JP2008133309A - Grease composition and rolling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a grease composition that makes the best use of heat resistance and low wear properties being characteristics of an ionic liquid without corroding a rolling device made of iron. <P>SOLUTION: The grease composition comprises a base oil, a thickening agent and an ionic liquid. The content of the ionic liquid is 0.5-30 wt.% based on the total amount of the composition. The rolling device that is usable in a wide temperature range and has a long life is obtained by sealing the grease composition in the rolling device. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a grease composition containing a base oil, a thickener, and an ionic liquid, and a rolling device in which the grease composition is enclosed.

  It has been found that an ionic liquid which is a room temperature molten salt has a low viscosity and excellent thermal stability by combining various organic ions.

  In recent years, many uses and applications of lubricants have been reported (for example, see Patent Document 1 and Non-Patent Documents 1 to 5). Grease containing an ionic liquid is excellent in heat resistance and low wear and is expected to be applied to various rolling elements.

  However, there are many unclear points regarding the performance and properties of ionic liquids, and there remains much room for investigation as to what conditions can be suitably used.

In particular, ionic liquids exist due to ionic bonds between anions and cations. Therefore, when grease containing ionic liquids is enclosed in steel bearings (SUJ2 etc.) and used, metallic elements contained in steel (of steel) In some cases, there was a problem that an oxidation-reduction reaction mainly with Fe) could cause corrosion of the steel.
JP 2004-183868 A The Tribology Society of Japan Proceedings Tokyo 2004.5 p163-164 Japan Tribology Society Proceedings Tokyo 2004.5 p165-167 Functional Materials CMC Publishing November 2004, p63-68 Japan Tribology Society Proceedings Tottori 2004.11 p569-570 Proceedings of the Japanese Society of Tribology Tottori 2004.11 p571-572

  In view of such circumstances, an object of the present invention is to provide a grease composition that can make use of the heat resistance and low wear characteristics of an ionic liquid without corroding a steel rolling device. And

  In order to solve the above problems, the grease composition according to the present invention contains a base oil, a thickener, and an ionic liquid, and the content of the ionic liquid is 0.5 to 30% by weight of the whole. It is characterized by being.

  If the content of the ionic liquid is kept in the above range, the base oil covers the surface of the metal constituting the rolling element when enclosed in the rolling element, so that the reaction of the ionic liquid to the steel is alleviated and the metal Corrosion can be suppressed. If the content of the ionic liquid is 30% by weight or more, the effect of suppressing steel corrosion cannot be obtained, and the seizure life is shortened. Therefore, the content of the ionic liquid is preferably 20% by weight or less. On the other hand, when the content of the ionic liquid is less than 0.5% by weight, the heat resistance and low frictional effects of the ionic liquid cannot be obtained. Therefore, the content of the ionic liquid is preferably 1% by weight. % Or more.

  The base oil is preferably a synthetic hydrocarbon oil. With such a configuration, the effect of suppressing corrosion of steel can be further enhanced.

  Moreover, this invention also includes the rolling device which enclosed the grease composition of this invention. Such a rolling device does not easily corrode even if a grease composition containing an ionic liquid is enclosed, and has the advantages of a grease composition containing an ionic liquid that is excellent in heat resistance and low friction. It will be utilized in.

  The grease composition of the present invention can effectively utilize the characteristics of an ionic liquid that is excellent in heat resistance and low friction without corroding the metal of the rolling device. By enclosing such a grease composition, a long-life rolling device that can be used in a wide temperature range can be obtained.

  Hereinafter, preferred embodiments of the grease composition and the rolling device of the present invention will be described.

  The grease composition according to the present invention contains a base oil, a thickener, and an ionic liquid. Hereinafter, each component will be specifically described.

(Ionic liquid)
An ionic liquid is a non-volatile salt which is liquid at room temperature and consists of a cation and an anion, and is excellent in conductivity and heat resistance.

Examples of the ionic liquid used in the present invention include a pyridine series represented by the following general formula (I), an imidazolium series represented by the general formula (II), and an alicyclic group represented by the general formula (III). A combination of an anion (X ⁻ ) and a cation such as an amine, an aliphatic amine represented by the general formula (IV), and a phosphonium based represented by the general formula (V) can be given. The anion (X ⁻ ) can be selected from BF ₄ ⁻ , PF ₆ ⁻ , [(CF ₃ SO ₂ ) ₂ N] ⁻ , Cl ⁻ , Br ^{− and the} like. In the formula, R represents an alkyl group or an alkoxy group.
it can.

As the ionic liquid has a larger number of carbon atoms and a larger molecular weight in the above chemical formula, the kinematic viscosity increases. The kinematic viscosity at 40 ° C. is known to be approximately 12 mm ² / s to 260 mm ² / s, and an appropriate viscosity can be obtained by using ionic liquids alone or in combination. Moreover, the thing whose melting | fusing point is -45 degrees C or less exists, and fully satisfy | fills the use range of lubricating oil.

  In addition, since an ionic liquid is expensive, when there are many compounding quantities, since a grease composition will also become expensive, it is more preferable to reduce the compounding quantity to grease.

(About base oil)
The base oil used for this invention is not specifically limited, All the oils normally used as a base oil of lubricating oil can be used. A base oil having a kinematic viscosity at 40 ° C. of 10 to 400 mm ² / s is preferable, more preferably, in order to avoid generation of abnormal noise at low-frequency startup due to insufficient low-frequency fluidity and seizure due to insufficient oil film formation at high temperatures. 20~250mm ² / s, more preferably from 25 to 150 mm ² / s.

  Specific examples include mineral oil-based, synthetic oil-based or natural oil-based lubricating oils. As the mineral oil-based lubricating oil, it is possible to use a refined oil obtained by appropriately combining mineral oil under reduced pressure distillation, oil removal, solvent extraction, hydrocracking, solvent dewaxing, sulfuric acid washing, white clay purification, hydrorefining, etc. it can. Examples of the synthetic oil base oil include hydrocarbon oils, aromatic oils, ester oils, ether oils and the like. Examples of the hydrocarbon oil include normal paraffin, isoparaffin, polybutene, polyisobutylene, 1-decene oligomer, poly-α-olefin such as 1-decene and ethylene co-oligomer, and hydrides thereof. Examples of the aromatic oil include alkylbenzenes such as monoalkylbenzene and dialkylbenzene, and alkylnaphthalenes such as monoalkylnaphthalene, dialkylnaphthalene and polyalkylnaphthalene. Examples of the ester oil include dibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, ditridecyl glutarate, and methyl acetyl cinnolate, or trioctyl trimellitate. , Aromatic ester oils such as tridecyl trimellitate and tetraoctyl pyromellitate, as well as trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol belargonate, etc. Examples thereof include polyol ester oils, and complex ester oils that are oligoesters of polyhydric alcohols and mixed fatty acids of dibasic acids and monobasic acids. Examples of the ether oil include polyglycols such as polyethylene glycol, polypropylene glycol, polyethylene glycol monoether, polypropylene glycol monoether, monoalkyl triphenyl ether, alkyl diphenyl ether, dialkyl diphenyl ether, pentaphenyl ether, tetraphenyl ether, mono And phenyl ether oils such as alkyl tetraphenyl ether and dialkyl tetraphenyl ether. Other synthetic lubricating base oils include tricresyl phosphate, silicone oil, perfluoroalkyl ether and the like. Examples of the natural oil-based lubricating base oil include beef tallow, lard, soybean oil, rapeseed oil, rice bran oil, coconut oil, palm oil, palm kernel oil, and other oils and hydrides thereof. These base oils can be used alone or as a mixture, and are adjusted to the above-mentioned preferable kinematic viscosity.

(About thickener)
The thickener used in the present invention is not particularly limited as long as it has the ability to form a gel structure and retain the base oil in the gel structure. Metal soap can be used, and benton, silica gel, urea can be used. Non-soaps such as compounds, urea / urethane compounds and urethane compounds may be appropriately selected and used. Considering the heat resistance of the grease, a urea compound, a urea / urethane compound, a urethane compound, or a mixture thereof is preferable. Specific examples of the urea compound, urea / urethane compound, and urethane compound include diurea compounds, triurea compounds, tetraurea compounds, polyurea compounds, urea / urethane compounds, diurethane compounds, and mixtures thereof. , Urea / urethane compounds, diurethane compounds, or mixtures thereof are more preferred. In view of heat resistance and acoustic properties, a diurea compound is desirable.

  As the blending amount of the thickener, the initial blending degree of the grease is NLGI No. In order to make it 1-3, it is desirable to mix | blend 8-30 weight%. If it is less than 8% by weight, the grease becomes too soft and there is a concern about grease leakage at high temperatures. On the other hand, if it exceeds 30% by weight, it will cause torque unevenness and abnormal noise during low sound.

(About additives)
In the grease composition of the present invention, known antioxidants, rust inhibitors, metal deactivators, oil agents, extreme pressure agents, antiwear agents and the like can be used as necessary. The ionic liquid of the present application is soluble in alcohol or the like, but is insoluble in hexane. Since the grease itself is a semi-solid substance, it can be uniformly mixed by kneader or milling, but the additive is preferably soluble in an ionic liquid.

(Grease composition production method)
There are no particular restrictions on the method for preparing the grease composition of the present invention. However, it can generally be obtained by reacting a thickener in the base oil. It is preferable to add a predetermined amount of the additive to the obtained grease composition. The mixture may be sufficiently stirred with a kneader or a roll mill, and may be heated when performing this treatment.

(Rolling device)
The structure itself of the rolling device according to the present invention is not limited, and examples thereof include a rolling bearing, a ball screw, and a linear guide. The rolling device according to the present invention is a long-life device excellent in durability in a wide temperature range from a low temperature to a high temperature because the above-described grease composition of the present invention is enclosed.

  Hereinafter, although an example and a comparative example explain still more concretely, the present invention is not limited at all by these.

  First, grease compositions having compositions shown in Table 1 and used as examples and comparative examples were synthesized.

  A compound represented by the following formula (VI) was used as the ionic liquid, a synthetic hydrocarbon oil was used as the base oil, and a urea compound was used as the thickener.

As shown in FIG. 1, a deep groove ball bearing 11 with a contact rubber seal having an inner diameter of 17 mm, an outer diameter of 40 mm, and a width of 12 mm was produced. The inner ring 19, the outer ring 17, and the rolling element 20 were made of steel (SUJ2). In these deep groove ball bearings, the greases of the examples and comparative examples are filled with 30% of the bearing space volume, and the inner ring rotational speed is 6000 min ⁻¹ , the bearing outer ring temperature is 180 ° C., the radial load is 19.6 N, and the axial load is 196 N. The bearing was rotated continuously. The test was terminated when seizure occurred and the bearing outer ring temperature rose to 190 ° C or higher. The seizure life time of Comparative Example 1 was set to 1, and a comparison with Examples was performed. The results are shown in FIG.

  When a grease composition having an ionic liquid content of 0.5 to 30% by weight is used, a seizure life ratio is high, corrosion caused by the ionic liquid is suppressed, and a rolling device with excellent high-temperature durability is obtained. It was confirmed that

It is a schematic sectional drawing which shows one Embodiment of the rolling device which concerns on this invention. The result of the seizure test of the rolling device enclosing the grease composition according to the present invention is shown.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Deep groove ball bearing, 17 ... Outer ring, 19 ... Inner ring, 20 ... Rolling element, 23 ... Bearing space

Claims (4)

  A grease composition comprising a base oil, a thickener, and an ionic liquid, wherein the content of the ionic liquid is 0.5 to 30% by weight of the whole.   The grease composition according to claim 1, wherein the base oil is a synthetic oil.   The grease composition according to claim 1 or 2, wherein the base oil is a synthetic hydrocarbon oil.   The rolling device which enclosed the grease composition of any one of Claim 1 to 3.

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