Description:FIELD OF THE INVENTION
The present invention relates to the field of polymer technology. The present invention in particular relates to a tyre sidewall rubber composition and its method of preparation to provide tyre with fatigue to failure resistance.

BACKGROUND OF THE INVENTION
Certain current "road" tyres are designed to run at high speed for longer distances, because of the improvement in road networks and the expansion of motorway networks throughout the world. However, since fuel savings and the need to protect the environment have become a priority, it is important for the tyres to have a low energy consumption. One of the sources of energy dissipation is the heating of the tyre, especially due to the flexural stresses to which a tyre is subjected and more particularly to which the sidewalls of the tyre are subjected. These prolonged static or dynamic stresses of the sidewalls, in the presence of ozone make weather checking or cracks that are pronounced appear, the propagation of which under the effect of the persistence of the stresses may give rise to significant damage of the sidewall.

Tyre sidewall is continuously subjected to distortion under the normal road operating conditions, and the tyre sidewall is subjected to extensive continuous flexing which leads to tyre sidewall crack under such flexing conditions. Efforts has been made in order to overcome the above drawback, while maintaining the properties of the sidewall in terms of resistance to cracks, the present invention aims to provide a rubber composition and its method for tyre sidewall to provide fatigue to failure resistance using PAN (Polyacrylonitrile) based carbon fibre as a reinforcing nano filler.

Reference made to the following:
IN1991/DELNP/2011 relates to a tyre sidewall, having a rubber composition based on at least one diene elastomer, a reinforcing filler comprising carbon black and a vulcanization system, characterized in that the carbon black has a CTAB specific surface area greater than or equal to 90 m2/g and that the proportion of this carbon black is between 30 and 40 phr. The referred patent discusses about the use of reinforcing fillers carbon black having CTAB value greater than 90 m2/gm in NR: BR (50:50) blend based rubber composition for tyre sidewall whereas the present invention discusses about the use of carbon fibre in diene rubber based rubber composition in tyre sidewall. Both the reinforcing fillers are entirely different from each other.

Publication No. CN208515300 The utility model discloses a tire containing matrix resin and carbon fiber, comprising a tire crown, the outer surface of the tire crown is fixedly provided with main grooves along the circumferential direction, and the outer surface of the tire crown is symmetrically fixed and opened along the axial direction There are grooves, shoulder grooves are fixedly opened on both sides of the outer surface of the tire crown along the circumferential direction, sidewalls are fixedly installed on both sides of the outer surface of the tire crown, and the outer surface of the bottom end of the sidewall is fixed. The rim is movably installed, the outer surface of the bottom end of the sidewall is fixedly provided with a protection device, the outer surface of the upper end of the sidewall is fixedly provided with air lines, and the outer surface of the bottom end of the tire crown is fixedly fitted with a belt layer, the outer surface of the bottom end of the belt layer is fixedly attached with a crown belt layer. The tire containing matrix resin and carbon fiber according to the utility model can enhance the service life, bearing performance and flexural resistance of automobile tires, and bring better application prospects.
This patent discusses about the tyre comprising matrix resin and carbon fibre enhances the strength of a carcass whereas the present invention discusses about the use of PAN (Polyacrylonitrile) based carbon fibre in diene-based tyre sidewall rubber composition to provide fatigue to failure resistance.

Publication No. CN208438995 the utility model proposes a wear-resistant tire, which comprises a tire body, the tire body includes a tread layer, a cord layer and an airtight layer from the outside to the inside, and the tread layer includes a tire crown, a tire shoulder and a sidewall. The thickness of the tire crown is 3-5 cm, the thickness of the sidewall is 1-3 cm, the surface of the tire crown is distributed with a deep groove and a horizontal shallow groove, the depth of the deep groove is 2-4 cm, and the width of the horizontal shallow groove is 2-4 cm. The depth is 0.5 – 1 c, the interval between each horizontal shallow groove is 5-10 cm, the cord layer includes a steel belt layer and a braided layer, the steel belt layer is located outside the braided layer, and the braided layer is woven from carbon fiber silk. The inner wall of the airtight layer is provided with a sound-absorbing layer, the sound-absorbing layer and the tire crown are located on the same vertical line, and the sound-absorbing layer is made of polyurethane foam sound-absorbing material, which has good wear resistance and explosion resistance, and is not easy to wear and tear, safer driving, better sound absorption, reduce tire noise, and make driving more comfortable. This patent discusses about a tyre containing carcass ply comprising carbon fibre system knitted with silk as a weaving layer and is just above the steel belt layer whereas the present invention discusses about the use of carbon fibre in diene-based tyre sidewall rubber composition to provide fatigue to failure resistance.

Publication No. CN206264699 the utility model discloses a carbon fibre bicycle wheel rim, which comprises a central shaft and a rim arranged on the outside of the central shaft. The rim is provided with an escape space, and spokes connected to the central shaft run through the escape space. A spoke nipple is connected to one end of the spoke extending into the avoidance space. The rim structure of the utility model solves the problems of reduced strength, tire pads, and water ingress caused by drilling holes at the bottom of the U-shape, and a space for avoidance is set up on the sidewall of the carbon fiber bicycle rim, so that the spoke caps can enter directly without passing through Holes drilled at the bottom of the U shape make it easier to install the spokes. The referred patent discusses about the use of carbon fibre in a bicycle rim whereas the present invention discusses about the use of carbon fibre as a filler in tire sidewall rubber composition.

Publication No. CN205523442 the utility model relates to the technical field of tires, in particular to a tire using a carbon fiber material S-shaped tread. The tire has high strength and good elastic performance. Wear resistance, and the tire has good anti-skid performance, improving the stability and safety of the vehicle. The sidewall rubber and the steel belt layer are arranged inside the carcass, the carbon fiber layer is arranged inside the steel belt layer, the polyester ply is arranged inside the carcass, and the airtight layer is arranged inside the polyester ply, the inner tube is arranged inside the carcass, the bead reinforcement layer and the bead are arranges inside the carcass, the elastic reinforcing ring is arranged inside the carcass, and the nylon reinforcing layer is arranged outside the elastic reinforcing ring. The tread is connected to the outer wall of the carcass, and the S-shaped anti-skid pattern is arranged on the outer wall of the tread. The base tread compound is provided between the tread and the carcass. Multiple side skid rings are evenly connected to the carcass and the left and right outer walls of the tread. The referred patent discussed about the S shaped tyre tread containing carbon fibre as layer whereas the present invention discusses about the use of carbon fibre as a filler in tire sidewall rubber composition.

Publication No. CN206264710 the utility model discloses a wear-resistance carbon fibre mountain bicycle wheel hub, which comprises an annular hollow structure formed by an upper wall, a lower wall and two side walls which are ring-connected. Second, the inner side of the side wall is integrally provided with a carbon fiber reinforced layer at the wear-resistant layer; the hollow structure is integrally formed with support walls on the two side walls diagonally. The wear-resistant carbon fiber mountain bicycle wheel hub of the utility model adopts an extra layer of wear-resistant layer on the braking surface of the wheel hub, and at the same time, a carbon fiber reinforced layer is added on the inner side of the braking surface, and the supporting wall structure is adopted, which is not only improves the wear-resistant performance of the wheel hub, while improving its overall strength and structural stability. The referred patent discusses about the use of a wear-resistant carbon fiber as a layer in bike wheel rim to improve its overall strength and structural stability whereas the present invention discusses about the use of carbon fibre nano material as a filler in the tire sidewall rubber composition. Hence the present invention is different.

IN9309/DELNP/2013 relates to a composite cord (8; 80-82; 90-92) comprising a rubber core (83; 93) and a rubber sheath (84-86; 94-96) enclosing the core at least partially, the compositions of the core and of the sheath being different, said cord being characterized in that the rubber core is based on at least one diene elastomer and more than 30 weight percent of elastomer of a filler A, the particles of which are nanoparticles having an average size by weight of less than 500 nm, and in that the rubber sheath is based on at least one diene elastomer having 0 to less than 30 pce of filler A", the particles of which are nanoparticles having an average size by weight of less than 500 nm, and more than 70 pce of a filler B, the particles of which are particles having a median size by weight greater than 1 µm. The referred patent discusses about the composite cord comprising NR based rubbery core and rubber sheath rubber composition containing silica, carbon black and chalk as a filler whereas the present invention discusses about use of carbon fibre in tire sidewall rubber composition to provide fatigue to failure resistance.

IN201741024431 relates to the curable rubber composition for improved crack growth resistance in tyre sidewalls A cross-linkable rubber composition comprises a first diene-based elastomer, wherein the first diene-based elastomer further comprises structural units according to formula la) and/or lb): wherein POLY is a polymer chain of the diene-based elastomer and Z is a triazole residue according to one or more of formulas Ha) to lid): with R and R" independently of each other are H, SCH3, OH, SH, COOCH3 or CH3.

This patent discusses about the use of curable rubber composition containing triazole, maleic anhydride along with carbon black and silica filler in tyre sidewall rubber composition to provide crack growth resistance whereas the present invention discusses about use of PAN based carbon fibre in tire sidewall rubber composition to provide fatigue to failure resistance.

Publication No. KR100761583 relates to run flat tire having a side wall reinforcing structure is provided to form a thickness of the side wall as that of a radial tire by connecting a pulling member from an inner section of a reinforcing member and extending to the side wall, thereby improving driving comfort of a vehicle while enhancing the durability of the tire. A run flat tire having a side wall reinforcing structure comprises a thick rubber layered tread(17) directly contacting the ground, a shoulder(11) having the thickest layer of the tire, a carcass(14) providing a frame of the tire and comprised of plural cords, belts(15) arrayed in plural layers between the tread and the carcass, an inner liner(16) installed inside the carcass for preventing air leakage, a side wall(12) protecting the carcass, and a bead(13) wrapping the cords and mounts the tire to a rim(20).

This patent discusses about use of pulling member made up of any one of the materials selected from the group consisting of nylon, polyester, rayon, aramid, carbon fibre, and steel cord into the tire sidewall to improve driving comfort of a vehicle and to enhance the durability of the tire whereas the present invention discusses about use of carbon fibre nanomaterial as a reinforcing filler in tire sidewall rubber composition to provide fatigue to failure resistance.

Publication No. JP2008044550 provides a pneumatic radial tire having superior durability compared with the conventional one by effectively suppressing progress of breakage from the end part of the belt in a belt layer formed by a treating material using organic fibre cord and the treating material using a steel cord. The pneumatic radial tire is reinforced by carcass layer 1 which has a bead part 11, a side wall part 12, and a crown part 13, and toroidally extends between bead pars, and a belt layer 2 made of two or more treating materials disposed at the outer periphery of the crown part. At least one piece 2A of the treating materials composing the belt layer is made of rubber-coated fabric where organic fibre cord or carbon fibre cord is arranged in parallel, the treating material 2B other than that is made of rubber-coated fabric of the steel cord, and the twisting direction of the belt cord arranged in parallel in the treating material is different by every strand of cord. This patent discusses about laminating rubberized cloth using carbon fibre cord or steel cord in the belt layer to provide superior durability in tire whereas the present invention discusses about use of carbon fibre as a reinforcing filler in tire sidewall rubber composition to provide fatigue to failure resistance.

Publication No. JP2004203350 provides a tire for effectively reducing a tire temperature, superior in exothermal durability by improving the heat radiating effect of sidewall rubber having the large contact area with outside air. This tire has a pair of bead parts respectively positioned on the inner periphery of a pair of sidewall parts continuing both sides of a tread part and a carcass locked by folding back both end parts in the bead parts and is characterized in that the side wall rubber is composed of a rubber composition blended with a reinforcing filler including at least carbon fibre. The referred patent discusses about the tyre sidewall rubber composition containing natural rubber and diene based synthetic rubber along with reinforcing filler carbon fibre grade vapor grown carbon fiber (VGCF) to provide superior exothermal durability by improving the heat radiating effect of sidewall rubber having the large contact area with outside air whereas the present invention discusses about use of polyacrylonitrile (PAN) based carbon fibre as a reinforcing filler in tire sidewall rubber composition to provide fatigue to failure resistance. Both the carbon fibre structural arrangements of carbon atoms are entirely different from each other.

Publication No. JP2018016201 relates to improve ride comfort performance and weight saving property while maintaining run-flat durability. A run flat tire includes a cross section substantially crescent-shaped side-reinforcement rubber layer 9 disposed on an inner side of a carcass 6 and in a side wall part 3; an inner reinforcement layer 10 provided along a tire inner surface Si; and an outer reinforcement layer 11 provided along a tire outer surface. So, the inner reinforcement layer 10 is disposed in a range of 90% or more of a first region G1, while the outer reinforcement layer 11 is disposed in a range of 90% or more of a second region G2. The inner and outer reinforcement layers 10, 11 are constituted of a carbon fibre-reinforced plastic. The referred patent discusses about the use of reinforced filler carbon fibre reinforced plastics in tire inner and outer surface to attain ride comfort and weight reduction of tire whereas the present invention discusses about use of PAN based carbon fibre as a reinforcing filler in tire sidewall rubber composition to provide fatigue to failure resistance.

Publication No. CN107353462 The invention discloses an automobile tire, which comprises an outer tire, an inner tube and a cushion belt; wherein, the outer tire includes a carcass, a buffer layer, a tread, a sidewall and a bead, and the tread is made of the following raw materials : Rubber, rosin resin, micron-sized white jade, micron-sized steel fiber, micron-sized elemental tungsten, micron-sized potassium feldspar, kaolin, carbon black, titanium dioxide, styrene-acrylonitrile-acrylic rubber copolymer, stearic acid , sulfur, silane coupling agent, ethylenediamine, paraffin. The invention modifies the properties of the tire tread, namely, adding micron-level white jade, micron-level steel fiber, micron-level elemental tungsten, and micron-level potassium feldspar with specific particle size based on the original material of the tire tread, styrene-acrylonitrile-acrylic rubber copolymer, etc. are modified to improve the wear resistance of the tire tread, to improve the overall wear resistance of automobile tires. This patent discusses about the use of modified tread made up of micron-scale white jade steel, steel fibre, elemental tungsten, and potassium feldspar to improve the wear resistance of the tread of the outer tire whereas the present invention discusses about use of PAN based carbon fibre reinforced filler in tire sidewall rubber composition to provide fatigue to failure resistance.

Publication No. JP2016216609 provides a pneumatic tire having a side wall excellent in steering stability, rolling resistance characteristics and durability in a well-balanced manner and excellent in flexure crack growth resistance by using a modified cellulose fibre-containing rubber composition achieving excellent rigidity and fracture characteristics as well as a low energy loss by improving dispersibility of cellulose fibres in rubber. The pneumatic tire has a side wall manufactured by using a modified cellulose fibre-containing rubber composition which comprises modified cellulose fibres (A) prepared by adding a cyclic polybasic acid anhydride (a) having a hydrophobic group and 15 or more carbon atoms to cellulose fibres to esterify, a polymer (B) for dispersion having a softening point of 135°C or lower, and a rubber component (C).

This patent discusses about the use of modified cellulose fibre in the tire sidewall to provide excellent steering stability, rolling resistance characteristics and excellent in flexure crack growth resistance whereas the present invention discusses about use of carbon fibre as a reinforcing filler in tire sidewall rubber composition.

Publication No. CN105754151 the invention relates to the field of tire manufacturing in particular to a rubber composition for tire sidewalls containing chopped carbon fibers. The composition is formed by mixing the following components by weight (parts): 30-60 parts of natural rubber, 40-70 parts of synthetic rubber, 35-65 parts of reinforcing agent, 2-10 parts of chopped carbon fiber, and 0.5 part of vulcanizing agent – 3 parts, 0.5-5 parts of vulcanization accelerator, 3-10 parts of vulcanization activator, 2-8 parts of anti-aging agent, and other additives. The kneading method of the rubber composition for tire sidewalls containing chopped carbon fibres of the present invention comprises two stages of kneading steps.

This patent discusses about the use of rubber composition containing natural rubber, synthetic rubber and chopped carbon fibers in the tire sidewall to improve the stress at definite elongation of sidewall whereas the present invention discusses about use of PAN (polyacrylonitrile) based carbon fibre as a reinforcing filler in tire sidewall rubber composition to provide fatigue to failure resistance.

Publication No. CN105175804 the invention discloses a rubber composition for tire sidewalls containing a resin composition with high corrosion resistance and aging resistance and a preparation method thereof. The rubber composition is prepared from the following components in parts by weight: 100 parts of a rubber matrix, 10-20 parts of polyacetal resin, 5-10 parts of furan epoxy resin, 3-5 parts of carbon fiber, 1-3 parts of silane coupling agent, 2-5 parts of environmentally friendly aromatic oil, 1-3 parts of accelerator, white 20-30 parts of carbon black and 2-5 parts of sulfur. The resin mixture of the present invention includes polyacetal resin, furan epoxy resin and carbon fiber, and the three are added to the rubber matrix to improve the corrosion resistance and aging resistance of the rubber composition body, and at the same time improve the rubber composition itself. Mechanical strength and hardness, thereby increasing tire life. The referred patent discusses about the use of rubber composition containing natural rubber, styrene butadiene rubber and polybutadiene rubber along with 3 to 5 parts of carbon fiber and polyacetal/epoxy resin for tire sidewall to provide corrosion resistance aging whereas the present invention discusses about the use of NR:BR blend based tyre sidewall rubber composition along with 5 to 15 phr of PAN (polyacrylonitrile) based carbon fibre as a reinforcing filler in tire sidewall rubber composition to provide fatigue to failure resistance.

Publication No. CN204322935 The utility model relates to an engineering retreaded tire containing chopped carbon fiber reinforcement. In the process of tire tumbling of domestic construction machinery, problems such as disintegration of blocks, easy to be punctured and fast wear and other problems often occur. The utility model consists of a tire, and the crown area of the tire is sequentially composed of a tread layer cylindrical wall (1), a middle cushion rubber layer cylindrical wall (2) and a composite belt layer cylindrical wall (3) from outside to inside; the side of the tire is the side tire ring piece (5) compounded with the ports on both sides of the belt cylindrical wall (3), the inner wall of the belt cylindrical wall (3) and the side tire ring piece (5) The inner wall is compounded with a continuous carcass layer (4); chopped carbon fibers (6) are distributed in the cylindrical wall (1) of the tread layer and the cylindrical wall (3) of the belt layer, and the carcass layer (4) is close to the tire of the tire. The chopped carbon fibers (6) with a volume content of 6-8% are distributed in the 1/11 region of the crown, and the chopped carbon fibers (6) with a volume content of 6-8% are distributed in the bead region of the carcass layer (4). The utility model is applied to engineering retreading tires. This patent discusses about the use of chopped carbon fibre reinforcements for retreaded tire tread whereas the present invention discusses about use of PAN based carbon fibre as a reinforcing filler in tire sidewall rubber composition.

Publication No. CN204020405 The utility model provides a carbon fiber straight edge rim, which has a main body, two sides of the main body protrude upwards with side edges, and the two side edges and the main body form a tread groove, which is characterized in that the inner wall of each side edge and the top end of the outer wall connected with a smooth arc transition, the inner wall is straight, and the bottom surface of the tire groove has a groove. Since the side of the tire groove has no hook and undercut structure and double grooves, the utility model avoids various disadvantages brought by the hook and undercut structure, so that the carbon fiber rim of the present utility model is easier to manufacture than the prior art., more material saving, more convenient when loading and unloading tires, wider use. This patent discusses about use of carbon fibre at tire straight-edge rim to provide easier mounting and demounting of tire whereas present invention discusses about use of PAN based carbon fibre as a reinforcing filler in tire sidewall rubber composition to provide fatigue to failure resistance.

Publication No. CN202294054 The utility model mainly provides a combination structure of a carbon fiber wheel rim, which comprises: a carbon fiber wheel rim, which has a bridge plate and two side frames, the two side frames are oppositely provided with a hook portion, and the bridge plate and the two side frames are provided A groove is formed; a tire is provided with a bead part on both sides to be combined with the hook part; a reinforcing piece is in the shape of a sheet; A first and second combination piece of the reinforcing element can be fixed between the carbon fiber rim and the tire lip by joining together. The assembly and disassembly are simple and fast, which effectively saves man-hours and costs. The overall structure can achieve convenience, practicability, and cost-effectiveness. This patent discusses about the use of carbon fibre reinforcing structure at the rim of tire to provide stiffness whereas the present invention discusses about use of carbon fibre as a reinforcing filler in tire sidewall rubber composition to provide fatigue to failure resistance.

Publication No. CN201951161 The utility model provides a carbon fiber bicycle wheel rim assembly structure, comprising a carbon fiber wheel rim body, a plurality of spokes and a hub, the carbon fiber wheel rim body is provided with a tire position slot and a cavity, and a plurality of spaced holes and a cavity are arranged on the outer side of the bottom of the cavity. A spoke seat that is integrally formed with the wall and matched with the number of spokes, one end of the spoke is attached to the spoke seat and is fixedly connected with screws, and the other end of the spoke is fixed on the hub. Since there is no need to process an angle hole on the bottom wall of the tire position slot, the integrity of the wall is maintained, manpower and material resources are saved, it is easy to fold and assemble, and the tensile strength and service life of the rim body are increased. Since the components of the hub are made of carbon fiber material, the weight of the bicycle is reduced; the inner end of the carbon fiber spoke is equipped with a metal bracket, which increases the strength and tensile force of the spoke; the body of the spoke nut passes through the carbon fiber hub base to lock the inner end of the spoke. The head is set in the concave surface, which is convenient for the assembly and disassembly of the spoke nut and the spoke, which can better adjust the tension of the spoke and the roundness of the rim. This patent discusses about the use of carbon fibre in the rim of bicycle tire whereas the present invention discusses about use of PAN based carbon fibre as a reinforcing filler in tire sidewall rubber composition to provide fatigue to failure resistance.

Publication No. CN201646243 The utility model provides an improved bicycle carbon fiber rim structure. The carbon fiber layer is integrally formed with two independent inner and outer cavities. The open body, the upper part of the wheel rim and the two side walls constituting the outer cavity are parallel to each other, and the inner wall of the outer cavity is provided with a shell reinforcement which matches the shape thereof. Since the inner wall of the outer cavity of the carbon fiber rim of the present invention is provided with a metal shell reinforcement that matches its shape, the metal shell reinforcement increases the rigidity of the outer cavity, and when the brake pad clamps the rim When there are two side walls, the two side walls will not be deformed by the clamping force, and the friction force will not be weakened, so that the bicycle can improve the braking reliability; The sidewall body is clamped by the brake pads, which is not easy to be damaged by cracks, which increases the service life of the rim; and because the metal reinforcement is a shell that matches the inner cavity of the outer cavity, it still has the function of installing an inner tube. This patent discusses to develop a carbon fibre rim to improve the service life and braking reliability of tire whereas the present invention discusses about use of PAN based carbon fibre as a reinforcing filler in tire sidewall rubber composition to provide fatigue to failure resistance.

Publication No. JP2010235084 provides a side wall part reinforcement type run flat tire having more improved emergency traveling life than ever before. The run flat tire having a pair of right and left bead parts 1, a pair of side wall parts 2 continuing respectively from the bead parts 1 to the outside in a tire radial direction, and a tread part 3 continuing to both side wall parts 2 includes: a carcass 4 comprising one or more carcass plies extending to a space between the pair of bead parts 1 in a toroidal shape and reinforcing each of these parts; a side reinforcement rubber layer 5 with a crescent-shaped cross section arranged inside the carcass 4 in the side wall part 2. A short fibre made of carbon fibres exists in the rubber constituting the side wall part 2, and a fibre cord forming the carcass 4 is a polyketone fibre cord. This patent discusses about use of polyketone fibre in carcass and pitch-based carbon fibre reinforcement in tire sidewall to improve the emergency running life more than before whereas the present invention discusses about use of polyacrylanitrile (PAN) based carbon fibre as a reinforcing filler in tire sidewall rubber composition to provide fatigue to failure resistance.

Publication No. JP2010155576 provides a run-flat tire 2 capable of traveling a long distance under a flat-tire condition. This tire 2 comprises a tread 4, a wing 6, a side wall 8, a clinch part 10, a bead 12, a carcass 14, a supporting layer 16, a belt 18, a band 20, an inner liner 22, and a chafer 24. The supporting layer 16 is molded by crosslinking a rubber composition. The rubber composition includes a base rubber and a coal pitch base carbon fibre dispersed in the base rubber. An amount of the coal pitch base carbon fibre is 1 mass portion or more and 60 mass portion or less relative to 100 mass portion of the base rubber. Thermal conductivity of the supporting layer 16 is 0.40 W/m×K or more. Dimples 62 are formed on the side wall 8 and the clinch part 10. When air flows into the dimples, a turbulent flow occurs. By this turbulent flow, heats of the tire 2 is released to an atmosphere. The referred patent discusses about the support layer inside tire sidewall comprised of diene-based rubber and a coal pitch-based carbon fibre of 1 to 60 mass portion to suppress the bending of the tire in the puncture state whereas the present invention discusses about use of polyacrylanitrile (PAN) based carbon fibre along with diene-based rubber in tire sidewall rubber composition to provide fatigue to failure resistance.

Publication No. KR20100062907 provides rubber composition for side wall reinforcement layer or side wall is provided to ensure high thermal conduction rate, rigidity, and durability of run flat tire. A rubber composition for side wall reinforcement layer or side wall contains 100.0 weight parts of diene-based rubber and 1-50 weight parts of coal tar pitch-based carbon fibres. The coal tar pitch-based carbon fibre has an average of fibre diameter of 1-80 micron and average length of 0.1-30 mm. The rubber composition has 500 or more rupture energy (TB x EB/2). This patent discusses about the use of rubber composition containing diene-based rubber and coal tar pitch-based carbon fibres in tire sidewall to ensure high thermal conduction rate, rigidity, and durability of tire whereas the present invention discusses about use of polyacrylanitrile (PAN) based carbon fibre as a reinforcing filler in tire sidewall rubber composition to provide fatigue to failure resistance.

Publication No. US4255296 relates to a composition comprising a polybutadiene rubber containing a polymer obtained by block or graft polymerization of cis-1,4-polybutadiene with syndiotactic (syn)-1,2-polybutadiene, alone or blended with the other diene rubber, said syn-1,2-polybutadiene being crystallized and in a short fibre-like shape, and a breaking resistance characteristic and reinforcement characteristic being considerably improved by specifying the diameter and length of said short fibre, which is suitable for various parts of tire or industrial materials, and further relates to a composition of said polybutadiene rubber to which a carbon black is added for preferably used as a chafer or tread of tire, and still further relates to said composition to which a carbon black and an antioxidant are added for preferably used as a rubber blend composition for side wall. This patent discusses about use of rubber composition containing polybutadiene rubber along with the reinforcing filler carbon black for tread and sidewall of tire whereas the present invention discusses about the use of carbon fibre nanomaterial as a reinforcing filler in tire sidewall rubber composition. Both the reinforcing fillers are entirely different from each other.

Publication No. US5526859 relates to the cap tread that has a tan delta peak temperature of not less than -30 DEG C. Base tread comprises not less than 30 parts of a carbon black having an iodine adsorption number of 30 to 90 mg/g and not less than 10 parts of a short fibre oriented in the axial direction. Side wall comprises not more than 30 parts of the carbon black and not less than 10 parts by weight of the short fibre oriented in the peripheral direction. Bead apex comprises not less than 65 parts by weight of a carbon black which has an iodine adsorption number of 60 to 100 mg/g and not less than 20 parts by weight of the short fibre oriented in the axial direction or a direction which crosses the axial direction. This radial tire is light and has a low energy loss and can provide an excellent steering stability. This patent discusses about the use of reinforcing carbon black having an iodine adsorption number ranging from 30 to 90 mg/g in solution-polymerized SBR rubber composition for tire sidewall whereas the present invention discusses about the use of carbon fibre nanomaterial for as a reinforcing filler in tire sidewall rubber composition. Both the reinforcing fillers are entirely different from each other.

Publication No. JP2002059713 provides a lightened pneumatic tire devised to prevent lowering of cutting resistance even at the time of decreasing blending quantity of carbon black and to improve both of low fuel consumption and side cutting resistance within a range not to spoil riding comfortability. The pneumatic tire 1 furnished with a rim guard 2 made thicker toward the outside in the axial direction of the tire on a side wall part of the tire at a position corresponding to a flange end part of a rim on which at least the tire is installed is constituted as a rubber composition constituting the rim guard is composed by blending at least one kind of rubber 100 pts.wt. Selected from a group made of natural rubber and diene synthetic rubber and not less than 1 pts.wt. and not more than 10 pts.wt. of monofilament made of organic fibre. This patent discusses about the rubber composition containing natural rubber and diene based synthetic rubber along with organic fibres and carbon black to provide improved fuel economy and side cut resistance without impairing riding comfort whereas the present invention discusses about the use of carbon fibre nanomaterial as reinforcing filler in tire sidewall rubber composition to provide fatigue to failure resistance.

Publication No. JPH07186609 provides a pneumatic tire wherein the weight of a tire is reduced and rolling resistance can be decreased while maintaining steering stability and riding comfortableness. A pneumatic tire is provided with a carcass 6 locked by turning up both ends at a bead core of a bead part 4 from a tread part 2 through a side wall part 3, a belt layer 7 to be arranged outside the carcass 6, an inner liner 10 stuck along a tire inner space 9, and a protective rubber layer 11 extended between this inner liner 10 and the carcass 6, and arranged from a buttress part 13 to the bead part 4 through the side wall part 3. Moreover, the protective rubber layer is formed by rubber composition wherein carbon black of 20 to 70 parts weight and fibre reinforcing materials made of short fibres to be orientated in the tire circumferential direction are mixed to base rubber of 100 parts weight containing natural rubber or isoprene rubber of 20 to 100 parts weight and polybutadiene rubber of 80 to 0 parts weight. This patent discusses about the use of the protective rubber layer comprising containing natural rubber or isoprene rubber and polybutadiene rubber along with reinforcing carbon black and fibre reinforcing materials made with short fibres in the carcass to reduce rolling resistance and tire weight whereas the present invention discusses about the use of carbon fibre nanomaterial as reinforcing filler in tire sidewall rubber composition to provide fatigue to failure resistance.

Publication No. JPH08175119 provides a pneumatic tire capable of reducing the rolling resistance without impairing the stability and controllability and the riding comfort. A carcass fold-back end X1 is located at the height Hc of <=0.15 time the height H of the tire section, and a short fibre reinforced layer 11 of >=0.3mm and <=1.0mm in thickness is arranged on the outer surface of the carcass in the area Y of a side wall part between a belt end X2 and the fold-back end X1. In the short fibre reinforced layer, the short fibre and the carbon black are contained in the rubber component where 30-60 pts.wt., Natural rubber and/or isoprene rubber is blended in 40-70 pts.wt., butadiene rubber, and >=90% short fibre is oriented at the angle in the range of ±20 deg. relative to the circumferential direction of the tire, and the ratio of the complex elasticity E*a in this direction of orientation to the complex elasticity E*b in the direction orthogonal to the direction of orientation is >=5. This patent discusses about use of short fibre reinforcing layer having specific physical properties of a plate-like thickness of 0.3 mm or more and 1.0 mm or less, for achieving the reduction of rolling resistance in the tire sidewall whereas the present invention discusses about the use of carbon fibre nanomaterial as reinforcing filler in tire sidewall rubber composition to provide fatigue to failure resistance.

Publication No. JPH09150610 relates to reducing resistance to rolling without deteriorating steering stability and riding comfort. Tread rubber 10 is made of rubber of 0.14 or less in loss tangent and inner liner rubber 11 is made of rubber composition mainly containing butyl rubber and a layer 12 reinforced by short fibre of 0.7 to 1.2mm thick is disposed between a carcass 6 and the inner liner rubber 11 and in a restricted shoulder side wall zone S. The layer 12 reinforced by short fibre contains 100 by weight of rubber composition comprising 30 to 50 by weight of butadiene rubber and 50 to 80 by weight of natural rubber and/or isoprene rubber, 10 to 30 by weight of short fibre and 30 or less by weight of carbon black of 30 to 90mg/g in iodine absorption number and 90% or more of the above described short fibre is oriented in the circumferential direction of the tire and the ratio (E*a/ E*b) of a complex modulus E*a in the orienting direction to a complex modulus E*b in the direction orthogonal to the orienting direction is 5 or more. This patent discusses about the use of rubber composition containing butyl rubber along with a layer of reinforced short fibre of 0.7 to 1.2 mm thick in a restricted shoulder sidewall zone to reduce rolling resistance without deteriorating steering stability and riding comfort whereas the present invention discusses about the use of carbon fibre nanomaterial as reinforcing filler in tyre sidewall rubber composition to provide fatigue to failure resistance.

Publication No. JPH06234303 provides a radial tire lightweight with small energy loss to realize excellent manoeuvring stability by forming the cap tread, base tread, and sidewall and bead apex of the tire respectively of rubber compositions containing material with specified properties. The cap tread of a tire 4 is formed of a rubber composition of -30 deg.C or higher in tan delta peak temperature after curing. The base tread 1 and a side wall are formed of a rubber composition containing 30wt. parts or less of carbon black of 30-90mg/g in the iodine adsorption number and 10wt. parts or more of short fibre 2 to 10wt. parts of a rubber component, with the direction of the short fibre 2 oriented in the axial direction of the tire 4 in the base tread 1 and circumferentially in the side wall. The bead apex is formed of a rubber composition containing 65wt. parts or more of carbon black of 60-100mg/g in the iodine adsorption number to 100wt. parts of a rubber composition, with short fibre 2 oriented in the axial direction of the tire 4 or in the direction intersecting the axial direction. The tire 4 is thereby lightweight and small in rolling resistance so as to improve fuel consumption and attain excellent manoeuvring stability and riding comfort. This patent refers to the use of reinforcing filler carbon black of 30-90 mg/g in the iodine adsorption number along with short fibre oriented circumferentially in the tire side wall whereas the present invention discusses about the use of carbon fibre nanomaterial as reinforcing filler in tyre sidewall rubber composition.

Publication No. JPS6194803 relates to prevent worsening of uniformity due to a splice part, by a method wherein the coefficient of twist is set to a specified value so that elongation of a carbon fibre cord is about 2%. A radial tire comprises a pair of right and left bead parts 1, a side wall part 2, and a tread part 3. A carcass layer 4, having a cord angle of 90 deg. with the peripheral direction of a tire, is spanned between the bead parts 1, and plural belt layers 5, crossing each other at a cord angle of 10-35 deg., are disposed on the layer 4. A reinforcing cord 5a of the belt layer 5 is formed with a steel cord, a reinforcing cord 6a of a belt cover layer 6, being the outermost layer of the belt layer 5, is formed by carbon fibre cord having the coefficient K of twist of 300<=K<=1800, and is further vulcanized by a sectional mode. This patent discusses about the use of reinforcing carbon fibre cord for belt layer of tire to prevent worsening of uniformity due to splice part whereas the present invention discusses about the use of carbon fibre nanomaterial as reinforcing filler in tyre sidewall rubber composition to provide fatigue to failure resistance.

Publication No. JP2001030708 relates to lengthen the life of an open-side bicycle tire by preventing early breakdown caused by breakage of textile on a tire side face. In an open-side bicycle tire in which a carcass is exposed at a side wall portion 3 of a tire 1, the carcass 5 is formed with a textile processed with resorcin-formalin-latex liquid in which carbon black is mixed by 0.5 to 5 weight content with respect to 100 rubber weight content of rubber latex. Material of the textile is at least one fibre selected from polyamide, polyester, rayon, aramid and cotton yarn. This patent discusses about use of rubber composition containing rubber latex along with resorcin-formalin-latex and reinforcing carbon black filler in the tire sidewall whereas the present invention discusses about the use of carbon fibre nanomaterial as a reinforcing filler in tire sidewall rubber composition. Both the reinforcing fillers are entirely different from each other.

Publication No. JPS616006 relates to a pneumatic radial tire lightweight and to enhance the durability thereof, by using carbon fibre cords for a lower belt reinforced layer and aromatic polyamide fibre cords for an upper belt reinforced layer. A radial tire 1 is composed of a tread rubber 1, a side wall 2, a bead wire 3, a carcass layer 4, a bead filler 6 and an inner liner 7. In a belt reinforced layer, a lower belt reinforced layer 5d is made of carbon fibre cords, and an upper belt reinforced layer 5u is made of aromatic polyamide fibre cords. A belt cover 8 made of organic fibre cords is arranged over the entire range of spread width of the tread, between the upper belt reinforced layer 5u and the tread rubber 1. Further, the direction of cords of the belt cover 8 is coincident with the peripheral direction EE' of the tire. This patent discusses about the use of carbon fibre cords for a lower belt reinforced layer and aromatic polyamide fibre cords for an upper belt reinforced layer in tire to provide high steering performance whereas the present invention discusses about the use of carbon fibre nanomaterial as a reinforcing filler in tire sidewall rubber composition to provide fatigue to failure resistance.

Publication No. JPS60255509 relates to obtain full effect on reinforcement, high-speed performance and stability of operation and further improve said performance and comfortableness to ride due to low bending rigidity by using carbon fibre for reinforcement layer of the bead part. A tread part 1 is in continuity to a side wall part 2 of the tire side, and a bead wire 3 is circularly provided in the centre of a bead part 9. An inner liner 7 is provided inside the tire, while two-layer belt reinforcement layers 5, 5 are provided inside the tread part 1. Further, the bead part reinforcement layer 8, formed by carbon fibre cords, is provided outside the carcass layer 4 of the bead part 9. This increases the effect on reinforcement and attains high- speed performance and stability of operation. This patent discusses about the use of carbon fibre as a reinforcing layer in the bead portion of tire to provide more excellent steering stability, ride comfort and high-speed durability whereas the present invention discusses about the use of carbon fibre nanomaterial as a reinforcing filler in tire sidewall rubber composition to provide fatigue to failure resistance.

Publication No. JPS60255502 relates to increase casing rigidity of a tire so as to restrict the phenomenon of rising of the belt layer due to centrifugal force during high-speed traveling of the tire by using a carbon fibre cord in the carcass reinforcement layer. Belt reinforcement layers 5, 5 formed in two layers are provided in the circumferential direction of a tire on a tread part 1. A bead part is provided with a circular bead wire 3, above which a bead filler 6 is provided. The carcass reinforcement layer 4 which is formed by carbon fibre cords and enclosing the bead filler 6 and the head wire 3, is provided covering the whole direction of a tire section. Further, the side part of a tire main body is covered by means of a side wall 2. Thus, rigidity of a tire casing is increased, and the phenomenon of rising is restricted due to lack of creeping property. This patent discusses about the use of carbon fibre cord reinforcing layer for tire carcass to provide high-speed durability, excellent handling stability and excellent productivity whereas the present invention discusses about the use of carbon fibre nanomaterial as a reinforcing filler in tire sidewall rubber composition to provide fatigue to failure resistance.

Publication No. JPS57104405 relates to obtaining a pneumatic tire with excellent durability and small rolling resistance by using a micro-organic short fibre reinforced rubber composite consisting of short fibres with specific melting points and fibre lengths in the side wall of a tire. A side wall section is composed of a composite in which the carbon black 10-100pts.wt. and micro-organic short fibre 3-30pts.wt. are blended with at least one kind of rubber 100pts.wt. that is selected from natural rubber, synthetic polyisobutylene rubber, isobutylene-isoprene rubber, halogenation isobutylene- isoprene rubber, polybutadiene rubber, styrene butadiene copolymer rubber, ethylene/ propylene/diene terpolymer rubber, and acrylonitrile/butadiene copolymer rubber. The micro-organic short fibre in the composite has 30 deg.C or less or 120 deg.C or more glass transfer temperature of the amorphous section and 160 deg.C or more melting point of the crystal section. Its average length and diameter are 0.8-30mum and 0.02-0.8mum, respectively.
This patent discusses about the use of rubber composition containing natural rubber, synthetic polyisoprene rubber, butyl rubber along with carbon black and micro-organic short fibres having the glass transition temperature of 30°C or higher than 720°C higher and mean short fibre length 30 μm in the tire sidewall whereas the present invention discusses about the use of reinforcing carbon fibre nanomaterial in tire sidewall rubber composition.

Publication No. JPH06255321 relates to improving cut resistance, and anti-road-hazard property of a side wall part while reducing the weight of a tire. A pneumatic radial tire is provided with a carcass 6 consisting of a carcass ply, for which an organic fibre chord is provided radially, and a belt layer 7 consisting of two belt-ply provided in a tread part and above the carcass, by having a steel chord crossed. A side wall rubber SR comprises an inner layer 10 that is near the carcass, and an outer layer 11 forming the outside of the inner layer 10 and the outer wall surface. The inner layer 10 comprises a rubber composition containing 20-50 wt. part of carbon black which absorbs 35-90mgr/gr of iodine, and 10-40 wt. part of short fibre made of organic fibre, in relation to 100 wt. part of rubber component. This patent discusses about the use of filler organic fibres in the inner layer of tyre sidewall to enhance the cut resistance and to impart anti-road hazard property whereas the present invention discusses about the use of carbon fibre nanomaterial as reinforcing filler in tyre sidewall rubber composition to provide fatigue to failure resistance. Both the reinforcing fillers are entirely different from each other.

Publication No. JPH05185810 relates to improving safety by enhancing cut resistance of a pneumatic tire and at the same time, make weight reduction of the tire possible. Protective rubber layers 11 that extend within the range of the length equal to 15-70% of the length along the outside of a tire formed with the neighbourhood of the top end positions P where side rubber 10 that constitute side wall parts appear on the outside of the tire as upper points A and extend from the said upper points A till lower points B that are the upper end points F of the flanges of rims R and constitutes the outside of the tire are provided, and at the same time, these protective rubber layers are formed out of a rubber composition that is made up by combining carbon black 20-70 parts by weight and fibre reinforcing material made of short fibre oriented in the circumferential direction of the tire 50-10 parts by weight with backing rubber of 100 parts by weight containing natural rubber or isoprene rubber of 20-100 parts by weight and polybutadiene rubber of 80-0 parts by weight. This patent discusses about the use of protective rubber layer containing natural rubber or isoprene rubber and polybutadiene rubber along with carbon black and reinforcing short fibre oriented in the tire circumferential direction in the outer surface of tyre sidewall to prevent damage of sidewall and thereby to reduce the weight of a tire whereas the present invention discusses about the use of carbon fibre nanomaterial as reinforcing filler in tyre sidewall rubber composition. Both the reinforcing fillers are entirely different from each other.

As numerous documents illustrate, it is known for a person skilled in the art to use more preferentially for the manufacture of sidewalls, rubber compositions based on a blend of natural rubber and synthetic rubber, "coarse" carbon blacks that correspond to an ASTM grade N300 to N700, carbon blacks having a CTAB specific surface area of less than 90 m2/g.

Hence, there needed improved rubber composition for tyre sidewall that can provide fatigue to failure resistance.

In order to overcome above listed prior art, the present invention aims to provide a tyre side wall rubber composition and its method of preparation, for tyre sidewall that provides fatigue to failure resistance.

OBJECT OF THE INVENTION
The principal object of the present invention is to provide a tyre side wall rubber composition and its method of preparation.

Another object of present invention is natural rubber and polybutadiene rubber blend-based tyre sidewall rubber composition.

Another object of the present invention is to provide tyre sidewall rubber composition containing PAN (polyacrylanitrile) based carbon fibre as a reinforcing filler.

Yet another object of invention is to provide tyre sidewall rubber composition with better fatigue to failure resistance.

Yet another object of the present invention is to provide tyre sidewall rubber composition with lower modulus.

Yet another object of invention is to provide tyre sidewall rubber composition with better processing properties.

SUMMARY OF THE INVENTION
One or more problems of the conventional prior arts may be overcome by various embodiments of the present invention.

It is primary aspect of the present invention to provide a rubber composition for a tyre side wall, comprising of:
rubber blend – 100 phr;
reinforcing filler – 45-55 phr;
nano-reinforcing filler – 5-15 phr;
activators – 1.65- 4.4 phr;
tackifiers – 2 phr;
process aid – 10 phr;
anti-oxidant – 1.75 – 3.95 phr;
anti-degradant – 1.20 phr;
accelerator – 1.45 phr; and
vulcanization agent – 1 phr,
wherein the nano-reinforcing filler is selected from poly acrylonitrile-based carbon fibre having a nominal size of
150 micron and a fibre diameter 7 to 9 microns, and
wherein the rubber blend is Natural rubber and Polybutadiene rubber in a weight ratio of 65:35.

It is another aspect of the present invention to provide the rubber composition for the tyre sidewall, wherein the nano-reinforcing filler, polyacrylonitrile-based carbon fiber having a tensile strength of 2-3.8 GPa.

It is another aspect of the present invention to provide the rubber composition for the tyre sidewall, wherein the reinforcing fillers is selected from Carbon black (N660) having Iodine absorption No. range between 31 and 41 mg/gm, statistical thickness surface area value between 29 and 39 m2/gm, and Carbon black (N326) having Iodine absorption No. 77 -87 mg/gm, tinting strength value 106-116% ITRB, statistical thickness surface area value between 71 – 81 m2/gm, in a weight ratio of 40: 5-15 phr.

It is another aspect of the present invention to provide the rubber composition for the tyre sidewall, wherein the reinforcing filler from carbon black grade N326 is replaced with polyacrylonitrile-based carbon fiber, in a weight ratio of 20: 5 to 15.

It is another aspect of the present invention to provide the rubber composition for the tyre sidewall, wherein the activators are selected from zinc oxide and stearic acid, in a weight ratio of 2.75:1.65.

It is another aspect of the present invention to provide the rubber composition for the tyre sidewall, wherein the tackifier is Wood rosin.

It is another aspect of the present invention to provide the rubber composition for the tyre sidewall, wherein the process aid is TDAE oil.

It is another aspect of the present invention to provide the rubber composition for the tyre sidewall, wherein the anti-oxidants are selected from TDQ (2,2,4-trimethyl-1.2-dihydroquinoline), 6PPD (N-(1,3-dimethylbutyl)-N’-phenyl-p-phenylenediamine) and combinations thereof, in a weight ratio of 1.75:2.20.

It is another aspect of the present invention to provide the rubber composition for the tyre sidewall, wherein the anti-degradant is Microcrystalline wax (MC wax).

It is another aspect of the present invention to provide the rubber composition for the tyre sidewall, wherein the accelerator is CBS (N-cyclohexyl-2-benzothiazolesulfenamide).

It is another aspect of the present invention to provide the rubber composition for the tyre sidewall, wherein the vulcanization agent is sulphur.

It is another aspect of the present invention to provide the method of preparation of a rubber composition for a tyre sidewall, comprising of steps:
Master batch preparation comprising of steps:
Step 1:
forming a band by masticating of rubbers selected from Natural rubber and Poly butadiene rubber in a two-roll mill at a temperature between 65 and 75 degrees Celsius and dispersing a nano-reinforcing filler polyacrylonitrile based carbon fiber into the rubber polymer matrix;
Step 2:
mixing of the step 1 master batch rubber compound for 0-35 seconds, addition of reinforcing fillers carbon black, rubber chemicals 6PPD, MC wax, TDQ, Wood rosin, TDAE oil, zinc oxide and stearic acid and mixing for 90-230 seconds;
sweeping down in the orifice and mixing for 80-102 seconds; and dumping at the temperature range of 130 and 165 degree Celsius, and sheet out using the two-roll mill,
wherein the processing parameters of the step 2 master batch includes head temperature of a Banbury mixer maintained between 65 and 85 degrees Celsius and the unloaded rotor speed maintained between 50 to 65 rpm,
Step 3:
mixing of the step 2 master batch rubber compound in the Banbury mixer for 60 – 180 seconds and dumping at the temperature range of 100 and 130 degree Celsius, and sheet out using the laboratory two roll mill; and
Final batch preparation comprising of steps:
mixing of step 3 masterbatch rubber compound along with curatives includes CBS, accelerator and sulphur, vulcanization agent for 60 to 90 seconds; and dumping of the rubber compound at the temperature range of 100 and 120 degree Celsius, and sheet out using the laboratory two-roll mill,
wherein the nano-reinforcing filler is selected from poly
acrylonitrile-based carbon fibre having a nominal size of 150 micron, a fibre diameter 7 to 9 microns and tensile strength of
2-3.8 GPa.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a rubber composition and its method of preparation for a tyre side wall. The polyacrylonitrile (PAN) based carbon fibre is used in diene rubber-based rubber composition in tyre sidewall. The use of PAN based carbon fibre nanomaterial in diene-based rubber composition for tyre sidewall provides fatigue to failure resistance, lower modulus, and better processing properties.

The rubber composition for tyre sidewall, comprises at least one diene elastomer in particular Natural rubber (NR): Polybutadiene rubber (PBR) diblend, reinforcing fillers comprising 40 phr of N660, 20 phr of N326 carbon black is replaced with 5 phr to 15 phr of PAN (Poly acrylonitrile) based carbon fibre and a vulcanization system.

The present invention relates to rubber composition according to Table 1 intended for the manufacture thereof and to provide fatigue to failure resistance in tyre sidewall. The rubber composition for tyre sidewall according to the invention, comprises of
a. The tyre sidewall rubber composition according to the present invention consisting of 65 parts by weight of Natural rubber and 35 parts by weight of poly butadiene rubber blend (NR:PBR). The natural rubber used in present invention is ISNR 20 with the Mooney Viscosity, ML (1+4) @100°C is 76 MU.
b. Reinforcing filler, Carbon black of ASTM grade N660 having the Iodine adsorption No. ranges from 31 to 41 mg/gm, statistical thickness surface area value between 29 to 39 m2/gm and ASTM grade N326 having the Iodine adsorption No. 77 to 87 mg/gm, tinting strength value 106 to 116% ITRB, Statistical thickness surface area value between 71 to 81 m2/gm.
c. Reinforcing filler, PAN (Polyacrylonitrile) based carbon fibre (Grade: AGM94MF0150) nano filler having a nominal size of 150 micron , a fibre diameter 7 to 9 microns and a tensile strength of 2.0 to 3.8 GPa is used to provide better fatigue to failure resistance of tyre sidewall.
d. Zinc oxide is an activator added to the rubber compound to activate sulphur vulcanization.
e. Stearic acid is used as a Process aid. Also, Zinc oxide and Stearic acid are added to form zinc soap, improves the solubility of zinc oxide in the compound, and with the accelerator to form a complex, this complex reacts with sulphur to produce a strong cure activating system.
f. 6PPD (N-(1,3-dimethylbutyl)-N’-phenyl-p-phenylenediamine) is added to the rubber composition to provide resistance to thermo-oxidative ageing of elastomers.
g. TDQ 2, 2, 4-trimethyl-1, 2-dihydroquinoline (oligomers) is an antioxidant and it is added to the rubber composition to provide resistance to oxidative aging in ambient and elevated temperatures.
h. MC Wax (Microcrystalline wax) is used to protect against degradation by ozone.
i. Wood rosin is a tackifier and softener to increase the green tack of the rubber compound.
j. TDAE oil is an environmentally friendly process oil used as a processing aid.
k. CBS (N-cyclohexyl-2-benzothiazolesulfenamide). It is a delayed an action accelerator suitable for diene rubbers.
l. Sulphur is the vulcanizing agent.

The rubber composition for tyre sidewall according to the present invention, comprising natural rubber and butadiene rubber blend (NR:PBR), reinforcing fillers comprising 40 phr of N660, 20 phr of N326 carbon black is replaced with 5 phr to 15 phr of PAN (Poly acrylonitrile) based carbon fibre and a vulcanization system to provide fatigue to failure resistance.

Table 1: Rubber Compositions in Phr
Composition No:
Ingredients C1, phr
Control
Rubber composition F1, phr
Rubber composition
related to invention F2, phr
Rubber composition related to invention
ISNR 201 65.00 65.00 65.00
PBR 12202 35.00 35.00 35.00
N 6603 40.00 40.00 40.00
N 3264 20.00 15.00 5.00
PAN based carbon fibre5 - 5.00 15.00
Zinc oxide6 2.75 2.75 2.75
Stearic acid7 1.65 1.65 1.65
Wood Rosin8 2.00 2.00 2.00
TDAE oil9 10.00 10.00 10.00
TDQ10 1.75 1.75 1.75
MC Wax11 1.20 1.20 1.20
6PPD12 2.20 2.20 2.20
CBS13 1.45 1.45 1.45
Sulphur14 1.00 1.00 1.00

1. Indian Standard Natural Rubber ISNR 20 from Kurian Abraham (P) Ltd, Kanyakumari District, Tamilnadu, India with the Mooney Viscosity, ML (1+4) @100°C is 76 MU.
2. PBR 1220 from Reliance Industries limited-Gujarat, India
3. ASTM Grade N660 from Birla Carbon India Pvt Ltd, Gummidipoondi, India.
4. ASTM Grade N326 from Continental carbon Ghaziabad, India
5. PAN (polyacrylonitrile) based carbon fibre reinforcing nano filler, Grade: AGM94MF0150 having a nominal size of 150 micron , a fibre diameter 7 to 9 microns and a tensile strength of 2.0 to 3.8 GPa from Asbury Graphite Mills, Inc. USA
6. Zinc oxide from Pondy Oxides & chemicals Ltd, Kancheepuram, Tamilnadu, India
7. Stearic Acid from 3F Industries, Andhrapradhesh, India.
8. Wood Rosin from Ivax Paper Chemicals Ltd (Kanchi Karpooram Ltd) Kancheepuram, Tamilnadu, India
9. TDAE oil from Indian oil corporation, Chennai, India
10. TDQ from 2, 2, 4-trimethyl-1, 2-dihydroquinoline from NOCIL Limited, Mumbai, India
11. MC Wax from Mahatha petroleum private Limited, India.
12. 6PPD (N-(1, 3-dimethylbutyl)-N’-phenyl-p-phenylenediamine) from NOCIL Limited, Mumbai, India.
13. CBS (N-cyclohexyl-2-benzothiazolesulfenamide) from NOCIL Limited, Mumbai
14. Sulphur from The Standard Chemical Co Pvt Ltd, Tamilnadu, India

Method for preparation of the Rubber Compositions:
Step I: Mixing in two roll mill:
Rubber is masticated in a two-roll mill with the roll temperature maintained between 65 to 75 deg C to form a band and then the carbon fibre with a nominal size of 150-micron PAN (polyacrylonitrile) based carbon fibre added into the rubber to attain uniform dispersion of PAN (polyacrylonitrile) based carbon fibre in polymer matrix.
Step II: Mixing has been done with the head temperature of the Banbury Mixer with a tangential rotor maintained between 65 to 80°C and the unloaded rotor speed maintained between 50 to 65 rpm. The mixing cycle is to be followed as: a) Mixing chamber has been charged with step I rubber compound and allowed to mix for 0 to 35 seconds b) and further carbon black, rubber chemicals 6PPD, MC wax, TDQ, Wood rosin, TDAE oil, zinc oxide and stearic acid are added and allowed to mix for 90 to 230 seconds c) sweeping has been done in the orifice and allowed to mix for another 80 to 102 seconds, the compound has been dumped at the temperature in the range of 130°C to 165°C and sheeted out in the laboratory two roll mill.
Step III: Add the step II master batch in the Banbury Mixer and allowed to mix it for 60 seconds to 180 seconds and the compound has been dumped at the temperature in the range of 100°C to 130°C and sheeted out in the laboratory two roll mill.
Preparation of Final Batch: Thermo mechanical mixing in at least one preparatory mixing step - final batch is as follows:
Mixing chamber charged with the Step III (master batch) rubber compound and the curatives CBS, accelerator and Sulphur are added, and allowed to mix for 60 to 90 seconds and the compound has been dumped at the temperature in the range of up to the temperature 100°C to 120°C. The final batch sheet out has been done in the laboratory two roll mill.

Characterization of Cured Rubber Vulcanizate and Uncured Rubber Compound:
The Rubber compound and Rubber vulcanizate properties are listed in Table 2 mentioned below-
Measurements and Tests:
Better processability (Process Requirements) of a Rubber Compound:
M1. Mooney Scorch Characteristics (pre vulcanization characteristics using large rotor) for processability:
The Mooney Scorch measurements are carried out in a Mooney Viscometer (MV 2000 Alpha technologies, USA) according to ASTM D1646. MV indicates the minimum viscosity, t5 indicates the time to scorch (MV+5) which indicates the processing properties (process safety) and t35 indicates the time to cure (MV+35).
M2: Physical properties of the Rubber Vulcanizate
300% modulus of the Rubber Vulcanizate is measured in a Universal testing machine (Instron Make) in accordance with ASTM D412.

M3: Fatigue to Failure test results of Rubber vulcanizate:
The Fatigue to Failure resistance of the rubber vulcanizates are measured in Fatigue to failure tester (Alpha Technologies, USA) in accordance with ASTM D 4482 with the test conditions Frequency: 1.67 Hz (100 cycles per minute) with an extension ratio of 1.61.
Table 2: Rubber compound and Rubber vulcanizate properties
Properties C1, Phr
Control F1, Phr
F2,
Phr
C1 Control, Index F1, Index F2,
Index
Control
Rubber composition Rubber Composition related to invention Rubber Composition related to invention against control rubber composition
Better processability:
Mooney Scorch @ 125°C
Mooney Viscosity, MU
(Lower the index value is better i.e., better processability) 26.10 25.20 22.40 100 96.55 85.82
t5, minutes: seconds:
higher the index value is better
i.e., better processability 33.03 34.48 43.90 100 104.38 132.90
t35, minutes: seconds:
higher the index value is better
i.e., better processability 36.11 37.92 48.34 100 105.01 133.86
300% Modulus, MPa
Lower index value is better
i.e., Lower Modulus 5.59
5.41 4.76 100 96.77 85.15
Fatigue to Failure Resistance:
Fatigue to Failure (cycles in lakhs)
Higher index value is better
i.e., better fatigue to failure resistance. 5.23 7.81 8.07 100 149.33 154.30

RESULTS:
The purpose of these tests is to measure the improved properties of the rubber composition related to the invention against control rubber composition. For this, control composition C1 prepared based on NR:PBR (65 phr:35 phr) diblend containing reinforcing fillers consisting of 40 phr of N660 and 20 phr of N326 carbon black is compared against F1 & F2 composition related to invention based on NR:PBR (65 phr:35 phr) diblend containing reinforcing fillers consisting of 40 phr of N660, 20 phr of N326 carbon black is replaced with 5 phr to 15 phr of PAN (Poly acrylonitrile) based carbon fibre nano reinforcing filler are prepared and evaluated.

The present invention provides 100 parts by weight of rubber composition F1, NR: PBR (65 phr :35phr) diblend based rubber composition containing reinforcing fillers consisting of 40 phr of N660, 20 phr of N326 carbon black is replaced with 5 phr of PAN (Poly acrylonitrile) based carbon fibre nano reinforcing filler gave Mooney viscosity value lowered by 3.45 % (i.e., better compatibility with polymer matrix) when compared to NR: PBR (65phr: 35phr) blend based rubber composition containing reinforcing fillers consisting of 40 phr of N660, 20 phr of N326 carbon black C1, control rubber composition.

Also, the present invention provides 100 parts by weight of rubber composition F1, NR: PBR (65 phr :35phr) diblend based rubber composition containing reinforcing fillers consisting of 40 phr of N660, 20 phr of N326 carbon black is replaced with 15 phr of PAN (Poly acrylonitrile) based carbon fibre nano reinforcing filler gave Mooney viscosity value lowered by 14.18 % (i.e., better compatibility with polymer matrix) when compared to NR: PBR (65phr: 35phr) blend based rubber composition containing reinforcing fillers consisting of 40 phr of N660, 20 phr of N326 carbon black C1, Control rubber composition.

The present invention provides 100 parts by weight of rubber composition F1, NR: PBR (65 phr :35phr) diblend based rubber composition containing reinforcing fillers consisting of 40 phr of N660, 20 phr of N326 carbon black is replaced with 5 phr of PAN (Poly acrylonitrile) based carbon fibre nano reinforcing filler gave process safety, t5 & t35 value improved by 4.38 % & 5.01% respectively when compared to NR: PBR (65phr: 35phr) blend based rubber composition containing reinforcing fillers consisting of 40 phr of N660, 20 phr of N326 carbon black C1, control rubber composition.

Also, the present invention provides 100 parts by weight of rubber composition F1, NR: PBR (65 phr :35phr) diblend based rubber composition containing reinforcing fillers consisting of 40 phr of N660, 20 phr of N326 carbon black is replaced with 15 phr of PAN (Poly acrylonitrile) based carbon fibre nano reinforcing filler gave process safety, t5 & t35 value improved by 32.90 % & 33.86 % respectively when compared to NR: PBR (65phr: 35phr) blend based rubber composition containing reinforcing fillers consisting of 40 phr of N660, 20 phr of N326 carbon black C1, Control rubber composition.

The present invention provides 100 parts by weight of rubber composition F1, NR: PBR (65 phr :35phr) diblend based rubber composition containing reinforcing fillers consisting of 40 phr of N660, 20 phr of N326 carbon black is replaced with 5 phr of PAN (Polyacrylonitrile) based carbon fibre nano reinforcing filler gave lower modulus value by 3.23 % when compared to NR: PBR (65phr: 35phr) blend based rubber composition containing reinforcing fillers consisting of 40 phr of N660, 20 phr of N326 carbon black C1, control rubber composition.

Also, the present invention provides 100 parts by weight of rubber composition F1, NR: PBR (65 phr :35phr) diblend based rubber composition containing reinforcing fillers consisting of 40 phr of N660, 20 phr of N326 carbon black is replaced with 15 phr of PAN (Polyacrylonitrile) based carbon fibre nano reinforcing filler gave lower modulus value by 14.85 % when compared to NR: PBR (65phr: 35phr) blend based rubber composition containing reinforcing fillers consisting of 40 phr of N660, 20 phr of N326 carbon black C1, control rubber composition.

The present invention provides 100 parts by weight of rubber composition F1, NR: PBR (65 phr :35phr) diblend based rubber composition containing reinforcing fillers consisting of 40 phr of N660, 20 phr of N326 carbon black is replaced with 5 phr of PAN (Polyacrylonitrile) based carbon fibre nano reinforcing filler gave better fatigue to failure value in cycles improved by 49.33% when compared to NR: PBR (65phr: 35phr) blend based rubber composition containing reinforcing fillers consisting of 40 phr of N660, 20 phr of N326 carbon black C1, control rubber composition.

Also, the present invention provides 100 parts by weight of rubber composition F1, NR: PBR (65 phr :35phr) diblend based rubber composition containing reinforcing fillers consisting of 40 phr of N660, 20 phr of N326 carbon black is replaced with 15 phr of PAN (Polyacrylonitrile) based carbon fibre nano reinforcing filler gave lower modulus value by 54.30 % when compared to NR: PBR (65phr: 35phr) blend based rubber composition containing reinforcing fillers consisting of 40 phr of N660, 20 phr of N326 carbon black C1, control rubber composition.

Hence, the present invention provides 100 parts by weight of rubber composition F1 & F2, NR: PBR (65phr :35phr) diblend based rubber composition containing reinforcing fillers consisting of 40 phr of N660, 20 phr of N326 carbon black is replaced with 5 to 15 phr of PAN (polyacrylonitrile) based carbon fibre nano reinforcing filler provides better fatigue to failure resistance, lower modulus along with better process properties when compared to NR: PBR (65phr: 35phr) blend based rubber composition containing reinforcing fillers consisting of 40 phr of N660, 20 phr of N326 carbon black C1, control rubber composition.
, C , C , Claims:WE CLAIM:
1. A rubber composition for a tyre side wall, comprising of:
rubber blend – 100 phr;
reinforcing filler – 45-55 phr;
nano-reinforcing filler – 5-15 phr;
activators – 1.65- 4.4 phr;
tackifiers – 2 phr;
process aid – 10 phr;
anti-oxidant – 1.75 – 3.95 phr;
anti-degradant – 1.20 phr;
accelerator – 1.45 phr; and
vulcanization agent – 1 phr,
wherein the nano-reinforcing filler is selected from poly acrylonitrile-based carbon fibre having a nominal size of
150 micron and a fibre diameter 7 to 9 microns, and
wherein the rubber blend is Natural rubber and Polybutadiene rubber in a weight ratio of 65:35.

2. The rubber composition for the tyre sidewall as claimed in claim 1, wherein the nano-reinforcing filler, polyacrylonitrile-based carbon fiber having a tensile strength of 2-3.8 GPa.

3. The rubber composition for the tyre sidewall as claimed in claim 1, wherein the reinforcing fillers is selected from Carbon black (N660) having Iodine absorption No. range between 31 and 41 mg/gm, statistical thickness surface area value between 29 and 39 m2/gm, and Carbon black (N326) having Iodine absorption No. 77 -87 mg/gm, tinting strength value 106-116% ITRB, statistical thickness surface area value between 71 – 81 m2/gm, in a weight ratio of 40: 5-15 phr.

4. The rubber composition for the tyre sidewall as claimed in claim 1, wherein the reinforcing filler from carbon black grade N326 is replaced with polyacrylonitrile-based carbon fiber, in a weight ratio of 20: 5 to 15.

5. The rubber composition for the tyre sidewall as claimed in claim 1, wherein the activators are selected from zinc oxide and stearic acid, in a weight ratio of 2.75:1.65.

6. The rubber composition for the tyre sidewall as claimed in claim 1, wherein the tackifier is Wood rosin.

7. The rubber composition for the tyre sidewall as claimed in claim 1, wherein the process aid is TDAE oil.

8. The rubber composition for the tyre sidewall as claimed in claim 1, wherein the anti-oxidants are selected from TDQ (2,2,4-trimethyl-1.2-dihydroquinoline), 6PPD (N-(1,3-dimethylbutyl)-N’-phenyl-p-phenylenediamine) and combinations thereof, in a weight ratio of 1.75:2.20.

9. The rubber composition for the tyre sidewall as claimed in claim 1, wherein the anti-degradant is Microcrystalline wax (MC wax).

10. The rubber composition for the tyre sidewall as claimed in claim 1, wherein the accelerator is CBS (N-cyclohexyl-2-benzothiazolesulfenamide).

11. The rubber composition for the tyre sidewall as claimed in claim 1, wherein the vulcanization agent is sulphur.

12. A tyre sidewall of a tyre comprising a rubber composition as claimed in
claim 1.

13. A method of preparation of a rubber composition for a tyre sidewall, comprising of steps:
Master batch preparation comprising of steps:
Step 1:
forming a band by masticating of rubbers selected from Natural rubber and Poly butadiene rubber in a two-roll mill at a temperature between 65 and 75 degrees Celsius and dispersing a nano-reinforcing filler polyacrylonitrile based carbon fiber into the rubber polymer matrix;
Step 2:
mixing of the step 1 master batch rubber compound for 0-35 seconds, addition of reinforcing fillers carbon black, rubber chemicals 6PPD, MC wax, TDQ, Wood rosin, TDAE oil, zinc oxide and stearic acid and mixing for 90-230 seconds;
sweeping down in the orifice and mixing for 80-102 seconds; and dumping at the temperature range of 130 and 165 degree Celsius, and sheet out using the two-roll mill,
wherein the processing parameters of the step 2 master batch includes head temperature of a Banbury mixer maintained between 65 and 85 degrees Celsius and the unloaded rotor speed maintained between 50 to 65 rpm,
Step 3:
mixing of the step 2 master batch rubber compound in the Banbury mixer for 60 – 180 seconds and dumping at the temperature range of 100 and 130 degree Celsius, and sheet out using the laboratory two roll mill; and
Final batch preparation comprising of steps:
mixing of step 3 masterbatch rubber compound along with curatives includes CBS, accelerator and sulphur, vulcanization agent for 60 to 90 seconds; and dumping of the rubber compound at the temperature range of 100 and 120 degree Celsius, and sheet out using the laboratory two-roll mill,
wherein the nano-reinforcing filler is selected from poly
acrylonitrile-based carbon fibre having a nominal size of 150 micron, a fibre diameter 7 to 9 microns and tensile strength of
2-3.8 GPa.