US2491055A - Grease compositions - Google Patents

Description

Patented Dec. 13, 1949 UNITED S TATES iAili'E'N T O F Fl CE GREASE COMPOSITIONS Arnold J. Mot-way, Glarlmand .David W. :Young,

iRoselle,JN. 1J., assignors to {Standard OilDevelopment Company, a corporation of Delaware NoDrawingn Application October 25,1947,

Serial No. $82,230

3 Claims. .1

The ;present invention relates ato improved lubricating .grease compositions and particularly :to greases having good adhesive and non-spatter- -ing characteristics and compositions for impart- .ing: such characteristics.

In the past, lubricants 'designed forsautomotive equipment, 1 such as :automobile chassis and. re-

Llated 'mechanisms, have usually "consisted of either lime soap .or aluminum soapzthickened s'greases selected because of their resistance to water. These greases consist essentially f mineralbase lubricating oils ofi-appropriate grade 1 and viscosity thickened with :a :metal :soap of fatty acidsian'd compoundedxwith a minor :pro-

portion of some tackiness agent, such as a mineral oil solution of polybutene or rubber latex, or the like. Greases lacking such tackiness agent spatter badly under vsudden impact of chassis parts, rendering suchgreasesdiificult to retain in lubricating position between-metallic or other frictionally engaged elements. :Greases which spatter away because'ofe-lack ofadhesiveness and 1 cohesiveness :tend -to be lost :rather .rapidly from the surfaces theyarewdesigned to protect, particularly where-.impactmay occur-between such surfaces.

While mineral oilsolution's iof naturaliandsynthetic rubber compositions, :suchas rubber latex randpolybutene, havebeen used with some: success to impart such adhesive characteristics, they have not been entirely successful. Other materials, such as methacrylate polymers of high molecular weight, have also been employed 'for this purpose. 'All these materials have the quality of imparting considerable Stringinessor .adhesiveness to the aluminum, calcium, Lan'd other soap greases, even when used in relatively small proportions. This stringiness oriadhesive property is desirable in certain respects, but it also has the objectionable characteristic of causing the lubricant to smear'and string on, touching any surface, which makes it 'difiicultand objectionable to handle when excessive amounts of the string imparting materials'are employed.

Another disadvantage common to'the'adhesive agents mentioned above, when'used inlubricating greases, is that none of them' is as stableltoshearing stresses as desired. In other words, they tend "to lose their adhesive characteristics under conditions of high shear, 'for example, under the shearing stresses which are set up when such .grease compositions are forcedthrou'gh ordinary mechanical lubricating equipment. The, passage of lubricating greases containing such adhesive of their constituents.

.ortackiness agents, such as rubber latex, methacrylate polymers, and polybutene, through the nozzles of mechanical or even manual grease guns destroys much of the adhesive and cohesive properties with the result that such greases upon extrusion spatterbadly upon shock impact in the bearing and almost resemble the uncompounded .jected in preparation are such as to substantially reduce the effectiveness of the polymeradditives described. above.

It is, therefore-an object of our invention to incorporate in lubricating compositions, par- .ticularly in lubricating greases, tackiness and stringiness additives which are more stable against shear and heat, which may be subjected -.to grease cooking-temperatures without substantialinjury totheir desired-propertiesand which .arehighly effective in small proportions to.im- .prove the lubricating greases.

A furtherobject is to use a material for imparting tackinessand adhesive characteristics- Which is very effective in small concentrations, but which may also be used in somewhat larger concentrations Without imparting stringiness and-adhesive-properties to an undue or undesirable degree. Other and fur- -ther-objects willappear as thisdescription proceeds.

We have discovered that a high molecular weight copolymer of styrene andisobutylene, or equivalent materials, such as described in U. S. Patent 2,274,749, may be employed in combination with a high molecular Weight aliphatic polymer stringiness agent, to accomplish the purposes outlined above. This copolymer .material .is effective to increase the adhesiveness of lubricating greases, particularly lubricating greases of the lime base and aluminum stearate base type which are used as the thickening soaps inthe majority of chassis greases. ..It appears :also

highly .stable to shearing stresses, and greases containing it do not lose in anymaterialdegree their adhesive, non-spattering properties during 3 passage through a grease gun or equivalent dispensing apparatus.

The preferred copolymers, which serve prim-arily as spatter-preventing agents, are aromatic-aliphatic copolymers of a polymerizable mono-olefinic compound having a cyclic nucleus, and a mono-olefin having 3 to 8 carbon atoms, said copolymer containing about 40 to 65% b weight Of combined cyclic constituent, and having an intrinsic viscosity greater than 0.5 preferably 0.6 to about 1.5. Instead of styrene other cyclic constituents may be used such as alphamethyl styrene, para-methyl styrene, para-methoxy styrene, alpha-vinyl naphthalene, indene, etc. Instead of isobutylene, other lower olefins may be used such as methyl 2-butene-1 or other iso-olefins, or even some of the most active normal olefins such as normal butenes, propylene, etc. Such copolymers having the desired high molecular weight, as indicated by having an intrinsic viscosity greater than 0.5, may be made by Friedel-Crafts polymerization at a, temperature below -50 C., preferably in the presence of a lower alkyl halide solvent such as methyl chloride or ethyl chloride, using as catalyst materials such as aluminum chloride, boron fluoride, etc. or some of the known Friedel-Crafts catalyst complexes, and preferably using such Friedel-Crafts catalyst already predissolved in a lower alkyl halide solvent such as methyl chloride.

As stringiness agent, poylisobutylene is preferred because of its good solubility and adhesive characteristics, and for best stringiness purposes this polymer should have an average molecular weight of about 30,000 to 450,000, preferably about 50,000 to about 100,000. Other aliphatic polymers which may be used as stringiness agents to cooperate in this invention, include polylauryl methacrylate or other polymers of monomeric esters and ethers having a polymerizable olefinic linkage, or small amounts of unvulcanized natural rubber or synthetic rubber such as the one made by low temperature Friedel-Crafts copolymerization of isobutylene containing about 1 to 3% of isoprene, or equivalent materials.

The styrene-isobutylene type copolymer, which serves essentially as spatter-preventer, imparts only slight stringiness at ordinary temperatures, although more at temperatures above their thermoplastic softening point. However, due to its high molecular weight linear polymeric structure, it cooperates with and greatly stabilizes the adhesiveness and stringiness imparted by adding a small amount of the stringiness agents described.

If desired, the polybutene, methacrylate polymer,

natural rubber or latex, or other adhesive and stringiness agent may be added in an oil solution.

The amount of the copolymer to be used should generally range from about 0.1% to 5% or even more, preferably from 0.5 to about 2.0% of the copolymer, by weight, based on the total lubricating composition. The amount of stringiness agent required is slightly less, i. e. about .01 to 3 Preferably about .05% to 1% by weight of the total composition.

The copolymer spatter-preventing agents used in this invention are quite heat-stable up to temperatures of about 500 F. or 550 F., which imparts good thermal stability to the over-all composition. They also have good light-stability, even in thin films.

The following tests will serve more :fully to set forth our invention, Test 4 representing the invention, as distinguished from other compositions shown in Tests 1-3.

4 Test 1 A composition was prepared consisting of: 7.5% aluminum stearate, 1.0% of styrene-isobutylene copolymer having an intrinsic viscosity of 0.8 and 60% combined styrene, and 91.5% of a mineral base lubricating oil of naphthenic type having 70 Vis/210 F. and 950 at F. The aluminum stearate and the copolymer were added to mineral oil and heated to a temperature of about 300 F. The copolymer preferably is used in a powdered, finely divided or granular form for ease of dispersion and it may be dispersed in part of the mineral oil as a concentrate before adding to the grease kettle. After heating has been completed, the molten grease is cooled in a conventional manner and upon cooling it forms a slightly stringy gel having excellent adhesive properties.

Test 2 A composition consisting of 7.5% by weight of aluminum stearate, 0.5% of a 10% solution of polybutene of 60,000 mol. wt. in mineral oil as a tackiness agent and 92% of the same mineral oil as used in Test 1, was prepared in the same manner except that the polybutene solution, as a tackiness agent, was added just prior to drawing the grease composition from the kettle for cooling. The resulting product was a grease of good appearance, having apparently excellent stringiness and adhesive properties. As indicated in the table below, however, upon dispensing of the grease through a mechanically operated grease gun, the good stringiness was substantially destroyed, and the grease spattered in the spatter test.

Test 3 Another composition employing 7.5% by weight of aluminum stearate, 0.5% of a rubber latex concentrate of 5% by weight in mineral oil, and 92% of the same mineral lubricating oil as referred to above, was prepared in the same manner as the grease in Test 1. The resulting product appeared to be a good stringy grease of satisfactory adhesive properties. However, on standing in thin layers in sunlight it was found that the grease soon lost all the added adhesiveness imparted by the rubber latex and also lost its adhesiveness and non-spatter properties after passage through a. grease gun.

Test 4 Now, a composition illustrating this invention, consisting of 7.5% by weight of aluminum stearate, 0.3% of the same polybutene concentrate in mineral oil as used in Test 2 above, 1.0% of the same styrene-isobutylene copolymer as used in Test 1, and 91.2% of the same mineral lubricating oil as described above was prepared in the same manner as the grease of Test 1. The resulting product was found to have excellent stringiness and adhesiveness, and good spatter resistance, even after passage through the grease gun.

stringiness, adhesiveness, and tendency to spatter were measured as follows. stringiness was measured by applying the tip of the finger to a portion of the grease and drawing the adhesive portion upward and away from the grease, noting the length to which such grease could be drawn before breaking. Spatter was measured by a hammer test. The hammer consisted of a 5 pound hammer head guided for a vertical fall grease compositions to be tested were applied in small quantities. The hammer was dropped upon the anvil and the distance to which the grease was thrown or spread was noted. In the table where no spatter is shown, the grease spread not more than two inches away from the hammer head upon impact of the hammer against the anvil. Where spatter is shown, the grease fiew feet or more in all directions. The grease gun employed in the tests was a standard Balcrank gun, air operated, with a Zerk needle fitting and a hose outlet. The results of the tests are shown in Table l.

Although the foregoing data apply particularly to aluminum soap greases, the invention applies also to greases of other soap bases, such as soda, lime, lithium, or mixed base greases. For instance, results similar to those shown in Table 1 in regard to an aluminum soap base grease, were also obtained with a lime soap base grease made with the following lime grease basestock:

Per cent Lime soap of animal fat 10.5

Water '1.0 Naphthenic type mineral oil distillate of 70 Vie/210 F 88.5

As indicated above, an additional feature which may be of advantage in the use of the styrene-isobutylene copolymer of the type described lies in the fact that relatively large amounts of this copolymer may be added to the grease without detrimental effects, whereas polymers of the stringiness agent type, when employed in excessive quantities, tend to make the greases extremely hard to dispense and handle, due to excessive stringiness. In addition, when used in excess quantities, additives of the prior art tend to cause too great cohesiveness, causing the greases to peel away from the surfaces lubricated, leaving them unprotected, whereas the high intrinsic viscosity copolymers are no more adhesive than cohesive.

We claim:

1. A lubricating grease composition consisting essentially of a major proportion of lubricating oil, about 3 to 30% by weight of a metal soap of a fatty acid, about 0.1 to 5.0% by weight, based on the total composition, of a high molecular weight copolymer of about 40 to 65% by weight of a poiymerizable mono-olefinio compound having a cyclic nucleus, and about to 35% of an aliphatic olefin of 3 to 8 carbon atoms, said copolymer having an intrinsic viscosity greater than 0.5, said grease also containing about .01% to 3% by weight of an aliphatic linear polymer stringiness agent havin an average molecular weight of at least 30,000.

2. A lubricating grease composition consisting essentially of about 75 to 95% by weight of a mineral oil, about 5-25% of an aluminum soap of a higher fatty acid of about 10 to 30 carbon atoms, 0.1 to 5.0% by weight, based on the total composition, of a high molecular weight copolymer of about 40 to by weight of styrene and 60 to 35% of isobutylene having an intrinsic viscosity greater than 0.5, and .01% to 3% of polyisobutylene having an average molecular weight of at lease 30,000.

3. A grease composition consisting essentially of to by weight of mineral lubricating oil, 5 to 25% of aluminum stearate soap, 0.5 to 2.0% of a high molecular weight copolymer of about 50 to 60% by weight of styrene and 50 to 40% of isobutylene, having an intrinsic viscosity of about 0.6 to 1.5, and about .1-1.0% by weight of polyisobutylene having an average molecular weight of about 50,000 to 100,000.

ARNOLD J. MORWAY. DAVID W. YOUNG.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,084,500 Otto et al June 22, 1937 2,189,873 Zimmer et al Feb. 13, 1940 2,215,423 Wiezevich Sept. 3, 1940 2,274,749 Smyers Mar. 3, 1942 2,282,456 Christmann et al. May 12, 1942 2,335,608 Pings Nov. 30, 1943 2,421,082 Pier et a1 May 27, 1947