US3853772A - Lubricant containing alkali metal borate dispersed with a mixture of dispersants - Google Patents

Abstract

Lubricant composition comprising: A. LUBRICATING OIL BASE B. HYDRATED ALKALI METAL BORATE C. ALKALINE EARTH METAL SULFONATE D. SUCCINIMIDES.

Description

United States Patent Adams Dec. 10, 1974 1 LUBRICANT CONTAINING ALKALI [58] Field of Search 252/18, 25, 33, 33.4; METAL BORATE DISPERSED WITH A 72/42 MIXTURE OF DISPERSANTS [75] Inventor: John Howard Adams, San Rafael, [56] References cued Calif. UNITED STATES PATENTS m1 21212: 2122: 5:211,1111--- 2:1: Franclsco, Callf- 3,213,024 10/1965 Blake et a1 252/18 y 9 3,249,538 5/1966 Freier 252/18 3,313,727 4/1967 Peeler 1 252/18 [21] Appl. N0.I 358,749 3,544,679 12/1970 McCoy 252/18 3,565,802 2/1971 West et a1 252/25 [30] Foreign Application Priority Data Primary Examiner Daniel E. wyman May 12, 1972 Belgium Assistant Examiner l Vaughn May 29, 1972 Belgium 3434 Attorney Agent or F Magdeburger; May 9, Canada 141712 Tonkin; Nelson May 25, 1972 France 72.18677 May 29, 1972 Germany 2225985 57 ABSTRACT June 1, 1972 ,Great Britain.... 1,25699/72 Lubricant com osition com risin May 30, 1972 Italy 25047/72 lubricatingpoil base p May 31, 1972 Japan 47-54233 b hydrated alkali metal borate 52' US. Cl 252/18, 72/42, 252/25, 3' metal sulfcnate 252/33, 252/334 [51] Int. Cl..... C10m 1/40, C10m l/32, C10m 1/10 11 Claims, No Drawings CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of U.S. application Ser. No. 237,536, filedlVlar. 23, 1 972, which in turn is a continuation-in-part of U.S. application Ser. No. 150,865, filed June 1, 1971, both now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention concerns the extreme-pressure (EP) lubricating oils.

High load conditions often occur in the gear sets used in automotive transmission differentials, pneumatic tools, gas compressors, high pressure hydraulic systems, metal working and similar devices as well as in many types of bearings. In order to avoid the undesirable effects which result when using an uncompounded oil under these high load conditions, the lubricants for use in such service contain EP agents." For the most part, EP agents have been organic or metallo-organic compounds which are oil-soluble or easily incorporated as a stable dispersion in the oil.

Recently Peeler in U.S. Pat. No. 3,313,727 disclosed an EP lubricant produced by the dispersion in a nonpolar lubricating oil of an inorganic hydrated sodium or potassium borate. The borate, water, and a single emulsifier were introduced into the nonpolar medium. The mixture was then agitated to produce a dispersion of the water in the oil and heated to dehydrate the borate. Peeler also disclosed that conventional additives such as rust inhibitors, detergents, foam inhibitors, etc. could be present in the finished lubricating composition containing the borate.

The borate-containing oils described by Peeler have, however, a very serious deficiency in service. If water is introduced into the system containing the borate lubricant, the borate crystallizes out of the oil and forms hard granules. These granules cause severe noise in the system and can in some cases damage the gears or bearings themselves. Further, loss of the borate by crystallization substantially decreases the EP function of the lubricant.

2. Prior Art The Peeler patent described above broadly discloses sodiumand potassium-borate-containing lubricants. The borate is dispersed in a lubricating oil medium by means of a single emulsifier or dispersant. This single dispersant may be chosen from a wide variety of ionic and nonionic materials, many of which, including sulfonates and succinimides, are cited by Peeler. The Peeler patent in turn refers to U.S. Pat. No. 2,987,476, for detailed descriptions of many ionic dispersants which are useful for incorporating inorganic boric acid compounds into substantially nonpolar oils. U.S. Pat. No. 1,101,449 describes an aqueous solution containing sodium borate and a colloidal dispersant. U.S. Pat. No. 2,753,305 describes a metal rolling lubricant containing an alcohol, an alkali metal borate, a soap solvent coupling agent," paraffin wax, and a sulfonated oil. U.S. Pat; No. 2,781,314 describes incorporation into oils of solid particulate rust inhibitors of 0.1 to 100 microns in diameter; these include metal sulfonates. Gear lubrication is discussed in Guthrie, Petroleum Products Handbook (1st Ed., McGraw-Hill Book Co., 1960) on pages 9-47 through 9-49, and in Boner, Gear and Transmission Lubricants (Reinhold Publ. Corp., 1964), pages 85-100. Rock drill lubrication is discussed in Lubrication (Texaco, Inc., Vol. 56, No. 511970) on pages 61-76.

SUMMARY OF THE INVENTION I have now invented'a novel extreme-pressure lubricating composition having improved water tolerance. This lubricant, comprises an oil of lubricating viscosity having dispersed therein 1 to weight percent (based on the entire composition) of amorphous particles of less than one micron in size of hydrated alkali metal borate having 0.5 to 4 waters of hydration. The borate is dispersed in the oil by means of a mixture consisting of 40 to 99.9 weight percent of a lipophilic anionic surface-active agent containing a Group 11 metal and sulfur and 0.1 to 60 weight percent of a lipophilic nonionic surface-active agent. Typical anionic dispersants include metal petroleum sulfonates and sulfurized, phenates, while the nonionic dispersants include succinimides and pentaerythritol derivatives.

DESCRIPTION OF THE INVENTION The compositions of this invention are stable EP lubricants having improved water tolerance properties. They perform well in standard EP tests such as the Four-Ball test. There is no crystal formation when the lubricants are exposed to water. They are useful in numerous applications wherein extreme pressures are encountered and particularly as automotive differential lubricants. They have fluid or semi-fluid consistencies and many are transparent, a property which is highly advantageous where visual appearance is important or where it is desirable to be able to inspect the lubricated gears or bearings while they are in service. They are also capable of being atomized for use in mist oil lubrication systems anddo not ignite under high pressures. In most cases, they are nontoxic and nonirritating to human skin.

Each composition of this inventionis an EP lubricant having improved water tolerance properties which comprises an oil of lubricating viscosity, a hydrated alkali metal borate containing 0.5 to 4 waters of hydration, and a mixture of dispersants consisting of 40 to 99.9 percent by weight of an anionic lipophilic surfaceactive agent containing a Group 11 metal and sulfur and 0.1 to 60 percent by weight of a lipophilic nonionic surface-active agent.

THE HYDRATED ALKALI METAL BORATE The hydrated borates of this lubricant composition are hydrated alkali metal borates of the formula wherein x is a number from 0.68 to 4, preferably from 0.7 to 2, and more preferably from 1 to 2, and y is a number up to 5, and preferably from 0.5 to 4. This formula is intended to be empirical and not to define the exact form in which the borate and water exist in the oil. Individual borate particles dispersed in the oil may have compositions falling outside this formula, but the over-all composition averaged over all particles will be as defined above.

The borate particles are almost entirely less than one micron in size and for the most part are less than 0.5 micron in size.

The alkali metal borates useful herein include the metaborates and tctraborates having from 0.5 to 4 waters of hydration and mixtures of such borates. The preferred compositions are the sodium metaborates having from 1.5 to 2.5 waters of hydration.

In one embodiment, there will be a mixture containing at least one sodium borate and one borate of another alkali metal, preferably potassium. These compositions can be represented by the formula wherein m represents a number greater than and up to 5, x and y are as noted above, and z is a number from 0.2 to 0.75. M represents an alkali metal other than sodium. Preferably M is lithium or potassium, more preferably potassium. The coefficient z preferably represents 0.25 to 0.50.

The above formulae are meant to be empirical and not structural. The exact structure in which the borate exists in the compositions is unknown and varies with different amounts of water of hydration. Numerical values for quantities such as percentage contents will, therefore, be based on the empirical formulae. Where a mixture of sodium and other alkali metal borates is involved, references to borate as a basis for such parameters as content of other components will mean the total borate mixture.

The compositions of this invention will generally have from about 1 to 25 weight percent (including waters of hydration) of the alkali metal borate and preferably from about 5 to weight percent. However, by reducing the amount of oil, concentrates can be obtained having 25 to 60 weight percent of the hydrated alkali metal borate. These concentrates are diluted to the desired borate concentration by addition of oil prior to use.

The Lubricating Oil The oil medium in which the borate is dispersed 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 100F. The fluid medium or oil may be derived from either natural or synthetic sources. Included among the natural hydrocarbonaceous oils are paraffin base, naphthenic base and mixed base oils. Synthetic oils include polymers of various olefms (generally of from two to six carbon atoms), alkylated aromatic hydrocarbons, etc. Nonhydrocarbon oils include polyalkylene oxides (e.g., polyethylene oxide), aromatic ethers, silicones, etc. The preferred media are the hydrocarbonaceous oils, both natural and synthetic. Preferred among the hydrocarbonaceous oils are those having SAE viscosity numbers of SW to W and 20 to 250 (see Guthrie, page 9-1 3), and especially those having SAE viscosity numbers in the range of 75 to 250.

The lubricating oil content of the composition will depend on the concentrations of the other components, for the lubricating oil constitutes the balance of the composition after the concentrations of the alkali metal borate, the dispersant mixture, and any desired additives have been specified. Ordinarily the oil concentration will range from 65 to about 99 weight percent. preferably to about weight percent in the working composition, and from about 10 to about 65 weight percent in the concentrate.

The Dispersant Mixture An important feature of this invention and one which permits the present compositions to function in the presence of water without crystallization is the inclusion of a mixture of dispersants to disperse the alkali metal borate particles in the oil. This dispesant mixture contains two components: a lipophilic anionic suffaceactive agent (or dispersant) containing a Group II metal and sulfur and a lipophilic nonionic surfaceactive agent (or dispersant). (The expression lipophilic" as employed herein is 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 concentrations of the anionic dispersant and the nonionic dispersant in the dispersant mixture will be in the range of 40 to 99.9 weight percent anionic and 60 to 0.1 weight percent nonionic dispersant. Preferably there will be 50 to 95 weight percent anionic and 50 to 5 weight percent nonionic dispersant. The weight ratio of anionic to nonionic dispersant will usually be in the range of 6l:l, perferably 4-] :l.

Anionic Dispersant The lipophilic anionic surface-active agent will be a compound or mixture of compounds each containing a Group I or Group II metal-containing dispersants. The dispersants are salts of Group l and Group II metals in which the anionic portion of the salt contains an oilsolubilizing group. They can be used alone or as mixtures.

The oil-solubilizing group generally has at least nine and usually 12-18 or more carbon atoms, preferably from about 12 to 200 carbon atoms. The oiisolubilizing groups are usually, but not necessarily, hydrocarbyl groups. Hydrocarbyl groups are organic radi cals composed of carbon and hydrogen except for minor, sometimes adventitious, amounts of other elements, such as oxygen, chlorine, etc. The term denotes an aliphatic or aromatic radical, or a radical which is a combination thereof, e. g., aralkyl. Preferably, the hydrocarbyl group is relatively free of aliphatic unsaturation, i.e., ethyleneic and acetylenic, particularly acetylenic. When the hydrocarbyl groups are of low moiecular weight, the average number of hydrocarbyl substituents per dispersant molecule may be greater than I. The hydrocarbyl groups are preferably aliphatic, having preferably from ()2 sites of ethylenic saturation and most preferably O-l site. Hydrocarbyl groups derived from a polyolefin, itself derived from olefins (normally l-olefins) having from two six carbon atoms (ethylene being copolymerized with an olefin or at least three carbon atoms), or from a high molecular weight petroleum-derived hydrocarbon, are preferred, and of these, polyisobutylene is most preferred.

Illustrative sources for the high molecular weight hydrocarbyl substituents are petroleum mineral oil such as naphthenic bright stocks, polypropylene, polyisobutenylene, polyl -butene, copolymers of ethylene and isobutylene, polypropylene and isobutylene, poly lpentene, poly-4-methyl-l-pentene, poly-l-hexene, and poly-3-methylbutylene-1, etc.

The acid reacting functional group can be a variety of well-known groups which include the sulfonic acid group, the phenolic group and the carboxylic acid group. These groups, when in the form of the metal salts, are known as sulfonates, phenates and carboxylates, respectively.

The term sulfonates is intended to encompass the salts of sulfonic acids derived from petroleum products. Such acids are well known in the art. They can be obtained by treating petroleum products with sulfuric acid or sulfur trioxide. The acids thus obtained are known as petroluem sulfonic acids and the salts as petroleum sulfonates. Most of the compounds in the petroleum product which become sulfonated contain an oil-solubilizing group as discussed above. Also included within the meaning of sulfonates are the salts of sulfonic acids of synthetic alkyl aryl compounds. These acids also are prepared by treating an alkyl aryl compound with sulfuric acid or sulfur trioxide. At least one alkyl substituent of the aryl ring is an oil-solubilizing group as discussed above. The acids thus obtained are known as alkyl aryl sulfonic acids and the salts as alkyl aryl sulfonates. The sulfonates wherein the alkyl is straight-chain are the well-known linear alkyl sulfonates (LAS).

The acids obtained by sulfonation are converted to the metal salts by neutralizing with a basic reacting alkali or alkaline earth metal compound to yeild the Group I or Group II metal sulfonates. Generally, the acids are neutralized with an alkali metal base. Alkaline earth metal salts are obtained from the alkali metal salt by metathesis. Alternatively, the sulfonic acid can be neutralized directly withan alkaline earth metal base.

The sulfonates can then be overbased although for purposes of this invention, overbasing is not necessary. Overbased materials and methods of preparing such materials are well known to those skilled in the art. See, for example, LeSuer US. Pat. No. 3,496,105, issued Feb. 17, 1970, particularly cols. 3 and 4.

The term carboxylates encompasses the salts of carboxylic acids. Acids which are useful in the present invention generally contain at least 12 and generally 15 or more carbon atoms, part of which are contained in the oil-solubilizing group discussed above for the sulfonates. Examples include palmitic, steric, myristic, oleic, linoleic, etc., acids. Other carboxylic acids include the cyclic acids. Among these are acids containing an aryl group, i.e., benzene, naphthalene, etc., substituted with an oil-solubilizing radical or radicals having a total of at least 15-18 carbon atoms or more, e.g., alkyl benzoic acid, alkyl naphthoic acid, alkyl salicyclic acid, etc. Preferred are the cyclic acids which contain a cycloaliphatic group substituted with an oil-solubilizing group.

Examples of such acids are dilaurel decahydronaphthalene carboxylic acid, the petroleum naphthenic acids, e.g., alkyl cyclohexane carboxylic acid, etc. The petroleum naphthenic acids are preferred. The salts of this preferred class of cycloaliphatic acids are commonly known as naphthenates.

The term phenates encompasses the salts of oilsoluble phenols. The phenols contain at least 12 and generally 18 or more carbon atoms, part of which is contained in the oil-solubilizing group discussed above for the sulfonates. These phenols can be obtained by alkylating phenol, e.g., reacting phenol with an olefin such as tetrapropylene. The alkylphenols can be further reacted such as by the Mannich" reaction with formaldehyde and an amine, preferably a monoamine to yield higher molecular weight complex compounds. A wide variety of such phenols are available and well known.

The sulfonates, phenates and carboxylates are present in the lubricating oil composition in the form of their Group I and Group II metal salts. Group I metals include lithium, sodium and potassium. Group II metals include strontium, magnesium, calcium and barium, of

which the latter three are preferred. A number of these compounds are described in the aforesaid U.S. Pat. Nos. 3,313,727 and 2,987,476. Particularly preferred are the metal salts of oil-soluble sulfur-containing carbocyclic compounds, including those containing a benzenoid structure and those containing a cycloaliphatic structure. These include the salts of the carbocyclic sulfur acids.

The salts of these acids will be salts metathetical the metals conventionally referred to as Group II metals, i.e., the alkaline earth metals, and usually those of magnesium, strontium, calcium and barium, particularly calcium and magnesium. These salts may be prepared by directly reacting the acid with a Group II metal base or a Group II metal salt. Alternatively, the salt may be prepared by first forming a Group I metal salt of the acid, by neutralizing the acid with a Group I metal base and then converting the Group I metal salt to the Group II metal salt by the methathetical reaction of the Group I metal salt with Group II metal salt or base. Methods for preparing the Group II metal salts by all of these methods are well known in the art.

The oil-soluble carbocyclic sulfur acids whose salts are used herein include the carbocyclic sulfonic acids, sulfamic acids, sulfinic acids, thiosulfonic acids, and the like. These acids can be of either cycloaliphatic of alkyl substituted aromatic configuration. I

A particularly desirable group of oil-soluble salts of carbocyclic sulfur acids comprises the salts of sulfonic acids of various types including cycloaliphatic, hydroaromatic, aromatic, (including both benzene sulfonic acids and naphthalene sulfonic acids) and heterocyclic acids and acidsof mixed types. Examples of salts of suitable acids include the salts of sulfonic acids such as benzene sulfonic acids, toluene sulfonic acids, naphthalene sulfonic acids, triisopropyl naphthalene sulfonic acids, polyamyl naphthalene sulfonic acids, diphenyl sulfonic acids, and the like. Salts of sulfonic acids of aromatic hydrocarbon substituted by a higher alkyl group or groups and in which the alkyl substituent group or groups contain a total of at least about eight, preferably not more than about 22, carbon atoms are of particular interest. Salts of sulfonic acids of phenols which can be monocyclic as well as polycyclic, monohydric as well as polyhydric, and which preferably also contain alkyl and/or aryl substituent groups are also suitable. Examples of this class of salts include the oilsoluble salts of cresol sulfonic acids, xylenol sulfonic acids, naphthol sulfonic acids, catechol sulfonic acids and the like. Salts of sulfonic acids of completely or partly hydrogenated aromatic compounds, for example tetrahydro-naphthalene sulfonic acid, are also suitable.

Particularly preferred, however, because of their wide availability, are salts of the petroleum sulfonic acids, particularly the petroleum sulfonic acids which are obtained by sulfonating various hydrocarbon fractions, such as lubricating oil fractions and extracts rich in aromatics which are obtained by extracting a hydrocarbon oil with a selective solvent, which extracts may, if desired, by alkylated before sulfonation by reacting them with olefins or alkyl chlorides by means of an alkylation catalyst; organic polysulfonic acids such as benzene disulfonic acid, which may or may not be alkylated; and the like. The preferred salts for use in the present invention are those of alkylated aromatic sulfonic acids in which the alkyl radical(s) contain at least about eight carbon atoms, for example, from about eight to about 22 carbon atoms. Exemplary members of this preferred group of sulfonate starting materials are the aliphatic-substituted cyclic sulfonic acids in which the aliphatic substituent(s) contain a total of at least 12 carbon atoms, such as the alkyl aryl sulfonic acids, alkyl cycloaliphatic sulfonic acids and alkylheterocyclic sulfonic acids, and aliphatic sulfonic acids in which the aliphatic radical(s) contain a total of at least 12 carbon atoms. Specific examples of these oilsoluble sulfonic acids include: petroleum sulfonic acids, petrolatum sulfonic acids, mono and polywaxsubstituted naphthalene sulfonic acids, substituted sulfonic acids, such as cetyl-chlorobenzene sulfonic acids, cetylphenol sulfonic acids, and the like, aliphatic sulfonic acids, such as paraffin wax sulfonic acids, unsaturated paraffin wax sulfonic acids, hydroxy-substituted paraffin wax sulfonic acids, etc.; cyclo-aliphatic sulfonic acids, such as petroleum naphthalene sulfonic acids, cetyl-cyclopentyl sulfonic acids, monoand poly wax-substituted cyclohexyl sulfonic acids, and the like.

The term petroleum sulfonic acids is intended to cover all sulfonic acids which are derived directly from petroleum products.

Typical Group [1 metal sulfonates suitable in this composition include the metal sulfonates exemplified as follows: calcium white oil benzene sulfonate, barium white oil benzene sulfonate, magnesium white oil benzene sulfon'ate, calcium dipolypropene benzene sulfonate, barium dipolypropene benzene sulfonate, magnesium dipolypropene benzene sulfonate, calcium mahogany petroleum sulfonate, barium mahogany petroleum sulfonate, magnesium mahogany petroleum sulfonate, calcium triacontyl sulfonate, magnesium triacontyl sulfonate, calcium lauryl sulfonate, barium lauryl sulfonate, magnesium lauryl sulfonate, etc,

Nonionic Dispersant The lipophilic nonionic surface-active agents include those generally referred to as ashless detergents. Preferably the nonionic surfactants have an HLB factor (hydrophilic-lipophilic balance) below about 7 and preferably below about 5. These ash-less detergents are well known and include hydrocarbyl-substituted amines, ariiides an d cyclo-iiriides. The hydrocarbyl group or groups act as the oil-solubilizing group, as mentioned supra.

A principal class of lipophilic nonionic surface-active agents is the N-substituted alkenyl succinimides, derived from alkenyl succinic acidi or anhydride and alkylene polyamines. These compounds are generally considered to have the formula wherein R is a hydrocarbon radical having a molecular 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 two to six, carbon atoms, and x is a number from O to 6, preferably 0 to 3. (The actual reaction product of alkenyl succinic acid or anhydride and alkylene polyamine will comprise a mixture of compounds, including succinamic acids and succinimides. However, it is customary to designate this reaction product as succinimide" of the described formula, since that will be a principal component of the mixture. See US. Pat. Nos. 3,202,678; 3,024,237; and 3,172,892.)

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 derived from an olefin containing from two to five carbon atoms. Thus, the alkenyl radical is obtained by polymerizing an olefin containing from two to five carbon atoms to form a hydrocarbon having a molecular weight ranging from about 400 to 3,000. Such olefins are exemplified by ethylene, propylene, Lbutene, Z-butene, isobutene, and mixtures thereof. Since the methods of polymerizing the olefins to form polymers thereof is immaterial in the formation of the new compound described herein, any of the numerous processes available can be used therefor.

The alkylene amines used to prepare the succinimides are of the formula H-N R lid-N Y wherein y is an integer from 1 to 10, preferably 1-6, A and R are each a substantially hydrocarbon or hydrogen radical, and the alkylene radical Alk is preferably a lower alkylene radical having less than about eight carbon atoms. The alkylene amines include principally methylene amines, ethylene amines, butylene amines, propylene 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-alkylsubstituted piperazines. They are exemplified specifically by: ethylene diamine, triethylene tetramine, propylene diamines, decamethylene diamine, octarnethylene diamine, di(heptamethylene) triamine, tripropylene tetramine, tetraethylene pentamine, trimethylene diamine, pentaethylene hexamine, di(trimethylene)- triamine, Z-heptyl 3-(2-aminopropyl) imidazoline, 4- methyl-imidazoline, l,3bis-(2-aminoethyl) imidazoline, pyrimidine, l-( 2-aminopropyl)piperazine, 1-4- bis(2-aminoethyl)piperazine, and 2-methyll-(2- aminobutyl)piperazine. Higher homologs such as are obtained by condensing two or more of the aboveillustrated alkylene amines likewise are useful.

The ethylene amines are especially useful. They are described in some detail under the heading Ethylene Amines" in Encyclopedia of Chemical Technology, Kirk and Othmer, Vol. 5, pages 898905, (Interscience Publishers, New York, 1950).

The term ethylene amine is used in a generic sense to denote a class of polyamines conforming for the most part to the structure a mcir cnuu) a in which R is a lower alkyl radical of one to four carbon atoms or hydrogen and y is as defined above. Thus it includes, for example, ethylene diamine, diethylene triamine, triethylene tetramine, tetraethylene pentamine, pentaethylene hexamine, 1,2-diaminopropane, N,N-di( l-methyl-2-aminomethyl)amine, etc.

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 anhydride or with a polyolefin and a phosphorus sulfide. The polyolefins are the polymers of monomeric olefins having two to six 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 P 8 P 8 P 5 P 5 and related materials. Of these, P 8 (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 withvinyl pyrrolidone, acrylimide or methacrylimide.

The mixture of dispersants of lipophilic surfaceactive agents will generally be present in from about 0.25 to 5 weight percent, more usually from about 0.5 to 3 weight percent, of the composition. The actual amount of dispersant mixture required will vary from the particular mixture used and the total amount of borate in the oil. Generally about 0.05 to 0.5, more usually about 0.1 to 0.3, part by weight of mixture 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 mixture concentration will be used with the upper ranges of the alkali metal borate concentration.

Additives Other materials may also be presentas 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, foam inhibitors, viscosity index improvers, pour point depressants, etc. Usually these will be in the range from about 0.01 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.

Preparation of the Lubricants The novel compositions of this invention are prepared by dehydrating a water-and-oil emulsion of an aqueous solution of an alkali metal borate, 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, nonpolar oil medium an alkali metal borate, water, and the desired emulsifier mixture, vigorously agitating to provide a dispersion of the water in the oil and then heating at a temperature and for a time which provides the desired degree of dehydration of the alkali metal borate. The borate may conveniently be added as an aqueous solution to the oil.

The temperature at which the emulsion is heated will be generally at least 250F., more usually at least 290F. Temperatures of up to 450F, may be used, although it is preferred that the temperature not exceed 350F. Lower temperatures may be used at reduced pressures. However, the process is conveniently carried out at atmospheric pressures and at temperatures in the range described.

The time of reaction will depend on the degree of de hydration, the amount of water present and the temperature. Time is not critical, and will be determined for the most part by the variables mentioned. The water initially present will be sufficient to dissolve the alkali metal borate, but should not be in such excess as to make dehydration difficult.

Performance The following data will illustrate the unexpectedly superior nature of the compositions of this invention as compared to those of the prior art. The data in the Table illustrate the EP characteristics and water tolerance of the present compositions. Each sample is prepared for the test described in the Table by dispersing an aqueous solution of sodium borate in a paraffinic SAE mhydrocarbon oil by means of the single dispersant or dispersant mixture noted in the Table. Also present in most cases is a small amount of a silicone antifoaming agent. The mixture is dehydrated at the temperature noted until a water content in the range of about 1.5 to 2.5 mols of water per mol of borate is obtained.

The tendency of the test mixture to crystallize is determined by either of two comparable tests. In the first test, water is added to an oil containing 5 weight percent borate solids until the water content is 10 percent. The mixture is then heated up to 230$F. until only 2 percent water remains in the oil. The partially dehy drated solution is checked daily for quantity and hardness of any deposits. In the second test, a modification of Coordinating Research Counsel L-33 Test is used. In this test, 2 k pints of test lubricant are placed in a bench-mounted automotive differential assembly and water added. The differential assembly is then turned while heating and subsequently subjected to additional heating without turning. In the modification of the test used herein, water in an amount of about cc. (rather than 28.3 cc.) is added and the differential assembly is turned continuously during heating. Since both of the tests produce comparable results for the purposes of this invention, there is no designation in the Table of the particular test used to derive the crystallization data for each one.

The EP characteristics of the composition are deter mined by using the composition as the test lubricant in the well-known Four-Ball test. This test is described in Boner, pages 222-224. In the test three V; inch steel atmosphere at the lubrication point is called stray mist. Stray mist is undesirable not only because it represents lubricant unused and wasted, but also because it represents severe atmospheric contamination and balls of the type commonly used in ball bearings are can have an adverse effect on the health of workers explaced in a Steel cup and clamped in fixed position. A posed to the contaminated atmosphere. The lubricants fourth ball of the same type is held rigidly on the end of this invention effectively suppress the formation of of a shaft which rotates about a vertical axis. The balls stray mist. are immersed in the test lubricant and the fourth ball The compositions of this invention also have low dieis forced against the other three under a measured load. seling characteristics when employed in pneumatic The fourth ball is then rotated at a designated speed for tools. These tools are lubricated by injecting a mist lua fixed period. At the end of this period the wear scar bricant into the inlet air stream of the pneumatic dediameters on the three fixed balls are measured and avvice. The lubricant contacts the various internal parts eraged, and the average scar size reported as the result f the tool and forms a continuous protection film on of the test. The smaller the wear scar, the better the EP h exposed part5, Di ii Occurs h h temperacharacteristics of the test lubricant. In order to be COnture of the compressed air used to drive the pneumatic sidered a satisfactory EP lubricant, the lubricant must device exceeds the autogenous ignition temperature of not have a four-ball scar of greater than 0.5 mm, and the mist oil and spontaneous combustion results. Diepreferably not greater than 0.45 mm. seling not only results in high-pressure surges, but also TABLE Borate Content, Dispersant Mixture Wt.% as Dehydration Anionic Nonionic Four-Ball Run No. NaBO .H O Temp, F. Type Wt.% Type** Wt7r Scar. mm. Crystallization l 5 300 A 2 None 0.39 yes 2 5 300 B I None 05?. yes 3 5 300 A/C 1.5/0.5 None 0.37 yes 4 5 300 C 2 None 0.70 no 5 S 300 None L 0.5 0.55 no 6 5 300 A 0.5 K 0.5 0.45 no 7 5 300 A 0.75 L 0.25 0.49 no 8 5 300 A 0.75 M 0.25 0.39 no 9 5 300 A 0.75 N 0.25 0.41 no 10 4 300 A 0.75 P 0.25 0.36 no ll 5 300 B 0.75 L 0.25 0.38 no 12 2.5 290 A 0.37 L 0.12 0.40 no 13 5 300 A 0.65 L 0.35 0.44 no Anionic dispersants:

Az'Calcium petroleum sulfonate, 1.67% Ca.

B: Magnesium petroleum sulfonate. l.4l% Mg.

C: Barium polyisobulenyl phosphonate. commercially available as AMOCO l2]. "Nonionic dispcrsants:

K: Alkenyl substituted succinimide prepared by reacting polyisobutenyl (MWE9S0) succinic anhydride (PIES/kl with triethylcnetetrarnrne ITETA) in a TETA:PIBSA mol ratio ofOJS; 2% N.

L: Succinimide similar to K but using tetraethylenepentamine (TEPA) in a TEPAzPIBSA mol ratio of 0.87; 2.l% N

M: Succinimide similar to K, but having a TETAzPlBSA mol ratio of 0.5; 1.08% N.

N: Succinimide similar to L, but having PIBSA derived from a poly-isobuiene of MWEMO and TETAPIBSA ratio of 0.5; L N.

P: Reaction product of polyisobutene (MW QSO), P,S,. and pentaerythritol.

The data in the Table show clearly that use of either type of dispersant alone will not produce the waterresistant, superior lubricants of this invention. When a single type of dispersant is used, it is found that the lubricant either is subject to crystallization or has insufficient antiwear character to pass the standard four-ball test. Only with the synergistic combination of the two types of dispersants can the superior borate-containing compositions of this invention be obtained.

The compositions of this invention are also useful as mist lubricants. In a mist lubrication system, the lubricant is atomized in a mist generator and carried through conduits by an air stream. The lubricant droplets are coalesced and collected at the lubrication site. Such systems permit simultaneous lubrication of several remote and inaccessible lubrication points from a central lubricant reservoir.

In order to be suitable for use in a mist oil system, the lubricant must not only be readily atomized (either with or without heating) but must also be readily coalesced and collected at the lubrication point. Lubricant which remains in mist form and disperses into the causes internal temperatures to greatly increase. The increased temperatures in turn result in an ensuing loss of protective oil films and binding of the metallic parts. With the compositions of this invention, dieseling is greatly diminished, and in many instances eliminated, under normal operating conditions.

The advantages associated with the compositions of this invention can be realized in any oil lubricating system where high pressures or load are encountered. Exemplary systems include gear sets found in automotive transmissions and transmission differentials, high load bearings, pneumatic tools such as jack-hammers, sinkers, stoppers, drifters, downhole drills, etc., gas compressors, hydraulic devices wherein extreme pressures are encountered, and metal working such as drilling, cutting, lapping, grinding, honing, etc.

It will be evident to those skilled in the art from the above description that there are numerous embodiments within the scope and spirit of this invention. It is intended that these embodiments be encompassed within the invention, even though they may not be set forth specifically as examples above.

What is claimed is:

1. A lubricant comprising an oil of lubricating viscosity having dispersed therein from 1 to 60 weight percent, based on the entire composition, of amorphous particles of less than one micron in size of a hydrated alkali metal borate having 0.5 to 4 waters of hydration, said borate being dispersed in said oil by means of a dispersant mixture consisting of 40 to 99 weight percent of a lipophilic anionic surface-active agent which is an alkaline earth metal sulfonate and from 0.1 to 60 weight percent of a lipophilic nonionic surface-active agent which is a succinimide derived from alkenyl succinic acid or anhydride and alkylene polyamines.

2. The composition of claim 1 wherein said alkali metal borate is a sodium borate and is present in a concentration of 1 to 25 weight percent and said dispersant mixture is present in a concentration of 0.5 to 3 weight percent.

3. The composition of claim 2 wherein said sodium borate is present in a concentration of to weight percent and said dispersant mixture is present in a concentration of 0.5 to 3 weight percent.

4. The composition of claim 1 wherein said dispersant mixture consists of 50 to 95 weight percent of said lipophilic anionic surface-active agent and 50 to 5 weight percent of said lipophilic nonionic surfaceactive agent.

5. The composition of claim 4 wherein said lipophilic anionic surface-active agent and said lipophilic nonionic surface-active agent are present in a weight ratio in the range of 6-1:1, respectively.

6. The composition of claim 5, wherein said weight ratio is in the range of 4-l:l.

7. A process for making a lubricating oil which comprises:

admixing (I) an oil of lubricating viscosity, (2) from 1 to 60 weight percent of an alkali metal borate, based on the weight of said oil, (3) a sufficient amount of water to dissolve said alkali metal borate, and (4) from 0.05 to 3 weight percent of a dispersant mixture consisting of 40 to 99.9 weigh percent of a lipophilic anionic surface-active agent which is an alkaline earth metal sulfonate and 0.1 to 60 weight percent of a lipophilic nonionic surface-active agent which is a succinimide derived from alkenyl succinic acid or anhydride and alkylene polyamines;

vigorously agitating the admixture to provide a stable emulsion of water-in-oil; and heating the emulsified mixture to a temperature greater than 250F at substantially atmospheric pressure to remove free water from said mixture.

8. The process defined in claim 7 wherein said alkali metal borate is sodium borate.

9. The process defined in claim 8 wherein said anionic surface-active agent is a calcium of barium petroleum sulfonate.

10. The composition defined in claim 1 wherein said alkali metal borate is sodium borate and said lipophilic surface-active agent is calcium petroleum sulfonate.

11. The composition defined in claim 10 wherein the weight ratio of said anionic lipophilic surface-active agent to nonionic lipophilic surface-active agent is from 6-l:l.

Claims (11)

1. A LUBRICANT COMPRISING AN OIL OF LUBRICATING VISCOSITY HAVING DISPERSED THREIN FROM 1 TO 60 WEIGHT PERCENT, BASED ON THE ENTIRE COMPOSITIONS, OF AMORPHOUS PARTICLES OF LESS THAN ONE MICRON IN SIZE OF A HYDRATED ALKALI METAL BORATE HAVING 0.5 TO 4 WATERS OF HYDRATION, SAID BORATE BEING DISPERSED IN SAID OIL BY MEANS OF A DISPERSANT MIXTURE CONSISTING OF 40 TO 99 WEIGHT PERCENT OF A LIPOPHILIC ANIONIC SURFACE-ACTIVE AGENT WHICH IS AN ALKALINE EARTH METAL SULFONATE AND FROM 0.1 TO 60 WEIGHT PERCENT OF A LIPOPHILIC NONIONIC SURFACE-ACTIVE AGENT WHICH IS A SUCCINIMIDE DERIVED FROM ALKENYL SUCCINI ACID OR ANHYDRIDE AND ALKYLENE POLYAMINES.

2. The composition of claim 1 wherein said alkali metal borate is a sodium borate and is present in a concentration of 1 to 25 weight percent and said dispersant mixture is present in a concentration of 0.5 to 3 weight percent.

3. The composition of claim 2 wherein said sodium borate is present in a concentration of 5 to 15 weight percent and said dispersant mixture is present in a concentration of 0.5 to 3 weight percent.

4. The composition of claim 1 wherein said dispersant mixture consists of 50 to 95 weight percent of said lipophilic anionic surface-active agent and 50 to 5 weight percent of said lipophilic nonionic surface-active agent.

5. The composition of claim 4 wherein said lipophilic anionic surface-active agent and said lipophilic nonionic surface-active agent are present in a weight ratio in the range of 6-1:1, respectively.

6. The composition of claim 5, wherein said weight ratio is in the range of 4-1:1.

7. A process for making a lubricating oil which comprises: admixing (1) an oil of lubricating viscosity, (2) from 1 to 60 weight percent of an alkali metal borate, based on the weight of said oil, (3) a sufficient amount of water to dissolve said alkali metal borate, and (4) from 0.05 to 3 weight percent of a dispersant mixture consisting of 40 to 99.9 weigh percent of a lipophilic anionic surface-active agent which is an alkaline earth metal sulfonate and 0.1 to 60 weight percent of a lipophilic nonionic surface-active agent which is a succinimide derived from alkenyl succinic acid or anhydride and alkylene polyamines; vigorously agitating the admixture to provide a stable emulsion of water-in-oil; and heating the emulsified mixture to a temperature greater than 250*F at substantially atmospheric pressure to remove free water from said mixture.

8. The process defined in claim 7 wherein said alkali metal borate is sodium borate.

9. The process defined in claim 8 wherein said anionic surface-active agent is a calcium of barium petroleum sulfonate.

10. The composition defined in claim 1 wherein said alkali metal borate is sodium borate and said lipophilic surface-active agent is calcium petroleum sulfonate.

11. The composition defined in claim 10 wherein the weight ratio of said anionic lipophilic surface-active agent to nonionic lipophilic surface-active agent is from 6-1:1.