rexresearch.com


Ali ERDEMIR

Boric Acid Lubricant




Simple Boric Acid / Alcohol solution in fuel or oil reduces engine friction up to 2/3, & increases mpg. Ditto with buckyballs...








http://keelynet.com [ 08/09/07 ]
http://www.greencarcongress.com/2007/08/nano-boric-acid.html#more

Nano-Boric Acid could Decrease Fuel Consumption 4-5%

Scientists at the US Department of Energy’s Argonne National Laboratory have begun to combine nanoparticles of boric acid -- known primarily as a mild antiseptic and eye cleanser -- with traditional motor oils in order to improve their lubricity and by doing so increase energy efficiency.

In laboratory tests, these new boric acid suspensions have reduced by as much as two-thirds the energy lost through friction as heat.

This could result in a four or five percent reduction in fuel consumption, according to Ali Erdemir, senior scientist in Argonne’s Energy Systems Division.



US7547330
Methods to improve lubricity of fuels and lubricants

Inventor(s):     ERDEMIR ALI

A method for providing lubricity in fuels and lubricants includes adding a boron compound to a fuel or lubricant to provide a boron-containing fuel or lubricant. The fuel or lubricant may contain a boron compound at a concentration between about 30 ppm and about 3,000 ppm and a sulfur concentration of less than about 500 ppm. A method of powering an engine to minimize wear, by burning a fuel containing boron compounds. The boron compounds include compound that provide boric acid and/or BO3 ions or monomers to the fuel or lubricant.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority to and is a continuation-in-part of U.S. patent application Ser. No. 10/027,241, filed Dec. 20, 2001, which in turn claims priority to U.S. Provisional Patent Application No. 60/257,829, the entire contents of which are incorporated herein by reference.

GOVERNMENT RIGHTS

This invention was conceived under Contract No. W-31-109-ENG-38 between the U.S. Department of Energy (DOE) and the University of Chicago representing Argonne National Laboratories. The United States Government has certain rights in this invention.

FIELD OF THE INVENTION

This invention pertains generally to lubricant and fuel composition containing boron ions and molecules for improved lubricity and methods relating to the same.

BACKGROUND OF THE INVENTION

Sulfur is found naturally in crude oil and carries through into diesel and gasoline fuels unless specifically removed through distillation. As a result, diesel and gasoline fuels used in engines may contain sulfur in concentrations up to 3000 parts per million (ppm). At such high concentrations, sulfur provides high lubricity in fuel pumps and injector systems that deliver the fuel to the combustion chamber in an engine. However, fuel sulfur also causes polluting emissions, particularly SO2 and soot particles, and poisons the advanced emission-control and after treatment devices that are being developed to enable diesel engines to meet progressively more stringent emissions standards. Sulfur dioxide emissions are associated with environmental problems such as acid rain. However, when the current sulfur level is reduced in fuels, high friction and wear occur on sliding surfaces of fuel delivery systems and cause catastrophic failure.

Fuels with lower sulfur content have lower lubricity compared to those with higher sulfur content. Thus, low-sulfur diesel fuels do not provide sufficient lubricity for use in diesel engines, and the use of low-sulfur diesel fuels results in high friction and catastrophic wear of fuel pumps and injectors. When lubricity is compromised, wear increases in fuel injection systems, most of which were originally designed with the natural lubricating properties of traditional diesel fuel in mind. The lower lubricity of low-sulfur fuels poses significant problems for producers as well as for end-users of diesel fuels. Reduction in lubricity also contributes to a loss in useable power due to the increased friction the engine has to overcome. Because fuels with lower sulfur contents exhibit increased friction characteristics compared to fuels with higher sulfur contents, a perfectly tuned engine experiences a noticeable drop in efficiency when the fuel is changed from a high-sulfur fuel to a low-sulfur fuel. The typical diesel fuel currently used by trucks is a high-sulfur diesel fuel having a sulfur content of about 500 ppm. Low-sulfur diesel fuels have a sulfur content of approximately 140 ppm. Ultra low-sulfur diesel fuels have a sulfur content of 3 ppm. Fischer Tropsch fuels, the cleanest of all fuels, have a sulfur content of approximately zero. Because of its zero sulfur content, Fischer Tropsch fuel is an attractive diesel fuel, creating the least amount of pollution. Unfortunately, because it contains zero sulfur, it has no lubricity at all. Thus, Fischer Tropsch fuel causes the highest wear damage on sliding test samples. If it were used in today's engines, it would cause the instant failure of fuel pumps and injectors. Thus, it is not sufficient to simply reduce the sulfur content of fuels, because doing so would rob diesel fuels of their value as effective lubricants.

New mandates by the Environmental Protection Agency (EPA) call for the reduction of sulfur in diesel fuels to levels as low as 40 ppm in 2004 and to 15 ppm beginning Jun. 1, 2006. Such a move would quickly lead to the catastrophic failure of diesel fuel system components. The same requirements are also in place in Europe and Japan. The United States has been closely monitoring the use of low-sulfur fuels around the world. In Sweden and Canada, low-sulfur diesel fuels have been used for several years. Problems with increased wear have been encountered in both countries. The wholesale introduction of low-sulfur fuel in Sweden has had a disastrous effect on diesel engine operation. Swedish refiners are now using additives to prevent excessive wear in fuel injection systems, and their problems are apparently under control. Certain major Canadian refining companies are also adding lubricants before delivering low-sulfur fuels to customers.

The American Society of Tool and Manufacturing Engineers (ASTME), the Society of Automotive Engineers (SAE), and the International Organization for Standardization (ISO), have not yet set fuel lubricity specifications for supplying or testing low-sulfur fuels. Because of added costs, refiners are unlikely to consider supplying a pre-additized fuel before a specification has been set. Until the lubricity specification is written and followed, responsibility rests with diesel equipment end users to use fuel additives to maintain the reliability of their diesel engines.

A common approach to the problem of low-sulfur fuels has been to add lubricant compositions to fuels that reduce friction in internal combustion engines. Various patents disclose additives formulated as lubricating oils and blended into fuels. Alcohols are well known for their lubricity properties when included in lubricating oil formulations. Alcohols are also known for their water-scavenging characteristics when blended into fuels. The use of vicinal hydroxyl-containing alkyl carboxylates, such as the ester glycerol monooleate, have also found widespread use as lubricity additives or as components in lubricating oil compositions.

Borated lubrication compounds are well known lubrication additives for fuel compositions. Borated lubrication compounds are known to have high viscosity indices and favorable low temperature characteristics. Such boron-containing compounds are known to be non-corrosive to copper, to possess antioxidant and potential antifatigue characteristics, and to exhibit antiwear and high temperature dropping point properties for greases. Borated esters and hydrocarbyl vicinal diols have long been proposed as fuel or lubricant additives, especially as mixtures of long chain alcohols or hydroxyl-containing aliphatic, preferably alkyl, carboxylates. Borated lubrication compounds are generally obtained by synthetic methods known in the art. Typically, these borated lubrication compounds are prepared by reacting boric acid or boric oxide with appropriate aliphatic or alkoxylated compounds.

Borated derivatives of phosphorus are also known additives for liquid fuel or lubricant compositions. Such borated phosphorus derivatives include borated dihydrocarbyl hydrocarbylphosphonates. Borated phosphite additives may be synthesized by reacting dihydrocarbyl phosphites with such boron-containing compounds as boric oxide, metaborates, alkylborates or boric acid in the presence of a hydrocarbyl vicinal diol.

Organometallic boron-containing compounds are yet another class of fuel additives. In low-sulfur fuels, such organometallic compounds effect a lowering of the ignition temperature of exhaust particles in diesel engines equipped with an exhaust system particulate trap. Organometallic compounds contain a metal capable of forming a complex with an organic compound. Useful metals for use in such compounds include Na, K, Mg, Ca, Sr, Ba, Ti, Zr, V, Cr, Ni, Mn, Fe, Co, Cu, Zn, B, Pb, and Sb. Borated versions of such organometallic complexes are derived or synthesized from both aliphatic and heterocyclic organic compounds.

Although various patents describe boron-containing additives that provide lubricity to fuel compositions, all the conventional additives are based on compositions that require prior synthesis before addition to the fuel. Some, such as phosphates and amines, require complex formulations and lengthy preparation, and therefore are not cost effective as fuel ingredients. These synthetics have not readily been taken up to replace sulfur in fuel compositions.

In terms of cost and effectiveness, the synthetics are impractical for several reasons. First, large amounts of additives are needed in order to achieve the same level of lubricity that a sulfur concentration of 500 ppm can provide in fuels. In addition, some of the current additives are “one shot” or “point-of-use” additives. These have to be added to the fuel tank at refills because they cannot easily be incorporated into the distillation processes in refiners. Other additives may fail when fuel injectors begin to operate at high pressures, such as 30,000 psi, because higher pressures mean smaller clearances between an injector's plunger and barrel, which results in more opportunity for engine wear. These higher pressures will soon be required by the EPA as part of the more advanced emission control technologies. Finally, the current additives may harm metallic or plastic fuel system components by causing corrosion and producing deposits in the long run.

Thus, a need remains for a readily available ingredient that can be easily and simply combined with low-sulfur fuel compositions to provide an additive that is inexpensive, non-toxic, and confers enhanced lubricity to low-sulfur fuels.

SUMMARY OF THE INVENTION

The present invention relates to methods for providing lubricity in fuels and lubricants, to fuel and lubricant compositions that include boron, and to a method of powering engines to minimize wear.

The present invention provides for boron additives that, when mixed with either low-sulfur or sulfur free diesel and gasoline fuels, solve the friction, galling, and severe wear problems encountered with sulfur free fuels. The increase in lubricity that occurs upon addition of the boron compounds or boric acid of the invention to low-sulfur fuels results in lower wear in fuel pumps and injector systems. The replacement of sulfur in fuels with boron compounds provides for a cleaner environment, at a low cost relative to other additive technologies currently in use. The inventive approach should stimulate increased use of sulfur-free diesel and gasoline fuels. Easy adaptation by industry is possible, since the additives are easily and cheaply obtained and can be mixed directly with fuels without the necessity for any intervening chemical synthesis, or the use of other ingredients of questionable toxicity. Alcohol containing gasoline fuels can also be formulated with these inventive boron additives.

Demonstration of the application and use of these additives in diesel fuels should generate immediate and widespread industrial interest. Primary beneficiaries should be the companies that manufacture diesel engines and those that produce diesel fuels. The production and use of small size diesel engines in passenger cars providing very good fuel economy and very low emissions will also be feasible. Use of the boron compounds and additives should lead to a cleaner environment and longer engine life. Thus, people who drive and live or work in areas where diesel powered transportation systems are used will also benefit from this technology.

The invention provides a method for providing lubricity in a fuel or lubricant such as an oil product. The method includes adding a boron compound (primarily based on boron, oxygen and hydrogen) or boric acid to a fuel and/or oil to provide a boron-containing fuel or lubricant. The additives of the present invention can be any simple boron compound that dissolves in a common solvent to form a solution, preferably fully miscible with a diesel or gasoline fuel or a lubricant, to produce a concentration of boric acid molecules and/or BO3 ions or monomers in the fuel or lubricant composition. Suitable boron compounds for use in providing increased lubricity in a fuel or lubricant include, but are not limited to, boric acid, borax, boron oxide, nanometer-sized boric acid powders, trimethylborate, trimethoxyboroxin or combinations of these. The fuels to be used with the invention may contain a boron compound at a level of from about 30 ppm to about 3,000 ppm, and a concentration of sulfur of less than about 500 ppm. Lubricants to be used with the invention may contain a boron compound such as a borate, boroxin or combination thereof at a concentration of about 100 to about 80,000 ppm.

Suitable fuels for use with the present methods for providing lubricity in a fuel include, but are not limited to, diesel, gas, kerosene, dimethyl ether, liquid propane gas, liquid propane fuels, liquefied natural gas, or combinations of these.

Suitable lubricants for use with the present methods for providing lubricity in a lubricant include, but are not limited to, oil products such as base or formulated vegetable oils, mineral oils, synthetic oils, greases and combinations thereof. Glycols such as polyethylene glycol and combinations thereof can also be used as a lubricant with inventive methods.

In certain embodiments of the invention the boron compound or boric acid is added to a solvent prior to adding the boron compound to the fuel. In such embodiments the solvent may be an alcohol, such as methanol or ethanol. In one embodiment of the invention, a concentrated methanolic solution of boric acid is mixed with a low-sulfur or sulfur free diesel fuel, providing a boric acid concentration of from about 200 to about 2000 ppm in the fuel.

A method of powering an engine to minimize wear is also provided. The method includes burning a fuel which may have a sulfur content of less than about 150 ppm, wherein the fuel contains a boron compound or boric acid at a concentration of from about 30 ppm to about 3,000 ppm. An average wear scar diameter of less than about 0.40 mm occurs under standard conditions when such a method is used.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a bar graph showing the effects of methanolic solutions of boric acid on the lubricity performance, as measured by the wear scar diameter according to standard conditions described herein, of low-sulfur (140 ppm sulfur content) diesel fuel.

FIG. 2a. is a cut-away side view diagram showing the (ball-on-three-disk) BOTD Fuel Lubricity Test Machine, and the standard conditions used for testing fuel lubricity, as described herein. FIG. 2b. is a diagram showing a pin-on-disk machine, as described herein.

FIG. 3 is a bar graph showing the solubility of boric acid in various solvents.

FIG. 4 is a bar graph showing the effects of boric acid on the lubricity performance, as measured by the wear scar diameter according to standard conditions described herein, of ultra low-sulfur (3 ppm sulfur content) diesel fuel.

FIG. 5 is a bar graph showing the effects of trimethylborate on the lubricity performance, as measured by the wear scar diameter according to standard conditions described herein, of low-sulfur (140 ppm sulfur content) diesel fuel.

FIG. 6 is a bar graph showing the effects of trimethoxyboroxin on the lubricity performance, as measured by the wear scar diameter according to standard conditions described herein, of no sulfur (0 ppm sulfur content) and low-sulfur (140 ppm sulfur content) diesel fuels.

FIG. 7 is a bar graph showing the effects of nanometer-sized boric acid powders on the lubricity performance, as measured by the wear scar diameter according to standard conditions described herein, of ultra low-sulfur (3 ppm sulfur content) diesel fuel.

FIG. 8 is a graph showing the effect of nanometer-sized boric acid powders on the lubricity performance, as measured by the friction coefficient, of pure synthetic oil (Poly alpha olefin, PAO) with a steel pin and steel disk test pair under lubricated sliding conditions.

FIG. 9 is a graph showing the effect of nanometer-sized boric acid powders upon the lubricity performance, as measured by the friction coefficient, of paraffinic oil with a steel pin and magnesium alloy disk test pair under lubricated sliding conditions.

FIG. 10 is a graph showing the effect of a nano-structured boric acid coating upon the lubricity performance, as measured by the friction coefficient, of pure synthetic oil (PAO) with a steel pin and boron-carbide coated steel disk test pair under lubricated sliding conditions.

FIG. 11 is a graph showing the effect of a trimethoxyboroxin upon the lubricity performance, as measured by the friction coefficient, of pure synthetic oil (PAO) with a steel pin and steel disk test pair under lubricated sliding conditions.

FIG. 12 is a graph showing the effect of a trimethoxyboroxin upon the lubricity performance, as measured by the friction coefficient, of sunflower oil with a steel pin and steel disk test pair under lubricated sliding conditions.

FIG. 13 . is a graph showing the effect of trimethoxyboroxin upon the lubricity performance, as measured by the friction coefficient, of a 50/50 mixture of mineral oil and sunflower oil with a steel pin and steel disk test pair under lubricated sliding conditions.

FIG. 14 a graph that shows the effect of trimethoxyboroxin upon the lubricity performance, as measured by the friction coefficient, of pure synthetic oil (PAO) with a steel pin and an aluminum alloy 319 disk pair under lubricated sliding conditions



DETAILED DESCRIPTION OF THE INVENTION

Generally, the present invention provides a method for providing enhanced lubricity in a fuel. The same concept can be used to achieve lubricity in oil products, such as, mineral, vegetable, and synthetic base and formulated oils and greases, as well as other lubricants such as polyethylene glycols. The inventive approach exploits a family of simple, inexpensive, and environmentally-benign boron compounds which, when added to a fuel or lubricant, improve the lubricating properties of those fuels and lubricants. The addition of the boron compounds to a fuel improves the lubricity of the fuel by compensating for the lower lubricity that occurs when fuels with lower levels of sulfur are used.

The additives of the present invention can be any simple boron compound that dissolves in a common solvent to form a solution, which may be fully miscible with a diesel or gasoline fuel or a lubricant, to produce a concentration of boric acid molecules and/or BO3 ions or monomers in the fuel or lubricant composition. Without intending to be bound to any particular theory, it is believed that solutionized boric acid molecules and negatively charged BO3 monomers in the fuel or lubricant solutions bind strongly to the metallic surfaces of fuel pump and injector systems and protect these surfaces against wear and high-friction losses. Once bonded to these surfaces, the boric acid molecules and BO3 ions are thought to rearrange themselves in a plate-like boric acid structure, providing an unusual capacity to enhance the anti-friction and anti-wear properties of sliding metallic surfaces. Tests show that boric acid films formed by dipping steel, aluminum, titanium, and magnesium surfaces in water or methanolic solutions of boric acid are strongly bonded to these surfaces, making them very slippery and resistant to wear. Such films provide excellent lubrication to these metals when subjected to metal forming operations (such as stamping, rolling, deep-drawing, and forging).

Since the most effective components for improving lubricity are boric acid molecules and BO3 monomers or ions, any simple boron compound that generates boric acid molecules or BO3 may be used to increase lubricity in low-sulfur fuels. Boron compounds that are known to release boric acid and/or BO3 in water or alcohol solutions are: borax, kernite, ulexite, and colemanite. Other suitable boron compounds include boric acid, borax, boric oxide and other anhydrous or hydrated forms of boron. These compounds easily and readily form concentrated solutions in solvents such as methanol or ethanol. In addition, borates, boroxins, and combinations thereof can be mixed with solvents and fuels. For example, trimethylborate and trimethoxyboroxin are also ideal additives since they exist in liquid forms and are completely miscible with fuels.

Suitable fuels for use with the present methods for providing lubricity in a fuel include, but are not limited to diesel, gas, kerosene, dimethyl ether, liquid propane gas, liquid propane fuels, liquefied natural gas, or combinations of these. The fuels may also include a lubricant other than the boron compound such as those described herein.

Suitable lubricants for use with the present compositions and methods for providing lubricity in a lubricant include, but are not limited to, oil products such as base and formulated vegetable oils, mineral oils, synthetic oils, greases, and combinations thereof; polyethylene glycols and combinations thereof.

One embodiment of the method includes adding the boron compound or boric acid to a fuel to provide a boron-containing fuel that comprises boron compounds or boric acid at a level of from about 30 ppm to about 3,000 ppm. In various embodiments, the method provides a boron-containing fuel having a boron compound at a level of from about 200 to about 2000 ppm in the fuel, alternatively from about 50 ppm to about 1,000 ppm, or from about 100 ppm to about 500 ppm.

In some embodiments of the invention, a boron compound is added to a lubricant to provide a lubricant comprising a boron compound at a concentration of from about 100 ppm to about 80,00 ppm. In other embodiments, the amount of boron compound may vary from about 100 ppm to about 60,000 ppm, from about 100 ppm to about 50,000 ppm, and from about 500 or 1000 ppm to about 50,000 ppm.

Generally, the boron compounds or boric acid can be added to any fuel regardless of the sulfur content. In certain embodiments, the fuel has a sulfur concentration of less than about 500 ppm, possibly less than about 150 ppm, or even less than about 5 ppm, less than about 3 ppm, or even about 0 ppm. A fuel composition according to the invention, for example, includes a fuel having a sulfur content of less than about 500 ppm mixed with boric acid. The boric acid is typically present at a concentration of from about 100 ppm to about 3,000 ppm.

The invention also provides a method of powering an engine to minimize wear. The method includes burning a fuel which may have a sulfur content of less than about 500 ppm or less than about 150 ppm. The fuel includes a boron compound or boric acid at a concentration of from about 30 ppm and 3,000 ppm to the fuel. The boron compounds may be in the form of ionic compounds.

The lubricity of a given fuel can be determined through wear scar diameter measurements taken on a ball-on-three-disks (BOTD) instrument, as described in greater detail in the Examples section below. FIGS. 1 and 4-7 show the effects of the boron additives of this invention on the lubricity performance of diesel fuels, as measured by wear scar diameters. As shown in these figures, the average wear scar diameter for fuels treated with the boron compounds of this invention is approximately 3 to 4 mm when the fuel is tested according to the standard procedures described below. This is similar to the wear scar diameter produced with high-sulfur (500 ppm) diesel fuel and is considerably smaller than the wear scar diameters produced by untreated low-sulfur (150 ppm), ultra low-sulfur (3 ppm), and no sulfur (0 ppm) diesel fuels.

The lubricity of a given lubricant, such as an oil or grease, can be determined through friction coefficient measurements taken on a pin-on-disk instrument, as described in greater detail in the Examples section below. FIGS. 8-10 and table 5 show the effects of the boron additives of this invention on the lubricity performance of various oil products, as measured by friction coefficients. As shown in the figures and table, the friction coefficients for lubricants treated with boron additives are lower than those for untreated lubricants. This is consistent with improved lubricity performance for the treated lubricants.

In certain embodiments, the inventive additives are prepared in the form of concentrated solutions of simple, readily available boron compounds such as boric acid, borax, boron oxide, boron anhydrides, hydrates and other such materials. Such solutions are easily mixed with sulfur-free or low-sulfur diesel and gasoline fuels. Among others, ethanol and methanol are particularly effective solvents, and are among the most suitable candidates for introducing boron into gasoline fuels. Other suitable solvents include, but are not limited to, isobutyl alcohol, isoamyl alcohol, n-propanol alcohol, 2-methylbutanol alcohol, glycerol, glycol, ethylene glycol, glycerin, pyridine, lactate esters (such as ethyl lactate) or combinations of these solvents.

In one embodiment, the inventive method exploits the fact that boric acid dissolves in an ethanol or methanol solution in great quantities such that the solvents can be used as a carrier of boron as a lubricity additive. Boric acid is most soluble in methanol, approximately 175 grams of boric acid dissolve readily in one liter of solvent. Lower solubilities are found in ethanol, pyridine, isobutyl alcohol, acetone, and water. The solubility of boric acid in these solvents is shown in FIG. 3. Boric acid is an attractive additive because it is a very mild, non-toxic acid that is environmentally benign—water solutions of boric acid are often used to wash eyes. Concentrated water solutions of boric acid have a pH value of 4.5 at room temperature. Boric acid is not expected to cause any corrosion in the fuel delivery systems. Indeed, in certain corrosion experiments, boric acid has been used as a buffer solution to control and adjust pH.

FIG. 1 shows the effect of a highly concentrated (18%) methanolic solution of boric acid when mixed with low-sulfur diesel fuel (140 ppm). FIG. 4 shows the effect of a highly concentrated methanolic solution of boric acid when mixed with ultra low-sulfur diesel fuel (3 ppm). As shown in the figures, low and ultra low-sulfur diesel fuels containing between 100 and 2000 ppm boric acid have a lubricity performance comparable to high-sulfur diesel fuel, which is substantially better than the lubricity performance of untreated, low and ultra low-sulfur diesel fuels. Methanol and ethanol-based solvents are produced from cornstalks in the Midwest by Archer Daniels Midland. These solvents are already used with current gasoline in diesel fuels up to a level of 10%, but the United States government is urging their use in much greater quantities since methanol and ethanol are renewable non-polluting fuels. If necessary, the solubility of the boron compounds in these alcohols can be increased by heating them, but the concentrations achieved at room temperature are more than sufficient to restore the lubricity of low-sulfur diesel fuels.

Another effective way to achieve lubricity in low-sulfur diesel fuels and in lubricants is to add to the fuel or lubricant a borate, boroxin or combination thereof. Suitable borates include trialkylborates such as trimethylborate, and suitable boroxins include trimethylboroxin, trimethoxyboroxin, and tributoxyboroxin. These commercial products come in liquid forms. They are clear and transparent and mix and blend quite well with gasoline or diesel fuels. They burn clean and have some calorific value. They are perfectly soluble in diesel and gasoline fuels and, once added to diesel fuel, dramatically improve the lubricity of low-sulfur diesel fuels. Thus, trimethylborate and trimethoxyboroxin may be added directly to the fuel. For example, as shown in FIG. 5, trimethylborate provides the best improvement of the lubricity behavior of low-sulfur diesel fuels of all the boron additives tested. Notably, FIG. 5 shows that low-sulfur fuels to which trimethylborate has been added exhibit an average wear scar diameter even lower than that of the highest sulfur content diesel fuel. As shown in FIGS. 6(a) and (b), addition of trimethoxyboroxin into no sulfur (0 ppm) and low-sulfur (140 ppm) diesel fuels also makes a huge positive difference in fuel's lubricity. Other trialkylborates may also be used to improve lubricity in fuels. Examples of such trialkylborates include, but are not limited to, triethylborate, tri(n-propyl)borate, tri(n-butyl)borate, and mixed alkyl borates such as diethylmethylborate.

In other embodiments of the invention, nanometer size powders of solid boron compounds, such as boric acid, may be solutionized or dispersed in fuels and oil products to achieve improved lubricity. Nanometer-sized particles of boron compounds may also be mixed and fully dispersed in or miscible with fuels and oil products to achieve lubricity.

Nanometer-sized powders of boric acid (3-100 nm) can be produced by methods well known in the art. These methods include mechanical attrition, chemical precipitation, low pressure gas condensation and low temperature evaporation of ethyl borates or methanol or ethanol solutions of boric acid into or through the fuels or oils, etc. Because of a very high surface atom to bulk atom ratio, these nanometer-sized boron or boric acid particles can directly be incorporated into fuel and oil products such as base and formulated vegetable, mineral, and synthetic oils, greases and combinations thereof. Most of the atoms in these nanometer-sized particles reside on the surface of the particles and they are chemically very active. With very high surface energy, they are both physically and chemically attracted to the hydrocarbon molecules in fuels and oils. At such very low concentrations as 50 to 1000 ppm, they remain uniformly dispersed in fuels and act as self-lubricating entities. Such nanometer-sized particles may also be mixed or blended with lubricants such as oils, greases or combinations thereof; or polyethylene glycols, and combinations thereof, to achieve improved lubrication and superior anti-friction and wear properties in these products. FIG. 7 shows the lubricity performance of diesel fuels containing nanometer-sized boric acid powders in dispersion. It can be seen from the figure that treating ultra low-sulfur (3 ppm) diesel fuels with between about 500 and 1000 ppm nanometer-sized boric acid powders increases the lubricity performance of the fuel compared to untreated low and ultra low diesel fuels. In fact, as shown in the figure, the treated ultra low-sulfur fuels have a lubricity performance comparable to that of untreated high-sulfur diesel fuels. FIGS. 8, 9, and 10 show the lubricity performance, as measured by friction coefficients, of nanometer-sized boric acid powders mixed with various oils on steel and magnesium alloys. In these figures, lubricity performance is determined through friction coefficient measurements taken with a pin-on-disk instrument, as described in more detail in the Examples section below. Briefly, FIGS. 8-10 show that adding nanometer-sized boric acid powders to synthetic and paraffinic oils leads to a decrease in the friction coefficient, which corresponds to an increase in the lubricity performance of the oils.

The invention is further described in the following non-limiting examples.

EXAMPLES

Preparation of Test Fuels and Oils Containing Boron Additives

Various fuels and oils were tested for lubricity by measurement of wear scar diameters and friction coefficients. These fuels were obtained by adding concentrated solutions of boron compounds to the fuel in quantities sufficient to provide a concentration of boron, boric acid and/or BO3 monomers of between 100 ppm and 2000 ppm in the fuel composition. Similarly, oils were obtained by adding concentrated solutions of boron compounds to the oils in quantities sufficient to provide a concentration of boron, boric acid, and/or BO3 monomers of up to 8 percent by volume. In certain embodiments the boron compounds were present in an amount of between 0.1 and 8 percent by volume.

Fuel Wear Testing Protocol:

Lubricity additives were evaluated using wear scar diameter measurements. Friction and wear measurements were carried out using a ball-on-three-disk (BOTD) Fuel Lubricity Test Machine according to the standard conditions described below, and as shown in FIG. 2a. The data obtained with this testing apparatus under standard testing conditions show the improvement in diesel fuel lubricity that occurs when boron compounds such as boric acid are added to the fuel.

Diesel fuel lubricity tests were conducted in a BOTD lubricity test machine whose detailed description can be found in C. D. Gray, G. D. Webster, R. M. Voitik, P. S T Pierre, and K. Michell, “Falex Ball-on-Three Disk (BOTD-M2) Used to Determine the Low Temperature Lubricity and Associated Characteristics of Lubricity Additives for Diesel Fuels,” Proc. 2<nd >Int. Colloquium on Fuels, W. J. Bartz, ed., Technische Akademie Esslingen, Ostfildem, Germany, pp. 211-217 (1999), which is herein incorporated by reference. In brief, the test configuration for the BOTD machine consists of a highly polished 12.7-mm-diameter alumina ball (Al2O3) pressed against three stationary 52100 grade steel flats under a load of 24.5 N, creating a peak Hertz pressure of about 1 GPa. The steel disks were 6.35 mm in diameter and had a surface finish between 0.1 and 0.2 μm, root mean square. The Rockwell C hardness value of the steel disks was 57 to 63. The lubricant cup of the BOTD machine was filled with the diesel fuels, and the rubbing surfaces of the steel specimens were immersed in fuel throughout the tests. Rotational velocity of the ceramic ball was 60 rpm and the test duration was 45 min. At the conclusion of each test, the dimensions of the wear scars on the flat steel specimens were measured by an optical microscope equipped with a digital micrometer display unit. The average wear scar diameters are expressed in mm. In terms of fuel lubricity and wear analyses, this is presently the most widely used procedure to assess the lubricity of diesel fuels.

The BOTD Lubricity Test Machine shown in FIG. 2a was developed to evaluate the anti-wear performance of diesel fuels. The amount of wear achieved was measured during point to point contact of the test ball specimen under high load and rotational speed with each test diesel fuel as the lubricant. Average wear scar diameter on the flat 52100 test steel was measured in control fuels (respectively, high-sulfur diesel fuel containing 500 ppm sulfur, and low-sulfur diesel fuel containing 140 ppm) that did not contain any boron additive. The effect on average wear scar diameter of various boron additives according to the present invention was then measured in low-sulfur diesel fuel (0-140 ppm sulfur content), the test fuel having boron and/or boron compound concentrations of between 100 and 2000 ppm.

When standard lubricity tests are performed on a diesel fuel having a sulfur content of from about 400 to about 800 ppm, the typical wear scar diameter forming on a flat 52100 steel is around 0.35 mm. The data for untreated fuels appears in tables 1-4. The data show that Fischer Tropsch fuel (sulfur content of approximately zero) has the highest wear index of 0.75 mm scar diameter. Ultra low-sulfur fuel (3 ppm sulfur content) has a wear index of 0.57 mm. Low-sulfur diesel fuel (140 ppm sulfur content) has a wear scar index of 0.49 mm. Finally, high-sulfur diesel fuel, (500 ppm sulfur content) has the lowest wear index of 0.35 mm.

The change in lubricity and increase in wear was measured for fuels treated with various boron compounds. The data for these treated fuels appears in tables 1-4. The results demonstrate that diesel fuels of very low-sulfur content (140 ppm or lower sulfur content) with boric acid additive exhibited smaller wear scar diameters (in one case less than 0.28 mm) than did untreated fuels having the highest sulfur content (0.35 mm or greater wear scar diameter). It was concluded that low-sulfur fuels containing the boron additives of the present invention have increased lubricity compared to untreated high-sulfur fuels (500 ppm sulfur content).

The effect of boric acid on low-sulfur diesel is dramatic. Table 1 lists the changes in the wear scar diameter for different boric acid concentrations in low-sulfur diesel fuel. The effect upon average wear scar diameter of low-sulfur diesel fuel (having a sulfur content of 140 ppm) when an 18% concentrated methanol solution of boric acid is added to low-sulfur diesel fuel is shown in the table. The addition of the boron compound to the low-sulfur diesel fuel results in a dramatic increase in lubricity as indicated by the lower wear scar diameter.

TABLE 1

Effect of highly concentrated methanolic solution of boric acid (18% boric acid in methanol) on anti-wear properties of low-sulfur diesel fuel (140 ppm sulfur content).

Boric Acid (H3BO3)  
Concentration in  Wear Scar
Low-Sulfur Diesel (ppm)  Diameter (mm)

0  0.498 ± 0.043
100  0.336 ± 0.011
250  0.284 ± 0.068
500  0.297 ± 0.065
1,000  0.296 ± 0.038
2,000  0.348 ± 0.072

FIG. 1 illustrates these values graphically, showing the effect on lubricity performance of a variation in boron concentration in the fuel between 100 ppm (3<rd >bar) and 2000 ppm (7thbar). Average wear scar diameters for two control fuels, high-sulfur diesel fuel (500 ppm) and low-sulfur diesel fuel (140 ppm), are shown by bars 1 and 2. It is evident from the graph that more lubricity is provided to low-sulfur diesel fuel (140 ppm) by adding methanol solutions of boric acid, than is conferred to diesel fuel by 500 ppm sulfur content.

Table 2 shows the changes in the wear scar diameter for different concentrations of highly concentrated methanol solutions of boric acid (18%) in ultra low-sulfur diesel fuel (3 ppm sulfur content).

TABLE 2

Effect of highly concentrated methanolic solution of boric acid (18% boric acid in methanol) on anti-wear properties of ultra low-sulfur diesel fuel (3 ppm sulfur content).
Boric Acid (H3BO3)  
Concentration in Ultra   Wear Scar
Low-Sulfur Diesel (ppm)  Diameter (mm)
0  0.571 ± 0.008
500  0.356 ± 0.020
2000  0.346 ± 0.023

FIG. 4 illustrates these values graphically. This figure shows the effect of methanolic solution of boric acid upon the lubrication performance of 3 ppm sulfur containing diesel fuel. The graph shows that 500 ppm boric acid provides approximately the same lubricity as that found in standard high-sulfur diesel fuel. Bars 4 and 5 of the graph show the effect that addition of boron (500 ppm and 2,000 ppm boric acid content respectively) has upon average wear scar diameter of ultra low-sulfur diesel fuel. Bars 1, 2 and 3 show lubricity in three control fuels, respectively high-sulfur diesel fuel (500 ppm), low-sulfur diesel fuel (140 ppm), and ultra low-sulfur diesel fuel (3 ppm). Average wear scar diameter is the highest in the ultra low-sulfur diesel fuel without boron.

Table 3 lists the changes in the wear scar diameter exhibited for different concentrations of trimethylborate in low-sulfur diesel fuel (140 ppm sulfur content).

TABLE 3

Effect of trimethylborate on the anti-wear properties of low-sulfur diesel fuel (140 ppm sulfur content).

Trimethylborate  
Concentration in Low-  Wear scar
sulfur Diesel (ppm)  diameter (mm)
0  0.498 ± 0.043
500  0.266 ± 0.020
2,000  0.286 ± 0.042

FIG. 5 illustrates these values graphically. The bar graph in the figure shows the effect of addition of trimethylborate to low-sulfur diesel fuel (140 ppm), demonstrating a lower average wear scar diameter than in the control fuels containing no borate. Both controls, high-sulfur diesel fuel (500 ppm) (bar 1) and low sulfur diesel fuel (140 ppm) (bar 2), show a higher wear index than the lower sulfur containing fuel with boron present. Low-sulfur diesel fuel (140 ppm) (bar 2) without boron has the greatest wear index, as expected.

Table 4 lists the changes in the wear scar diameter when trimethoxyboroxin is added to a sulfur free diesel fuel (Fischer Tropsch, 0 ppm) and a low-sulfur diesel fuel (140 ppm).

TABLE 4

Effect of trimethoxyboroxin on the anti-wear properties of Fischer Tropsch diesel fuel (0 ppm sulfur content) and low-sulfur diesel fuel (140 ppm sulfur content).

Wear scar  Wear scar
Trimethoxyboroxin  diameter (mm)  diameter (mm)
Concentration  for Fischer  for low-sulfur (ppm) in fuels  Tropsch fuel  diesel fuel

0   0.75 ± 0.008  0.498 ± 0.004
250  0.405 ± 0.004  0.395 ± 0.007
500  0.370 ± 0.006  0.359 ± 0.008
1000  0.362 ± 0.008  0.345 ± 0.005

FIG. 6 graphically represents the effect upon the fuel wear scar diameter of the addition of trimethoxyboroxin to a sulfur free diesel fuel (FIG. 6a) and a low-sulfur diesel fuel (FIG. 6b), in the amounts respectively of 250, 500, and 1000 ppm. The first two bars in FIG. 6a represent the average wear scar diameter for control diesel fuels having a sulfur content of 500 ppm and 0 ppm, respectively. Similarly, the first two bars in FIG. 6b represent the average wear scar diameter for control diesel fuels having a sulfur content of 500 ppm and 140 ppm, respectively. FIGS. 6a and 6b both show that the addition of trimethoxyboroxin at a concentration of between 250 and 1000 ppm results in a lowering of the average wear scar diameter.

FIG. 7 graphically represents the effect of nanometer-sized boric acid powders on the lubricity performance of 3 ppm sulfur containing diesel fuel. The nanometer-sized powders of boric acid (3-100 nm) were produced by low pressure gas condensation and low temperature evaporation of ethyl borates or methanol or ethanol solutions of boric acid into or through the fuels or oils. The first three bars in FIG. 7 represent the average wear scar diameter for control diesel fuels having a sulfur content of 500 ppm, 140 ppm, and 3 ppm, respectively. The remaining two bars show that the addition of nanometer-sized boric acid powders at concentrations between about 250 and about 1000 ppm results in a lowering of the average wear scar diameter.

Lubricant Friction Coefficient Testing Protocol:

In addition to evaluating diesel fuels using wear scar diameter measurements, lubricants were evaluated using friction coefficient measurements. Friction coefficient measurements were carried out using a pin-on-disk Test Machine according to the standard conditions described below. The testing apparatus and standard testing conditions show the improvement in lubricant lubricity that occurs when boron compounds such as boric acid are added to lubricants, such as oils and greases.

Diesel fuel lubricity tests were conducted in a pin-on-disk test machine whose detailed description can be found in the 1990 Annual Book of ASTM Standards, Volume 3.02, pages 391-395, which is herein incorporated by reference. In brief, the machine consists of a stationary top-mounted pin that rubs against a unidirectional rotating disk or flat. The pins can be either flat pins, hemispherically tipped pins (typically, the pins that have a 5″ radius ground onto one of the faces). Alternatively, 3⁄8″ or 1⁄2″ diameter balls can be used. Disks up to approximately 3″ in diameter (approximately 1⁄4″ thick) can be tested on the machine. The chuck that holds the discs can also hold flats up to 2″×2″. The lubricants are applied to the disk surface, and the pins are rubbed against the disk. A load is applied to the pin by using dead weights. For the specific tests performed, 20 to 50 N loads were used and the sliding velocity of the rotating disk was adjusted to give linear velocities of 0.01 and 0.1 m/s. Tests were run at room temperature and in open air whose relative humidity varied between 30 and 60%. A schematic of this test system can be found in FIG. 2b.

FIG. 8 is a graph showing the effect upon the lubricity performance of nanometer-sized boric acid powders, which were sprayed on the surface of a steel disk, to pure synthetic oil (PAO).

FIG. 9 is a graph showing the effect of nanometer-sized boric acid powders, which were sprayed on the surface of a steel disk, upon the lubricity performance of a paraffinic oil on a magnesium alloy sample.

FIG. 10 is a graph showing the effect of a nano-structured boric acid coating mixed with PAO upon the lubricity performance of a steel pin and boron-carbide coated steel disk test pair under lubricated sliding conditions. These coatings are prepared by either spraying of methanolic solutions of boric acid to the surface or chemically extracting them from the boron carbide coatings by a high temperature chemical conversion method as described in U.S. Pat. No. 5,840,132, which is herein incorporated by reference.

As shown in FIGS. 8-10, the presence of nanometer-sized boric acid powders on a sliding surface significantly reduces the friction coefficient of the oil.

Table 5 shows the changes in lubricity performance, as measured by both wear scar diameters and friction coefficients, for various test pairs when trimethoxyboroxin is added to a base mineral oil. The data in table 5 demonstrate that the addition of trimethoxyboroxin (5 percent by volume) to pure mineral oil dramatically decreases the friction coefficient and the wear scar diameter, which corresponds to an improvement in the lubricity performance of the oil.

TABLE 5

Effect of 5 vol. % trimethoxyboroxin addition to the anti-wear properties of a pure mineral oil. This test was performed on a pin-on disk machine whose function and main features may be found in the 1990 Annual Book of ASTM Standards,

Volume 3.02, Section 3, pages 391-395.
Wear scar  
diameters  Wear scar
(WSD) (mm)  diameters (WSD) and friction  (mm) and friction coefficients  coefficients (FC) with  with mineral pure  oil + 5 vol. % mineral oil  trimethoxyboroxinFC<a>FC<a>

Test Pairs  WSD    WSD  
Steel pin/Steel disk<b>

  0.454  0.05  Non-measurable  0.01Steel pin/Steel disk<c>
  1.11  0.06  Non-measurable  0.01Steel pin/Steel disk<d>
  1.695  0.2  Non-measurable  0.02Steel ball/Steel disk<e>
  0.67  0.14  0.43  0.085Steel pin/titanium disk<f>
  2.564  0.35  1.998  0.15Steel pin/aluminum disk<g>
  3.778  0.16  2.035  0.13

Steady state friction coefficients

Test Conditions: 2 kg load, 10 cm/s speed, using steel pin with 127 mm radius of curvature, sliding distance: 135 m.<c>
Test Conditions: 5 kg load, 10 cm/s speed, using steel pin with 127 mm radius of curvature, sliding distance: 135 m.<d>
Test Conditions: 2 kg load, 1 cm/s speed, using steel pin with 127 mm radius of curvature, sliding distance: 135 m, sliding distance: 375 m.<e>
Test Conditions: 2 kg load, 1 cm/s speed, using 10 mm diameter steel ball, instead of pin, sliding distance: 135 m.<f>
Test Conditions: 2 kg load, 10 cm/s speed, sliding distance: 135 m.<g>
Test Conditions: 5 kg load, 10 cm/s speed, sliding distance: 135 m.

FIG. 11 shows the some of the data from table 5 graphically. Specifically, FIG. 11 shows the actual frictional traces for a steel pin and a steel disk under the test conditions denoted by footnote “d” of the table, tested under 20 N using pure mineral oil and 5 vol. % trimethoxyboroxin containing mineral oil. The figure demonstrates that the presence of trimethoxyboroxin in the mineral oil significantly reduces the friction coefficient, consistent with improved lubricity performance of the oil.

FIG. 12 shows the effect of trimethoxyboroxin on lubrication performance of sunflower oil (a vegetable base oil). Likewise, FIG. 13 shows the effect of the addition of trimethoxyboroxin on the lubrication performance of a 50/50 mixture of sunflower oil and pure mineral oil. Finally, FIG. 14 shows the effect of the addition of trimethoxyboroxin to a pure synthetic oil (PAO). In each case, the addition of trimethoxyboroxin dramatically decreased the friction coefficient and wear scar diameter.

Thus, in the data shown, both fuels and oils containing the boron compounds of the present invention show significantly reduced wear and friction compared to untreated fuels and oils.



[ Abridged ]
NOVEL MATERIALS AS ADDITIVES FOR ADVANCED LUBRICATION   
US8648019


This invention relates to carbon-based materials as anti-friction and anti-wear additives for advanced lubrication purposes. The materials comprise carbon nanotubes suspended in a liquid hydrocarbon carrier. Optionally, the compositions further comprise a surfactant (e.g., to aid in dispersion of the carbon particles). Specifically, the novel lubricants have the ability to significantly lower friction and wear, which translates into improved fuel economies and longer durability of mechanical devices and engines.

FIELD OF THE INVENTION

This invention relates to novel lubricant compositions comprising a particulate carbon material suspended in a liquid carrier, which provide beneficial anti-friction and anti-wear properties. The particulate materials have various shapes, sizes, and structures and are synthesized by autogenic reactions under extreme conditions of high temperature and pressure. Specifically, the lubricant compositions have the ability to significantly lower friction and wear, which translates into the advantages of improving the durability and fuel economies of motorized and mechanical devices.

BACKGROUND OF THE INVENTION

The transportation share of U.S. energy consumption is around 28% (or 28.4 quadrillion Btu) with petroleum accounting for 96% of this amount (every day, the U.S. consumes about 13 million barrels of petroleum for transportation). Engine and drive-train friction accounts for 10-15% of the fuel's total energy used in current vehicles, which translates to about 1.3 to 2 million barrels of petroleum/day lost to friction alone. Furthermore, a significant amount of energy is spent to remanufacture and/or replace worn parts in these systems. In short, the energy efficiency, durability, and environmental compatibility of all motorized and mechanical devices are closely related to the effectiveness of the lubricants on rolling, rotating, and sliding contact surfaces. Poor or inefficient lubrication results in higher friction and severe wear losses, which in turn adversely impacts performance and durability [1]. In addition, lubricants can include additives such as viscosity index improvers, anti-oxidant agents, anti-corrosion agents, wear-protection agents, acid neutralizers, dispersants and the like to provide beneficial properties.

The energy efficiency, durability, and environmental compatibility of all kinds of moving mechanical systems (including engines) are closely related to the effectiveness of the lubricants being used on their rolling, rotating, and sliding surfaces. Therefore, lubricants play a vital role in machine life, efficiency, and overall performance. Poor or inefficient lubrication always result in higher friction and severe wear losses, which can in turn adversely impact the performance and durability of mechanical systems. In particular, progressive wear due to inadequate lubrication is one of the most serious causes of component failure. Inadequate lubrication can also cause significant energy losses in the above-mentioned industrial systems mainly because of high friction.

Currently, there are numerous solid lubricants available at sizes ranging from 1 nm to more than 500 nm in powder forms. The finer solids (i.e. 1 to 30 nm range) are mostly made of nanostructured carbons, like C60, nano-tubes, nano-fibers, and nano-onions while intermediate range lubricants (30 to 100 nm) are made of inorganic solids, such as MoS2, WS2, h-BN and pure metals (like gold, silver, tin, bismuth, etc.). WS2 is synthesized typically in the form of fullerene-like particles and hence it is often referred to as inorganic fullerene or, IF. Most of these materials are manufactured using a bottom-up approach involving multi-step chemical synthesis routes (e.g. gas phase chemical processing, combustion synthesis, sonochemistry, etc.) and the uses of environmentally unsafe chemicals. Many current processes also generate large amounts of toxic by-products to deal with after the manufacturing.

There is an ongoing need for new lubricant compositions that are environmentally friendly or benign, and which provide reduced friction and wear. The present invention addresses this need.

SUMMARY OF THE INVENTION

The present invention relates to the development of various carbon-based additive materials for improving the anti-friction and anti-wear properties of lubricants, for example, in engine oils, diesel fuels and greases. Conventional lubricants do not yet meet the expectations of providing the performance requirements of motorized and mechanical devices. Carbon is an extremely versatile material that exists in numerous forms with diverse physical, chemical, electrical and electrochemical properties. Certain carbonaceous particles, such as carbon nano-onions, carbon nano-fibers, carbon nano-tubes and sub-micron graphite particles have all been considered for lubrication purposes in the past but they tend to be expensive, ineffective, and difficult to scale-up.

The present invention relates to the design and development of novel carbon-based materials as anti-friction and anti-wear additives for advanced lubrication purposes. The carbon-based materials have various shapes, sizes, and structures and are synthesized by autogenic reactions under extreme conditions of high temperature and pressure. The materials of the invention are created typically by the dissociation of organic, organo-metallic or polymeric compounds, such as plastic waste in absence or presence of a catalyst in a closed, ventable reactor in which the pressure in the reactor is provided solely by vaporization of carbon-based precursors (i.e., autogenic pressure generation). The resulting carbon products are typically in the form of carbon nanotubes, fibers, spheres or clusters that can optionally contain elements such as B, Fe, Co, Ni, Mo, W, Ag, Au, Sn, Bi or their oxides, carbides, borides, nitrides and sulfides. Under severe tribological conditions, these carbon-based additives can improve lubrication properties without having a negative environmental impact. Specifically, the novel lubricants have the ability to significantly lower friction and wear, which can translate, for example, into improved fuel economies and longer durability of engines and mechanical devices.

In one embodiment, the present invention provides a lubricant composition comprising carbon particles suspended in a liquid hydrocarbon carrier. The carbon particles are prepared by heating a neat, high or low density polyethylene-containing precursor composition in a sealed reactor at a temperature in the range of at least about 700° C. and under an autogenic, self generated pressure in the range of about 800 to about 2000 pounds-per-square inch (psi), subsequently cooling the reactor to less that 100° C., and isolating the resulting particulate carbon material from the reactor. Preferably, the carbon particles are present in the composition at a concentration in the range of about 0.1 to about 2 percent by weight (wt %), more preferably about 0.5 to about 1 wt %.

In some preferred embodiments, the composition further comprises a surfactant (e.g., to aid in suspension of the carbon particles. Non-limiting examples of suitable surfactants include non-ionic surfactants such as sorbitan trioleate. Other suitable surfactants include sorbitan sesquioleate (SSO) and Surfonic LF-17 (an ethoxylated and propoxylated linear C12-C12 alcohol). Preferably, the surfactant is present in the composition at a concentration in the range of about 1000 to about 20000 parts-per-million (ppm), more preferably about 5000 to about 10000 ppm.

The liquid hydrocarbon carrier preferably comprises a poly(alpha olefin). Examples of suitable hydrocarbon carriers include poly(alpha olefin) materials. Preferred poly(alpha olefin) materials have a kinematic viscosity in the range of about 4 to about 10 centistokes (cSt) at about 100° C., e.g., about 4 cSt.

In some preferred embodiments, the precursor composition of the carbon particles is high or low density polyethylene, and the particles are generally spherical in shape, not hollow, and have an average diameter in the range of about 1 to about 5 micrometers. Optionally, the spherical particles can be heat-treated under an inert atmosphere at a temperature in the range of about 1000 to about 3000° C. prior to suspending in the liquid hydrocarbon carrier, and the carbon particles have a density of about 2 grams-per-cubic centimeter (g/cc) to about 2.3 g/cc (e.g., about 2.1 g/cc).

In other preferred embodiments, the precursor composition of the carbon particles the precursor composition comprises a combination of low or high density polyethylene and about 5 to about 20 wt % of a metal-containing compound. For example, the metal-containing compound can be a metal carboxylate salt, metal phosphate salt, a metal oxide, a metal sulfide, a metal carbine, a metal boride, a metal nitride, or an organometallic compound. Examples of suitable metals for the metal-containing compound include B, Fe, Co, Ni, Mo, W, Ag, Au, Sn, and Bi.

In one preferred embodiment, the metal-containing compound comprises cobalt acetate, and the carbon particles comprise metallic cobalt nanoparticles with face-centered cubic crystal symmetry encapsulated within carbon nanotubes having an average tubular diameter of less than about 100 nm. When the metal-containing compound comprises ferrocene, the carbon particles comprise metallic iron nanoparticles with face-centered cubic crystal symmetry encapsulated at the tip of carbon nanotubes having an average tubular diameter of less than about 100 nm.

Tribological studies of lubricant compositions of the present invention demonstrate a 30 to 40% reduction in wear relative to pure hydrocarbon-based lubricant is feasible even under severe sliding conditions. Reduction in friction was also substantial. Further improvements in lubrication properties can be expected by tailoring the reaction conditions and morphological properties of the carbon materials, for example, by graphitization of the carbon spheres or nanotubes, controlling particle size and surface properties to ensure that individual particles remain in suspension, preferably as a colloid through steric stabilization or electrostatic stabilization, to prevent aggregation of the particles. Overall, the lubricant compositions of the present invention have high potential to further enhance the lubricity of current lubricants formulations and hence improve the engine efficiency and performance of motorized and mechanical devices. Moreover, the autogenic processes described in this invention to prepare the carbon-based particle component of the lubricants is very versatile and can be used to synthesize a wide variety of nano-lubricant additive materials, such as boron oxides, metal sulfides, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides (a) Scanning electron micrograph (SEM) of carbon spheres synthesized by an autogenic reaction; (b) High resolution SEM image of single carbon sphere; (c) Transmission electron micrograph (TEM) cross section of carbon sphere; and (d) High resolution TEM image cross section of carbon sphere.

FIG. 2 provides (a) Raman spectrum of as-prepared carbon spheres; (b) Transmission electron micrograph of carbon single sphere; and (c) Electron diffraction image of carbon spheres.

FIG. 3 provides (a-b) Scanning electron micrograph of carbon spheres heat treated at 2400° C. in an inert atmosphere at different magnifications; (c) Comparative energy dispersive X-ray spectroscopy analysis of carbon spheres prepared at 700° C. and subsequent heat-treatment at 2400° C.; and (d) Comparative X-ray diffraction (XRD) patterns of carbon spheres prepared at 700° C. and subsequent heat-treatment at 2400° C.

FIG. 4 provides (a-b) Scanning electron micrographs of cobalt encapsulated carbon nanotubes at various resolution; and (c) powder X-ray diffraction pattern of cobalt encapsulated carbon nanotubes.

FIG. 5 provides (a-b) Scanning electron micrographs of iron encapsulated carbon nanotubes at various resolution; (c) transmission electron micrograph of iron encapsulated carbon nanotubes; and (d) powder X-ray diffraction pattern of iron encapsulated carbon nanotubes.

FIG. 6 illustrates friction (top) and wear (bottom) performance of a base oil when used in a sliding experiment where a steel ball slides against a steel plate.

FIG. 7 illustrates friction (top) and wear (bottom) performance of a carbon sphere additive lubricant of this invention. The size of wear scar is reduced more than 30% and the severe abrasive wear marks are eliminated from the sliding surfaces.

FIG. 8 illustrates friction (top) and wear (bottom) performance of a carbon fiber-containing lubricant of this invention. The wear scar is reduced more than 40%, while the abrasive wear marks are eliminated from the sliding surface.

FIG. 9 illustrates improved friction performance of a carbon sphere-containing lubricant using the as-prepared spheres (700° C.) with the addition of a surfactant. The friction coefficient is reduced by more than 30% with improved wear resistance.

FIG. 10 illustrates improved friction performance of a carbon fiber-containing lubricant with the addition of surfactant. The friction coefficient is reduced by more than 30% with improved wear resistance.

FIG. 11 illustrates improved friction performance of a carbon sphere-based lubricant using the spheres that had been heat-treated at 2400° C. with the addition of a surfactant. The friction coefficient is reduced by more than 30% with improved wear resistance.

FIG. 12 illustrates a reaction film observed on the steel surface when tested with a carbon sphere-containing lubricant and sorbitan trioleate surfactant. The reaction film was carefully cross-sectioned using a Focused Ion Beam (FIB) method and observed with a transmission electron microscope. Points a, b, c confirm the presence of a carbon rich species in those areas.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following examples are provided to illustrate certain preferred embodiments of the present invention, and are not to be considered a limiting the scope of the appended claims. The examples demonstrate, in particular, the versatility of autogenic reactions in synthesizing carbon-based materials with a diverse range of particle morphologies, conducive to their use as additives for lubrication technology.

Description of Test Equipment and Facilities

Autogenic Reactor.

The typical custom made reactor used in the making of the carbon-based additives can operate up to a maximum working pressure of about 2000 pounds per square inch and a maximum temperature of about 800° C. To fabricate the wide range of carbon-based materials in our invention, various autogenic reaction parameters such as heating rate, temperature, duration, reactant concentration, stoichiometry, pressure, and atmosphere (either oxidizing, reducing or inert) have to be carefully controlled. The additives can be synthesized either in amorphous or crystalline form. Moreover, the autogenic method can produce, in situ, distinct ‘core-shell’ materials, for example, those with a metal, metal alloy, or metal oxide core and an outer shell containing carbon moieties. Preferably, the reactor operates under conditions ranging from a minimum working pressure of about 100 pounds per square inch and a minimum temperature of about 100° C., to a maximum working pressure in the range of about 800 to about 2000 pounds per square inch and a maximum temperature in the range of about 300 to about 800° C. The novel carbon additives produced by the specific reactor of this invention can be used in a wide range of lubrication applications, including, for example, internal combustion engines, wind turbines, compressors, space mechanisms, and hydraulics.

Lubricant Test-Sample Preparation.

Tribological Test Set-Up.


Ball-on-Disc Tribo-Tester.

HFRR Tribo-Tester.

Post-Test Analysis.


Example 1
Preparation of Carbon Spheres

The controlled thermal decomposition of high density or low density polyethylene at about 700° C. for about 1 min to 3 hours in a closed reactor under autogenic (self-generating) pressure yielded solid carbon microspheres, approximately 1-5 μm in diameter, as illustrated in the scanning electron microscope images in FIG. 1, panels (a) and (b). The particles are almost perfectly spherical in shape and have smooth surfaces. The cross-section transmission electron micrograph confirmed that the carbon spheres are solid and not hollow (FIG. 1, panel c). Elemental C, H, N, S analyses showed that the carbon spheres are comprised of more than 98 wt. % carbon and less than 0.4 wt. % hydrogen; no significant amounts of N or S were detected. EDX elemental analyses confirmed that the spheres were essentially carbon; no impurities are detected by this method. The turbostratically disordered structure of the as-prepared spheres is reflected by the broad X-ray diffraction peaks centered at approximately 25, 42.3 and 44.3° 2θ that correspond to the layering (002), (100), and (101) reflections, respectively. The broad (002) peak, in particular, encompasses diffuse sets of interlayer distances that, on average, are larger than those in crystalline graphite (typically 0.344-0.355 nm). The high resolution transmission electron micrograph of a cross section of carbon spheres is depicted in FIG. 1d. The short order graphitic planes and some disorder are observed. The interlayer spacing results are analogous to XRD measurements.

Raman spectra were obtained at room temperature using an In Via Raman spectrometer using 633 nm red laser with 10% intensity to determine the extent of graphitic disorder within the carbon spheres. The Raman spectrum of the as-prepared carbon spheres (FIG. 2a) is typical for a hard carbon, with a broad band at 1315 cm<−1 >representing a highly disordered (D) graphite arrangement within the carbon spheres and a band at 1585 cm<−1>, characteristic of a more ordered graphitic (G) structure. The D band has been attributed to the vibration of carbon atoms with dangling bonds for the in-plane terminated disordered graphite component. The G-band, corresponding to the E2g mode, is closely related to the vibration of sp<2 >bonded carbon atoms in a 2-dimensional hexagonal lattice, as in graphene. Methodically measuring the peak heights of D and G bands, the ID/IG ratio was calculated for the carbonaceous materials. The intensity ratio of the D- and G-bands (ID/IG) of 1.1 further quantifies the relative levels of disordered glassy carbons, indicating that the processing temperature at which the spheres were synthesized (700° C.) was not sufficiently high to allow for the alignment and growth of graphitic sheets within the carbon macrostructure. The graphitic content within the carbon spheres can be increased and controlled by subsequent heating in an inert atmosphere or under vacuum, for example, about 1000 to about 3000° C., preferably about 2000 to about 3000° C. to increase the inherent strength and toughness of the spheres. The transmission electron micrograph of the as-prepared carbon spheres showed a very smooth surface with several micrometer diameters (FIG. 2b). The BET (Brunauer, Emmett, Teller) surface area measurements were carried out using a Quantachrome Instrument after outgassing the carbon spheres at 150° C. for 12.0 hrs. The BET surface area of carbon sphere was measured to be 4.6 m<2>/g, with a total pore volume of 0.0078 cc/g. The density measurements of carbon spheres were determined using an automatic density analyzer (Quantum Instruments, Ultrapyc 1200e at 22° C.) with purging He gas. The measured average density of carbon spheres was 2.3 g/cc, which is close to the theoretical value for graphitic carbon. The diffuse X-ray diffraction image due to an amorphous carbon product (FIG. 2c) is consistent with the Raman data.

Furthermore, the above-mentioned carbon spheres prepared at 700° C. were heated at 2400° C. for 1 hour under inert conditions to enhance the graphitic character of the spheres. It is apparent from FIGS. 3a-b that the heat treatment process had a negligible effect on the spherical shape and overall morphology of the particles, confirming the remarkable stability of the spheres when heated to an extremely high temperature. EDX elemental analyses confirmed that the spheres were essentially carbon; no impurities could be detected by this method in both as-prepared and heated carbon spheres samples (FIG. 3c). The measured average density of heat treated carbon spheres is approximately 2.1 g/cc. The BET surface area of heated carbon spheres is reduced to 1.05 m<2>/g after high temperature heat treatments (2400° C.) for 1 hour in an inert atmosphere. The decrease in the surface area in the heated carbon spheres is attributed to the removal of pores during the high temperature treatment and sintering of the spheres that is believed to increase their strength and toughness. The XRD patterns of the heat-treated carbon sphere products are shown in FIG. 3d (top, (700° C.) and bottom (2400° C.), respectively). The increase in graphitic order on heating the carbon spheres to 2400° C. is observed. The increased strength and toughness of the heated carbon spheres is believed to account for the improved friction and wear behavior, as described more fully in the following sections. In particular, it is believed that the carbon spheres may act as ball bearings that employ a “rolling” mechanism to reduce the friction between sliding surfaces, and the wear thereof.

Example 2
Synthesis of Cobalt Encapsulated Carbon Nanotubes

Using two different catalysts, carbon nanotubes were prepared under autogenic conditions. In the first case, the thermal decomposition of 2 g of low density polyethylene (LDPE) and 20 wt % cobalt acetate, Co(C2H3O2)2 catalyst was carried out by a similar procedure to that described above. Up to 680° C., the pressure within the reactor reached about 50 psi (3.4 atm) before increasing rapidly to 1000 psi (68 atm) at 700° C. At 700° C., the reactor was heated for 2 hours before being cooled to room temperature. The yield of carbon nanotubes (CNTs) was 40 wt. %. SEM images of the carbon nanotubes prepared by the thermolysis of low density polyethylene in the presence of a cobalt acetate catalyst, are shown in FIGS. 4a and 4b; the CNTs are several micrometers in length and have an average diameter of less than 100 nm. The CNTs encapsulate nanosized metallic Co particles, less than 100 nm in size, as confirmed by transmission electron microscopy. X-ray diffraction data indicated that the carbon was largely graphitic in character and that the entrapped cobalt had face-centered-cubic symmetry (FIG. 4c). Similarly, the high density polyetheylene was used as a source of hydrocarbons for the production of carbon nanotubes under autogenic conditions.

Example 3
Synthesis of Iron Encapsulated Carbon Nanotubes

Because cobalt is relatively expensive element, iron based catalysts were evaluated. For example, the thermal decomposition of 2 g of low density polyethylene (LDPE) and 20 wt % ferrocene, C10H10Fe catalyst at about 700° C. for about 3 hours in a closed reactor under autogenic (self generating) pressure yielded Fe-containing carbon nanotubes (CNTs). SEM images of these carbon nanotubes are shown in FIGS. 5a and 5b. The CNTs are several micrometers in length and have an average diameter of less than 100 nm. The transmission electron micrograph of an individual CNT shows a cylindrical form (FIG. 5c) that encapsulates the iron nanoparticle catalyst at the tip of the tube. CNTs with an approximate 30 nm inner diameter and a shell thickness of 20 nm are depicted in the TEM image. X-ray diffraction data (inset in FIG. 5d) indicated that the carbon nanotubes were largely graphitic in character and that the entrapped iron had face-centered-cubic symmetry. Additionally, small reflection peaks belongs to Fe3C (marked with asterisks) were observed indicating that the carbide phase can be formed at relatively low temperature under autogenic conditions.

These novel particles are derived from disposable plastics by the autogenic reaction process in the forms of spheres, tubes, tubes with metal encapsulation, and fibers. When mixed with appropriate lubricants, these particles have the capacity to significantly lower the friction and enhance wear resistance of sliding steel surfaces.

Example 4
Tribological Testing of Conventional Base-Lubricants

Tribological testing was conducted using the Ball-on-Disc Tribo-tester as described herein. A base-lubricant of poly(alpha olefin) having a viscosity of about 4 centiStokes (cSt) was tested under these extreme conditions. As shown in the FIG. 6(a), there was high friction under all sliding speeds. Moreover, the friction was very high (0.16) under lowest speed test conditions.

The wear of the sliding surfaces after testing in base lubricant is shown in FIG. 6(b). There was a large wear scar formed on the ball surface after the tribological test. The diameter of this wear scar was about 330 μm. The high wear was most likely the result of poor performance of the base-lubricant. Moreover, the wear scar was not covered with a protective boundary film; hence, it was shiny and metallic looking The roughness results are presented in FIG. 6(c). The wear scar had a roughness value of about 122 nm.

The data indicate that the base-lubricant was unable to react with the sliding contact surfaces of ball and plate to form any type of protective boundary layer, and hence, resulted in high friction and high wear. The high friction affects efficiency and high wear affects durability of mechanical system. Thus, the base-lubricant was unable to provide any significant tribological advantages.

Example 5
Tribological Testing of Carbon Sphere Based Lubricants

Tribological testing was conducted using the Ball-on-Disc Tribo-tester as described herein. The carbon spheres produced under the autogenic conditions of this invention as in Example 1 were dispersed in the base-lubricant described in Example 4 at a concentration of about 1 wt % and then were tested under the extreme test conditions mentioned above. As shown in the FIG. 7(a), there was substantial reduction in friction at all sliding speeds compared to the base-lubricant discussed in Example 4. Moreover, the friction was relatively moderate (0.12) under the lowest speed test conditions where more frequent metal-to-metal contacts occur.

The wear result from the carbon sphere-based lubricant is shown in FIG. 7(b). There was a partially dark wear scar on the ball surface after tribological testing and the wear scar was much smaller (i.e., 230 μm) than the scar observed in the test in base-lubricant (FIG. 6(b)). The wear scar was covered (about 50%) with a protective film. The roughness results are presented in FIG. 7(c). The wear scar had lower roughness (about 83 nm) than what was measured on a wear scar created in pure base-lubricant.

The data indicate that the carbon sphere-based lubricant was able to react with the contact surfaces of ball and plate to form a protective boundary layer. The wear scar was partially covered by a dark (black) layer of the carbon material, which resulted in reduction of friction and wear compared to the base-lubricant performance. The reduced friction can improve the efficiency while low wear enhances the durability of mechanical systems. Thus, the carbon sphere-based lubricant additive was able to provide superior friction and wear properties.

Example 6
Tribological Testing of Carbon Fiber-Based Lubricants

Tribological testing was conducted using the Ball-on-Disc Tribo-tester as described herein. Carbon fiber materials (about 1 wt %) produced under autogenic conditions were dispersed in the base-lubricant described in Example 4 and then tested under the extreme conditions of the Ball-on-Disc test. As shown in the FIG. 8(a), there was a marked reduction in the friction coefficient under all steps of sliding speed compared to what was observed from the base-lubricant alone. Moreover, the friction was still reasonable (i.e., 0.12) under the lowest speed test conditions.

Wear results for the carbon fiber-based lubricant is presented in FIG. 8(b). There was a significantly smaller and darker wear scar formed on the sliding ball surface after tribological tests. The actual size of the wear scar was about 190 μm in size compared to 330 um diameter wear scar formed during tests with the base-lubricant alone (FIG. 6(b)). The wear scar was mostly covered (about 70%) with a protective darker-looking carbon film. The roughness results are presented in FIG. 8(c). The wear scar had a roughness value of about 115 nm.

It is believed that the carbon fiber-based lubricant was able to react with the sliding contact surfaces of ball and plate to form a highly protective carbon-rich boundary layer. Formation of such a boundary film resulted in the reduction of friction and wear compared to the base-lubricant performance. The reduction in friction improves the efficiency and low wear enhances the durability of the mechanical system. Thus, the new carbon fiber-based lubricant provided excellent tribological results.

Example 7
Improved Performance of Carbon Sphere Based Lubricants

It was demonstrated in Example 5 that carbon spheres (heat-treated at 700° C.) provided good tribological performance when used as an additive to a base-lubricant. However, there were two factors that may have limited optimum performance, i.e., (1) dispersibility of the carbon particles in the carrier oil over an extended period of time, and (2) relatively higher friction values under extreme boundary conditions.

In order to keep the carbon particles suspended in the carrier oil, a surfactant was added (sorbitan trioleate (STO) about 10000 ppm), which provided very good performance and very consistent and long-duration shelf life without particle agglomeration, separation or settlement. It is believed that the particles were covered by the hydrophilic chains of STO, and therefore, increased the homogeneous dispersion/suspension of the carbon sphere particles in the base-lubricant.

Tribological tests were conducted under severe line contact conditions and at high temperatures using the High Frequency reciprocating rig (HFRR Tribo-tester) as described herein. As shown in FIG. 9, there was a 30% reduction in the friction when the carbon sphere additive and STO based lubricant composition was used, when compared to the carbon sphere-based lubricant alone. Addition of surfactant (STO) to the carbon sphere-based lubricant additive of this invention significantly improved the dispersibility of the carbon spheres and it was also able to further improve the friction performance of the carbon sphere-based lubricant composition.

Example 8
Improved Performance of Carbon Fiber-Based Lubricants

Tribological tests under extreme severe line contact conditions were conducted using the High Frequency reciprocating rig (HFRR Tribo-tester) as in Example 7. Carbon-fiber particles produced by the autogenic reactions of this invention were dispersed in the base-lubricant with and without the STO surfactant (10000 ppm) and then tested under these extreme conditions. As shown in the FIG. 10, there was a 30% reduction in friction when the carbon sphere and STO based lubricant compared to the carbon fiber-based lubricant without surfactant. Addition of the STO surfactant to the carbon fiber-based lubricant additive of this invention significantly improved the dispersion/suspension of the carbon spheres and the friction performance of the carbon fiber based lubricant.

Example 9
Improved Performance of High-Temperature Treated Carbon Sphere-Based Lubricants

Tribological tests were conducted under severe line contact conditions and at high temperatures using the High Frequency reciprocating rig (HFRR Tribo-tester) as in Example 7 and 8. Heat treated carbon spheres produced under autogenic conditions as in Example 1 were dispersed in the base-lubricant (at a concentration of about 1 wt %) with and without the STO surfactant (10000 ppm) and then tested under the severe test conditions mentioned above. As shown in FIG. 11, there was a 30% reduction in the friction of this carbon sphere- and STO-based lubricant composition compared to the carbon sphere-based lubricant alone. Moreover, there was excellent wear resistance offered by these carbon spheres (heat-treated at 2400° C.) with, and without, surfactant. Carbon spheres heat-treated at 2400° C. provided excellent wear-resistance compared to carbon spheres heat-treated at 700° C. thereby indicating the benefit of heating the carbon spheres to significantly high temperatures (2000-3000° C.) prior to use. Addition of the STO surfactant to the carbon sphere-based lubricant significantly improved the dispersibility of the carbon spheres; it also further improved the friction properties of the carbon sphere-based lubricant composition.

Example 10

Although the carbon materials produced by autogenic reactions offered excellent tribological performance, there are several ways to optimize their properties even further. Treatment of particles with surfactants did influence the surface chemistry of these particles and hence their interactions with sliding surfaces. In particular, the addition of polar surfactants into the carrier oils improved the interaction of the particles. Sorbitan trioleate (STO), provided a very desirable performance (FIG. 9, FIG. 10 and FIG. 11). When STO was added to the carbon particle-containing blends, the friction was reduced by 30%. The reason for this good performance may be attributed to the hydrophilic sorbitan portion of the STO surfactant enhancing the interaction of the carbon particles with the steel surfaces, and keeping the particles uniformly dispersed in the base oils. The hydrophobic oleate portion of the molecule likely participates in the tribochemical reaction along with carbon particles and forms durable boundary films on the sliding surfaces.

A high resolution transmission electron microscopy image in cross-section, using the Focused Ion Beam (FIB) technique, of the reaction or boundary film resulting from the reaction of the carbon spheres with the STO-MO surfactant is shown in FIG. 12. The reaction or boundary film looks rather thick, featureless and discreet on the steel surface. The reaction film was distinctly darker in color, suggesting that the film was carbon-rich due to carbon sphere interaction. Moreover, the reaction film was more than 200 nm thick, suggesting very robust processes that lead to the formation of such reaction films. Thus, it appears that the addition of the STO surfactant to the carbon sphere-based lubricant provides excellent tribological performance due to the enhanced interaction of the lubricant with the sliding surface to form a highly durable and protective boundary film.



WO9640847
IMPROVED LUBRICATION WITH BORIC ACID ADDITIVE

Inventor: ERDEMIR ALI     

This invention relates to carbon-based materials as anti-friction and anti-wear additives for advanced lubrication purposes. The materials have various shapes, sizes, and structures and are synthesized by autogenic reactions under extreme conditions of high temperature and pressure. The lubricant compositions comprise carbon-based particles suspended in a liquid hydrocarbon carrier. Optionally, the compositions further comprise a surfactant (e.g., to aid in dispersion of the carbon particles). Specifically, the novel lubricants have the ability to significantly lower friction and wear, which translates into improved fuel economies and longer durability of mechanical devices and engines.



US2013079262
WO2013048616
NOVEL MATERIALS AS ADDITIVES FOR ADVANCED LUBRICATION  

FIELD OF THE INVENTION

[0002] This invention relates to novel lubricant compositions comprising a particulate carbon material suspended in a liquid carrier, which provide beneficial anti-friction and anti-wear properties. The particulate materials have various shapes, sizes, and structures and are synthesized by autogenic reactions under extreme conditions of high temperature and pressure. Specifically, the lubricant compositions have the ability to significantly lower friction and wear, which translates into the advantages of improving the durability and fuel economies of motorized and mechanical devices.



PT646161
IMPROVED LUBRICATION FROM MIXTURE OF BORIC ACID WITH OILS AND GREASES

Inventor: ERDEMIR ALI    




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