Rubber composition and tires

Abstract

To provide a rubber composition capable of realizing a wet-grip performance and a rolling resistance performance simultaneously at a high level.SOLUTION: A rubber composition includes diene rubber and silica. A rate of change of a distance between aggregates is 1.30 or more, the rate of change of a distance between aggregates expressed by V50 / V0 calculated with an inertial radius V50 of a silica aggregate obtained by a small angle X-ray scattering measurement with vulcanized rubber obtained by vulcanizing the rubber composition extended by 50% and an inertial radius V0 of the silica aggregate obtained by a small angle X-ray scattering measurement with the vulcanized rubber in an unextended state.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a rubber composition and a tire using the same.

Background Art

[0002] In tires, it is required to achieve both wet grip performance, which is grip performance on a wet road surface, and rolling resistance performance that contributes to low fuel consumption. Therefore, for example, in Patent Document 1, in order to improve low electrical resistance, low rolling resistance performance, wet grip performance, mechanical strength, and processability, it is proposed to blend a silane coupling agent having polyethylene glycol in the main chain skeleton in a silica-filled rubber composition.

[0003] Patent Document 2 describes that in order to produce a tire excellent in wet performance and rolling resistance, an alkyltriethoxysilane is blended in a silica-filled rubber composition together with a silane coupling agent having a mercapto group.

[0004] Patent Document 3 describes that in order to improve processability and low heat generation performance, two types of rubber mixtures with different silane coupling agents are prepared, and both are mixed to produce a rubber composition.

[0005] Conventionally, various proposals have been made to improve wet grip performance and rolling resistance performance. However, since wet grip performance and rolling resistance performance are conflicting performances in which one decreases when the other improves, it is difficult to achieve both. [[ID=(25)]]

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

[0007] Embodiments of the present invention aim to provide a rubber composition that can improve the conflicting performance characteristics of wet grip performance and rolling resistance performance, and a tire using the same. [Means for solving the problem]

[0008] The rubber composition according to the embodiment of the present invention is a rubber composition comprising a diene rubber and silica, wherein the rate of change of the distance between aggregates, expressed as V50 / V0 calculated by V50 / V0 (the radius of inertia of the silica aggregate obtained by measuring the vulcanized rubber in an unstretched state) is 1.30 or more.

[0009] The vulcanized rubber according to one embodiment of the present invention is a vulcanized rubber obtained by vulcanizing a rubber composition containing diene rubber and silica, wherein the rate of change of the distance between aggregates, expressed as V50 / V0 calculated by V50 / V0 (the radius of inertia of the silica aggregate obtained by small-angle X-ray scattering measurement of the vulcanized rubber when it is stretched to 50%) and V0 / V0 (the radius of inertia of the silica aggregate obtained by small-angle X-ray scattering measurement of the vulcanized rubber when it is not stretched), is 1.30 or more.

[0010] The rubber composition may further contain nitrogen-containing alkoxysilane and alkylalkoxysilane. The silica content may be 5 to 150 parts by mass per 100 parts by mass of the diene rubber. The total content of the nitrogen-containing alkoxysilane and alkylalkoxysilane may be 3 to 15% by mass relative to the silica content. The nitrogen-containing alkoxysilane content in the total content of the nitrogen-containing alkoxysilane and alkylalkoxysilane may be 10 to 80 mol%. The nitrogen-containing alkoxysilane may have at least one functional group selected from the group consisting of amino groups, ureido groups, isocyanate groups, cyano groups, azi groups, and amide groups. The vulcanized rubber may have orientation to silica in its unstretched state. In that case, the radius of inertia V50 is the value obtained by small-angle X-ray scattering measurement with the vulcanized rubber stretched 50% in a direction perpendicular to the orientation direction of silica.

[0011] A tire according to an embodiment of the present invention is manufactured using the above-mentioned tire rubber composition. [Effects of the Invention]

[0012] According to embodiments of the present invention, it is possible to improve the trade-off performance between wet grip performance and rolling resistance performance. [Brief explanation of the drawing]

[0013] [Figure 1] Figure showing an example of a two-dimensional scattering image obtained from small-angle X-ray scattering measurements. [Modes for carrying out the invention]

[0014] The rubber composition according to this embodiment includes diene rubber as a rubber component and silica.

[0015] Diene rubber refers to rubber that has repeating units corresponding to diene monomers with conjugated double bonds, and has double bonds in the polymer backbone. Specific examples of diene rubber include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), nitrile rubber (NBR), chloroprene rubber (CR), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, and various other diene rubbers commonly used in rubber compositions. These can be used individually or in combination of two or more. Furthermore, the concept of diene rubber also includes those with modified ends or backbone as needed (e.g., end-modified SBR) or those modified to impart desired properties (e.g., modified NR).

[0016] In one embodiment, the diene rubber preferably contains at least one selected from the group consisting of natural rubber, styrene-butadiene rubber, and butadiene rubber. More preferably, the diene rubber contains styrene-butadiene rubber. For example, 100 parts by mass of the diene rubber preferably contains 50 parts by mass or more of styrene-butadiene rubber, more preferably 70 parts by mass or more of styrene-butadiene rubber, or it may contain styrene-butadiene rubber alone.

[0017] As the styrene-butadiene rubber, for example, solution-polymerized styrene-butadiene rubber (SSBR) or emulsion-polymerized styrene-butadiene rubber (ESBR) may be used. As the styrene-butadiene rubber, modified styrene-butadiene rubber in which the ends or main chain are modified may be used as needed.

[0018] As silica, it is preferable to use wet silica such as wet sedimentation silica or wet gelation silica. The nitrogen adsorption specific surface area (BET) of silica according to JIS K6430:2008 Annex E (Multipoint nitrogen adsorption method: BET method) is, for example, 150 to 250 m². 2 It is preferable that the nitrogen adsorption specific surface area of ​​silica is 180 to 220 m². 2It is / g.

[0019] The silica content is preferably, for example, 5 to 150 parts by mass, more preferably 30 to 120 parts by mass, still more preferably 50 to 100 parts by mass, and may also be 60 to 90 parts by mass with respect to 100 parts by mass of the diene rubber.

[0020] The rubber composition according to the present embodiment may further contain a nitrogen-containing alkoxysilane and an alkylalkoxysilane. Thereby, when the vulcanized rubber obtained by vulcanizing the rubber composition is deformed, the deformation followability of the rubber polymer around the silica can be increased. Therefore, the change in the distance between aggregates during rubber deformation can be increased, and it becomes easier to make the value of V50 / V0 described later 1.30 or more. In addition, by improving the deformation followability, it becomes easier to achieve both wet grip performance and rolling resistance performance. Specifically, the alkylalkoxysilane hydrophobizes the silica surface, improving the dispersibility of the silica, improving the followability of the rubber to external stimuli, and improving the wet grip performance. In addition, the rubbing between silicas is alleviated, the energy loss is reduced, and the rolling resistance performance is improved. Further, the function of the hydrogen bonding site of the nitrogen-containing alkoxysilane can suppress the decrease in rubber hardness.

[0021] The nitrogen-containing alkoxysilane is an alkoxysilane containing a nitrogen atom in the molecule. Examples of the nitrogen-containing alkoxysilane include compounds having a functional group selected from the group consisting of an amino group, a ureido group, an isocyanate group, a cyano group, an azide group, and an amide group, and an alkoxy group bonded to a silicon atom, and generally those called silane coupling agents in which a nitrogen atom is contained in the molecule can be used.

[0022] Specific examples of nitrogen-containing alkoxysilanes include aminoalkoxysilanes such as 3-aminopropylalkoxysilane (e.g., 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane) and 3-(2-aminoethylamino)propylalkoxysilane (e.g., 3-(2-aminoethylamino)propyltriethoxysilane, 3-(2-aminoethylamino)propyltrimethoxysilane, 3-(2-aminoethylamino)propylmethyldimethoxysilane); Ureidoalkoxysilanes such as 3-ureidopropyl alkoxysilanes (e.g., 3-ureidopropyltriethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropylmethyldimethoxysilane, 3-ureidopropylmethyldiethoxysilane), 2-ureidoethyl alkoxysilanes (e.g., 2-ureidoethyltrimethoxysilane, 2-ureidoethyltriethoxysilane, 2-ureidoethylmethyldimethoxysilane), and ureidomethyl alkoxysilanes (e.g., ureidomethyltrimethoxysilane, ureidomethylmethyldimethoxysilane, ureidomethyltriethoxysilane, ureidomethylmethyldiethoxysilane); Isocyanate alkoxysilanes such as 3-isocyanatetopropylalkoxysilane (e.g., 3-isocyanatetopropyltriethoxysilane, 3-isocyanatetopropyltrippropoxysilane), 2-isocyanate ethylalkoxysilane (e.g., 2-isocyanatetoethyltrimethoxysilane, 2-isocyanatetoethyltriethoxysilane), and isocyanate methylalkoxysilane (e.g., isocyanate methyltrimethoxysilane, isocyanate methyltriethoxysilane); cyanoalkoxysilanes such as 3-cyanopropylalkoxysilane (e.g., 3-cyanopropyltrimethoxysilane, 3-cyanopropyltriethoxysilane); azidoalkoxysilanes such as 3-azidopropylalkoxysilane (e.g., 3-azidopropyltriethoxysilane, 3-azidopropyltrimethoxysilane) and 11-azidundecylalkoxysilane (e.g., 11-azidundecyltrimethoxysilane); Examples include amide-bonded alkoxysilanes such as triethoxysilylpropylmaleamidic acid.These can be used individually or in combination of two or more types.

[0023] The alkylalkoxysilane mentioned above may be an alkyldialkoxysilane, but alkyltrialkoxysilane is preferred. The alkylalkoxysilane is preferably one having an alkyl group with 3 to 20 carbon atoms, and specifically, an alkyltriethoxysilane represented by the following formula (1) is preferably used. In formula (1), R 1 represents an alkyl group having 3 to 20 carbon atoms. The number of carbon atoms in the alkyl group is more preferably 6 to 20, and even more preferably 10 to 20. [ka]

[0024] The combined content of nitrogen-containing alkoxysilane and alkylalkoxysilane in the rubber composition is preferably, for example, 3 to 15% by mass relative to the silica content. That is, the total amount of nitrogen-containing alkoxysilane and alkylalkoxysilane is preferably 3 to 15 parts by mass per 100 parts by mass of silica. The combined content of nitrogen-containing alkoxysilane and alkylalkoxysilane is more preferably 5 to 12% by mass, and even more preferably 6 to 12% by mass, relative to the silica content.

[0025] The blending ratio of nitrogen-containing alkoxysilane to alkylalkoxysilane is preferably such that the nitrogen-containing alkoxysilane accounts for 10 to 80 mol%, more preferably 20 to 60 mol%, and even more preferably 25 to 50 mol% of the total content of both.

[0026] In addition to the above-mentioned components, the rubber composition according to this embodiment may contain various additives commonly used in rubber compositions, such as fillers other than silica, zinc oxide, stearic acid, antioxidants, oils, waxes, vulcanizing agents, and vulcanization accelerators. While sulfur-containing silane coupling agents, which are usually added when silica is included, may be included, in one embodiment, it is preferable not to include sulfur-containing silane coupling agents.

[0027] In addition to silica, carbon black may also be added as a filler. That is, the filler may consist of silica alone, or a combination of silica and carbon black. Preferably, the filler is mainly composed of silica, and the carbon black content is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less, per 100 parts by mass of diene rubber.

[0028] Sulfur is preferably used as the vulcanizing agent. The content of the vulcanizing agent is not particularly limited, but is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, and may also be 1 to 3 parts by mass, per 100 parts by mass of diene rubber.

[0029] Examples of vulcanization accelerators include sulfenamide-based, thiuram-based, thiazole-based, and guanidine-based vulcanization accelerators, which can be used individually or in combination of two or more. The content of the vulcanization accelerator is not particularly limited, but is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, and may also be 1 to 4 parts by mass, per 100 parts by mass of diene rubber.

[0030] The rubber composition according to this embodiment can be prepared by kneading in accordance with conventional methods using a commonly used mixer such as a Banbury mixer, kneader, or roll. That is, for example, in the first mixing stage (non-progressive kneading stage), additives other than the vulcanizing agent and vulcanization accelerator are added and mixed with silica to the diene rubber. Then, in the final mixing stage (progressive kneading stage), the vulcanizing agent and vulcanization accelerator are added and mixed to the resulting mixture. This allows for the preparation of an unvulcanized rubber composition.

[0031] The rubber composition according to this embodiment has a change rate V50 / V0 of the inter-aggregate distance when the vulcanized rubber obtained by vulcanizing the rubber composition is deformed from an elongation rate of 0% to 50%, which is 1.30 or higher. The larger the change rate V50 / V0, the higher the deformation-following ability of the rubber polymer around the silica during deformation of the vulcanized rubber, and the more it is possible to improve the trade-off performance between wet grip performance and rolling resistance performance. V50 / V0 is preferably 1.32 or higher, and more preferably 1.34 or higher. There is no particular upper limit to V50 / V0, but it is preferably 2.0 or lower, and more preferably 1.50 or lower.

[0032] Here, V50 is the radius of inertia (nm) of the silica aggregate obtained by small-angle X-ray scattering (SAXS) measurement with the vulcanized rubber stretched 50% in a direction perpendicular to the orientation of the silica. V0 is the radius of inertia (nm) of the silica aggregate obtained by small-angle X-ray scattering measurement with the vulcanized rubber in an unstretched state. The rate of change of the distance between the aggregates is the value (quotient) obtained by dividing the radius of inertia V50 at 50% stretch by the radius of inertia V0 at 0% stretch.

[0033] The orientation direction of silica can be confirmed by performing SAXS measurements on unstretched vulcanized rubber. For vulcanized rubber in which silica does not have orientation in the unstretched state (i.e., vulcanized rubber that does not show anisotropy in the two-dimensional scattering image), SAXS measurements are performed with the rubber stretched 50% in any direction. In other words, V50 is the radius of inertia of the silica aggregate obtained by performing SAXS measurements with the rubber stretched 50% in a direction perpendicular to the orientation direction for vulcanized rubber in which silica has orientation (i.e., anisotropy) in the unstretched state, and the radius of inertia of the silica aggregate obtained by performing SAXS measurements with the rubber stretched 50% in any direction for vulcanized rubber that does not exhibit anisotropy in the unstretched state.

[0034] Note that the values ​​of V0 and V50 may be, for example, 1.0 to 100 nm, 5.0 to 50 nm, or 10 to 40 nm.

[0035] V0 and V50 are values ​​obtained by measuring using vulcanized rubber obtained by vulcanizing a rubber composition. Therefore, the embodiment may also be a vulcanized rubber in which V50 / V0 is 1.30 or higher. That is, the vulcanized rubber according to one embodiment is obtained by vulcanizing a rubber composition containing diene rubber and silica, and is a vulcanized rubber in which V50 / V0 is 1.30 or higher. The vulcanized rubber may constitute a part of a rubber product such as a tire, or it may constitute the entire rubber product.

[0036] The radius of inertia of a silica aggregate is obtained by irradiating vulcanized rubber with X-rays and performing small-angle X-ray scattering measurements. Small-angle X-ray scattering (SAXS) is a technique that measures scattered X-rays with a scattering angle of a few degrees or less (usually 10° or less). When X-rays are irradiated onto vulcanized rubber, the X-rays are scattered according to the electron density of the materials constituting the vulcanized rubber. The radius of inertia of the silica aggregate can be determined from the scattering profile obtained.

[0037] Specifically, the radius of inertia is determined by the method described in Japanese Patent Publication No. 6578200. That is, 10 10 (photons / s / mrad 2 / mm 2 By irradiating with high-brightness X-rays of 0.1% bw or higher and performing small-angle X-ray scattering measurements, a two-dimensional scattering image showing the magnitude of the scattering intensity, as shown in Figure 1, is obtained. In Figure 1, the closer to white, the greater the scattering intensity, and the closer to black, the smaller the scattering intensity, with the contour lines shown as white lines (dotted lines). The black area at the scattering center and the black lines extending downward from there are shadows cast by the beam stopper. The two-dimensional scattering image has constrictions on both the left and right sides of the scattering center, and the left and right directions of these constrictions are the orientation direction of the silica. A one-dimensional scattering profile is obtained by averaging the scattering intensity (annular averaging) of the two-dimensional scattering image over a predetermined angular range β = 30° (a range of 15° on each side of the extension direction centered on the extension direction) in a direction perpendicular to the orientation direction of the silica (sector-shaped area). The scattering profile is a curve showing the magnitude of the scattering intensity I(q) with respect to the scattering vector q (= (4π / λ)sin(θ / 2), where θ is the scattering angle and λ is the wavelength of the X-ray). The radius of inertia of the silica aggregate is determined by fitting it to the obtained scattering profile. When determining V0 for vulcanized rubber that does not exhibit anisotropy in its unstretched state, the above circular averaging is performed over an angular range β=30° centered on the stretching direction during V50 measurement.

[0038] As described in Japanese Patent Publication No. 6578200, the radius of inertia calculated from the angular range β of the sector increases with increasing elongation, and is greatly influenced by structural factors (spatial structure information of the filler). Therefore, by using the radius of inertia calculated from the angular range β of the sector and observing the change in the radius of inertia due to differences in elongation, it can be used as an indicator of the deformation-following ability of the rubber polymer around the filler. Accordingly, in this embodiment, the radius of inertia V0 measured at no elongation (i.e., elongation rate 0%) and the radius of inertia V50 measured at an elongation rate of 50% are determined, and the ratio of the two is calculated, and this ratio V50 / V0 is defined as the rate of change of the distance between aggregates. Details of the measurement conditions in small-angle X-ray scattering measurement and the method for calculating the radius of inertia are described in the examples below.

[0039] The rubber composition according to this embodiment can be suitably used as a rubber composition for tires. Examples of tires include pneumatic tires for various applications and sizes, such as passenger car tires and heavy-duty tires for trucks and buses.

[0040] A tire according to one embodiment is a tire manufactured using the above-mentioned rubber composition. That is, the tire comprises vulcanized rubber made of the above-mentioned rubber composition. Examples of application parts of the tire include tread rubber and sidewall rubber, and the tread rubber is preferred.

[0041] The tread rubber of a tire may have a two-layer structure consisting of a cap rubber and a base rubber, or a single-layer structure in which both are integrated. In the case of a single-layer structure, the tread rubber may be formed from the above-mentioned rubber composition. In the case of a two-layer structure, the outer cap rubber that contacts the road surface may be formed from the above-mentioned rubber composition, the base rubber placed inside the cap rubber may be formed from the above-mentioned rubber composition, or both the cap rubber and the base rubber may be formed from the above-mentioned rubber composition.

[0042] The method for manufacturing the tire is not particularly limited. For example, the rubber composition may be molded into a predetermined shape by extrusion according to a conventional method and combined with other components to produce an unvulcanized tire (green tire). For example, a tread rubber may be made using the rubber composition and combined with other tire components to produce an unvulcanized tire. Subsequently, the tire can be manufactured by vulcanization molding at, for example, 140 to 180°C. [Examples]

[0043] The following are examples, but the present invention is not limited to these examples.

[0044] Rubber compositions were prepared according to the formulations (parts by mass) listed in Tables 1-3 below. Specifically, using a Daihan Corporation lab mixer (300cc), the diene rubber was kneaded for 30 seconds. Then, components other than sulfur and vulcanization accelerator were added to the lab mixer and kneaded for 240 seconds before being discharged. The discharged kneaded material was put back into the lab mixer and kneaded for 180 seconds before being discharged. Next, the discharged kneaded material was added to the lab mixer together with sulfur and vulcanization accelerator and kneaded for 60 seconds before being discharged. Using two rolls, the obtained unvulcanized rubber composition was sheeted to a thickness of 1.0 mm, and then vulcanized by pressing at 160°C for 20 minutes to obtain a 1.0 mm thick vulcanized rubber sample.

[0045] The details of each component in Tables 1-3 are as follows. • S-SBR: JSR Corporation's "HPR350", amino-terminated solution polymerized SBR • Silica: Tosoh Corporation's "Nipseal AQ" (nitrogen adsorption specific surface area 205 m²) 2 / g) • Sulfur-containing silane coupling agent: "Si75" manufactured by Evonik Japan Co., Ltd. • Alkylalkoxysilane: Octadecyltriethoxysilane, manufactured by Tokyo Chemical Industry Co., Ltd. • Aminoalkoxysilane 1: Manufactured by Tokyo Chemical Industry Co., Ltd., 3-aminopropyltriethoxysilane • Aminoalkoxysilane 2: Manufactured by Tokyo Chemical Industry Co., Ltd., 3-(2-aminoethylamino)propyltrimethoxysilane • Ureidoalkoxysilane: "1-[3-(Triethoxysilyl)propyl]urea (40-52% in Methanol)" and 3-ureidopropyltriethoxysilane, manufactured by Tokyo Chemical Industry Co., Ltd. • Isocyanate alkoxysilane: Manufactured by Tokyo Chemical Industry Co., Ltd., 3-isocyanate propyltriethoxysilane • Zinc oxide: "Zinc Oxide No. 3" manufactured by Mitsui Mining & Smelting Co., Ltd. • Stearic acid: "Lunaq S-20" manufactured by Kao Corporation • Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industries, Ltd. • Vulcanization accelerator 1: "Soxinol CZ" manufactured by Sumitomo Chemical Co., Ltd. • Vulcanization accelerator 2: "Noxellar D" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0046] In Tables 1-3, the "molar ratio of nitrogen-containing alkoxysilane (%)" refers to the percentage of nitrogen-containing alkoxysilane in the total content of nitrogen-containing alkoxysilane and alkylalkoxysilane (molar %). The amount of ureidoalkoxysilane in Tables 1 and 2 includes the amount of methanol in the product.

[0047] For the obtained vulcanized rubber samples, the rate of change in aggregate distance V50 / V0 was calculated. The measurement method is as follows.

[0048] Based on the method described in Japanese Patent Publication No. 6578200, SAXS measurements were performed at elongation rates of 0% and 50%, taking into account the orientation direction of silica. Specifically, using a double-ended tensile device that can be fixed at any strain, the sample was first fixed at an elongation rate of 0%, and SAXS measurements were performed by irradiating the sample with X-rays in that state. Next, based on the orientation direction of silica confirmed by this measurement, the sample was stretched to 50% in a direction perpendicular to the orientation direction and fixed, and SAXS measurements were performed by irradiating the sample with X-rays in that state.

[0049] SAXS measurements were performed using beamline BL08B2 of SPring-8 at the Japan Synchrotron Radiation Research Institute (JASRI), which emits high-intensity X-rays, under the following measurement conditions. • Wavelength of incident X-rays: 0.15 nm • Camera length: 6m • Exposure time: 1 second • q range: 0.015~0.8nm -1 • Detector: PILATUS

[0050] From the two-dimensional scattering image obtained by small-angle X-ray scattering measurements, the scattering intensity was annularly averaged over an angular range β=30° (see Figure 1) in the direction perpendicular to the orientation direction (meridian direction) to obtain a one-dimensional scattering profile. The radius of inertia of the silica aggregate was determined by fitting it to the obtained scattering profile. The radius of inertia determined at 0% elongation was defined as V0, and the radius of inertia determined at 50% elongation was defined as V50. The rate of change of the distance between aggregates, V50 / V0, was then calculated. Note that if there was no constriction in the two-dimensional scattering image at 0% elongation (i.e., no anisotropy), V0 was determined by annular averaging over an angular range β=30° in an arbitrary direction, and then V50 was determined by elongating in that direction by 50%.

[0051] The fitting was performed using the least squares method with the fitting function given by the following equation (source: G. Beaucage, J.Appl.Cryst. 28, 717-728 (1995)).

number

[0052] Furthermore, using samples of the unvulcanized rubber composition obtained above, which were vulcanized at 160°C for 20 minutes, the wet grip performance (wet) and rolling resistance performance (RR) were measured, the balance between the two (wet / RR index) was evaluated, and the hardness was measured. The measurement and evaluation methods are as follows.

[0053] [Wet grip performance] The loss coefficient tanδ was measured using a viscoelasticity testing machine manufactured by Ueshima Seisakusho Co., Ltd., at a frequency of 10 Hz, static strain of 10%, dynamic strain of 1%, and temperature of 0°C. In Tables 1 and 2, the values ​​for Comparative Example 1 are expressed as an exponential value, with the values ​​for Comparative Example 6 in Table 3 set to 100. A larger exponent indicates a larger tanδ, which in turn indicates superior wet grip performance when used in tires.

[0054] [Rolling resistance performance] The loss factor tanδ was measured using a viscoelasticity testing machine manufactured by Ueshima Seisakusho Co., Ltd., at a frequency of 10 Hz, static strain of 10%, dynamic strain of 1%, and temperature of 60°C. In Tables 1 and 2, the values ​​for Comparative Example 1 are expressed as an exponential value, with the values ​​for Comparative Example 6 in Table 3 set to 100. A smaller exponent indicates a smaller tanδ, which in turn indicates superior rolling resistance performance when used in tires.

[0055] [wet / RR index] The wet grip performance (wet), represented by the tanδ value at 0°C, was divided by the rolling resistance performance (RR), represented by the tanδ value at 60°C. The resulting index (wet / RR index) was defined as the balance performance. Tables 1 and 2 show the values ​​for Comparative Example 1, while Table 3 shows the values ​​for Comparative Example 6, both expressed as an index with a base of 100. A higher index indicates a greater improvement in the conflicting performance characteristics of wet grip and rolling resistance, and demonstrates superior performance in these areas.

[0056] [hardness] Using a Type A durometer conforming to JIS K6253-3:2012, hardness was measured at 23°C. Tables 1 and 2 show the values ​​for Comparative Example 1, while Table 3 shows the values ​​for Comparative Example 6, both set to an index of 100. A higher index indicates higher hardness and superior handling stability when used in tires.

[0057] [Table 1]

[0058] [Table 2]

[0059] [Table 3]

[0060] The results are shown in Tables 1-3. As shown in Table 1, in Comparative Examples 2-5, the V50 / V0 was less than 1.30, indicating poor deformation-following ability of the rubber polymer around the silica during vulcanized rubber deformation. Therefore, the wet / RR index was equivalent to or lower than that of Comparative Example 1, which contained a sulfur-containing silane coupling agent, and the trade-off performance between wet grip performance and rolling resistance performance was not improved. In contrast, as shown in Table 2, in Examples 1-8, the V50 / V0 was 1.30 or higher, indicating excellent deformation-following ability of the rubber polymer around the silica during vulcanized rubber deformation. As a result, the wet / RR index was higher than that of Comparative Example 1, improving the trade-off performance between wet grip performance and rolling resistance performance, and achieving a high level of balance between both performances. Furthermore, by using nitrogen-containing alkoxysilane and alkylalkoxysilane in combination, the decrease in hardness was suppressed compared to Comparative Example 1, which used a sulfur-containing silane coupling agent. Therefore, in Examples 1-8, it was possible to enhance the balance between wet grip performance and rolling resistance performance while maintaining hardness.

[0061] In the experimental example shown in Table 3, the amount of silica added was reduced to 50 parts by mass per 100 parts by mass of diene rubber, compared to the experimental examples shown in Tables 1 and 2. In this case as well, Example 9, where V50 / V0 is 1.30 or higher, had a larger wet / RR index than the reference comparative example 6, demonstrating a high level of balance between wet grip performance and rolling resistance performance. Furthermore, the hardness was maintained compared to comparative example 6 by using nitrogen-containing alkoxysilane and alkylalkoxysilane in combination.

[0062] Furthermore, the various numerical ranges described in this specification can be any combination of their upper and lower limits, and all such combinations are described herein as preferred numerical ranges. Also, the description of a numerical range as "X~Y" means X or greater and Y or less.

Claims

1. A rubber composition comprising diene rubber, silica, nitrogen-containing alkoxysilane, and alkylalkoxysilane, The aforementioned diene rubber (100 parts by mass) contains 70 parts by mass or more of amino group-modified styrene-butadiene rubber. The silica content is 5 to 150 parts by mass per 100 parts by mass of the diene rubber, the total content of the nitrogen-containing alkoxysilane and the alkylalkoxysilane is 3 to 15% by mass relative to the silica content, and the nitrogen-containing alkoxysilane content within the total content of the nitrogen-containing alkoxysilane and the alkylalkoxysilane is 10 to 80 mol%. A rubber composition in which the rate of change of the distance between aggregates, expressed as V50 / V0 calculated by measuring the radius of inertia of a silica aggregate V50 obtained by measuring the radius of inertia of a silica aggregate V50 obtained by measuring the radius of inertia of a silica aggregate V0 obtained by measuring the radius of inertia of a silica aggregate V0 obtained by measuring the radius of inertia of a silica aggregate V0 obtained by measuring the vulcanized rubber Vulcanized rubber V50 when it is stretched to 50%, is 1.30 or more.

2. The rubber composition according to claim 1, wherein the nitrogen-containing alkoxysilane has at least one functional group selected from the group consisting of an amino group, a ureido group, an isocyanate group, a cyano group, an azi group, and an amide group.

3. The rubber composition according to claim 1 or 2, wherein the vulcanized rubber has orientation toward silica in an unstretched state, and the radius of inertia V50 is a value obtained by small-angle X-ray scattering measurement when the vulcanized rubber is stretched by 50% in a direction perpendicular to the orientation direction of silica.

4. A pneumatic tire made using the rubber composition described in any one of claims 1 to 3.

5. A vulcanized rubber obtained by vulcanizing a rubber composition containing diene rubber, silica, nitrogen-containing alkoxysilane, and alkylalkoxysilane, The aforementioned diene rubber (100 parts by mass) contains 70 parts by mass or more of amino group-modified styrene-butadiene rubber. The silica content is 5 to 150 parts by mass per 100 parts by mass of the diene rubber, the total content of the nitrogen-containing alkoxysilane and the alkylalkoxysilane is 3 to 15% by mass relative to the silica content, and the nitrogen-containing alkoxysilane content within the total content of the nitrogen-containing alkoxysilane and the alkylalkoxysilane is 10 to 80 mol%. A vulcanized rubber in which the rate of change of the distance between aggregates, expressed as V50 / V0 calculated by taking the radius of inertia of the silica aggregate V50 obtained by taking small-angle X-ray scattering measurements of the vulcanized rubber when it is stretched to 50%, and the radius of inertia of the silica aggregate V0 obtained by taking small-angle X-ray scattering measurements of the vulcanized rubber when it is not stretched, is 1.30 or more.

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