JP2013060533A - Lubricant composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lubricant composition having a low dynamic friction coefficient and exhibiting a high wear resistance.SOLUTION: The lubricant composition contains a base oil, and 0.001 to 10 mass% of a silicone oil based on the total amount of the composition, and 0.001 to 10 mass% of a metal sulfonate having a total base value of ≥100 mgKOH/g based on the total amount of the composition; the silicone oil preferably has one substituent of a hydroxyl group, a carboxylic acid group and an ester group; and the composition preferably further contains one of an amide compound, a urea compound and a fatty acid soap, and is semisolid at normal temperature.

Description

  The present invention relates to a lubricant composition having excellent wear resistance, and more particularly to a semi-solid lubricant composition at room temperature.

  In recent years, multi-functionality, high performance, environmental friendliness, energy saving, and long life have become important key technologies in various industrial technologies. There are many environmental issues such as reduction of carbon dioxide emissions, power saving, energy saving, and effective use of resources. For this reason, various mechanical systems such as small precision machines, industrial machines, and transportation systems have been devised to be environmentally friendly, and have been given characteristics such as longer life, improved reliability, and higher performance. I came.

  As an example of extending the life, it is required to maintain the lubrication performance of the sliding portion of the machine without a problem until the product life. Recently, the lubrication conditions of mechanical systems have become more severe, and lubricating oils require higher performance lubricity.

  The present inventor has been developing a semi-solid lubricant composition that is excellent in wear resistance and extreme pressure at room temperature, and blends an alkaline earth metal salt and an amide compound with a liquid lubricant base oil. Thus, a lubricant composition that is semi-solid at room temperature and has high lubricity even in a thin film state and exhibits a high dynamic friction coefficient advantageous for power transmission has been proposed (Patent Document 1). Examples of such applications include opening and closing of two parts, such as a notebook personal computer and a mobile phone, and a hinge that maintains the angle.

JP 2008-239840 A

  However, lower dynamic friction coefficients are required for lubricants used for lubrication, such as bearings in many mechanical systems such as automobile engine mechanisms and various mechanical systems. In addition, high wear resistance is required in applications of mechanical systems using mechanical elements such as gears, vane pumps, and piston pumps. An object of the present invention is to provide a lubricant composition having a low coefficient of dynamic friction and exhibiting high wear resistance.

  As a result of diligent research to solve the above-mentioned problems, the inventors presumed that the formation of a reaction film when silicone oil and a specific metal sulfonate were blended with a lubricating base oil, but the dynamic friction coefficient was remarkably high. Surprisingly, the inventors have found that the wear resistance is improved, and have arrived at the present invention. That is, the present invention is the following lubricant composition.

(1) The base oil contains 0.001 to 10% by mass of silicone oil based on the total amount of the composition, and 0.001 to 10% by mass of metal sulfonate having a total base number of 100 mgKOH / g or more based on the total amount of the composition. Lubricant composition.

(2) The lubricant composition according to (1), wherein the silicone oil is a silicone oil having a substituent of any one of a hydroxyl group, a carboxylic acid group, and an ester group.

  Furthermore, the lubricant composition according to (1), which contains any one of an amide compound, a urea compound, and a fatty acid soap and is semi-solid at normal temperature.

  According to the lubricant composition of the present invention, it is possible to simultaneously achieve a low coefficient of dynamic friction and a high wear resistance by containing silicone oil and a metal sulfonate having a total base number of 100 mgKOH / g or more. This effect seems to be due to the formation of a specific reaction membrane by silicone oil and metal sulfonate having a total base number of 100 mgKOH / g or more.

[Base oil]
As the base oil used in the present invention, a lubricating base oil usually used for a lubricating oil, for example, a mineral base oil or a synthetic base oil (such as an ester base or an ether base) can be used. In particular, a hydrocarbon base oil such as a mineral oil composed of a hydrocarbon compound is preferable, and an α-olefin oligomer is particularly preferable. As the base oil, kinematic viscosity at 40 ° C., 5 to 5000 mm ² / s, especially 5 to 500 mm ² / s, further preferably those of 10 to 200 mm ² / s.

[Silicone oil]
Silicone oil is a compound having a kinematic viscosity at 25 ° C. of 5 to 5000 mm ² / s having a siloxane bond as a main skeleton, such as dimethylpolysiloxane. It is preferable to use a modified silicone into which a substituent is introduced in addition to the silicone oil into which only a methyl group or a phenyl group is introduced. Examples of such a substituent include a hydroxyl group, a carboxylic acid group (carboxyl group), an ester group, an ester group, an amino group, and a polyether group.

  The content of the silicone oil is preferably 0.01 to 10% by mass, particularly 0.1 to 5% by mass, and more preferably 0.2 to 5% by mass with respect to the total mass of the lubricant composition.

[Metal sulfonate]
The metal sulfonate is a metal salt of sulfonic acid. In the present invention, a metal sulfonate commercially available as a metal detergent and dispersant may be used. Usually, alkaline earth metal salts such as Ca, Ba and Mg are preferred, and Ca salts are particularly preferred. The total base number is 100 mgKOH / g or more, preferably 150 to 700 mgKOH / g, more preferably 300 to 600 mgKOH / g.

  The content of the metal sulfonate is preferably 0.01 to 10% by mass, particularly 0.1 to 5% by mass, and more preferably 0.2 to 5% by mass with respect to the total mass of the lubricant composition.

[Amide compound]
In order to make the lubricant of the present invention semi-solid at room temperature, it is preferable to contain any one of an amide compound, a urea compound, and a fatty acid soap. As the urea compound and the fatty acid soap, a compound that is usually used as a thickener for so-called grease can be used. Here, “normal temperature” means a normal temperature in the room, specifically, a temperature environment of about −20 to 50 ° C., more generally about −10 to 30 ° C.

  In particular, an amide compound is preferably used. The amide compound is a fatty acid amide compound having one or more amide groups (—NH—CO—), and includes a monoamide having one amide group represented by the following formula (1), and formulas (2) and (3 The bisamide having two amide groups represented by) can be preferably used, and bisamide is particularly preferable.

In the above formula, R ¹ and R ² are each independently a saturated or unsaturated chain hydrocarbon group having 5 to 25 carbon atoms, and R ² may be hydrogen.

In the above formulas (2) and (3), R ³ , R ⁴ , R ⁵ and R ⁶ are each independently a saturated or unsaturated chain hydrocarbon group having 5 to 25 carbon atoms, and A ¹ And A ² is a divalent hydrocarbon group having 1 to 10 carbon atoms selected from an alkylene group having 1 to 10 carbon atoms, a phenylene group, or an alkylphenylene group having 7 to 10 carbon atoms. In the case of an alkylphenylene group, it may be a divalent hydrocarbon group in which two or more of a phenylene group and an alkyl group and / or an alkylene group are bonded.

The bisamide compound is a compound represented by the above formula (2) or (3) in the form of a diamine acid amide or a diacid acid amide. In addition, in the hydrocarbon groups represented by R ³ , R ⁴ , R ⁵ and R ⁶ , and A ¹ and A ² in the formulas (2) and (3), some hydrogens are substituted with hydroxyl groups (—OH). May be.
Specific examples of the amide compound represented by the formula (2) include ethylene bis stearic acid amide, ethylene bis isostearic acid amide, ethylene bis oleic acid amide, methylene bis lauric acid amide, hexamethylene bis oleic acid amide, and hexamethylene. Examples thereof include bishydroxystearic acid amide and m-xylylene bisstearic acid amide. Specific examples of the amide compound represented by the formula (3) include N, N′-distearyl sebacic acid amide.

Among these bisamide compounds, R ³ and R ⁴ in formula (2) and R ⁵ and R ^{6 in} formula (3) are each independently an amide compound having a saturated chain hydrocarbon group having 12 to 20 carbon atoms and / or At least one of R ³ and R ⁴ and R ⁵ and R ⁶ is preferably an amide compound having an unsaturated chain hydrocarbon group having 12 to 20 carbon atoms, and a mixture of both amide compounds is more preferable.

  The content of the amide compound is 0.1 to 90% by mass, preferably 1 to 50% by mass, and more preferably 5 to 20% by mass with respect to the total weight of the lubricant composition. If the content of the amide compound is less than this range, a gel-like composition cannot be formed at room temperature. On the other hand, even if the content exceeds this range, it becomes too hard and difficult to handle.

  In the composition of the present invention, additives such as well-known extreme pressure agents, corrosion inhibitors, antiwear agents, rust inhibitors, antioxidants, and antifoaming agents can be appropriately blended. Antioxidants such as extreme pressure agents, zinc dialkyldithiophosphates, sulfur compounds and phosphorus compounds as antiwear agents, thiadiazole derivatives, benzotriazole and derivatives thereof as corrosion inhibitors, fatty acid partial esters and phosphorus compounds as rust inhibitors Examples of the agent include phenolic and amine compounds, and PMA polymer, pour point depressant, and viscosity index improver include PMA polymer. The various additives can also be used in the form of a so-called additive package in which several kinds are mixed in advance.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

Base oils for preparing lubricant compositions for Examples and Comparative Examples include α-olefin oligomers (kinematic viscosity (40 ° C.): 46.6 mm ² / s, kinematic viscosity (100 ° C.): 7.8 mm. ² / s, BP DURASYN 168) was used.
As additives, N-stearyl stearamide as a gelling agent, Shin-Etsu Chemical Co., Ltd. reactive silicone oil X22-3710 (kinematic viscosity (25 ° C.): 60 mm ² / s, functional as a carboxy-modified silicone oil) Group equivalent: 1450 mol / g), high base value calcium sulfonate (total base value TNB: 400 mg KOH / g, TLA414 manufactured by Texaco), low base value calcium sulfonate (total base value TNB: 50 mg KOH / g, NA- manufactured by KING INDUSTRIES) SUL CA) was used.

[Preparation of Lubricant Composition]
Sample oils (lubricant compositions) of Example 1 and Comparative Examples 1 to 4 were prepared by the following procedure by blending the base oil and additives in the proportions shown in Table 1 (mass% based on the total mass of the lubricant). .
In a stainless steel beaker, weigh out a specified amount of each base oil and additive so that about 100 ml of test oil can be obtained, and use a tabletop electromagnetic heater to heat above the melting point of the gelling agent (melting point + 20 ° C). While stirring. After judging the appearance of uniform dissolution by observing the appearance, about 100 ml of the uniform solution was transferred to a heat-resistant glass container (inner diameter 60 mm × height 90 mm) and allowed to cool to room temperature of Example 1 and Comparative Examples 1-3. A semi-solid lubricant composition was prepared.

  The base oil and the additive were blended in the proportions shown in Table 1 (mass% with respect to the total mass of the lubricant), stirred using a desktop electromagnetic heater while heating to about 60 ° C., Example 2 and Comparative Examples 5 to 5. 7 sample oil (lubricant composition) was prepared.

[Evaluation method]
Evaluation tests (such as measurement of friction coefficient) of the lubricant compositions of Examples 1 and 2 and Comparative Examples 1 to 6 were performed according to the method described below. The results are shown at the bottom of Table 1.

  A ball-on-disk reciprocating friction tester was used. The ball is a ball bearing steel ball of 6.35mm in diameter made of SUJ-2 bearing steel, and the disc is a disk-shaped test piece of material 24mm in diameter and 7mm in thickness made of SUJ-2 bearing steel. It was. The discs were polished with # 0, # 1000 and # 2000 emery papers and used for experiments.The friction test was performed for 60 minutes at a load of 20 N, amplitude of 1 Hz, amplitude of 4 mm, and room temperature for 60 minutes. The dynamic friction coefficient was measured from 60 minutes to 60 minutes, and after the friction was stopped, the wear scar diameter micrometer (μm) unit of the test ball was measured. The test was started, and the average value of values obtained by measuring the dynamic friction coefficient for 15 minutes to 60 minutes every 5 minutes was defined as the average friction coefficient.

  In Example 1, the average friction coefficient and the friction coefficient after 60 minutes are almost the same numerical value, the wear scar diameter is as small as 158 μm, and the wear resistance is excellent. When this surface was observed with a laser microscope (VIOLET LASER 3D PROFILE MICROSCOPE VK-9510, manufactured by KEYENCE), the formation of a reaction film was confirmed at the interface, which seems to improve the wear resistance.

  On the other hand, in Comparative Examples 1 to 4, the friction coefficient after 60 minutes is larger than the average friction coefficient. The wear scar diameter of Comparative Example 2 is as large as 200 μm and is inferior in wear resistance.

The friction coefficient of Example 2 is lower than that of Comparative Examples 5 and 6. Although the wear scar diameter is 172 μm in Example 2, Comparative Example 6 is as large as 287 μm, and Example 2 is excellent in wear resistance.
From the above results, it can be seen that the examples of the present invention have a low coefficient of friction and excellent wear resistance.

  As is clear from the above, the lubricant composition according to the present invention can ensure sufficient lubrication over a long period of time by exhibiting a low dynamic friction coefficient and excellent wear resistance. For example, gears, belts, chains, wire ropes, etc. , Hinges, mechanical continuously variable transmissions, bearings, constant velocity joints, ball screws, linear motion guides, and other mechanical systems having transmission element mechanisms.

Claims (3)

  Lubricant composition comprising 0.001 to 10% by mass of silicone oil based on the total amount of the composition and 0.001 to 10% by mass of metal sulfonate having a total base number of 100 mgKOH / g or more based on the total amount of the composition. .   The lubricant composition according to claim 1, wherein the silicone oil is a silicone oil having a substituent of any one of a hydroxyl group, a carboxylic acid group, and an ester group.   The lubricant composition according to claim 1, further comprising any one of an amide compound, a urea compound, and a fatty acid soap and being semi-solid at normal temperature.