FIELD OF THE INVENTION
The present invention relates to the field of rubber compositions for tyres. In particular, the
present invention relates to a curable rubber composition comprising carbon black filler and
method of preparation thereof.
5 BACKGROUND OF THE INVENTION
For a tyre to turn and move an automobile, it has to overcome a host of factors, which makes
it resistant to movement, one of which is the tyre’s rolling resistance. Rolling resistance is
the energy required to maintain movement/ rolling of the tyre at a constant speed over a
surface. A main contributor to rolling resistance is hysteresis, which is the energy loss that
10 occurs as a tyre rolls on its footprint. Therefore, there is an obvious need to reduce the rolling
resistance of a tyre, which can lead to improved fuel efficiency of the vehicle.
While there are various factors that affect the rolling resistance of a tyre, such as tread
patterns, wheel speed, weight of the vehicle, deformation on the surface of the wheel, and
surface condition, an intrinsic factor is the make-up of the tyre itself.
15 Therefore, there is a continual need to improve upon tyre compositions which provide lower
rolling resistance, while at the same time balancing between the needs of lower rolling
resistance and other characteristics of the tyre.
CN114656699A discloses a low rolling resistance and high grip tread rubber composition
which comprises a solution polymerized styrene-butadiene rubber I (50.0-90.0 parts); a
20 solution polymerized styrene-butadiene rubber II (20.0 to 40.0 portions); a solution
polymerized styrene-butadiene rubber III (10.0-40.0 parts); a high dispersion white carbon
black (50.0-120.0 parts); a silane coupling agent I (8.0-15.0 parts); and a silane coupling
agent II (2.0-8.0 parts). Since the white carbon black is a polar substance and is difficult to
disperse in nonpolar rubber, it is necessary to add a silane coupling agent to the tread
25 formulation to improve the dispersion of white carbon black in rubber.
CN113736208A discloses a rubber composition, a preparation method thereof and an inner
support of a run-flat tyre, for providing heat resistance, mechanical strength and low
hysteresis loss without losing its flex resistance, low hysteresis and processability. The
invention also provides a preparation method of the rubber composition to solve the problem
3
of mixing difficulty caused by huge difference of Mooney viscosities of hydrogenated
integral rubber and polybutadiene rubber. However, employment of the disclosed
composition of the invention is limited to provide zero-air-pressure durability to the inner
support of a run-flat tyre.
5
SUMMARY OF THE PRESENT INVENTION
In an aspect of the present invention, there is provided a curable rubber composition
comprising a rubber component in an amount of 100phr; and at least a filler in an amount in
10 the range of 10 to 50phr, characterized in that said at least a filler comprises carbon black
having nitrogen surface area (BET) ≤ 40m2
/g; oil absorption number (OAN) in the range of
124-134m3
/kg; and iodine adsorption number ≤ 35g/kg.
In another aspect of the present invention, there is provided a cured rubber composition
comprising a curable rubber composition comprising a rubber component in an amount of
15 100phr; and at least a filler in an amount in the range of 10 to 50phr, characterized in that
said at least a filler comprises carbon black having nitrogen surface area (BET) ≤ 40m2
/g; oil
absorption number (OAN) in the range of 124-134m3
/kg; and iodine adsorption number ≤
35g/kg; and a curing composition in an amount in the range of 1.5 to 5phr.
In yet another aspect of the present invention, there is provided a method of preparing a cured
20 rubber composition comprising a rubber component in an amount of 100phr; and at least a
filler in an amount in the range of 10 to 50phr, characterized in that said at least a filler
comprises carbon black having nitrogen surface area (BET) ≤ 40m2
/g; oil absorption number
(OAN) in the range of 124-134m3
/kg; and iodine adsorption number ≤ 35g/kg; and a curing
composition in an amount in the range of 1.5 to 5phr, said method comprising mixing rubber
25 component and filler at a temperature in the range of 90-160°C; adding curing composition
and mixing at a temperature in the range of 90-130°C to obtain a curable rubber composition;
and curing the curable rubber composition in a rubber curing press to obtain said cured rubber
composition.
DETAILED DESCRIPTION OF THE INVENTION
4
Those skilled in the art will be aware that the present disclosure is subject to variations and
modifications other than those specifically described. It is to be understood that the present
disclosure includes all such variations and modifications. The disclosure also includes all
such steps, features of the process and the product referred to or indicated in this
5 specification, individually or collectively, and any and all combinations of any or more of
such steps or features.
For convenience, before further description of the present invention, certain terms employed
in the specification, examples are collected here. These definitions should be read in light of
the remainder of the disclosure and understood as by a person of skill in the art. Unless
10 defined otherwise, all technical and scientific terms used herein have the same meaning as
commonly understood by a person of ordinary skill in the art. The terms used throughout this
specification are defined as follows, unless otherwise limited in specific instances.
As used in the specification and the claims, the singular forms “a,” “an,” and “the” include
plural referents unless the context clearly dictates otherwise.
15 The term “rolling resistance coefficient (RRC)” indicates the amount of force required to
overcome the hysteresis of the material as the tyre rolls. Tyre pressure, vehicle weight and
velocity all play a role in how much force is lost to rolling resistance. Tyre rolling resistance
is defined as the energy consumed per unit travel distance when the tyre rolls under a load.
Therefore, lower energy use of vehicle can be obtained by using low rolling resistance tyre.
20 The term “phr” represents parts per hundred rubber and provides the weight of additives per
100 units of the base rubber.
The present invention provides a curable rubber composition comprising a rubber component
in an amount of 100phr; and at least a filler in an amount in the range of 10 to 150phr,
characterized in that said at least a filler comprises carbon black having nitrogen surface area
(BET) ≤ 40m2
/g; oil absorption number (OAN) in the range of 124-134m3 25 /kg; and iodine
adsorption number ≤ 35g/kg.
5
In a preferred embodiment, the filler in the said curable rubber composition is carbon black
having nitrogen surface area (BET) ≤ 40m2
/g; oil absorption number (OAN) in the range of
124-134m3
/kg; and iodine adsorption number ≤ 35g/kg.
In a specific embodiment, BET of the carbon black in 29 ± 5m2
/g. In another specific
embodiment, OAN of the carbon black is 127 ± 5 m3 5 /kg. In yet another specific embodiment,
iodine absorption number of the carbon black is 30 ± 5g/kg.
In an embodiment, the carbon black is further characterized by statistical thickness surface
area (STSA) of 27 ± 5m2
/g. In an embodiment, the carbon back is still further characterized
by compressed oil absorption number (COAN) of 78 ± 5 m3
/kg.
10 In an embodiment, the filler amount in the curable rubber composition is in the range of 40-
70 phr. In a preferred embodiment, the filler amount in the curable rubber composition is 55
phr. In an embodiment, the carbon black amount in the curable rubber composition is in the
range of 40-70 phr. In a preferred embodiment, the carbon black amount in the curable rubber
composition is 55 phr.
15 In an embodiment, the curable rubber composition comprises natural rubber. In another
embodiment, the curable rubber composition comprises synthetic rubber. In yet another
embodiment, the curable rubber composition comprises natural rubber and at least a synthetic
rubber. The synthetic rubber in the curable rubber composition can be butadiene rubber,
styrene butadiene rubber, polyisobutylene rubber, or any combination thereof.
20 In an embodiment, the curable rubber composition comprises natural rubber in an amount in
the range of 50-100 phr and synthetic rubber in an amount in the range of 20-100phr. In a
preferred embodiment, the curable rubber composition comprises natural rubber in an
amount in the range of 50-80 phr and synthetic rubber in an amount in the range of 20-50
phr. In a preferred embodiment, the curable rubber composition comprises natural rubber in
25 an amount of 50 phr and synthetic rubber in an amount of 50 phr. In another preferred
embodiment, the curable rubber composition comprises natural rubber in an amount of 40
phr and synthetic rubber in an amount of 60 phr.
6
In an exemplary embodiment of the present invention, there is provided a curable rubber
composition comprising natural rubber in an amount of 50 phr , synthetic rubber in an amount
of 50 phr, and carbon black as filler in an amount in the range of 40-70 phr, preferably 55
phr, characterized in that the carbon black has BET of 29 ± 5m2
/g, OAN of 127 ± 5 m3
/kg,
5 iodine absorption number of 30 ± 5g/kg, statistical thickness surface area (STSA) of 27 ±
5m2
/g, and compressed oil absorption number (COAN) of 78 ± 5 m3
/kg.
In another exemplary embodiment of the present invention, there is provided a curable rubber
composition comprising natural rubber in an amount of 40 phr , synthetic rubber in an amount
of 60 phr, and carbon black as filler in an amount in the range of 40-70 phr, preferably 55
phr, characterized in that the carbon black has BET of 29 ± 5m2
/g, OAN of 127 ± 5 m3 10 /kg,
iodine absorption number of 30 ± 5g/kg, statistical thickness surface area (STSA) of 27 ±
5m2
/g, and compressed oil absorption number (COAN) of 78 ± 5 m3
/kg
The present invention also provides a cured rubber composition comprising a curable rubber
composition as described herein; and a curing composition in an amount in the range of 1.5-
15 5phr. The curing composition comprise sulfur in amount in the range of 1-3 phr, and at least
one of at least an accelerator, and at least a retarder.
In an embodiment, the accelerator is selected from the group consisting of sulfenamide
accelerator, thiuram accelerator, and combinations thereof. In an embodiment, the
sulfenamide accelerator is N-tert-butyl-2-benzothiazolimesulfonamide (TBBS). In an
20 embodiment, the sulfenamide accelerator is benzothiazyl-2-dicyclohexyl sulfenamide
(DCBS). In an embodiment, the sulfenamide accelerator is in an amount in the range of 0.5-
3phr. In another embodiment, the thiuram accelerator is in an amount in the range of 0.1-
1phr. In a preferred embodiment, the accelerator is 1.5 phr. In an embodiment, the retarder
is present in an amount in the range of 0.01-0.3phr. In a preferred embodiment, the retarder
25 is pthalimide.
In an embodiment, the cured rubber composition further comprises zinc oxide, at least an
antioxidant, and ozone protector. In an embodiment, zinc oxide is present in an amount in
the range of 2-4 phr. In an embodiment, antioxidant is present in an amount in the range of
7
1-2.5 phr. In an embodiment, ozone protector is present in an amount in the range of 0.4-1.5
phr.
In an embodiment, the cured rubber composition is a tread base comprising natural rubber in
an amount of 50 phr and synthetic rubber is an amount of 50 phr. In another embodiment,
5 the cured rubber composition is a side wall comprising natural rubber in an amount of 40 phr
and synthetic rubber in an amount of 60 phr.
In an exemplary embodiment of the present invention, there is provided a cured rubber
composition, which is a tread base, comprising natural rubber in an amount of 50 phr and
polybutadiene rubber in an amount of 50 phr; carbon black as a filler in an amount in the
10 range of 40-70phr, preferably 55 phr, characterized in that the carbon black has BET of 29 ±
5m2
/g, OAN of 127 ± 5 m3
/kg, iodine absorption number of 30 ± 5g/kg, statistical thickness
surface area (STSA) of 27 ± 5m2
/g, and compressed oil absorption number (COAN) of 78 ±
5 m3
/kg; sulfur in an amount in the range of 1-3 phr; accelerator in an amount in the range of
1-3 phr, preferably 1.5 phr; stearic acid in an amount in the range of 1.5-2.5 phr, zinc oxide
15 in an amount in the range of 2-4 phr, antioxidant in an amount in the range of 1-2.5 phr, and
ozone protecting wax PE in an amount in the range of 0.4-1.5 phr.
In another exemplary embodiment of the present invention, there is provided a cured rubber
composition, which is a sidewall, comprising natural rubber in an amount of 40 phr and
polybutadiene rubber in an amount of 60 phr; carbon black as a filler in an amount in the
20 range of 40-70phr, preferably 55 phr, characterized in that the carbon black has BET of 29 ±
5m2
/g, OAN of 127 ± 5 m3
/kg, iodine absorption number of 30 ± 5g/kg, statistical thickness
surface area (STSA) of 27 ± 5m2
/g, and compressed oil absorption number (COAN) of 78 ±
5 m3
/kg; sulfur in an amount in the range of 1-3 phr; accelerator in an amount in the range of
1-3p hr, preferably 1.5 phr; stearic acid in an amount in the range of 1.5-2.5 phr, zinc oxide
25 in an amount in the range of 2-4 phr, antioxidant in an amount in the range of 1-2.5 phr, and
ozone protecting wax PE in an amount in the range of 0.4-1.5 phr
The present invention also provides a method of preparing a cured rubber composition
comprising: a) mixing rubber component and filler at a temperature in the range of 90-160°C;
8
b) adding curing composition and mixing at a temperature in the range of 90-130°C to obtain
a curable rubber composition; and c) curing the curable rubber composition in a rubber curing
press.
The present invention also provides carbon black as substantially described herein, for use
5 as a filler in rubber compositions in tyre, with enhanced characteristics as compared to
conventional fillers, including conventional carbon black.
The present invention also provides a tread base for a tyre comprising a curable rubber
composition as substantially described herein.
The present invention also provides a sidewall for a tyre comprising a curable rubber
10 composition as substantially described herein.
The present invention also provides a tyre comprising the curable rubber composition as
substantially described herein.

We Claim
1. A curable rubber composition comprising:
a. a rubber component in an amount of 100phr;
5 b. at least a filler in an amount in the range of 10 to 150phr;
characterized in that said at least a filler comprises carbon black having nitrogen
surface area (BET) ≤ 40m2
/g; oil absorption number (OAN) in the range of 124-
134m3
/kg; and iodine adsorption number ≤ 35g/kg.
10
2. The composition as claimed in claim 1, wherein said at least a filler is carbon black.
3. The composition as claimed in claim 1, wherein carbon black is characterized by
having BET of 29 ± 5m2
/g, OAN of 127 ± 5 m3
/kg; and iodine absorption number of
15 30 ± 5g/kg.
4. The composition as claimed in claim 3, wherein carbon black is further characterized
by having statistical thickness surface area (STSA) of 27 ± 5m2
/g, and compressed
oil absorption number (COAN) of 78 ± 5 m3
/kg.
20
5. The composition as claimed in claim 1, wherein at least a filler is in an amount in the
range of 40-70phr.
6. The composition as claimed in claim 1, wherein the rubber component comprises
25 natural rubber in an amount in the range of 50-100phr.
7. The composition as claimed in claim 1, wherein the rubber component comprises
synthetic rubber in an amount in the range of 20-100phr.
15
8. A cured rubber composition comprising a curable rubber composition as claimed in
claim 1 and a curing composition in an amount in the range of 1.5 to 5phr.
9. The composition as claimed in claim 8, wherein the curing composition comprises
5 sulfur in an amount in the range of 1-3 phr, and at least one of at least an accelerator,
and at least a retarder.
10. The composition as claimed in claim 9, wherein at least an accelerator is selected
from the group consisting of sulfenamide accelerator, thiuram accelerator, and
10 combinations thereof.
11. The composition as claimed in claim 10, wherein sulfenamide accelerator is in an
amount in the range of 0.5-3phr, and thiuram accelerator is in an amount in the range
of 0.1-1phr.
15
12. The composition as claimed in claim 9, wherein at least a retarder is pthalimide.
13. The composition as claimed in claim 9, wherein retarder is in an amount in the range
of 0.01-0.3phr.
20
14. A method of preparing a cured rubber composition as claimed in claim 8, comprising:
a. mixing rubber component and filler at a temperature in the range of 90-160°C;
b. adding curing composition and mixing at a temperature in the range of 90-
25 130°C to obtain a curable rubber composition; and
c. curing the curable rubber composition in a rubber curing press to obtain said
cured rubber composition.

16
15. The method as claimed in claim 14, wherein step (a) further comprises mixing at least
an additive selected from the group consisting of at least an anti-oxidant, at least a
process oil, at least a wax, at least an activator, and combinations thereof.