JPH0959664A - Grease composition for rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a grease compsn. for rolling bearing which is excellent not only in high-temp. durability but also in rust-preventing performance. SOLUTION: This compsn. is prepd. by compounding a grease compsn. contg. at least either a silicone oil or a fluorine-contg. oil as the lube base oil with a magnesium compd. and 0.5-10wt.% anticorrosive agent essentially contg. a volatile anticorrosive agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grease composition for rolling bearings, and more particularly to a grease composition to be sealed in rolling bearings used at high temperatures such as automobile electrical components and OA equipment.

[0002]

2. Description of the Related Art Fluid couplings for cooling fans, fuel injection control devices (I
SCV, EGR), electric fan motors, rolling bearings used for electric parts such as powder clutches, rolling bearings used for hard disk drives (HDD), laser beam printers (LBP), copiers and other OA equipment. In many cases, durability at high temperature and torque performance at low temperature are required, and a grease composition using an ether oil type lubricating oil having excellent heat resistance as a base oil is generally used. Further, particularly in a portion exposed to a high temperature of 160 ° C. or higher, a grease composition using a silicone oil-based or fluorine-based lubricating oil having a higher heat resistance as a base oil is used.

By the way, in a rolling bearing containing a grease composition, a seal bearing or a shield bearing structure is adopted.
Further, a slinger is attached to prevent the grease composition from leaking to the outside and prevent the intrusion of substances from the outside. However, because of the structure of the rolling bearing, it is impossible to completely seal the rolling bearing even with the above-described structure and members, so that infiltration of substances from the outside cannot be avoided. These infiltrated substances from the outside include substances and water that are sources of rust, and condensation may occur due to a sudden temperature change.Therefore, the grease composition used should have rust prevention performance. Is essential.

A rust preventive agent is usually added to the grease composition for imparting rust preventive performance. Although various substances are known as rust preventives, nitrites and organic sulfonic acid metal salts are widely used because of their excellent rust preventive performance. However, nitrite is not preferable because amine which is a carcinogenic substance may be generated when used at high temperature, and the amount may be limited even when used, and its rust preventive performance is not sufficiently exhibited. In some cases.
Further, the rust preventive agent exhibits rust preventive property by forming an anticorrosive film on the metal surface. Therefore, in order to form a uniform anticorrosive coating over the raceway surface of the bearing and the entire rolling element, it is necessary for the rust preventive to dissolve in the base oil. Grease compositions using oil-based lubricating oil as a base oil cannot be used because the organic sulfonic acid metal salt is insoluble in these base oils. Therefore, in a grease composition using a silicone oil type or a fluorine oil type lubricating oil as a base oil, it is dealt with by adding a fluorine compound having a functional group such as a carbonyl group, an alcohol group or an ester group in the skeleton. However, these fluorine compounds have low rust preventive performance, and it is hard to say that they can be put to practical use.

As described above, there is an increasing demand for heat resistance of grease compositions, and a grease composition for rolling bearings having both high heat resistance and anticorrosive performance is also desired, but it is desired. It is in a situation that is not compatible with. Therefore, an object of the present invention is to provide a grease composition for rolling bearings, which is excellent not only in durability at high temperatures but also in rust preventive performance.

[0006]

The present invention has been completed as a result of extensive studies to solve the above problems, and the above object is to achieve at least one of the silicone oil-based or fluorine oil-based lubricating oils of the present invention. A grease composition for a rolling bearing, characterized in that a rust preventive agent containing a magnesium compound and a vaporizable rust preventive agent as essential components is blended in a ratio of 0.5 to 10 wt. Achieved by things.

[0007]

The present invention improves the heat resistance of the grease composition as a whole by using at least one type of the base oil as a silicone oil type or a fluorine oil type lubricating oil, and at the same time as a magnesium compound and a vaporizing agent as a rust preventive agent. When used in combination with a rust preventive agent, a synergistic effect is exhibited in rust preventive performance, and higher rust preventive properties can be obtained. The synergistic effect of this rust preventive performance is not clear, but in addition to the addition of the rust preventive effect by the vaporizable rust preventive agent, the magnesium compound forms an anticorrosive film and exhibits a substantial rust preventive effect. It is considered that the vaporizable rust preventive penetrates into the fine cracks and pores of the anticorrosive coating to generate a polymer at the infiltrated portion to reinforce the anticorrosive coating. Therefore, as compared with the case where only the anticorrosive coating is used, the rust preventive performance and its durability can be significantly improved.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The grease composition for rolling bearings according to the present invention will be described in detail below. The base oil used in the present invention is selected from at least one type of silicone oil type or fluorine oil type lubricating oil. Examples of the silicone oil-based lubricating oil include alkyl silicone oil, alkylphenyl silicone oil, phenyl silicone oil, fluorosilicone oil and silicate ester oil. Examples of the fluorine-based lubricating oil include branched or linear fluoropolyether oils.
Also, a mixed oil containing two or more of these may be used as the base oil. The kinematic viscosity of the base oil is not particularly limited and may be the same as that used or commercially available as the base oil of so-called fluorine-based grease.

As a thickener to be added to the base oil, P
Fluorine resin powders and suspensions typified by TFE (polytetrafluoroethylene), and metal soaps typified by lithium soap can be used, and they are appropriately selected and used in consideration of compatibility with the base oil. The grease composition can be obtained by mixing and heating a base oil and a thickener. At that time, from the viewpoint of fluidity of the grease composition,
No. in the grade specified by NLGI (ASTM) as the workability. It is preferable to select the mixing ratio of the base oil and the thickener so as to be 1-2.

The grease composition according to the present invention is characterized by containing a magnesium compound as a rust preventive agent and a vaporizable rust preventive agent as essential components. The magnesium compound is an inorganic magnesium compound, and examples thereof include magnesium oxide, chloride, fluoride, boride, nitride and sulfide. Specifically, magnesium oxide, magnesium molybdate, magnesium stannate,
Magnesium titanate, magnesium tungstate,
Examples thereof include magnesium zirconate, magnesium aluminate, anhydrous magnesium chloride, anhydrous magnesium fluoride, magnesium boride, magnesium nitride and magnesium sulfide. In addition, magnesium / iron oxide (eg magnesium / ferrite) and dolomite (MgCO ₃ · C)
It may be a mixed oxide, a mixed chloride, a mixed fluoride, a mixed boride, a mixed nitride or a mixed sulfide with other elements such as aCO ₃ ). Among these, magnesium oxide and magnesium zirconate are particularly preferable from the viewpoint of rust preventive performance.

Further, examples of the vaporizable rust preventive agent include benzotriazole, methylbenzotriazole, dicyclohexylammonium nitrite (DICHAN),
Cyclohexylamine carbamate (CHC), diisopropylammonium nitrite (DIPAN), nitronaphthalene ammonium nitrite (NITA)
N), dicyclohexylammonium caprylate, cyclohexylammonium laurate, and the like, and triazole compounds such as benzotriazole and methylbenzotriazole and dicyclohexylammonium nitrite are particularly preferable.

Although the magnesium compound alone has rust-preventing performance, further rust-preventing performance can be obtained by using the vaporizable rust preventive together. The total amount of these rust preventive agents is 0.5 to 10% by weight based on the total amount of the grease composition.
Is preferably blended in a ratio of, more preferably,
It is 1 to 6% by weight. If the content of the rust preventive agent is less than 0.5% by weight, the rust preventive effect is insufficient, while the content is 10% by weight.
If the amount is larger, the rust preventive effect is not increased by increasing the amount and there is no cost merit, and the lubricating performance (for example, acoustic performance) is adversely affected, which is not preferable. Further, the mixing ratio of the magnesium compound and the vaporizable rust preventive agent is not particularly limited, but the anticorrosive effect is substantially borne by the anticorrosive coating made of the magnesium compound, and the vaporizable rust preventive agent is its own protective agent. Since it is considered that the effect of reinforcing the anticorrosive coating is greater than the effect of rust, it is preferable that the proportion of the magnesium compound is high.

Further, the grease composition according to the present invention comprises
Various substances can be added within a range that does not impair the effects of the present invention. For example, an antioxidant or an oiliness improver or the like which is usually added to a bearing grease composition may be added in an appropriate amount.

In the grease composition according to the present invention, a thickening agent is added to a base oil, and a semi-solid product obtained by heating and stirring is slowly cooled, and then the magnesium compound and a vaporizable rust inhibitor are added. In addition, it can be obtained by uniformly mixing with a roll mill or the like. Manufacturing conditions such as heating temperature, stirring and mixing time are appropriately set depending on the base oil, thickener, rust preventive and the like used.

[0015]

[Production of grease composition]

Examples 1 to 12 and Comparative Examples 1 to 9 When a PTFE (polytetrafluoroethylene) suspension was added to perfluoropolyether oil (PFAE) or fluorosilicone oil and heated with stirring, a semisolid state was obtained. After the gradual cooling, a rust preventive agent was added, and the grease composition was obtained by passing through a roll mill. The types and addition amounts (unit:% by weight with respect to the total amount of the composition) of the rust preventive agent used in Examples and Comparative Examples are as shown in Tables 1 and 2.

Examples 13-14 Lithium soap was added to methylphenyl silicone oil,
When heated with stirring, it became semisolid. After the gradual cooling, a rust preventive agent was added, and the grease composition was obtained by passing through a roll mill. The type of rust preventive agent used and the amount added (unit:% by weight relative to the total amount of the composition) are as shown in Table 1.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

[Table 3]

[0020]

[Table 4]

[0021]

[Table 5]

The rust preventives represented by the symbols A, B and C in Comparative Examples 1 to 3 are oil-soluble corrosion inhibitors soluble in base oil, and A is fluorine having a carboxyl group as a functional group. A compound derivative, B is a fluorine compound derivative having an alcohol group as a functional group, and C is a fluorine compound derivative having an ester group as a functional group. The test grease composition prepared as described above was subjected to the rust prevention test and acoustic test shown below.

[Rust Prevention Test] 2.4 g of the test grease composition was enclosed in a sealed deep groove ball bearing (# 6303) with a rubber seal, and the mixture was rotated at 1800 rpm for 30 seconds. After that, 0.1 cc of 0.1 wt% salt water was injected into the bearing,
It was rotated again at 1800 rpm for 30 seconds. Next, the bearing was left in a thermo-hygrostat kept at 80 ° C. and 100% RH for 48 hours and then decomposed to observe the rust condition of the bearing raceway. The evaluation and judgment criteria are as follows, and are shown in Tables 1 and 2 by symbols # 1 to # 7. Evaluation (visual inspection) # 1: No rust # 2: Stain rust (stainless micro rust) # 3: Point rust (φ0.3 mm or less) # 4: Small rust (φ1.0 mm or less) # 5: Medium rust (φ5 0.06 mm or less) # 6: Large rust (φ10.0 mm or less) # 7: Maximum rust (rust occurs on almost the entire surface) Good or bad judgment criteria Good: # 1 to # 4 Bad: # 5 or more

[Acoustic test] 2.4 g of the test grease composition was enclosed in a sealed deep groove ball bearing (# 6303) with a rubber seal, and the sound was measured after rotating at 1800 rpm for 30 seconds. The measurement results are shown in Tables 1 and 2 in terms of Anderon value (numerical value), and 7 Anderon or less, which is a standard for judging whether the quality is normal or not, was regarded as acceptable. Here, the reason why 7 anderon or less was passed is that it was judged to be equal to or higher than the acoustic level of the commercially available fluorine oil type grease.

From Table 1, it can be seen that the grease composition according to the present invention does not contain any grease composition (Comparative Examples 1 to 3) containing other rust preventive agents or the same rust preventive agent. A grease composition (Comparative Example 4), a grease composition containing only a magnesium compound as a rust preventive (Comparative Example 5), and both a magnesium compound and a vaporizable rust preventive as a rust preventive, the contents of which are It can be seen that the rust preventive performance and the acoustic characteristics are excellent as compared with the grease compositions (Comparative Examples 6 and 7) out of the range specified in the present invention. Also,
Although the grease composition according to the present invention is excellent in rust preventive performance, it has the same or better rust preventive performance and acoustic properties as the grease composition (Comparative Examples 8 and 9) containing nitrite which is not preferable in terms of carcinogenicity as a rust preventive agent. It can be seen that the characteristics can be obtained.

[0026]

As described above, the grease composition according to the present invention is excellent in high-temperature durability, but can significantly improve the rust preventive performance of the fluorine-based grease having a problem in rust preventive performance. Automotive electrical components and office automation
It can be suitably applied to rolling bearings that are required to have high-temperature durability as well as rust preventive performance, such as rolling bearings that are used at high temperatures in equipment and the like.

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Claims (1)

[Claims] 1. A rust preventive agent containing a magnesium compound and a vaporizable rust preventive agent as an essential component is added to a grease composition containing at least one kind of a silicone oil type lubricant or a fluorine oil type lubricant as a base oil. A grease composition for rolling bearings, which is blended in a weight percentage.