JP7261420B2 - Rubber composition for tire - Google Patents

Description

The present invention relates to a rubber composition for tires. More particularly, it relates to a rubber composition for tires having improved mechanical properties over conventional levels.

Rubber compositions that constitute tires are required to have excellent mechanical properties such as elastic modulus and hardness. And, in order to improve the mechanical properties, a technique of blending a filler such as carbon black or silica is known.

Furthermore, by dispersing and containing fine fibers obtained through modification and defibration by oxidation called oxidized cellulose nanofibers in the rubber composition, a rubber composition with excellent rigidity, strength and fatigue resistance is provided. A technique for doing so is also known (Patent Document 1).

JP 2015-098576 A

However, since this oxidized cellulose nanofiber has a polar group, it is difficult to mix and disperse when blended with a hydrophobic rubber raw material, and the oxidized cellulose nanofiber tends to aggregate and bundle in the drying process to remove moisture. Therefore, even if the oxidized cellulose nanofibers are blended into the rubber composition, it is difficult to uniformly disperse them.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a tire rubber composition in which oxidized cellulose nanofibers are homogeneously dispersed and whose mechanical properties are improved beyond the conventional level.

In order to solve the above problems, the present inventors have made intensive studies and found a modified rubber containing a diene rubber, a filler, and oxidized cellulose nanofibers, wherein the diene rubber has a carboxyl group formed by a nitrone compound. A rubber composition for a tire containing 5% by mass or more of a diene rubber and containing 1 to 50 parts by mass of the oxidized cellulose nanofibers with respect to 100 parts by mass of the diene rubber is homogeneous in the oxidized cellulose nanofibers. The present inventors have completed the present invention based on the finding that they are dispersed in a high modulus, have a low elongation ratio at break, and have improved mechanical properties over conventional levels.

That is, the present invention is the following (1) to (6).
(1) containing a diene rubber, a filler, and oxidized cellulose nanofibers, the diene rubber containing 5% by mass or more of a modified diene rubber having a carboxyl group formed by a nitrone compound, and the oxidation A rubber composition for tires, wherein the content of cellulose nanofibers is 1 to 50 parts by mass, preferably 1 to 30 parts by mass, per 100 parts by mass of the diene rubber.
(2) The rubber composition for tires according to (1), wherein the content of the filler is 30 to 90 parts by mass with respect to 100 parts by mass of the diene rubber.
(3) the nitrone compound is N-phenyl-α-(4-carboxyphenyl) nitrone, N-phenyl-α-(3-carboxyphenyl) nitrone, N-phenyl-α-(2-carboxyphenyl) nitrone, At least one selected from the group consisting of N-(4-carboxyphenyl)-α-phenyl nitrone, N-(3-carboxyphenyl)-α-phenyl nitrone and N-(2-carboxyphenyl)-α-phenyl nitrone The rubber composition for tires according to (1) or (2).
(4) The rubber composition for tires according to any one of (1) to (3), wherein the filler is carbon black and/or silica.
(5) The tire rubber composition according to any one of (1) to (4), wherein the oxidized cellulose nanofibers are oxidized cellulose nanofibers containing 0.5 to 3.0 mmol/g of carboxy groups. thing.
(6) By pulse NMR measurement, the relaxation time T ₂ m of the intermediate component when the relaxation time T ₂ component measured by the solid echo method at 60° C. is separated into three types is 50 to 100 μs. (5) The rubber composition for tires according to any one of (5).

According to the present invention, there is provided a tire rubber composition in which oxidized cellulose nanofibers are homogeneously dispersed and which has a high modulus and a low breaking elongation ratio, that is, a tire rubber composition with improved mechanical properties beyond conventional levels. can do. A tire formed from this rubber composition for tires has excellent steering stability and durability.

With the logarithm of M50 (log(M50 (MPa))) on the horizontal axis and the logarithm of λb (logλb) on the vertical axis, each data for the tire rubber compositions of Examples 1 to 4 and Comparative Examples 1 to 14 is plotted is a scatter plot. The black square plots are the data of Examples 1 to 4 (silica + CNF + nitrone modification), the black triangle plots are the data of Comparative Examples 1, 3, 5 and 6 (silica), and the white triangle plots are of Comparative Example 2. and 4 data (silica + CNF), the open circle plots are the data of Comparative Examples 7, 8 and 10 (CB), the open square plots are the data of Comparative Examples 9 and 11 (CB + CNF), the black circle data are compared Data for Examples 12 to 14 (increase in CB cross-linking agent).

The present invention will be described.
The present invention contains a diene-based rubber, a filler, and oxidized cellulose nanofibers, the diene-based rubber contains 5% by mass or more of a modified diene-based rubber having a carboxyl group formed by a nitrone compound, and an oxidized The rubber composition for tires contains 1 to 50 parts by mass of cellulose nanofibers per 100 parts by mass of diene rubber.

The diene rubber used as a rubber raw material in the rubber composition for tires according to the present invention is a rubber having a double bond in the polymer main chain, such as natural rubber (NR), butadiene rubber (BR), styrene-butadiene. Copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), chloroprene rubber (CR), isoprene rubber (IR) and the like are indicated. Such diene rubber latex and/or liquid rubber can be used alone or in combination of two or more. The weight average molecular weight of the diene rubber is preferably 50,000 to 3,000,000, more preferably 100,000 to 2,000,000. In the present invention, the term "weight-average molecular weight" means a value measured by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent in terms of standard polystyrene.

The diene rubber used in the rubber composition for tires according to the present invention is a modified diene rubber having a carboxyl group formed by a nitrone compound (hereinafter referred to as nitrone It is necessary to contain 5% by mass or more of modified diene rubber), preferably 8 to 100% by mass, more preferably 10 to 100% by mass, of nitrone-modified diene rubber. For example, a diene-based rubber composed of nitrone-modified diene-based rubber may be used, a diene-based rubber composed of nitrone-modified diene-based rubber and other modified diene-based rubber, or a nitrone-modified diene-based rubber and non-modified diene-based rubber. A diene rubber made of rubber may also be used. In the present invention, the term "modified diene rubber" means that a polar group such as a carboxy group, epoxy group, amino group, hydroxy group, alkoxy group, silyl group, or amide group is added to the terminal and/or side chain of the molecular chain. "Unmodified diene rubber" means a diene rubber having no polar group at the terminal and/or side chain of its molecular chain.

This nitrone-modified diene-based rubber is a modified diene-based rubber having a carboxyl group formed by reacting the above-mentioned diene-based rubber with a nitrone compound, and the modified diene-based rubber can be obtained simply and easily by the reaction with the nitrone compound. It is characterized by being able to In addition, from the viewpoint of improving the affinity with oxidized cellulose nanofibers and maintaining the properties of the diene rubber, 0.02 to 5.0 mol% of the total amount of double bonds possessed by the diene rubber used in the reaction is this nitrone compound. In other words, the modification rate of this nitrone-modified diene rubber is preferably 0.02 to 5.0 mol%, preferably 0.1 to 4.0 mol%. is more preferable.

The nitrone compound used in the production of the nitrone-modified diene-based rubber in the present invention is a compound having a carboxy group and a nitrone bond (nitron group: a group represented by the chemical formula (1) of Chemical Formula 1 below), This nitrone bond undergoes a cycloaddition reaction with the double bond of the diene rubber to form a five-membered ring. It is preferable that one molecule of the nitrone compound has 1 to 4 carboxyl groups and 1 to 3 nitrone bonds in terms of obtaining a modified diene rubber having a suitable modification rate. More preferably, the nitrone compound of the molecule has one carboxy group and one nitrone bond.

なお、上記化学式（１）中の＊は結合点を表す。

Note that * in the above chemical formula (1) represents a bonding point.

In the present invention, in particular, N-phenyl-α-(4-carboxyphenyl) nitrone represented by chemical formula (2) in Chemical Formula 2 below, N-phenyl-α-(4-carboxyphenyl) nitrone represented by chemical formula (3), and N-phenyl-α-( 3-carboxyphenyl) nitrone, N-phenyl-α-(2-carboxyphenyl) nitrone represented by chemical formula (4), N-(4-carboxyphenyl)-α-phenyl nitrone represented by chemical formula (5) , N-(3-carboxyphenyl)-α-phenyl nitrone represented by chemical formula (6), and N-(2-carboxyphenyl)-α-phenyl nitrone represented by chemical formula (7). It is more preferable to use at least one of

The nitrone-modified diene rubber can be produced by mixing the raw material diene rubber and the nitrone compound at 80 to 200° C. for 1 to 60 minutes for reaction. The amount of the nitrone compound used in this reaction is preferably 0.3 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, with respect to 100 parts by mass of the diene rubber used as a raw material. Moreover, the obtained nitrone-modified diene rubber may contain an unreacted nitrone compound.

The carboxyl group content of the terminal and/or side chain of the rubber molecular chain in the modified diene rubber or tire rubber composition is determined according to JIS K6230: 2006 "Rubber - identification method by infrared spectroscopic analysis". , can be determined based on a previously prepared calibration curve from the absorption of C═O in the carboxy group (1580 cm ⁻¹ spectrum) and the absorption of the methylene group (1460 cm ⁻¹ spectrum).

Fillers to be compounded in the rubber composition for tires according to the present invention include carbon black, silica, clay, aluminum hydroxide, calcium carbonate, mica, talc, aluminum hydroxide, aluminum oxide, titanium oxide, barium sulfate, Examples include lecithin and the like. These fillers can be blended singly or in combination. In particular, blending carbon black and/or silica is useful for improving the strength and hardness of the rubber composition for tires, and oxidizing cellulose nanofibers. is more preferable from the viewpoint of dispersing more homogeneously. The content of the filler in the rubber composition for tires is preferably 30 to 90 parts by mass, more preferably 40 to 70 parts by mass, relative to 100 parts by mass of the diene rubber.

In the present invention, “carbon black” means fine carbon particles having a diameter of about 3 to 500 nm manufactured under industrial quality control, and “silica” means silicon dioxide (SiO ₂ ) or silicon dioxide. means the substance of which it is composed.

Furthermore, the rubber composition for tires according to the present invention contains oxidized cellulose nanofibers. , a phosphite group and a xanthate group.

Cellulose, which is a raw material for oxidized cellulose nanofibers, may be either wood-derived or non-wood-derived (bacteria, algae, cotton, etc.), and is not particularly limited. As a method for producing oxidized cellulose nanofibers, for example, water is added to cellulose as a raw material, and the mixture is treated with a mixer or the like to prepare a slurry in which cellulose is dispersed in water. A method of denaturing cellulose to make it easier to defibrate and then applying a mechanical shear force with a disperser or the like to defibrate is exemplified. By defibrating in this way, the oxidized cellulose nanofibers can be defibrated more finely and homogeneously with low energy. Examples of chemical oxidation treatment include 2,2,6,6-tetramethylpiperidine-1-oxyl (hereinafter referred to as "TEMPO"), 4-acetamido-TEMPO, 4-carboxy-TEMPO, 4-amino-TEMPO. , 4-hydroxy-TEMPO, 4-phosphonooxy-TEMPO, phosphoric acid ester, treatment with an oxidizing agent such as periodic acid. Alternatively, cellulose may be mechanically defibrated by a high-pressure or ultrasonic device, and then chemically oxidized.

It is preferable that the oxidized cellulose nanofibers have a carboxy group as a polar group (modifying group) because the affinity with diene rubbers including nitrone-modified diene rubbers is enhanced. The content of carboxy groups contained in the oxidized cellulose nanofibers is preferably 0.5 to 3.0 mmol/g, more preferably 0.6 to 2.5 mmol/g, and still more preferably 0.8 to 2.2 mmol. /g, still more preferably 1.0 to 2.0 mmol/g. The carboxyl group content can be adjusted by adjusting the amount of the oxidation treatment agent added and/or the oxidation treatment time.

Moreover, the carboxy group content in the oxidized cellulose nanofibers can be measured by the following method.
First, a 0.5-1% by mass slurry was prepared from a cellulose sample whose dry mass was precisely weighed, and after adjusting the pH to about 2.5 with a 0.1M hydrochloric acid aqueous solution, a 0.05M sodium hydroxide aqueous solution was added dropwise. and perform conductivity measurement. Measurements are continued until the pH is approximately 11. From the amount of sodium hydroxide (V) consumed in the neutralization step of the weak acid, whose electrical conductivity changes slowly, the carboxy group content is determined using the following formula.
Carboxy group content (mmol/g) = V (ml) x 0.05/dry mass of cellulose sample (g)

In addition to being chemically modified by the oxidation treatment described above, the oxidized cellulose nanofibers are treated with cellulase after the fibrillation process in order to further increase the affinity with diene rubbers including nitrone-modified diene rubbers. Treatment, carboxymethylation, esterification, treatment with a cationic polymer, etc. can be applied.

The average fiber diameter of the oxidized cellulose nanofibers is 1 to 1000 nm, preferably 1 to 200 nm. The average aspect ratio (average fiber length/average fiber diameter) of the oxidized cellulose nanofibers is preferably 10-1000, more preferably 50-500. If the average fiber diameter is less than the above range and/or the average aspect ratio exceeds the above range, the dispersibility of the oxidized cellulose nanofibers may deteriorate. Further, when the average aspect ratio is less than the above range and/or the average fiber diameter exceeds the above range, the rubber reinforcing performance of the oxidized cellulose nanofibers may deteriorate.

Here, in the present invention, the "average fiber diameter" and "average fiber length" of oxidized cellulose nanofibers are obtained by preparing an oxidized cellulose nanofiber aqueous dispersion having a solid content of 0.05 to 0.1% by mass. By TEM observation or SEM observation, an electron microscope image is obtained by appropriately setting the magnification according to the size of the constituent fibers, and the average value of the fiber diameter and fiber length measured in at least 50 or more in this image means Then, the average aspect ratio is calculated from the average fiber length and average fiber diameter thus obtained.

In the present invention, 1 to 50 parts by mass, preferably 3 to 45 parts by mass, more preferably 5 to 40 parts by mass, and even more preferably 5 to 30 parts by mass of the oxidized cellulose nanofibers are added to 100 parts by mass of the diene rubber. Mix parts by mass. If the amount of the oxidized cellulose nanofibers is less than 1 part by mass, it may not be possible to sufficiently improve the mechanical properties of the tire rubber composition obtained. Moreover, when the amount of the oxidized cellulose nanofibers exceeds 50 parts by mass, the production cost of the tire rubber composition may increase.

The rubber composition for tires according to the present invention further contains a silane coupling agent, zinc oxide (zinc white), stearic acid, an adhesive resin, an adhesive, mastication, as long as the effects of the present invention are not greatly affected. Tire rubber compositions such as accelerators, anti-aging agents, waxes, processing aids, aromatic oils, liquid polymers, terpene resins, thermosetting resins, vulcanizing agents (e.g. sulfur), vulcanization accelerators, cross-linking agents, etc. Various additives generally used in products can be blended in appropriate amounts, and these additives are kneaded by a known method to form a rubber composition for tires, which can be used for vulcanization, crosslinking, etc. can be done.

Then, the rubber composition for tires of the present invention obtained in this way was separated into three types (three components) of relaxation time _T2 components measured by the solid echo method at 60° C. by pulse NMR measurement. The relaxation time T ₂ m of the intermediate component at the time is preferably 50 to 100 μs (microseconds). This relaxation time T ₂ (hydrogen nucleus spin-spin relaxation time) means that the shorter the molecular mobility, the lower the molecular mobility. This indicates that the interaction between In other words, it can be said that the tire rubber composition having the above relaxation time has the oxidized cellulose nanofibers and the like dispersed more homogeneously, the reinforcing property is further improved, and the mechanical properties are further improved.

The method of pulse NMR measurement of the tire rubber composition, the measurement conditions, and the method of determining the relaxation time T ₂ m of the intermediate component can be performed as follows.
A test piece of a rubber composition for tires, which has been immersed in toluene for 24 hours three times to remove soluble components, is injected into an NMR tube with a diameter of 9 mm, and a pulse NMR apparatus JNM-MU25 (manufactured by JEOL Ltd.) is used. Then, the spin-spin relaxation time (T ₂ ) at 60° C. is determined by the solid echo method. As for the conditions for measuring T ₂ , if the amount of rubber is 0.3 g or more, the number of times of accumulation is preferably between 1,000 and 10,000. Weibull coefficients _{( W :} where W _{1 ≤} W ₂ ≦W ₃ ) is used to perform curve fitting according to Equation (1) shown in Equation 1 below, thereby separating into three components. It is more preferable to separate into three components using three different Weibull coefficients (W ₁ <W ₂ <W ₃ ). From the above, the relaxation time and the composition of hydrogen atoms can be obtained for each component. In the case of the oxidized cellulose nanofiber-containing rubber composition, the shortest relaxation time at 60° C. is considered to be due to the hydrogen atoms derived from the oxidized cellulose nanofiber crystals, and the relaxation time T ₂ m of the intermediate component is oxidized. It is believed to be due to the rubber molecules binding to the cellulose nanofibers.

In Equation (1) shown in Equation 1 above, M(t) is the magnetic moment magnetization in the plane perpendicular to the static magnetic field at the elapsed time (t) after pulse application, and M ₀ is the maximum means magnetic moment magnetization.

The method for producing the rubber composition for tires according to the present invention may be a conventional method, and is not particularly limited. As an example of the production method, a diene rubber latex containing nitrone-modified diene rubber and/or a liquid rubber, a filler, oxidized cellulose nanofibers and other components are kneaded and mixed to prepare a rubber composition for tires. can be manufactured. When using vulcanization components (sulfur and vulcanization accelerator) or a cross-linking agent, it is advisable to first mix the other components at a high temperature, and then mix the vulcanization components after cooling. preferable.

Alternatively, a predetermined amount of an oxidized cellulose nanofiber aqueous dispersion containing oxidized cellulose nanofibers, a diene rubber latex containing nitrone-modified diene rubber, and/or a liquid rubber is mixed to prepare a slurry solution, which is then subjected to a conventional method. It may be produced by drying to produce a rubber masterbatch, kneading and mixing the obtained rubber masterbatch with other components. Then, using the obtained rubber composition for tires, tires can be manufactured through processes such as processing, molding and vulcanization.

The concentration of the oxidized cellulose nanofiber aqueous dispersion used in the production of the tire rubber composition is preferably 0.1 to 10% by mass, more preferably 0.1 to 5% by mass. By setting the concentration of the oxidized cellulose nanofiber aqueous dispersion within such a range, the defibrated oxidized cellulose nanofibers can be more uniformly dispersed in the aqueous dispersion. The method of mixing the diene rubber and the oxidized cellulose nanofibers is not particularly limited, and for example, a roll kneading device, a propeller stirring device, a homogenizer, a rotary stirring device, an electromagnetic stirring device, or the like can be used. In particular, it is preferable to mix by a roll kneading method using a roll kneading device.

Examples of the present invention will be described below, but the present invention is not limited to the following examples, and various modifications are possible within the technical concept of the present invention.

Styrene-butadiene copolymer rubber (SBR; Nippon Zeon Co., Ltd., NIPOL SBR 1502, weight average molecular weight 5.0×10 ⁵ ) 100 parts by mass and N-phenyl-α-(4-carboxyphenyl) nitrone 3 parts by mass are mixed in a mixer at 170° C. for 3 minutes to obtain a nitrone-modified diene rubber (modified SBR), which is an SBR having a carboxyl group formed by N-phenyl-α-(4-carboxyphenyl) nitrone. Obtained. In this modified SBR, 0.8 mol % of the total amount of double bonds in the SBR was modified into carboxy groups with N-phenyl-α-(4-carboxyphenyl) nitrone. That is, the modification rate of this modified SBR was 0.8 mol %.

Using the above SBR (unmodified SBR) or modified SBR, the raw materials shown in Table 1 below were blended to produce rubber compositions for tires.
Specifically, silica particles (manufactured by Solvay, Zeosil 1165), oxidized cellulose nanofibers (CNF: containing 1.5 mmol/g of carboxy groups, manufactured by Nippon Paper Industries, Cellenpia), carbon black (CB, manufactured by Tokai Carbon Co., Ltd.) , Seast KH), zinc oxide (ZnO, manufactured by Seido Chemical Industry Co., Ltd.), stearic acid (manufactured by NOF Corporation), the ratio (phr: The amounts shown in Table 1 below were blended as per hundred rubber) and kneaded with a tangential mixer at a mixing temperature of 160° C. for 3 minutes and 30 seconds to obtain each mixture. Next, each mixture contains vulcanization system components (vulcanization accelerator (Ouchi Shinko Kagaku Kogyo Co., Ltd., Noxcellar NS-P), sulfur (Shikoku Kasei Kogyo Co., Ltd., Mucron OT-20)) and a cross-linking agent. Peroxide (manufactured by NOF Corporation, Permil D) was blended in the amount shown in Table 1 below, kneaded with an open roll at a mixing temperature of 100 ° C., and pressed in a predetermined mold at 160 ° C. for 15 minutes. Vulcanized to obtain rubber compositions for tires of Examples 1 to 4 and Comparative Examples 1 to 14 prepared as vulcanized rubber test pieces.

A JIS No. 3 dumbbell-shaped test piece (thickness 2 mm) was punched out from the vulcanized rubber test pieces of Examples 1 to 4 and Comparative Examples 1 to 14, and a tensile test was performed at a tensile speed of 500 mm / min according to JIS K6251: 2010. and the tensile stress (M50: MPa) at 50% elongation was measured at room temperature (20°C). It should be noted that the larger the logarithm of M50, the harder the tire rubber compound.

In addition, for each dumbbell-shaped test piece, the elongation at break (= elongation at break: Eb) was measured at a temperature of 20 ° C. and a tensile speed of 500 mm / min in accordance with JIS K6251: 2010. The elongation ratio (λb) was calculated. The elongation ratio at break (λb) means the value obtained by dividing the elongation at break (%) defined in JIS K6251 by 100 and then adding 1, and the larger the logarithm of λb, the easier the rubber for tires to stretch. It is meant to be a composition.

Furthermore, for the vulcanized rubber test pieces of Examples 1 to 4 and Comparative Examples 1 to 14, the relaxation time _T measured by the solid echo method at 60 ° C. by pulse NMR measurement. The relaxation time T ₂ m of the component was determined. Specifically, immersion in toluene for 24 hours was repeated three times to remove soluble matter, and each test piece was injected into an NMR tube with a diameter of 9 mm, and a pulse NMR apparatus JNM-MU25 (manufactured by JEOL Ltd.) was used. Then, the spin-spin relaxation time (T ₂ ) at 60° C. was determined by the solid echo method. The conditions for measuring _T2 are that the number of times of integration is 5000, and the attenuation curves of the obtained signals are set to Weibull coefficients _W1 of 1 and _W2 from the longest relaxation time _T2 , as shown in Table 2 below. Using 2 as the value W ₃ shown, curve fitting was performed according to Equation (1) shown in Equation 1 to separate into three components, and the relaxation time T ₂ m of the intermediate component was obtained.

These results are shown in Table 2 below and plotted on a graph with the logarithm of M50 on the horizontal axis and the logarithm of λb on the vertical axis (FIG. 1). As a result, as can be seen from the comparison of the results of Comparative Examples 1 to 6 and Examples 1 to 4, a rubber composition for tires using modified SBR and containing a predetermined amount of filler (silica) and oxidized cellulose nanofibers. By making it into a product, it becomes a (tough) tire rubber composition having a high modulus while maintaining a breaking elongation ratio (elongation), that is, oxidized cellulose nanofibers are uniformly dispersed and mechanical properties are improved It was shown that a rubber composition for tires improved over conventional levels can be obtained. In addition, all of the tire rubber compositions of Examples 1 to 4 are measured by pulse NMR measurement, and the relaxation time T measured by the solid echo method at 60 ° C. The relaxation time of the intermediate component when _{the two} components are separated into three types The T ₂ m was less than 100 μs, and the composition was found to have uniformly dispersed oxidized cellulose nanofibers.
On the other hand, from the comparison of the results of Comparative Examples 7, 8, 10 and Comparative Examples 9, 11 to 14, the rubber composition for tires produced by using unmodified SBR and blending a filler (carbon black) On the other hand, it was shown that the rubber composition for tires to which the oxidized cellulose nanofibers were further added and the cross-linking agent was increased, although the hardness increased, but the elongation characteristics decreased.

Claims (5)

containing a diene rubber, a filler, and oxidized cellulose nanofibers,
The diene rubber contains 5% by mass or more of a modified diene rubber having a carboxy group,
The carboxy group of the modified diene rubber is formed by modifying with a nitrone compound having a carboxy group and a nitrone bond, and the modification rate of the modified diene rubber with the nitrone compound is 0.1. ~ 4.0 mol%,
The oxidized cellulose nanofibers are oxidized cellulose nanofibers containing 0.5 to 3.0 mmol/g of carboxy groups,
A rubber composition for tires, wherein the content of the oxidized cellulose nanofiber is 1 to 50 parts by mass with respect to 100 parts by mass of the diene rubber. The rubber composition for tires according to claim 1, wherein the content of said filler is 30 to 90 parts by mass with respect to 100 parts by mass of said diene rubber. The nitrone compound is
N-phenyl-α-(4-carboxyphenyl) nitrone,
N-phenyl-α-(3-carboxyphenyl) nitrone,
N-phenyl-α-(2-carboxyphenyl) nitrone,
N-(4-carboxyphenyl)-α-phenyl nitrone,
The tire rubber according to claim 1 or 2, which is at least one selected from the group consisting of N-(3-carboxyphenyl)-α-phenyl nitrone and N-(2-carboxyphenyl)-α-phenyl nitrone. Composition. The rubber composition for tires according to any one of claims 1 to 3, wherein said filler is carbon black and/or silica. 5. Any one of claims 1 to 4 , wherein the relaxation time T ₂ m of the middle component when the relaxation time T ₂ component measured by the solid echo method at 60° C. is separated into three types by pulse NMR measurement is 50 to 100 μs. 1. The rubber composition for tires according to claim 1.

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