US3794585A - Lubricants comprising a dimer or a trimer of a c18 monocarboxylic acid - Google Patents

Abstract

LUBRICAANTS COMPRISING FROM AOUT 8% TO ABOUT 95% OF A TRIMER OR DIMER OF A C18 ALIPHATIC MONOCARBOXYLIC ACID OR MIXTURE TEREOF AND AN OLEOPHILIC SURFACE MODIFIED CLAY HAVE IMPROVED RETENTION PROPERTIES AS GEAR LUBRICANTS.

Description

United States Patent Office Patented Feb. 26, 1974 U.S. Cl. 252-28 10 Claims ABSTRACT OF THE DISCLOSURE Lubricants comprising from about 8% to about 95% of a trimer or dimer of a C aliphatic monocarboxylic acid or mixtures thereof and an oleophilic surface modified clay have improved retention properties as gear lubricants.

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of US. application Ser. No. 114,334, filed Feb. 10, 1971, now abandoned.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to improved lubricant compositions, and relates more particularly to improved lubricant compositions in the form of gear lubricants which possess superior retention properties under use conditions.

Description of the prior art Among the desired characteristics of gear oils is the ability of the composition to exhibit the aforementioned retention properties. It is therefore necessary that a successful gear lubricant be able to withstand the destructive forces of local high temperatures and pressure. Failure to do so results in a breakdown of the entire film covering the gear surface and a consequent scoring of such gear.

One important specification test for determining the effectiveness of open gear lubricants is the well-known Timken Retention Test. Conventionally, in choosing a material which will pass this test one skilled in this art will choose materials having very high viscosities and softening points near room temperature. Such characteristics make dispensing the lubricant very difiicult.

From the following disclosure it will be seen that the dimer and trimer acids of this invention permit the use of vehicles having lower viscosities in preparing gear lubricants. No art is known that teaches the use of the said acids for such purpose.

SUMMARY OF THE INVENTION In accordance with the invention there is provided a gear lubricant composition comprising from about 8% to about 95 preferably from about 10% to about 30%, by weight of a trimer or a dimer of a C aliphatic monocarboxylic acid, or a mixture thereof, containing from about 15% to about 95 by weight of the trimer, preferably at least about 25%, and from about to about 92% by weight of an oil and from about 0.5% to about 15 by Weight of an oleophilic surface modified clay. To this mixture may be added other materials, such as viscosity modifiers and the like. The resulting gear lubricant has improved retention properties.

DESCRIPTION OF SPECIFIC EMBODIMENTS The trimer or dimer acid useful in the practice of this invention is made by polymerizing a C monocarboxylic acid, either saturated or unsaturated. Examples of useful acids are oleic and linoleic acids. A further example, and the one specifically illustrated for the practice of this invention, is a trimer acid containing about 90% of the trimer, about 5% of the dimer and about 5% unreacted acid. It is a tribasic acid having an average of about 54 carbon atoms and a molecular weight of 845. This acid, according to Emery Industries Technical Bulletin No. 43 8C, dated April 1969, has the following proposed structure R R and R being an alkyl group and X represents undetermined linkages resulting from polymerization of three unsaturated C fatty acid molecules.

The dimer acid illustrated in the practice of this invention contains about 97-99% dimer, about 1-3% trimer and essentially no unreacted C monobasic acid. Its proposed structure, as found in the same bulletin referred to above, is:

R and R are alkyl side chains and X is an undetermined linkage resulting from polymerizing two molecules of fatty acid molecules.

Optionally, the composition may contain viscosity modifiers such as a high viscosity resin. An example of the resin used in the practice of this invention according to the specific illustration is one having a viscosity of 4000 SUS at 210 F. Others which will be useful in the gear lubricant of the invention are resins having viscosities of from about 1,000 to about 12,000 SUS at 210 F. Such resins are often referred to as Kendall resins, which are oxidized high viscosity Pennsylvania oil stocks. These resins, when used at all, may be used in an amount of up to about 40% by weight of the mixture of acids and oil, and preferably from about 10% to about 20% by weight thereof.

It is contemplated that gear lubricants useful in the practice of this invention can be prepared from mineral oils, both naphthenic and paraflinic as well as aromatic, and synthetic oils. Such synthetic oils will include synthetic hydrocarbon oils prepared by polymerizing olefins, phosphorus-containing organic esters, silicates, siloxanes and esters made from polyhydric alcohols and monocarboxylic acids or from polycarboxylic acids and monohydric alcohols. These oils, usually lubricating oils, may have viscosities ranging from about SUS to about 250 SUS at 210 F., and preferably from about SUS to about SUS at 210 F.

The compositions are formulated and used as greases by adding to the composition a grease-forming quantity of a thickening agent. It has been found that the oleophilic surface modified clays are unobviously superior to the metal soap thickeners, such as lithium hydroxy stearate. This is shown in Example 6 hereinbelow.

It is known that all clays comprise some form of alumina and silica in combination, usually in the hydrated form. Examplary of such clays are montmorillonite and bentonite (principally montmorillonite). However, no intention to limit the clays to these should be inferred, since it is contemplated that all clays modified with certain ammonium compounds will be useful in the composition herein disclosed.

The surface modified clays, generally referred to as non-soap thickeners, are useful at all concentrations of acid, and especially at concentrations from the minimum 8% up to about 50% of acid. These thickening agents are most effective when they are present in the compo- 3 sition to the extent of from about 0.5 to about 10% by weight thereof.

The organic portion of the organic ammonium may, for example, be benzyl or an alkyl having from 1 to about 20 carbon atoms. The surface modified clays are prepared by reacting the clay with a compound of the formula wherein R R R and R are selected from the group consisting of hydrogen, benzyl and alkyl having from 1 to 20 carbon atoms, at least one of said Rs being other than hydrogen and X is halogen (e.g. chlorine, bromine, fluorine and iodine). Examples of hydrocarbyl ammonium halides that may be used are dimethyldioctadecylammonium halide, dimethylbenzyloctadecylammonium halide, diethyldiodecylammonium halide and methylethyldicicosyl halide. There may be used singly or in combination. Furthermore the various surface modified clays may be combined if desired.

It is not known precisely how the contemplated amine compounds modify the surface of the clays to form an oleophilic agent. The manner in which the surfaces are modified, however, is of no moment. The main consideration is that applicant has discovered a class of nonsoap grease modifiers that will produce an elfective gear lubricant over a wide range of compositions. Soaps like lithium hydroxy stearate, on the other hand, do not give useful compositions with the dimer and trimer acids of this invention.

As illustrations of the oleophilic surface modified clays that may be used, there might be mentioned Baragel, refined montmorillonite, hectorite and bentone, which is bentonite (principally a montmorillonite) that has been reacted with an organic ammonium halide, as e.g. dimethyldioctadecyl or dimethylbenzyloctadecylammonium halide.

Other additives, e.g. certain lead salts of fatty acids (such as lead oleate) and certain filler materials such as lampblack, may also be present along with the thickener.

DESCRIPTION OF SPECIFIC EMBODIMENTS Example 1 The following will serve to illustrate how effectively the compositions of this invention are retained on gears. In the following the oil used was a solvent-refined paraffinic oil having a viscosity of 150 SUS at 210 F., the resin was an oxidized high viscosity Pennsylvania oil stock, the resin having a viscosity of 4000 SUS at 210 F., and the acid used was predominantly a trimer (90%) of a C carboxylic acid containing some dimer (5%) and some unreacted C acid (5%). It averaged about 54 carbon atoms per molecule and had a molecular weight of about 845.

The test used to measure the retention of the lubricant composition by a gear was the well-known Timken Retention Test as described in U.S. Steel Lubrication Engineers Manual (D-51). This test evaluates the time to failure of a film lubricating for extended periods without lubricant replenishment. In essence, the face of a lubricated cup is brought into contact with a block. A definite load is placed on the block, and the length of time before scoring occurs measures the elfectiveness of the gear lubricant.

More specifically, the test is run as follows:

The Timken test cup and block are washed with a petroleum spirit and dried at room temperature prior to assembly. Four grams of test sample are weighed to the nearest 0.1 gram and all of this is applied to the bearing surface of the test cup and block. The test is Trimer Oil, Resin. acid, percent; percent percent Example by wt. by wt. by wt. Results 28. 0 50.0 0 Fall in 4 minutes. 53. 0 25. 0 0 Do. 48. 0 25. 0 5.0 Fail in 27 minutes. 48. 0 27. 5 2. 5 Fail in 4 minutes. 48. 0 20. 0 10. 0 Pass. 30 minutes.

Each of the compositions of Examples 1-5 also contained 6% of lead oleate, 6% of lampblack and 10% of Baragel, which is a mixture of dimethyldioctadecyl and dimethylbenzyloctadecylammoniurn bentonite.

The results indicate that Example 5, although it contains almost 50% of a comparatively light oil, passes the Timken Retention Test. From Example 1, it is clear that when the percentages of light (oil) and heavy (resin) portions are reversed and the acid is eliminated, the composition fails in 4 minutes. With about the same amounts of oil and resin as shown in Example 5 but with no acid, the same failure is observed in Example 2. These two tests appear to indicate that the efiectiveness of the acid is not due to any viscosity effect and that the mere use of a more viscous material is not the reason for retention. Examples 3 and 4 would seem to establish that the minimum amount of acid necessary for completely successful results in the retention test is somewhat above 5% by weight.

Example 2 Using dimer acid (97-99% dimer and l-3% trimer as described hereinabove) and the procedure described in Example 1, the following results were obtained:

2 Same resin as in Example 1.

Example 3 A composition of oil and trimer made from 5% of the oil of Example 1 and of the trimer acid as described in Example 1, when evaluated in the Timken Test, gave a pass result. Baragel was present as in Example 1.

Example 4 A gear lubricant consisting of oil and mixed dimer and trimer acids made up from 5% of the oil of Example 1 and 95% of a mixture of 75% of dimer acid and 25% of trimer acid, Baragel, etc. as defined in Example 1, was evaluated in the Timken Test. The result was a pass."

Example 5 An oil and dimer acid gear lubricant made up from 5% of the oil of Example 1 and 95% of dimer acid passed the Timken Test. It contained the Baragel of Example 1.

Example 6 To demonstrate that metal soaps do not produce effective gear lubricants with the dimer and trimer acids of this invention, the following compositions were prepared:

1 Same oil as in Example 1. 2 Merely an agent for darkening the composition.

Both 1) and (2) failed in the Timken Retention Test in less than 5 minutes.

Example 7 A grease was prepared from the following:

Parts by Percent by Material weight weight Oil 1 300 30. 0 Primer acid 1 490 49. 0 Bentone 34 2 100 10. 0 Lead olmte 50 5. 0 Lamphlack 6O 6. 0

Total 1, 000 100. 0

1 Same as Example 1. 1 Dimethyldioctadeeylammonium bentomte.

Although the present invention has been described with certain specific embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of this invention as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the appended claims.

I claim:

1. A lubricant composition suitable for use as a gear lubricant comprising from about 8% to about 95% by weight of a dimer or a trimer of a C aliphatic monocarboxylic acid, or a mixture of such acids, and from about 5% to about 92% by weight of a lubricating oil having a viscosity of from about SUS to about 250 SUS at 210 F., and from about 0.5 to about 15% by weight thereof of an oleophilic surface modified clay.

2. The composition of claim I wherein said lubricating oil is a mineral lubricating oil.

3. The composition of claim 1 wherein the acid is a trimer.

4. The composition of claim 1 wherein the acid is a dimer.

5. The composition of claim 1 comprising a grease.

6. The composition of claim 1 containing a viscosity modifier.

7. The composition of claim 3 wherein the acid contains about of trimer prepared from unsaturated C monocarboxylic acid.

8. The composition of claim 4 wherein the acid contains about 97-99% of dimer prepared from unsaturated C monocarboxylic acid.

9. The composition of claim 6 wherein said viscosity modifier is an oxidized lubricating oil stock having a viscosity of from about 1,000 to about 12,000 SUS at 210 F.

10. The composition of claim 1 containing from about 0.5 to about 10% by weight of said oleophilic surface modified clay when the dimer acid, trimer acid or mixture thereof is present to the extent of from about 8% to about 50% by weight.

References Cited UNITED STATES PATENTS 3,180,832 4/1965 Furey 25257 3,223,635 12/1965 Dwyer et a1 25256 R X 3,329,611 7/1967 Chao 252-56 R X 3,433,743 3/1969 Morway et a1 25228 X FOREIGN PATENTS 814,864 6/ 1959 Great Britain.

DANIEL E. WYMAN, Primary Examiner W. H. CANNON, Assistant Examiner US. Cl. X.R. 25256 R