Extreme-pressure mixed metal borate lubricant

Abstract

Mixed metal borate lubricant: A. react boric acid with alkaline earth metal carbonate overbased metal sulfonate in a lubricating oil or grease medium to form an intermediate B. react alkali metal base with intermediate to form mixed alkali and alkaline earth metal borate dispersion.

Description

DESCRIPTION OF THE INVENTION

Numerous additives are incorporated into lubricating oils and greases to enhance their lubricating properties. A wide variety of materials have been employed to increase the load-carrying capacity of lubricants employed under boundary or extreme-pressure (EP) conditions. When moving surfaces are separated by oil or a grease, 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-pressue lubrication is reached. Scuffing, galling, and rapid wear or seizure may occur. Welding of two contacting surfaces occurs, followed by metal transfer (galling) or cleavage and production of metal fragments.

In order to avoid the undesirable effects which result when using an uncompounded lubricant under high load conditions, extreme-pressure agents are added. For the most part, the extreme-pressure agents have been oil-soluble agents containing a chemically reactive element, e.g., chlorine, sulfur, or phosphorus, which react with the metal surface at the high temperatures produced under load conditions. This chemical bond to the EP agent then provides relatively good boundary protection.

Recently, a new type of additive has been developed which, unlike the chemically reactive chlorine-, sulfur- or phosphorus-containing EP agent, does not react with the metal surfaces to become chemically bonded thereto. Instead, this extreme-pressure additive is a dispersion of microparticulate alkali metal borates which is believed to deposit on the metal surface a viscous lubricating film. These borates and their preparation are disclosed in U.S. Pat. No. 3,313,727.

The microparticulate metal borates are typically prepared by dissolving an alkali metal borate, or its precursors, in water and emulsifying the aqueous solution in oil to form a micro-emulsion. The emulsion is then dehydrated, leaving amorphous or glassy particles of the hydrated alkali metal borate dispersed within the lubricating oil.

We have now found that a mixed alkali and alkaline earth metal borate dispersion exhibits excellent extreme-pressure properties in lubricating oils. These dispersions may be prepared by contacting boric acid with an alkaline earth metal carbonate overbased alkali or alkaline earth metal sulfonate to prepare an alkaline earth metal borate, which is then contacted with an alkali metal base to form the mixed metal borate. (As referred to herein, overbased materials are characterized by a metal content in excess of that stoichiometrically required by the reaction of the metal with the particular sulfonic acid. The base ratio is the ratio of the chemical equivalents of excess metal in the product to the chemical equivalents of the metal required to neutralize the sulfonic acid.)

By employing a mixed alkaline earth metal and alkali metal borate, it was found that the lubricant exhibited excellent extreme-pressure properties. In addition, it was discovered that the mixed metal borate dispersions exhibited improved compatibility with other additives which are normally incorporated into lubricating oils.

DETAILED DESCRIPTION OF THE INVENTION

The borate dispersions of this invention are stable dispersions of micronic size particles of a mixed alkaline earth metal and alkali metal borate. The borate particles are almost entirely less than 1 micron, and more usually less than 0.1 micron, in size. The product may be filtered to remove the larger microparticles.

The borate mixture may be a physical mixture of alkaline earth metal borates and alkali metal borates; a chemical mixture, such as alkaline earth and alkali metal borate; or a mixture thereof.

Exemplary types of mixed metal borates which may be employed in the practice of this invention include calcium and sodium borate, barium and sodium borate, calcium and potassium borate, barium and potassium borate, etc. Borates containing magnesium or lithium may also be employed, but are less preferred. In addition, mixtures of alkaline earth metals and mixtures of alkali metals may be employed; for example, calcium-barium and sodium borate, calcium and sodium-potassium borate, etc.

The mixed metal borates may also have from 0 to 8 waters of hydration, although from 0 to 3 waters of hydration are preferred, and more preferably from 0 to 2 waters of hydration.

In a preferred embodiment, the borate dispersion is prepared by the following steps: (1) contacting within an inert, stable, oleophilic reaction medium from 2 to 6 molar parts of boric acid per molar part of an alkaline earth metal carbonate, which is present as an overbased oil-soluble alkali or alkaline earth metal sulfonate, to form an alkaline earth metal borate; and (2) contacting the alkaline earth metal borate with an alkali metal base to form the mixed alkaline earth metal and alkali metal borate. This exemplary processing scheme may be conducted in a continuous manner or in a batch manner, or a combination of both. The optimum reaction conditions may vary, depending on whether continuous or batch processing is selected; however, the broad conditions set forth hereinafter are substantially inclusive of both types of processing.

The alkaline earth metal carbonate overbased alkaline earth or alkali metal sulfonate which is one of the reactants herein is prepared by overbasing neutral alkali or alkaline earth metal sulfonate.

NEUTRAL METAL SULFONATE

The neutral or alkaline earth metal sulfonates which may be overbased in the practice of this invention can comprise any oil-soluble alkali or alkaline earth metal sulfonate. Preferably, these sulfonates are aromatic and have the following generalized chemical formula: ##SPC1##

wherein: R is hydrogen or an alkyl having from 10 to 22 carbons (preferably from 15 to 21 carbons) and preferably attached to the benzene ring through a secondary carbon atom; R.sup.1 is selected from (a) an alkyl having from 3 to 10 carbons when R is an alkyl, or (b) an alkyl having from 8 to 22 carbons when R is hydrogen; M is an alkali or alkaline earth metal; and P is an integer from 1 to 2 and sufficient to make M electroneutral.

In a particular embodiment, the neutral metal sulfonate is a dialkylbenzene sulfonate of the above formula wherein R is a straight-chain aliphatic hydrocarbon radical of 17 to 21 carbon atoms, usually having at least 2 homologs present, and having secondary carbon attachment to the benzene ring; and R.sup.1 is a branched-chain alkyl group of 3 to 10 carbon atoms, more usually from 4 to 9 carbon atoms, having at least 1 homolog present, and preferably having at least 2 homologs present, and there being at least 1 branch of 1 to 2 carbon atoms, more usually of 1 carbon atom, i.e., methyl, per 2 carbon atoms along the longest chain. The attachment of the shorter alkyl group will generally be secondary or tertiary. Particular compositions have R.sup.1 with an average of 5 to 8 carbon atoms.

Usually, the difference in average number of carbon atoms between the short- and long-chain alkyl groups will be at least 10 and more usually at least 12, and not more than 16.

The preferred dialkylbenzene sulfonates which may be employed in the practice of this invention will generally have small amounts of monoalkylbenzene sulfonate, wherein the alkyl group is of from 17 to 21 carbon atoms, present within the admixture. Preferably the amount of monoalkylbenzene sulfonate will not exceed 30 percent and more preferably the monoalkylbenzene sulfonate will not exceed 20 percent by weight of the total sulfonate. Generally, it will be in the range of about 5 to 20 weight percent.

The positions of the alkyl group and the sulfonate on the benzene ring in relation to each other are not critical to this invention. Generally, most of the isomeric possibilities will be encountered -- with the particular isomers having the least steric hindrance being predominant. Also, there will be a broad spectrum of isomers based on the carbon of the alkyl group bonded to the benzene ring, depending on the method of preparation and the reactants used in the preparation.

Illustrative short-chain alkyl groups are isopropyl, tert.-butyl, neopentyl, diisobutyl, dipropenyl, tripropenyl, etc.

Illustrative of the long-chain alkyl groups are heptadecyl, octadecyl, nonadecyl, eicosyl and heneicosyl.

The monoalkyl benzenes can be prepared by simply reacting benzene with a mono-olefin in a simple alkylation process. Typical alkylation catalysts include Friedel-Crafts catalysts such as hydrogen fluoride, aluminum chloride, phosphoric acid, etc. The alkylation temperatures will ordinarily be in the range of about 4.degree.C (40.degree.F.) to 38.degree.C. (100.degree.F.).

The particular dialkylbenzenes can be prepared in substantially the same manner. A description of its preparation is disclosed in U.S. Pat. No. 3,470,097.

The mono- or dialkylbenzenes may then be readily sulfonated, using conventional sulfonation procedures and agents, including oleum, chlorosulfonic acid, sulfur trioxide (complexed or thin-film dilution techniques) and the like.

Various methods may be used to neutralize the sulfonic acid obtained, these methods being extensively described in the art. See for example U.S. Pat. Nos. 2,485,861, 2,402,325 and 2,732,344. The neutralization step is conveniently conducted by contacting the sulfonated alkyl- or dialkylbenzenes with an aqueous alkali metal hydroxide solution. The product is a neutral alkali metal sulfonate. The neutral alkaline earth metal sulfonate is prepared by a simple metal-exchange process. The alkali metal sulfonate is contacted with an alkaline earth metal salt, typically the halide salt, and the mixture heated. The exchange process may be accomplished at temperatures of 50.degree. to 150.degree.C. and contact times of 0.5 to 10 hours, usually from 1 to 3 hours.

Ordinarily, the neutralized product will be mildly overbased, having from about 0.02 to 0.7 mol percent excess of basic metal over that required for neutralizing the acid. Alkalinity values of these neutral compositions will generally be in the range of about 1 to 30, more usually from about 1 to 10 mg KOH/g.

Specific examples of exemplary metal sulfonates which may be overbased for use in this invention are disclosed in U.S. Pat. Nos. 3,691,075, 3,629,209, 3,595,790, and 3,537,996. These patents are herein incorporated by reference.

Illustrative individual compositions are sodium isopropyl eicosylbenzene sulfonate, potassium or barium tert.-butyl nonadecylbenzene sulfonate, calcium dipropenyl octadecylbenzene sulfonate, calcium diisobutyl octadecylbenzene sulfonate, sodium (propylene trimer) nonadecylbenzene sulfonate, barium isopropyl eicosylbenzene sulfonate, etc.

OVERBASING OF THE NEUTRAL METAL SULFONATE

Various methods of overbasing neutral metal sulfonates have been reported in the literature. See for example U.S. Pat. Nos. 2,695,910, 3,282,835 and 3,155,616, as well as Canadian Pat. No. 570,814. The preferred method employs a method similar to that described in U.S. Pat. No. 3,155,616.

The overbasing process can be conveniently conducted by charging to a suitable reaction zone the neutral metal sulfonate and an inert hydrocarbon solvent. An alkaline earth metal base (usually the oxide or hydroxide) and a C1 to C4 alkanol is added while the mixture is agitated and maintained at a temperature and pressure to retain most of the alkanol charged. Carbon dioxide is simultaneously contacted with the reaction medium, preferably sparged or bubbled through the liquid mixture. The introduction of the carbon dioxide is continued until its absorption rate into the mixture ceases or substantially subsides. Generally, from 0.2 to 1.6 equivalents and more usually from 0.9 to 1.3 equivalents of carbon dioxide will be absorbed by the mixture for every equivalent of alkaline earth metal base present.

The crude reaction product is then heated to strip out the residual alkanol and water of reaction. The stripping will generally be conducted at temperatures below 150.degree.C. and usually below 125.degree.C. After stripping the alkanol and water, the product may be filtered.

In a different embodiment, the hydrocarbon diluent is first stripped and then the product is filtered. Also, further addition of oil may be made to obtain a product having a somewhat lower viscosity. The choice of the particular route will depend on the equipment, the materials used, their physical properties, and the product desired.

The alkanol used, preferably methanol, will generally have from about 0.01 to 1 weight percent water, more usually from about 0.1 to 0.7 percent water. The alkanol will generally be present from about 0.1 to 20, more usually from about 1 to 10 weight parts per part of alkaline earth metal base.

The hydrocarbon dilutent will be one having a boiling point higher than alkanol to permit its retention when the alcohol is removed during processing. The boiling point should generally be less than about 280.degree.C. and preferably less than about 250.degree.C. Usually the hydrocarbon diluent will form an azeotrope with water. The usual diluents contain aromatic hydrocarbons of 7 to 10 carbon atoms, having boiling points in the range of about 100.degree. to 180.degree.C. These include toluene, xylene, cumene and cymene. The hydrocarbonaceous diluent can be present in an amount to form about a 5- to 20-weight-percent dispersion of alkaline earth metal base in the intital composition, usually an 8 to 15 weight percent dispersion.

The amount of overbasing varies greatly, depending upon the amount of borate dispersion ultimately wanted. Typically, from 1 to 20 equivalents of alkaline earth metals base will be used per equivalent of neutral metal sulfonate, more usually from about 5 to 15 equivalents of alkaline earth metal base per equivalent of neutral metal sulfonate. Thus, alkalinity values range from 50 to 460 mg KOH/g, and preferably from about 150 to 300 mg KOH/g.

It should be recognized that mixtures of alkaline earth metal carbonates may be employed as well as mixtures of alkali and alkaline earth metal sulfonates. Thus, a calcium and barium carbonate overbased sodium and calcium sulfonate may be present in the same mixture, which may be further reacted with the boric acid to form the intermediate borate particulate dispersion.

OLEOPHILIC REACTION MEDIUM

The overbased metal sulfonate is contacted with boric acid within a suitable oleophilic reaction medium. As referred to herein, "oleophilic" is defined as a property of a substance having a strong affinity to oils. The liquid oleophilic medium is generally present in the preparation of the overbased sulfonate, and hence extraneous addition of the medium is normally not necessary. The oleophilic reaction medium can comprise any stable, inert, organic oil having a viscosity ranging from 50 to 1,000 SUS at 38.degree. C. (100.degree.F.) and preferably from 50 to 350 SUS at 38.degree.C. Examples of stable organic oils which may be employed include a wide variety of hydrocarbon lubricating oils (preferred), such as naphthenic-base, paraffin-base and mixed-base lubricating oils. Other oleophilic oils include oils derived from coal products and synthetic oils, e.g., alkylene polymers (such as polymers of propylene, butylene, etc,. and mixtures thereof), alkylene oxide-type polymers (e.g., alkylene oxide polymers prepared by polymerizing alkylene oxide, e.g., propylene oxide polymers, etc., in the presence of water or alcohols, e.g., ethyl alcohol), liquid esters of acids of phosphorus, alkylbenzenes, polyphenols (e.g., biphenols and terphenols), alkyl biphenol ethers, polymers of silicon, e.g., hexyl(4-methyl-2-pentoxy)-disilicone, poly(methyl)siloxane, and poly(methylphenyl)siloxane, etc. The oleophilic lubricating oils may be used individually or in combinations, whenever miscible or whenever made so by use of mutual solvents.

When concentrates are desired, the viscosity of the overbased sulfonate in the oleophilic reaction medium is generally too high for normal processing. In these instances, it is preferred that a light hydrocarbon diluent be employed to reduce the viscosity of the reaction medium. The diluent may be aliphatic or aromatic and boiling below 250.degree.C. and preferably below 200.degree.C. Exemplary aromatic diluents include benzene, toluene, xylene, etc.; exemplary aliphatic diluents include cyclohexane, the heptanes, octanes, etc. The diluent should not boil below 70.degree.C. and preferably not below 100.degree.C.

At the end of the processing steps, the diluent may be stripped from the system. Any of the conventional stripping techniques may be employed.

PREPARATION OF MIXED METAL BORATES

The mixed metal borate dispersion may be prepared, in a preferred embodiment, by the following steps: a suitable reaction vessel is charged with the alkaline earth metal carbonate overbased metal sulfonate within the oleophilic reaction medium (typically the hydrocarbon medium employed to prepare the overbased metal sulfonate) and, preferably, a light hydrocarbon diluent. The boric acid is then charged to the reaction vessel and the contents heated, while vigorously agitated. The reaction product is an alkaline earth metal borate dispersed within the oleophilic reaction medium.

The reaction may be conducted for a period of 0.5 to 7 hours, usually from 1 to 3 hours, at a reaction temperature of 20.degree. to 200.degree.C., preferably from 20.degree. to 150.degree.C., and more preferably from 40.degree. to 125.degree.C. At the end of the reaction period, the temperature may be raised to 100.degree. to 200.degree.C., preferably from 100.degree. to 150.degree.C., to strip the medium of any water and a portion up to the whole thereof of the reaction diluent. The stripping may be done at atmospheric pressure or under reduced pressure 700 mm to 10 mm Hg absolute.

The amount of boric acid charged to the reaction medium may vary from 2 to 6 molar parts and preferably from 3 to 5 molar parts per molar part of alkaline earth metal carbonate. Preferred compositions are prepared when approximately 4 molar parts of boric acid are contacted with each molar part of alkaline earth metal carbonate.

The alkaline earth metal borate within the oleophilic reaction medium and diluent is then contacted with an alcoholic solution of an alkali metal base to form the mixed metal borate dispersion. Exemplary alkali metal bases include sodium hydroxide, potassium hydroxide, lithium hyroxide, sodium alcoholate (C1-C3), potassium alcoholate (C1-C3), etc. Preferred alkali metal bases are the hydroxides. An alcoholic solution is preferred, and can comprises any of the lower alcohols, e.g. C1-C5 alkanols. Methanol is preferred. The use of an alcoholic medium only represents a preferred embodiment of the practice of the present invention. Any person skilled in the art could easily select other media which may be successfully employed.

This reaction is conducted at a temperature of 90 to 140.degree.C. and preferably from 110.degree. to 120.degree.C. for a period varying from 0.1 to 3 hours. The resulting product may be filtered to remove any large particulate matter.

The amount of alkali metal base which may be charged to the reaction medium may vary over a wide range. Generally from 1 to 3 molar parts, preferably from 1.5 to 2.5 molar parts of alkali metal base is contacted with each molar part of alkaline earth metal borate.

The preferred borate dispersion is a mixed calcium sodium borate having from 0 to 8 waters of hydration (preferably 0 to 3 and prepared by reacting a calcium carbonate overbased sodium, calcium or barium petroleum sulfonate with boric acid followed by reaction with sodium hydroxide.

LUBRICANT

The amount of mixed metal borate which may be present in the lubricating oil to form the lubricant may vary from 0.1 to 60 weight percent, depending on whether a concentrate or final lubricant is desired. Generally, for concentrates, the mixed metal borate content varies from 20 to 50 weight percent, and preferably from 35 to 45 weight percent. For lubricants, the amount of mixed metal borate generally varies from 0.1 to 20 weight percent and preferably from 4 to 15 weight percent, based on the total composition. The lubricating oil which may be employed herein can comprise any stable oil of lubricating viscosity, i.e., viscosity ranging from 50 to 1000 SUS at 38.degree.C. (100.degree.F.) and preferably from 50 to 350 SUS at 38.degree.C. Exemplary lubricating oils are illustrated under the discussion of exemplary oleophilic reaction media.

OTHER ADDITIVES

The water-tolerance properties of the mixed metal borate dispersion may be improved by the addition of a lipophilic, nonionic, surface-active agent to the lubricant. The lipophilic, nonionic, surface-active agents include those generally referred to as "ashless detergents." Preferably the nonionic surfactants will have an HLB value (hydrophiliclipophilic balance)below about 7 and preferably below about 5. These ashless detergents are well known in the art and include hydrocarbyl-substituted amines, amides and cyclo-imides. The hydrocarbyl group or groups act as the oil-solubilizing group, and the amine, amide or imide groups act as the polar-liquid solubilizing group.

A principal class of lipophilic, nonionic, surface-active agents is the N-substituted alkenyl succinimides, derived from alkenyl succinic acid or anhydride and alkylene polyamines. These compounds are generally considered to have the formula: ##SPC2##

wherein R is a hydrocarbon radical having weight from about 400 to about 3,000 (that is, R is a hydrocarbon radical containing about 30 to about 200 carbon atoms), Alk is an alkylene radical of 2 to 10, preferably 2 to 6, carbon atoms, A is hydrogen or an alkyl having from 1 to 6 carbons; n is an integer from 0 to 6, preferably 0 to 3, and m is an integer from 0 to 1, preferably 0. (The actual reaction product of alkenyl succinic acid or anhydride akylene polyamine will comprise a mixture of compounds, including succinamic acids and succinimides. However, it is customary to deisignate this reaction product as "succinimide" of the described formula, since that will be a principal component of the dispersant mixture. See U.S. Pat. Nos. 3,202,678; 3,024,237; and 3,172,891.)

These N-substituted alkenyl succinimides can be prepared by reacting maleic anhydride with an olefinic hydrocarbon, followed by reacting the resulting alkenyl succinic anhydride with the alkylene polyamine. The "R" radical of the above formula, that is, the alkenyl radical, is preferably derived from an olefin containing from 2 to 5 carbon atoms. Thus, the alkenyl radical may be obtained by polymerizing an olefin containing from 2 to 5 carbon atoms to form a hydrocarbon having a molecular weight ranging from about 400 to 3,000. Such olefins are exemplified by ethylene, propylene, 1-butene, 2-butene, isobutene, and mixtures thereof. Since the methods of polymerizing the olefins to form polymers thereof are not the invention described herein, any of the numerous processes available in the art can be used.

The alkylene amines used to prepare the succinimides are of the formula ##SPC3##

wherein Y is an integer from 1 to 10, preferably from 1 to 6, A and R.sup.1 are each a substantially hydrocarbon radical having from 1 to 6 carbons or hydrogen, and the alkylene radical Alk.sup.1 is preferably a lower alkylene radical having less than about 8 carbon atoms. The alkylene amines include ethylene amines, propylene amines, butylene amines, pentylene amines, hexylene amines, heptylene amines, octylene amines, other polymethylene amines, and also the cyclic and the higher homologs of such amines as piperazines and amino-alkyl-substituted piperazines. They are exemplified specifically by: propylene diamine, decamethylene diamine, octamethylene diamine, di(heptamethylene) triamine, tripropylene tetramine, trimethylene diamine, di(trimethylene)triamine, 2-heptyl 3-(2-aminopropyl) imidazoline, 1,3-bis(2-aminoethyl) imidazoline, 1-(2-aminopropyl)piperazine, and 2-methyl-1-(2-aminobutyl)piperazine. Higher homologs such as are obtained by condensing two or more of the above-illustrated alkylene amines likewise are useful.

A second group of important nonionic dispersants comprises certain pentaerythritol derivatives. Particular derivatives which find use in this invention are those in which pentaerythritol is combined with a polyolefin and maleic anhydrife or with a polyolefin and a phosphorus sulfide. The polyolefins are the polymers of monomeric olefins having 2 to 6 carbon atoms, such as polyethylene, polypropylene, polybutene, polyisobutylene, and the like. Such olefins generally contain a total of 20 to 250 carbon atoms and preferably 30 to 150 carbon atoms. The phosphorus sulfides include P2S3, P2S5, P4S7, P4S3 and related materials. Of these, P2S5 (phosphorus pentasulfide) is preferred principally because of its ready availability.

Other nonionic emulsifiers which may be used include polymethacrylates and copolymers of polymethacrylate or polyacrylate with vinyl pyrrolidone, acrylamide or methacrylamide.

If a lipophilic, nonionic, surface-active agent is employed, it will generally be present in about 0.01 to 5 weight percent, more usually from about 0.1 to 3 weight percent, of the final composition. The actual amount of dispersant required will vary with the particular dispersant used and the total amount of borate in the oil. Generally, about 0.001 to 1, more usually about 0.01 to 0.5, part by weight of nonionic surface-active agent will be used per part by weight of the borate. In the concentrates, the mixture concentration will be based on the relationship to borate rather than on the fixed percentage limits of the lubricant, noted above, Generally, the upper ranges of the nonionic surface-active agent concentration will be used with the upper ranges of the alkali metal borate concentration.

Other materials may also be present as additives in the composition of this invention. Such materials may be added for enhancing some of the properties which are imparted to the lubricating medium by the alkali metal borate or providing other desirable properties to the lubricating medium. These include additives such as rust inhibitors, antioxidants, oiliness agents, viscosity index improvers, etc. Usually, these will be in the range from about 0.1 to 5 weight percent, preferably in the range from about 0.1 to 2 weight percent, of the total composition. An antifoaming agent may also be added with advantage. The amount required will generally be about 0.5 to 50 ppm, based on the total composition.

The borate dispersions are preferably employed in lubricating oils, such as gear and bearing oils, cutting oils, etc.

The borate dispersion may also be employed in greases to impart extreme-pressure properties. The grease composition may be prepared by adding a thickening agent to the borate dispersion in the oleophilic lubricating oil. The thickening agent may be added directly to the borate dispersion or produced "in situ" within the oleophilic oil. Typical thickening agents which may be employed include organic or metal organic thickeners such as polyurea, alkali metal terephthalamate, lithium hydroxy stearate, calcium complex soap, aluminum complex soap, polymeric thickeners, or combinations thereof.

Exemplary polyurea greases which may be employed are disclosed in U.S. Pat. No. 3,243,372. These greases are prepared by reacting, within the lubricating oil to be thickened, a polyamine having from 2 to 20 carbons, a diisocyanate having from 6 to 16 carbons and a monoamine or monoisocyanate, each having from 10 to 30 carbons. Typically, these greases contain from 5 to 15 weight percent of the polyurea thickener, although lesser amounts may be used if other thickening agents are present. A particularly preferred polyurea is a tetraurea prepared by reacting one molar part of ethylene diamine with two molar parts of tolylene diisocyanate and two molar parts of a monoamine having from 16 to 20 carbons.

Exemplary alkali metal terephthalamate greases are disclosed in U.S. Pat. Nos. 2,820,012 and 2,892,778. These greases may be prepared by reacting a monoester of terephthalic acid with an alkali metal base in the presence of a solvent. A particularly preferred grease contains from 8-15 weight percent of a sodium N-(hydrocarbyl) terephthalamate having from 5 to 24 carbons in the hydrocarbyl group, such as sodium N-octadecyl terephthalamate.

The lithium hydroxy-stearate greases are the most widely employed multi-purpose greases. These greases have the properties which render them particularly suitable for use in the practice of this invention. The lithium thickening agent is typically prepared by reacting lithium hydroxide with hydrogenated castor oil and is present within a lubricating oil at a concentration of 10 to 20 percent.

Another class of high-temperature greases which may be employed is the calcium complex greases. These greases are composed of 5-20 percent of a calcium soap, e.g., calcium hydroxystearate, 4-20 percent of calcium acetate and 1-10 percent of calcium carbonate. A small amount of calcium hydroxide may also be employed. Exemplary greases of this type are described in U.S. Pat. Nos. 3,186,944 and 3,159,575.

Exemplary aluminum complex greases are described in U.S. Pat. Nos. 3,476,684 and 3,514,400. These greases are prepared by incorporating into a lubricating oil from 5-20 percent of the reaction product of a long-chain fatty acid, an aromatic acid and aluminum isopropoxide.

The amount of thickener employed in making the greases of this invention varies, depending upon the type thickener, type of lubricating oil, hardness of the grease desired and the presence of other additives. When greases having the preferred hardness of No. 2-4 NLGI (ASTM work penetration varying from 340 to 175) are employed, the amount of thickener generally varies from 5 to 25 weight percent and more usually from 8 to 15 weight percent of the grease composition.

EXAMPLE 1

This example is presented to illustrate the preparation of a dialkylbenzene sulfonate which may be used to prepare the overbased metal sulfonates.

Benzene is alkylated using a tetramer polypropylene fraction and HF alkylation catalyst, a reaction temperature of about 18.degree.C. (65.degree.F), and efficient mixing. The hydrocarbon phase is separated, washed and fractionated. The lower alkybenzene fraction (boiling range 159.degree.C. ?318.degree.F.! to 248.degree.C. ?478.degree.F.!, ASTM D-447 distillation) is collected as feed for the second-stage alkylation with a mixture of straight-chain 1-olefins. The average molecular weight of the above branchedchain alkylbenzene is 164. This corresponds to an average of 6 carbon atoms per alkyl group in the mixture. The over-all alkyl carbon atom content corresponding to the above boiling range is the C4-C9 range.

Using the above branched-chain monoalkylbenzene and a substantially straight-chain C17-C21 1-alkene fraction obtained from cracked wax, and hydrogen fluoride catalyst, the desired dialkylbenzene is produced in a stirred, continuous reactor.

The 1-alkene feed has the following characteristics:

Average mol weight 268 Average No. of carbon atoms per molecule 19 Olefin distribution, weight percent: C17 2 C18 22 C19 39 C20 32 C21 5 Reaction conditions: LHSV 2 Temperature 38.degree.C. (100.degree.F.) Monoalkylbenzene to alpha-olefin, mol ratio 2-1 Hydrocarbon to HF ratio, volume 2.3-1

After reaction, the settled product is separated into an organic phase and a lower HF-acid phase. The crude dialkylbenzene organic phase is washed and then fractionated by distillation. A minor amount of forecut, mainly monoalkylbenzene, is collected up to an overhead temperature of about 232.degree.C. (450.degree.F.) at a pressure of 10 mm Hg absolute. The balance of the distillate is the desired product, and has an average molecular weight of about 405. The difference between the average carbon atom content of the alkyl-chain types is about 13.

The dialkylbenzene is charged to a stirred reaction vessel fitted for temperature control, along with 130 neutral oil which is substantially free of sulfonatable material. The volume ratio of the two materials is 3-1/2 to 4, respectively, and to this mixture is added, over a period of several hours, 2 volumes of 25 percent oleum. The reaction temperature is maintained at about 38.degree.C. (100.degree.F.). Two phases develop in the settled mixture, the lower being a spent mineral acid phase and the upper being the desired sulfonic acid phase.

The separated sulfonic acid-oil mixture is then neutralized with one volume of 50 percent aqueous caustic diluted with 15 volumes of 2-butanol. During the neutralization the temperature is maintained below about 43.degree.C. (110.degree.F.), and after completion thereof the neutral solution is heated and maintained at 60.degree.C. (140.degree.F.) during a second phase separation. Two phases develop, a lower brine-alcohol solution and an upper neutral alcohol-sodium sulfonate solution.

EXAMPLE 2

The preparation of a neutral calcium sulfonate is illustrated in this example. A 3-liter glass flask is charged with 80 g of calcium chloride and 800 ml of water. Thereafter, 1500 g of the sodium sulfonate solution of the type prepared by the method of Example 1 is charged to the flask. The contents are heated to 30.degree.C. (85.degree.F.) under agitation and maintained at these conditions for 1 hour. The contents are allowed to phase-separate and the water layer drawn off. 800 ml of distilled water is admixed with the sulfonate and heated for one hour. The phases are allowed to separate and the aqueous phase drawn off. The sulfonate is washed three additional times with water and one time with an aqueous isobutyl alcohol solution. The mixture is heated to 112.degree.C. to remove any residual water and isobutyl alcohol. 500 ml of toluene is added to the sulfonate and the admixture filtered through Celite 512. The product is stripped to 185.degree.C at 3 mm Hg pressure to yield 740 grams of neutral calcium sulfonate. Analysis of the product reveals

Wt.% sulfated ash 6.09 Wt.% metal 1.92 calcium

EXAMPLE 3

A calcium carbonate overbased calcium sulfonate which may be employed to prepare the mixed borate dispersion of the present invention may be prepared by the method of Example 5 of U.S. Pat. No. 3,155,616. Following that procedure, a calcium carbonate overbased calcium-petroleum sulfonate is prepared having a base ratio of 9.3 and containing 11.4 weight percent calcium.

EXAMPLE 4

A calcium tetraborate is prepared by charging to a 2-liter glass flask 308 g of the calcium carbonate overbased calcium sulfonate prepared by the method of Example 3 and 700 ml of an aliphatic hydrocarbon diluent having a boiling range from 158.degree.C. to 202.degree.C. and containing 17 percent aromatics. The contents are heated to 50.degree.C. and 200 g of boric acid are added. The temperature is slowly increased to 150.degree.C. over a 75-minute period. The contents are cooled and filtered; the filtrate is stripped to 165.degree.C. at 5 mm Hg pressure absolute to recover 403 g of product. The product had an alkalinity value of 211 mg KOH/g.

EXAMPLE 5

A mixed calcium and sodium borate dispersion is prepared by the method of this example. A 2-liter glass flask is charged with 308 g of a calcium carbonate overbased calcium sulfonate prepared by the method of Example 3 and 750 ml of an aliphatic hydrocarbon diluent of the type described in Example 4. The contents are then heated to 50.degree.C. and 200 g of boric acid added. The temperature is raised to 150.degree.C. over a 95-minute period. The contents are cooled and filtered. A 2-liter flask is charged with 978 g of the above-described filtrate (alkalinity value of 85.5 mg KOH/g) and heated to 110.degree.C. A solution of 30 g of sodium hydroxide in 150 ml of methanol is added to the flask over a 65-minute period at 110.degree.C. The temperature is raised to 140.degree.C. and then cooled under vacuum. The product is filtered and then stripped to 165.degree.C. at 5 mm Hg pressure absolute. A total of 406 g of product is recovered. The product has an alkalinity value of 284 mg KOH/g.

EXAMPLE 6

This example is presented to demonstrate the preparation of a representative mixed metal borate dispersion. A 2-liter flask is charged with 308 grams of the calcium carbonate overbased calcium sulfonate of the type prepared by the method of Example 3 along with 700 ml of an aliphatic hydrocarbon diluent having a boiling range from 158.degree.C. to 202.degree.C and containing 17 percent aromatics. 200 grams of boric acid are added to the flask and contents raised to a temperature of 160.degree.C. in a period of 13/4 hours. The contents of the flask are cooled under a pressure of 150 mm Hg absolute. The calcium borate intermediate product is then filtered and reheated to a temperature of 110.degree.C. Thereafter, a solution of 56 g of sodium hydroxide in 300 ml methanol is added over a 2-1/2 hour period at 110.degree.C. Upon completion of the addition of the sodium hydroxide/methanol solution to the flask, the temperature is raised to 150.degree.C., then cooled and filtered. The filtrate is stripped by heating to 160.degree.C. at a pressure of 5 mm Hg absolute. A total of 343 g of product is recovered. Product is analyzed and contains 5.86 weight percent calcium and 7.07 weight percent boron. The product has an alkalinity value of 346 mg KOH/g.

EXAMPLE 7

A mixed calcium and sodium metaborate dispersion is prepared by the method of this example. The procedure of Example 6 is duplicated, except that 17 g of a polyisobutenyl succinimide dispersant are present during the reaction steps and 60 g of sodium hydroxide and 300 ml of methanol are employed. A total of 351 g of product is recovered, having an alkalinity value of 345 mg KOH/g.

EXAMPLE 8

A 2-liter flask is charged with 100 g of a 38% sodium sulfonate solution prepared by neutralizing a sulfonated 480 neutral oil with sodium hydroxide as described in Example 1. The contents are thereafter heated to 165.degree.C. under a pressure of 150 mm Hg absolute to strip 60 g of solvent from the solution. After cooling, 750 ml of an aliphatic hydrocarbon thinner of the type described in Example 4 are added along with 270 g of a calcium carbonate overbased calcium sulfonate of the type described in Example 3. The combined contents of the flask are heated to 50.degree.C. and thereafter 176 g of boric acid are charged. The temperature of the flask is then raised to 145.degree.C. over a 120-minute period. A 150-mm Hg absolute pressure is applied to the flask to cool the contents. Thereafter, a solution of 54 g of sodium hydroxide in 250 ml methanol is added over a period of 150 minutes at 110.degree.-115.degree.C. After all of the solution has been charged, the contents of the flask are heated to a temperature of 150.degree.C. The contents are then cooled and filtered. The filtrate is then stripped to 165.degree.C. at a pressure of 5 mm Hg absolute. A total of 390 g of product is recovered and analyzed to contain 5.64 percent calcium and 6.57 percent boron. The alkalinity value of the product is 330 mg KOH/g.

EXAMPLE 9

A 2-liter flask is charged with 100 g of a 38 percent sodium sulfonate solution of the type described in Example 8 and thereafter heated to 165.degree.C. under pressure of 150 mm of Hg absolute to strip 60 g of solvent from the solution. After cooling, 750 ml of an aliphatic hydrocarbon thinner of the type described in Example 4 are added along with 270 g of a calcium carbonate overbased calcium sulfate of the type described in Example 3. The combined contents of the flask are heated to 50.degree.C and thereafter 176 g of boric acid are charged. The temperature of the flask is then raised to 150.degree.C. over a 127-minute period. Thereafter, a pressure of 150 mm Hg absolute is applied to cool the contents to a temperature below 110.degree.C. A solution of 86 g of potassium hydroxide in 250 ml methanol is added to the solution over a period of 145 minutes at 115.degree.-120.degree.C. After all of the solution has been charged, the contents of the flask are raised to a temperature of 150.degree.C. The contents are then cooled and 300 ml of an aliphatic hydrocarbon solvent are added. The combined contents are then filtered. The filtrate is stripped to 165.degree.C. at a pressure of 5 mm Hg absolute. A total of 405 g of product is recovered and analyzed to contain 5.33 percent calcium and 6.02 percent boron. The alkalinity value of the product is measured to be 299 mg KOH/g.

EXAMPLE 10

A mixed calcium, sodium and potassium metaborate dispersion is prepared by the method of this example. A 2-liter glass flask is charged with (1) 38 g of sodium sulfonate prepared by neutralizing a sulfonated 480 neutral hydrocarbon oil with sodium hydroxide, (2) 100 ml of aliphatic hydrocarbon diluent, (3) 270 g of calcium carbonate overbased calcium sulfonate of the type prepared by the method of Example 3, and (4) 650 ml of aliphatic hydrocarbon diluent. The contents are heated to 50.degree.C. and 176 g of boric acid are added. The temperature is slowly increased to 150.degree.C. over a 127-minute period. The contents are cooled to 116.degree.C. and a filtered solution of: (1) 43 g of potassium hydroxide; (2) 27 g of sodium hydroxide; and (3) 250 ml of methanol is added. The addition temperature is 115.degree.C. and the addition time is 131 minutes. The temperature is raised to 150.degree.C. and 477 ml of methanol and diluent taken off overhead. An additional 250 ml of aliphatic hydrocarbon diluent are added. The contents are filtered and stripped to 165.degree.C. at a pressure of 5 mm Hg absolute. A total of 399 g of product is recovered having an alkalinity value of 301 mg KOH/g. The product contains 5.63 weight percent calcium and 6.30 weight percent boron.

EXAMPLE 11

A 2-liter glass flask is charged with 242 grams of a 38 percent sodium sulfonate solution of the type described in the preceding examples. This solution is stripped to 165.degree.C. under a pressure of 150 mm Hg absolute to strip out 148 grams solvent. The remaining product is then cooled and 750 ml of an aliphatic thinner of the type described in Example 4 are added along wtih 216 grams of a calcium carbonate overbased calcium sulfonate of the type described in Example 3. The combined contents are heated to 50.degree.C. and thereafter 176 g of boric acid are added. The temperature is then raised to 150.degree.C. over a 110-minute period. The contents are then cooled to 116.degree.C. and a solution of 66 g of sodium hydroxide in 300 ml methanol are slowly added to the flask. The addition time is 147 minutes and the addition temperature is maintained at 115.degree.-120.degree.C. After all of the sodium hydroxide/methanol solution has been added, the temperature of the flask is raised to 150.degree.C. Thereafter, vacuum is applied to the flask and 610 ml of solvent taken off overhead. Then, 200 ml of an aliphatic hydrocarbon thinner are added and the product filtered. The filtrate is stripped to 165.degree.C. at 5 mm Hg pressure absolute. A total of 362 grams of product is recovered and is analyzed to have an alkalinity value of 318 mg KOH/g.

EXAMPLE 12

A mixed calcium-potassium tetraborate dispersion is prepared by the method of this example. A 2-liter glass flask is charged with: (1) 278 g of a calcium carbonate overbased calcium sulfonate prepared by the method of Example 3; (2) 38 g of sodium sulfonate as described in Example 10 and dissolved in 100 ml of aliphatic hydrocarbon diluent; and (3) 650 ml of an aliphatic hydrocarbon diluent of the type described in Example 4. The contents are heated to 50.degree.C. and 176 g of boric acid are added. The temperature is slowly raised to 145.degree.C. over a 140-minute period. The contents are cooled under vacuum to 116.degree.C. and a solution of 86 g of potassium hydroxide in 250 ml of methanol are slowly added over a 154-minute period at 115.degree.-120.degree.C. The temperature is increased to 150.degree.C. and then cooled by applying vacuum to the flask. A total of 480 ml of methanol and diluent is taken off overhead. 300 ml of aliphatic hydrocarbon diluent are then added and the product filtered and stipped to 165.degree.C. at 5 mm of Hg pressure absolute. A total of 391 g of calcium-potassium metaborate product is recovered.

The calcium-potassium metaborate described above is converted into the tetraborate counterpart by charging to the flask 700 ml of aliphatic hydrocarbon diluent and an additional 130 g of boric acid. The contents are slowly heated to 150.degree.C. over a 2-hour period. The contents are cooled, filtered and stripped to a temperature of 170.degree.C. at a pressure of 5-10 mm of Hg absolute. A total of 469 g of calcium-potassium tetraborate is recovered. The product has an alkalinity value of 242 mg KOH/g and contains 4.01 weight percent calcium and 10.25 weight percent boron.

EXAMPLE 13

This example illustrates the preparation of a mixed magnesium-sodium metaborate dispersion. A 2-liter glass flask is charged with 176 g of boric acid and 500 ml of aliphatic hydrocarbon diluent of the type described in Example 4. The contents are heated to 100.degree.C. and the following solution slowly added:

256 g of Mg-overbased petroleum sulfonate having an alkalinity valve of 303 mg KOH/g;

52 g of sodium sulfonate of the type described in Example 10; and

250 ml of an aliphatic hydrocarbon diluent of the type described in Example 4.

The solution is added to the flask over a 30-minute period at an addition temperature of 105.degree.-110.degree.C. The temperature of the flask is maintained at 110.degree.-120.degree.C. for an additional 30-minute period and then raised to 150.degree.C. over a 30-minute period. The flask contents are cooled to 110.degree.C. by applying a slight vacuum and 200 ml of diluent are removed overhead. A solution of 54 g of sodium hydroxide in 250 ml methanol is slowly added to the flask over a 158-minute period at 110.degree.-115.degree.C. The flask contents are heated to 150.degree.C. and thereafter cooled by applying a vacuum. 480 ml of diluent are taken off overhead. 200 ml of an aliphatic hydrocarbon diluent are added, the contents filtered and the filtrate stripped to 165.degree.C. at 5 mm Hg pressure absolute. A total of 256 g of product is recovered having an alkalinity value of 304 mg KOH/g. The product contained 3.88 weight percent magnesium and 6.41 weight percent boron.

EXAMPLE 14

This example is presented to illustrate a few of the performance properties of the mixed metal borate dispersions of this invention. A series of tests is performed with each borate dispersion prepared by the methods of the preceding examples to measure the extreme-pressure properties (Timken E.P. Test), the anti-wear properties (4-Ball Wear Test) and the compatibility properties (Compatability Test). The Timken E.P. Test is described in ASTM D-2782-69T, which test procedure is herein incorporated by reference. The 4-Ball Wear Test is described in ASTM D-2873-695, which test procedure is also herein incorporated by reference. (The conditions are 50-kg force, 1/2-hour period at 1,750 RPM, room temperature.) The Compatibility Test is conducted by admixing with each weight part of a lube oil containing 5 percent by weight of the mixed metal borate 1 weight part of a lube oil containing 3 to 5 weight percent of a conventional sulfurized ester additive. The admixture is placed in an oven at 300.degree.F. for 24 hours. After this period, if a stable gel of 5 percent to 100 percent of the mixture has formed, the compatibility is noted as "Fail." If a light gel or sediment representing less than 5 percent of the mixture has formed, the compatibility is rated as "Pass."

A group of 9 test samples is employed in these experiments. The samples consist of a lubricating oil containing 10 weight percent of the borate dispersion made in the preceding examples. One test is conducted without any additive and one test is conducted with a calcium carbonate dispersion. The data from these tests are reported in the following Table I. As can be seen from Table I, the use of a mixed metal borate exhibits good EP and anti-wear properties.

TABLE I __________________________________________________________________________ PERFORMANCE PROPERTIES OF BORATE DISPERSIONS 4-Ball Wear Timken Compatability Test Test-Scar Test Test, No. Dia.(mm) (lbs, Pass) (Pass/Fail) __________________________________________________________________________ 1 None -- 5 -- 2 CaCO.sub.3 Dispersion (Ex. 3) -- 10 -- 3 Calcium Borate (Ex. 4) 0.8 30 -- 4 Ca/Na Borate (Ex. 5) 0.59 30 -- 5 Ca/Na Metaborate (Ex. 6) 0.51 80 -- 6 Ca/Na Metaborate (Ex. 8) 0.52 90 Pass 7 Ca/K Metaborate (Ex. 9) 0.47 100 Pass 8 Ca/K/Na Metaborate (Ex. 10) 0.54 100 Pass 9 Ca/Na Metaborate (Ex. 11) 0.54 75 -- 10 Ca/K Tetraborate (Ex. 12) 0.55 60 -- 11 Mg/Na Metaborate (Ex. 13) 0.62 90 -- __________________________________________________________________________

Claims

What is claimed is:

1. A lubricating composition comprising a major portion of an oil of lubricating viscosity and from 0.1 to 60 weight percent of a particulate mixed alkali and alkaline earth metal borate prepared by reacting within an inert, stable, oleophilic, reaction medium: (1) boric acid, with (2) an alkaline earth metal carbonate overbased alkali or alkaline earth metal sulfonate dispersant, wherein the molar ratio of boric acid to alkaline earth metal carbonate is from about 2 to about 6, to form an intermediate reaction product which is then reacted with an alkali metal base to form said mixed alkali and alkaline earth metal borate, wherein the molar ratio of alkali metal base to said intermediate is from about 1 to about 3.

2. The lubricating composition defined in claim 1 wherein said particulate mixed alkali and alkaline earth metal borate has a mean particle size below about 1 micron.

3. The lubricating composition defined in claim 2 wherein said oil of viscosity vescosity is a hydrocarbon petroleum oil having a viscosity of 50 to 1,000 SUS at 38.degree.C.

4. The lubricating composition defined in claim 3 wherein a lipophilic, nonionic, surface-active agent having a hydrophilic-lipophilic balance value below 7 is also present at a concentration of 0.01 to 5 weight percent.

5. The lubricating composition defined in claim 2 wherein said particulate mixed alkali and alkaline earth metal borate is present at a concentration of 4 to 15 weight percent.

6. The lubricating composition defined in claim 5 wherein a thickener selected from the group consisting of polyurea, alkali metal terephthalamate, lithium hydroxy stearate, calcium complex soap and aluminum complex soap is also present in an amount to thicken said lubricating oil to the consistency of a grease.

7. The lubricating composition defined in claim 5 wherein said mixed alkali and alkaline earth metal borate is sodium and calcium borate.

8. The lubricating composition defined in claim 5 wherein said mixed alkali and alkaline earth metal borate is potassium and calcium borate.

9. The lubricating composition defined in claim 5 wherein said alkaline earth metal carbonate is calcium carbonate and wherein said alkali or alkaline earth metal sulfonate is sodium, calcium or barium sulfonate.

10. The lubricating composition defined in claim 9 wherein said particulate alkali and alkaline earth metal borate has from 0 to 8 waters of hydration.

11. A particulate dispersion of an alkali and alkaline earth metal borate prepared by contacting two molar parts of boric acid with each molar equivalent part of an alkaline earth metal carbonate overbased alkali or alkaline earth metal sulfonate within a stable, inert, oleophilic, liquid reaction medium to form an intermediate reaction product, which is then reacted with two molar parts of an alkali metal hydroxide per molar part of said intermediate reaction product to form a mixed alkali and alkaline earth metal borate dispersion.

12. The composition defined in claim 11 wherein said alkaline earth metal carbonate is calcium carbonate and wherein said alkali or alkaline earth metal sulfonate is sodium, calcium or barium sulfonate.

13. A process for preparing a particulate alkali and alkaline earth metal borate dispersion which comprises contacting an alkaline earth metal carbonate overbased alkali or alkaline earth metal sulfonate with boric acid within a stable, inert, oleophilic, liquid reaction medium, wherein the molar ratio of broic acid to alkaline earth metal carbonate is from about 2 to about 6, and the temperature is 20.degree.- 200.degree.C. to form an intermediate reaction product which is thereafter contacted with an alkali metal base to form said mixed alkali and alkaline earth metal borate, wherein the molar ratio of alkali metal base to said intermediate is from about 1 to about 3 and the temperature is 90.degree.- 140.degree.C.

14. The process defined in claim 13 wherein said reaction of boric acid with alkaline earth metal carbonate is conducted at a temperature of 20.degree. to 200.degree.C. for a period of 0.5 to 7 hours and the reaction of said intermediate reaction product and said alkali metal base is conducted at a temperature of 90.degree. to 140.degree.C. for a period of 0.1 to 3 hours.

15. The process defined in claim 13 wherein from 3 to 5 molar parts of boric acid are contacted for each molar part of alkaline earth metal carbonate.

16. The process defined in claim 15 wherein said alkaline earth metal carbonate is calcium carbonate and said alkali or alkaline earth metal sulfonate is sodium, calcium or barium sulfonate.

17. The process defined in claim 16 wherein said particulate mixed alkali and alkaline earth metal borate has from 0 to 8 waters of hydration.

18. The process defined in claim 17 wherein said mixed alkali and alkaline earth metal borate is a sodium and calcium borate or a potassium and calcium borate, wherein said alkaline earth metal carbonate is calcium carbonate, and said alkali or alkaline earth metal sulfonate is calcium sulfonate.