US2847380A

US2847380A - Lubricating composition containing surface-esterified siliceous solid and organophilic clay

Info

Publication number: US2847380A
Application number: US482383A
Authority: US
Inventors: Jacques L Zakin
Original assignee: Socony Mobil Oil Co Inc
Current assignee: ExxonMobil Oil Corp
Priority date: 1955-01-17
Filing date: 1955-01-17
Publication date: 1958-08-12
Anticipated expiration: 1975-08-12

Description

United States Patent LUBRICA'IING COMPOSITION CONTAINING SUR- FACE-ESTERIFIED SILICEOUS SOLID AND OR- GANOPHILIC CLAY Jacques L. Zakin, Flushing, N. Y., assignor to Socony Mobil Oil Company, Inc., a corporation of New York Application January 17, 1955 Serial No. 482,383

No Drawing.

9 Claims.

inorganic gelling agents.

Lubricating greases may be considered as thickened oils. Various materials have been employed in the past to effect the desired thickening. Thus, it has been common practice to employ metal soaps of fatty acids, such as metal stearates or metal oleates, as thickening or gelling agents. In recent years, a variety of inorganic grease thickening agents have been used, particularly where it has been desired to obtain a grease characterized by structural sta bility at elevated temperatures. This property makes such greases of particular interest in the lubrication of ball bearings and other machinery parts as well as in turbo jet engines and insteel rolling mills. Such non-soap greases, however, have not possessed rust-preventive properties equal to the earlier soap-type greases. The usual rust inhibitors generally recommended for use in industry have afforded little or no improvement in rust-preventive properties of the non-soap grease. Accordingly, despite the excellent high temperature characteristics of these greases,

. they have had the disadvantage of being unable to provide satisfactory protection against rust. Such disadvantage has, in many instances, severely limited the application of non-soap greases. Various suggestions and attempts have been made to overcome this deficiency, such as the addition of water repelling agents, extreme pressure agents, or anti-corrosion agents. None of the foregoing, however, have provided a non-soap grease affordingsatisfactory protection against rust.

The principal object of the present invention, accordingly, is to provide a non-soap grease having improved rust-preventive properties.

The above and other objects which will be apparent to those skilled in the art are achieved by the grease composition described herein. It has been found, in accordance with the present invention, that a non-soap grease having unexpected rust preventive properties may be prepared by providing a composition containing a substantial amount of'two inorganic grease thickening agents. Thus, the grease composition of this invention comprises an oleaginous liquid thickened with the combination of an organophilic clay and an organophilic esterified product comprising amorphous silica of specified surface area coated with alkoxy groups containing from 2 to 18 carbon atoms.

Each of the above thickening agents essential to the present composition have heretofore been separately employed in grease formulation. However, in so far as is known, grease containing these agents in combination have not been previously produced. It has been discoveredlthat combination of the above inorganic thickeners in grease manufacture imparts to the resultant product rust preventive properties far superior to rust-preventive prop erties of greases made with either of the same thickening Tee agents separately. It would appear that the combination of thickening agents employed in the present grease results in an unpredictable synergistic action. Such unexpected action has, in accordance with the instant invention, been found to afford a non-soap grease having unusual rustpreventive properties.

organophilic clay, employed herein as one of the thickening agents of the aforesaid combination, has, as indicated above, heretofore been employedseparately in the production of non-soap greases. The clays used comprise those which have been treated with organic cationic surface active agents, such as onium compounds, so as to destroy their inherent hydrophilic nature and to impart organophilic characteristics thereto. The preparation of these clays has been described in detail in the literature, for example, in U. S. Patent 2,531,427 to Hauser. In accordance with the general method of preparation, clays are dispersed in a swelling medium, such as water, and treated with an onium compound which causes the formation of a hydrogel wherein either absorption or ion exchange reaction has occurred so that a-closely bonded composition of the clay and oniurn radical has resulted. Clays which are useful for the above purpose includeespecially montmorillonite clays, such as Wyoming bentonite or hectorite, although other cation-exchangeable clays such as attapulgite, vermiculite, saponite, biotite, sepiolite, and the like may also be used to advantage.

Typical of the greases which have been prepared with an organophilic clay are the so-called Bentone greases. Bentones are the reaction products of montmorillonite or, more accurately, bentonite and various organic cations. Bentonite' is a species of the class of minerals known as the montmorillonites and in its natural state is a highly hydrophilic hydrous aluminum silicate with a micaceous structure and an exceptionally small ultimate particle size. It customarily occurs as the salt of a moderately strong acid in which the cation is predominantly sodium. It has heretofore been known that bentonite may be converted into a hydrophobic and organophilic condition by the introduction of long chain hydrocarbon radicals into the surface of the montmorillonite clay particles. The nature and preparation of organophilic bentonites has been described in detail by J. W. Jordan in the Journal of Physical and Colloid Chemistry, volume 53, No. 2, 1949, pp. 294306. Briefly, the preparation of an organophilic bentonite involves hydration of the montmorillonite in a very dilute dispersion to separate the unit particles and to achieve complete removal of non-clay impurities. This step is resorted to since most montmorillonite in the crude state contains relatively large quantities of quartz which, if allowed to remain, would impart an abrasivecharacter to the resulting product. The reactive sodium atoms of the clay particles are then replaced by organic cations and the product is washed, filtered, and dried. By proper choice of the organic cation, the properties of the resulting modified montmorillonite product can be controlled. Generally, for imparting the desired organophilic properties, an organic ammonium compound having a carbon chain of at least 10 carbon atoms is employed. Increasing the chain length of the ammonium compound gives a product of increasing organophilic properties. The ammonium compounds are usually converted to the form of salts before use. Thus, organophilic bentonites have been prepared by the reaction of bentonite withvarious aliphatic ammonium salts, including the salts of long chain amines and quaternary ammonium compounds having one or more aliphatic chains. The resulting products are generally referred to as alkyl ammonium bentonites and are more commonly known to the trade as Bentones. The figure following the trade name Bentone indicates the number of carbon atoms in the hydrocarbon radical or 2,847,380 Patented Aug. 12,1958 s,

radicals attached to the silicate structure of the bentonite. For example, Bentone 34 is a modified montmorillonite produced as above-stated and having as cations the secondary amine radicals formed by reacting hydrated montmorillonite with technical distearyl amine. Thesemodified montmorillonite products have substantially no affinity for water but, because of the long hydrocarbon chainscoating the particles and the platelets of clay, they are subject to ready dispersion in organic liquids.

The other essential thickening agent utilized in the grease composition of this invention is an estersil. Estersils are organophilic solids made by chemically reacting primary or secondary alcohols with certain siliceous solids. For a detailed description of estersils and a method for'preparing the same,'reference is made to U. S. 2,657,149. Briefly, the estersils which have been employed as thickening agents in the manufacture of lubricating greases are powders or pulverized materials having an internal structure or substrate of inorganic siliceous material having an average specific surface area of at least 25 square meters per gram to which- -OR groups are chemically bound, R being the hydrocarbon radical of a primary or secondary alcohol containing 2 'to 18 carbon atoms; that is, a radical in which the carbon attached to the oxygen is also attached to hydrogen.

The substrates of the estersils are solid inorganic siliceous materials containing substantially no chemical- 1y bound organic groups prior to esterification and having silanol groups (-SiOH) on their surfaces. They can be mineral or synthetic in origin and thus can be amorphous silica,- insoluble metal silicates or such silicates coated with amorphous silica. The substrate is in particulate form, the particles being of super-colloidal, that is, larger than colloidal size and hence generally larger than 150 millimicrons in at least one dimension. Such particles may be aggregates of much smaller particles, i. e., ultimate units which are so firmly attached to each other that they are not readily separated by simple stirring in a fluid medium.

In estersils to be used as thickening agents in the present grease composition, substrate particles are preferred in which the ultimate units have an average diameter greater than. millimicrons or in which the ultimate units are below 10 millimicrons and are joined in very open networks to provide a large pore size. Solids having average pore diameters of at least 4 millimicrons are especially preferred. Suitable substrates have a specific surface area of at least square meters per gram and preferably at least 200 square meters per gram. For precipitated amorphous silica, which is a preferred substrate, there is an optimum range of about ZOO-to 400 square meters per gram. Very voluminous siliceous aerogels having surface areas as great as 900 square meters per gram, and preferably from 200 to 900 square meters per gram, afford very suitable substrates because of the great thickening efficiency of estersils produced therefrom.

While various inorganic siliceous solids having properti'es as aforementioned can be used as substrates for making estersils for use in the present grease compositions, precipitated amorphous silica is preferred. This silica consists of coherent aggregates of non-porous ultimate units in which the ultimate units are quite uniform in size and have an average diameter greater than about 10 millimicrons or ultimate units below 10 millimicrons diameter joined in very open networks.

The general method for preparing the estersils involves esterification of the above-described siliceous solid with a primary or secondary monohydric alcohol containing from 2 to 18 carborf atoms. Mixtures of alcohols can also be used as the esterifying agent. Alcohols containing from 3 to 6 carbon atoms are particularly preferred since the estersils made therefrom are more stable toward hydrolysis than those made from 9.1-

cohols of fewer carbon atoms and are more economical to use than those made from alcohols having a greater number of carbon atoms.

The esterified inorganic siliceous solids, i. e., the estersils, are in the form of powders or easily pulverable particles. They are generally exceedingly fine, light, flutfy powders, as indicated by their low bulk densities. In particular, estersils having a bulk density not greater than 0.20 gram per cubic centimeter at 3 pounds per square inch and not greater than 0.30 gram per cubic centimeter at 78 pounds per square inch are preferred. All of the above described estersils are organophilic. In order to make an inorganic siliceous solid organophilic, it is necessary to react a certain minimum proportion of the surface silanol groups with an alcohol containing at least 2 carbon atoms. With most alcohols, the esterified material becomes organophilic when it contains more than about 80 ester groups per square millimicrons of surface of the internal structure or substrate. The products are markedly organophilic when there are chemically attached more than about 100 ester groups per 100 square millimicrons of substrate surface. Preferred organophilic and hydrophobic estersils are obtained by esterifying the inorganic siliceous material to give an estersil containing at least 200 ester groups per- 100 square millimicrons of substrate surface. In the case of the preferred alcohols, which are those containing 3 to 6 carbon atoms, it is generally prefered to provide an estersil having at least about 270 ester groups per 100 square millimicrons of substrate surface by employing more severe reaction conditions, a greater number of alcohol molecules; that is, 300 to 400 may be made to react per 100 square millimicrons of surface area of the siliceous substrate.

The oil component used incompounding present greases may be broadly described as an oleaginous lubricant base, which would include the conventional mineral oils, hydrogenated fish oils, animal oils, vegetable oils, fluorocarbon oils such as the perfluorinated petroleum oils, the synthetic lubricating oils prepared by cracking and polymerizing products of the Fischer-Tropsch process, and the like, or a synthetic oleaginous compound within the lubricating oil viscosity range.

Typical of the latter type compounds are the liquid polyorganosiloxanes, also known as silicones. These compounds are polymers composed of alternate silicon and oxygen atoms wherein the silicon atoms may be variously substituted with alkyl, aryl, alkaryl, aralkyl, and cycloalkyl radicals. The above siloxanes may be prepared by any appropriate method. It is contemplated that any of the various types of silicone polymers may be employed for purposes of the present invention. Representative compounds are the dimethyl silicone polymers, the diethyl silicone polymers, the ethyl-phenyl silicone polymers, and the methyl-phenyl silicone polymers.

Other synthetic oleaginous compounds which may be substituted in whole or part for the conventional mineral lubricating oils in present greases include synthetic organic lubricating compounds. The choice of the particular compounds used in the preparation of present greases will depend in part upon the type of lubrication and the temperature range within which the grease is intended to be employed. Greases prepared from these compounds are generally particularly adapted to specialized lubrication outside the conventional lubricating temperature ranges, such as excessively low temperature operation found in refrigeration systems or to general purpose lubrication over a wide lubricating temperature range. The types of compounds which are recognized or have been proposed as synthetic organic lubricants include the aliphatic ethers, aromatic acid esters, aliphatic monoand dicarboxylic acid esters, phosphorous acid esters, and halogenated aromatic compounds. For the purposes of the present invention and as illustrative square millimicrons of surface and characterized of the synthetic oleaginous compounds utilized herein, those compounds falling within the category of aliphatic dicarboxylic acid esters are typical. The compounds within this particular class are the esters of such acids as sebacic, adipic, pimelic, azelaic, etc. The esters thereof are preferably the aliphatic esters and particularly the branch chain aliphatic esters. Specific representative oleaginous compounds include di-iso-octyl adipate, di-2- ethyl hexyl amyl sebacate, di-sec-amyl sebacate, etc. These oleaginous compounds, as well as the abovedescribed polyorganosiloxanes, may be used as the sole oil component of the greases or they may be blended with a mineral lubricating oil as desired. If desired, various addition agents may be incorporated with the oleaginous compounds to impart desired characteristics. Thus, an extreme pressure agent may be incorporated to improve the anti-wear characteristics of the compound, or an antioxidant may be incorporated to improve the anti-oxidant properties of the finished grease.

'The greases of the invention may be prepared by a mixing or blending of the combination of thickening agents and oleaginous liquid. The mixing can be carried out in milling and mixing devices of the kind used heretofore for producing non-soap greases wherein a single thickening agent was employed. Ball mills, colloid mills, homogenizers, and similar devices can be used in preparing the present greases to give the desired thorough dispersion of the combination of thickening agents in the homogeneous liquid. The type of milling or mixing device used depends in part upon the physical and chemical characteristics desired in the finished grease product. Thus, a ball mill generally aifords good results While a high pressure homogenizer which produces high shearing forces affords maximum dispersion and thickening efficiency.

The amount of the above two thickening agents employed in formulation of the present grease is usually such as to thicken the base oleaginous liquid to a consistency Within the range conventionally ascribed to greases. As little as 0.5 percent by weight of the combined organophilic clay and estersil may be employed to give a semi-fluid grease. Generally, however, greater amounts of the thickening agents will be used, ordinarily from about 2 to about 30 percent by weight and more particularly from about 5 to about weight percent. It is important that the weight ratio of organophilic clay to estersil in the combination thickening agent employed be between about 3:1 to about 1:3. It is particularly preferred that the aforementioned weight ratio be between about 1:1 and about 1:3.

The following formulae and test results embody comparative data establishing the exceptional rust-preventive properties of the grease of this invention:

Example 1 2 3 Estersil GT is an estersil marketed bv E. I. du Pont de Nemours and Company consisting essentially of an amorphous silica coated with approximately 340 butoxy groups 213111103 mate particle size of 8-10 millimicrons, a surfac area of 275-325 m."/g. and a bulk density of 19-20 lb./ft..

0f the above examples, Example 2 represents a grease made. with an estersil as the only thickening agent. Example 3 represents a grease composition in which the only thickening agent is an organophilic clay.

Example 1 embodies the grease of the invention containing a combination of an estersil and an organophilic clay as thickening agents. It is to be noted that the total amount of thickening agents employed in this example does not exceed the amount of either of the single thickening agents in Examples 1 and 2.

Pentaerythritol was included in Examples 1 and3 as I a high temperature stability agent. Such material, however, is not an essential component of the present grease composition but the inclusion thereof may be' found de--' rials familiar to those in the art, as well as water, may

also be used for such purpose and when so employed will be present in only very minute amounts of less than 1 percent by weight. V

The above illustrative greases were made by charging to percent of the mineral oil to a kettle, adding the organophilic clay thickener and pentaerythritol solution,

and heating to 240-250 F. while passing one time through a high pressure homogenizer at 3000 5000 pounds per square inch gauge. Thereafter, the remaining oil, estersil thickener, and water, if necessary as a dispersing aid, were added. The resulting mixture was then heated to 280-300" F. while passing 2 to 5 times through a high pressure homogenizer at 3000-5000 pounds per square inch gauge. In those instances (Examples 2 and 3) where only a single thickening agent was employed, all of such agent was added initially with 60 to 70 percent of the mineral oil.

It is-evident from the above illustrative data that the rust-preventive properties of the grease of this invention are unexpectedly high.

The method of determining rust-preventive properties is a modification of that described in paragraph No. 4.4.2.5 of Specification MIL-G-l0924. This method involves coating test panels oflow carbon steel with 0.004 of the grease to be tested and exposing the grease-coated panel to a salt spray for a minimum of 100 hours. The face of the panel is then examined for evidence of corrosion or rusting. The panels are approximately 3 inches long and one inch wide with slightly rounded edges. Panel thickness may be from A: tol inch with the latter preferred to allow regrinding of used panels. The panels are supported at an angle of 15 degrees from the vertical and parallel to the principal direction of horizontal flow of a salt spray through an exposure chamber. The salt solution employed is of the following composition:

The temperature in the exposure zone is maintained at approximately F. The conditions maintained in all parts of the exposure zone are such that a suitable receptacle placed at any point in the exposure zone will collect from 0.5 to 3 milliliters of the aforementioned salt solution per hour for each 80 square centimeters of horizontal collecting area based on an average run of at least 16 hours. The test panels are exposed to the atomized salt solution for a minimum of hours or until failure. Specimens are examined daily for evidence of corrosion or rusting and the condition of the grease film. Rust anywhere on the 0.004 inch coated surface except within M inch to /2 inch of the edges indicates failure. The test results are reported as the time of exposure in days before the test panel shows evidence of rusting.

In addition to the essential ingredients of an oleaginous liquid and the combination of organophilic clay and estersil thickening agents, the greases of this invention may contain additional ingredients, for example, antiwear agents, such as oil-soluble ureayor thiourea derivatives, e. g., urethanes, carbazides, carbazones, etc.; or rubber, polyisobutylene, polyvinyl esters, etc.; V. 1. improvers such as polyisobutylenes having a molecular weight above about 800, volatilized paraffin wax, unsaturated polymerized esters of fatty acids and monohydric alcohols, etc.; oiliness agents such as stearic and v oleic acids and pour point depressors such as an alkylated naphthalene.

The greases described herein, if desired, may be stabilized against oxidation by the addition of a minor amount of an oxidation inhibitor. Suitable anti-oxidants efiective with grease compositions of the present invention are: N-alkyl paraphenylenediamine and condensed polynuclear aromatic monoamines. Such inhibitors are N- butyl paraphenylenediamine, N-N-dibutyl paraphenylenediamine, etc. Also effective as oxidation inhibitors are alpha or betanaphthylamine, phenyl-alpha or betanaphthylamine, alpha-alpha, beta-beta, or alpha-betadinaphthylarnine, diphenylamine, tetramethyldiamino, diphenylmethane, petroleum alkyl phenols, and 2,4ditertiary butyl-6.methyl phenol.

The grease compositions of this invention may also contain extreme pressure agents. Such suitable agents comprise esters of phosphorous'acids such as triaryl, alkylhydroxy, aryl, or aralkyl phosphates, thiophosphates or phosphites, etc.; neutral aromatic sulfur compounds such as diaryl sulfides and polysulfides, e. g., diphenyl sulfide, dicresyl sulfide, dibenzyl sulfide, methyl butyl diphenyl sulfide, etc.; diphenyl selenide and diselenide; sulfurized fatty oils or esters of fatty acids and monohydric alcohols, e. g., sperm oil, jojoba oil, etc., in which the sulfur is tightly bound; sulfurized long-chain olefins obtained by dehydrogenating or cracking of wax; sulfurized phosphorized fatty oils, acids, esters and ketones, phosphorous acid esters having sulfurized organic radicals, such as esters of phosphoric or phosphorous acids with hydroxy fatty acids, chlorinated hydrocarbons such as chlorinated paraffins, aromatic hydrocarbons, terpenes, mineral lubricating oil, etc., or chlorinated esters of fatty acids containing the chlorine in position other than alpha position.

It is to be understood that the above description is merely illustrative of preferred embodiments of the invention, of which many variations may be made within the scope of the following claims by those skilled in the art without departing from the spirit thereof.

I claim:

1. A grease composition consisting essentially of an oleaginous lubricant liquid and a sufiicient amount to thicken said liquid to a grease consistency of a thickening agent consisting essentially of a mixture of an organophilic bentonite in which the exchangeable inorganic cation has been replaced by an organic ammonium base having a carbon chain of at least l carbon atoms and an organophilic estersil comprising a supercolloidal substrate coated with -OR groups, the substrate having a surface of silica and having a specific surface area of from 25 to 900 square meters per gram, the coating of --OR groups being chemically bound to said silica, R being a hydrocarbon radical of from 2 to l8 carbon atoms, wherein the carbon atom attached to oxygen is also attached to hydrogen in which the weight ratio of said bentonite to said estersil is between about 3:1 to about 1:3.

2. A grease composition consisting essentially of an oleaginous lubricant liquid and a sufiicient amount to thicken said liquid to a grease consistency of a thickening agent consisting essentially of a mixture of an organo philic bentonite in which the exchangeable inorganic cation has been replaced by an organic ammonium base having a carbon chain of at last 10 carbon atoms and an organophilic estersil comprising a supercolloidal substrate coated with OR groups, the substrate having a surface of silica and having a specific surface area of from 25 to 900 square meters per gram. the coating of OR groups being chemically bound to said silica, R being a hydrocarbon radical of from 2 to 18 carbon atoms, wherein the carbon atom attached to oxygen is also attached to hydrogen in which the weight ratio of said bentonite to said estersil is between about 1:1 to about 1:3.

major amount of a mineral lubricating oil and a minor" amount, sufiicient to thicken said oil'to a grease consisteucy, of a mixture of an organophilic bentonite in which the inorganic cation has been replaced by an organic ammonium base having a carbon chain of at least 10 carbon atoms and an organophilic estersil comprising a supercolloidal substrate coated with OR groups, the Substrate having a surface of silica and having a surface area of from 25 to 900 square meters per gram. the coating of ,OR groups being chemically bound to said silica, R being a hydrocarbon radical of from 2 to 18 carbon atoms, wherein the carbon atom attached to oxygen is also attached to hydrogen, the weight ratio of the former'to the latter component in said mixture being between about 3 :l and about 1 :3.

5. A lubricating composition comprising a major amount of a mineral lubricating oil and a minor amount sufiicient to thicken said oil to a grease consistency of a mixture of an organophilic bentonite in which the inorganic cation has been replaced by an organic ammonium base having a carbon chain of at least 10 carbon atoms and an organophilic estersil comprising a supercolloidal substrate coated with OR groups, the substrate having a surface of silica and having a surface area of from 25 to 900 square meters per gram, the coating of OR groups being chemically bound to said silica, R

being a hydrocarbon radical of from 2 to 18 carbon atoms, wherein the carbon atom attached to oxygen is also attached to hydrogen, the weight ratio of the former to the latter component in said mixture being between about 1:1 and about 1:3.

6. A grease composition comprising an oleaginous lubricant liquid and a sufficient amount to thicken said liquid to a grease consistency of a thickening agent consisting essentially of a mixture of an organophilic bentonite in which the exchangeable inorganic cation has been replaced by an organic ammonium base having a carbon chain of at least 10 carbon atoms and an organophilic estersil comprising a supercolloidal substrate of amorphous silica coated with alkoxy groups, the substrate having an average pore diameter of at least 4 millimicrons and a specific surface area of from 200 to 900 square meters per gram and the alkyl radical of the alkoxy group in the coating being a hydrocarbon radical of from 2 to 18 carbon atoms, wherein the carbon attached to oxygen is also attached to hydrogen, the weight ratio of said organophilic bentonite to said organphilic estersil being between 3:l and 1:3.

7. A grease composition comprising a mineral lubricating oil thickened with from about 5 to about 20 weight per cent of a gelling agent consisting essentially of: (1) an organophilic bentonite having the exchangeable inorganic cation thereof replaced by an organic ammonium base having a carbon chain of at least 10 carbon atoms, and (2) an organophilic estersil comprising a supercolloidal substrate coated with alkoxy groups, the substrate having a surface of silica and having a specific surface area of from 25 to 900 square meters per gram, there being in the alkoxy group coating chemically bound to said silica, at least alkoxy groups per 100 square millimicrons of substrate surface area, the alkyl radical of the alkoxy group being a hydrocarbon of from 2 to 18 carbon atoms, wherein the carbon attached to oxygen is also attached to hydrogen, the weight ratio of said organophilic bentonite to said organophilic estersil in said mixture being between about 1:1 and about 1:3.

8. A grease composition comprising an oleaginous lubricant liquid and a grease-forming amount of a mixture of an organophilic bentonite in which the exchangeable inorganic cation has been replaced by an organic asa'nsee ammonium base having a carbon chain of at least 10 carbon atoms and an organophilie estersil comprising a supcrcolloidal siliceous substrate coated with -OR groups, the substrate having a surface of silica and having a specific surface area of from 25 to 900 square meters per gram, the coating of --OR groups being chemically bound to said silica and R being a hydrocarbon radical of from 3 to 6 carbon atoms, wherein the carbon atom attached to oxygen is also attached to hydrogen, the weight ratio of said organophilic bentonite to said organophilic estersil being between about 1:1 and about 1:3.

9. A grease composition comprising a mineral lubricating oil and from about 2 to about 30 percent by weight of a mixture consisting essentially of an organophilic bentonite in which the exchangeable inorganic cation has been replaced by an organic ammonium base having a carbon chain of at least 10 carbon atoms and an organophilic est'ersil comprising a supercolloidal substrata of amorphous silica coated with --OR groups, the substrate having a specific surface area of from 25 to 900 square meters per gram, the coating of -OR groups being chemically bound to said silica and R being a hydrocarbon radical of from 2 to 18 carbon atoms, wherein the carbon atom attached to oxygen is also attached to hydrogemthe weight ratio of said organophilic bentonite to said organophilic estersil in said mixture being between about 3:1 and 1:3.

References Cited in the file of this patent UNITED STATES PATENTS

Claims

1. A GREASE COMPOSITION CONSISTING ESSENTIALLY OF AN OLEAGINOUS LUBRICANT LIQUID AND A SUFFICIENT AMOUNT TO THICKEN SAID LIQUID TO A GREASE CONSISTENCY OF A THICKENING AGENT CONSISTING ESSENTIALLY OF A MIXTURE OF AN ORGANOPHILIC BENTONITE IN WHICH THE EXCHANGEABLE INORGANIC CATION HAS BEEN REPLACED BY AN ORGANIC AMMONIUM BASE HAVING A CARBON CHAIN OF AT LEAST 10 CARBON ATOMS AND AN ORGANOPHILIC ESTERSIL COMPRISING A SUPERCOLLOIDAL SUBSTATE COATED WITH -OR GROUPS, THE SUBSTRATE HAVING A SURFACE OF SILICA AND HAVING A SPECIFIC SURFACE AREA OF FROM 25 TO 900 SQUARE METERS PER GRAM, THE COATING OF -OR GROUPS BEING CHEMICALLY BOUND TO SAID SILICA, R BEING A HYDROCARBON RADICAL OF FROM 2 TO 18 CARBON ATOMS, WHEREIN THE CARBON ATOM ATTACHED TO OXYGEN IS ALSO ATTACHED TO HYDROGEN IN WHICH THE WEIGHT RATIO OF SAID BENTONITE TO SAID ESTERSIL IS BETWEEN ABOUT 3:1 TO ABOUT 1:3.