WO2012115141A1

WO2012115141A1 - Grease composition

Info

Publication number: WO2012115141A1
Application number: PCT/JP2012/054256
Authority: WO
Inventors: 山本　正道; 雄太佐藤
Original assignee: 協同油脂株式会社
Priority date: 2011-02-22
Filing date: 2012-02-22
Publication date: 2012-08-30
Also published as: DE112012000940T5; CN103415603A; KR20130118936A; JP2012172066A; US20130310292A1; CN103415603B

Abstract

The present invention provides a grease composition which comprises a thickening agent and a base oil, wherein the thickening agent is a diurea compound represented by formula (1) and the proportion of the thickening agent in the grease composition is 3-20 mass%. (In formula (1), R² represents a diphenylmethane group. R¹ and R³ may be the same or different and each represent a cyclohexyl group or a linear or branched C_8-22 alkyl group. In formula (1), the proportion of the number of moles of cyclohexyl groups to the total number of moles of cyclohexyl groups and alkyl groups [{(number of cyclohexyl groups)/((number of cyclohexyl groups)+(number of alkyl groups))}×100] is 70-80 mol%.)

Description

Grease composition

The present invention relates to a grease composition that can be used for lubricating various machine parts such as rolling bearings, gears, ball screws, linear motion bearings, cams, and joints.

In recent years, from the viewpoint of reducing energy consumption, electrical equipment and machine parts used in various industries including automobiles have been required to be highly efficient, and various studies have been made such as weight reduction of parts and improvement of structure. ing. In particular, the mechanical component having a rotating body stirs the lubricant, so that its resistance leads to energy loss. Therefore, there is a demand for a lubricant with low stirring resistance.
For example, in engine oil and transmission oil, low viscosity has been proposed in order to reduce the stirring resistance of lubricating oil (Non-patent Documents 1 and 2). However, these countermeasures cause oil film breakage due to low viscosity of the oil, and there is a concern about damage to the surface of the lubrication part.

Since grease can be lubricated without lubrication for a long period of time, the sealing device is simple, the required amount is small, and there is little fouling due to leakage. It is used in many machine parts that have a body. However, since grease is a semi-solid lubricant containing a base oil and a thickener, it has a higher apparent viscosity and a higher stirring resistance than a lubricant.
In the past, in order to reduce the agitation resistance of grease, it has been a common practice to make the kinematic viscosity of the base oil as low as possible as in the case of lubricating oil. For example, Patent Document 1 proposes a grease composition using a base oil containing a diester oil having a specific structure, and an example describes a diester oil having a kinematic viscosity at 40 ° C. of 20.16 mm ² / s. Has been.
However, if the kinematic viscosity of the base oil of the grease is lowered, the stirring resistance will be reduced. The base oil that can be used is limited because it disappears.

JP 2009-132754 A

The problem to be solved by the present invention is to provide a grease composition having a low stirring resistance.
Another object of the present invention is to provide a mechanical component enclosing the grease composition.

The present inventors solved this problem by selecting an appropriate thickener.
That is, according to the present invention, the following grease composition and machine parts are provided:
1. A thickener, a base oil, the thickener is a diurea compound represented by the following formula (1), and the amount of the thickener in the grease composition is 3 to 20% by mass: Grease composition.

(In formula (1), R ² represents a diphenylmethane group. R ¹ and R ³ may be the same or different, and represent a cyclohexyl group or a linear or branched alkyl group having 8 to 22 carbon atoms. In the formula (1), the ratio of the number of moles of cyclohexyl group to the total number of moles of cyclohexyl group and alkyl group [{(number of cyclohexyl groups) / (number of cyclohexyl groups + alkyl group Number)} × 100] is 70 to 80 mol%.)
2. 2. The grease composition as described in 1 above, wherein the thickener is a diurea compound in which the alkyl group is a linear alkyl group having 16 to 20 carbon atoms in the formula (1).
3. 3. The grease composition according to the above 1 or 2, which is used for rolling bearings, gears, ball screws, linear motion bearings, cams or joints.
4). A machine part in which the grease composition according to any one of 1 to 3 is encapsulated.

According to the present invention, a grease composition having a low stirring resistance can be provided. The grease composition of the present invention can suppress the occurrence of oil film breakage without lowering the kinematic viscosity of the base oil, and can satisfy a sufficiently long life.

[Thickener]
As a thickener for grease, diurea grease having a long lubrication life and general versatility is generally used. In this invention, the diurea grease manufactured by mix | blending an alicyclic amine and an aliphatic amine by specific molar ratio was selected. Such diurea grease is represented by the following formula (1):

In formula (1), R ² represents a diphenylmethane group. 4,4-diphenylmethane is preferred. R ¹ and R ³ may be the same or different and each represents a cyclohexyl group or a linear or branched, preferably linear alkyl group having 8 to 22 carbon atoms, preferably 16 to 20 carbon atoms. In formula (1), the ratio of the number of moles of cyclohexyl group to the total number of moles of cyclohexyl group and alkyl group [{(number of cyclohexyl groups) / (number of cyclohexyl groups + number of alkyl groups) )} × 100] is 70 to 80 mol%.

By using the thickener, the amount of the thickener can be reduced. By adding a specific amount of the thickener to the base oil, the stirring resistance of the grease can be reduced. Specifically, the content of the thickener is 3 to 20% by mass, preferably 5 to 15% by mass, based on the mass of the grease composition of the present invention.
Metal soaps, benton, and silica gel do not satisfy heat resistance, that is, bearing lubrication life at high temperatures. Fluorine-based thickeners are very expensive, although they are satisfactory in heat resistance, and lack versatility.

[Base oil]
The type and kinematic viscosity of the base oil in the present invention are not particularly limited. The type and kinematic viscosity of the base oil can be selected as necessary. However, the kinematic viscosity at 40 ° C. of the base oil contained in the grease used for the rolling bearing is preferably 10 to 200 mm ² / s, more preferably 15 to 100 mm ² / s. A base oil may be used individually by 1 type, and may use 2 or more types together.
The types of base oils that can be used in the present invention are roughly classified into mineral oils and synthetic oils. Examples of synthetic oils include diester oils, ester-based synthetic oils represented by polyol esters, poly-α-olefins, synthetic hydrocarbon oils represented by polybutene, ether-based synthetic oils represented by alkyl diphenyl ether, and polypropylene glycol. Representative examples include polyglycol-based synthetic oils, silicone-based synthetic oils, and fluorine-based synthetic oils. Of these, synthetic oil is preferred because of its excellent heat resistance. Synthetic hydrocarbon oils and ester synthetic oils are more preferred. When these base oils are included, the stirring resistance at low temperatures can be further reduced. The synthetic hydrocarbon oil is preferably poly-α-olefin. As the ester synthetic oil, pentaerythritol ester and trimethylolpropane ester are preferable.

〔Additive〕
The grease composition of the present invention can contain any additive as required. Examples include antioxidants typified by amines and phenols, inorganic passivating agents such as sodium nitrite, sulfonates, succinic acids, amines, rust inhibitors typified by carboxylates, and benzotriazoles. Representative metal corrosion inhibitors, fatty agents such as fatty acids, fatty acid esters and phosphate esters, antiwear and extreme pressure agents such as phosphorus, sulfur and organometallics, metal oxides and disulfides Examples thereof include solid lubricants typified by molybdenum. The amount of these components used is usually about 0.1 to 20% by mass, preferably 0.5 to 10% by mass.

[Mixing consistency]
The penetration of the grease composition of the present invention is adjusted according to the purpose of use, but is preferably 200 to 440. In particular, for bearings, if it is too soft, there is a concern of leakage, so 200 to 350 is preferable.

The grease composition of the present invention can be used by being enclosed in various machine parts. Examples of various machine parts include rolling bearings, gears, ball screws, linear motion bearings, cams, and joints. Specifically, various motors for industrial machines, various motors for office equipment, various motors for automobiles, rolling bearings used for automobile electrical parts and auxiliary machine parts, windmills, robots, reduction gears and speed increasers for automobiles, etc. Gears used in the above, ball screws used in electric power steering and machine tools, linear motion bearings used in industrial equipment and electronic equipment, cams or joints.

<Preparation of test grease>
Using the thickener and base oil shown in Table 1, grease compositions of Examples and Comparative Examples were prepared. Specifically, 4,4-diphenylmethane diisocyanate and a predetermined amine are reacted in a base oil, heated and cooled, and then kneaded with a three-roll mill. Examples 1 and 2 and Comparative Examples 1 to 9 grease compositions were obtained. As the base oil, JIS K2220 23. The poly-α-olefin oil is a synthetic hydrocarbon oil having a kinematic viscosity at 40 ° C. of 70.2 mm ² / s, or a diester oil having a kinematic viscosity at 40 ° C. of 11.6 mm ² / s. A dioctyl sebacate was used. The amount of the thickener was adjusted so that the grease composition had a blending degree of 300 (test method JIS K2220 7.).
The grease composition prepared above was evaluated by the following test method. The results are shown in Table 1.

<Test method>
・ Agitation resistance (rheometer)
The test was performed using a viscoelasticity measuring device manufactured by Anton Paar, Physica MCR301.
The test grease was applied between the predetermined plates, and after setting the predetermined distance between the plates, the excess grease that protruded was removed. Then, the shear stress when rotating at the shear rate shown below was read.
Test conditions are shown below.
Shear rate: 1 to 10 ⁴ s ^-1
Test temperature: 25 ° C
Distance between plates: 0.2mm
Plate diameter: 25mm
<Evaluation>
An average value of shear stress at a shear rate of 1 to 10 ⁴ s ⁻¹ was calculated and used as a measurement result.
Less than 2000Pa ・・・ Pass 2000Pa or more ・・・ Fail

The grease compositions of Examples 1 and 2 containing the diurea thickener of the present invention have good low shear stress (= stirring resistance), while they are not the diurea thickener of the present invention. No. 9 had high shear stress. Comparative Example 9 uses a low-viscosity diester oil as the base oil, but it was not a diurea thickener according to the present invention, and thus the shear stress was high.

Claims

A thickener, a base oil, the thickener is a diurea compound represented by the following formula (1), and the amount of the thickener in the grease composition is 3 to 20% by mass: Grease composition.

(In the formula (1), R 2 represents a diphenylmethane group. R 1 and R 3 may be the same or different, and represent a cyclohexyl group or a linear or branched alkyl group having 8 to 22 carbon atoms. In the formula (1), the ratio of the number of moles of cyclohexyl group to the total number of moles of cyclohexyl group and alkyl group [{(number of cyclohexyl groups) / (number of cyclohexyl groups + alkyl group Number)} × 100] is 70 to 80 mol%.)
The grease composition according to claim 1, wherein the thickener is a diurea compound in which the alkyl group in the formula (1) is a linear alkyl group having 16 to 20 carbon atoms.
The grease composition according to claim 1 or 2, which is used for rolling bearings, gears, ball screws, linear motion bearings, cams or joints.
A machine part in which the grease composition according to any one of claims 1 to 3 is enclosed.