JPH09208981A - Grease composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a grease composition with low coefficient of friction, excellent in abrasion resistance, and capable of prolonging the service life of machine/equipment when applied to an isotachojoint or high-temperature/high-speed bearing, by incorporating a base oil with a urea-based thickening agent and hexagonal boron nitride. SOLUTION: This grease composition is obtained by incorporating a base grease prepared by adding (B) a compound having urea group in the molecule as thickening agent to (A) a base oil with (C) hexagonal boron nitride. When the graphitization index of the ingredient C is <=3.5, the grease composition with good abrasion resistance and further favorable grease characteristics can be obtained. The amount of the ingredient B is normally 2-25wt.% based on the whole amount of the base grease, while the amount of the ingredient C is 0.5-20wt.% based on the grease composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grease composition suitable for automobile wheel bearings, constant velocity joints and other automobile greases, iron making facility greases, and high temperature and high speed bearing greases used in various applications. In particular, the present invention relates to a grease composition suitable for constant velocity joints.

[0002]

2. Description of the Related Art Grease is used as a lubricant for sliding parts of various machines such as transportation machines such as automobiles, steel-making machines, and construction machines. For the reason of efficiency improvement, the one having further excellent characteristics is required.

In particular, the recent demand for higher performance of automobiles is remarkable, and for example, as a grease for constant velocity joints used in FF vehicles, a base grease using refined mineral oil and lithium soap or a urea compound as a thickener. In addition, molybdenum disulfide added with a sulfur-phosphorus compound or lead compound is used, but the grease performance is not sufficient, the friction coefficient is low, the wear resistance is excellent, and therefore the long life is obtained. Grease is coveted.

[0004]

That is, the object of the present invention is to provide a low coefficient of friction and excellent wear resistance, which is suitable for use in, for example, constant velocity joints or high-temperature / high-speed bearings.
It is to provide grease effective for extending the life of the device.

[0005]

The present invention is a grease composition characterized in that a base oil contains a urea thickener and hexagonal boron nitride, and the hexagonal boron nitride is graphitized. The grease composition has the index of 3.5 or less. Further, the present invention is the grease composition for a constant velocity joint, wherein the hexagonal boron nitride has an average particle size of 1 μm or more and 30 μm or less.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

In the present invention, a base oil, a thickener and hexagonal boron nitride are contained, and various kinds of petroleum-based lubricating oils such as paraffin-based and naphthene-based lubricating oils and synthetic oils can be used as the base oil. A compound having a urea group in the molecule is added as a thickener to the base oil to prepare a base grease. The amount of the thickener added is generally 2 to 25% by weight based on the total amount of the base grease. In addition, the compound having a urea group is prepared by mixing diisocyanate with a compound of a primary amine or a secondary amine to obtain 1 in a base oil.
It can also be obtained by reacting at 0 to 200 ° C.

The types of thickeners used in the present invention are limited to compounds having a urea group (hereinafter referred to as "urea thickeners"). I'm not sure why,
When using a thickener other than a urea thickener, no matter how the hexagonal boron nitride is limited, it is impossible to obtain a grease having excellent friction characteristics. It is based on the knowledge obtained.

As the urea-based thickener, various ones such as aliphatic diurea, alicyclic diurea, aromatic diurea, triurea and tetraurea are known, and these can be used alone or in combination of two or more. .

Regarding boron nitride, cubic crystal, rhombohedral, and hexagonal crystal systems, PBN, and t-
Although various materials such as BN are known, in the present invention, hexagonal boron nitride is used. This is because only hexagonal boron nitride has a sliding deformability due to its crystal structure, and it is desirable that the hexagonal boron nitride has a developed crystal.

The following graphitization index is known as an index for knowing the degree of crystal growth of hexagonal boron nitride. Graphitization index = (Ia + Ib) / Ic Here, Ia represents the peak area in X-ray diffraction of (100), Ib (101), and Ic (102), and the smaller the graphitization index, the better the crystallinity. is there.

In the present invention, when it is limited to boron nitride having a graphitization index of 3.5 or less, a grease composition having good wear resistance and more preferable grease properties can be obtained, which is preferable.

Regarding the size of boron nitride, a method for evaluating the average particle diameter by Microtrac is known, and the following average particle diameter is also measured by the above method. The boron nitride of the present invention preferably has an average particle size of 1 μm or more and 30 μm or less. That is, the boron nitride powder is necessary for the grease composition to exhibit stable grease characteristics without the mutual aggregation of the boron nitride particles, and the lower limit value is the amount of boron nitride added and increased. Although it is affected by the amount of the agent added, etc., according to the experimental study by the present inventors,
The average particle size is 1 μm.

On the other hand, when the boron nitride particles are large, it is difficult for the individual boron nitride particles to easily enter the sliding surface, and as a result, the frictional characteristics of the grease are deteriorated. Although it is influenced by the addition amount, the addition amount of the thickener and the like, according to the study by the present inventors, it is about 100 μm and the average particle diameter is 30 μm.

The content of the boron nitride of the present invention in the grease composition is 0.5% by weight or more and 20% by weight or more.
It is as follows. If the amount is less than 0.5% by weight, sufficient amount of boron nitride particles are not supplied to the sliding surface, so that friction characteristics cannot be obtained. If the amount is more than 20% by weight, the viscosity of the obtained grease becomes too high. It becomes impossible to exhibit sufficient lubrication characteristics. Among these, 1% by weight or more and 10% by weight or less is a preferable range for the same reason as above.

In the present invention, components other than the base oil, the thickener and the hexagonal boron nitride can be added within the range where the grease characteristics are not deteriorated. Examples of the components include graphite, fluorinated graphite, molybdenum disulfide, polytetrafluoroethylene, antimony sulfide, solid lubricants such as borates of alkali metals and alkaline earth metals, and sulfur compounds and phosphorus compounds. Various extreme pressure agents, various antioxidants represented by phenolic compounds and amine compounds, oily agents such as laurylamine, viscosity index improvers such as polymethacrylate, and rust inhibitors. Can be

The present invention will be described in more detail based on the following examples.

【Example】

[Examples 1 to 5] Paraffin-based mineral oil was used as a base oil, and an aromatic diurea-based grease was added as a thickener to the total amount of both base greases in an amount of 18% by weight. A hexagonal boron nitride powder having a particle size and a graphitization index was blended so as to be 3% by weight with respect to the total amount of the grease composition and mixed by a three-stage roll mill to prepare a grease composition.

Using the shell type four-ball tester, the grease composition was slid under a test load of 40 kgf, a rotation speed of 1200 rpm, a grease temperature of 1200 rpm, a test time of 75 ° C., and a test time of 60 min based on ASTM D4172. A test was conducted and the coefficient of friction was measured. Then, in order to evaluate the wear resistance, the wear scar diameter of the test steel ball was measured. The results are shown in Table 1.

Comparative Example A grease composition was prepared under the same conditions as in the example except that molybdenum disulfide was used instead of boron nitride, and an evaluation test was conducted. It is also described in Table 1.

[0020]

[Table 1]

[Examples 6 and 7] The grease compositions of Examples 2 and 4 were continuously operated for 200 hours with an SRV needle tester, and none of them reached the end of their lives, and were good. It was Commercially available # 8 for the joint
7TJ was used.

[0022]

Since the grease composition of the present invention has a low friction coefficient and excellent wear resistance, it can be used in various applications such as automobile grease used for automobile wheel bearings, constant velocity joints, etc., or grease for iron making equipment. It is suitable for high temperature and high speed bearing greases used in, and helps to extend the service life of these greases, and is industrially useful. Further, the grease composition of the present invention, when used in a grease for constant velocity joints, has an excellent anti-vibration effect because of its low friction coefficient and is excellent, and also has excellent abrasion resistance and can prevent the occurrence of seizure and flaking. Good results are obtained.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area C10N 20:00 20:06 30:06 30:08 40:02 40:04 50:10

Claims (4)

[Claims] 1. A grease composition comprising a base oil, a urea thickener, and hexagonal boron nitride. 2. The graphitization index of the hexagonal boron nitride is 3.
The grease composition according to claim 1, which is 5 or less. 3. The hexagonal boron nitride has an average particle size of 1 μm.
The grease composition according to claim 2, wherein the grease composition has a size of not less than m and not more than 30 μm. 4. The grease composition for a constant velocity joint according to claim 2 or 3.