JP6743339B2 - Rubber composition and pneumatic tire - Google Patents

Description

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

In recent years, from the viewpoint of protecting the global environment, pneumatic tires have also been required to consider the environment, and specifically, performance to improve fuel consumption while maintaining high strength is desired.
In order to improve fuel efficiency, a pneumatic tire may be manufactured using a rubber composition capable of suppressing heat generation during running, and particularly, a cap tread that comes into contact with the road surface during running or a sidewall that has large repeated deformation during running. It is considered that the fuel consumption can be improved by reducing the heat generation of.

Then, in Patent Document 1, the applicant of the present invention, "natural rubber, butadiene rubber, styrene-butadiene copolymerization" for the purpose of achieving low exothermicity while maintaining hardness and modulus and imparting high elongation at break. 1 to 80 parts by mass of regenerated polyethylene terephthalate powder is blended with 100 parts by mass of at least one diene rubber selected from the group consisting of coalesced rubber, isoprene rubber and ethylene-propylene-diene terpolymer. A rubber composition for tires." ([Claim 1][0005]), and from the viewpoint of further enhancing the above-mentioned object (effect), "carboxyl group based on 100 parts by mass of diene rubber". Alternatively, 1 to 30 parts by mass of anhydrous carboxyl group-containing polyethylene is blended" ([Claim 2] [0007]).

JP, 2011-153168, A

Under such circumstances, when a rubber composition containing a compound having a carboxy group or the like was prepared with reference to Patent Document 1, the low heat buildup property of such a rubber composition may not satisfy the level required recently. It became clear.
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 obtained a predetermined effect by using a terpolymer of (meth)acrylic acid ester and maleic anhydride and an acid-modified polyolefin in combination. The inventors have found out that and have reached the present invention.
The present invention is based on the above findings and the like, and specifically solves the above problems by the following configurations.

1. A diene rubber, a terpolymer of ethylene, a (meth)acrylic acid ester and maleic anhydride, an acid-modified polyolefin, and at least one filler selected from the group consisting of carbon black and a white filler. Contains,
A rubber composition in which the total content of the terpolymer and the acid-modified polyolefin is 3 to 30 parts by mass with respect to 100 parts by mass of the diene rubber.
2. 2. The rubber composition according to 1 above, wherein the mass ratio of the content of the terpolymer to the content of the acid modified polyolefin (terpolymer/acid modified polyolefin) is 0.2 to 29.
3. The rubber composition according to 1 or 2 above, wherein the (meth)acrylic acid ester is at least one selected from the group consisting of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate and octyl acrylate. ..
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 according to any one of 1 to 4 above, wherein the acid-modified polyolefin is a copolymer of ethylene and an α-olefin modified with maleic anhydride.
6. The rubber composition according to the above 5, wherein the α-olefin is at least one selected from the group consisting of propylene, 1-butene and 1-octene.
7. 7. The rubber composition according to any one of 1 to 6 above, which is used for forming a pneumatic tire.
8. A pneumatic tire formed using the rubber composition according to any one of 1 to 7 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, (meth)acrylate represents acrylate or methacrylate, (meth)acryloyl represents acryloyl or methacryloyl, and (meth)acryl represents acryl or methacryl.
Further, in the present specification, the numerical range represented by using "to" means a range including the numerical values before and after "to" as the lower limit value and the upper limit value.
In the present specification, when the component contains two or more kinds of substances, the content of the above-mentioned component means 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
A diene rubber, a terpolymer of ethylene, a (meth)acrylic acid ester and maleic anhydride, an acid-modified polyolefin, and at least one filler selected from the group consisting of carbon black and a white filler. Contains,
In the rubber composition, the total content of the terpolymer and the acid-modified polyolefin is 3 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 estimated 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 a (meth)acrylic acid ester. The above dicarboxylic acid anhydride group and ester bond are functional groups capable of interacting with silica.
On the other hand, since the acid-modified polyolefin is modified with an acid, it can interact with silica.
Thus, the terpolymer and the acid-modified polyolefin each have a functional group capable of interacting with silica.
Since the terpolymer is formed from ethylene, (meth)acrylic acid ester and maleic anhydride, its main chain is a so-called polyolefin.
On the other hand, the main chain of the acid-modified polyolefin is also polyolefin.
As described above, the terpolymer and the acid-modified polyolefin have the same main chain skeleton in the polyolefin, and thus it is considered that they are easily compatible with each other.
Therefore, it is surmised that the rubber composition of the present invention can disperse silica more effectively than the case where the acid-modified polyolefin is used alone due to the compatibility with the functional groups. The present inventors believe that this allows the present invention to exhibit excellent low heat buildup.
Hereinafter, each component contained in the 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. Of these, SBR is preferred.

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 kind selected from the group consisting of aromatic vinyl-conjugated diene copolymer rubber and BR, the content of at least one kind selected from the group consisting of aromatic vinyl-conjugated diene copolymer rubber and BR 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.

<Ternary copolymer>
The terpolymer contained in the rubber composition of the present invention is a copolymer composed of ethylene, (meth)acrylic acid ester and maleic anhydride. That is, it is a copolymer composed only of repeating units derived from ethylene, (meth)acrylic acid ester and maleic anhydride.
Since the rubber composition of the present invention contains the terpolymer, it is excellent in low exothermic property and also in processability.

<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%.

<(Meth)acrylic acid ester>
The (meth)acrylic acid ester forming the terpolymer is preferably an acrylic acid ester, and more preferably an acrylic acid alkyl ester, from the viewpoint that the effect of the present invention is excellent.
The ester residue of the (meth)acrylic acid ester is not particularly limited. For example, a hydrocarbon group may be mentioned. 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 alkyl group constituting the ester of the acrylic acid alkyl ester may be linear, branched or cyclic. 1-8 are preferable and, as for the number of carbon atoms which an alkyl group has, 2-6 are more preferable.

The (meth)acrylic acid ester is preferably at least one alkyl acrylate ester selected from the group consisting of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate and octyl acrylate.

The content of the repeating unit derived from the (meth)acrylic acid ester in the ternary copolymer is 3 to 40% by mass based on the whole terpolymer in that the effect of the present invention is more excellent. It is preferable, and 5-30 mass% is more preferable.

<Maleic anhydride>

The content of the repeating unit derived from maleic anhydride in the terpolymer is 0.1 to 10% by mass based on the whole terpolymer in that the effect of the present invention is more excellent. Is preferable, and 0.2-8 mass% is more preferable.

-Total amount of repeating units of (meth)acrylic acid ester and maleic anhydride The total amount of repeating units of (meth)acrylic acid ester and maleic anhydride is a terpolymer because the effect of the present invention is more excellent. It is preferably from 3 to 50% by mass, more preferably from 5 to 40% by mass, based on the whole.

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

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 each represent the number of repeating units derived from ethylene. Note that X and Y are not 0 at the same time.
m represents the number of repeating units derived from the (meth)acrylic acid 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 the hydrocarbon group as the ester residue of the (meth)acrylic acid ester. The alkyl group is the same as the alkyl group constituting the ester of the acrylic acid alkyl ester.
In addition, the total amount of X and Y, m, and n can each be a numerical range corresponding to the content of each repeating unit described above.

The melting point of the ternary copolymer is preferably 50 to 130° C., more preferably 60 to 120° C., because the effect of the present invention is more excellent and the dispersion in the diene rubber is excellent.
Further, when the melting point of the terpolymer is lower than the mixing temperature (or kneading temperature) at the time of producing the rubber composition of the present invention, the compatibility of the terpolymer with the diene rubber is increased, which is preferable. ..
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 300 g/10 min, more preferably 2 to 200 g/10 min, from the viewpoint that the effect of the present invention is more excellent and the processability is 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.
Moreover, a commercial item can be used as a terpolymer. Examples of commercially available products include BONDINE (registered trademark) and LOTDER (registered trademark) MAH grade (all manufactured by Arkema). BONDINE and LOTADER MAH grade correspond to the compound represented by the above formula (1).
The terpolymers may be used alone or in combination of two or more.

The content of the terpolymer is preferably 3 to 28 parts by mass, and preferably 4 to 25 parts by mass, relative to 100 parts by mass of the diene rubber, because the effect of the present invention is more excellent and the processability is excellent. Parts are more preferred.

In the present invention, the total content of the acid-modified polyolefin and the terpolymer described later is 3 to 30 parts by mass with respect to 100 parts by mass of the diene rubber. The total content is preferably 4 to 30 parts by mass, and more preferably 5 to 25 parts by mass with respect to 100 parts by mass of the diene rubber, because the effect of the present invention is more excellent and the processability is excellent. ..

The mass ratio of the content of the terpolymer to the content of the acid-modified polyolefin (terpolymer/acid-modified polyolefin) is 0 because the effect of the present invention is more excellent and the processability or cost is excellent. 0.2 to 29 is preferable, and 0.3 to 20 is more preferable.

<Acid-modified polyolefin>
The acid-modified polyolefin contained in the rubber composition of the present invention is a polymer obtained by modifying a polyolefin resin with an unsaturated carboxylic acid. However, in the present invention, the acid-modified polyolefin does not include the above terpolymer.

Examples of the acid-modified polyolefin include a copolymer modified with an unsaturated carboxylic acid and having one repeating unit selected from the group consisting of ethylene and α-olefins.
The α-olefin that can form the acid-modified polyolefin is not particularly limited as long as it is a hydrocarbon compound having an unsaturated bond at the terminal. In the present invention, the α-olefin does not contain ethylene. It is mentioned as one of the preferable embodiments that the α-olefin is composed of only carbon atoms and hydrogen atoms.
The α-olefin is preferably at least one selected from the group consisting of propylene, 1-butene and 1-octene, for example.

The acid-modified polyolefin preferably has, for example, a modifying group formed by an unsaturated carboxylic acid.
Examples of the modifying group include groups represented by the following formula (3).
In formula (3), * represents a point of attachment.
The acid-modified polyolefin is mentioned as one of the preferred embodiments in which the side chain has a modification group with maleic anhydride.

The acid-modified polyolefin is preferably a copolymer of ethylene and α-olefin modified with maleic anhydride.

Further, the acid-modified polyolefin is preferably a copolymer having a modifying group with maleic anhydride in the side chain and having as a main chain one kind of repeating unit selected from the group consisting of ethylene and α-olefin. ..

Examples of the acid-modified polyolefin include compounds represented by the following formula (2).
In the formula (2), l is 1 or more, preferably 2 to 10,000.
m is 1 or more, preferably 2 to 10,000.
n is 1 or more, preferably 2 to 10,000.

(Polyolefin)
As the polyolefin constituting the skeleton of the acid-modified polyolefin, for example,
Homopolymers such as polypropylene, polybutene, polyhexene and polyoctene;
Propylene/ethylene copolymer, propylene/1-butene copolymer, propylene/1-hexene copolymer, propylene/4-methyl-1-pentene copolymer, propylene/1-octene copolymer, propylene/1 -Decene copolymer, propylene/1,4-hexadiene copolymer, propylene/dicyclopentadiene copolymer, propylene/5-ethylidene-2-norbornene copolymer, propylene/2,5-norbornadiene copolymer, Propylene-5-ethylidene-2-norbornene copolymer, 1-octene/ethylene copolymer, 1-butene/ethylene copolymer, 1-butene/propylene copolymer, 1-butene/1-hexene copolymer , 1-butene/4-methyl-1-pentene copolymer, 1-butene/1-octene copolymer, 1-butene/1-decene copolymer, 1-butene/1,4-hexadiene copolymer , 1-butene/dicyclopentadiene copolymer, 1-butene/5-ethylidene-2-norbornene copolymer, 1-butene/2,5-norbornadiene copolymer, 1-butene/5-ethylidene-2- Two-component copolymers such as norbornene copolymers;
Ethylene/propylene/1-butene copolymer, ethylene/propylene/1-hexene copolymer, ethylene/propylene/1-octene copolymer, ethylene/propylene/1-octene copolymer, ethylene/propylene/1. 4-hexadiene copolymer, ethylene/propylene/1,4-hexadiene copolymer, ethylene/propylene/dicyclopentadiene copolymer, ethylene/propylene/dicyclopentadiene copolymer, ethylene/propylene/5-ethylidene- 2-norbornene copolymer, ethylene/propylene/5-ethylidene-2-norbornene copolymer, ethylene/propylene/2,5-norbornadiene copolymer, ethylene/propylene/2,5-norbornadiene copolymer, ethylene/ Propylene/5-ethylidene-2-norbornene copolymer, ethylene/propylene/5-ethylidene-2-norbornene copolymer, 1-butene/ethylene/propylene copolymer, 1-butene/ethylene/1-hexene copolymer Coal, 1-butene/ethylene/1-octene copolymer, 1-butene/propylene/1-octene copolymer, 1-butene/ethylene/1,4-hexadiene copolymer, 1-butene/propylene/1 ,4-hexadiene copolymer, 1-butene/ethylene/dicyclopentadiene copolymer, 1-butene/propylene/dicyclopentadiene copolymer, 1-butene/ethylene/5-ethylidene-2-norbornene copolymer , 1-butene/propylene/5-ethylidene-2-norbornene copolymer, 1-butene/ethylene/2,5-norbornadiene copolymer, 1-butene/propylene/2,5-norbornadiene copolymer, 1- Multicomponent copolymers such as butene/ethylene/5-ethylidene-2-norbornene copolymer and 1-butene/propylene/5-ethylidene-2-norbornene copolymer; and the like.

Among these, polyethylene, polypropylene, polybutene, polyoctene, propylene/ethylene copolymer, 1-butene/ethylene copolymer, 1-butene/propylene copolymer, ethylene/propylene/1-butene copolymer, 1- It is preferable to use an octene/ethylene copolymer.

(Unsaturated carboxylic acid)
On the other hand, examples of the unsaturated carboxylic acid that modifies the above-mentioned polyolefin include maleic acid, fumaric acid, acrylic acid, crotonic acid, methacrylic acid, itaconic acid, or acid anhydrides of these acids. ..
Of these, maleic anhydride, maleic acid, and acrylic acid are preferably used.

The above-mentioned acid-modified polyolefin may be produced by a commonly used method, for example, a method in which the unsaturated carboxylic acid is graft-polymerized to the above-mentioned polyolefin under commonly used conditions, for example, stirring under heating, or a commercially available product. May be used.
Examples of commercially available products include maleic anhydride-modified propylene/ethylene copolymers such as Tufmer MA8510 (manufactured by Mitsui Chemicals) and MP0620 (manufactured by Mitsui Chemicals); maleic anhydride-modified such as Tuffmer MH7020 (manufactured by Mitsui Chemicals). Ethylene/1-butene copolymer; maleic anhydride modified polypropylene such as Admer QE060 (manufactured by Mitsui Chemicals, Inc.); and the like.

The melt mass flow rate (MFR) of the acid-modified polyolefin is preferably 0.1 to 10 g/10 min, and more preferably 0.2 to 8 g/10 min in terms of the effects of the present invention being more excellent and the hardness being excellent.
In the present invention, the MFR of the acid-modified polyolefin was measured by a capillary rheometer according to ASTM D1238 under the conditions of 230° C. and a load of 2.16 kg.

Further, the melting point of the acid-modified polyolefin is preferably higher than the melting point of the terpolymer. In this case, when the rubber composition of the present invention is produced, the terpolymer is first melted in the system, the composition is easily mixed, and then the temperature in the system is increased to melt the acid-modified polyolefin. It is believed that this further facilitates the mixing of the composition and improves the dispersion of silica. It is also presumed that the ternary copolymer may be melted first to induce melting and dispersion of the acid-modified polyolefin.
The case where the MFR of the acid-modified polyolefin is smaller than that of the terpolymer is also preferable for the same reason as above.

In the present invention, the content of the acid-modified polyolefin is preferably 3 to 29 parts by mass, and preferably 4 to 25 parts by mass, based on 100 parts by mass of the diene rubber, from the viewpoint that the effect of the present invention is excellent. Is more preferable.

<Filler>
The filler contained in the rubber composition of the present invention is at least one selected from the group consisting of carbon black and white filler.

(Carbon black)
Carbon black as a filler is not particularly limited. For example, those similar to carbon black that can be generally used in rubber compositions can be mentioned. Specific examples include SAF, ISAF, IISAF, N339, HAF, FEF, GPE and SRF. 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 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.

(White filler)
The white filler as a filler is not particularly limited. For example, those similar to those generally used in rubber compositions can be mentioned. Specific examples include silica, calcium carbonate, talc, mica and the like. Of these, silica is preferred.

-Silica Examples of silica include fumed silica, calcined silica, precipitated silica, pulverized silica, fused silica, and colloidal silica.

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 was measured according to JIS K6217-3:2001 "Part 3: Determination of specific surface area-CTAB adsorption method" for the adsorption amount of n-hexadecyltrimethylammonium bromide on the surface of silica. It is a value.
The white fillers may be used alone or in combination of two or more.

The content of the filler is preferably 5 to 150 parts by mass and more preferably 10 to 130 parts by mass with respect to 100 parts by mass of the diene rubber.
When carbon black and silica are used together as the filler, the content of carbon black is preferably 1 to 100 parts by mass, and more preferably 2 to 80 parts by mass with respect to 100 parts by mass of the diene rubber. Further, in this case, the content of silica is preferably 5 to 150 parts by mass, and more preferably 10 to 140 parts by mass with respect to 100 parts by mass of the diene rubber.

(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 effect. Examples of the additive include polymers other than diene rubber, terpolymer and acid-modified polyolefin; silane coupling agents, vulcanizing agents, cross-linking agents, vulcanization accelerators, zinc oxide, stearic acid, etc. Examples thereof include vulcanization accelerating aids, vulcanization retarders, oils, antioxidants, plasticizers and the like, which can be generally compounded in the rubber composition. The content of the additive can be appropriately selected.

-Silane coupling agent It is preferable that the rubber composition of the present invention further contains a silane coupling agent from the viewpoint of being excellent in the effects of the present invention.
The silane coupling agent 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 these, 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 preferably 1 to 30 parts by mass, and 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. More preferably.

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 180°C, more preferably 100 to 180°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 the premixing and the mixing after adding the vulcanizing components can be the same as the above mixing temperature.

The device used for 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 using the above-mentioned rubber composition of the present invention.
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, and a carcass portion.

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 the cap tread and the 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 an end portion of the carcass layer 4 is 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 on the outer side of the carcass layer 4 over the entire 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 by, for example, a conventionally known method. Further, as the gas to be filled in the tire, for example, in addition to normal air or air whose oxygen partial pressure is adjusted, 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 formulation shown in Table 1 below, each component other than the vulcanization system (sulfur, vulcanization accelerator) was used in the amounts (parts by mass) shown in the table, and these were used in a 1.7-liter closed Banbury mixer. After kneading at 170° C. for 5 minutes, the obtained mixture was discharged to the outside of the mixer and cooled to room temperature. Subsequently, the vulcanization system was added to the 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.
The diene rubber 1 is an oil-extended product. In each of the examples in Table 1, two amounts of the diene rubber 1 are shown. The upper value is the amount of the diene rubber 1 used as an oil-extended product, and the lower value is the net amount of SBR in the diene rubber 1.

<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>
The physical properties of the vulcanized rubber test pieces 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 as 100.

・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.

・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) under the conditions of elongation deformation strain rate 10±2%, frequency 20 Hz, and temperature 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, Tuffden E581 (oil extended product), manufactured by Asahi Kasei Chemicals Ltd., Diene rubber 2: butadiene rubber (BR), Nipol BR 1220 manufactured by Zeon Corporation.

-Acid-modified polyolefin 1: Maleic anhydride-modified ethylene/1-butene copolymer (Tufmer MH7020, manufactured by Mitsui Chemicals, Inc.). It has a modifying group on its side chain with maleic anhydride. MFR 1.5 g/10 min.
-Acid-modified polyolefin 2: Maleic anhydride-modified propylene/ethylene copolymer (Tufmer MP0620, manufactured by Mitsui Chemicals, Inc.). It has a modifying group on its side chain with maleic anhydride. MFR 0.3 g/10 min.

-Ternary copolymer 1 (E-EA-MAH): A terpolymer of ethylene-acrylic acid ethyl ester-maleic anhydride. The content of the repeating unit derived from ethyl acrylate in the terpolymer was 13% by mass, and the content of the repeating unit derived from maleic anhydride was 2.8% by mass. Repeating units derived from maleic anhydride form part of the main chain. Melting point 95[deg.]C. MFR 3g/min. Product name BONDINE TX8030, manufactured by Arkema.

-Ternary copolymer 2 (E-BA-MAH): a terpolymer of ethylene-acrylic acid butyl ester-maleic anhydride. The content of the repeating unit derived from butyl acrylate in the terpolymer was 6.5% by mass, and the content of the repeating unit derived from maleic anhydride was 3.6% by mass. Repeating units derived from maleic anhydride form part of the main chain. Melting point 105[deg.]C. MFR 9.5 g/min. Product name LOTADER 4210, manufactured by Arkema.
-Ternary copolymer 3 (E-MA-MAH): a terpolymer of ethylene-acrylic acid methyl ester-maleic anhydride. The content of the repeating unit derived from acrylic acid methyl ester in the terpolymer was 19% by mass, and the content of the repeating unit derived from maleic anhydride was 0.3% by mass. Repeating units derived from maleic anhydride form part of the main chain. Melting point 80[deg.]C. MFR 8 g/min. Product name LOTADER4503, manufactured by Arkema.

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

Silica: Zeosil (registered trademark) 1165MP, Solvay S.M. A. Made by the company. CTAB adsorption specific surface area 160 m ² /g
・Carbon black: Show black N339, N ₂ SA 81 m ² /g, HAF manufactured by Cabot Japan
Zinc oxide: Zhuanghua No. 3 manufactured by Shodo Kagaku Co., Ltd.-Stearic acid: Stearic acid manufactured by NOF Corporation, Antiaging Agent: Antigen 6C (S-13) manufactured by Sumitomo Chemical Co., Ltd.
・Oil: Extract No. 4S manufactured by Showa Shell Sekiyu KK
・Sulfur: Sulfur and vulcanization accelerator (CZ) produced by Karuizawa Smelter Co., Ltd.: N-cyclohexyl-2-benzothiazolyl sulfenamide, Sanshin Chemical Co., Ltd. CM-PO
・Vulcanization accelerator (DPG): diphenylguanidine, Sanshin Kagaku Sancellar DG

As shown in Table 1, Comparative Examples 2 and 3 further containing the acid-modified polyolefin 1 based on Comparative Example 1 did not have a high effect of low heat buildup.

On the other hand, in Table 1, the composition of the present invention was excellent in low heat buildup.
Comparing Examples 5 to 7 with Examples 1 to 4, in Examples 5 to 7 in which the total content of the acid-modified polyolefin and the terpolymer exceeds 10 parts by mass, the total content is 10 parts by mass. Parts 1 to 4 which are excellent in low exothermic property and higher in hardness.
Comparing Examples 1, 6, and 7, it was found that the higher the content of the acid-modified polyolefin, the better the low heat build-up property and the higher the hardness.

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 (7)

A diene rubber, a terpolymer of ethylene, a (meth)acrylic acid ester and maleic anhydride, an acid-modified polyolefin, and at least one filler selected from the group consisting of carbon black and a white filler. Contains,
The acid-modified polyolefin is a maleic anhydride-modified copolymer of ethylene and α-olefin,
A rubber composition in which the total content of the terpolymer and the acid-modified polyolefin is 10 to 25 parts by mass with respect to 100 parts by mass of the diene rubber. The rubber composition according to claim 1, wherein a mass ratio of the content of the terpolymer to the content of the acid-modified polyolefin (terpolymer/acid-modified polyolefin) is 0.2 to 29. .. The rubber composition according to claim 1 or 2, wherein the (meth)acrylic acid ester is at least one selected from the group consisting of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, and octyl acrylate. Stuff. The rubber composition according to any one of claims 1 to 3, wherein the repeating unit derived from maleic anhydride constitutes a part of the main chain of the terpolymer. The rubber composition according to any one of claims 1 to 4, wherein the α-olefin is at least one selected from the group consisting of propylene, 1-butene and 1-octene. Used to form the pneumatic tire, the rubber composition according to any one of claims 1-5. A pneumatic tire formed using the rubber composition according to any one of claims 1-6.