JP5265069B2 - Refrigerating machine oil for carbon dioxide refrigerant and fluid composition for refrigerating machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain both a refrigerating machine oil for a carbon dioxide refrigerant which has a sufficiently wide composition range exhibiting compatibility in mixing with a carbon dioxide refrigerant under a low-temperature condition and excellent lubricating properties and stability and sufficiently prevents a bad lubrication in use in a refrigerating machine for a carbon dioxide refrigerant, with which a sufficiently high heat exchange ratio can be obtained and a fluid composition for a refrigerating machine using the same. SOLUTION: This refrigerating machine oil for carbon dioxide refrigerant is characterized by comprising a polyalkylene glycol represented by general formula (1): R1-(OR3)n-OR2 [R1 and R2 are each a 1-5C alkyl group or a 2-5C acyl group; R3 is a 2-4C alkylene group; n is an integer of making a number- average molecular weight 500-3,000] and having 5-20 mm2/s kinematic viscosity.

Description

  The present invention relates to a refrigerating machine oil and a refrigerating machine fluid composition, and more particularly to a refrigerating machine oil useful when used together with a carbon dioxide refrigerant, and a refrigerating machine fluid composition using the same.

  Due to the problem of ozone depletion in recent years, CFC (chlorofluorocarbon) and HCFC (hydrochlorofluorocarbon), which have been used as refrigerants for refrigeration equipment, are subject to regulation, and HFC (hydrofluorocarbon) as a refrigerant instead. It is being used. However, such HFC refrigerants also have problems such as high global warming ability. Therefore, the use of natural refrigerants such as carbon dioxide, ammonia and hydrocarbons as alternative refrigerants to replace these fluorocarbon refrigerants has been studied.

Among them, carbon dioxide (CO ₂ ) is harmless to the environment and is excellent in terms of safety, and since it has been used as a refrigerant for refrigerators, etc., which has not been mainstream until now, Its application is being studied as a refrigerant for car air conditioners, room air conditioners, or hot water supply heat pumps using open compressors or hermetic electric compressors.

  Moreover, as a base material of the refrigerating machine oil for carbon dioxide refrigerant, use of polyalkylene glycol (PAG) as disclosed in, for example, Japanese Patent Application Laid-Open No. 10-46169 has been studied.

Problems to be solved by the invention

  By the way, as refrigeration equipment, what is generally provided with a refrigerant circulation system composed of a refrigerant compressor, a gas cooler, an expansion mechanism, an evaporator, etc., and the refrigeration oil used in such refrigeration equipment includes: In addition to lubricity for lubricating the refrigerant compressor, when discharged together with the refrigerant from the refrigerant compressor, the characteristic of returning to the refrigerant compressor again through the flow path (circulation path) (hereinafter referred to as “oil returnability”) ) To ensure refrigerant compatibility and low-temperature fluidity, as well as a wide range of temperature changes and stability to various substances such as refrigerant. In particular, due to the mechanism of the refrigerant compressor, the phenomenon that the refrigeration oil is discharged from the refrigerant compressor into the flow path is unavoidable, and the composition of the mixture of the refrigerant and the refrigeration oil at a predetermined position of the refrigerant circulation system is controlled. Since it is very difficult, it is desirable to use a refrigerating machine oil that exhibits refrigerant compatibility in a wide range of temperatures and composition ranges.

  However, although the conventional refrigeration oil for carbon dioxide refrigerant exhibits a certain degree of compatibility under relatively high temperature conditions, the compatibility is not necessarily sufficient, such as a narrow composition range showing compatibility under low temperature conditions. And when such refrigerating machine oil is used for the above-mentioned refrigerating equipment, the refrigerating machine oil is in a part where the ratio of one of carbon dioxide refrigerant or refrigerating machine oil is high and low, such as an expansion mechanism or an evaporator in the refrigerant circulation system. As a result, the amount of refrigerating machine oil in the refrigerant compressor is reduced and lubrication is likely to occur, or heat exchange in the evaporator is liable to be hindered by refrigerating machine oil. In such a refrigerating machine oil, it is possible to reduce the viscosity of the PAG and improve the oil return, but in that case, the refrigerating machine oil inherently has insufficient lubricity, which is a fundamental problem. It will not be a solution.

  The present invention has been made in view of the above-mentioned problems of the prior art, and has a sufficiently wide composition range showing compatibility when mixed with a carbon dioxide refrigerant under low temperature conditions, and is excellent in lubricity and stability. And, when used in a carbon dioxide refrigerant refrigerator, sufficiently prevent lubrication failure of the refrigerant compressor and obtain a sufficiently high heat exchange rate, as well as using the same It aims at providing the fluid composition for refrigerators.

Means for solving the problem

  As a result of intensive studies to achieve the above object, the present inventors have included a polyalkylene glycol having a specific structure and a kinematic viscosity at 100 ° C. satisfying a specific condition in the refrigerator. The present inventors have found that the above problems can be solved and have completed the present invention.

That is, the refrigerating machine oil for carbon dioxide refrigerant of the present invention has the following general formula (1):
R ^1- (OR ³ ) n-OR ² (1)
[Wherein R ¹ and R ² may be the same or different and each represents an alkyl group having 1 to 5 carbon atoms or an acyl group having 2 to 5 carbon atoms, and R ³ represents an alkylene group having 2 to 4 carbon atoms. N represents an integer such that the number average molecular weight of the polyalkylene glycol represented by the general formula (1) is 600 to 2000 ]
And a polyalkylene glycol having a kinematic viscosity at 100 ° C. of 5 to 20 mm ² / s and a ratio Mw / Mn of the weight average molecular weight Mw to the number average molecular weight Mn of 1.00 to 1.20. It is characterized by this.

  Moreover, the fluid composition for refrigerators of this invention contains the refrigerating machine oil for carbon dioxide refrigerants of the said invention, and a carbon dioxide refrigerant.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

The refrigerating machine oil of the present invention has the following general formula (1):
R ^1- (OR ³ ) _n -OR ² (1)
[Wherein, R ¹ and R ² may be the same or different and each represents an alkyl group having 1 to 5 carbon atoms or an acyl group having 2 to 5 carbon atoms, and R ³ represents an alkylene group having 2 to 4 carbon atoms. N represents an integer such that the number average molecular weight of the polyalkylene glycol represented by the general formula (1) is 500 to 3000]
And is characterized by containing a polyalkylene glycol having a kinematic viscosity of 5 to 20 mm ² / s at 100 ° C., and exhibits compatibility when mixed with a carbon dioxide refrigerant under low temperature conditions. The composition range is sufficiently wide and the lubricity and stability are excellent. Then, by using the carbon dioxide refrigerant refrigerator oil of the present invention for the carbon dioxide refrigerant refrigerator, it is possible to sufficiently prevent poor lubrication of the refrigerant compressor and obtain a sufficiently high heat exchange rate.

  As shown in FIG. 1, the refrigeration and air-conditioning apparatus includes a refrigerant circulation system in which a refrigerant compressor 1, a gas cooler 2, an expansion mechanism 3 (capillary, expansion valve, etc.), and an evaporator 4 are sequentially connected through a flow path 5. Generally, in such a refrigerant circulation system, first, a high-temperature (usually 70 to 120 ° C.) refrigerant discharged from the refrigerant compressor 1 into the flow path 5 is mixed with a high-density fluid (super Critical fluid). Subsequently, the refrigerant is liquefied by passing through a narrow flow path of the expansion mechanism 3 and further vaporized by the evaporator 4 to become a low temperature (usually −40 to 0 ° C.).

  Here, a mixed state of a mixture of carbon dioxide refrigerant and refrigerating machine oil (hereinafter simply referred to as “mixture”) circulating in the refrigerant circulation system will be described with reference to FIG. FIG. 2 is a graph showing an example of the correlation between the concentration of refrigerating machine oil in the mixture and the separation temperature. The two curves in FIG. 2 indicate the lower limit values of the temperatures at which the refrigerant and the refrigerating machine oil are compatible with each other in a predetermined composition, the solid line is the refrigerating machine oil for carbon dioxide refrigerant of the present invention, and the broken line is the conventional one. It is about refrigeration oil for carbon dioxide refrigerant. The upper side of the curve is a compatible region, and the lower side is an incompatible region. Further, points a to d in FIG. 2 indicate the relationship between the concentration of the refrigerating machine oil and the temperature in the mixture at a to d in the flow path in FIG. 1, respectively.

  In the refrigerant compressor 1 in FIG. 1, a small amount of carbon dioxide refrigerant and a large amount of refrigerating machine oil coexist under high temperature (usually 70 to 120 ° C.) conditions. The refrigerant discharged from the refrigerant compressor 1 into the flow path 5 is gaseous and contains a small amount (usually 1 to 10%) of refrigerating machine oil as mist. The mist refrigerating machine oil contains a small amount of refrigerant. Is dissolved (point a in FIG. 2). Next, in the gas cooler 2, the gaseous refrigerant is compressed to become a high-density fluid, and a large amount of refrigerant and a small amount of refrigerating machine oil coexist at a relatively high temperature (usually around 50 to 70 ° C.). (Point b in FIG. 2). Furthermore, the mixture of a large amount of refrigerant and a small amount of refrigerating machine oil is 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. 2). It is returned to the refrigerant compressor 1 again.

  In such a refrigeration cycle, it is desirable that a large amount of refrigerant and a small amount of refrigerating machine oil are in a compatible state in the entire temperature range (for example, −40 to 70 ° C.) in the system. Accordingly, for example, under a high temperature condition between points a and b in FIG. 2, even if the refrigerant and the refrigerating machine oil are not in a compatible state, the viscosity of the refrigerating machine oil is reduced and the fluidity is improved. Since the refrigerating machine oil separated by the flow is easily flowed together, there are many cases where the oil return property does not become a problem even with the conventional refrigerating machine oil for carbon dioxide refrigerant. However, as shown in FIG. 2, most or all of the process under low temperature conditions (between points cd in FIG. 2) in which the mixture of refrigerant and refrigerating machine oil is sent to the evaporator 4 through the expansion mechanism 3. Is performed in the incompatible region (the region below the broken line), refrigeration oil that cannot be flowed by the flow of refrigerant due to the increase in viscosity under low-temperature conditions is retained. Insufficient lubrication and heat exchange in the evaporator are likely to occur.

  On the other hand, since the refrigerating machine oil for carbon dioxide refrigerant of the present invention has a sufficiently wide composition range showing compatibility when mixed with carbon dioxide refrigerant under low temperature conditions, it is between points cd in FIG. The ratio of the part performed in the compatible area | region (area | region above a continuous line) of a process can fully be raised. Further, normally, even if the refrigerant and the refrigerating machine oil are in a phase-separated state, a predetermined amount of the refrigerant dissolves in the refrigerating machine oil and the viscosity of the refrigerating machine oil decreases. The saturation solubility of carbon dioxide at the bottom is sufficiently high, and the viscosity of the refrigerating machine oil is sufficiently lowered by the dissolution of the refrigerant, so that part of the process between points cd in FIG. 2 is in the incompatible region. Even if it is carried out, it is possible to obtain a sufficiently high oil return property. Therefore, it is possible to sufficiently prevent stagnation of refrigeration oil in the expansion mechanism and the evaporator, as well as the resulting poor lubrication of the refrigerant compressor and inhibition of heat exchange in the evaporator.

  Incidentally, Japanese Patent Laid-Open No. 10-46169 discloses a refrigerating machine oil for carbon dioxide refrigerant containing polyalkylene glycol, and it is described that such a refrigerating machine oil dissolves a predetermined amount of carbon dioxide refrigerant. This publication does not describe the temperature conditions for dissolving the carbon dioxide refrigerant in the refrigerating machine oil. According to the study by the present inventors based on the correlation between the saturated vapor pressure of carbon dioxide refrigerant and the dissolved amount, the measurement result of the dissolved amount of carbon dioxide refrigerant described in the publication is obtained under a temperature condition of 15 ° C. or higher. Is. As will be described later, the conventional refrigerating machine oil has a narrow composition range showing compatibility under low temperature conditions, and also has a small effect of reducing the viscosity due to the dissolution of the refrigerant in the incompatible region. It is very difficult to prevent poor lubrication of the refrigerant compressor and hindering heat exchange in the evaporator.

As described above, the polyalkylene glycol used in the present invention has a structure represented by the general formula (1). In the above formula (1), R ¹ and R ² may be the same or different and each represents an alkyl group having 1 to 5 carbon atoms or an acyl group having 2 to 5 carbon atoms. When R ¹ and R ² are each an alkyl group or an acyl group, they may be linear or branched. Specific examples of such an alkyl group include a methyl group, an ethyl group, a linear or branched propyl group, a linear or branched butyl group, and a linear or branched pentyl. Specific examples of the acyl group include an acetyl group, a linear or branched propanoyl group, a linear or branched butanoyl group, a linear or branched pentanoyl group, and the like. Is mentioned. Among these alkyl groups and acyl groups, methyl group, ethyl group, linear or branched propyl group, linear or branched butyl group, acetyl group from the viewpoint of compatibility with carbon dioxide refrigerant A linear or branched propanoyl group, a linear or branched butanoyl group is more preferable, a methyl group, a nithyl group, or an acetyl group is more preferable, and a methyl group or an acetyl group is most preferable. In addition, when the carbon number of the alkyl group and acyl group exceeds 5, the composition range showing compatibility with the carbon dioxide refrigerant under a low temperature condition is narrowed, resulting in poor lubrication of the refrigerant compressor and inhibition of heat exchange in the evaporator. Is likely to occur.

Further, in the above general formula (1), R ³ represents an alkylene group having 2 to 4 carbon atoms. Specific examples of such an alkylene group include an ethylene group (—CH ₂ CH ₂ —), a propylene group (—CH (CH ₃ ) CH ₂ —), and a trimethylene group (—CH ₂ CH ₂ CH ₂ —). , Butylene group (—CH (CH ₂ CH ₃ ) CH ₂ —), tetramethylene group (—CH ₂ CH ₂ CH ₂ CH ₂ —) and the like. Among these alkylene groups, an ethylene group, a propylene group, a butylene group, and a tetramethylene group are more preferable.

Further, in the above general formula (1), n represents the number of repetitions (polymerization degree) of the oxyalkylene group represented by OR ³ , but the number average molecular weight of the polyalkylene glycol represented by the formula (1) Is 500 to 3000, preferably 600 to 2000, more preferably 600 to 1500, and n is an integer such that the number average molecular weight of the polyalkylene glycol satisfies the above-mentioned conditions. When the number average molecular weight of the polyalkylene glycol is less than the lower limit, the lubricity in the presence of a carbon dioxide refrigerant becomes insufficient. On the other hand, when the upper limit is exceeded, the composition range that is compatible with the carbon dioxide refrigerant under low temperature conditions is narrowed, and poor lubrication of the refrigerant compressor and inhibition of heat exchange in the evaporator are likely to occur. In the polyalkylene glycol represented by the above general formula (1), weight average molecular weight (M _w) and number average molecular weight ratio _{(M n) (M w /} M n) is 1.00 to 1.20 The following is preferable. When Mw / Mn exceeds 120, the compatibility between the carbon dioxide refrigerant and the refrigerating machine oil tends to be insufficient.

Furthermore, in the polyalkylene glycol represented by the general formula (1), the proportion of the ethylene group in the alkylene group represented by R ³ is preferably 80 mol% or less, and 60 mol% or less. More preferably, it is more preferably 50 mol% or less, and particularly preferably 40 mol% or less. When the proportion of ethylene groups in the alkylene group represented by R ³ exceeds 80 mol%, the refrigerating machine oil tends to be solid at room temperature or its pour point tends to be high.

The polyalkylene glycol according to the present invention can be synthesized by a conventionally known method ("alkylene oxide polymer", Mitsuta Shibata et al., Kaibundo, issued on November 20, 1990). For example, an alcohol (R ¹ OH; R ¹ represents the same definition as R ¹ in the general formula (1)) by addition polymerization of one or more predetermined alkylene oxide to, etherified or further terminal hydroxyl group By esterification, the polyalkylene glycol represented by the general formula (1) is obtained. When two or more different alkylene oxides are used in the above production process, the resulting polyalkylene glycol may be either a random copolymer or a block copolymer, but tends to be more excellent in oxidative stability. Therefore, a block copolymer is preferable, and a random copolymer is preferable because it tends to be more excellent in low-temperature fluidity.

In the present invention, the kinematic viscosity at 100 ° C. of the polyalkylene glycol represented by the general formula (1) needs to be 5 to 20 mm ² / s, preferably 6 to 18 mm ² / s, more preferably 7~16mm ² / s, more preferably from 8 to 15 mm ² / s, and most preferably 10-15 mm ² / s. If the kinematic viscosity at 100 ° C. is less than 5 mm ² / s, the lubricity in the presence of carbon dioxide will be insufficient, and if it exceeds 20 mm ² / s, it will be compatible with the carbon dioxide refrigerant under low temperature conditions. The composition range to be shown is narrowed, and poor lubrication of the refrigerant compressor and hindrance to heat exchange in the evaporator are likely to occur. Further, the kinematic viscosity at 40 ° C. of the polyalkylene glycol is not particularly limited as long as the kinematic viscosity at 100 ° C. satisfies the above conditions, but the kinematic viscosity at 40 ° C. is 10 to 200 mm ² / s. It is preferably 20 to 150 mm ² / s. Tend kinematic viscosity 10mm sealability is less than ² / s lubricity and compressor is reduced at 40 ° C., also if it exceeds 200 mm ² / s, with respect to carbon dioxide refrigerant under low temperature conditions The composition range showing the compatibility is narrowed, and the refrigerant compressor tends to be poorly lubricated and the heat exchange in the evaporator tends to be hindered.

  Moreover, the pour point of the polyalkylene glycol represented by the general formula (1) is preferably −10 ° C. or less, and more preferably −20 to −50 ° C. When a polyalkylene glycol having a pour point of −10 ° C. or higher is used, the refrigerating machine oil tends to solidify in the refrigerant circulation system at low temperatures.

  Further, in the production process of the polyalkylene glycol represented by the general formula (1), an alkylene oxide such as propylene oxide may cause a side reaction to form an unsaturated group such as an allyl group in the molecule. When an unsaturated group is formed in the polyalkylene glycol molecule, the thermal stability of the polyalkylene glycol itself is reduced, a polymer is produced and sludge is produced, or the antioxidant property (antioxidant property) is lowered. Therefore, a phenomenon such as generation of peroxide is likely to occur. In particular, when a peroxide is produced, it decomposes to produce a compound having a carbonyl group, and the compound having a carbonyl group reacts with a carbon dioxide refrigerant to produce an acid amide, which easily causes capillary clogging.

  Accordingly, the polyalkylene glycol according to the present invention preferably has a low degree of unsaturation derived from an unsaturated group or the like, specifically preferably 0.04 meq / g or less, and 0.03 meq / g or less. It is more preferable that it is 0.02 meq / g or less. The peroxide value is preferably 10.0 meq / kg or less, more preferably 5.0 meq / kg or less, and most preferably 1.0 meq / kg. Furthermore, the carbonyl value is preferably 100 ppm by weight or less, more preferably 50 ppm by weight or less, and most preferably 20 ppm by weight or less.

In addition, the degree of unsaturation, the peroxide value, and the carbonyl value according to the present invention are values measured by a standard oil analysis test method established by the Japan Oil Chemists' Society. That is, the degree of unsaturation according to the present invention refers to reacting a sample with a Wis solution (ICl-acetic acid solution), leaving it in the dark, and then reducing excess ICl to iodine, and converting the iodine content with sodium thiosulfate. Titration is performed to calculate the iodine value, and the iodine value is converted to a vinyl equivalent (meq / g);
The peroxide value according to the present invention is a value obtained by adding potassium iodide to a sample, titrating the resulting free iodine with sodium thiosulfate, and converting this free iodine into the number of milliequivalents per 1 kg of the sample (meq / kg )
The carbonyl value according to the present invention is determined by reacting 2,4-dinitrophenylhydrazine on a sample to produce a chromoid quinoid ion, measuring the absorbance at 480 nm of this sample, and obtaining cinnamaldehyde in advance as a standard substance. The value (weight ppm) converted into the amount of carbonyl based on the calibration curve.

  In the present invention, in order to obtain a polyalkylene glycol having a low degree of unsaturation, peroxide value, and carbonyl value, the reaction temperature when reacting propylene oxide is 120 ° C. or lower (more preferably 110 ° C. or lower). preferable. In addition, if an alkali catalyst is used in the production, the use of an inorganic adsorbent, such as activated carbon, activated clay, bentonite, dolomite, aluminosilicate, etc., to remove it may reduce the degree of unsaturation. Can do. Further, when the polyalkylene glycol is produced or used, contact with oxygen is avoided as much as possible, and an increase in the peroxide value or carbonyl value can also be prevented by adding an antioxidant.

  The refrigerating machine oil for carbon dioxide refrigerant of the present invention contains a polyalkylene glycol having the above-described configuration, and even when only the polyalkylene glycol is used alone, low-temperature fluidity, lubricity and stability. Is sufficiently high and has an excellent characteristic such that it has a sufficiently wide compatible region with a carbon dioxide refrigerant, but other base oils and additives described later may be added as necessary. In addition, the content of the polyalkylene glycol in the refrigerating machine oil for carbon dioxide refrigerant of the present invention is not particularly limited as long as the above excellent characteristics are not impaired, but is 50% by mass or more based on the total amount of refrigerating machine oil. Is more preferable, 70% by mass or more is more preferable, 80% by mass or more is further preferable, and 90% by mass or more is particularly preferable. If the content of the polyalkylene glycol represented by the general formula (1) is less than 50% by mass, any one of various performances such as refrigerating machine oil lubricity, refrigerant compatibility, thermal / chemical stability, etc. It tends to be insufficient.

  In the refrigerating machine oil for carbon dioxide refrigerant of the present invention, as the base oil that can be used together with the above polyalkylene glycol, specifically, a hydrocarbon base oil such as mineral oil, olefin polymer, naphthalene compound, alkylbenzene; ester, Examples include ketones, polyphenyl ethers, silicones, polysiloxanes, perfluoroethers, polyvinyl ethers, and synthetic oils containing oxygen such as polyglycols other than polyalkylene glycols according to the present invention. As the synthetic oil containing oxygen, among the above, polyvinyl ether and / or polyglycols other than the polyalkylene glycol according to the present invention are preferably used.

  Thus, the refrigerating machine oil for carbon dioxide refrigerant of the present invention contains the above polyalkylene glycol and, if necessary, a hydrocarbon-based oil and / or a synthetic oil containing oxygen. Used as oil. The refrigerating machine oil for carbon dioxide refrigerant of the present invention can be suitably used even if the additive is not added, but it can also be used by blending various additives described later as required.

  In order to further improve the wear resistance and load resistance of the refrigerating machine oil of the present invention, phosphoric acid ester, acidic phosphoric acid ester, amine salt of acidic phosphoric acid ester, chlorinated phosphoric acid ester, phosphorous acid ester and phosphor At least one phosphorus compound selected from the group consisting of thionates can be blended. These phosphorus compounds are esters or derivatives of phosphoric acid, phosphorous acid or thiophosphoric acid and alkanol or polyether type alcohol.

Specifically, for example, as phosphate ester, tributyl phosphate, tripentyl phosphate, trihexyl phosphate, triheptyl phosphate, trioctyl phosphate, trinonyl phosphate, tridecyl phosphate, triundecyl phosphate, tridodecyl phosphate, tritridecyl Phosphate, tritetradecyl phosphate, tripentadecyl phosphate, trihexadecyl phosphate, triheptadecyl phosphate, trioctadecyl phosphate, trioleyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, xyl Renyl diphenyl phosphate and the like;
Examples of acidic phosphate esters include monobutyl acid phosphate, monopentyl acid phosphate, monohexyl acid phosphate, monoheptyl acid phosphate, monooctyl acid phosphate, monononyl acid phosphate, monodecyl acid phosphate, monoundecyl acid phosphate, monododecyl Acid phosphate, monotridecyl acid phosphate, monotetradecyl acid phosphate, monopentadecyl acid phosphate, monohexadecyl acid phosphate, monoheptadecyl acid phosphate, monooctadecyl acid phosphate, monooleyl acid phosphate, dibutyl acid phosphate, dipentyl acid , Dihexyl reed Dophosphate, diheptyl acid phosphate, dioctyl acid phosphate, dinonyl acid phosphate, didecyl acid phosphate, diundecyl acid phosphate, didodecyl acid phosphate, ditridecyl acid phosphate, ditetradecyl acid phosphate, dipentadecyl acid, dipentadecyl acid Hexadecyl acid phosphate, diheptadecyl acid phosphate, dioctadecyl acid phosphate, dioleyl acid phosphate, etc .;
Examples of the amine salt of acidic phosphate ester include methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, dimethylamine, diethylamine, dipropylamine, and dibutylamine. , Salts with amines such as dipentylamine, dihexylamine, diheptylamine, dioctylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, tripentylamine, trihexylamine, triheptylamine, trioctylamine;
Examples of the chlorinated phosphate ester include tris-dichloropropyl phosphate, tris-chloroethyl phosphate, tris-chlorophenyl phosphate, polyoxyalkylene bis [di (chloroalkyl)] phosphate;
As phosphites, dibutyl phosphite, dipentyl phosphite, dihexyl phosphite, diheptyl phosphite, dioctyl phosphite, dinonyl phosphite, didecyl phosphite, diundecyl phosphite, didodecyl phosphite, dioleyl Phosphite, diphenyl phosphite, dicresyl phosphite, tributyl phosphite, tripentyl phosphite, trihexyl phosphite, triheptyl phosphite, trioctyl phosphite, trinonyl phosphite, tridecyl phosphite, triundecyl phosphite Phyto, tridodecyl phosphite, trioleyl phosphite, triphenyl phosphite, tricresyl phosphite, etc .;
The phosphorothioates include tributyl phosphorothioate, tripentyl phosphorothioate, trihexyl phosphorothionate, triheptyl phosphorothionate, trioctyl phosphorothionate, trinonyl phosphorothionate, tridecyl Phosphorothioate, triundecyl phosphorothionate, tridodecyl phosphorothioate, tritridecyl phosphorothioate, tritetradecyl phosphorothioate, tripentadecyl phosphorothionate, trihexadecyl phosphorothionate , Triheptadecyl phosphorothioate, trioctadecyl phosphorothioate, trioleyl phosphorothioate, triphenyl phosphorothioate, tri Resyl phosphorothioate, trixylenyl phosphorothioate, cresyl diphenyl phosphorothioate, xylenyl diphenyl phosphorothioate, tris (n-propylphenyl) phosphorothionate, tris (isopropylphenyl) phos Phosphorthionate, tris (n-butylphenyl) phosphothionate, tris (isobutylphenyl) phosphothionate, tris (s-butylphenyl) phosphothionate, tris (t-butylphenyl) phosphothionate, etc. ,
Is mentioned.

  When these phosphorus compounds are blended in the refrigerating machine oil for carbon dioxide refrigerant of the present invention, the blending amount is not particularly limited, but is usually contained based on the total amount of refrigerating machine oil (based on the total amount of base oil and all blended additives). It is desirable to mix the phosphorus compound in such an amount that the amount is 0.01 to 10.0% by mass, more preferably 0.02 to 5.0% by mass.

Further, in the refrigeration oil for carbon dioxide refrigerant of the present invention, in order to further improve its thermal and hydrolysis stability,
(1) Phenyl glycidyl ether type epoxy compound (2) Alkyl glycidyl ether type epoxy compound (3) Glycidyl ester type epoxy compound (4) Allyl oxirane compound (5) Alkyl oxirane compound (6) Alicyclic epoxy compound (7) Epoxy It is preferable to blend at least one epoxy compound selected from the group consisting of epoxidized fatty acid monoester (8) epoxidized vegetable oil.

  (1) Specific examples of the phenyl glycidyl ether type epoxy compound include phenyl glycidyl ether and alkylphenyl glycidyl ether. As used herein, the alkylphenyl glycidyl ether includes those having 1 to 3 alkyl groups having 1 to 13 carbon atoms, and those having one alkyl group having 4 to 10 carbon atoms, such as n-butylphenyl glycidyl. Ether, i-butylphenyl glycidyl ether, sec-butylphenyl glycidyl ether, tert-butylphenyl glycidyl ether, pentylphenyl glycidyl ether, hexylphenyl glycidyl ether, heptylphenyl glycidyl ether, octylphenyl glycidyl ether, nonylphenyl glycidyl ether, decylphenyl A glycidyl ether etc. can be illustrated as a preferable thing.

  (2) As the alkyl glycidyl ether type epoxy compound, specifically, decyl glycidyl ether, undecyl glycidyl ether, dodecyl glycidyl ether, tridecyl glycidyl ether, tetradecyl glycidyl ether, 2-ethylhexyl glycidyl ether, neopentyl glycol di Examples thereof include glycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, 1,6-hexanediol diglycidyl ether, sorbitol polyglycidyl ether, polyalkylene glycol monoglycidyl ether, and polyalkylene glycol diglycidyl ether.

  (3) As the glycidyl ester type epoxy compound, specifically, the following general formula (2):

（式（２）中、Ｒは炭素数１〜１８の炭化水素基を表す）
で表される化合物が挙げられる。

(In the formula (2), R represents a hydrocarbon group having 1 to 18 carbon atoms)
The compound represented by these is mentioned.

  In the above formula (2), R represents a hydrocarbon group having 1 to 18 carbon atoms. Examples of such a hydrocarbon group include an alkyl group having 1 to 18 carbon atoms, an alkenyl group having 2 to 18 carbon atoms, and carbon. A cycloalkyl group having 5 to 7 carbon atoms, an alkylcycloalkyl group having 6 to 18 carbon atoms, an aryl group having 6 to 10 carbon atoms, an alkylaryl group having 7 to 18 carbon atoms, an arylalkyl group having 7 to 18 carbon atoms, and the like. Can be mentioned. Among these, an alkylphenyl group having an alkyl group having 5 to 15 carbon atoms, an alkenyl group having 2 to 15 carbon atoms, a phenyl group, and an alkyl group having 1 to 4 carbon atoms is preferable.

  Among the glycidyl ester type epoxy compounds, specific examples include glycidyl-2,2-dimethyloctanoate, glycidyl benzoate, glycidyl-tert-butyl benzoate, glycidyl acrylate, glycidyl methacrylate, and the like.

  (4) Specific examples of the allyloxirane compound include 1,2-epoxystyrene and alkyl-1,2-epoxystyrene.

  (5) Specific examples of the alkyloxirane compound include 1,2-epoxybutane, 1,2-epoxypentane, 1,2-epoxyhexane, 1,2-epoxyheptane, 1,2-epoxyoctane, 1 , 2-epoxynonane, 1,2-epoxydecane, 1,2-epoxyundecane, 1,2-epoxydodecane, 1,2-epoxytridecane, 1,2-epoxytetradecane, 1,2-epoxypentadecane, 1, 2,2-epoxyhexadecane, 1,2-epoxyheptadecane, 1,1,2-epoxyoctadecane, 2-epoxynonadecane, 1,2-epoxyicosane and the like.

  (6) As an alicyclic epoxy compound, the following general formula (3):

で表される化合物のように、エポキシ基を構成する炭素原子が直接脂環式環を構成している化合物が挙げられる。

And a compound in which the carbon atom constituting the epoxy group directly constitutes an alicyclic ring.

  Specific examples of the alicyclic epoxy compound include 1,2-epoxycyclohexane, 1,2-epoxycyclopentane, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, bis (3, 4-epoxycyclohexylmethyl) adipate, exo-2,3-epoxynorbornane, bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate, 2- (7-oxabicyclo [4.1.0] hept-3 -Yl) -spiro (1,3-dioxane-5,3 ′-[7] oxabicyclo [4.1.0] heptane, 4- (1′-methylepoxyethyl) -1,2-epoxy-2- Examples thereof include methylcyclohexane and 4-epoxyethyl-1,2-epoxycyclohexane.

  (7) Specific examples of the epoxidized fatty acid monoester include esters of an epoxidized fatty acid having 12 to 20 carbon atoms and an alcohol or phenol having 1 to 8 carbon atoms or an alkylphenol. In particular, butyl, hexyl, benzyl, cyclohexyl, methoxyethyl, octyl, phenyl and butylphenyl esters of epoxy stearate are preferably used.

  (8) Specific examples of epoxidized vegetable oils include epoxy compounds of vegetable oils such as soybean oil, linseed oil, and cottonseed oil.

  Among these epoxy compounds, phenyl glycidyl ether type epoxy compounds, glycidyl ester type epoxy compounds, alicyclic epoxy compounds, and epoxidized fatty acid monoesters are preferable because glycidyl ether can be further improved in heat and hydrolysis stability. An ester type epoxy compound and an alicyclic epoxy compound are more preferable.

  When these epoxy compounds are blended in the refrigerating machine oil for carbon dioxide refrigerant of the present invention, the blending amount is not particularly limited, but is usually contained based on the total amount of refrigerating machine oil (based on the total amount of base oil and all blended additives). It is desirable to mix the epoxy compound in such an amount that the amount is 0.1 to 5.0% by mass, more preferably 0.2 to 2.0% by mass.

  Of course, two or more of the above phosphorus compounds and epoxy compounds may be used in combination.

  Furthermore, in the refrigerating machine oil for carbon dioxide refrigerant of the present invention, conventionally known additives for refrigerating machine oil, such as di-tert-butyl-p-cresol, bisphenol A, etc., are used as necessary in order to further enhance the performance. Phenolic antioxidants, amine-based antioxidants such as phenyl-α-naphthylamine, N, N-di (2-naphthyl) -p-phenylenediamine, antiwear agents such as zinc dithiophosphate, chlorinated paraffin, sulfur Additives such as extreme pressure agents such as compounds, oily agents such as fatty acids, antifoaming agents such as silicones, metal deactivators such as benzotriazole, viscosity index improvers, pour point depressants, and cleaning dispersants alone It is also possible to mix them in combination of several kinds. The total blending amount of these additives is not particularly limited, but is preferably 10% by mass or less, more preferably 5% by mass or less based on the total amount of refrigerating machine oil (based on the total amount of base oil and all blending additives).

Although the kinematic viscosity of the carbon dioxide refrigerant refrigerating machine oil of the present invention is not particularly limited, preferably a kinematic viscosity at 40 ° C. is 10 to 200 mm ² / s, more preferably 20 to 150 mm ² / s. When the kinematic viscosity at 40 ° C. is less than 10 mm ² / s, the lubricity and the hermeticity of the compressor tend to decrease, and when it exceeds 200 mm ² / s, the ratio of the refrigerating machine oil to the carbon dioxide refrigerant is high. Or, when the ratio is low, the compatibility tends to be insufficient. Moreover, the kinematic viscosity at 100 ° C. of the refrigerating machine oil for carbon dioxide refrigerant of the present invention is preferably 5 to 20 mm ² / s, and more preferably 6 to 18 mm ² / s. When the kinematic viscosity at 100 ° C. is less than 5 mm ² / s, the lubricity and the hermeticity of the compressor tend to decrease, and when it exceeds 20 mm ² / s, the ratio of the refrigerating machine oil to the carbon dioxide refrigerant is high. Or, when the ratio is low, the compatibility tends to be insufficient.

  In the refrigerant circulation system, it is usually necessary to reduce the amount of moisture mixed into the system as much as possible. In this respect, the moisture content of the refrigerating machine oil for carbon dioxide refrigerant of the present invention is preferably 500 ppm or less. 200 ppm or less is more preferable, and 100 ppm or less is more preferable. In general, since polyalkylene glycol has a relatively high hygroscopicity, it is preferable to pay close attention to the water content when introducing the refrigerating machine oil for carbon dioxide refrigerant of the present invention into the refrigerant circulation system. On the other hand, however, if polyalkylene glycol with high hygroscopicity coexists, the mixed water is trapped in the polyalkylene glycol molecule and is not released, so the effect of preventing adverse effects such as deterioration of refrigerant and piping and freezing can be obtained. It is done.

  The refrigerating machine oil for carbon dioxide refrigerant of the present invention having the above configuration is used as a fluid composition mixed with carbon dioxide refrigerant in the refrigerating machine for carbon dioxide refrigerant. That is, the fluid composition for a refrigerator of the present invention contains the above-described refrigerator oil for a carbon dioxide refrigerant of the present invention and a carbon dioxide refrigerant. Here, the mixing ratio of the refrigerating machine oil and the refrigerant in the refrigerating machine fluid composition of the present invention is not particularly limited, but the refrigerating machine oil is preferably 1 to 500 parts by weight, more preferably 2 to 100 parts by weight of the refrigerant. 400 parts by weight.

  The fluid composition for a refrigerator according to the present invention contains a carbon dioxide refrigerant as described above, but may further contain other refrigerants such as hydrofluorocarbon (HFC), hydrocarbon, and ammonia. .

  Here, examples of the hydrofluorocarbon refrigerant according to the present invention include hydrofluorocarbons having 1 to 3 carbon atoms, preferably 1 to 2 carbon atoms. Specifically, for example, difluoromethane (HFC-32), trifluoromethane (HFC-23), pentafluoroethane (HFC-125), 1,1,2,2-tetrafluoroethane (HFC-134), 1, 1,1,2-tetrafluoroethane (HFC-134a), 1,1,1-trifluoroethane (HFC-143a), 1,1-difluoroethane (HFC-152a), or a mixture of two or more of these Is mentioned. These refrigerants are appropriately selected depending on the application and required performance. For example, HFC-32 alone; HFC-23 alone; HFC-134a alone; HFC-125 alone; HFC-134a / HFC-32 = 60 to 80 mass % / 40-20 mass% mixture; HFC-32 / HFC-125 = 40-70 mass% / 60-30 mass% mixture; HFC-125 / HFC-143a = 40-60 mass% / 60-40 mass % Mixture; HFC-134a / HFC-32 / HFC-125 = 60 wt% / 30 wt% / 10 wt% mixture; HFC-134a / HFC-32 / HFC-125 = 40-70 wt% / 15- 35 mass% / 5 to 40 mass% mixture; HFC-125 / HFC-134a / HFC-143a = 35-55 mass% / 1-15 mass% / 40-60 mass Such as a mixture of preferred examples include. More specifically, a mixture of HFC-134a / HFC-32 = 70/30 mass%; a mixture of HFC-32 / HFC-125 = 60/40 mass%; HFC-32 / HFC-125 = 50/50 mass % Mixture (R410A); HFC-32 / HFC-125 = 45/55 wt% mixture (R410B); HFC-125 / HFC-143a = 50/50 wt% mixture (R507C); HFC-32 / HFC -125 / HFC-134a = 30/10/60 wt% mixture; HFC-32 / HFC-125 / HFC-134a = 23/25/52 wt% mixture (R407C); HFC-32 / HFC-125 / HFC-134a = 25/15/60 mass% mixture (R407E); HFC-125 / HFC-134a / HFC-143a = Mixtures of 4/4/52 wt% (R404A), and the like.

  Moreover, as a hydrocarbon refrigerant | coolant concerning this invention, a gaseous thing is preferably used at 25 degreeC and 1 atmosphere. Specifically, it is an alkane, cycloalkane, alkene or a mixture thereof having 1 to 5 carbon atoms, preferably 1 to 4 carbon atoms. Specific examples include methane, ethylene, ethane, propylene, propane, cyclopropane, butane, isobutane, cyclobutane, methylcyclopropane, or a mixture of two or more thereof. Among these, propane, butane, isobutane, or a mixture of two or more thereof is preferable.

  The mixing ratio of carbon dioxide and hydrofluorocarbon and / or hydrocarbon is not particularly limited, but is preferably 1 to 200 parts by weight as the total amount of hydrofluorocarbon and hydrocarbon with respect to 100 parts by weight of carbon dioxide. Preferably it is 10-100 weight part.

  The refrigerating machine oil for carbon dioxide refrigerant and the fluid composition for refrigerating machine of the present invention sufficiently satisfy all required performances such as lubricity, refrigerant compatibility, low-temperature fluidity, stability, etc. in a well-balanced manner, and is reciprocating. Alternatively, it can be suitably used for refrigeration equipment or heat pumps having a rotary open type or hermetic compressor. More specifically, examples of the refrigeration equipment include automobile air conditioners, dehumidifiers, refrigerators, refrigerator / freezer warehouses, vending machines, showcases, cooling devices for chemical plants, residential air conditioners, hot water supply heat pumps, and the like.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.

Examples 1-7, Comparative Examples 1-3
In Examples 1 to 7 and Comparative Examples 1 to 3, sample oils were prepared using base oils 1 to 10 shown below. Table 1 shows the kinematic viscosity, pour point, and total acid value of the obtained sample oil. In the following formulas (4) to (13), EO represents an oxyethylene group, PO represents an oxypropylene group, Me represents a methyl group, and Ac represents an acetyl group. -(EO, PO) _n- represents a polyoxyalkylene group formed by random copolymerization of ethylene oxide and propylene oxide.

Base oil 1
Me-O- (PO) _n -Me (4)
[Number average molecular weight: 1200, ratio of weight average molecular weight (M _w ) to number average molecular weight (M _n ) (M _w / M _n ): 1.1, ratio of oxyethylene groups in all oxyalkylene groups: 0 mol%]
Base oil 2 :
Me-O- (EO, PO) _n -Me (5)
[Number average molecular weight: 1200, ratio of weight average molecular weight (M _w ) to number average molecular weight (M _n ) (M _w / M _n ): 1.1, ratio of oxyethylene groups in all oxyalkylene groups: 10 mol%]
Base oil 3 :
Me-O- (PO) _n -Me (6)
[Number average molecular weight: 1500, ratio of weight average molecular weight (M _w ) to number average molecular weight (M _n ) (M _w / M _n ): 1.1, ratio of oxyethylene groups in all oxyalkylene groups: 0 mol%]
Base oil 4 :
Me-O- (EO, PO) _n -Me (7)
[Number average molecular weight: 1500, ratio of weight average molecular weight (M _w ) to number average molecular weight (M _n ) (M _w / M _n ): 1.1, ratio of oxyethylene groups in all oxyalkylene groups: 30 mol%]
Base oil 5 :
Me-O- (PO) _n -Me (8)
[Number average molecular weight: 1800, ratio of weight average molecular weight (M _w ) to number average molecular weight (M _n ) (M _w / M _n ): 1.1, ratio of oxyethylene groups in all oxyalkylene groups: 0 mol%]
Base oil 6 :
Me-O- (EO, PO) _n -Me (9)
[Number average molecular weight: 1800, ratio of weight average molecular weight (M _w ) to number average molecular weight (M _n ) (M _w / M _n ): 1.1, ratio of oxyethylene groups in all oxyalkylene groups: 40 mol%]
Base oil 7 :
Ac-O- (PO) _n -Ac (10)
[Number average molecular weight: 1000, ratio of weight average molecular weight (M _w ) to number average molecular weight (M _n ) (M _w / M _n ): 1.1, ratio of oxyethylene groups in all oxyalkylene groups: 0 mol%]
Base oil 8 :
Me-O- (PO) _n -Me (11)
[Number average molecular weight: 400, ratio of weight average molecular weight (M _w ) to number average molecular weight (M _n ) (M _w / M _n ): 1.1, ratio of oxyethylene groups in all oxyalkylene groups: 0 mol%]
Base oil 9 :
Me-O- (PO) _n -Me (12)
[Number average molecular weight: 2300, ratio of weight average molecular weight (M _w ) to number average molecular weight (M _n ) (M _w / M _n ): 1.1, ratio of oxyethylene groups in all oxyalkylene groups: 0 mol%]
Base oil 10 :
Me-O- (EO, PO) _n -Me (13)
[Number average molecular weight: 2700, ratio of weight average molecular weight (M _w ) to number average molecular weight (M _n ) (M _w / M _n ): 1.1, ratio of oxyethylene groups in all oxyalkylene groups: 30 mol%].

  Next, the test shown below was done using the sample oils of Examples 1 to 7 and Comparative Examples 1 to 3.

(Compatibility test with refrigerant 1)
A carbon dioxide refrigerant and sample oil were sealed in a pressure-resistant glass container having an internal volume of 10 ml so that the total amount became 5 g, and the state of the mixture (compatible or separated) when cooled to −30 ° C. was visually observed. . This test was started with a refrigerator oil concentration of 1% by weight (carbon dioxide refrigerant: 4.95 g, sample oil 0.05 g), and the total amount of carbon dioxide refrigerant and sample oil remained constant (5.00 g). The ratio is gradually increased, or starting from a refrigerator oil concentration of 90% by mass (carbon dioxide refrigerant: 0.50 g, sample oil 4.50 g), the total amount of carbon dioxide refrigerant and sample oil is constant (5.00 g The composition range in which the mixture of carbon dioxide refrigerant and sample oil is in a separated state was determined by gradually increasing the ratio of carbon dioxide refrigerant. The obtained results are shown in Table 1. In Table 1, “compatible” means that the mixture did not separate even when the mixing ratio of the carbon dioxide refrigerant and the sample oil was changed, and “<1” in the lower limit of the composition range is This means that the sample oil was already separated at a concentration of 1% by weight.

(Compatibility test with refrigerant 2)
Using the refrigerant solubility measuring apparatus shown in FIG. 3, the solubility of the carbon dioxide refrigerant in the sample oil was measured under the condition that the mixture of the carbon dioxide refrigerant and the sample oil was separated.

  The apparatus shown in FIG. 3 includes a pressure vessel 305 (made of stainless steel, internal volume: 200 ml) including a viscometer 301, a pressure gauge 302, a thermocouple 303, and a stirrer 304, and a constant temperature for controlling the temperature in the pressure vessel 305. A tank 306 and a sampling cylinder 308 provided with a valve and connected to the pressure vessel 305 via a flow path 307 are provided. The sampling cylinder 308 and the flow path 307 are detachable, and the sampling cylinder 308 measures its weight after vacuum degassing or after weighing a mixture of carbon dioxide refrigerant and sample oil. It is possible to do. The thermocouple 303 and the thermostat 306 are electrically connected to temperature control means (not shown), respectively, and sample oil (or a mixture of carbon dioxide refrigerant and sample oil) is transferred from the thermocouple 303 to the temperature control means. A data signal relating to the temperature of the sample oil is sent, and a control signal is sent from the temperature control means to the thermostatic chamber 306 to control the temperature of the sample oil or the mixture. Furthermore, the viscometer 301 is electrically connected to an information processing device (not shown), and measurement data relating to the viscosity of the liquid in the pressure vessel 305 is sent from the viscometer 301 to the information processing device, and a predetermined condition is obtained. It is possible to measure the viscosity below.

In this test, first, 30 g of sample oil was put in the pressure vessel 305 and the inside of the vessel was vacuum degassed, then 70 g of carbon dioxide refrigerant was introduced, and the mixture of the carbon dioxide refrigerant and sample oil was stirred with the stirrer 304. However, it was kept at −30 ° C. for 2 hours. Thereafter, stirring was stopped and the mixture was allowed to stand until the carbon dioxide refrigerant and the sample oil separated into two layers. Next, after the inside of the sampling cylinder 308 is vacuum degassed and its mass W ₁ is measured, it is connected to the flow path 307 and the sample oil layer is sampled using the pressure difference between the pressure vessel 305 and the sampling cylinder 308. Collected in a cylinder 308.

About the sampling cylinder 308 after performing the above sampling, its mass W ₂ (the sum of the masses of the sample oil in which the refrigerant is dissolved and the sampling cylinder 308) is measured, and further, the valve is opened and heated while vacuum degassing. After removing the carbon dioxide refrigerant dissolved in the sample oil, the weight W ₃ (the sum of the masses of the sample oil and the sampling cylinder 308) was measured.

Using the measured values thus obtained, the following formula:
(Solubility of carbon dioxide refrigerant [% by mass]) = [(W ₂ −W ₃ ) / (W ₃ −W ₁ )] × 100
Based on the above, the solubility of the carbon dioxide refrigerant in each sample oil was determined. The obtained results are shown in Table 1.

(Compatibility test with refrigerant 3)
In accordance with JIS K 2211 “Refrigerating machine oil” “Compatibility test method with refrigerant”, a temperature range showing compatibility when carbon dioxide refrigerant and sample oil were mixed with a predetermined composition was measured. The obtained results are shown in Table 1. The composition in this test was 50% by weight (carbon dioxide refrigerant: 1.5 g, sample oil: 1.5 g) and 60% by weight (carbon dioxide refrigerant: 1.2 g, sample oil 1.8 g). Two conditions and measurement temperature were performed at -55-30 degreeC. In Table 1, "<-55" among the lower limit values of the temperature range showing compatibility indicates that no phase separation was observed even when cooled to -55 ° C, and the upper limit of the temperature range showing compatibility. Among the values, “> 30” indicates that phase separation was not observed even when heated to 30 ° C., and “<−55 to> 30” indicates that phase separation was observed at any temperature within the measurement temperature range. It means that there was no.

(Stability test under refrigerant atmosphere)
Each sample oil 50 g, carbon dioxide refrigerant 10 g, and catalyst (1.6 mmφ × 50 mm iron wire, aluminum wire, and copper wire 3 each) were sealed in an autoclave, and then heated to 175 ° C. and held for 2 weeks. Thereafter, carbon dioxide was removed from the sample oil, the appearance of the sample oil and the appearance of the catalyst were observed, and the total acid value of the sample oil was measured. The obtained results are shown in Table 1.

(Lubricity test)
In accordance with ASTM D 3233, a carbon dioxide refrigerant was blown into 60 g of sample oil at a flow rate of 10 L / h, and a break-in operation was performed for 5 minutes under a 250 lb load under the condition of a sample oil temperature of 50 ° C. The load was measured. The obtained results are shown in Table 1.

  As is clear from the results shown in Table 1, the sample oils of Examples 1 to 7, which are the refrigerating machine oil for carbon dioxide refrigerant of the present invention, can be used either when the ratio to the carbon dioxide refrigerant is high or low. It was confirmed that a sufficient amount of carbon dioxide refrigerant was dissolved in the sample oil even when the carbon dioxide refrigerant and the sample oil were separated into two layers. . Further, the sample oils of Examples 1 to 7 were excellent in a well-balanced manner with respect to all the performances of lubricity, low-temperature fluidity, and stability.

  On the other hand, in the case of the sample oils of Comparative Examples 1 to 3 using a polyalkylene glycol compound other than the polyalkylene glycol according to the present invention, when used together with a carbon dioxide refrigerant, Either was insufficient.

Effect of the invention

  As described above, the refrigerating machine oil for carbon dioxide refrigerant of the present invention has a sufficiently wide composition range showing compatibility when mixed with carbon dioxide refrigerant under low temperature conditions, and is excellent in lubricity and stability. When the refrigeration oil and the refrigeration fluid composition using the refrigeration oil are used in a refrigeration machine for carbon dioxide refrigerant, it is possible to sufficiently prevent poor lubrication of the refrigerant compressor and obtain a sufficiently high heat exchange rate. It becomes.

  It is a schematic structure figure showing an example of a refrigerant circulation system.   It is a graph which shows the correlation with the refrigerant | coolant oil density | concentration in a refrigerant | coolant / refrigerator oil mixture, and the phase-separation temperature of a mixture.   It is a schematic block diagram which shows the refrigerant | coolant solubility measuring apparatus used in the Example.

  DESCRIPTION OF SYMBOLS 1 ... Refrigerant compressor, 2 ... Gas cooler, 3 ... Expansion mechanism, 4 ... Evaporator, 5 ... Flow path, 301 ... Viscometer, 302 ... Pressure gauge, 303 ... Thermocouple, 304 ... Stirrer, 305 ... Pressure vessel , 306 ... constant temperature bath, 307 ... flow path, 308 ... sampling cylinder.

Claims (3)

The following general formula (1):
R ^1- (OR ³ ) n-OR ² (1)
[Wherein R ¹ and R ² may be the same or different and each represents an alkyl group having 1 to 5 carbon atoms or an acyl group having 2 to 5 carbon atoms, and R ³ represents an alkylene group having 2 to 4 carbon atoms. N represents an integer such that the number average molecular weight of the polyalkylene glycol represented by the general formula (1) is 600 to 2000 ]
And a polyalkylene glycol having a kinematic viscosity at 100 ° C. of 5 to 20 mm ² / s and a ratio Mw / Mn of the weight average molecular weight Mw to the number average molecular weight Mn of 1.00 to 1.20. Refrigerating machine oil for carbon dioxide refrigerant characterized by the above.
In the polyalkylene glycol represented by the general formula (1), the proportion of ethylene groups in the alkylene groups represented by R ³ is 40 mol% or less. Refrigerating machine oil for carbon refrigerant.
  A fluid composition for a refrigerating machine, comprising the refrigerating machine oil for carbon dioxide refrigerant according to claim 1 or 2 and a carbon dioxide refrigerant.

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