ignition explosive properties, and in order to use them, refrigeration equipment such as refrigerators and refrigerators require strict explosion-proof measures, which makes the equipment expensive and easy to use. Is also bad. In addition, since the hydrocarbon-based refrigerant has no active group such as a chlorine group in the molecule and does not itself act as an extreme pressure agent, a refrigerating machine oil such as the above-described mineral oil (naphthene oil, paraffin oil) or alkylbenzene oil was used. However, the lubricating property is low, and there is a fear that seizure or abrasion caused by metal adhesion in sliding parts of the compressor may increase.

[0006]

SUMMARY OF THE INVENTION A first object of the present invention is to provide an R13 which has little effect on the stratospheric ozone layer and may have a small effect on global warming.
A mixed working fluid using a hydrocarbon refrigerant as an alternative to 4a together with a conventional mineral oil (naphthene oil, paraffin oil) or alkylbenzene oil containing a specific stabilizer,
A second object of the present invention is to provide a mixed working fluid which is excellent in stability and has no ignition explosion even if it leaks into a device having an ignition source. It is to provide a reliable refrigeration system.

[0007]

DISCLOSURE OF THE INVENTION The present inventors have conducted intensive studies to solve the conventional problems, and as a result, have found that isobutane (R
It was found that by using a refrigerant in which a small amount of non-flammable trifluoroiodide methane was mixed with respect to 600a), even if it leaked into an apparatus having an ignition source, ignition explosion would be lost.
In addition, we have found that the stability can be improved by using a lubricating oil containing a small amount of a specific stabilizer added to a mineral oil (naphthene oil, paraffin oil) or alkylbenzene oil, which has been conventionally used as a refrigerating machine oil for use in a refrigeration cycle. The invention has been completed.

[0008] In order to solve the above-mentioned problems, the invention of claim 1 is characterized in that 0.5% to less than 25% by weight of trifluoroiodide methane and 75% to 99.5% by weight of isobutane are contained. And a lubricating oil selected from naphthenic oil, paraffin oil, alkylbenzene oil and a mixture of two or more of these containing an epoxy stabilizer as an essential component as a refrigerating machine oil used in a refrigeration cycle. And a mixed working fluid without ignition explosion.

According to a second aspect of the present invention, in the mixed working fluid according to the first aspect, 0.05 to 2% by weight of an epoxy stabilizer with respect to the lubricating oil is contained.

According to a third aspect of the present invention, in the mixed working fluid according to the first or second aspect, an extreme pressure additive and / or a copper deactivator is further added to the lubricating oil. Is what you do.

[0011] The invention according to claim 4 is characterized in that from 0.5% by weight to 25%
Less than 75% by weight and less than 9%
A refrigerant consisting of 9.5% by weight or less of isobutane, and a naphthenic oil, a paraffin oil, an alkylbenzene oil containing an epoxy stabilizer as an essential component as a refrigerating machine oil used in a refrigeration cycle, and a mixture of two or more thereof. The present invention relates to a refrigerant system using a mixed working fluid having no ignition explosion containing lubricating oil.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
Methane trifluoride used in the present invention (CF ₃ I, boiling point -2
(2.7 ° C.) is composed of one carbon atom, three fluorine atoms and one iodine atom, and does not contain chlorine in its molecular structure, so that it has almost no ozone destruction ability. Also the GWP
Is 100% of GWP of fluorinated hydrocarbons with short atmospheric life
It is almost the same as carbon dioxide (CO ₂ ) at 1/0 or less.

It is known that trifluoroiodomethane is a non-flammable substance, which reduces the flammability of isobutane and can be made non-flammable by mixing about 25% by weight or more (for example, see Japanese Patent Application Laid-Open No. Hei 9-1997). 59609).

In the present invention, the ignition explosive property is increased by mixing isobutane with 0.5% by weight to less than 25% by weight of methane trifluoride methane (isobutane + trifluoromethane iodide = 100% by weight). It was found to be gone. If the amount of trifluoroiodomethane is less than 0.5% by weight, ignition explosive properties may be present, and if it exceeds 25% by weight, there is no ignition explosive property, but it is uneconomical and the stability with lubricating oil is poor. Getting worse.

On the other hand, trifluoroiodomethane does not impair the compatibility of isobutane with lubricating oils such as mineral oils (naphthenic oil, paraffin oil) and alkylbenzene oils, but decreases the stability of the lubricating oil. There's a problem.

Therefore, in the present invention, a lubricating oil obtained by adding an epoxy stabilizer to these lubricating oils is used. Isobutane trifluoride is added by adding an epoxy stabilizer, preferably 0.05 to 1 to 2% by weight based on the lubricating oil, and more preferably 0.25 to 1% by weight based on the lubricating oil. Lubricating oils such as conventional mineral oils (naphthenic oil, paraffin oil) and alkylbenzene oils can be used stably for a long time together with iodide methane.

[0017] The mixed working fluid of the present invention can be used as it is in an ordinary refrigeration system. As lubricating oils for refrigerators, not only conventional mineral oils (naphthenic oils, paraffin oils) and alkylbenzene oils, but also lubricating oils such as ether oils and fluorine oils can be used.

The refrigerant used in the present invention is a chlorine-free refrigerant.
It is a mixture of specific composition consisting of fluorinated methane and isobutane, which makes it possible to almost eliminate the influence on the stratospheric ozone layer, and the ODP in the specified composition range is expected to be zero.

The refrigerant used in the present invention is GW of R134a.
Almost carbon dioxide (CO ₂ ) at less than one thousandth of P
Trifluoroiodide methane, which may be about the same as
Since it is composed of isobutane (R600a) having almost no P, there is almost no influence on global warming.

The ignition explosion test in the present invention was carried out as follows as a simple experimental method. First, as a first method, a test container 1 as shown in FIG. 1 was used. The test container 1 is provided with a lid 2 on the front surface, and when an explosion occurs inside the container 3, the lid 2 is opened. Reference numeral 4 denotes a container containing a refrigerant, and supplies the refrigerant contained therein to the inside 3 of the container. Reference numeral 5 denotes an ignition source composed of an automobile plug using a dynamo, and reference numeral 6 denotes a fan, which stirs and uniformly disperses the refrigerant supplied to the inside 3 of the container. Reference numeral 7 denotes a viewing window through which the explosion of the interior 3 of the container can be seen. 8 is a refrigerant inlet.

When performing the ignition explosion test, a predetermined amount of refrigerant is supplied from the inlet 8 by operating the container 4 to the inside 3 of the container with the lid 2 closed at normal temperature and normal pressure. Then, the fan 6 is operated to uniformly disperse the refrigerant in the container interior 3. The ignition source 5 is operated from the start of the supply of the refrigerant to ignite the gas. The determination of the ignition explosive property is made based on whether or not an explosion occurs inside the container 3 and the lid 2 is opened.

As a result of the ignition explosion test, it was found that the isobutane alone always ignited and exploded when the concentration was within the explosion range. However, it was found that the ignition explosion was suppressed by mixing trifluoroiodomethane, and the ignition explosion was eliminated by mixing 0.5% by weight or more of trifluoroiodomethane with isobutane. Methane trifluoride is an unstable substance, and when added in an amount of 25% by weight or more, the stability of the lubricating oil is reduced. Therefore, the smaller the amount added, the better the upper limit is less than 25% by weight.

As a second method, a test as shown in FIG. 2 was conducted at normal temperature and normal pressure. That is, first, the burner 9 is ignited to form a flame 10, and the injection port 11 of the container 4 in which the sample is placed from the rear about 10 cm toward the flame 10.
Inject the sample from. Reference numeral 12 denotes a flame, and reference numeral 13 denotes an injected sample.

As a result of this test, in the case of isobutane alone, a flame 12 having a length of about 40 cm is formed, and the flame 12 propagates back to the injected isobutane 13 to be injected into the injection port 1.
1 has been reached. On the other hand, the flame 12 is less likely to reverse by mixing isobutane with trifluoromethane iodide little by little. By mixing isobutane with 0.5% by weight or more of methanefluoridiomethane, flame 12 is reduced. No longer goes backwards. The results of this test were taken into consideration in conjunction with the results of the above-mentioned ignition explosive test to determine the presence or absence of ignition explosion of the sample.

In the test of the stability of the lubricating oil used in the refrigerant in which isobutane and trifluoroiodide methane are mixed in the present invention, the following shield tube test was carried out as a simple experimental method. First, a tube 14 as shown in FIG.
The copper wire 15, the aluminum wire 16 and the iron wire 17 are put into the tube. Then, 1.5 cc of a lubricating oil sample 18 is put. Finally, 0.5 g of a refrigerant 19 obtained by mixing trifluorinated methane in isobutane is put in the tube 14, and The part 20 is sealed. The sealed tube 21 thus sealed is maintained at 150 ° C., and after 30 days, the change in the hue of the lubricating oil sample 18, the change in the hue of the copper wire 15, the aluminum wire 16, and the iron wire 17, and whether or not sludge is generated , Total acid value (mgKOH / 1.5m
l) was checked. Table 1 shows the results of testing the stability of the lubricating oil when a naphthenic lubricating oil was used and 0.25% by weight of the epoxy stabilizer was added to the lubricating oil and when it was not.

[0026]

[Table 1]

From Table 1, when isobutane is mixed with 8% by weight, 15% by weight, and 26% by weight of methane trifluoride iodide, if no epoxy stabilizer is added, the lubricating oil turns black and the stability becomes Δ to ×. When 45% by weight of methane trifluoride iodide was mixed, the lubricating oil was discolored black and became a muddy state, and the stability was poor, unless the epoxy stabilizer was added. On the other hand, when 0.25% by weight of the epoxy stabilizer is blended with the lubricating oil, the stability of fluorinated iodomethane is 8% by weight, and when the amount is 15% by weight, the stability is で. It can be seen that the stability is poor when the methane iodide is 26% by weight, and the stability is poor when the weight is 45% by weight.

The mixed working fluid of the present invention contains a lubricating oil selected from mineral oils (naphthenic oils, paraffin oils) and alkylbenzene oils, which contain an epoxy stabilizer as an essential component as a refrigerating machine oil, and mixtures of two or more thereof. But,
Specific examples of the epoxy stabilizer include, for example, monomethyl glycidyl ether, monobutyl glycidyl ether,
Monohexyl glycidyl ether, 2-ethylhexyl glycidyl ether, monodecyl glycidyl ether,
Monoalkyl glycidyl ethers such as isooctadecyl glycidyl ether and monostearyl glycidyl ether, and monophenyl glycidyl ether;
monoallyl glycidyl ether such as ec-butylphenyl glycidyl ether, and fatty acid glycidyl ether such as 2-ethylhexanoic acid glycidyl ether and nonanoic acid glycidyl ether; and epoxidized methyl oleate, epoxidized butyl oleate, and epoxidized octyl oleate. , Epoxidized methyl stearate,
Examples include epoxidized fatty acid monoesters such as epoxidized butyl stearate and epoxidized octyl stearate, and mixtures of two or more thereof.

In the present invention, in addition to the epoxy stabilizer,
Other stabilizers can be added. Specifically, compounds having a hindered phenol structure, an arylamine structure, a hindered piperidine structure, a thioether structure, or a phosphite structure can be used alone or in combination. For example, as those having a hindered phenol structure, 2,
6-di-tert-butyl-4-methylphenol,
Alkyl phenols such as 2,4,6-tritert-butylphenol, styrenated phenol and derivatives having the structure thereof, 2,2′-methylenebis (4-methyl-
6-tert-butylphenol), 4,4'-isopropylidene-bisphenol, 4,4'-butylidene-
Bis (6-tert-butyl-3-methyl) phenol,
Monoalkylene dialkylphenols such as 1,1-bis- (4-oxyphenyl) cyclohexane and derivatives having the structure thereof, and 2,6-bis (2′-hydroxy-
3'-tert-butyl-5'-methylbenzyl) -4
-Dialkylene trialkylphenols such as methylphenol and derivatives thereof, 2,2'-thiobis- (4-methyl-6-tert-butylphenol), 4,4'-
Typical examples include bisphenol monosulfide such as thiobis- (3-methyl-6-butyl butylphenol) and derivatives having the structure.

As the arylamine structure, phenyl-
α-naphthylamine, phenyl-β-naphthylamine,
N, N'-diphenyl-p-phenylenediamine, N,
N′-di-β-naphthyl-p-phenylenediamine, N
-Cyclohexyl-N'-phenyl-p-phenylenediamine, p-hydroxy-diphenylamine, p-hydroxyphenyl-β-naphthylamine, 2,2,4-trimethyl-1,2-dihydroquinoline and derivatives.

Further, thioethers such as thiobis (β-naphthol), mercaptobenzothiazole, mercaptobenzimidazole and dodecylmercaptan and derivatives thereof, and phosphites such as triphenyl phosphite, tri-2-ethylhexyl phosphite, and trinonylphenyl Organic phosphite compounds such as phosphite are used. These can be used alone or as a mixture of a plurality of them. The amount may be about several percent by weight based on the lubricating oil used, and depending on the selection of the compound, a sufficient effect can be obtained even at 1 percent by weight or less.

In the present invention, an extreme pressure additive and / or a copper deactivator can be further added to the lubricating oil. By adding the copper deactivator, corrosion of copper, copper alloy, and the like used in heat exchangers, pipes, and other components in the refrigeration cycle can be suppressed.

The copper deactivator used in the present invention is benzotriazole and its derivatives (eg, 5-methyl-1H
-Benzotriazole, 1-dioctylaminomethylbenzotriazole, etc.), imidazoline, pyrimidine,
Nitrogen compounds such as indazole, 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazolyl-
Compounds containing sulfur and nitrogen, such as 2,5-bisdialkyldithiocarbamate and 2- (alkyldithio) benzimidazole, and β- (o-carboxybenzylthio) propionnitrile or propic acid, zinc dialkyldithiophosphate, etc. There is no particular limitation.

However, among these, benzotriazole and its derivatives can be preferably used. The amount of the copper deactivator added to the lubricating oil is not particularly limited, but specific examples include, for example, about 1 to 100 ppm (weight), preferably about 5 to 50 ppm (weight).

Benzotriazole-based compounds are hardly soluble in saturated hydrocarbon-based refrigerants such as mineral oil and have low solubility in many cases. Therefore, sulfonates and the like can be further added as a dissolution aid.

As the extreme pressure additive used in the present invention, known extreme pressure additives can be used. Specifically, for example, extreme pressure additives composed of sulfur-based extreme pressure additives, halogen-based extreme pressure additives, phosphorus-based extreme pressure additives, organometallic compound-based extreme pressure additives, and combinations thereof are mentioned. it can.

Specific examples of sulfur-based extreme pressure additives include sulfurized oils and fats, dibenzyl sulfide, organic polysulfide, polyphenylene sulfide, aldehyde hydrocarbon sulfide, and diethanol disulfide fatty acid ester.

Specific examples of the halogen-based extreme pressure additive include chlorinated hydrocarbons such as chlorinated paraffin wax, chlorinated naphthalene, chlorinated polyphenyl and chlorinated alkylbenzene, methyl trichlorostearate,
Examples thereof include chlorinated carboxylic acid derivatives such as pentachloropentadienoic acid, iodine compounds such as benzyl iodide, and fluorine compounds such as polyfluoroaliphatic carboxylic acids and fluoroalkylpolysiloxanes.

Specific examples of the phosphorus-based extreme pressure additive include phosphates such as tricresyl phosphate and phosphites such as tributyl phosphite. Tricresyl phosphate can be preferably used in the present invention.

Specific examples of the organometallic compound extreme pressure additive include naphthenates and fatty acid salts such as lead naphthenate and lead oleate, thiophosphates such as zinc dialkyldithiophosphate, and thiocarbamine. Acid compounds, titanium compounds such as amine hexafluorotitanate, tin compounds such as dibutyltin sulfide, germanium compounds such as dimethyldiethylgermanium, boron compounds such as dibenzylborate, and silicon compounds such as bis (triorganosilyl) phosphate. Can be mentioned. In the present invention, two or more of the above-mentioned sulfur-based extreme-pressure additives, halogen-based extreme-pressure additives, phosphorus-based extreme-pressure additives, organometallic compound-based extreme-pressure additives, and the like or other kinds thereof are used in combination. it can.

In the present invention, a phenolic antioxidant having a hindered phenol structure (for example, DBPC) may be used for the lubricating oil without departing from the gist of the present invention.
), Phosphites (eg, triphenyl phosphite), and antifoaming agents (eg, silicon-based antifoaming agents).

FIG. 4 shows an embodiment of a refrigerating apparatus such as a freezing refrigerator. In FIG. 4, reference numeral 31 denotes a refrigerator main body, and a storage room 32 includes a refrigerator room 32a, a vegetable room 32b, and a freezing room 32.
c, an ice making chamber 32d, and a switching chamber 32e (not shown). The switching chamber 32e (not shown) is configured so that the user can use it by switching to an arbitrary temperature. An evaporator 33 is provided at the lower rear part of the storage chamber 32, and a duct 34 extending vertically from the evaporator 33 on the rear side of the storage chamber 32 and a blower fan 35 for circulating cool air are provided above the duct 34. And circulates the air cooled by the evaporator 33 to cool the inside of the storage chamber 32, so that the refrigerator compartment 32a, the vegetable compartment 32b, the freezing compartment 32c, the ice making compartment 32d, and a switching compartment (not shown) Cool air is circulated so that 32e is maintained at each set temperature. This refrigerator body 31
A machine room 36 is provided below the machine room. Inside the machine room 36, a compressor 37, a condenser (not shown) and a condenser fan are installed.

The refrigerator body 31 contains 0.5% by weight to less than 25% by weight of trifluoroiodide methane and 75% by weight or more and 99.5% by weight or less of isobutane (trifluoroiodide methane + Mixing operation without ignition explosion using mineral oil (naphthene oil, paraffin oil) or alkylbenzene oil containing an epoxy stabilizer as an essential component as a refrigerating machine oil for use in a refrigeration cycle (isobutane = 100% by weight). Fluid is enclosed.

The refrigerator body 31 uses a refrigerant in which a small amount of trifluorinated iodomethane, which is nonflammable with respect to isobutane, is mixed within a predetermined range. High safety because there is no ignition explosion. In addition, a small amount of an epoxy stabilizer within a predetermined range is added to a mineral oil (naphthene oil, paraffin oil) or an alkylbenzene oil which has been conventionally used as a refrigerating machine oil for use in a refrigeration cycle. . Therefore, the sliding member inside the compressor is not corroded, or a sludge component is generated due to abrasion, thereby clogging a capillary tube, etc., and seizure caused by metal adhesion in the sliding portion of the sliding member is eliminated. The amount of wear does not increase, and stable operation can be performed for a long time.

[0045]

The mixed working fluid of the present invention has no effect on the stratospheric ozone layer and has almost no effect on global warming. The mixed working fluid of the present invention is excellent in stability and does not ignite and explode even if it leaks into a device having an ignition source. The mixed working fluid of the present invention has a temperature of approximately −40 ° C. to approximately 40 ° C., which is a use temperature of a refrigerating device such as a refrigerator.
It can also be used with current equipment using 4a.

The refrigeration system using the mixed working fluid of the present invention can be used stably for a long period of time and has high reliability.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a simple experimental method for testing ignition explosiveness.

FIG. 2 is an explanatory diagram illustrating another experimental method for testing ignition explosion.

FIG. 3 is an explanatory diagram illustrating an experimental method for testing the stability of a lubricating oil.

FIG. 4 is an explanatory diagram illustrating an embodiment of a refrigeration apparatus of the present invention.

[Explanation of symbols]

 31 refrigerator main body 32 accommodation room 32a refrigerator room 32b vegetable room 32c freezer room 32d ice making room 33 evaporator 34 duct 35 blower fan 36 machine room 37 compressor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) C10M 129/18 C10M 129/66 129/66 129/70 129/70 F25B 1/00 395Z F25B 1/00 395 F25D 11/00 101U F25D 11/00 101 C09K 5/04 ZAB // C10N 30:00 40:30 (72) Inventor Yasuki Takahashi 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Miyuki Kawamura 2-5-5 Keihanhondori, Moriguchi-shi, Osaka F-term in SANYO Electric Co., Ltd. 3L045 AA04 BA01 CA02 DA02 PA01 PA04 4H028 AA25 BA05 4H104 BA04A BB09C BB22C BB30C DA02A EB08 EB11 LA20 PA20

Claims (4)

[Claims] 1. A refrigerant comprising 0.5% to less than 25% by weight of trifluoroiodomethane and 75% to 99.5% by weight of isobutane, and a refrigerating machine oil for use in a refrigeration cycle. And a lubricating oil selected from naphthenic oil, paraffin oil, alkylbenzene oil, and a mixture of two or more thereof, which contains an epoxy stabilizer as an essential component. 2. 0.05 to 2% by weight of the lubricating oil
The mixed working fluid according to claim 1, further comprising an epoxy stabilizer. 3. The mixed working fluid according to claim 1, wherein an extreme pressure additive and / or a copper deactivator is further added to the lubricating oil. 4. A refrigerant comprising 0.5% to less than 25% by weight of trifluoromethane iodide and more than 75% by weight to 99.5% by weight of isobutane, and a refrigerating machine oil used in a refrigeration cycle. Using a non-igniting explosive mixed working fluid containing a lubricating oil selected from naphthenic oil, paraffin oil, alkylbenzene oil and a mixture of two or more of these containing an epoxy stabilizer as an essential component. Refrigerant system.