JPH0741782A - Lubricating composition for bearing - Google Patents

Abstract

PURPOSE:To obtain a solid lubricating composition for bearing which does not flow out even when, e.g. water enters and is improved in extreme-pressure characteristics so that it can sufficiently enhance the pressure resistance of a bearing. CONSTITUTION:95-1wt.% powder of an ultra-high-molecular-weight polyolefin having an average molecular weight of 1X10<6> to 5X10<6> and 5-50wt.% extreme- pressure additive are dispersed and retained in 5-94wt.% lubricating grease at a temperature above the gel point of the polyolefin powder and below the dropping point of the grease, thus giving a solid lubricating composition for bearing excellent in extreme-pressure characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid lubricating composition for bearings, which is filled in various bearings.

[0002]

2. Description of the Related Art In general, various bearings are filled with a base oil such as mineral oil and a thickening agent such as lithium soap, aluminum soap or polyurea in order to enhance the internal lubricity thereof. And especially construction / steel /
For bearings mounted on machinery that requires water resistance, such as agricultural machinery or automobile parts, and various mechanical parts that perform centrifugal movement at high speed, such as a twisting machine, suppress the fluidity of the grease to be filled, and A sealing device is attached to ensure stable lubrication characteristics.

The bearings used in the construction, steel, agricultural machinery, automobile parts, etc. are not only water-resistant but also
Pressure resistance is required under load conditions according to the operating state of the bearing.

Sulfur-based, phosphorus-based, organometallic compounds and the like are known as extreme pressure additives added to increase the pressure resistance of lubricating grease.

[0005]

However, the above-mentioned conventional pressure-resistant grease contains about 1 to 5% by weight of an extreme pressure agent, and this grease is fluid-lubricated in the bearing under a high load condition. However, if a large amount of extreme pressure agent is added to further improve the pressure resistance, the grease loses the required viscosity and is softened, the additive is precipitated, and the lubricity is deteriorated.

Further, since it is difficult to mount a perfect sealing device on bearings of various shapes and sizes, rainwater and muddy water gradually infiltrate, and the grease inside the bearing gradually deteriorates. Often leaks out.

In view of the above, the present invention solves the above-mentioned problems and makes the bearing lubricating composition a solid bearing lubricating composition which is not washed away even when water or muddy water enters the bearing. It is an object of the present invention to improve the pressure resistance of the bearing by improving the extreme pressure characteristics.

[0008]

In order to solve the above problems, in the present invention, the lubricating grease is 5 to 94% by weight.
95% to 1% by weight of an ultrahigh molecular weight polyolefin powder having an average molecular weight of 1 × 10 ^{6 to} 5 × 10 ⁶ is mixed with 5 to 50% by weight of an extreme pressure agent, and the ultrahigh molecular weight polyolefin is added. The bearing lubricating composition was dispersed and held at a temperature not lower than the gel point of the powder and not higher than the dropping point of the lubricating grease.

In addition, 5 to 93% by weight of lubricating grease, 95 to 1% by weight of ultra-high molecular weight polyolefin powder having an average molecular weight of 1 × 10 ^{6 to} 5 × 10 ⁶ and 1 to 50% by weight of an oil exudation inhibitor. And 5 to 50% by weight of an extreme pressure agent are added and mixed to obtain 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 and not higher than the dropping point of the lubricating grease. . A solid wax can be used as the oil exudation inhibitor. The details will be described below.

The ultra-high molecular weight polyolefin powder in the present invention may be ultra-high-molecular-weight polyethylene, ultra-high-molecular-weight polypropylene, ultra-high-molecular-weight polybutene or a copolymer thereof, or a single powder of each, and the molecular weight of each powder. Has an average molecular weight of 1 × 10 ^{6 to} 5 × 10 ⁶ as measured by a viscosity method. 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.
~ 1% by weight, the amount of which depends on the desired oil separation, 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.

In addition to the above ultra high molecular weight polyolefin powder, a thermoplastic resin such as polyamide resin (nylon) or polyacetal resin, or a powder of thermosetting resin such as phenol resin, urea resin or epoxy resin is used in combination. You may add it.

The lubricating grease in the present invention is not particularly limited, and is a lubricating grease thickened with soap or non-soap, such as lithium soap-diester type, lithium soap-mineral oil type, sodium soap-mineral oil type. , Aluminum soap-mineral oil type, lithium soap-diester mineral oil type, non-soap-diester type, non-soap-mineral oil type, non-soap-polyol ester type, lithium soap-polyol ester type grease. Examples of the non-soap mentioned here include bentonite, silica, polyurea, indanthrene, and copper phthalocyanine.

As the extreme pressure agent used in the present invention,
For example, halogen-based extreme pressure agents, phosphorus-based extreme pressure agents, organometallic compound-based extreme pressure agents, etc. are not particularly limited. Examples of the halogen-based extreme pressure agent include chlorinated paraffin, methyldichlorostearate, and benzyl iodide, and examples of the sulfur-based extreme pressure agent include sulfurized oil and fat, dibenzyl disulfide, and xanthic disulfide. As an extreme pressure agent, tricresyl phosphate (hereinafter referred to as "TC
Abbreviated as "P"), triphenyl phosphite, and the like, and examples of the organometallic compound-based extreme pressure agent include lead naphthenate, diamyl lead dithiocarbamate, and zinc dithiophosphate.

Of these extreme pressure additives, halogen-based and sulfur-based additives chemically react with sliding iron by frictional heat to form a solid film of iron halide or iron sulfide.
Since this solid film has a low melting point and is soft, it prevents seizure of the friction surface in the bearing. When a lead-based extreme pressure agent and a sulfur-based extreme pressure agent are used together, a lead sulfide coating film is formed. Further, the phosphorus-based extreme pressure agent produces a metal phosphorus compound due to the corrosion of the metal surface and the reducing action of carbon,
Reduce pressure and temperature on the contact surface to prevent wear and seizure.

The oil exudation inhibitor according to the present invention moderately suppresses the oil separation rate of the oil exuded on the oily surface of the lubricating composition, that is, suppresses the oil exudation, and is a wax (wax). Of these, 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% by weight 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% by weight, the strength of the lubricating composition will be reduced, which is not preferable.

In order to disperse and retain the ultra-high molecular weight polyolefin, the extreme pressure agent and the oil exudation inhibitor in the lubricating grease described above, after mixing the above-mentioned materials, the temperature is raised to a temperature above the temperature at which the ultra-high molecular weight polyolefin causes gelation. Heating, then
It is cooled and solidified to obtain a lubricating composition having an oily surface, that is, a surface from which oil exudes.

[0017]

Since the lubricating composition for a bearing of the present invention is in a solid state, it does not flow out together with water that has entered the inside of the bearing, and the lubricating property of the grease can be maintained for a long period of time by appropriate leaching of oil. The extreme pressure agent forms a solid film or polymer film that reacts with the metal surface inside the bearings such as the inner and outer ring rolling surfaces, rolling elements or iron plate retainers, so the pressure and temperature on the friction surface are reduced to prevent wear and seizure. To prevent. Even if these extreme pressure additives are added in a large amount of 5% by weight or more, the ultra high molecular weight polyolefin stably holds the lubricating oil, so that the solid grease is softened or other additives are precipitated. There is no.

[0018]

【Example】

[Examples 1 to 3] Ultra-high molecular weight polyolefin (Mitsui Petrochemical Co., Ltd .: Miperon), solid wax containing low molecular weight polyolefin (Sanyo Chemical Co., Ltd .: Sun wax and Seiko Chemical Co., Ltd .: Suntite S), Lubricating grease (lithium soap-mineral oil system) and extreme pressure agent (TCP, triphenyl phosphite) were used as raw materials and mixed at the compounding ratio shown in Table 1, and this mixture was mixed with a radial ball bearing (6
204) was sealed in 4.00 ± 0.05 g, and this bearing was heated in a thermostatic layer at 150 to 180 ° C. for 30 minutes to solidify the above mixture. The solid lubricant thus obtained was subjected to (1) hardness test, (2) washing water resistance test and (3) load bearing oil film strength test by the following test methods, and the results are shown in Table 1.

(1) Hardness test Hs (spring hardness) was measured according to JIS K6301 5.2.

(2) Washing water resistance test According to JIS K 2220 5.12, test temperature 79 ° C
Loss (% by weight) was calculated.

(3) Load-bearing oil film strength test The mixture was applied between four steel balls, and the four steel balls were heated in a constant temperature bath at 150 to 180 ° C. for 30 minutes to cool and solidify the mixture. Was solidified. These steel balls and the solidified lubricating composition were soda-type 4-ball tester (JIS K
2519), the vertical axis is rotated at 200 rpm by the standard method (step method), and the load hydraulic pressure is 0.5 k / min.
Raise at a rate of gf / cm ² until seizure occurs,
The oil film strength (kgf / cm ² ) was determined.

[0022]

[Table 1]

[Comparative Example 1] Ultra-high molecular weight polyethylene (Mitsui Petrochemical Co., Ltd .: Miperon), low molecular weight polyolefin-containing solid wax (Sanyo Chemical Co., Ltd .: Sun Wax and Seiko Chemical Co., Ltd .: Suntite S) Using lubricating grease (lithium soap-mineral oil system) as a raw material, the other raw materials were mixed in the same proportions as shown in Table 1 in the same manner as in Examples 1 to 3, and further in the same manner as in Examples 1 to 3. It solidified. The solid lubricant thus obtained was tested in the same manner as above, and the results are also shown in Table 1.

[Comparative Example 2] The test described above using a commercially available lithium soap-mineral oil type grease having a consistency of 242.
(1) to (3) were performed, and the results are also shown in Table 1.

Comparative Example 3 The grease of Comparative Example 2 was replaced with TCP.
Test using the grease with 5 parts by weight of (1)
~ (3) was performed, and the results are also shown in Table 1.

As is clear from the test results shown in Table 1, Examples 1 to 3 are excellent in oil film strength and extremely excellent in extreme pressure property, and are solid in the same hardness as Comparative Example 1. It was a grease and showed excellent physical properties with improved water resistance to washing, which is a drawback of Comparative Example 2 or Comparative Example 3.

[0027]

[Effect] As described above, the present invention provides a lubricating grease for bearings, an ultra-high molecular weight polyolefin having a predetermined average molecular weight, or a lubricating composition for bearings in which an exudation inhibitor and an extreme pressure agent are added and mixed, A lubricating composition for a bearing, which is a solid lubricating composition for a bearing that does not flow away even if water or muddy water enters the bearing, and that improves its extreme pressure property well, and that can sufficiently enhance the pressure resistance of the bearing. There are advantages.

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Claims (3)

[Claims] 1. Lubricating grease 5 to 94% by weight is mixed with 95 to 1% by weight of ultra high molecular weight polyolefin powder having an average molecular weight of 1 × 10 ^{6 to} 5 × 10 ⁶ and 5 to 50% of an extreme pressure agent. % Of the ultra-high molecular weight polyolefin powder and dispersed and held at a temperature not lower than the gel point of the ultra-high molecular weight polyolefin powder and not higher than the dropping point of the lubricating grease. 2. Lubricating grease 5 to 99% by weight, ultra high 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
For bearings, which is mixed and mixed in an amount of 50 to 50% by weight and 5 to 50% by weight of an extreme pressure agent to be dispersed and held 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. Lubricating composition. 3. The lubricating composition for a bearing according to claim 2, wherein the oil exudation inhibitor is a solid wax.