RACING TIRE RUBBER COMPOSITION AND METHOD FOR MANUFACTURING SAME

Abstract

An embodiment of the present invention provides a racing tire rubber composition comprising: 30-60 wt % of rubber, 10-30 wt % of carbon black, 1-20 wt % of carbon nanotubes, and 10-50 wt % of oil; and a method for manufacturing same.

Claims

1. A racing tire rubber composition comprising: rubber at 30 to 60% by weight; carbon black at 10 to 30% by weight; carbon nanotubes at 1 to 20% by weight; and an oil at 10 to 50% by weight.

2. The racing tire rubber composition of claim 1, wherein the rubber is one selected from the group consisting of acrylonitrile-butadiene rubber, ethylene-propylene-diene ribber, styrene-butadiene rubber, butadiene rubber, natural rubber, isoprene rubber, butyl rubber, and a combination of two or more thereof.

3. The racing tire rubber composition of claim 1, wherein the carbon black includes: first carbon black having an iodine adsorption amount of 100 to 130 mg/g and a dibutyl phthalate (DBP) oil absorption amount of 115 to 135 ml/100 g; and second carbon black having an iodine adsorption amount of 120 to 140 mg/g and a DBP oil absorption amount of 120 to 145 ml/100 g.

4. The racing tire rubber composition of claim 3, wherein, in the carbon black, the first carbon black and the second carbon black are mixed in a weight ratio of 1:0.05 to 0.5.

5. The racing tire rubber composition of claim 1, wherein the carbon nanotubes are bundle-type carbon nanotubes in which a plurality of multi-walled carbon nanotubes having an average diameter of 5 to 50 nm are aggregated in a lengthwise direction.

6. The racing tire rubber composition of claim 5, wherein the bundle-type carbon nanotubes have an average bundle diameter of 0.1 to 10 μm and an average bundle length of 10 to 200 μm.

7. The racing tire rubber composition of claim 5, wherein the multi-walled carbon nanotubes have a Raman spectral intensity ratio (I.sub.G/I.sub.D) of 0.5 to 1.5.

8. The racing tire rubber composition of claim 5, wherein the multi-walled carbon nanotubes have an apparent density of 0.005 to 0.120 g/ml.

9. The racing tire rubber composition of claim 5, wherein the multi-walled carbon nanotubes have a carbon (C) content of 90% by weight or more.

10. A method of manufacturing a racing tire rubber composition, comprising: (a) preparing a masterbatch by mixing 100 parts by weight of a first rubber with 10 to 100 parts by weight of carbon nanotubes and 50 to 500 parts by weight of an oil; and (b) diluting the masterbatch by mixing the masterbatch with a second rubber, carbon black, and an oil so that a carbon nanotube content of the rubber composition is 1 to 20% by weight.

11. The method of claim 10, wherein the first rubber and the second rubber are one selected from the group consisting of acrylonitrile-butadiene rubber, ethylene-propylene-diene rubber, styrene-butadiene rubber, butadiene rubber, natural rubber, isoprene rubber, butyl rubber, and a combination of two or more thereof.

12. The method of claim 10, wherein the carbon black includes: first carbon black haying an iodine adsorption amount of 100 to 130 and a DBP oil absorption amount of 115 to 135 ml/100 g; and second carbon black haying an iodine adsorption amount of 120 to 140 mg/g and a DBP oil absorption amount of 120 to 145 ml/100 g.

13. The method of claim 12, wherein, in the carbon black, the first carbon black and the second carbon black are mixed in a weight ratio of 1:0.05 to 0.5.

14. The method of claim 10, wherein the carbon nanotubes are bundle-type carbon nanotubes in which a plurality of multi-walled carbon nanotubes having an average diameter of 5 to 50 nm are aggregated in a lengthwise direction.

15. The method of claim 14, wherein the bundle-type carbon nanotubes have an average bundle diameter of 0.1 to 10 μm and an average bundle length of 10 to 200 μm.

16. The method of claim 14, wherein the multi-walled carbon nanotubes have a Raman spectral intensity ratio (I.sub.G/I.sub.D) of 0.5 to 1.5.

17. The method of claim 14, wherein the multi-walled carbon nanotubes have an apparent density of 0.005 to 0.120 g/ml.

18. The method of claim 14, wherein the multi-walled carbon nanotubes have a carbon (C) content of 90% by weight or more.

Description

EXAMPLES

[0072] 137.5 parts by weight of styrene-butadiene rubber (emulsion SBR (E-SBR) expanded by mixing with 37.5 PHR of a treated distillate aromatic extract (TDAE) oil) was introduced into a 0.5 liter Banbury mixer and stirred for one minute at 50° C. and a rotation speed of 40 rpm, and 50 parts by weight of bundle-type carbon nanotubes (average bundle diameter: 2.4 μm, average bundle length: 30 μm), in which multi-walled carbon nanotubes (MWCNTs) having an average diameter of 13 nm, an apparent density of 0.025 g/ml, a Raman spectral intensity ratio (I.sub.G/I.sub.D) of 0.94 to 1.22, and a carbon (C) content of 95% by weight are aggregated in a lengthwise direction, and 50 parts by weight of a TDAE oil were added and stirred for three minutes at a rotation speed of 45 rpm and additionally stirred for three minutes at a rotation speed of 60 rpm. The mixed blend was added to an open roller with a 1 mm gap and subjected to three cycles of each of lowering and triangular folding, and then molded into a sheet to prepare a masterbatch.

[0073] The above masterbatch and styrene-butadiene rubber, zinc oxide, stearic acid, carbon black (N134, N234), and a TDAE oil were introduced to a Banbury mixer and kneaded at 60° C. and a rotation speed of 60 to 75 rpm for 7 minutes and 50 seconds, and thus a first compounding composition was obtained.

[0074] The first compounding composition, sulfur, and vulcanization accelerator (TBBS) were added to a Banbury mixer and kneaded for 2 minutes at 50 rpm at 50° C., and thus a rubber composition was obtained.

[0075] The ratios of raw materials used in the above-described compounding are shown in Tables 1 and 2 below. Table 1 shows the ratios of raw materials introduced according to the above process, and Table 2 shows the ratios of components included in finished rubber compositions.

[0076] N234: iodine adsorption amount: 113 to 127 mg/g, DBP oil absorption amount: 118 to 132 ml/100 g

[0077] N134: iodine adsorption amount: 114 to 128 mg/g, DBP oil absorption amount: 124 to 140 ml/100 g

TABLE-US-00001 TABLE 1 Compar- Classifi- ative cation Example Example 1 Example 2 Example 3 Example 4 E-SBR 42.4 39.9 38.2 34.0 29.7 TDAE oil 24.4 22.2 20.7 17.0 13.3 Zinc oxide 1.3 1.3 1.3 1.3 1.3 Stearic acid 0.8 0.8 0.8 0.8 0.8 Carbon black 21.2 21.2 21.2 21.2 21.2 (N234) Carbon black 8.5 7.2 6.4 4.2 2.1 (N134) Masterbatch 0 6.0 10.1 20.2 30.2 Sulfur 0.7 0.7 0.7 0.7 0.7 TBBS 0.6 0.6 0.6 0.6 0.6 Total 100 100 100 100 100 (Units: % by weight)

TABLE-US-00002 TABLE 2 Compar- Classifi- ative cation Example Example 1 Example 2 Example 3 Example 4 E-SBR 42.4 42.4 42.4 42.4 42.4 TDAE oil 24.4 24.4 24.4 24.4 24.4 Zinc oxide 1.3 1.3 1.3 1.3 1.3 Stearic acid 0.8 0.8 0.8 0.8 0.8 Carbon black 21.2 21.2 21.2 21.2 21.2 (N234) Carbon black 8.5 7.2 6.4 4.2 2.1 (N134) Carbon 0 1.3 2.1 4.2 6.4 nanotube Sulfur 0.7 0.7 0.7 0.7 0.7 TBBS 0.6 0.6 0.6 0.6 0.6 Total 100 100 100 100 100 (Units: % by weight)

[0078] Referring to the above Table 2, the rubber compositions of Examples and Comparative Example had the same filler (carbon black and carbon nanotubes) content of 70 parts by weight (PHR) relative to 100 parts by weight of E-SBR, but unlike the Comparative Example, a part of carbon black (N134) of was replaced with carbon nanotubes in Examples, and the percentages of carbon black replaced by carbon nanotubes were differently set in Examples 1 to 4.

[0079] The obtained rubber compositions were formed into sheets having a thickness of 2 mm using a roll mixer set at 50° C. and subjected to crosslinking in a hot press set at 160° C. while applying a pressure of 160 kgf/cm.sup.2 or more. The crosslinking time was measured with a rubber process analyzer. The processability, curing characteristics mechanical properties, and dynamic properties of the crosslinked specimen were evaluated and are shown in the following Table 3.

TABLE-US-00003 TABLE 3 Comparative Classification Example Example 1 Example 2 Example 3 Example 4 Mooney viscosity (@100° C.) 73.1 79.2 83.1 90.4 95.8 T.sub.10 (min) 5.53 5.62 5.81 5.93 6.10 T.sub.90 (min) 20.71 21.32 22.11 22.57 22.89 Hardness (Shore-A) 62 66 68 69 72 Modulus at 100% elongation 23.5 31.3 35.7 43.5 50.1 (kgf/cm.sup.2) Modulus at 300% elongation 132 132 141 153 161 (kgf/cm.sup.2) Tensile strength (kgf/cm.sup.2) 240 256 260 261 255 Tensile elongation (%) 521 535 541 544 540 Tg (° C.) −5.9 −4.3 −4.5 −4.3 −4.4 Tanδ (@Tg) 0.8407 0.8008 0.7845 0.7764 0.7579 Tanδ (@0° C.) 0.7163 0.7014 0.7153 0.7266 0.7312 E″ (@25° C.) 6.6143 8.6337 11.8 14.5 17.9 Tanδ (@60° C.) 0.2049 0.2341 0.2559 0.2711 0.2923

[0080] Referring to the above Table 3, it can be seen that as the carbon nanotube content of a rubber composition increased, the viscosity of the rubber composition increased and T.sub.10 and T.sub.90 measured with a rubber process analyzer (which measures a crosslinking time by monitoring torque values over time at about 160° C., wherein the crosslinking time is usually determined based on 90% of the maximum torque (T.sub.90)) increased. Therefore, it can be seen that in the case of the rubber compositions and specimens manufactured by the above-described process, although processability was slightly reduced, a satisfactory level of carbon nanotube dispersibility was achieved.

[0081] In regard to the mechanical properties of the specimen measured by a universal testing machine (UTM), all of modulus at 100% and 300% elongation, tensile strength, and tensile elongation of Examples were improved as compared to those of Comparative Example.

[0082] In addition, the dynamic properties of the specimens were evaluated by dynamic mechanical analysis (DMA). Among these, a tan δ value at 60° C. is related to fuel economy characteristics, and the larger the tan δ value at 60° C., the higher a loss modulus value by definition and thus the lower the fuel economy characteristics. This means that rolling resistance is increased, and this phenomenon occurs because the heating value and heating rate of the rubber specimens increase due to the inclusion of carbon nanotubes.

[0083] Referring to the dynamic property test results obtained from the specimens of Examples and Comparative Example, the tan δ value at 60° C. steadily increased as carbon nanotube content increased. This is because as a tire rotates, external stress is transmitted to the carbon nanotubes present in the rubber matrix, and accordingly, the carbon nanotubes which do not form any bonds with the molecular chains of the rubber components vibrate, generating heat.

[0084] In addition, the loss modulus (E″) represents grip properties on a road surface, and it is considered that the larger the loss modulus value, the better the grip properties. From the results showing that the E″ value increased as carbon nanotube content increased, it can be seen that the inclusion of carbon nanotubes can also improve the grip properties of a tire.

[0085] As shown in the above, carbon nanotubes can impart significantly improved heat generation characteristics, dynamic properties, and grip properties to tires, and these tires can be used as racing tires in which dynamic properties and dynamic performance are considered much more important than fuel economy characteristics.

[0086] The above description of the present invention is only for illustrative purposes, and those of ordinary skill in the art to which the present invention pertains should understand that the present invention can be easily implemented in other specific forms without changing the technical spirit or essential features of the present invention. Accordingly, it should be understood that the exemplary embodiments described above are illustrative and non-limiting in all respects. For example, each component described in a combined form may be implemented in a distributed manner, and similarly, a component described as being distributed may also be implemented in a combined form.

[0087] The scope of the present invention is indicated by the appended claims, and all changes or modified forms derived from the meaning and scope of the claims and equivalent concepts thereof should be construed as being included in the scope of the present invention.