Lubricant composition

Abstract

Lubricant compositions containing in an amount sufficient to impart antiwear and extreme pressure properties, a compound having the structure: ##SPC1## This compound is particularly useful as an extreme pressure additive in lubricant compositions.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to lubricant compositions and, in one of its aspects, relates more particularly to lubricating compositions such as lubricating oils and greases which exhibit insufficient antiwear and extreme pressure properties, under conditions of use.

2. Description of the Prior Art

It is known that extreme pressure properties can be incorporated in lubricant compositions such as liquid hydrocarbons and greases by incorporating therein sulfurized olefins as extreme pressure additives. Such additives are capable of imparting good extreme pressure and antiwear properties, but they contain relatively high corrosive sulfur contents, a deficiency which limits their use. Absence of corrosive sulfur content would be desirable. In additives of this type it is also highly desirable, from a commercial standpoint, that they be odorless and colorless. These latter characteristics have also been found lacking in present commercial sulfurized extreme pressure additives.

SUMMARY OF THE INVENTION

It has now been found that improved antiwear and extreme pressure properties can be imparted to lubricant compositions by incorporating therein minor amounts of a relatively high sulfur-content additive which, in addition, does not impart odor to the lubricant and is also colorless. As more fully hereinafter described, this novel extreme pressure additive is obtained by reacting isobutylene and a sulfur halide to produce the corresponding adduct; reacting the adduct thus produced with an alkali metal mercaptide in a non-reactive liquid medium to obtain a product comprising a compound having the structure: ##SPC2##

And separating the compound thus produced from the aforesaid reaction mixture. The compound thus produced is found to have a melting point of approximately 254.degree.C.

In general, the aforementioned reactions are conducted at ambient temperature. In most operations the reactions are conducted at a temperature from about 0.degree. to about 150.degree.C. and preferably at a temperature from about 20.degree. to about 60.degree.C. Insofar as the production of the adduct is concerned, sufficient sulfur halide is employed to react with all of the isobutylene. In general, for most operations, isobutylene and the sulfur halide are reacted in a mole ratio of from about 0.5:1 to about 2.5:1 and preferably in a mole ratio of from about 1:1 to about 2:1, by weight. Insofar as the reaction between the adduct and the alkali metal mercaptide is concerned, sufficient alkali metal mercaptide is employed to react with all of the adduct. In general, for most operations, the adduct and the alkali metal mercaptide are reacted in a mole ratio of from about 1:1 to about 1:5 and preferably in a mole ratio of from about 1:1 to about 1:2.5 by weight. Any sulfur monohalide may be employed for reaction with isobutylene and may include sulfur monochloride, or a combination of a sulfur dihalide and elemental sulfur to produce the corresponding sulfur monohalide may also be employed as a reagent. Any alkali metal mercaptide may be employed for reaction with the adduct, as hereinbefore described, and may include sodium mercaptide, potassium mercaptide, lithium mercaptide or calcium mercaptide.

Any non-reactive liquid medium may be employed for carrying out the reaction between the adduct and the alkali metal mercaptide and may include lower alcohols such as methanol, ethanol, propanol or butanol.

The resulting antiwear extreme pressure compound, suitable for use as an extreme pressure lubricant additive is found to have a sulfur content of about 50 percent, by weight, and is odorless and colorless. This compound represents about 45 percent, by weight, of the product resulting from the reaction of the aforementioned adduct and the alkali metal mercaptide. The remaining portion of the aforementioned product comprises about 55 percent, by weight, a mixture of unsaturated sulfides and polysulfides.

Of particular significance, in accordance with the present invention, is the ability to impart improved antiwear and extreme pressure properties to lubricants comprising liquid hydrocarbon oils in the form of either mineral oils or synthetic oils, or in the form of a grease in which any of the aforementioned oils are employed as a vehicle, in conjunction with a thickening agent. In general, mineral oils employed as the lubricant or grease vehicle, may be of any suitable lubricating viscosity range, as for example, from about 45 SSU at 100.degree.F. to about 6000 SSU at 100.degree.F., and preferably from about 50 SSU at 210.degree.F. to about 250 SSU at 210.degree.F. These oils may have viscosity indices varying from below 0 to about 100 or higher. The average molecular weights of these oils may range from about 250 to about 800. Where the lubricant is to be employed in the form of a grease, the lubricating oil is generally employed in an amount sufficient to balance the total grease composition after accounting for the desired quantity of the thickening agent and other additive components to be included in the grease formulation. In instances where synthetic oils, or synthetic oils employed as the vehicle for the grease, are desired in preferance to mineral oils or in combinations therewith, various compounds of this type may be successfully utilized. Typical synthetic vehicles include polyisobutylene, polybutenes, hydrogenated polydecenes, polypropylene glycol, polyethylene glycol, trimethylol propane esters, neopentyl and pentaerythritol esters, di (2-ethylhexyl) sebacate, di (2-ethyl hexyl) adipate, dibutyl phthalate, fluorocarbons, silicate esters, silanes esters of phosphorous-containing acids, liquid ureas, ferrocene derivatives, hydrogenated mineral oils, chain-type polyphenyls, siloxanes and silicones (polysiloxanes), alkyl-substituted diphenyl ethers typified by a butyl-substituted bis (p-phenoxy phenyl) ether, phenoxy phenylethers, etc.

With respect to imparting improved antiwear and extreme pressure properties to greases, which contain the above-described novel extreme pressure additives, any thickening agent normally employed in grease formulations may be successfully utilized. Particularly preferred are greases which contain in minor properties, such conventional thickening agents as lithium hydroxystearate, lithium complexes, calcium complexes, clay-based thickening agents, polyurea based thickening agents and a wide variety of other metallic soaps and thickeners normally employed in the grease-making art. In addition, other additives, normally employed for imparting extreme pressure properties may also be incorporated in the novel greases and may therefore include such extreme pressure additives as chlorinated paraffins, phosphorous-containing, calcium carbonate, calcium acetate or zinc phosphorodithioate-containing additives.

The following data and examples will serve to illustrate the marked degree in antiwear and extreme pressure improvement imparted by the novel additives of the present invention to lubricant compositions. It will be understood, however, that it is not intended the invention be limited to the particular lubricant compositions disclosed nor the particular additive for imparting extreme pressure properties. Various modifications thereof can be employed and will be readily apparent to those skilled in the art.

EXAMPLE 1

Sulfur monochloride (1013g, 7.5 moles) was charged into a 3-L. 4-necked reaction flask equipped with a mechanical stirrer, condenser (drying tube attached) a thermometer, and a sub-surface gas sparger. While keeping the temperature between 45.degree.-50.degree.C., isobutylene was passed over 60g of methanol into the reaction flask over an 8-hour period, during which 716g (12.8 moles) of isobutylene was consumed. The reaction mixture was then purged at 40.degree.C. with a stream of nitrogen for 30 minutes and then filtered to yield 1579g of a light amber liquid.

Sodium mercaptide, (1200g) and 1250 ml of ethanol were charged into a 5-L. reaction flask fitted with a stirrer, condenser, (drying tube attached) thermometer and an addition funnel. After stirring to get a good dispersion of the solids, 620g of the above, isobutylene-sulfur monochloride adduct was added rapidly and carefully at first to attain a temperature of 45.degree.C. and then dropwise from the addition funnel. The addition took about 2 hours. By carefully regulating the addition, the temperature was kept at close to 40.degree.C. and excessive foaming (H.sub.2 S evolution) was avoided.

Following the aforementioned addition, the reaction mixture was heated, while stirring at 45.degree.-50.degree.C. for an additional 3 hours. After cooling to room temperature, it was filtered, the solids washed with hexane, with water and ether and a water insoluble white solid product was collected. The filtrate was allowed to stay overnight under house vacuum. The solid product which precipitated from the filtrate was collected and washed several times with water and ether and dried. The combined solids were further purified by stirring vigorously in water and a little ether, collected and dried to yield 250g of white solid product, having a sulfur content of 53 percent. This product was found to have the structure hereinbefore described.

An SAE 90 solvent-refined Mid-Continent oil having a pour point of 25.degree.F. was next subjected to the standard Four-Ball Wear Tests for determining improvement in antiwear properties. This test is described in U.S. Pat. No. 3,423, 316. In general, in this test, three steel balls of 52100 steel are held fixed in a ball cup. The test lubricant is added to the ball cup and acts as a lubricant. A similar fourth ball positioned on a rotatable vertical spindle is brought into contact with the three balls and is rotated against them for a known time. The force with which the fourth ball is pressed against the three stationary balls may be varied to give a desired load. The temperature of the ball cup, stationary balls and lubricant may be brought to a desired temperature and held constant during the test. At the end of the test, the three stationary steel balls are examined for wear-scar diameter. The extent of scarring represents the antiwear effectiveness of the lubricant; the smaller the wear scar at the same load, speed, temperature and time, the more effective the antiwear characteristics of the lubricant. In the data of Table I, are shown the results obtained in which the aforementioned base stock oil was subjected to Four-Ball Wear Tests.

TABLE I ______________________________________ 4-Ball Wear Test-Scar Diameter (mm) 1/2" Balls, 52100 Steel, 60 Kg load, 1/2 hr. Lubricant: SAE 90 Base Oil Ex- Temp. Speed ample .degree.F. 500 RPM 1000 RPM 1500 RPM 2000 RPM ______________________________________ 2 Room 0.50 0.60 0.88 2.34 3 200 0.60 1.06 1.86 2.23 ______________________________________

The above-described product of Example I was next incorporated into the base stock lubricating oil of Table I in a concentration of 0.5 percent, by weight, and then subjected to the aforementioned Four-Ball Wear Tests. The results obtained are shown in the following Table II.

TABLE II ______________________________________ 4-Ball Wear Test-Scar Diameter (mm) 1/2" Balls, 52100 Steel, 60 Kg load, 1/2 hr. Lubricant: SAE 90 Base Oil + 0.5% (Wt.) of Product of Example I Ex- Temp Speed ample .degree.F 500 RPM 1000 RPM 1500 RPM 2000 RPM ______________________________________ 4 Room 0.46 0.50 0.60 0.80 5 200 0.50 0.63 0.75 0.90 ______________________________________

It will be apparent from the comparative data of Tables I and II that the novel sulfur compounds of the present invention are markedly effective as antiwear additives in lubricating oils.

In another series of experimental runs, the high sulfur solid compound of example 1 was blended into a series of grease formulations and extreme pressure properties were measured by a standard Four Ball EP test, ASTM D-2596 "Measurement of Extreme Pressure Properties of Lubricating Greases (Four Ball Method)". The comparative results obtained are shown in the following Table III.

TABLE III __________________________________________________________________________ Grease Characteristics Additive of Consistency Thermal Stability 4-Ball EP Test Base Grease Example I Change With at 300.degree.F. Load Weld Ex. Thickener Fluid Wt. % Color Odor Additive Odor Consistency Index, Load __________________________________________________________________________ kg 6 Baragel Clay Synthetic 0 Cream None -- None No softening 32.9 160 Hydrocarbon 7 Baragel Clay do. 3.5 Cream None Slight None No softening 82.3 500 Thickening 8 Baragel Clay do. 0.8 Cream None -- None No softening 52.5 315 9 Calcium Complex Paraffinic 3.5 Cream None Slight None No softening 141.7 800 Thickening 10 Calcium Complex do. 0.8 Cream None -- None No softening 75.2 500 11 Lithium Hydroxystearate Naphthenic/ 4 Tan None Slight None No softening 48.6 315 Bright Stock Thickening 12 Lithium do. 1 Tan None Slight None No softening 33.7 250 Hydroxystearate Thickening 13 Lithium Complex do. 0 Tan None -- None No softening 24.3 160 14 Lithium Complex do. 3.5 Tan None Slight None No softening 55.1 400 Thickening __________________________________________________________________________

In Table III, the synthetic hydrocarbon fluid of examples 6, 7 and 8 comprised 89 percent of the base grease.

The Baragel clay thickener of examples 6, 7 and 8 comprised 11 percent of the base grease, by weight.

The paraffinic mineral oil fluid of examples 9 and 10 comprised 83 percent of the base grease, by weight.

The calcium complex thickener of examples 9 and 10 comprised 17 percent of the base grease, by weight.

The naphthenic bright stock mineral oil blend of examples 11 and 12 comprised 90 percent of the base grease, by weight.

The lithium hydroxystearate thickener of examples 11 and 12 comprised 10 percent of the base grease, by weight.

The naphthenic bright stock mineral oil fluid of examples 13 and 14 comprised 90 percent of the base grease, by weight.

The lithium complex thickener of examples 13 and 14 comprised 10 percent of the base grease, by weight.

It will be apparent, also, from the comparative data of Table III that the aforementioned novel additives of the present invention, are markedly effective extreme pressure agents in grease formulations, as evidenced by imparting increased Load Wear Index and Weld Load Values.

As previously indicated, other extreme-pressure additives may be incorporated in the novel lubricant formulations such as chlorine-containing, phosphorous-containing, calcium-carbonate or calcium acetate containing additives, which may tend to enhance the extreme pressure characteristics of the lubricant formulation. Apart from the excellent extreme pressure properties exhibited in grease formulations, it should also be noted that superior extreme pressure characteristics may also be imparted in the use of the aforementioned sulfur material as a dispersion or emulsion in fluids, oils, synthetic hydrocarbon fluid, esters, fatty oils, and water emulsion lubricants. The novel high sulfur solid extreme pressure additive furthermore exhibits superior extreme pressure characteristics when employed as a finely divided powdered, solid lubricant and as part of a dry solid film lubricant. This additive also imparts extreme pressure characteristics when used as a dispersion or base in such media as cutting oils, metal processing and metal-working oils and in related applications such as extrusion compounds.

While this invention has been described with reference to preferred compositions and components therefore, it will be understood by those skilled in the art, that departure from the preferred embodiments can be effectively made and are within the scope of the specification.

Claims

We claim:

1. A lubricant composition containing lubricating amounts of a member selected from the group consisting of mineral oil of lubricating viscosity, synthetic lubricating oils, greases and water emulsion lubricants based on said oils containing, in an amount sufficient to impart antiwear and extreme pressure properties, a compound having the structure: ##SPC3##

2. A composition as defined in claim 1 wherein said composition comprises an oil of lubricating viscosity.

3. A composition as defined in claim 1 wherein said composition comprises an oil of lubricating viscosity within the range of 45 SSU at 100.degree.F. to about 6000 SSU at 100.degree.F.

4. A composition as defined in claim 1 wherein said composition comprises an oil of lubricating viscosity within the range of from about 50 SSU at 210.degree.F. to about 250 SSU at 210.degree.F.

5. A composition as defined in claim 1 wherein said composition comprises a grease.

6. A composition as defined in claim 1 wherein said composition comprises a grease containing, in minor proportion, lithium hydroxystearate as a thickening agent.

7. A composition as defined in claim 1 wherein said composition comprises a grease containing, in minor proportion, a lithium complex as a thickening agent.

8. A composition as defined in claim 1 wherein said composition comprises a grease containing, in minor proportion, a calcium complex as a thickening agent.

9. A composition as defined in claim 1 wherein said composition comprises a grease containing, in minor proportion, a clay-based thickening agent.

10. A composition as defined in claim 1 wherein said compound is present in minor proportion.

11. A composition as defined in claim 1 wherein said compound is present in an amount from about 0.1 to about 50 percent, by weight, of the total weight of said composition.

12. A composition as defined in claim 1 wherein said compound is present in an amount of from about 0.1 to about 10 percent, by weight, of the total weight of said composition.

13. A composition as defined in claim 1 wherein said composition contains a chlorinated paraffin in an amount sufficient to impart additional extreme pressure properties.