JP2011026414A - Rubber composition for tire and manufacturing method for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for a tire that permits enhancement of low-fuel consumption performance and a manufacturing method for the same. <P>SOLUTION: The rubber composition for a tire comprises a rubber component comprising a synthetic rubber component and a natural rubber component that is obtained by (a) a step of kneading a compounding agent with the synthetic rubber component to prepare a synthetic rubber master batch, (b) a step of kneading a compounding agent with the natural rubber component to prepare a natural rubber master batch and (c) a step of kneading the synthetic rubber master batch prepared in the step (a) with the natural rubber master batch prepared in the step (b), where the mass ratio of the compounding agent contained in the natural rubber master batch to the natural rubber component contained in the natural rubber master batch is higher than the mass ratio of the compounding agent contained in the synthetic rubber master batch to the synthetic rubber component contained in the synthetic rubber master batch. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a tire rubber composition and a method for producing the same.

In recent years, the development of fuel efficiency reduction technology for automobile tires has been accelerating, and the mainstream is to change the content of the rubber composition for tires. On the other hand, with respect to a technique for reducing fuel consumption by rubber kneading technique, a means for improving the dispersibility of reinforcing agents such as carbon black and silica is generally used.

In the prior art, in order to further improve the dispersibility of the reinforcing agent, “extending the kneading time / increasing the number of kneading” is generally performed. There was also a problem that the hardness characteristics of the finished rubber deteriorated and the effect of improving the fuel efficiency characteristics could not be fully exhibited.

As a method for improving the dispersibility of the reinforcing agent, for example, in Patent Document 1, after mixing carbon black and / or silica with a liquid polymer, the grip performance of the tire is improved by mixing the mixture and a rubber component. It is disclosed that it can be done. However, improving the grip performance of the tire means increasing energy loss. Therefore, even if the method of Patent Document 1 contrary to the reduction in fuel consumption is used, the reduction in fuel consumption cannot be realized.

Japanese Patent Laid-Open No. 2007-161818

An object of the present invention is to solve the above-mentioned problems and to provide a rubber composition for tires and a method for producing the same that can improve fuel efficiency.
In the present specification, the “low fuel consumption characteristic” is a value obtained by dividing tan δ indicating the heat generation characteristic in the viscoelastic characteristic of the rubber composition by G * indicating the dynamic complex elastic modulus of the rubber composition (tan δ / G *) As an indicator.

Conventionally, in a base kneading process in which a compounding agent (base kneading material) other than a vulcanizing agent and a vulcanization accelerator and a rubber component are kneaded, even when a plurality of types of rubber components are used, all rubber components and bases are used. The kneading material was kneaded at once. In contrast, the present inventors separately perform the above-mentioned base kneading step for a synthetic rubber component such as styrene butadiene rubber (SBR) and butadiene rubber (BR) and a natural rubber component such as natural rubber (NR). By preparing a synthetic rubber-based masterbatch and a natural rubber-based masterbatch, a synthetic-rubber-based masterbatch and a natural-rubber-based masterbatch can be used for the rubber components contained in the masterbatch. We found a method to vary the mass ratio of the base kneading materials contained in

As a result of further investigation by the present inventors, the mass ratio of the base kneading material contained in the master batch to the natural rubber component contained in the natural rubber master batch (hereinafter referred to as the base kneading material contained in the natural rubber master batch) And the mass ratio of the base kneading material contained in the master batch to the synthetic rubber component contained in the synthetic rubber master batch (hereinafter referred to as the base kneading contained in the synthetic rubber master batch). By reducing the blending ratio of the material, the rubber composition obtained by kneading both master batches can increase G * while maintaining tan δ constant, while the base kneading contained in the natural rubber master batch While reducing the blending ratio of the materials, the blending ratio of the base kneaded material contained in the synthetic rubber master batch The larger, the rubber composition obtained by kneading the two master batches, while tanδ is constant, and found to be able to lower the G *. That is, the present inventors use this technique to change G * while maintaining tan δ constant as compared with the conventional case even if the blending of the base kneading material in the rubber composition is the same. I found out that it would be possible.

From the above examination results, the inventors have made the blending ratio of the base kneading material contained in the natural rubber-based masterbatch larger than the blending ratio of the base kneading material contained in the synthetic rubber-based masterbatch, It has been found that the fuel efficiency of the rubber composition for tires obtained by kneading both master batches can be improved.

That is, the present invention is a tire rubber composition containing a rubber component comprising a synthetic rubber component and a natural rubber component, wherein (a) a compounding agent and a synthetic rubber component are kneaded to prepare a synthetic rubber-based masterbatch. A step of preparing, (b) a step of kneading the compounding agent and a natural rubber component to prepare a natural rubber-based master batch, (c) a synthetic rubber-based master batch prepared in the step (a), and The mass ratio of the compounding agent contained in the masterbatch to the natural rubber component contained in the natural rubber masterbatch obtained by the step of kneading the natural rubber masterbatch prepared in the step (b) is a synthetic rubber. It is related with the rubber composition for tires larger than the mass ratio of the compounding agent contained in this masterbatch with respect to the synthetic rubber component contained in a system masterbatch.

In this specification, “synthetic rubber-based masterbatch” refers to a mixture of a compounding agent (base kneaded material) and a synthetic rubber component, and “natural rubber-based masterbatch” refers to a base kneaded material and a natural kneaded material. A kneaded product with a rubber component.

In the tire rubber composition, the mass ratio of the compounding agent contained in the natural rubber masterbatch to the compounding agent contained in the synthetic rubber masterbatch is preferably 2/3 or more.

In the tire rubber composition, the content of the natural rubber component in 100% by mass of the rubber component is preferably 30 to 40% by mass.

The present invention also relates to a method for producing a rubber composition for a tire comprising a rubber component comprising a synthetic rubber component and a natural rubber component, wherein (a) a compounding agent and a synthetic rubber component are kneaded to produce a synthetic rubber-based master. A step of preparing a batch, (b) a step of kneading the compounding agent and a natural rubber component to prepare a natural rubber-based master batch, (c) a synthetic rubber-based master batch prepared in the step (a), and The mass ratio of the compounding agent contained in the masterbatch to the natural rubber component contained in the natural rubber masterbatch is synthesized, including the step of kneading the natural rubber masterbatch prepared in the step (b). The present invention relates to a method for producing a tire rubber composition that is larger than the mass ratio of the compounding agent contained in the master batch to the synthetic rubber component contained in the rubber master batch.

In the method for producing the tire rubber composition, the mass ratio of the compounding agent contained in the natural rubber masterbatch to the compounding agent contained in the synthetic rubber masterbatch is preferably 2/3 or more.

In the method for producing the rubber composition for a tire, the content of the natural rubber component in 100% by mass of the rubber component is preferably 30 to 40% by mass.

According to the present invention, a synthetic rubber component and a natural rubber component are separately subjected to a base kneading step to prepare a synthetic rubber master batch and a natural rubber master batch, and a natural rubber master batch. G * can be increased while tan δ remains constant by making the blending ratio of the base kneading material contained in the mixture larger than that of the base kneading material contained in the synthetic rubber-based masterbatch. As a result, the value of tan δ / G * can be reduced. That is, the low fuel consumption characteristic of the tire rubber composition can be improved.

Thus, according to the present invention, since the low fuel consumption characteristics of the tire rubber composition can be improved, each member of the tire (particularly, tread, base tread, sidewall, beat apex, clinch apex) Can be suitably used.

The rubber composition for tires of the present invention is a rubber composition for tires comprising a rubber component comprising a synthetic rubber component and a natural rubber component, and (a) a compound rubber and a synthetic rubber component are kneaded to form a synthetic rubber system (B) a step of preparing a natural rubber masterbatch by kneading the compounding agent and the natural rubber component, (c) a synthetic rubber master prepared in the step (a). The mass ratio of the compounding agent contained in the masterbatch to the natural rubber component contained in the natural rubber masterbatch obtained by kneading the batch and the natural rubber masterbatch prepared in the step (b) Is greater than the mass ratio of the compounding agent contained in the master batch to the synthetic rubber component contained in the synthetic rubber master batch.

<(A) Process>
In the step (a), for example, using a kneader, the compounding agent (base kneading material) and the synthetic rubber component are kneaded to prepare a synthetic rubber-based master batch. A conventionally known kneader can be used, and examples thereof include a Banbury mixer, a kneader, and an open roll. The same kneader can be used in the steps (b) and (c) described below.

The rotor rotation speed of the kneader in the step (a) is preferably 40 to 70 rpm. When the rotor rotational speed is less than 40 rpm, the base kneaded material tends to be poorly dispersed. When it exceeds 70 rpm, the temperature of the rubber component rises too much, so that a sufficient kneading time cannot be obtained, and the base kneading material tends to be poorly dispersed.

(A) From the start to the end of the process, the accumulated load power per kg of the rubber component applied to the motor of the kneader is preferably 0.05 to 0.15 kw · h / kg. When the integrated load power is less than 0.05 kw · h / kg, the base kneaded material tends to be poorly dispersed. When it exceeds 0.15 kw · h / kg, the rubber hardness tends to decrease due to excessive kneading.
Here, the load electric power applied to the motor of the kneading machine in the present invention is the electric power (kw) required to drive the motor when kneading (kneading) the rubber component.

Examples of the synthetic rubber component include butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), halogenated butyl rubber (Cl-IIR, Br-IIR, etc.), styrene- Examples include isoprene-butadiene copolymer rubber (SIBR). These synthetic rubber components may be used alone or in combination of two or more. Among these, SBR and BR are preferable, and SBR alone or a combination of SBR and BR is more preferable because it can be suitably used for a tread in a tire member contributing to low fuel consumption characteristics.

Examples of SBR include those obtained by a solution polymerization method and those obtained by an emulsion polymerization method, but are not particularly limited. Also, the BR is not particularly limited. For example, BR1220 manufactured by Nippon Zeon Co., Ltd., BR130B manufactured by Ube Industries, Ltd., BR150B and other high cis content BR, VCR412 manufactured by Ube Industries, Ltd., VCR617, etc. BR containing a syndiotactic polybutadiene crystal can be used.

The content of SBR in 100% by mass of the synthetic rubber component is preferably 50% by mass or more, more preferably 60% by mass or more, and further preferably 70% by mass or more. When the amount is less than 50% by mass, the synthetic rubber component is not well-organized when preparing a synthetic rubber-based masterbatch, so that the masterbatch becomes difficult to connect as a sheet, and the productivity is deteriorated.
Moreover, the upper limit of content of SBR is not specifically limited, 100 mass% may be sufficient.

When BR and SBR are used in combination, the BR content in 100% by mass of the synthetic rubber component is preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less, and 0% by mass. It may be. If it exceeds 50% by mass, the rubber sheet (synthetic rubber-based masterbatch) obtained in the step (a) is likely to be cut, and the productivity is significantly reduced.

As the compounding agent (base kneading material) kneaded in the step (a), for example, inorganic and organic fillers such as carbon black and silica, softening agents such as oil, vulcanization acceleration of silane coupling agents, stearic acid, etc. Auxiliaries, zinc oxide, various anti-aging agents, ozone degradation inhibitors, waxes and the like can be mentioned. Among the tire members that contribute to low fuel consumption characteristics, the base kneaded material kneaded in step (a) is at least carbon black, because it is suitably used for a tread that requires wear resistance and grip performance. Silica (and silane coupling agent) and a softening agent are preferably included.

The carbon black is not particularly limited, and examples thereof include GPF, FEF, HAF, ISAF, and SAF.

The silica is not particularly limited, and examples thereof include dry process silica (anhydrous silicic acid), wet process silica (hydrous silicic acid), and the like, but wet process silica is preferable because of its large number of silanol groups. Silica may be used alone or in combination of two or more.

As the softening agent, for example, process oil, vegetable oil or fat, or a mixture thereof can be used.

Examples of the process oil include paraffinic process oil, naphthenic process oil, and aromatic process oil (aromatic process oil). As vegetable oils and fats, castor oil, cottonseed oil, sesame oil, rapeseed oil, soybean oil, palm oil, palm oil, peanut water, rosin, pine oil, pineapple, tall oil, corn oil, rice bran oil, beet flower oil, sesame oil, Examples include olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. Among these, paraffinic process oil, naphthenic process oil, and aromatic process oil are preferably used because they are easily mixed with SBR, BR, and NR that are suitably used for tire rubber compositions.

The mass ratio of the base kneaded material kneaded in the step (a) to the synthetic rubber component (the mass ratio of the compounding agent contained in the master batch to the synthetic rubber component contained in the synthetic rubber master batch) will be described later (b The mass ratio of the base kneaded material kneaded in the step (b) relative to the natural rubber component in the step) may be smaller, but is preferably 0.50 or more, more preferably 0.60 or more. If it is less than 0.50, the ratio of the polymer (synthetic rubber component) is too large, and the rubber sheet obtained in the step (a) is not well-organized and the productivity is lowered.
The mass ratio is preferably 1.10 or less, more preferably 1.05 or less, and still more preferably 1.00. When it exceeds 1.10, there is a tendency that it is difficult to obtain a target low fuel consumption characteristic.
The mass ratio of the compounding agent contained in the master batch to the synthetic rubber component contained in the synthetic rubber master batch is the same as that of the compound rubber contained in the synthetic rubber master batch. It is the value divided by the mass of the synthetic rubber component contained.

<(B) Process>
In the step (b), for example, using a kneader, the base kneaded material and the natural rubber component are kneaded to prepare a natural rubber-based master batch.

The rotor rotation speed of the kneader in the step (b) is preferably 40 to 70 rpm. When it is less than the lower limit or exceeds the upper limit, the same problem as the rotor rotational speed in the step (a) tends to occur.

(B) From the start to the end of the process, the integrated load power per kg of the rubber component applied to the motor of the kneader is preferably 0.05 to 0.15 kw · h / kg. When it is less than the lower limit or exceeds the upper limit, the same problem as the rotor rotational speed in the step (a) tends to occur.

Examples of the natural rubber component include natural rubber (NR) and modified natural rubber. NR includes deproteinized natural rubber (DPNR) and high-purity natural rubber (HPNR). Modified natural rubber includes epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Etc. These natural rubber components may be used alone or in combination of two or more. Among these, NR (non-modified natural rubber) is preferable because it can be suitably used for a tread. As the NR, for example, those commonly used in the tire industry such as RSS # 3 and TSR20 can be used. Of these, TSR20 is preferable because it is easily available.

The content of NR (unmodified natural rubber) in 100% by mass of the natural rubber component is preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 100% by mass. If it is less than 80% by mass, it is difficult to obtain the targeted low fuel consumption characteristics.

As the compounding agent (base kneading material) kneaded in step (b), the same base kneading material as in step (a) can be used. Among the tire members that contribute to low fuel consumption characteristics, the base kneaded material kneaded in step (b) is at least carbon black, because it is suitably used for treads that require wear resistance and grip performance. Silica (and silane coupling agent) and a softening agent are preferably included. In addition, as carbon black, silica, silane coupling agent, and softening agent, those similar to the above-mentioned step (a) can be preferably used.

The mass ratio of the compounding agent contained in the natural rubber-based masterbatch to the compounding agent contained in the synthetic rubber-based masterbatch is preferably 2/3 or more, more preferably 3/4 or more. If it is less than 2/3, it tends to be difficult to obtain the targeted low fuel consumption characteristics.
The mass ratio of the compounding agent contained in the natural rubber-based masterbatch to the compounding agent contained in the synthetic rubber-based masterbatch is the mass ratio of the compounding agent contained in the natural rubber-based masterbatch. It is the value divided by the mass of the compounding agent contained in the batch.

The mass ratio of the base kneaded material kneaded in the step (b) to the natural rubber component (the mass ratio of the compounding agent contained in the master batch to the natural rubber component contained in the natural rubber-based master batch) was described above. Although it should just be larger than the mass ratio of the base kneaded material kneaded at the (a) process with respect to the synthetic rubber component in the (a) process, it is preferably 1.00 or more, more preferably 1.10 or more. If it is less than 1.00, the target low fuel consumption characteristic tends to be difficult to obtain. The mass ratio is preferably 2.00 or less, more preferably 1.80 or less. If it exceeds 2.00, the amount of polymer (natural rubber component) is too small, and the tear resistance of the rubber sheet (natural rubber-based masterbatch) obtained in the step (b) becomes weak, and the productivity decreases.
The mass ratio of the compounding agent contained in the masterbatch to the natural rubber component contained in the natural rubber-based masterbatch is the same as that of the natural rubber-based masterbatch. It is the value divided by the mass of the natural rubber component contained.

<(C) Process>
In the step (c), for example, using a kneader, the synthetic rubber master batch prepared in the step (a), the natural rubber master batch prepared in the step (b), a vulcanizing agent, and the like. (Finish kneaded material) is kneaded to prepare an unvulcanized rubber composition.

The finish kneading material may contain at least a vulcanizing agent, but preferably further contains a vulcanization accelerator and a vulcanization acceleration aid. Thereby, the tact time of the vulcanization process performed later can be shortened.

(C) It is preferable that the rotor rotation speed of the kneading machine in a process is 20-50 rpm. If it is less than 20 rpm, the uniform dispersibility of the synthetic rubber masterbatch, the natural rubber masterbatch, and the finish kneaded material tends to be insufficient.
If it exceeds 50 rpm, the temperature of the rubber component rises too much, so that sufficient kneading time cannot be obtained, and the uniform dispersibility of the synthetic rubber masterbatch, the natural rubber masterbatch, and the finished kneaded material is insufficient. Tend to be.

(C) From the start to the end of the process, the integrated load power per kg of the rubber component applied to the motor of the kneader is preferably 0.03 to 0.08 kw · h / kg. When the integrated load power is less than 0.03 kW · h / kg, the base kneaded material tends to be poorly dispersed. When it exceeds 0.08 kw · h / kg, the rubber hardness tends to decrease due to excessive kneading.

The unvulcanized rubber composition obtained in the step (c) can be vulcanized by performing a vulcanization reaction at 170 to 180 ° C. for 10 to 16 minutes.

In the rubber composition obtained by the above production method, the content of the natural rubber component in 100% by mass of the rubber component composed of the synthetic rubber component and the natural rubber component is preferably 30% by mass or more, more preferably 32% by mass or more. . If it is less than 30% by mass, it is difficult to sufficiently obtain the effects of the present invention. The content of the natural rubber component is preferably 40% by mass or less, more preferably 38% by mass or less. If it exceeds 40% by mass, it tends to be difficult to ensure the grip performance of the tire.

In the rubber composition obtained by the above production method, the content of the synthetic rubber component in 100% by mass of the rubber component is preferably 60% by mass or more, more preferably 62% by mass or more. When the amount is less than 60% by mass, the natural rubber component exceeds 40% by mass, and the same problem as described above tends to occur. Further, the content of the synthetic rubber component is preferably 70% by mass or less, more preferably 68% by mass or less. When it exceeds 70 mass%, a natural rubber component will be less than 30 mass%, and there exists a tendency for the same problem as the above to arise.

The rubber composition obtained by the above production method can be suitably used for each member of a tire such as a tread, a base tread, a sidewall, a beat apex, and a clinch apex.

Using the rubber composition, a pneumatic tire can be produced by a normal method. That is, the rubber composition is extruded in accordance with the shape of the tire member at an unvulcanized stage, molded by a normal method on a tire molding machine, and bonded together with other tire members to form an unvulcanized tire. To do. This unvulcanized tire can be heated and pressurized in a vulcanizer to produce a tire.

When the rubber composition contains a filler such as carbon black or silica, the total content of the filler is preferably 50 parts by mass or more, more preferably 60 parts by mass or more with respect to 100 parts by mass of the rubber component. It is. If it is less than 50 parts by mass, it is difficult to obtain sufficient reinforcement. Further, the total content of the filler is preferably 120 parts by mass or less, more preferably 100 parts by mass or less. When the amount exceeds 120 parts by mass, the ratio of the polymer (rubber component) becomes too small, and the rubber sheet (unvulcanized rubber composition) obtained in the step (c) is easily cut and the productivity is lowered.

When the rubber composition contains a softening agent, the content of the softening agent is preferably 5 parts by mass or more, more preferably 10 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 5 parts by mass, softening of the rubber component is insufficient, and even if kneaded, it does not work well and the productivity tends to decrease. The softener content is preferably 50 parts by mass or less, more preferably 40 parts by mass or less. When the amount exceeds 50 parts by mass, the rubber composition becomes too soft, and the rubber sheet (unvulcanized rubber composition) obtained in the step (c) is easily cut and the productivity is lowered.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
(1) SBR: S-SBR HPR355 manufactured by JSR Corporation (vinyl content: 57 mass%, styrene content: 27 mass%)
(2) BR: BR150B manufactured by Ube Industries, Ltd.
(3) NR: SIR20
(4) Carbon black: Carbon ISAF (N ₂ SA: 114 m ² / g) manufactured by Mitsubishi Chemical Corporation
(5) Silica: Silica 115Gr (N ₂ SA: 112 m ² / g) manufactured by Rhodia Japan Co., Ltd.
(6) Zinc oxide: Zinc flower manufactured by Mitsui Mining & Smelting Co., Ltd. (7) Stearic acid: Stearic acid manufactured by NOF Corporation (8) Anti-aging agent: 6C manufactured by FLEXSYS (SANTOFLEX, 6PPD)
(9) Oil: NC300S manufactured by Japan Energy Co., Ltd.
(10) Wax: Ozoace made by Nihon Seiki Co., Ltd. (11) Sulfur: Oil-treated sulfur produced by Nippon Suizo Co., Ltd. (12) Vulcanization accelerator CBS: CBS made by Sanshin Chemical Industries, Ltd.
(13) Vulcanization accelerator DPG: DPG manufactured by FLEXSYS Corporation
The above (1) and (2) were used as synthetic rubber components. Moreover, said (3) was used as a natural rubber component. Moreover, said (4)-(10) was used as a base kneading material. Moreover, said (11)-(13) was used as a finishing kneading material.

Comparative Example 1
(Base kneading process)
According to the composition shown in Table 1, using a Banbury mixer BB240 (11D rotor) manufactured by Kobe Steel, the filling rate was set to 72%, and the rubber temperature of the synthetic rubber component, natural rubber component and base kneaded material was 150 ° C. or higher. The kneaded material was kneaded until it became (rotor rotation speed 60 rpm).
(Finish kneading process)
Next, the final kneaded material was added to the kneaded material obtained in the base kneading step, and kneaded until the rubber temperature reached 100 ° C. (rotor rotation speed: 35 rpm) to obtain an unvulcanized rubber composition.

Comparative Example 2
In Comparative Example 2, the kneading time in the base kneading step was extended by 10% compared to Comparative Example 1. Other conditions were the same as in Comparative Example 1.

Comparative Example 3
In Comparative Example 3, the kneaded product is discharged from the Banbury mixer when the rubber temperature becomes 150 ° C. or higher, and then the kneaded product is again charged into the Banbury mixer and kneaded when the rubber temperature becomes 30 ° C. or lower. By providing this process, the kneading time in the base kneading process was extended by 50% compared to Comparative Example 1. Other conditions were the same as in Comparative Example 1.

Comparative Examples 4 and 5
(First base kneading process (preparation of synthetic rubber masterbatch))
According to the composition shown in Table 1, using a Banbury mixer BB240 (11D rotor) manufactured by Kobe Steel, the filling rate was set to 72%, and the synthetic rubber components (SBR, BR) and the base kneaded material were kneaded, and the synthetic rubber A master batch of the system was obtained (rotor rotation speed 60 rpm, integrated load power 0.1 kw · h / kg in the first base kneading step). The kneading time (base kneading time) was set to the same time as the base kneading step of Comparative Example 1 described above. In Table 1, which will be described later, the base kneading time is indicated as an index with the time in Comparative Example 1 being 100.
(Second base kneading process (preparation of natural rubber masterbatch))
Next, according to the formulation shown in Table 1, the natural rubber component (NR) and the base kneaded material were kneaded under the same conditions as in the first base kneading step to obtain a natural rubber-based masterbatch.
(Finish kneading process)
Next, according to the composition shown in Table 1, using the Banbury mixer BB240 (11D rotor) manufactured by Kobe Steel, the finish kneading material is added to the two types of master batches obtained in the first and second base kneading steps. Then, kneading was carried out until the rubber temperature reached 100 ° C. (rotor rotation number: 35 rpm, integrated load power of 0.05 kw · h / kg in the finishing kneading process) to obtain an unvulcanized rubber composition.

Examples 1 and 2
Except for the point changed to the formulation shown in Table 1, the first and second base kneading steps and the finishing kneading step were performed under the same conditions as in Comparative Examples 4 and 5, and an unvulcanized rubber composition was obtained. .

(Evaluation)
Hereinafter, the evaluation method of an Example and a comparative example is demonstrated.

(Carbon dispersion)
The obtained unvulcanized rubber composition was cut into a 40 mm square and subjected to press vulcanization at 165 ° C. for 10 minutes to prepare a vulcanized rubber sheet.
The carbon dispersion degree of the prepared vulcanized rubber sheet was measured according to ISO11345. It shows that the dispersibility of carbon black is excellent, so that a numerical value is large. A numerical value of 90% or more was judged acceptable.

(Low fuel consumption characteristics)
The obtained unvulcanized rubber composition was subjected to a vulcanization test at 165 ° C. for 15 minutes using an RPA2000 type testing machine manufactured by Alpha Technologies, and after obtaining the rubber composition, the measurement temperature was lowered to 30 ° C. G * and tan δ of the rubber composition were measured at 10 Hz and an amplitude angle of 1 °.
In Table 1 to be described later, G * and tan δ are indicated by an index with the measurement result of Comparative Example 1 as 100. The smaller the index value of tan δ / G *, the better the fuel efficiency characteristics. When it was reduced by 5% or more compared to Comparative Example 1, it was determined that there was an effect of improving the fuel efficiency characteristics.

The base kneading process is performed separately for the synthetic rubber component and the natural rubber component, and the blending ratio of the base kneading material contained in the natural rubber masterbatch is mixed with the blending ratio of the base kneading material contained in the synthetic rubber masterbatch. In Examples 1 and 2, which were larger than those in Comparative Example 1, G * increased while maintaining tan δ. That is, in Examples 1 and 2, the low fuel consumption characteristics were improved. On the other hand, in Comparative Examples 2 and 3 in which the base kneading time was increased, compared with Comparative Example 1, the carbon dispersibility was improved, but tan δ was reduced, but the fuel efficiency characteristics were only slightly improved. In addition, although the base kneading process was performed separately for the synthetic rubber component and the natural rubber component, the blending ratio of the base kneading material contained in the natural rubber master batch was adjusted to the base kneading material contained in the synthetic rubber master batch. In Comparative Examples 4 and 5 having a blending ratio or less, G * decreased while maintaining tan δ as compared with Comparative Example 1. That is, in Comparative Examples 4 and 5, the fuel efficiency characteristics deteriorated.

Claims (6)

A tire rubber composition comprising a rubber component comprising a synthetic rubber component and a natural rubber component,
(A) kneading a compounding agent and a synthetic rubber component to prepare a synthetic rubber-based masterbatch;
(B) kneading the compounding agent and the natural rubber component to prepare a natural rubber-based masterbatch,
(C) obtained by kneading the synthetic rubber-based masterbatch prepared in the step (a) and the natural rubber-based masterbatch prepared in the step (b),
The mass ratio of the compounding agent contained in the master batch to the natural rubber component contained in the natural rubber-based master batch is the mass ratio of the compounding agent contained in the master batch to the synthetic rubber component contained in the synthetic rubber-based master batch. Larger tire rubber composition. 2. The tire rubber composition according to claim 1, wherein a mass ratio of the compounding agent contained in the natural rubber-based masterbatch to the compounding agent contained in the synthetic rubber-based masterbatch is 2/3 or more. The rubber composition for a tire according to claim 1 or 2, wherein a content of the natural rubber component in 100% by mass of the rubber component is 30 to 40% by mass. A method for producing a rubber composition for a tire comprising a rubber component comprising a synthetic rubber component and a natural rubber component,
(A) kneading a compounding agent and a synthetic rubber component to prepare a synthetic rubber-based masterbatch;
(B) kneading the compounding agent and the natural rubber component to prepare a natural rubber-based masterbatch,
(C) including a step of kneading the synthetic rubber masterbatch prepared in the step (a) and the natural rubber masterbatch prepared in the step (b),
The mass ratio of the compounding agent contained in the master batch to the natural rubber component contained in the natural rubber-based master batch is the mass ratio of the compounding agent contained in the master batch to the synthetic rubber component contained in the synthetic rubber-based master batch. The manufacturing method of the rubber composition for tires larger than this. The method for producing a rubber composition for a tire according to claim 4, wherein a mass ratio of the compounding agent contained in the natural rubber-based masterbatch to the compounding agent contained in the synthetic rubber-based masterbatch is 2/3 or more. The method for producing a tire rubber composition according to claim 4 or 5, wherein the content of the natural rubber component in 100% by mass of the rubber component is 30 to 40% by mass.