JP2016108370A - Lubricating oil composition and refrigerating machine system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a lubricating oil composition having a high viscosity index while maintaining insulation properties; and a refrigerating machine system.SOLUTION: There is provided a lubricating oil composition which comprises an oxygen-containing synthetic oil-based base oil (A) and an alkylene oxide adduct (B) of a hydroxyl group-containing compound. The oxygen-containing synthetic oil-based base oil (A) is preferably either one or both of a polyvinyl ether and a polyol ester. The oxygen-containing synthetic oil-based base oil (A) preferably has an oxygen atom content of 15 to 30 mass%. The alkylene oxide adduct (B) of a hydroxyl group-containing compound preferably has a mass-average molecular weight of 1000 or more and 200000 or less. The alkylene oxide adduct (B) of a hydroxyl group-containing compound preferably is a propylene oxide adduct of a hydroxyl group-containing compound.SELECTED DRAWING: None

Description

  The present invention relates to a lubricating oil composition and a refrigerator system.

When the viscosity change with respect to the temperature change is small, the lubricating oil composition has a wider use temperature range and is easy to use. Generally, a viscosity index (abbreviated as “VI”) is used as a numerical value indicating the rate of change in viscosity of the lubricating oil composition with respect to temperature. The higher the viscosity index, the smaller the viscosity change with respect to the temperature change, and the easier to use the lubricating oil composition.
In order to improve the viscosity index of the lubricating oil composition, an additive called a viscosity index improver may be added to the lubricating oil composition.

  By the way, the base oil contained in the lubricating oil composition is classified into a mineral oil system and a synthetic oil system. Mineral oil base oil is a base oil refined from crude oil without chemical synthesis. On the other hand, a synthetic oil base oil is a base oil obtained by chemical synthesis such as a polymerization reaction from a low molecular weight compound or a chemical reaction such as chemical modification from various oils such as refined crude oil.

  Examples of the viscosity index improver include, for example, Non-Patent Document 1, a polymethacrylate type represented by the following formula (1), an olefin copolymer represented by the following formula (2), and a polymethacrylate represented by the following formula (3). Isobutylene and the like are disclosed. At present, most of the base oils for which such viscosity index improvers are blended are mineral oil base oils for engine oils with an overwhelmingly high production volume.

In formula (1), R ¹ is an alkyl group. m is an integer of 1 or more.
In formula (2), n and p are each an integer of 1 or more.
In formula (3), q is an integer of 1 or more.

On the other hand, synthetic base oils used in lubricating oil compositions that require high insulation properties, such as those mixed with refrigerants in electrical products such as refrigerators and room air conditioners, have a viscosity index of around 90. The viscosity index is small compared to other lubricating oils (viscosity index 150 to 200), which are often not required for insulation. Such synthetic base oils are difficult to use because of the narrow operating temperature range.
Therefore, in a lubricating oil composition containing a synthetic base oil having high insulating properties, an improvement in the viscosity index is desired in order to increase the ease of use.

Satoshi Nishida, Sanyo Chemical Group's performance chemicals 80, high performance viscosity index improver, Sanyo Kasei News, 2009, No. 455

The following has been found by the inventors' research.
The viscosity index improver of Non-Patent Document 1 is easy to dissolve in a lubricating oil composition containing a mineral oil base oil having a high hydrocarbon compound content, but in a lubricating oil composition that requires high insulation. It is difficult to dissolve in a lubricating oil composition containing a synthetic base oil having a high oxygen atom content. Therefore, even if the viscosity index improver of Non-Patent Document 1 is used in a lubricating oil composition containing a synthetic base oil, an improvement in the viscosity index cannot be expected.
Moreover, although the lubricating oil composition containing polypropylene glycol used as a base oil for car air conditioners has a high viscosity index, its insulating property is low. Therefore, it is difficult to use as a lubricating oil composition to be mixed with a refrigerant in electrical appliances such as refrigerators and room air conditioners that require high insulation.

  Accordingly, an object of the present invention is to provide a lubricating oil composition and a refrigerator system having a high viscosity index while maintaining insulation.

As a result of intensive studies, the present inventors have found that an alkylene oxide adduct of a hydroxyl group-containing compound has appropriate solubility in an oxygen-containing synthetic lubricating oil and functions as a viscosity index improver. It came to complete.
That is, the present invention has the following aspects [1] to [7].

[1] A lubricating oil composition containing an oxygen-containing synthetic base oil (A) and an alkylene oxide adduct (B) of a hydroxyl group-containing compound.
[2] The lubricating oil composition according to [1], wherein the oxygen-containing synthetic base oil (A) is one or both of polyvinyl ether and polyol ester.
[3] The lubricating oil composition according to [1] or [2], wherein the oxygen-containing content of the oxygen-containing synthetic base oil (A) is 15 to 30% by mass.

[4] The lubricating oil composition according to any one of [1] to [3], wherein the alkylene oxide adduct (B) of the hydroxyl group-containing compound has a mass average molecular weight of 1,000 or more and 200,000 or less.
[5] The lubricating oil composition according to any one of [1] to [4], wherein the alkylene oxide adduct (B) of the hydroxyl group-containing compound is a propylene oxide adduct of the hydroxyl group-containing compound.
[6] The lubricating oil composition according to any one of [1] to [5], which is for a refrigerator.
[7] A refrigerator system using the lubricating oil composition according to [6].

  According to the present invention, it is possible to provide a lubricating oil composition and a refrigerator system having a high viscosity index while maintaining insulation.

In the present specification, the “monomer” means a compound having a polymerizable unsaturated bond, that is, a polymerization-reactive carbon-carbon double bond.
The “unit” means a unit based on the monomer formed by polymerization of the monomer. The unit may be a unit directly formed by a polymerization reaction, or may be a unit in which a part of the unit is converted into another structure by treating the polymer.

<Lubricating oil composition>
The lubricating oil composition of the present invention contains an oxygen-containing synthetic base oil (A) and an alkylene oxide adduct (B) of a hydroxyl group-containing compound.

(Oxygen-containing synthetic base oil (A))
The oxygen-containing synthetic base oil (A) is a synthetic oil base oil having an oxygen atom in the molecule.
The oxygen atom content in the oxygen-containing synthetic oil base oil (A) is preferably 15 to 30% by mass, and more preferably 18 to 22% by mass.
If the oxygen atom content in the oxygen-containing synthetic base oil (A) is equal to or higher than the lower limit, the compatibility between the base oil and the refrigerant is good. Good stability and insulation.
In the present specification, the oxygen atom content of the oxygen-containing synthetic oil base oil (A) is determined by calculation from the chemical structure estimated by NMR.

The specific compound of the oxygen-containing synthetic base oil (A) is a synthetic oil-based base oil contained in the lubricating oil composition and is not particularly limited as long as it has an oxygen atom in the molecule. .
Specific examples of the oxygen-containing synthetic oil base oil (A) include ether-based lubricant base oils and ester-based lubricant base oils.
Examples of the ether-based lubricating base oil include polyvinyl ether, polyalkylene glycol (polyethylene glycol, polypropylene glycol and the like) and the like.
Examples of the ester-based lubricating base oil include polyol esters, hindered esters, and triglycerides.
Among these, one or both of polyvinyl ether and polyol ester is preferable from the viewpoints of low-temperature characteristics, insulation, and compatibility.

Polyvinyl ether is a polymer having units based on vinyl ether monomers.
Examples of the polyvinyl ether include a compound having a unit represented by the following formula (4).

In formula (4), R ² , R ³ and R ⁴ are each a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, and may be the same or different from each other. R ⁵ is a divalent hydrocarbon group having 1 to 10 carbon atoms or a divalent ether bond oxygen-containing hydrocarbon group having 2 to 20 carbon atoms. R ⁶ is a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. r is a number from 0 to 10 on average within the same molecule. R ^{2 to} R ⁶ and r may be the same or different between the units. When r is 2 or more in one unit, all R ⁵ in the unit may be the same or different.

R ² , R ³ and R ⁴ are preferably a hydrocarbon group having 1 to 4 carbon atoms, more preferably a hydrocarbon group having 1 to 2 carbon atoms, and most preferably a hydrocarbon group having 1 carbon atom.
R ⁵ is preferably a divalent hydrocarbon group having 2 to 4 carbon atoms, more preferably a divalent hydrocarbon group having 2 to 3 carbon atoms, and most preferably a divalent hydrocarbon group having 2 carbon atoms. .
R ⁶ is preferably a hydrocarbon group having 1 to 6 carbon atoms, more preferably a hydrocarbon group having 1 to 4 carbon atoms, and most preferably a hydrocarbon group having 1 carbon atom.
The average value of r in the same molecule is preferably 0 to 4, more preferably 0 to 2, and most preferably 0.

Units based on vinyl ether monomers are preferably units based on methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, isobutyl vinyl ether, etc., and units based on ethyl vinyl ether and isobutyl vinyl ether are particularly preferred.
The unit based on a vinyl ether monomer may have 1 type independently, and may have it in combination of 2 or more type.

The polyvinyl ether may have a unit based on another monomer other than the vinyl ether monomer.
Examples of other monomers include ethylene, propylene, various butenes, various pentenes, various hexenes, various heptenes, various octenes, diisobutylene, triisobutylene, styrene, α-methylstyrene, various alkyl-substituted styrenes, and the like. .

The copolymerization composition (molar ratio) of vinyl ether monomer / other monomer is preferably 80/20 to 100/0, and more preferably 90/10 to 100/0.
If the copolymerization composition (molar ratio) of vinyl ether monomer / other monomer is equal to or higher than the lower limit, the compatibility with the refrigerant is excellent. On the other hand, if it is equal to or lower than the upper limit, the lubricity is excellent.

The mass average molecular weight of polyvinyl ether is preferably from 200 to 3,000, more preferably from 300 to 2,000.
If the mass average molecular weight of the polyvinyl ether is not less than the lower limit, the viscosity of the base oil is easily maintained. On the other hand, if it is not more than the upper limit, the low temperature fluidity is easily maintained.

  Polyvinyl ether can be produced by a known polymerization method using the above-mentioned vinyl ether monomer as a raw material. The polyvinyl ether may be a commercially available product.

The polyol ester is an ester of a polyhydric alcohol and an organic acid.
The number of hydroxyl groups of the polyhydric alcohol is 2 or more, preferably 2 to 6, more preferably 3 to 4, and most preferably 4.

  Among polyhydric alcohols, from the viewpoint of hydrolysis stability, neopentyl glycol, trimethylol ethane, trimethylol propane, trimethylol butane, pentaerythritol, dipentaerythritol are more preferable, and compatibility with refrigerant and hydrolysis stability Pentaerythritol is most preferable because of its particularly excellent low temperature fluidity.

The organic acid is not particularly limited.
From the viewpoint of lubricity, the organic acid preferably has 1 or more carbon atoms, more preferably 3 or more carbon atoms, still more preferably 4 or more carbon atoms, and most preferably 5 or more carbon atoms. Further, from the viewpoint of compatibility with the refrigerant, the number of carbon atoms is preferably 24 or less, more preferably 18 or less, even more preferably 12 or less, and most preferably 9 or less.
The bond between carbons in the carbon chain in the organic acid may have an unsaturated bond.
When the number of carbon atoms is 3 or more, the carbon chain in the organic acid may be linear or branched. From the viewpoint of lubricity, a straight chain is preferable, and from a viewpoint of low temperature fluidity, a branched chain is preferable.

  Among organic acids, carboxylic acid is preferable from the viewpoint of ester bond formation. Among carboxylic acids, fatty acids having 7 to 9 carbon atoms are preferred from the viewpoint of kinematic viscosity, and 2-ethylhexanoic acid (octylic acid) and 3,5,5-trimethylhexanoic acid are preferred from the viewpoint of low-temperature fluidity. More branched fatty acids are more preferred.

Examples of the polyol ester include esters of a polyhydric alcohol having 2 to 20 hydroxyl groups and a carboxylic acid having 1 to 24 carbon atoms.
Preferable examples of the polyol ester include esters of pentaerythritol and 2-ethylhexanoic acid represented by the following formula (5).

  One type of oxygen-containing synthetic base oil (A) may be contained alone in the lubricating oil composition, or two or more types may be contained in combination.

The content of the oxygen-containing synthetic base oil (A) in the lubricating oil composition is preferably 60 to 98% by mass, more preferably 70 to 95% by mass, and most preferably 80 to 90% by mass.
If the content of the oxygen-containing synthetic base oil (A) is equal to or higher than the lower limit, the lubricity and insulating properties are excellent, while if it is equal to or lower than the upper limit, the viscosity index and stability are excellent.

(Alkylene oxide adduct of hydroxyl group-containing compound (B))
The alkylene oxide adduct (B) of a hydroxyl group-containing compound is a compound obtained by adding an alkylene oxide to a hydroxyl group-containing compound.

Examples of the hydroxyl group-containing compound include water and alcohol.
The number of hydroxyl groups in the alcohol is preferably 1 to 8, more preferably 1 to 4, and most preferably 1 to 2.

Specific alcohols include monools such as methanol, ethanol, propanol, butanol and hexanol, polyols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, trimethylolpropane, glycerin, pentaerythritol, sorbitol, and sucrose. Can be mentioned.
Among the hydroxyl group-containing compounds, water, propylene glycol, glycerin, methanol, ethanol, pentaerythritol and dipentaerythritol are preferable.

Examples of the alkylene oxide include ethylene oxide, propylene oxide, 1,2-butylene oxide, 2,3-butylene oxide, styrene oxide and the like. Among these, ethylene oxide and propylene oxide are preferable, and propylene oxide is particularly preferable.
One type of alkylene oxide may be added singly in the alkylene oxide adduct (B) of the hydroxyl group-containing compound, or two or more types may be added in combination.

  The hydroxyl group present at the terminal of the alkylene oxide adduct (B) of the hydroxyl group-containing compound may remain unmodified or may be modified by alkyl etherification or alkyl esterification.

  The alkylene oxide adduct (B) of the hydroxyl group-containing compound is preferably a propylene oxide adduct of the hydroxyl group-containing compound. Among propylene oxide adducts of hydroxyl group-containing compounds, propylene oxide adducts of glycerin, polypropylene glycol, propylene oxide and ethylene oxide adducts of methanol whose terminal hydroxyl groups are methyl etherified, propylene oxide adducts of pentaerythritol, glycerin An adduct of propylene oxide and ethylene oxide is preferred.

The mass average molecular weight of the alkylene oxide adduct (B) of the hydroxyl group-containing compound is preferably 1,000 or more and 200,000 or less, more preferably 10,000 or more and 200,000 or less, and most preferably 20,000 or more and 200,000 or less. preferable.
If the mass average molecular weight of the alkylene oxide adduct (B) of the hydroxyl group-containing compound is not less than the lower limit, the viscosity index of the lubricating oil composition will be higher, whereas if it is not more than the upper limit, the lubricating oil composition Mixability at the time of manufacture becomes easy.
The alkylene oxide adduct (B) of the hydroxyl group-containing compound may be contained alone in the lubricating oil composition, or may be contained in combination of two or more.

Addition of alkylene oxide to a hydroxyl group-containing compound is usually performed using a catalyst. Examples of the catalyst include basic catalysts, acid catalysts, and metal catalysts.
Examples of the basic catalyst include alkali metal catalysts such as potassium hydroxide and sodium hydroxide, and organic basic catalysts such as amine compounds and phosphazenes. Examples of the acid catalyst include Lewis acid catalysts such as boron trifluoride and tris (pentafluorophenyl) borane. Examples of the metal catalyst include titanium-based and composite metal cyanide complex catalysts.
Among these, a double metal cyanide complex catalyst is preferable because an alkylene oxide adduct (B) having a mass average molecular weight of 10,000 or more, which is difficult to produce with other catalysts, can be produced.

The content of the alkylene oxide adduct (B) of the hydroxyl group-containing compound in the lubricating oil composition is preferably 1 to 30% by mass, more preferably 3 to 20% by mass, and most preferably 5 to 10% by mass.
When the content of the alkylene oxide adduct (B) is not less than the lower limit, the viscosity index can be improved. On the other hand, when the content is not more than the upper limit, a decrease in insulation can be suppressed.
The lubricating oil composition of the present invention is particularly proper to operate the refrigeration system, and to ensure high efficiency, a kinematic viscosity of preferably 5~300mm ² / s at 40 ° C., and more is 7~250mm ² / sec Preferably, 32 to ²⁰⁰ mm ² / sec is most preferable.

(Other additives)
In the lubricating oil composition, in addition to the alkylene oxide adduct (B) of the hydroxyl group-containing compound as long as the effects of the present invention are not impaired, an antioxidant, an extreme pressure agent, an antiwear agent, a dehydrating agent, an extreme pressure agent, You may contain other additives, such as a rust preventive agent, an antifoamer, a dispersing agent, a flame retardant, and a heat stabilizer.
Among these, as an additive contained in the lubricating oil composition for a refrigerator system, an antioxidant, a dehydrating agent, an extreme pressure agent, an antifoaming agent, and a heat stabilizer are preferable.

Specific examples of antioxidants include 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-P-cresol, 4,4-methylene-bis- (2,6-di-tertiary). And tertiary alkyl-substituted hindered phenol compounds such as (butyl-P-cresol).
Specific examples of the dehydrating agent include glycidyl ethers such as butyl glycidyl ether, 2-ethylhexyl glycidyl ether, trimethylolpropane polyglycidyl ether, neopentyl glycol diglycidyl ether, and t-butylphenyl glycidyl ether, adipic acid glycidyl ester, Examples include glycidyl esters such as 2-ethylhexanoic acid glycidyl ester, isononanoic acid glycidyl ester, neodecanoic acid glycidyl ester, epoxidized fatty acid monoesters such as epoxidized methyl stearate, and epoxidized vegetable oils such as epoxidized soybean oil. It is done.

Examples of extreme pressure agents include sulfur extreme pressure agents and phosphorus extreme pressure agents.
Examples of the antifoaming agent include silicone-based antifoaming agents.
Examples of the heat stabilizer include phosphite compounds such as dimethyl phosphite, diisopropyl phosphite and diphenyl phosphite, and phosphine sulfide compounds such as triphenoxyphosphine sulfide and trimethylphosphine sulfide.

  In addition, when hydrofluoroolefin is used as the refrigerant in the refrigerator system, carbodiimide such as diphenylcarbodiimide, di (alkylphenyl) carbodiimide or bis (alkylphenyl) carbodiimide is added to improve the stability of double bonds in the refrigerant. It is preferable to do.

When mix | blending another additive, 0.05-10 mass% is preferable, as for the total content of the other additive in a lubricating oil composition, 0.1-5 mass% is more preferable, 0.5- 3% by mass is more preferable.
If the total content of other additives is equal to or higher than the lower limit value, the effect of each additive can be easily obtained.

(Use)
The use of the lubricating oil composition is not particularly limited. Specifically, refrigeration oil, cutting oil, grinding oil, rolling oil, drawing oil, punching oil, drawing oil, press oil, forging oil, sliding surface oil, hydraulic oil, water-glycol hydraulic fluid, electrical insulation Oil, gasoline engine oil, diesel engine oil, air compressor oil, turbine oil, gear oil, compressor oil, vacuum pump oil, bearing oil, heat medium oil, mist oil, rock drill oil, brake oil, torque converter oil, etc. Can be used for various purposes.
Among these, the lubricating oil composition is preferably used as a point refrigerating machine oil in terms of good compatibility with the refrigerant used in the refrigeration system. Specific refrigerator systems include car air conditioners, gas heat pumps, residential and commercial air conditioners, refrigerators, refrigerated warehouses, vending machines, showcases, and the like.

(Production method)
The lubricating oil composition is prepared by mixing an oxygen-containing synthetic base oil (A) with an alkylene oxide adduct (B) of a hydroxyl group-containing compound and, if necessary, other additives so as to obtain a desired mixing ratio. can get.
The mass mixing ratio of the oxygen-containing synthetic base oil (A) and the alkylene oxide adduct (B) of the hydroxyl group-containing compound is preferably 99: 1 to 65:35, more preferably 97: 3 to 75:25, 95: 5-85: 15 is most preferred. If the mixing amount of the alkylene oxide adduct (B) of the hydroxyl group-containing compound with respect to the oxygen-containing synthetic oil base oil (A) is equal to or higher than the lower limit in the mass mixing ratio, the viscosity index can be improved, while the upper limit is lower than the upper limit. If it is, the fall of insulation will be suppressed.

<Refrigerator system>
The refrigerator system uses the above-described lubricating oil composition.
In the refrigerator system, the lubricating oil composition is used by being mixed with a refrigerant.

  Examples of the refrigerant include a hydrocarbon compound, carbon dioxide, a hydrofluorocarbon compound, a hydrofluoroolefin compound, and an ammonia refrigerant. Among these, a hydrofluorocarbon compound, a hydrofluoroolefin compound, or a mixture thereof is preferable.

Examples of the hydrocarbon compound include alkanes such as methane, ethane, ethylene, propane, cyclopropane, propylene, n-butane, isobutane, n-pentane, and isopentane.
As a hydrofluoroolefin type compound, a C2-C3 hydrofluoroolefin type compound is preferable, and the fluoride of ethylene, such as trifluoroethylene, and the fluoride of various propenes is mentioned, The fluoride of propene is more preferable. Examples of the propene fluoride include 3,3,3-trifluoropropene, 1,3,3,3-tetrafluoropropene, and 2,3,3,3-tetrafluoropropene. In particular, 1,2,3,3,3-pentafluoropropene (HFO1225ye), 1,3,3,3-tetrafluoropropene (HFO1234ze), 2,3,3,3-tetrafluoropropene (HFO1234yf) preferable.

Examples of the hydrofluorocarbon-based compound include hydrofluorocarbons having 1 to 3 carbon atoms, preferably 1 to 2 carbon atoms. Specifically, for example, difluoromethane (HFC-32), trifluoromethane (HFC-23), pentafluoroethane (HFC-125), 1,1,2,2-tetrafluoroethane (HFC-134), 1 , 1,1,2-tetrafluoroethane (HFC-134a), 1,1,1-trifluoroethane (HFC-143a), 1,1-difluoroethane (HFC-152a) and other HFCs, or two of these The above mixture is mentioned. Examples of the mixture include HFC-32 / HFC-125 = 50/50 mass% mixture (R410A), HFC-32 / HFC-125 / HFC-134a = 23/25/52 mass% mixture (R407C), and the like. It is done.
The hydrofluorocarbon-based compound may be obtained by halogenating the above alkane fluoride with a halogen atom other than fluorine, and examples thereof include trifluoroiodomethane (CF3I).

  In the refrigerator system of the present invention, the mixing ratio of the lubricating oil composition and the refrigerant is preferably 10/90 to 50/50 in terms of the mass ratio of the lubricating oil composition / refrigerant. If the lubricating oil composition is 10% by mass or more, the lubricity in the refrigerator system becomes better, while if the refrigerant is 50% by mass or more, the cooling capacity of the refrigerator system can be prevented from being lowered.

  The polyalkylene glycol adduct (B) of the hydroxyl group-containing compound has appropriate solubility in the oxygen-containing synthetic lubricating oil (A) and functions as a viscosity index improver. Moreover, the oxygen-containing synthetic base oil (A) used as the base oil has high insulation. Therefore, the lubricating oil composition of the present invention is improved in viscosity index while maintaining insulation.

[material]
Base oil A-1: Polyvinyl ether copolymer (“Dafney Hermetic Oil (registered trademark) FV68S” manufactured by Idemitsu Kosan Co., Ltd.), ethyl vinyl ether / isobutyl vinyl ether (9/1 (molar ratio)), oxygen atom content 21.6%, Weight average molecular weight 720).
Base oil A-2: Polyol SS ("Ze-GLESRB68" manufactured by JX Nippon Oil & Energy Corporation, pentaerythritol and 2-ethylhexanoic acid, ester of 3,5,5-trimethylhexanoic acid 1/1 (molar ratio) , Oxygen atom content 19.2%).

Polyol B-1: Propylene oxide adduct of glycerin (mass average molecular weight 10,000).
Polyol B-2: Propylene oxide adduct of glycerin (mass average molecular weight 25,000).
Polyol B-3: Polypropylene glycol (mass average molecular weight 20,000).
Polyol B-4: an adduct of propylene oxide and ethylene oxide of methanol in which the terminal hydroxyl group is methyl etherified (mass average molecular weight 1,200).

Polyol B-5: Propylene oxide adduct of pentaerythritol (mass average molecular weight 32,000).
Polyol B-6: Adduct of propylene oxide and ethylene oxide (average molecular weight 3,800) of glycerin.
Polyol B-7: Polypropylene glycol (mass average molecular weight 1,000).
Methacrylate copolymer B ′: “Aclude (registered trademark) 504” manufactured by Sanyo Chemical Industries.

[Evaluation method]
(Solubility evaluation)
Whether the alkylene oxide adduct (B) or the methacrylate copolymer B ′ of the hydroxyl group-containing compound was dissolved in the oxygen-containing synthetic base oil (A) was visually confirmed.
When the alkylene oxide adduct (B) or the methacrylate copolymer B ′ of the hydroxyl group-containing compound was uniformly dissolved, it was defined as “dissolved”. When it did not dissolve uniformly, it was set as “insoluble”.

(Kinematic viscosity)
Using an Ubbelohde kinematic viscometer (manufactured by Shibata Kagaku), the kinematic viscosity (mm ² / sec) at 40 ° C. or 100 ° C. was measured.
The measurement method conformed to JIS K 2283.
The viscosity index is JIS K 2283 6. It calculated from the method as described in the viscosity index calculation method.

(Volume resistivity)
Volume resistivity (TΩ · cm) was measured using Hiresta UP (Mitsubishi Chemical Analytech Co., Ltd.).
The measurement method conformed to JIS C2101.

[Examples 1 to 14]
Addition and mixing of the alkylene oxide adduct (B) of the hydroxyl group-containing compound to the oxygen-containing synthetic base oil (A) at a mass ratio shown in Table 1 gives the lubricating oil compositions of Examples 1-14. It was.

[Comparative Examples 1-6]
A lubricating oil composition containing only polyol B-7 was designated as Comparative Example 1.
A lubricating oil composition containing only polyol B-4 was referred to as Comparative Example 2.
The methacrylate copolymer B ′ was added and mixed in a mass ratio shown in Table 1 to the oxygen-containing synthetic base oil (A) to obtain lubricating oil compositions of Comparative Examples 3 and 4.
A lubricating oil composition containing only base oil A-1 was designated as Comparative Example 5.
A lubricating oil composition containing only base oil A-2 was designated as Comparative Example 6.

  Each lubricating oil composition was evaluated for solubility evaluation, kinematic viscosity measurement, and volume resistivity. The evaluation results are shown in Table 1. Since Comparative Examples 1 and 2 were only the alkylene oxide adduct (B) of the hydroxyl group-containing compound and Comparative Examples 5 and 6 were lubricating oil compositions containing only the oxygen-containing synthetic base oil (A), solubility evaluation was performed. Did not do.

As shown in Table 1, the lubricating oil compositions of Comparative Examples 1 and 2 containing only the alkylene oxide adduct (B) of a hydroxyl group-containing compound have a high viscosity index, but have a low volumetric efficiency and poor insulating properties. It was.
In Comparative Examples 3 and 4, the methacrylate copolymer B ′ was not uniformly dissolved in the oxygen-containing synthetic oil base oil (A). Therefore, kinematic viscosity measurement and volume resistivity evaluation were not performed.
In addition, the lubricating oil compositions of Comparative Examples 5 and 6 containing only the oxygen-containing synthetic oil base oil (A) had a high volume resistivity but a low viscosity index.
On the other hand, the lubricating oil compositions of Examples 1 to 14 using the alkylene oxide adduct (B) of the hydroxyl group-containing compound had a high viscosity index and a high volume resistivity.

  The lubricating oil composition of the present invention comprises a refrigerating machine oil, a cutting oil, a grinding oil, a rolling oil, a drawing oil, a punching oil, a drawing oil, a press oil, a forging oil, a sliding surface oil, a hydraulic oil, and a water-glycol system operation. Liquid, electric insulation oil, gasoline engine oil, diesel engine oil, air compressor oil, turbine oil, gear oil, compressor oil, vacuum pump oil, bearing oil, heat transfer oil, mist oil, rock drill oil, brake oil, torque converter It can be used for various applications such as oil. Among these, it is preferable to be used as refrigerating machine oil.

Claims (7)

  A lubricating oil composition comprising an oxygen-containing synthetic base oil (A) and an alkylene oxide adduct (B) of a hydroxyl group-containing compound.   The lubricating oil composition according to claim 1, wherein the oxygen-containing synthetic oil base oil (A) is one or both of polyvinyl ether and polyol ester.   The lubricating oil composition according to claim 1 or 2, wherein the oxygen-containing content of the oxygen-containing synthetic base oil (A) is 15 to 30% by mass.   The lubricating oil composition according to any one of claims 1 to 3, wherein the alkylene oxide adduct (B) of the hydroxyl group-containing compound has a mass average molecular weight of 1,000 or more and 200,000 or less.   The lubricating oil composition according to any one of claims 1 to 4, wherein the alkylene oxide adduct (B) of the hydroxyl group-containing compound is a propylene oxide adduct of the hydroxyl group-containing compound.   The lubricating oil composition according to any one of claims 1 to 5, which is for a refrigerator.   A refrigerator system using the lubricating oil composition according to claim 6.