METHOD TO SYNTHESIZE FLUORINATED ZDDP

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to U.S. patent application serial number 11/446,820 filed June 5, 2006, entitled "Method to Synthesize Fluorinated ZDDP," which claims priority to U.S. provisional patent application serial number 60/511,290 filed on October 15, 2003, entitled "Engine Oil Additive," and co-pending, commonly assigned U.S. patent application serial number 10/965,686 filed October 14, 2004, entitled "Engine Oil Additive," the disclosures of which are hereby incorporated by reference herein.

METHOD TO SYNTHESIZE FLUORINATED ZDDP

TECHNICAL FIELD

[0002] The present application relates generally to lubricants, and more particularly, to synthesis of fluorinated zinc dialkyldithiophosphate (ZDDP).

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 dialkyldiothiophosphate (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 or to modify ZDDP to have more desirable characteristics 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.

BRIEF SUMMARY OF THE INVENTION

[0005] Embodiments of the current invention are several methods for preparing lubricant additives and lubricants by reacting together organophosphates and organothiophosphates and their derivatives, such as zinc dialkyldithiophosphate (ZDDP), and fluorine compounds, such as metal fluorides, organoflourides and fluorinating agents. Certain embodiments of the invention comprise methods for preparing lubricant additives by reacting at least one organophosphate compound and at least one fluorinating agent wherein the at least one of the fluorinating agent participates in the reaction primarily as a reactant. Organophosphates used in embodiments of the invention may comprise metal organophosphates, ashless 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. Other embodiments include ashless phosphates, thiophosphates, thiostanates, and the like.

[0006] In one embodiment, at least one organophosphate and at least one metal fluoride are reacted together at about -20°C to about 150°C. In 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. Both supernatants and precipitates formed during the reaction may be used as lubricant additives in certain embodiments of the present invention.

[0007] In a second embodiment, at least one organophosphate, ashless organothiophosphate, metal organothiophosphate, or a derivative thereof, and at least one metal fluoride and/or organofluoride are mixed together in a ball mill, centrifugal mill, rotary mill, vibratory mill, planetary mill and/or attrition mill together with milling media that may constitute steel balls, tungsten carbide, ceramic balls such as alumina, zirconia, silicon carbide, silicon nitride among other ceramics. The mixture is milled between 10 minutes and 30 days depending on the method used and the temperature is held between -20 ⁰ C and 150°C. In a preferred embodiment, the mixture is milled at room temperature for a period between 72 hrs and 168 hours. Both the supernatant and

the precipitates formed during the reaction may be used as lubricant additives in certain embodiments of the present invention.

[0008] In a third embodiment, at least one organophosphate, ashless organothiophosphate, metal organothiophosphate, or a derivative thereof, and at least one fluorinating agent are mixed together and the reaction is conducted at temperatures between -20 to 150 ⁰ C for durations ranging from 1 minute to 24 hours. The solution formed during the reaction, separated from any solids present during the reaction, if any, may be used as lubricant additives in certain embodiments of the present invention.

[0009] hi a preferred embodiment, the liquid product, separated from any solids present formed in any of the above mentioned processes is added to fully formulated GF-4 oil, automatic transmission fluid, gear oils and/or greases.

[0010] 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 may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art 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 by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of 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.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

[0012] FIGURE 1 is a table showing representative organophosphate compounds that may be used with embodiments of the present invention;

[0013] FIGURES 2A-2C show structures associated with some of the organophosphates that may be used with embodiments of the present invention;

[0014] FIGURE 3 is a table presenting experimental results showing the presence of fluorine in reaction supernatants;

[0015] FIGURE 4 shows a 31 P NMR spectra of supernatant from a reaction between ZDDP and ferric fluoride;

[0016] FIGURE 5 is a 3 IP NMR spectrum of supernatant from a reaction between ZDDP and ferric fluoride;

[0017] FIGURE 6 is another 3 IP NMR spectrum of supernatant from a reaction between ZDDP and ferric fluoride;

[0018] FIGURES 7-10 show organophosphate structures that may be used with embodiments of the present invention;

[0019] FIGURE 1 IA is 3 IP NMR spectrum of supernatant from a reaction between ZDDP and ferric fluoride by Ball milling for 24 hours;

[0020] FIGURE 11 B is a 31 P NMR spectrum of supernatant from a reaction between ZDDP and ferric fluoride by Ball milling for 72 hours; and

[0021] FIGURE 12 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 150°C for 20 minutes.

DETAILED DESCRIPTION OF THE INVENTION

[0022] 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 lubricants including, but not limited to, greases, crankcase oils, and hydrocarbon solvents comprising from about 0.01 weight percent phosphorous to about 0.1 weight percent phosphorous, hi 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 herein to illustrate certain embodiments of the present invention is used to describe 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, hi 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 or its derivatives.

[0023] 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, including but not limited to metal organophosphates such as ZDDP, and one or more metal halides, such as ferric fluoride, wherein the metal halide participates in the reaction primarily as a reactant. Metal halides preferably used with embodiments of the present invention include, for example, aluminum trifluoride, zirconium tetrafluoride, titanium trifluoride, titanium tetrafluoride, and combinations thereof, hi other embodiments, transition metal halides are used, such as, for example, chromium difluoride, chromium trifluoride, manganese difluoride, manganese trifluoride, nickel difluoride, stannous difluoride, stannous tetrafluoride, and combinations thereof. Ferric fluoride is preferably used in a preferred embodiment 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.

[0024] hi a first embodiment, ferric fluoride is mixed with one or more of the organophosphates, such as ZDDP, and baked in an inert environment, such as argon nr nitrncrfin , or an air environment at temperatures between -20 and 15O ⁰ C for a period of

time ranging from 20 minutes to several days. Preferably, the mixture is baked at 80°C for 1 hour. The product is centrifuged, and the decant is a fluorinated organothiophosphate compound and to be utilized as an additive at phosphorous levels between 0.01 and 0.1 wt.% P in GF-4 oils.

[0025] In another embodiment, ferric fluoride is mixed with ZDDP and subjected to an attrition milling process. In an attrition mill, kinetic and mechanical energy of the milling media is used to break up particles of ferric fluoride and enhance the interaction between the ferric fluoride and the ZDDP, thiophosphate or organophosphate to produce a fluorinated ZDDP, fluorinated thiophosphate, or fluorinated organophosphate compound respectively. There are several types of attrition mills that can be used which are well known in the art.

[0026] In the first method a ball mill preferably may be used wherein milling media made up of balls of tungsten carbide, alumina, zirconia, stainless steel, silicon carbide or silicon nitride, for example, are tumbled together with ferric fluoride and ZDDP in a cylindrical container for a period of 24-300 hours at temperatures between -20 and 150°C. In a preferred embodiment a mixture of ZDDP and ferric fluoride in the ratio of 1 :0.4 is ball milled for a period of 168 hours at room temperature. The reaction product is centrifuged to separate out the unreacted ferric fluoride as well as any other solid reaction products from the decant that comprises fluorinated ZDDP. The recovered unreacted ferric fluoride can then be mixed with a new batch of ZDDP and then ball milled to yield a new batch of fluorinated ZDDP. The ferric fluoride may be recycled 2-10 times before the reactivity of the ferric fluoride diminishes to the point where it may be no longer useful.

[0027] ha another method of attrition milling, an Attritor (which is often referred to generically as a "stirred ball mill") may be used. The operation of an Attritor is simple and effective. The material to be ground is placed in a stationary tank with the grinding media. Carbon steel, stainless steel, chrome steel, tungsten carbide and ceramic balls are preferably used as grinding media. The material to be ground and the grinding media are then agitated by a shaft with arms, rotating at high speed. The agitation at high speed result in the grinding media exerting both shearing and impact forces on the material The final result of this efficient process is an extremely fine material, measured

in microns or fractions of microns, when distributed on a very narrow curve. It should be appreciated that a laboratory Attritor works up to ten times faster than the conventional ball, pebble or jar mill. In this mill the ferric fluoride and ZDDP is added and milled together for periods between 20 minutes and 168 hours. The reaction product is centrifuged and the decant is separated out and used in liquid form as fluorinated ZDDP. The solids remaining comprise recyclable active ferric fluoride. This process preferably may be repeated at least 2-10 times to repeat the fluorination process using the recycled ferric fluroide.

[0028] In a further method, a centrifugal or planetary ball mill is preferably used. With a planetary ball mill, the material to be milled is placed in a chamber together with the milling media and the chamber is rotated such that the balls cascade against each other and collide with maximum energy against the opposite wall. Carbon steel, stainless steel, chrome steel, tungsten carbide and ceramic balls are preferably used milling media. Using this type of ball mill, ferric fluoride and ZDDP are added and milled together for periods ranging from 20 minutes to 168 hours. The reaction product is centrifuged and the decant is separated out and used in liquid form as fluorinated ZDDP. The remaining solids comprise recyclable recovered ferric fluoride. This process can be repeated at least 2-10 times to repeat the fluorination process using the recycled ferric fluoride.

[0029] Fluorination of ZDDP and other phosphorous and thiophosphorous compounds can also be preferably conducted by reacting these types of compounds with a fluorinating agent. Fluorinating agents are a class of fluorine containing compounds that can easily donate a fluorine atom to the acceptor molecule thereby forming a new fluorinated compound. There are numerous fluorinating agents; however, as listed in the table below, some of the more commonly used fluorinating agents include, but are not limited to:

[0030] The list of fluorinating agents in the table above, while extensive is not exhaustive, and it should be appreciated that there are other fluorine-containing compounds that can serve as fluorinating agents. These compounds when reacted with ZDDP, organophosphate or organothiophosphate, or metal derivatives thereof, or other derivatives thereof, result in fluorine transfer from the fluorinating agent to the ZDDP, organophosphate or organothiophosphate compound in the form of a P-F bond yielding a fluorinated organothiophosphate compound. Further reactions provide additional fluorination and formation of C-F bonds on the alkyl side chains in the phosphate compounds.

[0031] 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

)hates may preferably be used. Other organophosphates listed in FIGURE 1

include 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)SZn-; (RO) ₂ P(S)(SR); R(R ⁵ S) ₂ PS where R=CH ₃ and R'>CH ₃ ; (RO) ₃ PS where R=CH ₃ and R'=alkyl; MeP(S)Cl ₂ ; (RO) ₂ (S)PSP(S)(OR) ₂ ; P(S)(SH); (RO)(R ⁵ S)P(O)SZn-, SPH(OCH ₃ ) ₂ , where R= any alkyl and R'=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 preferably 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 utilize 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.

[0032] FIGURE 3 is a table presenting experimental results demonstrating 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, treated 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 treated 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 supernatant samples, indicating that the fluorine present in the supernatant has bonded to an element other than iron.

[0033] FIGURE 4 shows a 3 IP 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.

[0034] FIGURES 5-10 show experimental results and possible structures for reaction products formed by embodiments of the present invention. FIGURE 5 is a 3 IP NMR spectrum (IH 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 triplet located at approximately 57 ppm and 66 ppm are due to a phosphorous-fluorine bond with J=I 080. Each triplet peak is composed of multiple peaks that are apparent triplets.

[0035] FIGURE 6 is a 3 IP NMR spectrum (19F 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 triplets 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 as opposed to from a phosphorous-hydrogen or phosphorous-fluorine backbone.

[0036] The three peaks in the triplets of FIGURES 5 and 6 can be from spin-spin splits from at least three different interacting phosphorous atoms in the same structure. Chemical shifts of three 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 refers to F or another halogen. However, it should be appreciated that at least one Y present in the structure will be equal to F.

[0037] 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 preferably result from the different environment surrounding the phosphorous atoms. In structure (d) shown in FIGURE 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 results from the different environment surrounding the phosphorous atoms. In all of the structures shown in FIGURE 8, the presence of a phosphorous-fluorine bond has been confirmed, hi each of the structures shown in FIGURE 8, R is equal to an alkyl group.

[0038] 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.

[0039] FIGURE 10 shows additional organophosphate compounds that can be used with embodiments of the present invention. The organophosphate structures should be appreciated as representative structures and not considered to be in any way limiting this invention to these structures. Many embodiments of this invention use organophosphate structures that may not be specifically illustrated in FIGURE 10.

[0040] FIGURE 1 l(a) is a 3 IP NMR spectrum (IH decoupled to suppress phosphorous-hydrogen peaks) of supernatant from a reaction between ZDDP and ferric fluoride showing the formation of a fluoro-phosphorous compound. This reaction preferably occurred when ZDDP and ferric fluoride were mixed together and milled for a period of 24 hours in a rotary ball mill. 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.

[0041] FIGURE 1 l(b) is a 3 IP NMR spectrum (IH decoupled to suppress phosphorous-hydrogen peaks) of supernatant from a reaction between ZDDP and ferric fluoride showing the formation of a fluoro-phosphorous compound. This reaction occurred when ZDDP and ferric fluoride were mixed together and milled for a period of 72 hours in a rotary ball mill. 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.

[0042] 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, hi order to preferably generate consistent results, a protocol was established to prepare the surface prior to wear testing. The protocol comprises two phases: break-in and actual test.

[0043] 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 is applied to the center of the surface of the ring. For 2000 cycles, a constant load of 6 kg is applied. The rotation is then stopped, and the ring and the ball cleaned on the spot without removing them.

[0044] 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.

[0045] FIGURE 12 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 150 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.

[0046] 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 spirit and scope of 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 of ordinary skill in the art will readily appreciate from the disclosure of the present invention, 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 according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.