FORM 2
THE PATENTS ACT, 1970
(Act 39 of 1970)
AND
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION (See section 10; rule 13)
HIGHLY PROCESSABLE SILICA TREAD WITH ENHANCED PRODUCT PERFORMANCE
APPLICANT CEAT LIMITED
RPG HOUSE, 463, Dr. Annie Besant Road,
Worli, Mumbai - 400 030, India
An Indian Company
INVENTORS
DEY Pranab, GILBERT Rupesh and Nair Sujith Sasidharan
all of CEAT LIMITED,
Getmuvala, Chandrapura,
Halol, Panchmahal, Gujarat, Halol – 389350, India
All Indian Nationals
PREAMBLE TO THE DESCRIPTION
The following specification describes the invention and the manner in which it is
to be performed.

FIELD OF INVENTION
The present invention relates to a rubber composition comprising rubber, thermoplastic resin, reinforcing agent, silica and silane, this composition has good physico-mechanical properties and abrasion resistance. The present invention also relates to a simple process with less number of steps for preparation of said rubber composition for tire(s).
BACKGROUND OF THE INVENTION
A tire is required to have excellent physical characteristics such as grip performance, abrasion resistance etc. Rubber compositions which contain particulate organic compounds are known. The manufacturing of certain rubber articles, including rubber components that may be found in tires, require a rubber composition that has a high rigidity. Tires and other articles that are made of rubber are manufactured from rubber compositions that include rubber, e.g., natural rubber, synthetic rubber or combinations thereof, as well as fillers, plasticizers, vulcanizing agents and other chemicals that improve the physical characteristics of the cured rubber composition.
US6135180 discloses incorporation of polyethylene thermoplastic resin (L-LDPE), foaming agent (ADCA) and foaming aid (urea) in rubber compound in order to achieve better abrasion resistance, tear resistance, crack resistance, extrusion stability and ice traction.
US2013/0146194 describes incorporation of polyamide resin, thermoplastic vinyl alcohol and polyamide modified rubber component in order to achieve low air permeability in compounded rubber.
Many times there may be a compromise in its processability and/or mixing characteristics and/or in its cured cohesiveness characteristics. Therefore, there is a need for the rubber composition which has good and desired characteristics for its use in tire.
The present invention is provided to solve the existing problem of effective silanization and smooth processing of silica compound. The present invention relates to a rubber composition comprising silica tread and thermoplastic resin

compound improved abrasion index, reduced payne effect, lower mooney viscosity and high wears resistance. The present invention also relates to process for preparation of said rubber composition.
SUMMARY OF THE INVENTION
In one aspect the present invention relates to a rubber composition comprising rubber, thermoplastic resin, reinforcing agent, silica and silane, this composition has good physico-mechanical properties and abrasion resistance.
In another aspect the present invention relates to simple process with less number of steps for preparation of rubber composition for tire.
BRIEF DESCRIPTION OF DRAWINGS
The foregoing summary, as well as the following detailed description of the present invention, will be better understood when read in conjunction with the appended drawings. For the purpose of assisting in the explanation of the invention, there are shown in the drawings embodiments which are presently preferred and considered illustrative. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown therein. In the drawing, dispersion of filler particles in polymer blend is shown:
Fig.1. Dispersion filler particles in polymer blend observed through Scanning Electron Microscopy.
DETAILED DESCRIPTION OF THE INVENTION
In describing and claiming the invention, the following terminology will be used in accordance with the definitions set forth below. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any sensing device, methods, system and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred sensing device, methods, system and materials are

described herein. As used herein, each of the following terms has the meaning associated with it in this section. Specific and preferred values listed below for individual components, substituents, and ranges are for illustration only; they do not exclude other defined values or other values within defined ranges for the components and substituents.
The terms “preferred” and “preferably” refer to embodiments of the invention that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the invention.
As used herein, the terms “comprising,” “including,” “having,” “containing,” “involving,” and the like are to be understood to be open-ended, i.e. to mean including but not limited to.
Thus, before describing the present invention in detail, it is to be understood that this invention is not limited to particularly exemplified systems or process parameters that may of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments of the invention only, and is not intended to limit the scope of the invention in any manner.
In one aspect the present invention provides a rubber composition comprising
rubber, thermoplastic resin, reinforcing agent, silica and silane, this composition
has good physico-mechanical properties and abrasion resistance.
The rubber used is at least one of natural rubber, polybutadiene rubber and styrene
butadiene rubber.
The natural rubber is one the major components of the rubber blend used in this
invention. It helps in achieving good physico-mechanical properties and abrasion

resistance. The Styrene Butadiene Rubber used helps in achieving good rolling resistance, grip and magic triangle properties from cured rubber compounds. The amount of natural rubber used in composition is from 1 to 100 phr and the amount of styrene butadiene rubber used in composition is from 1 to 100 phr.
The thermoplastic resin used is selected from the group consisting of ethylene vinyl acetate, ethylene acrylic acid, ethylene methacrylic acid, Polyethylene oxide, polyglycidol, polypropylene oxide, poly(vinyl methyl ether), polyvinyl alcohol, polyvinylpyrrolidone, polyallylamine, branched polyethylenimine, linear polyethylenimine, poly(acrylic acid), poly(methacrylic acid), poly(vinylacetate) copolymers and combinations thereof, which helps in better dispersion of silica filler particles in rubber and also helps in improving the compound modulus. The amount of thermoplastic resin used in composition is from 1 to 30 phr.
Any reinforcing agent/filler known to those skilled in the art may be used in the
rubber composition either by themselves or in combination with other reinforcing
fillers. In particular embodiments of the rubber composition disclosed herein, the
filler is selected from carbon black, silica, clay and their functional equivalents
thereof, to improve the physical, dynamic and abrasion performance of the
compound.
The amount of filler used in composition is from 5 to 60 phr.
The silica used is having a surface area on nitrogen absorption ranges from 120-230 (m2/g), which is reinforcing non-petroleum based filler used to improve the physical, dynamic and abrasion performance of the compound. The amount of silica used in composition is from 30 to 100 phr.
The silane is selected from the group consisting of bis[3-(triethoxysilyl)propyl] disulfide, bis[3-(triethoxysilyl)propyl] tetrasulfide, trialkoxymercaptoalkyl-silane, S-[3-(triethoxysilyl)propyl]ester and/or octanethionic acid, which acts as a coupling agent between silica and rubber. It reacts with the silanol groups of silica

and forms stable covalent chemical bonds during mixing. It also makes stable covalent chemical bonds with the rubber during the process of vulcanization and thus resulting excellent filler-polymer interaction in the compound. The amount of silane used in composition is from 1 to 30 phr.
The rubber composition of the present invention further comprises zinc oxide which acts as accelerator activator during the process called vulcanization to form sulphur cross-links in rubber compound, stearic acid which acts as lubricant in rubber compound, softener and filler dispersing agent, micro crystalline wax which prevents the ozone attack by migrating (blooming) to the surface of the rubber product and creating a barrier film to ozone molecules and antioxidants (6PPD and TQ) as protecting agents to restrict the degradation on exposure to the severe environments, process oil which improves processing behavior and assist in plasticizing the rubber compounds and also improves the flow property and helps in reducing the cost of the final compound, sulfur to provide desired physico-mechanical properties to the rubber vulcanizates, accelerator to increase the speed of vulcanization and to permit vulcanization to proceed at lower temperature and with greater efficiency selected from the group consisting of amine and aldehyde amine (BA. HMT), guanidine (DPG, DOTG), thiazole (MBT, MBTS, ZMBT), thiophosphate (ZBDP), sulfenamides (CBS, TBBS, MBS, DCBS), Thiourea (TMTM, TMTD, DPTT, TBzTD), Dithiocarbamate (ZDMC, ZDEC, ZDBC, ZBEC), Xanthates (ZIX) and functional equivalents thereof, and retarder as pre-vulcanization inhibitor (PVI) to avoid compound scorch (premature vulcanization) with faster curing systems and/or with higher processing temperatures and prolonged storage.
The rubber composition of the present invention further comprises aromatic and non-aromatic hydrocarbon resin selected from the group consisting of phenol formaldehyde, condensation product of tert-butyl phenol and acetylene and zinc naphthenate, coumarone indene, styrene indene, dicyclopentadiene to aid the

processing of rubber and modify the reinforcing and adhesive properties of rubber
vulcanizates.
In an embodiment the rubber composition of the present invention is as
represented in below table.

Ingredient Ranges (phr)
Natural Rubber 1-100
Styrene Butadiene Rubber 1-100
Thermoplastic Resin 1-30
Carbon Black 5-60
Silica 30-100
Silane 1-30
Zinc Oxide 1-5
Stearic Acid 1-5
Micro Crystalline Wax 1-5
Antioxidant 6PPD 0-5
Antioxidant TQ 0-5
Hydrocarbon Resin 0-5
Process Oil 0-30
Sulfur 1-3
MBTS 0.01-0.15
DPG 1-3
CBS 2-4
PVI 0.1-0.3
According to the present invention silica tread composition containing thermoplastic resin wherein conventional silica tread compound formulated with thermoplastic resin (EVA) in order to improve the processibility.
Further it is surprisingly observed presence of thermoplastic resin reduces the Mooney viscosity, enhances the dynamic modulus, lowers the glass transition temperature, and enhances the abrasion index.

For example the unexpected advantages of the present rubber composition are listed in below table.

Properties Unexpected Improvement
Mooney Viscosity about - 20%
Elongation at the break about + 20%
Dynamic Modulus about + 25%
Glass transition temperature about - 50%
Abrasion Index about + 15%
The rubber composition of the present invention is applicable to the tread layer of the tires. Preferably the rubber composition is applicable for passenger car radial and/or bias tires.
In another aspect the present invention relates to simple process with less number of steps for preparation of rubber composition for tire. The process comprises Preparation of rubber composition in internal mixer or Banbury & Sheeted out two-roll mill Mixing the ingredients in internal mixer or a Banbury mill involves –
(1) Master batch mixing of ingredients as per the formulation except Sulphur & Accelerators.
(2) Remixing/repass of master batch.
(3) Optionally Master/repass batch from previous step ((1) or (2)).
The rubber composition formed is them sheeted out in 6 mm at the end of third step in twin screw sheeter and processed for testing of (1) Mooney viscosity (2) Shear modulus.

The superior wear resistance is envisaged from the newly developed tread
compound formulation. Consistent Mooney viscosity is envisaged over a period
of time from the newly developed tread compound formulation and consistent
dynamic modulus is envisaged above the melting/softening temperature of
thermoplastic resin from the newly developed tread compound formulation.
The present invention provides effective silanization and smooth processing by
using thermoplastic resin technology.
The process of the present invention involves less number of steps than
conventional processes. In accordance with present invention reduction of
multiple mixing stages in silica mixing have advantages in the effective
silanization and reduced Payne effect multiple mixing stages required in
conventional silica compound.
The present invention will now be more particularly described with reference to
the following examples. It is to be understood that these are intended to illustrate
the invention and in no manner to limit its scope.
EXAMPLES
Example 1
This example provides a rubber composition according to the present invention.
(Regular)

Ingredient phr
Natural Rubber 40
Styrene Butadiene Rubber 60
Thermoplastic Resin -
Carbon Black 7
Silica 82
Silane 6.4
Zinc Oxide 4.5
Stearic Acid 2
Micro Crystalline Wax 2

Antioxidant 6PPD (N'-phenyl-p-phenylenediamine)
2.5
Antioxidant TQ (2,2,4-Trimethyl-1,2-Dihydroquinoline polymer) 1
Hydrocarbon Resin 1.5
Process Oil 23
Sulfur 1.1
MBTS 0.1
DPG 1.6
CBS 2.2
PVI
(N-(cyclhexyl thio) phthalimide) 0.2
Example 2
This example provides a rubber composition according to the present invention
(Trial -1)

Ingredient phr
Natural Rubber 40
Styrene Butadiene Rubber 60
Thermoplastic Resin 10
Carbon Black 7
Silica 82
Silane 6.4
Zinc Oxide 4.5
Stearic Acid 2
Micro Crystalline Wax 2
Antioxidant 6PPD (N'-phenyl-p-phenylenediamine)
2.5
Antioxidant TQ (2,2,4-Trimethyl-1,2-Dihydroquinoline polymer) 1
Hydrocarbon Resin 1.5

Process Oil 23
Sulfur 1.1
MBTS 0.1
DPG 1.6
CBS 2.2
PVI
[N-(cyclhexyl thio) phthalimide] 0.2
Example 3
This example provides a rubber composition according to the present invention
(Trial-2)

Ingredient phr
Natural Rubber 40
Styrene Butadiene Rubber 60
Thermoplastic Resin 10
Carbon Black 7
Silica 82
Silane 4.92
Zinc Oxide 4.5
Stearic Acid 2
Micro Crystalline Wax 2
Antioxidant 6PPD(N'-phenyl-p-phenylenediamine)
2.5
Antioxidant TQ (2,2,4-Trimethyl-1,2-Dihydroquinoline polymer) 1
Hydrocarbon Resin 1.5
Process Oil 23
Sulfur 1.1
MBTS 0.1
DPG 1.6
CBS 2.2

PVI
[N-(cyclhexyl thio) phthalimide] 0.2
Example 4
This example provides a rubber composition according to the present invention
(Trial-3)

Ingredient phr
Natural Rubber 35
Styrene Butadiene Rubber 55
Thermoplastic Resin 10
Carbon Black 7
Silica 82
Silane 6.4
Zinc Oxide 4.5
Stearic Acid 2
Micro Crystalline Wax 2
Antioxidant 6PPD (N'-phenyl-p-phenylenediamine)
2.5
Antioxidant TQ
(2,2,4-Trimethyl-1,2-Dihydroquinoline
polymer) 1
Hydrocarbon Resin 1.5
Process Oil 20
Sulfur 1.1
MBTS 0.1
DPG 1.6
CBS 2.2
PVI
[N-(cyclhexyl thio) phthalimide] 0.2

Example 5
Process for preparation rubber composition
Stage 1 (Master) mixing:
The rubbers and all other ingredients as in example 1 - 4 were weighed as per the
decided recipe.
The rubber composition of example 1 is prepared by following stage 1 to stage 3
as described below.
The rubber composition of example 2 to 4 is prepared by following stage 1 and
stage 3 as described below.

Sl Step Charge Mixing Charge Mixing Temp.
No Time Time R.P.M R.P.M (°C)
1 (Sec) (Sec)

Load 0 45 20 67 80
Rubbers/thermoplastic
2 resin - Ram Down

Load ¾ Silics + ¾ 0 60 25 62 140
Silane + Stearic acid+ ½
3 Oil

Load ¼ Silica + ¼ 0 45 25 62 155
Silane + ½ Carbon
4 Black + Resin + ½ Oil

Load ½ Carbon black+ 0 100 25 55 145
Antioxidant + Wax +
5 Zinc Oxide + ½ Oil

Sweep – Ram Up & 0 100 - Variabl 150
6 Down e RPM

Mixing 0 140 - Variabl 150
7 e RPM

Dump - - - - 150

Care should be taken to avoid shooting up of the temperature above 150°C. Sheet Out in Mill:
Set roll nip to 5.0 mm. After weighing the dumped stock, load onto the mill. Give minimum number of cuts (3 or 4) to get a smooth sheet (2 number from each side generally). Sheet out the continuous smooth stock.
Stage-2 (Repass) mixing:

Sl Step Charg Mixing Charge Mixing Temp.
No e Time Time (Sec) R.P.M R.P.M (°C)
1 (Sec)

Load 1st stage Master 0 60 40 55 80
2 3 4 compound

Mixing 0 60 40 55 145

Mixing 0 90 40 55 155

Dump - - - - 155
Sheet Out in Mill:
Set roll nip to 5.0 mm. After weighing the dumped stock, load onto the mill. Give
minimum number of cuts (3 or 4) to get a smooth sheet (2 number from each side
generally). Sheet out the continuous smooth stock.
The process parameters are as below.
Stage-3 (Final) mixing:
The stage 1or stage 2 materials was mixed in the Banbury as below:

Sl Step Charg Mixin Charge Mixing Temp.
No e
Time
(Sec) g
Time
(Sec) R.P.M R.P.M (°C)

1
2 3 4 Load 1st stage/2nd
stage Master/Repass compound 0 20 35 35 80

Mixing 0 30 35 35 95

Mixing 0 150 35 35 100

Dump - - - - 100
Sheet Out in Mill:
Adjust the nip to 0.8 mm. Pass the stock through the nip endwise six times,
alternating the right and left ends.
Adjust the nip to 6 mm and pass the batch four times without banding or rolling.
Adjust the nip to 3 mm and load the remaining compound onto the mill and sheet
out into continuous smooth stock.
Mixing time, dump temperature and mixing energy for all stages are given below.
1. Mixing time:
- Master: 470 sec
- Repass: 190 sec
- Final: 150 sec
2. Dump temperature:
- Master: 150 °C
- Repass: 155 °C
- Final: 100 °C
3. Mixing energy
- Master: 1.85 kWh
- Repass: 1.69 kWh
- Final: 0.85 kWh

Example 6

PARAMETER MOONEY VISCOSITY TENSILE STRENGTH (MPa) ELONGATION AT BREAK (%)
REGULAR 98.0 227 586
TRIAL-1 74.6 220 652
TRIAL-2 87.1 232 735
TRIAL-3 81.8 229 652
Example 7 Methods and study
Payne effect: This was carried out by Rubber Process Analyzer. Frequency was set at 100 cpm for frequency controlled dynamic strain sweep and the strain range was selected between 0.1% and 500%. The measurements were done in ambient atmosphere at a temperature of 100°C. During each experiment, the temperature was maintained at the desired constant value by constantly heating the sample. Mooney viscosity: This was carried out in Monsanto Mooney viscometer. Rotation was set at 2 rpm. Sample was preheated at 100°C for 1 min and then the experiment was further carried out for another 4 min. at 100°C. Viscosity value was recorded after end of the experiment.
Dynamic mechanical analysis: DMA measurements were performed with a Dynamic Mechanical Analyzer. The temperature sweep experiments were carried out using tension mode of the DMA instrument over a temperature range of -50°C to +70°C, at a rate of 2°C /min. The samples were scanned at a frequency of 10 Hz, and a dynamic strain level of 0.25%. The storage modulus (E′) and loss tangent (tanδ) were recorded as a function of temperature.
Wear resistance: This was measured in DIN abrader in which standard test sample were tested into the instrument at the travel speed of 0.32 m/s and drum speed of 40 rpm. Result was noted after measuring the weight loss of each specimen after the test.

Payne Effect:

RUBBER PROCESS ANALYZER
SHEAR MODULUS (ΔG) 1 - 450%
COMPOUND CODE MASTER REPASS FINAL
REGULAR 1177.5 690.9 562.9
TRIAL-1 534.0 - 525.0
TRIAL-2 708.0 - 656.0
TRIAL-3 770.0 - 655.0
Wear Resistance:

DIN ABRASION :
COMPOUND CODE REGULAR TRIAL-1 TRIAL-2 TRIAL-3
STD. LOSS AVG (g) 0.206 0.210 0.210 0.209
SAMPLE LOSS (g) 0.272 0.191 0.213 0.195
VOL LOSS mm3 213.33 181.45 202.44 186.86
INDEX % 69.97 82.27 73.73 79.85
Dynamic Properties:

D.M.T.A TEST TEMP : 60 °C
COMPOUND CODE REGULAR TRIAL-1 TRIAL-2 TRIAL-3
E' Mpa 16.60 20.30 20.80 25.60
TAN DELTA 0.143 0.140 0.140 0.145
Example 8
This example provides a comparison of various rubber compositions of present
invention and known compositions.

S. Property Regular Trial-1 Trial-2 Trial-3
no.
1 Wear Resistance (higher is better) 69.97 82.27 73.73 79.85

2 Mooney Viscosity (lower is better) 98.0 74.6 87.1 81.8
3 Dynamic Modulus (higher is better) 16.60 20.30 20.80 25.60
Conclusion from the above table:
- The superior wear resistance obtained from the newly developed tread compound formulations.
- Lower Mooney viscosity obtained for the newly developed tread compounds formulation which is easily processable.
- Higher dynamic modulus obtained for the newly developed tread recipes beneficial for tire performance properties.

We Claim
1. A rubber composition comprising a rubber component, thermoplastic resin, reinforcing agent, silica and silane.
2. The composition as claimed in claim 1 wherein said rubber component is selected from natural rubber or styrene butadiene rubber.
3. The composition as claimed in claim 1 wherein said natural rubber is used in an amount from 1 to 100 phr and styrene butadiene rubber is used in an amount from 1 to 100 phr.
4. The composition as claimed in claim 1 wherein said thermoplastic resin used is selected from the group consisting of ethylene vinyl acetate, ethylene acrylic acid, ethylene methacrylic acid, polyethylene oxide, polyglycidol, polypropylene oxide, poly(vinyl methyl ether), polyvinyl alcohol, polyvinylpyrrolidone, polyallylamine, branched polyethylenimine, linear polyethylenimine, poly(acrylic acid), poly(methacrylic acid), poly(vinylacetate) copolymers and combinations thereof.
5. The composition as claimed in claim 1 wherein said thermoplastic resin is used in an amount from 1 to 30 phr.
6. The composition as claimed in claim 1 wherein said reinforcing agent or filler is selected from carbon black, silica, clay and their functional equivalents thereof, and is used in an amount from 5 to 60 phr.
7. The composition as claimed in claim 1 wherein said silica is having a surface area on nitrogen absorption ranges from 120-230 (m2/g) and used in an amount from 30 to 100 phr.

8. The composition as claimed in claim 1 wherein said silane is selected from the group consisting of bis[3-(triethoxysilyl)propyl] disulfide, bis[3-(triethoxysilyl)propyl] tetrasulfide, trialkoxymercaptoalkyl-silane, S-[3-(triethoxysilyl)propyl]ester and/or octanethionic acid.
9. The composition as claimed in claim 1 wherein said silane is used in an amount from 1 to 30 phr.
10. The composition as claimed in claim 1 further comprises zinc oxide.
11. A tire having a tread of rubber composition comprising rubber, thermoplastic resin, reinforcing agent, silica and silane.
12. A simple process for preparation of rubber composition comprising the steps of
a) Mixing the ingredients in internal mixer or a Banbury mill involves master batch mixing of ingredients as per the formulation except Sulphur & Accelerators.
c) Remixing/repass of master batch.
d) Optionally Master/repass batch from previous step (a) or (b).
13. The process as claimed in claim 3 wherein said rubber composition formed
is sheeted out in 6 mm at the end of third step in tween screw sheeter.