JP6736050B2 - Antiwear additive, refrigerator oil and working fluid composition for refrigerator - Google Patents

Description

The present invention relates to antiwear additives, refrigerating machine oils and working fluid compositions for refrigerators.

Refrigerators such as refrigerators, car air conditioners, room air conditioners, and vending machines include a compressor for circulating a refrigerant in a refrigeration cycle. Then, the compressor is filled with refrigerating machine oil for lubricating the sliding member. Refrigerating machine oils generally contain a base oil and additives which are compounded according to the desired properties. Examples of the additives include sulfur-based antiwear agents, phosphorus-based antiwear agents, alcohol-based antiwear agents, polyhydric alcohol partial ester-based wear agents that are added to improve the wear resistance of sliding members in refrigerators. Inhibitors, polyhydric alcohol partial ether antiwear agents, etc. are known (see Patent Documents 1 to 3).

JP-A-3-243697 JP, 2001-200285, A JP, 2011-178990, A

An object of the present invention is to provide a wear resistance additive capable of improving the wear resistance of a sliding member, and a refrigerating machine oil and a refrigerating machine working fluid composition containing the same.

The present invention provides an antiwear additive containing at least one selected from the group consisting of silicone oil, a modified silicone oil obtained by modifying the ends of the main chain of the silicone oil with polyalkylene glycol, and a fluorinated silicone oil.

The present invention also provides a refrigerating machine oil containing a base oil and the above antiwear additive.

The content of the antiwear additive is preferably 0.1 mass ppm or more and 500 mass ppm or less based on the total amount of the refrigerating machine oil.

The base oil preferably contains an ester of a fatty acid and an alcohol including a polyhydric alcohol.

The ester is at least one selected from polyhydric alcohols having 2 to 4 hydroxyl groups, at least one selected from polybasic acids having 6 to 12 carbon atoms, a monohydric alcohol having 4 to 18 carbon atoms, and It is preferable to contain an ester synthesized from at least one selected from monovalent fatty acids having 2 to 12 carbon atoms.

Further, the present invention provides a working fluid composition for a refrigerator containing the above-mentioned refrigerator oil and a refrigerant.

ADVANTAGE OF THE INVENTION According to this invention, the abrasion resistance additive which can improve the abrasion resistance of a sliding member, and the refrigerator oil and refrigerator working fluid composition containing the same can be provided.

The antiwear additive according to the present embodiment is at least one selected from the group consisting of silicone oil, modified silicone oil in which the end of the main chain of silicone oil is modified with polyalkylene glycol, and fluorinated silicone oil (hereinafter, “ Also referred to as "predetermined silicone oil").

That is, a composition containing at least one selected from the group consisting of silicone oil, a modified silicone oil obtained by modifying the ends of the main chain of silicone oil with polyalkylene glycol, and a fluorinated silicone oil is suitable as an antiwear additive. Used for. Further, a composition containing at least one selected from the group consisting of silicone oil, a modified silicone oil obtained by modifying the end of the main chain of the silicone oil with polyalkylene glycol, and a fluorinated silicone oil is used to produce an antiwear additive. It is preferably used for.

Examples of the silicone oil include dimethylpolysiloxane, methylphenylpolysiloxane, and diphenylpolysiloxane. Among them, dimethylpolysiloxane is particularly preferable because of its versatility and availability.

The modified silicone oil in which the end of the main chain of silicone oil is modified with polyalkylene glycol includes modified silicone oil in which the end of the main chain of dimethyl polysiloxane is modified with polypropylene glycol, and the end of the main chain of dimethyl polysiloxane with polyethylene glycol. An example is a modified modified silicone oil.

Examples of the fluorinated silicone oil include fluorinated silicone oil in which the side chain of dimethylpolysiloxane is modified with a fluoroalkyl group, and fluorinated silicone oil in which the side chain of dimethylpolysiloxane is modified with a fluoropolyether group.

The kinematic viscosity of a given silicone oil is not particularly limited. The kinematic viscosity of the predetermined silicone oil at 25° C. is preferably 50 mm ² /s or more, more preferably 100 mm ² /s or more, still more preferably 300 mm ² /s or more, from the viewpoint of being more excellent in abrasion resistance, as one aspect. There also is preferably 100,000 mm ² / s or less, more preferably 40000 mm ² / s, more preferably not more than 10000 mm ² / s.

The kinematic viscosity of a given silicone oil at 25° C. is preferably 100 mm ² because, in another aspect, it has a high wear resistance effect per addition amount and excellent dispersibility in a lubricating oil and storage stability over a long period of time. / s or higher, more preferably 500 mm ² / s or more, more preferably 5000 mm ² / s or more, particularly preferably 20000 mm ² / s or more, and preferably 100,000 mm ² / s or less, more preferably 80000Mm ² / s Hereafter, it is more preferably 60,000 mm ² /s or less.

The antiwear additive may be composed of a predetermined silicone oil, and may further contain other components in addition to the predetermined silicone oil.

The antiwear additive according to the present embodiment is suitable for use in a lubricating oil that requires improved wear resistance, and is particularly suitable for a refrigerating machine oil.

The refrigerating machine oil according to the present embodiment contains at least one selected from the group consisting of a base oil, a silicone oil, a modified silicone oil obtained by modifying the end of the main chain of the silicone oil with a polyalkylene glycol, and a fluorinated silicone oil. Antiwear additive to The refrigerating machine oil according to the present embodiment includes a mode in which the base oil and the antiwear additive according to the present embodiment are contained.

As the base oil, hydrocarbon oil, oxygen-containing oil and the like can be used. Examples of the hydrocarbon oil include mineral oil type hydrocarbon oil and synthetic type hydrocarbon oil. Examples of the oxygen-containing oil include ester, polyvinyl ether, polyalkylene glycol, carbonate, ketone, polyphenyl ether, silicone, polysiloxane, and perfluoroether. The base oil preferably contains an oxygen-containing oil, and more preferably contains an ester.

Mineral oil-based hydrocarbon oil is a lubricant fraction obtained by distilling crude oil such as paraffin-based and naphthene-based crude oil under atmospheric pressure and vacuum distillation to remove solvent, solvent refinement, hydrorefining, hydrocracking, solvent desorption. It can be obtained by purification by a method such as wax, hydrodewaxing, clay treatment, and sulfuric acid washing. These purification methods may be used alone or in combination of two or more.

Examples of the synthetic hydrocarbon oil include alkylbenzene, alkylnaphthalene, poly α-olefin (PAO), polybutene, ethylene-α-olefin copolymer and the like.

Examples of the ester include aromatic ester, dibasic acid ester, polyol ester, complex ester, carbonic acid ester and a mixture thereof. The ester is preferably an ester of a fatty acid and an alcohol containing a polyhydric alcohol (polyol ester, complex ester) from the viewpoint of more effectively exhibiting the abrasion resistance of the anti-wear agent according to the present embodiment, and the complex ester. Is more preferable.

The content of the base oil is preferably 80 mass% or more, more preferably 90 mass% or more, still more preferably 95 mass% or more, based on the total amount of the refrigerating machine base oil. The content of the ester of a fatty acid and an alcohol containing a polyhydric alcohol is preferably 10% by mass or more, more preferably 30% by mass or more, still more preferably 50% by mass or more, based on the total amount of the refrigerating machine oil. The content of the complex ester is, based on the total amount of the refrigerating machine oil, preferably 5% by mass or more, more preferably 10% by mass or more, and further preferably 20% by mass or more.

Polyol ester is an ester synthesized from polyhydric alcohol and fatty acid. As the fatty acid, saturated fatty acid is preferably used. The fatty acid preferably has 4 to 20 carbon atoms, more preferably has 4 to 18 carbon atoms, still more preferably has 4 to 9 carbon atoms, and particularly preferably has 5 to 9 carbon atoms. The polyol ester may be a partial ester in which some of the hydroxyl groups of the polyhydric alcohol are not esterified and remain as hydroxyl groups, or may be a complete ester in which all hydroxyl groups are esterified. It may be a mixture of an ester and a complete ester. The hydroxyl value of the polyol ester is preferably 10 mgKOH/g or less, more preferably 5 mgKOH/g or less, and further preferably 3 mgKOH/g or less.

Of the fatty acids constituting the polyol ester, the proportion of fatty acids having 4 to 20 carbon atoms is preferably 20 to 100 mol%, more preferably 50 to 100 mol%, and 70 to 100 mol%. Is more preferable, and 90 to 100 mol% is particularly preferable.

Specific examples of the fatty acid having 4 to 20 carbon atoms include linear or branched butanoic acid, linear or branched pentanoic acid, linear or branched hexanoic acid, linear or branched. Heptanoic acid, linear or branched octanoic acid, linear or branched nonanoic acid, linear or branched decanoic acid, linear or branched undecanoic acid, linear or branched Dodecanoic acid, linear or branched tridecanoic acid, linear or branched tetradecanoic acid, linear or branched pentadecanoic acid, linear or branched hexadecanoic acid, linear or branched Heptadecanoic acid, linear or branched octadecanoic acid, linear or branched nonadecanoic acid, linear or branched icosanoic acid. More specifically, a fatty acid having a branch at the α-position and/or the β-position is preferable, and 2-methylpropanoic acid, 2-methylbutanoic acid, 2-methylpentanoic acid, 2-methylhexanoic acid, 2-ethylpentanoic acid, 2-Methylheptanoic acid, 2-ethylhexanoic acid, 3,5,5-trimethylhexanoic acid, 2-ethylhexadecanoic acid and the like are more preferable, and among them, 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid are more preferable. preferable.

The fatty acid may contain a fatty acid other than the C4-20 fatty acid. As the fatty acid other than the C4-20 fatty acid, for example, a C21-24 fatty acid may be contained. Specific examples thereof include linear or branched henicoic acid, linear or branched docosanoic acid, linear or branched tricosanoic acid, and linear or branched tetracosanoic acid.

As the polyhydric alcohol constituting the polyol ester, a polyhydric alcohol having 2 to 6 hydroxyl groups is preferably used. As carbon number of polyhydric alcohol, 4-12 are preferable and 5-10 are more preferable. Specifically, hindered alcohols such as neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, di-(trimethylolpropane), tri-(trimethylolpropane), pentaerythritol, and dipentaerythritol are preferable. .. Pentaerythritol or a mixed ester of pentaerythritol and dipentaerythritol) is more preferable because it has particularly excellent compatibility with a refrigerant and hydrolysis stability.

The complex ester is, for example, an ester synthesized by the following method (a) or (b).
(A) The molar ratio of the polyhydric alcohol and the polybasic acid is adjusted to synthesize an ester intermediate in which a part of the carboxyl group of the polybasic acid remains without being esterified, and then the residual carboxyl group is Method of esterification with monohydric alcohol (b) The molar ratio of polyhydric alcohol and polybasic acid is adjusted to synthesize an ester intermediate in which some of the hydroxyl groups of the polyhydric alcohol remain without being esterified, Next, a method of esterifying the remaining hydroxyl group with a monovalent fatty acid

The complex ester obtained by the method (b) is slightly inferior in stability to the complex ester obtained by the method (a) because a relatively strong acid is generated when it is hydrolyzed when used as a refrigerating machine oil. There is a tendency. As the complex ester in the present embodiment, a complex ester having higher stability and obtained by the method (a) above is preferable.

As the complex ester, at least one selected from polyhydric alcohols having 2 to 4 hydroxyl groups, at least one selected from polybasic acids having 6 to 12 carbon atoms, and monovalent having 4 to 18 carbon atoms An ester synthesized from an alcohol and at least one selected from monovalent fatty acids having 2 to 12 carbon atoms is preferable.

Examples of the polyhydric alcohol having 2 to 4 hydroxyl groups include neopentyl glycol, trimethylolpropane, pentaerythritol and the like. As the polyhydric alcohol having 2 to 4 hydroxyl groups, neopentyl glycol and trimethylolpropane are preferred from the viewpoint of securing a suitable viscosity when using a complex ester as a base oil and obtaining good low temperature properties. Neopentyl glycol is more preferable from the viewpoint that viscosity can be widely adjusted.

From the viewpoint of further improving the lubricity, the polyhydric alcohol constituting the complex ester is a polyhydric alcohol having 2 to 4 hydroxyl groups, and a polyhydric alcohol having 2 to 10 carbon atoms other than neopentyl glycol. It is preferable to further contain the dihydric alcohol. Examples of the dihydric alcohol having 2 to 10 carbon atoms other than neopentyl glycol include ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, 2-methyl-1,3-propanediol, 3-methyl-1,5. -Pentanediol, 2,2-diethyl-1,3-pentanediol and the like are mentioned, and butanediol having a well-balanced property of the synthesized base oil is preferable. Examples of butanediol include 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and 2,3-butanediol. Butanediol and 1,4-butanediol are more preferable. The dihydric alcohol having 2 to 10 carbon atoms other than neopentyl glycol is preferably 1.2 mol or less and 0.8 mol or less with respect to 1 mol of the polyhydric alcohol having 2 to 4 hydroxyl groups. Is more preferable and 0.4 mol or less is further preferable.

Examples of the polybasic acid having 6 to 12 carbon atoms include adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid and trimellitic acid. Among these, adipic acid and sebacic acid are preferable, and adipic acid is more preferable, from the viewpoint that the synthesized ester has an excellent balance of properties and is easily available. The polybasic acid having 6 to 12 carbon atoms is preferably 0.4 mol to 4 mol, and 0.5 mol to 3 mol per 1 mol of the polyhydric alcohol having 2 to 4 hydroxyl groups. It is more preferable that the amount is 0.6 mol to 2.5 mol.

Examples of the monohydric alcohol having 4 to 18 carbon atoms include linear or branched butanol, linear or branched pentanol, linear or branched hexanol, linear or branched heptanol, linear or branched octanol, and linear chain. Or, a branched nonanol, a linear or branched decanol, a linear or branched dodecanol, or an aliphatic alcohol such as oleyl alcohol can be used. The monohydric alcohol having 4 to 18 carbon atoms is preferably a monohydric alcohol having 6 to 10 carbon atoms, and more preferably a monohydric alcohol having 8 to 10 carbon atoms, from the viewpoint of the balance of properties. Among these, 2-ethylhexanol and 3,5,5-trimethylhexanol are more preferable from the viewpoint of improving the low-temperature characteristics of the synthesized complex ester.

Examples of the monohydric fatty acid having 2 to 12 carbon atoms include straight-chain or branched ethanoic acid, straight-chain or branched propanoic acid, straight-chain or branched butanoic acid, straight-chain or branched pentanoic acid, straight-chain or branched hexane. Examples thereof include acids, straight-chain or branched heptanoic acid, straight-chain or branched octanoic acid, straight-chain or branched nonanoic acid, straight-chain or branched decanoic acid, and straight-chain or branched dodecanoic acid. The monovalent fatty acid having 2 to 12 carbon atoms is preferably a monovalent fatty acid having 8 to 10 carbon atoms, and among them, 2-ethylhexanoic acid and 3,5,5-trimethyl are more preferable from the viewpoint of low temperature characteristics. Hexanoic acid.

The content of the antiwear additive is preferably 0.1 mass ppm or more, more preferably 1 mass ppm or more, still more preferably 3 mass, based on the total amount of the refrigerating machine oil, from the viewpoint of improving lubricity under a refrigerant atmosphere. ppm or more, particularly preferably 5 mass ppm or more. The content of the antiwear additive is preferably 500 mass ppm or less, more preferably 100 mass ppm or less, and further preferably 50 mass ppm or less, based on the total amount of the refrigerating machine oil, from the viewpoint of precipitation properties in a refrigerant atmosphere. .. An antiwear additive containing a predetermined silicone oil exhibits excellent antiwear properties with a smaller content as compared with conventional antiwear additives (for example, the antiwear agents described in Patent Documents 1 to 3).

The refrigerating machine oil may further contain other additives in addition to the antiwear additive according to the present embodiment. Examples of other additives include antioxidants, friction modifiers, antiwear agents other than the antiwear additive according to the present embodiment, extreme pressure agents, rust preventives, metal deactivators, and the like.

Kinematic viscosity at 40 ° C. of the refrigerating machine oil is preferably ^{3 mm} 2 / s or more, more preferably ^{4 mm} 2 / s or more, more preferably at ^{5 mm} 2 / s or more, and preferably not more than 1000 mm ² / s, more preferably Can be 500 mm ² /s or less, and more preferably 400 mm ² /s or less. The kinematic viscosity of the refrigerating machine oil at 100° C. is preferably 1 mm ² /s or more, more preferably 2 mm ² /s or more, and preferably 100 mm ² /s or less, more preferably 50 mm ² /s or less. You can

The pour point of the refrigerating machine oil can be preferably -10°C or lower, more preferably -20°C or lower.

The volume resistivity of the refrigerating machine oil is preferably 1.0×10 ⁹ Ω·m or more, more preferably 1.0×10 ¹⁰ Ω·m or more, still more preferably 1.0×10 ¹¹ Ω·m or more. be able to. In particular, when it is used for a closed type refrigerator, it is preferable that it has high electric insulation. The volume resistivity in the present invention means a value at 25° C. measured according to JIS C2101:1999 “Electrical Insulating Oil Test Method”.

The water content of the refrigerating machine oil can be preferably 200 ppm or less, more preferably 100 ppm or less, still more preferably 50 ppm or less, based on the total amount of the refrigerating machine oil. In particular, when used for a closed type refrigerator, it is preferable that the water content is low from the viewpoint of the influence on the thermal/chemical stability of the refrigerator oil and the electric insulation.

The acid value of the refrigerating machine oil can be preferably 1.0 mgKOH/g or less, more preferably 0.1 mgKOH/g or less, from the viewpoint of preventing corrosion of the metal used in the refrigerator or piping. The acid value in the present invention means the acid value measured according to JIS K2501:2003 "Petroleum products and lubricating oils-Neutralization number test method".

The ash content of the refrigerating machine oil can be preferably 100 ppm or less, and more preferably 50 ppm or less, from the viewpoint of increasing the thermal and chemical stability of the refrigerating machine oil and suppressing the generation of sludge and the like. The ash content in the present invention means the value of ash content measured according to JIS K2272: 1998 "Crude oil and petroleum products-Test method for ash content and sulfated ash content".

The working fluid composition for a refrigerator according to the present embodiment is selected from the group consisting of a base oil, a silicone oil, a modified silicone oil obtained by modifying the end of the main chain of the silicone oil with a polyalkylene glycol, and a fluorinated silicone oil. A refrigerating machine oil containing at least one wear additive and a refrigerant. The working fluid composition for a refrigerator according to the present embodiment includes a mode including the refrigerator oil according to the present embodiment and a refrigerant.

Examples of the refrigerant include saturated fluorohydrocarbon refrigerants, unsaturated fluorohydrocarbon refrigerants, hydrocarbon refrigerants, fluorine-containing ether refrigerants such as perfluoroethers, bis(trifluoromethyl)sulfide refrigerants, and trifluoroiodomethane. Examples of the refrigerant include natural refrigerants such as ammonia and carbon dioxide.

The saturated fluorohydrocarbon refrigerant is preferably a saturated fluorohydrocarbon having 1 to 3 carbon atoms, and more preferably 1 to 2 carbon atoms. Specifically, difluoromethane (R32), trifluoromethane (R23), pentafluoroethane (R125), 1,1,2,2-tetrafluoroethane (R134), 1,1,1,2-tetrafluoroethane (R134a), 1,1,1-trifluoroethane (R143a), 1,1-difluoroethane (R152a), fluoroethane (R161), 1,1,1,2,3,3,3-heptafluoropropane ( R227ea), 1,1,1,2,3,3-hexafluoropropane (R236ea), 1,1,1,3,3,3-hexafluoropropane (R236fa), 1,1,1,3,3 -Pentafluoropropane (R245fa), 1,1,1,3,3-pentafluorobutane (R365mfc), or a mixture of two or more thereof.

The saturated fluorohydrocarbon refrigerant is appropriately selected from the above depending on the application and the required performance, but for example, R32 alone; R23 alone; R134a alone; R125 alone; R134a/R32=60 to 80 mass%/40 ˜20 mass% mixture; R32/R125=40-70 mass%/60-30 mass% mixture; R125/R143a=40-60 mass%/60-40 mass% mixture; R134a/R32/R125=60 Mass%/30 mass%/10 mass% mixture; R134a/R32/R125=40-70 mass%/15-35 mass%/5-40 mass% mixture; R125/R134a/R143a=35-55 mass% A preferable example is a mixture of /1 to 15% by mass/40 to 60% by mass. More specifically, a mixture of R134a/R32=70/30% by mass; a mixture of R32/R125=60/40% by mass; a mixture of R32/R125=50/50% by mass (R410A); R32/R125=45 /55 mass% mixture (R410B); R125/R143a=50/50 mass% mixture (R507C); R32/R125/R134a=30/10/60 mass% mixture; R32/R125/R134a=23/25 /52 mass% mixture (R407C); R32/R125/R134a=25/15/60 mass% mixture (R407E); R125/R134a/R143a=44/4/52 mass% mixture (R404A) be able to.

As the unsaturated fluorohydrocarbon (HFO) refrigerant, fluoropropene having a fluorine number of 3 to 5 is preferable, and 1,2,3,3,3-pentafluoropropene (HFO-1225ye), 1,3,3,3. 3-tetrafluoropropene (HFO-1234ze), 2,3,3,3-tetrafluoropropene (HFO-1234yf), 1,2,3,3-tetrafluoropropene (HFO-1234ye), and 3,3,3 It is preferable that it is any one kind of 3-trifluoropropene (HFO-1243zf) or a mixture of two or more kinds. From the viewpoint of the physical properties of the refrigerant, one or more selected from HFO-1225ye, HFO-1234ze, and HFO-1234yf are preferable.

The hydrocarbon refrigerant is preferably a hydrocarbon having 1 to 5 carbon atoms, and specifically, for example, methane, ethylene, ethane, propylene, propane (R290), cyclopropane, normal butane, isobutane, cyclobutane, methylcyclopropane, 2-Methylbutane, normal pentane, or a mixture of two or more thereof. Among these, those which are gaseous at 25° C. and 1 atm are preferably used, and propane, normal butane, isobutane, 2-methyl butane or a mixture thereof is preferable.

The refrigerator oil according to the present embodiment is usually present in a refrigerator in the form of a working fluid composition for a refrigerator mixed with a refrigerant. The content of the refrigerating machine oil in the working fluid composition for a refrigerator according to the present embodiment is not particularly limited, but is preferably 1 part by mass or more, more preferably 2 parts by mass or more, relative to 100 parts by mass of the refrigerant, Further, it is preferably 500 parts by mass or less, more preferably 400 parts by mass or less.

The refrigerator oil and the working fluid composition for a refrigerator according to the present embodiment include an air conditioner having a reciprocating or rotating hermetic compressor, a refrigerator, an open or hermetic car air conditioner, a dehumidifier, a water heater, and a freezer. It is preferably used for freezers, refrigerating warehouses, vending machines, showcases, cooling devices for chemical plants, etc., and those having a centrifugal compressor.

Hereinafter, the present invention will be described more specifically based on Examples, but the present invention is not limited to the following Examples.

As the base oil, the esters (A-1) to (A-5) produced by the following procedure were used.
[Production of ester (A-1)]
Ester intermediate by reacting neopentyl glycol, 1,4-butanediol and adipic acid with neopentyl glycol/1,4-butanediol/adipic acid=1/0.3/2.4 (molar ratio) Got This ester intermediate was further reacted with 3,5,5-trimethylhexanol at neopentyl glycol/3,5,5-trimethylhexanol=1/2.5 (molar ratio) without using a catalyst or solvent. Then, the remaining unreacted material was removed by distillation. Then, in the final step, adsorption treatment (clay treatment) was performed to remove a trace amount of impurities, and an ester (kinematic viscosity at 40° C., 67.8 mm ² /s, viscosity index 145, pour point −50° C.) was obtained.

[Production of ester (A-2)]
Trimethylolpropane and adipic acid were reacted with trimethylolpropane/adipic acid=1/2.4 (molar ratio) to obtain an ester intermediate. 2-Ethylhexanol was further reacted with this ester intermediate so that trimethylolpropane/2-ethylhexanol=1/1.9 (molar ratio), and the remaining unreacted material was removed by distillation. Then, in the final step, adsorption treatment (clay clay treatment) was performed to remove a trace amount of impurities, and an ester (kinematic viscosity at 40° C., 68.8 mm ² /s, viscosity index 120, pour point −55° C.) was obtained.

[Example 3: Production of ester (A-3)]
Neopentyl glycol and adipic acid were reacted with neopentyl glycol/adipic acid=1/0.8 (molar ratio) to obtain an ester intermediate. This ester intermediate was further reacted with 3,5,5-trimethylhexanoic acid so that neopentyl glycol/3,5,5-trimethylhexanoic acid=1/0.5 (molar ratio) and remained. Unreacted material was removed by distillation. Then, in the final step, adsorption treatment (clay clay treatment) was performed to remove a small amount of impurities, and an ester (kinematic viscosity 71.5 mm ² /s, viscosity index 114, pour point −55° C.) was obtained.

[Example 4: Production of ester (A-4)]
Ester intermediate by reacting neopentyl glycol, 1,4-butanediol and adipic acid with neopentyl glycol/1,4-butanediol/adipic acid=1/0.1/1.2 (molar ratio) Got This ester intermediate was further reacted with 3,5,5-trimethylhexanol at neopentyl glycol/3,5,5-trimethylhexanol=1/0.3 (molar ratio) without using a catalyst or solvent. Then, the remaining unreacted material was removed by distillation. Then, in the final step, an adsorption treatment (clay clay treatment) was performed to remove a trace amount of impurities, and an ester (kinematic viscosity at 40° C. of 275.9 mm ² /s, viscosity index 117, pour point of −35° C.) was obtained.

[Example 5: Production of ester (A-5)]
Neopentyl glycol and adipic acid were reacted with neopentyl glycol/adipic acid=1/0.8 (molar ratio) to obtain an ester intermediate. To this ester intermediate, 3,5,5-trimethylhexanoic acid was further added with neopentyl glycol/3,5,5-trimethylhexanoic acid=1/0.3 (molar ratio) without using a catalyst or solvent. And the remaining unreacted material was removed by distillation. Then, adsorption treatment (clay clay treatment) was performed in the final step to remove a small amount of impurities, and an ester (kinematic viscosity at 40° C., 300 mm ² /s, viscosity index 114, pour point −35° C.) was obtained.

The following esters (b-1) to (b-5) were used as the base oil.
(B-1) Pentaerythritol and a mixed acid of 2-methylpropanoic acid and 3,5,5-trimethylhexanoic acid (2-methylpropanoic acid:3,5,5-trimethylhexanoic acid=1:1 (mass ratio )) ester with mixed acid (kinematic viscosity at 40° C. 69.4 mm ² /s, viscosity index 95, pour point −45° C.)
(B-2) Dipentaerythritol and a mixed acid of normal butanoic acid and 3,5,5-trimethylhexanoic acid (normal butanoic acid:3,5,5-trimethylhexanoic acid=7:3 (mass ratio)) Ester with mixed acid (kinematic viscosity at 40°C 68.1 mm ² /s, viscosity index 90, pour point -45°C)
(B-3) Ester of trimethylolpropane and oleic acid (kinematic viscosity at 40° C. 50.3 mm ² /s, viscosity index 176)
(B-4) Ester of pentaerythritol, pentanoic acid, and 3,5,5-trimethylhexanoic acid (kinematic viscosity at 40° C., 31.4 mm ² /s, viscosity index 118, pour point: less than −55° C.)
(B-5) Ester of pentaerythritol, 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid (kinematic viscosity at 40°C 68.3 mm ² /s, viscosity index 87, pour point -45°C)

The kinematic viscosity and viscosity index of the esters (A-1) to (A-5) and (b-1) to (b-5) were measured according to JIS K2283:2000. The pour point was measured according to JIS K2269:1987. Further, the esters (b-1) to (b-5) were also subjected to adsorption treatment (white clay treatment) in the final step of production to remove a trace amount of impurities.

The following additives 1 to 4 were used as antiwear additives. Incidentally, the kinematic viscosity at 25 ° C. of additives 1 to 4 were in the ranges of 100mm ² / s~50000mm ² / s.
Additive 1: dimethylpolysiloxane (kinematic viscosity at 25°C: 30,000 mm ² /s)
Additive 2: Modified silicone oil in which the end of the main chain of dimethylpolysiloxane is modified with polyalkylene glycol Additive 3: Modified silicone oil in which the end of the main chain of dimethylpolysiloxane is modified with ester 4: Addition of dimethylpolysiloxane Fluorinated silicone oil with side chain modified to fluoropolyether group

Sample oils were prepared by blending the above base oils and additives in the blending ratios shown in Tables 1-6. The following abrasion resistance test was performed on each sample oil. The results are shown in Tables 1-6. Incidentally, kinematic viscosity of 100 mm ² / ^s at 25 ℃, 1000mm 2 / s, for even dimethylpolysiloxane 50,000 mm ² / s, at ranges of content 1 to 50 mass ppm (sample oil total amount), additives Similar results can be obtained with 1.

(Abrasion resistance test)
Performs refrigerant pressure fluctuation wear resistance test using a high-pressure atmosphere friction tester (rotary sliding method between rotating vane material and fixed disk material) manufactured by Shinko Machinery Co., Ltd. that can create a refrigerant atmosphere similar to that of an actual compressor. It was The test conditions were any of the following wear resistance tests-(1) to (6) for each type of evaluation refrigerant.
Abrasion resistance test-(1): R134a was used as the refrigerant, and the pressure inside the test container was 1.6 MPa.
Abrasion resistance test-(2): R410A was used as the refrigerant, and the pressure inside the test container was 1.6 MPa.
Abrasion resistance test-(3): R32 was used as the refrigerant, and the pressure inside the test container was 1.6 MPa.
Abrasion resistance test-(4): HFO-1234yf was used as the refrigerant, and the pressure inside the test container was 1.6 MPa.
Abrasion resistance test-(5): n-hexane (20% by volume blended with refrigerating machine oil. Hydrocarbon refrigerants such as R290 are used as a substitute due to safety concerns). Pressure slightly higher than normal pressure.
Abrasion resistance test-(6): CO ₂ was used as the refrigerant, and the pressure inside the test container was 1.6 MPa.

For each of the abrasion resistance test-(1) to (6), the amount of oil was 600 ml, the test temperature was 100° C., the rotation speed was 650 rpm, and the load load was 70 kgf. The pressure was reduced to atmospheric pressure, and the test was continued for another 30 minutes in this state. Further, it is common that SKH-51 is used as the vane material and FC250 is used as the disk material. The wear resistance was evaluated by the wear depth of the vane material, because the wear amount of the disk material was extremely small. The results are shown in Tables 1-6.

Claims (8)

A base oil consisting of at least one selected from the group consisting of a polyol ester composed of a polyhydric alcohol and a fatty acid having 4 to 9 carbon atoms, and a complex ester ;
From the group consisting of dimethylpolysiloxane silicone oil, modified silicone oil in which the end of the main chain of dimethylpolysiloxane is modified with polyalkylene glycol, and fluorinated silicone oil in which the side chain of dimethylpolysiloxane is modified with a fluoropolyether group. An antiwear additive which is at least one kind selected ,
The content of the base oil is 95% by mass or more based on the total amount of refrigerating machine oil, and
Refrigerating machine oil in which the content of the antiwear additive is 0.1 mass ppm or more and 500 mass ppm or less based on the total amount of refrigerating machine oil. The refrigerating machine oil according to claim 1, which is used with a refrigerant containing difluoromethane. The refrigerating machine oil according to claim 1, which is used with a refrigerant containing an unsaturated fluorohydrocarbon refrigerant. The refrigerator oil according to any one of claims 1 to 3 , wherein the base oil contains the polyol ester . The base oil, as the complex ester, is at least one selected from polyhydric alcohols having 2 to 4 hydroxyl groups, at least one selected from polybasic acids having 6 to 12 carbon atoms, and 4 carbon atoms. The refrigerator oil according to any one of claims 1 to 4 , containing a complex ester synthesized from at least one monohydric alcohol selected from monohydric alcohols having 18 to 18 carbon atoms and at least one monohydric fatty acid having 2 to 12 carbon atoms. A working fluid composition for a refrigerator, comprising the refrigerator oil according to any one of claims 1 to 5 and a refrigerant. The working fluid composition for a refrigerator according to claim 6, wherein the refrigerant contains difluoromethane. The working fluid composition for a refrigerator according to claim 6 or 7, wherein the refrigerant contains an unsaturated fluorohydrocarbon refrigerant.