JP2000211313A - Rubber composite and pneumatic tire using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase abrasion resistance while ensuring low heat characteristics, by adding to a rubber component a specific quantity of carbon black having equal to or greater than predetermined values of nitrogen absorbing specific surface area and dibutyl phthalate oil absorption, a specific formula of aromatic polycarboxylic derivative, and specific type of hydrazide compound, respectively. SOLUTION: To approximately 100 wt. parts of rubber component composed of natural rubber and/or diene-based synthetic rubber is added 42-65 wt. parts of carbon black having 120 m2/g or more of nitrogen absorbing specific surface area and 110 ml/100 g or more of dibutyl phthalate oil absorption, 0.2-3.0 wt. parts of at least one from a group of aromatic polycarboxylic derivatives expressed with expression I, and 0.2-2.0 wt. parts of at least one from a group of hydrazide compounds expressed with expression II or formula III. The aromatic polycarboxylic derivative expressed with expression I acts as a reactive plasticizer. By using the above carbon black, both an increase in abrasion resistance and restriction of heat build-up are achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition capable of improving abrasion resistance without sacrificing low heat build-up, workability and other rubber properties, and a rubber composition for a tire member. The present invention relates to a pneumatic tire capable of realizing both heat resistance for trucks and buses and tire life by using the tire.

[0002]

2. Description of the Related Art Conventionally, from the standpoint of lowering the floor to meet the needs for increasing the loading capacity of trucks and improving the ease of getting on and off buses,
Flat and small diameter pneumatic tires for trucks and buses (TB, the same applies hereinafter) are required. Such flattening also has the advantage of reducing the number of double wheels used to one, and therefore needs are high in terms of maintenance reduction such as internal pressure management.

[0003] However, such flattening results in an increase in the input to each member forming the tire. Also in the tread rubber, the self-heating amount of the tread rubber portion increases in inverse proportion to the decrease in the aspect ratio of the pneumatic tire for TB due to an increase in input and an increase in the number of revolutions due to a reduction in diameter. Accordingly, the flattened TB tread rubber must be reduced in volume to reduce heat or to reduce the self-heating of the rubber itself.

[0004] When the volume of the tread rubber is reduced, the amount of the tread rubber itself is reduced, which naturally leads to a decrease in the life of the tire. In addition, when the self-heating of the tread rubber itself is reduced, the tread rubber is generally used. In the compounding, heat generation suppression and wear resistance and tear resistance (breaking characteristics) are contrary, so even if the volume is secured by the compounding that suppresses the self-heating of rubber, it is not easy to secure the specified tire life. .

[0005] In order to achieve both low heat build-up and abrasion resistance, a flat pneumatic tire at present uses a rubber composition in which a high-structure carbon black is blended with a NR / BR mixed polymer. Has been addressing this problem.

However, according to the current production technology, when a large amount of high-structure SAF-grade carbon black is blended with the rubber component, the productivity is greatly reduced, and from the viewpoint of providing an inexpensive and stable product. , 50
There is a problem that the limit is about parts by weight. Further, at present, the flattening rate (aspect ratio) can be controlled up to 60% by increasing the amount of carbon black, but flattening is further progressing, and high abrasion resistance capable of coping with the one exceeding 60% is achieved. There is a need for a rubber composition having the same, particularly a rubber composition for a tire tread.

On the other hand, JP-A-4-20579 discloses that
Disclosed is a carbon black dispersant for rubber comprising an ester of an unsaturated fatty acid having 8 to 24 carbon atoms or an ester of an unsaturated alcohol having 8 to 24 carbon atoms. Comparative Example 16 discloses a phthalic acid monoester (phthalic anhydride). An example using an acid and stearyl alcohol) is disclosed. However, this phthalic acid monoester is a comparative example and has a low effect of dispersing carbon black, and differs from the present invention in the composition of each component and clearly has a different technical idea.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and aims to solve the problem.
While ensuring low heat generation, without sacrificing workability and other performance, by providing a rubber composition that improves abrasion resistance and by using this rubber composition in a tire member, particularly a tread portion, An object of the present invention is to provide a pneumatic tire that can achieve both heat resistance and tire life for TB and the like without lowering workability and productivity.

[0009]

The inventors of the present invention have conducted intensive studies on the above-mentioned conventional problems. As a result, the wear resistance is improved by increasing the filling amount of carbon black having a high structure, and the productivity is reduced by increasing the carbon black. Can be compensated for by the compounding of a specific compound, and similarly, the decrease in tear resistance due to an increase in carbon black can be suppressed by the compounding of the specific compound, that is, the colloidal properties and the compounding amount of carbon black, each of the above specific compounds By appropriately adjusting each combination such as the compounding amount of the rubber composition, the above rubber composition and the pneumatic tire using the same were successfully obtained, and the present invention was completed. That is,
The present invention resides in the following (1) to (6). (1) With respect to 100 parts by weight of a rubber component composed of natural rubber and / or a diene-based synthetic rubber, a nitrogen adsorption specific surface area (N ₂ S
A) From 42 to 65 parts by weight of carbon black having an oil absorption of 120 m ² / g or more and a dibutyl phthalate oil absorption (DBP) of 110 ml / 100 g or more, an aromatic polycarboxylic acid derivative represented by the following general formula (I) At least one selected from 0.2 to 3.0 parts by weight and at least one hydrazide compound represented by the following general formula (II) or (III)
A rubber composition comprising 0.2 to 2.0 parts by weight of a seed.

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Embedded image (2) The aromatic polycarboxylic acid derivative represented by the general formula (I) is at least one selected from phthalic acid, trimellitic acid, pyromellitic acid or anhydride thereof (1). The rubber composition as described in the above. (3) The rubber components are polybutadiene rubber (BR), natural rubber (NR) and solution-polymerized styrene-butadiene rubber (So
1-SBR), and BR in 100 parts by weight of the rubber component
10-60 parts by weight, NR40-90 parts by weight and Sol-
The rubber composition according to the above (1) or (2), comprising 0 to 50 parts by weight of SBR. (4) A pneumatic tire using the rubber composition according to any one of the above (1) to (3) for a tire member. (5) A pneumatic tire using the rubber composition according to any one of (1) to (4) above in a tire tread portion. (6) The pneumatic tire has an aspect ratio of 70% or less.
The pneumatic tire according to (4) or (5).

[0010]

Embodiments of the present invention will be described below in detail. The rubber composition of the present invention contains natural rubber and / or
Alternatively, the nitrogen adsorption specific surface area (N ₂ SA) is 120 m ² / g or more and the dibutyl phthalate oil absorption (DBP) is 110 with respect to 100 parts by weight of a rubber component composed of a diene-based synthetic rubber.
42-65 parts by weight of carbon black of at least 100 ml / 100 g, and at least one selected from the group consisting of aromatic polycarboxylic acid derivatives represented by the following general formula (I).
0 parts by weight, and 0.2 to 2.0 parts by weight of at least one hydrazide compound represented by the following general formula (II) or (III).

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The carbon black used in the present invention has an N ₂ SA of 120 to improve wear resistance and suppress heat generation.
m ² / g or more and DBP 110 ml / 100 g or more are required. When each value of the above N ₂ SA · DBP is less than the above value, a sufficient improvement in wear resistance cannot be obtained and a filling amount is increased, so that the heat resistance is reduced. It is difficult to apply, which is not preferable. More preferably, the N ₂ SA is at least 130 m ² / g,
BP of 115 ml / 100 g or more is desirable. Also,
Since the compounding amount is intended to improve the wear resistance, the rubber component 1
42 parts by weight to 65 parts by weight, preferably 50 parts by weight to 60 parts by weight with respect to 00 parts by weight. If the compounding amount is less than 42 parts by weight, the abrasion resistance is reduced, and the intended rubber composition cannot be obtained. If the compounding amount is more than 65 parts by weight, the productivity due to the aromatic polycarboxylic acid derivative described below is obtained. It is not preferable because the productivity and the tear resistance decrease more than the decrease inhibition effect and the tear resistance reduction effect of the hydrazide compound described later.

The aromatic polycarboxylic acid derivative represented by the above general formula (I) used in the present invention acts as a reactive plasticizer to increase carbon black while maintaining abrasion resistance and fracture resistance. Unvulcanized viscosity (Mooney viscosity:
ML _{1 + 4} ) can be prevented from increasing, and a decrease in workability and productivity can be suppressed. Many of the conventional workability improvers and plasticizers (typically, process oils)
Although it is possible to suppress the rise of ML _{1 + 4,} the wear resistance and heat resistance are remarkably reduced, and it is difficult to use as a flat TBR tread. This is considered to be due to the fact that such a plasticizer remains in the rubber composition as it is even after vulcanization and is released in the rubber without being involved in any reinforcement. On the other hand, in the present invention, the aromatic polycarboxylic acid derivative represented by the above general formula (I) has the same plasticity improving effect as oil when unvulcanized, but also contains It reacts with polymer and does not release unlike oil, so there are great merits in terms of abrasion resistance and low heat generation.

As the aromatic polycarboxylic acid derivative represented by the general formula (I), for example, a derivative of phthalic acid, trimellitic acid, pyromellitic acid or an anhydride thereof is preferable. In the aromatic polycarboxylic acid derivative represented by the general formula (I), R ¹ has ¹ carbon atom.
And X is preferably O or (R ⁴ O) q, and particularly preferably X is O. Further, the aromatic polycarboxylic acid derivative represented by the general formula (I) is a derivative of any one of phthalic acid, trimellitic acid, pyromellitic acid or an anhydride thereof, and (I) wherein R ¹ has ¹ carbon atom
And X is preferably O or (R ⁴ O) q, and particularly preferably X is O. Specific examples include monostearyl phthalate, monodecyl phthalate, monooctylamide phthalate, monodecyl trimellitate, monostearyl trimellitate, monostearyl pyromellitate, and distearyl pyromellitate. Among these, monoalkyl phthalate is preferred from the viewpoints of the effects of reducing the amount of gel, plasticizing effect and low cost, which are the objective effects, and more preferably monostearyl phthalate (PME).

The amount of the aromatic polycarboxylic acid derivative represented by the general formula (I) is 0.2 to 3.0 parts by weight, preferably 0.5 to 3.0 parts by weight, based on 100 parts by weight of the rubber component.
2.0 parts by weight. If the compounding amount is less than 0.2 parts by weight, a sufficient plasticity improving effect is not exhibited, and productivity and
It is not preferable because the workability is reduced. Also,
If the compounding amount exceeds 3.0 parts by weight, the reaction with the polymer reaches saturation, and some are left free,
It is not preferable because abrasion resistance and heat resistance are reduced. By using the carbon black in the range of 0.5 to 3.0 parts by weight, even if the carbon black is added in an amount of 5 to 10 parts by weight as compared with the conventional compounding amount, the viscosity at the time of unvulcanization is increased. , And the same workability and productivity as before increasing the blending can be ensured.

Among the hydrazide compounds represented by the above general formula (II), preferably, in the general formula (II), A is an aromatic ring, and Y is the following formula:

Embedded image At least one selected from a hydroxy group and an amino group, wherein R _{5 to} R ₈ are hydrogen and a linear or branched alkyl group having 1 to 18 carbon atoms, a cycloalkyl group, an aromatic ring (each of which is the same); However, it is desirable that the at least one selected from the above (which may be different) is used. Specific hydrazide compound represented by the formula (II), for example, N ^2, N ⁴ - di (1-methylethylidene) isophthalic acid dihydrazide, N ^2, N ⁴ - di (1-methyl-propylidene) Isophthalic dihydrazide, N ² , N ⁴ -di (1,3-dimethylbutylidene) isophthalic dihydrazide, N ′-(1-methylethylidene) salicylic hydrazide, N ′-(1-methylpropylidene) salicylic hydrazide, N '-(1-Methylbutylidene) salicylic acid hydrazide, N'-(1,3-dimethylbutylidene)
Salicylic acid hydrazide, N '-(2-furylmethylene)
And salicylic acid hydrazide.
Specific hydrazide compounds represented by I) include:
For example, 1-hydroxy-N '-(1-methylethylidene) -2-naphthoic acid hydrazide, 1-hydroxy-
N '-(1-methylpropylidene) -2-naphthoic acid hydrazide, 1-hydroxy-N'-(1-methylbutylidene) -2-naphthoic acid hydrazide, 1-hydroxy-
N '-(1,3-dimethylbutylidene) -2-naphthoic acid hydrazide, 1-hydroxy-N'-(2-furylmethylene) -2-naphthoic acid hydrazide, 3-hydroxy-N '-(1-methyl (Ethylidene) -2-naphthoic acid hydrazide, 3-hydroxy-N '-(1-methylpropylidene) -2-naphthoic acid hydrazide, 3-hydroxy-N'-(1-methylbutylidene) -2-naphthoic acid hydrazide 3-hydroxy-N '-(1,3-dimethylbutylidene) -2-naphthoic acid hydrazide, 3-hydroxy-N'-(2-furylmethylene) -2-naphthoic acid hydrazide, 3-hydroxy-N ' -(1,2-diphenylethylidene) -2-naphthoic acid hydrazide and the like. The hydrazide compound represented by the general formula (II) or (III) is a starting material for 3-hydroxy-2-
It can be easily synthesized by heating and reacting naphthoic acid hydrazide and the like with acetone, methyl isobutyl ketone and the like.

The preferred hydrazide compounds represented by the above general formulas (II) and (III) are 3-hydroxy-N 'from the viewpoint of easiness of synthesis, cost and low heat generation.
-(1,3-dimethylbutylidene) -2-naphthoic acid hydrazide, 3-hydroxy-N '-(1,3-diphenylethylidene) -2-naphthoic acid hydrazide and 3-hydroxy-N'-(1-methyl (Ethylidene) -2-naphthoic acid hydrazide hydrazide, more preferably
3-hydroxy-N '-(1,3-diphenylethylidene) -2-naphthoic acid hydrazide [BMH] is desirable.

In particular, Eb in the middle to late stage of aging during running
In order to improve the hydrazide compound represented by the general formula (II) or (III), 0.2 to 2.0 parts by weight, preferably 0.5 to 1.
It is desirable to mix in 5 parts by weight. The above general formula (II)
Alternatively, the hydrazide compound represented by (III) has an anti-aging effect of greatly improving Eb when a tread rubber compound having a high structure, for example, a SAF grade is used. When the amount is less than 0.2 parts by weight, the effect of preventing aging is insufficient, and when it exceeds 2.0 parts by weight, the effect is saturated and it is not economical. When the amount is in the range of 1.5 to 2.0 parts by weight, saturation is not achieved, but the manifestation of the effect is slowed. Therefore, the use of 0.5 to 1.5 parts by weight is most preferable. Furthermore, even from the type and blending amount of carbon black,
It is necessary to add 0.2 parts by weight or more, preferably 0.5 part by weight.

The rubber component used in the present invention is a natural rubber (N
R) and / or a diene-based synthetic rubber, preferably polybutadiene rubber (BR), natural rubber (NR) and solution-polymerized styrene-butadiene rubber (Sol-SB)
R), and BR10 in 100 parts by weight of the rubber component.
60 parts by weight, 40 to 90 parts by weight of NR and Sol-SBR
Those prepared at a ratio of 0 to 50 parts by weight are preferred. B
R exhibits an effect of improving wear resistance particularly under conditions of high wear severity. On the other hand, in the case where the use of low stability is mainly used, in the range of 0 to 50 parts by weight, terminal modification and control of molecular weight distribution become possible, and a merit is exhibited in heat resistance. Also, solution polymerization SBR (Sol-SBR) can be applied. Use of more than 50 parts by weight of sol-SBR is not preferable because it is difficult to ensure heat resistance.

In the present invention, in addition to the above, addition of vulcanizing agents, vulcanization accelerators, antioxidants, zinc white (ZnO), stearic acid, waxes, antioxidants and the like which are usually used in the rubber industry. An agent can also be compounded.

In the present invention, the rubber component, carbon black, the aromatic polycarboxylic acid derivative represented by the general formula (I) and the hydrazide compound represented by the general formula (II) or (III) are rolled. The rubber composition can be prepared by kneading using a kneading machine such as an internal mixer.

In the rubber composition thus constituted, the amount of Eb / tea resistance improved by the addition of the hydrazide compound represented by the above general formula (II) or (III) is transferred to the heat resistance. It can be divided. In general,
Increasing the BR ratio in the polymer component achieves both improvement in abrasion resistance and heat resistance, while decreasing Eb / tea resistance.
Therefore, the BR increase has been used only in the conditions of use on a good road or in a pattern with a small edge component with improved tear resistance (there is a corresponding decrease in WET resistance). The compounding of the hydrazide compound represented by the general formula (II) or (III) can eliminate the disadvantage of decreasing the Eb by increasing BR without affecting other performances.

The rubber composition of the present invention comprises the above rubber component, carbon black, the aromatic polycarboxylic acid derivative represented by the above general formula (I) and the above general formula (II) or (III)
By appropriately optimizing the combination of the hydrazide compound and the like represented by the formula, it is possible to improve the abrasion resistance without sacrificing workability and other performances while securing low heat generation. Therefore, a product suitable for a tire tread is provided.

The pneumatic tire of the present invention is characterized in that the above rubber composition is used for a tire member.
Generally, a pneumatic tire includes a tread portion, a pair of side portions connected on both sides of the tread portion, and a pair of bead portions formed on an inner periphery of the side portion, respectively. And a carcass ply surrounding the carcass ply and a belt layer buried inside the tread portion and reinforced.

[0024] The pneumatic tire of the present invention uses the rubber composition having the above characteristics in accordance with the tire member having the above-mentioned tire structure. However, for example, tread rubber, belt coating rubber, carcass ply rubber,
If it is a bead filler rubber, a rubber chafer, or a sidewall rubber, the above rubber composition will be used according to these tire rubber member applications. By using the rubber composition having the above characteristics in a tire member, particularly in a tread portion, it becomes possible to achieve both heat resistance and tire life without lowering workability and productivity.

The present invention is suitable for pneumatic tires having an aspect ratio (aspect ratio) of strictly 70% or less, preferably 60% or less, and particularly for pneumatic tires for TB, for which low heat generation is required. In the production of the pneumatic tire of the present invention, first, the rubber composition obtained above is applied to each tire member according to the various types of tire members to be applied. These members are formed into green tires on a drum and then vulcanized by a vulcanizer to obtain a desired pneumatic tire.

[0026]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Examples 1 to 4 and Comparative Examples 1 to 9] Rubber compositions were prepared according to the composition shown in Table 1 below. Using the obtained rubber compositions of Examples 1 to 5 and Comparative Examples 1 to 9,
The tread rubber properties (Mooney viscosity, Eb after aging) and tire performance (tread rubber wear resistance, tire life, heat resistance and tear resistance) were evaluated by the following evaluation methods.

[Evaluation Method for Physical Properties of Tread Rubber] (Evaluation Method for Mooney Viscosity: ML _{1 + 4} ) JIS K63
3. 00 (unvulcanized rubber physical test method) Was measured at 130 ° C. using the method specified in, and was taken as a value after 5 minutes. The Mooney viscosity value that can be a target rubber composition for improving workability is 105 or less. (Evaluation method of Eb after aging) Aged vulcanized rubber samples were placed in an oven at 100 ° C for 24 hours under an atmosphere of 100 ° C,
The breaking elongation at the time of the tensile breaking test in IS-3 was measured. The Eb value after aging that can be the target rubber composition is
400 or more.

[Evaluation Method of Tire Performance] (Evaluation Method of Tread Rubber Wear Resistance) Each of the rubber compositions obtained above was used for tread rubber to obtain 435/50 R.
A 19.5 test tire was manufactured and installed on a bus.
The amount of wear at the time of traveling m was controlled in Comparative Example 2 (10
0), indexed and evaluated. The higher the value, the better the wear resistance.

(Evaluation method of tire life) From the value calculated by the above-mentioned actual wear resistance index × tread rubber volume (index when 11R22.5 is set to 100), the rejection limit when the tire is actually used ( Life) was estimated, and Comparative Example 2 was compared as a control (100).
It was indexed and evaluated.

[Method of Evaluating Heat Resistance] JIS D 423
It was evaluated by a drum test based on 0. The durability calculated from the QC drum was controlled in Comparative Example 2 (10
0), indexed and evaluated.

[Evaluation method of tear resistance] The tire was mounted on a bus, and the tire was evaluated at the time of running 30,000 km. The (maximum) length of the rib tear and cybtea that occurred during the above-mentioned actual driving ×
The value calculated from the sum of the areas calculated by the (maximum) depth was compared with Comparative Example 2 as a control (100), and evaluated by indexing.

[0033]

[Table 1]

(Consideration of Table 1) As is evident from the results of Table 1, the tread rubber properties of Examples 1-4, which fall within the scope of the present invention, are higher than those of Comparative Examples 1-9, which fall outside the scope of the present invention. It was found to be excellent in [Mooney viscosity, Eb after aging] and excellent in tire performance (tread rubber wear resistance, tire life, heat generation resistance and tear resistance). Example 1
4, Examples 1 and 2 show that the rubber components NR and B
R is set to 70/30, and the third embodiment has the NR and BR of 50/30.
In Example 4, the NR and the solution polymerization SBR and BR were set to 50/20/30. Based on 100 parts by weight of these rubber components, N ₂ SA was 120 m ² / g or more, and DBP11 was used.
0 ml / 100 g or more of carbon black, monostearyl phthalate (PME) selected from the aromatic polycarboxylic acid derivatives represented by the general formula (I), and carbon black represented by the general formula (II) or (III) 3-hydroxy-N '-(1,3-diphenylethylidene) -2-naphthoic acid hydrazide [BM selected from the hydrazide compounds represented
H] and a specific amount, respectively, to provide excellent tread rubber physical properties (Mooney viscosity, Eb after aging) and excellent tire performance (tread rubber wear resistance, tire life, heat resistance and tear resistance). It turns out.

Looking specifically at Comparative Examples 1 to 9, Comparative Example 1
To 3 are at least one kind of the aromatic polycarboxylic acid derivative represented by the general formula (I);
Comparative Example 1 is a normal rubber compounding of a non-flat tire, and Comparative Example 2 is a normal rubber compounding (control) of a flat tire, in which at least one hydrazide compound represented by I) is not compounded. In this case, it can be seen that the tire life is inferior. Comparative Example 3 had N ₂ SA of 135 m ² / g and D
In this case, carbon black of BP 124 ml / 100 g was used. In this case, the Mooney viscosity was high and the workability was poor. In Comparative Examples 4 to 9, the rubber component, which is an essential component of the present invention, carbon black, at least one aromatic polycarboxylic acid derivative represented by the general formula (I), and the general formula (II) Or a case where at least one of the hydrazide compounds represented by (III) is blended. Comparative Example 4 was a case where the hydrazide compound was 3.0 parts by weight (> 2.0 parts by weight). In this case, it can be seen that the tear resistance was poor. In Comparative Example 5, 4.0 parts by weight (> 3.0 parts) of the aromatic polycarboxylic acid derivative hydrazide compound was used.
Parts by weight), in this case tire life,
It turns out that heat resistance is inferior. Comparative Example 6 is N ₂ SA11
8m ² / g (<120), DBP100ml / 100g
(<110), in which case the tire life and heat resistance are inferior. In Comparative Examples 7 to 9, the compounding amount of carbon black was 42 to 65.
In these cases, the Eb after aging, tire life, and heat resistance are inferior.

[0036]

According to the present invention, a rubber composition capable of improving abrasion resistance without sacrificing low heat build-up, workability and other rubber performances, and a tire member comprising the rubber composition In particular, a pneumatic tire capable of realizing both heat resistance and tire life by using the tread portion without lowering workability and productivity is provided.

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Claims (6)

[Claims] 1. A nitrogen component having a nitrogen adsorption specific surface area (N ₂ SA) of at least 120 m ² / g and a dibutyl phthalate oil absorption (DBP) of 110 ml per 100 parts by weight of a rubber component composed of natural rubber and / or diene synthetic rubber. / 100 g or more of 42 to 65 parts by weight of carbon black, and 0.2 to 3.0 parts by weight of at least one selected from aromatic polycarboxylic acid derivatives represented by the following general formula (I): A rubber composition comprising at least one hydrazide compound represented by the general formula (II) or (III) in an amount of 0.2 to 2.0 parts by weight. Embedded image Embedded image Embedded image 2. The aromatic polycarboxylic acid derivative represented by the general formula (I) is at least one selected from phthalic acid, trimellitic acid, pyromellitic acid or anhydride thereof. 2. The rubber composition according to 1. 3. The rubber component is a polybutadiene rubber (B).
R), natural rubber (NR) and solution-polymerized styrene-butadiene rubber (Sol-SBR).
The rubber composition according to claim 1 or 2, comprising 10 to 60 parts by weight of BR, 40 to 90 parts by weight of NR, and 0 to 50 parts by weight of Sol-SBR in 0 parts by weight. 4. A pneumatic tire using the rubber composition according to claim 1 for a tire member. 5. A pneumatic tire using the rubber composition according to any one of claims 1 to 4 for a tire tread. 6. The pneumatic tire according to claim 4, wherein the flatness of the pneumatic tire is 70% or less.