LOW-PHOSPHOROUS LUBRICANTS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. patent application serial number 11/221,400 filed September 7, 2005, entitled "LOW-PHOSPHOROUS LUBRICANTS."

LOW-PHOSPHOROUS LUBRICANTS

TECHNICAL FIELD

[0002] The present application relates generally to lubricants and, more particularly, to lubricants with reduced quantities of zinc dialkyldithiophosphate (ZDDP) and phosphorous.

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BACKGROUND OF THE INVENTION

[0003] Lubricants comprise a variety of compounds selected for desirable characteristics such as anti-wear and anti-friction properties. Many of these compounds are used in enormous quantities. For example, more than four billion quarts of crankcase oil are used in the United States per year. However, many compounds currently in use also have undesirable characteristics. Currently available crankcase oils generally include the anti-wear additive zinc dialkyldithiophosphate (ZDDP), which contains phosphorous and sulfur. Phosphorous and sulfur poison catalytic converters causing increased automotive emissions. It is expected that the EPA eventually will mandate the total elimination of ZDDP or will allow only extremely low levels of ZDDP in crankcase oil. However, no acceptable anti-wear additives to replace ZDDP in engine oils are currently available.

[0004] It is an object of the present invention to provide environmentally friendly lubricants, wherein the amounts of phosphorous and sulfur in the lubricants are significantly reduced and approach zero. It is another object of the present invention to produce lubricants with desirable anti-wear and anti-friction characteristics.

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BRIEF SUMMARY OF THE INVENTION

[0005] Certain embodiments of the invention comprise methods for preparing lubricant additives by reacting at least one organophosphate compound and at least one metal halide where the at least one metal halide participates in the reaction primarily as a reactant. Organophosphates used in embodiments of the invention may comprise metal organophosphates, organothiophosphates, metal organothiophosphates, and other compounds comprising organophosphate groups. The organophosphate used in a preferred embodiment is a metal organophosphate, such as ZDDP. In other embodiments, one of the organophosphate compounds used is ZDDP mixed with smaller molecular weight organophosphates. hi one embodiment, the at least one organophosphate and at least one metal halide are reacted together at about -20°C to about 15O ⁰ C. hi a preferred embodiment, the reactant mixture is heated to a temperature of about 60 ⁰ C to about 150°C. The reaction is allowed to continue from about 20 minutes to about 24 hours. Both supernatants and precipitates formed during the reaction may be used as lubricant additives in certain embodiments of the present invention. These lubricant additives may be added to low phosphorous lubricants such as oils, greases, automatic transmission fluids, crankcase fluids, engine oils, hydraulic oils, and gear oils comprising from about 0.01 weight percent phosphorous to about 0.1 weight percent phosphorous..

[0006] Other embodiments of the present invention react a mixture of powdered, masticated metal halide with an organophosphate or an organophosphate mixture to form a lubricant additive. The metal halide used is metal fluoride in a preferred embodiment of the invention, hi a preferred embodiment, the metal fluoride and the organophosphate are reacted together at about -2O ⁰ C to about 150 ⁰ C to form a lubricant additive. The lubricant additive is then added to a low phosphorous lubricant. The lubricants to which the lubricant additive is added are preferably fully formulated GF4 engine oils without ZDDP. However, other lubricants maybe used such as those listed above.

[0007] The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows maybe better understood. Additional features and advantages of the

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invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized that such equivalent constructions do not depart from the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.

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BRIEF DESCRIPTION OF THE DRAWINGS

[0008] For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which:

[0009] FIGURE 1 is a table showing representative organophosphate compounds that may be used with embodiments of the present invention;

[0010] FIGURES 2A-2C show structures associated with some of the organophosphates that may be used with embodiments of the present invention;

[0011] FIGURE 3 is a table presenting experimental results showing the presence of fluorine in reaction supernatants;

[0012] FIGURE 4 shows a ³¹ P NMR spectra of supernatant from a reaction between ZDDP and ferric fluoride;

[0013] FIGURE 5 is a ³¹ P NMR spectrum of supernatant from a reaction between ZDDP and ferric fluoride;

[0014] FIGURE 6 is another ³¹ P NMR spectrum of supernatant from a reaction between ZDDP and ferric fluoride;

[0015] FIGURES 7-10 show organophosphate structures that may be used with embodiments of the present invention; and

[0016] FIGURE 11 shows a wear volume experiment comparing lubricant oils to which were added different lubricant additives.

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DETAILED DESCRIPTION OF THE INVENTION

[0017] Embodiments of the present invention provide low phosphorous lubricants comprising improved lubricant additives. Lubricant additives according to embodiments of the present invention may be added to low phosphorous lubricants such as greases, crankcase oils, hydrocarbon solvents, etc. comprising from about 0.01 weight percent phosphorous to about 0.1 weight percent phosphorous. In a preferred embodiment of the present invention, lubricant additives are mixed with a fully formulated engine oil without ZDDP. The term "fully formulated oil" as used here to illustrate certain embodiments of the present invention are engine oils that include additives, but not zinc dialkyldithiophosphate (ZDDP), and comprise from about 0.01 weight percent phosphorous to about 0.1 weight percent phosphorous. In certain embodiments, the fully formulated oil may be, for example, a GF4 oil with an additive package comprising standard additives, such as dispersants, detergents, and antioxidants, but without ZDDP.

[0018] Certain embodiments of the present invention comprise methods for preparing lubricant additives to be added to low phosphorous lubricant bases by reacting together one or more organophosphates such as metal organophosphates like ZDDP and one or more metal halides such as ferric fluoride, where the metal halide participates in the reaction primarily as a reactant. Metal halides used with embodiments of the present invention may be, for example, aluminum trifluoride, zirconium tetafluori.de, titanium trifiuoride, titanium tetrafluoride, and combinations thereof. In other embodiments, other transition metal halides are used, such as, for example, chromium difluoride and trifluoride, manganese difluoride and trifluoride, nickel difluoride, stannous difluoride and tetrafluoride, and combinations thereof. Ferric fluoride is used in preferred embodiments of the present invention. Ferric fluoride may be produced according to a process described in co-pending U.S. Patent Application Serial No. 10/662,992 filed September 15, 2003, the contents of which are herein incorporated by reference.

[0019] FIGURE 1 is a table showing several of the organophosphate compounds that may be used with embodiments of the present invention. Generally, dithiophosphates and amine and amine salts of monothiophosphates and dithiophosphates may be used. Other organophosphates listed in FIGURE 1 include

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neutral ZDDP (primary), neutral ZDDP (secondary), basic ZDDP, (RS) ₃ P(s) where R>CH ₃ , (RO)(R ⁵ S)P(O)SZn , (RO) ₂ (RS)PS where R>CH ₃ , P(S)(S)Zn , (RO) ₂ P(S)(SR), R(R ⁵ S) ₂ PS where R=CH ₃ and R ⁵ >CH ₃ , (RO) ₃ PS where R=CH ₃ and R'=alkyl, MeP(S)Cl ₂ , (RO) ₂ (S)PSP(S)(OR) ₂₅ P(S)(SH), (RO)(R ⁵ S)P(O)SZn , SPH(OCH ₃ ) ₂ , where R= any alkyl and R ⁵ =any alkyl, and combinations thereof. The chemical structures of representative compounds from FIGURE 1 and additional organophosphate compounds that may be used with the invention are shown in FIGURES 2a-2c. In certain embodiments of the present invention, organophosphates not shown in FIGURES 1 and 2a-2c may be used. The organophosphate ZDDP is used in preferred embodiments of the present invention Embodiments using ZDDP, alone or in combination with other organophosphates, can use ZDDP in one or more moieties. Preferably, the ZDDP used is the neutral or basic moiety. Some of the ZDDP moieties are shown in FIGURE 2a as structures 1 and 5.

[0020] The organophosphate and metal halide are reacted together at about -20°C to about 150°C. hi a preferred embodiment, the reactant mixture is heated to a temperature of about 60°C to about 150 ⁰ C. The reaction is allowed to continue from about 20 minutes to about 24 hours. Generally, as temperature is decreased in embodiments of the invention, the duration of the reaction is increased. Various additional reaction parameters may be used, such as performing the reaction under certain gases such as nitrogen or noble gases, or stirring the reactants to encourage reaction progress. In certain embodiments, the organophosphate and metal halide are reacted together in a low phosphorous lubricant base to form an improved low phosphorous lubricant. Both supernatants and precipitates formed during a reaction may be used as lubricant additives in certain embodiments of the present invention. Supernatants and precipitates may be separated using standard techniques such as filtration or centrifugation known to those skilled in the art. Precipitates remaining after reactions between organophosphates and metal halides may comprise metal-containing solid compounds such as iron alkyl ethers, fluorocarbons, organofluorophosphorous compounds, and/or organothiophosphates.

[0021] In one embodiment of the present invention, a lubricant additive is added to a low phosphorous commercial engine oil containing an additive package without ZDDP and with either 0 ppm or 80 ppm of a molybendum-containing additive.

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In this embodiment, masticated ferric fluoride is prepared from powder by combining ferric fluoride with a suspending agent and a base oil. In certain embodiments of the invention, masticated ferric fluoride and ZDDP with 0.01 wt % phosphorous content are mixed together and heated at 6O ⁰ C for one hour to produce a reaction mixture. In other embodiments, different heating times and/or temperatures are used. The reaction mixture supernatant is then separated from precipitate solids to produce a lubricant additive. This lubricant additive is then added to a low phosphorous engine oil that does not include ZDDP. The resultant improved engine oil is then used in an appropriate application such as, for example, an engine crankcase. Improved engine oil produced according to an embodiment of the present invention are used in engines found in, for example, automobiles, trucks, motorcycles, generators, lawn equipment, etc.

[0022] FIGURE 3 is a table presenting experimental results showing that fluorine, presumably donated by the metal halide ferric fluoride, remains in a reaction supernatant formed using an embodiment of the present invention. In this experiment, samples of untreated ZDDP, untreated ZDDP under an inert atmosphere, and ZDDP reacted with ferric fluoride under an inert atmosphere were chemically analyzed. The ASTM D3120 protocol was used for sulfur and ASTM D5185 for phosphorous, zinc, and iron. Fluorine analysis was conducted separately by completely combusting to a fluoride and using iron chromatography. The results of the analysis shown in FIGURE 3 indicate that no fluorine was present in the supernatant samples from either the untreated ZDDP or the untreated ZDDP under inert atmosphere. However, significant quantities of fluorine (163 parts per million) were found in supernatant samples taken from the ZDDP reacted with ferric fluoride. Also, iron levels were extremely low (1-2 parts per million) in those samples, indicating that the fluorine present in the supernatant has bonded to an element other than iron.

[0023] FIGURE 4 shows a ³¹ P NMR spectrum of supernatant from a reaction between ZDDP and ferric fluoride. The spectra shows the presence of doublets resulting from the interaction of bound phosphorous and fluorine atoms in compounds present in the supernatant sample. The experiments summarized in FIGURES 3 and 4 illustrate that the metal halide participates primarily as a reactant in embodiments of the present invention.

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[0024] FIGURES 5-10 show experimental results and possible structures for reaction products formed by embodiments of the present invention. FIGURE 5 is a ³¹ P NMR spectrum ( ¹ H decoupled to suppress phosphorous-hydrogen peaks) of supernatant from a reaction between ZDDP and ferric fluoride showing the formation of a fluoro-phosphorous compound. A doublet located at approximately 57 ppm and 66 ppm is due to a phosphorous-fluorine bond with J=I 080. Each doublet peak is composed of multiple peaks that are apparent triplets.

[0025] FIGURE 6 is a ³¹ P NMR spectrum ( ¹⁹ F decoupled to suppress phosphorous-fluorine peaks) of supernatant from a reaction between ZDDP and ferric fluoride. Comparison with FIGURE 5 shows that the triplets present in FIGURE 5 have merged to a single triplet at approximately 61 ppm located midway between the former triplet locations at approximately 57 ppm and 66 ppm. The merging of the two triplets indicates that the origin of the doublet in FIGURE 5 was from a phosphorous-fluorine bond. Also, the fact that a triplet still remains in this spectrum indicates that the origin of the triplet is from a phosphorous-phosphorous backbone and not from a phosphorous- hydrogen or phosphorous-fluorine backbone.

[0026] The three peaks in the triplets of FIGURES 5 and 6 can be from spin-spin splits from at least 3 different interacting phosphorous atoms in the same structure. Chemical shifts of 3 phosphorous atoms are nearly the same, such that relative chemical shifts are less than or equal to coupling constants of the phosphorous, i.e. the origin of the shifts result from a second order spectra rather than a first order. Four possible compounds that can produce the NMR spectra of FIGURES 5 and 6 are shown in FIGURE 7. In all structures shown in FIGURE 7, X=R, OR, and/or SR. R refers to an alkyl group, and may be the same or different at the same time within the same structure. The O(S) refers to either an oxygen or sulfur atom being present at one time. Y equals F or another halogen. At least one Y equals F.

[0027] If the peaks in the triplets of FIGURES 5 and 6 are not arising from a phosphorous-phosphorous backbone, then chemical structures such as those shown in FIGURE 8 may be responsible for the spectra. In the case of structures (a)-(c) shown in FIGURE 8, the origin of the multiple peaks in the spectra may result from the different environment surrounding the phosphorous atoms. In compound (d) shown in FIGURE

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8, the separation of the phosphorous atoms is large enough to suppress any interaction between them and the origin of the multiple peaks in the spectra result from the different environment surrounding the phosphorous atoms. Li all of the structures shown in FIGURE 8, the presence of a phosphorous-fluorine bond is certain. In all of the FIGURE 8 structures, R equals an alkyl group.

[0028] If two of the shoulder peaks in the NMR triplets shown in FIGURES 5 and 6 arise from spin-spin coupling of two phosphorous atoms on the backbone then the third dominant peak at the center may arise from any one of the compounds shown in FIGURE 8. The shoulder peaks (smaller peaks within FIGURE 5 and 6) arise from the structure of the kind shown in FIGURE 9. The dominant peak (the middle peak) can arise from any one of the three structures (a), (b), or (c) shown in FIGURE 8.

[0029] Additional organophosphate structures that may be usable with embodiments of the present invention are shown in FIGURE 10. The organophosphate structures specifically disclosed herein are representative structures and are in no way intended to limit embodiments of the present invention to those structures. Many embodiments of the present invention utilize organophosphate compounds not specifically shown.

[0030] Experiments were performed to evaluate low phosphorous lubricant formulations comprising lubricant additives produced according to embodiments of the invention. Generally, wear volume comparisons were used to compare the lubricants and lubricant additives produced according to embodiments of the invention. The experiments were conducted on a modified Ball on Cylinder machine. The machine was modified to accept standard Timken Roller Tapered Bearings, where the outer surface of the cup was used for wear testing. In order to generate consistent results a protocol was established to prepare the surface prior to wear testing. The protocol comprises two phases: break in and the actual test.

[0031] The break in protocol begins with preparation of the ring and the ball by cleaning with hexane and acetone followed by brushing. Then 50 μL of break in oil comprising base oil plus ZDDP with 0.1 wt% phosphorous is applied to the center of the surface of the ring. For the first 500 cycles, a constant load of 6 kg is applied, then

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increased gradually to 15 kg for the next 1500 cycles at 700 rpm. The rotation is then stopped and the ring and the ball cleaned on the spot without removing them.

[0032] For the actual test, the lubricant being tested is applied to the center of the surface of the ring. As with break in, a constant load of 6 kg is applied for the first 500 cycles. For the next 1500 cycles, the load is gradually increased to 24 kg. The weight used for the protocol may vary in some tests. Up to 23000 additional cycles at 700 rpm may be used in certain variations of the protocol during which the load is applied constantly and data acquisition is performed.

[0033] FIGURE 11 illustrates a profilometric wear volume result comparison of lubricant oils to which were added ZDDP alone, supernatant from ZDDP and ferric fluoride that were combined, but not heated, and supernatant from ZDDP and ferric fluoride that were combined and heated at 15O ⁰ C for 20 minutes. The data from the experiment shows that there is a greater than 50% reduction in wear volume when comparing the addition of ZDDP alone to the addition of supernatant produced by reacting ZDDP and ferric fluoride with heat. The experiment also shows that the reaction between ZDDP and ferric fluoride appears to progress at room temperature, as there was a significant reduction in wear volume when using the room temperature supernatant with a lubricant oil. The results show that the lubricant oil comprising lubricant additive produced according to an embodiment of the present invention is superior in minimizing the wear volume of a bearing used in the modified Ball on Cylinder test described above.

[0034] Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one will readily appreciate from the disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized. Accordingly, the

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appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

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