JPH06248287A - Lubricating composition for bearing - Google Patents

Abstract

PURPOSE:To provide a bearing with an electric function by making the bearing exhibit electrification function and antistatic function in the state of the bearing packed with a lubricating composition for bearing. CONSTITUTION:5-99wt.% of ultra-high-molecular-weight polyolefin powder having 1X10<6>-5X10<6> average molecular weight is mixed with 1-50wt.% of solid wax containing low-molecular-weight polyethylene, 5-99wt.% lithium soap-mineral oil-based lubricating grease and carbon black and dispersed at >= the gel point of an ultra-high-molecular-weight polyolefin and <= the dropping point of the lubricating grease to give a bearing composition for bearing having low electric resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing lubricating composition filled in various bearings, and more particularly to a bearing lubricating composition applied to a bearing which is required to have an energizing function and an antistatic function.

[0002]

2. Description of the Related Art Generally, various rolling bearings are filled with a grease in which a base oil such as mineral oil is mixed with a thickener such as lithium soap, aluminum soap or polyurea in order to enhance internal lubricity. In rolling bearings, which are required to withstand harsh operating conditions such as high-speed rotation and large inertial force, suppress the fluidity of grease to ensure stable lubrication characteristics for a long time. In addition, a sealing device is attached.

However, it is technically difficult and production cost difficult to completely seal such a bearing for a long period of time.

As a lubricating composition for a bearing which solves such a problem, as described in JP-B-63-23239, it has an ultrahigh molecular weight polyethylene and a dropping point higher than the melting temperature of the polyethylene. It is known that a lubricating grease is blended and heated above the melting temperature to fill the bearing and solidify.

Since the lubricating composition for bearings does not leak grease and is excellent in cost, it is also widely used as a bearing for power transmission systems such as office equipment and automobiles.

[0006]

However, although the solid lubricating composition for bearings disclosed above satisfies various lubricating characteristics required for various bearings, it does not transmit power to the ground of electronic devices. There is a problem that it is not possible to send and receive an electric signal when it is performed through a system or in a sliding state.

In view of the above, the present invention solves the above-mentioned problems, and it is assumed that the bearing lubricating composition can exhibit an energizing function and an antistatic function while being filled in the bearing. The issue is to be able to add.

[0008]

In order to solve the above problems, in the present invention, the lubricating grease is 5 to 99 wt%.
In addition, 95 to 1 wt% of ultrahigh molecular weight polyolefin powder having an average molecular weight of 1 × 10 ^{6 to} 5 × 10 ⁶ and a conductive powder are added and mixed to obtain a gelling point of the ultrahigh molecular weight polyolefin powder or more and The lubricating composition for bearings is obtained by dispersing and holding the lubricating grease at a temperature equal to or lower than the dropping point of the lubricating grease and solidifying the bearing.

Alternatively, 5 to 99 wt% of lubricating grease, 95 to 1 wt% of ultrahigh molecular weight polyolefin powder having an average molecular weight of 1 × 10 ^{6 to} 5 × 10 ⁶ and oil exudation inhibitor 1
It is also possible to add and mix ˜50 wt% and a conductive powder to disperse and hold at a temperature not lower than the gel point of the ultra-high molecular weight polyolefin and not higher than the dropping point of the lubricating grease to be solidified.

The above-mentioned conductive powder may be acetylene black.

The details will be described below.

The ultrahigh molecular weight polyolefin powder in the present invention may be a powder composed of polyethylene, polypropylene, polybutene or a copolymer thereof, or a mixed powder prepared by mixing individual powders, and the molecular weight of each powder is determined by a viscosity method. The average molecular weight measured by
It is 0 ^{6 to} 5 × 10 ⁶ . Polyolefins having such an average molecular weight range are superior to low molecular weight polyolefins in rigidity and oil retention, and hardly flow even when heated to a high temperature. The blending ratio of such ultra-high molecular weight polyolefin in the lubricating composition is 95 to 1 wt%, and the amount thereof depends on the desired oil separation degree, tenacity and hardness of the composition. Therefore, the greater the amount of ultra-high molecular weight polyolefin, the greater the hardness of the gel after being dispersed and held at a predetermined temperature.

The lubricating grease in the present invention is not particularly limited, and as a lubricating grease thickened with soap or non-soap, lithium soap-diester type,
Lithium soap-mineral oil system, sodium soap-mineral oil system,
Examples of greases include aluminum soap-mineral oil-based, lithium soap-diester mineral oil-based, non-soap-diester-based, non-soap-mineral oil-based, non-soap-polyol ester-based, and lithium soap-polyol ester-based greases.

The conductive powder used in the present invention is not particularly limited as long as it is a powder that imparts antistatic property or electrical conductivity to the gel-like lubricating composition, and specific examples thereof include acetylene. Carbon black such as black, ketjen black, channel black and the like having conductivity, fine metal powder such as copper, iron, gold, silver, aluminum, platinum, zinc, tin, silver oxide, silver nitrate, silver, etc. Powders of metals or these organic compounds may be mentioned.

Of these, acetylene black is particularly preferable because it has a structure in which a carbon structure is developed by a thermal decomposition method and has high conductivity. This carbon structure has primary particles (average particle size 0.026 to 0.04) in which crystallites having overlapping carbon net planes are aggregated.
2 μm, electron microscopy), and a large number of primary particles are connected to form a chain-like or resin-like structure. Among the acetylene blacks, those having a quality with a hydrogen content which is considered to fix the transfer of π electrons as small as possible are preferable because the conductivity is further improved. Commercially available acetylene black may be in the form of powder or in the form of particles convenient for handling.

It is needless to say that carbon black other than acetylene black can be used as the above-mentioned carbon black, such as gas black, which has a developed structure of carbon structure.

The oil exudation inhibitor according to the present invention is an agent that suppresses the oil separation rate of the oil exuded on the oily surface of the lubricating composition to an appropriate degree, that is, suppresses the oil exudation. Of the above), a solid wax or a low-molecular polyolefin containing the same may be blended. Specific examples of the solid wax include vegetable waxes such as carnauba wax and candelina wax, animal waxes such as beeswax and insect white wax, and petroleum waxes such as paraffin wax. The blending ratio of such an oil exudation inhibitor is 1 to 50 wt% in the lubricating composition. The higher the blending ratio, the more the oil separation rate can be suppressed, and the speed at which the oil exudes decreases. However, if the amount exceeds 50 wt%, the strength of the lubricating composition is reduced, which is not preferable.

In order to disperse and retain the ultra-high molecular weight polyolefin, the conductive powder and the oil exudation inhibitor in the lubricating grease described above, after mixing the above-mentioned materials, the temperature above the temperature at which the ultra-high molecular weight polyolefin causes gelation, For example, 15
It is heated to about 0 to 200 ° C., then cooled to room temperature and solidified to obtain a lubricating composition having an oily surface, that is, a surface from which oil exudes.

[0019]

Since the lubricating composition for a bearing of the present invention is in a solid state, it is stably held between the inner and outer races of the bearing, and the proper lubrication of oil from the surface prolongs the lubricating characteristics of the grease. While being maintained for a period of time, the added conductive powder allows the transfer of earth or electrical signals through the bearing.

[0020]

[Examples] The raw materials used in Examples and Comparative Examples are summarized below.

The blending ratio is such that the ultrahigh molecular weight polyolefin, the solid wax, and the lubricating grease are% by weight,
The conductive powder is shown in parts by weight based on 100 parts by weight of the above-mentioned three kinds of materials.

(1) Ultra High Molecular Weight Polyolefin Mitsui Petrochemical Co., Ltd .: Miperon (2) Solid Wax Containing Low Molecular Weight Polyolefin Mitsui Kasei: Sun Wax and Seiko Chemical Co .: Suntite S Mixture (3) Lubrication Grease (Base oil: mineral oil, thickener: lithium soap) (4) Acetylene black Denki Kagaku Kogyo: Granular acetylene black (average particle size of primary particles 0.042 μm) (5) Carbon black Asahi carbon: Asahi carbon Black HAF70 (non-conductive, average particle size 0.026 μm) [Examples 1 to 3, Comparative Example 1] Raw materials were mixed in a mixing ratio shown in Table 1, and this mixture was filled in a mold for forming a column,
This mold was heated in a thermostatic layer at 150 to 180 ° C. for 30 minutes, allowed to cool and solidified, and then removed from the mold to obtain a cylindrical solid substance having an outer diameter of 12 mm and a length of 8 mm.

In order to check the conductivity of the obtained solid substance,
The electrical resistance between the widths of 8 mm was measured with a tester, and the results are also shown in Table 1.

[0024]

[Table 1]

As is clear from the results shown in Table 1, in Examples 1 and 2 in which acetylene black was blended as the conductive material, the electric resistance was as low as 50 to 230 ohms, and it was possible to conduct electricity or send and receive electric signals. Example 3
Had a resistance low enough to prevent charging.

On the other hand, in Comparative Example 1 in which the conductive powder was not added, the electric resistance value was 20 M ohms or more, and the current-carrying and antistatic functions could not be expected at all.

[0027]

As described above, the present invention provides a lubricating composition for a bearing in which a lubricating grease, an ultra-high molecular weight polyolefin having a predetermined average molecular weight, an oil exudation inhibitor and a conductive powder are mixed in respective predetermined amounts. It withstands severe operating conditions such as inertial force, exhibits stable lubrication characteristics in the bearing for a long period of time, and also exhibits energization function and antistatic function.
It has the advantage of increasing the electrical function of the filled bearing. Therefore, by using such a lubricating composition for a bearing, it is possible to fill a bearing for a device that grounds electronic devices through a power transmission system or a device that transmits and receives an electric signal in a sliding state to obtain an optimum electric power. It can be said that it has a high industrial utility value because it can obtain specific characteristics.

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Claims (3)

[Claims] 1. A lubricating grease of 5 to 99 wt% and an electrically conductive powder are added and mixed with 95 to 1 wt% of ultrahigh molecular weight polyolefin powder having an average molecular weight of 1 × 10 ^{6 to} 5 × 10 ^6. A lubricating composition for a bearing, which is dispersed and held at a temperature not lower than the gel point of the ultrahigh molecular weight polyolefin powder and not higher than the dropping point of the lubricating grease to be solidified. 2. Lubricating grease 5 to 99% by weight, ultrahigh molecular weight polyolefin powder 95 to 1% by weight having an average molecular weight of 1 × 10 ^{6 to} 5 × 10 ⁶ and oil exudation inhibitor 1 to 50
A lubricating composition for a bearing, which is obtained by adding and mixing wt% and a conductive powder to disperse and hold at a temperature not lower than the gel point of the ultrahigh molecular weight polyolefin and not higher than the dropping point of the lubricating grease to be solidified. 3. The bearing lubricating composition according to claim 1, wherein the conductive powder is acetylene black.