Patent Publication Number: US-2018051223-A1

Title: Lubricant Composition and Methods of Manufacture

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 62/377,560, filed Aug. 20, 2016, which is herein incorporated by reference. 
    
    
     BACKGROUND 
     Field of the Invention 
     This invention relates to a neat oil lubricant and its methods of manufacture. 
     Background Discussion 
     Lubricants have multiple uses in a machining process. They are used to reduce friction between a cutting tool and the surfaces being machined. They also serve as coolants that carry away heat generated during machining operations such as grinding, drilling, milling, and cutting. The quality of the lubricant used in a machining process greatly affects the efficiency, service life, and other performance characteristics of both the tool and the machine. As a result, there is an ongoing demand for better lubricants, particularly those that are biobased and environmentally friendly. 
     An important factor in selecting an optimal machining lubricant is cost. Machining lubricants are typically required to be disposed of at waste management sites. An effective nontoxic, biobased metalworking lubricant can significantly reduce disposal costs and related compliance costs. Another factor is that it is also is desirable to use non-toxic lubricants. Currently, the most effective machining lubricants emit an unhealthy amount of volatile organic compounds (VOC). A low VOC machining lubricant that is equally or more effective would be a significant improvement in the field. The specification herein describes an improved composition that successfully meets each of the above mentioned objectives. 
     SUMMARY 
     The invention described herein is a lubricant made by a method of modifying fluid suspended metal sulfide particles. The metal sulfides can be molybdenum disulfide, tungsten disulfide, antimony trisulfide, antimony pentasulfide, or a similar compound or a composition comprising at least one of the previously mentioned metal sulfides. It is a significantly improved version of the prior art disclosed in U.S. Pat. No. 8,211,329 (“the &#39;329 patent”), incorporated in its entirety by reference herein. This method produces a superior metalworking lubricant that outperforms current products and does not require the use of hazardous additives. A key feature of the invention is that the base oil is derived from a proprietary ester lubricant formulation, preferably from a vegetable source. A second key feature of the invention is the use of a centrifugation step. This step removes non-colloidal metal sulfide particles so that only colloidal particles remain suspended in the fluid. The centrifuged colloidal formulation performs as well or better than products containing larger metal sulfide particles, while also providing a suspended state and a lighter olive oil-colored appearance more acceptable to users. 
     The inventive production steps solve several problems with the prior art compositions and methods. The original formulation as described in the &#39;329 patent consisted of soybean seed oil and treated molybdenum disulfide (MoS 2 ). In use the soy oil accumulated on equipment surfaces and degraded the plastic seals common to CNC and other machinery. The soy oil version formed shellac or gummy byproducts that accumulated and were extremely difficult to remove and frequently required machinery to be disassembled for cleaning and/or to replace seals. The original food grade soybean base oil therefore failed due to these accumulations and cleaning problems. 
     By contrast, the new vegetable oil derived product of the present invention is easily cleaned off machine surfaces even after being present for an extended time. The new formulation even serves to clean the machinery as it operates. The centrifugation step also resolves the issue of particles dropping out of suspension. The old formulation had to be stirred continually to keep the particles in suspension; otherwise a thick sludge would form at the bottom of any container, requiring agitation to return the formula to its proper state. Thus, the new base oil solves these cleaning and suspension issues and can be adapted to a variety of applications. 
     After centrifuging, the non-colloidal metal sulfide particles removed in the process can be recycled and used to make more lubricant. A high throughput exfoliation process is used to turn this recycled material into colloidal metal sulfide, thereby increasing the amount of lubricant that can be made from a given amount of metal sulfide. This makes the production method more economical than the prior art, which lacked both the centrifugation and recycling steps. 
     The new and improved lubricant can be adapted to many types of lubrication, including those involving oils, greases, and pastes. One application is a metalworking neat oil that can operate in screw machines, CNC machines, Minimum Quantity Lubrication Systems (MQLS), and holding tanks at machinist work stations. A paste version using the new vegetable ester product can be used for working difficult-to-machine alloys such as super alloys. The new methodology can also be used to develop mechanical lubricants for areas such as automotive applications. Due to its extremely hydrophobic nature, these products can be used around both fresh and salt water. The new base oil can also be used to develop a variety of greases that can be adapted to virtually any requirement while maintaining biobased ratings from the USDA. In yet another application, the new formulation can be modified for use with petroleum or synthetic oils and perform as an engine oil additive for reducing emissions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an apparatus for mixing and processing the inventive lubricant. 
     
    
    
     DETAILED DESCRIPTION 
     Disclosed herein is a lubricant composition that is environmentally friendly and that can significantly reduce costs by improving tool life. The inventive composition is a single oil suitable for machining all metals, alloys, super alloys while increasing machine life during machining operations. The lubricant comprises a fluid containing dispersed metal sulfide particles. It may also contain other additives depending on the intended use. The metal sulfide particles are suspended in the fluid and remain in suspension for significantly longer periods of time compared with other existing lubricant compositions. 
     Also disclosed is a method of manufacturing a lubricant composition that comprises dispersing metal disulfide particles in a base oil while subjecting the lubricant composition to an electrical field as well as a magnetic field. The lubricant is then subject to a centrifugation step. Further additives may be added to the lubricant composition at this time, depending on end use. In one embodiment, the dispersing is accomplished by the application of shear forces to the lubricant composition while simultaneously subjecting the lubricant composition to an electrical field and a magnetic field. The lubricant then undergoes a centrifugation step to remove large-size treated metal sulfide particles while leaving colloidal-size treated particles which maintains or enhances the lubricants performance. 
     As described in prior art, current base oils may be derived from several sources, such as crude, biological products, forest products or some combination of these. Oils derived from crude include petroleum-based oils. Biological oils include algae oil, fish oils, and animal fats, as well as chemically esterified versions of these biological oils, including methyl, ethyl, propyl, isopropyl or butyl esters. Agricultural products such as soybean oil are also known. 
     Petroleum-based oils are not generally desirable because they are not environmentally friendly and contain hazardous compounds. Soybean oil is environmentally friendly, but it has proven unsuitable. Lubricants using a soybean oil base containing suspended metal sulfide particles, such as those described in U.S. Pat. No. 8,211,329, leave a soy oil shellac or gummy accumulation on machine surfaces. This is caused by the oxidation of the soy oil and is extremely difficult to clean off, often requiring the affected machinery to be completely disassembled, cleaned, and then reassembled, which is inefficient, costly, and time consuming. 
     Another difficulty with current base oils is that the suspended metal sulfide particles, such as molybdenum disulfide, drop out of suspension, forming a thick sludge. The sludge must be agitated to return it to a suspended state. This is undesirable because the current machining technology is moving away from mixing lubricants just prior to being added to machinery and/or having mixers built into holding tanks. Current industries that use lubricants prefer a ready-to-use compound with suspended lubricants, even though many current products are toxic. 
     An improved lubricant is needed, one that is environmentally friendly, does not leave difficult to clean residue behind, and that stays in suspension. Such a lubricant is disclosed herein. The base oil is a vegetable oil-derived, methyl ester formulation and contains suspended metal sulfide particles. It is easily cleaned off machine surfaces and does not cause the above mentioned problems. 
     The inventive lubricant also undergoes a centrifugation process, unlike current compounds. This step provides two benefits. First, it removes non-colloidal metal sulfide particles, leaving only colloidal metal sulfide behind, which prevents the metal sulfide particles from dropping out of suspension and forming an undesirable sludge. Second, the metal sulfide particles removed during this step may be recycled and used to form more colloidal metal sulfide. The recycling results in less waste and makes the process more economical. 
     A preferred metal sulfide compound is molybdenum disulfide, such as Tech Fine Grade MoS 2 , which is commercially available 
     It is desirable for the metal sulfide particles to have an average particle size of up to about 6 micrometers prior to dispersion. In one embodiment, the metal sulfide particles have an average particle size of about 0.1 micrometers to about 5.5 micrometers after dispersion. In another embodiment, the metal sulfide particles have an average particle size of about 1.0 to about 4.0 micrometers after dispersion. 
     In one embodiment, the metal sulfide particles have a minimum particle size that is greater than or equal to about 1.0 micrometer after dispersion. In another embodiment, the metal sulfide particles have a minimum particle size greater than or equal to about 2.0 micrometers after dispersion. In yet another embodiment, the metal sulfide particles have an average particle size of greater than or equal to about 3.0 micrometers after dispersion. 
     The metal sulfide particles may have particle sizes in the submicron range. In one embodiment, the metal sulfide particles are less than or equal to about 75 nanometers after dispersion. In yet another embodiment, the metal sulfide particle sizes less than or equal to about 50 nanometers after dispersion. In yet another embodiment, the metal sulfide particle sizes are less than or equal to about 10 nanometers after dispersion. 
     If the metal sulfide particles added prior to dispersion are larger than the preferred size, the particles may be reduced in size after they are suspended in the base oil. This may be accomplished by particle-to-particle ablation, milling, ball milling, chemical particle size reduction, or electro-chemical particle size reduction. This step may take place at the same time the electric and magnetic fields are applied, or it may be done afterwards, prior to centrifuging process mentioned below. 
     It is preferable that the initial lubricant composition contain the metal sulfide in an amount of about 0.1 pounds (lbs.) to about 6 lbs. per 11 gallons of the base oil. In one embodiment, the metal sulfide is present in an amount of about 0.8 to about 2.0 lbs. per gallon of the base oil. In an exemplary embodiment, the metal sulfide is present is an amount of about 0.1 pounds per gallon of the base oil. 
     In one method of manufacturing the lubricant, the base oil is mixed with the metal sulfide in a reactor to which is applied a magnetic field as well as an electrical field. The base oil is disposed in a reactor. The metal sulfide is added to the reactor gradually while the contents of the reactor are being agitated. A magnetic field and an electrical field are applied to the reactor during the agitation. The agitation is conducted for a period of about 1 minute to about 120 minutes. In one embodiment, the agitation can be achieved with a stirrer. In another embodiment, ultrasonic agitation can be used. 
     In one embodiment, the reactor is a 55 gallon drum. When the reactor is a 55 gallon drum, the metal sulfide is added to the base oil over a period of about 5 to about 35 minutes, specifically over a period of about 20 minutes. The stirring in the 55 gallon drum is conducted for a period of about 20 minutes, beginning with the first addition of the metal sulfide to the 55 gallon drum. 
     There are numerous types of commercially available mixing machines that can replace the 55 gallon drum. The only requirement is that the electrical, magnetic and shear forces are able to be applied during mixing. Large mixing machines make the process scalable to industrial production levels. 
     The magnetic field is generally applied using regular permanent magnets or electromagnets. The magnets are generally applied to the outside of the reactor, though they can be applied to the inside of the reactor as well. The magnetic field applied across the reactor generally must have a strength greater than the earth&#39;s magnetic field. More preferably, the magnetic field has a strength of greater than or equal to about 3,000 gauss (0.3 Wb), and still more preferably or even greater than or equal to about 20,000 gauss (2 Wb), with any of a number of ranges between 3,000 gauss and 20,000 gauss as possible options. 
     An electric field is applied to the drum during the mixing of the base oil with the metal sulfide. The electric field can be applied using either a direct current (DC) voltage or using an alternating current (AC) voltage. In an exemplary embodiment, the electric field is applied using a DC voltage. The electric field is applied by placing the positive electrode in the reactor while the negative electrode is generally applied to the surface of the reactor. 
     The electric field is generally applied using a voltage of greater than or equal to about 3 volts, preferably greater than or equal to about 6 volts, more preferably greater than or equal to about 9 volts, and still more preferably greater than or equal to about 12 volts. 
     It is generally desirable for the electrical field and the magnetic field to be applied simultaneously. However, they may also be applied sequentially if desired. Thus the electrical field can be applied prior to applying the magnetic field or vice versa. In one embodiment, only an electrical field may be applied to the reactor. 
     After these steps, the treated base oil with its suspended metal sulfide is pumped directly to a centrifuge. The centrifugal forces applied are related to the sedimentation coefficient sufficient to remove all but the colloidal metal sulfides. The centrifuging step removes larger particles of metal sulfide that would otherwise come out of suspension, forming an undesirable sludge at the bottom of containers containing the treated oil and requiring remixing to return the particles to suspension. The metal sulfide left behind is entirely in colloidal suspension, obviating the problem with particles coming out of suspension over time. 
     These larger metal sulfide particles recovered from the centrifuge&#39;s discharge may be reused, which is also a novel step in the lubrication production process. Metal sulfide is an ingredient previously used only once when applied to oils. The centrifuge process allows the residue to be reconstituted and reused. The metal sulfide mixed with the base oil, subjected to electric and magnetic fields, and then removed by the centrifuge retains the characteristics of the treated metal sulfide that remains in suspension and can be exfoliated to obtain more colloidal metal sulfide without any degradation in performance. This colloidal metal sulfide obtained from exfoliating the larger particles removed by the centrifuge can be mixed with more base oil, thereby creating much more product from a single run and correspondingly reducing production costs. 
     In one embodiment the lubricant compound formed after performing the above steps of mixing while applying electric and magnetic fields and then centrifugation is sufficient for many lubricant applications. 
     If a product such as oil for CNC and screw machines is needed, another step is desirable. In this embodiment an additive to provide complete colloidal suspension is added to the reactor during the mixing of the base oil with the metal sulfide before electrical and magnetic fields are applied and before the centrifugation step. An example is nano-cellulose, which is unaffected by the centrifugation process. The end composition can be used in spray bottles, CNC machines, screw machines, and Minimum Quantity Lubrications Systems (MQLS). It will machine any known alloy or super alloy. 
     In another embodiment, the metal sulfides are mixed with a petroleum-based or synthetic oil while exposed to electric and magnetic fields and then centrifuged. The resulting lubricant will work in all but two-cycle combustion engines. When used in gasoline or diesel powered engines two noticeable improvements are made. First, the engine runs cooler due to this lubricant. The more strain the engine is under, the more cooling effect the lubricant provides. Second, there is a reduction in carbon emissions from the engine. 
     In a preferred embodiment, a vegetable oil-derived, methyl ester base oil is used. Technical Fine Molybdenum Disulfide, which is 6 microns in size, is added. The molybdenum disulfide is mixed into the base oil while the mixture is subjected to electric and magnetic fields provided by one of the methods described above. If a machining oil is desired, one to five percent of nano-cellulose is mixed to obtain the desired viscosity. The resulting mixture is then put through a centrifuge to remove larger molybdenum disulfide particles and leaving only colloidal molybdenum disulfide in suspension in the base oil. This produces an olive oil-colored fluid with no visible suspended solids. 
     Lubricants made with this vegetable oil-derived, methyl ester base oil and treated in any of the previously mentioned ways have several advantages. The treated oil and subsequent products are both hydrophobic and free of bacterial growth. They also transfer heat very efficiently. In addition, the new formulation is greater than 90% biobased and all additives are 100 percent biobased. The percentage that is not biobased in the composition is non-toxic and non-hazardous. This allows all products made with this base oil to qualify for the USDA Biopreferred Program. 
     Example 1 
     This example demonstrates one manner of manufacturing the lubricant composition. A first 55 gallon drum ( 1 ) and a second 55 gallon drum ( 2 ) are placed next to one another. The first 55 gallon drum ( 1 ) contains vegetable oil-derived methyl ester base oil. The second 55 gallon drum ( 2 ) is empty and is fitted with a pair of 150 lb. electromagnets ( 3 ). The magnets ( 3 ) are placed on the outer surface of the drum and are disposed generally opposite one another (i.e., rotated roughly 180 around the circumference of the drum. The magnets ( 3 ) are placed approximately at the midpoint of the height of the drum. The second 55 gallon drum ( 2 ) is also fitted with electrodes ( 4  and  5 ). The positive electrode ( 5 ) is placed inside the drum ( 2 ) and is vertically supported in the drum ( 2 ) on a rubber pad. The negative electrode ( 4 ) is affixed directly to the second 55 gallon drum ( 2 ). Both electrodes ( 4  and  5 ) are connected to a direct current power supply ( 8 ). The second 55 gallon drum ( 2 ) is fitted with a stirrer ( 9 ) to facilitate agitation of the contents of the drum. 
     A hose ( 7 ) connects the first 55 gallon drum ( 1 ) to the second 55 gallon drum ( 2 ). The hose ( 7 ) is in communication with a utility pump ( 6 ) that pumps the vegetable derived methyl ester base oil from the first 55 gallon drum ( 1 ) to the second 55 gallon drum ( 2 ) at a rate of approximately 350 gallons per hour. Once the oil has been emptied into the second 55 gallon drum ( 2 ), the magnets ( 3 ) are turned on, as is the DC voltage supply ( 8 ). The stirrer ( 9 ) is started to agitate the oil in the second 55 gallon drum ( 2 ). Once a vortex is created in the drum ( 2 ), a total of 5 lbs. of the metal sulfide is added incrementally to the second 55 gallon drum ( 2 ) as the oil is being mixed and subjected to the electrical and magnetic force fields. The addition of the metal sulfide in this incremental manner prevents agglomeration. After the addition of the 5 lbs. of metal sulfide is completed, the agitation is continued for a period of about 20 to 25 minutes. The stirring is conducted with the vegetable derived methyl ester base oil and the metal sulfide being subjected to a magnetic field and an electric field provided by the magnets ( 3 ) and the DC voltage supply ( 8 ) respectively. During the course of the agitation, the mixture becomes black with silver swirls and the metal sulfide is suspended in the vegetable derived methyl ester oil to form the base lubricant composition. 
     After the treated suspension containing metal sulfides is formed, it is pumped directly to a centrifuge ( 10 ) and subjected to centrifugation. The centrifuged oil with the colloidal metal sulfide is then pumped to holding tank ( 11 ) as it comes out of the centrifuge for analysis prior to packaging. The non-colloidal metal sulfides are recovered and further processed using exfoliation methods. They are moved to another drum ( 12 ), which is connected to the centrifuge ( 10 ). This larger metal sulfide suspension has additional feedstock vegetable ester base oil added. It is then cycled through a high speed blender that subjects the metal sulfides to powerful shear forces. This mechanical energy peels away the stacked layers of the metal sulfide in a process called exfoliation. The exfoliated particles are subjected to the shear forces until they achieve comparable colloidal size as is present in the supernatant. This newly formed colloidal metal sulfide is then adjusted with feedstock base oil to the proper metal sulfide concentration. The resulting oil is then run through the centrifuge step again to clarify the exfoliated metal sulfide to the correct particle size. This step substantially increases the quantity of lubricant produced per unit of metal sulfide. 
     While the invention has been described with reference to certain preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. It is intended that the invention not be limited to any particular embodiment described above.