Improved rubber composition for tyres

Abstract

The present invention relates to a curable rubber composition for tyres comprising at least a rubber component and at least a filler comprising carbon black. The rubber composition provides for reduced Rolling Resistance coefficient (RRc) for improving fuel efficiency and reduced caron footprint.

Description

[0001] IMPROVED RUBBER COMPOSITION FOR TYRES

[0002] FIELD OF THE INVENTION

[0003] 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.

[0004] BACKGROUND OF THE INVENTION

[0005] 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 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.

[0006] 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.

[0007] 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.

[0008] CN 114656699 A 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 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 formulation to improve the dispersion of white carbon black in rubber.

[0009] 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 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.

[0010] SUMMARY OF THE PRESENT INVENTION

[0011] In an aspect of the present invention, there is provided a curable rubber composition comprising a rubber component in an amount of lOOphr; 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.

[0012] 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 lOOphr; 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.

[0013] In yet another aspect of the present invention, there is provided a method of preparing a cured rubber composition comprising a rubber component in an amount of lOOphr; 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 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.

[0014] DETAILED DESCRIPTION OF THE INVENTION

[0015] 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 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 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.

[0016] As used in the specification and the claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0017] 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.

[0018] The term “phr” represents parts per hundred rubber and provides the weight of additives per 100 units of the base rubber.

[0019] The present invention provides a curable rubber composition comprising a rubber component in an amount of lOOphr; 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 / kg; and iodine adsorption number < 35g / kg.

[0020] 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.

[0021] 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 / kg. In yet another specific embodiment, iodine absorption number of the carbon black is 30 ± 5g / kg.

[0022] 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. 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.

[0023] 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.

[0024] 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 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.

[0025] 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, 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.

[0026] 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 / 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

[0027] 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 1.5-5phr. 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.

[0028] 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 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-lphr. 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 is pthalimide.

[0029] 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 1-2.5 phr. In an embodiment, ozone protector is present in an amount in the range of 0.4- 1.5 phr.

[0030] 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, 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.

[0031] 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 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 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.

[0032] 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 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 l-3p hr, preferably 1.5 phr; stearic acid in an amount in the range of 1.5-2.5 phr, zinc oxide 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

[0033] 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; 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.

[0034] The present invention also provides carbon black as substantially described herein, for use as a filler in rubber compositions in tyre, with enhanced characteristics as compared to conventional fillers, including conventional carbon black.

[0035] The present invention also provides a tread base for a tyre comprising a curable rubber composition as substantially described herein.

[0036] The present invention also provides a sidewall for a tyre comprising a curable rubber composition as substantially described herein.

[0037] The present invention also provides a tyre comprising the curable rubber composition as substantially described herein.

[0038] EXAMPLES

[0039] The examples given below serve to illustrate embodiment of the present invention. However, they do not intend to limit the scope of the present invention.

[0040] Example 1

[0041] Tyre sidewall composition was prepared using the filler of the present invention (Sample A) and using conventional filler (CB-N550) (Reference A). The recipe is provided below in Table 1.

[0042] Table 1

[0043] The sidewall compositions (Reference A and Sample A) were evaluated for Mooney viscosity (processing performance) and Scorch (measure of premature vulcanization). As seen in Table 2 below, the characteristics of Sample A is comparable to Reference A.

[0044] Table 2 Next, the rheological characteristics of the sidewall compositions (Reference A and Sample A) were evaluated. As seen in Table 3 below, the characteristics of Sample A is comparable to Reference A.

[0045] Table 3

[0046] Next, the unaged physical properties (slab cured at 160°C for 20 mins) of the sidewall compositions (Reference A and Sample A) were evaluated. As seen in Table 4 below, the characteristics of Sample A are consistently higher than that of Reference A, which is a clear advantage of Sample A over Reference A.

[0047] Table 4

[0048] Next, the Dynamic Mechanical Analysis (DMA) (25-80) Dynamic strain 6.0%, 10Hz was evaluated for the sidewall compositions (Reference A and Sample A). As seen in Table 5 below, the characteristics of Sample A are consistently better than that of Reference A, which is a clear advantage of Sample A over Reference A (higher E’ (storage modulus) and lower Tan Delta).

[0049] Table 5

[0050] Lastly, the Rolling Resistance coefficient (RRc) of the sidewall composition of Reference A and Sample A was evaluated. As seen in Table 6 below, the composition of Sample A has lower RRc as compared to composition of Reference A. It is to be noted that lower RRc is preferable.

[0051] Table 6

[0052] Overall, these data show that sidewall composition using carbon black of the present invention as a filler over conventional carbon black provides for a superior sidewall compound.

[0053] Example 2 Tyre tread base composition was prepared using the filler of the present invention (Sample B) and using conventional filler (CB-N550) (Reference B). The recipe is provided below in Table 7.

[0054] Table 7

[0055] The tread base compositions (Reference B and Sample B were evaluated for Mooney viscosity (processing performance) and Scorch (measure of premature vulcanization). As seen in Table 8 below, the characteristics of Sample B is comparable to Reference B.

[0056] Table 8 Next, the rheological characteristics of the tread base compositions (Reference B and Sample B) were evaluated. As seen in Table 9 below, the characteristics of Sample B is comparable to Reference B.

[0057] Table 9

[0058] Next, the unaged physical properties (slab cured at 160°C for 20 mins) of the tread base compositions (Reference B and Sample B) were evaluated. As seen in Table 10 below, the characteristics of Sample B are comparable to that of Reference B, which confirms the use of the carbon black in the disclosed composition for tyre application.

[0059] Table 10

[0060] Next, the Dynamic Mechanical Analysis (DMA) (25-80) Dynamic strain 6.0%, 10Hz was evaluated for the tread base compositions (Reference B and Sample B). As seen in Table 11 below, the characteristics of Sample B is better than that of Reference B, which is a clear advantage of Sample B over Reference B (comparable E’ (storage modulus) and lower Tan Delta).

[0061] Table 11

[0062] Lastly, the Rolling Resistance coefficient (RRc) of the tread base composition of Reference B and Sample B was evaluated. As seen in Table 12 below, the composition of Sample B has lower RRc as compared to composition of Reference B. It is to be noted that lower RRc is preferable.

[0063] Table 12 Overall, these data show that tread base composition using carbon black of the present invention as a filler over conventional carbon black provides for a superior tread base compound. Advantageously, the present invention provides for rubber composition for tyres, which at least exhibit reduced RRc, which can result in improved vehicle fuel efficiency and reduce carbon footprint.

Claims

I / We Claim1. A curable rubber composition comprising: a. a rubber component in an amount of lOOphr; 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.

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 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.

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 natural rubber in an amount in the range of 50- lOOphr.

7. The composition as claimed in claim 1, wherein the rubber component comprises synthetic rubber in an amount in the range of 20- lOOphr.

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 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 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-lphr.

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.

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 90-130°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.

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.

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