JP5068619B2 - Refrigerating machine oil for carbon dioxide refrigerant and refrigerating machine oil for carbon dioxide refrigerant - Google Patents

Description

The present invention relates to a refrigerating machine oil used in a refrigerating and air-conditioning apparatus in which carbon dioxide (carbon dioxide, CO ₂ ) refrigerant is used, and a base oil used in the refrigerating machine oil.

  Due to the problem of ozone layer destruction in recent years, CFC (chlorofluorocarbon) and HCFC (hydrochlorofluorocarbon), which have been used as refrigerants in conventional refrigeration equipment, are subject to regulation, and HFC (hydrofluorocarbon) is used as a refrigerant instead. It is being done. However, such HFC refrigerants also have problems such as high global warming ability, and the use of natural refrigerants as alternative refrigerants to replace these fluorocarbon refrigerants has been studied. Among them, carbon dioxide refrigerant is harmless to the environment and is superior in terms of safety, and has advantages such as compatibility with oil and machine materials and availability. It has been used as. In recent years, its application has been studied as a refrigerant for car air conditioners using an open type compressor or a hermetic type electric compressor.

As a refrigerating machine oil for carbon dioxide refrigerant, the following Patent Document 1 discloses a refrigerating machine oil containing an ester base oil.
JP 2000-104084 A

  However, in the case of the conventional refrigerating machine oil using the above-mentioned conventional ester base oil, the lubricity in the coexistence of the carbon dioxide refrigerant is not necessarily sufficient. The viscosity at the time of dissolution of carbon (hereinafter sometimes referred to as “dissolution viscosity”) is greatly reduced, and the viscosity necessary for lubricating the refrigeration equipment cannot be sufficiently maintained.

  As a method for maintaining the lubricity of the refrigerating machine oil, it is conceivable to maintain the oil film thickness by increasing the viscosity of the base oil. In this method, however, the handling property by using the high viscosity base oil is improved. Decrease and stirring efficiency are problems.

  The present invention has been made in view of such circumstances, and when used together with a carbon dioxide refrigerant, has excellent stability and electrical insulation, and has an appropriate compatibility with the refrigerant, and further a base oil. It is an object of the present invention to provide a carbon dioxide refrigerant refrigerating machine base oil and a carbon dioxide refrigerant refrigerating machine oil that exhibit sufficient lubricity without increasing the viscosity of the carbon dioxide refrigerant.

  In order to achieve the above-mentioned object, the present inventors first examined improvement in lubricity of an ester-based refrigerating machine oil in the presence of a carbon dioxide refrigerant that is considered to be particularly difficult to achieve among the above problems. As a result, such lubricity is not necessarily improved by simply increasing the viscosity of the base oil or suppressing the decrease in dissolution viscosity, and the ester of a fatty acid (aliphatic monocarboxylic acid) and a polyhydric alcohol. It was found that the fatty acid composition in S was an important determinant for lubricity in the presence of carbon dioxide refrigerant. As a result of further investigation based on such knowledge, the present inventors solved the above problem by using a fatty acid having a specific fatty acid composition as a constituent fatty acid of an ester and a polyhydric alcohol as a constituent alcohol. As a result, the present invention has been completed.

  That is, the present invention provides at least one selected from fatty acids in which the proportion of branched chain fatty acids having 14, 16, 18, 20, and 22 carbon atoms is 80 to 100 mol%, pentaerythritol, ditrimethylolpropane, and dipentaerythritol. A base oil for refrigerating machine oil for carbon dioxide refrigerant (hereinafter referred to as “base of the present invention”), which comprises a complete ester (hereinafter also referred to as “polyol ester according to the present invention”) with a polyhydric alcohol of a kind. Oil ”).

  In the base oil of the present invention, the proportion of branched chain fatty acids having 16, 18 and 20 carbon atoms in the total fatty acids constituting the polyol ester according to the present invention is preferably 80 to 100 mol%.

In the base oil of the present invention, the proportion of tertiary carbon in the constituent carbon of the fatty acid constituting the polyol ester according to the present invention obtained by ¹³ C-NMR analysis is 2% by mass or more. preferable.

  The present invention also provides a carbon dioxide refrigerant refrigerating machine oil (hereinafter also referred to as “the refrigerating machine oil of the present invention”) characterized by containing the carbon dioxide refrigerant refrigerating machine base oil of the present invention. .

  The refrigerating machine oil of the present invention is at least selected from fatty acids in which the proportion of branched chain fatty acids having 14, 16, 18, 20, and 22 carbon atoms is 80 to 100 mol%, pentaerythritol, ditrimethylolpropane, and dipentaerythritol. It may be characterized by containing a complete ester of one kind of polyhydric alcohol.

  As described above, according to the present invention, when used together with a carbon dioxide refrigerant, it has excellent stability and electrical insulation, has an appropriate compatibility with the refrigerant, and further does not increase the viscosity of the base oil. It becomes possible to provide a base oil for a refrigerating machine oil for carbon dioxide refrigerant and a refrigerating machine oil for carbon dioxide refrigerant exhibiting sufficient lubricity.

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

  Physical properties of the base oil of the present invention and the refrigerating machine oil of the present invention, the polyol ester according to the present invention contained therein, specific embodiments and preferred embodiments of the base oil and additives other than the polyol ester according to the present invention, and their blending forms Are common. Therefore, hereinafter, unless otherwise specified, the description of the refrigerating machine oil of the present invention holds true even if the refrigerating machine oil of the present invention is replaced with the base oil of the present invention.

  The refrigerating machine oil of the present invention contains the polyol ester according to the present invention by containing the base oil of the present invention, but the refrigerating machine oil of the present invention contains components other than the polyol ester according to the present invention. In this case, the refrigerating machine oil of the present invention may be prepared in advance using the base oil of the present invention containing the component, or the component may be added separately from the base oil of the present invention. A refrigerating machine oil may be prepared. For example, the refrigerating machine oil of the present invention may contain a base oil other than the polyol ester according to the present invention, but the base oil other than the polyol ester according to the present invention is previously contained in the base oil of the present invention. Alternatively, when preparing the refrigerating machine oil of the present invention, a base oil not containing the polyol ester according to the present invention (hereinafter also referred to as “second base oil” for convenience) may be added separately. . Similarly, the refrigerating machine oil of the present invention can contain various additives. However, the additive may be previously contained in the base oil or the second base oil of the present invention, or the present invention. In addition to the refrigerating machine oil or the second base oil of the present invention, the refrigerating machine oil may be added separately. Furthermore, in the base oil of the present invention and the refrigerating machine oil of the present invention, whether the components other than the polyol ester according to the present invention are derived from the base oil, the second base oil or the additive of the present invention. Is not particularly limited.

  The refrigerating machine oil for carbon dioxide refrigerant of the present invention comprises fatty acids in which the ratio of branched chain fatty acids having 14, 16, 18, 20, and 22 carbon atoms is 80 to 100 mol%, pentaerythritol, ditrimethylolpropane, and dipentaerythritol. And a complete ester of at least one polyhydric alcohol selected from:

  The ratio of the branched chain fatty acids having 14, 16, 18, 20, and 22 carbon atoms in the fatty acid (hereinafter referred to as “constituent fatty acid”) constituting the polyol ester according to the present invention is preferably 40 to 100 mol%, and preferably Is 50 to 100 mol%, more preferably 60 to 100 mol%. When the proportion of the branched chain fatty acids having 14, 16, 18, 20, and 22 carbon atoms is less than 40 mol%, the lubricity in the presence of the carbon dioxide refrigerant becomes insufficient.

  In addition, the proportion of branched chain fatty acids having 16, 18 and 20 carbon atoms in the constituent fatty acids of the polyol ester according to the present invention is preferably 80 to 100 mol%, more preferably 90 to 100 mol%, still more preferably. Is 95 to 100 mol%, particularly preferably 98 to 100 mol%. When the proportion of branched chain fatty acids having 16, 18 and 20 carbon atoms is less than 80 mol%, the lubricity in the presence of a carbon dioxide refrigerant tends to be insufficient.

  Furthermore, in the polyol ester according to the present invention, from the viewpoint of suitably ensuring fluidity and lubricity in the presence of a carbon dioxide refrigerant, the ratio of the branched chain fatty acid having 18 carbon atoms in the constituent fatty acid is 50 to 50. It is preferable that it is 100 mol%, More preferably, it is 60-100 mol%, More preferably, it is 70-100 mol%.

  Specific examples of branched fatty acids having 14, 16, 18, 20, and 22 carbon atoms include branched tetradecanoic acid, branched hexadecanoic acid, branched octadecanoic acid, branched icosanoic acid, and branched chain. Type docosanoic acid is preferred.

  In addition, the constituent fatty acid of the polyol ester according to the present invention is a fatty acid other than these branched chain fatty acids as long as the ratio of the branched chain fatty acids having 14, 16, 18, 20, and 22 carbon atoms is 80 to 100 mol%. May be included. Examples of fatty acids other than branched chain fatty acids having 14, 16, 18, 20, and 22 carbon atoms include, for example, linear or branched chain fatty acids having 5 to 13, 15, 17, 19, 21, 23, or 24 carbon atoms. And straight chain fatty acids having 14, 16, 18, 20 or 22 carbon atoms.

Moreover, it is preferable that the ratio of the tertiary carbon to the component carbon of the fatty acid which comprises the polyol ester which concerns on this invention obtained by a ¹³ C-NMR analysis method is 2 mass% or more, and is 2-15 mass%. More preferably, it is more preferably 2.5 to 12% by mass. The ratio of the tertiary carbon can be determined by a ¹³ C-NMR analysis method as the ratio of the integrated value of the tertiary carbon resonance spectrum to the integrated value of the resonance spectrum of all carbon.

  Moreover, as a polyhydric alcohol which comprises the polyol ester concerning this invention, at least 1 sort (s) chosen from a pentaerythritol, ditrimethylol propane, and dipentaerythritol is used.

  The polyhydric alcohol constituting the polyol ester according to the present invention may be any one of pentaerythritol, ditrimethylolpropane and dipentaerythritol, or may be a mixed alcohol of two or more of these. Good. From the viewpoint of ensuring suitable handling properties, the polyhydric alcohol constituting the polyol ester according to the present invention preferably contains pentaerythritol.

  The polyol ester according to the present invention may be composed of one kind of polyol ester having a single structure, or may be a mixture of two or more kinds of polyol esters having different structures.

  In addition, the polyol ester according to the present invention is a complete ester of one fatty acid and one polyhydric alcohol, a complete ester of two or more fatty acids and one polyhydric alcohol, one fatty acid and two kinds. Either a complete ester with the above polyhydric alcohol, a complete ester with two or more fatty acids and two or more polyhydric alcohols may be used. A polyol ester using two or more fatty acids, particularly a polyol ester according to the present invention comprising two or more fatty acids in a complete ester molecule, is excellent in low temperature characteristics and compatibility with a refrigerant.

  The polyol ester according to the present invention is a complete ester in which all the hydroxyl groups of the polyhydric alcohol are esterified, but the refrigerating machine oil according to the present invention is used as long as the excellent effect of the polyol ester according to the present invention is not impaired. Moreover, you may contain the partial ester of the fatty acid and polyhydric alcohol whose ratio of branched chain type fatty acid is 40-100 mol%. Here, the partial ester means a polyol ester in which a part of the hydroxyl group of the polyhydric alcohol is not esterified and remains as a hydroxyl group. The partial ester is also present as a by-product when the polyol ester according to the present invention is synthesized. The purity of the polyol ester according to the present invention obtained by synthesis is defined by the hydroxyl value of the synthesized product, the hydroxyl value is preferably 20 mgKOH / g or less, more preferably 10 mgKOH / g or less, and even more preferably 5 mgKOH / g or less. .

The kinematic viscosity at 40 ° C. of the polyol ester according to the present invention is preferably 80 mm ² / s or more, more preferably from 80 to ² from the viewpoint of imparting appropriate lubricity when a refrigerating machine oil is constituted with this polyol ester. 1000 mm ² / s, more preferably 80~500mm ² / s, more preferably 80~400mm ² / s, particularly preferably 100 to 300 mm ² / s, most preferably 100 to 200 mm ² / s. Moreover, suitable handling property can be ensured by making kinematic viscosity in 40 degreeC of the polyol ester which concerns on this invention into 1000 mm < ² > / s or less, By coexistence of a carbon dioxide refrigerant by making it 80 mm < ² > / s or more. Therefore, suitable lubricity can be ensured.

  Although the base oil of this invention and the refrigerating machine oil of this invention may consist only of the polyol ester concerning this invention, you may further contain base oils other than the said polyol ester. Base oils other than the polyol ester according to the present invention include mineral oils, olefin polymers, naphthalene compounds, hydrocarbon oils such as alkylbenzene, and ester base oils other than the polyol esters according to the present invention, polyglycol, polyvinyl ether, Synthetic oils containing oxygen such as ketones, polyphenyl ethers, silicones, polysiloxanes, perfluoroethers may be used in combination. Among the above, as the synthetic oil containing oxygen, ester base oils other than the polyol ester according to the present invention, polyglycol, and polyvinyl ether are preferably used.

  In the refrigerating machine oil of the present invention, the content of the polyol ester according to the present invention is not particularly limited, but the total amount of refrigerating machine oil is superior in terms of various properties such as lubricity, refrigerant compatibility, thermal / chemical stability, and electrical insulation. On the basis, 80% by mass or more is preferable, 90% by mass or more is more preferable, 95% by mass or more is further preferable, and 100% by mass is particularly preferable. In addition, the content of the polyol ester according to the present invention in the base oil of the present invention is such that the content of the polyol ester according to the present invention based on the total amount of the refrigerating machine oil when the base oil is used in the refrigerating machine oil satisfies the above conditions. It is preferable to select so as to satisfy.

  Further, the refrigerating machine oil of the present invention contains the base oil of the present invention, and since the polyol ester according to the present invention is contained in the base oil, it can be suitably used even in a state where no additive is added. If necessary, it can be used in a form in which various additives are blended.

  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, thiophosphoric acid ester, amine salt of acidic phosphoric acid ester, chlorinated phosphoric acid ester and phosphorous acid At least one phosphorus compound selected from the group consisting of esters can be blended. These phosphorus compounds are esters of phosphoric acid or phosphorous acid with alkanols and polyether type alcohols or derivatives thereof.

  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 Examples include rhenyl diphenyl phosphate.

  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 Examples include hexadecyl acid phosphate, diheptadecyl acid phosphate, dioctadecyl acid phosphate, dioleyl acid phosphate, and the like.

  Examples of thiophosphates include tributyl phosphorothioate, tripentyl phosphorothionate, trihexyl phosphorothionate, triheptyl phosphorothionate, trioctyl phosphorothionate, trinonyl phosphorothionate, tridecyl phosphorothioate. Phorothionate, triundecyl phosphorothionate, tridodecyl phosphorothionate, tritridecyl phosphorothionate, tritetradecyl phosphorothionate, tripentadecyl phosphorothionate, trihexadecyl phosphorothionate, Triheptadecyl phosphorothioate, trioctadecyl phosphorothionate, trioleyl phosphorothionate, triphenyl phosphorothionate, tricresyl phosphorothionate, trixyl Cycloalkenyl phosphorothionate, cresyldiphenyl phosphorothionate, like carboxymethyl Les sulfonyl diphenyl phosphorothionate.

  Examples of the amine salt of acidic phosphate ester include methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, Examples thereof include 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, and the like. 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 and the like can be mentioned. Mixtures of these can also be used.

  When the refrigerating machine oil of the present invention contains the above phosphorus compound, the content of the phosphorus compound is not particularly limited, but is 0.01 to 5.5 based on the total amount of refrigerating machine oil (based on the total amount of base oil and all blended additives). The content is preferably 0% by mass, and more preferably 0.02 to 3.0% by mass. In addition, the said phosphorus compound may be used individually by 1 type, and may use 2 or more types together.

  Further, the refrigerating machine oil of the present invention has a phenyl glycidyl ether type epoxy compound, an alkyl glycidyl ether type epoxy compound, a glycidyl ester type epoxy compound, an allyl oxirane compound, an alkyl oxirane compound, an alicyclic type, in order to further improve its stability It can contain at least one epoxy compound selected from an epoxy compound, an epoxidized fatty acid monoester, and an epoxidized vegetable oil.

  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.

  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 diglycidyl ether, Examples thereof include trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, 1,6-hexanediol diglycidyl ether, sorbitol polyglycidyl ether, polyalkylene glycol monoglycidyl ether, and polyalkylene glycol diglycidyl ether.

  Specific examples of the glycidyl ester type epoxy compound include phenyl glycidyl ester, alkyl glycidyl ester, alkenyl glycidyl ester, etc., and preferable ones are glycidyl-2,2-dimethyloctanoate, glycidyl benzoate, glycidyl acrylate. And glycidyl methacrylate.

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

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

  Specific examples of the alicyclic epoxy compound include 1,2-epoxycyclohexane, 1,2-epoxycyclopentane, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, and 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-methyl Examples include cyclohexane and 4-epoxyethyl-1,2-epoxycyclohexane.

  Specific examples of the epoxidized fatty acid monoester include esters of an epoxidized fatty acid having 12 to 20 carbon atoms with 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.

  Specific examples of the epoxidized vegetable oil 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 preferred. Of these, phenyl glycidyl ether type epoxy compounds and glycidyl ester type epoxy compounds are more preferred, and phenyl glycidyl ether, butylphenyl glycidyl ether, alkyl glycidyl esters or mixtures thereof are particularly preferred.

  When the refrigerating machine oil of the present invention contains the epoxy compound, the content of the epoxy compound is not particularly limited, but is preferably 0.1 to 5.0% by mass based on the total amount of the refrigerating machine oil, 0.2 to More preferably, it is 2.0 mass%. In addition, the said epoxy compound may be used individually by 1 type, and may use 2 or more types together.

  Furthermore, the refrigerating machine oil of the present invention can contain conventionally known refrigerating machine oil additives as necessary in order to further enhance its performance. Examples of such additives include phenolic antioxidants such as di-tert-butyl-p-cresol and bisphenol A, phenyl-α-naphthylamine, N, N-di (2-naphthyl) -p-phenylenediamine, and the like. Amine-based antioxidants, anti-wear agents such as zinc dithiophosphate, extreme pressure agents such as chlorinated paraffin and sulfur compounds, oil-based agents such as fatty acids, antifoaming agents such as silicones, metal inertness such as benzotriazole Agents, viscosity index improvers, pour point depressants, detergent dispersants and the like. These additives may be used individually by 1 type, and may be used in combination of 2 or more type. The content 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.

Kinematic viscosity at 40 ° C. of the refrigerating machine oil of the present invention is preferably 80 mm ² / s or more, more preferably 80~1000mm ² / s, more preferably 80~500mm ² / s, more preferably 80～400Mm ² / s, particularly preferably from 100 to 300 mm ² / s, most preferably 100 to 200 mm ² / s. The kinematic viscosity at 100 ° C. is preferably 1 to 100 mm ² / s, more preferably 5 to 50 mm ² / s.

  Further, the volume resistivity of the refrigerating machine oil of the present invention is not particularly limited, but is preferably 0.01 TΩ · cm or more, more preferably 0.1 TΩ · cm or more, and most preferably 1.0 TΩ · cm or more. . In particular, when it is used for a hermetic refrigerator, high electrical insulation tends to be required. In the present invention, the volume resistivity means a value at 25 ° C. measured based on JIS C 2101 “Electrical insulating oil test method”.

  Further, the water content of the refrigerating machine oil of the present invention is not particularly limited, but can be preferably 200 ppm or less, more preferably 100 ppm or less, and most preferably 50 ppm or less based on the total amount of refrigerating machine oil. In particular, when it is used for a hermetic refrigerator, it is required to have a low water content from the viewpoint of the effect on oil stability and electrical insulation.

  Further, the acid value of the refrigerating machine oil of the present invention is not particularly limited, but it prevents the corrosion of the metal used in the refrigerating machine or piping, and prevents the decomposition of the ester oil contained in the refrigerating machine oil of the present invention. Therefore, it is preferably 0.1 mgKOH / g or less, more preferably 0.05 mgKOH / g or less. In addition, in this invention, an acid value means the acid value measured based on JISK 2501 "Petroleum products and lubricating oil-neutralization number test method".

  Further, the ash content of the refrigerating machine oil of the present invention is not particularly limited. However, in order to enhance the stability of the refrigerating machine oil of the present invention and suppress the generation of sludge and the like, the ash content is preferably 100 ppm or less, more preferably 50 ppm or less. In the present invention, ash means the value of ash measured based on JISK 2272 “Testing method for ash and sulfated ash of crude oil and petroleum products”.

  The refrigerating machine oil of the present invention exhibits an excellent effect when used together with a carbon dioxide refrigerant. However, the refrigerant used may be a carbon dioxide refrigerant alone, or a carbon dioxide refrigerant and other refrigerants. It may be a mixed refrigerant with a refrigerant. Examples of other refrigerants include HFC refrigerants, fluorine-containing ether refrigerants such as bar fluoroethers, dimethyl ether, ammonia, and hydrocarbons.

  Examples of the HFC refrigerant 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, HFC such as 1,1,2-tetrafluoroethane (HFC-134a), 1,1,1-trifluoroethane (HFC-143a), 1,1-difluoroethane (HFC-152a), or two or more of these And the like. 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.

  Specific examples of the fluorinated ether refrigerant include HFE-134p, HFE-245mc, HFE-236mf, HFE-236me, HFE-338mcf, HFE-365mcf, HFE-245mf, HFE-347mmy, HFE-347mcc, HFE. -125, HFE-143m, HFE-227me and the like.

  As the hydrocarbon refrigerant, a gas refrigerant at 25 ° C. and 1 atm is preferably used. 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 thereof is preferable.

  The mixing ratio of carbon dioxide refrigerant and HFC refrigerant, fluorine-containing ether refrigerant, dimethyl ether and ammonia is not particularly limited, but the total amount of refrigerant used in combination with carbon dioxide refrigerant is preferably 1 with respect to 100 parts by mass of carbon dioxide. -200 mass parts, More preferably, it is 10-100 mass parts. In a preferred embodiment, the carbon dioxide refrigerant and the hydrofluorocarbon and / or hydrocarbon are preferably 1 to 200 parts by mass, more preferably 10 to 10 parts by mass as the total amount of the hydrofluorocarbon and hydrocarbon with respect to 100 parts by mass of carbon dioxide. The mixed refrigerant | coolant which mix | blended 100 mass parts is mentioned.

  The refrigerating machine oil of the present invention is usually present in the form of a refrigerating machine fluid composition mixed with a refrigerant containing carbon dioxide as described above in refrigerating and air-conditioning equipment. The blending ratio of the refrigerating machine oil and the refrigerant in this composition is not particularly limited, but the refrigerating machine oil 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.

  The refrigerating machine oil of the present invention is preferably used for a room air conditioner, a packaged air conditioner and a refrigerator having a reciprocating or rotating hermetic compressor because of its excellent electrical characteristics and low hygroscopicity. Moreover, the refrigerating machine oil of the present invention is preferably used for cooling devices for automobile air conditioners, dehumidifiers, water heaters, freezers, refrigerated warehouses, vending machines, showcases, chemical plants, and the like. Furthermore, the refrigerating machine oil of the present invention is also preferably used for those having a centrifugal compressor.

  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 1-11, Comparative Examples 1-5]
In Examples 1 to 11 and Comparative Examples 1 to 5, base oils consisting of complete esters of fatty acids and alcohols shown in Table 1 were prepared. The kinematic viscosities at 40 ° C. and 100 ° C. of the obtained base oil are also shown in Table 1.

  In Table 1, “PET” in the column of “alcohol composition ratio” means pentaerythritol, “DiTMP” means ditrimethylolpropane, and “DiPET” means dipentaerythritol. In Table 1, in the column of “fatty acid composition”, linear fatty acids having m carbon atoms are shown as nCm acids, and branched fatty acids having m carbon atoms are shown as iCm acids. For example, “nC8 acid” means a straight chain fatty acid having 8 carbon atoms, and “iC14 acid” means a branched chain fatty acid having 14 carbon atoms. In the same column, “2EH acid” means 2-ethylhexanoic acid.

  Next, each base oil obtained in Examples 1 to 11 and Comparative Examples 1 to 5 was used as a refrigerating machine oil, and the following evaluation tests were performed.

(Refrigerant compatibility)
Based on “Testing compatibility with refrigerant” in JIS-K-2211 “Refrigerator oil”, 2 g of refrigerating machine oil is blended with 2 g of carbon dioxide refrigerant. Whether it was dissolved or not was evaluated as “compatible”, “white turbidity”, and “separation”. The obtained results are shown in Table 1.

(Refrigerant melt viscosity)
The apparatus shown in FIG. 1 includes a pressure vessel 5 (stainless steel, internal volume: 200 ml) having a viscometer 1, a pressure gauge 2, a thermocouple 3, and a stirrer 4, and a constant temperature for controlling the temperature in the pressure vessel 5. A tank 6 and a sampling cylinder 8 provided with a valve and connected to the pressure vessel 5 through a flow path 7 are provided. The sampling cylinder 8 and the flow path 7 are detachable, and the sampling cylinder 8 measures its weight after vacuum degassing or after weighing a mixture of carbon dioxide refrigerant and refrigerating machine oil. It is possible to do. The thermocouple 3 and the thermostat 6 are each electrically connected to a temperature control means (not shown), and sample oil (or a mixture of carbon dioxide refrigerant and refrigerator oil) is transferred from the thermocouple 3 to the temperature control means. A data signal relating to the temperature of the refrigeration oil is sent, and a control signal is sent from the temperature control means to the thermostatic chamber 6 to control the temperature of the refrigerating machine oil or the mixture. Furthermore, the viscometer 1 is electrically connected to an information processing device (not shown), and measurement data relating to the viscosity of the liquid in the pressure vessel 5 is sent from the viscometer 1 to the information processing device, and a predetermined condition is obtained. It is possible to measure the viscosity below.

  In this test, first, 100 g of refrigerating machine oil was put in the pressure vessel 5 and the inside of the vessel was vacuum degassed. Then, a carbon dioxide refrigerant was introduced, and the mixture of the carbon dioxide refrigerant and the refrigerating machine oil was stirred with the stirrer 4. And it adjusted so that it might become 5MPa at 40 degreeC, removing a refrigerant | coolant. After stabilization, the viscosity of the mixture of carbon dioxide refrigerant and refrigeration oil was measured. Table 1 shows the measurement results of the obtained refrigerant dissolution viscosity at 40 ° C.

(Electrical insulation (volume resistivity))
Based on JIS-C-2101 “Electrical Insulating Oil Test Method”, volume resistivity of refrigerating machine oil at 25 ° C. was measured. The obtained results are shown in Table 1.

(Thermal stability (acid value))
In an autoclave, 90 g of refrigerating machine oil, 10 g of carbon dioxide refrigerant and a catalyst (iron, copper, and aluminum wires) were sealed, and then heated to 200 ° C. and held for 2 weeks. The acid value of the refrigerator oil after 2 weeks was measured. The obtained results are shown in Table 1.

(Lubricity (Abrasion amount))
Based on ASTM D 2670 “FALEXWEAR TEST”, the running-in operation was performed for 1 minute under a load of 150 lb under the condition of the temperature of the refrigerator oil of 100 ° C. Next, the test machine was operated for 2 hours under a load of 250 lb while blowing carbon dioxide refrigerant 10 L / h, and the amount of wear of the test journal (pin) after the test was measured. The obtained results are shown in Table 1.

  As is clear from the results shown in Table 1, when the refrigerating machine oils of Examples 1 to 11 were used together with a carbon dioxide refrigerant, all of lubricity, refrigerant compatibility, thermal stability, electrical insulation and kinematic viscosity were obtained. It can be seen that the performance of is well balanced.

It is a schematic block diagram which shows the refrigerant | coolant melt viscosity measuring apparatus used in the Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Viscometer, 2 ... Pressure gauge, 3 ... Thermocouple, 4 ... Stirrer, 5 ... Pressure vessel, 6 ... Constant temperature bath, 7 ... Flow path, 8 ... Sampling cylinder.

Claims (5)

  A fatty acid in which the ratio of branched chain fatty acids having 14, 16, 18, 20, and 22 carbon atoms is 80 to 100 mol%, and at least one polyhydric alcohol selected from pentaerythritol, ditrimethylolpropane, and dipentaerythritol; A base oil for refrigerating machine oil for carbon dioxide refrigerant, characterized by containing a complete ester of   2. The base oil for a refrigerating machine oil for carbon dioxide refrigerant according to claim 1, wherein the proportion of the branched chain fatty acid having 16, 18 and 20 carbon atoms in the fatty acid is 80 to 100 mol%. The ratio of tertiary carbon to the constituent carbon of the fatty acid obtained by ¹³ C-NMR analysis method is 2% by mass or more, for a refrigerating machine oil for carbon dioxide refrigerant according to claim 1 or 2 Base oil.   A refrigerating machine oil for carbon dioxide refrigerant comprising the base oil for refrigerating machine oil for carbon dioxide refrigerant according to any one of claims 1 to 3.   A fatty acid in which the ratio of branched chain fatty acids having 14, 16, 18, 20, and 22 carbon atoms is 80 to 100 mol%, and at least one polyhydric alcohol selected from pentaerythritol, ditrimethylolpropane, and dipentaerythritol; A refrigerating machine oil for carbon dioxide refrigerant, comprising a complete ester of

Images