US 3313727 A
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United States Patent 3,313,727 ALKALI METAL BORATE E.P. LUBRICANTS Robert L. Peeler, Albany, Califi, assignor to Chevron Research Company. a corporation of Delaware No Drawing. Filed Feb. 9, 1965, Ser. No. 431,433 17 Claims. (Cl. 252-18) This invention concerns novel compositions of amorphous alkali metal borates as a stable dispersion in inert lubricating media and methods for their preparation. More particularly, this invention concerns stable dispersions of alkali metal borates of stringently limited water content in inert lubricating media, methods for their preparation and their use as additives in media of lubricating viscosity.
Numerous additives are incorporated in oils and greases to enchance their lubricating properties. A Wide variety of materials have been employed to reduce friction and increase the load carrying capacity of lubricants employed under boundary or extreme pressure (E.P.) conditions. When moving surfaces are separated by oil, as the load is increased and the clearance is reduced between the surfaces, the condition of boundary, or thin film, lubrication is reached. Metal-to-metal contact occurs, and wear or seizure results. Under these conditions, the effectiveness of lubricants in reducing wear or friction varies widely. At still higher loads, the condition commonly known as extreme-pressure (E.P.) lubrication is reached. Scufling, galling, and rapid wear on seizure may occur. The term extreme-pressure is a misnomer since the damage results from the high temperatures reached. Welding of asperities of two contacting surfaces occurs followed by metal transfer (galling) or cleavage and production of wear fragments.
In order to avoid the undersirable effects which result when using an uncompounded oil under high load conditions, E.P. agents are added. For the most part, the BF. agents have been oil soluble or easily dispersed as a stable dispersion in the oil. Most of the BF. agents which provide the high load capacity are chemically reactive, containing chlorine, sulfur or phosphorous which react with the metal surface at the high temperatures produced under the high load.
Recently, US. Patent No. 2,987,476 reported stable dispersions of boric acid or metal borates in oils of lubricating viscosity were useful as extreme-pressure agents in lubricating oils and greases. The dispersions were achieved by hydrolizing borate esters in the presence of an alcohol and a surfactant and then distilling ofi? any water and the alcohol by means of an azeotroping agent. Relatively low concentrations of the boric acid and borates in the non-polar media were reported.
Pursuant to this invention, stable dispersions of alkali metal borates are provided which are useful as extremepressure additives, as Well as for enhancing other properties of lubricating media. These novel compositions are prepared by dispersing as a water and oil emulsion, an oil solution of a alkali metal borate and then dehydrating the system to obtain amorphous or glassy particles of the alkali metal borate, at the desired hydration, dispersed in the non-polar media.
The novel compositions of this invention comprise a liquid non-polar medium of lubricating viscosity, a minor amount by weight of a hydrated alkali metal borate of the formula M mB O HHZO wherein M is an alkali metal of atomic number in the range of 11 to 19, i.e., sodium and potassium, m is a number of from 1 to 2 (both whole and fractional), and n is a number of from 1 to 4 (both whole and fractional); and an emulsifying agent in an amount suflicient to main- 2 tain the borate glass particles as a stable dispersion in the non-polar medium. The particles are almost entirely less than i in size, and for the most part less than 0.5,u.
The alkali metal borates are the metaborates and tetraborates of sodium and potassium having from 1 to 4 waters of hydration, i.e., sodium metaborate, potassium metaborate, sodium tetraborate, potassium tetraborate or mixtures therof. The preferred compositions are the sodium metaborates and the potassium tetraborates having from 1.5 to 2.5 water of hydration.
The non-polar fluid medium can be any fluid of low dielectric constant, which is inert under the reaction conditions (particularly nonsaponifiable) and of lubricating viscosity. Fluids of lubricating viscosity, generally have viscosities of from 35 to 50,000 Saybolt Universal Seconds (SUS) at F. (V The fluid medium or oil may be derived from either natural or synthetic sources. Included among the natural hydrocarbonaceous oils are paraflin base, naphthenic base and mixed base oils. Synthetic oils include polymers of various olefins, generally of from 2 to 6 carbon atoms, alkylated aromatic hydrocarbons, etc. Nonhydrocarbon oils include polyalkylene oxide, e.g., polyethylene oxide, aromatic ethers, silicones, etc. The preferred media are the hydrocarbonaceous media, both natural and synthetic.
A wide variety of emulsifying agents or dispersants may be used. Particularly useful are those dispersants which find use as detergents in lubricating oils. These dispersants are exhaustively described in US. Patent No. 2,987,476, which disclosure is incorporated herein by reference. However, while no attempt will be made to repeat all that is said in that patent, only the highlights of the discussion will be repeated here.
The above-cited patent describes the materials as lyophilic ionic surface active agents. However, since in this invention, neutral dispersants such as alkenyl succinimides of alkylene amines, disclosed in US. Patents Nos. 3,024,195, 3,018,291 and 3,131,150, and addition polymers of esters and amides, e.g., copolymers of acrylates and vinyl pyrrolidone, may be used, the dispersants will be referred to as lyophilic surface active agents. By lyophilic is intended a term synonymous with hydrophobic which means a compound substantially insoluble in and immiscible with water, and which is readily soluble in organic liquids having electric dipole moments of 0.5 Debye unit or less.
The group of emulsifying agents may be broken down into two major classes, ionic emulsifying agents and neutra-l emulsifying agents. Exemplifying the ionic materials are the metal salts of oil soluble acidic organic compounds, e.g., sulfonates, carboxylates, phenolates and quaternary ammonium salts. Exemplifying the neutral surface active agents are the alkenyl succinimides, aliphatic amine amides of maleic anhydride modified hydrocarbon polymers and addition copolymers of acrylates and amides.
Of particular interest among the lyophilic ionic surface active agents are the carboxylates, phenates and sulfonates of alkaline earth metals, e.g., calcium and barium. The hydrocarbon chain bonded to the acidic group, i.e., carboxyl, phenolic hydroxy or sulfonyl, is generally of at least 8 carbon atoms and more usually of from 10 to 26 carbon atoms. The group attached to the acidic functionality may be aliphatic, alicyclic or aromatic or combinations thereof, e.g., aralkyl and will be defined as hydrocarbyl.
Illustrative of the non-ionic surface active agents are: alkenyl succinimides of alkylene amines, having an alkenyl group of from 30 to 200 carbon atoms and an alkylene amine of from 2 to 10 carbon atoms and from 1 to 6 nitrogen atoms; copolymers of polymethacrylate or polyexcess as to make dehydration difiicult.
acrylate with vinyl pyrrolidone, acrylamide or methac-rylamide; or, amides of maleic anhydride modified polymers of hydrocarbons such as ethylene, octene, dodecene, octadecene, etc.
The effectiveness of the alkali metal borate compositions of this invention varies with the particular dispersant. Greatly superior results are obtained with oilsoluble polyvalent metal sulfonates, particularly alkaline earth metal sulfonates, e.g., calcium and barium, wherein the hydroca-r byl group bonded to the sulfur is of from 8 to 26 carbon atoms, more usually of from 10 to 22 carbon atoms. The radical bonded to the sulfur may be alicyclic as in naphthenic sulfonic acid, al karyl as in octylphenyl sulfonate, or alkyl as in cetyl sulfonate. The metals may be calcium, magnesium, barium, etc.
The novel compositions of this invention will generally have from about 2 to 25 weight percent (including waters of hydration) of the alkali metal borate, more usually from about to 15 weight percent. The emulsifying agent or surface active agent will generally be present in from about 0.25 to 5 weight percent, more usually from about 0.5 to 3 weight percent. Generally, the upper ranges of the emulsifier will be used with the upper ranges of the alkali metal borate.
By reducing the amount of oil, concentrates can be obtained having as high as 60 weight percent of the hydrated alkali metal borate. The concentrates may then be diluted prior to use.
Other materials may also be present in the compositions of this invention; materials may be added for enhancing the emulsifying effect of the emulsifier, enhancing some of the properties which are imparted to the lubricating medium by the alkali metal borates or providing other desirable properties to the lubricating medium. These include such additives as rust inhibitors, antioxidants, oiliness agents, detergents, foam inhibitors, viscosity index improvers, pour point depressants, etc. Usually, these will be in the range of from about 0.1 to 5 weight percent, more usually in the range of about 0.1 to 2 weight percent of the total composition.
As already indicated, the novel compositions of this invention are prepared by dehydrating a water and oil emulsion of an aqueous solution of an alkali metal borate, providing the desired dispersion of the hydrated alkali metal borate in the oil medium. The method is carried out 'by introducing into the inert non-polar medium the alkali metal borate, water and the desired emulsifier, vigorously agitating to provide a dispersion ofthe water in the oil and then heating the mixture at a temperature and for a time which provides the desired degree of hydration of the alkali metal borate. Conveniently, the borate may be added as an aqueous solution to the oil.
An antifoaming agent may be added with advantage. The amount required will generally be about 0.00005 to 0.005 weight percent of the total composition.
The amount of alkali metal borate added will depend on the weight percent desired and as indicated will generally range from about 2 to 25 weight percent of the oil composition. The water added will be sufiicient to dissolve the alkali metal 'borate, but should not be in such Generally, from about 0.5 to 3 parts of water will be used per part of alkali metal borate, more usually from about 0.5 to 1.5 parts of water.
The amount of the emulsifier required will vary with the particular emulsifier used and the total amount of borate in the medium. Generally, about 0.05-0.5, more usually about 0.1-0.3, parts emulsifier will be used per part of borate salt.
The temperature at which the emulsion is heated will generally be at least 250 F., more usually at least 300 F. Lower temperatures may be used at reduced pressures. However, the process is conveniently carried out at atmospheric pressures and at temperatures above the boiling point of water.
The time will depend on the degree of dehydration, the amount of water present and the temperature. Time is not critical and will be determined for the most part by the variables mentioned.
As already indicated, various other additives may also be present and will generally be in total amount of from 0.1 to 5 weight percent of the total composition. The remainder of the composition will be a fluid or oil of lubricating viscosity.
The following examples are offered by way of illustration and not by way of limitation.
Example I A blend of 83 parts by weight of SAE base oil, 2 parts of neutral calcium petroleum sulfonate (1.67 percent Ca) and 0.001 part dimethylsilicone of 350 cs. (an antifoaming agent) was placed in a one-quart container of a Waring Blender equipped with a heating jacket and heated to 200 F. with stirring. A solution of 15 parts of sodium metaborate octahydrate (Na O'B O -8H O) dissolved in 15 parts of water, also at 200 F., was added gradually with continuous vigorous blending, and the resulting emulsion was partially dehydrated by heating to 300 F. in 25 mins. with continuous vigorous stirring. A stable fluid suspension was obtained containing 9.56 weight percent of a glass of composition: Na O-B O -LS4H O. Viscosity V =1144 SUS; V =94.6 SUS; viscosity index=95. Base oil viscosity V =1061 SUS; V -=88.1 SUS; viscosity index=89.
Numerous other samples were prepared using varying dehydrating temperatures to vary the amount of hydration and composition of the borates. The method for the preparation of the glasses was as described in Example I. The following table describes the various compositions, the temperature of dehydration, the degree of hydration of the product, the stability of the resulting composition, and the results of the Mean Hertz Screen Test. The Mean Hertz Load Test comprises placing three steel balls together horizontally, with a fourth ball on top resting on these three. The four balls are lubricated by the test composition, and a vertical pressure is applied for 10 seconds to the rotating top ball and the wear scars measured on the stationary balls as a function of load. Calculation of Mean Hertz Load from these data is described in Method 6503 of Federal Test Method Standard No. 791a, dated Dec. 30, 1961. The Mean Hertz Screen is a correlation with Mean Hertz Load which depends on measuring the load which gives a 1 mm. wear scar during a 10 second run. Results are reported as the equivalent Mean Hertz Load value. The following table indicates the resu ts:
1 Percent solids added to dispersion before dehydration.
It is evident from the above table that the compositions of this invention provide stable dispersions at high temperatures for long periods of time (good storage capability) and provide excellent extreme pressure properties (high load carrying capacity) to lubricating compositions.
The sodium metaborate octahydrate at 15 weight percent in SAE 90 oil was dispersed with a variety of emulsifiers using 2 weight percent emulsifier, then dehydrated at a temperature of 300 F. to approximately 1.8 waters of hydration. Using the Mean Hertz Screen Test to analyze for extreme pressure properties, the following results were obtained with a variety of emulsifiers:
TABLE II Emulsifier: Mean Hertz Screen Neutral calcium sulfonate 90+ Overbased calcium sulfonate 85 Lactone amide 33 Tetralkylene amine succinirnide 35 N,N-dialkylalkyleneamine succinimide 44 Copolymer methacrylate-vinyl pyrrolidone 28 Maleic anhydn'de modified hydrocarbon polymer of C1040 olefins 36 As already indicated, the sulfonates are far superior as emulsifiers providing values of 80 or better at 15 Weight percent solids in the Mean Hertz Screen Test.
The compositions of this invention can be prepared in a simple manner with a variety of emulsifiers to form a lubricating composition having extreme pressure properties. The compositions are stable for long periods of time and do not separate on standing, properties essential to an acceptable lubricant. The lubricants are fluid, and flow readily to bearings and other critical lubrication areas. The extremely high load carrying capacity in both bench tests and automotive axles combined with excellent antiwear properties is not available in conventional corrosive types of hypoid lubricants. The following results demonstrate further the excellence of the compositions of this invention as extreme pressure agents.
TABLE III It is one of the most severe test for evaluating performance under tion and deceleration. methods currently used shock conditions.
The present invention provides a simple easily carried out process for preparing compositions which provide excellent extreme pressure and anti-wear properties to various fluids of lubricating viscosity. While it is not intended to provide a theory explaining how the borates work, the appearance of the surfaces would seem to indicate that the alkali metal bor-ates are not acting as corrosive extreme pressure agents which react with the metal surface to form a protective coating, but rather in some different manner. This invention therefore provides a convenient procedure for introducing a stable non-corrosive agent which provides the unique combination of extremely high load carrying (extreme pressure or anti-seize) ability with excellent wear preventive properties. Chemically reactive additives generally provide one or the other of these properties, but not both. Because of their non-corrosive nature, excellent rust protection is also obtained with the borate dispersions.
As will be evident to those skilled in the art, various modifications on this process can be made or followed, in the light of the foregoing disclosure and discussion, without departing from the spirit or scope of the disclosure or from the scope of the following claims.
1. A lubricating composition having improved extreme pressure properties comprising an oil of lubricating viscosity and, dispersed in said oil by means of a lyophilic surface active agent, in an amount of from 2 to 60 weight Additive Reference MIL-L-2l05B 10-90 13. 4% 9. 56% K-2B203-L86II20 Niko-1320343413110 BENCH TESTS SAE E? at 1,000 r.p.m., lb Tirnken EP, lb Mean Hertz Screen SAE Wear, mg, 4 hours 1 Run in truck axle on dynamometer.
2 Run in actual vehicles.
It is evident from the above table that wear is dramatically reduced and significantly higher pressures are required before failure of the lubricant is observed.
The Timken test is described in Lubricants and Lubrication by Clower, published by McGraw-Hill Book Company, 1939, pages l-8, inclusive. In this test, a hardened steel ring is rotated against a steel test block while the lubricant is fed to the point of contact of the two test members. The speed of the machine was at a mandrel speed of 500 r.p.m. The pounds recorded in Table III are the pounds load at which seizure took place, that is, the load at which the lubricant failed. Several of these test methods are described in Federal Test Method Standard No. 791a, dated December 31, 1961:
Method SAE E.P. 6501.1 L-37 Axle Test 6506 The Buick 6A is an industry-recognized procedure developed by General Motors Corporation to evaluate the ability of gear lubricants to prevent surface distress of a Buick differential under conditions of severe accelerapercent of the composition, amorphous particles of less than 1 in size of hydrated alkali metal borate of the formula wherein M is an alkali metal of atomic number in the range of 11 to 19, m is a number of from 1 to 2 and n is a number of from 1 to 4, wherein said lyophilic surface active agent is present in from about 0.05 to 0.5 part per part of said alkali metal borate.
2. A lubricating composition according to claim 1 having 2 to 25 weight percent of said hydrated alkali metal borate.
3. A composition according to claim 1 wherein M is sodium and n is in the range of 1.5 to 2.5.
4. A composition according to claim 1 wherein M is potassium and n is in the range of 1.5 to 2.5.
5. A composition according to claim 1 wherein said hydrated alkali metal borate is K O-2B O -1.5-2.5H O.
6. A composition according to claim 1 wherein said hydrated alkali metal borate is Na O-B O' -1.52.5H O.
7. A lubricating composition having improved extreme pressure properties comprising an oil of lubricating viscosity and dispersed in said oil by means of an oilsoluble polyvalent metal sulfonate emulsifying agent in an amount of from 2 to 60 weight percent of the composition, amorphous particles of less than i in size of hydrated alkali metal borate of the formula M20 171E203 III 120 wherein M is an alkali metal of atomic number in the range of 11 to 19, m is a number of from 1 to 2 and n is a number of from 1 to 4, wherein said oil-soluble polyvalent metal sulfonate emulsifying agent is present in from about 0.05 to 0.5 part per part of hydrated alkali metal borate.
8. A composition according to claim 7 wherein said hydrated alkali metal borate is present in an amount of from 2 to 25 weight percent of the composition.
9. A composition according to claim 7 wherein said metal sult'onate is calcium sulfonate, said M is sodium and said It is in the range of 1.5 to 2.5.
10. A composition according to claim 6 wherein said metal sulfonate is calcium sulfonate, said M is potassium and said 11 is in the range of 1.5 to 2.5.
11. A method of preparing a lubricating composition having improved extreme pressure properties, which comprises emulsifying in an oil of lubricating viscosity an alkali metal borate of the formula M -m-B O dissolved in water by means of a lyophilic surface active agent, and dehydrating the resulting emulsion by heating to a temperature of at least 250 F. for a time sufficient to provide the desired degree of hydration, wherein m is a number of from 1 to 2 and M is an alkali metal of atomic number in the range of ll to 19 and wherein sufiicient alkali metal borate is added to provide a final composition having from 2 to 25 weight percent of hydrated alkali metal borate having from 1 to 4 waters of hydration, wherein said lyophilic surface active agent is present in from about 0.05 to 0.5 part per part of said alkali metal borate.
12. A method according to claim 11 wherein said lyophilic surface agent is a metal sulfonate.
13. A method according to claim 11 wherein said lyophilic surface agent is calcium sulfonate.
14. A method of preparing a lubricating composition having improved extreme pressure properties which comprises, in an oil of lubricating viscosity, emulsifying sodium metaborate dissolved in from about 0.5 to 3 parts of water per part of sodium metaborate by means of a cal cium sulfonate emulsifying agent present in from 0.1 to 0.3 part per part of said sodium metaborate, and dehydrating the resulting emulsion by heating to a temperature of at least 300 F. for a time sufficient to provide amorphous sodium metaborate having from 1.5 to 2.5 waters of hydration.
15. A method of preparing a lubricating composition having improved extreme pressure properties which comprises, in an oil of lubricating viscosity, emulsifying potas sium metaborate dissolved in from about 0.5 to 3 parts of water per part of potassium metaborate by means of calcium sulfonate emulsifying agent present in from 0.1 to 0.3 part per part of said potassium metaborate, and dehydrating the resulting emulsion by heating to a temperature of at least 300 F. for a time sufficient to provide amorphous sodium metaborate having from 1.5 to 2.5 waters of hydration.
16. A method of preparing a lubricating composition having improved extreme pressure properties which comprises, in an oil of lubricating viscosity, emulsifying sodium tetraborate dissolved in from about 0.5 to 3 parts of water per part of sodium tetraborate by means of a calcium sulfonate emulsifying agent present in from 0.1 to 0.3 part per part of said sodium tetraborate, and dehydrating the resulting emulsion by heating to a temperature of at least 300 F. for a time sufficient to provide amorphous sodium tetraborate having from 1.5 to 2.5 waters of hydration.
17. A method -of preparing a lubricating composition having improved extreme pressure properties which comprises, in an oil of lubricating viscosity, emulsifying potassium tetraborate dissolved in from about 0.5 to 3 parts of water per part of potassium tetraborate by means of a calcium sulfonate emulsifying agent present in from 0.1 to 0.3 part per part of said potassium tetraborate, and dehydrating the resulting emulsion by heating to a temperature of at least 300 F. for a time sufficient to provide amorphous potassium tetraborate having from 1.5 to 2.5 waters of hydration.
References Cited by the Examiner UNITED STATES PATENTS DANIEL E. WYMAN, Primary Examiner. P. P. GARVIN, Assistant Examiner.