JP5613395B2 - Electric motor oil composition - Google Patents

Description

  The present invention relates to a lubricating oil used in an electric motor-equipped vehicle such as a hybrid vehicle or an electric vehicle, and relates to an electric motor oil composition for an electric motor device or a device in which a lubricating system for an electric motor and a transmission is shared.

  In order to prevent global warming, there is a strong demand for improving the fuel efficiency of automobiles, and hybrid cars that combine engines and batteries are spreading. In addition, it is considered that electric vehicles will be widely used in the future, and there is a demand for new oils (electric motor oils) excellent in electrical insulation, cooling and thermal oxidation stability for vehicles equipped with these electric motors. Yes.

Conventionally, a base oil having a urea adduct value of 4% by mass or less, a kinematic viscosity at 40 ° C. of 25 mm ² / s or less, and a viscosity index of 100 or more is used as a vehicle transmission oil suitable for an electric motor-equipped vehicle. A composition of 720 W / m ² · ° C. or higher (Patent Document 1), transmission oil mounted in an electric vehicle or hybrid vehicle, transmission / electric motor combined oil, or a transmission / electric motor lubrication system is shared. Phosphorus compound selected from the group consisting of hydrocarbon oil-containing zinc dithiophosphate and triarylthiophosphate as base oil having a kinematic viscosity at 80 ° C. of 1.5 to 4.0 mm ² / s And a composition having a volume resistivity at 80 ° C. of 1 × 10 ⁸ Ω · m or more (Patent Document 2) containing an ashless dispersant.

By the way, the electric motor oil is required to have electrical insulation, cooling, thermal oxidation stability, and the like. From the viewpoint of cooling, an oil having a lower viscosity is preferable, but it is necessary to increase the flash point from the viewpoint of safety. is there. Also, higher thermal oxidation stability is required to increase the reliability of the automobile. In order to share the electric motor oil and to reduce the size and weight of the electric motor and transmission as a package, it is necessary to further improve the lubricity when the electric motor oil is used as a transmission oil, that is, as a combined oil. Moreover, the thing excellent in biodegradability from the viewpoint of environmental conservation is calculated | required preferably.
The transmission oil composition described above does not satisfy the required properties such as electrical insulation, cooling, thermal oxidation stability, flash point, lubricity, low temperature startability, and biodegradability in a well-balanced manner.

JP 2009-161604 A JP 2008-285682 A

  The object of the present invention is excellent in electrical insulation, cooling, and thermal oxidation stability, has a high flash point from the viewpoint of safety, and has lubricity and low temperature startability that can be used as a transmission oil as a combined oil. Is to provide an electric motor oil composition excellent in biodegradability.

  The present inventors pay attention to ester compounds as a base material that has excellent thermal oxidation stability, good electrical insulation, and has a high flash point even when the viscosity is lowered in order to enhance cooling properties, and the structure and characteristics thereof. In order to further improve the properties, to give more resistance to hydrolysis, which is a weak point of ester compounds, and to study the additives so that they can be used as a transmission oil as a combined oil, The present inventors have found that a combination of an ester compound having a structure and a predetermined additive can solve the above-mentioned problems, and have completed the present invention. In addition, the present invention has also been found to be superior in biodegradability, which is a more preferable characteristic, in which an ester compound having a specific structure is used as a base oil.

That is, the present invention as means for solving the above problems is as follows.
(1) An ester synthesized from adipic acid and / or sebacic acid and an alcohol having 5 to 14 carbon atoms, and / or an ester synthesized from neopentyl glycol and / or trimethylolpropane and a carboxylic acid having 5 to 14 carbon atoms. Among them, the base oil is one or more esters having a hydroxyl value of 50 mg KOH / g or less, a total acid value of 2 mg KOH / g or less, and a flash point of 150 ° C. or more, and an amine compound and / or a phenol compound are based on the total amount of the composition. An electric motor oil composition added at 0.01 to 3.0% by weight.
(2) The electric motor oil composition according to (1), wherein 0.01 to 5.0% by weight of a carbodiimide compound and / or an epoxy compound is added based on the total amount of the composition.

(3) an ester synthesized from adipic acid and / or sebacic acid and an alcohol having 5 to 14 carbon atoms, wherein 60% by weight or more of the alcohol is a linear alcohol, and / or neopentyl glycol and / or trimethylolpropane The electric motor according to (1) or (2), wherein the electric motor is synthesized from a carboxylic acid having 5 to 14 carbon atoms, and the base oil is one or more of esters in which 60% by weight or more of the carboxylic acid is a linear carboxylic acid. Oil composition.
(4) The electric motor oil composition according to any one of (1) to (3), wherein 0.1 to 5.0% by weight of a phosphate ester compound is added based on the total amount of the composition.

  The electric motor oil composition of the present invention is excellent in electrical insulation, thermal oxidation stability, and hydrolytic stability, has a high flash point, excellent in cooling properties, low temperature startability, and lubricity, and is used in hybrid vehicles and electric vehicles. The electric motor device and the lubrication system of the electric motor and the transmission satisfy the required performance of the oil for the device with a shared balance, and have an excellent effect of being excellent in practical performance. The thing has the effect that it is excellent also in biodegradability.

The electric motor oil composition of the present invention includes adipic acid that is a dibasic acid ester, an ester synthesized from sebacic acid and an alcohol having 5 to 14 carbon atoms, a neopentyl glycol that is a polyol ester, and trimethylolpropane as a base oil. Esters synthesized from carboxylic acids having 5 to 14 carbon atoms and any mixtures thereof can be used.
These esters should be esterified in the usual way in the presence of a non-catalyzed mixture of alcohol and acid, or a strong acid catalyst such as sulfuric acid or alkylsulfonic acid, or a metal chloride catalyst such as tin chloride or titanium chloride. Can be manufactured. Moreover, the obtained ester is good to refine | purify by a series of processes, such as deoxidation, water washing, dehydration, adsorption decoloring, and filtration similarly to the case where the normal ester is refine | purified.

These esters have a hydroxyl value of 50 mg KOH / g or less, preferably 20 mg KOH / g or less, more preferably 10 mg KOH / g, and a total acid value of 2 mg KOH / g or less, preferably 1 mg KOH / g or less, more preferably 0. It has a flash point of 150 ° C. or higher, preferably 160 ° C. or higher, more preferably 180 ° C. or higher.
The smaller the hydroxyl value and the total acid value, the better the stability of the ester, and the higher the flash point, the higher the safety. In particular, in the case of a hybrid vehicle, there is a portion or case in which the temperature rises to about 150 ° C. in the engine room, and it is important in terms of safety that the oil flash point be 150 ° C. or higher.

Examples of the alcohol having 5 to 14 carbon atoms include linear alcohols such as n-pentanol, n-hexanol, n-heptanol, n-octanol, n-nonanol, n-decanol, n-undecanol, n-dodecanol, and 2 -Branched alcohols such as ethylhexanol and 3,5,5-trimethylhexanol.
Examples of the carboxylic acid having 5 to 14 carbon atoms include n-pentanoic acid, n-hexanoic acid, n-heptanoic acid, n-octanoic acid, n-nonanoic acid, n-decanoic acid, n-undecanoic acid, n- Examples thereof include linear carboxylic acids such as dodecanoic acid and branched carboxylic acids such as 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid.
When an alcohol or carboxylic acid having 4 or less carbon atoms is used, the flash point of the synthesized ester becomes too low, and when an alcohol or carboxylic acid having 15 or more carbon atoms is used, the viscosity of the synthesized ester is high. It becomes too much and cooling performance falls.
The lower the viscosity of the ester base oil, the better the cooling performance, but it must be set in balance with other characteristics such as the flash point and evaporation characteristics, and the kinematic viscosity at 40 ° C. is 5 to 32 mm ² / Those in the range of s are preferred. As for the density, the smaller the density, the larger the heat transfer coefficient, but the difference is not so great as long as it is within the range of the ester structure.

When synthesizing a dibasic acid ester, 60% by weight or more of the alcohol is a linear alcohol, and when synthesizing a polyol ester, the base oil is obtained by converting 60% by weight or more of the carboxylic acid to a linear carboxylic acid. Esters become biodegradable and become more preferred properties. This biodegradability is measured by a method defined in ASTM D5864.
The ester may be contained as a main component of the base oil, and the base oil of the present invention includes hydrocarbon oils such as mineral oil and olefin polymer in addition to the ester, esters and ethers other than the ester, etc. These oxygen-containing synthetic oils may be used. It is preferable that the ester of the present invention is contained in an amount of 60% by mass or more, particularly 90% by mass or more.

As the additive, an amine compound or a phenol compound is essential from the viewpoint of the thermal oxidation stability of the electric motor oil, and the addition amount is from 0.01 to 3.0% by weight, preferably from 0.1 to 3.0% based on the total amount of the composition. 1.0% by weight. If it is less than 0.01% by weight, the effect of improving the stability is small, and if it exceeds 3.0% by weight, the additive itself tends to become sludge.
Examples of the amine compound include aromatic amines, specifically, phenyl-α-naphthylamine, N, N-di (2-naphthyl) -p-phenylenediamine, dioctyldiphenylamine, and the like.
Phenol compounds include 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-P-cresol, 4,4-methylene-bis- (2,6-di-tert-butyl-P- A tertiary alkyl-substituted phenolic compound such as (cresol) is typically used.
In order to further improve the thermal oxidation stability of the ester base oil, an amine compound is preferred.

  Further, in order to increase resistance to hydrolysis, which is a weak point of esters, it is preferable to add 0.01 to 5.0% by weight of a carbodiimide compound and / or an epoxy compound based on the total amount of the composition, and 0.1 to 3. 0 weight% is more preferable and 0.2 to 2.0 weight% is further more preferable. If the addition amount is less than 0.01% by weight, there is no effect of inhibiting hydrolysis, and if it exceeds 5.0% by weight, the additive itself tends to become sludge.

  The carbodiimide compound is represented by a general formula of R′—N═C═N—R ″. Here, R ′ and R ″ are hydrocarbon groups or hydrocarbon groups containing nitrogen and oxygen, which may be the same. May be different. These hydrocarbon groups preferably contain a benzene ring, and diphenylcarbodiimide, di (alkylphenyl) carbodiimide or bis (alkylphenyl) carbodiimide is preferably used. Specific examples of bis (alkylphenyl) carbodiimide include ditolylcarbodiimide, bis (isopropylphenyl) carbodiimide, bis (diisopropylphenyl) carbodiimide, bis (triisopropylphenyl) carbodiimide, bis (butylphenyl) carbodiimide, bis (dibutyl) Phenyl) carbodiimide, bis (nonylphenyl) carbodiimide, and the like. A carbodiimide compound is preferred to an epoxy compound because it can exert the effect of inhibiting hydrolysis at a relatively low temperature.

Examples of the epoxy compound include phenyl glycidyl ether, phenyl glycidyl ester, alkyl glycidyl ether having 5 to 18 carbon atoms, and the same alkyl glycidyl ester.
Specifically, glycidyl ethers such as 2-ethylhexyl glycidyl ether, trimethylolpropane polyglycidyl ether, neopentyl glycol diglycidyl ether, t-butylphenyl glycidyl ether, adipic acid glycidyl ester, 2-ethylhexanoic acid glycidyl ester, Examples thereof include glycidyl esters such as isononanoic acid glycidyl ester and neodecanoic acid glycidyl ester, epoxidized fatty acid monoesters such as epoxidized methyl stearate, and epoxidized vegetable oils such as epoxidized soybean oil. Preferable epoxy compounds are glycidyl ethers represented by the following general formulas 1 and 2 or glycidyl esters represented by the following formula 3, and glycidyl esters are particularly preferable.

上記式中R₁は炭素数２から１５までの直鎖あるいは分岐のアルキル基、または炭素数６から１５までのフェニル基またはアルキルフェニル基を示す。

In the above formula, R ₁ represents a linear or branched alkyl group having 2 to 15 carbon atoms, or a phenyl group or alkylphenyl group having 6 to 15 carbon atoms.

上記式中、R₂は炭素数１から１２までの直鎖、あるいは分岐のアルキレン基を示す。

In the above formula, R ₂ represents a linear or branched alkylene group having 1 to 12 carbon atoms.

上記式中、R₃は炭素数４から１４までの直鎖あるいは分岐のアルキル基、または炭素数６から１５までのフェニル基またはアルキルフェニル基を示す。

In the above formula, R ₃ represents a linear or branched alkyl group having 4 to 14 carbon atoms, or a phenyl group or alkylphenyl group having 6 to 15 carbon atoms.

  Since electric motor oil is sometimes used as transmission oil as transmission oil, in that case, lubricity is also required as a characteristic of the oil. Since the ester has a polar group, the ester base oil is much better in lubricity than the mineral oil, but it is preferable to further improve the lubricity with an additive. As an additive in this case, phosphoric acid ester can be mentioned, and the addition amount is preferably 0.1 to 5.0% by weight, more preferably 0.3 to 3.0% by weight, based on the total amount of the composition. More preferably, it is 0.5 to 3.0% by weight. If the addition amount is less than 0.1% by weight, there is no effect of improving the lubricity, and if it is added more than 5.0% by weight, the thermal oxidation stability of the oil is lowered. Examples of phosphoric acid esters include trialkyl phosphates having an alkylphenyl group having 7 to 10 carbon atoms such as triphenyl phosphate and tricresyl phosphate, trialkyl phosphates having an alkyl group having 5 to 18 carbon atoms, etc. Can be illustrated.

  In addition to the above additives, extreme pressure agents such as sulfur compounds, general antiwear agents, viscosity index improvers, pour point depressants, detergent dispersants, antifoaming agents, etc., alone or in combination , Can be added in combination. In addition, since the base oil is an ester, it is desirable to avoid the use of an additive having a high acid value or base number that serves as a catalyst for the hydrolysis reaction.

The electric motor oil composition as described above can be used in a transmission as a dual-purpose oil, has high thermal oxidation stability, is highly reliable, has a well-balanced characteristic, has high safety, and is useful. is there. In addition, depending on the structure, it is excellent in biodegradability and becomes an environmentally friendly oil.
The electric motor oil of the present invention can be used as a lubricating oil for the electric motor oil, but is particularly preferably used as a combined oil for the electric motor oil and gear oil such as transmission oil. This combined oil can be used for both the transmission and the electric motor, but is particularly preferably used when the transmission and the electric motor are lubricated by the same lubrication system.

  Hereinafter, the present invention will be described in more detail based on examples. In addition, this invention is not restrict | limited at all by the following examples.

Table 1 shows sample oils used as examples. Test oils 1 to 3 were prepared by synthesizing dibasic acid esters of adipic acid or sebacic acid and 2-ethylhexanol or 3,5,5-trimethylhexanol at the mole percentages shown in Table 1 and adding them. The test oils 4 to 7 are neopentyl glycol or trimethylolpropane and n-pentanoic acid, n-heptanoic acid, n-decanoic acid, 2-ethylhexanoic acid, 3,5,5 -A trimethylhexanoic acid was synthesized with a polyol ester in the proportion of mol% shown in Table 1, and an additive was added to this. All the esters were synthesized and prepared so that the hydroxyl value was 10 mgKOH / g or less.
Table 2 shows the evaluation results of the characteristics of the sample oil and the comparative example as examples. Comparative Example 1 is a commercially available insulating oil “JOMO No. 2 Transformer” (manufactured by Japan Energy Co., Ltd.), and Comparative Example 2 is a commercially available SP-based (sulfur, phosphorus added) gear oil “JOMO Gear 5, 80W- “90” (manufactured by Japan Energy Co., Ltd.) and Comparative Example 3 used “JOMO ATF Special” (manufactured by Japan Energy Co., Ltd.), which is a commercially available ATF (auto transmission fluid).

Each property shown in Table 2 was measured by the following method.
(1) Kinematic viscosity: Measured at 40 ° C. by the method defined in JIS K 2283.
(2) Flash point: measured by the method defined in JIS K 2265.
(3) Pour point: measured by the method defined in JIS K 2269.
(4) Total acid value: measured by the method defined in JIS K2514.
(5) Volume resistivity: measured by a method defined in JIS C 2101.
(6) Oxidation stability test: evaluated by the method defined in JIS C 2101 (120 ° C., 75 hours).
(7) Shell four-ball wear test: evaluated by measuring the wear scar diameter of a steel ball at room temperature (oil temperature) at a rotation speed of 1200 rpm, a load of 40 kgf, and a test time of 1 hr in accordance with ASTM D4172.
(8) Biodegradability: Measured by the method specified in ASTM D5864.

As is clear from Table 2, the electric motor oil examples of the present invention (sample oils 1 to 7) are excellent in thermal oxidation stability, have a high flash point from the safety aspect, and also have an electrically insulating volume resistivity. High, good lubricity and well-balanced characteristics. Moreover, the thing of a specific structure is biodegradable (60% or more), and can be said to be environmentally friendly.
On the other hand, although Comparative Example 1 has good electrical insulation, it has a low flash point for automobiles and has a safety problem. Moreover, thermal oxidation stability is insufficient and lubricity is inferior. Comparative Examples 2 and 3 have good lubricity, but have low electrical insulation properties and insufficient thermal oxidation stability.

  The electric motor oil of the present invention can be used as a lubricating oil for the electric motor oil. In particular, the electric motor oil can be used as a combined oil for the electric motor oil and gear oil such as transmission oil. This combined oil can be used for both the transmission and the electric motor, but is particularly useful when the transmission and the electric motor are lubricated by the same lubrication system.

Claims (5)

Of the ester le synthesized from alcohols adipic acid and 5 to 14 carbon atoms, a hydroxyl value of 50 mg KOH / g or less, total acid number 2 mg KOH / g or less, one or more esters flash point of 0.99 ° C. or higher A volume resistivity at 80 ° C. measured by the method defined in JIS C 2101 is 1. As a base oil, 0.03 to 3.0% by weight of an amine compound and / or a phenol compound is added based on the total amount of the composition . An electric motor oil composition of 7 × 10 ¹¹ Ω · m or more.   The electric motor oil composition according to claim 1, wherein 0.01 to 5.0 wt% of a carbodiimide compound and / or an epoxy compound is added based on the total amount of the composition. Synthesized from an alcohol of adipic acid and 5 to 14 carbon atoms, an electric motor oil composition as claimed in claim 1 or 2 or more 60 wt% of the alcohol to a base oil one or more of the ester le a linear alcohol object.   The electric motor oil composition according to any one of claims 1 to 3, wherein a phosphate ester compound is added in an amount of 0.1 to 5.0% by weight based on the total amount of the composition.   The electric motor oil composition according to any one of claims 1 to 4, wherein the biodegradability measured by a method defined in ASTM D5864 is 47% or more.