JPH06313184A - Grease composition - Google Patents

Abstract

PURPOSE:To obtain a grease compsn. excellent in abrasion resistance and suitable got lubricating an easily abradable section by compounding a base oil, a thickener, an organomolybdenum compd., and glycerol. CONSTITUTION:This grease compsn. is prepd. by compounding a base oil (e.g. 2-ethylhexyl sebacate), a thickener (e.g. a lithium soap), an organomolybdenum compd. (e.g. molybdenum oxysulfide dithiocarbamate), and glycerol. The compsn. pref. further contains an organozinc compd. (e.g. zinc dialkyldithiophosphate). Pref. the compounding ratio of the base oil to the thickener is (70:30) to (95:5),and the amts. of the molybdenum compd. and the zinc compd. are about 1-5wt.%. and 0.3-2wt.%. of the compsn., respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grease composition having excellent wear resistance, and more specifically, to a lubricated portion such as a gear which is easily worn, an industrial machine, an industrial robot, a machine tool or the like which requires high accuracy. Can be used for lubrication points,
The present invention relates to a grease composition having excellent wear resistance.

[0002]

2. Description of the Related Art A lubricated portion such as a gear is likely to be worn. In such lubricated areas where wear is likely to occur, it is extremely important to prevent wear in order to improve the driving efficiency and extend the machine life. In addition, the lubrication points of industrial machines, industrial robots, machine tools, etc., which require high accuracy, have low accuracy even if a little wear occurs, resulting in shortened machine life. In other words, in an industrial machine that requires high accuracy, when the wear of the lubricated part progresses, the accuracy of the machine deteriorates, and even if lubrication is possible, the machine becomes substantially unusable and the machine must be replaced. Therefore, at these lubrication points,
Preventing wear becomes even more important. Conventionally, lead-sulfur-based additives, sulfur-
An extreme pressure type grease containing a phosphorus-based additive, a metal dithiophosphate-based additive, a metal dithiocarbamate-based additive, etc. has been used.

However, the conventional grease mainly composed of extreme pressure has a drawback that it is not necessarily sufficient in abrasion resistance even though it has excellent extreme pressure. Therefore, it has been earnestly desired to develop a grease having excellent wear resistance, which can reduce the deterioration of precision of an industrial machine that requires precision, improve the reliability of the machine, and prolong the service life.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned state of the art, and when used in a lubricated portion of an industrial machine that is excellent in wear resistance and requires precision, It is an object of the present invention to provide a grease composition which can reduce deterioration of machine accuracy, improve machine reliability, and prolong the service life.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have paid attention to an organic molybdenum compound which decomposes by frictional heat as an additive, and as a result of further earnest research, As a result of combining the organomolybdenum compound and glycerin, a synergistic effect is produced and the wear resistance is significantly improved. Further, by using an organozinc compound in combination with these two additives, the wear resistance is further improved. Based on this finding, the present invention has been completed. That is, the present invention provides a grease composition containing a base oil, a thickener, an organic molybdenum compound, and glycerin. Hereinafter, the present invention will be described in detail.

As the base oil used in the grease composition of the present invention, various lubricating oils such as mineral oil-based lubricating base oil, synthetic lubricating base oil or a mixture thereof which are usually used for grease are used. Base oil is used. Examples of the mineral oil-based lubricating base oil include those obtained by refining crude oil by appropriately combining solvent refining, hydrorefining, and the like. Examples of the synthetic lubricating base oil include carbon such as α-olefin oligomer which is a polymer of α-olefin having 3 to 12 carbon atoms, 2-ethylhexyl sebacate, sebacate including dioctyl sebacate, azelate and adipate. Number 4
To 12 dialkyl diesters, 1-trimethylolpropane, polyols including esters obtained from pentaerythritol and monobasic acids having 3 to 12 carbon atoms, alkylbenzenes having an alkyl group having 9 to 40 carbon atoms, and butyl Examples include polyglycols such as polyglycols obtained by condensing alcohol with propylene oxide, phenyl ethers such as polyphenyl ethers having about 2 to 5 ether chains and about 3 to 6 phenyl groups. . The mineral base lubricating oil base oil and the synthetic base lubricating oil base oil may be used alone or in combination of two or more. The amount of the base oil can be appropriately selected according to the required characteristics, but is usually 60 to 97% by weight with respect to the base grease composed of the base oil and the thickener.
And preferably in the range of 70 to 95% by weight.

Examples of the thickener used in the grease composition of the present invention include thickeners based on soaps such as aluminum, barium, calcium, lithium, sodium, complex lithium, complex calcium and complex aluminum, and urea. , Thickening agents such as terephthalamate and bentonite. These thickeners may be used alone or in combination of two or more. The amount of the thickener is not particularly limited, but is usually 3 to 40% by weight, preferably 5 to 3% by weight with respect to the base grease composed of the base oil and the thickener.
It is 0% by weight.

As the organic molybdenum compound used in the grease composition of the present invention, various organic molybdenum compounds can be used as long as they can be decomposed by frictional heat at the lubrication site. Specific examples of preferred organic molybdenum compounds include molybdenum such as di-μ-oxy-disulfide dithiocarbamate dimolybdenum, molybdenum oxysulfide dithiocarbamate, molybdenum dialkyldithiocarbamate including molybdenum sulfide dithiocarbamate and molybdenum diaryldithiocarbamate. Dithiocarbamate; molybdenum dithiophosphates such as molybdenum dialkyldithiophosphate, molybdenum diaryldithiophosphate and the like can be mentioned, particularly preferably molybdenum dithiocarbamate, most preferably molybdenum dialkyldithiocarbamate. These organic molybdenum compounds may be used alone, or
You may use it in combination of 2 or more type. The content ratio of the organic molybdenum compound is not particularly limited,
Usually, it is 0.5 to 10% by weight, preferably 1 to 5% by weight in the grease composition.

Glycerin is used in the grease composition of the present invention. The content ratio of glycerin is not particularly limited, and when the amount of the organic molybdenum compound or the organic zinc compound is used in combination, it may be appropriately contained depending on the total amount of the organic molybdenum compound and the organic zinc compound, It is usually 0.1 to 5% by weight, preferably 0.3 to 2% by weight in the grease composition.

The grease composition of the present invention preferably contains an organic zinc compound. As the organozinc compound, various organozinc compounds can be used as long as they are decomposed by frictional heat at the lubrication site. Specific examples of preferable organic zinc compounds include zinc dithiophosphates such as zinc dialkyldithiophosphates and zinc diaryldithiophosphates. Specific examples of particularly preferable organozinc compounds include zinc dialkyldithiophosphate whose alkyl group is a primary alkyl group. These organozinc compounds may be used alone or in combination of two or more. The content ratio of the organozinc compound is not particularly limited,
It is usually 0.1 to 5% by weight, preferably 0.3 to 2% by weight in the grease composition. If the amount of the organic molybdenum compound, glycerin and the organic zinc compound is less than the lower limit value of the above range, the wear resistance effect may be too small, and even if the amount exceeds the upper limit value of the above range, the wear resistance effect may be equal or worse. There is.

In the grease composition of the present invention, in addition to the above components, alkyl polysulfide, dibenzyl disulfide, methyl dichlorostearate, tricresyl phosphate, triphenyl phosphite, lead diamyldithiocarbamate, Extreme pressure agents such as graphite, molybdenum disulfide, antimony sulfide, boron compounds, polytetrafluoroethylene, diphenylamine, 2,6-ditertiarybutyl-p-hydroxytoluene, octylated diphenylamine, phenyl-α-naphthylamine, 4, Antioxidants such as 4'-tetramethyldiaminodiphenylmethane, barium sulfonates such as barium dinonylnaphthalene sulfonate,
Contains various additives such as sodium nitrite, petroleum sulfonate, polyoxyethylene soyaamine, rust preventive such as sorbitan monooleate, viscosity index improver such as polymethacrylate, pour point depressant, tackifier, dye, etc. Can be made.

[0012]

In the grease composition of the present invention, by using glycerin in combination with the organic molybdenum compound, the wear resistance is significantly improved. However, the synergistic effect of this organic molybdenum compound and glycerin is At the time of decomposition, glycerin acts catalytically as well as glycerin, and the decomposition product of the organic molybdenum compound reacts with the decomposition product of glycerin to become another compound, and this compound works effectively for abrasion resistance. It is thought that this is due to a matter. Furthermore, when an organozinc compound is used in combination, the wear resistance is further synergistically improved, but this also decomposes the organozinc compound along with the above-mentioned catalytic action, and decomposes the three components of the organomolybdenum compound, glycerin and the organozinc compound. It is considered that reaction products due to the products are generated, and the reaction products of these three members have improved wear resistance.

Therefore, in the grease composition of the present invention, the degree of decomposability of the organomolybdenum compound and the organozinc compound due to frictional heat at the lubrication site is not an essential problem, and the organomolybdenum compound and the organozinc compound are decomposed and produced. It is considered that the reaction product of the product with the decomposition product of glycerin is important. Degradability of the organic molybdenum compound due to frictional heat is greater in molybdenum dithiophosphate than molybdenum dithiocarbamate, but in the present invention, the less degradable molybdenum dithiocarbamate is preferable because of the above reason. it is conceivable that. Further, the decomposability of the organozinc compound due to frictional heat at the lubricated portion decreases in the order of secondary alkyl zinc dithiophosphate, primary alkyl zinc dithiophosphate, aryl zinc dithiophosphate,
It is considered that the primary alkyl zinc dithiophosphate is preferable in the present invention for the same reason.

Next, a method for preparing the grease composition of the present invention will be described. The grease composition of the present invention can be prepared by mixing the above components. The order of addition of each component is not particularly limited and may be appropriately added, but a base grease composed of a base oil and a thickener is adjusted in advance in a grease pot, and other components are added to this. It is preferable to mix them. The base grease may be adjusted by simply mixing the base oil and the thickener, but after the precursor of the thickener is mixed and dispersed in the base oil, the precursor is reacted to increase the viscosity. It is preferable to use a method in which a thickener is produced and the thickener is dispersed in the base oil.
The grease composition of the present invention can be used in all lubrication points to which grease can be applied, including lubrication points such as rolling bearings, sliding bearings, sliding surfaces, and gears. In particular, the grease composition of the present invention is effective when it is used in a lubricated place with a large amount of wear or in a lubricated place such as an industrial machine, an industrial robot, a machine tool, etc., which requires precision.

[0015]

EXAMPLES Next, the present invention will be specifically described by way of examples. However, the present invention is not limited to these examples. The test method in the examples of the present invention was performed by the following method. Consistency (60 W) Consistency was measured according to JIS K 2220 5.3.3. That is, after the sample was kept at 25 ° C., the consistency was measured immediately after mixing 60 times with a regular mixer.

Abrasion Resistance Evaluation Abrasion resistance was measured according to ASTM D 2266.
The measurement conditions were as follows. Test condition Tester: Four-ball wear tester Test ball: JIS B 1501 (steel ball for ball bearing) Load: 40kgf Rotation speed: 1200rpm Temperature: 75 ° C Time: 60min Evaluation: Wear scar diameter

Preparation of Base Grease The base grease used in Examples and Comparative Examples of the present invention was prepared by the following method. Using poly-α-olefin (kinematic viscosity at 100 ° C .: 6 cst) as the base oil, reacting diphenylmethane-4,4-diisocyanate and cyclohexylamine in the base oil so that the content of the produced urea compound becomes 18% by weight. A urea grease uniformly mixed and dispersed in a base oil was prepared.

Further, refined mineral oil (kinematic viscosity at 100 ° C .: 6 cst) was used as the base oil, and 12-hydroxystearic acid and lithium hydroxide were heated and reacted in the base oil to produce lithium-12-hydroxystearate. A lithium grease was prepared by uniformly mixing and dispersing in a base oil so that the content was 8% by weight.

Example 1 3 wt% of molybdenum dialkyldithiocarbamate (MoDTC) and 1 wt% of glycerin were added to 96 wt% of urea grease prepared by the above-mentioned base grease preparation method, and a uniform grease composition was obtained by a colloid mill. did.
Table 1 shows the measurement results of the composition and performance of the obtained grease composition.

Example 2 96% by weight of urea grease prepared by the method for preparing a base grease described above was added to molybdenum dialkyldithiophosphate (MoDTP) in which the alkyl group was a secondary alkyl group.
(Secondary alkyl)) in an amount of 3% by weight and glycerin in an amount of 1% by weight to obtain a uniform grease composition by a colloid mill.
Table 1 shows the measurement results of the composition and performance of the obtained grease composition.

Example 3 95% by weight of urea grease prepared by the method for preparing the above base grease, 3% by weight of molybdenum dialkyldithiocarbamate (MoDTC) and 1% by weight of glycerin.
Further, 1% by weight of zinc dialkyldithiophosphate (ZnDTP (primary alkyl)) whose alkyl group is a primary alkyl group was added, and a uniform grease composition was obtained by a colloid mill. Table 1 shows the measurement results of the composition and performance of the obtained grease composition.

Example 4 Molybdenum dialkyldithiophosphate (MoDTP) having an alkyl group as a secondary alkyl group was added to 95% by weight of urea grease prepared by the above method for preparing a base grease.
(Secondary alkyl)) 3% by weight, glycerin 1% by weight
Further, 1% by weight of zinc dialkyldithiophosphate (ZnDTP (primary alkyl)) whose alkyl group is a primary alkyl group was added, and a uniform grease composition was obtained by a colloid mill. Table 1 shows the measurement results of the composition and performance of the obtained grease composition.

Example 5 95% by weight of lithium grease prepared by the above method for preparing a base grease, 3% by weight of molybdenum dialkyldithiocarbamate (MoDTC), 1% by weight of glycerin, and zinc having an alkyl group as a primary alkyl group 1% by weight of dialkyldithiophosphate (ZnDTP (primary alkyl)) was added, and a uniform grease composition was obtained by a colloid mill. Table 1 shows the measurement results of the composition and performance of the obtained grease composition.

Comparative Example 1 Example 1 was repeated except that the amount of urea grease was 97% by weight and no glycerin was added. Table 2 shows the composition and performance measurement results of the obtained grease composition.

Comparative Example 2 In Comparative Example 1, instead of molybdenum dialkyldithiocarbamate, molybdenum dialkyldithiophosphate (MoDT) in which the alkyl group was a primary alkyl group was used.
Comparative Example 1 except that the same amount of P (primary alkyl)) was used
It carried out similarly to. Table 2 shows the composition and performance measurement results of the obtained grease composition.

Comparative Example 3 The procedure of Example 3 was repeated, except that the amount of urea grease was 99% by weight and molybdenum dialkyldithiocarbamate and glycerin were not added. Table 2 shows the composition and performance measurement results of the obtained grease composition.

Comparative Example 4 In Comparative Example 3, zinc dialkyldithiophosphate (ZnDTP) in which the alkyl group was a primary alkyl group was used.
Instead of (primary alkyl)), the same procedure as in Comparative Example 3 was performed except that zinc dialkyldithiophosphate (ZnDTP (secondary alkyl)) whose alkyl group was a secondary alkyl group was used in the same amount. Table 2 shows the composition and performance measurement results of the obtained grease composition.

Comparative Example 5 As in Example 1, except that zinc dialkyldithiophosphate (ZnDTP (secondary alkyl)) having an alkyl group of a secondary alkyl group was used in the same amount in place of glycerin. It carried out similarly. Table 2 shows the composition and performance measurement results of the obtained grease composition.

[0029]

[Table 1]

[0030]

[Table 2]

Note) The abbreviations in Tables 1 and 2 have the following meanings. MoDTC: molybdenum dialkyldithiocarbamate MoDTP (primary alkyl): molybdenum dialkyldithiophosphate whose alkyl group is a primary alkyl group MoDTP (secondary alkyl): molybdenum dialkyldithiophosphate whose alkyl group is a secondary alkyl group ZnDTP ( Primary alkyl): zinc dialkyldithiophosphate whose alkyl group is a primary alkyl group ZnDTP (secondary alkyl): zinc dialkyldithiophosphate whose alkyl group is a secondary alkyl group

From the descriptions in Tables 1 and 2 above, the grease compositions of Examples 1 and 2 have significantly better wear resistance and synergistic effect than the grease compositions containing the organic molybdenum compound alone. I understand. In addition, the grease compositions of Examples 3 to 5 are better than the grease compositions containing the organic molybdenum compound alone or the organic zinc compound alone.
It can be seen that the wear resistance performance is extremely good and there is a further synergistic effect.

[0033]

EFFECTS OF THE INVENTION The grease composition of the present invention has excellent wear resistance due to the synergistic action of an organic molybdenum compound and glycerin, a lubricated portion that is easily worn, an industrial machine or an industrial robot that requires precision, It can be used for lubrication points of machine tools. Therefore, the grease composition of the present invention is extremely useful in practice.

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Claims (2)

[Claims] 1. A grease composition comprising a base oil, a thickener, an organic molybdenum compound and glycerin. 2. The grease composition according to claim 1, further containing an organozinc compound.