JP6701714B2 - Rubber composition and pneumatic tire - Google Patents

Description

  The present invention relates to a rubber composition and a pneumatic tire.

Currently, the performance required for tires is diverse. Above all, there is a strong demand for reducing the heat generation property of the rubber constituting the tire in order to reduce the fuel consumption of automobiles.
In order to achieve both low heat buildup and stability on wet road surfaces, silica is blended as a reinforcing filler in the rubber composition for tires.

On the other hand, Patent Document 1 aims to provide a rubber composition having good moldability and a rubber molded product having a high balance of high rigidity (hardness), mechanical properties (elongation) and rubber elasticity. As
[I] 100 parts by weight of synthetic rubber,
[II] A thermoplastic resin having a melting point of 60 to 120° C. and being at least one selected from the group consisting of a maleic anhydride-modified ethylene copolymer, an ethylene/unsaturated carboxylic acid copolymer, or an ionomer thereof. A rubber composition containing 3 to 40 parts by weight and 5 to 200 parts by weight of the [III] reinforcing material is described.
In Patent Document 1, the ethylene/unsaturated carboxylic acid copolymer may be a multi-component copolymer obtained by copolymerizing other vinyl monomers, but those containing a large amount of such other monomers are generally used. It is described that it is flexible and has a low melting point and may impair heat resistance (paragraph 0034).

JP, 2010-235685, A

Under such circumstances, when a rubber composition containing a synthetic rubber, a thermoplastic resin and a reinforcing material was prepared and evaluated with reference to Patent Document 1, such a rubber composition had a low heat build-up level required recently. It has become clear that there are cases where the above is not satisfied.
An object of the present invention is to provide a rubber composition excellent in low heat buildup. Another object of the present invention is to provide a pneumatic tire.

As a result of intensive studies to solve the above problems, the present inventors have found that a predetermined effect can be obtained by using a terpolymer of ethylene, vinyl ester and maleic anhydride, leading to the present invention. It was
The present invention is based on the above findings and the like, and specifically solves the above problems by the following configurations.

1. Containing a diene rubber, silica, a silane coupling agent, and a terpolymer of ethylene, vinyl ester and maleic anhydride,
The content of the silica is 5 to 150 parts by mass with respect to 100 parts by mass of the diene rubber,
The content of the silane coupling agent is 1 part by mass or more based on 100 parts by mass of the diene rubber,
The content of the terpolymer is 1 part by mass or more based on 100 parts by mass of the diene rubber,
The rubber composition, wherein the total content of the silane coupling agent and the terpolymer is 5 to 30 parts by mass with respect to 100 parts by mass of the diene rubber.
2. The rubber composition according to 1 above, wherein the mass ratio of the content of the terpolymer to the content of the silane coupling agent (terpolymer/silane coupling agent) is 0.2 to 29. object.
3. The rubber composition according to 1 or 2 above, wherein the vinyl ester is vinyl acetate.
4. The rubber composition according to any one of 1 to 3 above, wherein the repeating unit derived from maleic anhydride constitutes a part of the main chain of the terpolymer.
5. The rubber composition as described in any one of 1 to 4 above, which is used for forming a pneumatic tire.
6. A pneumatic tire formed using the rubber composition according to any one of 1 to 5 above.

  The rubber composition of the present invention is excellent in low heat buildup. The present invention also provides a pneumatic tire having excellent low heat buildup.

FIG. 1 is a schematic partial cross-sectional view of a tire showing an example of an embodiment of a pneumatic tire of the present invention.

The present invention will be described in detail below.
In addition, in this specification, the numerical range represented using "-" means the range which includes the numerical value described before and after "-" as a lower limit and an upper limit.
In addition, in the present specification, when the component includes two or more kinds of substances, the content of the above component refers to the total content of the two or more kinds of substances.

The rubber composition of the present invention (the composition of the present invention) is
Contains a diene rubber, silica, a silane coupling agent, and a terpolymer of ethylene, vinyl ester and maleic anhydride,
The content of the silica is 5 to 150 parts by mass with respect to 100 parts by mass of the diene rubber,
The content of the silane coupling agent is 1 part by mass or more based on 100 parts by mass of the diene rubber,
The content of the terpolymer is 1 part by mass or more based on 100 parts by mass of the diene rubber,
A rubber composition in which the total content of the silane coupling agent and the terpolymer is 5 to 30 parts by mass with respect to 100 parts by mass of the diene rubber.

Since the composition of the present invention has such a constitution, it is considered that a desired effect can be obtained. The reason for this is not clear, but it is presumed to be approximately as follows.
That is, the predetermined terpolymer has a dicarboxylic acid anhydride group derived from maleic anhydride and an ester bond derived from vinyl ester. The above dicarboxylic acid anhydride group and ester bond are functional groups capable of interacting with silica.
The binary copolymer formed from ethylene and unsaturated carboxylic acid has only a carboxy group as a functional group capable of interacting with silica.
Therefore, the predetermined terpolymer has more kinds of functional groups capable of interacting with silica than the above binary copolymer and can interact with silica in various ways, so that the dispersibility of silica can be further improved. It is speculated that it can be done. The present inventors believe that this allows the present invention to exhibit excellent low heat buildup.
Hereinafter, each component contained in the rubber composition of the present invention will be described in detail.

[Rubber composition]
<Diene rubber>
The diene rubber contained in the rubber composition of the present invention is not particularly limited as long as it has a double bond in the main chain. Examples of the diene rubber include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), aromatic vinyl-conjugated diene copolymer rubber, chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), ethylene. -Propylene-diene copolymer rubber (EPDM), styrene-isoprene rubber, isoprene-butadiene rubber, nitrile rubber, hydrogenated nitrile rubber and the like can be mentioned.
The diene rubbers can be used alone or in combination of two or more.
Among them, aromatic vinyl-conjugated diene copolymer rubber, NR and BR are preferable.
Examples of the aromatic vinyl-conjugated diene copolymer rubber include styrene butadiene rubber (SBR) and styrene isoprene rubber. Among them, SBR is preferable.

  The weight average molecular weight of the diene rubber is not particularly limited, but from the viewpoint of processability, it is preferably 50,000 to 3,000,000, more preferably 100,000 to 2,000,000. The weight average molecular weight (Mw) of the diene rubber is a standard polystyrene conversion value based on the value measured by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent.

  When the diene rubber contains at least one selected from the group consisting of aromatic vinyl-conjugated diene copolymer rubber and BR, at least one selected from the group consisting of aromatic vinyl-conjugated diene copolymer rubber and BR is included. The amount is preferably 5 to 100% by mass based on the diene rubber from the viewpoint of excellent balance between low heat buildup and wet grip properties.

  When the diene rubber contains an aromatic vinyl-conjugated diene copolymer rubber and BR, the ratio of the content of the aromatic vinyl-conjugated diene copolymer rubber to BR (aromatic vinyl-conjugated diene copolymer rubber/BR) is It is preferably 10 to 1000% by mass.

<Silica>
Examples of the silica contained in the rubber composition of the present invention include the same silicas that can be generally used in rubber compositions. Specific examples include fumed silica, calcined silica, precipitated silica, pulverized silica, fused silica, colloidal silica and the like.

The silica from the viewpoint of suppressing aggregation of the silica, preferably CTAB adsorption specific surface area of ^{50~300m 2 / g, 80~250m 2 /} g is more preferable.
Here, the CTAB adsorption specific surface area is measured by measuring the adsorption amount of n-hexadecyltrimethylammonium bromide on the silica surface according to JIS K6217-3:2001 "Part 3: Determination of specific surface area-CTAB adsorption method". It is a value.
Silica may be used alone or in combination of two or more kinds.

  In the present invention, the content of silica is 5 to 150 parts by mass with respect to 100 parts by mass of the diene rubber, and is preferably 5 to 140 parts by mass from the viewpoint that the low exothermic property is more excellent, and 10 to 10 parts by mass. 130 parts by mass is more preferable.

<Silane coupling agent>
The silane coupling agent contained in the rubber composition of the present invention is not particularly limited. Among them, a silane coupling agent having a sulfur atom (sulfur-containing silane coupling agent) is mentioned as one of the preferable embodiments.
The sulfur-containing silane coupling agent is not particularly limited as long as it is a silane coupling agent having a sulfur atom. For example, polysulfide-based silane coupling agents such as bis(3-triethoxysilylpropyl)tetrasulfide, 3-trimethoxysilylpropylbenzothiazoletetrasulfide, and bis(3-triethoxysilylpropyl)disulfide; γ-mercaptopropylmethyl Dimethoxysilane, γ-mercaptopropyltrimethoxysilane, 3-[ethoxybis(3,6,9,12,15-pentaoxaoctacosan-1-yloxy)silyl]-1-propanethiol (Si363 manufactured by Evonik Degussa). A mercapto-based silane coupling agent such as; a thiocarboxylate-based silane coupling agent such as 3-octanoylthiopropyltriethoxysilane; and a thiocyanate-based silane coupling agent such as 3-thiocyanatopropyltriethoxysilane. ..
Among them, polysulfide-based silane coupling agents are preferable, and bis(3-triethoxysilylpropyl)tetrasulfide and bis(3-triethoxysilylpropyl)disulfide are more preferable.
The silane coupling agents can be used alone or in combination of two or more.
As the silane coupling agent, one kind or two or more kinds of the above silane coupling agents may be condensed in advance. The method of condensing the silane coupling agent is not particularly limited. For example, conventionally known ones can be mentioned.

  In the present invention, the content of the silane coupling agent is 1 part by mass or more based on 100 parts by mass of the diene rubber. The content of the silane coupling agent is preferably 1 to 30 parts by mass, and more preferably 1 to 25 parts by mass with respect to 100 parts by mass of the diene rubber, in that the effect of the present invention is more excellent.

<Ternary copolymer>
The terpolymer contained in the rubber composition of the present invention is a copolymer composed of ethylene, a vinyl ester and maleic anhydride. That is, it is a copolymer composed only of repeating units derived from ethylene, vinyl ester and maleic anhydride.
By containing the terpolymer, the rubber composition of the present invention is excellent not only in low heat buildup but also in processability and vulcanization physical properties.

<Ethylene>
The content of the repeating unit derived from ethylene in the terpolymer is 70 to 98 relative to the whole terpolymer because the effect of the present invention is more excellent and the content in the diene rubber is excellent. It is preferably mass%, and more preferably 75 to 95 mass%.

<Vinyl ester>
In the present invention, vinyl ester is a compound having a structure of C=CO-CO- as a monomer.
Examples of the vinyl ester include compounds represented by the following formula (3).

In formula (3), A, B and D are each independently a hydrogen atom, and E is a hydrocarbon group.
The hydrocarbon group is not particularly limited. Examples of the hydrocarbon group include aliphatic hydrocarbon groups (including linear, branched, and cyclic), aromatic hydrocarbon groups, and combinations thereof. The hydrocarbon group may have an unsaturated bond. The hydrocarbon group is preferably an alkyl group. The alkyl group preferably has 1 to 10 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, a butyl group, a hexyl group, an octyl group, and a decyl group.

The repeating unit derived from the vinyl ester contained in the terpolymer includes, for example, a structure represented by the following formula (4).

In the formula (4), A, B, D, and E are the same as A, B, D, and E in the formula (3), respectively.

  The vinyl ester is preferably vinyl acetate from the viewpoint of being excellent in the effect of the present invention and being excellent in the balance in the dispersion in the diene rubber and the interaction with silica.

  The content of the repeating unit derived from the vinyl ester in the terpolymer is preferably 5 to 40% by mass with respect to the entire terpolymer in that the effect of the present invention is more excellent. 10 to 30 mass% is more preferable.

<Maleic anhydride>

  The content of the repeating unit derived from maleic anhydride in the terpolymer is 0.1 to 5.0 mass% with respect to the entire terpolymer, in that the effect of the present invention is more excellent. It is preferably present, and more preferably 0.15 to 3.0% by mass.

-Total amount of repeating units of vinyl ester and maleic anhydride The total amount of repeating units of vinyl ester and maleic anhydride is 5 to 45 with respect to the entire terpolymer in that the effect of the present invention is more excellent. It is preferably mass%, and more preferably 10 to 35 mass%.

  Examples of the terpolymer include a random copolymer and a block copolymer.

  One of the preferred embodiments in which the repeating unit derived from maleic anhydride constitutes a part of the main chain of the terpolymer from the viewpoint that the effect of the present invention is more excellent and the dispersion in the diene rubber is excellent. As. When the repeating unit derived from maleic anhydride constitutes a part of the main chain of the terpolymer, the hydrophilicity is lower than that in the case where maleic anhydride is grafted, which results in the above case. It is presumed that the terpolymer of (3) improves compatibility with hydrophobic diene rubber.

Examples of the terpolymer include compounds represented by the following formula (1).

In formula (1), X and Y respectively represent the number of repeating units derived from ethylene. X and Y are not 0 at the same time.
m represents the number of repeating units derived from vinyl ester.
n represents the number of repeating units derived from maleic anhydride.
R represents a hydrocarbon group. The hydrocarbon group is not particularly limited. Of these, an alkyl group is preferable. The hydrocarbon group is the same as E in the above formula (4). The alkyl group is also the same as E in the above formula (4).
Note that the total amount of X and Y, m, and n can each be set to a numerical range corresponding to the content of each repeating unit described above.

The melting point of the terpolymer is preferably 50 to 120° C., more preferably 60 to 110° C., because the effect of the present invention is more excellent and the dispersion in the diene rubber is better.
In the present invention, the melting point was measured by differential scanning calorimetry (DSC) according to ASTM D3418 at a temperature rising rate of 10°C/min.

The melt mass flow rate (MFR) of the ternary copolymer is preferably 1 to 250 g/10 min, more preferably 2 to 200 g/10 min, from the viewpoint that the effect of the present invention is more excellent.
In the present invention, the melt mass flow rate was measured by a capillary rheometer according to ASTM D1238 under the conditions of 190° C. and a load of 2.16 kg.

The method of producing the terpolymer is not particularly limited. For example, conventionally known ones can be mentioned.
Further, a commercially available product can be used as the terpolymer. Examples of commercially available products include OREVAC (registered trademark) T grade (manufactured by Arkema). OREVAC (registered trademark) T grade corresponds to the compound represented by the above formula (1).
The terpolymers may be used alone or in combination of two or more.

  In the present invention, the content of the terpolymer is 1 part by mass or more based on 100 parts by mass of the diene rubber. The content of the terpolymer is preferably 3 to 28 parts by mass with respect to 100 parts by mass of the diene rubber from the viewpoint that the effect of the present invention is more excellent and the tensile properties (vulcanization properties) are excellent. It is more preferably 4 to 25 parts by mass.

  In the present invention, the total content of the silane coupling agent and the terpolymer is 5 to 30 parts by mass with respect to 100 parts by mass of the diene rubber. When the total content is in the above range, the effect of the present invention and the tensile properties (vulcanized physical properties) are excellent. The total content is preferably 6 to 30 parts by mass, and 7 to 25 parts by mass, relative to 100 parts by mass of the diene rubber, in that the effect of the present invention is more excellent and the tensile properties (vulcanized physical properties) are excellent. The mass part is more preferable.

  The mass ratio of the content of the terpolymer to the content of the silane coupling agent (terpolymer/silane coupling agent) is more excellent in the effect of the present invention and excellent in tensile properties (vulcanized physical properties). In this respect, 0.2 to 29 is preferable, and 0.4 to 20 is more preferable.

(Other ingredients)
The rubber composition of the present invention may further contain other components (additives), if necessary, within a range that does not impair the purpose and effects. Examples of additives include fillers other than silica (for example, carbon black); polymers other than diene rubber and the above terpolymer; vulcanizing agents such as vulcanizing agents, cross-linking agents, and vulcanization accelerators. System components; vulcanization accelerating aids such as zinc oxide and stearic acid; vulcanization retarders, oils, antioxidants, plasticizers, and the like, which can be generally added to rubber compositions. The content of the additive can be appropriately selected.

(Carbon black)
The rubber composition of the present invention preferably further contains carbon black. Examples of the carbon black include those similar to the carbon black that can be generally used in rubber compositions. Specific examples include SAF, ISAF, IISAF, N339, HAF, FEF, GPE, SRF and the like. Of these, SAF, ISAF, IISAF, N339, HAF and FEF are preferable.

The nitrogen adsorption specific surface area (N ₂ SA) of the carbon black is preferably 30 to 250 m ² /g, and more preferably 40 to 240 m ² /g from the viewpoint of being more excellent in the processability of the rubber composition.
Here, N ₂ SA is a value obtained by measuring the amount of nitrogen adsorbed on the surface of carbon black according to JIS K 6217-2:2001 “Part 2: Determination of Specific Surface Area-Nitrogen Adsorption Method-Single Point Method”. ..
Carbon black may be used alone or in combination of two or more kinds.

  The content of carbon black is preferably 1 to 100 parts by mass and more preferably 3 to 90 parts by mass with respect to 100 parts by mass of the diene rubber.

Examples of the method for producing the rubber composition of the present invention include a method of mixing the above components.
The temperature at the time of mixing (mixing temperature) may be, for example, 10 to 180°C, preferably 50 to 170°C, more preferably 70 to 170°C.
You may further add the additive which can be used as needed to the said component.

  Further, components other than the vulcanizing component such as a vulcanizing agent and a vulcanization accelerator may be mixed in advance and the vulcanizing component may be added thereto. At this time, the mixing temperature in at least one or both of pre-mixing and mixing after adding the vulcanizing components can be the same as the above-mentioned mixing temperature.

The device used when mixing the above components is not particularly limited. For example, conventionally known ones can be mentioned.
Mixing as used herein shall include kneading.

  The rubber composition of the present invention can be vulcanized or crosslinked under conventionally known vulcanization or crosslinking conditions.

  The rubber composition of the present invention can be used, for example, for pneumatic tires.

[Pneumatic tire]
Next, the pneumatic tire of the present invention will be described.
The pneumatic tire of the present invention is a pneumatic tire formed by using the rubber composition of the present invention described above.
The rubber composition used for the pneumatic tire of the present invention is not particularly limited as long as it is the rubber composition of the present invention.

The rubber composition can be used for a structural member constituting a pneumatic tire.
Examples of the structural member include a tire tread portion, a sidewall portion, a bead portion, a carcass layer, and a belt layer.

  Among them, it is preferable to form the tire tread portion with the rubber composition of the present invention, and it is more preferable to form at least one selected from the group consisting of a cap tread and an undertread with the rubber composition of the present invention. Treads are more preferred.

FIG. 1 shows a schematic partial cross-sectional view of a tire showing an example of an embodiment of a pneumatic tire of the present invention. The present invention is not limited to the attached drawings.
In FIG. 1, the pneumatic tire has a bead portion 1, a sidewall portion 2, and a tire tread portion 3. A carcass layer 4 in which a fiber cord is embedded is mounted between the pair of left and right bead portions 1, and the ends of the carcass layer 4 are folded back from the tire inner side to the outer side around a bead core 5 and a bead filler 6. Has been wound up. In the tire tread portion 3, the belt layer 7 is arranged outside the carcass layer 4 over the circumference of the tire. In the bead portion 1, a rim cushion 8 is arranged at a portion in contact with a rim (not shown).

  The pneumatic tire of the present invention can be manufactured, for example, according to a conventionally known method. As the gas to be filled in the tire, for example, in addition to normal air or oxygen partial pressure-adjusted air, an inert gas such as nitrogen, argon or helium can be used.

The present invention will be specifically described below with reference to examples. However, the present invention is not limited to these.
<Production of rubber composition>
In the formulations shown in the following tables, each component other than the vulcanization system (sulfur, sulfur-containing vulcanization accelerator, vulcanization accelerator) was used in the amounts (parts by mass) shown in the table, and these were used. After kneading in a liter closed Banbury mixer for 5 minutes at 170° C., the obtained mixture was discharged to the outside of the mixer and cooled to room temperature. Then, the above-mentioned vulcanization system was added to the above mixture in an amount (parts by mass) shown in the same table, and these were kneaded with an open roll at 140°C to produce a rubber composition.

<Preparation of vulcanized rubber test piece>
The rubber composition produced as described above was press-vulcanized in a predetermined mold at 160° C. for 20 minutes to prepare a vulcanized rubber test piece.

<Evaluation>
Physical properties of the rubber composition and the vulcanized rubber test piece manufactured as described above were measured by the following test methods. The results are shown in each table.
The evaluation results of each example are shown in Table 1 as an index with the result of Comparative Example 1 being 100. In Table 2, the result of Comparative Example 5 is shown as an index with 100. In Table 3, the result of Comparative Example 6 is shown as an index with 100.

・Moonie viscosity (processability)
According to JIS K6300-1:2013, the Mooney viscosity of the rubber composition produced as described above was determined under the condition of 100°C.
The smaller the Mooney viscosity index, the better the processability of the rubber composition.

・Hardness (20℃) (Vulcanization properties)
The hardness (type A durometer hardness) of the vulcanized rubber test piece manufactured as described above was measured at 20° C. according to JIS K6253-3:2012.

-Modulus (M100, M300), elongation at break ( _Eb ) (vulcanized physical properties)
A JIS No. 3 dumbbell-shaped test piece is punched out from the vulcanized rubber test piece produced as described above, and a tensile test is performed at a tensile speed of 500 mm/min according to JIS K-6251:2010, and a tensile stress at 100% elongation is obtained. (M100), tensile stress at 300% elongation (M300), and elongation at break (E _b ) were measured at 20°C.

・Tan δ (60℃)
With respect to the vulcanized rubber test piece manufactured as described above, a loss tangent tan δ was measured using a viscoelasticity spectrometer (manufactured by Iwamoto Seisakusho Co., Ltd.) under conditions of an elongation deformation strain rate of 10±2%, a frequency of 20 Hz, and a temperature of 60° C. (60° C.) was measured.
The smaller the tan δ (60° C.) index, the better the low heat buildup.

Details of each component shown in each of the above tables are as follows.
Diene rubber 1: styrene-butadiene rubber (E-SBR) produced by emulsion polymerization, Nipol1502, manufactured by Zeon Corporation, weight average molecular weight 400,000.
Diene rubber 2: butadiene rubber (BR), Nipol BR 1220 manufactured by Zeon Corporation, weight average molecular weight 400,000.

-Ternary copolymer 1 (E-VA-MAH): A terpolymer of ethylene-vinyl acetate-maleic anhydride. The content of the repeating unit derived from vinyl acetate in the terpolymer was 26% by mass, and the content of the repeating unit derived from maleic anhydride was 0.16% by mass. The repeating unit derived from maleic anhydride constitutes a part of the main chain of the terpolymer 1. Melting point 77[deg.]C. MFR 7 g/min. Product name OREVAC T9304, manufactured by Arkema.

-Ternary copolymer 2 (E-VA-MAH): A terpolymer of ethylene-vinyl acetate-maleic anhydride. The content of the repeating unit derived from vinyl acetate in the terpolymer was 18% by mass, and the content of the repeating unit derived from maleic anhydride was 0.16% by mass. The repeating unit derived from maleic anhydride constitutes a part of the main chain of the terpolymer 2. Melting point 85[deg.]C. MFR 7 g/min. Product name OREVAC T9318, manufactured by Arkema.

-Comparative binary copolymer 1 (E-VA): ethylene-vinyl acetate copolymer, trade name Novatec LV430, manufactured by Nippon Polyethylene Corporation

-Silane coupling agent: bis(triethoxysilylpropyl) tetrasulfide. Sulfide-based silane coupling agent, Si69 manufactured by Degussa

Silica: Wet silica, CTAB adsorption specific surface area 170 m ² /g, Nipseal AQ manufactured by Nihon Silica Co., Ltd.
・Carbon black: Show black N339M, N ₂ SA 81m ² /g, HAF manufactured by Showa Cabot
・Zinc oxide: Zhonghua No. 3 manufactured by Shodo Kagaku Co., Ltd.・Stearic acid: Stearic acid manufactured by NOF CORPORATION ・Anti-aging agent: Antigen 6C (S-13) manufactured by Sumitomo Chemical Co., Ltd.
・Oil: Extract No. 4S manufactured by Showa Shell Sekiyu Co., Ltd.
・Sulfur: Sulfur/sulfur-containing vulcanization accelerator (CZ) produced by Karuizawa Smelter Co., Ltd.: N-cyclohexyl-2-benzothiazolyl sulfenamide, Sanshin Chemical Co., Ltd.
・Vulcanization accelerator ( DPG ): diphenylguanidine, Sanshin Kagaku Sancellar DG

As shown in Table 1, Comparative Example 2 containing Comparative Binary Copolymer 1 on the basis of Comparative Example 1 was not highly effective in low heat buildup.
Comparative Example 4 (ternary copolymer 1:15 parts by mass) containing the ternary copolymer but not the silane coupling agent was used in Example 2 (total of the ternary copolymer and the silane coupling agent). It was inferior in low exothermic property than the content of 15 parts by mass).
Further, Comparative Example 3 in which the total content of the terpolymer and the silane coupling agent was out of the specific range was inferior to Comparative Example 1 in low heat buildup.

On the other hand, in Table 1, the composition of the present invention was excellent in low heat buildup. Specifically, comparing Example 1 with Comparative Examples 1 and 3, Example 1 was superior to Comparative Examples 1 and 3 in low heat generation. Moreover, when Examples 2 to 4 and Comparative Examples 2 and 4 are compared, Examples 2 to 4 are superior to Comparative Examples 2 and 4 in low heat generation.
Comparing Examples 1 to 3, as the content of the terpolymer increased, the workability, hardness, and M100 were more excellent, and the low exothermic property was more excellent.

As shown in Table 2, Comparative Example 6 in which the amount of the silane coupling agent was increased based on Comparative Example 5 was inferior to Comparative Example 5 in low heat buildup.
Comparative Example 4 containing the terpolymer but not the silane coupling agent was inferior to Example 6 in low heat buildup.
Further, in Comparative Example 7 in which the total content of the terpolymer and the silane coupling agent was outside the specific range, the effect of low heat buildup was not high.

On the other hand, in Table 2, the composition of the present invention was excellent in low heat buildup. Specifically, comparing Example 5 with Comparative Examples 5 to 7, Example 5 was superior to Comparative Examples 5 to 7 in low heat buildup. Further, comparing Examples 6 and 7 with Comparative Example 4, Examples 6 and 7 were superior to Comparative Example 4 in low heat buildup.
Comparing Examples 5 to 7, the higher the content of the terpolymer, the more excellent the workability and hardness, and the more excellent the low heat buildup.

As shown in Table 3, the composition of the present invention was excellent in low heat buildup. Specifically, comparing Example 8 with Comparative Example 6, Example 8 was superior to Comparative Example 6 in low heat buildup. Further, comparing Examples 9 and 10 with Comparative Example 4, Examples 9 and 10 were superior to Comparative Example 4 in low heat buildup.
Comparing Examples 8 to 10, as the content of the terpolymer increased, the workability, hardness, and M100 were more excellent, and the lower heat generation was more excellent.

  Thus, the rubber composition of the present invention is excellent not only in low exothermicity but also in processability and vulcanization physical properties.

1 Bead Part 2 Sidewall Part 3 Tire Tread Part 4 Carcass Layer 5 Bead Core 6 Bead Filler 7 Belt Layer 8 Rim Cushion

Claims (5)

Contains a diene rubber, silica, a silane coupling agent, and a terpolymer of ethylene, vinyl ester and maleic anhydride,
The content of the silica is 5 to 150 parts by mass with respect to 100 parts by mass of the diene rubber,
The content of the silane coupling agent is 1 part by mass or more based on 100 parts by mass of the diene rubber,
The content of the terpolymer is 1 part by mass or more based on 100 parts by mass of the diene rubber,
Total content of said terpolymer and said silane coupling agent is, with respect to the diene rubber 100 parts by weight, Ri 5 to 30 parts by mass der,
Repeating units derived from the maleic anhydride, constitute the backbone of the terpolymer, a rubber composition.   The rubber according to claim 1, wherein a mass ratio of the content of the terpolymer to the content of the silane coupling agent (terpolymer/silane coupling agent) is 0.2 to 29. Composition.   The rubber composition according to claim 1 or 2, wherein the vinyl ester is vinyl acetate. Used to form the pneumatic tire, the rubber composition according to any one of claims 1-3. A pneumatic tire formed using the rubber composition according to any one of claims 1-4.