Claims:WE CLAIM:
1. A tire bead, comprising of:
bead wire; and
a rubber composition comprising of nanoclay,
wherein the nanoclay is organically unmodified Fullers Earth Clay of acicular particles of diameter of 1-30 nm and length of 10-5000 nm.

2. A tire bead rubber composition, comprising by weight of:
one or more elastomers-100 parts;
FE clay or Fullers earth clay- 1-30 parts;
calcium carbonate- 1-10 parts;
carbon black- 80-100 parts;
cure chemical- 8-20 parts;
additives- 2-5 parts;
accelerator-1-2 parts; and
processing oil- q.s.,
wherein the FE clay is an unmodified Fullers Earth Clay nanoclay of acicular particles of diameter 1-30 nm and length 10-5000 nm.

3. The tire bead rubber composition as claimed in claim 2, wherein the cure chemical is selected from Sulfur, MBTS and the like.

4. The tire bead rubber composition as claimed in claim 2, wherein the accelerator is 2-2´-Dithiobis(benzothiazole).

5. The tire bead rubber composition as claimed in claim 2, wherein the processing oil is aromatic oil.

6. The tire bead rubber composition as claimed in claim 2, wherein in the additives comprises Zinc oxide (5 parts) and Stearic acid (2 parts).

7. The tire bead rubber composition as claimed in claim 2, wherein the elastomers comprises of 15 parts by weight of natural rubber of Grade ISNR 20 and 85 parts by weight of stirene butadiene rubber of grade SBR 1500.

8. The tire bead rubber composition as claimed in claim 2, wherein stiffness of the rubber composition is in the range of 11.48 MPa to 11.95 MPa and bead adhesion strength in the range of 18 kgf to 33 kgf.

9. The tire bead rubber composition as claimed in claim 2, wherein compression set value of the composition is in the range of 21.45 % to 27.12%.

10. A process of preparation of tire bead rubber composition, comprising of the steps:
mastication of elastomers for a time period of 25-30 secs;
addition of FE clay and mixing for a period of 80-100 secs;
addition of half the weight of carbon black and half the quantity of processing oil after 90 seconds;
addition of additives and calcium carbonate with remaining half of the weight of carbon black and processing oil and mixing for a time period of 80-100 seconds, in an internal mixer at a rotor speed of 45 rpm, at a chamber and rotor temperature of 50°C and ram pressure of 5 kgf/cm2 and mixing time of 6 minutes to yield a master batch mix;
sweeping of the chemicals from the chamber walls of the internal mixer and further mixing for a time period of 55-75 seconds to yield rubber nanocomposite;
dumping of the nanocomposite at a dumping temperature of 150°C; and
final batch mixing comprising of mixing of the master batch at an rpm of 30 with a starting temperature for mixing at 30°C, warming of master batch mix for a time period of 30°C, addition of cure chemicals and accelerator and mixing for a time period of 120 second at a dump temperature of 110°C to yield the tire bead rubber composition,
wherein the elastomers comprise of natural rubber and stirene butadiene rubber in a weight ratio of 15:85, and
wherein the FE clay is an unmodified Fullers Earth Clay nanoclay of acicular particles of diameter 1-30 nm and length 10-5000 nm. , Description:FIELD OF INVENTION
The present invention relates to the field of rubber composition, more importantly it relates to a rubber composition for bead insulation with improved rubber metal adhesion and compression set employing Fuller’s earth clay as an adhesion promoter and reinforcing filler. The invention further relates to a tire comprising of the rubber composition, with Fuller’s earth clay as an adhesion promoter.

BACKGROUND OF INVENTION
Good bead insulation is critical for superior performance and high-speed durability. It also ensures the retainment of air pressure in the tire for prolonged period of time. Conventionally different types of organic resins are used in rubber compounding for improving adhesion of rubber with metallic parts like bead wire. These are very costly and hazardous chemicals.

KR101000813B1 discloses a heavy load tire bead insulation rubber composition comprising 100.0 parts by weight of a raw material rubber mixture, 70-95 parts by weight of carbon black, 10-25 parts by weight of clay, 5-15 parts by weight of calcium carbonate, 4-20 parts by weight of novolac type phenol resin, 2-10 parts by weight of pentamethoxy methyl melamine, and 6-10 parts by weight of sulfur. In this publication, 4-20 parts by weight of novolac type phenol resin and 2-10 parts by weight of pentamethoxy-methylmelamine, and novolac type phenol resin is the thermoplastic resin and pentamethoxy-methylmelamine is a methylene donor type curing agent. These two react to form a cross-linked material which increases the crosslink density and stiffness. The above two ingredients of this background art, as disclosed makes the entire process of manufacture expensive.

In the present invention, un-modified fuller’s earth clay is used as an adhesion promoter and reinforcing filler avoiding the usage of PMMA. Hence crosslink novolac type phenolic resin is not needed to impart good adhesion strength. Unmodified Fuller’s earth clay is used, which is a nanoclay and it is different from the general clay.

JP2010012909 relates to a rubber composition for tire bead insulation and a tire bead cover and a pneumatic tire using the same, and more particularly to a rubber composition for a tire bead insulation and a tire bead cover includes 5-30 parts by weight of oil extended white clay, 80-30 parts by weight of carbon black and 30-30 parts by weight of inorganic filler are blended to 100 parts mass diene-based rubber, the total blend quantity of the oil extended white clay, the carbon black and the inorganic filler is 140-180 parts by weight. However, the present invention is not using oil extended white clay.
JP2012246413 relates to the rubber composition which has high elongation at break and hardness and maintains a low viscosity at insulation work and a pneumatic tire. The rubber composition is obtained by formulating 100 parts by weight of rubber containing 10-90 parts by weight of natural rubber and 90-10 parts by weight of stirene butadiene copolymer rubber; 160-220 parts by weight of filler containing 100-150 parts by weight of carbon black having an NSA of 50 m/g or less; 0.1-10 parts by weight of the following resin solution; and 0.1-10 parts by weight of a curing agent. However, the present invention is disclosing a rubber composition for a tire bead wire insulation compound with un-modified fuller's earth as an adhesion promoter where no organic solvent is used to dissolve any resin.

KR100902392 relates to a bead wire coated rubber composition having a lime saturation factor (LSF) of 93 to 95% and a siliceous modulus 2.5 to 2.5%, and Iron Modulus (IM) of 1.4 to 1.7%. The bead wire coating rubber composition further comprises any one 30~95 parts by weight selected from the group consisting of carbon black, syndiotactic-1,2-polybutadiene, silica, titanium dioxide, clay, layered silicate and tungsten. However, in the present invention the lime saturation factor in the inorganic adhesion promotor (Fuller's earth) is zero % since there is no lime (CaO) present.

KR20040044760 relates to a back side wall rubber composition for a pneumatic tire which comprises a sulfur-containing alkylphenol based polymer capable of simultaneously improving adhesion and heat aging resistance. The rubber composition for a white ribbon sidewall of a pneumatic tire comprises: 100 parts by weight of a diene rubber; 10-50 parts by weight of calcium carbonate as a reinforcing agent; 10-50 parts by weight of clay; and 5-30 parts by weight of white pigment, wherein the rubber composition further comprises 0.1-3 parts by weight of a sulfur donor-type alkylphenol polymer. Particularly, in the sulfur donor type alkylphenol polymer, the alkyl group bonded at a para-position of a phenol group is t-amyl or t-butyl, and the average number of sulfur chains connecting two alkyl phenol groups is 2.0-8.0. However, the present invention is disclosing a rubber composition for a tire bead wire insulation compound with un-modified fuller's earth as an adhesion promoter where no sulfur donating polymer is involved.

EP2607098B1 relates to a pneumatic tire with a component containing syndiotactic polybutadiene expressed as weight per 100 parts by weight rubber (phr). The invention particularly relates to a tire with a tread configured with an outer cap rubber layer and an inner or internal underlying rubber layer where the underlying rubber layer comprises 0 to 80 phr of syndiotactic-1,2-polybutadiene, and (2) 90 to 20 phr of at least one additional diene-based elastomer comprising at least one of polymers and copolymers of at least one of isoprene and 1,3-butadiene and copolymers of stirene and at least one of isoprene and 1,3-butadiene; and (B) up to 40 phr or 1 phr to 40 phr of a filler reinforcement comprising: (1) carbon black, or (2) silica such as amorphous, synthetic silica or precipitated silica, or (3) a combination of carbon black and silica, or (4) platelets of exfoliated clay such as exfoliated montmorillonite clay in an amount of up to 10 phr or 1 phr to 10 phr, and unexfoliated clay such as kaolinite clay in an amount of up to 40 phr or 1 phr to 40 phr..

US6103811 relates to a rubber composition suitable for bead insulation or while side tread of a tire for a passenger car, truck or bus comprising: 100 parts by weight of a starting rubber; 10 to 150 parts by weight of a carbon black; 0.1 to 20 parts by weight of a sulfur; and 40 parts by weight or less of a polysiloxane having the following alkoxysilyl group (I) or acyloxysilyl group (II) and having an average degree of polymerization of 3 to 10,000: 3BOND Si-OR1(I) 3BOND Si-OCOR2(II).

CN106977801 relates to a base composition comprising A material and B material, used for preparing a silane crosslinked polyolefin elastomer insulating material; wherein the composition of the A material comprises: 100 parts polyolefin elastomer, 5-50 parts of linear low density polyethylene, 0-50 parts of clay, 1-3 parts of silane coupling agent, 0.1 part of antioxidant, 0.15-0.2 part of peroxide initiator; the composition of material B includes: 100 parts of poly Olefin elastomer, 5-50 parts of linear low density polyethylene, 0.4-4 parts of polyurethane catalyst. However, the present invention is disclosing a cured elastomeric nanocomposite with fuller's earth as reinforcement where no linear low density polyethylene is employed.

Hence, the present invention aims to provide an improved rubber composition employing unmodified Fuller’s earth clay as an adhesion promoter as well as reinforcement filler for the bead formulation which improves physical properties as well as adhesion to the bead wire.

OBJECTS OF INVENTION
It is a primary object of the invention to provide unmodified Fuller’s earth clay as an adhesion promoter, as well as, reinforcement filler for the bead formulation which improves physical properties as well as adhesion to the bead wire.

Another object of the present invention is to provide a rubber composition for bead insulation with improved rubber metal adhesion and compression set.

Another object of the present invention is to use naturally available fuller’s earth clay which is cost effective.

Yet another object of the present invention is to eliminate the use of costly and toxic resins for improving adhesion with bead wire

Still another object of the present invention is to provide a tire bead comprising of bead wire and a rubber composition comprising of naturally available fuller’s earth clay as adhesion promoter as well as reinforcement filler for bead insulation with improved rubber metal adhesion.

SUMMARY OF THE INVENTION
Thus, according to the present invention, there is provided a tire bead, comprising of:
bead wire; and a rubber composition comprising of nanoclay, wherein the nanoclay is organically unmodified Fullers Earth Clay of acicular particles of diameter of 1-30 nm and length of 10-5000 nm.

It is another aspect of the present invention to provide a tire bead rubber composition, comprising by weight of:
one or more elastomers-100 parts;
FE clay or Fullers earth clay- 1-30 parts;
calcium carbonate- 1-10 parts;
carbon black- 80-100 parts;
cure chemical- 8-20 parts;
additives- 2-5 parts;
accelerator-1-2 parts; and
processing oil- q.s.,
wherein the FE clay is an unmodified Fullers Earth Clay nanoclay of acicular particles of diameter 1-30 nm and length 10-5000 nm.

It is another aspect of the present invention to provide a tire bead rubber composition, wherein the cure chemical is selected from Sulfur, MBTS and the like.

It is another aspect of the present invention to provide a tire bead rubber composition, wherein the accelerator is 2-2´-Dithiobis(benzothiazole).

It is another aspect of the present invention to provide a tire bead rubber composition, wherein the processing oil is aromatic oil.

It is another aspect of the present invention to provide a tire bead rubber composition, wherein in the additives comprises Zinc oxide (5 parts) and Stearic acid (2 parts).

It is another aspect of the present invention to provide a tire bead rubber composition, wherein the elastomers comprises of 15 parts by weight of natural rubber of Grade ISNR 20 and 85 parts by weight of stirene butadiene rubber of grade SBR 1500.

It is another aspect of the present invention to provide a tire bead rubber composition, wherein stiffness of the rubber composition is in the range of 11.48 MPa to 11.95 MPa.

It is another aspect of the present invention to provide a tire bead rubber composition, wherein bead adhesion strength of the composition in the range of 18 kgf to 33 kgf.
It is another aspect of the present invention to provide a tire bead rubber composition, wherein compression set value of the composition is in the range of 21.45% to 27.12%

It is another aspect of the present invention to provide a process of preparation of tire bead rubber composition, comprising of the steps:
mastication of elastomers for a time period of 25-30 secs;
addition of FE clay and mixing for a period of 80-100 secs;
addition of half the weight of carbon black and half the quantity of processing oil after 90 seconds;
addition of additives and calcium carbonate with remaining half of the weight of carbon black and processing oil and mixing for a time period of 80-100 seconds, in an internal mixer at a rotor speed of 45 rpm, at a chamber and rotor temperature of 50°C and ram pressure of 5 kgf/cm2 and mixing time of 6 minutes to yield a master batch mix;
sweeping of the chemicals from the chamber walls of the internal mixer and further mixing for a time period of 55-75 seconds to yield rubber nanocomposite;
dumping of the nanocomposite at a dumping temperature of 150°C; and
final batch mixing comprising of mixing of the master batch at an rpm of 30 with a starting temperature for mixing at 30°C, warming of master batch mix for a time period of 30°C, addition of cure chemicals and accelerator and mixing for a time period of 120 second at a dump temperature of 110°C to yield the tire bead rubber composition,
wherein the elastomers comprise of natural rubber and stirene butadiene rubber in a weight ratio of 15:85, and
wherein the FE clay is an unmodified Fullers Earth Clay nanoclay of acicular particles of diameter 1-30 nm and length 10-5000 nm.

BRIEF DESCRIPTION OF DRAWINGS:
The annexed drawings show an embodiment of the present invention, wherein:
Figure 1: illustrates acicular particles of Fullers Earth Clay.
Figure 2: illustrates comparative graph of Bead adhesion strength in Kgf of compounds FE-10, FE-20 and FE-30.
Figure 3: illustrates comparative graph of Bead stiffness MPa of compounds FE-10, FE-20 and FE-30.
Figure 4: illustrates comparative graph of % compression set at 70°C for 22 hours for various compounds FE-10, FE-20 and FE-30.

DETAILED DESCRIPTION OF THE INVENTION ACCOMPANYING FIGURES
Hereinafter, a rubber composition for tire bead insulation of the present invention and a pneumatic tire in which the rubber composition for tire bead insulation of the present invention is used in a bead insulation portion will be described.
The present invention provides a rubber composition for bead insulation with improved rubber-metal adhesion, stiffness and compression set using Fuller’s earth (FE) clay as an adhesion promoter and reinforcing filler. The present invention also relates to the use of the environmentally friendly, naturally available, cost-effective inorganic filler as an alternative for the conventional organic resins used for improving rubber to metal adhesion.

The composition according to the invention also contains conventional additives in conventional amounts. The materials used for the development rubber composition for bead insulation with improved rubber-metal adhesion, stiffness and compression set employing FE clay as an adhesion promoter and reinforcing filler are unmodified FE clay as filler, Zinc oxide, Sulphur, stearic acid, MBTS [4], carbon black, calcium carbonate etc.

Bead insulation composition, according to an embodiment of the present invention consists of 100 parts by weight of elastomer(s); fuller’s earth clay, preferably acicular in structure, having a length of 10 nm to 5000 nm and without any organic modification containing at a concentration of 10-30 parts by weight; calcium carbonate 1-10 parts by weight; carbon black 80-100 parts by weight; 8-20 parts by weight of cure chemical, wherein the cure chemical is selected from Sulfur, MBTS and the like. 2-5 parts by weight of Zinc oxide (5 parts) and Stearic acid (2 parts) as additives, 1-2 parts by weight of accelerator, preferably 2-2´ Dithiobis(benzothiazole). Preferably the cure chemical is added at a concentration of 12.50 parts by weight sulphur and a rubber composition consisting of conventional additives and mixing procedure thereof. Processing oil used for the composition is an aromatic oil.

The elastomer can be natural rubber, epoxidized natural rubber (ENR), deproteinized natural rubber (DPNR), hydrogenated natural rubber, stirene butadiene rubber (SBR), modified stirene butadiene rubber, butadiene rubber (BR), modified butadiene rubber, chlorosulfonated polyethylene rubber, epichlorohydrin rubber, fluorine rubber, silicone rubber, nitrile rubber, hydrogenated nitrile rubber, nitrile butadiene rubber (NBR), modified nitrile butadiene rubber, chlorinated polyethylene rubber, stirene ethylene butylene stirene (SEBS) rubber, ethylene propylene rubber, ethylene propylene diene (EPDM) rubber, Hypalon rubber, chloroprene rubber, ethylene vinylacetate rubber, acrylic rubber, hydrin rubber, vinyl benzyl chloride stirene butadiene rubber, bromomethyl stirene butyl rubber, maleic acid stirene butadiene rubber, carboxylic acid stirene butadiene rubber, epoxy isoprene rubber, maleic acid ethylene propylene rubber, carboxylic acid nitrile butadiene rubber, brominated polyisobutyl isoprene-co-paramethylstirene (BIMS), or a combination thereof.

In reference to Table 1: different compositions of rubber are formulated with the ratios of the ingredients as provided. FE-10, FE-20 and FE-30 are compositions varying in amount of Fuller’s earth (FE) nanoclay having a length between 10-5000 nanometer and diameter of 1-30 nanometer without any chemical modification and varying in parts by weight.

Table 1 shows the composition details of the compound according to the present invention. Four formulations with different ratio of ingredients have been prepared.
Table 1: Compounds and formulations
Designation
Ingredients Control FE-10 FE-20 FE-30
ISNR 201 15.00 15.00 15.00 15.00
SBR 15002 85.00 85.00 85.00 85.00
Zinc Oxide 5.00 5.00 5.00 5.00
Stearic acid 2.00 2.00 2.00 2.00
FE3 10.00 20.00 30.00
Carbon black 80.00 80.00 80.00 80.00
Aromatic oil 10.00 10.00 10.00 10.00
Calcium carbonate 1.00 1.00 1.00 1.00
MBTS4 1.50 1.50 1.50 1.50
Sulphur 12.50 12.50 12.50 12.50
Total 212.00 222.00 232.00 242.00
[1] Indian standard natural rubber grade 20 having Mooney viscosity [ML (1+4) @ 100°C] 78
[2] Emulsion polymerized stirenebutadiene rubber having Mooney viscosity [ML(1+4) @ 100°C] 52, and bound Stirene of 23.5 %, from Relflex elastomers, Gujrat, India.
[3] Fuller’s earth (FE) nanoclay having a length between 10-5000 nanometer and diameter of 1-30 nanometer without any chemical modification (Figure 1.)
[4] 2-2’-Dithiobis(benzothiazole) – an ultra-fast thiazole type accelerator used to accelerate the crosslinking reaction of rubber chain with sulfur.

Method of preparation of the rubber composition:
An embodiment of the present invention discloses, a method of preparation of the rubber composition with different concentrations of the Fuller’s Earth. The steps comprises of a. Masterbatch mixing process: The ingredients are initially mixed in an internal mixture. The rotor speed is continuously maintained around 45 rotations per minute (rpm). The temperature of the rotor of the internal mixer is maintained around 50°C and the temperature of the chamber of the internal mixer is maintained around 50°C.The ram pressure is kept to 5 kp/cm2. The batch weight is decided based in the chamber volume of the mixer. The fill factor of the chamber is 0.90. The total mixing time of the master batch compound is around 6 minutes. Rubber is initially masticated for 30 seconds. The FE clay is then added and mixed for 90 seconds without changing the rotor rpm. Half of the carbon black along with half of the processing oil is added after 90 seconds. Further, rubber chemicals (Zinc oxide, stearic acid, calcium carbonate) along with the rest half of carbon black and processing oil is added and mixed for 90 seconds. This is followed by sweeping off the chemicals from the chamber walls and again the mixing is continued up to 60 seconds. Finally, the mixed rubber nanocomposite is dumped. The dump temperature of the rubber nanocomposite is kept at 150°C. The initial addition of fuller’s earth clay helps in fine dispersion of the nano material into the rubber matrix.

Final Batch Mixing Process:
Rotor speed is maintained at 30 rpm and the starting temperature of mixing is 30°C. The ram pressure is kept to 5 kp/cm2. The master batch is warmed for 30 seconds. The cure chemical (Sulphur) and accelerator (MBTS) were added further and mixed for 120 seconds. The dump temperature is kept at 110°C.

Results:
The rubber to metal adhesion is tested in accordance with the ASTM standard D 1871-04 using an advanced universal testing machine (model: 5966, Instron, MA, USA) and 14. Specimens per sample were tested and the average value is reported. The maximum force required to pull out a standard brass coated bead wire form the rubber slab is taken as the bead adhesion strength of the said rubber compound. For the control compound the said bead adhesion strength is found to be 16 kgf while adding 30 phr of un modified FE nanoclay it has been increased to 33 kgf, about 106% increase as shown in Table 2 and Figure 2.

Table 2: Properties of compounds
Compound Bead adhesion strength (Kgf) Stiffness(MPa) Compression set at 70°C for 22 hours (%)
Control 16 8.87 31.55
FE-10 18 11.48 24.93
FE-20 26 11.79 27.12
FE-30 33 11.95 21.45

Since the dimensions of the specimens are same for all tests the increase in the bead adhesion strength can be directly interpreted as the adhesion promoting effect of un modified FE clay in the rubber matrix.

Stiffness is an important property for tire bead compounds. High-stiff bead compound will have more resistance to deformation in service, hence it will hold the tire rim firmly ensuring the minimal loss of air pressure and reducing the maintenance of the tire. As per ASTM standard D 575-91 the compressive stress offered by a compound at constant deflection can be taken as a direct measure of its stiffness. In present invention the stiffness of the compounds is measured in accordance with the ASTM standard D 575-91 at a constant deflection of 5 mm using an advanced universal testing machine (model: 5966, Instron, MA, USA) and values are reported as stiffness of the respective compounds in MPa. For the control compound the stiffness value is recorded as 8.87 MPa for 5mm deflection and the same gets increased to 11.95 MPa (Table 2, Figure 3) for 30 phr un-modified FE nanoclay reinforced compound, representing the positive effect of un-modified FE nanoclay loading on stiffness of the rubber compound.

The compression set of the compounds were measured as per the ASTM standard D 395 at 70°C for 22 hours and it is found that the developed un modified FE nanoclay loaded compounds are regulating the compression set values on higher loading (Table 2, Figure 4). The 30 phr un-modified FE nanoclay reinforced compound shows a compression set value of 21.45 % which is 32% less than the control compound.