DESC:TECHNICAL FIELD
The present disclosure generally relates to the field of tyre technology, and pertains to a process for preparing compositions employed for manufacturing of tyres. More particularly, the present disclosure provides a solvent based process for preparing a tyre composition that allows incorporation of a layered compound. The said layered compound includes but is not limited to graphene, molybdenum disulphide, boron nitride and clay, or a combination thereof. When a composition is prepared using the process of the present disclosure, and when the composition is used in manufacturing of tyres, they have an enhanced properties and life, when compared to a tyre manufactured using a composition lacking the layered compound.
BACKGROUND OF THE DISCLOSURE
With an ever-increasing number of cars worldwide, automotive and tyre industries play a vital role in reducing carbon dioxide footprint by reducing car fuel consumption and increasing tyre mileage without compromising on driving safety and ride quality. A tyre is one of the most complex pieces of equipment of a vehicle and consist hundreds of different components. It is the only part of a vehicle which comes into direct contact with the road surface and performs a myriad of functions such as vehicle stability, passenger comfort, mileage, grip, wear resistance etc.
For this reason, tyre industries have been in a continuous development activity to expand the so-called magic triangle comprising of rolling resistance, abrasion resistance, and wet grip. A detailed look at the magic triangle reveals that lowering the rolling resistance of tyres reduces the fuel consumption of a car, whereas the higher abrasion resistance of tyres ensures higher mileage and higher lifetime, while high wet grip ensures safety.
A tyre's composition affects grip, fuel economy and its lifetime. To adapt the property profiles of elastomer materials for car tyres with respect to the requirements of energy efficiency, adhesion and expanded life time, an incorporation and finest possible dispersion of nanoscale filler particles in the polymer matrix is necessary.
In a typical tyre formulation used widely in industries, 45 to 55 parts of high abrasion furnace carbon black such as N330 is employed as a reinforcing filler to improve mechanical properties of the elastomer.
Graphene is a two-dimensional wonder material that holds great potential to enter new markets and replace existing materials. With the advent of new graphene-based products every day, it is certain that graphene is a disruptive technology waiting to be commercialized. One such application is in car tyres. However, handling of graphene in powder form is difficult due to its low bulk density and fluffy nature which prevents it from being stable and often flies off while mixing and possesses health hazard. Further, while prior literatures have tried to employ graphene in tyre compositions, it has been possible to mix up to a maximum of 10 parts of graphene only along with an external processing aid, e.g. mineral oils. Further, conventional melt processing only allows a maximum of only 2.5 parts of high surface area graphene to be incorporated in the formulations.
Thus, while graphene can be employed for weight reduction of the tyre thereby allowing for better fuel efficiency and tensile modulus, keeping in mind the properties of graphene, its impact on rolling resistance, abrasion loss, fatigue failures, and heat build-up must be tested. Accordingly, tyre compositions comprising varying amounts of graphene are desired for longer life of tyre tread and improved properties. However, none of the currently available processes allow stable incorporation of graphene in tyre compositions at specific amounts, and without substantial use of an external processing aid. Thus, there is a need to find alternative processes and compositions that improve the quality of tyres to achieve the desired results.
SUMMARY OF THE DISCLOSURE
The present disclosure relates to a process for preparing tyre composition comprising a layered compound.
In embodiments of the present disclosure, the layered compound includes but is not limited to graphene, molybdenum disulphide, boron nitride and clay, or a combination thereof.
The process of the present disclosure comprises steps including but not limited to mixing of the layered compound with a combination of solvents followed by adding the mixture to a combination of one or more rubbers or elastomers employed for preparing a tyre composition. Once mixed, a different type of solvent is used to coagulate the rubber(s) or elastomer(s) from the mixture, to obtain a layered compound-rubber/elastomer master batch, which is then used for manufacturing of tyres.
In particular, the present disclosure provides a process for preparing a layered compound-rubber elastomer for tyre composition, comprising a layered compound and at least one rubber, said process comprising steps of:
a. mixing of the layered compound with at least one of the first solvents using a high-shear mixer to obtain mixture 1;
b. obtaining a slurry or latex of at least one rubber followed by adding the slurry or the latex to the mixture 1 and subjecting to a high-shear mixer, to obtain mixture 2; and
c. subjecting the mixture 2 to a second solvent for facilitating coagulation to obtain the layered compound-rubber elastomer.
In embodiments of the present disclosure, the process allows incorporation of graphene or other layered compounds in form of rubber masterbatch, in concentrations ranging from about 0.01% to about 18%.
The present disclosure also relates to a process for preparing a tyre composition having at least one improved property selected from a group comprising rolling resistance, abrasion loss, tensile modulus, heat build-up and fatigue failure, or any combination thereof, said process comprising steps of:
a. preparing a layered compound-rubber elastomer as per the process of the present disclosure; and
b. incorporating at least one additional component selected from a group comprising processing oil, stearic acid, antioxidant, tackifier, sulfur, pre vulcanization inhibitor, peptiser, wax, zinc oxide and accelerator, or any combination of components thereof, to prepare the tyre composition having at least one improved property.
The present disclosure provides a tyre composition comprising the layered compound-rubber elastomer prepared by the process as above, wherein the layered compound is at a concentration ranging from about 0.01% to about 3.5%.
In embodiments of the present disclosure, the corresponding composition so prepared comprises at least one rubber including but not limited to styrene-butadiene rubber (SBR), polybutadiene rubber (PBR) and natural rubber, along with a layered compound such as graphene in a masterbatch at a concentration ranging from about 0.01% to about 18%.
In embodiments of the present disclosure, the tyre composition prepared by the process of the present disclosure provides for better fuel efficiency and tensile modulus, and results in reduction of rolling resistance, abrasion loss, fatigue failures, and heat build-up.
The present disclosure also relates to the use of the tyre composition for manufacturing of tyres having enhanced properties, performance and life.
DETAILED DESCRIPTION OF THE DISCLOSURE
In view of the drawbacks associated, and to remedy the need created by the art available in the field of tyre technology, the present disclosure aims to provide a process that allows incorporation of a layered compound in a composition comprising one or more types of rubbers. More particularly, the present disclosure provides a process for preparing a tyre composition, comprising steps including but not limiting to solvent assisted incorporation of layered compound including but not limited to graphene, molybdenum disulphide, boron nitride and clay, with at least one rubber including but not limited to styrene-butadiene rubber (SBR), polybutadiene rubber (PBR), butyl rubber, halo butyl rubber, ethylene propylene diene methylene rubber (EPDM), silicone rubber and natural rubber. The disclosure also provides a corresponding composition comprising the said graphene along with one or more of the said rubbers for use in manufacturing of tyres.
However, before describing the process in greater detail, it is important to take note of the common terms and phrases that are employed throughout the instant disclosure for better understanding of the technology provided herein.
Throughout the present disclosure, the term ‘layered compound’ is intended to convey the ordinary conventional meaning of the term known to a person skilled in the art in the field of material science and intends to cover compounds such as graphene, molybdenum disulphide, boron nitride and clay, or a combination thereof. These compounds typically comprise of two dimensional atomic-level thickness layers which are held together by van-der Waals forces and having high specific surface area from 100 to about 2630 m2/gm. For example, the graphene sheets completely or almost completely comprise fully exfoliated, preferably single layer (>70%) or may be up to 15 layers of exfoliated graphite.
Throughout the present disclosure, the term ‘graphene’ is intended to convey the ordinary conventional meaning of the term known to a person skilled in the art and intends to cover
Throughout the present disclosure, the term ‘graphene’ is intended to convey the ordinary conventional meaning of the term known to a person skilled in the art and intends to cover ‘graphene’ as an allotrope of carbon consisting of a single or multiple layers, including up to about 15 layers, of carbon atoms. Thus, the graphene employed in the present disclosure maybe a single layered or multi layered graphene. The graphene employed herein is preferably of high surface area, typically ranging between 1500 to 3000 m2/g.
Throughout the present disclosure, the term ‘tyre’ is intended to convey the ordinary conventional meaning of the term known to a person skilled in the art and intends to cover tyre of any composition, comprising at least one rubber/elastomer. Accordingly, in the present disclosure, any reference to a ‘composition’ is intended to refer to any composition known to a person skilled in the art which is used in manufacturing of a tyre.
Throughout the present disclosure, technical terms such as ‘fuel efficiency’, ‘tensile modulus’, ‘rolling resistance’, ‘abrasion resistance’, ‘abrasion loss’, ‘fatigue failure’, and ‘heat build-up’ are used to describe the properties of a tyre or characteristics of a composition that makes up the tyre, and are intended to convey the ordinary conventional meaning of the terms known to a person skilled in the art.
Throughout the present disclosure, the term ‘solvent’ is intended to convey the ordinary conventional meaning of the term known to a person skilled in the art and intends to cover polar and non-polar organic solvents.
Accordingly, to reiterate, the present disclosure relates to a process for preparing a tyre composition having a layered compound and at least one rubber including but not limited to styrene-butadiene rubber (SBR), polybutadiene rubber (PBR), butyl rubber, halo butyl rubber, ethylene propylene diene methylene rubber (EPDM), silicone rubber and natural rubber. The said layered compound includes but is not limited to graphene, molybdenum disulphide, boron nitride and clay or a combination thereof, and the composition is typically used for manufacturing a tyre and improves its properties such as rolling resistance, abrasion resistance and wet grip.
More particularly, the present disclosure provides a process for preparing a layered compound-rubber elastomer for tyre composition, comprising a layered compound and at least one rubber, said process comprising steps of:
a. mixing of the layered compound with at least one of the first solvents using a high-shear mixer to obtain mixture 1;
b. obtaining a slurry or latex of at least one rubber followed by adding the slurry or the latex to the mixture 1 and subjecting to a high-shear mixer, to obtain mixture 2; and
c. subjecting the mixture 2 to a second solvent for facilitating coagulation to obtain the layered compound-rubber elastomer.
While the conventionally known processes such as conventional melt processing only allows a maximum of small amounts, typically only about 2.5 parts of high surface area graphene to be incorporated in a composition, the process of the present disclosure allows incorporation of graphene or other layered compounds in a rubber masterbatch, ranging from about 0.01% to about 18%.
While the concentration of graphene in rubber masterbatch (comprising graphene with one or more rubber) ranges from about 0.01% to about 18%, the final tyre formulations prepared using the said masterbatch has the final graphene concentration of not more than 3.5phr. Thus, the maximum concentration of graphene at 18% refers to the maximum graphene content in masterbatch which is added to the final tyre formulations to get the effective graphene content to less than 3.5phr. Thus, accordingly, the concentration of the graphene in the final composition also ranges between about 0.01% to about 3.5%.
The quantity of the graphene with respect to the final composition prepared by the process of the present disclosure ranges from about 0.01phr to about 3.5phr. Further, the graphene employed in the present disclosure is a monolayer graphene or a multilayered graphene comprising a maximum of about 15 layers.
The process of the present disclosure comprises steps including but not limited to mixing of the layered compound with a combination of solvents using a high-shear mixer, followed by adding the mixture to a combination of one or more rubbers or elastomers employed for preparing a tyre composition, and once again subjecting the mix to a high-shear mixture. Once mixed, a different type of solvent, referred to herein as a ‘third solvent’, is used to coagulate the rubber(s) or elastomer(s) from the mixture, to obtain a layered compound-rubber/elastomer master batch, which is then used in formulations for tyre tread.
In a preferred embodiment, when the layered compound is graphene, the final product obtained is a graphene-rubber/elastomer master batch.
In a non-limiting embodiment of the present disclosure, the mixing of the layered compound with a combination of solvents takes place in a high-shear mixer for a time duration ranging from about 20 minutes to about 60 minutes. Preferably, the mixing is for about 60 minutes. This mixture is designated as ‘mixture 1’ in the present disclosure and is subsequently mixed with elastomer employed for preparing the masterbatch, and ultimately a tyre composition. However, before this addition, the rubber or elastomer employed for preparing the masterbatch is also independently mixed with the combination of same solvents to obtain a slurry or latex. Accordingly, when PBR is used to prepare the rubber masterbatch of the present disclosure, prior to mixing with graphene containing mixture 1, a PBR slurry is prepared or obtained. Alternatively, when natural rubber is used to prepare the rubber masterbatch of the present disclosure, prior to mixing with graphene containing mixture 1, NR latex is prepared or obtained.
In an exemplary embodiment, the slurry (also called as cement) is obtained from the plant where it is an intermediate product for the manufacturing of poly butadiene rubber from butadiene as a feed stock. The said slurry/cement comprises about 20% of solid PBR and about 80% of combination of solvents (n-heptane and toluene in the ratio as per present disclosure). Alternatively, the said slurry of PBR is prepared by mixing 20% of elastomer (such as PBR) with 80% of combination of said solvents.
In an exemplary embodiment, the solvent(s) of the present disclosure and the graphene herein are taken together in a stainless steel (SS) container and then subjected to high-shear mixing.
Thus, in the present disclosure, mixture 1 refers to the mixture of the layered compound with a combination of solvents, whereas slurry refers to PBR in the same combination of solvents.
In a non-limiting embodiment, the solvents used to arrive at the mixture 1 and the slurry include but are not limited to non-polar organic solvents, such as heptane, n-Hexane, cyclopentane, chloroform, pentane, benzene, octane, decane, dimethyl ether, dichloromethane, carbon tetrachloride and toluene, or any combination thereof. In preferred embodiments, the mixture 1 and the slurry are subjected to combination of solvents including but not limited to a combination of two different non-polar organic solvents, such as heptane, n-Hexane, cyclopentane, chloroform, pentane, benzene, octane, decane, dimethyl ether, dichloromethane, carbon tetrachloride and toluene, or any combination thereof.
In an exemplary embodiment, the two different non-polar organic solvents, such as heptane and toluene are combined in a ratio ranging from about 10:90 to about 90:10 v/v. In an embodiment, the ratio ranges from about 55:45 to about 50:50 v/v. In a preferred embodiment, the ratio is of about 55:45 v/v.
In an alternative embodiment, the solvent employed is water, when the rubber employed for preparing the rubber masterbatch is natural rubber. Accordingly, to prepare mixtures 1 and 2 of the present disclosure, when natural rubber is employed, water is employed as the suitable solvent.
As mentioned, once the solvent(s) and the graphene (to prepare the mixture 1) or the solvent(s) and the elastomer (to prepare the slurry or latex) are contacted together, they are subjected to high shear mixing for a time period of about 20 minutes to about 60 minutes, wherein the speed of the mixer is kept in the range of about 2500 to about 4000 RPM.
As mentioned above, the mixture 1 of the present disclosure is prepared when solvent(s) herein and graphene are mixed. In an embodiment, when the mixture 1 is prepared through the PBR masterbatch, the ratio employed between the PBR slurry and graphene containing solvent is kept in between 1:1 to about 1:1.5. In other words the solvent employed for mixing of graphene would be equal to or up to about 1.5 times more that that of PBR slurry. For example, when 1kg of PBR is employed (constituting 20% of the slurry), the PBR slurry would comprise 1kg PBR in remaining 80% solvent, to prepare a total of about 5kg of PBR slurry. Accordingly, the solvent employed for mixing of graphene would be 1.3 times that of PBR slurry, i.e., about 6500 ml. Of course, the amount of graphene to be mixed with this solvent will depend on the final concentration (phr) of graphene that is desired in the composition.
Similarly, in an alternative embodiment, when the mixture 1 is prepared through the NR masterbatch, the ratio employed between the NR latex and solvents is kept at about 1:5. For example, when 100 gms of NR is employed (constituting 60% of the NR latex), the total amount of NR latex employed is about 167 ml. Accordingly, the water employed for preparing mixture 1 and thereafter mixing mixture 1 with the latex would be 5 times that of NR latex, i.e., a total of about 840 ml. Of course, the amount of graphene to be mixed with this water will depend on the final concentration (phr) of graphene that is desired in the composition. Additionally, stabilizing agent such as polyvinyl pyrrolidone is added in the same container at a concentration of about 10% of the weight of the RFC, to stabilize graphene in water dispersion.
Thus, the amount of the first solvent employed is equal to or up to a maximum of about 1.5 times the amount of the slurry or about 5 times the amount of latex that is employed in the step b) of the process.
Upon preparation of the mixture 1 and the slurry or the latex, the two are mixed to obtain ‘mixture 2’ in a high-shear mixer. In a non-limiting embodiment, the mixture 1 and the slurry or latex are mixed in a high-shear mixer for a time duration ranging from about 10 minutes to about 75 minutes, wherein the speed of the mixer is kept in the range of about 2500 to about 4000 RPM. Preferably, the mixing is for about 60 minutes.
Once mixed, the third solvent is used to coagulate the rubber(s) or elastomer(s) from the mixture 2, to obtain a coagulated elastomer, which is then used for manufacturing of tyres. In a non-limiting embodiment, when the rubber employed to prepare the masterbatch is PBR, the third solvent is a polar organic solvent such as isopropyl alcohol, methanol, ethanol, butanol and pentanol. As an alternative, steam stripping method can also be utilized in industrial scale for the said coagulation. In a non-limiting embodiment, the third solvent is added to the mixture 2 slowly until the elastomer is separated out.
The amount of third solvent employed to coagulate the elastomer is calculated with respect to the total amount of solvent(s) used to prepare the mixture 1 with graphene, and 80% of the total PBR slurry used. For example, when 6500ml of solvent was employed for preparing mixture 1 with graphene, and PBR slurry prepared was about 5000gms, the amount of IPA was calculated as - [6500ml + (80% of 5000gms)] ml i.e. 10500ml.
Alternatively, when the rubber employed to prepare the rubber masterbatch is natural rubber, the mixture 2 is transferred to a large SS tray, followed by slow addition of acids such as formic acid or acetic acid, with stirring and the pH is checked at each interval of acid addition. When pH reaches 4, acid addition is stopped. At this stage, the mixture 2 separates out from water. The elastomer mass produced is divided it into about 1 inch cube pieces and passed through corrugated rollers and washed simultaneously with DM water to remove excess acid. The mixture 2 is then kept at about 60°C for drying. The dried rubber-graphene elastomer is used for two roll mill process.
Accordingly, when the rubber is in form of a slurry in the step b), amount of the second solvent is a sum of amount of solvent employed to prepare mixture 1 and about 80% of amount of slurry; whereas when the rubber is in form of a latex in the step b), the second solvent is added till the pH of the mixture 2 reaches about 4.

The coagulated elastomer (prepared through the slurry or the latex route) is pressed to squeeze out the trapped solvents. Alternatively, or in addition to the squeezing, the excess solvent was removed by using a filter. Thereafter, the coagulated elastomer is passed through a two-roll mill to obtain layered compound-rubber/elastomer master batch free of solvents. In a non-limiting embodiment, the temperature of the roller used in two-roll milling for rendering the elastomer solvent/moisture free (while keeping the rubber intact from decomposition) ranges from about 40°C to about 130°C. Preferably, the temperature is set at about 115°C. As an example, when PBR-graphene is used, the roll temperature is kept at about 110° ± 5°C, whereas when NR-graphene is used, the temperature is kept at about 50° ± 5°C.
In another non-limiting embodiment, the overall master batch preparation process of the present disclosure, prior to the step of milling, is carried out at a temperature ranging from about 15°C to about 45°C. Preferably, the process is carried out at a temperature of about 20°C.
In an exemplary embodiment, the roll nip opening is set at about 2.5 mm, and the rubber is added into the mill nip and band, as a continuous sheet, onto the front roll. Further, 2-3 cuts from each side are made and the rubber is allowed to move through the nip gap a few times until a smooth rolling bank is formed on the nip. Solvent evaporation occurred during two roll milling process so the area is properly ventilated and scrubber is used for proper disposal of solvent vapours.
Further, for addition of other ingredients, first, the batch weight of the rubber-graphene elastomer is calculated according to the fill factor. The graphene containing elastomer(s) and other raw materials are weighed as per the recipe and charged into a mixing chamber that is set at about 100°C in TCU at about 60 rpm. For ease of mixing, the elastomer sample is cut into thin strips of about 1-2 inch width and about 5-6 inch length and charged in the mixing chamber after reaching the temperature. The ram is then raised and the chemicals are added (except sulphur and accelerator) into the chamber, followed by carbon black, post which the ram is lowered. The mixture is processed for a total of about 300 seconds. Maximum allowable temperature limit is 150°C. Next, processing oil is injected and mixed further for 60 seconds. The batch is allowed to cool for a minimum of 4 hrs in air before proceeding with second-stage mix.
In the second stage, the initial temperature is kept at about 70°C in TCU at about 45 rpm. The material obtained at the previous step is cut into thin strips of about 1-2inch width and about 5-6inch length and charged in the mixing chamber after reaching the temperature. The ram is raised and sulphur and accelerator are added into the mixing chamber and the ram is lowered. Mixing is performed for a total of 180 seconds. Maximum allowable temperature limit is 95°C. After mixing, the ram is raised and discharge door is opened. The batch is kept in a tray and dump temperature is recorded. The batch weight is measured and recorded. The batch is allowed to cool for minimum of about 4hrs before proceeding for testing of properties.
As the high surface area graphene is an extremely low density material, the conventional process requires several stages of melt mixing to incorporate a larger quantity of graphene in a elastomer matrix. On the other hand, the process of the present disclosure allows quick, efficient and large-scale incorporation of graphene or other such layered compounds at concentrations of up to 18% and even higher in a rubber masterbatch composition. As mentioned previously, this maximum concentration of graphene at 18% refers to the maximum graphene content in masterbatch which is added to the final tyre formulations to get the effective graphene content to less than 3.5phr. Thus, accordingly, the concentration of the graphene in the final composition ranges between about 0.01% to about 3.5%.
Further, as mentioned previously, since handling of graphene in powder form is difficult due to its low bulk density and fluffy nature, causing it to often fly off while mixing, thereby possessing health hazard, the present high shear solvent mixing route drastically reduces environmental and health hazards with minimum loss of material into the atmosphere. In addition, the process of the present disclosure also ensures homogenous mixing.
Further, while the conventional melt mixing process is carried out at temperatures as high as 110°C, as stated above, the process of the present disclosure is carried out at a temperature ranging from about 15°C to about 45°C. Accordingly, the process of the present disclosure offers energy savings and reduces thermal degradation of elastomers.
Since the most commonly used rubber is styrene-butadiene copolymer, the process of the present disclosure involves mixing of the layered compound through the solvent based method of the present disclosure with the copolymer for preparing the tyre composition. In a non-limiting embodiment, in tyre composition where the rubber employed is different from the said copolymer, the layered compound is mixed after a combination of such rubbers is prepared. For example, if the rubber employed are styrene-butadiene rubber (SBR) and polybutadiene rubber (PBR), the rubbers are first mixed together to form a combination, post which, the layered compound is mixed with the said combination, as per the process of the present disclosure. Once the layered compound and the rubber are mixed, other ingredients/components are added in the final formulation during the melt processing stage. As mentioned, in a preferred embodiment, the layered compound is graphene. In another example, first a master batch of graphene and PBR or natural rubber (via the slurry or the latex route as mentioned previously) is prepared via the solution method of the present disclosure. Thereafter, in the tyre tread formulation, the graphene-PBR or graphene-NR master batch is mixed with SBR and other elastomers along with curing additives in an internal mixer.
In a non-limiting embodiment, for about 1 kg of polybutadiene rubber (PBR), about 100 gms of high surface area graphene was used, along with about 4 to 6 litres of a combination of solvents at a ratio of 55:45 (v/v). The isopropyl alcohol used for coagulation ranges from about 9 to 10 litres.
As the tyre compositions employ different compounds as reinforcing filler, with carbon black and silica being the most common; in embodiments of the present disclosure, the process herein allows incorporation of the layered compound, such as graphene, molybdenum disulfide, boron nitride, clay etc., in a manner so as to completely or partially replace the pre-existing reinforcing fillers, or in addition to the traditional reinforcing filler. Thus, the process of the present disclosure allows for incorporation of the layered compound as a reinforcing filler in a previously known tyre composition or a new tyre composition. When the layered compound is graphene, the graphene so employed is of high surface area, typically ranging between 300 to 3000 m2/g, and preferably of about 2000 m2/g.
As mentioned previously, the process of the present disclosure allows for inclusion of the layered compound such as graphene as a reinforcing filler in a composition, which enhances or improves the magic triangle of tyre manufactured from such composition, which includes properties such as rolling resistance, abrasion resistance and wet grip of the tyre, along with other properties including but not limited to tensile modulus, fatigue failures, and heat build-up. The properties are enhanced or improved in tyre compositions where traditional reinforcing fillers, such as carbon black, are replaced completely or partially by a layered compound such as graphene, or where the layered compound is included in addition to said traditional reinforcing fillers.
Thus, the present disclosure also relates to a process for preparing a tyre composition having at least one improved property selected from a group comprising rolling resistance, abrasion loss, tensile modulus, heat build-up and fatigue failure, or any combination thereof, said process comprising steps of:
a. preparing a layered compound-rubber elastomer as per the process described above; and
b. incorporating at least one additional component selected from a group comprising processing oil, stearic acid, antioxidant, tackifier, sulfur, pre vulcanization inhibitor, peptiser, wax, zinc oxide and accelerator, or any combination of components thereof, to prepare the tyre composition having at least one improved property.
In embodiments of the present disclosure, the amount of processing oil ranges between about 1 to about 15 parts, stearic acid ranges between about 1 to about 5 parts, antioxidant ranges between about 0.25 to about 5 parts, tackifier ranges between about 0.5 to about 1.5 parts, sulfur ranges between about 1 to about 2 parts, pre vulcanization inhibitor ranges between about 0.05 to about 0.15 parts, peptiser ranges between about 0.1 to about 0.5 parts, wax ranges between about 0.5 to about 2.5 parts, zinc oxide ranges between about 1 to about 6 parts and accelerator ranges between about 1 to about 5 parts.
In embodiments of the present disclosure, the layered compound-rubber elastomer and at least one additional component are charged into a mixing chamber in a predetermined order, at a temperature ranging from about 70°C to about 150 °C.
Thus, in a non-limiting embodiment, the process for preparing the tyre composition in the present disclosure allows for reduction in the rolling resistance of a tyre (measured by Tand @ 60°C or 70°C), manufactured using such a composition, by about 3% to about 25%.
In another non-limiting embodiment, the process for preparing the tyre composition in the present disclosure allows for reduction in the abrasion loss (or increases the abrasion resistance) of a tyre, manufactured using such a composition, by about 5% to about 40%.
In another non-limiting embodiment, the process for preparing the tyre composition in the present disclosure allows reduction in the weight of tread of a tyre, manufactured using such a composition, by about 10% to about 30%. This reduction in weight of the tread translates into reduction in overall weight of the tyre and adds to better fuel efficiency. The compositions containing graphene prepared herein, have less amount of material. The less weight corresponds to the carbon black replaced by the graphene. Typically, the density of carbon black is 1.85g/cc compared to 0.02gm/cc of graphene. Thus, it is evident that replacing carbon black with low density graphene will have a positive effect on the weight reduction.
In another non-limiting embodiment, the process for preparing the tyre composition in the present disclosure allows increase in the tensile modulus (measured by modulation @ 200% or 300% elongation) of a tyre, manufactured using such a composition, by about 10% to about 40%.
In another non-limiting embodiment, the process for preparing the tyre composition in the present disclosure allows reduction in the fatigue failure of a tyre [measured by fatigue to failure test (FTFT)], manufactured using such a composition, by about 40%.
In another non-limiting embodiment, the process for preparing the tyre composition in the present invention allows reduction in the heat build-up of a tyre (measured by Tand @ 100°C), manufactured using such a composition, by about 2% to about 15%.
The low rolling resistance of the tyres and flexible nature of the graphene sheets help in achieving better NVH (Noise-Vibration-Harshness) levels of the vehicle owing to less friction generated between the tyre and the road surface. Graphene containing tyres having high abrasion resistance, can also be considered as less polluting alternatives to the conventional carbon black containing tyres. They release lesser carbon particulates to the environment generated due to the friction between tyre and road surface during the movement of the vehicle.
Accordingly, the layered compound-rubber elastomer prepared by the process of the present disclosure, when present in the tyres, reduces the rolling resistance of the tyre by about 3% to about 30%, reduces the abrasion loss of the tyre by about 5% to about 40%, increases the tensile modulus of the tyre by about 10% to about 40%, reduces the heat build-up of the tyre by about 2% to about 25%, and reduces the fatigue failure of the tyre by about 40%, when compared to a tyre that does not comprise the said layered compound-rubber elastomer prepared by the process herein.
The present disclosure also relates to a scalable process of preparing monolayer graphene. The process allows flexibility of using different types of precursor materials including but not limited to graphene nano-platelets to graphene precursor to make graphene. In an exemplary embodiment, the formation of graphene from intercalated graphite is carried out using high shear mixing via liquid phase exfoliation process. Such a process is described in US Patent No. 9790334 B2, which is completely incorporated herein as a reference.
In a non-limiting embodiment, the graphene is formed in situ from graphene precursors using high shear mixing.
As mentioned, the process of the present disclosure allows incorporation of a layered compound such as graphene, molybdenum disulphide, boron nitride and clay, or a combination thereof, in a composition comprising one or more types of rubbers. Accordingly, the present disclosure also relates to the composition obtained by the process of the present disclosure.
In non-limiting embodiments, the present disclosure provides a composition comprising at least one rubber including but not limited to styrene-butadiene rubber (SBR), polybutadiene rubber (PBR), butyl rubber, halo butyl rubber, ethylene propylene diene methylene rubber (EPDM), silicone rubber and natural rubber, along with a layered compound such as graphene at a concentration ranging from about 0.01% to about 18%.
As mentioned above, the present disclosure either provides a composition comprising only layered compound as reinforcing fillers as per the present disclosure or a composition comprising layered compound herein, in addition to other reinforcing fillers. In such a case, in non-limiting embodiments, the concentration of the layered compound ranges from about 2% to about 10%, and that of other reinforcing fillers ranges from about 25% to about 70%.
In the present disclosure, while the concentration of the layered compound such as graphene, molybdenum disulphide, boron nitride and clay, or a combination thereof, ranges from about 0.01% to about 18%, the at least one rubber forming part of the composition including but not limited to styrene-butadiene rubber (SBR), polybutadiene rubber (PBR), butyl rubber, halo butyl rubber, ethylene propylene diene methylene rubber (EPDM), silicone rubber and natural rubber, is at a concentration ranging from about 10% to about 80%.
Thus, in an exemplary embodiment, the present disclosure provides a composition comprising at least one rubber including but not limited to styrene-butadiene rubber (SBR), polybutadiene rubber (PBR), butyl rubber, halo butyl rubber, ethylene propylene diene methylene rubber (EPDM), silicone rubber and natural rubber, at a concentration ranging from about 10% to about 80%, along with graphene in a rubber masterbatch at a concentrating ranging from about 0.01% to about 18%, as a reinforcing filler.
Accordingly, the present disclosure provides for a tyre composition comprising the layered compound-rubber elastomer prepared by the process herein, wherein the layered compound in the final composition is at a concentration ranging from about 0.01% to about 3.5%. In embodiments herein, the layered compound is graphene and wherein quantity of the graphene with respect to the composition ranges from about 0.01phr to about 3.5phr.
As mentioned above, the composition of the present disclosure is a typical tyre composition that comprises all conventional ingredients known to be a part of or constitute a tyre, with an inclusion of graphene as a reinforcing filler. Accordingly, apart from the rubber and the reinforcing filler, the tyre composition of the present disclosure comprises components including but not limited to plasticizers, chemicals, metal reinforcements, textile reinforcements, additives, zinc oxide, sulphur, processing oil, accelerator, stearic acid and anti-oxidant. In an exemplary embodiment, typical concentration of these components are as follows: processing oil between 1 to 8 parts, stearic acid between 1 to 5 parts, antioxidant between 0.25 to 5 parts, zinc oxide between 1 to 6 parts and accelerator between 1 to 5 parts. In another exemplary embodiment, the tyre composition comprises about 41% elastomer, about 28% filler, about 14 to 15% steel, and about 16 to 17% fabric and other additives.
In an embodiment, the tyre composition herein comprises additional components selected from processing oil ranging between about 1 to about 15 parts, stearic acid ranging between about 1 to about 5 parts, antioxidant ranging between about 0.25 to about 5 parts, tackifier ranging between about 0.5 to about 1.5 parts, sulfur ranging between about 1 to about 2 parts, pre vulcanization inhibitor ranging between about 0.05 to about 0.15 parts, peptiser ranging between about 0.1 to about 0.5 parts, wax ranging between about 0.5 to about 2.5 parts, zinc oxide ranging between about 1 to about 6 parts and accelerator ranging between about 1 to about 5 parts, or any combination of components thereof.
In a related embodiment, the anti-oxidant is selected from a group comprising 2,2,4-trimethyl-1,2-dihydroquinoline (TMQ) and N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) or any combination thereof; wherein the stearic acid in presence of the zinc oxide forms zinc stearate for acting as accelerator activator; wherein the hydrocarbon resin acts as tackifier; wherein the pre vulcanization inhibitor is N-(cyclohexylthio)-phthalimide (CTP); wherein the processing oil is residual aromatic extract (RAE); wherein the plasticizer is CCF resin; and wherein the accelerator is selected from a group comprising N-tert-butyl-2-benzothiazyl sulfenamide (TBBS) and Tetrabenzylthiuram disulfide (TBzTD) or any combination thereof.
Accordingly, in an exemplary embodiment, the tyre composition of the present disclosure comprises components selected from a group comprising 2,2,4-trimethyl-1,2-dihydroquinoline (TMQ) as antioxidant, stearic acid in presence of zinc oxide which forms zinc stearate for acting as accelerator activator, hydrocarbon resin to act as tackifier, N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) as anti-oxidant and anti-ozonant for elastomers, N-(cyclohexylthio)-phthalimide (CTP) as pre vulcanization inhibitor (to prevent premature curing of elastomer), peptiser to reduce viscosity of natural rubber and help in processing, residual aromatic extract (RAE) as oil, CCF resin as plasticizer, wax, sulphur, and N-tert-butyl-2-benzothiazyl sulfenamide (TBBS) & Tetrabenzylthiuram disulfide (TBzTD) as accelerator, or any combination thereof.
The tyre composition herein, further comprises components selected from a group of chemicals, metal reinforcements, textile reinforcements and additives, or any combination thereof.
Accordingly, in an exemplary embodiment, the composition of the present disclosure comprises about 10phr of technically specific rubber (TSR20), about 20.6phr of Trinseo solution styrene butadiene rubber - SLR 6430 (SSBR SLR 6430), about 52.5 phr of Trinseo solution styrene butadiene rubber - SLR 4601 (SSBR SLR 4601), about 25phr of PBR masterbatch (having about 2.5phr graphene), about 5phr of RAE, about 42.50phr of carbon black (N339), about 2.50phr of stearic acid, about 0.75phr of TMQ, about 1phr of HC resin, about 3phr of ZnO, about 3phr of 6PPD, about 1.50phr of wax, about 1.10phr of sulphur, about 1.60phr of TBBS and about 0.35phr of TBzTD.
In another exemplary embodiment, the composition of the present disclosure comprises about 77.50phr of styrene butadiene rubber (SBR), about 25phr of polybutadiene rubber (PBR) masterbatch (having about 2.5phr graphene), about 12phr of RAE oil, about 42.50phr of N339 carbon black, about 2.5phr of stearic Acid, about 0.75phr of TMQ, about 1phr of resin, about 3phr of ZnO, about 2phr of 6PPD, about 1.50phr of wax, about 1.10phr of sulphur, about 1.60phr of TBBS and about 0.35phr of TBzTD.
In another exemplary embodiment, the composition of the present disclosure comprises about 77.50phr of natural rubber, about 34.50phr of N 220 carbon black, about 5phr of ZnO, about 4phr of RAE/TDAE, about 2.50phr of stearic acid, about 25phr of PBR masterbatch(comprising about 2.5phr graphene), about 2.50phr of Ozone Prt. Wax, about 2.50phr of DTPD/6PPD, about 1.05phr of TBBS, about 1.55phr of sulphur and about 0.10phr of CTP.
In another exemplary embodiment, the composition of the present disclosure comprises about 101.9phr of natural rubber masterbatch (having about 2phr graphene), about 0.2phr of peptiser, about 34phr of N134 (carbon black), about 5phr of ZnO, about 3phr of stearic acid, about 2phr of 6PPD, about 0.7phr of TMQ, about 1.4phr of sulfur and about 1.4phr of TBBS.
In another exemplary embodiment, the composition of the present disclosure comprises about 103.05phr of natural rubber masterbatch (having about 3.05phr of graphene), about 0.2phr of peptiser, about 36phr of N134+A5:C27, about 5phr of ZnO, about 3phr of stearic acid, about 2phr of 6PPD, about 0.7phr of TMQ, about 1.4phr of sulfur and about 1.4phr of TBBS.
In another exemplary embodiment, the composition of the present disclosure comprises about 87.18phr of natural rubber masterbatch and about 15.44phr of PBR masterbatch (cumulatively having about 2.62phr of graphene), about 38phr of N134, about 6phr of oil, about 5phr of ZnO, about 3phr of stearic acid, about 2phr of 6PPD, about 0.7phr of TMQ, about 1.4phr of sulfur and about 1.4phr of TBBS.
In another exemplary embodiment, the composition of the present disclosure comprises about 70phr of SBR, about 7.50phr PBR, about 25phr of PBR masterbatch (having about 2.5phr of graphene), about 3phr of ZnO, about 1phr of stearic acid, about 1phr of TBBS and about 1.75phr of Sol S.
The inclusion of the layered compound in tyre compositions, as provided by the present disclosure enhances or improves the magic triangle of tyre technology, which includes properties such as rolling resistance, abrasion resistance and wet grip of the tyre (measured by Tand, 0°C), along with other properties including but not limited to tensile modulus, fatigue failures, and heat build-up.
The present disclosure accordingly also relates to use of the composition herein comprising a layered compound such as graphene, molybdenum disulphide, boron nitride and clay, or a combination thereof, and one or more types of rubbers, for manufacturing of tyres. The said composition is prepared by the process of the present disclosure.
The advantage of the process of the present disclosure is highlighted by the fact that mixing of graphene directly with elastomer to obtain uniform dispersion via conventional melt mixing process is difficult to achieve due to large surface area of graphene (~2600m2/gm). In contrast, due to relatively small surface area (~7 - ~150 m2/gm), conventional fillers, such as carbon black can be easily mixed in large quantities with elastomers using widely accepted melt mixing process. To overcome this difficulty, incorporating graphene through a solvent mediated masterbatch method is the focal point the present disclosure. By this method, large quantities of graphene can be incorporated in elastomer without fly-off losses. Moreover, the high shear mixing method employed to prepare the graphene-elastomer masterbatch ensures homogeneous and molecular level mixing of graphene and elastomer which is reflected in the improvement in the magic triangle properties.
While the instant disclosure is susceptible to various modifications and alternative forms, specific aspects thereof have been shown by way of examples and drawings and are described in detail below. However, it should be understood that it is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and the scope of the invention as defined by the appended claims.
EXAMPLES
The present disclosure is further described with reference to the following examples, which are only illustrative in nature and should not be construed to limit the scope of the present disclosure in any manner.
Further, within the present disclosure, properties as measured are abbreviated as follows:
ML- Minimum torque
MH- Maximum torque
Ts1, Ts2- Scorch time
Tc10, Tc25, Tc40, Tc50, Tc90- Cure time for 10%, 25%, 40%, 50% and 90% curing
Mod@100% elongation- Modulus at 100% elongation.
FTFT- Fatigue to failure test.
DMA- Dynamic mechanical analysis.
Tan d- Tangent delta.
Example 1
Process for preparation of a tyre composition comprising graphene and combination of PBR and SBR
About 100 gms of high surface area graphene (at 10phr) was mixed with about 4 to 6 litres of a combination of solvents containing n-heptane and toluene at a ratio of 55:45 (v/v) and mixed for 30 minutes using a high shear mixer, to obtain mixture 1.
Separately, about 4.5 kgs of PBR cement, is obtained from the RIL elastomer manufacturing plant. The said cement comprises about 20% of solid elastomer (PBR) and about 80% of solvent mixture of heptane and toluene (55:45).
Subsequently, the mixture 1 and the PBR slurry were mixed for about 1 hour for proper dispersion of graphene and to obtain mixture 2.
Mixture 2 was then subjected to coagulation by about 9 to 10 litres of isopropyl alcohol. The isopropyl alcohol added slowly, was used to coagulate the PBR containing graphene from the mixture of solvents.
The coagulated elastomer was then first pressed using two-roll mill at ambient temperature to squeeze out most of the trapped solvents and then passed again through a two-roll mill with roller temperature set at 115°C to obtain graphene-PBR master batch free of solvents.
For addition of other ingredients, first, the batch weight of the rubber-graphene elastomer was calculated according to the fill factor. The graphene containing elastomer(s) and other raw materials were weighed as per the recipe and charged into a mixing chamber that was set at 100°C in TCU for 60 rpm. For ease of mixing, the elastomer sample was cut into thin strips of about 1-2 inch width and 5-6 inch length and charged in the mixing chamber after reaching the temperature.
The ram was then raised and the chemicals were added (except sulphur and accelerator) into the chamber, followed by carbon black, post which the ram was lowered. The mixture was processed for a total of about 300 seconds. Maximum allowable temperature limit is 150°C. Next, processing oil was injected and mixed further for 60 seconds. The batch was allowed to cool for a minimum of 4 hrs in air before proceeding with second-stage mix.
In the second stage, the initial temperature was kept at 70°C in TCU for 45 rpm. The material obtained at the previous step was cut into thin strips of about 1-2inch width and 5-6inch length and charged in the mixing chamber after reaching the temperature. The ram was raised and sulphur and accelerator were added into the mixing chamber and the ram was lowered. Mixing was performed for a total of 180 seconds. Maximum allowable temperature limit is 95°C. After mixing, the ram was raised and discharge door was opened. The batch was kept in a tray and dump temperature was recorded. The batch weight was measured and recorded. The batch was allowed to cool for minimum of 4hrs before proceeding for testing.
The composition as provided in table 1 below was prepared using the process as disclosed above and was used in various tread formulations and tested for properties as provided in table 2 below. This composition comprises of 2.5 parts of graphene. A 10% (11.11phr) PBR-graphene master batch was prepared. Accordingly, in the formulation 25 phr masterbatch contains 2.5 phr graphene and 22.5 phr PBR. Thus, 2.5phr graphene corresponds to 1.47% graphene in the final composition. As can be seen from table 2, the control sample had 55phr of carbon black whereas in the experimental formulation the carbon black amount is reduced to 42.5phr. In other words, 5 parts of carbon black is replaced by one part of graphene.
Ingredients (phr) Control Experiment containing 2.5phr graphene % Values for the experimental compound
TSR 20 10.00 10.00 5.8685446
PBR 15.00 0.00 0
Trinseo SSBR SLR 6430 20.6 20.6 12.0892019
Trinseo SSBR SLR 4601 60 52.5 30.8098592
PBRM 0.00 25.00 14.6713615
RAE 5.00 5.00 2.9342723
N339 55.00 42.50 24.9413146
ST Acid 2.50 2.50 1.46713615
TMQ 0.75 0.75 0.44014085
HC Resin 1.00 1.00 0.58685446
ZnO 3.00 3.00 1.76056338
6PPD 3.00 3.00 1.76056338
WAX 1.50 1.50 0.88028169
Total Master 177.35 167.35 98.2100939

Master 177.35 167.35 98.2100939
Sulphur 1.10 1.10 0.64553991
TBBS 1.60 1.60 0.93896714
TBzTD 0.35 0.35 0.20539906
Total Final 180.40 170.40
Table 1
Data generated as per ASTM standards showed improvement in properties, and thus longer life when compared with the conventional composition comprising same amount of carbon black.
Properties Formulation with only carbon black Formulation with graphene and carbon black

Rheo Study (MDR 2000) @160°C / 30 min


ML(dN-M) 1.55 2.19
MH(dN-M) 13.98 16.28
Ts1 (Min) 3.37 2.44
Ts2 (Min) 3.72 2.79
TC10 (Min) 3.48 2.62
TC25 (Min) 3.93 3.04
TC40 (Min) 4.21 3.32
TC50 (Min) 4.42 3.54
TC90 (Min) 6.85 6.23
Final Tq.(dN-M) 13.75 15.79
Percentage Reversion 1.85 3.48
Cure Rate Index (CRI)(min¯¹) 3.97 4.10
Delta Tq.(dN-M) 12.43 14.09

Physicals - Unaged (Cured @160°C / Tc90+2 Min)

Mod @100% Elong.(MPa) 2.4 3.9
Mod @200% Elong.(MPa) 6.1 8.4
Mod @300% Elong.(MPa) 11.5 13.3
Tensile Strength (MPa) 22.8 21
% Elong @ Brk. 503 469
Hardness (Shore A) 59 63
Specific gravity - -

Physicals -Aged (@ 100 C/ 72 hrs) (Cured @160°C / Tc90+2 Min)

Mod @100% Elong.(MPa) 3.6 5.6
Mod @200% Elong.(MPa) 9.4 11.3
Mod @300% Elong.(MPa) 15.8 17
Tensile Strength (MPa) 19.6 18.5
% Elong @ Brk. 365 328
Hardness (Shore A) 67 70

FTFT (moulded@160°C, Tc90+2 min)

Failure(KC) 74.3 98.1

Abrasion Loss

Abrasion loss(in grams) 0.1162 0.1083
Abrasion loss(in mm cube) 104.97 99.45
Abrasion Resistance Index (%) 142.19 150.08
Specific gravity(g/cc) 1.107 1.089

DMA Temp Sweep @ 10 Hz, 2% static & 1% Dynamic Strain
Tan d @ 30°C 0.236 0.210
Tan d @ 70°C 0.171 0.158
Tan d @ 100°C 0.138 0.130
Table 2
Data generated as per ASTM D5279 standard (table 1 below) by tangent delta plots at 70°C obtained by dynamic mechanical analysis show a minimum of 7% less rolling resistance when compared with the conventional composition comprising carbon black.
Data generated (table 1 above) as per ASTM D5963-04(2015) standard show a minimum of 5% reduction in abrasion loss when compared with the conventional composition comprising carbon black.
Data generated as per ASTM D4482-11(2017) standard show a minimum of 30% reduction in fatigue failure when compared with the conventional composition comprising same amount of carbon black. Further, the composition also exhibited about 20% increase in tensile modulus [measured @200% Elong.(MPa)] as well as about 5.8% decrease in heat build-up.
Similarly, other layered compounds as mentioned in the present disclosure are used to prepare compositions for commercial tyre applications, using the process of the present disclosure.
Example 2
Process for preparation of a tyre composition comprising graphene and PBR [1kg PBR containing 3phr graphene]
About 6500 ml of dry solvent (mixture of toluene and N-heptane in a ratio of about 50:45) was taken in stainless steel (SS) container and about 30 gms of RFC (graphene) was added to it. The solution was mixed in a high-shear mixer for about 1 hour at anywhere between about 2500 to about 4000 RPM, to obtain mixture 1. The process condition was checked frequently after every 30 minutes.
The ratio employed between the PBR slurry and graphene containing solvent was kept at about 1.3.
Accordingly, about 5000 gms of fresh PBR cement obtained as an industrially available intermediate of solid PBR was used as the slurry as such. The said cement/slurry comprises about 20% of solid PBR (i.e., 1kg PBR) and about 80% of combination of solvents (n-heptane and toluene in the same ratio as above). Alternatively, the said slurry of PBR can be prepared by mixing 20% of elastomer (such as PBR) with 80% of combination of said solvents.
Once prepared, the slurry is added into mixture 1 and mixed in high-shear mixer for about 1 hour to obtain mixture 2. The speed of the mixer was kept anywhere between about 2500RPM to about 4000 RPM.
For the next step of coagulation, the amount of isopropyl alcohol (IPA) was calculated with respect to the total amount of n-heptane and toluene used to prepare the mixture 1 with graphene, and 80% of the total PBR slurry used. Thus, in the present case, since 6500ml of solvent was employed for preparing mixture 1 with graphene, and PBR slurry prepared was about 5000gms, the amount of IPA was calculated as - [6500ml + (80% of 5000gms)] ml i.e. 10500ml.
Accordingly, after an hour of mixing to obtain mixture 2, the mixer was stopped and about 10500 ml of isopropyl alcohol (IPA) was slowly added to mixture 2 until black PBR elastomer separated out from the clear solution. Excess solvent was removed by using filter and then by squeezing from the black PBR elastomer. The black PBR elastomer was used for two roll mill process.
The roll nip opening was set at about 2.5 mm and temperature at about 110° ± 5°C. The rubber was added into the mill nip and band, as a continuous sheet, onto the front roll. Using a hand knife, 2-3 cuts from each side were made and the rubber was allowed to move through the nip gap quite a few times until a smooth rolling bank was formed on the nip. Solvent evaporation occurred during two roll milling process so the area was properly ventilated and scrubber was used for proper disposal of solvent vapours.
Inclusion of additional ingredients was as per the protocol disclosed in Example 1.
Example 3
Process for preparation of a tyre composition comprising graphene and PBR [1kg PBR containing 11.1phr (10%) graphene]
About 5900 ml of dry solvent (mixture of toluene and n-heptane in a ratio of about 50:45) was taken in SS container and about 100 gms of RFC (graphene) was added to it. The solution was mixed in a high-shear mixer for about 1 hour at anywhere between about 2500 to about 4000 RPM, to obtain mixture 1. The process condition was checked frequently after every 30 minutes.
The ratio employed between the PBR slurry and graphene containing solvent was kept at about 1.3.
Accordingly, about 4500 gms of fresh PBR cement was made into a slurry (which is also an industrially available intermediate material, which can also be used directly). The slurry so prepared, comprises about 20% of solid PBR (i.e., 900gms PBR) and about 80% of combination of solvents (n-heptane and toluene in the same ratio as above).
Once prepared, the slurry is added into mixture 1 and mixed in high-shear mixer for about 1 hour to obtain mixture 2. The speed of the mixer was kept anywhere between about 2500 RPM to about 4000 RPM.
For the next step, similarly to example 2, calculations were done to determine the amount of IPA to be used for coagulation, which was about 9500ml.
Accordingly, after an hour of mixing to obtain mixture 2, the mixer was stopped and about 9500 ml of isopropyl alcohol (IPA) was slowly added to mixture 2 until black PBR elastomer separated out from the clear solution. Excess solvent was removed by using filter and then by squeezing from the black PBR elastomer. The black PBR elastomer was used for two roll mill process.
The roll nip opening was set at about 2.5 mm and temperature at about 110° ± 5°C. The rubber was added into the mill nip and band, as a continuous sheet, onto the front roll. Using a hand knife, 2-3 cuts from each side were made and the rubber was allowed to move through the nip gap quite a few times until a smooth rolling bank was formed on the nip. Solvent evaporation occurred during two roll milling process so the area was properly ventilated and scrubber was used for proper disposal of solvent vapours.
Inclusion of additional ingredients was as per the protocol disclosed in Example 1.
Example 4
Process for preparation of a tyre composition comprising graphene and natural rubber [100 gms natural rubber containing 3phr graphene]
About 420 ml of water was taken in SS container and about 3 gms of RFC (graphene) was added to it. Polyvinyl pyrrolidone (used as stabilizing agent in graphene water dispersion) was added in the same container at a concentration of about 10% of the weight of the RFC. The solution was mixed in a high-shear mixer for about 20 minutes at anywhere between 2500 RPM to about 4000 RPM, to obtain mixture 1.
About 167 ml of fresh natural rubber latex (DRC 60%) was added into mixture 1. The natural rubber latex comprises about 60% natural rubber dissolved in water. Accordingly, the effective amount of natural rubber in 167ml of latex was about 100gms. To the mixture about 420 ml of DM water was added (to dilute the latex for ensuring homogenous coagulation process) and mixed in high-shear mixer for about 5 minutes to obtain mixture 2. The speed of the mixer was kept at anywhere between 2500 RPM to about 4000 RPM.
After 5 minutes, the prepared mixture 2 was transferred to a large SS tray. About 5% formic acid was added slowly with stirring and the pH was checked at each interval of acid addition. When pH reaches 4, acid addition is stopped. At this stage, the mixture 2 separated out from water. The elastomer mass produced was divided it into about 1 inch cube pieces and passed through corrugated rollers and washed simultaneously with DM water to remove excess acid. The mixture 2 was kept at about 60°C for drying. The dried natural rubber-graphene elastomer was used for 2 roll mill process.
The roll nip opening was set at about 2.5 mm and temperature at about 50° ± 5°C. The rubber was added into the mill nip and band, as a continuous sheet, onto the front roll. Using a hand knife, 2-3 cuts from each side were made and the rubber was allowed to move through the nip gap quite a few times until a smooth rolling bank was formed on the nip. Solvent evaporation occurred during two roll milling process so the area was properly ventilated and scrubber was used for proper disposal of solvent vapours.
Inclusion of additional ingredients was as per the protocol disclosed in Example 1.
Example 5
Examples of tyre compositions prepared by the process of the present disclosure, and improvement in properties thereof
The process of the present disclosure was employed to manufacture tyre compositions as provided in tables below. Inferences with respect to improvement in properties are also provided:
Compositions were prepared as per the protocol of the present disclosure of with 2.5 parts of graphene. The rubbers used were SBR and PBR for one composition (table 3); and natural rubber and PBR for the other (table 4). Respective tyre was manufactured using the said composition and tested for rolling resistance and heat build-up. Data generated as per ASTM D623-07(2014) standards are provided below. A significant reduction in heat build-up shows longer life when compared with the conventional composition comprising same amount of carbon black.
Ingredients (phr)/ Properties Control (No graphene) Experiment containing 2.5phr (parts per hundred) graphene
(1.4% graphene) % Values for the experimental compound
Styrene butadiene rubber 77.50 77.50 45.37470726
Polybutadiene rubber (PBR) 22.5 0 0
PBR rubber containing graphene 0.00 25.00 14.63700234
RAE (Residual aromatic extract) oil 12.00 12.00 7.025761124
N339 carbon black 55.00 42.50 24.88290398
Stearic Acid 2.50 2.50 1.463700234
TMQ (anti oxidant) 0.75 0.75 0.43911007
Resin 1.00 1.00 0.585480094
ZnO 3.00 3.00 1.756440281
6PPD (anti oxidant and anti ozonant) 2.00 2.00 1.170960187
CCF Resin (plasticizer) 0.00 0.00 0
WAX 1.50 1.50 0.878220141
Sulphur 1.10 1.10 0.644028103
TBBS (accelerator) 1.60 1.60 0.93676815
TBzTD (accelerator) 0.35 0.35 0.204918033
Total Final 180.80 170.80

DMA Temp Sweep @ 10 Hz, 2% static & 1% Dynamic Strain
Tan d @ 0°C 0.310 0.279
Tan d @ 25°C 0.292 0.257
Tan d @ 60°C 0.240 0.207
Tan d @ 100°C 0.181 0.157
Table 3
Inference: As is seen, the composition comprising graphene (table 3) shows an improvement in each of rolling resistance as well as heat build-up by about 13%.
Ingredients(phr)/ Properties Control (No graphene) Experiment containing 2.5phr graphene
(1.6% graphene) % Values for the experimental compound
RMA 4 (Natural Rubber) 100.00 77.50 49.61588
N 220 Black 25.00 24.50 15.68502
Zinc Oxide 5.00 5.00 3.201024
RAE/TDAE 4.00 4.00 2.560819
St. Acid 2.50 2.50 1.600512
Master-1:Total 136.50 113.50 72.66325
0
Master-1 136.50 113.50 72.66325
PBRM (PBR master Batch) 0.00 25.00 16.00512
N 220 Black 22.00 10.00 6.402049
Ozone Prt. Wax 2.50 2.50 1.600512
DTPD/6PPD 2.50 2.50 1.600512
Total Master-2 163.50 153.50 98.27145
0
Master-2 163.50 153.50 98.27145
TBBS 1.00 1.05 0.672215
Standard Suphur 1.50 1.55 0.992318
CTP 0.10 0.10 0.06402
Final Total 166.10 156.20

Physicals - Unaged (Cured @ 141oC / Tc90+2 mins)
Mod @100% Elong.(MPa) 2.4 3.7
Mod @200% Elong.(MPa) 5.9 8.3
Mod @300% Elong.(MPa) 11.2 13.6
Tensile Strength (MPa) 32.1 30.9
% Elong @ Brk. 725 656
Hardness (Shore A) 60 63
Specific gravity

Abrasion Loss
Abrasion loss(in grams) 0.137 0.0827
Abrasion loss(in mm cube) 124.21 77.65
Abrasion Resistance Index (%) 120.17 192.21
Specific gravity(g/cc) 1.103 1.065

DMA Temp Sweep @ 10 Hz, 2% static & 1% Dynamic Strain
Tan d @ 30°C 0.224 0.177
Tan d @ 70°C 0.199 0.14921466
Tan d @ 100°C 0.177 0.131221719
Table 4
Inference: As is seen, the composition comprising graphene (table 4) shows an improvement in each of rolling resistance as well as heat build-up by about 25%. Further, the abrasion loss is reduced by about 37%, and the tensile modulus is improved by about 40%.
Further, a composition comprising natural rubber was prepared as per the instant disclosure with 14 phr of carbon black replaced by 2 phr of graphene. Respective tyre was manufactured using the said composition and tested for various properties. Data generated as per ASTM D623-07(2014) standard is provided below:

Ingredients(phr)/ Properties Control Experiment containing 2phr graphene
(1.3% graphene) % Values for the experimental compound
NR 100 -- --
NR-Graphene -- 101.9 68.11497326
Peptiser 0.2 0.2 0.13368984
N134 48 34 22.72727273
ZnO 5 5 3.342245989
St. Acid 3 3 2.005347594
6PPD 2 2 1.336898396
TMQ 0.7 0.7 0.467914439
Sulfur 1.4 1.4 0.935828877
TBBS 1.4 1.4 0.935828877
Final 161.7 149.6

Stress-Strain properties - Unaged (Cured @ 141oC)
Mod @100% Elong.(MPa) 3 3.8
Mod @200% Elong.(MPa) 8.8 10.3
Mod @300% Elong.(MPa) 17.2 18.2
Tensile Strength (MPa) 29.7 32.3
% Elong @ Brk. 478 487
Hardness (Shore A) 67 65

Abrasion Loss
Specific gravity(g/cc) 1.108 1.076
Abrasion loss (in grams) 0.1134 0.1065
Abrasion loss (in mm cube) 102 99

DMA Temp Sweep Shear Mode @ 10 Hz, 1% Dynamic Str+B48:S48ain (-60 to 80)
tand, 0°C 0.329 0.334
tand, 30°C 0.231 0.182
tand, 70°C 0.179 0.125
Table 5
Inference: As is seen, the composition comprising graphene (table 5) shows an improvement in rolling resistance by about 30%. Further, the abrasion loss is reduced by about 6%, and the tensile modulus is improved by about 17%. The composition also shows a significant improvement in wet grip characteristics.
Another composition comprising natural rubber was prepared as per the instant disclosure with 12 phr of carbon black replaced by 3.05 phr of graphene. Respective tyre was manufactured using the said composition and tested for various properties. Data generated as per ASTM D623-07(2014) standard is provided below:
Ingredients(phr)/ Properties Control Experiment containing 3.05phr graphene
(1.9% graphene) % Values for the experimental compound
NR 100 -- --
NR-Graphene -- 103.05 67.46317512
Peptiser 0.2 0.2 0.130932897
N134+A5:C27 48 36 23.56792144
ZnO 5 5 3.273322422
St. Acid 3 3 1.963993453
6PPD 2 2 1.309328969
TMQ 0.7 0.7 0.458265139
Sulfur 1.4 1.4 0.916530278
TBBS 1.4 1.4 0.916530278
Final 161.7 152.75

Stress-Strain properties - Unaged (Cured @ 141oC)
Mod @100% Elong.(MPa) 3 4.8
Mod @200% Elong.(MPa) 8.8 12
Mod @300% Elong.(MPa) 17.2 19.7
Tensile Strength (MPa) 29.7 28.4
% Elong @ Brk. 478 420
Hardness (Shore A) 67 69

DMA Temp Sweep Shear Mode @ 10 Hz, 1% Dynamic Str+B48:S48ain (-60 to 80)
tand, 0°C 0.329 0.303
tand, 30°C 0.231 0.186
tand, 70°C 0.179 0.139
Table 6
Inference: As is seen, the composition comprising graphene (table 6) shows an improvement in rolling resistance by about 22%. Further, the tensile modulus is improved by about 36%.
Further, another composition comprising natural rubber and PBR was prepared as per the present disclosure with 12 phr of carbon black replaced by 2.62 phr graphene. Respective tyre was manufactured using the said composition and tested for various properties. Data generated as per ASTM D623-07(2014) standard is provided below:
Ingredients(phr)/ Properties Control Experiment containing 2.62phr graphene
(1.6% graphene) % Values for the experimental compound
NR 85 - -
NR-Graphene - 87.18 54.44667
PBR 15 - -
PBR-Graphene - 15.44 9.642768
N134 50 38 23.7322
Oil 6 6 3.74719
ZnO 5 5 3.122658
St. Acid 3 3 1.873595
6PPD 2 2 1.249063
TMQ 0.7 0.7 0.437172
Sulfur 1.4 1.4 0.874344
TBBS 1.4 1.4 0.874344
Final 169.5 160.12

Stress-Strain properties - Unaged (Cured @ 141oC)
Mod @100% Elong.(MPa) 2.8 4.3
Mod @200% Elong.(MPa) 7.6 10.7
Mod @300% Elong.(MPa) 14.1 17.5
Tensile Strength (MPa) 30.4 29.2
% Elong @ Brk. 506 486
Hardness (Shore A) 65 67

Abrasion Loss
Specific gravity(g/cc) 1.111 1.078
Abrasion loss (in grams) 0.1049 0.0860
Abrasion loss (in mm cube) 94 80

DMA Temp Sweep Shear Mode @ 10 Hz, 1% Dynamic Str+B48:S48ain (-60 to 80)
tand, 0°C 0.315 0.300
tand, 30°C 0.224 0.194
tand, 70°C 0.176 0.147
Table 7
Inference: As is seen, the composition comprising graphene (table 7) shows an improvement in rolling resistance by about 16%. Further, the abrasion loss is reduced by about 15%, and the tensile modulus is improved by about 40%.
Yet another composition according to the present disclosure is prepared as per the specifics provided in table 8 below, wherein, 20phr of carbon black is completely replaced by 2.5phr of graphene. Respective tyre was manufactured using the said composition and tested for rolling resistance, tensile modulus and heat build-up.
Ingredients(phr)/ Properties Control (No graphene) Experiment containing 2.5phr graphene
Raw SBR 1502 (HMD) 70.00 70.00
Raw PBR CISAMER 01 30.00 7.50
PBR MB 0.00 25.00
Carbon N330 20.00 0.00
ZnO 3.00 3.00
ST ACID 1.00 1.00
TBBS 1.00 1.00
Sol S 1.75 1.75
Total Phr 126.75 109.25

Rheo Study (MDR 2000) @160°C / 30'
ML(dN-M) 1.45 1.56
MH(dN-M) 14.34 15.1
Ts1 (Min) 4.61 4.29
Ts2 (Min) 5.8 5.93
TC10 (Min) 5.12 5.1
TC25 (Min) 6.4 6.76
TC40 (Min) 7.13 7.52
TC50 (Min) 7.64 8
TC90 (Min) 12.49 12.36
Final Tq.(dN-M) 14.25 13.54
Delta Tq.(dN-M) 12.89 14.94
Cure Rate 1.93 2.32

Physicals - Unaged (Cured @ 160°C / t90+2 min)
Mod @100% Elong.(MPa) 1.8 2.6
Mod @200% Elong.(MPa) 3.7 5.2
Mod @300% Elong.(MPa) 6.7 8
Tensile Strength (MPa) 11.4 8.8
% Elong @ Brk. 415 331
Hardness (Shore A) 53 55

DMA Temp Sweep (10Hz / 1% dynamic Strain/2 %static strain)
Tan d @ 30°C 0.105 0.090
Tan d @ 70°C 0.084 0.073
Tan d @ 100°C 0.067 0.058
Table 8
Inference: As is seen, the composition comprising graphene (table 9) shows an improvement in each of rolling resistance as well as heat build-up by about 13%. Further, the tensile modulus is improved by about 40%.
Additional embodiments and features of the present disclosure will be apparent to one of ordinary skill in art based on the description provided herein. The embodiments herein provide various features and advantageous details thereof in the description. Descriptions of well-known/conventional methods and techniques are omitted so as to not unnecessarily obscure the embodiments herein.
The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments in this disclosure have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
Any discussion of documents, acts, materials, devices, articles and 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.
While considerable emphasis has been placed herein on the particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other modifications in the nature of the disclosure or the preferred embodiments 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. ,CLAIMS:We Claim:
1. A process for preparing a layered compound-rubber elastomer for tyre composition, comprising a layered compound and at least one rubber, said process comprising steps of:
a. mixing of the layered compound with at least one of the first solvents using a high-shear mixer to obtain mixture 1;
b. obtaining a slurry or latex of at least one rubber followed by adding the slurry or the latex to the mixture 1 and subjecting to a high-shear mixer, to obtain mixture 2; and
c. subjecting the mixture 2 to a second solvent for facilitating coagulation to obtain the layered compound-rubber elastomer.
2. The process as claimed in claim 1, wherein the layered compound is selected from a group comprising graphene, molybdenum disulphide, boron nitride and clay, or a combination thereof.
3. The process as claimed in claim 2, wherein the graphene is a monolayer graphene or a multilayered graphene comprising a maximum of about 15 layers.
4. The process as claimed in claim 1, wherein the rubber is selected from a group comprising styrene-butadiene rubber (SBR), polybutadiene rubber (PBR), butyl rubber, halo butyl rubber, ethylene propylene diene methylene rubber (EPDM), silicone rubber and natural rubber (NR) or any combination thereof, at a concentration ranging from about 10% to about 80%.
5. The process as claimed in claim 1, wherein the first solvent is selected from a group comprising heptane, n-Hexane, cyclopentane, chloroform, pentane, benzene, octane, decane, dimethyl ether, dichloromethane, carbon tetrachloride, toluene and water or any combination thereof.
6. The process as claimed in claim 5, wherein the solvent is a combination of heptane and toluene at a ratio ranging from about 55:45 to about 50:50.
7. The process as claimed in claim 1, wherein amount of the first solvent employed is equal to or up to a maximum of about 1.5 times the amount of the slurry or about 5 times the amount of latex that is employed in the step b) of the process.
8. The process as claimed in claim 1, wherein the slurry is a PBR slurry and comprises about 20% solid in about 80% of at least one of the first solvents; whereas the latex is a NR latex and comprises about 60% solid in about 40% of at least one of the first solvents.
9. The process as claimed in claim 1, wherein the layered compound is present alongside the rubber in form of a rubber masterbatch, and wherein concentration of the graphene with respect to the masterbatch ranges from about 0.01% to about 18%.
10. The process as claimed in claim 1, wherein the high-shear mixing is carried out for a time period ranging from about 10 minutes to about 75 minutes, and wherein the speed of the mixer ranges from about 2500 to about 4000 RPM.
11. The process as claimed in claim 1, wherein the second solvent is selected from a group comprising isopropyl alcohol, methanol, ethanol, butanol, pentanol, formic acid and acetic acid, or any combination thereof.
12. The process as claimed in claim 1, wherein when the rubber is in form of a slurry in the step b), amount of the second solvent is a sum of amount of solvent employed to prepare mixture 1 and about 80% of amount of slurry.
13. The process as claimed in claim 1, wherein when the rubber is in form of a latex in the step b), the second solvent is added till the pH of the mixture 2 reaches about 4.
14. The process as claimed in claim 1, wherein the coagulated elastomer obtained at the end of the step c) is further squeezed or subjected to filtration to remove any trapped solvent.
15. The process as claimed in claim 1, wherein the coagulated elastomer is passed through a two-roll mill to obtain layered compound-rubber elastomer free of solvent.
16. The process as claimed in claim 15, wherein temperature of roller used in the two-roll milling ranges from about 40°C to about 130°C.
17. A process for preparing a tyre composition having at least one improved property selected from a group comprising rolling resistance, abrasion loss, tensile modulus, heat build-up and fatigue failure, or any combination thereof, said process comprising steps of:
a. preparing a layered compound-rubber elastomer as per the process of claim 1; and
b. incorporating at least one additional component selected from a group comprising processing oil, stearic acid, antioxidant, tackifier, sulfur, pre vulcanization inhibitor, peptiser, wax, zinc oxide and accelerator, or any combination of components thereof, to prepare the tyre composition having at least one improved property.
18. The process as claimed in claim 17, wherein amount of processing oil ranges between about 1 to about 15 parts, stearic acid ranges between about 1 to about 5 parts, antioxidant ranges between about 0.25 to about 5 parts, tackifier ranges between about 0.5 to about 1.5 parts, sulfur ranges between about 1 to about 2 parts, pre vulcanization inhibitor ranges between about 0.05 to about 0.15 parts, peptiser ranges between about 0.1 to about 0.5 parts, wax ranges between about 0.5 to about 2.5 parts, zinc oxide ranges between about 1 to about 6 parts and accelerator ranges between about 1 to about 5 parts.
19. The process as claimed in claim 17, wherein the layered compound-rubber elastomer and at least one additional component are charged into a mixing chamber in a predetermined order, at a temperature ranging from about 70°C to about 150 °C.
20. The process as claimed in claim 17, wherein the layered compound-rubber elastomer in the tyre reduces the rolling resistance of the tyre by about 3% to about 30%, reduces the abrasion loss of the tyre by about 5% to about 40%, increases the tensile modulus of the tyre by about 10% to about 40%, reduces the heat build-up of the tyre by about 2% to about 25%, and reduces the fatigue failure of the tyre by about 40%, when compared to a tyre that does not comprise the said layered compound-rubber elastomer prepared by the process of claim 1.
21. A tyre composition comprising the layered compound-rubber elastomer prepared by the process of claim 1, wherein the layered compound is at a concentration ranging from about 0.01% to about 3.5%.
22. The tyre composition as claimed in claim 21, wherein the layered compound is graphene and wherein quantity of the graphene with respect to the composition ranges from about 0.01phr to about 3.5phr.

Dated this 25th day of February 2019

Signature:
Name: DURGESH MUKHARYA
IN/PA-1541
To: Of K&S Partners, Bangalore
The Controller of Patents Agent for the Applicant
The Patent Office, at Mumbai