Lubricant composition comprising alkali metal borate and polyalkylene succinic anhydride

Abstract

Disclosed are lubricant compositions comprising a dispersed hydrated alkali metal borate and a polyalkylene succinic anhydride, a mixture of polyalkylene succinic anhydrides or derivatives thereof. Also disclosed are methods for improving the water tolerance of a lubricant composition comprising an alkali metal borate. Such methods employ compositions comprising a dispersed hydrated alkali metal borate and a polyalkylene succinic anhydride, a mixture of polyalkylene succinic anhydrides or derivatives thereof.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of U.S. patent application Ser. No. 09/292,627, filed Apr. 15, 1999, which application is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

[0002] This invention is directed, in part, to novel lubricant compositions. These compositions comprise an alkali metal borate and a polyalkylene succinic anhydride, a mixture of polyalkylene succinic anhydrides or derivatives thereof. Surprisingly, these compositions have improved compatibility, extreme pressure properties and/or water tolerance over similar compositions comprising a dispersant other than a polyalkylene succinic anhydride or derivatives thereof.

[0003] This invention is also directed, in part, to methods for improving the water tolerance of a lubricant composition comprising an alkali metal borate. Such methods employ compositions comprising an alkali metal borate and a polyalkylene succinic anhydride, a mixture of polyalkylene succinic anhydrides or derivatives thereof.

[0004] References

[0005] The following references are cited in this application as superscript numbers:

[0006] 1 Peeler, U.S. Pat. No. 3,313,727, Alkali Metal Borate E. P. Lubricants, issued Apr. 11, 1967

[0007] 2 Adams, U.S. Pat. No.3,912,643, Lubricant Containing Neutralized Alkali Metal Borates, issued Oct. 14, 1975

[0008] 3 Sims, U.S. Pat. No. 3,819,521, Lubricant Containing Dispersed Borate and a Polyol, issued Jun. 25, 1974

[0009] 4 Adams, U.S. Pat. No. 3,853,772, Lubricant Containing Alkali Metal Borate Dispersed with a Mixture of Dispersants, issued Dec. 10, 1974

[0010] 5 Adams, U.S. Pat. No. 3,997,454, Lubricant Containing Potassium Borate, issued Dec. 14, 1976

[0011] 6 Adams, U.S. Pat. No. 4,089,790, Synergistic Combinations of Hydrated Potassium Borate, Antiwear Agents, and Organic Sulfide Antioxidants, issued May 16, 1978

[0012] 7 Adams, U.S. Pat. No. 4,163,729, Synergistic Combinations of Hydrated Potassium Borate, Antiwear Agents, and Organic Sulfide Antioxidants, issued Aug. 7, 1979

[0013] 8 Frost, U.S. Pat. No. 4,263,155, Lubricant Composition Containing an Alkali Metal Borate and a Sulfur-Containing Polyhydroxy Compound, U.S. Pat. No. 5,461,184, issued Oct. 24, 1995

[0014] 9 Frost, U.S. Pat. No.4,401,580, Lubricant Composition Containing an Alkali Metal Borate and an Ester-Polyol Compound, issued Aug. 30, 1983

[0015] 10 Frost, U.S. Pat. No. 4,472,288, Lubricant Composition Containing an Alkali Metal Borate and an Oil-Soluble Amine Salt of a Phosphorus Compound, issued Sep. 18, 1984

[0016] 11 Clark, U.S. Pat. No.4,584,873, Automotive Friction Reducing Composition, issued Aug. 13, 1985

[0017] 12 Brewster, U.S. Pat. No. 3,489,619, Heat Transfer and Quench Oil, issued Jan. 13, 1970

[0018] All of the above references are herein incorporated by reference in their entirety to the same extent as if each individual publication or patent was specifically and individually indicated to be incorporated by reference in its entirety.

[0019] State of the Art

[0020] High load conditions often occur in gear sets such as those used in automobile transmissions and differentials, pneumatic tools, gas compressors, centrifuges, high-pressure hydraulic systems, metal workings and similar devices as well as in many types of bearings. When employed in such environments, it is conventional to add an extreme-pressure agent to the lubricant composition and, in this regard, alkali metal borates are well known extreme-pressure agents for such compositions.1-12 1 Peeler, U.S. Pat. No. 3,313,727, Alkali Metal Borate E. P. Lubricants, issued Apr. 11, 1967 2 Adams, U.S. Pat. No.3,912,643, Lubricant Containing Neutralized Alkali Metal Borates, issued Oct. 14, 1975 3 Sims, U.S. Pat. No. 3,819,521, Lubricant Containing Dispersed Borate and a Polyol, issued Jun. 25, 1974 4 Adams, U.S. Pat. No. 3,853,772, Lubricant Containing Alkali Metal Borate Dispersed with a Mixture of Dispersants, issued Dec. 10, 1974 5 Adams, U.S. Pat. No. 3,997,454, Lubricant Containing Potassium Borate, issued Dec. 14, 1976 6 Adams, U.S. Pat. No. 4,089,790, Synergistic Combinations of Hydrated Potassium Borate, Antiwear Agents, and Organic Sulfide Antioxidants, issued May 16, 1978 7 Adams, U.S. Pat. No. 4,163,729, Synergistic Combinations of Hydrated Potassium Borate, Antiwear Agents, and Organic Sulfide Antioxidants, issued Aug. 7, 1979 8 Frost, U.S. Pat. No. 4,263,155, Lubricant Composition Containing an Alkali Metal Borate and a Sulfur-Containing Polyhydroxy Compound, U.S. Pat. No. 5,461,184, issued Oct. 24, 1995 9 Frost, U.S. Pat. No.4,401,580, Lubricant Composition Containing an Alkali Metal Borate and an Ester-Polyol Compound, issued Aug. 30, 1983 10 Frost, U.S. Pat. No. 4,472,288, Lubricant Composition Containing an Alkali Metal Borate and an Oil-Soluble Amine Salt of a Phosphorus Compound, issued Sep. 18, 1984 11 Clark, U.S. Pat. No.4,584,873, Automotive Friction Reducing Composition, issued Aug. 13, 1985 12 Brewster, U.S. Pat. No. 3,489,619, Heat Transfer and Quench Oil, issued Jan. 13, 1970

[0021] Because the alkali metal borate is insoluble in lubricant oil media, it is conventional to include a dispersant in such compositions in order to facilitate the formation of a homogenous dispersion. Examples of dispersants include lipophilic surface-active agents such as alkenyl succinimides or other nitrogen containing dispersants.1-4 It is also conventional to employ the alkali metal borate at particle sizes of less than 1 micron in order to facilitate the formation of the homogenous dispersion.11 1 Peeler, U.S. Pat. No. 3,313,727, Alkali Metal Borate E. P. Lubricants, issued Apr. 11, 1967 2 Adams, U.S. Pat. No.3,912,643, Lubricant Containing Neutralized Alkali Metal Borates, issued Oct. 14, 1975 3 Sims, U.S. Pat. No. 3,819,521, Lubricant Containing Dispersed Borate and a Polyol, issued Jun. 25, 1974 4 Adams, U.S. Pat. No. 3,853,772, Lubricant Containing Alkali Metal Borate Dispersed with a Mixture of Dispersants, issued Dec. 10, 1974 11 Clark, U.S. Pat. No.4,584,873, Automotive Friction Reducing Composition, issued Aug. 13, 1985

[0022] The use of alkali metal borates in lubricant compositions is complicated by the presence of water in the environment where the composition is employed. Conventional preparation methods remove essentially all the water from the media12. However, when the presence of water exceeds a threshold concentration in the lubricant composition, the borate crystallizes out of the composition and forms hard granules. These granules cause severe noise in the lubricated systems and can severely damage the gears or bearings themselves as well as leading to seal leakage.10 Further, borate lost by crystallization decreases the extreme pressure properties of the lubricant composition. 10 Frost, U.S. Pat. No. 4,472,288, Lubricant Composition Containing an Alkali Metal Borate and an Oil-Soluble Amine Salt of a Phosphorus Compound, issued Sep. 18, 1984 12 Brewster, U.S. Pat. No. 3,489,619, Heat Transfer and Quench Oil, issued Jan. 13, 1970

[0023] On the other hand, lubricant compositions employing alkali metal borates are often employed in environments where water is invariably present.

[0024] In view of the above, enhanced water tolerance of lubricant compositions comprising an alkali metal borate would be particularly beneficial.

SUMMARY OF THE INVENTION

[0025] This invention is directed to the novel and unexpected discovery that enhanced water tolerance and lubricant oil compatibility for alkali metal borates can be achieved by employing a dispersant selected from the group consisting of a polyalkylene succinic anhydride, a non-nitrogen containing derivative of the polyalkylene succinic anhydride and mixtures of polyalkylene succinic anhydrides, mixtures of non-nitrogen containing derivatives of the polyalkylene succinic anhydride or mixtures of both polyalkylene succinic anhydrides and non-nitrogen containing derivatives of the polyalkylene succinic anhydride.

[0026] Accordingly, in one of its composition aspects, this invention is directed to a lubricant composition which comprises a base oil of lubricating viscosity, a dispersed hydrated alkali metal borate, and a dispersant that is selected from the group consisting of a polyalkylene succinic anhydride, a non-nitrogen containing derivative of the polyalkylene succinic anhydride, mixtures of polyalkylene succinic anhydrides, mixtures of non-nitrogen containing derivatives of the polyalkylene succinic anhydride and mixtures of both polyalkylene succinic anhydrides and non-nitrogen containing derivatives of the polyalkylene succinic anhydride.

[0027] In addition to improved water tolerance, it has now been discovered that the use of such dispersants in these lubricant compositions gives far superior compatibility than other possible dispersants.

[0028] Preferably, the dispersed hydrated alkali metal borate is a dispersed hydrated sodium borate. A preferred dispersed hydrated sodium borate has a sodium to boron metal ratio of from about 1:2.5 to about 1:4.5 and more preferably about 1:3.

[0029] Preferably, the hydrated alkali metal borate contains small amounts of a water soluble oxo anion. Only from 0.001 moles to 0.11 moles of water soluble oxo anion should be present per mole of boron. This water-soluble oxo anion can include nitrate, sulfate, carbonate, phosphate, pyrophosphate, silicate, aluminate, germanate, stannate, zincate, plumbate, titanate, molybdate, tungstate, vanadate, niobate, tantalate, uranates, or can include the isopolymolybdates and isopolytungstates, or the heteropolymolybdates and heteropolytungstates, or mixtures thereof.

[0030] Preferably, the dispersant is a polyalkylene succinic anhydride or a mixture of polyalkylene succinic anhydrides. More preferably, the polyalkylene succinic anhydride is a polyisobutenyl succinic anhydride. In one preferred embodiment, the polyalkylene succinic anhydride is a polyisobutenyl succinic anhydride having a number average molecular weight of at least 500, more preferably at least 900 and still more preferably from at least about 900 to about 3000.

[0031] Preferably, the dispersed hydrated alkali metal borate is present in a ratio of at least 2:1 relative to the polyalkylene succinic anhydride dispersant. More preferably the ratio of dispersed hydrated alkali metal borate to dispersant is from 2:1 up to 10:1. Most preferably the ratio is at least 5:2. In a preferred embodiment, the dispersed hydrated alkali metal borate is a hydrated sodium metal borate, preferably a NaB3 condensed borate and the polyalkylene succinic anhydride is a polyisobutenyl succinic anhydride.

[0032] In another preferred embodiment, a mixture of polyalkylene succinic anhydrides are employed. In this embodiment, the mixture preferably comprises a low molecular weight polyalkylene succinic anhydride component and a high molecular weight polyalkylene succinic anhydride component. More preferably, the low molecular weight component has a number average molecular weight of from about 500 to below 1000 and the high molecular weight component has a number average molecular weight of from 1000 to about 3000. Still more preferably, both the low and high molecular weight components are polyisobutenyl succinic anhydrides.

[0033] Preferably, the lubricant composition also comprises a detergent, such as a metal sulfonate. A preferred metal sulfonate is a calcium alkyl aromatic sulfonate.

[0034] This invention is also directed to methods for enhancing the water tolerance of lubricant compositions comprising alkali metal borate. Accordingly, in one of its method aspects, this invention is directed to a method for enhancing the water tolerance of lubricant compositions comprising alkali metal borate which method comprises adding an anti-wear effective amount of a dispersed hydrated alkali metal borate to a base oil of lubricating viscosity in combination with a dispersant effective amount of a dispersant selected from the group consisting of a polyalkylene succinic anhydride, a non-nitrogen containing derivative of the polyalkylene succinic anhydride, mixtures of polyalkylene succinic anhydrides, mixtures of non-nitrogen containing derivatives of the polyalkylene succinic anhydride and mixtures of both polyalkylene succinic anhydrides and non-nitrogen containing derivatives of the polyalkylene succinic anhydride.

[0035] This invention is still further directed to methods for the preparation of such lubricant compositions. Accordingly, in another of its method aspects, this invention is directed to a method for preparing a lubricant composition comprising a base oil of lubricating viscosity, a dispersed hydrated alkali metal borate, and a polyalkylene succinic dispersant that is selected from the group consisting of a polyalkylene succinic anhydride, a non-nitrogen containing derivative of the polyalkylene succinic anhydride, mixtures of polyalkylene succinic anhydrides, mixtures of non-nitrogen containing derivatives of the polyalkylene succinic anhydride and mixtures of both polyalkylene succinic anhydrides and non-nitrogen containing derivatives of the polyalkylene succinic anhydride which method comprises:

[0036] mixing, under agitation, (1) an aqueous solution of boric acid and alkali metal hydroxide, and (2) a diluent oil containing the polyalkylene succinic dispersant (and any metal sulfonate); and then heating the mixture to remove the water. Preferably the lubricant composition comprises a hydrated sodium borate and, more preferably, the hydrated sodium borate has a hydroxyl to boron ratio (OH:B) of from about 0.8:1 to 1.6:1, preferably from about 0.9:1 to 1.50:1, and more preferably from about 1.00:1 to 1.40: 1, as disclosed in concurrently filed U.S. application Ser. No. ___,___ (Attorney Docket No. 005950-699, T-5928) and entitled “Dispersed Hydrated Sodium Borate Compositions Having Improved Properties In Lubricating Oil Compositions” which is incorporated herein by reference in its entirety.

DETAILED DESCRIPTION OF THE INVENTION

[0037] This invention is directed, in part, to novel lubricant compositions comprising a base oil of lubricating viscosity, a dispersed hydrated alkali metal borate and a dispersant selected from the group consisting of a polyalkylene succinic anhydride, a non-nitrogen containing derivative of the polyalkylene succinic anhydride, mixtures of polyalkylene succinic anhydrides, mixtures of non-nitrogen containing derivatives of the polyalkylene succinic anhydride and mixtures of both polyalkylene succinic anhydrides and non-nitrogen containing derivatives of the polyalkylene succinic anhydride.

[0038] Each of these components in the claimed composition will be defined herein.

[0039] The Dispersed Hydrated Alkali Metal Borate

[0040] Hydrated alkali metal borates are well known in the art. Representative patents disclosing suitable borates and methods of manufacture include: U.S. Pat. Nos. 3,313,727; 3,819,521; 3,853,772; 3,912,643; 3,997,454; and 4,089,790.1-6 1 Peeler, U.S. Pat. No. 3,313,727, Alkali Metal Borate E. P. Lubricants, issued Apr. 11, 1967 2 Adams, U.S. Pat. No.3,912,643, Lubricant Containing Neutralized Alkali Metal Borates, issued Oct. 14, 1975 3 Sims, U.S. Pat. No. 3,819,521, Lubricant Containing Dispersed Borate and a Polyol, issued Jun. 25, 1974 4 Adams, U.S. Pat. No. 3,853,772, Lubricant Containing Alkali Metal Borate Dispersed with a Mixture of Dispersants, issued Dec. 10, 1974 5 Adams, U.S. Pat. No. 3,997,454, Lubricant Containing Potassium Borate, issued Dec. 14, 1976 6 Adams, U.S. Pat. No. 4,089,790, Synergistic Combinations of Hydrated Potassium Borate, Antiwear Agents, and Organic Sulfide Antioxidants, issued May 16, 1978

[0041] The hydrated alkali metal borates can be represented by the following formula:

M2O•mB2O3•nH2O

[0042] where M is sodium or potassium, m is a number preferably from 2.5 to 4.5 (both whole and fractional), and n is a number preferably from 1.0 to 4.8. Preferred hydrated alkali metal borates are hydrated potassium borates and more preferably the hydrated sodium borates because of their improved water tolerance. Most preferred are the hydrated sodium borates having a sodium-to-boron ratio of about 1:3. In another of its preferred embodiment, the hydrated borate particles generally have a mean particle size of less than 1 micron.

[0043] The hydrated alkali metal borates will generally comprise about 10 to 75 weight percent, preferably 25 to 50 weight percent, more preferably about 35 to 40 weight percent of the lubricant composition. (Unless otherwise stated, all percentages are in weight percent.) The hydrated alkali metal borate dispersions have been found to be reactive in the presence of water. The presence of water has been found to alter the size, shape, and composition of the dispersed, amorphous borate particles, which have the overall composition MB3O5H2O, to ultimately produce a number of crystalline borates which have the compositions MB3O5•3H2O, MB5O8•4H2O, M2B5O8(OH)•2H2O, M2B4O7•4H2O, and the like. These crystals generally separate out from the oil phase to form deposits in the oil, and can damage the elastomer seals in various engine parts and cause leakage.

[0044] We have also found that sodium borates give better water tolerance and compatibility than potassium borates.

[0045] Preferably, the hydrated alkali metal borates contain small amounts of a water soluble oxo anion. Only from 0.001 moles to 0.11 moles of water soluble oxo anion should be present per mole of boron. This water-soluble oxo anion can include nitrate, sulfate, carbonate, phosphate, pyrophosphate, silicate, aluminate, germanate, stannate, zincate, plumbate, titanate, molybdate, tungstate, vanadate, niobate, tantalate, uranates, or can include the isopolymolybdates and isopolytungstates, or the heteropolymolybdates and heteropolytungstates, or mixtures thereof.

[0046] The presence of small amounts of water soluble oxo anions in the alkali metal borates is thought to improve the water tolerance of the alkali metal borates by disrupting the crystal structure of the hydrolysis products. This results in a lower tendency to form crystals or in a reduced rate of crystallization.

[0047] The Polyalkylene Sussinic Dispersant

[0048] The dispersant can be a polyalkylene succinic anhydride or a non-nitrogen containing derivative of the polyalkylene succinic anhydride and is preferably selected from the group consisting of a polyalkylene succinic anhydride, a non-nitrogen containing derivative of the polyalkylene succinic anhydride, mixtures of polyalkylene succinic anhydrides, mixtures of non-nitrogen containing derivatives of the polyalkylene succinic anhydride and mixtures of both polyalkylene succinic anhydrides and non-nitrogen containing derivatives of the polyalkylene succinic anhydride. Non-nitrogen containing derivatives of polyalkylene succinic anhydrides preferably include, succinic acids, Group I and/or Group II mono- or di-metal salts of succinic acids, succinate esters formed by the reaction of a polyalkylene succinic anhydride, acid chloride, or other derivative with an alcohol and the like.

[0049] The polyalkylene succinic anhydride is preferably a polyisobutenyl succinic anhydride. In one preferred embodiment, the polyalkylene succinic anhydride is a polyisobutenyl succinic anhydride having a number average molecular weight of at least 500, more preferably at least 900-3000 and still more preferably from at least about 900 to about 2300.

[0050] In another preferred embodiment, a mixture of polyalkylene succinic anhydrides are employed. In this embodiment, the mixture preferably comprises a low molecular weight polyalkylene succinic anhydride component and a high molecular weight polyalkylene succinic anhydride component. More preferably, the low molecular weight component has a number average molecular weight of from about 500 to below 1000 and the high molecular weight component has a number average molecular weight of from 1000 to about 3000. Still more preferably, both the low and high molecular weight components are polyisobutenyl succinic anhydrides.

[0051] Preferably, the dispersed hydrated alkali metal borate is employed in a weight ratio of at least 2:1 relative to the polyalkylene succinic anhydride dispersant, while being more preferably in the range of 2:1 to 10:1. Most preferably, the ratio is at least 5:2. In a preferred embodiment, mixtures as defined above of the polyalkylene succinic anhydrides are employed.

[0052] The polyalkylene succinic anhydride is the reaction product of a polyalkylene (preferably polyisobutene) with maleic anhydride. One can use conventional polyisobutene, or high methylvinylidene polyisobutene in the preparation of such polyalkylene succinic anhydrides. One can use thermal, chlorination, free radical, acid catalyzed, or any other process in this preparation. Examples of suitable polyalkylene succinic anhydrides are thermal PIBSA (polyisobutenyl succinic anhydride) described in U.S. Pat. No. 3,361,673; chlorination PIBSA described in U.S. Pat. No. 3,172,892; a mixture of thermal and chlorination PIBSA described in U.S. Pat. No. 3,912,764; high succinic ratio PIBSA described in U.S. Pat. No. 4,234,435; PolyPIBSA described in U.S. Pat. Nos. 5,112,507 and 5,175,225; high succinic ratio PolyPIBSA described in U.S. Pat. Nos. 5,565,528 and 5,616,668; free radical PIBSA described in U.S. Pat. Nos. 5,286,799, 5,319,030, and 5,625,004; PIBSA made from high methylvinylidene polybutene described in U.S. Pat. Nos. 4,152,499, 5,137,978, and 5,137,980; high succinic ratio PIBSA made from high methylvinylidene polybutene described in European Patent Application Publication No. EP 355 895; terpolymer PIBSA described in U.S. Pat. No. 5,792,729; sulfonic acid PIBSA described in U.S. Pat. No. 5,777,025 and European Patent Application Publication No. EP 542 380; and purified PIBSA described in U.S. Pat. No. 5,523,417 and European Patent Application Publication No. EP 602 863. The disclosures of each of these documents is incorporated herein by reference in their entirety.

[0053] The number average molecular weight of the polyalkylene tail in the polyalkylene succinic anhydride should be from about 300 to about 5000. This should be compatible with the previous ranges given before with the particular molecular weight depending on dispersant or mixture of dispersants to be employed. Preferably, the polyalkylene succinic anhydride component comprises from 2 to 40 weight percent, more preferably 10 to 15 weight percent of the weight of the lubricant composition.

[0054] Most preferable is the case where the polyalkylene succinic anhydride component is a polyisobutenyl succinic anhydride.

[0055] This invention is based, in part, on the discovery that the presently employed non-nitrogen containing polyalkylene succinic anhydrides and derivatives thereof provide significantly better water tolerance and compatibility than the use of conventional polyalkylene succinimides, such as polyisobutenyl succinimides, in lubricating compositions comprising an alkali metal borate. It has also been found that a mixture of polyalkylene succinic anhydrides can be effectively employed. The mixture preferably comprises a low molecular weight polyalkylene succinic anhydride component and a high molecular weight polyalkylene succinic anhydride component. Alternatively, various molecular weights polyalkylene succinic anhydride components can be combined as a dispersant.

[0056] The Detergent

[0057] There are a number of materials that are suitable as detergents for the purpose of this invention. These materials include phenates (high overbased or low overbased), high overbased phenate stearates, phenolates, salicylates, and sulfonates. Preferably, sulfonates are used, such as high overbased sulfonates, low overbased sulfonates, or phenoxy sulfonates. In addition the sulfonic acids themselves can also be used.

[0058] The term “metal sulfonate” 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 petroleum sulfonic acids and the salts as petroleum sulfonates. Most of the compounds in the petroleum product which become sulfonated contain an oil-solubilizing group. 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. 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.

[0059] The acids obtained by sulfonation are converted to the metal salts by neutralizing with a basic reacting alkali or alkaline earth metal compound to yield 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 with an alkaline earth metal base.

[0060] Alternatively, the sulfonic acid can be used directly, instead of the sulfonic acid salt.

[0061] Preferably, the metal sulfonate is a calcium alkyl aromatic sulfonate and the metal sulfonate comprises from 0 to 20 weight percent, more preferably 2 to 10 weight percent, of the lubricant composition.

[0062] The Oil of Lubricating Viscosity

[0063] The lubricating oil to which the borates and the dispersant are added can be any hydrocarbon-based lubricating oil or a synthetic base oil stock. The hydrocarbon-based lubricating oils may be derived from synthetic or natural sources and may be paraffinic, naphthetic or asphaltenic base, or mixtures thereof. The diluent oil can be natural or synthetic, and can be different viscosity grades.

[0064] The lubricating oil comprises from 30 to 70 weight percent, more preferably from 45 to 55 weight percent of the lubricant composition.

[0065] Formulations

[0066] The borate lubricating compositions of the present invention are generally blended at a level of 20-80% with other conventional additives such as ashless dispersants (1-20%), sulfurized hydrocarbons (0-30%), dialkyl hydrogen phosphates (0-10%), zinc dithiophosphates (0-20%), dialkyl hydrogen phosphates (0-10%), pentaerythritol monooleate (0-10%), 2,5-dimercapto thiadiazole (0-5%), benzotriazole (0-5%), dispersed molybdenum disulfide (0-5%), overbased sulfonates (0-10%), imidazolines (0-10%), and the like. Such additive mixtures can be used to provide a gear oil package which can then be blended at 5-15% level in an oil of lubricating viscosity, along with a polymethacrylate viscosity index improver at a level of 2-12%, and 0-1% pour point depressant to form a gear oil finished oil.

[0067] A variety of other additives can be present in lubricating oils of the present invention. Those additives include antioxidants, other viscosity index improvers, rust inhibitors, corrosion inhibitors, other anti-wear agents, and a variety of other well-known additives.

EXAMPLES

[0068] The invention will be further illustrated by the following examples, which set forth particularly advantageous method embodiments. While the Examples are provided to illustrate the present invention, they are not intended to limit it.

[0069] As used herein, the following abbreviations have the following meanings. If not defined, the abbreviation will have its art recognized meaning. 1 cSt = centistokes g = gram LOB = low overbased M = metal mm = millimeters mL = milliliter Mn or Mn = number average molecular weight PIB = polyisobutylene PIBSA = polyisobutenyl succinic anhydride PSD = particle size distribution TBN = total base number vis = viscosity

COMPARATIVE EXAMPLE A

Preparation of the Lubricant Composition Using Nitrogen Containing Succinimides

[0070] To a 2-liter beaker were added 272.8 grams of water, 219.6 grams of boric acid (3.55 moles), and 148.3 grams of 45% potassium hydroxide solution (1.19 moles). The potassium hydroxide solution typically contained about 2% potassium carbonate. The alkali metal/boron charge mole ratio was 1:3. This was heated with stirring until the ingredients dissolved. Then this solution was divided in half and then each half, 594 grams, was added to a mixture of a mono tetraethylenepentamine succinimide made from 950 molecular weight PIB (polyisobutene) (30.25 grams), and a low overbased 5 TBN calcium natural sulfonate (13.15 grams) dissolved in 136.15 grams neutral diluent oil. The dispersant/boric acid weight ratio was 0.276:1, and the sulfonate/boric acid weight ratio was 0.121:1.

[0071] The two solutions were stirred rapidly for thirty minutes using Waring blenders and then poured together into a 2-liter beaker. This solution was then stirred and heated to 270° C. under a stream of nitrogen. Then it was allowed to cool. A total of about 561 grams product was produced. This product was found to contain a total base number of 122 mg KOH/g sample, 6.8% K, 5.9% B, 0.24% N, and had a vis at 100° C. of 15.9 cSt. The PSD (particle size distribution) was 90% less than 0.42 micron, and 50% less than 0.33 micron. This data is shown in Table 1.

COMPARATIVE EXAMPLES B-D

Preparation of Other Lubricant Compositions Using Different Amounts of Succinimide and Sulfonate

[0072] A number of other examples of lubricant compositions were prepared using the procedure outlined above with different amounts of the dispersant and the detergent. Comparative example B did not use a dispersant while comparative example C did not use a sulfonate. Comparative example D also used sodium hydroxide instead of potassium hydroxide. The sodium hydroxide typically contained about 0.6% sodium carbonate. These are also summarized in Table 1.

EXAMPLE 1

Preparation of the Lubricant Composition Using PIBSA as the Dispersant

[0073] To a beaker was added water, boric acid, and potassium hydroxide. The potassium to boron molar ratio was 0.33:1. This was heated until the boric acid dissolved. Then this was slowly added to a vigorously stirred solution of PIBSA made from polyisobutene that had a number average molecular weight of 1000 and a low overbased 5 TBN calcium natural sulfonate, dissolved in neutral diluent oil. This was stirred for one half hour, the mixture was heated with stirring until the temperature increased to 270° F. The excess water was removed with a stream of nitrogen gas during the heating stage. The levels of dispersant and sulfonate, and chemical and physical properties of this product are reported in Table 1.

EXAMPLES 2-16

Preparation of Other Lubricant Compositions

[0074] Other lubricant compositions were prepared using the general procedure of Example 1. Different amounts of polyisobutenyl succinic anhydrides made from different molecular weight polyisobutenes, as well as mixtures of molecular weight polysiobuentenes, were used in these preparations. Also in some cases sodium hydroxide was used instead of potassium hydroxide. The sodium hydroxide employed typically contained about 0.6% sodium carbonate. Furthermore, examples 14-16, employed a calcium low overbased 28 TBN synthetic sulfonate, i.e., calcium alkylbenzene sulfonate, in place of the low overbased calcium natural sulfonate. These results are summarized in Table 1. 2 TABLE 1 Chemical and Physical Properties of the Borate Dispersions. PIB Dispersant Sulfonate PSD PDS Ex. M Mn Level Level TBN % M % B % N Vis. 90% 50% Dispersant - succinimide; sulfonate - natural sulfonate A K 1000 11% 5% 122 6.8 5.9 0.24 15.9 0.42 0.33 B K — — 5.3%   129 9.0 7.3 0.15 9.1 0.58 0.38 C K 1000 11% — 129 8.5 6.9 0.26 12.4 0.53 0.33 D Na 1000 11% 5% 129 4.3 5.9 0.29 14.1 0.37 0.32 Dispersant - polyalkylene succinic anhydride; sulfonate - natural sulfonate 1 K 1000 11% 5% 115 6.7 6.4 — 18.9 0.60 0.34 2 K 1300 11% 5% 118 6.7 6.4 — 21.7 0.52 0.33 3 K 2300 11% 5% 118 6.9 6.1 — 20.0 0.60 0.38 4 K 1000 11.3%   — 123 7.0 6.7 — 17.3 0.58 0.35 5 K 1300 11.3%   — 124 6.8 6.4 — 21.6 0.59 0.35 6 K 2300 11.3%   — 108 6.0 5.3 — 15.8 1.50 0.40 7 Na 1000 11% 5% 121 4.8 6.8 — 17.5 0.57 0.34 8 Na 1300 11% 5% 123 4.5 6.7 — 20.3 0.47 0.32 9 Na 2300 16.7%   4.4%   114 4.3 6.1 — 27.0 0.57 0.35 10 Na 1000 11.3%   — 129 4.9 6.9 — 16.0 0.63 0.36 11 Na 1300 11.3%   — 129 4.6 7.0 — 18.9 0.54 0.34 12 Na 2300 16.7%   — 120 4.3 6.1 — 24.1 0.63 0.36 13 Na 1000 + 17.6%   — 121 4.2 6.3 — 0.17 0.13 2300 Dispersant - polyalkylene succinic anhydride; sulfonate - synthetic sulfonate 14 Na 1000 11% 5% 123 4.2 6.6 — 0.19 0.15 15 Na  500 + 11% 5% 121 4.6 6.3 — 0.17 0.13 1000 + 2300 16 Na 1000 + 11% 5% 120 5.0 6.6 — 0.17 0.13 2300

[0075] Compatibility Testing of the Borate Lubricating Composition

[0076] The compatibility testing of a number of borate lubricating compositions in the absence of water was carried out at 80° C. This was carried out by the following procedure. Borate lubricating compositions of the present invention were blended at 3% level into a typical automotive gear oil formulation comprising ashless dispersant, calcium sulfonate, corrosion inhibitor, EP agent, friction modifier, multifunctional additives, metal deactivator, etc. This gear oil formulation was then added at the level of 6.5% to diluent oil to make an 80W90 formulation. This formulation was then placed in an oven at 60° C. and inspected on a regular basis. The results are reported in Table 2. 3 TABLE 2 Compatibility of Borate Lubricating Compositions at 60° C. Compatibility Results Ex. 1 day 1 week 2 weeks 1 month  A Slightly cloudy Bright Bright Bright no sediment heavy sediment heavy sediment heavy sediment (15 mm) (10 mm) (10 mm)  D Bright Bright Bright very heavy very heavy heavy sediment sediment sediment (6 mm) (5 mm) (5 mm)  7 Bright Bright Very slight Very slight no sediment no sediment cloud cloud no sediment no sediment  8 Bright Bright Bright Bright no sediment no sediment no sediment no sediment 11 Bright Bright Very slight Very slight no sediment no sediment cloud cloud no sediment no sediment 12 Bright Bright Very slight Very slight no sediment no sediment cloud cloud no sediment no sediment 13 Bright Bright Bright Bright no sediment no sediment no sediment no sediment 16 Bright Bright Bright Bright no sediment no sediment no sediment no sediment

[0077] These results show that the borate lubricating compositions that used the PIBSA and mixtures of PIBSA's gave better performance (less sediment) than the borate lubricating compositions that used the succinimides.

[0078] Water Tolerance Data for Borates

[0079] In order to measure and quantify the water tolerance and compatibility properties of the borate lubricating compositions of this invention, we ran the following procedures listed below.

[0080] In the first procedure, we first blended the borate lubricating compositions of the present invention at the 3% level into a typical automotive gear oil formulation comprising, ashless dispersant, calcium sulfonate, corrosion inhibitor, EP agent, friction modifier, multifunctional additives, metal deactivator, etc. This gear oil formulation was then added at the level of 6.5% to diluent oil to make an 80W90 formulation. This formulation was then run in a modified L60 test. This test is a standardized test described in the ASTM Special Technical Publication 512A, “Laboratory Performance Tests for Automotive Gear Lubricants Intended for API GL-5 Service STP 512A”. This information is available from ASTM, 1916 Race Street, Philadelphia, Pa. 19103. We modified the L60 test by omitting the copper coupon, eliminating air bubbling, and plugging the air holes in the gear case assembly. The gear case assembly was charged with 360 mL oil, and kept at 297° F. for 100 minutes. Then the oil was cooled to 175° F. and 3% water was added. Then the gear case assembly was held at 175° F. for 12 hours and then the temperature was increased to 275° F. The oil was kept at 275° F. for 12 hours, then the oil was drained. After draining the oil, the deposits were collected, measured, and reported in milliliters. The collected deposits were rinsed with hexane to remove the oily part, and then the deposits were measured again and reported in milliliters. The results from the water tolerance testing of a number of borate additives are shown in Table 3. 4 TABLE 3 Water Tolerance Testing for Borate Lubricating Compositions Using a Modified L60 Test Deposits Deposits before after Ex. Metal Dispersant Detergent hexane hexane A K Succinimide Sulfonate A 3.4 3.4 B K None Sulfonate A 6.6 0.3 C K Succinimide None 16.2 1.2 D Na Succinimide Sulfonate A 0.1 0 1 K PIBSA (1000) Sulfonate A 17.6 0.4 2 K PIBSA (1300) Sulfonate A 10.2 0.5 3 K PIBSA (2300) Sulfonate A 6.0 0.8 4 K PIBSA (1000) None 5.2 1.6 5 K PIBSA (1300) None 3.6 2.4 6 K PIBSA (2300) None 4.6 1.8 9 Na PIBSA (2300) Sulfonate A 0.4 0 10 Na PIBSA (1000) None 1.2 1.2 12 Na PIBSA (2300) None 0 0 Sulfonate A = Calcium low overbased 5 TBN natural sulfonate

[0081] The data in Table 3 shows that better water tolerance (lower amount of deposits) was observed when the metal used in the borate lubricating composition was sodium compared to potassium.

[0082] Additional water tolerance data for the borate lubricating compositions was obtained by the following procedure. We first blended the borate lubricating compositions of the present invention at the 3% level into a typical automotive gear oil formulation comprising, ashless dispersant, calcium sulfonate, corrosion inhibitor, EP agent, friction modifier, multifunctional additives, metal deactivator, etc. This gear oil formulation was then added at the level of 6.5% to diluent oil to make an 80W90 formulation. Then a mixture of the finished oil and 0.5 weight percent water was placed in an oven that was held at a temperature of 60° C. This was inspected for compatibility. The results of this study are shown in Table 4. 5 TABLE 4 Water Tolerance Results for Borate Lubricating Compositions with 0.5% Water at 60° C. Compatibility Results Ex. 1 day 5 days 1 week 2 weeks  A Very slight Bright Bright Bright cloudy heavy sediment heavy sediment heavy sediment heavy sediment (4 mm) (4 mm) (5 mm) (4 mm)  D Bright Bright Bright Bright slight sediment slight sediment slight sediment slight sediment (1 mm) (1 mm) (1 mm) (1 mm)  7 Medium Medium Medium Medium moderate cloud moderate cloud moderate cloud moderate cloud no sediment very slight slight sediment slight sediment sediment (1 mm) (1 mm)  8 Medium Medium Medium Medium moderate cloud moderate cloud moderate cloud moderate cloud no sediment very slight slight sediment slight sediment sediment (2 mm) (3 mm) 11 Medium Medium Medium Medium moderate cloud moderate cloud moderate cloud moderate cloud no sediment very slight slight sediment slight sediment sediment (1 mm) (2 mm) 12 Moderate cloud Moderate cloud Medium Medium no sediment no sediment moderate cloud moderate cloud very slight very slight sediment sediment 13 Flock Flock Flock Flock no sediment no sediment no sediment no sediment

[0083] These results show that the borate lubricating compositions that used the PIBSA and mixtures of PIBSA gave better performance (less sediment) than the borate lubricating compositions that used the succinimides.

[0084] Additionally the water tolerance and performance of lubricant compositions comprising a mixture of polyalkylene succinic anhydrides was evaluated. Specifically, the lubricant composition of this example employs a mixture of PIBSA's made from 1000 and 2300 Mn PIB (polyisobutene). Otherwise, this composition was identical to that of Example 11 above which is a borate prepared from a PIBSA made from a 1300 molecular weight PIB. The data for this composition as compared to that of Example 11 is shown in Table 5 below. The Coordinating Research Counsel L-33 test was used for testing and evaluating rust and corrosion inhibiting properties of the compounds of this invention, see U.S. Pat. No. 4,089,790 incorporated herein by reference. This test utilizes the compounds of interest in a bench mounted automotive differential assembly adding water to simulate a severe service in which corrosion promoting moisture in the form of condensed water vapor has accumulated in the axle assembly. 6 TABLE 5 Water Tolerance Performance of Sodium Borates Prepared from Mixtures of PIBSA Ex. PIB Ma Metal L-33 % deposits 11 1300 Na 2 13 1000 + 2300 Na 3 13 1000 + 2300 Na 9 13 1000 + 2300 Na 4 13 1000 + 2300 Na 4

[0085] These results indicate that the composition of Example 13 performs substantially as well as that of Example 11. Other mixtures of different molecular weights are anticipated to behave with similar results.

[0086] The performance of lubricant compositions comprising an alkali metal borate, a polyalkylene succinic anhydride and different LOB sulfonates (Examples 7 and 14) as well as lubricant compositions comprising an alkali metal borate, a mixture of molecular weight polyalkylene succinic anhydrides employing a LOB sulfonate (Examples 15 and 16). Specifically, the lubricant compositions of this comparison employ a mixture of PIBSA's made from either 500+1000+2300 Mn PIB or 1000+2300 Mn PIB and LOB sulfonate A and are compared to compositions employing a 1000 Mn PIB and LOB sulfonates A or B. Formulations and physical property data for Examples 7, and 14-16 were previously shown in Table 1. These borate lubricating compositions were blended at the 3% level into a typical automotive gear oil formulation comprising, ashless dispersant, calcium sulfonate, corrosion inhibitor, EP agent, friction modifier, multifunctional additives, metal deactivator, etc. This gear oil formulation was then added at the level of 6.5% to diluent oil to make an 80W90 formulation. The data for these compositions as compared to that of Examples 7 and 14 are shown in Table 6 below. 7 TABLE 6 Water Tolerance Performance of Sodium Borates Prepared from Mixtures of PIBSA plus a LOB sulfonate. LOB OH:B L-33 % Ex. No. PIB Mn Sulfonate Metal Ratio deposits Ex. 7 1000 A Na 1.01:1 2 Ex. 7 1000 A Na 0.90:1 4 Ex. 14 1000 B Na 0.85:1 3 Ex. 14 1000 B Na 0.85:1 14 Ex. 15 500 + 1000 + 2300 B Na 1.10:1 2 Ex. 15 500 + 1000 + 2300 B Na 1.10:1 2 Ex. 16 1000 + 2300 B Na 1.01:1 2 Ex. 16 1000 + 2300 B Na 1.06:1 4 Ex. 16 1000 + 2300 B Na 1.06:1 6 LOB Sulfonate A = Calcium low overbased 5 TBN natural sulfonate LOB Sulfonate B = Calcium low overbased 28 TBN synthetic sulfonate

[0087] The data in Table 6 shows that the lubricant compositions employing a mixture of PIBSA's plus a LOB sulfonate perform equally as well as the borate prepared from a single PIBSA plus a LOB sulfonate.

EXAMPLES 17-23

Preparation of Borates That Contain Oxo Anions

[0088] The procedure for Example A was followed exactly except that different amounts (based on boric acid) of different oxo anions were added to the water solution of the boric acid and alkali metal hydroxide. The chemical and physical properties of these materials are shown in Table 7. 8 TABLE 7 Chemical and Physical Properties that include Oxo Anions % Met- Oxo an- % % % PSD PSD Ex al anion ion TBN M B N vis 90% 50% 17 K Na2MoO3 3 143 8.4 6.5 0.29 16.8 0.59 0.32 18 K Na2SO4 3 130 8.3 6.9 0.29 13.9 0.58 0.35 19 K Na2WO3 1 130 8.5 6.7 0.22 14.3 0.54 0.34 20 K Na2SO4 + 3+ 153 7.9 6.2 0.44 15.0 0.57 0.35 Na3PO4 3 21 K Na4SiO4 3 210 9.6 3.9 0.19 16.2 0.51 0.34 22 Na Na2SO4 3 140 5.4 6.8 0.25 — 0.46 0.32 23 K NaNO3 3 132 8.2 6.6 0.52 15.7 0.38 0.31

[0089] In Table 7, the column “PSD 90%” refers to particle size distribution and is a measure of particle size wherein at least 90% of the particles are less than the indicated value, in microns. Similarly, the column “PSD 50%” measures particle size wherein at least 50% of the particles are less than the indicated value, in microns.

[0090] While the present invention has been described with reference to specific embodiments, this application is intended to cover those various changes and substitutions that may be made by those skilled in the art without departing from the spirit and scope of the appended claims.

Claims

1. A lubricant composition which comprises:

a) a base oil of lubricating viscosity,

b) a dispersed hydrated alkali metal borate, and

c) a dispersant that is selected from the group consisting of a polyalkylene succinic anhydride, a non-nitrogen containing derivative of the polyalkylene succinic anhydride, mixtures of polyalkylene succinic anhydrides, mixtures of non-nitrogen containing derivatives of the polyalkylene succinic anhydride and mixtures of both polyalkylene succinic anhydrides and non-nitrogen containing derivatives of the polyalkylene succinic anhydride.

2. The lubricant composition according to claim 1, wherein the dispersed hydrated alkali metal borate is a dispersed hydrated sodium borate.

3. The lubricant composition according to claim 2, wherein the dispersed hydrated sodium borate has a sodium to boron metal ratio of from about 1:2.5 to about 1:4.5.

4. The lubricant composition according to claim 1, wherein the dispersant is a mixture of polyalkylene succinic anhydrides.

5. The lubricant composition according to claim 4, wherein the mixture of polyalkylene succinic anhydrides is a mixture of polyisobutenyl succinic anhydrides.

6. The lubricant composition according to claim 5, wherein the mixture of polyisobutenyl succinic anhydrides comprises a low molecular weight polyisobutenyl succinic anhydride component and a high molecular weight polyisobutenyl succinic anhydride component.

7. The lubricant composition according to claim 6, wherein the low molecular weight polyisobutenyl succinic anhydride component has a number average molecular weight of from about 500 to below 1000 and the high molecular weight polyisobutenyl succinic anhydride component has a number average molecular weight of from 1000 to about 3000.

8. The lubricant composition according to claim 1, wherein the dispersed hydrated alkali metal borate has a ratio of at least 2:1 relative to the dispersant.

9. The lubricant composition according to claim 8, wherein the dispersed hydrated alkali metal borate has a ratio of from 2:1 to 10:1 relative to the dispersant.

10. The lubricant composition according to claim 8, wherein the dispersed hydrated alkali metal borate has a ratio of at least 5:2 relative to the dispersant.

11. The lubricant composition according to claim 1, which further comprises a metal sulfonate.

12. The lubricant composition according to claim 11, wherein said metal sulfonate is a calcium alkyl aromatic sulfonate.

13. The lubricant composition according to claim 1, which further comprises from about 0.001 moles to about 0.11 moles of a water soluble oxo anion per mole of boron.

14. The lubricant composition according to claim 13, wherein said oxo anion is selected from the group consisting of nitrate, sulfate, carbonate, phosphate, pyrophosphate, silicate, aluminate, germanate, stannate, zincate, plumbate, titanate, molybdate, tungstate, vanadate, niobate, tantalate, uranate, isopolymolybdate, isopolytungstate, heteropolymolybdate, heteropolytungstates, and mixtures thereof.

15. A method for enhancing the water tolerance of lubricant compositions comprising alkali metal borate which method comprises adding an anti-wear effective amount of a dispersed hydrated alkali metal borate to a base oil of lubricating viscosity in combination with a dispersant effective amount of a dispersant selected from the group consisting of a polyalkylene succinic anhydride, a non-nitrogen containing derivative of the polyalkylene succinic anhydride, mixtures of polyalkylene succinic anhydrides, mixtures of non-nitrogen containing derivatives of the polyalkylene succinic anhydride and mixtures of both polyalkylene succinic anhydrides and non-nitrogen containing derivatives of the polyalkylene succinic anhydride.

16. The lubricant composition according to claim 1, wherein the dispersed hydrated alkali metal borate is a dispersed hydrated sodium borate having a hydroxyl to boron ratio of from about 0.8:1 to 1.6:1.