JP2024027603A - Method for improving flame resistance of working fluid, use of amine antioxidant as flame resistance improver, and flame resistance improver - Google Patents

Abstract

[Problem] To reduce the risk of combustion of a working fluid even if air is accidentally mixed in when pumping down a refrigerator. A method for improving the combustion resistance of a working fluid in a refrigerator filled with a working fluid containing refrigerating machine oil and a refrigerant, the method comprising incorporating an amine-based antioxidant into the refrigerating machine oil. [Selection diagram] None

Description

The present invention relates to a method for improving the flame resistance of a working fluid, the use of an amine antioxidant as a flame resistance improver, and a flame resistance improver.

A refrigerator such as a room air conditioner is filled with refrigerator oil and a refrigerant (a composition containing these is called a working fluid). When maintaining, relocating, or removing a refrigerator, a method called "pump down" is sometimes used for the purpose of recovering refrigerant (for example, see Patent Document 1 below). Pumping down, which operates the compressor and collects refrigerant gas into the equipment, is a safe technique when done according to proper procedures.

However, if you perform the pump down operation described above with the piping removed due to a mistake in valve operation, etc., the equipment will suck in a large amount of air, and as the compressor continues to operate, the pressure and temperature inside the compressor will decrease. It may rise. In this case, the refrigerating machine oil and refrigerant filled in the refrigerating machine may burn, which may lead to an explosion (diesel explosion). Such a phenomenon requires special attention in refrigerators using low GWP flammable refrigerants, which have been attracting attention in recent years, as refrigerants. On the other hand, Patent Document 2 describes G-tert. A method of improving the flammability resistance of a working fluid composition for a refrigerator containing refrigerator oil and a refrigerant by adding -butyl-p-cresol is disclosed.

Japanese Patent Application Publication No. 2016-035356 Japanese Patent Application Publication No. 2020-90605

When pumping down a refrigerator, it is desirable to reduce the possibility of combustion of the working fluid as much as possible. Furthermore, even if ignition occurs, it is desirable to be able to control the propagation of the combustion, do not increase the combustion pressure, and reduce the degree of danger. Accordingly, one aspect of the present invention aims to reduce the risk of combustion of the working fluid even if air is accidentally mixed in when pumping down the refrigerator.

The present inventors have found that by incorporating an amine antioxidant into refrigerating machine oil, compared to the conventional method (for example, the method using di-tert.-butyl-p-cresol described in Patent Document 2), It has been found that the combustion resistance of the working fluid can be further improved. The amine antioxidant is di-tert., which is also known as a type of antioxidant (phenolic antioxidant). It is surprising that it exhibits a higher effect of improving flame resistance than -butyl-p-cresol.

One aspect of the present invention is a method for improving the combustion resistance of a working fluid in a refrigerator filled with a working fluid containing refrigerating machine oil and a refrigerant, the method comprising making the refrigerating machine oil contain an amine-based antioxidant. It is.

Another aspect of the present invention is the use of an amine-based antioxidant as a flame resistance improver, in which a working fluid containing refrigeration oil and a refrigerant is treated by incorporating the amine-based antioxidant into refrigeration oil. It is used to improve the combustion resistance of working fluid in refrigerators filled with

Another aspect of the present invention is a flame resistance improver that improves the flame resistance of a working fluid in a refrigerator filled with a working fluid containing refrigerator oil and a refrigerant, the agent containing an amine antioxidant. It is a flame resistance improver.

式中、Ｒ^１は、水素原子又はアルキル基を表す。 In each of the above aspects, the amine antioxidant may include a compound represented by the following formula (1).

In the formula, R ¹ represents a hydrogen atom or an alkyl group.

In each of the above aspects, the refrigerant may include a flammable refrigerant, a highly flammable refrigerant, and a slightly flammable refrigerant.

According to the present invention, even if air is accidentally mixed in when pumping down the refrigerator, the risk of combustion of the working fluid can be reduced. More specifically, the combustion range and maximum pressure of a working fluid containing refrigerating machine oil and refrigerant filled in a refrigerating machine can be reduced under self-ignition/combustion conditions of high temperature and high pressure in the coexistence of air. In other words, since the combustion resistance of the working fluid can be improved, even if air is accidentally mixed in when pumping down the refrigerator, the risk of accidents due to combustion and explosion of the working fluid is significantly reduced. can do.

It is a schematic diagram showing one embodiment of a refrigerator. It is a schematic diagram of a combustion test device. It is a graph showing an example of the relationship between refrigerant concentration and maximum pressure inside the compressor.

Embodiments of the present invention will be described in detail below. One embodiment of the present invention is a method for improving the combustion resistance of a working fluid in a refrigerator filled with a working fluid containing refrigerator oil and a refrigerant. Another embodiment of the present invention is the use (application) of an amine-based antioxidant as a flame resistance improver, which is applied to a working fluid in a refrigerator filled with a working fluid containing refrigerator oil and a refrigerant. It can also be said to be a use (application) to improve flame resistance. Another embodiment of the present invention is a flame resistance improver that improves the flame resistance of a working fluid in a refrigerator filled with a working fluid containing refrigerator oil and a refrigerant, the flame resistance improver comprising an amine antioxidant. It can also be said that it is a flame resistance improver.

The above method, use, and flame resistance improver are effective when the working fluid is exposed to high temperature and high pressure self-ignition/combustion conditions in the presence of air, and when pumping down a refrigerator. , is particularly effective.

The above-mentioned methods for improving the flame resistance of the working fluid include, for example, methods for improving the flame retardance of the working fluid, methods for suppressing combustion of the working fluid, methods for narrowing the combustion range of the working fluid, and methods for improving the flame resistance of the working fluid. It may be expressed in other words, such as a method for reducing the maximum pressure (degree of danger) due to combustion, or a method for reducing the risk of accidents due to combustion and explosion of the working fluid.

The above-mentioned use (application) as a flame resistance improver includes, for example, use (application) as an agent that improves the flame retardancy of a working fluid (flame retardancy improver), agent (application) that suppresses combustion of a working fluid ( Use as a combustion suppressant) (application), use as an agent to narrow the combustion range of working fluids, agent to reduce the maximum pressure (hazard level) due to combustion of working fluids (maximum pressure reducer, hazard reduction agent) It may be expressed in other words, such as use as an agent (application) for reducing the risk of accidents caused by combustion or explosion of working fluids (accident risk reduction agent).

The above flame resistance improvers include, for example, agents that improve the flame retardancy of the working fluid (flame retardant improvers), agents that suppress combustion of the working fluid (combustion suppressants), and agents that narrow the flammability range of the working fluid. Agents, agents that reduce the maximum pressure (hazard level) due to combustion of working fluids (maximum pressure reducing agents, hazard reducing agents), agents that reduce the risk of accidents due to combustion and explosion of working fluids (accident risk reducing agents) etc., may be expressed in another way.

Further, an embodiment of the present invention is a working fluid containing refrigerating machine oil and a refrigerant, and the flammability resistance (during pump down) is improved by incorporating an amine antioxidant into the refrigerating machine oil. Regarding working fluids. This working fluid is effective when exposed to high-temperature, high-pressure self-ignition/combustion conditions in the presence of air, and is particularly effective when pumping down a refrigerator. Examples of working fluids with improved combustion resistance include working fluids with improved flame retardancy, working fluids with narrowed combustion range, working fluids with reduced maximum pressure (hazard level) due to combustion, and working fluids with improved combustion resistance. It may be expressed in other words, such as a working fluid with a reduced risk of accidents due to explosion.

Similar to phenolic antioxidants, amine antioxidants have the effect of capturing active radicals and stopping the oxidation chain reaction of lubricating oil in the air. Amine-based antioxidants capture active species (hydrocarbon radicals, peroxide radicals, and refrigerant molecule radicals) that are generated in the very early stages of ignition and combustion when pumping down refrigerators, and prevent combustion and explosion reactions. It is assumed that it is suppressed. However, as demonstrated in the Examples and Comparative Examples described later, when the base oil (refrigeration oil) contains an amine antioxidant, the flammability range (flammability We were able to confirm the surprising effect of being able to significantly reduce the occurrence probability (probability of occurrence) and the maximum pressure within the compressor (occurrence pressure (degree of danger)). This is because the radical scavenging speed of amine antioxidants is faster than that of phenolic antioxidants, and the radicals that are the active species are inactivated more quickly even under diesel combustion conditions of higher temperature and pressure. It is thought that the effect of improving flame resistance was high. Such effects are particularly noticeable when an oxygen-containing oil such as polyol ester is used as the base oil and a phenyl-α-naphthylamine compound is used as the amine antioxidant.

Hereinafter, the embodiments of the present invention will be described in more detail, but unless otherwise specified, the matters described below are common to any of the embodiments of the method, use, and flame resistance improver described above. be.

FIG. 1 is a schematic diagram showing one embodiment of a refrigerator. As shown in FIG. 1, the refrigerator 10 includes a compressor (refrigerant compressor) 1, a condenser (gas cooler) 2, an expansion mechanism 3 (capillary, expansion valve, etc.), and an evaporator (heat exchanger). 4 are sequentially connected to each other through a flow path 5. The refrigerator 10 (refrigerant circulation system 6) is filled with a working fluid containing refrigerator oil and a refrigerant. The refrigerant circulation system 6 further includes an accumulator 7 between the evaporator 4 and the compressor 1 (on the side of the compressor 1) in order to suppress and prevent liquid refrigerant from directly flowing into the compressor 1. It's okay to do so.

Examples of such a refrigerator 10 include an automobile air conditioner, a dehumidifier, a refrigerator, a refrigerated warehouse, a vending machine, a showcase, a cooling device in a chemical plant, etc., a residential air conditioner, a packaged air conditioner, and a hot water supply device. One example is a heat pump.

In the refrigerant circulation system 6, first, high-temperature (usually 70 to 120°C) refrigerant discharged from the compressor 1 into the flow path 5 becomes a high-density fluid (supercritical fluid, etc.) in the condenser 2. . Subsequently, the refrigerant is liquefied by passing through the narrow flow path of the expansion mechanism 3, and further vaporized in the evaporator 4 to become low temperature (usually -40 to 0°C). Cooling by the refrigerator 10 utilizes a phenomenon in which heat is taken away from the surroundings when the refrigerant evaporates in the evaporator 4.

Inside the compressor 1, a small amount of refrigerant and a large amount of refrigerating machine oil coexist under high temperature conditions (usually 70 to 120° C.). The refrigerant discharged from the compressor 1 into the flow path 5 is in a gaseous state and contains a small amount (usually 1 to 10% by volume) of refrigerating machine oil as a mist. The refrigerant is dissolved (point a in Figure 1).

In the condenser 2, the gaseous refrigerant is compressed to become a high-density fluid, and a large amount of refrigerant and a small amount of refrigeration oil coexist under relatively high temperature conditions (usually 40 to 80°C) (Figure 1 Point b) in the middle. Furthermore, the mixture of a large amount of refrigerant and a small amount of refrigeration oil is sequentially sent to the expansion mechanism 3 and the evaporator 4 and rapidly becomes low temperature (usually -40 to 0°C) (points c and d in Fig. 1). It is returned to the compressor 1 again.

Refrigerating machine oil contains base oil. The base oil may include at least one selected from mineral oil and synthetic oil.

Mineral oil is produced by distilling lubricating oil fractions obtained by atmospheric distillation and vacuum distillation of paraffinic and naphthenic crude oils through solvent deasphalting, solvent refining, hydrorefining, hydrocracking, solvent dewaxing, and hydrogenation. It may be a paraffinic or naphthenic mineral oil obtained by refining by methods such as dewaxing, clay treatment, and sulfuric acid washing. These purification methods may be used alone or in an appropriate combination of two or more.

The synthetic oil may be, for example, a synthetic hydrocarbon oil, an oxygenated oil, etc., and is preferably an oxygenated oil. Examples of oxygen-containing oils include esters, polyvinyl ethers, polyalkylene glycols, carbonates, ketones, polyphenyl ethers, silicones, polysiloxanes, and perfluoroethers. The base oil preferably contains an ester.

Examples of esters include aromatic esters, dibasic acid esters, polyol esters, complex esters, carbonate esters, and mixtures thereof. The ester is preferably a polyol ester.

Polyol esters are esters of polyhydric alcohols and fatty acids. Fatty acids may be linear or branched. The fatty acids are preferably saturated fatty acids. The number of carbon atoms in the fatty acid is preferably 4 or more, more preferably 5 or more, and preferably 20 or less, more preferably 18 or less, and even more preferably 9 or less. The fatty acid preferably contains a fatty acid having a branch at the α-position and/or the β-position, and more preferably contains one or both of 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid.

The polyhydric alcohol constituting the polyol ester is preferably a polyhydric alcohol having 2 to 6 hydroxyl groups. The number of carbon atoms in the polyhydric alcohol is preferably 4 or more, more preferably 5 or more, and preferably 12 or less, more preferably 10 or less. The polyhydric alcohol is preferably a hindered alcohol such as neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, di-(trimethylolpropane), tri-(trimethylolpropane), pentaerythritol, dipentaerythritol, etc. Pentaerythritol is more preferred because it is an alcohol and has particularly excellent compatibility with refrigerants and hydrolytic stability.

The kinematic viscosity at 40° C. of the base oil is preferably 1 mm ² /s or more, more preferably 2 mm ² /s or more, 3 mm ² /s or more, or 4 mm ² /s or more, preferably 500 mm ² /s or more. s or less, more preferably 400 mm ² /s or less. The kinematic viscosity at 100° C. of the base oil is preferably 1 mm ² /s or more, more preferably 2 mm ² /s or more, and preferably 50 mm ² /s or less, more preferably 30 mm ² /s or less. good. The viscosity index of the base oil is preferably -50 or higher, more preferably -40 or higher, even more preferably -30 or higher, preferably 300 or lower, more preferably 120 or lower, even more preferably 115 or lower, particularly preferably may be 110 or less. Kinematic viscosity and viscosity index in this specification mean values measured in accordance with JIS K2283:2000.

The base oil content is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, based on the total amount of refrigerating machine oil.

Refrigerating machine oil contains an amine antioxidant in addition to the base oil. Methods for incorporating the amine-based antioxidant into the refrigerating machine oil include, for example, adding the amine-based antioxidant directly to the refrigerating machine oil and dissolving or dispersing it, or adding the amine-based antioxidant to a solvent that can dissolve the amine-based antioxidant. Examples include a method in which a concentrated solution is prepared in advance by dissolving the agent, and the concentrated solution is added to refrigerating machine oil.

式中、Ｒ^１は、水素原子又はアルキル基を表す。 In one embodiment, the amine antioxidant may include a compound represented by the following formula (1) (phenyl-α-naphthylamine compound).

In the formula, R ¹ represents a hydrogen atom or an alkyl group.

The alkyl group represented by R ¹ may be linear or branched. The number of carbon atoms in the alkyl group may be 1 or more and 16 or less. The alkyl group may preferably be a branched alkyl group having 8 to 16 carbon atoms.

式中、Ｒ^２及びＲ^３は、それぞれ独立にアルキル基を表す。 In another embodiment, the amine antioxidant may include a compound represented by the following formula (2) (dialkylated diphenylamine compound).

In the formula, R ² and R ³ each independently represent an alkyl group.

The alkyl group represented by R ² and R ³ may be linear or branched. The number of carbon atoms in the alkyl group may be 1 or more and 16 or less. The alkyl group may preferably be a branched alkyl group having 3 to 16 carbon atoms. The compound represented by formula (2) (dialkylated diphenylamine compound) is a compound (p,p'-dialkylated diphenylamine) in which the alkyl groups represented by R ² and R ³ are both bonded to the para position. good.

The content (addition amount) of the amine antioxidant may be 0.1% by mass or more, 0.5% by mass or more, or 1% by mass or more, and 10% by mass or less, 7% by mass or more, based on the total amount of refrigerating machine oil. It may be less than 5% by mass, or less than 5% by mass. The content of this amine-based antioxidant can be determined at any point in time (for example, at the time of filling the refrigerator with refrigerating machine oil, at the time of pumping down the refrigerator, or with respect to the refrigerating machine oil filled in the refrigerator. It may be the content of the amine-based antioxidant at the time of replenishment, etc.).

The refrigeration oil may further contain additives other than the amine antioxidant. The additives include antioxidants other than amine antioxidants, acid scavengers, anti-wear agents, extreme pressure agents, oil agents, antifoaming agents, metal deactivators, viscosity index improvers, and pour point depressants. agent, detergent and dispersant, etc. These additives may be used alone or in combination of two or more.

The kinematic viscosity of the refrigerating machine oil at 40° C. is preferably 1 mm ² /s or more, more preferably 2 mm ² /s or more, 3 mm ² /s or more, or 4 mm ² /s or more, and preferably 500 mm ² /s or more. s or less, more preferably 400 mm ² /s or less. The kinematic viscosity of the refrigerating machine oil at 100° C. is preferably 1 mm ² /s or more, more preferably 2 mm ² /s or more, and preferably 50 mm ² /s or less, more preferably 30 mm ² /s or less. good. The viscosity index of the refrigerating machine oil is preferably -50 or more, more preferably -40 or more, even more preferably -30 or more, preferably 300 or less, more preferably 120 or less, still more preferably 115 or less, particularly preferably may be 110 or less.

The refrigerant may include a flammable refrigerant or a non-flammable refrigerant. According to this embodiment, even if the refrigerant contains a flammable refrigerant, the combustion resistance of the working fluid can be improved. The flammable refrigerant may be at least one type selected from the group consisting of a slightly flammable refrigerant, a weakly flammable refrigerant, and a highly flammable refrigerant. Nonflammable refrigerants, slightly flammable refrigerants, weakly flammable refrigerants, and highly flammable refrigerants are categorized as Class 1 (non-flammable refrigerants) and Class 2L (non-flammable refrigerants), respectively, in the refrigerant safety class standards of ISO 817:2014. It means a refrigerant included in Class 2 (slightly flammable refrigerant), Class 2 (slightly flammable refrigerant), and Class 3 (strongly flammable refrigerant).

Nonflammable refrigerants include trichlorofluoromethane (R11), dichlorodifluoromethane (R12), chlorodifluoromethane (R22), 2,2-dichloro-1,1,1-trifluoroethane (R123), 1,1, 1,2-tetrafluoroethane (R134a), azeotrope of difluoromethane and pentafluoroethane (R410a), 1,1,1,3,3-pentafluoropropane (R245fa), 1-chloro-3,3 , 3-trifluoropropene (R1233zd), a mixture of HFC and HFO (R513A), carbon dioxide (CO ₂ ), and the like.

Examples of slightly flammable refrigerants include difluoromethane (R32), 2,3,3,3-tetrafluoropropene (R1234yf), 1,3,3,3-tetrafluoropropene (R1234ze), and ammonia (R717). be done.

Examples of the weakly flammable refrigerant include 1-chloro-1,1-difluoroethane (R142b) and 1,1-difluoroethane (R152a).

Examples of highly flammable refrigerants include propane (R290) and isobutane (R600a).

In the embodiment described above, in the above-described refrigerator 10, when pumping down the compressor 1 to collect refrigerant gas for the purpose of recovering refrigerant, the combustion resistance of the working fluid is improved. be able to. The fact that the combustion resistance of the working fluid can be improved is shown in the combustion tests in the examples described later, as shown in Figure 3 in a mixed atmosphere of refrigerating machine oil, refrigerant, and air. This can be confirmed by the fact that the combustion range of the working fluid is narrow (the probability of combustion occurring is low).

According to this embodiment, by including an amine antioxidant in the refrigerating machine oil, the combustion resistance of the working fluid can be improved, and furthermore, the pump down can be prevented due to incorrect operation such as air being mixed in. Even if this occurs, the risk of explosion of the working fluid (diesel explosion) can be significantly reduced.

In one embodiment, the refrigerating machine oil is added to the refrigerating machine so that 0.1% by mass or more (preferably 0.5% by mass or more or 1% by mass or more) of the amine antioxidant remains in the refrigerating machine oil at the time of pump down. It is possible to set the content of amine antioxidant when filling. For example, if the lifespan of a refrigerator is assumed to be 10 years, an accelerated test assuming 10 years of operation is performed in advance, and the period until the amine antioxidant is consumed and disappears to 0.1% by mass or less is 10 years. One example is to determine the content of the amine antioxidant so that the content is as above, and to mix it in advance with the refrigerating machine oil before use. More specifically, if the amount of amine antioxidant that disappears during the recommended replacement period (10 to 20 years) of refrigeration oil is X% by mass (0.1 to 10% by mass), then The initial blending amount of the amine antioxidant may be set to 1.1X mass % or more.

In one embodiment, the refrigerating machine is filled with the amine antioxidant so that 0.1% by mass or more (preferably 0.5% by mass or more or 1% by mass or more) of the amine antioxidant remains in the refrigerating machine oil at the time of pump down. An amine antioxidant may be added to the refrigerating machine oil. In addition, in order to prevent the amine-based antioxidant in the refrigerating machine oil or working fluid from disappearing, we also add additives that can suppress the generation of acids due to deterioration of the refrigerating machine oil or working fluid (others such as acid scavengers and anti-wear agents). (formulation of additives) may be adjusted.

Hereinafter, the present invention will be explained in more detail based on Examples, but the present invention is not limited to the Examples.

The base oil was a polyol ester of pentaerythritol and 2-ethylhexanoic acid/3,5,5-trimethylhexanoic acid (molar ratio: 50/50) (kinematic viscosity at 40°C: 68 mm ² /s, at 100°C). Kinematic viscosity: 8.3 mm ² /s, viscosity index: 88) was prepared.

[Example 1]
In Example 1, a refrigerating machine oil was prepared by containing, in addition to the above base oil, 1% by mass of an amine antioxidant (phenyl-α-naphthylamine) based on the total amount of the refrigerating machine oil.

[Comparative example 1]
In Comparative Example 1, a refrigerating machine oil (refrigerating machine oil not containing an amine antioxidant) consisting only of the above base oil was prepared.

[Comparative Examples 2 and 3]
In Comparative Examples 2 and 3, in addition to the above base oil, the refrigerating machine oil contained 1% by mass and 5% by mass of a phenolic antioxidant (di-tert.-butyl-p-cresol), respectively, based on the total amount of the refrigerating machine oil. Refrigerating machine oil was prepared.

<Combustion test>
FIG. 2 is a schematic diagram of the combustion test apparatus used in the combustion test. As shown in FIG. 2, the combustion test device 21 reproduces the mixing of air into the refrigerant piping and the compressor during pump down, and the adiabatic compression of the refrigerant, air, and refrigerating machine oil mixture. The combustion test device 21 mainly includes a refrigerant supply section 22, an air supply section 23, an oil supply section 24, a temperature control section 25, and a compressor (model engine) 26.

After the refrigerant is supplied from the refrigerant supply section 22, the flow rate is controlled by a mass flow controller 27 (manufactured by Fujikin; FCST1050LC-4F2-F50L-N2, accuracy ±2% F.S.), and the refrigerant is supplied to the temperature control section 25. Ru. After the air is supplied from the air supply section 23, it is dehumidified by a dehumidifier 28, and the flow rate is controlled by a mass flow controller 29 (manufactured by COFLOC; MODEL 8550MC-0-1-1), and then supplied to the temperature control section 25. The refrigerant and air mixed in the temperature control unit 25 are heated to a predetermined temperature (260° C.) and then supplied to the compressor 26 .

Refrigerating machine oil is supplied from the oil supply section 24, then pressurized to 150 MPa by the compressor 30, and then the above-mentioned refrigerant and Atomized into a mixture of air.

The mixture of refrigerant, air, and refrigeration oil obtained above is supplied to the compressor 36 (manufactured by ENYA; R155-4C, 4-stroke engine, stroke volume 25.42 cc, compression ratio 16.0). It is compressed by driving with a motor 32 connected to. The pressure inside the compressor is measured using a pressure gauge (manufactured by Kistler; 6045A, linearity ±0.4% F.S.O.). Further, the rotation speed and crank angle of the motor 32 can be controlled by an encoder 33.

Using each refrigerating machine oil and each refrigerant of Examples and Comparative Examples shown in Table 1, and using the above-mentioned combustion test apparatus, the refrigerant concentration (volume %) and the refrigerating machine oil equivalent ratio (equivalent ratio: complete The pressure inside the compressor was measured when the ratio of the oil flow rate actually supplied to the oil flow rate required for combustion was varied. Propane (R290), difluoromethane (R32), and 2,3,3,3-tetrafluoropropene (R1234yf) were used as refrigerants. Based on the measurement results, the horizontal axis shows the refrigerant concentration (volume %), and the vertical axis shows the maximum pressure inside the compressor (pressure made dimensionless by dividing by the maximum pressure inside the compressor in a blank test without using refrigerant). Plotted on a graph. As an example, FIG. 3 shows plots of Example 1, Comparative Example 1, and Comparative Example 2 when R32 was used. Then, from the plots, the combustion range (maximum concentration of refrigerant at which an increase in compressor internal pressure was observed: volume %) and maximum pressure (maximum pressure value in each plot: dimensionless) were read. The results are shown in Table 1.

As shown in Table 1 and Figure 3, the refrigerating machine oil containing an amine-based antioxidant is compared to the refrigerating machine oil not containing an amine-based antioxidant and the refrigerating machine oil containing an antioxidant. , it was possible to significantly reduce the combustion range (probability of combustion occurrence) and the maximum pressure inside the compressor (generated pressure (hazard level)). The magnitude of this effect can be clearly understood from the fact that the area surrounded by the plot in FIG. 3 is significantly narrower. In particular, it can be seen that the flammability range almost disappears when R290 or R1234yf is used compared to when R32 is used. Therefore, refrigeration oil containing an amine-based antioxidant can improve the combustion resistance of the working fluid even if air is accidentally mixed in during pump-down of the refrigeration machine. The risk of combustion and explosion (diesel explosion) can be significantly reduced.

DESCRIPTION OF SYMBOLS 1... Compressor, 2... Condenser, 3... Expansion mechanism, 4... Evaporator, 5... Channel, 6... Refrigerant circulation system, 7... Accumulator, 10... Refrigerator, 21... Combustion test device, 22... Refrigerant supply Part, 23... Air supply section, 24... Oil supply section, 25... Temperature control section, 26... Compressor (model engine), 27, 29... Mass flow controller, 28... Dehumidifier, 30... Compressor, 31... Oil spray System, 32...Motor, 33...Encoder.

Claims (15)

A method for improving the combustion resistance of a working fluid in a refrigerator filled with a working fluid containing refrigerating machine oil and a refrigerant, the method comprising:
A method of incorporating an amine antioxidant into the refrigerating machine oil. The method according to claim 1, wherein the amine antioxidant contains a compound represented by the following formula (1).

[In the formula, R ¹ represents a hydrogen atom or an alkyl group. ] 3. A method according to claim 1 or 2, wherein the refrigerant comprises a flammable refrigerant. 3. A method according to claim 1 or 2, wherein the refrigerant comprises a flammable refrigerant. 3. A method according to claim 1 or 2, wherein the refrigerant comprises a slightly flammable refrigerant. Use of an amine antioxidant as a flame resistance improver,
Use of improving the combustion resistance of a working fluid in a refrigerator filled with a working fluid containing the refrigerating machine oil and a refrigerant by incorporating the amine-based antioxidant into the refrigerating machine oil. The use according to claim 6, wherein the amine antioxidant contains a compound represented by the following formula (1).

[In the formula, R ¹ represents a hydrogen atom or an alkyl group. ] 8. Use according to claim 6 or 7, wherein the refrigerant comprises a flammable refrigerant. 8. Use according to claim 6 or 7, wherein the refrigerant comprises a flammable refrigerant. 8. Use according to claim 6 or 7, wherein the refrigerant comprises a slightly flammable refrigerant. A combustion resistance improver that improves the combustion resistance of a working fluid in a refrigerator filled with a working fluid containing refrigeration oil and a refrigerant,
A flame resistance improver containing an amine antioxidant. The flame resistance improver according to claim 11, wherein the amine antioxidant contains a compound represented by the following formula (1).

[In the formula, R ¹ represents a hydrogen atom or an alkyl group. ] The flame resistance improver according to claim 11 or 12, wherein the refrigerant includes a flammable refrigerant. The flame resistance improver according to claim 11 or 12, wherein the refrigerant contains a highly flammable refrigerant. The flame resistance improver according to claim 11 or 12, wherein the refrigerant contains a slightly flammable refrigerant.

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