JP5159089B2 - Synthetic lubricant - Google Patents

Description

  The present invention relates to a synthetic lubricating oil containing an ionic liquid composed of an organic cation and a bis (fluorosulfonyl) imide anion.

  Conventionally, as a lubricating oil used for mechanical devices, power transmission devices, metalworking oils, greases, etc., base oils of the types closest to the target physical properties among base oils such as poly α-olefins, diesters, polyol esters, silicones, etc. Were selected, combined as necessary, and further added with appropriate additives and the like. However, these lubricating oils have a risk of ignition or evaporation under special circumstances such as high temperature and high degree of vacuum, and more suitable lubricating oils have been desired. In addition, with higher performance and higher efficiency of the apparatus, there is a demand for a lubricating oil having better oxidation resistance and evaporation resistance and excellent lubricating performance over a long period of time.

  As means for solving these problems, for example, Non-Patent Document 1 reports that a compound composed of a combination of an organic cation and an inorganic anion (ionic liquid, room temperature molten salt) can be applied as a lubricating oil. In addition, the ionic liquid is not only non-volatile, excellent in stability over a wide temperature range and flame retardancy, but also has a high viscosity index and also has physical properties that satisfy the friction coefficient and wear scar diameter required of the lubricant. Therefore, it is known that there is a possibility as a lubricating oil material.

  On the other hand, properties common to all ionic liquids are often high in viscosity and specific gravity, and ionic liquids with low viscosity are desired from the viewpoint of practicality.

  However, in general, many ionic liquids have a high viscosity, and in order to put them into practical use as a lubricating oil, it is necessary to find an ionic liquid having a low viscosity, and further development has been advanced.

  And in patent document 1, although the ionic liquid which has a bis (trifluoromethanesulfonyl) imide anion as an anion is mention | raise | lifted as an ionic liquid with low viscosity, In the ionic liquid by a combination with this anion, the reduction rate of a viscosity is mentioned. Was not enough.

R.A.Reich et al., Journal of the Society of Tribologists and Lubrication Engineers, July 2003, p. 16-21 JP 2005-89667 A

  Therefore, an object of the present invention is to provide a synthetic lubricating oil having a stable lubricating performance in a wide temperature range under such a background.

However, as a result of intensive studies in view of the above circumstances, the present inventor has found that an organic cation selected from the group consisting of an imidazolium cation, a pyridinium cation, a quaternary ammonium cation, and a quaternary phosphonium cation , particularly an imidazolium cation. By using a bis (fluorosulfonyl) imide anion as an anionic species in an ionic liquid using a succinic acid, surprisingly, an ionic liquid having a very low viscosity and excellent viscosity stability can be obtained. It was found to be suitable for.

That is, the present invention relates to a synthetic lubricating oil containing an ionic liquid composed of an imidazolium cation and a bis (fluorosulfonyl) imide anion.

  According to the present invention, since an ionic liquid comprising an organic cation having a specific structure and a bis (fluorosulfonyl) imide anion is used, it has excellent wear resistance, more stable fluidity, and viscosity required for lubricating oil It is possible to provide a synthetic lubricating oil having characteristics and having a stable lubricating performance over a wide temperature range and use conditions.

  The present invention is described in detail below.

  In addition, the ionic liquid in this invention shows the ionic substance which is in a molten state at normal temperature (25 degreeC).

The present invention contains an organic cation selected from the group consisting of an imidazolium cation, a pyridinium cation, a quaternary ammonium cation, and a quaternary phosphonium cation , particularly an ionic liquid consisting of an imidazolium cation and a bis (fluorosulfonyl) imide anion. It relates to synthetic lubricating oil.

  Examples of the organic cation in the present invention include imidazolium cation, pyridinium cation, quaternary ammonium cation and quaternary phosphonium cation. By combining these organic cations with bis (fluorosulfonyl) imide anions, the viscosity of the ionic liquid as a synthetic lubricating oil can be greatly reduced.

  Although it does not specifically limit as an imidazolium cation, For example, what has the structure of following General formula (1) can be mention | raise | lifted.

(In the formula (1), each of the substituents R ^{1 to} R ⁵ is independently a hydrogen atom, a halogen atom, a linear or branched alkyl group having 1 to 16 carbon atoms, an alkenyl group, an alkynyl group, an alkoxyl group, an acyl group. A group, an amide group, a cyano group, a nitro group, an amino group, and an alkyl group, an alkenyl group, an alkynyl group, an alkoxyl group, or an acyl group containing a heteroatom selected from N, S, and O And may contain conjugated or independent double or triple bonds.)

When the substituents R ^{1 to} R ⁵ are an alkyl group, an alkenyl group, an alkynyl group, an alkoxyl group, or an acyl group, the carbon number is preferably 1 to 16, more preferably 1 to 12, and 1 to 6 More preferably. These substituents may be either a straight chain or a branched structure, but if the number of carbons is too large, there is a tendency for the viscosity to increase because of the intermolecular interaction of the side chain.

  The alkyl group, alkenyl group, alkynyl group, alkoxyl group and acyl group may contain a heteroatom selected from N, S and O, and the number of heteroatoms contained is not particularly limited. . Further, it may contain a conjugated or independent double bond or triple bond, and the number of these unsaturated bonds is not particularly limited.

  Specific examples of such an alkyl group include, for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a secondary butyl group, a tertiary butyl group, a pentyl group, and a hexyl group. , Cyclopropyl group, cyclopentyl group, cyclohexyl group and the like. Examples of the alkenyl group include vinyl group, allyl group, 1-propenyl group, isopropenyl group, 2-butenyl group, 1,3-butadienyl group, 2-pentenyl group, and 2-hexenyl group. Furthermore, examples of the alkynyl group include ethynyl group, 1-propynyl group, 2-propynyl group and the like, and examples of the alkoxyl group include methoxy group, ethoxy group, n-propoxy group, isopropoxy group, t- Examples of the acyl group such as butoxy group include acetyl group, propionyl group, butyryl group, and benzoyl group. Examples of amino group include N, N-dimethylamino group and N, N-diethylamino group. It is done. Considering industrial utility, it is effective to increase the biodegradability by making it easily susceptible to degradation by enzymes. From this point, alkoxyl groups, acyl groups, amide groups, cyano groups, nitro groups, amino groups, etc. can give.

  As the imidazolium cation represented by the above formula (1), a 1,3-substituted imidazolium cation and a 1,2,3-substituted imidazolium cation are preferably used from the viewpoint of ease of synthesis. The substituents in these derivatives may be the same or different, and are preferably substituents that may have multiple bonds or branches.

  The substituent is the same as the substituent in the general formula (1), and is appropriately selected from these.

  In the present invention, in addition to the imidazolium cation, a pyridinium cation, a quaternary ammonium cation, and a quaternary phosphonium cation can be mentioned. Examples of the pyridinium cation include N-methylpyridinium, N-ethylpyridinium, Examples thereof include a pyridinium cation substituted with an alkyl group having 1 to 16 carbon atoms such as N-butylpyridinium and N-propylpyridinium.

  Examples of the quaternary ammonium cation include an ammonium cation substituted with an alkyl group having 1 to 16 carbon atoms such as tetramethylammonium, tetraethylammonium, and tetrabutylammonium.

  Examples of the quaternary phosphonium cation include a quaternary phosphonium cation substituted with an alkyl group having 1 to 16 carbon atoms such as tetramethylphosphonium, tetraethylphosphonium, and tetrabutylphosphonium.

  In the present invention, the anion used together with the organic cation as the anion part constituting the ionic liquid is a bis (fluorosulfonyl) imide anion. By using the anion, the viscosity is very low and the viscosity is stable. In addition, an excellent ionic liquid can be obtained.

  The production method of the ionic liquid in the present invention is not particularly limited, and a known method such as an ion exchange method or a metathesis reaction can be applied. For example, it can be obtained by an anion exchange reaction using a halogenated salt of an organic cation to be used and an alkali metal salt of a bis (fluorosulfonyl) imide anion. The halogen of the halogenated salt includes chlorine or bromine. Examples of the alkali metal of the alkali metal salt include sodium and potassium.

  The blending amount of the organic cation halide salt and the alkali metal salt of the bis (fluorosulfonyl) imide anion used in the above reaction is not particularly limited. The alkali metal salt of the (sulfonyl) imide anion is preferably 0.5 to 2 equivalents, and more preferably 0.8 to 1.2 equivalents. Even if the amount of the alkali metal salt of the bis (fluorosulfonyl) imide anion is too large, it does not affect the reaction yield, so the economy tends to deteriorate. If it is too small, a large amount of unreacted raw material remains. Therefore, the reaction yield tends to decrease.

  The synthetic lubricating oil containing an ionic liquid composed of the organic cation and the bis (fluorosulfonyl) imide anion may contain a commonly used lubricating base oil in addition to the ionic liquid, and if necessary Additives such as rust inhibitors and pour point depressants can also be used. The amount of these additives used is not particularly limited as long as it does not interfere with the effects of the present invention, but in order to take advantage of the characteristics of the ionic liquid itself, 0.001 to 0.001 with respect to the ionic liquid. It is preferably 50% by weight.

  The viscosity at 25 ° C. of the synthetic lubricating oil of the present invention is usually preferably 30 mPa · s or less, more preferably 20 mPa · s or less. When the viscosity is too high, energy loss due to the viscosity of the lubricating oil itself tends to occur. Further, the lower limit of the viscosity is usually 2 mPa · s. If it is too low, the viscosity tends to be scattered due to low viscosity.

The kinematic viscosity of the synthetic lubricating oil of the present invention is preferably ² to 20 mm ² / sec at 40 ° C., more preferably 4 to 10 mm ² / sec. Further, the kinematic viscosity is preferably 1~13mm ² / sec in 100 ° C., more preferably from 2 to 7 mm ² / sec. If the kinematic viscosity is too high at each temperature, energy loss due to the viscosity of the lubricating oil itself tends to occur. If it is too low, it tends to be scattered due to low viscosity.

  The viscosity index of the synthetic lubricating oil is preferably 180 or more, more preferably 200 or more, and particularly preferably 220 or more. The upper limit of the viscosity index is usually 700. Here, the viscosity index is an index representing the relationship between temperature and viscosity, and the calculation method of the viscosity index is Japan Industrial Standard (JIS) K2283 (kinematic viscosity test method for crude oil and petroleum products and petroleum product viscosity index calculation method). ).

  In addition, the higher the viscosity index, the smaller the change in viscosity due to temperature, which means that it is excellent as a lubricating oil.

  Lubricating oils can be used in cases where the absolute viscosity is important depending on the application, or where other physical properties such as the contact angle with the metal are more important than the absolute viscosity. In this case, the organic cation is selected from imidazolium cation, pyridinium cation, quaternary ammonium cation and quaternary phosphonium cation according to the required physical properties, and further, if necessary, the physical properties are adjusted by changing the substituent. Also in this case, the viscosity index is a physical property regarded as important. If the viscosity index is too low, the rate of change in viscosity with temperature tends to be too high.

  The synthetic lubricating oil of the present invention exhibits excellent viscosity characteristics at low viscosity and high temperature, and also has excellent physical properties such as non-volatility and thermal stability. It can be widely used as lubricating oil for equipment, precision machinery, metalworking oil and lubricating oil under special environment.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.

  In the examples, “parts” and “%” mean weight basis unless otherwise specified.

  The viscosity was determined by the following method.

(Viscosity measurement conditions)
Equipment used: AR-1000 type rotational rheometer (TA Instruments)
Measurement method: The apparatus was set at 25 ° C., a sample of 0.6 ml was placed on the sample stage, a cone was placed, and the viscosity value when the cone was rotated with a constant force (20 Pa) was read.

(Kinematic viscosity at 40 ° C and 100 ° C)
The kinematic viscosities at 40 ° C. and 100 ° C. were obtained by measuring the viscosity values at each temperature using the above-described apparatus and measurement method, and calculating from the values. Moreover, the viscosity index was calculated | required by calculation using the value of these kinematic viscosities.

Example 1
Into a flask equipped with a reflux tube, 6.28 g (76.5 mmol) of 1-methylimidazole was added, 33.0 g (302.9 mmol) of ethyl bromide and 8.20 g of acetonitrile were added, and the mixture was reacted at 40 ° C. for 8 hours. As a result, 13.4 g (70.2 mmol, yield 91.8%) of 1-ethyl-3-methylimidazolium bromide was obtained. 11.0 g (57.8 mmol) of the obtained 1-ethyl-3-methylimidazolium bromide and 13.3 g (60.6 mmol) of a potassium salt of bis (fluorosulfonyl) imide were stirred in 20 g of water at 40 ° C. for 5 hours. did. After completion of the reaction, 80 ml of methylene chloride was added and sufficiently stirred, and the methylene chloride layer was separated. The methylene chloride layer was further washed with 40 ml of water 5 times, and then the methylene chloride layer was concentrated under reduced pressure to give 15.9 g (54.4 mmol, yield 94.2%) of 1-ethyl-3-methylimidazolium bis (fluorosulfonyl) imide. )

Table 1 shows the results obtained by measuring various physical properties of the obtained 1-ethyl-3-methylimidazolium bis (fluorosulfonyl) imide .

Comparative Example 1
11.0 g (60.6 mmol) of 1-ethyl-3-methylimidazolium bromide obtained in the same manner as in Example 1 and 20.3 g (63.7 mmol) of the potassium salt of bis (trifluoromethanesulfonyl) imide anion were used. After reacting in 20 g of water-methylene chloride at 40 ° C. for 4 hours, the aqueous layer was removed by a separatory funnel, the organic layer was washed with water, and concentrated under reduced pressure to give 1-ethyl-3-methylimidazolium. 22.5 g (57.6 mmol, yield 95.0%) of bis (trifluoromethanesulfonyl) imide was obtained.

  The physical properties of the obtained 1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide were measured in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 2 (Poly α-olefin)
Physical properties were measured in the same manner as in Example 1 using poly α-olefin (Sinfluid 801 (manufactured by Chevron Phillips)). The results are shown in Table 1.

Comparative Example 3 (Diester)
Physical properties were measured in the same manner as in Example 1 using a diester (dioctyl adipate: Plashall DOA (manufactured by The CP Hall)). The results are shown in Table 1.

Comparative Example 4 (polyol ester)
Physical properties were measured in the same manner as in Example 1 using a polyol ester (polyol ester (trivalent): Caorb 190 (manufactured by Kao Corporation)). The results are shown in Table 1.

Comparative Example 5 (fluid paraffin)
Physical properties were measured in the same manner as in Example 1 using liquid paraffin (Cosmo Neutral 150: (manufactured by Cosmo Oil Lubricants Co., Ltd.)). The results are shown in Table 1.

As can be seen from the results in Table 1, synthetic lubricating oils comprising a specific organic cations and bis (fluorosulfonyl) ionic liquid consisting of imide anion of the present invention, bis known for low viscosity (trifluoromethane Compared to the case of an ionic liquid composed of (sulfonyl) imide anion and other conventional base oils, it shows a low viscosity and a high viscosity index, and it can be seen that the properties as a synthetic lubricating oil are very excellent.

  In addition, if the cation is made easily degradable by introducing a substituent for enhancing biodegradability, the remaining anion becomes an inorganic compound, so there is no need to consider the biodegradability of the anion, and in terms of the environment. It will be suitable.

  The synthetic lubricating oil of the present invention is non-volatile, has low viscosity, is excellent in viscosity characteristics at high temperature, and is excellent in thermal stability, so that it has a stable lubricating performance in a wide temperature range. It is useful as mechanical equipment for ships, electrical products, etc., power transmission equipment, lubricating oil for precision machinery, metalworking oil, and lubricating oil in special environments.

Claims (2)

A synthetic lubricating oil comprising an ionic liquid composed of an imidazolium cation and a bis (fluorosulfonyl) imide anion. In the imidazolium cation, the substituents at the 1- and 3-positions may be the same or different. The 1,3-substituted imidazolium cation or the substituents at the 1-, 2-, and 3-positions may be the same or different. synthetic lubricating oils according to claim 1, characterized in that the good 1,2,3-substituted imidazolium cation.