JP2017002233A - Rubber composition, manufacturing method therefor and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To overcome extreme difficulty to enhance both of low rolling resistance and reinforcement performance of a rubber even by using methods such as blending silica, blending carbon black with a large particle diameter or reducing the blended amount of the carbon black under a condition that it is desired to reduce rolling resistance of a tire with increased environmental concerns recently.SOLUTION: The above-described problem is solved by a rubber composition obtained by mixing 100 pts.mass of diene rubber containing butadiene rubber of 50 pts.mass or more, 20 to 60 pts.mass of carbon black having nitrogen adsorption specific surface area (NSA) of 30 to 150 m/g and a sulfide compound such as 2,2'-bis(benzimidazolyl-2)ethyldisulfide (2EBZ) of 0.1 to 10 mass% based on the carbon black and having mixing temperature when the sulfide compound is mixed of 120°C or less.SELECTED DRAWING: None

Description

  The present invention relates to a rubber composition, a method for producing the same, and a pneumatic tire. Specifically, even if a specific sulfide compound is used, the scorch and processability are not deteriorated, the rolling resistance is low, and The present invention relates to a rubber composition having excellent rubber reinforcing performance, a method for producing the same, and a pneumatic tire.

With the recent increase in environmental awareness, it is desired to reduce the rolling resistance of tires. Conventionally, in order to increase the low rolling resistance, techniques such as blending silica, blending carbon black having a large particle diameter, and reducing the blending amount of carbon black have been used.
However, when silica is blended, there is a problem that it is difficult to achieve both wear resistance and reinforcing performance, and silica is aggregated in rubber, so that simple mixing cannot be performed.
Further, when the particle size of carbon black is increased or the blending amount is reduced, the reinforcing performance for rubber is lowered.
On the other hand, the sidewall of the tire is a portion that easily generates heat due to repeated large deformation during traveling, and has a great influence on the fuel consumption performance of the tire. For this reason, it has been studied to reduce the heat generation or to reduce the thickness of the rubber composition constituting the sidewall portion, but in this case, the reinforcement performance required for the sidewall of the tire is lowered, and the bending fatigue resistance is improved. Durability represented will deteriorate.
Therefore, in the prior art, it has been very difficult to improve both the low rolling resistance and the rubber reinforcing performance.

Patent Document 1 listed below proposes a coupling agent for rubber and carbon black containing a sulfide compound having a specific structure, and the compound has an aromatic condensed heterocyclic ring in the molecule. Is disclosed that a bond having a good rolling resistance is provided when a rubber composition containing the compound is used as a tire raw material. is there.
However, when the sulfide compound is added to the rubber composition, there is a problem that scorch is deteriorated and processability is deteriorated.

JP 2013-23610 A

  Accordingly, an object of the present invention is to provide a rubber composition that does not deteriorate the scorch and workability even when the sulfide compound described in Patent Document 1 is used, has low rolling resistance, and has excellent rubber reinforcing performance. And a manufacturing method thereof and a pneumatic tire.

As a result of extensive research, the present inventor has found that a carbon black having a specific nitrogen adsorption specific surface area (N ₂ SA) and a specific sulfide described in Patent Document 1 are compared with a diene rubber having a specific composition. It was found that the above problems could be solved by blending the compound in a specific amount and mixing the sulfide compound at a specific temperature or lower, and the present invention could be completed.
That is, the present invention is as follows.

1. 20 to 60 parts by mass of carbon black having a nitrogen adsorption specific surface area (N ₂ SA) of 30 to 150 m ² / g and 100 parts by mass of diene rubber containing 50 parts by mass or more of butadiene rubber, and the following formula (I) A rubber composition obtained by mixing 0.1 to 10% by mass of the sulfide compound represented with respect to the carbon black,
A rubber composition, wherein a mixing temperature when mixing the sulfide compound is 120 ° C. or less.

(In the formula, R ₁ represents a hydrogen atom, a linear or branched alkyl group or alkenyl group having 1 to 6 carbon atoms, or a cyclic alkyl group or alkenyl group having 3 to 6 carbon atoms. Represents O, S, NH, or NR _2. R ₂ represents a linear or branched alkyl group or alkenyl group having 1 to 6 carbon atoms, or a cyclic alkyl group or alkenyl group having 3 to 6 carbon atoms. N represents an integer of 1 to 6, and x represents an integer of 1 to 4.)
2. An initial mixing step of mixing one or two or more types of compounds excluding the vulcanized compound n times (where n represents a number of 1 or more), and after the initial mixing step, the vulcanized compound The rubber composition according to 1 above, further comprising a final mixing step of mixing and mixing a product, wherein the sulfide compound is mixed and mixed in the final mixing step.
3. 3. The rubber composition as described in 1 or 2 above, wherein x is 2 in the sulfide compound represented by the formula (I).
4). 20 to 60 parts by mass of carbon black having a nitrogen adsorption specific surface area (N ₂ SA) of 30 to 150 m ² / g and 100 parts by mass of diene rubber containing 50 parts by mass or more of butadiene rubber, and the following formula (I) A method for producing a rubber composition comprising mixing a sulfide compound represented by 0.1 to 10% by mass with respect to the carbon black,
A method for producing a rubber composition, wherein a mixing temperature when mixing the sulfide compound is 120 ° C. or lower.

(In the formula, R ₁ represents a hydrogen atom, a linear or branched alkyl group or alkenyl group having 1 to 6 carbon atoms, or a cyclic alkyl group or alkenyl group having 3 to 6 carbon atoms. Represents O, S, NH, or NR _2. R ₂ represents a linear or branched alkyl group or alkenyl group having 1 to 6 carbon atoms, or a cyclic alkyl group or alkenyl group having 3 to 6 carbon atoms. N represents an integer of 1 to 6, and x represents an integer of 1 to 4.)
5). An initial mixing step of mixing one or two or more types of compounds excluding the vulcanized compound n times (where n represents a number of 1 or more), and after the initial mixing step, the vulcanized compound 5. A method for producing a rubber composition as described in 4 above, wherein the sulfide compound is blended and mixed in the final mixing step.
6). 6. The method for producing a rubber composition as described in 4 or 5 above, wherein x is 2 in the sulfide compound represented by the formula (I).
7). A pneumatic tire using the rubber composition according to any one of 1 to 3 as a sidewall.

According to the present invention, carbon black having a specific nitrogen adsorption specific surface area (N ₂ SA) and a specific sulfide compound described in Patent Document 1 in a specific amount with respect to a diene rubber having a specific composition. In addition to blending, the sulfide compound is mixed at a specific temperature or lower, so that the scorch and processability are not deteriorated, the rolling composition has low rolling resistance, and has excellent rubber reinforcement performance and its A manufacturing method and a pneumatic tire can be provided.

Hereinafter, the present invention will be described in more detail.
(Diene rubber)
The diene rubber used in the present invention contains butadiene rubber (BR) as an essential component. The blending amount of BR is required to be 50 parts by mass or more, preferably 60 parts by mass or more when the whole diene rubber is 100 parts by mass. When the blending amount of BR is less than 50 parts by mass, the fatigue properties are deteriorated, which is not preferable. In addition to BR, other diene rubbers can be used, for example, natural rubber (NR), synthetic isoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber. (NBR) and the like. These may be used alone or in combination of two or more. The molecular weight and microstructure are not particularly limited, and may be terminally modified with an amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl group or the like, or may be epoxidized.

(Carbon black)
The carbon black used in the present invention needs to have a nitrogen adsorption specific surface area (N ₂ SA) of 30 to 150 m ² / g, and from the viewpoint of improving the effect of the present invention, 30 to 100 m ² / g. It is preferable that it is 30-50 m < ² > / g. The nitrogen adsorption specific surface area (N ₂ SA) is a value determined in accordance with JIS K6217-2.
As the carbon black used in the present invention, for example, furnace black, acetylene black, thermal black, channel black and the like can be used. However, in the case of tire use, furnace black can be preferably used.

(Sulfide compound)
The sulfide compound used in the present invention is disclosed in Patent Document 1. Specifically, it is represented by the following formula (I).

(In the formula, R ₁ represents a hydrogen atom, a linear or branched alkyl group or alkenyl group having 1 to 6 carbon atoms, or a cyclic alkyl group or alkenyl group having 3 to 6 carbon atoms. Represents O, S, NH, or NR _2. R ₂ represents a linear or branched alkyl group or alkenyl group having 1 to 6 carbon atoms, or a cyclic alkyl group or alkenyl group having 3 to 6 carbon atoms. N represents an integer of 1 to 6, and x represents an integer of 1 to 4.)

The sulfide compound used in the present invention has a bilaterally symmetric structure (bis structure) in which aromatic condensed heterocycles are bonded via an alkylene group at both ends of the sulfide portion.
As the compound, for example,
Bis (benzimidazolyl-2) methyl sulfide,
2,2′-bis (benzimidazolyl-2) ethyl sulfide,
2,2′-bis (benzimidazolyl-2) ethyl disulfide,
2,2′-bis (benzimidazolyl-2) ethyl trisulfide,
2,2′-bis (benzimidazolyl-2) ethyl tetrasulfide,
3,3′-bis (benzimidazolyl-2) propyl disulfide,
3,3′-bis (benzimidazolyl-2) propyl trisulfide,
3,3′-bis (benzimidazolyl-2) propyl tetrasulfide,
4,4′-bis (benzimidazolyl-2) butyl disulfide,
4,4′-bis (benzimidazolyl-2) butyl trisulfide,
4,4′-bis (benzimidazolyl-2) butyl tetrasulfide,
5,5′-bis (benzimidazolyl-2) pentyl disulfide,
5,5′-bis (benzimidazolyl-2) pentyl trisulfide,
5,5′-bis (benzimidazolyl-2) pentyl tetrasulfide,
6,6′-bis (benzimidazolyl-2) hexyl disulfide,
6,6′-bis (benzimidazolyl-2) hexyl trisulfide,
6,6′-bis (benzimidazolyl-2) hexyl tetrasulfide,
2,2′-bis (1-methylbenzimidazolyl-2) ethyl disulfide,
2,2′-bis (4-methylbenzimidazolyl-2) ethyl disulfide,
2,2′-bis (5-methylbenzimidazolyl-2) ethyl disulfide,
3,3′-bis (1-methylbenzimidazolyl-2) propyl disulfide,
3,3′-bis (4-methylbenzimidazolyl-2) propyl disulfide,
3,3′-bis (5-methylbenzimidazolyl-2) propyl disulfide,
2,2′-bis (1-ethylbenzimidazolyl-2) ethyl disulfide,
2,2′-bis (4-ethylbenzimidazolyl-2) ethyl disulfide,
2,2′-bis (5-ethylbenzimidazolyl-2) ethyl disulfide,
3,3′-bis (1-ethylbenzimidazolyl-2) propyl disulfide,
3,3′-bis (4-ethylbenzimidazolyl-2) propyl disulfide,
3,3′-bis (5-ethylbenzimidazolyl-2) propyl disulfide,
3,3′-bis (1-n-propylbenzimidazolyl-2) propyl disulfide,
3,3′-bis (4-n-propylbenzimidazolyl-2) propyl disulfide,
3,3′-bis (5-n-propylbenzimidazolyl-2) propyl disulfide,
3,3′-bis (1-isopropylbenzimidazolyl-2) propyl disulfide,
3,3′-bis (4-isopropylbenzimidazolyl-2) propyl disulfide,
3,3′-bis (5-isopropylbenzimidazolyl-2) propyl disulfide,
3,3′-bis (1-tert-butylbenzimidazolyl-2) propyl disulfide,
3,3′-bis (4-tert-butylbenzimidazolyl-2) propyl disulfide,
3,3′-bis (5-tert-butylbenzimidazolyl-2) propyl disulfide,
2,2′-bis (benzoxazolyl-2) ethyl disulfide,
2,2′-bis (benzoxazolyl-2) ethyl trisulfide,
2,2′-bis (benzoxazolyl-2) ethyl tetrasulfide,
3,3′-bis (benzoxazolyl-2) propyl disulfide,
4,4′-bis (benzoxazolyl-2) butyl disulfide,
5,5′-bis (benzoxazolyl-2) pentyl disulfide,
6,6′-bis (benzoxazolyl-2) hexyl disulfide,
2,2′-bis (4-methylbenzoxazolyl-2) ethyl disulfide,
2,2′-bis (4-methylbenzoxazolyl-2) ethyl trisulfide,
2,2′-bis (4-methylbenzoxazolyl-2) ethyl tetrasulfide,
2,2′-bis (5-methylbenzoxazolyl-2) ethyl disulfide,
2,2′-bis (5-methylbenzoxazolyl-2) ethyl trisulfide,
2,2′-bis (5-methylbenzoxazolyl-2) ethyl tetrasulfide,
3,3′-bis (6-methylbenzoxazolyl-2) propyl disulfide,
3,3′-bis (6-methylbenzoxazolyl-2) propyl trisulfide,
3,3′-bis (6-methylbenzoxazolyl-2) propyl tetrasulfide,
2,2′-bis (benzthiazolyl-2) ethyl disulfide,
2,2′-bis (benzthiazolyl-2) ethyl trisulfide,
2,2′-bis (benzthiazolyl-2) ethyl tetrasulfide,
3,3′-bis (benzthiazolyl-2) propyl disulfide,
4,4′-bis (benzthiazolyl-2) butyl disulfide,
5,5′-bis (benzthiazolyl-2) pentyl disulfide,
6,6′-bis (benzthiazolyl-2) hexyl disulfide,
3,3′-bis (4-methylbenzthiazolyl-2) propyl disulfide,
3,3′-bis (4-methylbenzthiazolyl-2) propyl trisulfide,
3,3′-bis (4-methylbenzthiazolyl-2) propyl tetrasulfide,
3,3′-bis (5-ethylbenzthiazolyl-2) propyl disulfide,
3,3′-bis (5-ethylbenzthiazolyl-2) propyl trisulfide,
3,3′-bis (5-ethylbenzthiazolyl-2) propyl tetrasulfide,
3,3′-bis (6-n-propylbenzthiazolyl-2) propyl disulfide,
3,3′-bis (6-n-propylbenzthiazolyl-2) propyl trisulfide,
3,3′-bis (6-n-propylbenzthiazolyl-2) propyl tetrasulfide,
3,3′-bis (7-isopropylbenzthiazolyl-2) propyl disulfide,
3,3′-bis (7-isopropylbenzthiazolyl-2) propyl trisulfide,
3,3′-bis (7-isopropylbenzthiazolyl-2) propyl tetrasulfide and the like. These sulfide compounds may be used alone or in combination of two or more.
The sulfide compound can be easily obtained by reacting either a 1,2-diaminobenzene compound, a 2-aminothiophenol compound or a 2-aminophenol compound with a thiodicarboxylic acid compound in 4N dilute hydrochloric acid. The production method can be synthesized in detail in Patent Document 1.

  In the sulfide compound, the aromatic condensed heterocycle in the molecule interacts with the carbon black surface, and the sulfide bond in the molecule is broken when the rubber is kneaded, and the interaction with the rubber is further enhanced by the generated radical. In particular, in the sulfide compound represented by the formula (I), when x is 2, the effect is enhanced, which is preferable.

(Rubber composition ratio)
In the rubber composition of the present invention, 20 to 60 parts by mass of carbon black having a nitrogen adsorption specific surface area (N ₂ SA) of 30 to 150 m ² / g with respect to 100 parts by mass of the diene rubber, and the formula (I) Is blended in an amount of 0.1 to 10% by mass with respect to the carbon black.
When the blending amount of carbon black is less than 20 parts by mass, the reinforcing performance is deteriorated. Conversely, when it exceeds 60 mass parts, rolling resistance and bending fatigue resistance will deteriorate.
When the compounding amount of the sulfide compound is less than 0.1% by mass, the addition amount is too small to achieve the effects of the present invention. On the other hand, if it exceeds 10% by mass, the rolling resistance and the bending fatigue resistance deteriorate, and the hardness also decreases.

A more preferable blending amount of the carbon black is 30 to 50 parts by mass with respect to 100 parts by mass of the diene rubber.
A more preferable blending amount of the sulfide compound is 0.5 to 3.0% by mass with respect to carbon black.

The rubber composition of the present invention is characterized in that the mixing temperature when mixing the sulfide compound is 120 ° C. or less. By mixing at 120 ° C. or lower, it is presumed that the sulfide compound appropriately promotes crosslinking between carbon black and diene rubber.
When the mixing temperature of the sulfide compound exceeds 120 ° C., the scorch deteriorates and the workability deteriorates. The mixing temperature is preferably 90 to 110 ° C.

Moreover, in this invention, the effect of this invention can further be heightened by specifying the time when the said sulfide compound is mixed.
Generally, the rubber composition is prepared by combining, for example, the following mixing steps.
(1) A mastication process in which only diene rubber is masticated;
(2) An NP (non-processing) process in which various compounds other than a vulcanized compound are added to a diene rubber that has been masticated or not masticated, and mixed (this NP process is divided into a plurality of And (3) a final mixing step of adding and mixing the vulcanized compound to the rubber after the NP step.
In the present invention, the step (1) and / or (2) is “an initial mixing step in which one or two or more compounds excluding a vulcanized compound are mixed n times” (where n is 1). Represents the above number).
As described above, the sulfide compound can be added and mixed in each of the above steps if the mixing temperature is 120 ° C. or lower. In the present invention, the sulfide compound is added in the above (3) final mixing step. It is preferable to add. In general, the above (1) mastication step and (2) NP step are carried out at a temperature of 140 ° C. or higher, and in order to mix the sulfide compound at a temperature of 120 ° C. or lower, the compound is once added in each step. It needs to be cooled. On the other hand, since the final mixing step is generally performed at 120 ° C. or lower, the addition of the sulfide compound does not require the time for cooling and the like, and an increase in manufacturing cost can be avoided.
In addition, the vulcanization | cure type | system | group compound said by this invention means a vulcanizing agent like sulfur or a vulcanization accelerator. Any conventionally known vulcanization accelerator can be used. For example, thiuram vulcanization accelerator, sulfenamide vulcanization accelerator, guanidine vulcanization accelerator, thiazole vulcanization accelerator. And the like. Among them, a sulfenamide accelerator is preferable.

  In the present invention, it is more preferable to prepare in advance a master batch containing a diene rubber and a sulfide compound, and blend and mix the obtained master batch in the final mixing step. This form is advantageous in that the sulfide compound is uniformly dispersed in the rubber composition in the final mixing step and is excellent in scorch and rolling resistance. In this case, the ratio of the sulfide compound in the master batch is, for example, 20 to 50% by mass.

  Furthermore, in the present invention, it is more preferable to prepare a master batch including a diene rubber, a sulfide compound and a vulcanized compound in advance, and mix and mix the obtained master batch in the final mixing step. According to this embodiment, the dispersibility, scorch and rolling resistance of the sulfide compound are further improved. In this case, the ratio of the sulfide compound in the master batch is, for example, 20 to 30% by mass, and the ratio of the vulcanized compound is, for example, 20 to 30% by mass. In this embodiment, the vulcanizing compound may be only sulfur, or both sulfur and the vulcanization accelerator may be masterbatched.

  In the present invention, the mixing time of the sulfide compound is, for example, 1 minute to 5 minutes, and a known apparatus conventionally used in the initial mixing process or the final mixing process may be used as the mixing apparatus.

  In addition to the above-described components, the rubber composition of the present invention is generally used for rubber compositions such as vulcanization or crosslinking agents, vulcanization or crosslinking accelerators, various fillers, various oils, anti-aging agents, and plasticizers. Various additives blended in the above can be blended, and such additives can be kneaded by a general method to form a composition, which can be used for vulcanization or crosslinking. The blending amounts of these additives can be set to conventional general blending amounts as long as the object of the present invention is not violated.

  Further, the rubber composition of the present invention does not deteriorate the scorch and processability, has low rolling resistance, and has excellent rubber reinforcing performance, so that it is used as a rubber composition for tire applications, particularly tire sidewalls. It is preferred to use. Moreover, the rubber composition of this invention can manufacture a pneumatic tire according to the manufacturing method of the conventional pneumatic tire.

  EXAMPLES Hereinafter, although an Example and a comparative example further demonstrate this invention, this invention is not restrict | limited to the following example.

Comparative Example 1
In the composition (parts by mass) shown in Table 1, the composition excluding the vulcanized composition was placed in a 1.7 liter closed Banbury mixer and kneaded for 5 minutes so that the maximum temperature during mixing was 160 ° C. ( Initial mixing step). Subsequently, the vulcanized compound was added and mixed with an open roll for 2 minutes so that the maximum temperature during mixing was 110 ° C. (final mixing step). The obtained rubber composition was press vulcanized in a predetermined mold at 160 ° C. for 20 minutes to obtain a vulcanized rubber test piece, and the physical properties of the rubber composition and the vulcanized rubber test piece were measured by the following test methods. did. In this example, no sulfide compound is blended.

Comparative Example 2
Comparative Example 1 except that 2,2′-bis (benzimidazolyl-2) ethyl disulfide (2EBZ) was used as the sulfide compound in Comparative Example 1 and was mixed and mixed with the amounts shown in Table 1 in the initial mixing step. 1 was repeated. The results are shown in Table 1.

Examples 1-3
Comparative Example 1 except that 2,2′-bis (benzimidazolyl-2) ethyl disulfide (2EBZ) was used as the sulfide compound in Comparative Example 1 and was mixed and mixed with the amounts shown in Table 1 in the final mixing step. 1 was repeated. The results are shown in Table 1.

Example 4
In Example 2, Example 2 was repeated except that 2,2′-bis (benzimidazolyl-2) ethyl tetrasulfide (4EBZ) was used as the sulfide compound. The results are shown in Table 1.

Comparative Example 3
In Example 1, Example 1 was repeated except that the blending amount of the sulfide compound was changed to the blending amount shown in Table 1. The results are shown in Table 1.

Scorch: The time for the viscosity to rise by 5 Mooney units at a temperature of 125 ° C. was measured for the rubber composition in accordance with JIS K6300. The value of Comparative Example 1 was taken as 100 and displayed as an index. A higher value means better scorch.
Hardness (20 ° C.): Measured at 20 ° C. according to JIS K6253. The results are shown as an index with the value of Comparative Example 1 being 100. The larger the index, the higher the hardness and the better the reinforcing performance.
tan δ (60 ° C.): Using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho, tan δ (60 ° C.) was measured under the conditions of initial strain 10%, amplitude ± 2%, frequency 20 Hz, and temperature 60 ° C. The results are shown as an index with the value of Comparative Example 1 being 100. The smaller the index, the lower the rolling resistance.
Bending fatigue resistance: Based on JIS K 6251, 100% strain was repeatedly applied to No. 3 dumbbell, and the number of breaks was measured. The number of breaks was measured at n = 6, and the 50% residual probability based on the normal probability distribution was determined from the number of breaks. The result was expressed as an index with the value of Comparative Example 1 being 100. A larger index means better bending fatigue resistance and better rubber reinforcement performance.
The results are also shown in Table 1.

* 1: NR (TSR20)
* 2: BR (NIPOL BR 1220 manufactured by Nippon Zeon Co., Ltd.)
* 3: Carbon black (Toast Carbon Co., Ltd. Seest F, nitrogen adsorption specific surface area (N ₂ SA) = 40 m ² / g)
* 4: Zinc oxide (3 types of zinc oxide manufactured by Shodo Chemical Industry Co., Ltd.)
* 5: Stearic acid (bead stearic acid YR manufactured by NOF Corporation)
* 6: 2EBZ (2,2′-bis (benzimidazolyl-2) ethyl disulfide manufactured by Shikoku Chemicals Co., Ltd.)
* 7: 4EBZ (2,2′-bis (benzimidazolyl-2) ethyl tetrasulfide manufactured by Shikoku Chemicals Co., Ltd.)
* 8: Sulfur (Tsurumi Chemical Industry Co., Ltd. Jinhua Indian Oil Fine Powdered Sulfur)
* 9: Vulcanization accelerator (Ouchi Shinsei Chemical Co., Ltd. Noxeller CZ-G)

As is clear from Table 1 above, the rubber compositions prepared in Examples 1 to 4 are carbon black having a specific nitrogen adsorption specific surface area (N ₂ SA) with respect to the diene rubber having a specific composition. And a specific sulfide compound in a specific amount and prepared by mixing the sulfide compound at a temperature of 120 ° C. or lower, so that it has lower rolling resistance than the conventional representative comparative example 1. And has excellent rubber reinforcement performance. Further, the scorch is improved as compared with Comparative Example 2 in which the sulfide compound is mixed at a temperature exceeding 120 ° C.
Since the compounding quantity of the specific sulfide compound exceeds the upper limit prescribed | regulated by this invention in the comparative example 3, scorch and bending fatigue resistance deteriorated.

Claims (7)

20 to 60 parts by mass of carbon black having a nitrogen adsorption specific surface area (N ₂ SA) of 30 to 150 m ² / g and 100 parts by mass of diene rubber containing 50 parts by mass or more of butadiene rubber, and the following formula (I) A rubber composition obtained by mixing 0.1 to 10% by mass of the sulfide compound represented with respect to the carbon black,
A rubber composition, wherein a mixing temperature when mixing the sulfide compound is 120 ° C. or less.

(In the formula, R ₁ represents a hydrogen atom, a linear or branched alkyl group or alkenyl group having 1 to 6 carbon atoms, or a cyclic alkyl group or alkenyl group having 3 to 6 carbon atoms. Represents O, S, NH, or NR _2. R ₂ represents a linear or branched alkyl group or alkenyl group having 1 to 6 carbon atoms, or a cyclic alkyl group or alkenyl group having 3 to 6 carbon atoms. N represents an integer of 1 to 6, and x represents an integer of 1 to 4.)   An initial mixing step of mixing one or two or more types of compounds excluding the vulcanized compound n times (where n represents a number of 1 or more), and after the initial mixing step, the vulcanized compound The rubber composition according to claim 1, further comprising a final mixing step of mixing and mixing a product, wherein the sulfide compound is mixed and mixed in the final mixing step.   3. The rubber composition according to claim 1, wherein x is 2 in the sulfide compound represented by the formula (I). 20 to 60 parts by mass of carbon black having a nitrogen adsorption specific surface area (N ₂ SA) of 30 to 150 m ² / g and 100 parts by mass of diene rubber containing 50 parts by mass or more of butadiene rubber, and the following formula (I) A method for producing a rubber composition comprising mixing a sulfide compound represented by 0.1 to 10% by mass with respect to the carbon black,
A method for producing a rubber composition, wherein a mixing temperature when mixing the sulfide compound is 120 ° C. or lower.

(In the formula, R ₁ represents a hydrogen atom, a linear or branched alkyl group or alkenyl group having 1 to 6 carbon atoms, or a cyclic alkyl group or alkenyl group having 3 to 6 carbon atoms. Represents O, S, NH, or NR _2. R ₂ represents a linear or branched alkyl group or alkenyl group having 1 to 6 carbon atoms, or a cyclic alkyl group or alkenyl group having 3 to 6 carbon atoms. N represents an integer of 1 to 6, and x represents an integer of 1 to 4.)   An initial mixing step of mixing one or two or more types of compounds excluding the vulcanized compound n times (where n represents a number of 1 or more), and after the initial mixing step, the vulcanized compound 5. A method for producing a rubber composition according to claim 4, wherein the sulfide compound is blended and mixed in the final mixing step.   6. The method for producing a rubber composition according to claim 4, wherein x is 2 in the sulfide compound represented by the formula (I).   A pneumatic tire using the rubber composition according to claim 1 as a sidewall.