JP2023028917A - Rubber composition and tire - Google Patents

Abstract

To provide a rubber composition that achieves improved overall performances including dry grip performance, wet grip performance and fuel economy, and a tire including the same.SOLUTION: A rubber composition contains modified rubber having at least one selected from the group consisting of carboxylic acid, sulfonic acid, and salts thereof in each molecule, and at least one metal oxide selected from the group consisting of lithium oxide, sodium oxide, potassium oxide, rubidium oxide, cesium oxide, beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide and the like. The action of water causes a reversible change in complex elastic modulus (E*) and loss tangent (tanδ). The rubber composition satisfies the following formula (1) and/or the following formula (2). E* under water-wet condition/E* under dry condition≤0.90 (1) and tanδ under water-wet condition/tanδ under dry condition≥1.10 (2).SELECTED DRAWING: None

Description

The present disclosure relates to rubber compositions and tires.

The grip performance of a tire is important in that it is directly linked to safety, and various studies have been conducted to improve the grip performance (see Patent Document 1, for example). In addition, from an environmental point of view, low fuel consumption is also important, and further improvements in grip performance (dry grip performance, wet grip performance) and low fuel consumption are required.

JP 2008-285524 A

An object of the present disclosure is to solve the above problems and to provide a rubber composition that improves the overall performance of dry grip performance, wet grip performance, and fuel efficiency, and a tire using the same.

The present disclosure provides a modified rubber having in its molecule at least one selected from the group consisting of carboxylic acids, sulfonic acids, and salts thereof;
Lithium oxide, sodium oxide, potassium oxide, rubidium oxide, cesium oxide, beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide, scandium oxide, titanium oxide, vanadium oxide, chromium oxide, manganese oxide, iron oxide, cobalt oxide , nickel oxide, copper oxide, yttrium oxide, zirconium oxide, niobium oxide, molybdenum oxide, technetium oxide, ruthenium oxide, rhodium oxide, palladium oxide, silver oxide, hafnium oxide, tantalum oxide, tungsten oxide, osmium oxide, iridium oxide, oxide At least one metal oxide selected from the group consisting of platinum, gold oxide, aluminum oxide, gallium oxide, cadmium oxide, indium oxide, tin oxide, thallium oxide, lead oxide, bismuth oxide, and polonium oxide,
It relates to a rubber composition whose complex elastic modulus (E*) and loss tangent (tan δ) reversibly change with water and which satisfies the following formula (1) and/or the following formula (2).
E* when wet with water / E* when dry ≤ 0.90 (1)
tan δ when wet with water/tan δ when dry ≥ 1.10 (2)
(In the formula, E* and tan δ are the complex elastic modulus 30 minutes after the start of measurement measured under the conditions of temperature 30 ° C., initial strain 10%, dynamic strain 1%, frequency 10 Hz, extension mode, measurement time 30 minutes and the loss tangent.)

According to the present disclosure, the rubber composition contains the modified rubber having a carboxylic acid or the like in the molecule and a metal oxide such as lithium oxide, and satisfies the formulas (1) and/or (2). , dry grip performance, wet grip performance, and overall fuel efficiency can be improved.

1 is a cross-sectional view showing a portion of a pneumatic tire; FIG.

<Rubber composition>
The present disclosure includes a modified rubber having in the molecule at least one selected from the group consisting of carboxylic acids, sulfonic acids, and salts thereof, and the metal oxide, and the formula (1) and/or It is a rubber composition that satisfies (2). The rubber composition improves overall performance of dry grip performance, wet grip performance and fuel efficiency.

Although the reason why the rubber composition achieves the above effects is not necessarily clear, it is presumed to be due to the following mechanism.
When the modified rubber having a carboxylic acid or the like in its molecule and the metal oxide are used, an ionic bond is formed between the carboxylic acid or the like and the metal of the metal oxide. Then, while the ionic bonds are formed when dry, the ionic bonds are dissociated when wet with water (when in contact with water), so that the rubber composition "E* decreases" and / or "tan δ increases". Therefore, when wet (when in contact with water), the contact area with the road surface increases and/or the energy loss increases, improving friction (μ) on wet road surfaces (wet road surfaces) and improving wet grip performance. It is thought that Furthermore, since the dissociation and bonding of the ionic bonding portion are reversible, ionic bonding occurs again during drying, and E* and/or tan δ return. In other words, it is possible to improve wet grip performance while maintaining good friction (μ) and low fuel consumption when driving on a dry road surface (dry road surface). Therefore, it is presumed that the rubber composition improves overall dry grip performance, wet grip performance, and low fuel consumption.

Thus, the present disclosure includes a modified rubber having a carboxylic acid or the like in the molecule and the metal oxide, and satisfies the parameters of the above formulas (1) and / or (2). By doing so, the problem (purpose) of improving the overall performance of dry grip performance, wet grip performance, and fuel efficiency is solved. That is, the parameter does not define a problem (purpose), but the problem of the present application is to improve the overall performance of dry grip performance, wet grip performance, and fuel efficiency. ) and/or satisfy the parameters of (2).

In this specification, E* and tan δ of the rubber composition mean E* and tan δ of the vulcanized rubber composition. E* and tan δ are values obtained by conducting a viscoelasticity test on the vulcanized rubber composition.

As used herein, water reversibly changes complex elastic modulus (E*) and loss tangent (tan δ) means that E* and tan δ of a rubber composition (after vulcanization) reversibly change due to the presence of water. It means to get bigger or smaller. It should be noted that, for example, E* and tan δ may reversibly change when dry→wet with water→dry. or may have the same E* and tan δ in the previous drying and the subsequent drying.

In the present specification, E* and tan δ at the time of drying mean E* and tan δ of the rubber composition in a dry state (after vulcanization). Means E* and tan δ of the dry rubber composition (after vulcanization).
In the present specification, E* and tan δ when wet with water mean the E* and tan δ of the rubber composition (after vulcanization) in a state of being wet with water, and are specifically described in Examples. means E* and tan δ of the rubber composition (after vulcanization) wetted with water by the method of .

In this specification, E* and tan δ of the rubber composition (after vulcanization) were measured under the conditions of a temperature of 30° C., an initial strain of 10%, a dynamic strain of 1%, a frequency of 10 Hz, an elongation mode, and a measurement time of 30 minutes. Complex elastic modulus and loss tangent 30 minutes after the start of measurement.

The rubber composition (after vulcanization) preferably satisfies the following formula (1).
E* when wet with water / E* when dry ≤ 0.90 (1)
(In the formula, E* is the complex elastic modulus 30 minutes after the start of measurement measured under the conditions of temperature 30 ° C., initial strain 10%, dynamic strain 1%, frequency 10 Hz, extension mode, measurement time 30 minutes. .)
E* when wet with water/E* when dry is preferably 0.87 or less, more preferably 0.84 or less, still more preferably 0.82 or less, and particularly preferably 0.80 or less. The lower limit of E* when wet with water/E* when dry is not particularly limited, but is preferably 0.50 or more, more preferably 0.60 or more, still more preferably 0.70 or more, and particularly preferably 0.75 or more. is. Within the above range, the effect can be suitably obtained.

The rubber composition (after vulcanization) has a dry E* of preferably 4.0 MPa or more, more preferably 4.5 MPa or more, even more preferably 5.0 MPa or more, and particularly preferably 5.4 MPa or more. Although the upper limit of E* during drying is not particularly limited, it is preferably 20.0 MPa or less, more preferably 17.0 MPa or less, even more preferably 16.0 MPa or less, and particularly preferably 15.0 MPa or less. Within the above range, the effect can be suitably obtained.

The rubber composition (after vulcanization) preferably satisfies the following formula (2).
tan δ when wet with water/tan δ when dry ≥ 1.10 (2)
(In the formula, tan δ is the loss tangent 30 minutes after the start of measurement measured under the conditions of temperature 30 ° C., initial strain 10%, dynamic strain 1%, frequency 10 Hz, extension mode, measurement time 30 minutes.)
The ratio of tan δ when wet with water/tan δ when dry is preferably 1.15 or more, more preferably 1.18 or more, still more preferably 1.20 or more, and particularly preferably 1.21 or more. The upper limit of tan δ when wet with water/tan δ when dry is not particularly limited, but is preferably 1.60 or less, more preferably 1.50 or less, still more preferably 1.40 or less, and particularly preferably 1.35 or less. . Within the above range, the effect can be suitably obtained.

The rubber composition (after vulcanization) has a dry tan δ of preferably 0.18 or more, more preferably 0.20 or more, even more preferably 0.21 or more, and particularly preferably 0.22 or more. Although the upper limit of tan δ during drying is not particularly limited, it is preferably 0.60 or less, more preferably 0.40 or less, still more preferably 0.30 or less, and particularly preferably 0.25 or less. Within the above range, the effect can be suitably obtained.

The reversible E* change and tan δ change due to water represented by the above formulas (1) and/or (2) of the rubber composition are, for example, from the group consisting of carboxylic acid, sulfonic acid, and salts thereof. It can be achieved by blending a modified rubber having at least one selected type in the molecule and the metal oxide. Specifically, for example, modified rubber such as carboxylic acid-modified SBR having at least one selected from the group consisting of carboxylic acid, sulfonic acid, and salts thereof in the molecule, and metal oxide such as magnesium oxide By using together with, it is possible to realize the reversible E* change and tan δ change due to water represented by the above formulas (1) and/or (2) of the rubber composition. This is because, by the combined use, for example, cations derived from metal oxides and anions derived from carboxylic acids, sulfonic acids, and salts thereof form ionic bonds between the modified rubber and metal oxides, and Between the modified rubber and the metal oxide, the addition of water causes the ionic bonds to break and the ionic bonds to recombine when the water dries. / Or it is thought that it can be realized by the occurrence of tan δ decrease.

E* at the time of drying can be adjusted by the type and amount of chemicals (especially rubber components, fillers, softeners such as oils) blended in the rubber composition. By decreasing the amount or increasing the amount of the filler, the dry E* tends to increase.

The dry tan δ can be adjusted by adjusting the type and amount of chemicals (particularly rubber components, fillers, softeners, resins, sulfur, vulcanization accelerators, and silane coupling agents) compounded in the rubber composition. For example, using a softening agent (e.g., resin) that has low compatibility with the rubber component, using unmodified rubber, increasing the amount of filler, increasing the amount of oil as a plasticizer, adding sulfur , the vulcanization accelerator, or the silane coupling agent, the tan δ at the time of drying tends to increase.

Regarding E* and tan δ at the time of drying, E *, tan δ can be adjusted. Specifically, when the content of acidic functional groups in the modified rubber and the content of the metal oxide are increased, there is a tendency that E* during drying tends to increase and tan δ during drying tends to decrease.

E* and tan δ when wet with water are compared to those when dry, for example, by using a rubber composition in which part or all of the modified rubber and the metal oxide are crosslinked by ionic bonds. , E* when wet with water and/or tan δ can be increased, and E* and tan δ when dry and when wet with water can be adjusted. Specifically, by using the modified rubber and the metal oxide together, a rubber composition crosslinked by ionic bonds is obtained, and E* when wet with water is reduced compared to when dry, and/or tan δ can be increased. In addition, E* and tan δ when wet with water can be adjusted depending on the type and amount of chemicals blended in the rubber composition. Similar tendencies can be obtained for E* and tan δ when wet with water by using the same method as in .

And, specifically, after adjusting E* and tan δ at the time of drying within the desired range, it has at least one selected from the group consisting of carboxylic acids, sulfonic acids, and salts thereof in the molecule. By using the modified rubber together with the metal oxide, it is possible to realize the reversible E* change and/or tan δ change due to water represented by the above formulas (1) and/or (2) of the rubber composition. .

(rubber component)
The rubber composition includes, as rubber components, carboxylic acid (carboxylic acid group (—COOH)), sulfonic acid (sulfonic acid group (—SO ₃ H)), and salts thereof (carboxylic acid ion (—COO ⁻ ) and and/or a modified rubber having in the molecule at least one selected from the group consisting of sulfonate ions (-SO ₃ ^- ) and their counter cations). The salt is not particularly limited, and includes monovalent metal salts such as alkali metal salts (sodium salts, potassium salts, etc.), divalent metal salts such as alkaline earth metal salts (calcium salts, strontium salts, etc.), and the like. mentioned. Among them, a carboxylic acid group is preferable from the viewpoint of obtaining more effects.

The modified rubber has in its molecule at least one ionic functional group 1 selected from the group consisting of carboxylic acid, sulfonic acid, and salts thereof. The content of the ionic functional group 1 in 100% by mass of rubber having group 1 in the molecule) is preferably 0.5% by mass or more, more preferably 0.8% by mass or more, and 1.0% by mass or more. is more preferred. Although the upper limit is not particularly limited, it is preferably 40% by mass or less, more preferably 35% by mass or less.
The content of the ionic functional group 1 can be measured by performing NMR measurement and calculating the content (% by mass) based on the peak corresponding to the ionic functional group 1.

In the rubber composition, the content of the modified rubber in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 20% by mass or more, still more preferably 40% by mass or more, and particularly 50% by mass or more. preferable. Although the upper limit is not particularly limited, it is preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, and particularly preferably 75% by mass or less. Within the above range, the effect can be suitably obtained.

The rubber constituting the skeleton of the modified rubber preferably has at least one monomer selected from the group consisting of styrene, butadiene and isoprene as a structural unit, from the viewpoint of suitably obtaining the effect. Specific examples of the rubber include isoprene-based rubber, butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene-butadiene rubber (SIBR), and the like. A rubber component may be used independently and may be used in combination of 2 or more type. Among them, SBR, BR, and isoprene-based rubbers are preferable from the viewpoint of tire physical properties.

The SBR is not particularly limited, and for example, emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc. can be used. These may be used alone or in combination of two or more.

The styrene content of SBR is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 15% by mass or more. Also, the styrene content is preferably 60% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. Within the above range, the effect tends to be obtained more favorably.
In this specification, the styrene content of SBR is calculated by ¹ H-NMR measurement.

The vinyl content of SBR is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 15% by mass or more. The vinyl content is preferably 75% by mass or less, more preferably 70% by mass or less. Within the above range, the effect tends to be obtained more favorably.
The vinyl content (1,2-bonded butadiene unit amount) can be measured by infrared absorption spectrometry.

As SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Co., Ltd., Asahi Kasei Co., Ltd., Nippon Zeon Co., Ltd., etc. can be used.

When the rubber composition contains, as the modified rubber, modified SBR having in the molecule at least one ionic functional group 1 selected from the group consisting of carboxylic acid, sulfonic acid, and salts thereof, rubber component 100 The content of the modified SBR in mass % is preferably 5 mass % or more, more preferably 20 mass % or more, still more preferably 40 mass % or more, and particularly preferably 50 mass % or more. Although the upper limit is not particularly limited, it is preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, and particularly preferably 75% by mass or less. Within the above range, the effect can be suitably obtained.

BR is not particularly limited, and for example, high cis BR having a high cis content, BR containing syndiotactic polybutadiene crystals, BR synthesized using a rare earth catalyst (rare earth BR), and the like can be used. These may be used alone or in combination of two or more. Among them, high-cis BR having a cis content of 90% by mass or more is preferable because it improves wear resistance.

When the rubber composition contains, as the modified rubber, a modified BR having in the molecule at least one ionic functional group 1 selected from the group consisting of carboxylic acid, sulfonic acid, and salts thereof, rubber component 100 The content of the modified BR in % by mass is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and particularly preferably 20% by mass or more. Although the upper limit is not particularly limited, it is preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, and particularly preferably 75% by mass or less. Within the above range, the effect can be suitably obtained.

The isoprene rubber includes natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, modified IR, and the like. As NR, those commonly used in the rubber industry, such as SIR20, RSS#3, and TSR20, can be used. The IR is not particularly limited, and for example IR2200 or the like commonly used in the rubber industry can be used. Modified NR includes deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), etc. Modified NR includes epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc. Examples of modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, and the like. These may be used alone or in combination of two or more.

When the rubber composition contains, as the modified rubber, a modified isoprene rubber having in the molecule at least one ionic functional group 1 selected from the group consisting of carboxylic acid, sulfonic acid, and salts thereof, rubber The content of the modified isoprene rubber in 100% by mass of the component is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and particularly preferably 20% by mass or more. Although the upper limit is not particularly limited, it is preferably 80% by mass or less, more preferably 50% by mass or less, even more preferably 40% by mass or less, and particularly preferably 35% by mass or less. Within the above range, the effect can be suitably obtained.

The rubber composition may contain rubber components other than the modified rubber. The other rubber component preferably contains, for example, at least one selected from the group consisting of SBR, BR and isoprene rubber. The SBR, the BR, and the isoprene-based rubber may be modified rubbers other than the above modified rubbers or unmodified rubbers, but unmodified SBR, unmodified BR, and unmodified isoprene-based rubber are preferable, and unmodified BR , non-modified isoprene-based rubber is more preferred.

When the rubber composition contains a rubber component other than the modified rubber, the content of the other rubber component in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, 15% by mass or more is more preferable, and 20% by mass or more is particularly preferable. Although the upper limit is not particularly limited, it is preferably 80% by mass or less, more preferably 50% by mass or less, even more preferably 40% by mass or less, and particularly preferably 35% by mass or less. Within the above range, the effect can be suitably obtained. When non-modified isoprene-based rubber or non-modified BR is used as the other rubber component, the content of non-modified isoprene-based rubber and the content of non-modified BR are preferably within the same range.

(metal oxide)
The rubber composition includes lithium oxide, sodium oxide, potassium oxide, rubidium oxide, cesium oxide, beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide, scandium oxide, titanium oxide, vanadium oxide, chromium oxide, and manganese oxide. , iron oxide, cobalt oxide, nickel oxide, copper oxide, yttrium oxide, zirconium oxide, niobium oxide, molybdenum oxide, technetium oxide, ruthenium oxide, rhodium oxide, palladium oxide, silver oxide, hafnium oxide, tantalum oxide, tungsten oxide, oxide At least one metal selected from the group consisting of osmium, iridium oxide, platinum oxide, gold oxide, aluminum oxide, gallium oxide, cadmium oxide, indium oxide, tin oxide, thallium oxide, lead oxide, bismuth oxide, and polonium oxide Contains oxides. These metal oxides may be used individually by 1 type, and may use 2 or more types together.

Among them, at least selected from the group consisting of lithium oxide, sodium oxide, potassium oxide, rubidium oxide, cesium oxide, beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, and barium oxide, from the viewpoint of suitably obtaining the effect. It preferably contains one, more preferably at least one selected from the group consisting of beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, and barium oxide, and still more preferably magnesium oxide.

Although the reason why the above effects are more obtained when these metal oxides are used is not necessarily clear, it is presumed to be due to the following mechanism.
Modified rubber having a carboxylic acid or the like in the molecule and these specific metal oxides form an ionic bond with the carboxylic acid or the like and the metal of the metal oxide, and the transition metal oxide also has a similar ion. Bonds are formed and exhibit water responsiveness. However, the transition metal oxide has a regular and stable coordination structure due to its tetracoordinate tetrahedral structure, whereas the specific metal oxide does not have such a structure. Therefore, it is considered that the reinforcing property and water responsiveness are high. In addition, since the specific metal oxide easily dissociates with water, it is considered that the water responsiveness is further improved. Therefore, in the case of a rubber composition using the specific metal oxide, it is presumed that the overall performance of dry grip performance, wet grip performance and low fuel consumption is further improved.

In the rubber composition, the content of the metal oxides (total amount of the metal oxides) is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, relative to 100 parts by mass of the rubber component. , More preferably 2.0 parts by mass or more, particularly preferably 2.2 parts by mass or more, and preferably 10.0 parts by mass or less, more preferably 5.0 parts by mass or less, still more preferably 4.0 parts by mass It is not more than 3.0 parts by mass, particularly preferably not more than 3.0 parts by mass. Within the above range, the effect tends to be obtained more favorably. The total amount of at least one selected from the group consisting of lithium oxide, sodium oxide, potassium oxide, rubidium oxide, cesium oxide, beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, and barium oxide, beryllium oxide, and magnesium oxide , the total amount of at least one selected from the group consisting of calcium oxide, strontium oxide, and barium oxide, and the content of magnesium oxide, the same range is preferable.

The apparent specific gravity of the metal oxide is preferably less than 0.4 g/ml, more preferably 0.3 g/ml or less, still more preferably 0.25 g/ml or less, and preferably 0.05 g/ml. 0.15 g/ml or more, more preferably 0.15 g/ml or more. Within the above range, the effect tends to be obtained more favorably. Moreover, it is preferable that the apparent specific gravity of magnesium oxide is also within the same range.
The apparent specific gravity of the metal oxide is a value obtained by weighing 30 ml in apparent volume into a 50 ml graduated cylinder and calculating from the mass.

The d50 of the metal oxide is preferably less than 10 μm, more preferably 4.5 μm or less, even more preferably 1.5 μm or less, particularly preferably less than 0.75 μm, and more preferably 0.05 μm or more, more preferably is 0.45 μm or more. Within the above range, the effect tends to be obtained more favorably. Also, the d50 of magnesium oxide is preferably within the same range.
The d50 of the metal oxide is the particle diameter at 50% of the integrated value in the mass-based particle size distribution curve obtained by the laser diffraction scattering method.

The nitrogen adsorption specific surface area (N ₂ SA) of the metal oxide is preferably 100 m ² /g or more, more preferably 115 m ² /g or more, and is preferably 250 m ² /g or less, more preferably 225 m ^{2 .} /g or less, more preferably 200 m ² /g or less. Within the above range, the effect tends to be obtained more favorably. Also, N ₂ SA of magnesium oxide is preferably within the same range.
The N ₂ SA of the metal oxide is a value measured by the BET method according to JIS Z8830:2013.

Commercially available metal oxides include Kyowa Chemical Industry Co., Ltd., Fujifilm Wako Pure Chemical Industries, Ltd., Kishida Chemical Co., Ltd., Kyowa Chemical Industry Co., Ltd., Tateho Chemical Industry Co., Ltd., JHE Co., Ltd., Products such as Nippon Kagaku Kogyo Co., Ltd. and Ako Kasei Co., Ltd. can be used.

(filler)
The rubber composition desirably contains a filler (filler). As the filler, inorganic fillers such as silica, carbon black, calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide and mica; hard-to-disperse fillers and other materials known in the rubber field can be used. Among them, silica and carbon black are preferred.

Silica is not particularly limited, and examples thereof include dry silica (anhydrous silica) and wet silica (hydrous silica). Among them, wet-process silica is preferable because it has many silanol groups.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 30 m ² /g or more, more preferably 100 m ² /g or more, still more preferably 125 m ² /g or more. The N ₂ SA of silica is preferably 300 m ² /g or less, more preferably 250 m ² /g or less, and even more preferably 200 m ² /g or less. Within the above range, the effect can be suitably obtained.
The N ₂ SA of silica is a value measured by the BET method according to ASTM D3037-93.

As silica, for example, products of Degussa, Rhodia, Tosoh Silica, Solvay Japan, Tokuyama, etc. can be used.

In the rubber composition, the content of silica is preferably 20 parts by mass or more, more preferably 40 parts by mass or more, still more preferably 45 parts by mass or more, and particularly preferably 50 parts by mass with respect to 100 parts by mass of the rubber component. That's it. Although the upper limit of the content is not particularly limited, it is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, and still more preferably 80 parts by mass or less. Within the above range, the effect can be suitably obtained.

When the rubber composition contains silica, it preferably further contains a silane coupling agent.
The silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, Bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-trimethoxysilylbutyl) trisulfide, bis ( 3-triethoxysilylpropyl) disulfide, bis(2-triethoxysilylethyl) disulfide, bis(4-triethoxysilylbutyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide, bis(2-trimethoxysilylethyl) ) disulfide, bis(4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3- sulfides such as triethoxysilylpropyl methacrylate monosulfide; mercaptos such as 3-mercaptopropyltrimethoxysilane and 2-mercaptoethyltriethoxysilane; vinyls such as vinyltriethoxysilane and vinyltrimethoxysilane; Amino compounds such as propyltriethoxysilane and 3-aminopropyltrimethoxysilane, glycidoxy compounds such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane, 3-nitropropyltrimethoxysilane, Nitro-based agents such as 3-nitropropyltriethoxysilane and chloro-based agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane can be mentioned. Commercially available products such as Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Dow Corning Toray Co., Ltd., and the like can be used. These may be used alone or in combination of two or more.

In the rubber composition, the content of the silane coupling agent is preferably 1.0 parts by mass or more, more preferably 5.0 parts by mass or more, and still more preferably 8.0 parts by mass with respect to 100 parts by mass of silica. That's it. Also, the content is preferably 20.0 parts by mass or less, more preferably 15.0 parts by mass or less, and even more preferably 10.0 parts by mass or less. Within the above range, the effect can be suitably obtained.

Usable carbon blacks include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762 and the like. These may be used alone or in combination of two or more. Commercially available products include Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Co., Ltd., Lion Corporation, Shin Nikka Carbon Co., Ltd., Columbia Carbon Co., Ltd., etc. can be used.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 50 m ² /g or more, more preferably 80 m ² /g or more, and even more preferably 100 m ² /g or more. The N ₂ SA is preferably 200 m ² /g or less, more preferably 150 m ² /g or less, and even more preferably 130 m ² /g or less. Within the above range, the effect tends to be obtained more favorably.
The nitrogen adsorption specific surface area of carbon black is determined according to JIS K6217-2:2001.

In the rubber composition, the content of carbon black is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and still more preferably 5 parts by mass or more with respect to 100 parts by mass of the rubber component. The upper limit is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

(Plasticizer)
The rubber composition preferably contains a plasticizer. Here, the plasticizer is a material that imparts plasticity to the rubber component. ) and the like.

In the rubber composition, the plasticizer content (total amount of plasticizer) is preferably 5 parts by mass or more, more preferably 20 parts by mass or more, and still more preferably 25 parts by mass or more, relative to 100 parts by mass of the rubber component. Particularly preferably, it is 30 parts by mass or more. The upper limit is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 90 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

Liquid plasticizers that can be used in rubber compositions (plasticizers in liquid state at room temperature (25° C.)) are not particularly limited, and include oils, liquid polymers (liquid resins, liquid diene-based polymers, liquid farnesene-based polymers, etc.). is mentioned. These may be used alone or in combination of two or more.

In the rubber composition, the content of the liquid plasticizer is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, still more preferably 8 parts by mass or more, and particularly preferably 10 parts by mass with respect to 100 parts by mass of the rubber component. Department or above. The upper limit is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less. Within the above range, the effect tends to be obtained more favorably. The content of the liquid plasticizer also includes the amount of oil contained in the oil-extended rubber. Also, the same range is suitable for the oil content.

Oils include, for example, process oils, vegetable oils, or mixtures thereof. As the process oil, for example, paraffinic process oil, aromatic process oil, naphthenic process oil, etc. can be used. Vegetable oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice bran oil, safflower oil, sesame oil, and olive oil. , sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil and the like. Commercially available products include Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Co., Ltd., Orisoi Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Showa Shell Oil Co., Ltd., Fuji Kosan Co., Ltd., Products such as Nisshin OilliO Group Co., Ltd. can be used. Among them, process oils (paraffinic process oils, aromatic process oils, naphthenic process oils, etc.) and vegetable oils are preferred.

Liquid resins include terpene resins (including terpene phenolic resins and aromatic modified terpene resins), rosin resins, styrene resins, C5 resins, C9 resins, C5/C9 resins, and dicyclopentadiene (DCPD) resins. , coumarone-indene resins (including coumarone and indene simple substance resins), phenol resins, olefin resins, polyurethane resins, acrylic resins, and the like. Hydrogenated products of these can also be used.

Examples of the liquid diene polymer include liquid styrene-butadiene copolymer (liquid SBR), liquid butadiene polymer (liquid BR), liquid isoprene polymer (liquid IR), liquid styrene-isoprene copolymer (liquid SIR), liquid styrene butadiene styrene block copolymer (liquid SBS block polymer), liquid styrene isoprene styrene block copolymer (liquid SIS block polymer), liquid farnesene polymer, liquid farnesene butadiene copolymer, and the like. . These may be modified with a polar group at the terminal or main chain. Hydrogenated products of these can also be used.

Examples of the resins (resins in a solid state at room temperature (25°C)) that can be used in the rubber composition include aromatic vinyl polymers that are in a solid state at room temperature (25°C), coumarone-indene resins, coumarone resins, and indene. Resins, phenol resins, rosin resins, petroleum resins, terpene resins, acrylic resins, and the like. Also, the resin may be hydrogenated. These may be used alone or in combination of two or more. Among them, aromatic vinyl polymers, petroleum resins, and terpene resins are preferred.

In the rubber composition, the content of the resin is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, still more preferably 15 parts by mass or more, and particularly preferably 20 parts by mass with respect to 100 parts by mass of the rubber component. That's it. The upper limit is preferably 60 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

The softening point of the resin is preferably 50°C or higher, more preferably 55°C or higher, and even more preferably 60°C or higher. The upper limit is preferably 160°C or lower, more preferably 150°C or lower, and even more preferably 145°C or lower. Within the above range, the effect tends to be obtained more favorably. The softening point of the resin is the temperature at which the ball descends when the softening point specified in JIS K6220-1:2001 is measured with a ring and ball type softening point measuring device.

The aromatic vinyl polymer is a polymer containing an aromatic vinyl monomer as a structural unit. Examples thereof include α-methylstyrene and/or resins obtained by polymerizing styrene. Specifically, styrene homopolymers (styrene resins), α-methylstyrene homopolymers (α-methylstyrene resins ), copolymers of α-methylstyrene and styrene, and copolymers of styrene and other monomers.

The coumarone-indene resin is a resin containing coumarone and indene as main monomer components constituting the skeleton (main chain) of the resin. Examples of monomer components contained in the skeleton other than coumarone and indene include styrene, α-methylstyrene, methylindene, and vinyltoluene.

The coumarone resin is a resin containing coumarone as a main monomer component that constitutes the skeleton (main chain) of the resin.

The indene resin is a resin containing indene as a main monomer component that constitutes the skeleton (main chain) of the resin.

As the phenolic resin, for example, known polymers obtained by reacting phenol with aldehydes such as formaldehyde, acetaldehyde and furfural with an acid or alkali catalyst can be used. Among them, those obtained by reacting with an acid catalyst (such as novolac phenolic resins) are preferable.

Examples of the rosin resin include natural rosin, polymerized rosin, modified rosin, ester compounds thereof, and rosin-based resins represented by hydrogenated products thereof.

Examples of the petroleum resins include C5-based resins, C9-based resins, C5/C9-based resins, dicyclopentadiene (DCPD) resins, and hydrogenated products thereof. Among them, DCPD resin and hydrogenated DCPD resin are preferable.

The terpene-based resin is a polymer containing terpene as a structural unit. Examples thereof include polyterpene resins obtained by polymerizing terpene compounds, and aromatic modified terpene resins obtained by polymerizing terpene compounds and aromatic compounds. Aromatic modified terpene resins include terpene phenol resins made from terpene compounds and phenol compounds, terpene styrene resins made from terpene compounds and styrene compounds, and terpene compounds, phenol compounds and styrene compounds as raw materials. Terpene phenol styrene resins can also be used. The terpene compounds include α-pinene and β-pinene, the phenolic compounds include phenol and bisphenol A, and the aromatic compounds include styrene compounds (styrene, α-methylstyrene, etc.).

The acrylic resin is a polymer containing an acrylic monomer as a structural unit. Examples thereof include styrene-acrylic resins such as styrene-acrylic resins, which have a carboxyl group and are obtained by copolymerizing an aromatic vinyl monomer component and an acrylic monomer component. Among them, solvent-free carboxyl group-containing styrene-acrylic resins can be preferably used.

Examples of plasticizers include Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical, Nichinuri Chemical Co., Ltd. Products of Nippon Shokubai, ENEOS Co., Ltd., Arakawa Chemical Co., Ltd., Taoka Chemical Co., Ltd., etc. can be used.

(other ingredients)
From the viewpoint of crack resistance, ozone resistance, etc., the rubber composition preferably contains an anti-aging agent.

Antiaging agents are not particularly limited, but naphthylamine antiaging agents such as phenyl-α-naphthylamine; diphenylamine antiaging agents such as octylated diphenylamine and 4,4′-bis(α,α′-dimethylbenzyl)diphenylamine. ; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylene p-phenylenediamine antioxidants such as diamines; quinoline antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; 2,6-di-t-butyl-4-methyl monophenol antioxidants such as phenol and styrenated phenol; bis, tris and polyphenols such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane anti-aging agent, etc. Among them, p-phenylenediamine-based antioxidants and quinoline-based antioxidants are preferable, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, 2,2,4-trimethyl-1 , 2-dihydroquinoline polymers are more preferred. As commercially available products, for example, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Kagaku Kogyo Co., Ltd., Flexis, etc. can be used.

In the rubber composition, the content of the antioxidant is preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the rubber component. The content is preferably 7.0 parts by mass or less, more preferably 4.0 parts by mass or less.

The rubber composition may contain stearic acid. In the rubber composition, the stearic acid content is preferably 0.5 to 10 parts by mass or more, more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the rubber component.

As the stearic acid, conventionally known ones can be used, for example, products of NOF Corporation, Kao Corporation, FUJIFILM Wako Pure Chemical Industries, Ltd., Chiba Fatty Acids Co., Ltd., etc. can be used.

The rubber composition may contain zinc oxide. In the rubber composition, the zinc oxide content is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, per 100 parts by mass of the rubber component.

As the zinc oxide, conventionally known ones can be used. products can be used.

Wax may be blended in the rubber composition. In the rubber composition, the wax content is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, per 100 parts by mass of the rubber component.

The wax is not particularly limited, and examples thereof include petroleum waxes and natural waxes. Synthetic waxes obtained by refining or chemically treating a plurality of waxes can also be used. These waxes may be used alone or in combination of two or more.

Examples of petroleum wax include paraffin wax and microcrystalline wax. The natural wax is not particularly limited as long as it is derived from a resource other than petroleum. Examples include plant waxes such as candelilla wax, carnauba wax, Japan wax, rice wax, and jojoba wax; beeswax, lanolin, spermaceti, and the like. animal waxes; mineral waxes such as ozokerite, ceresin and petrolactam; and refined products thereof. As commercially available products, for example, products of Ouchi Shinko Kagaku Kogyo Co., Ltd., Nippon Seiro Co., Ltd., Seiko Kagaku Co., Ltd., etc. can be used.

The rubber composition may contain sulfur from the viewpoint of forming appropriate crosslinked chains in the polymer chains and imparting a good balance of performance.

In the rubber composition, the sulfur content is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and still more preferably 0.7 parts by mass or more with respect to 100 parts by mass of the rubber component. be. The content is preferably 6.0 parts by mass or less, more preferably 4.0 parts by mass or less, and even more preferably 3.0 parts by mass or less.

Sulfur includes powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur and the like commonly used in the rubber industry. As commercially available products, products of Tsurumi Chemical Industry Co., Ltd., Karuizawa Io Co., Ltd., Shikoku Kasei Kogyo Co., Ltd., Flexis Co., Ltd., Nippon Kantan Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

The rubber composition may contain a vulcanization accelerator.
In the rubber composition, the content of the vulcanization accelerator is usually 0.3-10 parts by mass, preferably 0.5-7 parts by mass, per 100 parts by mass of the rubber component.

The type of vulcanization accelerator is not particularly limited, and commonly used ones can be used. Vulcanization accelerators include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiazylsulfenamide; tetramethylthiuram disulfide (TMTD ), tetrabenzyl thiuram disulfide (TBzTD), tetrakis (2-ethylhexyl) thiuram disulfide (TOT-N) and other thiuram vulcanization accelerators; N-cyclohexyl-2-benzothiazolesulfenamide, Nt-butyl- Sulfenamide-based vulcanization accelerators such as 2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N,N'-diisopropyl-2-benzothiazolesulfenamide; diphenylguanidine, Guanidine-based vulcanization accelerators such as dioltolylguanidine and orthotolylbiguanidine can be mentioned. These may be used alone or in combination of two or more. Among them, sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators are preferred.

Among vulcanization accelerators, sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators are preferred. Although the content of the sulfenamide-based vulcanization accelerator is not particularly limited, it is preferably 0.3 to 4.0 parts by mass, preferably 0.5 to 2.5 parts by mass, based on 100 parts by mass of the rubber component. More preferably, it is 0.7 to 1.6 parts by mass. Although the content of the guanidine-based vulcanization accelerator is not particularly limited, it is preferably 0.5 to 5.0 parts by mass, preferably 0.8 to 3.0 parts by mass, more preferably 0.8 to 3.0 parts by mass, relative to 100 parts by mass of the rubber component. is 1.0 to 2.3 parts by mass.

In addition to the components described above, the rubber composition may also contain additives such as release agents and pigments, which are commonly used in the application, as appropriate.

A known method can be used as a method for producing the rubber composition. For example, each component can be kneaded using a rubber kneading device such as an open roll mixer or a Banbury mixer, and crosslinked as necessary. As for kneading conditions, the kneading temperature is usually 50 to 200° C., preferably 80 to 190° C., and the kneading time is usually 30 seconds to 30 minutes, preferably 1 minute to 30 minutes.

Although the tire member using the rubber composition is not particularly limited, it can be suitably used for a tread (cap tread).

<Tire>
The rubber composition can be suitably used for tires. Tires include pneumatic tires, non-pneumatic tires, etc. Among them, pneumatic tires are preferred. In particular, it can be suitably used as a summer tire (summer tire) and a winter tire (studless tire, snow tire, studded tire, etc.). Tires can be used as tires for passenger cars, tires for large passenger cars, tires for large SUVs, tires for heavy loads such as trucks and buses, tires for light trucks, tires for two-wheeled vehicles, tires for racing (high performance tires), and the like.

A tire is manufactured by a normal method using the above rubber composition. For example, a rubber composition blended with various materials is extruded in an unvulcanized stage to match the shape of a tire member, and then molded together with other tire members on a tire molding machine by a normal method. Forms an unvulcanized tire. A tire is obtained by heating and pressurizing this unvulcanized tire in a vulcanizer.

An example of a tire using the rubber composition will be described with reference to FIG.
In FIG. 1 , the vertical direction is the radial direction of the tire 2 , the horizontal direction is the axial direction of the tire 2 , and the direction perpendicular to the paper surface is the circumferential direction of the tire 2 . The tread 4 includes a cap layer 30 and a base layer 28, and the cap layer 30 is preferably made of the rubber composition.

Although FIG. 1 shows an example of a two-layer tread 4 consisting of a cap layer 30 and a base layer 28, a single-layer tread or a tread having three or more layers may also be used. It is desirable that the outermost layer in contact with is composed of the rubber composition.

In tire 2 , each sidewall 6 extends radially generally inward from the edge of tread 4 . A radially outer portion of this sidewall 6 is joined to the tread 4 . A radially inner portion of this sidewall 6 is joined with a clinch 10 . This sidewall 6 can prevent the carcass 14 from being damaged.

Each wing 8 is located between the tread 4 and sidewall 6 . A wing 8 joins with each of the tread 4 and the sidewall 6 .

Each clinch 10 is positioned substantially radially inside the sidewall 6 . The clinch 10 is located outside the bead 12 and the carcass 14 in the axial direction.

Each bead 12 is located axially inside the clinch 10 . The bead 12 has a core 32 and an apex 34 extending radially outward from the core 32 . Core 32 is ring-shaped and preferably comprises a wound non-stretchable wire. Apex 34 tapers radially outward.

The carcass 14 includes carcass plies 36 . In this tire 2, the carcass 14 is composed of one carcass ply 36, but may be composed of two or more plies.

In this tire 2 , the carcass ply 36 is spanned between the beads 12 on both sides and along the tread 4 and the sidewalls 6 . The carcass ply 36 is folded back around each core 32 from the axial inner side to the outer side. By this folding, the carcass ply 36 is formed with a main portion 36a and a pair of folded portions 36b. That is, the carcass ply 36 includes a main portion 36a and a pair of folded portions 36b.

Although not shown, the carcass ply 36 preferably consists of a large number of parallel cords and a topping rubber. The absolute value of the angle formed by each cord with respect to the equatorial plane is preferably 75° to 90°. In other words, this carcass 14 preferably has a radial structure.

The belt 16 is positioned radially inside the tread 4 . The belt 16 is laminated with the carcass 14 . Belt 16 reinforces carcass 14 . Belt 16 consists of an inner layer 38 and an outer layer 40 . As is apparent from FIG. 1, the width of the inner layer 38 is preferably slightly greater than the width of the outer layer 40 in the axial direction. In this tire 2, the axial width of the belt 16 is preferably 0.6 times or more and preferably 0.9 times or less the cross-sectional width of the tire 2 (see JATMA).

Although not shown, each of the inner layer 38 and the outer layer 40 preferably comprises a number of parallel cords and a topping rubber. In other words, the belt 16 includes multiple cords arranged side by side. Each chord is tilted with respect to the equatorial plane. A general absolute value of the tilt angle is 10° or more and 35° or less. The direction of inclination of the cords of the inner layer 38 with respect to the equatorial plane is opposite to the direction of inclination of the cords of the outer layer 40 with respect to the equatorial plane.

The band 18 is located radially outside the belt 16 . In the axial direction, band 18 has a width equal to the width of belt 16 . This band 18 may have a width greater than the width of this belt 16 .

Although not shown, the band 18 preferably consists of a cord and a topping rubber. The cord is spirally wound. This band 18 has a so-called jointless structure. The cord extends substantially circumferentially. The angle of the cords with respect to the circumferential direction is preferably 5° or less, more preferably 2° or less. Since the belt 16 is constrained by this cord, lifting of the belt 16 is suppressed.

Belt 16 and band 18 constitute a reinforcing layer. The reinforcing layer may be composed only of the belt 16 .

The inner liner 20 is positioned inside the carcass 14 . An inner liner 20 is joined to the inner surface of the carcass 14 . A typical base rubber for the inner liner 20 is butyl rubber or halogenated butyl rubber. The inner liner 20 retains the internal pressure of the tire 2 .

Each chafer 22 is positioned near the bead 12 . In this embodiment, the chafer 22 is preferably made of cloth and rubber impregnated in the cloth. This chafer 22 may be integrated with the clinch 10 .

In this tire 2 , the tread 4 has main grooves 42 as the grooves 26 . As shown in FIG. 1, the tread 4 is provided with a plurality of, more specifically, three main grooves 42 . These main grooves 42 are spaced apart in the axial direction. The tread 4 is formed with four ribs 44 extending in the circumferential direction by cutting three main grooves 42 . That is, the main groove 42 is between the ribs 44 .

Each main groove 42 extends in the circumferential direction. The main groove 42 is continuous in the circumferential direction. The main groove 42 facilitates drainage of water existing between the road surface and the tire 2, for example, in rainy weather. Therefore, even if the road surface is wet, the tire 2 can sufficiently contact the road surface.

The tire 2 having the tread 4 made of the rubber composition preferably has a negative rate (S) of 50% or less.
The negative rate (S) of the tread 4 is preferably 40% or less, more preferably 35% or less, even more preferably 30% or less. The negative rate is preferably 5% or more, more preferably 10% or more, still more preferably 15% or more. Within the above range, the effect tends to be obtained more favorably.

Although the reason why such an effect is obtained is not necessarily clear, it is presumed to be due to the following mechanism.
As described above, by satisfying the formulas (1) and (2), the friction (μ) on the wet road surface is improved due to the increase in the contact area with the road surface and/or the increase in energy loss when wet with water, The wet grip performance improves, and when dry, ionic bonding occurs again, and the complex elastic modulus E* returns. It is thought that the low negative rate of the tread further improves friction (μ) on wet road surfaces and further improves wet grip performance. Therefore, it is presumed that a tire having a tread composed of the rubber composition has improved overall dry grip performance, wet grip performance, and low fuel consumption.

In the tire 2 having the tread 4 composed of the rubber composition, the E* of the rubber composition when wet with water and E* when dry, and the negative rate S (%) of the tread 4 are calculated by the following formula (3) is preferably satisfied.
(E* when wet with water/E* when dry) x S ≤ 30.0 (3)
(E* when wet with water/E* when dry)×S is preferably 27.0 (%) or less, more preferably 26.0 (%) or less, and still more preferably 25.0 (%) or less. be. Although the lower limit is not particularly limited, it is preferably 5.0 (%) or more, more preferably 10.0 (%) or more, and still more preferably 15.0 (%) or more. Within the above range, the effect tends to be obtained more favorably.

Although the reason why such an effect is obtained is not necessarily clear, it is presumed to be due to the following mechanism.
As described above, by satisfying the above formula (1), the friction (μ) on the wet road surface is improved due to the increase in the contact area with the road surface when wet, and the wet grip performance is improved. , It is presumed that good friction (μ) and low fuel consumption can be maintained when driving on dry roads by ionic bonding occurring again and E* returning. Friction (μ) is further improved, and wet grip performance is considered to be further improved. Therefore, it is presumed that a tire having a tread composed of a rubber composition that satisfies the formula (3) will further improve overall dry grip performance, wet grip performance, and low fuel consumption.

In the tire 2 having the tread 4 composed of the rubber composition, the tan δ of the rubber composition when wet with water and the tan δ when dry, and the negative rate S (%) of the tread 4 satisfy the following formula (4). is preferred.
(tan δ when wet with water/tan δ when dry)/S≧0.030 (4)
(tan δ when wet with water/tan δ when dry)/S is preferably 0.035 (1/%) or more, more preferably 0.040 (1/%) or more, and still more preferably 0.042 (1/ %) or more. Although the upper limit is not particularly limited, it is preferably 0.100 (1/%) or less, more preferably 0.060 (1/%) or less, and still more preferably 0.050 (1/%) or less. Within the above range, the effect tends to be obtained more favorably.

Although the reason why such an effect is obtained is not necessarily clear, it is presumed to be due to the following mechanism.
As described above, by satisfying the above formula (2), the friction (μ) on the wet road surface is improved due to the increase in energy loss when wet with water, and the wet grip performance is improved. It is speculated that good friction (μ) and fuel efficiency can be maintained when driving on dry road surfaces by returning tan δ, but the low negative rate of the tread reduces friction (μ) on wet road surfaces. It is thought that the wet grip performance will further improve. Therefore, it is presumed that a tire having a tread composed of a rubber composition that satisfies the formula (4) will further improve overall dry grip performance, wet grip performance, and low fuel consumption.

The negative rate (negative rate within the contact surface of the tread portion) is the ratio of the total groove area within the contact surface to the total area of the contact surface, and is measured by the following method.
In this specification, when the tire is a pneumatic tire, the land ratio is calculated from the ground contact shape under normal rim, normal internal pressure, and normal load conditions. Non-pneumatic tires can be similarly measured without the need for regular internal pressure.
A "regular rim" is a rim defined for each tire in a standard system including the standard on which the tire is based. If there is, it means "Measuring Rim".
"Normal internal pressure" is the air pressure specified for each tire by the above-mentioned standards. For JATMA, it is the maximum air pressure. If there is, it means "INFLATION PRESSURE", which is 180 kPa in the case of a passenger car tire.
"Normal load" is the load defined for each tire by the above standards. For JATMA, the maximum load capacity, for TRA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", ETRTO. If so, it means the load obtained by multiplying "LOAD CAPACITY" by 0.88.
As for the shape of the ground contact, the tire tread surface was painted with ink after being assembled on a regular rim, applying regular internal pressure, and allowed to stand at 25°C for 24 hours. obtained by transferring to
The tire is rotated by 72° in the circumferential direction and transferred at five locations. That is, the ground shape is obtained five times.
Let L be the average value of the maximum length in the axial direction of the tire, and W be the average value of the length in the direction perpendicular to the axial direction of the five ground contact shapes.
The negative rate (%) is calculated by [1−{Average area of 5 transferred ground shapes (black parts) of cardboard/(L×W)}]×100 (%).
Here, the average value of length and area is a simple average of five values.

The present disclosure will be specifically described based on Examples, but the present disclosure is not limited thereto.

Various chemicals used in Examples and Comparative Examples will be collectively described.
Carboxylic acid-modified SBR: Synthesized according to Production Example 1 below (Carboxylic acid group content: 5% by mass, styrene content: 23% by mass, butadiene content: 72% by mass)
Carboxylic acid-modified BR: Synthesized according to Production Example 2 below (Carboxylic acid group content: 5% by mass, butadiene content: 95% by mass)
NR: TSR20
SBR: Nipol 1502 (E-SBR) manufactured by ZEON Co., Ltd.
BR: BR150B manufactured by Ube Industries, Ltd.
Carbon black: Diablack I manufactured by Mitsubishi Chemical Corporation (N220, N ₂ SA114m ² /g, DBP 114ml/100g)
Silica 1: Ultrasil VN3 from Evonik Degussa (N ₂ SA 175 m ² /g)
Silica 2: 9000GR (N ₂ SA 235 m ² /g) manufactured by Evonik Degussa
Stearic acid: stearic acid "Tsubaki" manufactured by NOF Corporation
Magnesium oxide 1: Kyowamag 150 manufactured by Kyowa Chemical Industry Co., Ltd. (apparent specific gravity 0.36 g/ml, d50: 4.46 μm, N ₂ SA: 145 m ² /g)
Magnesium oxide 2: Kyowamag 150MF manufactured by Kyowa Chemical Industry Co., Ltd. (apparent specific gravity 0.23 g/ml, d50: 0.72 μm, N ₂ SA: 119 m ² /g)
Calcium oxide: Calcium oxide manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Kinzoku Co., Ltd. Oil: VIVATEC 400/500 (TDAE oil) manufactured by H&R
Silane coupling agent: Si69 (bis(3-triethoxysilylpropyl)tetrasulfide) from EVONIK-DEGUSSA
Resin: SYLVARES SA85 manufactured by Arizona Chemical Co. (a copolymer of α-methylstyrene and styrene, Tg 43°C, softening point 85°C)
Anti-aging agent: Antigen 6C manufactured by Sumitomo Chemical Co., Ltd. (anti-aging agent, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine)
Sulfur: Powdered sulfur vulcanization accelerator manufactured by Tsurumi Chemical Industry Co., Ltd. DPG: Noccellar D (1,3-diphenylguanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Vulcanization accelerator NS: Noxcellar NS (N-tert-butyl-2-benzothiazylsulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

<Production Example 1: Synthesis of carboxylic acid-modified SBR>
(Preparation of latex)
A pressure-resistant reactor equipped with a stirrer was charged with 2000 g of distilled water, 45 g of emulsifier (1), 1.5 g of emulsifier (2), 8 g of electrolyte, 250 g of styrene, 50 g of methacrylic acid, 700 g of butadiene and 2 g of molecular weight modifier. The reactor temperature was set to 5° C., and an aqueous solution in which 1 g of a radical initiator and 1.5 g of SFS were dissolved and an aqueous solution in which 0.7 g of EDTA and 0.5 g of a catalyst were dissolved were added to the reactor to initiate polymerization. After 5 hours from the initiation of polymerization, 2 g of a polymerization terminator was added to terminate the reaction to obtain a latex.
(Preparation of rubber)
Unreacted monomers were removed from the resulting latex by steam distillation. Thereafter, the latex was added to alcohol and coagulated while adjusting the pH to 3 to 5 with a saturated sodium chloride aqueous solution or formic acid to obtain a crumb-like polymer. The polymer was dried in a vacuum dryer at 40° C. to obtain a solid rubber (emulsion polymerized rubber).

<Production Example 2: Synthesis of carboxylic acid-modified BR>
(Preparation of latex)
A pressure-resistant reactor equipped with a stirrer was charged with 2000 g of distilled water, 45 g of emulsifier (1), 1.5 g of emulsifier (2), 8 g of electrolyte, 50 g of methacrylic acid, 950 g of butadiene and 2 g of molecular weight modifier. The reactor temperature was set to 5° C., and an aqueous solution in which 1 g of a radical initiator and 1.5 g of SFS were dissolved and an aqueous solution in which 0.7 g of EDTA and 0.5 g of a catalyst were dissolved were added to the reactor to initiate polymerization. After 5 hours from the initiation of polymerization, 2 g of a polymerization terminator was added to terminate the reaction to obtain a latex.
(Preparation of rubber)
Unreacted monomers were removed from the resulting latex by steam distillation. Thereafter, the latex was added to alcohol and coagulated while adjusting the pH to 3 to 5 with a saturated sodium chloride aqueous solution or formic acid to obtain a crumb-like polymer. The polymer was dried in a vacuum dryer at 40° C. to obtain a solid rubber (emulsion polymerized rubber).

Materials used in Production Examples 1 and 2 are as follows.
Emulsifier (1): rosin acid soap manufactured by Harima Chemicals Co., Ltd. Emulsifier (2): fatty acid soap manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd. Electrolyte: sodium phosphate styrene manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.: Fuji Styrene methacrylic acid manufactured by Film Wako Pure Chemical Industries, Ltd.: Butadiene methacrylate manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.: 1,3-butadiene manufactured by Takachiho Chemical Industry Co., Ltd. Molecular weight modifier: Fuji Film Wako Pure Chemical Industries, Ltd. ( Co., Ltd. tert-dodecyl mercaptan radical initiator: NOF Corporation paramenthan hydroperoxide SFS: FUJIFILM Wako Pure Chemical Co., Ltd. sodium formaldehyde sulfoxylate EDTA: FUJIFILM Wako Pure Chemical ( Co., Ltd. Sodium ethylenediaminetetraacetate Catalyst: FUJIFILM Wako Pure Chemical Co., Ltd. ferric sulfate Polymerization terminator: FUJIFILM Wako Pure Chemical Co., Ltd. N,N'-dimethyldithiocarbamate Alcohol: Kanto Chemical Co., Ltd. methanol, ethanol Formic acid: Kanto Kagaku Co., Ltd. Sodium formate chloride: Fujifilm Wako Pure Chemical Co., Ltd. sodium chloride

<NMR measurement>
Using ¹ H-NMR, the content of carboxylic acid groups in the modified rubber was calculated.

(Examples and Comparative Examples)
Chemicals other than sulfur and a vulcanization accelerator were kneaded at 160°C for 4 minutes using a 16L Banbury mixer manufactured by Kobe Steel, Ltd. according to the compounding recipe shown in each table to obtain a kneaded product. rice field. Next, sulfur and a vulcanization accelerator were added to the resulting kneaded material, and the mixture was kneaded at 80° C. for 4 minutes using an open roll to obtain an unvulcanized rubber composition. The resulting unvulcanized rubber composition was molded into a tread shape, laminated together with other tire members on a tire building machine to form an unvulcanized tire, and then vulcanized at 170° C. for 12 minutes. A tire (size: 195/65R15) was manufactured.

<Negative rate>
The resulting test tire was measured for negative rate by the following method (measured negative rates are shown in Tables 1 and 2).
The ground contact shape of the tread of the test tire is attached to the regular rim, the regular internal pressure is applied, and after standing at 25°C for 24 hours, the tire tread surface is painted with ink, a regular load is applied, and it is pressed against a cardboard (camber angle is 0°), obtained by transfer to paper. The tire was rotated by 72° in the circumferential direction and transferred at five locations to obtain five contact shapes. With respect to the five ground contact shapes, the negative rate (%) was measured by the following formula, where L is the average maximum length in the tire axial direction, and W is the average length in the direction orthogonal to the axial direction. The average value of length and area was a simple average of five values.
Negative rate (%) = [1-{average area of 5 ground shapes (black parts) transferred to cardboard/(L x W)}] x 100

The physical properties of the obtained test tire were measured and evaluated as described below. The results are shown in each table. The reference comparative example in Table 1 was Comparative Example 1-1, and the reference comparative example in Table 2 was Comparative Example 2-1.

<Viscoelasticity test>
A viscoelasticity measurement sample of length 40 mm x width 3 mm x thickness 0.5 mm was taken from the inside of the rubber layer of the tread of each test tire so that the tire circumferential direction was the long side, and tan δ and E* of the tread rubber were measured. , Using the RSA series manufactured by TA Instruments, temperature 30 ° C., initial strain 10%, dynamic strain 1%, frequency 10 Hz, extension mode, measurement time 30 minutes, 30 minutes from the start of measurement Later measurements were obtained.
In addition, the thickness direction of the sample was set to the tire radial direction.

<Drying E* and tan δ>
The viscoelasticity measurement sample (length 40 mm×width 3 mm×thickness 0.5 mm) was dried under the conditions of normal temperature and normal pressure until the weight became constant. The complex elastic modulus E* and the loss tangent tan δ of the obtained dry vulcanized rubber composition (rubber piece) were measured by the above-described viscoelasticity test method, and were defined as dry E* and tan δ.

<E* and tan δ when wet with water>
The viscoelasticity was measured by the above viscoelasticity test method in water using an RSA immersion measurement jig, and E* and tan δ when wet with water were obtained. The water temperature was set at 30°C.

<Wet grip performance>
Each test tire was mounted on all wheels of a vehicle (made in Japan FF2000cc), and the braking distance from an initial speed of 100 km/h on a wet asphalt road surface was determined. Taking the braking distance of the reference comparative example as 100, each formulation was indicated by an index. The larger the index, the better the wet grip performance.

<Dry grip performance>
Each test tire was mounted on all wheels of a vehicle (made in Japan FF 2000cc), and the braking distance from an initial speed of 100 km/h on a dry asphalt road surface was determined. Taking the braking distance of the reference comparative example as 100, each formulation was indicated by an index. The larger the index, the better the dry grip performance.

<Fuel efficiency (rolling resistance)>
Using a rolling resistance tester, measure the rolling resistance when running the test tire with a rim (15 × 6 JJ), internal pressure (230 kPa), load (3.43 kN), speed (80 km / h), and compare with the reference. It is indicated by an index when the example is set to 100. The larger the index, the better the fuel efficiency on dry roads.

From each table, the modified rubber having in the molecule at least one selected from the group consisting of carboxylic acid, sulfonic acid, and salts thereof, and the metal oxide, the formula (1) and / or ( The tire of the example having a tread composed of a rubber composition satisfying 2) has a comprehensive performance of dry grip performance, wet grip performance and fuel efficiency (three indexes of dry grip performance, wet grip performance, fuel efficiency ) was remarkably superior.

The present disclosure (1) provides a modified rubber having in its molecule at least one selected from the group consisting of carboxylic acids, sulfonic acids, and salts thereof;
Lithium oxide, sodium oxide, potassium oxide, rubidium oxide, cesium oxide, beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide, scandium oxide, titanium oxide, vanadium oxide, chromium oxide, manganese oxide, iron oxide, cobalt oxide , nickel oxide, copper oxide, yttrium oxide, zirconium oxide, niobium oxide, molybdenum oxide, technetium oxide, ruthenium oxide, rhodium oxide, palladium oxide, silver oxide, hafnium oxide, tantalum oxide, tungsten oxide, osmium oxide, iridium oxide, oxide At least one metal oxide selected from the group consisting of platinum, gold oxide, aluminum oxide, gallium oxide, cadmium oxide, indium oxide, tin oxide, thallium oxide, lead oxide, bismuth oxide, and polonium oxide,
The rubber composition reversibly changes the complex elastic modulus (E*) and the loss tangent (tan δ) with water and satisfies the following formula (1) and/or the following formula (2).
E* when wet with water / E* when dry ≤ 0.90 (1)
tan δ when wet with water/tan δ when dry ≥ 1.10 (2)
(In the formula, E* and tan δ are the complex elastic modulus 30 minutes after the start of measurement measured under the conditions of temperature 30 ° C., initial strain 10%, dynamic strain 1%, frequency 10 Hz, extension mode, measurement time 30 minutes and the loss tangent.)

The present disclosure (2) is a rubber composition according to the present disclosure (1) that satisfies the following formula.
E*≧4.5MPa when dry

The present disclosure (3) is a rubber composition according to the present disclosure (1) or (2) that satisfies the following formula.
Dry tan δ≧0.20

The present disclosure (4) is based on the present disclosure (1) to (3), wherein the rubber constituting the skeleton of the modified rubber has at least one monomer selected from the group consisting of styrene, butadiene, and isoprene as a structural unit. A rubber composition according to any one of the above.

The present disclosure (5) includes a rubber component other than the modified rubber,
The rubber component is the rubber composition according to any one of the present disclosure (1) to (3), which contains at least one selected from the group consisting of styrene-butadiene rubber, butadiene rubber and isoprene-based rubber.

The present disclosure (6) provides that the metal oxide is selected from the group consisting of lithium oxide, sodium oxide, potassium oxide, rubidium oxide, cesium oxide, beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, and barium oxide. A rubber composition according to any one of the present disclosure (1) to (5) containing at least one.

The present disclosure (7) is the present disclosure (1) to (6), wherein the metal oxide includes at least one selected from the group consisting of beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, and barium oxide. A rubber composition according to any one of the above.

The present disclosure (8) is the rubber composition according to any one of the present disclosures (1) to (7), which contains 5 parts by mass or more of a resin with respect to 100 parts by mass of the rubber component.

(9) of the present disclosure is a tire having a tread composed of the rubber composition according to any one of (1) to (8) of the present disclosure.

The present disclosure (10) is the tire according to the present disclosure (9), wherein E* when wet with water and E* when dry of the rubber composition and the negative rate S (%) of the tread satisfy the following formula (3). is.
(E* when wet with water/E* when dry) x S ≤ 30.0 (3)

The present disclosure (11) is the present disclosure (9) or (10), wherein the tan δ of the rubber composition when wet with water and the tan δ when dry, and the negative rate S (%) of the tread satisfy the following formula (4). tires.
(tan δ when wet with water/tan δ when dry)/S≧0.030 (4)

(12) of the present disclosure is the tire according to any one of (9) to (11) of the present disclosure, wherein the negative rate of the tread is 40% or less.

2 pneumatic tire 4 tread 6 sidewall 8 wing 10 clinch 12 bead 14 carcass 16 belt 18 band 20 inner liner 22 chafer 24 tread surface 26 groove 28 base layer 30 cap layer 32 core 34 apex 36 carcass ply 36a main portion 36b Folded portion 38 Inner layer 40 Outer layer 42 Main groove 44 Rib CL Equatorial plane of tire 2

Claims (12)

a modified rubber having in its molecule at least one selected from the group consisting of carboxylic acids, sulfonic acids, and salts thereof;
Lithium oxide, sodium oxide, potassium oxide, rubidium oxide, cesium oxide, beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide, scandium oxide, titanium oxide, vanadium oxide, chromium oxide, manganese oxide, iron oxide, cobalt oxide , nickel oxide, copper oxide, yttrium oxide, zirconium oxide, niobium oxide, molybdenum oxide, technetium oxide, ruthenium oxide, rhodium oxide, palladium oxide, silver oxide, hafnium oxide, tantalum oxide, tungsten oxide, osmium oxide, iridium oxide, oxide At least one metal oxide selected from the group consisting of platinum, gold oxide, aluminum oxide, gallium oxide, cadmium oxide, indium oxide, tin oxide, thallium oxide, lead oxide, bismuth oxide, and polonium oxide,
A rubber composition whose complex elastic modulus (E*) and loss tangent (tan δ) reversibly change with water and which satisfies the following formula (1) and/or the following formula (2).
E* when wet with water / E* when dry ≤ 0.90 (1)
tan δ when wet with water/tan δ when dry ≥ 1.10 (2)
(In the formula, E* and tan δ are the complex elastic modulus 30 minutes after the start of measurement measured under the conditions of temperature 30 ° C., initial strain 10%, dynamic strain 1%, frequency 10 Hz, extension mode, measurement time 30 minutes and the loss tangent.) The rubber composition according to claim 1, which satisfies the following formula.
E*≧4.5MPa when dry The rubber composition according to claim 1 or 2, which satisfies the following formula.
Dry tan δ≧0.20 4. The rubber composition according to any one of claims 1 to 3, wherein the rubber constituting the skeleton of the modified rubber has at least one monomer selected from the group consisting of styrene, butadiene and isoprene as a structural unit. including a rubber component other than the modified rubber,
The rubber composition according to any one of claims 1 to 3, wherein the rubber component contains at least one selected from the group consisting of styrene-butadiene rubber, butadiene rubber and isoprene-based rubber. The metal oxide comprises at least one selected from the group consisting of lithium oxide, sodium oxide, potassium oxide, rubidium oxide, cesium oxide, beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, and barium oxide. 6. The rubber composition according to any one of 1 to 5. The rubber composition according to any one of claims 1 to 6, wherein the metal oxide contains at least one selected from the group consisting of beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, and barium oxide. The rubber composition according to any one of claims 1 to 7, which contains 5 parts by mass or more of the resin with respect to 100 parts by mass of the rubber component. A tire having a tread made of the rubber composition according to any one of claims 1 to 8. 10. The tire according to claim 9, wherein the E* of the rubber composition when wet with water, the E* of the dry state, and the negative rate S (%) of the tread satisfy the following formula (3).
(E* when wet with water/E* when dry) x S ≤ 30.0 (3) 11. The tire according to claim 9 or 10, wherein tan δ of said rubber composition when wet with water, tan δ of said rubber composition when dry, and negative rate S (%) of said tread satisfy the following formula (4).
(tan δ when wet with water/tan δ when dry)/S≧0.030 (4) The tire according to any one of claims 9 to 11, wherein the tread has a negative rate of 40% or less.

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