JP2007224068A - Rubber composition and pneumatic tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition suitably used in a heavy-duty pneumatic tire and an off-road tire and having low heat build-up properties and cut resistance/chipping and abrasion resistances and to provide the pneumatic tire using the rubber composition. <P>SOLUTION: The rubber composition is obtained by compounding 100 pts.mass of a rubber component with 0.1-50 pts.mass of a compound having a moiety Q containing dipolar nitrogens and a moiety B containing a 4- to a 6-membered nitrogen-containing heterocycle containing an oxygen or a sulfur and further compounding carbon fibers. The dipolar nitrogen moiety is specifically selected from at least one or more of A1-C(A2)=N(A3)→O, A1-C≡N→O and A1-C≡N→N-A4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rubber composition and a pneumatic tire using the same, and more particularly, to improve heat generation while maintaining cut and chipping properties in a rubber tire, and to meet demanding heavy load pneumatic tires and off-road. The present invention relates to a rubber composition suitable for use in a tire and its pneumatic tire.

In general, a pneumatic tire requires low fuel consumption and stability of an automobile. In particular, heavy-duty pneumatic tires used for trucks, buses and the like require improved heat generation and excellent heat dissipation. Further, for off-road tires, the tread rubber is required to have cut resistance, chipping resistance, and wear resistance on rough roads. Conventionally, in order to improve wear resistance, a synthetic rubber component such as SBR or a resin is used for the tread rubber composition to increase the elastic modulus.
Moreover, when improving the heat dissipation of rubber and improving the cutting and chipping properties of the tire, it is conceivable to reduce the filling amount of carbon black or use carbon black having a large particle size. However, in this case, the reinforcing property, wear resistance, etc. are reduced. Therefore, it has been proposed to add carbon fiber or the like to a rubber product to improve heat dissipation to improve heat generation, and to improve cut, chipping and wear resistance (see, for example, Patent Document 1). . However, even in such a case, further improvement of the low heat generation property of rubber is desired, and even in heavy duty pneumatic tires and off-road tires, both lower heat generation properties and heat dissipation properties, as well as cut and chipping resistance. Improvement in wear resistance and wear resistance is required.
JP 2004-143187 A

  In view of the above problems, the present invention provides a rubber composition having low heat build-up, cut resistance, chipping resistance, and wear resistance that can be suitably used for heavy load pneumatic tires and off road tires, and a pneumatic tire using the rubber composition. It is to provide.

In order to solve the above-mentioned problems, the present inventors have reacted with a double bond site such as a rubber component in a rubber composition containing a rubber component such as natural rubber and synthetic rubber, particularly a synthetic rubber such as SBR. A part Q containing dipolar nitrogen which shows the property and a part B containing a nitrogen-containing heterocyclic ring containing oxygen or sulfur which shows reactivity with a filler such as carbon black and white carbon (or silica filler). When the compound is added, the dispersibility of carbon and the like in the rubber component is enhanced, the low heat buildup of the rubber composition is improved, and even when carbon fiber is contained in such a composition, low heat buildup is achieved. The present invention has been found to maintain excellent heat dissipation and cut and chipping properties.
That is, the present invention is characterized by the following means or configurations.

(1) For 100 parts by mass of the rubber component, 0.1 to 50 parts by mass of a compound having a part Q containing dipolar nitrogen and 4 to 6 nitrogen-containing heterocyclic parts B containing oxygen or sulfur are blended, And a rubber composition comprising carbon fiber.

(2) The dipolar nitrogen portion is selected from at least one of A1-C (A2) = N (A3) → O, A1-C≡N → O, and A1-C≡N → N-A4. A1 to A4 may be different from each other, hydrogen or a group having 20 or less carbon atoms or a linking chain connecting the B, and the compound is bonded to at least one of A1 to A4 and the B is connected. The rubber composition as described in (1) above.
(3) A1 to A4 of the above compound are hydrogen, an alkyl group having 1 to 20 carbon atoms, and an aryl group having 6 to 20 carbon atoms (however, the aromatic ring has a nitro group) , A cyano group, a chloro group, a bromo group, an acyl group, a carbonylalkyl group, an alkyl group, and an alkoxyl group), or a group thereof selected from the above ( 2) The rubber composition as described.
(4) The rubber composition according to the above (1), wherein the nitrogen-containing heterocycle of the B part is oxazoline or thiazoline.

(5) The above compound is 4- (2-oxazolyl) -phenyl-N-methyl-nitrone, 4- (2-thiazolyl) -phenyl-N-methyl-nitrone, 4- (2-oxazolyl) -phenyl- N-phenyl-nitrone, 4- (2-thiazolyl) -phenyl-N-phenyl-nitrone, phenyl-N-4- (2-oxazolyl) -phenyl-nitrone, phenyl-N-4- (2-thiazolyl)- Phenyl-nitrone, 4-tolyl-N-4- (2-oxazolyl) -phenyl-nitrone, 4-tolyl-N-4- (2-thiazolyl) -phenyl-nitrone, 4-methoxyphenyl-N-4- ( 2-Oxazolyl) -phenyl-nitrone, 4-methoxyphenyl-N-4- (2-thiazolyl) -phenyl-nitrone, 4- (2-oxazolyl) -phenyl-nitrile Oxide, 4- (2-thiazolyl) -phenyl-nitrile oxide, 4- (2-oxazolyl) -phenyl-N-methyl-nitrileimine, 4- (2-thiazolyl) -phenyl-N-methyl-nitrileimine, 4 -(2-thiazolyl) -phenyl-nitrile oxide, 4- (2-oxazolyl) -phenyl-N-phenyl-nitrileimine, 4- (2-thiazolyl) -phenyl-N-phenyl-nitrileimine, phenyl-N- The rubber composition according to (4) above, comprising at least one of 4- (2-oxazolyl) -phenyl-nitrileimine and phenyl-N-4- (2-thiazolyl) -phenyl-nitrileimine.

(6) The rubber composition as described in (1) above, wherein the carbon fiber is a vapor grown carbon fiber.
(7) The rubber composition as described in (1) above, wherein carbon fiber is blended in an amount of 1 to 50 parts by mass per 100 parts by mass of the rubber component.

(8) A pneumatic tire formed using the rubber composition described in the above (1) to (7).
(9) The pneumatic tire according to (8), wherein the pneumatic tire is a heavy duty pneumatic tire.
(10) The pneumatic tire according to (8), wherein the pneumatic tire is an off-road tire.

  According to the above means, when the above compound is added to rubber components such as natural rubber and synthetic rubber, the double bond portion (P) in the rubber component and the Q portion of the compound are represented by the following reaction formulas (1) to (3). Reaction occurs.

  Furthermore, the reaction of the following reaction formulas (4) to (15) occurs between the carbon black (CB) or white carbon (or silica filler) and the compound B portion.

このような化合物の作用により、ゴム組成物においてカーボンブラック及びホワイトカーボンが十分に拡散される。その結果として、ゴムの低発熱性及び低ヒステリシスロス性を改善し、また炭素繊維を配合して放熱性を高めて低発熱性化とカット・チッピング性の両立を十分に維持させる。そして、これにより重荷重用空気入りタイヤ及びオフロードタイヤとしての良好な使用を可能にするものである。

By the action of such a compound, carbon black and white carbon are sufficiently diffused in the rubber composition. As a result, the low heat build-up and low hysteresis loss of the rubber are improved, and carbon fiber is added to enhance the heat dissipation to sufficiently maintain both the low heat build-up and the cut and chipping properties. As a result, it can be used as a heavy-duty pneumatic tire and an off-road tire.

Hereinafter, embodiments of the present invention will be described in detail.
The rubber composition of the present invention has a compound 0.1 having a part Q containing dipolar nitrogen and a part B containing 4 to 6 nitrogen-containing heterocycles containing oxygen or sulfur with respect to 100 parts by mass of the rubber component. 30 mass parts is mix | blended, It is characterized by the above-mentioned.

  The above compound is a compound of the present invention as long as it contains a dipolar nitrogen moiety. Specific examples of particularly preferred dipolar nitrogen moieties include A1-C (A2) = N (A3) → O (nitrone system), A1-C≡N → O (nitrile oxide system), and A1-C≡. N → N-A4 (nitrile imine type) can be mentioned. These dipolar nitrogen portions Q are reactively bonded to double bond portions in a polymer such as a rubber component as shown in the above reaction formulas (1) to (3).

The groups A1 to A4 in the nitrone-based, nitrile oxide-based, and nitrileimine-based dipolar nitrogen portions Q are preferably hydrogen, a group having 20 or less carbon atoms, or a connecting chain. When the number of carbon atoms exceeds 20, the molecular weight of the compound itself increases, and the reactivity with the rubber component becomes worse.
Since the said compound has B part, A1-A4 can become a connecting chain which connects B part. However, in the case of A1 to A3, in the case of only A1, or in the case of A1 and A4, at least one or more are connected to the B portion, and a plurality of B portions may exist. A1 to A4 may be different or the same.

  As specific groups or connecting chains of A1 to A4 of the above compound, specifically, hydrogen, an alkyl group having 1 to 20 carbon atoms, and an aryl group having 6 to 20 carbon atoms ( However, the aromatic ring may have a nitro group, a cyano group, a chloro group, a bromo group, an acyl group, a carbonylalkyl group, an alkyl group, and an alkoxyl group). Or a connecting chain thereof. The alkyl group, acyl group, carbonylalkyl group, and alkoxyl group may have a branched chain or a cyclo ring. A1 to A4 may be different from each other.

The B portion of the above compound consists of a nitrogen-containing heterocycle having oxygen or sulfur such as oxetine, thiozetin, oxazoline, thiazoline, tetrahydrooxazine and tetrahydrothioxazine. In particular, it consists of a 4- to 6-membered nitrogen-containing heterocyclic ring represented by the following structural formulas (I) to (III) (X in the table is oxygen: O or sulfur: S). Of these, oxazoline and thiozoline of the structural formula (II) are preferable. In each structural formula, R1 to R7 are hydrogen, a group having 20 or less carbon atoms, or a connecting chain. Moreover, in each structural formula similarly to the case of A1 to A4, in the case of R1 to R3, in the case of R1 to R5, or in the case of R1 to R7, at least one or more of A1 to A4 connected to Q Equivalent to.
As described above, the B part undergoes a binding reaction of the following reaction formulas (4) to (15), and carbon black and white carbon can be uniformly incorporated into the polymer of the rubber component.

  Specific examples of the above compounds include 4- (2-oxazolyl) -phenyl-N-methyl-nitrone, 4- (2-thiazolyl) -phenyl-N-methyl-nitrone, and 4- (2-oxazolyl). -Phenyl-N-phenyl-nitrone, 4- (2-thiazolyl) -phenyl-N-phenyl-nitrone, phenyl-N-4- (2-oxazolyl) -phenyl-nitrone, phenyl-N-4- (2- Thiazolyl) -phenyl-nitrone, 4-tolyl-N-4- (2-oxazolyl) -phenyl-nitrone, 4-tolyl-N-4- (2-thiazolyl) -phenyl-nitrone, 4-methoxyphenyl-N- 4- (2-oxazolyl) -phenyl-nitrone, 4-methoxyphenyl-N-4- (2-thiazolyl) -phenyl-nitrone, 4- (2-oxazolyl) -fe Ru-nitrile oxide, 4- (2-thiazolyl) -phenyl-nitrile oxide, 4- (2-oxazolyl) -phenyl-N-methyl-nitrileimine, 4- (2-thiazolyl) -phenyl-N-methyl-nitrile Imine, 4- (2-thiazolyl) -phenyl-nitrile oxide, 4- (2-oxazolyl) -phenyl-N-phenyl-nitrileimine, 4- (2-thiazolyl) -phenyl-N-phenyl-nitrileimine, phenyl -N-4- (2-oxazolyl) -phenyl-nitrileimine, phenyl-N-4- (2-thiazolyl) -phenyl-nitrileimine and the like can be mentioned.

  Examples of such compounds include 4- (2-oxazolyl) -phenyl-N-methyl-nitrone (hereinafter referred to as 4OPMN) and 4- (2-oxazolyl) -phenyl-N-phenyl-nitrone (hereinafter referred to as 4OPPN). Can be specifically mentioned.

The method for producing the above compound can be produced without undue experimentation. For example, with respect to 4OPMN and 4OPPN, the manufacturing method can be shown in the examples described later.
Also, other compounds can be produced by typical production methods by appropriately selecting other starting materials and intermediate materials.
Said compound is contained in 0.1-50 mass parts with respect to 100 mass parts of rubber components. In particular, it is preferable to contain in 0.1-5 mass parts. If the compounding amount is less than 0.1, the effects of low heat generation and low hysteresis loss are not sufficient. When the compounding amount of the compound exceeds 50 parts by mass, the cost is significantly increased, which is not preferable.

  In the rubber composition of the present invention, the rubber component may be appropriately selected from natural rubber and synthetic rubber and may be blended. Moreover, as a synthetic rubber, it can select suitably from well-known things according to the objective. Conjugated rubber is particularly preferable, and it is preferable to appropriately select at least one from styrene-butadiene copolymer (SBR), polyisoprene (IR), polybutadiene (BR), acrylonitrile-butadiene rubber, chloroprene rubber, and butyl rubber. . Particularly preferably, when SBR is selected, the wear resistance is improved.

In the rubber composition according to the present invention, the amount of the carbon fiber is preferably in the range of 1 to 50 parts by mass per 100 parts by mass of the rubber component. In particular, the range of 5 to 30 parts by mass is preferable. If the carbon fiber is blended within the above range, the rubber composition is sufficiently improved in heat dissipation, and compatibility between cut, chipping and wear resistance is enhanced.
If the amount is less than 1 part by mass, the heat dissipation of the rubber composition cannot be sufficiently improved. If the blending amount exceeds 50 parts by mass, cost performance, workability, and wear resistance are reduced.

The carbon fiber may be in the form of a fiber or tube (hollow shape), and the average diameter of the carbon fiber is preferably in the range of 0.5 nm to 500 nm, more preferably in the range of 1 nm to 400 nm. It is desirable.
Further, when the carbon fiber average diameter is in the range of 0.5 nm to 500 nm, particularly in the range of 1 nμm to 400 nm, by kneading the carbon fiber with the rubber component, it is almost equivalent to the metal powder, Alternatively, the rubber temperature is quickly lowered while maintaining a higher thermal conductivity. In addition, the dispersion in the rubber component during kneading is combined with the effect of the above compound to improve the low heat build-up. Therefore, in the present invention, the carbon fiber is preferably made of nanofibers or nanotubes. When the average diameter of the cross-sectional area of the carbon fiber is less than 0.5 nm, the carbon fiber is broken during kneading and does not contribute to thermal conductivity. In the case where the average diameter of the cross-sectional area of the carbon fiber exceeds 500 nm, it is not preferable because the fracture characteristics are significantly lowered.

The carbon fiber length is preferably in the range of 0.5 μm to 50 μm, more preferably in the range of 1 μm to 40 μm. The aspect ratio of the carbon fiber is preferably 10 or more. If the length of the carbon fiber to be blended is in the range of 0.5 μm to 50 μm, particularly in the range of 1 μm to 40 μm, the dispersibility of the carbon fiber in the rubber component during kneading is good and the aspect ratio is 10 or more. Therefore, sufficient heat conductivity can be imparted to the rubber composition.
If the carbon fiber length is less than 0.5 μm, the production is difficult, and a sufficient aspect ratio cannot be obtained, and the blending effect may not be sufficiently exhibited. On the other hand, when the carbon fiber length exceeds 50 μm, the abrasion resistance of the rubber composition may not be sufficient. Moreover, if the aspect ratio of the carbon fiber is less than 10, the blending effect may not be sufficiently exhibited.
The carbon fiber satisfying these conditions is not particularly limited by its production method, but is particularly preferably a vapor growth carbon fiber produced by a vapor deposition method. Examples of such carbon fibers include VGCF manufactured by Showa Denko Co., Ltd.

In the rubber composition of the present invention, carbon black and / or white carbon (silica filler) can be blended with the rubber component. These are preferably blended in the range of 30 to 70 parts by mass with respect to 100 parts by mass of the rubber component. When the amount of carbon black and white carbon decreases, the elastic modulus tends to decrease. Further, when the amount of carbon or the like is increased, the low exothermic property tends to deteriorate.
The carbon black can be appropriately selected from those usually used in the rubber industry, and examples thereof include SAF, SRF, GPF, FEF, HAF, and ISAF. Carbon black or the like is desirably activated by appropriately adjusting the oil absorption (DBP value or the like) and the surface (N ₂ SA value or the like).

  The rubber composition of the present invention can contain various components usually used in the rubber industry in addition to the above rubber component and carbon black. For example, as various components, fillers (for example, reinforcing fillers such as silica; and inorganic fillers such as calcium carbonate and calcium carbonate); vulcanization accelerators; anti-aging agents; zinc oxide; stearic acid; And additives such as an ozone degradation inhibitor. As vulcanization accelerators, thiazole vulcanization accelerators such as MBTS (dibenzothiazyl disulfide) and CZ (N-cyclohexyl-2-benzothiazylsulfenamide); thiurams such as TT (tetramethylthiuram sulfide) And guanidine-based vulcanization accelerators such as DPG (diphenylguanidine).

  The rubber composition of the present invention can be used for general rubber products such as hoses and belts. Moreover, it is suitable to use for a pneumatic tire. Pneumatic tires are suitable for heavy-duty pneumatic tires and off-road pneumatic tires that require long-term durability on rough roads because of their high cutting, chipping, wear resistance, and low heat build-up. it can. In the pneumatic tire of the present invention, air or an inert gas such as nitrogen can be used as the gas to be filled.

Examples of the present invention will be described below, but the present invention is not limited to these examples.
(Examples 1-6 and Comparative Examples 1-5)
The rubber composition of each Example and Comparative Example is shown in Table 1 below, and a rubber composition before crosslinking was prepared using a Banbury mixer according to the formulation table in Table 1 below. Tires were created on 3700R57.

In each note in Table 1,
* 1) # 1500; Emulsion polymerization SBR
* 2) Carbon fiber: Vapor grown carbon fiber (VGCF-H: Showa Denko KK)
* 3) 4OPPN; (4- (2-oxazolyl) -phenyl-N-phenylnitrone)
* 4) 4OPMN; (4- (2-oxazolyl) -phenyl-N-methylnitrone)
* 5) Anti-aging agent 6PPD; N-phenyl-N'-isopropyl-p-phenylenediamine * 6) Vulcanization accelerator CZ; N-cyclohexyl-2-benzothiazylsulfenamide

* 3) 4OPPN and * 4) 4OPMN were produced as follows.
<Manufacture of 4OPPN>
To a solution obtained by stirring and mixing 15.0 g of 4-formyl-benzoyl chloride (1 equivalent) in 300 ml of chloroform, a solution obtained by adding 10.9 g of 2-aminoethanol (2 equivalents) to 200 ml of chloroform was added dropwise at −10 ° C. And added. After the solution was placed at 25 ° C. for 2 hours, the white precipitate was removed by filtration. The filtrate was dried by a rotary evaporator to obtain 17.4 g of 4-formyl-N- (2-hydroxyethyl) -benzamide as a yellow liquid.
To 50 ml of concentrated sulfuric acid, 17.4 g of 4-formyl-N- (2-hydroxyethyl) -benzamide was added dropwise with stirring, and the mixture was heated at 100 ° C. for 1 hour. To this solution, 500 ml of 20% sodium hydroxide and chloroform were added dropwise with stirring and mixing, and the temperature was maintained at 15 ° C. or lower. The product layer was separated and dried to give 6.3 g of 4- (2-oxazolyl) -benzaldehyde.
A mixture of 4- (2-oxazolyl) -benzaldehyde (1 eq, 6.3 g) and N-phenyl-hydroxyamine (1 eq, 3.9 g) was refluxed in 100 ml ethanol for 30 min to a volume of 50 ml. Concentrated. The same amount of 50 ml of water was added and the mixture was cooled to 5 ° C. overnight in a refrigerator. Filtration separation and drying gave white crystals, yielding 6.7 g of 4- (2-oxazolyl) -phenyl-N-phenylnitrone.

<Manufacturing of 4OPMN>
To a solution obtained by stirring and mixing 4-formyl-benzoyl chloride (15.0 g, 89 mmol) in 300 ml of chloroform, a solution obtained by adding 2-aminoethanol (10.9 g, 178 mmol) to 200 ml of chloroform was added dropwise at −10 ° C. added. After the solution was placed at 25 ° C. for 2 hours, the white precipitate was removed by filtration. The filtrate was dried by a rotary evaporator to obtain 17 g (88 mmol) of yellow liquid 4-formyl-N- (2-hydroxyethyl) -benzamide.
4-Formyl-N- (2-hydroxyethyl) -benzamide (17 g, 88 mmol) was added dropwise to 50 ml of concentrated sulfuric acid with stirring, and the mixture was heated at 100 ° C. for 1 hour. To this solution, 500 ml each of 20% sodium hydroxide solution and chloroform were mixed and added dropwise with stirring, and the temperature was maintained at 15 ° C. or lower. The product layer was separated and dried to give 6.3 g (36 mmol) of 4- (2-oxazolyl) -benzaldehyde (41% yield).
A mixture of 4- (2-oxazolyl) -benzaldehyde (1 eq, 6.3 g) and N-methyl-hydroxyamine (1.7 g, 36 mmol) was refluxed in 100 ml of ethanol for 30 minutes and concentrated to a volume of 50 ml. did. The same amount of 50 ml of water was added and the mixture was cooled to 5 ° C. overnight in a refrigerator. White crystals were obtained by filtration and drying, yielding 5.1 g of 4- (2-oxazolyl) -phenyl-N-methylnitrone (69% yield).

Next, tire performance tests for each of the examples and comparative examples were performed. In the performance test, the following evaluation of low exothermic property and the evaluation of cut resistance, chipping resistance, and wear resistance were evaluated as follows.
<Evaluation of low heat generation>
A drum system with a speed and step load condition of 10 km / h was implemented, the temperature at a position at a constant depth of the tread was measured, and each example was displayed as an index, with Comparative Example 1 as a control value (control) 100. It shows that it is excellent in low exothermic property, so that the value of an index | exponent is large.
<Evaluation of cut / chipping resistance / wear resistance>
The tread rubber in the tire after running for 2000 hours was observed, the number of cuts, the depth, and the number of chippings were measured, and each example was indexed and displayed with Comparative Example 1 as a control value (control) 100. The larger the index value, the better the cutting, chipping and wear resistance.

Table 1 shows the evaluation results of low heat build-up and cut / chipping / wear resistance.
When Example 1 is compared with the results of Comparative Example 1, it can be seen that the example is extremely excellent in low heat build-up. Further, when the results of Example 3 and Comparative Example 2 are compared, it can be seen that the example is excellent in low heat generation, cut / chipping property / wear resistance. Further, when the results of Example 4 and Comparative Examples 3 and 5 are compared, the example is excellent in low heat generation, cut / chipping property and wear resistance. Further, when the results of Examples 5 and 6 using SBR and Comparative Example 4 are compared, the Examples have a high index value, excellent low heat build-up, and cut, chipping and wear resistance are maintained.

  The rubber composition of the present invention and the pneumatic tire using the rubber composition are excellent in low heat generation, cut, chipping and wear resistance. Therefore, when it is used for a tire tread or the like, a heavy load tire or off-road is used. Since it can be used suitably for a tire, industrial utility value is high.

Claims (10)

  Carbon fiber is blended with 100 parts by mass of the rubber component and 0.1 to 50 parts by mass of a compound having a part Q containing dipolar nitrogen and 4 to 6 nitrogen-containing heterocyclic parts B containing oxygen or sulfur. A rubber composition comprising:   The dipolar nitrogen portion is selected from at least one of A1-C (A2) = N (A3) → O, A1-C≡N → O, and A1-C≡N → N-A4, and the A1 -A4 is hydrogen which may be different from each other, or a group having 20 or less carbon atoms or a linking chain that links the B, and the compound is bonded to at least one of A1 to A4. The rubber composition according to 1.   A1 to A4 of the above compound are hydrogen, an alkyl group having 1 to 20 carbon atoms, and an aryl group having 6 to 20 carbon atoms (however, the aromatic ring has a nitro group, a cyano group) A chloro group, a bromo group, an acyl group, a carbonylalkyl group, an alkyl group, and an alkoxyl group), or a connecting chain thereof. Rubber composition.   The rubber composition according to claim 1, wherein the nitrogen-containing heterocycle of the B moiety is oxazoline or thiazoline.   The above compounds are 4- (2-oxazolyl) -phenyl-N-methyl-nitrone, 4- (2-thiazolyl) -phenyl-N-methyl-nitrone, 4- (2-oxazolyl) -phenyl-N-phenyl. -Nitrone, 4- (2-thiazolyl) -phenyl-N-phenyl-nitrone, phenyl-N-4- (2-oxazolyl) -phenyl-nitrone, phenyl-N-4- (2-thiazolyl) -phenyl-nitrone 4-tolyl-N-4- (2-oxazolyl) -phenyl-nitrone, 4-tolyl-N-4- (2-thiazolyl) -phenyl-nitrone, 4-methoxyphenyl-N-4- (2-oxazolyl) ) -Phenyl-nitrone, 4-methoxyphenyl-N-4- (2-thiazolyl) -phenyl-nitrone, 4- (2-oxazolyl) -phenyl-nitrileoxy 4- (2-thiazolyl) -phenyl-nitrile oxide, 4- (2-oxazolyl) -phenyl-N-methyl-nitrileimine, 4- (2-thiazolyl) -phenyl-N-methyl-nitrileimine, 4- (2-thiazolyl) -phenyl-nitrile oxide, 4- (2-oxazolyl) -phenyl-N-phenyl-nitrileimine, 4- (2-thiazolyl) -phenyl-N-phenyl-nitrileimine, phenyl-N-4 The rubber composition according to claim 4, comprising at least one of-(2-oxazolyl) -phenyl-nitrileimine and phenyl-N-4- (2-thiazolyl) -phenyl-nitrileimine.   The rubber composition according to claim 1, wherein the carbon fiber is a vapor grown carbon fiber.   2. The rubber composition according to claim 1, wherein the carbon fiber is blended in an amount of 1 to 50 parts by mass per 100 parts by mass of the rubber component.   A pneumatic tire using the rubber composition according to any one of claims 1 to 7.   The pneumatic tire according to claim 8, wherein the pneumatic tire is a heavy duty pneumatic tire.   The pneumatic tire according to claim 8, wherein the pneumatic tire is an off-road tire.