DESC:FORM –2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

ECO- FRIENDLY LUBRICANT COMPOSITION
Applicant: Bharat Forge Limited,
Mundhwa, Pune 411036,
Maharashtra, India
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.
FIELD OF INVENTION
[0001] This invention relates to eco-friendly lubricants. More particularly, the present invention relates to eco-friendly lubricant compositions for forging applications.
BACKGROUND
[0002] Forging is a process for increasing the density, toughness and strength of the metal by grain deformation. It can be performed while the metal is in the hot state or cold. Both processes have advantages and disadvantages. While cold forging upgrades metallurgical properties, hot forging requires the expenditure of less energy and permits greater deformation. The temperature range at which forging process is carried out varies with each metal. For Example, in case of ferrous alloys and steels, the temperature varies from 760°C to 1350°C, and for aluminum alloys it may be in between 315°C to 500°C.
[0003] During forging, the hot metal billets or slugs are usually heated and they are hammered or stamped in a forging die, or the like, to form them into the desired shape. These dies, which are generally made of extremely hard alloy steel, are nonetheless subject to scoring and heat checking by the hot metal billets, which also have a tendency to be "welded" to the die. This causes rapid wearing and deterioration of these dies, which must then be discarded and replaced.
[0004] Two primary factors which are especially important in forging operations are the rate of production and die life. The dies are very expensive and every precaution, including the choice of proper lubricants, is taken to extend die life. The use of lubricants is to minimize metal pick-up and wear.
[0005] A wide variety of lubricants have been used over a period of time in forgings applications. Oil and graphite mixtures used to be the preferred mixtures in the olden days. Oil-based lubricants suffer from several limitations which include their flammability and tendency to explode at the operating temperatures which poses a great risk to the workers.
[0006] Water based lubricants for forging applications are also available. Water based lubricants are increasingly being preferred since they offer numerous advantages. However, there still exists a need for water based lubricants that can improve die-life and overall productivity which in turn also reduces high costs associated with frequent die-replacements.
[0007] It is an object of the present invention to provide eco-friendly water based lubricants with enhanced anti-friction properties as compared to the known water-based lubricants.
[0008] It is another object of the present invention to provide eco-friendly water based lubricants that improve the productivity of the forging processes by improving the life of a die.
[0009] Other objects and advantages of the present disclosure will be more apparent from the following description which is not intended to limit the scope of the present disclosure.
SUMMARY
[0010] In one aspect, there is provided a water-based lubricant composition that comprises: at least one di-alkali metal salt of a dicarboxylic acid in an amount ranging from 0.05 to 0.35% wt; surface stabilized two dimensional carbonaceous graphene particles with particle size ranging from 3 to 10nm and at least one surfactant in an amount ranging from 0.001% to 0.003%.
[0011] In another aspect, there is provided a method for preparation of lubricant composition. The method of the present invention comprises :
preparing a base lubricant and diluting it with de-ionized water in the proportion ranging from 1:5 to 1:20 to obtain a diluted base lubricant;
preparing an inoculate of surface stabilized two dimensional graphene particles having particle size ranging from 3nm to 10 nm by treating a dispersion of two dimensional graphene particles in deionized water with a surfactant in an amount ranging from 0.001% to 0.003% at pH ranging from 7 to 8 followed by ultrasonication; and
incorporating the inoculate of surface-stabilized to the base lubricant and subjecting the resulting composite to dispersion a composition without an particulate aggregates.
[0012] In another aspect, there is provided a method for forging metals that comprises: applying to forging dies a water based composition comprising at least one di-alkali metal salt of a dicarboxylic acid in an amount ranging from 0.05 to 0.35% wt; surface stabilized two dimensional carbonaceous graphene particles with particle size ranging from 3 to 10nm and at least one surfactant in an amount ranging from 0.001 to 0.003%.; and placing the metal between the dies, closing the dies under pressure, opening the dies and removing the forged metal.
[0013] Definitions:
[0014] The terms and phrases as indicated in quotation marks (“ ”) in this section are intended to have the meaning ascribed to them in this ‘Definitions’ section applied to them throughout this document, including in the claims, unless clearly indicated otherwise in context. The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.
[0015] The term “Forging Applications” means all types of forging applications including hot forging, cold Forging and warm forging irrespective of the type of metal involved in the forging process.
[0016] The base lubricant in the context of the present invention means a water based lubricant that comprises at least one di-alkali salt of at least one dicarboxylic acid selected from the group consisting of adipic acid, phthalic acid, orthophthalic acid, isophthalic acid and terephthalic acid; and one or more additives.
[0017] The term “nano-material” in the context of the present specification refers to carbonaceous graphene particles with a particle size ranging between 3 nm and 10 nm.
[0018] The term “surface modification/stabilization” means, optimizing surface charges on 2D graphene particles to enhance their stability and maintain them in the de-agglomerated state when they are inoculated in the base lubricant.
[0019] BRIEF DESCRIPTION OF DRAWINGS:
[0020] Fig 1 shows Scanning Electron Microscope (SEM ) Images of (A & B), shows prior art lubricant and a lubricant with 2D Nanoparticles incorporated in accordance with the present invention with 30 & 3 KX magnification respectively. The incorporation of 2 D nano structured materials in the image B shows elongated and sharp edges, which improves the lubricant properties.
[0021] Figure 2 shows die images before and after run using conventional water based lubricant
[0022] Figure 3 shows Fourtier Transform Infrared spectroscopy for conventional base lubricant and the lubricant of the present invention
[0023] DESCRIPTION:
[0024] In one aspect, there is provided in accordance with the present invention an eco-friendly water-based lubricant composition comprising at least one di-alkali salt of at least one dicarboxylic acid selected from the group consisting of adipic acid, phthalic acid, orthophthalic acid, isophthalic acid and terephthalic acid; and surface treated carbonaceous graphene nano-material dispersed in the composition using at least one surfactant selected from the group consisting of anionic surfactant and neutral surfactant.
[0025] The alkali metal may be at least one elected from the group consisting of sodium, potassium and lithium. The lubricant composition of the present invention further may include various additives which include but are not limited to wetting agent, stabilizing agent, anti-bacterial agent, dispersants, rheology modifiers, biocides, corrosion inhibitors, extreme pressure additives, antifoaming agents, and mixtures thereof containing additional ingredients.
[0026] Typically, the amount of the di-alkali metal salts of dicarboxylaic acids in the lubricant composition of the present invention may range from about 0.005 to about 0.35%wt. Typically, the amount of thickening agents and other additives in the lubricant composition of the present invention may range from about 0.0005 to about 0.25%wt.
[0027] Typically, the carbon nano-material present in the water based lubricants of the present invention is two dimensional carbonaceous graphene nano-material. Inventors have identified that carbonaceous nano-particle with a particle size lesser than 20nm, preferably below 10 nm result in relatively higher enhancement in anti-friction properties. The carbonaceous graphene nano-particles as employed in the composition of the present invention are further characterized by average lateral size varying from about 5 to about 10 microns and surface area ranging from about 250 to 300 m2/g.
[0028] These smaller sized nano-particles are deposited on the surface of the large sized particles and they compensate for the loss of mass. Further, they also reduce the roughness of the tribological surfaces.
[0029] In one embodiment, the particle size of the carbonaceous nano-particles varies from about 3 to about 10 nm. The two dimensional carbonaceous graphene nano-material incorporated in the lubricant composition of the present invention is dispersed in the base lubricant by ultra-sonication method and the nano-materials stability in aqueous systems.
[0030] Surfactant employed in the lubricant composition of the present invention is at least one selected from the group consisting of anionic surfactants and cationic surfactants and non-ionic surfactants. Different kinds of surfactants that may be used include anionic surfactant, Sodium dodecyl benzene sulfonate (SDBS), cationic surfactant, Cetyl-trimethyl-ammonium bromide (CTAB) and non-ionic surfactant, Triton X-100.
[0031] In one embodiment, Triton X-100 is used as the surfactant. Surfactants enhance the stability of the nano-particles in the fluids. The use of surfactant improves the compatibility of nano-particles by binding with phthalate group in the white base lubricant, which favors the dispersion of the carbonaceous nano-particles and prevents the aggregation of the nanoparticles in the base lubricant. Typically, the concentration of the surfactant in the lubricant composition of the present invention ranges from 0.001 to 0.003%wt.
[0032] The average nano-particle size ranging from 3-10 nm of the nano-carbonaceous graphene possesses high surface area reactivity which ensures better stability in the dispersion as compared to the comparatively grosser micro-meter sized graphene particles. Typically, amount of carbonaceous graphene nano-particles in the present lubricant composition varies from 0.001 to 0.1%, preferably from 0.02 % to 0.09 % and most preferably from 0.04 to 0.07 % in the dispersion based on earlier research. It has been found by the present inventors that the amount of carbonaceous graphene nano-particles is linked with the anti-frictional properties of the lubricant.
[0033] Morphology of nano-treated lubricant of the present invention is confirmed by the presence of sharp discrete elongated tubular structure with sharp edges when it is observed in scanning electron microscope. The lubricant composition of the present invention retains native structure of both synthetic lubricant as well as carbonaceous graphene nano-particles. This ensures enhanced rheological and antifriction properties.
[0034] Strong interactions of the surfactant with the graphene surface leads to uniform dispersion. FTIR spectrum and scanning electron microscopy reveals the presence of monolayer when the surfactant interacts with graphene due to hydrophilic charged head-group exposed in solution and the planar region in direct contact with graphene to maximize the strength of van der Waals interactions with the substrate. This is show in Figure 3A and 3B.
[0035] Typically, the water based lubricant composition of the present invention is characterized by pH ranging from 7 to 8. Apart from particle size of the carbonaceous graphene nano-particles and the concentration of the surfactant, it is the pH of the composition that affects the stability of the lubricant composition.
[0036] In a further aspect of the present invention, there is also provided a method for preparation of the lubricant composition of the present invention. It comprises following steps:
• diluting the base lubricant with de-ionized water in a proportion ranging from 1:5 to 1:20 under constant stirring to obtain a uniformly dispersed diluted base lubricant dispersion;
• preparing an inoculate of surface-stabilized 2D graphene particles by dispersing them in de-ionized water with at least one neutral surfactant in an amount ranging from 0.001 to 0.003% at pH ranging from about 7 to about 8.5 through ultrasonication;
• inoculating the dispersion of surface stabilized nano-particles in the diluted base lubricant to and subjecting the inoculated dispersion to homogenization to obtain a lubricant composition.
[0037] In a further aspect, there is provided a forging method that employs the lubricant composition of the present invention. Typically, the forging process of the present invention improves the productivity count by at least 20%.
[0038] Lubrication takes place in the vapor phase by sublimation process which helps in creating a good sliding and anti-friction and also holding the billet by formation of the thin film. The load bearing capacity increases by decreasing the coefficient of friction.
[0039] The inventors have found out the lubricant of the present invention offers superior mold release properties, substantially increase the die-life and significantly boost the productivity of the forging applications in comparison to graphene based lubricants and other synthetic lubricants when it is used independently.
[0040] The water based, nano-material enriched, graphite-free lubricant composition of the present invention offers numerous distinct advantages which include significant reduction in die-wear pattern which in turn reciprocally increases the rate of production. The lubricant composition also offers superior combination of anti-corrosive and anti-oxidant properties.
[0041] The 2D Graphene is able to drastically reduce the wear rate and the coefficient of friction (COF) of lubricant. The marked reductions in friction and wear are attributed to the low shear and highly protective nature of graphene, which also prevents oxidation (tribo-corrosion) of the steel surfaces when present at sliding contact interfaces.
[0042] Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
[0043] The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.
[0044] While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.
[0045] EXAMPLE 1
A water based synthetic lubricant with following composition was used
as a base lubricant.
CONSTITUENT PERCENTAGE (%)
Isophthalic Acid 10.2
Adipic Acid 10.2
Sodium Hydroxide (50% soln) 11
Hydroxyethylcellulose (HEC)
1
Germicide (Dowicil 75)
0.1
Deionized water 67.5
The base lubricant was analyzed. Provided herein below are the findings of the analysis: Pigment : White Non Graphitic; Carrier: Water; Density: 1.5 g/cm; Moisture Content: 72 % and pH : 9.2
[0046] This combination was allowed to mix with the dilution of 1:15 with water, in the blending tank, that was further allowed to stirring for 30 to 45 minutes using magnetic heavy rotor blades at rpm 15,000 to 20,000 rpm (IKA Stirrer RW 15000, heavy rotor) to ensure homogenization. The liquid composite phase compensated loss of mass during friction. The final diluted lubricant mixture was then dispensed onto the surface of the dies with the help of automated spraying systems, which were timed with the stroke of the forging press.
[0047] The final diluted lubricant mixture was then dispensed onto the surface of upset dies with the help of automated spraying systems, which were timed with the stroke of the forging press. Lubricant composition mixture was sprayed uniformly at every 5 seconds per stroke. The forging operation was carried out at temperature 150-200°C and a pressure of 2500 Tons.
[0048] Analysis of Die wear Pattern:
[0049] Type of component – Gear components flat surface
[0050] Material of the component- Din, Hardness -48-52HRC
[0051] Cycles completed – 2500 / die
[0052] There was no substantial improvement in the die wear pattern and finish quality of the die analyzed by high resolution picto-graphical images shown in Fig.2.
EXAMPLE 2: BASE LUBRICANT WITH 2D GRAPHENE NANO PARTICLES
[0053] The two dimensional graphene (2D) with an average size of 3-10 nm were evaluated using zeta potential measurements and steady shear rheological measurements to assess stability as a function of pH. For zeta potential measurements, a dilute dispersion of the material was made up in de-ionised water ready for analysis using a Malvern Zetasizer Nano ZS in conjunction with an MPT2 autotitrator. The titrator was set up with 0.25M and 0.025M HCl to titrate from the start/sample pH to an end pH of 1.0 and record 3 repeat zeta potential measurements at 10 equally spaced pH intervals across the range. The surface charges and size of the nanoparticle were measured in the dispersed solution measured using KINEXUS SERIES Malvern series software.
[0054] All tests were performed at 25ºC with the inclusion concentration of 0.02%, of 2D graphene nanoparticles with particle thickness 3-10 nm and average lateral size 5-10 µm. The surface modification technique was employed using ultra-sonication method at the anionic pH condition of about 9 wherein 0.001 % of anionic surfactant agent SDBS (Sodium Dodecyl Benzene Sulphonate), Merck, India was used to disperse graphene nano-particles to avoid aggregation. The composite was stored at room temperature for further applications. A sample of nano-composites was subjected to characterization.
The synthetic lubricant doped with 2D Carbon Nanoparticles is kept at room temperature for further analysis. Following parameters are observed: Appearance : Grey; pH value: 9;Precipitation was observed.
The precipated solution was not suitable for forging application due to agglomeration of nanoparticles.
EXAMPLE 3: BASE LUBRICANT WITH 2D GRAPHENE NANOPARTICLES
[0055] The same procedure as in Example 2 was repeated except that the inclusion concentration of carbonaceous graphene nano-particles was 0.04%. Further, the pH maintained was about 8.2 and the surfactant employed was 0.001 % of cationic surfactant Cetyltrimethylammonium bromide (CTAB) agent Merck, India. A sample of nano-composites was subjected to characterization.
The synthetic lubricant doped with 2D Carbon Nanoparticles was kept at room temperature for further analysis. Following parameters are observed:Appearance : Grey; pH value: 8.2; Precipitation was observed.
The precipated solution was not suitable for forging application due to agglomeration of nanoparticles.
EXAMPLE 4: BASE LUBRICANT WITH 2D GRAPHENE NANOPARTICLES
[0056] The same procedure as in Example 4 was repeated except that the inclusion concentration of carbonaceous graphene nano-particles was 0.06%. Further, the pH maintained was about 7.4 and the surfactant employed was 0.001 % of neutral surfactant Triton X 100; octyl-phenolethoxylate; Merck, India.
Triton X-100 was observed to be a better stabilizer and it blended s well with the phthalate group of the white lubricant.
A sample of nano-composites was subjected to characterization
[0057] The viscosity was measured by VISCOMETER(Digital Cone Viscometer, CPD 2000,Chem-Tech Lab,Pune) which was around 245 cSt.
[0058] Carrier: de-ionized Water
[0059] Density: 2.2 g/cm3
[0060] Moisture Content: 68%
[0061] pH : 7.4
The resultant dispersion was found to be stable. As a result it was chosen to be inoculated to the base lubricant to obtain the lubricant composition of the present invention.
[0062] The inoculated as prepared in Example 4 was mixed with the diluted base composition mixture in the blending tank, that was further allowed to stirring for 30 to 45 minutes using magnetic heavy rotor blades at rpm 15,000 to 20,000 rpm (IKA Stirrer RW 15000, heavy rotor) to ensure homogenization. The liquid composite phase compensated loss of mass during friction. The final diluted lubricant mixture was then dispensed onto the surface of the dies with the help of automated spraying systems, which were timed with the stroke of the forging press. The resulting lubricant composition in accordance with the present invention was then applied to upset die surfaces in a manner as described in Example 1 and the forging operations were performed for 2480 cycles for gear components under same conditions of temperature and pressure as mentioned in Example 1.The comparative results of the die wear pattern are provided in Table 1 and Table 2.
[0063] TESTS: Coefficient of Friction
[0064] Coefficient of friction was found out for the base lubricant as described in Example 1 and the nanop-doped lubricant of the composition as prepared in Example 4 by using pin on disc tribometer; a type of mechanical method of wear test. Provided herein below are Technical Specifications of the machine:
TEST PARAMETER VALUES
Specimen Pin : 10-14 mm;Diameter: 32 mm long Ball Spherical ball ?10

Wear disc size Diameter 165 mm, 8mm thick
Wear track diameter Min.: 50 mm, Max.: 500 mm
Disc rotation Min.: 200 rpm, Max.: 2000 rpm
Normal Load Min.: 5N, Max.: 200 N
Frictional Force Min.: 0N, Max. : 200 N

[0065] The water based nano-enriched composition of the present invention as prepared in Example 4 was characterized by a coefficient of friction that was evaluated by constant load, constant speed and constant time as 457, 678 and 598 µm respectively and the coefficient of friction of the base lubricant was found out to be 2298, 2109 and 910 µm respectively. This is shown in Figure 4.
[0066] In variable speed range, keeping time and load constant, the wear pattern was observed to be 229 µm for the base lubricant when compared to nano-composite lubricant which was observed as 457 µm with 1500 rpm speed.
[0067] In variable load range parameter, keeping time and speed constant the wear pattern was observed to be 2109 µm for the base lubricant when compared to nano-composite lubricant of the present invention which was observed to be 678 µm with load of 10 kg.
[0068] In variable time range parameter, keeping constant speed and load the wear pattern for the base lubricant was observed to be 910 µm when compared to nano-composite lubricant of the present invention which was observed to be 598µm in 90 minutes of time duration.
[0069] Coefficient of friction test analysis confirmed the reduced wear pattern with the use of lubricant composition of the present invention in comparison to the base lubricant.
ANALYSIS OF BASE LUBRICANT AND LUBRICANT COMPOSITION OF THE PRESENT INVENTION BY FTIR-SPECTROSCOPY
[0070] The base lubricant and the lubricant of the present invention as prepared in Example 4 was further characterized by Fourier Transform Infrared spectroscopy (FT-IR) and Scanning Electron Microscopy.
[0071] Fourier transform spectroscopy (FT-IR) confirmed the OH bending and C=O stretching as shown in Fig.3A. Its characteristic adsorption bands are assigned mainly to the iso-phthalic acid and carboxyl group. The FTIR spectroscopy further confirmed the presence of phthalate group in nano-lubricant composition which revealed that existence of both synthetic base lubricant and nano doped particulate property in mixture shown in Fig.3B.
[0072] The comparative outcome for all the 4 examples as provided above in terms of characteristics of the final lubricant composition and its lubricating properties is provided herein below in Tables 1and 2.
Table 1
Graphene Particle size (2D) Test Example
Example 1
Nil Example 2
3-10 nm and average lateral size 5-10 µm. Example 3
3-10 nm and average lateral size 5-10 µm. Example 4
3-10 nm and average lateral size 5-10 µm.
Concentration of Graphene (2D) Nil 0.02 % 0.04% 0.06%
Surfactant Nil SDBS CTAB TRITON X-100
Surfactant Concentration Nil 0.001 % 0.001% 0.001%
Alkali salt of dicarboxylic acid Pthalate group, Adipic Acid and water as a carrier Pthalate group, Adipic Acid and water as a carrier Pthalate group, Adipic Acid and water as a carrier Pthalate group, Adipic Acid and water as a carrier

Table 2
Parameter Example 1 Example 2 Example 3 Example 4
pH 9.2 9 8.2 7.4
Surface characteristics of finished components rough finishing, missing shiny appearance, negligible error in ID and OD value NA NA Smooth finishing, perfect ID,OD value, shiny apperaence
Productivity Count 2000 cycles NA NA 2480- cycles

Considerable improvement in the wear behavior was observed which resulted boosting the productivity count by about 23 -25 %.

,CLAIMS:1. A water-based lubricant composition comprising at least one di-alkali metal salt of a dicarboxylic acid in an amount ranging from 0.05 to 0.35% wt; surface stabilized two dimensional carbonaceous graphene particles with particle size ranging from 3 to 10nm and at least one surfactant in an amount ranging from 0.001% to 0.003%.
2. A lubricant composition as claimed in claim 1 further comprising a thickeners and additives in an amount ranging between 0.005 to about 0.25%wt.
3. A lubricant composition as claimed in claim 1, wherein the di-alkali metal is at least one selected from the group consisting of sodium, potassium and lithium.
4. A lubricant composition as claimed in claim 1, wherein the dicarboxylic acid is at least one selected from the group consisting of adipic acid, orthophthalic acid, isophthalic acid, and terephthalic acid.
5. A lubricant composition as claimed in claim 1, wherein the surfactant is a neutral surfactant selected from the group consisting of octyl-phenolethoxylate, Lauryl Glucoside, polyethelene glycol.
6. A lubricant composition as claimed in claim 1, wherein the surfactant is octyl-phenolethoxylate.
7. A lubricant composition as claimed in claim 1, wherein the concentration of the carbonaceous two dimensional graphene particles in the composition ranges from 0.001 to 0.009%.
8. A lubricant composition as claimed in claim 1, wherein the pH of the composition ranges from 7 to 8.
9. A method for preparation of lubricant composition, said method comprising :
a. preparing a base lubricant and diluting it with de-ionized water in the proportion ranging from 1:5 to 1:20 to obtain a diluted base lubricant;
b. preparing an inoculate of surface stabilized two dimensional graphene particles having particle size ranging from 3nm to 10 nm by treating a dispersion of two dimensional graphene particles in deionized water with a surfactant in an amount ranging from 0.001% to 0.003% at pH ranging from 7 to 8 followed by ultrasonication;
c. incorporating the inoculate of surface-stabilized to the base lubricant and subjecting the resulting composite to dispersion a composition without an particulate aggregates.
10. A forging process for metals comprising applying to forging dies a water based composition comprising at least one di-alkali metal salt of a dicarboxylic acid in an amount ranging from 0.05 to 0.35% wt; surface stabilized two dimensional carbonaceous graphene particles with particle size ranging from 3 to 10nm and at least one surfactant in an amount ranging from 0.001 to 0.003%.;, placing the metal between the dies, closing the dies under pressure, opening the dies and removing the forged metal.