JPH0631376B2 - Dispersant for solid lubricants - Google Patents

Description

The present invention relates to a novel dispersant for solid lubricants. More specifically, it relates to a dispersant for a solid lubricant having good dispersibility and excellent stability.

(Prior Art) Efforts have been made to impart extreme pressure and abrasion resistance to lubricating oils by blending various solid or liquid additives with so-called lubricating oils such as mineral oils, synthetic oils and animal and vegetable oils.

Conventionally, it has been known that it is useful to add fluorocarbon or fluorine resin powder as a solid lubricant to a lubricating oil in order to improve extreme pressure resistance and abrasion resistance.

However, since fluorocarbon and fluorocarbon resin powders have very poor affinity for oil, they have very poor dispersion stability in lubricating oil, and have the drawback of agglomerating and settling within one day after preparation. There is. As the dispersant for solid lubricants, for example, JP-A-60-56760 discloses nonionic surfactants such as polyoxypropylene alkyl ether, polyoxypropylene, and alkylphenyl ether.

(Disadvantages of conventional technology) However, in such a conventional solid lubricant dispersant, the dispersion stability is not sufficient, the lubricating performance is not practically exhibited, and the sedimentation layer is formed when stored for a long time. Since it formed, it was not completely satisfactory as a lubricating oil. Therefore, lubricating oils having excellent dispersion stability of these solid lubricants are required. As a result of intensive studies on the dispersion stability of solid lubricants in oil in order to solve the above problems, the present inventors have found a dispersant excellent in extremely long-term stability that cannot be achieved by conventional dispersants. The present invention has been completed.

(Means for Solving Defects) The present invention has been made by paying attention to such conventional problems. That is, the lanolin fatty acid has a acid value lower than 90 mg-KOH / g, which is reduced by the high temperature dehydration reaction.
It has been found that the object can be achieved by using a dispersant for a solid lubricant, which is characterized by containing a lanolin fatty acid or a salt thereof having an acid value of less than 25 mg-KOH / g as an essential component.

(Requirements Constituting Means) Examples of the lanolin fatty acid used in the present invention include wool grease and those obtained by saponification of lanolin, and these are a mixture of the constituent components shown in Table 1.

The acid value and the saponification value are usually 130 to 160 and 160 to 180, respectively. As can be seen from the above composition, the main component of lanolin fatty acid is a higher fatty acid having a very wide distribution of 9 to 32 carbon atoms and an α-hydroxy fatty acid having 12 to 25 carbon atoms. Therefore, by esterifying lanolin fatty acid by a high temperature dehydration reaction to reduce the acid value, the amount of 125 mg-KOH / g larger than 90 mg-KOH / g of the present invention can be obtained.
Lanolin fatty acids with smaller acid numbers are obtained.

This ester reaction is allowed to occur, and it is greater than 90 mg-KOH / g 1
By setting the acid value to less than 25 mg-KOH / g, it exerts its effect as an excellent dispersant for solid lubricants for the first time, and has an unexpectedly excellent stability that cannot be obtained with lanolin fatty acid or lanolin fatty acid salt. It is possible to improve the sex.

The dispersant of the present invention is preferably used in the presence of no catalyst or any esterification catalyst for lanolin fatty acid, preferably 160 to 2
It can be obtained by heating under reduced pressure at a temperature within the range of 20 ° C. until the required acid value is reached. By heating such a lanolin fatty acid containing a hydroxy fatty acid under reduced pressure, a lactide obtained by dehydration of two molecules of the water or a cyclic ester such as a lactone by intramolecular dehydration, and a linear mono-, poly-, or ester are produced. This is well known. The acid value of the lanolin fatty acid of the present invention is preferably 125 mg-KOH
The value is smaller than / g and larger than 90, more preferably smaller than 115 and larger than 100. When the acid value is out of this range, the dispersibility is slightly inferior, so it is important for the dispersant of the present invention to control the acid value.

That is, the reduction of hydroxyl groups related to hydroxy fatty acids due to the high temperature dehydration state of lanolin fatty acid reduces esterification of non-aqueous dispersion medium and solid fine powder by esterification consisting of special structure of lipophilic group consisting of branched alkyl group with very wide distribution It is considered that good results can be obtained with the improvement effect.

Water produced in the esterification reaction is removed from the reaction medium, preferably under a nitrogen stream or in the presence of a solvent,
This can be done by distilling as water is formed. The obtained lanolin fatty acid having an acid value of more than 90 mg-KOH / g and less than 125 mg-KOH / g can be isolated by a conventional method. Alternatively, the lanolin fatty acid may be dissolved in a lubricating oil in advance to carry out the esterification reaction.

Further, a salt of lanolin fatty acid having an acid value of more than 90 mg-KOH / g and less than 125 mg-KOH / g is also effective.

Examples of the salt type include alkali metals such as sodium, potassium and lithium, and alkaline earth metals such as calcium, barium and magnesium, lead and zinc. Further, it may be a salt such as ammonia or amine.

Examples of amines include polyamines such as alkylamines, ethylenediamine, diethylenetriamine and triethylenetetramine, morpholine, piperidine, alkanolamines and the like.

Such neutralization reaction is greater than 90 mg-KOH / g and 125 mg-KOH
It is obtained by heating and stirring a lanolin fatty acid having an acid value smaller than / g and a base commensurate with the acid value at a temperature in the range of 200 ° C. In this case, the base is obtained by dissolving in the presence of an organic solvent, for example petroleum fraction.

Further, as the lanolin fatty acid having an acid value of more than 90 mg-KOH / g and less than 125 mg-KOH / g, the lubricating oil-containing solution can be used as it is. If necessary, unreacted metal oxides and hydroxides are removed by a conventional method. It is to be noted that the alkaline earth metal is more preferable as the salt in terms of wear resistance and frictional relaxation.

Next, as the solid lubricant dispersible using the present invention,
Carbon fluoride, aluminum fluoride, calcium fluoride,
Organo molybdenum such as natural graphite, molybdenum dithiocarbamate, molybdenum dithiophosphate, etc., silicon nitride, boron nitride, molybdenum disulfide, lead oxide, aluminum oxide, metal oxides such as boron oxide, fluororesin such as polytetrafluoroethylene, etc. Powders, melamine cyanurate resin powders, and solid lubricants such as lead sulfide, molybdenum disulfide, and calcium fluoride coated with boron oxide are listed.

These dispersants of the present invention are effective for solid lubricants having any particle size, but are usually 20 μm or less, have an average particle size of 0.02 to 10 microns, and have a particle size distribution as uniform as possible. Those are preferable.

Further, as the lubricating oil to which the solid lubricant is added, any of those usually used as an oily lubricating oil can be used, and among them, preferred ones include mineral oils such as naphthenic hydrocarbon oils and paraffinic hydrocarbon oils. , Synthetic hydrocarbon oil, olefin polymerized oil, alkylated aromatic oil,
Polyether oil, ester oil, halogenated hydrocarbon oil,
Examples thereof include synthetic oils such as silicone oils and fluoro oils, animal and vegetable oils, and the like, which usually have a viscosity of 5 to 3000 cp at room temperature.

The concentration of the solid lubricant in the lubricating oil composition may be any concentration that produces a dispersion, but is usually 0.05 to 40% by weight, and if it is less than 0.05% by weight, satisfactory lubricating performance is obtained. Is not obtained, and it is economically unfavorable when the content is simply more than 40% by weight. Further, the dispersant of the present invention is desirably added in an amount of 0.01 to 20% by weight, preferably 0.02 to 10% by weight, based on the entire lubricating oil composition.

As a method for producing a lubricating oil composition, for example, a predetermined amount of a solid lubricant is added to a lubricating oil in which the dispersant of the present invention is dissolved,
Then, a disperser having a shearing force capable of breaking down the secondary particles of the solid lubricant, specifically, three rolls, colloid mill, homogenizer, ball mill kneader,
Mix thoroughly with a line mixer.

(Effect of the Invention) The lubricating oil composition thus obtained has excellent dispersion stability of the solid lubricant, and is left at a temperature of 80 to 90 ° C., for example, even if it is left for a long period of time such as 6 months or more.
It has excellent stability even at high temperatures.

Further, the lubricating oil composition containing a solid lubricant containing the dispersant of the present invention has good extreme pressure properties and a low friction coefficient, and can be used as a lubricating oil for general machines such as refrigerating oil, various engine oils, spindle oils, dynamo. It is mixed with oil, machine oil, turbine oil, gear oil, cylinder oil, and other various operating oils to prevent seizure even under severe conditions, and exerts a great effect in reducing the amount of wear on the sliding surface. . Furthermore, it is also effective as a metalworking oil, a lubricating oil for treating fibers, and the like.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

(Example) As a lubricating oil, 2 g of a dispersant was dissolved in 196 g of spindle oil, 2 g of a solid lubricant was added, and the mixture was thoroughly mixed by a ball mill and uniformly dispersed. The prepared lubricating oil was transferred to a graduated cylinder of 100 m and stored in a constant temperature bath at 25 ° C. for 90 days, and the sedimentation layer in the cylinder was observed to confirm the dispersion stability. The results are shown in Table 2. The symbols in the table mean the following.

◯: No sediment is observed.

Δ: A small amount of sediment is observed.

X: A large amount of sediment is observed.

From the above test results, a long-term stable lubricating oil was obtained when the dispersant of the present invention was used.

On the other hand, when the dispersant of Comparative Example was used, a large amount of sedimented layer was observed. As is clear from these results, it can be seen that the use of the dispersant of the present invention makes it possible to obtain a lubricating oil having excellent long-term stability of a solid lubricant.

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Claims (2)

[Claims] 1. A dispersant for a solid lubricant, which comprises, as an essential component, a lanolin fatty acid or a salt thereof having an acid value of more than 90 mg-KOH / g and less than 125 mg-KOH / g. 2. A method for dispersing a solid lubricant, which comprises using the dispersant according to claim 1.