JP2007224076A - 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 excellent low heat build-up properties and good operation efficiency and to provide the pneumatic tire using the rubber composition. <P>SOLUTION: The rubber composition is obtained by compounding at least one kind of rubber component selected from the group consisting of natural rubber and synthetic rubbers with a compound having a moiety Q containing one or more dipolar nitrogens represented by A1-C(A2)=N(A3)→O, A1-C≡N→O and A1-C≡N→N-A4 (wherein, A1 to A4 are each a hydrogen or a ≤20C group or a linking group to B) and a moiety B containing a 4- to a 6-membered nitrogen-containing heterocycle containing an oxygen or a sulfur and simultaneously including a 3-30C saturated or unsaturated fatty acid metal salt. The pneumatic tire is prepared by using the rubber composition in a tire member. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a rubber composition and a pneumatic tire using the rubber composition. More specifically, the present invention relates to a demanding heavy load pneumatic tire and an off tire which improve heat resistance in a tread and improve wear resistance. The present invention relates to a rubber composition suitable for use in a road tire and a pneumatic tire using the same.

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 are required to have further improved heat generation. Further, for off-road tires, the tread rubber is required to have low hysteresis loss (low rolling resistance) and wear resistance. In general, in order to improve low heat generation, it is preferable to suppress the deformation of the tread rubber and lower tan δ in a high temperature range.
Particularly for off-road tires, in order to improve wear resistance, synthetic rubber components such as SBR have been used in the tread rubber composition to improve cutability and fatigue resistance. In order to improve low hysteresis loss and low heat generation, it has also been proposed to add a modified conjugated diene polymer such as a modified styrene-butadiene copolymer (see, for example, Patent Document 1). . However, if the amount of the modified conjugated diene polymer is excessively increased, the wear resistance cannot be sufficiently improved, and the fracture resistance is deteriorated.

Conventionally, silica is known as a filler for improving low heat build-up (for example, Patent Documents 2 to 9). However, in order to improve the dispersion of the silica in the rubber, it is necessary to lengthen the kneading time, and the viscosity increases and the workability deteriorates. Furthermore, low heat build-up and a decrease in elastic modulus occur due to reversion after long-term vulcanization, making it difficult to blend a large amount of silica.
Accordingly, there is a need for a rubber composition that combines a synthetic rubber such as SBR and its modified rubber and improves it to some extent, and further improves workability and is excellent in low heat generation.
Japanese Patent Laid-Open No. 9-316132 JP-A-3-252431 JP-A-6-248116 JP-A-7-70369 JP-A-7-188466 JP-A-7-196850 JP-A-8-225684 JP-A-8-245838 JP-A-8-337687

  In view of the above problems, the present invention provides a rubber composition that achieves both wear resistance and low heat buildup suitable as a heavy-duty pneumatic tire and off-road tire without impairing workability and productivity during tire production. It is in providing a thing and a pneumatic tire using the same.

In order to solve the above-mentioned problems, the present inventors include a part containing dipolar nitrogen that exhibits reactivity to a double bond site such as a rubber component in a rubber composition containing natural rubber and / or synthetic rubber, And carbon black, a compound containing a nitrogen-containing heterocyclic ring containing oxygen or sulfur that shows reactivity with a filler such as silica filler, and a fatty acid metal salt when blended into the composition, carbon black, It has been found that the dispersibility of silica is enhanced, the low heat build-up of the rubber composition is further improved, and the increase in viscosity due to gelation during the kneading operation of the rubber composition is suppressed, so that the workability is not deteriorated. This has led to the present invention.
That is, the present invention is characterized by the following means or configurations.

(1) A part Q containing dipolar nitrogen and 4-6 nitrogen-containing heterocycles containing oxygen or sulfur with respect to 100 parts by mass of at least one rubber component selected from the group consisting of natural rubber and synthetic rubber The rubber composition characterized by including 0.1-30 mass parts of compound D which has the part B containing this, and 0.5-20 mass parts of fatty-acid metal salts simultaneously.

(2) The dipolar nitrogen portion Q of the compound D is at least one of A1-C (A2) = N (A3) → O, A1-C≡N → O, and A1-C≡N → N-A4. Wherein 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 at least one of A1 to A4 and the B is The rubber composition according to the above (1), which is a linked compound.
(3) A1 to A4 of the compound D are hydrogen, an alkyl group having 1 to 20 carbon atoms, and an aryl group having 6 to 20 carbon atoms (provided that 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 heterocyclic ring at the B portion of the compound D is oxazoline or thiazoline.

(5) Compound D 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-oxazoly ) -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- (2-oxazolyl) -phenyl-nitrileimine, phenyl-N-4- (2 The rubber composition as described in (4) above, which is at least one selected from -thiazolyl) -phenyl-nitrileimine.

(6) The rubber composition according to any one of (1) to (5), wherein the fatty acid metal salt is a linear or branched saturated or unsaturated fatty acid metal salt having 3 to 30 carbon atoms.
(7) The rubber composition according to (6), wherein the fatty acid metal salt is at least one metal salt selected from Zn, Na, Mg, Ca, Co, Ni, Ba, Fe, Al, Cu, and Mn. object.
(8) A pneumatic tire using the rubber composition according to any one of (1) to (7) as a tire member.
(9) The pneumatic tire according to (8), wherein the pneumatic tire is a heavy duty pneumatic tire.
(10) The pneumatic tire according to (9), wherein the heavy-duty pneumatic tire is an off-road tire.

According to the above means, the wear resistance and low heat build-up can be improved, the tire can be improved, and the workability is not deteriorated due to the increase in viscosity.
Moreover, when said compound D is added, the reaction of following reaction formula (1)-(3) will arise with the double bond part (P) in a rubber component, and Q part of a compound.

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

  By such an action of the compound D, carbon black and silica filler are sufficiently diffused in the rubber composition. As a result, in addition to wear resistance, the low heat build-up and low hysteresis loss of the tread rubber are further improved, and the use performance as a heavy duty pneumatic tire and off-road tire is further enhanced.

Hereinafter, embodiments of the present invention will be described in detail.
The rubber component of the rubber composition of the present invention is at least one selected from natural rubber and diene synthetic rubber. Examples of the diene synthetic rubber include polyisoprene synthetic rubber (IR) and polybutadiene rubber (BR). Styrene-butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and the like. The rubber component natural rubber and diene synthetic rubber may be used alone or in combination of two or more.

  In the rubber composition, carbon black is blended with the rubber component. The blending amount is in the range of 30 to 70 parts by mass, preferably 50 to 60 parts by mass with respect to 100 parts by mass of the rubber component. When the amount of carbon black decreases, the wear resistance tends to decrease. In addition, when the amount of carbon black is increased, the low heat build-up of the vulcanized rubber composition is reduced, and the viscosity is increased, resulting in poor workability.

  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 desirably activates its surface by utilizing oil absorption.

  In the rubber composition of the present invention, the compound D having a part Q containing a 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 is reduced to 0.0. It mix | blends 1-30 mass parts, It is characterized by the above-mentioned.

  Compound D 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 compound D has a B portion, A1 to A4 can be a connecting chain that connects the B portions. 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.

  Specific groups or connecting chains of A1 to A4 of the above compound D include hydrogen, an alkyl group having 1 to 20 carbon atoms, and an aryl group having 6 to 20 carbon atoms (provided that 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 group selected from them The connecting chain. 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 compound D is composed of a nitrogen-containing heterocycle having oxygen or sulfur such as oxetine, thiozetin, oxazoline, thiazoline, tetrahydrooxazine and tetrahydrothioxazine. In particular, it consists of a 4-6 membered nitrogen-containing heterocyclic ring represented by the following structural formulas (I) to (III) (wherein X is oxygen: O or sulfur: S). Of these, oxazoline and thiazoline 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 portion undergoes the binding reaction of the above reaction formulas (4) to (15), and carbon black and silica can be uniformly incorporated into the polymer of the rubber component.

  Specific examples of the compound D 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). The structural formula is specifically listed.

The method for producing the above compound D can be produced without undue experimentation. For example, regarding 4OPMN and 4OPPN, the manufacturing method can be shown in the examples described later.
Further, other compounds D can also be produced by typical production methods by appropriately selecting other starting materials and intermediate materials.

  Said compound D is contained in 0.1-30 mass parts with respect to 100 mass parts of rubber components. Preferably it is the range of 0.1-5 mass parts, More preferably, it is the range of 0.5-2.0 mass parts. If the compounding amount of compound D is less than 0.1, the effects of low heat generation and low hysteresis loss are not sufficient. In addition, if it exceeds 30 parts by mass, an effect commensurate with it cannot be expected, which is preferable from the viewpoint of cost, and when the rubber component is natural rubber, a significant increase in viscosity occurs due to gelation, from the viewpoint of workability. Is also not preferred.

Next, the rubber composition of the present invention contains a fatty acid metal salt as a processing aid. The fatty acid is a saturated or unsaturated fatty acid having 3 to 30 carbon atoms, and examples thereof include lauric acid, palmitic acid, stearic acid, and oleic acid. The metal that forms these fatty acid salts is preferably at least one selected from Zn, Na, Mg, Ca, Co, Ni, Ba, Fe, Al, Cu, and Mn. In particular, Zn is preferable.
The fatty acid metal salts may be used alone or in combination of two or more.

  The said fatty acid metal salt is added in 0.5-20 mass parts with respect to 100 mass parts of rubber components. Preferably it is the range of 0.5-10 mass parts. The fatty acid metal salt has a great effect on the dispersion of carbon black, and this dispersibility improving effect makes it possible to reduce the viscosity and suppress the increase in viscosity.

  The rubber composition containing the above compound D and the fatty acid metal salt can reduce the amount of the natural rubber polymer gel without reducing the molecular weight of the natural rubber molecule, and increase the slip between the rubber molecules. While improving workability | operativity of a shaping | molding, the physical-property fall of an unvulcanized or vulcanized rubber composition is suppressed. In addition, when the rubber component does not contain natural rubber, the molding workability is improved by increasing the slip between the rubber molecules, and in this case as well, there is no decrease in the molecular weight of the rubber. The physical properties of the vulcanized rubber composition do not deteriorate. In any case, in the present invention, excellent rubber processability can be obtained without adversely affecting the physical properties of the rubber.

  The rubber composition of the present invention can contain various components usually used in the rubber industry in addition to the rubber component, carbon black, compound D, and fatty acid metal salt. For example, fillers (eg, reinforcing fillers such as silica; and inorganic fillers such as calcium carbonate and calcium carbonate); vulcanization accelerators; anti-aging agents; zinc oxide; stearic acid; softeners; An additive such as an agent can be mentioned. Examples of the vulcanization accelerator include thiazole vulcanization accelerators such as MBTS (dibenzothiazyl disulfide) and CZ (N-cyclohexyl-2-benzothiazylsulfenamide); TT (tetramethylthiuram sulfide) and the like. Examples include thiuram vulcanization accelerators; and guanidine vulcanization accelerators such as DPG (diphenylguanidine).

  The method for preparing the rubber composition of the present invention is not particularly limited, and the rubber composition can be obtained by kneading the rubber component using an ordinary kneader such as a Banbury mixer, a roll, an intensive mixer or the like.

  Said rubber composition is used suitably for the tread rubber and tread base rubber of a pneumatic tire. A pneumatic tire is manufactured by a normal method using the above rubber composition. That is, if necessary, the rubber composition containing various chemicals as described above is extruded into a tread member, for example, at an unvulcanized stage, and pasted and molded by a usual method on a tire molding machine. A green tire is formed. The green tire is heated and pressed in a vulcanizer to obtain a tire. Since the workability of the rubber composition is good, the productivity is excellent.

  Since the tread portion of the tire contributes greatly to wear resistance and low heat generation, the pneumatic tire of the present invention is a heavy-duty pneumatic tire and an off-road pneumatic tire requiring long-term rough road durability. Can be suitably used. In such a pneumatic tire, an inert gas such as air or nitrogen can be used as a gas to be filled.

Examples of the present invention will be described below, but the present invention is not limited to these examples.
(Examples 1-7 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. A tire of 3700R57 was produced and applied to a tread member.

The compounding amount in Table 1 is part by mass, and in each comment,
* 1) # 1500; Emulsion polymerization SBR
* 2) 4OPPN; (4- (2-oxazolyl) -phenyl-N-phenylnitrone)
* 3) 4OPMN; (4- (2-oxazolyl) -phenyl-N-methylnitrone)
* 4) Fatty acid metal salt: Actiplast PP (Rhein Chemi)
* 5) Anti-aging agent 6PPD; N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine * 6) Vulcanization accelerator DPG; 1,3-diphenylguanidine * 7) Vulcanization accelerator CZ; N-cyclohexyl-2-benzothiazylsulfenamide * 8) Vulcanization accelerator MBTS; Dibenzothiazyl disulfide

* 5) 4OPPN and * 6) 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 6.3 g (1 equivalent) of 4- (2-oxazolyl) -benzaldehyde and 3.9 g (1 equivalent) of N-phenyl-hydroxyamine was refluxed in 100 ml of ethanol for 30 minutes and concentrated to a volume of 50 ml. . 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 15.0 g (89 mmol) of 4-formyl-benzoyl chloride in 300 ml of chloroform, a solution obtained by adding 10.9 g (178 mmol) of 2-aminoethanol to 200 ml of chloroform was added dropwise at −10 ° C. . 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.
To 50 ml of concentrated sulfuric acid, 17 g (88 mmol) 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 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 6.3 g (1 equivalent) of 4- (2-oxazolyl) -benzaldehyde and 1.7 g (36 mmol) of N-methyl-hydroxyamine was refluxed in 100 ml of ethanol for 30 minutes and concentrated to a volume of 50 ml. 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, the workability of the rubber composition and the performance test of the tire for each example and each comparative example were performed. The results are shown in Table 1. The workability was measured by Mooney viscosity, and the performance test was evaluated for exothermicity as follows.
<Measurement of Mooney viscosity>
Using MOMONYVISCOMETER SMV201 manufactured by SHIMAZU, the rubber composition sample was heated at 130 ° C. for 1 minute, the rotor was started, and the value after 4 minutes was measured as ML _{1 + 4} . Each example was indicated by an index with Comparative Example 1 as a control value (control) 100. The larger the index value, the lower the viscosity and the better the workability.
Index = (measured viscosity / control viscosity) × 100
<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.

  When only compound D is used from Table 1, the results of Examples 1-2, Comparative Example 2, and Examples 3-4, and Comparative Example 3 are improved, while the low heat build-up is improved. When using both the compound D and the fatty acid metal salt, it can be seen that the workability is almost the same as when no compound is added, while the low exothermicity is remarkably increased. The same can be said when Example 5 is compared with Comparative Example 4 and Examples 6 to 7 are compared with Comparative Example 5.

  Since the rubber composition of the present invention and the pneumatic tire using the rubber composition are excellent in low heat buildup and wear resistance, they can be suitably used for heavy load tires and off-road tires, and have high industrial utility value.

Claims (10)

  A part Q containing dipolar nitrogen and a part containing 4-6 nitrogen-containing heterocycles containing oxygen or sulfur with respect to 100 parts by mass of at least one rubber component selected from the group consisting of natural rubber and synthetic rubber A rubber composition comprising 0.1 to 30 parts by mass of the compound D having B and 0.5 to 20 parts by mass of a fatty acid metal salt at the same time.   The dipolar nitrogen portion Q of the compound D 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 according to claim 1, which is a compound.   A1 to A4 of the compound D are hydrogen, an alkyl group having 1 to 20 carbon atoms, and an aryl group having 6 to 20 carbon atoms (provided that the aromatic ring has a nitro group or 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 heterocyclic ring at the B portion of the compound D is oxazoline or thiazoline.   Compound D 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-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, wherein the rubber composition is one or more selected from-(2-oxazolyl) -phenyl-nitrileimine and phenyl-N-4- (2-thiazolyl) -phenyl-nitrileimine.   The rubber composition according to any one of claims 1 to 5, wherein the fatty acid metal salt is a linear or branched saturated or unsaturated fatty acid metal salt having 3 to 30 carbon atoms.   The rubber composition according to claim 6, wherein the fatty acid metal salt is at least one metal salt selected from Zn, Na, Mg, Ca, Co, Ni, Ba, Fe, Al, Cu, and Mn.   A pneumatic tire using the rubber composition according to any one of claims 1 to 7 as a tire member.   The pneumatic tire according to claim 8, wherein the pneumatic tire is a heavy duty pneumatic tire.   The pneumatic tire according to claim 9, wherein the heavy duty pneumatic tire is an off-road tire.