Rubber composition and tire

Abstract

To provide a rubber composition capable of improving conflicting performances of a wet-grip performance and rigidity.SOLUTION: A rubber composition includes diene rubber, silica and nitrogen-containing alkoxysilane. A value V / S obtained through dividing a content V of the nitrogen-containing alkoxysilane by a total area S of a silica aggregate is 5.4×10-5 to 5.4×10-4 mL / m2. Here, V is a content (mL) of the nitrogen-containing alkoxysilane per 100 g of the dien rubber. S is a total surface area (m2) of the silica aggregate per 100 g of the dien rubber, obtained by an inertial radius of the silica aggregate obtained by a small angle X-ray scattering measurement through irradiating, with X-rays, vulcanized rubber obtained by vulcanizing the rubber composition, and a silica content per 100 g of the dien rubber.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Tires are required to have improved wet grip performance, which is the grip performance on wet road surfaces, and therefore, various proposals have been made to improve the wet grip performance of rubber compositions used in tires.

[0003] For example, Patent Document 1 describes that a rubber composition containing a conjugated diene polymer whose terminals have been reacted with an alkoxysilane compound is blended with a special silica having a branched structure, thereby improving fuel economy, wet grip performance, and abrasion resistance.

[0004] Patent Document 2 describes that dry silica treated with silicone oil is compounded into a rubber composition together with a silane coupling agent, thereby improving low rolling resistance performance, wet performance, and rubber hardness.

[0005] However, wet grip performance and hardness are trade-offs, and it is difficult to achieve both at the same time, since increasing hardness reduces wet grip performance. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-105242 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-104840 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of an embodiment of the present invention is to provide a rubber composition capable of improving the trade-off between wet grip performance and hardness, and a tire using the same. [Means for solving the problem]

[0008] The rubber composition according to the present embodiment is a rubber composition containing a diene rubber, silica, and a nitrogen-containing alkoxysilane, and the content of the nitrogen-containing alkoxysilane per 100 g of the diene rubber is represented by V (mL), and the total surface area of ​​the silica aggregates per 100 g of the diene rubber is represented by S (m ), which is calculated from the radius of gyration of the silica aggregates obtained by irradiating X-rays on a vulcanized rubber obtained by vulcanizing the rubber composition and performing small-angle X-ray scattering measurement, and the content of the silica per 100 g of the diene rubber. 2 ), and the value V / S obtained by dividing the content V of the nitrogen-containing alkoxysilane by the total surface area S of the silica aggregate is 5.4 × 10 -5 mL / m 2 Over 5.4 x 10 -4 mL / m 2 The following is the result.

[0009] A vulcanized rubber according to one embodiment of the present invention is obtained by vulcanizing a rubber composition containing a diene rubber, silica, and a nitrogen-containing alkoxysilane, and the content of the nitrogen-containing alkoxysilane per 100 g of the diene rubber is defined as V (mL), and the total surface area of ​​the silica aggregates per 100 g of the diene rubber is defined as S (m ), which is calculated from the radius of gyration of the silica aggregates obtained by small-angle X-ray scattering measurement after irradiating the vulcanized rubber with X-rays and the content of the silica per 100 g of the diene rubber. 2 ), and the value V / S obtained by dividing the content V of the nitrogen-containing alkoxysilane by the total surface area S of the silica aggregate is 5.4 × 10 -5 mL / m 2 Over 5.4 x 10 -4 mL / m 2 The following is the result.

[0010] The rubber composition may further contain an alkylalkoxysilane. The content of the silica may be 5 to 150 parts by mass relative to 100 parts by mass of the diene rubber. The total content of the nitrogen-containing alkoxysilane and the alkylalkoxysilane may be 3 to 15 mass% relative to the content of the silica. The content ratio of the nitrogen-containing alkoxysilane in the total content of the nitrogen-containing alkoxysilane and the alkylalkoxysilane may be 10 to 80 mol%. The alkylalkoxysilane may have an alkyl group having 3 to 20 carbon atoms.

[0011] A tire according to an embodiment of the present invention is produced using the rubber composition for a tire. [Effects of the Invention]

[0012] According to an embodiment of the present invention, it is possible to improve the trade-off between wet grip performance and hardness. [Brief explanation of the drawings]

[0013] [Figure 1] An example of a two-dimensional scattering image in small-angle X-ray scattering measurement. DETAILED DESCRIPTION OF THE INVENTION

[0014] The rubber composition according to the present embodiment contains a diene rubber as a rubber component, silica, and a nitrogen-containing alkoxysilane.

[0015] Diene rubber refers to rubber having repeating units corresponding to diene monomers with conjugated double bonds, and has double bonds in the polymer backbone. Specific examples of diene rubber include various diene rubbers commonly used in rubber compositions, such as 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, and styrene-isoprene-butadiene copolymer rubber. These may be used alone or in combination of two or more. The concept of diene rubber also includes those whose terminals or backbone have been modified as necessary (e.g., terminal-modified SBR) and those modified to impart desired properties (e.g., modified NR).

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

[0017] The styrene butadiene rubber may be, for example, solution polymerized styrene butadiene rubber (SSBR) or emulsion polymerized styrene butadiene rubber (ESBR). As the styrene butadiene rubber, modified styrene butadiene rubber whose terminals or main chain are modified may also be used as necessary.

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

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

[0020] Nitrogen-containing alkoxysilanes are alkoxysilanes that contain nitrogen atoms in their molecules. By incorporating nitrogen-containing alkoxysilanes, the hydrogen bonding sites act as a bridge between dispersed silica particles, making it easier to maintain a consistent high-order structure. This enhances the reinforcing effect of silica and improves rubber hardness.

[0021] As the nitrogen-containing alkoxysilane, it is preferable to have at least one functional group selected from the group consisting of amino group, ureido group, isocyanate group, cyano group, azide group and amide group.That is, the nitrogen-containing alkoxysilane can also be a compound that has a functional group selected from the group consisting of amino group, ureido group, isocyanate group, cyano group, azide group and amide group and an alkoxy group bonded to silicon atom, and among those generally called silane coupling agents, those that contain nitrogen atoms 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-ureidopropylalkoxysilanes (e.g., 3-ureidopropyltriethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropylmethyldimethoxysilane, 3-ureidopropylmethyldiethoxysilane), 2-ureidoethylalkoxysilanes (e.g., 2-ureidoethyltrimethoxysilane, 2-ureidoethyltriethoxysilane, 2-ureidoethylmethyldimethoxysilane), and ureidomethylalkoxysilanes (e.g., ureidomethyltrimethoxysilane, ureidomethylmethyldimethoxysilane, ureidomethyltriethoxysilane, ureidomethylmethyldiethoxysilane); Isocyanate alkoxysilanes such as 3-isocyanatepropylalkoxysilane (e.g., 3-isocyanatepropyltriethoxysilane, 3-isocyanatepropyltripropoxysilane), 2-isocyanateethylalkoxysilane (e.g., 2-isocyanateethyltrimethoxysilane, 2-isocyanateethyltriethoxysilane), and isocyanatemethylalkoxysilane (e.g., isocyanatemethyltrimethoxysilane, isocyanatemethyltriethoxysilane); cyanoalkoxysilanes such as 3-cyanopropylalkoxysilane (e.g., 3-cyanopropyltrimethoxysilane, 3-cyanopropyltriethoxysilane); azidoalkoxysilanes such as 3-azidopropylalkoxysilane (e.g., 3-azidopropyltriethoxysilane, 3-azidopropyltrimethoxysilane), and 11-azidoundecylalkoxysilane (e.g., 11-azidoundecyltrimethoxysilane); Examples include amide bond-containing alkoxysilanes such as triethoxysilylpropylmaleamic acid.These can be used alone or in combination of two or more.

[0023] The rubber composition according to the present embodiment may further contain an alkylalkoxysilane. By using a nitrogen-containing alkoxysilane and an alkylalkoxysilane in combination, the silica surface can be hydrophobized while maintaining a portion of the surface hydrophilic. Therefore, the alkylalkoxysilane improves dispersibility, thereby improving wet grip performance, while the nitrogen-containing alkoxysilane maintains a certain high-order structure, thereby improving rubber hardness. Furthermore, by incorporating an alkylalkoxysilane, the total surface area S of the silica aggregates, which will be described later, can be increased, thereby adjusting the V / S value. Specifically, the alkylalkoxysilane hydrophobizes the silica surface, improving the dispersibility of the silica, thereby reducing the size of the silica aggregates and increasing the total surface area S of the silica aggregates.

[0024] The alkylalkoxysilane may be an alkyldialkoxysilane, but is preferably an alkyltrialkoxysilane. The alkylalkoxysilane preferably has an alkyl group having 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 alkyl group more preferably has 6 to 20 carbon atoms, and even more preferably has 10 to 20 carbon atoms. [ka]

[0025] The total content of the nitrogen-containing alkoxysilane and alkylalkoxysilane in the rubber composition is preferably, for example, 3 to 15 mass% relative to the silica content. That is, the total content of the nitrogen-containing alkoxysilane and alkylalkoxysilane is preferably 3 to 15 mass parts relative to 100 mass parts of silica. The total content of the nitrogen-containing alkoxysilane and alkylalkoxysilane is more preferably 5 to 12 mass%, and even more preferably 8 to 12 mass%, relative to the silica content.

[0026] The compounding ratio of the nitrogen-containing alkoxysilane to the alkylalkoxysilane is, for example, preferably 10 to 80 mol %, more preferably 20 to 60 mol %, and even more preferably 25 to 50 mol %, of the nitrogen-containing alkoxysilane in the total content of both.

[0027] In addition to the above components, the rubber composition according to the present embodiment may contain various additives that are generally used in rubber compositions, such as fillers other than silica, zinc oxide, stearic acid, antioxidants, oils, waxes, vulcanizing agents, vulcanization accelerators, etc. Although a sulfur-containing silane coupling agent, which is usually compounded when compounding silica, may be compounded, in one embodiment, it is preferable not to compound a sulfur-containing silane coupling agent.

[0028] Carbon black may be blended as a filler in addition to silica. That is, the filler may be silica alone or a combination of silica and carbon black. Preferably, the filler is mainly composed of silica, and the content of carbon black is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, per 100 parts by mass of diene rubber.

[0029] As the vulcanizing agent, sulfur is preferably used. 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 be 1 to 3 parts by mass, per 100 parts by mass of the diene rubber.

[0030] Examples of the vulcanization accelerator include various vulcanization accelerators such as sulfenamide-based, thiuram-based, thiazole-based, and guanidine-based accelerators, and any one of them can be used alone 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 be 1 to 4 parts by mass, per 100 parts by mass of the diene rubber.

[0031] The rubber composition according to this embodiment can be prepared by kneading in a conventional manner using a commonly used mixer such as a Banbury mixer, kneader, or roll. That is, for example, in the first mixing stage (non-pro kneading step), additives other than the vulcanizing agent and vulcanization accelerator are added to and mixed with the diene rubber along with silica. Then, in the final mixing stage (pro kneading step), the vulcanizing agent and vulcanization accelerator are added to and mixed with the resulting mixture. This allows the preparation of an unvulcanized rubber composition.

[0032] In the rubber composition according to the present embodiment, the content (volume) of nitrogen-containing alkoxysilane per 100 g of diene rubber is represented by V (mL), and the total surface area of ​​silica aggregates per 100 g of diene rubber obtained by small-angle X-ray scattering measurement is represented by S (m 2 ), the nitrogen-containing alkoxysilane content V divided by the total surface area S of the silica aggregate (quotient), i.e., the nitrogen-containing alkoxysilane content V / S per total surface area of ​​the silica aggregate, is 5.4 × 10 -5 ~5.4×10 -4 mL / m 2 V / S is 5.4×10 -5 mL / m 2 If the V / S is less than 5.4×10, the reinforcing effect of the silica by the nitrogen-containing alkoxysilane becomes insufficient, making it difficult to maintain rubber hardness. -4 mL / m 2 If the V / S ratio is greater than 6.0×10, it becomes difficult to obtain the effect of improving wet grip performance due to the dispersibility of silica. By keeping the V / S ratio within the above range, it is possible to improve the trade-off between wet grip performance and hardness.-5 mL / m 2 It is preferable that the value is equal to or greater than 8.0×10 -5 mL / m 2 That's all. V / S is also 4.5 x 10 -4 mL / m 2 Here, the value of V / S is expressed in two significant digits, and fractions are rounded off.

[0033] The value of V may be, for example, 20 mL or less, 0.10 to 19 mL, 0.50 to 10 mL, or 0.60 to 8.0 mL. The value of S may be, for example, 2.0 × 10 3 ~2.0×10 4 m 2 But 3.0 x 10 3 ~1.5×10 4 m 2 But 4.0 x 10 3 ~1.0×10 4 m 2 That's fine too.

[0034] The total surface area S of the silica aggregates is a value obtained by measuring the surface area S of the rubber composition vulcanized using a vulcanized rubber. -5 ~5.4×10 -4 mL / m 2 That is, the vulcanized rubber according to one embodiment is obtained by vulcanizing a rubber composition containing a diene rubber, silica, and a nitrogen-containing alkoxysilane, and has a V / S of 5.4×10 -5 ~5.4×10 -4 mL / m 2 The vulcanized rubber may constitute a part of a rubber product such as a tire, or may constitute the entire rubber product.

[0035] Here, the total surface area S of silica aggregates is the sum of the surface areas of all silica aggregates contained per 100 g of diene rubber in the rubber composition. The total surface area S of silica aggregates is calculated from the radius of gyration Rg of silica aggregates obtained by small-angle X-ray scattering measurement after irradiating X-rays on the vulcanized rubber, and the content of silica per 100 g of diene rubber.

[0036] Small-angle X-ray scattering (SAXS) is a technique for measuring scattered X-rays at a scattering angle of a few degrees or less (usually 10 degrees or less). When vulcanized rubber is irradiated with X-rays, the X-rays are scattered, reflecting the electron density of the materials that make up the vulcanized rubber. The radius of gyration Rg of the silica aggregates can be calculated from the scattering profile obtained.

[0037] Specifically, Rg is determined by the method described in Japanese Patent No. 6578200. That is, the vulcanized rubber is stretched by 50% in a direction perpendicular to the silica orientation direction, and in the stretched state, the vulcanized rubber is subjected to 10 10 (photons / s / mrad 2 / mm 2 Small-angle X-ray scattering measurements are performed by irradiating the rubber with high-intensity X-rays (at least 0.1% bw). The orientation direction of silica can be confirmed by performing SAXS measurements on unstretched vulcanized rubber. For vulcanized rubber that does not show anisotropy in the two-dimensional scattering image in the unstretched state, SAXS measurements can be performed after stretching the rubber 50% in any direction.

[0038] This produces a two-dimensional scattering image showing the magnitude of the scattering intensity, as shown in Figure 1. In Figure 1, the whiter the color, the greater the scattering intensity, and the blacker the color, the weaker the scattering intensity. The contour lines are shown as white (dotted) lines. The black portion of the scattering center and the black lines extending downward from it are shadows cast by the beam stopper. The two-dimensional scattering image has constricted portions on both sides of the scattering center, and the left-right direction of these constricted portions corresponds to the silica orientation direction. A one-dimensional scattering profile is obtained by averaging (circular averaging) the scattering intensity of the two-dimensional scattering image in the silica orientation direction (the left and right constricted portions) over a predetermined angle range α = 30° (a range of 15° on each side of the orientation direction). The scattering profile is a curve showing the magnitude of the scattering intensity I(q) versus the scattering vector q (= (4π / λ) sin(θ / 2), where θ is the scattering angle and λ is the X-ray wavelength). The radius of gyration Rg of the silica aggregate is calculated by fitting the obtained scattering profile. Details of the measurement conditions are as described in the Examples below.

[0039] In this embodiment, the silica aggregate is regarded as a spherical particle, and the total surface area S (m 2 ) is calculated. In other words, if the silica aggregate is considered as a spherical particle, the silica aggregate volume Va is calculated as Va = (4 × π × Rg 3 ) / 3. The amount of silica contained in the rubber composition is expressed as the silica content (volume) Vs (mL) per 100 g of diene rubber by the formula Vs = M / d, where M is the silica mass (g) per 100 g of diene rubber, and d is the density of silica (g / cm 3 By dividing the silica content Vs by the silica aggregate volume Va, the number N of silica aggregates per 100 g of diene rubber is calculated as follows: N = Vs / Va = (M / d) / {(4 × π × Rg 3 ) / 3}.

[0040] On the other hand, the surface area of ​​the silica aggregate Sa is given by Sa = 4 × π × Rg from the radius of gyration of the silica aggregate Rg. 2Therefore, the total surface area of ​​silica aggregates per 100 g of diene rubber is expressed as S (m 2 ) is expressed as the product of the silica aggregate surface area Sa and the number of silica aggregates N, as shown in the following equation (2). S=Sa×N =4×π×Rg 2 ×(M / d) / {(4×π×Rg 3 ) / 3} =3×M / (d×Rg) (2) Therefore, V / S (mL / m 2 ) is expressed by the following equation (3). V / S=V / {3×M / (d×Rg)} (3)

[0041] The rubber composition according to the present embodiment can be suitably used as a rubber composition for tires, such as pneumatic tires of various sizes and for various uses, including tires for passenger cars and heavy-duty tires for trucks and buses.

[0042] A tire according to one embodiment is a tire manufactured using the rubber composition. That is, the tire includes a vulcanized rubber made of the rubber composition. Examples of the application site of the tire include tread rubber and sidewall rubber, and the tread rubber is preferred.

[0043] The tread rubber of a tire may have a two-layer structure of a cap rubber and a base rubber, or a single-layer structure in which the two are integrated. In the single-layer structure, the tread rubber may be formed from the above-mentioned rubber composition. In the two-layer structure, the outer cap rubber that comes into contact with the road surface may be formed from the above-mentioned rubber composition, the base rubber disposed 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.

[0044] The method for producing a tire is not particularly limited. For example, the rubber composition is extruded into a predetermined shape according to a conventional method, and then combined with other components to produce an unvulcanized tire (green tire). For example, tread rubber is produced using the rubber composition, and then combined with other tire components to produce an unvulcanized tire. Thereafter, a tire can be produced by vulcanizing and molding at, for example, 140 to 180°C. [Example]

[0045] Examples will be shown below, but the present invention is not limited to these examples.

[0046] Rubber compositions were prepared according to the formulations (parts by mass) listed in Tables 1 to 3 below. Specifically, a diene rubber was masticated for 30 seconds using a Daihan Corporation lab mixer (300 cc), and then all ingredients except sulfur and the vulcanization accelerator were added to the lab mixer and mixed for 240 seconds before being discharged. The discharged mixture was again added to the lab mixer and mixed for 180 seconds before being discharged. The discharged mixture was then added to the lab mixer together with sulfur and the vulcanization accelerator, mixed for 60 seconds, and discharged. The resulting unvulcanized rubber composition was sheeted using a two-roll mill to a thickness of 1.0 mm, and then subjected to a vulcanization press at 160°C for 20 minutes to obtain a vulcanized rubber sample having a thickness of 1.0 mm.

[0047] Details of each component in Tables 1 to 3 are as follows. S-SBR: JSR Corporation "HPR350", amino-terminated solution-polymerized SBR Silica: Tosoh Corporation's "Nipsil AQ" (nitrogen adsorption specific surface area 205 m 2 / g) Sulfur-containing silane coupling agent: "Si75" manufactured by Evonik Japan Co., Ltd. Aminoalkoxysilane: 3-aminopropyltriethoxysilane manufactured by Tokyo Chemical Industry Co., Ltd. Alkylalkoxysilane 1: Octadecyltriethoxysilane manufactured by Tokyo Chemical Industry Co., Ltd. Alkylalkoxysilane 2: Propyltriethoxysilane, manufactured by Tokyo Chemical Industry Co., Ltd. Zinc oxide: "Zinc oxide No. 3" manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Kao Corporation's "Lunac S-20" Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator 1: "Soxinol CZ" manufactured by Sumitomo Chemical Co., Ltd. Vulcanization accelerator 2: "Noccela D" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0048] In Tables 1 to 3, the "molar ratio (%) of nitrogen-containing alkoxysilane" refers to the content (mol %) of nitrogen-containing alkoxysilane in the total content of nitrogen-containing alkoxysilane and alkylalkoxysilane.

[0049] The content V (mL) of the nitrogen-containing alkoxysilane is the amount of the nitrogen-containing alkoxysilane added per 100 g of diene rubber when preparing the rubber composition.

[0050] Silica aggregate total surface area S (m 2 ) was determined by subjecting the obtained vulcanized rubber sample to SAXS measurement. The measurement method is as follows.

[0051] SAXS measurements were performed based on the method described in Japanese Patent No. 6578200. For the measurements, SAXS measurements were performed on an unstretched sample to confirm the silica orientation direction, and then the sample was stretched by 50% in the direction perpendicular to the orientation direction and irradiated with X-rays in the stretched state. SAXS measurements were performed using beamline BL08B2 at SPring-8 at the Japan Synchrotron Radiation Research Institute as a synchrotron emitting high-brilliance X-rays, under the following measurement conditions: Incident X-ray wavelength: 0.15 nm Camera length: 6m Exposure time: 1 second q range: 0.015~0.8nm -1 Detector: PILATUS

[0052] From the two-dimensional scattering image obtained by small-angle X-ray scattering measurement, the scattering intensity was circularly averaged over an angle range of α = 30° at the constrictions on both sides of the scattering center to obtain a one-dimensional scattering profile. The radius of gyration Rg of the silica aggregate was calculated by fitting the obtained scattering profile. The fitting was performed by the least-squares method using the following fitting function (formula source: G. Beaucage, J. Appl. Cryst. 28, 717-728 (1995)).

[0053]

number

[0054] The silica mass M (g) per 100 g of diene rubber compounded in the preparation of the rubber composition and the silica density d (1.95 g / cm 3 ) and the radius of gyration Rg of the silica aggregate obtained above, the total surface area S of the silica aggregate per 100 g of diene rubber was calculated according to the above formula (2): S = 3 × M / (d × Rg).

[0055] In addition, the content V (mL) of the nitrogen-containing alkoxysilane and the total surface area S (m 2 ) from the above formula (3): V / S = V / {3 × M / (d × Rg)}, V / S (mL / m 2 ) was calculated.

[0056] Furthermore, the unvulcanized rubber composition obtained above was vulcanized at 160°C for 20 minutes, and the hardness and wet grip performance of the sample were measured, and the balance between the two (Hs*Wet index) was evaluated. The measurement and evaluation methods were as follows.

[0057] [hardness] The hardness was measured at 23°C using a Type A durometer conforming to JIS K6253-3:2012, and is shown as an index with the value for Comparative Example 1 in Tables 1 and 2 and the value for Comparative Example 8 in Table 3 set to 100. A larger index indicates higher hardness and better steering stability when made into a tire.

[0058] [Wet grip performance] Using a viscoelasticity tester manufactured by Ueshima Seisakusho Co., Ltd., the loss factor tan δ was measured 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 value for Comparative Example 1, and in Table 3, the value for Comparative Example 8, are shown as indexes, with 100 being the index. A larger index indicates a larger tan δ, which indicates better wet grip performance when made into a tire.

[0059] [Hs*Wet index] The Hs*Wet index was calculated from the hardness index (Hs) and wet grip performance index (Wet) obtained above using the following formula. The larger this index, the greater the improvement effect on the trade-off between wet grip performance and hardness. (Hs*Wet index)=(Hs×Wet) / 100

[0060] [Table 1]

[0061] [Table 2]

[0062] [Table 3]

[0063] The results are shown in Tables 1 to 3. As shown in Tables 1 and 2, in Comparative Example 1, a sulfur-containing silane coupling agent was added to the silica compound, whereas in Comparative Example 2, the sulfur-containing silane coupling agent was replaced with aminoalkoxysilane. In Comparative Example 2, V / S was 5.5 × 10 -4 mL / m2 Although the hardness improved, the wet grip performance was significantly deteriorated. -4 mL / m 2 On the other hand, in Comparative Examples 6 and 7, the V / S was 5.4 × 10 -5 mL / m 2 Although the wet grip performance was improved, the hardness was significantly reduced and the trade-off performance could not be improved.

[0064] On the other hand, V / S is 5.4×10 -5 ~5.4×10 -4 mL / m 2 In Examples 1 to 8, which are in the range, the trade-off between hardness and wet grip performance is improved compared to Comparative Example 1, and a high level of balance between hardness and wet grip performance is achieved.

[0065] In the experimental example shown in Table 3, the amount of silica compounded was 50 parts by mass per 100 parts by mass of diene rubber, which was less than the amount in the experimental examples shown in Tables 1 and 2. In this case, too, the V / S was 5.4 × 10 -5 ~5.4×10 -4 mL / m 2 In Example 9, which is in the range, the trade-off between hardness and wet grip performance was improved compared to Comparative Example 8, which serves as the reference.

[0066] The various numerical ranges described in this specification can be arbitrarily combined with their upper and lower limits, and all such combinations are considered to be preferred numerical ranges described in this specification. Furthermore, a numerical range described as "X to Y" means from X to Y.

Claims

1. A rubber composition comprising a diene rubber, silica, a nitrogen-containing alkoxysilane, and an alkylalkoxysilane having an alkyl group having 3 to 20 carbon atoms, 100 parts by mass of the diene rubber contains 70 parts by mass or more of styrene-butadiene rubber, the content of the silica 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 based on the content of the silica, and the content ratio of the nitrogen-containing alkoxysilane in the total content of the nitrogen-containing alkoxysilane and the alkylalkoxysilane is 10 to 80 mol %, The content of the nitrogen-containing alkoxysilane per 100 g of the diene rubber is represented by V (mL), The total surface area of ​​the silica aggregates per 100 g of the diene rubber is determined from the radius of gyration of the silica aggregates obtained by irradiating X-rays on the vulcanized rubber obtained by vulcanizing the rubber composition and performing small-angle X-ray scattering measurement, and the content of the silica per 100 g of the diene rubber. S (m ２ ) as The value V / S obtained by dividing the content V of the nitrogen-containing alkoxysilane by the total surface area S of the silica aggregate is 5.4 × 10 －５ mL / m ２ 5.4 x 10 －４ mL / m ２ Below is the Rubber composition.

2. A pneumatic tire made using the rubber composition according to claim 1.

3. A vulcanized rubber obtained by vulcanizing a rubber composition containing a diene rubber, silica, a nitrogen-containing alkoxysilane, and an alkylalkoxysilane having an alkyl group having 3 to 20 carbon atoms, 100 parts by mass of the diene rubber contains 70 parts by mass or more of styrene-butadiene rubber, the content of the silica 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 based on the content of the silica, and the content ratio of the nitrogen-containing alkoxysilane in the total content of the nitrogen-containing alkoxysilane and the alkylalkoxysilane is 10 to 80 mol %, The content of the nitrogen-containing alkoxysilane per 100 g of the diene rubber is represented by V (mL), The total surface area of ​​the silica aggregates per 100 g of the diene rubber was calculated from the radius of gyration of the silica aggregates obtained by irradiating the vulcanized rubber with X-rays and measuring the small-angle X-ray scattering, and the content of the silica per 100 g of the diene rubber, and was defined as S (m ２ ) as The value V / S obtained by dividing the content V of the nitrogen-containing alkoxysilane by the total surface area S of the silica aggregate is 5.4 × 10 －５ mL / m ２ 5.4 x 10 －４ mL / m ２ Below is the Vulcanized rubber.

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