TWI490330B - Lubricant oil composition and method for manufacturing the same - Google Patents

Description

Lubricating oil composition and preparation method thereof

The present invention relates to a nano lubricating oil composition and a method for preparing the same, and more particularly to a nano lubricating oil composition which does not require the addition of a dispersing agent or a surfactant, and a method for preparing the same.

Environmental pollution is the most concerned global issue in recent years, especially the greenhouse effect caused by carbon dioxide emissions and ozone destruction is the global warming. Increasing mechanical power efficiency not only saves costs but also reduces energy use and indirectly reduces carbon dioxide emissions. Reducing the friction in the mechanical engine is a major way to increase energy efficiency, and the use of lubricating oil is a necessary method to reduce the friction to increase efficiency, and the lubricating oil characteristics also affect the efficiency of the entire internal combustion engine or mechanical components. In addition to the appropriate improvement in lubricating oil properties, the addition of suitable different additives to the lubricating oil can also reduce the frictional resistance. At present, higher-grade lubricating oil additives are organic sulfur, phosphorus, and chlorine derivatives. Although they have good lubricity, as disclosed in Japanese Patent No. 8-20786, molybdenum dithiocarbamate (MoDTC) and disulfide are disclosed. Molybdenum dithiophosphate (MoDTP), but its biggest disadvantage is that it is not resistant to high temperature, high pressure, short life and environmental pollution. Inorganic solid lubricating oil additives such as graphite, molybdenum disulfide, and nanodiamonds have high temperature and high pressure stability and high life. Among them, molybdenum disulfide is easily oxidized and causes environmental pollution, and most countries have banned the use of such solid additives. Graphite often precipitates and blocks the oil path because the particles are too large to float effectively.

The ultra-dispersed nano-diamond (UDD) core is a diamond structure, while the outermost layer covers the graphite layer structure and is a pure carbon material. Nano diamonds are environmentally friendly, resistant to high temperatures, excellent thermal conductivity, high core hardness and good lubricity on the surface. The ultra-dispersed diamond (UDD) has a particle size of about 4-6 nm. It is synthesized by an instantaneous explosion method. Under the condition of negative oxygen balance, the explosion produces a free carbon and turns into a diamond particle in a high-temperature and ultra-high pressure environment. In this instant explosion environment, not all carbon sources are completely converted into diamond structure, and some free carbon forms fullerene like structural carbon covering diamond particles and aggregates into particles of several hundred nanometers or even several micrometers in diameter. Such nanodiamond particles are about 4-6 nm, and have the general properties of diamonds such as maximum hardness, extremely high thermal conductivity, high wear resistance, and good chemical stability. However, such nano-diamonds have a very high specific surface area (280-420 m ² /g), and nano-diamonds not only have extremely high surface energy but also have a strong agglomeration tendency due to surface chemical bonding, self-aggregating into several micron coagulation bodies. These agglomeration phenomena cause the nano-diamonds to lose their nano-characteristics. These agglomerates have a size exceeding a few micrometers, and their friction characteristics, fluidity, and dispersibility are greatly affected.

In order to solve this problem, Chinese Patent No. CN02139764.3 discloses that ultra-dispersed nano-diamonds are collided with ultra-fine powder by high-speed airflow, and surfactant, dispersion stabilizer, pH adjuster, etc. are added to disperse by ultrasonic wave and stirring method. In an aqueous solution. However, this method is a hydrophilic surface modification of nano diamonds, and the dispersion effect cannot be achieved in the lubricating oil. Similarly, the similar patent CN02115230.6 disperse and agglomerate in an ultrasonic manner, and add different decane surfactants to disperse in the aqueous phase or the oil phase. Further, in Chinese patent CN001695779A, a high-speed shearing machine is used to deagglomerate the super-dispersed nano-diamond by ultrasonic vibration, and an interfacial agent is added to disperse it in the lubricating oil. U.S. Patent No. 2008248979A1 discloses a lubricating oil-adding surfactant and a nano-diamond, which enables the nano-diamond to be dispersed in the lubricating oil and effectively reduce the frictional resistance. Although the surfactant is physically dispersed in the lubricating oil by dispersing the nano-diamond, the excessive surfactant will also affect the overall lubricating property and be unstable under high temperature conditions by physical adsorption. Therefore, the lubricating oil gradually heats up during the operation of the machine. When the oil temperature rises to a certain extent, the nano-diamond reaggregates into a larger coagulation body due to the desorption of the surfactant, and the excessively large coagulated body not only has no lubricating property but instead produces Scratch damage.

Although nano-diamonds have good characteristics, they are agglomerated due to their incompatibility with lubricating oil. Although surfactants improve compatibility problems, lubricants with surfactants are caused by high temperature during long-term mechanical operation. Surfactant desorption eventually leads to the agglomeration of nanodiamonds, and its effectiveness and durability are still not effectively satisfactory. In addition, adding too much surfactant may even affect other lubricating additives such as detergents, corrosion and rust inhibitors, antioxidants, etc., causing loss or reduction of other additives.

The purpose of the present invention is to develop an organic/inorganic composite nanoparticle based on nano-diamonds based on the above reasons, which not only has an outer layer organic layer which is highly compatible with lubricating oil, but also has an inner layer inorganic layer nano-diamond characteristic. It does not require additional addition of surfactants or dispersants, and can improve its oil phase dispersion and durability problems. It is currently the most needed technology for nano diamonds for industrial applications.

The invention provides a lubricating oil composition and a preparation method thereof. The lubricating oil composition of the present invention comprises a base lubricating oil and an organic-inorganic nano composite particle uniformly dispersed in the base lubricating oil, and can still be achieved without adding any dispersing agent or surfactant. Greatly reduce wear resistance, oil temperature and wear.

The present invention provides a lubricating oil composition consisting essentially of: a base lubricating oil; and an organic/inorganic nanocomposite particle uniformly dispersed in the base lubricating oil.

The invention also provides a method for preparing a lubricating oil composition, comprising: mixing one nanometer diamond particles with a reactive monomer to obtain a mixture; performing a wet ball milling agglomeration process and a polymerization reaction on the mixture to form a nano-diamond particle having a grafted polymer chain on a surface; and a nano-diamond particle having a grafted polymer chain on the surface thereof is mixed with a base lubricating oil, and a dispersion process is performed.

The invention has the advantages of overcoming the prior art, and it is conventional to add too much surfactant dispersing nano diamond, which has poor durability and affects other lubricating oil additives, and the lubricating oil composition of the invention does not need to be added any dispersion. The organic or inorganic nano composite particles can be stably dispersed in the base lubricating oil even under long-term operation, thereby reducing the abrasion resistance. Therefore, the lubricating oil composition of the present invention can be applied to an internal combustion engine or a power mechanical sliding assembly, and the frictional force, oil temperature, and mechanical wear rate can be greatly reduced.

The method, features, and advantages of the present invention are further illustrated by the accompanying drawings, which are set forth in the accompanying drawings. quasi.

The present invention provides a lubricating oil composition comprising a base lubricating oil and an organic-inorganic nanodiamond composite particles uniformly dispersed in the base lubricating oil. The lubricating oil composition does not need to add any dispersing agent or surfactant, and the organic-inorganic nano composite particles can be stably dispersed in the base lubricating oil even under long-term operation, thereby reducing wear resistance. In the lubricating oil composition, the organic/inorganic nano composite particles may have a weight percentage of 0.01% to 2% (100 ppm to 20000 ppm) based on the total weight of the lubricating oil composition; preferably The organic/inorganic nanocomposite particle system has a weight percentage of from 0.15% to 0.5% (1500 ppm to 5000 ppm) based on the total weight of the lubricating oil composition.

The base lubricating oil may comprise: mineral oil, gear oil, semi-synthetic oil, fully synthetic oil, cut oil, grease, or a mixture thereof. Please refer to Fig. 1 for a schematic diagram of the deagglomeration of the organic/inorganic nano composite particles. As can be seen from the figure, the organic/inorganic nano composite particle 10 is a nano diamond particle 12 having a grafted polymer chain 16 on the surface thereof, wherein the nano diamond particle has a graphite layer 14 on its surface, and the graft polymer The chain 16 is grafted onto the graphite layer 14, so that the agglomerates of the original nano-diamonds are several micrometers in size, and are agglomerated by the grafting polymer to form a composite of several organic/inorganic nano composite particles. The smaller solution agglomerates, which are only a few tens of nanometers in size. The polymer chain used for grafting to the nanodiamond particles may be a hydrophobic polymer such as polymethylmethacrylate (PMMA) or poly(glycidyl methylacrylate). PGMA), polystyrene (PS), or a mixture thereof. The polymer chain can be selected and matched according to the polarity of the base lubricating oil, so that the nano-diamond bonded with the grafted polymer chain can be completely dispersed and stably stabilized in the lubricating oil for a long time. The organic/inorganic nano composite particles may have an average particle diameter of 10 nm to 250 nm. For the organic/inorganic nano composite particles, the graft polymer chain may constitute 4% by weight to 50% by weight of the total of the organic/inorganic nano composite particles; preferably 15% by weight to 40% by weight.

The preparation method of the organic/inorganic nano composite particles comprises the following steps: First, a nanometer diamond particle (for example, a super-dispersed nano diamond) is mixed with a reactive monomer to obtain a mixture, wherein the reaction monomer is in the subsequent one. The polymerization process forms a polymer chain grafted to the nanodiamond particles, such as methyl methacrylate, glycidyl methacrylate, styrene, or a mixture thereof. The above mixture may further comprise a solvent which may be a general polar solvent such as ethanol or acetone, or a non-polar solvent such as toluene, depending on the polarity of the graft monomer. Next, the solution is subjected to a wet ball milling agglomeration process, and a radical initiator is simultaneously added during the ball milling to carry out a polymerization reaction on the reaction monomer. In other words, the present invention is characterized in that a nano-diamond particle (for example, a super-dispersed nano-diamond) is deagglomerated and a graft polymer (polymerized from a reactive monomer) is bonded to the surface thereof. The wet ball milling agglomeration process uses a zirconium bead for ball milling, wherein the zirconium bead has a particle size between 15 and 200 microns, and the added zirconium beads have a weight with the nanodiamond to be ball milled. The ratio is between 40:1 and 400:1. The radical initiator may be a peroxide initiator or an azo compound initiator, such as diethoxy acetophenone, benzophenone, phenylbenzoin isobutyl ether (benzyl benzoin isobutyl ether), benzyl dimethyl ketal, 1-hydroxycyclohexyl phenyl ketone, diethyl thioxanthone, 2-B 2-ethyl anthraquinone, 2-hydroxy-2-methyl-1-phenylpropane-1-one, 1-(4) -isopropylphenyl)-2-hydroxy-2-methylpropan-1-one (1-(4-isopropylphenyl)-2-hydroxy-2-methylpropane-1-one), 2-methyl-[4 -(methylthio)phenyl]-2-morpholino-1-propane (2-methyl-[4-(meyhylthio)phenyl]-2-morpholino-1-propane), aromatic azozonium (aromatic azozonium) Salts, trially sulfonium salts, diallyiodonium salts, triallylselenium salts of Lewis acid as well as Metallocene compounds), or a mixture thereof. When energy is applied to the starter, the initiator is broken to form a radical, which in turn polymerizes the vinyl monomer into a polymer and grafts onto the graphite structure on the surface of the nanodiamond. When the polymer is grafted onto the graphite surface of the nano-diamond, the nano-diamond will be more easily dispersed in the solvent and expose more surface, so that other ungrafted polymers are more easily grafted onto the graphite surface of the nano-diamond. . When the surface of the nano-diamond is bonded to a large amount of polymer, it is completely dispersed and dissolved in the solvent. The wet ball agglomeration process can have a mechanical ball milling rate of 10-20 m/s and a ball milling time of several hours.

Next, the nano-diamond is precipitated by high-speed centrifugation, and the unbonded polymer is removed, and then the solvent is added to redisperse the nano-diamond, and after repeating the above-mentioned centrifugation and dispersion steps, the unbonded portion can be completely removed. Polymer.

The method for preparing the lubricating oil composition of the present invention comprises, in addition to the above steps of preparing the organic/inorganic nano composite particles, further comprising mixing the organic/inorganic nano composite particles with the base lubricating oil, and performing one Decentralized procedure. The dispersion procedure may be an ultrasonic oscillation of 20 kHz to 40 kHz, a ball milling of 60 rpm to 10,000 rpm, or a combination thereof. If the frequency of the ultrasonic oscillation is too low or the ball milling speed is too slow, the nano diamond cannot be effectively dispersed in the solvent. If the frequency of the ultrasonic oscillation is too high or the rotational speed of the ball mill is too fast, it is easy to cause local temperature overheating to degrade the organic compound, and the effect is lowered.

The above and other objects, features and advantages of the present invention will become more apparent and understood.

Preparation of organic/inorganic nano composite particles

Example 1

Mix 400 g of zirconia balls (particle size about 50 μm) with 10 g of ultra-dispersed nano-diamonds (product number UDD, purchased from ABBA group of Bakhan Enterprise Co., Ltd., in a closed explosion and acid-washed to remove impurities) Prepare) and add 80 g of methyl methacrylate monomer, and the resulting mixture is placed in a ball mill chamber. The external circulating water temperature of the ball mill chamber is set to 80 ° C, and the ball mill speed is set to 2,400 rpm. Finally, 10 g of the free radical initiator benzoyl peroxide was dissolved in 10 ml of toluene and injected into the chamber at a flow rate of about 5 ml at a flow rate during the ball milling process. The agglomerated nano-diamonds are dispersed by ball milling, and the free radical addition of monomer polymerization by benzoyl peroxide is applied to the surface of the nano-diamonds, so that the nano-diamonds are gradually grafted with the polymer and gradually dispersed in the solvent. The polymer is grafted onto the surface of the nano-diamond, and thus slowly dispersed in the solvent to expose more surface, so that more polymer can be grafted on the surface of the nano-diamond. Finally, high-speed centrifugation centrifuges the nano-diamond graft polymer, removes the ungrafted polymer and solvent, and after washing with toluene, the nano-diamond-nano diamond grafted with grafted polymer is obtained. Polymethyl methacrylate (UDD-PMMA). Please refer to Fig. 2 for the infrared absorption spectrum of the nano-diamond grafted polymethyl methacrylate. As shown, the infrared absorption spectrum has absorptions such as -20080 and 2932 cm ^-1 with carbon-hydrogen stretching, and absorption of lower-frequency carbon-hydrogen stretching such as 1430- In addition to the 1470 cm ^-1 region (proving that the functional group has a methylene structure), the strong absorption of the C=O vibration of the characteristic esters such as 1725 cm ^-1 , and the strong absorption band of the CO stretching of the ester characteristics such as 1050- 1300cm ^-1 .

Next, the nano-diamond-grafted polymethyl methacrylate was analyzed by a thermogravimetric analyzer to evaluate the weight ratio of the polymer grafted on the surface of the nano-diamond, and the results are shown in Fig. 3. As can be seen from the figure, most of the grafted polymers will thermally decompose from 200 ° C to 500 ° C, resulting in weight loss. It is estimated by thermogravimetric loss analysis that the proportion of surface polymer is about 32%. The nano-diamond grafted polymethyl methacrylate was analyzed for particle size distribution by particle size. As a result, as shown in Fig. 5, the particle size (d50) averaged about -20 nm.

Example 2-3

Examples 2 and 3 were carried out in the same manner as in Example 1, except that methyl methacrylate and styrene were substituted for methyl methacrylate as reaction monomers, respectively. Please refer to FIG. 4 , which is the nano diamond graft polyglycidyl methacrylate (UDD-PGMA) obtained in Example 2 and the nano diamond-grated polystyrene (UDD-PS) obtained in Example 3. Infrared absorption spectrum. On the other hand, the particle size analysis of the nanodiamond graft polyglycidyl methacrylate (UDD-PGMA) obtained in Example 2 shows that the average particle diameter (d50) is about 10 nm. On the other hand, Fig. 7 is a particle size analysis of the nanodiamond-polystyrene (UDD-PS) obtained in Example 3, and as a result, the average particle diameter (d50) was about 100 nm.

Preparation and quality measurement of lubricating oil composition

Example 4

The nano-diamond grafted polymethyl methacrylate obtained in Example 1 was added to the base lubricating oil at different concentrations (addition ratios of 0 ppm, 500 ppm, 1000 ppm, 1500 ppm, 2000 ppm, and 3000 ppm, respectively) (product number is CPC R68, The oil production and sales were tested to compare the friction coefficient, oil temperature and wear rate (the vanes-on-ring method was used to simulate the abrasion test of the lubricant when the machine was sliding). The results are shown in Table 1.

Further, referring to Fig. 8, a graph showing the relationship between the friction coefficient and the time of the lubricating oil composition in which the amount of the nano diamond grafted polymethyl methacrylate is 0 ppm, 1000 ppm, 2000 ppm, and 3000 ppm is added; The graph shows the oil temperature versus time for a lubricating oil composition in which nano diamond grafted polymethyl methacrylate is added in amounts of 0 ppm, 1000 ppm, 2000 ppm, and 3000 ppm.

The detailed measurement of the friction coefficient, oil temperature and wear rate is as follows: The oil temperature and friction coefficient are recorded by the abrasion tester (Falex #6, USA) test and data acquisition system (Red Lion CSMSTRSX, USA). The block-to-ring mode was chosen to simulate the annular and cylindrical piston assemblies in an internal combustion engine. In the test of the wing-to-ring, the block structure was a 2.4 mm x 4.8 mm x 6.3 mm rectangular block of SKD11 stainless steel, and the test piece on the block contacted the annular test piece in a vertical sliding direction with a roughness Ra of 0.044 μm before the test. The entire abradable test piece was immersed in an oil cup filled with lubricating oil at a sliding rate of 6.08 m/s and a contact pressure of 4.33 x 10 ⁶ Pa. The friction coefficient and oil temperature are recorded once per second. The entire test time is about 4320 seconds and the total sliding distance is about 26283 meters.

Comparative Example 1

Mix 400 g of zirconia balls (particle size about 50 μm) with 10 g of ultra-dispersed nano-diamonds (product number UDD, purchased from ABBA group of Bakhan Enterprise Co., Ltd., in a closed explosion and acid-washed to remove impurities) Prepare) and add about 100 ml of solvent tetrahydrofuran, and the resulting mixture is placed in a ball mill chamber. The external circulating water temperature of the ball mill chamber is set to 80 ° C, and the ball mill speed is set to 2,400 rpm. Next, the zirconium balls are sieved and the solvent is removed to obtain deagglomerated nanodiamond particles. Finally, the obtained deagglomerated nanodiamond particles were added to the base lubricating oil (commercial number CPC R68, sold by CNPC) (the deagglomerated nanodiamond particles were added in a ratio of 2000 ppm), and 2% interfacial activity was added. The sorbitan oleate (commercial number is Span 80) was shaken for 1 hour with ultrasonic waves to obtain a lubricating oil composition.

Next, the lubricating oil composition obtained in Comparative Example 1 was measured in the same manner as in Example 4, and the lubricating oil composition described in Example 4 (nano diamond grafted polymethyl methacrylate was added in an amount of 2000 ppm) was compared and the results are shown in Table 2.

Further, referring to Fig. 10, the lubricating oil composition obtained in Comparative Example 1 and the lubricating oil composition described in Example 4 (nano diamond grafted polymethyl methacrylate added in an amount of 2000 ppm) were rubbed. A graph showing the relationship between the coefficient and time; referring to Fig. 11, showing the lubricating oil composition obtained in Comparative Example 1 and the lubricating oil composition described in Example 4 (nano diamond grafted polymethyl methacrylate added) It is 2000 ppm) its oil temperature versus time. As can be seen from the above two figures, although the interfacially active dispersed nano-diamond (the lubricating oil composition obtained in Comparative Example 1) has a good lubricating effect at the initial stage of the lubricating oil, the lubricating effect is gradually lowered as the abrasion time increases. Until the final re-agglomeration of the nano-diamonds into larger aggregates caused more serious scratching. In contrast, the lubricating oil composition of the present invention uses the organic-inorganic nano-diamond composite particles as a lubricating oil additive, and can be uniformly and stably dispersed in the lubricating base oil, thereby having better lubricating effect and stability.

The lubricating oil composition of the present invention has the following advantages over the lubricating oil composition in which the surfactant is used to disperse the nanodiamond in the lubricating oil compared to other patent documents:

1. It can be used in a wide range of lubricants, gear oils, cutting oils and greases.

2. It has long-term stability and heat resistance, so it will not have agglomeration phenomenon and retain lubrication characteristics under long-term operation.

3. The composition is purely without the need to add too much reagent to affect the properties of the lubricating oil so as to affect the functional properties of the application.

While the present invention has been described in its preferred embodiments, the present invention is not intended to limit the invention, and the present invention may be modified and modified without departing from the spirit and scope of the invention. The scope of protection is based on the definition of the scope of the patent application.

10. . . Organic/inorganic nano composite particles

12. . . Nano diamond particles

14. . . Graphite layer

as well as

16. . . Grafted polymer chain

Fig. 1 is a schematic view showing the deagglomeration of organic/inorganic nano composite particles according to an embodiment of the present invention.

Fig. 2 is an infrared absorption spectrum of the ungrafted nanodiamond (UDD) and the nanodiamond grafted polymethyl methacrylate (UDD-PMMA) described in Example 1.

Figure 3 is a thermogravimetric analysis of the ungrafted nanodiamond (UDD) and the nanodiamond grafted polymethyl methacrylate (UDD-PMMA) described in Example 1.

Figure 4 is an infrared ray of the nano-diamond graft polyglycidyl methacrylate (UDD-PGMA) described in Example 2 and the nano-diamond-grafted polystyrene (UDD-PS) described in Example 3. Absorption spectrum.

Fig. 5 is a particle size analysis of the nanodiamond graft polymethyl methacrylate (UDD-PMMA) described in Example 1.

Fig. 6 is a particle size analysis of the nanodiamond graft polyglycidyl methacrylate (UDD-PGMA) described in Example 2.

Fig. 7 is a particle size analysis of the nanodiamond grafted polystyrene (UDD-PS) described in Example 3.

Fig. 8 is a graph showing the friction coefficient versus time for a lubricating oil composition in which different nanodiamond grafted polymethyl methacrylate is added.

Fig. 9 is a graph showing the relationship between the lubricating oil temperature and the time of a lubricating oil composition in which a different amount of nano-diamond grafted polymethyl methacrylate is added.

Fig. 10 is a graph showing the relationship between the friction coefficient of the lubricating oil composition obtained in Comparative Example 1 and the lubricating oil composition of Example 4 (the amount of nano-diamond grafted polymethyl methacrylate added is 2000 ppm) and time. Figure.

Figure 11 is a graph showing the lubricating oil composition obtained in Comparative Example 1 and the lubricating oil composition described in Example 4 (nano diamond grafted polymethyl methacrylate added in an amount of 2000 ppm). Diagram of the relationship.

10. . . Organic/inorganic nano composite particles

12. . . Nano diamond particles

14. . . Graphite layer

16. . . Grafted polymer chain

Claims (7)

A lubricating oil composition consisting essentially of: a base lubricating oil; and an organic/inorganic nano composite particle uniformly dispersed in the base lubricating oil, wherein the organic/inorganic nano composite particle is a surface a nano diamond particle having a graft polymer chain, wherein the nano diamond particle has a graphite layer on its surface, and the graft polymer chain is grafted onto the graphite layer, wherein the graft polymer chain has a The weight percentage is between 4% and 50%, based on the total weight of the organic/inorganic nano composite particles, and the grafted polymer chain includes polymethyl methacrylate, polyglycidyl methacrylate, and poly Styrene or a combination of the foregoing. The lubricating oil composition of claim 1, wherein the organic/inorganic nanocomposite particles have a weight percentage of from 0.01% to 2% based on the total weight of the lubricating oil composition. The lubricating oil composition according to claim 1, wherein the organic/inorganic nano composite particles have an average particle diameter of 10 nm to 250 nm. The lubricating oil composition of claim 1, wherein the base lubricating oil comprises: mineral oil, gear oil, semi-synthetic oil, total synthetic oil, cut oil, grease, or a mixture thereof. The lubricating oil composition according to claim 1, wherein the grafted polymer chain is a hydrophobic polymer chain. A method for preparing a lubricating oil composition for preparing the lubricating oil composition according to claim 1, comprising: mixing one nanometer diamond particles with a reactive monomer to obtain a mixture; Performing a wet ball milling agglomeration process and a polymerization reaction on the mixture to form a nano diamond particle having a graft polymer chain on the surface, wherein the graft polymer chain has a weight percentage of 4% to 50% And based on the total weight of the nano-diamond particles having a grafted polymer chain on the surface, and the grafted polymer chain comprises polymethyl methacrylate, polyglycidyl methacrylate, polystyrene or the foregoing a combination of the nanodiamond particles having a grafted polymer chain on the surface and a base lubricating oil, and performing a dispersion process. The method of preparing a lubricating oil composition according to claim 6, wherein the dispersing process comprises ultrasonic vibration, ball milling, or a combination thereof.