JP6848441B2 - Refrigerant oil for refrigerant R32 and composition containing it - Google Patents

Description

The present invention relates to a refrigerating machine oil for a refrigerant R32 having excellent ability to dissolve additives (additive solubility) and a composition containing the same.

Conventionally, fluorocarbon refrigerants containing chlorine have been used in air conditioners such as room air conditioners and packaged air conditioners, household refrigerators and refrigerators, industrial refrigerators, and car air conditioners such as hybrid cars and electric vehicles. In recent years, instead of these chlorine-based refrigerants that cause destruction of the ozone layer, the refrigerant R134a (1,1,1,2-tetrafluoroethane), the refrigerant R125 (pentafluoroethane), and the refrigerant R410A (refrigerant R32 (difluoro)) have been replaced. Hydrofluorocarbon (HFC) refrigerants such as (methane) and the refrigerant R125 (pentafluoroethane) mixed refrigerant) are used. However, although these HFC refrigerants have an ozone depletion potential of zero, they have a high global warming potential (GWP) of 1000 or more. Therefore, it is subject to regulations aimed at reducing the greenhouse effect, and its use is restricted, so the use of refrigerants with low GWP is being considered. For example, conversion to the single use of the refrigerant HFO-1234yf (2,3,3,3-tetrafluoropropene) having a GWP of 4 and the refrigerant R32 (difluoromethane) having a GWP of 675 is being promoted.

When the refrigerant R32 having a low GWP is used, the discharge temperature in the compressor becomes high, and the lubrication conditions in the compressor become stricter. Various additives have been studied so far in order to improve lubricity. For example, Patent Document 1 discloses a refrigerating machine oil composition containing a base oil, (a) a partial ester of a polyhydric alcohol and a fatty acid, and (b) an acidic phosphoric acid ester or an amine salt thereof. There is. Further, Patent Document 2 discloses a refrigerating machine oil containing a base oil and a specific phosphorus-based compound.

Japanese Unexamined Patent Publication No. 2000-256692 Japanese Unexamined Patent Publication No. 2016-50242

Since the refrigerant R32 is inferior in additive solubility as compared with the conventional refrigerant, the highly crystalline additive is likely to precipitate in the refrigerating machine oil that comes into contact with the refrigerant R32. Therefore, it may be difficult to use a conventional additive having an excellent effect of improving lubricity, and therefore, improvement of additive solubility of refrigerating machine oil is desired. The present invention has been made in view of such circumstances, and an object of the present invention is to provide a refrigerating machine oil for a refrigerant R32 having excellent additive solubility.

As a result of diligent studies to achieve the above object, the present inventors have found that a mixture containing a citric acid triester and an alkyl vinyl ether polymer in a specific amount ratio has excellent additive solubility. The present invention has been completed. The present invention based on this finding is as follows.

[1] A refrigerating machine oil containing the following component (A) and component (B), wherein the mass ratio of component (A) to component (B) (component (A) / component (B)) is 1 /. Refrigerating machine oil for refrigerant R32 which is 99 to 30/70.
(A) Citrate Triester (B) Alkyl Vinyl Ether Polymer [2] The component (B) is composed of the following monomer (b1) and monomer (b2), or is composed of the following monomer (b1). It is a polymer, and the molar ratio (monomer (b1) unit / monomer (b2) unit) of the monomer (b1) unit and the monomer (b2) unit in the alkyl vinyl ether-based polymer is 70/30 to 100/0. The refrigerating machine oil for the refrigerant R32 according to the above [1].
(B1) Ethyl vinyl ether (b2) Isobutyl vinyl ether [3] In the above [1] or [2], the component (A) is a citric acid triester composed of citric acid and an aliphatic monohydric alcohol having 2 to 10 carbon atoms. The refrigerating machine oil for the refrigerant R32 described.
[4] The component (A) is a citric acid triester composed of citric acid and the following components (a1) and (a2), and the component (a1) and the component (a2) constituting the citric acid triester. The refrigerating machine oil for the refrigerant R32 according to the above [1] or [2], which has a molar ratio (component (a1) / component (a2)) of 60/40 to 95/5.
(A1) Aliphatic monohydric alcohol having 2 to 5 carbon atoms (a2) Aliphatic monohydric alcohol having 6 to 10 carbon atoms

[5] The mass ratio of 1,1,1,3,3-pentafluorobutane to ethyl acetate (1,1,1,3,3-pentafluorobutane / ethyl acetate) is 75/25. An additive having a clouding point of −30 ° C. or higher when dissolved in a mixed solvent at a concentration of 10% by mass, and a refrigerating machine oil for the refrigerant R32 according to any one of the above [1] to [4]. A refrigerating machine oil composition for a refrigerant R32 containing the above-mentioned additive and having a content of the additive of 0.01 to 5% by mass.
[6] The refrigerating machine oil composition for the refrigerant R32 according to the above [5], wherein the additive is triphenylphosphine and / or glycerin monooleate.

[7] A working fluid composition for a refrigerator containing the refrigerating machine oil for the refrigerant R32 and the refrigerant R32 according to any one of the above [1] to [4].
[8] A working fluid composition for a refrigerator containing the refrigerating machine oil composition for the refrigerant R32 and the refrigerant R32 according to the above [5] or [6].

Since the refrigerating machine oil for the refrigerant R32 (difluoromethane) of the present invention has excellent additive solubility, it can be suitably used for compressors such as refrigerating and air-conditioning equipment and refrigerators, which are particularly required to have lubricity. Further, since the refrigerating machine oil for the refrigerant R32 of the present invention has high compatibility with the refrigerant R32 (difluoromethane), it can be suitably used for a working fluid composition for a refrigerating machine containing the refrigerant R32.

Hereinafter, the refrigerating machine oil for the refrigerant R32 of the present invention will be described in detail.
In addition, the numerical range defined by using the symbol "~" in this specification shall include the numerical values at both ends (upper limit and lower limit) of "~". For example, "2 to 10" represents 2 or more and 10 or less.

The refrigerating machine oil for the refrigerant R32 of the present invention (hereinafter, also simply abbreviated as “refrigerating machine oil of the present invention”) contains a mixture of the component (A) and the component (B).

Further, in the present invention, the "refrigerating machine oil" generally means a lubricating oil for a compressor in a refrigerating and air-conditioning device, and examples of the refrigerating and air-conditioning device include an air conditioner and the like. Further, in the present specification, the “refrigerant oil for the refrigerant R32” means a lubricating oil for a compressor or the like in a refrigerating and air-conditioning device using the refrigerant R32 (difluoromethane).

[Ingredient (A)]
The component (A) used in the present invention is a citric acid triester. As the component (A), only one kind may be used, or two or more kinds may be used in combination. As the citric acid for producing the citric acid triester, industrially available citric acid can be used. In addition, citric acid anhydride may be used for the production of citric acid triester.

The component (A) is a citric acid triester composed of citric acid and an aliphatic monohydric alcohol having 2 to 10 carbon atoms (that is, a citric acid triester formed from citric acid and an aliphatic monohydric alcohol having 2 to 10 carbon atoms. Ester) is preferred. The aliphatic monohydric alcohol preferably has 3 to 10 carbon atoms, and more preferably 3 to 9 carbon atoms. As the aliphatic monohydric alcohol, one kind or two or more kinds can be used. Specific examples of the aliphatic monohydric alcohol include an aliphatic monohydric alcohol having 2 to 5 carbon atoms (component (a1)) and an aliphatic monohydric alcohol having 6 to 10 carbon atoms (component (a2)), which will be described later. The same as the specific example can be mentioned.

As the aliphatic monohydric alcohol having 2 to 10 carbon atoms, an aliphatic monohydric alcohol having 2 to 5 carbon atoms (component (a1)) and an aliphatic monohydric alcohol having 6 to 10 carbon atoms (component (a2)) are used in combination. It is preferable to do so. As these components (a1) and components (a2), one kind or two or more kinds can be used respectively.

Examples of the component (a1) include ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 1-pentanol, 2-. Examples thereof include pentanol, 3-pentanol, 3-methyl-1-butanol and the like. The component (a1) is preferably an aliphatic monohydric alcohol having 3 to 5 carbon atoms, and more preferably a linear saturated aliphatic monohydric alcohol having 3 to 5 carbon atoms. When 1-butanol is used, a citric acid triester having excellent solubility in the refrigerant R32, lubricity, and low temperature stability can be obtained. Therefore, it is preferable that the component (a1) contains 1-butanol. It is more preferable that the component (a1) is 1-butanol.

Examples of the component (a2) include 1-hexanol, 2-hexanol, 3-hexanol, 2-methyl-1-pentanol, 2-ethyl-butanol, 1-heptanol, 2-heptanol, 3-heptanol, 2-. Methyl-1-hexanol, 2-ethyl-1-pentanol, 1-octanol, 2-octanol, 3-octanol, 2-methyl-1-heptanol, 2-ethyl-1-hexanol, 1-nonanol, 2-nonanol , 3-Nonanol, 2-Methyl-1-octanol, 2-ethyl-1-Heptanol, 1-decanol, 2-decanol, 3-decanol, 2-methyl-1-nonanol, 2-ethyl-1-octanol, etc. Can be mentioned. When the alkyl group derived from the alcohol in the refrigerating machine oil (citrate triester) is branched, the refrigerating machine oil tends to have excellent low temperature stability and compatibility with R32, so that the component (a2) is It is preferably a branched-chain saturated aliphatic monohydric alcohol having 6 to 10 carbon atoms, and more preferably a branched-chain saturated aliphatic monohydric alcohol having 7 to 9 carbon atoms. When 2-ethyl-1-hexanol is used, an ester excellent in the ability to redissolve the precipitated additive (additive resolubility), lubricity, and low temperature stability can be obtained, so that the component (a2) can be used. It preferably contains 2-ethyl-1-hexanol. It is more preferable that the component (a2) is 2-ethyl-1-hexanol.

The molar ratio of the component (a1) to the component (a2) in the citric acid triester (component (a1) / component (a2)) is preferably 60/40 to 95/5. By adjusting the molar ratio within this range, a citric acid triester having excellent additive resolubility can be obtained. The molar ratio (component (a1) / component (a2)) is more preferably 65/35 to 90/10, still more preferably 65/35 to 85/15.

The method for adjusting the molar ratio (component (a1) / component (a2)) of the component (a1) and the component (a2) constituting the citric acid triester is not particularly limited. For example, a mixture of citric acid or citric acid anhydride and component (a1) and component (a2) may be reacted, or citric acid or citric acid anhydride may be reacted with component (a1) and component (a2), respectively. The resulting products may be mixed.

The molar ratio of the component (a1) to the component (a2) (component (a1) / component (a2)) constituting the citric acid triester can be analyzed by gas chromatography. For example, citric acid triester (0.1 g) is diluted with a mixed solvent (5 g) of toluene / methanol having a mass ratio of 80/20, and then a 28 mass% sodium methoxide methanol solution (Wako Pure Chemical Industries, Ltd.). )) (0.3 g) is added and allowed to stand at room temperature for 30 minutes to decompose the citric acid triester with methanol. The obtained ester decomposition solution was analyzed by gas chromatography, and the peak area ratios of the obtained components (a1) and (a2) were used to determine the components (a1) and (a2) constituting the citric acid triester. The molar ratio (component (a1) / component (a2)) can be calculated. By analyzing the gas chromatography of each alcohol alone, the type of alcohol constituting the citric acid triester can be identified.

For the citric acid triester, for example, citric acid or citric acid anhydride and an aliphatic monohydric alcohol are charged into a reactor, and the reaction water is mixed under a nitrogen atmosphere at normal pressure or under reduced pressure, for example, at 150 to 250 ° C. It can be produced by carrying out an esterification reaction while distilling off. The acid value of the obtained citric acid triester is preferably 10 mgKOH / g or less, more preferably 5 mgKOH / g or less, still more preferably 2 mgKOH / g or less. The esterification reaction may be carried out without a catalyst, or a Bronsted acid catalyst or a Lewis acid catalyst may be used.

The esterification reaction for obtaining a citric acid triester is preferably carried out using an excess of an aliphatic monohydric alcohol with respect to citric acid or citric acid anhydride. In this case, after the esterification reaction, excess alcohol is distilled off under reduced pressure. The obtained citric acid triester is preferably purified using, for example, an adsorbent.
In the present invention, a hydroxyl group derived from citric acid acetylated with acetic anhydride or the like can also be used.

The kinematic viscosity of the citric acid triester at 40 ° C. is preferably 5 to 300 mm ² / s, more preferably 10 to 200 mm ² / s, and even more preferably 10 to 150 mm ² / s. The acid value thereof is preferably 10 mgKOH / g or less, more preferably 5 mgKOH / g or less, still more preferably 2 mgKOH / g or less, and particularly preferably 1 mgKOH / g or less. The kinematic viscosity can be measured according to JIS K2283. The acid value can be measured according to JIS C2101.

[Component (B)]
The component (B) used in the present invention is an alkyl vinyl ether-based polymer obtained by polymerizing an alkyl vinyl ether. As the component (B), only one kind may be used, or two or more kinds may be used in combination. Examples of the alkyl vinyl ether include ethyl vinyl ether, 1-propyl vinyl ether, isopropyl vinyl ether, 1-butyl vinyl ether, isobutyl vinyl ether, 1-hexyl vinyl ether, 1-octyl vinyl ether, 2-ethylhexyl vinyl ether, 1-decyl vinyl ether, isodecyl vinyl ether and the like. Can be mentioned. The alkyl group of the alkyl vinyl ether preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and further preferably 1 to 6 carbon atoms.

The alkyl vinyl ether-based polymer may contain units derived from other monomers in addition to the units derived from the above alkyl vinyl ether. The other monomer is not particularly limited as long as it is a monomer copolymerizable with an alkyl vinyl ether (for example, a monomer having an olefinic double bond), and examples thereof include polyoxyalkylene alkyl vinyl ether.

When the alkyl vinyl ether-based polymer is a copolymer, the polymer may be a random copolymer or a block copolymer.

The number average molecular weight of the alkyl vinyl ether polymer is preferably 500 to 3,000, more preferably 500 to 2,000, and even more preferably 500 to 1,500. Moreover, kinematic viscosity at 40 ° C. of vinyl ether-based polymer is preferably a 3~500mm ² / s, more preferably 5 to 200 mm ² / s, more preferably 5 to 150 mm ² / s. The number average molecular weight can be measured by gel permeation chromatography (GPC) using polystyrene as a standard sample. The kinematic viscosity can be measured according to JIS K2283.

The component (B) consists of the following monomer (b1) and monomer (b2) (that is, is formed from the following monomer (b1) and monomer (b2)), or consists of the following monomer (b1). It is preferably an alkyl vinyl ether-based polymer (that is, formed from the following monomer (b1)) (hereinafter, may be abbreviated as "alkyl vinyl ether-based polymer (P1)").
(B1) Ethyl vinyl ether (b2) Isobutyl vinyl ether

The molar ratio (monomer (b1) unit / monomer (b2) unit) of the monomer (b1) unit and the monomer (b2) unit in the alkyl vinyl ether-based polymer (P1) is preferably 70/30 to 100/0. It is preferably 75/25 to 100/0, more preferably 80/20 to 100/0. This molar ratio can be measured by ^{1 1 H-NMR. For example, in 1} H-NMR measurement (solvent: deuterated chloroform, reference: tetramethylsilane) of an alkyl vinyl ether-based polymer (P1), _{the signal derived from the alkyl terminal CH 3} of the ethyl vinyl ether has a chemical shift value of 1.05-1. At 25 ppm, the signal derived from the alkyl-terminated CH ₃ of the isobutyl vinyl ether is detected at a chemical shift value of 0.80 to 1.00 ppm. The molar ratio of each monomer unit can be calculated from the ratio of the integrated values of these signals.

The alkyl vinyl ether-based polymer can be produced by a known method. For example, it can be produced by radical polymerization or cationic polymerization of an alkyl vinyl ether and, if necessary, another monomer in the presence of a polymerization initiator. Examples of the polymerization initiator include Bronsted acid, Lewis acid, organometallic compounds and the like. Examples of Bronsted acid include trichloroacetic acid and trifluoroacetic acid. Examples of Lewis acid include boron trifluoride and zinc dichloride. Examples of the organometallic compound include diethylaluminum chloride and the like.

The polymerization is usually carried out in a solvent. Examples of the solvent include hexane, toluene, ethyl ether, tetrahydrofuran and the like. The polymerization temperature is, for example, −50 to 150 ° C., preferably −50 to 100 ° C. The polymerization time is, for example, 10 minutes to 10 hours, preferably 1 to 8 hours. The polymerization is preferably carried out in an atmosphere of an inert gas such as nitrogen. The polymerization is preferably stopped by alkali.

[Refrigerator oil]
The refrigerating machine oil of the present invention comprises the above-mentioned component (A) and component (B). The mixture of the component (A) and the component (B) may be abbreviated as "mixture (AB)" below. The mass ratio of the component (A) to the component (B) in the refrigerating machine oil (component (A) / component (B)) is 1/99 to 30/70. When the mass ratio is in this range, the desired excellent additive solubility can be obtained. The method of mixing the component (A) and the component (B) is not particularly limited, but for example, the component (A) and the component (B) are measured in an arbitrary amount in a beaker and mixed by stirring using a stirring blade. The method can be mentioned. The mass ratio of the component (A) to the component (B) (component (A) / component (B)) is preferably 1/99 to 25/75, more preferably 3/97 to 20/80. Excellent when the mass ratio of the component (A) to the component (B) (component (A) / component (B)) is in the range of 1/99 to 30/70 and the ratio of the component (A) is small. When it becomes difficult to obtain additive solubility and the proportion of component (A) increases, the performance reaches a plateau, and the additive solubility and the ability to dissolve freon corresponding to the content of component (A) (flon solubility) May be difficult to obtain.

The kinematic viscosity of the mixture (AB) at 40 ° C. is preferably 5 to 300 mm ² / s, more preferably 10 to 250 mm ² / s, and even more preferably 10 to 200 mm ² / s. The acid value of the mixture (AB) is preferably 10 mgKOH / g or less, more preferably 5 mgKOH / g or less, still more preferably 2 mgKOH / g or less, and particularly preferably 1 mgKOH / g or less. The kinematic viscosity can be measured according to JIS K2283. In addition, the acid value can be measured in accordance with JIS C2101.

[Refrigerant oil composition for refrigerant R32]
The present invention has a mass ratio of 1,1,1,3,3-pentafluorobutane to ethyl acetate (1,1,1,3,3-pentafluorobutane / ethyl acetate) of 75/25. Additive having a clouding point of −30 ° C. or higher when dissolved in a mixed solvent of 10% by mass, and a refrigerating machine oil for the above-mentioned refrigerant R32 (that is, a refrigerating machine oil containing the above-mentioned mixture (AB)). ) Is also provided for the refrigerating machine oil composition for the refrigerant R32.

The content of the additive is 0.01 to 5% by mass, preferably 0.1 to 4% by mass in the refrigerating machine oil composition for the refrigerant R32. The refrigerating machine oil composition for the refrigerant R32 can achieve an excellent effect that no additive is precipitated and the effects of various additives corresponding to the amount of the additive can be obtained.

As the additive, any additive can be used as long as the cloudiness point measured under the above conditions is −30 ° C. or higher. Further, as the additive, only one kind may be used, or two or more kinds may be used in combination. The refrigerating machine oil for the refrigerant R32 of the present invention has excellent additive solubility, and therefore, the refrigerating machine oil composition for the refrigerant R32 of the present invention has a high clouding point and can use an additive that is difficult to dissolve. .. The cloudiness point of the additive measured under the above conditions is preferably −20 ° C. or higher, more preferably −15 ° C. or higher. The cloudiness point can be measured according to JIS 2269 "Pour point of crude oil and petroleum products and cloud point test method for petroleum products".

Examples of the additive include a load-bearing additive, an antioxidant, a metal inactivating agent, and an acid scavenger. Since the lubrication conditions of the compressor using the refrigerant R32 are stricter than those when the conventional HFC refrigerant is used, a load-bearing additive is preferable as the additive. Here, the load-bearing additive means an additive that functions when the metal friction surfaces come into contact with each other without being able to separate the metal friction surfaces by an oil film. For example, an oiliness improver, an anti-wear agent, and an extreme pressure. Agents can be mentioned.

Examples of the load-bearing additive include fatty acid ester-based additives, ether-based additives, phosphate ester-based additives, and thiophosphate-based additives. Among these, fatty acid ester-based additives, phosphoric acid ester-based additives, and thiophosphate-based additives are preferable in terms of the effect of improving lubricity, and fatty acid ester-based additives and phosphoric acid ester-based additives are preferable. More preferable. Examples of the phosphoric acid ester-based additive include triphenyl phosphate and the like. Examples of the fatty acid ester-based additive include glycerin monoolate and the like. The additive is preferably triphenylphosphate and / or glycerin monoolate.

As described above, the "refrigerant oil for the refrigerant R32" means a lubricating oil for a compressor or the like in an air conditioner using the refrigerant R32 (difluoromethane), and the refrigerating machine oil for the refrigerant R32 of the present invention and its composition. The thing is also used in a compressor or the like in an air conditioner that uses the refrigerant R32. However, a refrigerant containing the refrigerant R32, for example, a refrigerant R410R (a mixture of a refrigerant R125 (pentafluoroethane) having a mass ratio of 50/50 / a refrigerant R32 (difluoromethane)) or R410B (a refrigerant having a mass ratio of 55/45). The refrigerating machine oil and refrigerating machine oil composition used in the compressor using R125 (pentafluoroethane) / refrigerant R32 (difluoromethane)) are also the refrigerating machine oil for the refrigerant R32 and the refrigerating machine oil composition for the refrigerant R32 of the present invention. Included in. Since the refrigerating machine oil for the refrigerant R32 of the present invention has excellent additive solubility which cannot be obtained by the refrigerating machine oil for the conventional refrigerant R32, the refrigerating machine oil for the refrigerant R32 of the present invention and its composition are used as a refrigerant. When used in a compressor that uses only the refrigerant R32 having poor additive solubility, its usefulness is most exhibited.

The present invention also provides a refrigerating machine oil for the refrigerant R32 or a refrigerating machine oil composition for the refrigerant R32 described above, and a working fluid composition for a refrigerating machine containing the refrigerant R32. The content of the refrigerating machine oil for the refrigerant R32 in these working fluid compositions for the refrigerator is preferably 1 to 500 parts by mass, more preferably 2 to 400 parts by mass with respect to 100 parts by mass of the refrigerant R32 (difluoromethane). Is.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the scope of the present invention is not limited by the following practical examples.

[Synthesis of component (A)]
Manufacturing example 1
Citric acid anhydride (282 g, 1.47 mol), 1-butanol (294 g, 3.97 mol), and 2-ethyl-1-hexanol (114 g, 0.87 mol) were placed in a four-necked flask and placed in a nitrogen atmosphere. The reaction was carried out at normal pressure for 5 hours while distilling off the reaction water at 200 ° C. Then, the reaction was continued at 200 ° C. until the acid value became 2 mgKOH / g or less. Then, excess alcohol was distilled off at 200 ° C. under a reduced pressure of 1 to 5 kPa to obtain a crude ester. The crude ester was cooled, and acidic clay and silica-alumina-based adsorbents were added thereto so as to be 1.0% by mass of the amount of the ester obtained theoretically, respectively, and the adsorption treatment was performed (adsorption treatment temperature: 100). ° C., pressure: 1-5 kPa, and adsorption treatment time: 2 hours). Finally, filtration was performed using a 1-micron filter to obtain the desired citric acid triester (acid value 0.1 mgKOH / g or less) (hereinafter referred to as "ester A1").

Manufacturing example 2
Citric acid anhydride (295 g, 1.53 mol), 1-butanol (326 g, 4.40 mol), and 1-octanol (86 g, 0.66 mol) were placed in a four-necked flask and reacted at 200 ° C. under a nitrogen atmosphere. The reaction was carried out at normal pressure for 5 hours while distilling off water. The subsequent steps were carried out in the same manner as in Production Example 1 to obtain the desired citric acid triester (hereinafter referred to as "ester A2").

Manufacturing example 3
Citric acid anhydride (307 g, 1.60 mol), 2-propanol (206 g, 3.43 mol), and 1-hexanol (189 g, 1.85 mol) were placed in a four-necked flask and reacted at 200 ° C. under a nitrogen atmosphere. The reaction was carried out at normal pressure for 6 hours while distilling off water. The subsequent steps were carried out in the same manner as in Production Example 1 to obtain the desired citric acid triester (hereinafter referred to as "ester A3").

Manufacturing example 4
Citric acid anhydride (269 g, 1.40 mol), 2-butanol (247 g, 3.33 mol), and 3,5,5-trimethylhexanol (187 g, 1.29 mol) were placed in a four-necked flask under a nitrogen atmosphere. The reaction was carried out at normal pressure for 6 hours while distilling off the reaction water at 200 ° C. The subsequent steps were carried out in the same manner as in Production Example 1 to obtain the desired citric acid triester (hereinafter referred to as "ester A4").

Production example 5
Citric acid anhydride (346 g, 1.80 mol), ethanol (137 g, 2.97 mol), and 1-butanol (220 g, 2.97 mol) were placed in a four-necked flask, and the reaction water was added to the reaction water at 180 ° C. under a nitrogen atmosphere. The reaction was carried out at normal pressure for 7 hours while distilling off. The subsequent steps were carried out in the same manner as in Production Example 1 to obtain the desired citric acid triester (hereinafter referred to as "ester A5").

Production example 6
Citric acid anhydride (307 g, 1.60 mol) and 1-butanol (391 g, 5.28 mol) were placed in a four-necked flask and reacted at normal pressure for 5 hours under a nitrogen atmosphere while distilling off the reaction water at 200 ° C. Was done. The subsequent steps were carried out in the same manner as in Production Example 1 to obtain the desired citric acid triester (hereinafter referred to as "ester A6").

Production example 7
Citric acid anhydride (218 g, 1.13 mol) and 2-ethyl-1-hexanol (487 g, 3.74 mol) were placed in a four-necked flask, and the reaction water was distilled off at 220 ° C. under a nitrogen atmosphere at normal pressure. The reaction was carried out for 5 hours. The subsequent steps were carried out in the same manner as in Production Example 1 to obtain the desired citric acid triester (hereinafter referred to as "ester A7").

The carboxylic acids and alcohols used in the production of the esters A1 to A7 of Production Examples 1 to 7 described above are shown in Tables 1 and 2 below. Moreover, the characteristics of esters A1 to A7 were measured by the method described later. The results are shown in Tables 1 and 2 below.

[Synthesis of component (B)]
Production Example 8
After charging ethanol (22.5 g), isobutyl alcohol (4.0 g), boron trifluoride diethyl ether complex (0.21 g) and toluene (150 mL) into a 1 L reaction vessel, the mixture was heated to 45 ° C. It was held at this temperature. A mixture of ethyl vinyl ether (415 g) and isobutyl vinyl ether (64 g) was continuously supplied to the reaction vessel over 5 hours to obtain a polymer.

The above polymer (200 g) and nickel catalyst (5 g) were charged into an autoclave, and the inside of the autoclave was replaced with nitrogen. Next, the inside of the autoclave was replaced with hydrogen, the hydrogen pressure was adjusted to 30 kg / cm ² G, the mixture was heated to 140 ° C., and a hydrogenation reaction was carried out at this temperature for 2 hours. Then, the reaction solution was cooled, the pressure in the autoclave was lowered, and then the reaction solution was taken out. Then, isooctane (50 g) was added to the reaction solution, and the obtained mixture was filtered to remove the catalyst. The obtained filtrate was evaporated under reduced pressure to remove the solvent and volatile components to obtain the desired alkyl vinyl ether-based polymer (hereinafter referred to as "polymer P11").

Manufacturing example 9
After charging ethanol (10.0 g), isobutyl alcohol (4.0 g), boron trifluoride diethyl ether complex (0.11 g) and toluene (80 mL) into a 1 L reaction vessel, the mixture was heated to 45 ° C. It was held at this temperature. A mixture of ethyl vinyl ether (185 g) and isobutyl vinyl ether (64 g) was continuously supplied to the reaction vessel over 5 hours to obtain a polymer.

The above polymer (200 g) and nickel catalyst (5 g) were charged into an autoclave, and the inside of the autoclave was replaced with nitrogen. Next, the inside of the autoclave was hydrogenated, the hydrogen pressure was 30 kg / cm ² G, the mixture was heated to 140 ° C., and a hydrogenation reaction was carried out at this temperature for 2 hours. Then, the reaction solution was cooled, the pressure in the autoclave was lowered, and then the reaction solution was taken out. Then, 50 g of isooctane was added to the reaction solution, and the obtained mixture was filtered to remove the catalyst. The obtained filtrate was distilled off under reduced pressure to remove the solvent and volatile components to obtain the desired alkyl vinyl ether-based polymer (hereinafter referred to as "polymer P12").

The properties of the polymers P11 and P12 obtained in Production Examples 8 and 9 were measured by the methods described below. The results are shown in Table 3 below.

[Mole ratio of alcohol components constituting esters A1 to A7]
Any of the esters A1 to A7 (0.1 g) is diluted with a mixed solvent (5 g) of toluene / methanol having a mass ratio of 80/20, and then a 28 mass% sodium methoxide methanol solution (Wako Pure Chemical Industries, Ltd. (Wako Pure Chemical Industries, Ltd.) (Made by Co., Ltd.) (0.3 g) was added, and the mixture was allowed to stand at room temperature for 30 minutes to decompose the ester with methanol. The obtained ester decomposition solution was analyzed by gas chromatography, and the molar ratio of alcohols constituting the ester was calculated from the peak area ratio of the obtained alcohol.

[Acid value]
The acid values of esters A1 to A7, polymers P11 and P12, and refrigerating machine oils 1 to 11, which will be described later, were measured according to JIS C2101.

[Pour point]
The pour points of esters A1 to A7, polymers P11 and P12, and refrigerating machine oils 1 to 11, which will be described later, were measured according to JIS K2269.

[Number average molecular weight]
The number average molecular weights of the polymers P11 and P12 were measured by gel permeation chromatography (GPC) using the following equipment and conditions.
Equipment: HLC-8220 made by TOSOH
Measurement column: shodex KF-805L
Guard column: shodex KF-G
Solvent: THF
Flow velocity: 1 mL / min
Column oven temperature: 40 ° C
Standard sample: polystyrene

[Molar ratio of monomer units in alkyl vinyl ether-based polymers]
The molar ratio of monomer (b1) units to monomer (b2) units in the polymers P11 and P12 was calculated by ¹ H-NMR using the following equipment and conditions.
Equipment: JEOL FT NMR System AL400 (400MHz)
Solvent: Deuterated chloroform Reference: Tetramethylsilane

The mass ratio (1,1,1) of 1,1,1,3,3-pentafluorobutane and ethyl acetate was added to the additives (triphenyl phosphate and glycerin monooleate) used in the production of the refrigerating machine oil composition described later. , 3,3-Pentafluorobutane / ethyl acetate) was 75/25, and the cloudiness point when dissolved in these mixed solvents at a concentration of 10% by mass was measured according to JIS 2269. The haze point of triphenylphosphine measured under these conditions was -3 ° C, and the haze point of glycerin monooleate was 25 ° C.

Examples 1-9 and Comparative Examples 1 and 2
The above esters A1 to A7, polymers P11 and P12 are mixed in the blending ratios shown in Table 4 below, and refrigerating machine oils 1 to 9 (Examples 1 to 9) and refrigerating machine oils 10 and 11 (Comparative Examples 1 and 2) are added. Prepared. Moreover, the acid value and the pour point of the refrigerating machine oils 1 to 11 were measured as described above. Further, the two-layer separation temperature of the refrigerating machine oils 1 to 11 was measured as follows. The results are shown in Table 4 below.

[Two-layer separation temperature]
Any one of the refrigerating machine oils 1 to 11 (1 g) and the refrigerant R32 (6 g) were sealed in a pressure-resistant glass tube, and cooled from 40 ° C. at a rate of 1 ° C./min using an ethanol bath containing dry ice. The temperature at which the refrigerating machine oil and the refrigerant R32 were separated into two layers was visually measured in the range of −20 ° C. to + 40 ° C. Those having already separated into two layers at 40 ° C. and becoming cloudy, or those having a two-layer separation temperature of 10 ° C. to 40 ° C. were evaluated as x.

Examples 10-18 and Comparative Examples 3 and 4
Any of refrigerating machine oils 1 to 11 (1 g), triphenyl phosphate (0.02 g), and refrigerant R32 (6 g) are sealed in a pressure-resistant glass tube and blended at 40 ° C. to prepare a working fluid composition for a refrigerator. 1-9 (Examples 10-18) and working fluid compositions for refrigerators 10 and 11 (Comparative Examples 3 and 4) were prepared.

[Solubility test 1]
The obtained working fluid compositions for refrigerators 1 to 11 were cooled from + 40 ° C. to + 5 ° C. at a rate of −5 ° C./hour, and the presence or absence of precipitates was visually confirmed. The temperature at which the precipitate was confirmed was recorded in 1 ° C. increments.
Those without precipitation at + 5 ° C. were evaluated as ◯. The working fluid composition 10 for a refrigerator was separated into two layers at + 15 ° C., and the refrigerator oil layer was in a cloudy state when cooled to +5. In the working fluid composition 11 for a refrigerator, the refrigerating machine oil did not dissolve with triphenylphosphine and the refrigerant R32 at + 40 ° C. and was separated into two layers, and the refrigerating machine oil layer became cloudy when cooled to + 5 ° C. .. These working fluid compositions for refrigerators 10 and 11 (Comparative Examples 3 and 4) were evaluated as x. The results are shown in Table 5 below.

Examples 19-27 and Comparative Examples 5 and 6
Any of refrigerating machine oils 1 to 11 (1 g), glycerin monooleate (0.01 g), and refrigerant R32 (6 g) are sealed in a pressure-resistant glass tube and blended at 40 ° C. to prepare a working fluid composition for a refrigerator. 12 to 20 (Examples 19 to 27) and working fluid compositions for refrigerators 21 and 22 (Comparative Examples 5 and 6) were prepared.

[Solubility test 2]
The obtained working fluid composition for a refrigerator 12 to 22 was cooled from + 40 ° C. to + 5 ° C. at a rate of −5 ° C./hour, and the presence or absence of precipitates was visually confirmed. The temperature at which the precipitate was confirmed was recorded in 1 ° C. increments.
Those without precipitation at + 5 ° C. were evaluated as ◯. The working fluid composition 21 for a refrigerator was separated into two layers at + 15 ° C., and the refrigerator oil layer was in a cloudy state when cooled to +5. In the working fluid composition 22 for a refrigerator, the refrigerating machine oil and the glycerin monooleate and the refrigerant R32 were separated into two layers at + 40 ° C., and the refrigerating machine oil layer was in a cloudy state when cooled to + 5 ° C. These working fluid compositions for refrigerators 21 and 22 (Comparative Examples 5 and 6) were evaluated as x. The results are shown in Table 6 below.

[Resolubility test]
The obtained working fluid composition for a refrigerator 12 to 22 was allowed to stand in a constant temperature bath set at −25 ° C. for 24 hours to precipitate glycerin monooleate in the mixture. Then, the mixture was immediately transferred to a constant temperature bath at 10 ° C., and the time required for the precipitate in the mixture to dissolve and become transparent was measured. The working fluid compositions 21 and 22 for the refrigerator were in a cloudy state because the refrigerating machine oil did not dissolve in the glycerin monooleate and the refrigerant R32 even at 10 ° C. These working fluid compositions for refrigerators 21 and 22 (Comparative Examples 5 and 6) were evaluated as x. The results are shown in Table 6 below.

As is clear from the results shown in Tables 5 and 6, the refrigerating machine oil for the refrigerant R32 of the present invention containing the component (A) and the component (B) is excellent in additive solubility.

The refrigerating machine oil for the refrigerant R32, the refrigerating machine oil composition for the refrigerant R32, and the working fluid composition for the refrigerating machine of the present invention can be suitably used in a compressor or the like in an air conditioner using the refrigerant R32.

Claims (8)

It is a refrigerating machine oil composed of the following component (A) and component (B), and the mass ratio of the component (A) to the component (B) (component (A) / component (B)) is 1/99 to 30. Refrigerant oil for refrigerant R32 which is / 70.
(A) Citric acid triester (B) Alkyl vinyl ether polymer The component (B) is an alkyl vinyl ether-based polymer composed of the following monomer (b1) and monomer (b2), or composed of the following monomer (b1), and is a monomer (b1) unit in the alkyl vinyl ether-based polymer. The refrigerating machine oil for the refrigerant R32 according to claim 1, wherein the molar ratio with the monomer (b2) unit (monomer (b1) unit / monomer (b2) unit) is 70/30 to 100/0.
(B1) Ethyl vinyl ether (b2) Isobutyl vinyl ether The refrigerating machine oil for the refrigerant R32 according to claim 1 or 2, wherein the component (A) is a citric acid triester composed of citric acid and an aliphatic monohydric alcohol having 2 to 10 carbon atoms. The component (A) is a citric acid triester composed of citric acid and the following components (a1) and (a2), and the component (a1) and the component (a2) constituting the citric acid triester The refrigerating machine oil for the refrigerant R32 according to claim 1 or 2, wherein the molar ratio (component (a1) / component (a2)) is 60/40 to 95/5.
(A1) Aliphatic monohydric alcohol having 2 to 5 carbon atoms (a2) Aliphatic monohydric alcohol having 6 to 10 carbon atoms In a mixed solvent of 1,1,1,3,3-pentafluorobutane and ethyl acetate having a mass ratio (1,1,1,3,3-pentafluorobutane / ethyl acetate) of 75/25. The additive comprises an additive having a clouding point of −30 ° C. or higher when dissolved at a concentration of 10% by mass, and a refrigerating machine oil for the refrigerant R32 according to any one of claims 1 to 4. A refrigerating machine oil composition for the refrigerant R32 having a content of 0.01 to 5% by mass. The refrigerating machine oil composition for the refrigerant R32 according to claim 5, wherein the additive is triphenylphosphine and / or glycerin monooleate. A working fluid composition for a refrigerator containing the refrigerating machine oil for the refrigerant R32 and the refrigerant R32 according to any one of claims 1 to 4. The working fluid composition for a refrigerator containing the refrigerating machine oil composition for the refrigerant R32 and the refrigerant R32 according to claim 5 or 6.