JPS6028877B2 - lubricating grease - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lubricating grease, particularly a lubricating grease with excellent heat resistance and long lubrication life.

Conventionally, amine antioxidants have been widely used to improve the heat resistance and oxidation stability of lubricating greases.

Generally, the addition of an amine-based antioxidant significantly improves oxidation stability and lubrication life, but the amine-based antioxidant changes color due to the action of oxygen in the air and light. For this reason, when grease containing amine-based antioxidants is used in bearings, etc., the lubricating grease often turns black, which not only makes it difficult to determine when to replace the lubricating grease, but also the network structure formed by the thickener. This results in an increase in the degree of stiffness, a decrease in the perfect score, and an increase in the degree of oil separation, as well as the disadvantage that oil or lubricating grease leaks from the bearing and contaminates the surrounding area. The object of the present invention is to improve these drawbacks and to provide a lubricating grease consisting of a base oil containing an additive having an antioxidant effect suitable for an amine antioxidant.

The inventors of the present invention have investigated various antioxidants from various angles and have found that the above object can be achieved by using two types of antioxidants in combination.

That is, the present invention provides a lubricating grease characterized by containing a mixed antioxidant consisting of 5 to 95% by weight of 1,1-bis-(4-hydroxyphenyl)-cyclohexane and 95 to 5% by weight of dialkylthiodipropionate. exists in

Both 1,1-bis-(4-hydroxy-phenyl)-cyclohexane and dialkylthiodipropionate, which constitute the mixed antioxidant in the present invention, are compounds known as antioxidants for rubber. According to the above, it has been found that by blending both within a specific quantitative range, it is surprisingly effective in preventing the oxidation of lubricating grease, which exhibits the above-mentioned aging phenomenon that is different from the aging phenomenon caused by oxidation of rubber.

1,1-bis-(4-hydroxy-phenyl)-cyclo
The combined use of hexane and dialkylthiodipropionate is unique in that it extends the lubricating life compared to when they are used alone, and from the practical point of view of other antioxidant effects, the former %, the latter of which can be mixed in a wide range from 5 to 95% by weight, and the amount of lubricating grease to be mixed with the base oil is from 0.2 to 1% by weight. As the dialkylthiodipropionate, commercially available dilaurylthiodipropionate or disallylthiodipropionate is used.

Although the number of carbon atoms in the alkyl group does not exceed that of the carbon chain of the base oil compound, it can be appropriately determined in consideration of the solubility in the base oil. In addition to mineral oil, base oils include esters of dibasic acids and monovalent aliphatic alcohols, polyhydric alcohols, and carbon dioxide.
Hydrocarbon oils such as polyhydric alcohol esters, polyolefins, diarylalkanes, alkylbenzenes, etc. with 5 to C, o fatty acids, or mixed oils thereof are used.

In addition, metal soaps such as lithium and sodium, calcium complexes, aluminum complexes, etc., which remain in the form of grease up to at least 150°C, or non-metallic soaps such as sodium terephthalamate, polyurea, bentonite, and silica, can be used as additives. Soap can be used. Next, the present invention will be described with reference to Examples, but the present invention is not limited thereto in any way.

Example 20 minutes of trimethylolpropane tricaprylate (base oil) was placed in a 150cc beaker, and 1.
1-bis(4-hydroxy-phenyl)-cyclohexane (hereinafter referred to as A), dilaurylthiodipropionate (hereinafter referred to as B) or distearylthiodipropionate (hereinafter referred to as C) alone or mixed in various blending ratios These are then added in an amount of 1% by weight based on the base oil.

These are heated while stirring to completely dissolve the additives, and then allowed to cool to room temperature. The evaporation loss when these samples were heated for 1000 hours in a 14000°C constant temperature bath was measured. Figure 1 shows A, B, C alone and A and B [in the drawing (A
It is a graph plotting the relationship between the mixing ratio of A and C [shown as (A+C) in the drawing] and the evaporation loss.

From FIG. 1, it can be seen that A
, B, or a combination of A and C, the evaporation loss is less than half of that when A is used alone, indicating that it has a practical effect.

Example 2 A mixture of equal amounts of A and C was added in various proportions to 20 days of trimethylolpropane tricaprylate to prepare Example 1
In the same manner as above, the evaporation loss when heated at 140q○ for 100 hours was measured.

FIG. 2 is a graph plotting the relationship between the amount of mixed antioxidant added to the base oil and the evaporation loss.

As is clear from FIG. 2, when the amount added becomes 0.2% by weight or less, the evaporation loss increases rapidly.

In addition, in the case of no addition, the anti-weight ratio is 1%. Further, when the amount exceeds 5% by weight, the evaporation loss increases slightly, but even if 1% by weight is added, it is less than 1'6 compared to when no addition is made. However, if the amount added is too large, the lubricating grease becomes too hard or the depth stability decreases, so it is preferable to add less than 1% by weight.Example 3 Mineral oil (#200 turbine oil) 8% by weight, A mixed antioxidant of 1% by weight of an equal mixture of A and B and an equal mixture of A and C in a grease base oil consisting of lithium 12-hydroxystearate IZ and a known amine-based inhibitor N- as a comparative example. Grease containing phenyl-Q-naphthylamine (hereinafter referred to as D) was applied to a thickness of three skins on a steel plate and heated in a constant temperature bath at 140°C.

The method for producing the grease is to gradually heat mineral oil and lithium 12-hydroxystearate to 200 qo while stirring well.

Thereafter, it is rapidly cooled to 160:00 pm and kept at a predetermined temperature for several hours. It was further cooled to room temperature and milled. The antioxidant is preheated and dissolved in 3% by weight oil based on the total base oil.
It was maintained at 0°C and added to the remaining base oil and lithium 12-hydroxystearate mixture at 16,000°C. Third
Figures 4 and 4 are graphs plotting the relationship between the heating time measured for lubricating greases to which A and B mixed antioxidants, A and C mixed antioxidants, and D were added, the steeliness of the lubricating grease, and the perfect score. It is.

From FIGS. 3 and 4, it can be seen that the thermal stability of the grease structure is improved by the addition of the mixed antioxidant of the present invention. Example 4 Grease with a basic composition consisting of 8% by weight of a mixed oil of equal amounts of trimethylolpropane tricaprylate and di(2-ethylhexyl) sebacate as a base oil and 8% by weight of lithium 12-hydroxystearate as a thickening agent. Grease was produced by adding 1% by weight of the antioxidant shown in the table below in the same manner as in Example 3.

Apply this grease to the non-contact double-sided rubber seal bearing 631 Misaki L.
Bearing outer ring temperature 14000, rotation speed 360
The time (lubrication life) during which the bearing was rotated until the bearing seized was measured under conditions where the ratio pm and the load ratio C/P were 60 (C: dynamic load rating). The results are also listed in the table. From this table, it can be seen that the mixed antioxidant of the present invention provides the amine antioxidant with the necessary lubricating life and exhibits a unique synergistic effect compared to when used alone.

As is clear from the above explanation, the present invention has 1.
By adding a mixed antioxidant of 1-bis-(4-hydroxyphenyl)cyclohexane and dialkylthiodipropionate, it provides a lubricating grease with excellent thermal stability, which improves the durability of rotating machinery. It can be improved.

[Brief explanation of the drawing]

FIG. 1 is a graph plotting the relationship between the mixing ratio of mixed antioxidants and the evaporation loss of grease in the present invention.
Figure 2 is a graph plotting the relationship between the amount of mixed antioxidant added and the evaporation loss of the grease, and Figures 3 and 4 are graphs showing the change over time in the degree of unsaturated steel of the grease of the present invention and the final score over time. This is a graph plotting changes. In the figure, A is 1,1-pis-(4-hydroxy-phenyl)-cyclohexane, B is dilaurylthiopropionate, C is distearylthiodipropionate, and D is N-
The use of phenyl-Q-naphthylamine is shown. 1 figure, 2 figures, 3 figures, 4 figures

Claims (1)

[Scope of Claims] 1. It is characterized by containing a mixed antioxidant consisting of 5 to 95% by weight of 1,1-bis-(4-hydroxy-phenyl)-cyclohexane and 95 to 5% by weight of dialkylthiodipropionate. Lubricating grease. 2 Mixed antioxidant 0.2 to 10% by weight based on base oil
A lubricating grease according to claim 1.