Rubber composition and pneumatic tire using the same

Abstract

To provide a rubber composition capable of improving a conflicting performance with regard to a rolling resistance and wet grip performance, while maintaining or enhancing rigidity, and also to provide a pneumatic tire.SOLUTION: A rubber composition includes, in diene rubber, silica, nitrogen-containing alkoxysilane and alkylalkoxysilane. In the rubber composition, by a pulse method NMR device solid echo method, each spin-spin relaxation time of an unvulcanized specimen composed of diene rubber and a vulcanized specimen is measured, and a relaxation curve (free induction decay curve) of the unvulcanized specimen is divided into two components of a component (S0) with shorter relaxation time and a component (L0) with longer relaxation time, and a relaxation curve of the vulcanized specimen is divided into two components of a component (S) with shorter relaxation time and a component (L) with longer relaxation time, then a weighted mean value (T0) of the relaxation time of the component (S0) and the relaxation time of the component (L0) and a relaxation time (TS) of the component (S) satisfy TS / T0≥0.26. A volume (VS) of the component (S) and a volume (VL) of the component (L) satisfy VS / VL≥0.26.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In recent years, environmental considerations have become a social requirement, and the demand for fuel-efficient vehicles has increased. Given this situation, there is a need to develop materials with low rolling resistance for automobile tires, particularly for the tire tread that contacts the ground. Furthermore, from the perspective of improving vehicle safety, there is a demand for improved braking performance on wet roads (wet grip performance).

[0003] To address these challenges, for example, Patent Document 1 describes that when a material contains three types of rubber components and two types of silica, and the dispersion ratio of silica in each rubber component is within a predetermined range, it is possible to achieve a high level of wet performance, abrasion resistance, and low rolling resistance simultaneously.

[0004] Furthermore, Patent Document 2 describes that when the Rs, which indicates the ratio of the restraining phase of a rubber reinforced with silica and a silane coupling agent as measured by pulsed NMR, is within a predetermined range, excellent low hysteresis loss, wet skid resistance, and abrasion resistance can be achieved while ensuring sufficient processability.

[0005] Thus, various proposals have been made to improve wet grip performance and rolling resistance performance. However, wet grip performance and rolling resistance performance are mutually exclusive properties; improving one leads to a decrease in the other. Therefore, there is a need to improve the other while suppressing the deterioration of one (improvement of mutually exclusive properties).

[0006] In the rubber composition described in Patent Document 1, a rubber component having a low Tg is disposed around the silica. In order to achieve such a configuration, it was necessary to standardize the modification of the rubber component and the mixing method of the components to be blended. Furthermore, the rubber component near the silica interface is constrained by the silica, and there is a risk that it cannot absorb stress due to external stimuli sensitively, and there is room for further improvement in the trade-off performance between rolling resistance and wet grip performance.

[0007] In Patent Document 2, the relaxation time of the polymer is not mentioned. When the restraint of the polymer is too strong, there is a risk that it cannot absorb stress due to external stimuli sensitively, and there is room for improvement in the trade-off performance between rolling resistance and wet grip performance.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0009] [[ID=3十一]]Also, if the trade-off performance between rolling resistance and wet grip performance is improved, the hardness tends to decrease, and it is required to improve the trade-off performance between rolling resistance and wet grip performance while maintaining the hardness.

[0010] In view of the above points, an object of the present invention is to provide a rubber composition that improves the trade-off performance between rolling resistance and wet grip performance while maintaining or improving the hardness, and a pneumatic tire using the same.

Means for Solving the Problems

[0011] The rubber composition according to the present invention is a rubber composition containing silica, nitrogen-containing alkoxysilane, and alkylalkoxysilane in a diene rubber. At 25°C, the spin-spin relaxation times of an unvulcanized sample made of the diene rubber and a sample of the rubber composition vulcanized are measured by solid echo method using a pulsed NMR spectrometer. The relaxation curve (free induction decay curve) obtained from the unvulcanized sample is separated into two components: a component with a short relaxation time (S0) and a component with a long relaxation time (L0). The relaxation curve (free induction decay curve) obtained from the vulcanized sample is separated into two components: a component with a short relaxation time (S) and a component with a long relaxation time (L). The weighted average value (T0) of the relaxation time of component (S0) and the relaxation time (T0) of component (S) are then calculated. S ) and T S The volume of component (S) (V) satisfies / T0≧0.26. S ) and volume (V) of component (L) L ) and V S / V L The condition must satisfy ≥ 0.26.

[0012] The silica content is 5 to 150 parts by mass per 100 parts by mass of diene rubber, the total content of nitrogen-containing alkoxysilane and alkylalkoxysilane is 3 to 15% by mass relative to the silica content, and the proportion of nitrogen-containing alkoxysilane in the total content of nitrogen-containing alkoxysilane and alkylalkoxysilane can be 10 to 80 mol%.

[0013] The above nitrogen-containing alkoxysilane may have at least one substituent 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.

[0014] The alkylalkoxysilane mentioned above may be a compound represented by formula (1). [ka] However, in equation (1), R 1This represents an alkyl group with 3 to 20 carbon atoms.

[0015] The pneumatic tire according to the present invention shall be manufactured using the above-mentioned rubber composition. [Effects of the Invention]

[0016] According to the rubber composition of the present invention, it is possible to improve the conflicting properties of rolling resistance and wet grip performance while maintaining or improving hardness. [Brief explanation of the drawing]

[0017] [Figure 1] A graph showing the T2 relaxation curve of the rubber in Example 1, and the results of fitting and separating it. [Modes for carrying out the invention]

[0018] The following describes in detail matters related to the implementation of the present invention.

[0019] The rubber composition according to this embodiment contains a diene rubber, silica, a nitrogen-containing alkoxysilane, and an alkylalkoxysilane.

[0020] The diene rubber according to this embodiment is not particularly limited, but examples include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), and butyl rubber (IIR). Furthermore, the concept of diene rubber also includes those with modified ends or main chains as needed (e.g., end-modified SBR) and those modified to impart desired properties (e.g., modified NR).

[0021] 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.

[0022] 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 with modified ends or main chain (for example, amine-modified SBR or tin-modified SBR) may be used as needed.

[0023] The silica in this embodiment is not particularly limited, but wet silica such as wet sedimentation silica or wet gel silica is preferably used. The silica content is not particularly limited, but it is preferably 5 to 150 parts by mass, and more preferably 30 to 100 parts by mass, per 100 parts by mass of diene rubber.

[0024] The nitrogen-containing alkoxysilane according to this embodiment is an alkoxysilane containing nitrogen in its molecule. Examples of nitrogen-containing alkoxysilanes 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 azi group, and an amide group, and an alkoxy group bonded to a silicon atom. These are generally referred to as silane coupling agents and include those that have a nitrogen atom in their molecule.

[0025] 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); Examples include isocyanate alkoxysilanes such as 3-isocyanatetopropylalkoxysilane (e.g., 3-isocyanatetopropyltrimethoxysilane, 3-isocyanatetopropyltriethoxysilane, 3-isocyanatetopropyltrippropoxysilane), 2-isocyanate ethylalkoxysilane (e.g., 2-isocyanatetoethyltrimethoxysilane, 2-isocyanatetoethyltriethoxysilane), isocyanate methylalkoxysilane (e.g., isocyanate methyltrimethoxysilane, isocyanate methyltriethoxysilane), cyanoalkoxysilane (e.g., 3-cyanopropyltrimethoxysilane, 3-cyanopropyltriethoxysilane), azidoalkylsilane (e.g., 3-azidopropyltriethoxysilane, 3-azidopropyltrimethoxysilane, 11-azidoundecyltrimethoxysilane), and alkylsilylamidic acids (e.g., triethoxysilylpropylmaleamidic acid). These can be used individually or in combination of two or more types.

[0026] The alkylalkoxysilane in this embodiment 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 This represents an alkyl group having 3 to 20 carbon atoms, preferably an alkyl group having 6 to 20 carbon atoms, and more preferably an alkyl group having 10 to 20 carbon atoms. [ka]

[0027] The total content of nitrogen-containing alkoxysilane and alkylalkoxysilane is preferably 3 to 15% by mass, more preferably 3 to 10% by mass, and even more preferably 3 to 8% 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, more preferably 3 to 10 parts by mass, and even more preferably 3 to 8 parts by mass, per 100 parts by mass of silica.

[0028] The proportion of nitrogen-containing alkoxysilanes in the total content of nitrogen-containing alkoxysilanes and alkylalkoxysilanes is 10 to 80. Mole It is preferably %, and 10 to 60 Mole It is more preferable that it be %, 20-50 Mole It is even more preferable that it be a percentage.

[0029] In addition to the components described above, the rubber composition according to this embodiment may contain, within normal limits, various compounding agents commonly used in the rubber industry, such as reinforcing fillers, process oils, softeners, plasticizers, waxes, antioxidants, sulfur, and vulcanization accelerators. While sulfur-containing silane coupling agents, which are typically added when silica is incorporated, may be included, in one embodiment, it is preferable not to include them.

[0030] As the reinforcing filler, in addition to silica, carbon black may be blended. That is, the reinforcing filler may be silica alone or a combination of carbon black and silica. The content of the reinforcing filler is not particularly limited, and for example, it is preferably 5 to 150 parts by mass, more preferably 30 to 100 parts by mass, and still more preferably 30 to 80 parts by mass with respect to 100 parts by mass of the diene rubber. 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 with respect to 100 parts by mass of the diene rubber.

[0031] The rubber composition according to the present embodiment can be prepared by kneading according to a conventional method using a mixer such as a commonly used Banbury mixer, kneader, roll, etc. In the first mixing stage, other additives except the vulcanizing agent and the vulcanization accelerator are added and mixed to the diene rubber, and then the vulcanizing agent and the vulcanization accelerator are added and mixed as the final mixing stage to prepare the rubber composition.

[0032] The rubber composition according to the present embodiment measures the spin-spin relaxation times of an unvulcanized sample composed of the above diene rubber and a sample obtained by vulcanizing the above rubber composition at 25 °C using a pulse method NMR apparatus by the solid echo method, respectively. The relaxation curve (free induction decay curve) obtained from the unvulcanized sample is separated into two components, a component with a short relaxation time (S0) and a component with a long relaxation time (L0), and the relaxation curve (free induction decay curve) obtained from the vulcanized sample is separated into two components, a component with a short relaxation time (S) and a component with a long relaxation time (L). The weighted average value (T0) of the relaxation time of component (S0) and the relaxation time of component (L0), and the relaxation time (T S ) and T S / T0≧0.26 is satisfied, and the volume (V S ) of component (S) and the volume (V L ) of component (L) satisfy V S / V L ≧0.26.

[0033] In the short phase, rubber components that are more strongly constrained by silica have shorter relaxation times, while rubber components that are less strongly constrained have longer relaxation times. This ratio (T S The molecular mobility of the rubber composition can be evaluated by ratio T0. That is, the molecular mobility of the rubber composition can be evaluated by ratio T0. S The condition / T0≧0.26 is satisfied, and in the short layer, a certain amount of rubber component with weak silica restraint is present, allowing for sensitive stress absorption in response to external stimuli, making it easier to improve the trade-off performance between rolling resistance and wet grip performance.

[0034] Furthermore, the rubber composition is ratio V S / V L The condition ≥ 0.26, and the presence of a certain amount of silica-bound rubber components in the rubber composition, makes it easier to improve the conflicting performance characteristics of rolling resistance and wet grip performance in the rubber composition as a whole.

[0035] The conditions for the rubber composition when measuring pulsed NMR, the measurement conditions, and the methods for calculating the short phase fraction and long phase fraction are described in the examples below.

[0036] The rubber composition obtained in this way can be applied to various parts of pneumatic tires, such as the tread and sidewall, for various applications and sizes, including passenger car tires and large tires for trucks and buses. Specifically, the rubber composition can be molded into a predetermined shape by conventional methods, for example by extrusion, and combined with other parts to produce a green tire. After that, the green tire can be vulcanized at, for example, 140°C to 180°C to produce a pneumatic tire. Among these uses, its use as a compound for tire treads is particularly preferred. [Examples]

[0037] The following are examples of the present invention, but the present invention is not limited to these examples.

[0038] According to the formulations (parts by mass) listed in Tables 1 and 2, the rubber components were kneaded for 30 seconds using a Daihan lab mixer (300cc). Then, silica, sulfur-containing silane coupling agent, nitrogen-containing alkoxysilane, alkylalkoxysilane, zinc oxide, and stearic acid were added and kneaded for 240 seconds before being discharged. Next, the discharged rubber composition was added to the lab mixer and kneaded for 180 seconds before being discharged. Furthermore, the discharged rubber composition, sulfur, and vulcanization accelerator were added to the lab mixer and kneaded for 60 seconds before being discharged. Using two rolls, the obtained unvulcanized rubber composition was sheeted to a thickness of 2 mm, and then vulcanized by pressing at 160°C for 20 minutes to obtain a vulcanized sample.

[0039] The details of each component in Tables 1 and 2 are as follows. • S-SBR: JSR Corporation's "SL563", terminally tin-modified • Silica: "Nip Seal AQ" manufactured by Tosoh Corporation • Sulfur-containing silane coupling agent: "Si75" manufactured by Evonik Japan Co., Ltd. • Nitrogen-containing alkoxysilane 1: Contains amino groups, "3-aminopropyltriethoxysilane" manufactured by Tokyo Chemical Industry Co., Ltd. • Nitrogen-containing alkoxysilane 2: Contains ureido group, "3-ureidopropyltriethoxysilane" manufactured by Tokyo Chemical Industry Co., Ltd., 40-52% by mass methanol solution • Nitrogen-containing alkoxysilane 3: Contains isocyanate groups, manufactured by Tokyo Chemical Industry Co., Ltd. as "3-isocyanatetopropyltriethoxysilane" • Alkylalkoxysilane 1: "Hexyltriethoxysilane" manufactured by Tokyo Chemical Industry Co., Ltd. • Alkylalkoxysilane 2: Octadecyltriethoxysilane manufactured by Tokyo Chemical Industry Co., Ltd. • 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.

[0040] Note that in Tables 1 and 2, the "Percentage of Nitrogen-Containing Alkoxysilane in the Total Amount of Silane Compounds (Molar Ratio (%))" refers to the percentage (molar %) of nitrogen-containing alkoxysilane in the total amount of nitrogen-containing alkoxysilane and alkylalkoxysilane. The amount of nitrogen-containing alkoxysilane 2 in Table 1 includes the amount of methanol in the product.

[0041] Pulse NMR measurements were performed on the obtained vulcanized samples. Specifically, using a JEOL JNM-MU25A at a measurement temperature of 25°C, approximately 1g of the sample cut into 1mm squares was placed in a 10mmΦ glass tube, and the relaxation time T2 was measured by the solid echo method. The obtained relaxation curve M(t) was approximated using the following equation to separate the relaxation time into two components, the short phase (S) and the long phase (L), and the T2 relaxation time (T) of each phase was calculated. S ·T L ), and component fraction (V S ·V L The following formula was calculated. Note that the Weibull coefficient (W) was assumed to be 1 in the calculation below.

[0042]

number

[0043] Furthermore, the relaxation time of each rubber component (in this case, S-SBR alone) used in each rubber composition was measured in its unvulcanized state. The relaxation time was separated into two components, the short phase (S0) and the long phase (L0), from the relaxation curve M(t) obtained in the same manner as above, and the T2 relaxation time (T S ·T L ), and component fraction (V S ·V L The following formula was used to calculate the relaxation time of the two components. The weighted average of the relaxation times of the two components was calculated and defined as T0. The ratio (T) of the calculated T0 to the relaxation time of the short phase of the above vulcanized sample was calculated. S The value of / T0 was calculated.

[0044]

number

[0045] Furthermore, the rolling resistance, wet grip performance, and hardness of the obtained vulcanized samples were evaluated, and the ratio of rolling resistance to wet grip performance was calculated. The results are shown in Tables 1 and 2. The measurement methods for each evaluation are as follows.

[0046] • Rolling resistance (RR): Using a viscoelasticity testing machine manufactured by Ueshima Seisakusho, the loss coefficient tanδ was measured at a frequency of 10 Hz, static strain of 10%, dynamic strain of 1%, and temperature of 60°C. In Table 1, the value for Comparative Example 1-1 is set to 100, and in Table 2, the value for Comparative Example 2-1 is set to 100 as an index. A smaller index indicates better rolling resistance.

[0047] • Wet grip performance (wet): Using a viscoelasticity testing machine manufactured by Ueshima Seisakusho, the loss coefficient tanδ was measured at a frequency of 10 Hz, static strain of 10%, dynamic strain of 1%, and temperature of 0°C. In Table 1, the value for Comparative Example 1-1 is set to 100, and in Table 2, the value for Comparative Example 2-1 is set to 100 as an index. A larger index indicates better wet grip performance.

[0048] • Ratio of rolling resistance to wet grip performance (wet / RR): The tanδ value at 0°C, which represents wet grip performance, was divided by the tanδ value at 60°C, which represents rolling resistance performance. The resulting indices are shown in Tables 1 and 2. In each table, the indices are expressed with the value of Comparative Example 1 set to 100 in Table 1, and with the value of Comparative Example 2-1 set to 100 in Table 2. A larger value indicates an improvement in the trade-off performance between rolling resistance and wet grip performance.

[0049] • Hardness: Measured at 23°C using a Type A durometer conforming to JIS K6253. Table 1 shows the value for Comparative Example 1-1, and Table 2 shows the value for Comparative Example 2-1 as an index of 100. A higher value indicates harder rubber.

[0050] [Table 1]

[0051] [Table 2]

[0052] The results are shown in Tables 1 and 2. Comparative Example 1-1 is an example in which a sulfur-containing silane coupling agent was used instead of alkylalkoxysilane and nitrogen-containing alkoxysilane, and the T was measured by pulsed NMR. S The value of / T0 is outside the specified range. Comparative Example 1-2 is an example in which a nitrogen-containing alkoxysilane is incorporated without a sulfur-containing silane coupling agent and alkylalkoxysilane. In Comparative Example 1-2, the trade-off performance between rolling resistance and wet grip performance worsened compared to Comparative Example 1-1.

[0053] Comparative Examples 1-3 are examples in which nitrogen-containing alkoxysilanes and alkylalkoxysilanes are used in combination, but the V measured by pulsed NMR S / V L The value is outside the specified range. Comparative Example 1-3 showed a deterioration in the trade-off performance between rolling resistance and wet grip performance compared to Comparative Example 1-1.

[0054] Comparative Examples 1-4 are examples in which nitrogen-containing alkoxysilanes and alkylalkoxysilanes are used in combination, but the V measured by pulsed NMR S / V L The value is outside the specified range. Compared to Comparative Example 1-1, Comparative Example 1-4 showed a deterioration in hardness.

[0055] Comparative Examples 1-5 are examples in which alkylalkoxysilanes were incorporated without the sulfur-containing silane coupling agent and nitrogen-containing alkoxysilane, and the V measured by pulsed NMR S / V L The value is outside the specified range. Compared to Comparative Example 1-1, Comparative Example 1-5 showed a deterioration in hardness.

[0056] Comparative Examples 1-6 are examples in which alkylalkoxysilanes were incorporated without the sulfur-containing silane coupling agent and nitrogen-containing alkoxysilane, and the V measured by pulsed NMR S / V L The value is outside the specified range. Compared to Comparative Example 1-1, Comparative Example 1-6 showed a deterioration in the trade-off performance between rolling resistance and wet grip performance.

[0057] Comparative Examples 1-7 and 1-8 are examples in which a nitrogen-containing alkoxysilane was incorporated without a sulfur-containing silane coupling agent and alkylalkoxysilane, and the T values ​​measured by pulsed NMR were measured. S The value of / T0 is outside the specified range. Comparative Examples 1-7 and 1-8 showed a deterioration in the trade-off performance between rolling resistance and wet grip performance compared to Comparative Example 1-1.

[0058] On the other hand, Examples 1-1 to 1-8 are examples in which nitrogen-containing alkoxysilanes and alkylalkoxysilanes are used in combination, and the T values ​​measured by pulsed NMR are shown. S The value of / T0 and V S / V L The value is within the predetermined range. Compared to Comparative Example 1-1, these embodiments maintain or improve hardness while improving the trade-off performance between rolling resistance and wet grip performance.

[0059] Comparative Example 2-1 is an example in which a sulfur-containing silane coupling agent was incorporated without the nitrogen-containing alkoxysilane and alkylalkoxysilane, and the V measured by pulsed NMR S / V L The value of is outside the specified range. Comparative Example 2-2 is an example in which a nitrogen-containing alkoxysilane is included without a sulfur-containing silane coupling agent and alkylalkoxysilane, V S / V L The value is outside the specified range. Compared to Comparative Example 2-1, Comparative Example 2-2 showed a deterioration in the trade-off performance between rolling resistance and wet grip performance.

[0060] Comparative Examples 2-3 are examples in which nitrogen-containing alkoxysilane and alkylalkoxysilane are used in combination, but the V measured by pulsed NMR S / V L The value of is outside the specified range. Compared to Comparative Example 2-1, Comparative Example 2-3 showed a deterioration in the trade-off performance between rolling resistance and wet grip performance.

[0061] Comparative Example 2-4 is an example in which nitrogen-containing alkoxysilane and alkylalkoxysilane are used in combination, but the V measured by pulsed NMR S / V L The value of is outside the specified range. Compared to Comparative Example 2-1, the hardness of Comparative Example 2-4 was worse.

[0062] Comparative Example 2-5 is an example in which an alkylalkoxysilane was incorporated without a sulfur-containing silane coupling agent and a nitrogen-containing alkoxysilane, and the V measured by pulsed NMR S / V L The value of is outside the specified range. Compared to Comparative Example 2-1, the hardness of Comparative Example 2-5 was worse.

[0063] Comparative Example 2-6 is an example in which an alkylalkoxysilane was incorporated without a sulfur-containing silane coupling agent and a nitrogen-containing alkoxysilane, and the V measured by pulsed NMR S / V L The value of is outside the specified range. Compared to Comparative Example 2-1, Comparative Example 2-6 showed a deterioration in the trade-off performance between rolling resistance and wet grip performance.

[0064] On the other hand, Examples 2-1 to 2-6 are examples in which nitrogen-containing alkoxysilanes and alkylalkoxysilanes were used in combination, and the T values ​​measured by pulsed NMR were measured. S The value of / T0 and V S / V L The value is within the predetermined range. Compared to Comparative Example 2-1, these examples maintain or improve hardness while improving the trade-off performance between rolling resistance and wet grip performance. [Industrial applicability]

[0065] The rubber composition of the present invention can be used in the treads, sidewalls, belts, carcasses, etc., of passenger car tires and large tires such as those for trucks and buses.

Claims

1. An unvulcanized rubber composition containing diene rubber, silica, at least one nitrogen-containing alkoxysilane selected from the group consisting of ureidoalkoxysilane and isocyanatealkoxysilane, and alkylalkoxysilane, At 25°C, the spin-spin relaxation times of an unvulcanized sample made of the diene-based rubber and a sample made by vulcanization of the rubber composition were measured using a pulsed NMR apparatus and the solid echo method. The relaxation curve (free induction decay curve) obtained from the unvulcanized sample is used for the component with the shortest relaxation time (S ０ ) and components with long relaxation times (L ０ ) is separated into two components, The relaxation curve (free induction decay curve) obtained from the vulcanized sample is separated into two components: a component with a short relaxation time (S) and a component with a long relaxation time (L). Ingredients (S ０ ) Relaxation time and component (L ０ ) Weighted mean of relaxation time (T ０ ) and the relaxation time (T) of component (S). Ｓ ) and T Ｓ / T ０ Satisfying ≥ 0.26, Volume (V Ｓ of component (S) and volume (V Ｌ of component (L) satisfy V Ｓ / V Ｌ ≧0.26, an unvulcanized rubber composition.

2. The silica content is 5 to 150 parts by mass per 100 parts by mass of diene rubber. The total content of the nitrogen-containing alkoxysilane and alkylalkoxysilane is 3 to 15% by mass relative to the silica content. The unvulcanized rubber composition according to claim 1, wherein the content of nitrogen-containing alkoxysilane is 10 to 80 mol% of the total content of nitrogen-containing alkoxysilane and alkylalkoxysilane.

3. The unvulcanized rubber composition according to claim 1 or 2, wherein the alkylalkoxysilane is a compound represented by formula (1). 【Chemistry 1】 However, in equation (1), R １ This represents an alkyl group having 3 to 20 carbon atoms.

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

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