Motor cycle tire

Abstract

To provide a motor cycle tire capable of exhibiting excellent steering stability even while a steel cord is used as a belt layer material.SOLUTION: This motor cycle tire comprises a steel cord having a belt layer helically wound in a tire circumferential direction. The steel cord has an m×n structure in which n (2-6) strands twining m (1-3) steel filaments are twined in the same direction as that of the steel filaments. The diameter of each of the steel filaments is 0.15-0.25 mm. The temperature of a rubber composition constituting a tread is 70°C, initial strain is 5%, dynamic strain is ±1%, a frequency is 10 Hz, and a deformation mode: a complex elastic modulus E*(MPa) measured under an elongation condition is 5.0 MPa. A product (S×E*) of a total sectional area S (mm2) and the complex elastic modulus E*(MPa) of the steel filaments in the steel cord is 2.00 or smaller.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a tire for a motorcycle, and more particularly to a tire for a motorcycle in which a steel cord is adopted in a belt layer.

Background Art

[0002] With the improvement of the performance of motorcycles, there has been an increasing demand for improving the performance such as handling stability of tires for motorcycles (hereinafter, also simply referred to as "tires"). In order to meet such requirements, in recent years, as a belt layer, a higher-strength aramid cord has been used instead of the conventionally used nylon 66 (registered trademark) cord.

[0003] However, aramid cord is very expensive, and chemicals that have an adverse impact on the environment, such as concentrated sulfuric acid, are used in its production. Therefore, in combination with the increasing environmental awareness in recent years, a cheaper and more environmentally friendly material is desired, and the adoption of a steel cord has been considered as such a material.

[0004] That is, the steel cord is cheaper than the aramid cord, and although it is a material that has a relatively small impact on environmental pollution, it has a high modulus like the aramid cord, so it is preferable if it can be adopted as a belt layer material.

[0005] Therefore, various techniques for adopting a steel cord as a belt layer material have been proposed (for example, Patent Documents 1, 2, etc.).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

[0007] However, steel cords have higher bending and compressive stiffness than aramid cords, and are prone to buckling when compressed excessively. The high bending stiffness can deform the contact patch of motorcycle tires, which have a curved tread surface, potentially leading to a deterioration in handling stability. Furthermore, the high compressive stiffness can cause buckling, a phenomenon where a portion of the tire lifts off the contact patch and undulates, particularly during high-speed cornering, further worsening handling stability. Therefore, there is room for improvement in enhancing handling stability during high-speed cornering when using steel cords as the belt layer material for motorcycle tires.

[0008] This invention has been made in view of the above-mentioned circumstances, and aims to provide a motorcycle tire that uses steel cord as the belt layer material while still providing excellent handling stability during high-speed turns. [Means for solving the problem]

[0009] The inventors of the present invention have diligently studied how to solve the above problems and have found that the above problems can be solved by the invention described below.

[0010] The present invention A motorcycle tire comprising a carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, and a belt layer disposed on the radially outer side of the carcass and on the inner side of the tread portion, The belt layer is a steel belt layer having steel cords, The steel cord is an m × n steel cord in which n strands of m steel filaments are twisted together, and these strands are twisted in the same direction as the steel filaments, where m is 1 or more and 3 or less, and n is 2 or more and 6 or less. The diameter of the steel filament is 0.15 mm or more and 0.25 mm or less. The complex modulus E of the rubber composition constituting the tread portion was measured under the following conditions: temperature: 70°C, initial strain: 5%, dynamic strain: ±1%, frequency: 10Hz, deformation mode: stretching. * The rubber composition has a pressure of 5.0 MPa or higher. The total cross-sectional area S(mm²) of the steel filaments in the cross-section of the steel cord. 2 ) and the complex modulus E * Product of (MPa) (S × E * This is a motorcycle tire characterized by having a coefficient of 2.00 or less. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a motorcycle tire that offers excellent handling stability even while using steel cord as the belt layer material. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic cross-sectional view of a motorcycle tire according to the present invention. [Figure 2] This is a schematic perspective view showing an example of the belt layer configuration in the present invention. [Figure 3] This is a schematic cross-sectional view showing an example of the steel cord configuration in the present invention. [Figure 4] This diagram illustrates the sample used for measuring and correcting the compressive stiffness of steel cord. [Figure 5] This is a schematic side view illustrating the method for measuring the compressive stiffness of steel cord. [Figure 6] This diagram illustrates the method for calculating the compressive stiffness value of steel cord. [Figure 7] This diagram illustrates a method for determining whether or not a steel cord has a buckling point. [Figure 8] This diagram illustrates a method for measuring the bending stiffness of steel cords. [Modes for carrying out the invention]

[0013] [1] Tire according to the present invention First, the motorcycle tire according to the present invention (hereinafter also simply referred to as "tire") will be described.

[0014] 1. Overall Structure Figure 1 is a schematic cross-sectional view of a part of the tire according to the present invention. In Figure 1, 1 is the tire, 2 is the tread portion, 3 is the sidewall portion, 4 is the bead portion, 5 is the bead core, 6 is the carcass, 7 is the belt layer, and 8 is the bead apex rubber.

[0015] As shown in Figure 1, the tire 1 according to the present invention comprises a carcass 6 extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a belt layer 7 positioned on the radially outer side of the carcass 6 and on the inner side of the tread portion 2. Note that Figure 1 shows 1 / 4 of the radial cross-section of the tire and is symmetrical with respect to the equatorial plane and the tire rotation axis.

[0016] 2. Components (1) Belt layer At least one belt layer 7 (two in Figure 1) is arranged.

[0017] Figure 2 is a schematic perspective view showing an example of the belt layer configuration in the present invention (in the case of one belt layer), where 10 is steel cord and G is covering rubber. As shown in Figure 2, the belt layer 7 is formed by covering a cord array made of aligned steel cords 10 with covering rubber G.

[0018] The number of steel cords 10 arranged in the cord array is determined appropriately, taking into consideration the rigidity and thickness of the steel cords used, but it is generally preferable that the number of cords (ends) per 50 mm width is between 30 and 50.

[0019] In the present invention, a steel belt layer having a steel cord is used as the belt layer. The steel cord has an m x n configuration in which n strands of m steel filaments are twisted together and twisted in the same direction as the steel filaments, where m is 1 or more and 3 or less, and n is 2 or more and 6 or less. The diameter of the steel filament is 0.15 mm or more and 0.25 mm or less.

[0020] Figure 3 is a schematic cross-sectional view showing an example of the steel cord configuration in the present invention. In Figure 3, a 3x3 configuration (m=3, n=3) of steel cord is shown, where three strands 12, each made by twisting three steel filaments f together, are twisted together to form the steel cord 10.

[0021] In the present invention, as the steel filament f, for example, "SWRH72A" (C: 0.69~0.75%, Mn: 0.30~0.60%, Si: 0.15~0.35%, P: 0.030% or less, S: 0.030% or less) as specified in JIS G3506-2017 can be used.

[0022] (2) Tread section The tread section 2 has a tread surface that curves in a convex arc shape from the tire equator C toward the tread edge Te. The tread width Tw is at its maximum width between the left and right Te sides of the tire equator C. This allows for cornering at a large bank angle. The tread section 2 may be divided into an outer region OUT and an inner region IN in the tire width direction, as will be described later, but the division point should be set appropriately considering the balance between the friction force generation function and the reaction force generation function of the tread section 2.

[0023] In the present invention, the rubber composition constituting the tread portion (tread rubber composition) is defined as having a complex modulus E measured under the following conditions: temperature: 70°C, initial strain: 5%, dynamic strain: ±1%, frequency: 10Hz, deformation mode: stretching. * A rubber composition with a pressure of 5.0 MPa or higher is used.

[0024] The complex elastic modulus E * can be measured using a viscoelasticity measuring device such as "E-Plexor (registered trademark)" manufactured by GABO Co., Ltd.

[0025] In addition, the total cross-sectional area S (mm 2 ) of the steel filaments in the cross-section of the steel cord and the complex elastic modulus E * (MPa) of the tread rubber composition satisfy (S × E * ) ≤ 2.00.

[0026] Note that the tread portion is not limited to being formed of a single rubber layer and may be composed of a plurality of rubber compositions such as a base layer and a cap layer. In this case, the above-mentioned complex elastic modulus E * refers to the complex elastic modulus E * of the outermost cap layer.

[0027] In addition, the complex elastic modulus E of the tread rubber composition * (MPa) can be appropriately adjusted by the compounding materials described later. For example, increasing the content of fillers such as silica and carbon black, reducing the content of plasticizer components such as oil and resin, increasing the content of sulfur and accelerators, etc., can increase the complex elastic modulus E * (MPa). Conversely, reducing the content of fillers such as silica and carbon black, increasing the content of plasticizer components such as oil and resin, reducing the content of sulfur and accelerators, etc., can reduce the complex elastic modulus E * (MPa).

[0028] (3) Others The carcass 6 has a toroidal ply body portion 6a that straddles the bead cores 5, 5, and at both ends of this ply folded portion 6b that is folded back from the axially inner side to the outer side of the tire around the bead core 5, with at least one (one in Figure 1) being arranged. Between the ply body portion 6a and the ply folded portion 6b, a bead apex rubber 8 is arranged that tapers outward from the bead core 5 in the radial direction of the tire. In addition, a belt reinforcement layer 9 is wound around the circumferential direction of the tire on the radially outer side of the belt layer.

[0029] In one embodiment of the present invention, the tire carcass 6 and belt reinforcement layer 9 include organic fiber cords formed from organic fibers. Examples of organic fibers include polyester, polyamide, and cellulose. These may be synthetic fibers or biomass-derived fibers. Furthermore, these fibers may be formed from a single component of synthetic fibers, biomass fibers, or recycled / regenerated fibers, and may be hybrid cords formed by twisting these together, cords using multifilaments formed by combining the respective filaments, or cords having a chemical structure in which the respective components are chemically bonded.

[0030] Examples of polyester cords include polyethylene terephthalate (PET) cord, polyethylene naphthalate (PEN) cord, and polyethylene furanoate (PEF). Compared to other polyester cords, PEF may be used because it has superior air permeability resistance and is good at maintaining air pressure inside the tire. Alternatively, a hybrid cord may be used in which a portion of the polyester cord is replaced with a cord made of other organic fibers such as polyamide fibers.

[0031] When the polyester cord is a biomass-derived polyester cord, biomass PET cords using biomass-derived terephthalic acid or ethylene glycol, or biomass PEFs using biomass-derived frangic acid, can be suitably used.

[0032] The aforementioned biomass polyester cord can be obtained by converting it from bioethanol, furfurals, carenes, cymenes, terpenes, etc., or by converting it from various plant and animal-derived compounds, or by directly producing biomass terephthalic acid, biomass ethylene glycol, etc., through fermentation from microorganisms.

[0033] Examples of polyamide codes include aliphatic polyamides, semi-aromatic polyamides, and fully aromatic polyamides.

[0034] Aliphatic polyamides are polyamides that have a backbone in which straight carbon chains are linked by amide bonds, and examples include nylon 4 (PA4), nylon 410 (PA410), nylon 6 (PA6), nylon 66 (PA66), nylon 610 (PA610), nylon 1010 (PA1010), nylon 1012 (PA1012), and nylon 11 (PA11). Among these, nylon 4, nylon 410, nylon 610, nylon 10, nylon 1010, and nylon 11 are particularly easy to obtain from partially or completely biomass-derived materials.

[0035] As nylon 6 and nylon 66, in addition to conventionally synthesized caprolactam obtained by ring-opening polymerization, hexamethylenediamine and adipic acid obtained by condensation polymerization, it is also possible to produce biocaprolactam, bioadipic acid, or biohexamethylenediamine using bio-derived cyclohexane as a starting material, and use nylon 6 or nylon 66 made from these. Furthermore, the aforementioned bio-raw materials may be obtained from sugars such as glucose. These nylon 6 and nylon 66 are expected to have the same strength as those conventionally used.

[0036] A typical example of nylon 4 is one obtained by converting glutamic acid derived from bio-fermentation into γ-aminobutyric acid, followed by 2-pyrrolidone, but it is not limited to this. Nylon 4 has good thermal and mechanical stability and is easy to design as a polymer structure, so it can be suitably used to improve the performance and strength of tires.

[0037] Nylon 410, nylon 610, nylon 1010, nylon 1012, nylon 11, etc., can be obtained using ricinoleic acid, which is derived from castor oil (Ricinus chinensis), as a raw material. Specifically, nylon 410, nylon 610, and nylon 1010 can be obtained by condensation polymerization of sebacic acid, dodecanediic acid, and an arbitrary diamine compound obtained from castor oil, and nylon 11 can be obtained by condensation polymerization of 11-aminoundecanoic acid obtained from castor oil.

[0038] Semi-aromatic polyamides are polyamides that have an aromatic ring structure in part of their molecular chain, and examples include nylon 4T (PA4T), nylon 6T (PA6T), and nylon 10T (PA10T).

[0039] Nylon 4T, Nylon 6T, and Nylon 10T can be obtained by condensation polymerization using terephthalic acid as the dicarboxylic acid and a diamine compound with any number of carbon atoms. It is also possible to obtain these nylon materials using the aforementioned biomass-derived terephthalic acid. Because these materials have a rigid cyclic structure within their molecular chains, they exhibit superior properties such as heat resistance.

[0040] Furthermore, as examples of the aliphatic polyamides and semi-aromatic polyamides mentioned above, we can cite polyamide 5X (where X is the number of carbon atoms derived from the dicarboxylic acid, and is an integer or T represents terephthalic acid) obtained by polymerizing lysine-derived 1,5-pentanediamine with dicarboxylic acids.

[0041] All-aromatic polyamides are polyamides having a skeleton in which aromatic rings are connected by amide bonds, and examples include poly(p-phenylene terephthalamide). Like the aliphatic polyamides and semi-aromatic polyamides mentioned above, all-aromatic polyamides may also be obtained by bonding biomass-derived terephthalic acid with phenylenediamine.

[0042] Examples of cellulose fibers include rayon, polynosic, cupro, acetate, lyocell, and modal, which are manufactured from plant materials such as wood pulp. These cellulose fibers are preferable because, in addition to being carbon neutral in their raw materials, they are biodegradable and do not emit harmful gases when incinerated after use, thus possessing excellent environmental performance. Among the above, rayon, polynosic, and lyocell are particularly preferred due to their balance of process efficiency, environmental friendliness, and mechanical strength.

[0043] Furthermore, the aforementioned cords may be recycled cords obtained by recovering and refining used items such as beverage bottles and clothing, regardless of whether they are synthetic or biomass-derived, and then respinning them.

[0044] The cords described above may be formed by twisting together one or more filaments. For example, two 1100 dsitex multifilaments are combined (in other words, 1100 / 2 dsitex), twisted 48 times / 10cm, and then these two under-twisted cords are combined and twisted the same number of times in the opposite or same direction as the under-twist. Alternatively, two 1670 dsitex multifilaments are combined (in other words, 1670 / 2 dsitex), twisted 40 times / 10cm, and then these two under-twisted cords are combined and twisted.

[0045] By having the above-described configuration, the tire according to the present invention can provide a motorcycle tire that offers excellent handling stability even while using steel cord as the belt layer material, as will be described later.

[0046] 3. Mechanism of effect in the tire according to the present invention The mechanism by which the tire exhibits its effects according to the present invention is presumed to be as follows.

[0047] (1) Composition of steel cord As mentioned above, when using steel cord as the belt layer material, there are concerns that its high compressive and bending stiffness may lead to a deterioration of handling stability during high-speed turns.

[0048] Therefore, the inventors first conducted thorough research on the configuration of a steel cord that has a low compressive stiffness value and an appropriate bending stiffness value.

[0049] As a result, we found that when m strands of steel filaments, each with a diameter of 0.15 mm or more and 0.25 mm or less, are twisted together to form a strand, and then n strands of this strand are twisted together in the same direction as the steel filaments to form an m x n steel cord, it has a low compressive stiffness and an appropriate bending stiffness, making it a suitable material for use as a belt layer.

[0050] Specifically, if the number of steel filaments (m) forming the strand exceeds 3, even if the diameter of the steel filaments is small, a thick strand will be formed, leading to an increase in the compressive stiffness of the steel cord. Furthermore, when combining the steel cord with the rubber composition, the degree of rubber penetration into the gaps within the strand decreases sharply, allowing moisture to penetrate into the strand, leading to rust formation and deterioration of adhesive performance. In contrast, if the number of steel filaments (m) forming the strand is 3 or less, a thick strand will not be formed, thus avoiding the problems described above.

[0051] Next, in an m×n steel cord, if n exceeds 6, the actual cross-sectional structure of the steel cord becomes a layered twist structure such as m×1 + m×(n-1), and the m×1 strand becomes the core strand, leading to an increase in compressive stiffness. In contrast, if n is between 2 and 6, a core strand is not formed, and this problem does not occur.

[0052] Next, if the diameter of the steel filament is less than 0.15 mm, there is a concern that the reaction force generated during rotation will decrease due to the low rigidity of the steel filament. On the other hand, if it exceeds 0.25 mm, it will lead to an increase in compressive rigidity. In contrast, if the diameter of the steel filament is 0.15 mm or more, or 0.25 mm, these problems will not occur.

[0053] Thus, in this invention, by employing steel cord with low compressive stiffness as the belt layer material, the tread surface can be appropriately followed during tire operation, particularly during high-speed and high-load conditions. As a result, the aforementioned buckling phenomenon is prevented, stable handling is obtained even during high-speed cornering, and driving stability is improved.

[0054] (2) Complex modulus of elasticity of the rubber composition constituting the tread The inventors believed that in order to consistently achieve excellent handling stability, simply using the steel cords described above as the belt layer material was insufficient, and that the physical properties of the tread rubber that directly contacts the road surface also needed to be considered. Therefore, they conducted further experiments and studies on the rubber composition (tread rubber composition) that constitutes the tread portion.

[0055] As a result, the complex modulus E of the tread rubber composition was measured under the following conditions: temperature: 70°C, initial strain: 5%, dynamic strain: ±1%, frequency: 10Hz, deformation mode: stretching. *It has been found that when a rubber composition with a MPa of 5.0 MPa or higher is used, the belt layer deforms flexibly during tire operation, making it easier to obtain a large reaction force, and sufficient force is applied from the tread rubber to the road surface, further improving handling stability during high-speed cornering. It is more preferable that the MPa be 6.5 MPa or higher, and although there is no particular upper limit, it is preferably 20 MPa or less, and more preferably 10.0 MPa or less.

[0056] Furthermore, in order to increase the reaction force generated across the entire tread section and improve handling stability during high-speed cornering, the area occupied by the steel filaments within the belt layer, that is, the total cross-sectional area S(mm²) of the steel filaments in the cross-section of a single steel cord, is important. 2 ) and the complex modulus E of the tread rubber composition * Product of (MPa) (S × E * It was found that ) needed to be controlled within an appropriate range, and further experiments and investigations were conducted. As a result, (S × E * It was found that the value should be 2.00 or less. More preferably it should be less than 1.70, and while there is no particular limit to the lower limit, it is preferable that it be 0.60 or more.

[0057] As a result, by reducing the compressive stiffness of the belt layer, it becomes easier to follow the road surface, and by making it easier to generate reaction forces in the tread and belt layer during cornering, it is thought that it is possible to improve handling stability during high-speed cornering.

[0058] [2] More preferred embodiment of the tire according to the present invention The tire according to the present invention can achieve even greater effects by adopting the following embodiments.

[0059] 1. Compressive stiffness value of steel cord As described above, in the present invention, the compressive stiffness value of the steel cord is kept low, but a value of 65 N / mm or less is preferable because it increases flexibility and allows for better conformity to the deformation of the tread. There is no particular lower limit, but a value of 40 N / mm or more is preferable.

[0060] The compressive stiffness value of the steel cord mentioned above can be measured according to the following procedure. First, three vulcanized rubber molded bodies (vulcanization conditions: 165°C x 18 minutes) are prepared as measurement samples for each specification, each consisting of a cylindrical rubber with a diameter of 25 mm and a height of 25 mm, with a 25 mm long steel cord embedded in the center. Next, one correction sample is prepared in the same manner, except that the steel cord is not embedded.

[0061] Next, each obtained sample is compressed in the height direction at a speed of 2.0 mm / min using a tensile testing machine, and the compressive load and compression amount are measured. Then, from the measurement data obtained from the measured samples, the maximum value of the slope is calculated from a graph with the compression amount on the X axis and the compressive load on the Y axis, and the simple average of the three measured samples is calculated. Next, the maximum value of the slope of the compressive load relative to the compression amount is calculated for the correction sample in the same way, and the compressive stiffness of the steel cord is calculated by subtracting this from the slope of the measured samples.

[0062] The specific measurement of this compressive stiffness value will be explained using Figures 4 to 6. Figure 4 is a diagram illustrating the measurement sample and the correction sample. In Figure 4, K0 is the correction sample without embedded steel cords. K1 to K3 are three measurement samples with embedded steel cords.

[0063] Figure 5 is a schematic side view illustrating the method for measuring the compressive stiffness of a steel cord. The cord is compressed at the speed described above, and an SS curve is obtained with the horizontal axis representing the compression distance (amount of compression) and the vertical axis representing the compressive load.

[0064] Figure 6 illustrates the method for calculating the compressive stiffness value, showing the SS curves obtained from each sample from K0 to K3. From Figure 6, it can be seen that the SS curve for K0 has a constant slope, while the SS curves for K1 to K3 show an increase in slope due to the force applied to the steel cord midway through, and then return to the original slope after the steel cord buckles. Since this change in slope is caused by the compressive stiffness of the steel cord, the compressive stiffness of the steel cord can be determined by subtracting the maximum slope value at K0 from the maximum slope value at K1 to K3, and the average value of the results obtained at K1 to K3 is taken as the compressive stiffness of the target steel cord (1133 N / mm in Figure 6).

[0065] 2. Buckling point of steel cord In this invention, it is preferable that the steel cord does not have buckling points. This is because the absence of buckling points prevents the steel cord from breaking even when subjected to large stresses during high-speed turns. Furthermore, it is possible to suppress the progression of strength reduction due to compression fatigue.

[0066] The buckling point of the steel cord described above can generally be determined from the point where the slope value changes from increasing to decreasing in the graph showing the relationship between the slope (N / mm) and the amount of compression (mm) during compression stiffness measurement, as shown in Figure 7. However, if the difference between the minimum value of the slope after the maximum value is small, it is not possible to clearly determine it as a bending point. Therefore, in this invention, the difference (CSmax-CSmin) between the maximum value of the slope (CSmax) and the subsequent minimum value of the slope (CSmin: the slope near the right end of Figure 7) is determined, and if this difference is 200 N / mm or less, it is determined as "no buckling point," and if it exceeds 200 N / mm, it is determined as "buckling point present."

[0067] 3. Bending stiffness value of steel cord As mentioned above, in this invention, the bending stiffness value of the steel cord is lowered, but 2.5 × 10 -3A value of N·m or less is preferable because the belt layer can easily conform to the curved tread surface of the tire, allowing the contact patch shape to be finished to the desired shape. 2.0×10 -3 It is more preferably less than or equal to N·m, and 1.5 × 10 -3 It is even more preferable if it is less than or equal to N·m. On the other hand, there is no particular limit to the lower limit, but 0.5 × 10 -3 It is preferable that it is N·m or greater.

[0068] The bending stiffness value of the steel cord described above can be measured using a stiffness testing machine (e.g., model 150-D) manufactured by TABER Corporation (USA) according to the following procedure. First, both ends of a 145 mm long steel cord are attached to the clamps of the stiffness testing machine, and the steel cord 10 is bent at angles of +15 degrees and -15 degrees, as shown in Figure 8. Then, the average value of the bending moment at +15 degrees and the bending moment at -15 degrees is defined as the bending stiffness value (N·m).

[0069] Furthermore, if the steel cord and tread rubber are too stiff, the tire's rigidity will increase, leading to a deterioration in ride comfort. Therefore, the bending stiffness value FR of the steel cord and the complex modulus of elasticity E are important. * Product of (MPa) (FR × E * ) but 25×10 -3 It is preferable that the pressure is (MPa·N·m) or less. 15×10 -3 It is more preferable that it is less than or equal to (MPa·N·m), and 10 × 10 -3 It is even more preferable if it is less than or equal to (MPa·N·m). The lower limit is not particularly limited, but is 5 × 10 -3 It is preferable that it be (MPa·N·m) or higher, 7 × 10 -3 It is more preferable if the pressure is (MPa·N·m) or higher.

[0070] 4. Rubber coating for the belt layer The belt layer can be obtained by coating the steel cord described above with a predetermined rubber composition. In the present invention, it is preferable that this rubber composition contains cobalt organic acid. This significantly improves the adhesive strength to the steel cord, ensuring good coating of the steel cord.

[0071] Specific examples of organic cobalt acids include cobalt stearate, cobalt boroneodecanoate, cobalt naphthenate, and cobalt neodecanoate. However, cobalt stearate is preferred in terms of its viscosity-reducing effect, while cobalt boroneodecanoate is preferred in terms of its good elongation at break after oxidative degradation and its good adhesion to steel cords after moist heat degradation.

[0072] The organic cobalt content is preferably 0.05 parts by mass or more, and more preferably 0.08 parts by mass or more, when converted to cobalt, per 100 parts by weight of the rubber component. Below 0.05 parts by mass, there is a risk that sufficient adhesion to steel cords cannot be ensured. On the other hand, it is preferably 0.20 parts by mass or less, and more preferably 0.17 parts by mass or less. Above 0.20 parts by mass, the elongation at break after oxidative degradation tends to decrease.

[0073] 5. Multilayering of the belt layer In the present invention, the belt layer may be a single layer, but it is preferable that it be multilayered with two or more layers. In this case, in at least one pair of adjacent belt layers in the radial direction of the tire, the average distance D (mm) between steel cords is preferably 0.6 mm or less, more preferably 0.5 mm or less, and even more preferably 0.45 mm or less.

[0074] As a result, a set of belt layers cooperate with each other to properly restrain the tread and suppress the amount of deformation of the tread during rolling, thereby further improving handling stability at high speeds.

[0075] The average distance D between steel cord layers, as used here, is the distance between the inner surface of the steel cords in the outer belt layer and the outer surface of the steel cords in the inner belt layer, on the equatorial plane of two overlapping belt layers.

[0076] Furthermore, in the case of multilayered belt layers, in at least one pair of adjacent belt layers in the radial direction of the tire, the angle between the steel cords in each belt layer in the tread portion in the tire circumferential direction is preferably 65° or less, more preferably 60° or less, and even more preferably 58° or less.

[0077] By stacking belt layers that are inclined to each other at appropriate angles, a hoop effect can be obtained, firmly restraining almost the entire width of the tread and suppressing the amount of deformation of the tread during rolling, thereby further improving handling stability at high speeds.

[0078] The aforementioned angle is the angle of the steel cords relative to the circumferential direction of the tire when the tire is not inflated, and can be confirmed by peeling off the tread portion of the tire from the radially outer side.

[0079] Furthermore, when there are two belt layers, it is preferable that the ratio (L2 / L1) of the length L2 (mm) of the outer belt layer in the tire width direction to the length L1 (mm) of the inner belt layer in the tire width direction is greater than 1.00. It is believed that by making the length of the outer belt layer in the tire width direction relatively longer, it is possible to obtain a hoop effect more easily and generate a larger reaction force in the tread area.

[0080] As mentioned above, the ratio (L2 / L1) of the tire width direction length L2 (mm) of the tire width direction belt layer to the tire width direction length L1 (mm) of the tire radial inner belt layer is preferably greater than 1.00, more preferably greater than 1.05, and even more preferably greater than 1.10. On the other hand, there is no particular upper limit, but it is preferably less than 1.30, more preferably less than 1.25, and even more preferably less than 1.20.

[0081] The length of the belt layer in the tire width direction, as used here, refers to the length of the arc traced by the belt layer in the tire width direction cross-section, and can be determined by measuring the bead portion of the tire cut radially, with the tire aligned to the standard rim width.

[0082] Furthermore, when there are three or more belt layers, it is preferable that the L2 / L1 relationship described above holds between adjacent belt layers, and that the belt layer width in the tire width direction gradually decreases from the outermost layer to the innermost layer.

[0083] 6. Tread section division In the present invention, it is preferable that the tread portion is divided in the tire width direction. That is, when driving in a straight line, the inner portion of the tread portion in the width direction mainly contacts the road surface with high contact pressure. On the other hand, when turning, the outer portion of the tread portion in the width direction tends to become the contact surface due to the lateral force, and this tendency becomes more pronounced at high speeds, potentially causing skidding due to centrifugal force.

[0084] Therefore, a strong reaction force is required in the inner part of the tread and a strong frictional force in the outer part, and it is preferable to divide the tread into an inner region and an outer region sandwiching it, according to the required function. In this case, both the inner and outer regions have the complex modulus E mentioned above. * (MPa) is 5.0 MPa or higher, (S×E * It is preferable that the value of ) is 2.00 or less.

[0085] In this case, it is preferable to use a rubber composition that contains 25% by mass or less of styrene in the rubber component and has a Tg of -18°C or higher as the rubber composition constituting the outer region of the tread. That is, by containing 25% by mass or less of styrene in the rubber component, the interaction and cohesive action of the styrene parts are weakened, allowing the polymer molecules to move flexibly and increasing the contact area between the road surface and the polymer, thereby improving grip performance during high-speed cornering and improving handling stability. Furthermore, because a certain amount of styrene is contained in the rubber component, the styrene parts in the flexibly moving polymer also tend to generate heat due to friction with each other, so the movement of polymer molecules is further promoted, further improving grip performance during high-speed cornering and obtaining better handling stability. In addition, rubber compositions with a high Tg of -18°C or higher tend to generate heat, so they further promote the movement of polymer molecules, improving grip performance during high-speed cornering and obtaining better handling stability.

[0086] For the reasons stated above, even when the tread portion is not divided, the rubber composition of the tread portion is preferably a rubber composition containing 25% by mass or less of styrene in the rubber component and having a Tg of -18°C or higher.

[0087] The glass transition temperature (Tg) of the rubber composition can be determined from the temperature distribution curve of tanδ measured using a viscoelasticity measuring device such as the "Iplexer®" series manufactured by GABO. Specifically, the temperature corresponding to the largest tanδ value in the obtained tanδ temperature distribution curve (tanδ peak temperature) is defined as the glass transition temperature (Tg). It is more preferable that the temperature is -16°C or higher, and even more preferable that it is -15°C or higher. On the other hand, there is no particular upper limit, but it is preferable that it is 0°C or lower, more preferably -8°C or lower, and even more preferable that it is -10°C or lower.

[0088] Furthermore, in the present invention, it is preferable that the carbon black content ratio in the outer region of the tread is higher than the carbon black content ratio in the inner region of the tread.

[0089] By increasing the carbon black content ratio in the outer region compared to the inner region, when a load is applied to the outer region during high-speed cornering, the temperature rises more easily due to friction between the carbon black and the polymer, which further promotes the movement of the polymer. This improves grip performance during high-speed cornering and enhances handling stability.

[0090] On the other hand, in the inner region, the lower amount of carbon black suppresses heat generation, ensuring the rigidity of the inner region which is more likely to make contact with the ground during the initial stages of a turn, and making it easier to apply load to the outer region during the turn. As a result, the temperature of the outer region rises more easily, further promoting the movement of the polymer, improving grip performance during high-speed turns, and thus improving handling stability.

[0091] The specific difference between the carbon black content ratio in the outer region and the carbon black content ratio in the inner region is preferably 20% by mass or more, and more preferably 30% by mass or more. On the other hand, there is no particular upper limit, but it is preferably 40% by mass or less, and more preferably 38% by mass or less.

[0092] 7. Relationship between tread width and belt layer width In this invention, it is preferable that the ratio (Lm / Tw) of the maximum length Lm (mm) of the belt layer in the tire width direction to the tread width Tw (mm) is 1.00 or greater. By satisfying this relationship, that is, by making the maximum length Lm of the belt layer in the tire width direction greater than or equal to the tread width Tw, the belt layer will form an arc inside the tire radially relative to the tread portion, further exerting a hoop effect that makes it easier to maintain the rounded shape of the tread surface. As a result, when a motorcycle turns, it becomes easier to tilt the vehicle body, improving handling stability at high speeds. Furthermore, even when the vehicle body is tilted, the belt layer remains inside the tire radially relative to the contact surface, making it easier to exert shear force, which is thought to further improve handling stability.

[0093] The maximum length Lm of the belt layer in the tire width direction, as used here, refers to the longest length among the aforementioned belt layers in the tire width direction. In other words, if there is only one belt layer, the length of that belt layer in the tire width direction is Lm, and if there are two or more layers, the longest of them is Lm.

[0094] Furthermore, the tread width Tw refers to the length of the tread portion parallel to the tire width direction, and can be measured in a cross-section cut from the tire in the width direction, with the bead portion aligned to the standard rim width.

[0095] The ratio (Lm / Tw) of the maximum length Lm (mm) of the belt layer in the tire width direction to the tread width Tw (mm) is preferably 1.00 or more, more preferably 1.05 or more, and even more preferably 1.10 or more, as described above. On the other hand, there is no particular upper limit, but it is preferably 1.50 or less, more preferably 1.45 or less, and even more preferably 1.40 or less.

[0096] [3] Embodiment The present invention will be described in detail below based on embodiments.

[0097] 1. Tread rubber composition In this embodiment, the tread rubber composition can be obtained from various compounding materials such as rubber components, fillers, softeners, vulcanizing agents, and vulcanization accelerators described below.

[0098] (1) Compounding materials (a) Rubber component In this embodiment, the rubber component is not particularly limited, and any rubber (polymer) commonly used in tire manufacturing can be used, such as isoprene rubber, butadiene rubber (BR), styrene-butadiene rubber (SBR), nitrile rubber (NBR), butyl rubber, thermoplastic elastomers such as styrene-butadiene-styrene block copolymer (SBS) and styrene-butadiene copolymer (SB). However, considering that the styrene content in the rubber component is preferably 25% by mass or less, as mentioned above, it is preferable to include one of the styrene-based polymers such as SBR, SBS, and SB, and preferably SBR. Furthermore, these styrene-based polymers may be used in combination with other rubber components, for example, a combination of SBR and BR, or a combination of SBR, BR, and isoprene rubber is preferred.

[0099] (i) SBR The weight-average molecular weight of SBR is, for example, greater than 100,000 and less than 2,000,000. The amount of vinyl bonded material (amount of 1,2-bonded butadiene units) in SBR is, for example, greater than 5 mol% and less than 70 mol%. Structural identification of SBR (measurement of styrene content and amount of vinyl bonded material) can be performed, for example, using the JNM-ECA series instrument manufactured by JEOL Ltd.

[0100] The SBR content in 100 parts by mass of rubber component is preferably 55 parts by mass or more, more preferably 60 parts by mass or more, and even more preferably 65 parts by mass or more.

[0101] The SBR is not particularly limited, and for example, emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc., can be used. The SBR may be either unmodified SBR or modified SBR. Hydrogenated SBR, obtained by hydrogenating the butadiene portion of the SBR, may also be used. Hydrogenated SBR may be obtained by subsequently hydrogenating the BR portion of the SBR, or by copolymerizing styrene, ethylene, and butadiene to obtain a similar structure. Oil-expanded SBR may also be used.

[0102] Modified SBRs can be any SBR having a functional group that interacts with a packing material such as silica. Examples include terminally modified SBRs (terminally modified SBRs having the functional group at the terminal) in which at least one end of the SBR is modified with a compound having the functional group (modifying agent), main-chain modified SBRs having the functional group in the main chain, main-chain terminally modified SBRs having the functional group in both the main chain and the terminal (for example, main-chain terminally modified SBRs having the functional group in the main chain and at least one end modified with the modifying agent), and terminally modified SBRs that are modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule, and in which hydroxyl groups or epoxy groups are introduced.

[0103] Examples of the above-mentioned functional groups include amino groups, amide groups, silyl groups, alkoxysilyl groups, isocyanate groups, imino groups, imidazole groups, urea groups, ether groups, carbonyl groups, oxycarbonyl groups, mercapto groups, sulfide groups, disulfide groups, sulfonyl groups, sulfinyl groups, thiocarbonyl groups, ammonium groups, imide groups, hydrazo groups, azo groups, diazo groups, carboxyl groups, nitrile groups, pyridyl groups, alkoxy groups, hydroxyl groups, oxy groups, epoxy groups, and the like. These functional groups may also have substituents.

[0104] Furthermore, as modified SBR, for example, SBR modified with a compound (modifying agent) represented by the following formula can be used.

[0105] [ka]

[0106] Note that in the formula, R 1 , R 2 and R 3 R represents, either identical or distinct, an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group (-COOH), a mercapto group (-SH), or a derivative thereof. 4 and R 5 R represents a hydrogen atom or an alkyl group, either identical or different. 4 and R 5These atoms may bond to form a ring structure with the nitrogen atom. n represents an integer.

[0107] As a modified SBR modified with the compound (modifying agent) represented by the above formula, SBR obtained by modifying the polymerization ends (active ends) of solution-polymerized styrene-butadiene rubber (S-SBR) with the compound represented by the above formula (such as the modified SBR described in Japanese Patent Publication No. 2010-111753) can be used.

[0108] R 1 , R 2 and R 3 A suitable alkoxy group is used (preferably an alkoxy group having 1 to 8 carbon atoms, more preferably an alkoxy group having 1 to 4 carbon atoms). 4 and R 5 A suitable alkyl group (preferably an alkyl group having 1 to 3 carbon atoms) is used. n is preferably 1 to 5, more preferably 2 to 4, and even more preferably 3. Also, R 4 and R 5 When the alkoxy group is bonded to form a ring structure with the nitrogen atom, it is preferably a 4- to 8-membered ring. Note that the alkoxy group also includes cycloalkoxy groups (such as cyclohexyloxy group) and aryloxy groups (such as phenoxy group and benzyloxy group).

[0109] Specific examples of the above-mentioned denaturing agents include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, and 3-diethylaminopropyltriethoxysilane. These may be used individually or in combination of two or more.

[0110] Furthermore, modified SBR can also be modified using the following compounds (modifying agents): For example, polyglycidyl ethers of polyhydric alcohols such as ethylene glycol diglycidyl ether, glycerin triglycidyl ether, trimethylolethane triglycidyl ether, and trimethylolpropane triglycidyl ether; polyglycidyl ethers of aromatic compounds having two or more phenol groups such as diglycidyl bisphenol A; polyepoxy compounds such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, and polyepoxylated liquid polybutadiene; epoxy group-containing tertiary amines such as 4,4'-diglycidyl-diphenylmethylamine and 4,4'-diglycidyl-dibenzylmethylamine; diglycidylaniline, N,N'-diglycidyl-4-glycidyloxyaniline, Diglycidylamino compounds such as diglycidyl orthotoluidine, tetraglycidylmetoxylendiamine, tetraglycidylaminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidylaminomethylcyclohexane, and tetraglycidyl-1,3-bisaminomethylcyclohexane; amino group-containing acid chlorides such as bis-(1-methylpropyl)carbamate chloride, 4-morpholine carbonyl chloride, 1-pyrrolidinecarbonyl chloride, N,N-dimethylcarbamate chloride, and N,N-diethylcarbamate chloride; epoxy group-containing silane compounds such as 1,3-bis-(glycidyloxypropyl)-tetramethyldisiloxane and (3-glycidyloxypropyl)-pentamethyldisiloxane;(Trimethylsilyl)[3-(trimethoxysilyl)propyl]sulfide, (Trimethylsilyl)[3-(triethoxysilyl)propyl]sulfide, (Trimethylsilyl)[3-(tributoxysilyl)propyl]sulfide, (Trimethylsilyl)[3-(methyldimethoxysilyl)propyl]sulfide, (Trimethylsilyl)[3-(methyldiethoxysilyl)propyl]sulfide, (Trimethylsilyl)[3-(methyldipropoxysilyl)propyl]sulfide Sulfide group-containing silane compounds such as [sisilyl)propyl]sulfide and (trimethylsilyl)[3-(methyldibutoxysilyl)propyl]sulfide; N-substituted aziridine compounds such as ethyleneimine and propyleneimine; methyltriethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane, N,N-bis(trimethylsilyl)aminoethyl Alkoxysilanes such as tiltriethoxysilane; (thio)benzophenone compounds having an amino group and / or a substituted amino group, such as 4-N,N-dimethylaminobenzophenone, 4-N,N-di-t-butylaminobenzophenone, 4-N,N-diphenylaminobenzophenone, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, 4,4'-bis(diphenylamino)benzophenone, and N,N,N',N'-bis-(tetraethylamino)benzophenone; 4-N,N- Benzaldehyde compounds having an amino group and / or a substituted amino group, such as dimethylaminobenzaldehyde, 4-N,N-diphenylaminobenzaldehyde, and 4-N,N-divinylaminobenzaldehyde; N-substituted pyrrolidones such as N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, Nt-butyl-2-pyrrolidone, and N-methyl-5-methyl-2-pyrrolidone; N-substituted piperidones such as N-methyl-2-piperidone, N-vinyl-2-piperidone, and N-phenyl-2-piperidone;N-substituted lactams such as N-methyl-ε-caprolactam, N-phenyl-ε-caprolactam, N-methyl-ω-laurylolactam, N-vinyl-ω-laurylolactam, N-methyl-β-propiolactam, and N-phenyl-β-propiolactam; as well as N,N-bis-(2,3-epoxypropoxy)-aniline, 4,4-methylene-bis-(N,N-glycidylaniline), and tris-(2,3-epoxypropyl)-1,3,5-triazine-2,4,6-triones. Examples include N,N-diethylacetamide, N-methylmaleimide, N,N-diethylurea, 1,3-dimethylethyleneurea, 1,3-divinylethyleneurea, 1,3-diethyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, 4-N,N-dimethylaminoacetophene, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenylamino)-2-propanone, and 1,7-bis(methylethylamino)-4-heptanone. Modification using the above compounds (modifiers) can be carried out by known methods.

[0111] For example, SBR manufactured and sold by companies such as Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, and Nippon Zeon Co., Ltd. can be used. SBR may be used alone or in combination of two or more types.

[0112] (b)BR In this embodiment, the tread rubber composition may further contain BR as needed. In this case, the BR content per 100 parts by mass of rubber component is preferably 30 parts by mass or more, more preferably 35 parts by mass or more. On the other hand, it is preferably 45 parts by mass or less, and more preferably 40 parts by mass or less.

[0113] The weight-average molecular weight of BR is, for example, greater than 100,000 and less than 2,000,000. The vinyl bond content of BR is, for example, greater than 1% by mass and less than 30% by mass. The cis content of BR is, for example, greater than 1% by mass and less than 98% by mass. The trans content of BR is, for example, greater than 1% by mass and less than 60% by mass.

[0114] The BR is not particularly limited, and can be high-cis content BR (cis content of 90% or more), low-cis content BR, or BR containing syndiotactic polybutadiene crystals. The BR can be either unmodified or modified, and modified BR can be modified BR into which the aforementioned functional groups have been introduced. These can be used individually or in combination of two or more. The cis content can be measured by infrared absorption spectroscopy.

[0115] For example, products from companies such as Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, and Nippon Zeon Corporation can be used as BRs.

[0116] (h) Isoprene rubber In this embodiment, the tread rubber composition may optionally further contain isoprene-based rubber. In this case, the isoprene-based rubber content in 100 parts by mass of the rubber component is preferably more than 20 parts by mass and less than 35 parts by mass.

[0117] Examples of isoprene-based rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR.

[0118] For NR, common types used in the tire industry can be used, such as SIR20, RSS#3, and TSR20. For IR, there are no particular limitations, and common types used in the tire industry can be used, such as IR2200. Examples of modified NR include deproteinized natural rubber (DPNR) and high-purity natural rubber (UPNR). Examples of modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Examples of modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These may be used individually or in combination of two or more types.

[0119] (ii) Other rubber components Furthermore, other rubber components may include rubbers (polymers) commonly used in tire manufacturing, such as nitrile rubber (NBR).

[0120] (b) Compounding materials other than rubber components (i) Filling agent In this embodiment, the rubber composition preferably contains a filler. Specific fillers include, for example, carbon black, silica, graphite, calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica.

[0121] (i) Carbon Black In this embodiment, the tread rubber composition preferably contains carbon black. The carbon black content per 100 parts by mass of rubber component is preferably 65 parts by mass or more, more preferably 70 parts by mass or more, and even more preferably 75 parts by mass or more. On the other hand, it is preferably 90 parts by mass or less, more preferably 85 parts by mass or less, and even more preferably 80 parts by mass or less.

[0122] Carbon black is not particularly limited and can include furnace blacks (furnace carbon blacks) such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, and ECF; acetylene black (acetylene carbon black); thermal blacks (thermal carbon blacks) such as FT and MT; and channel blacks (channel carbon blacks) such as EPC, MPC, and CC. These may be used individually or in combination of two or more types.

[0123] The specific surface area of ​​carbon black CTAB (Cetyl Tri-methyl Ammonium Bromide) is 130 m². 2 Preferably 160m / g or more. 2 It is more preferable that it is 170m or more / g. 2 It is even more preferable if it is 1 / g or more. On the other hand, 250m 2 Preferably less than / g, 200m 2It is more preferable that the value is less than or equal to / g. Note that the CTAB specific surface area is a value measured in accordance with ASTM D3765-92.

[0124] There are no specific limitations on the carbon black used, but examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercially available products include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin-Nippon Chemical Carbon Co., Ltd., and Columbia Carbon Corporation. These can be used individually or in combination of two or more types.

[0125] (ii-1) Silica In this embodiment, the tread rubber composition preferably contains silica together with a silane coupling agent, if necessary.

[0126] The BET specific surface area of ​​silica is 140 m² from the perspective of obtaining good durability performance. 2 Preferably more than / g, 160m 2 A value greater than / g is preferable. On the other hand, from the viewpoint of obtaining good rolling resistance at high speeds, 250m 2 Preferably less than / g, 220m 2 It is more preferable that the value be less than / g. The BET specific surface area mentioned above is the N2SA value measured by the BET method in accordance with ASTM D3037-93.

[0127] The silica content per 100 parts by mass of rubber component is preferably 30 parts by mass or more, more preferably 45 parts by mass or more, and even more preferably 60 parts by mass or more. On the other hand, it is preferably 170 parts by mass or less, more preferably 140 parts by mass or less, and even more preferably 80 parts by mass or less.

[0128] Examples of silica include dry-process silica (anhydrous silica) and wet-process silica (hydrated silica). Among these, wet-process silica is preferred because it contains a large number of silanol groups. Silica made from hydrated glass or silica made from biomass materials such as rice husks may also be used.

[0129] For example, silica products from companies such as Evonik Industries, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan Ltd., and Tokuyama Corporation can be used.

[0130] Furthermore, in the case of silica-based tread rubber compositions containing a large amount of silica, it is preferable to add conductive fillers such as graphite or fine metal fibers in order to efficiently dissipate the static electricity accumulated in the tire to the road surface.

[0131] Furthermore, a conductive rubber layer with a higher carbon black content may be provided in the center of the tread. However, since such a conductive rubber layer contributes little to handling stability during high-speed turns, it is not necessary to satisfy the relationship between physical properties, etc.

[0132] (ii-2) Silane coupling agents When silica is used as a filler and reinforcing agent, it is preferable that the rubber composition contains a silane coupling agent along with the silica. The silane coupling agent is not particularly limited and includes, for example, bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl) trisulfide, bis(4-trimethoxysilylbutyl) trisulfide, bis(3-triethoxysilylpropyl) disulfide, bis(2-triethoxysilylethyl) disulfide, bis(4-triethoxysilylbutyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide, bis(2-trimethoxysilylethyl) disulfide, bis(4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthioca Examples include sulfide compounds such as rubamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto compounds such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and NXT and NXT-Z from Momentive; vinyl compounds such as vinyltriethoxysilane and vinyltrimethoxysilane; amino compounds such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy compounds such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro compounds such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. These may be used individually or in combination of two or more.

[0133] Examples of silane coupling agents that can be used include products from Evonik Industries, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., and Toray Dow Corning Co., Ltd.

[0134] The silane coupling agent content is, for example, more than 3 parts by mass and less than 25 parts by mass per 100 parts by mass of silica.

[0135] (iii) Other fillers The rubber composition may, if necessary, further contain fillers commonly used in the tire industry, such as graphite, calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica, in addition to the carbon black and silica mentioned above. The amount of these fillers is, for example, more than 0.1 parts by mass and less than 200 parts by mass per 100 parts by mass of the rubber component.

[0136] (b) Plasticizer components The tread rubber composition may contain oil (including stretching oil), liquid rubber, and resin as plasticizers as components that soften the rubber. The plasticizer components are those that can be extracted from vulcanized rubber with acetone. The total content of the plasticizer components is preferably 10 parts by mass or more, and more preferably 30 parts by mass or more, per 100 parts by mass of the rubber component. On the other hand, it is preferably 50 parts by mass or less, and more preferably 40 parts by mass or less. The oil content also includes the amount of oil contained in the rubber (oil-stretched rubber).

[0137] The amount of acetone extracted can be determined by immersing a vulcanized rubber test piece in acetone for 72 hours in accordance with JIS K 6229 to extract soluble components, measuring the mass of each test piece before and after extraction, and using the following formula. Acetone extraction amount (%) = {(Mass of rubber test piece before extraction - Mass of rubber test piece after extraction)} / (mass of rubber test piece before extraction)} × 100

[0138] (i) oil Examples of oils include mineral oil (generally called process oil), vegetable oils, or mixtures thereof. Examples of mineral oils (process oils) include paraffinic process oil, aromatic process oil, and naphthenic process oil. Examples of vegetable oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. These may be used individually or in combination of two or more. Furthermore, from a life cycle assessment perspective, waste oil used as lubricant in rubber mixers or automobile engines, or waste cooking oil may be used as appropriate.

[0139] Specific process oils (mineral oils) that can be used include products from companies such as Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Orisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Showa Shell Sekiyu K.K., and Fuji Kosan Co., Ltd.

[0140] (ii) Liquid rubber The liquid rubber mentioned as a plasticizer is a polymer that is in a liquid state at room temperature (25°C) and is a rubber component that can be extracted from vulcanized tires by acetone extraction. Examples of liquid rubber include farnesene polymers, liquid diene polymers, and their hydrogenated derivatives.

[0141] Farnesene polymers are polymers obtained by polymerizing farnesene and have constituent units based on farnesene. Farnesene has isomers such as α-farnesene ((3E,7E)-3,7,11-trimethyl-1,3,6,10-dodecatetraene) and β-farnesene (7,11-dimethyl-3-methylene-1,6,10-dodecatriene).

[0142] The farnesene polymer may be a farnesene homopolymer (farnesene homopolymer) or a farnesene-vinyl monomer copolymer (farnesene-vinyl monomer copolymer).

[0143] Examples of liquid diene polymers include liquid styrene-butadiene copolymer (liquid SBR), liquid butadiene polymer (liquid BR), liquid isoprene polymer (liquid IR), and liquid styrene-isoprene copolymer (liquid SIR).

[0144] The liquid diene polymer has a weight-average molecular weight (Mw) on a polystyrene basis, measured by gel permeation chromatography (GPC), for example, 1.0 × 10⁻⁶. 3 Super, 2.0×10 5 It is less than. In this specification, the Mw of the liquid diene polymer is the polystyrene equivalent value measured by gel permeation chromatography (GPC).

[0145] The liquid rubber content (total content of liquid farnesene polymers, liquid diene polymers, etc.) is, for example, more than 1 part by mass and less than 100 parts by mass per 100 parts by mass of rubber components.

[0146] As for liquid rubber, products from companies such as Kuraray Co., Ltd. and Clay Valley Corporation can be used.

[0147] (iii) Resin components The resin component also functions as a tackifying agent and may be solid or liquid at room temperature. Specific resin components include, for example, rosin resins, styrene resins, coumarone resins, terpene resins, C5 resins, C9 resins, C5C9 resins, and acrylic resins, and two or more may be used in combination. The resin component content is preferably more than 2 parts by mass and less than 45 parts by mass, and more preferably less than 30 parts by mass, per 100 parts by mass of the rubber component. These resin components may be given modified groups that can react with silica or the like, as needed.

[0148] Rosin resins are resins whose main component is rosin acid, obtained by processing pine resin. These rosin resins (rosins) can be classified according to whether or not they are modified, and can be classified into unmodified rosin and rosin derivatives. Examples of unmodified rosin include tall rosin (also known as tall oil rosin), gum rosin, wood rosin, disproportionate rosin, polymerized rosin, hydrogenated rosin, and other chemically modified rosins. Rosin derivatives are modified forms of unmodified rosin and include rosin esters, unsaturated carboxylic acid-modified rosins, unsaturated carboxylic acid-modified rosin esters, rosin amide compounds, and rosin amine salts.

[0149] Styrene resins are polymers that use styrene monomers as constituent monomers, and include polymers polymerized with styrene monomers as the main component (50% by mass or more). Specifically, examples include homopolymers obtained by polymerizing styrene monomers (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.) individually, copolymers obtained by copolymerizing two or more styrene monomers, and copolymers of styrene monomers and other monomers that can copolymerize with them.

[0150] Examples of the aforementioned other monomers include acrylonitriles such as acrylonitrile and methacrylonitrile, unsaturated carboxylic acids such as acrylics and methacrylic acid, unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate, dienes such as chloroprene and butadiene isoprene, olefins such as 1-butene and 1-pentene; and α,β-unsaturated carboxylic acids such as maleic anhydride or their acid anhydrides.

[0151] Among coumarone-based resins, coumarone-indene resin is preferred. Coumarone-indene resin is a resin that contains coumarone and indene as monomer components that constitute the resin's backbone (main chain). Other monomer components that can be included in the backbone besides coumarone and indene include styrene, α-methylstyrene, methylindene, and vinyltoluene.

[0152] The coumaron indene resin content is, for example, more than 1.0 part by mass and less than 50.0 parts by mass per 100 parts by mass of rubber component.

[0153] The hydroxyl value (OH value) of coumarone indene resin is, for example, greater than 15 mg KOH / g and less than 150 mg KOH / g. The OH value is expressed in milligrams as the amount of potassium hydroxide required to neutralize the acetic acid bonded to the hydroxyl groups when acetylating 1 g of resin, and is measured by potentiometric titration (JIS K 0070:1992).

[0154] The softening point of coumaron indene resin is, for example, above 30°C and below 160°C. The softening point is determined by measuring the softening point as specified in JIS K 6220-1:2001 using a ring-type softening point measuring device, and it is the temperature at which the sphere descends.

[0155] Examples of terpene resins include polyterpenes, terpene phenols, and aromatically modified terpene resins. Polyterpenes are resins obtained by polymerizing terpene compounds and their hydrogenated products. Terpene compounds are (C5H8) n A hydrocarbon represented by the following composition and its oxygen-containing derivative, a monoterpene (C 10 H 16 ), sesquiterpenes (C 15 H 24 ), diterpene (C 20 H 32These are compounds with a terpene as their basic skeleton, classified as such, and examples include α-pinene, β-pinene, dipentene, limonene, myrcene, allocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, and γ-terpineol.

[0156] Polyterpenes include terpene resins such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin, and β-pinene / limonene resin, which are made from the terpene compounds mentioned above, as well as hydrogenated terpene resins obtained by hydrogenating these terpene resins. Terpene phenols include resins obtained by copolymerizing the above terpene compounds with phenolic compounds, and resins obtained by hydrogenating these resins. Specifically, resins obtained by condensing the above terpene compounds, phenolic compounds, and formalin are included. Examples of phenolic compounds include phenol, bisphenol A, cresol, and xylenol. Aromatically modified terpene resins include resins obtained by modifying terpene resins with aromatic compounds, and resins obtained by hydrogenating these resins. The aromatic compounds are not particularly limited as long as they are compounds having an aromatic ring, but examples include phenol compounds such as phenol, alkylphenol, alkoxyphenol, and phenol containing an unsaturated hydrocarbon group; naphthol compounds such as naphthol, alkylnaphthol, alkoxynaphthol, and naphthol containing an unsaturated hydrocarbon group; styrene derivatives such as styrene, alkylstyrene, alkoxystyrene, and styrene containing an unsaturated hydrocarbon group; coumarone, indene, and others.

[0157] "C5 resin" refers to a resin obtained by polymerizing a C5 fraction. Examples of C5 fractions include petroleum fractions with 4 to 5 carbon atoms, such as cyclopentadiene, pentene, pentadiene, and isoprene. Dicyclopentadiene resin (DCPD resin) is preferably used as a C5-based petroleum resin.

[0158] "C9 resin" refers to a resin obtained by polymerizing a C9 fraction, and may be hydrogenated or modified. Examples of C9 fractions include petroleum fractions with 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, indene, and methylindene. Specific examples include coumarone indene resin, coumarone resin, indene resin, and aromatic vinyl resins, which are suitably used. As aromatic vinyl resins, homopolymers of α-methylstyrene or styrene, or copolymers of α-methylstyrene and styrene are preferred, and copolymers of α-methylstyrene and styrene are more preferred, due to their economical nature, ease of processing, and excellent heat generation properties. Aromatic vinyl resins that are commercially available from companies such as Kraton and Eastman Chemical can be used.

[0159] "C5C9 resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and may be hydrogenated or modified. Examples of the C5 and C9 fractions include the petroleum fractions mentioned above. As for the C5C9 resin, commercially available products from companies such as Tosoh Corporation and LUHUA can be used.

[0160] While there are no particular limitations on the acrylic resin used, for example, a solvent-free acrylic resin can be used.

[0161] Solvent-free acrylic resins include (meth)acrylic resins (polymers) synthesized by high-temperature continuous polymerization (high-temperature continuous mass polymerization) (methods described in U.S. Patent No. 4,414,370, Japanese Patent Publication No. 59-6207, Japanese Patent Publication No. 5-58005, Japanese Patent Publication No. 1-313522, U.S. Patent No. 5,010,166, Toa Gosei Research Annual Report TREND2000 No. 3 pp. 42-45, etc.) with minimal use of polymerization initiators, chain transfer agents, organic solvents, etc. as auxiliary raw materials. In this invention, (meth)acrylic means methacrylic and acrylic.

[0162] Examples of monomer components constituting the above-mentioned acrylic resin include (meth)acrylic acid, (meth)acrylic acid esters (alkyl esters, aryl esters, aralkyl esters, etc.), (meth)acrylamide, and (meth)acrylic acid derivatives such as (meth)acrylamide derivatives.

[0163] Furthermore, as monomer components constituting the above-mentioned acrylic resin, aromatic vinyls such as styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, and divinylnaphthalene may be used along with (meth)acrylic acid and (meth)acrylic acid derivatives.

[0164] The above-mentioned acrylic resin may be a resin composed solely of (meth)acrylic components, or a resin that also contains components other than (meth)acrylic components. Furthermore, the above-mentioned acrylic resin may have hydroxyl groups, carboxyl groups, silanol groups, etc.

[0165] As resin components, products from companies such as Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical Company, Nippon Paint Chemical Co., Ltd., Nippon Shokubai Co., Ltd., ENEOS Corporation, Arakawa Chemical Industries, Ltd., and Taoka Chemical Industries, Ltd. can be used.

[0166] (H) Stearic acid In this embodiment, the tread rubber composition preferably contains stearic acid. The stearic acid content is, for example, more than 0.5 parts by mass and less than 10.0 parts by mass per 100 parts by mass of the rubber component. Conventional known stearic acid can be used, such as products from NOF Corporation, NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Corporation, Chiba Fatty Acid Co., Ltd., etc.

[0167] (ii) Anti-aging agents In this embodiment, the tread rubber composition preferably contains an anti-aging agent. The amount of the anti-aging agent is, for example, more than 0.5 parts by mass and less than 10 parts by mass, and more preferably 1 part by mass or more, per 100 parts by mass of the rubber component.

[0168] Examples of anti-aging agents include naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4′-bis(α,α′-dimethylbenzyl)diphenylamine; N-isopropyl-N′-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine, and N,N′-di-2-naphthyl-p-phenylenediamine. Examples include p-phenylenediamine-based antioxidants such as 2,2,4-trimethyl-1,2-dihydroquinoline polymers and other quinoline-based antioxidants; monophenol-based antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol-based antioxidants such as tetrakis-[methylene-3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionate]methane. These may be used individually or in combination of two or more types.

[0169] Furthermore, as an anti-aging agent, products from companies such as Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., and Flexis Co., Ltd. can be used.

[0170] (Ho) Wax In the present invention, the rubber composition preferably contains wax. The wax content is, for example, 0.5 to 20 parts by mass, preferably 1.0 to 15 parts by mass, and more preferably 1.5 to 10 parts by mass, per 100 parts by mass of the rubber component.

[0171] The waxes are not particularly limited and include petroleum-based waxes such as paraffin wax and microcrystalline wax; natural waxes such as plant-based waxes and animal-based waxes; and synthetic waxes such as polymers of ethylene and propylene. These may be used individually or in combination of two or more types.

[0172] For example, waxes from companies such as Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., and Seiko Chemical Co., Ltd. can be used.

[0173] (f) Zinc oxide The tread rubber composition may contain zinc oxide. The zinc oxide content is, for example, more than 0.5 parts by mass and less than 10 parts by mass per 100 parts by mass of the rubber component. Conventional known zinc oxides can be used, such as products from Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc.

[0174] (t) Crosslinking agents and vulcanization accelerators The tread rubber composition preferably contains a crosslinking agent such as sulfur. The crosslinking agent content is, for example, more than 0.1 parts by mass and less than 10.0 parts by mass per 100 parts by mass of the rubber component.

[0175] Examples of sulfur commonly used in the rubber industry include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur. These may be used individually or in combination of two or more types.

[0176] For sulfur, products from companies such as Tsurumi Chemical Industries, Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemicals Co., Ltd., Flexis Co., Ltd., Nippon Dry Distillation Co., Ltd., and Hosoi Chemical Industries Co., Ltd. can be used.

[0177] Other crosslinking agents besides sulfur include, for example, sulfur-containing vulcanizing agents such as Tackyrol V200 manufactured by Taoka Chemical Industries, Ltd. and KA9188 (1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane) manufactured by Lanxess, as well as organic peroxides such as dicumyl peroxide.

[0178] The tread rubber composition preferably contains a vulcanization accelerator. The vulcanization accelerator content is, for example, more than 0.3 parts by mass and less than 10.0 parts by mass per 100 parts by mass of the rubber component.

[0179] Examples of vulcanization accelerators include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiadylsulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazolesulfenamide, Nt-butyl-2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, and N,N'-diisopropyl-2-benzothiazolesulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, diortotrilguanidine, and orthotrilbiguanidine. These may be used individually or in combination of two or more.

[0180] (Chi) Others In addition to the above-mentioned components, the tread rubber composition may further contain additives commonly used in the tire industry, such as fatty acid metal salts, carboxylate metal salts, organic peroxides, and reversion (vulcanization reversal) inhibitors, as needed. The content of these additives is, for example, more than 0.1 parts by mass and less than 200 parts by mass per 100 parts by mass of the rubber component.

[0181] (2) Preparation of tread rubber composition The tread rubber composition is produced by appropriately adjusting the various compounding materials described above, using a general method that includes a base mixing step in which rubber components and fillers such as carbon black are mixed, and a finish mixing step in which the mixture obtained in the base mixing step is mixed with a crosslinking agent.

[0182] Mixing can be carried out using known (closed) mixers such as Banbury mixers, kneaders, and open roll mixers.

[0183] The mixing temperature in the base mixing process is, for example, more than 50°C and less than 200°C, and the mixing time is, for example, more than 30 seconds and less than 30 minutes. In the base mixing process, in addition to the above components, compounding agents conventionally used in the rubber industry, such as softeners such as oils, zinc oxide, antioxidants, waxes, and vulcanization accelerators, may be added and mixed as needed.

[0184] In the final mixing step, the mixture obtained in the base mixing step and the crosslinking agent are mixed together. The mixing temperature in the final mixing step is, for example, above room temperature but below 80°C, and the mixing time is, for example, more than 1 minute but less than 15 minutes. In the final mixing step, in addition to the above components, vulcanization accelerators, zinc oxide, etc., may be added and mixed as needed.

[0185] 2. Belt layer (1) Coating rubber composition In this embodiment, the coating rubber composition to which the steel cords are covered can be obtained from basically the same compound materials as the tread rubber composition described above.

[0186] (a) Rubber component In the coating rubber composition, the rubber component can be any rubber (polymer) commonly used in tire manufacturing, such as isoprene rubber, butadiene rubber (BR), styrene-butadiene rubber (SBR), nitrile rubber (NBR), or butyl rubber. Among these, isoprene rubber is preferred, and NR is preferred because its polyisoprene cis structure is close to 100%, and its tensile strength is superior to other rubber components. SBR or BR may also be used in combination as needed.

[0187] (i) Isoprene rubber In the coated rubber composition, the content of isoprene-based rubber in 100 parts by mass of rubber components is preferably 60 parts by mass or more, more preferably 80 parts by mass or more, and even more preferably 90 parts by mass or more.

[0188] (b) SBR In the coated rubber composition, the rubber component may, if necessary, contain NR along with 5 to 25 parts by mass of SBR.

[0189] (H)BR In the coated rubber composition, the rubber component may, if necessary, contain BR in addition to the above-mentioned NR and SBR in an amount of 5 to 25 parts by mass.

[0190] (ii) Other rubber components In addition, other rubber components may include, if necessary, nitrile rubber (NBR) or other rubbers (polymers) commonly used in tire manufacturing.

[0191] (b) Compounding materials other than rubber components (i) Filling agent (i) Carbon Black In the coated rubber composition, the carbon black content is preferably, for example, 10 parts by mass or more and 100 parts by mass or less, more preferably 40 parts by mass or more and 70 parts by mass or less, and even more preferably 50 parts by mass or more and 60 parts by mass or less, per 100 parts by mass of the rubber component.

[0192] (ii) Silica In the coated rubber composition, silica may be further included as needed, and a silane coupling agent may be used in combination. The silica content per 100 parts by mass of rubber component is preferably 3 parts by mass or more, and more preferably 5 parts by mass or more, when not used in combination with a silane coupling agent. On the other hand, it is preferably 25 parts by mass or less, and more preferably 15 parts by mass or less. When used in combination with a silane coupling agent, it is preferably 25 parts by mass or more. On the other hand, it is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less.

[0193] (iii) Silane coupling agents In the coated rubber composition, the content of the silane coupling agent is, for example, more than 3 parts by mass and less than 15 parts by mass per 100 parts by mass of silica.

[0194] (iv) Other fillers The coated rubber composition may further contain fillers such as graphite, calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica. The amount of these fillers is, for example, more than 0.1 parts by mass and less than 200 parts by mass per 100 parts by mass of the rubber component.

[0195] (b) Curable resin components In the coating rubber composition, it is preferable to include a curable resin component such as a modified resorcinol resin or a modified phenolic resin. This improves adhesion to the steel cord without significantly worsening heat generation or elongation at break, and makes it easier to generate a large reaction force in the rubber and steel cord.

[0196] Specific examples of modified resorcinol resins include, for instance, Sumikanol 620 (modified resorcinol resin) manufactured by Taoka Chemical Industries, Ltd., and for example, PR12686 (cashew oil modified phenol resin) manufactured by Sumitomo Bakelite Co., Ltd.

[0197] The content of the curable resin component is preferably 1 part by mass or more, and more preferably 2 parts by mass or more, per 100 parts by mass of the rubber component, from the viewpoint of sufficiently improving the complex modulus of elasticity and obtaining a large reaction force during deformation. On the other hand, from the viewpoint of maintaining the breaking strength, it is preferably 10 parts by mass or less, and more preferably 8 parts by mass or less.

[0198] When using modified resorcinol resin, it is preferable to include a methylene donor as a curing agent. Examples of methylene donors include hexamethylenetetramine (HMT), hexamethoxymethylolmelamine (HMMM), and hexamethylenemelamine pentamethyl ether (HMMPME), and it is preferable that they be included in an amount of, for example, 5 to 15 parts by mass per 100 parts by mass of the curable resin component. If the amount is too small, a sufficient complex modulus of elasticity may not be obtained. On the other hand, if the amount is too large, the viscosity of the rubber may increase, and the processability may deteriorate.

[0199] As a specific methylene donor, for example, Sumikanol 507 manufactured by Taoka Chemical Industries, Ltd. can be used.

[0200] (h) Resin components In coated rubber compositions, it is preferable to include a resin component as needed, from the viewpoint of processability (imparting tackiness). The resin component content is preferably more than 2 parts by mass and less than 45 parts by mass, and more preferably less than 30 parts by mass, per 100 parts by mass of rubber component.

[0201] (ii) Cobalt organic acid In the coated rubber composition, it is preferable to include organic cobalt. Organic cobalt plays a role in crosslinking the cord and the rubber, and by incorporating this component, the adhesion between the cord and the rubber can be improved.

[0202] Examples of organic cobalt acids include cobalt stearate, cobalt naphthenate, cobalt neodecanoate, and cobalt boron-3 neodecanoate.

[0203] The organic cobalt content is preferably 500 ppm or more, more preferably 700 ppm or more, and even more preferably 900 ppm or more, as a cobalt concentration in the coated rubber. On the other hand, it is preferably 1500 ppm or less, and more preferably 1300 ppm or less. If it is too low, there is a risk that sufficient adhesion between the plating layer of the steel cord and the rubber cannot be ensured. On the other hand, if it is too high, oxidative degradation of the rubber will become significant, and the fracture characteristics may deteriorate.

[0204] (e) Reversion (vulcanization reversal) The coated rubber composition preferably contains a reversion (vulcanization reversal) inhibitor as needed. This suppresses reversion and improves durability. The content of the reversion inhibitor is preferably 0.1 parts by mass or more and 3 parts by mass or less, more preferably 0.2 parts by mass or more and 2.5 parts by mass or less, and even more preferably 0.3 parts by mass or more and 2 parts by mass or less, per 100 parts by mass of the rubber component. As a specific reversion inhibitor, for example, Parkalink 900 (1,3-bis(citraconimidomethyl)benzene) manufactured by Flexis can be used.

[0205] (h) Anti-aging agents In the coated rubber composition, the content of the anti-aging agent is, for example, more than 1 part by mass and less than 10 parts by mass per 100 parts by mass of the rubber component.

[0206] (to)stearic acid In the coated rubber composition, the stearic acid content is, for example, more than 0.5 parts by mass and less than 10.0 parts by mass per 100 parts by mass of rubber component.

[0207] (C) Zinc oxide In the coated rubber composition, the zinc oxide content is, for example, more than 0.5 parts by mass and less than 15 parts by mass per 100 parts by mass of rubber component.

[0208] (i) Crosslinking agents and vulcanization accelerators In the coated rubber composition, the crosslinking agent content is, for example, more than 0.1 parts by mass and less than 10.0 parts by mass per 100 parts by mass of rubber component.

[0209] In the coated rubber composition, the content of the vulcanization accelerator is, for example, more than 0.3 parts by mass and less than 10.0 parts by mass per 100 parts by mass of the rubber component.

[0210] (Nu) Other In addition to the above-mentioned components, the coating rubber composition may further contain additives commonly used in the tire industry, such as fatty acid metal salts, carboxylate metal salts, and organic peroxides. The content of these additives is, for example, more than 0.1 parts by mass and less than 200 parts by mass per 100 parts by mass of the rubber component.

[0211] (2) Manufacturing of the belt layer (a) Preparation of coated rubber composition The coated rubber composition can be prepared through a base mixing process and a finish mixing process, similar to the preparation of the tread rubber composition described above.

[0212] (b) Manufacturing of the belt layer The resulting coated rubber composition is used to coat both sides of steel cords arranged at predetermined ends using a calender roll or the like, thereby forming a belt layer.

[0213] 3. Tire manufacturing The belt layer and tread portion are formed using known methods. The formed belt layer and tread portion are then molded together with other tire components on a tire molding machine using a conventional method to produce an unvulcanized tire.

[0214] Specifically, an inner liner, carcass, and belt layer, which are components to ensure the airtightness of the tire, are wound onto a molding drum. The ends of the carcass are fixed to both side edges, and a bead portion, which is a component to fix the tire to the rim, is placed to form a toroidal shape. After that, the tread is bonded to the center of the outer circumference, and the sidewall is bonded to the radially outward side to form the side portion, thereby producing an unvulcanized tire.

[0215] Subsequently, the prepared unvulcanized tire is heated and pressurized in a vulcanizing machine to obtain a tire. The vulcanization process can be carried out by applying known vulcanization methods. The vulcanization temperature is, for example, above 120°C and below 200°C, and the vulcanization time is, for example, above 5 minutes and below 15 minutes. [Examples]

[0216] The present invention will be described in more detail below with reference to examples. In the following, a motorcycle tire (for the rear wheel) with a tire size of 190 / 50ZR17 having the structure shown in Figure 1 was manufactured and its handling stability during high-speed cornering was evaluated.

[0217] 1. Fabrication of the belt layer First, the belt layer was fabricated following the procedure below.

[0218] (1) Production of coated rubber composition First, a coated rubber composition was manufactured.

[0219] Specifically, 100 parts by mass of NR (RSS3), carbon black (Sho Black N550:N2SA=42m² manufactured by Cabot Japan Co., Ltd.) 255 parts by mass of (g), 5 parts by mass of curable resin component (Sumikanol 620: modified resorcinol resin, manufactured by Taoka Chemical Industry Co., Ltd.), 3 parts by mass of curing agent (Sumikanol 507: methylene donor, manufactured by Taoka Chemical Industry Co., Ltd.), and cobalt organic acid (DICNATE, manufactured by DIC Corporation). NBC-2: Cobalt boron neodecanoate, cobalt content 22.5% by mass, 1 part by mass; zinc oxide (Zinc Oxide No. 1, manufactured by Mitsui Mining & Smelting Co., Ltd.), 11 parts by mass; antioxidant-1 (Nocrack 6C:N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), 1 part by mass; antioxidant-2 (Antage RD: (2,2,4-trimethyl-1,2-dihydroquinoline, manufactured by Kawaguchi Chemical Industry Co., Ltd.), 0.5 parts by mass; stearic acid (Stearic acid "Tsubaki", manufactured by NOF Corporation), 1 part by mass; sulfur (powdered sulfur, manufactured by Tsurumi Chemical Industries, Ltd.), 7 parts by mass; vulcanization accelerator (Noxella, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) Prepare 1.2 parts by mass of DZ (N,N-dicyclohexyl-2-benzothiazolyl sulfenamide), and mix all materials except sulfur and vulcanization accelerator with a Banbury mixer at 150°C for 5 minutes to obtain a mixture.

[0220] Next, sulfur and a vulcanization accelerator were added to the resulting mixture, and the mixture was kneaded using an open roll at 80°C for 5 minutes to obtain a coated rubber composition.

[0221] (2) Preparation of the belt layer Each steel cord in the cord configuration shown in Tables 2-5 was arranged to form an end of 25 cords / 5 cm, and the above and below were coated with the coating rubber composition obtained above, so that the total thickness was 1.15 mm, to obtain each belt layer.

[0222] Prior to the measurement, the presence or absence of buckling points, compressive stiffness, and bending stiffness of each steel cord were determined according to the method described above. The measurement results are shown in Tables 2 to 5.

[0223] 2. Manufacturing of tread rubber composition Next, the tread rubber composition was manufactured according to the following procedure, and then molded into tread rubber.

[0224] (1) Formulation materials First, the following formulation materials were prepared.

[0225] (a) Rubber component (i) SBR: Toughlene 3830 manufactured by Asahi Kasei Corporation (S-SBR: Styrene content: 33% by mass, Vinyl bond content: 31% by mass, 37.5% oil extended product) (ii) BR: Ube Pole BR150B manufactured by Ube Industries, Ltd. (High cis BR synthesized using Co-based catalyst: Cis content 97% by mass, Trans content 2% by mass, Vinyl content 1% by mass)

[0226] (b) Formulation materials other than rubber component (i) Carbon black: Show Black N110 manufactured by Cabot Japan, Ltd. (BET value 142 m 2 / g) (ii) Silica: Ultrasil VN3 manufactured by Evonik Industries AG (BET specific surface area: 175 m 2 / g) (iii) Silane coupling agent: Silane coupling agent Si69 manufactured by Evonik Industries AG (iv) Oil: Diana Process NH-70 manufactured by Idemitsu Kosan Co., Ltd. (v) Wax: Oz Ace 0355 manufactured by Nippon Seiro Co., Ltd. (vi) Resin: Syltraxx 4401 manufactured by Arizona Chemical (α-methylstyrene resin, softening point 85 °C) (vii) Liquid SBR: RICON 100 manufactured by Cray Valley (Random copolymer, Styrene content: 25% by mass, Vinyl content: 70%, Mn: 4500) (viii) Anti-aging agent: Antigen 6C manufactured by Sumitomo Chemical Co., Ltd. (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) (ix) Stearic acid: Bead Stearic Acid "Tsubaki" manufactured by NOF Corporation (x) Zinc oxide: "Ginrei R" manufactured by Toho Zinc Co., Ltd. (L) Sulfur: HK-200-5 (5% oil-containing powdered sulfur) manufactured by Hosoi Chemical Industry Co., Ltd. (Wo) Vulcanization accelerator: Noxellar-NS manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (N-tert-butyl-2-benzothiazolyl sulfenamide)

[0227] (2) Manufacture of tread rubber composition According to the formulations A to E shown in Table 1, the materials other than sulfur and vulcanization accelerator were kneaded in a Banbury mixer at 150°C for 5 minutes to obtain the kneaded product. The amounts of each ingredient are in parts by mass.

[0228] Subsequently, using each of the obtained tread rubber compositions, vulcanized rubber pieces measuring 40 mm in length and 4 mm in width were prepared as rubber test specimens for viscoelasticity measurement. Then, the complex modulus E was measured for each of the obtained rubber test specimens using a GABO iplexer under the following conditions: temperature: 70°C, initial strain: 5%, dynamic strain: ±1%, frequency: 10 Hz, deformation mode: stretching. * The pressure (MPa) was measured. The measurement results are shown in Table 1 and Tables 2-5.

[0229] [Table 1]

[0230] (3) Manufacturing of tread rubber Next, each of the obtained tread rubber compositions was extruded into a predetermined shape to produce tread rubber.

[0231] 3. Tire manufacturing The belt layer and tread rubber obtained above were bonded together with other tire components to form an unvulcanized tire, which was then press-vulcanized for 10 minutes under conditions of 170°C to produce the test tires for Examples 1 to 12 shown in Tables 2 and 3, and the test tires for Comparative Examples 1 to 10 shown in Tables 4 and 5.

[0232] 4. Calculation of parameters In conjunction with the manufacturing of the tires described above, the total cross-sectional area S(mm²) of the steel filaments in the cross-section of each steel cord was used as an evaluation parameter. 2 ) and each complex modulus E * Product of (MPa) (S × E * ), and the bending stiffness value FR and the complex modulus E of each steel cord. * Product of (MPa) (FR × E * The ratio of the length of the outer belt layer in the tire width direction (L2 / L1) to the length of the inner belt layer in the tire width direction (L1 / mm) was calculated. The ratio of the maximum length of the belt layer in the tire width direction (Lm / Tw) to the tread width (Tw / mm) was also calculated. The results are shown in Tables 2-5.

[0233] 5. Performance evaluation test (evaluation of handling stability during high-speed turns) Each test tire was mounted on a rim (MT6.00×17) and fitted to the rear wheel of a large motorcycle (1000cc) at an internal pressure of 200kPa. The motorcycle was then driven on a dry asphalt tire test course. Drivers then subjectively evaluated the change in handling when changing lanes at 120km / h on a 5-point scale from 1 (significant change) to 5 (almost no change). The total score from the evaluations of 20 drivers was then calculated.

[0234] Next, the results from Example 1 were set to 100 and indexed based on the following formula to evaluate the handling stability during high-speed turns. A higher numerical value indicates better handling stability during high-speed turns. Handling stability = [(Results for test tires) / (Results for Example 1)] × 100

[0235] [Table 2]

[0236] [Table 3]

[0237]

Table 4

[0238]

Table 5

[0239] As described above, the present invention has been described based on the embodiments, but the present invention is not limited to the above embodiments. Various modifications can be made to the above embodiments within the same and equivalent scope of the present invention.

[0240] The present invention (1) is a motorcycle tire comprising a carcass reaching from a tread portion through a sidewall portion to a bead core of a bead portion, and a belt layer disposed on the outer side in the tire radial direction of the carcass and inside the tread portion, wherein the belt layer is a steel belt layer having steel cords, the steel cords are steel cords having an m×n configuration in which n strands each formed by twisting m steel filaments are twisted in the same direction as the steel filaments, where m is 1 or more and 3 or less, and n is 2 or more and 6 or less, the diameter of the steel filaments is 0.15 mm or more and 0.25 mm or less, the rubber composition constituting the tread portion is a rubber composition having a complex elastic modulus E * (MPa) of 5.0 MPa or more measured under the conditions of temperature: 70°C, initial strain: 5%, dynamic strain: ±1%, frequency: 10 Hz, and deformation mode: extension, the total cross-sectional area S (mm 2 ) of the steel filaments in the cross-section of the steel cords and the complex elastic modulus E * (MPa) satisfy the product (S×E * ) of 2.00 or less, and is characterized by being a motorcycle tire.

[0241] The present invention (2) is The complex modulus E * The motorcycle tire according to (1) of the present invention is characterized in that the (MPa) is 6.5 MPa or higher.

[0242] The present invention (3) is, The aforementioned (S×E * The motorcycle tire according to (1) or (2) of the present invention is characterized in that the ratio is less than 1.70.

[0243] The present invention (4) is, The aforementioned steel cord has a compressive stiffness value of 65 N / mm or less, and is a motorcycle tire in any combination with any of the present invention (1) to (3).

[0244] The present invention (5) is, The steel cord is characterized in that it is a steel cord without buckling points, and is a motorcycle tire in any combination with any of the present invention (1) to (4).

[0245] The present invention (6) is, The bending stiffness value of the aforementioned steel cord is 2.5 × 10 -3 A motorcycle tire characterized by having a value of N·m or less, and in any combination with any of the present invention (1) to (5).

[0246] The present invention (7) is, The bending stiffness value of the aforementioned steel cord is 2.0 × 10 -3 The present invention (6) describes a motorcycle tire characterized by having a value of N·m or less.

[0247] The present invention (8) is, The bending stiffness value of the aforementioned steel cord is 1.5 × 10 -3 The present invention (7) describes a motorcycle tire characterized by having a value of N·m or less.

[0248] The present invention (9) is, The bending stiffness value FR and complex modulus E of the aforementioned steel cord *Product of (MPa) (FR × E * ) but 25×10 -3 A motorcycle tire characterized by having a pressure of (MPa·N·m) or less, and being in any combination with any of the present invention (1) to (8).

[0249] The present invention (10) is, The aforementioned (FR×E * ) but 15×10 -3 The motorcycle tire according to the present invention (9) is characterized by having a pressure of (MPa·N·m) or less.

[0250] The present invention (11) is, The aforementioned (FR×E * ) but 10 x 10 -3 The motorcycle tire according to the present invention (10) is characterized by having a pressure of (MPa·N·m) or less.

[0251] The present invention (12) is, The present invention provides a motorcycle tire characterized in that the rubber coating of the belt layer contains organic cobalt, and can be used in any combination with any of the present inventions (1) to (11).

[0252] The present invention (13) is, The motorcycle tire according to the present invention (12), characterized in that the content of the organic acid cobalt is 0.05 parts by mass or more in terms of cobalt per 100 parts by weight of the rubber component.

[0253] The present invention (14) is, The aforementioned belt layer is made up of multiple layers, A motorcycle tire in any combination of any of the present invention (1) to (13), characterized in that in at least one pair of radially adjacent belt layers of the multilayered belt layer tire, the average distance D (mm) between steel cords is 0.6 mm or less.

[0254] The present invention (15) is, The aforementioned belt layer is made up of multiple layers, The present invention provides a motorcycle tire characterized in that, in at least one pair of radially adjacent belt layers of the multilayered belt layer, the angle between the steel cords in each belt layer in the tread portion in the tire circumferential direction is 65° or less, and is available in any combination with any of the present invention (1) to (13).

[0255] The present invention (16) is, The motorcycle tire according to the present invention (15), characterized in that the angle between the steel cords in each belt layer in the tire circumferential direction is 60° or less.

[0256] The present invention (17) is, The aforementioned belt layer is made up of multiple layers, A motorcycle tire in any combination of any of the present invention (1) to (16), characterized in that, in adjacent belt layers, the ratio (L2 / L1) of the tire width direction length L2 (mm) of the belt layer on the outer side of the tire radially to the tire width direction length L1 (mm) of the belt layer on the inner side of the tire radially is greater than 1.00.

[0257] The present invention (18) is, The motorcycle tire is characterized in that the rubber composition of the tread portion contains 25% by mass or less of styrene in the rubber components and has a Tg of -18°C or higher, and is any combination of any of the present invention (1) to (17).

[0258] The present invention (19) is, The tread portion is characterized in that it is divided in the tire width direction into an inner region and an outer region sandwiching the inner region, and is a motorcycle tire in any combination with any of the present invention (1) to (18).

[0259] The present invention (20) is, The motorcycle tire according to the present invention (19), characterized in that the rubber composition constituting the outer region of the tread portion is a rubber composition containing 25% by mass or less of styrene in the rubber component and having a Tg of -18°C or higher.

[0260] The present invention (21) is, A motorcycle tire in any combination of any of the present invention (1) to (20), characterized in that the ratio (Lm / Tw) of the maximum length Lm (mm) of the belt layer in the tire width direction to the tread width Tw (mm) is 1.00 or more. [Explanation of Symbols]

[0261] 1 tire 2 Tread section 3. Sidewall section 4. Bead section 5 Bead core 6 Carcass 6a Main body 6b Ply folded section 7 Belt layer 8 Bead Apex Rubber 9 Belt reinforcement layer 10 Steel cord 12 Strands C Tire Equator f Steel filament G Coated rubber IN inner area K0 Correction Sample K1~K3 Measurement Samples OUT outer area Te tread edge Tw Tread width

Claims

1. A motorcycle tire comprising: a carcass extending from a tread portion through a sidewall portion to a bead core of a bead portion; and a belt layer disposed radially outward of the carcass and inward of the tread portion, the belt layer is a steel belt layer having a steel cord, The steel cord is a steel cord having an m×n configuration in which n strands, each strand having m steel filaments twisted together, are twisted together in the same direction as the steel filaments, and the m is 1 or more and 3 or less, and the n is 2 or more and 6 or less, The diameter of the steel filament is 0.15 mm or more and 0.25 mm or less; The rubber composition constituting the tread portion has a complex modulus E measured under the conditions of temperature: 70°C, initial strain: 5%, dynamic strain: ±1%, frequency: 10 Hz, and deformation mode: extension. ＊ (MPa) is a rubber composition having a modulus of 5.0 MPa or more, The total cross-sectional area S (mm ２ ) and the complex elastic modulus E ＊ (MPa) and the product (S × E ＊ ) is 2.00 or less.

2. The complex elastic modulus E ＊ 2. The motorcycle tire according to claim 1, wherein the tensile strength (MPa) is 6.5 MPa or more.

3. The (S × E ＊ 3. The motorcycle tire according to claim 1, wherein the tread width is less than 1.

70.

4. 3. The motorcycle tire according to claim 1, wherein the steel cord has a compressive rigidity of 65 N / mm or less.

5. 3. The motorcycle tire according to claim 1, wherein the steel cord is a steel cord that does not have a buckling point.

6. The bending rigidity of the steel cord is 2.5 × 10 －３ 3. The motorcycle tire according to claim 1, wherein the tensile strength is 1.0 N·m or less.

7. The bending rigidity of the steel cord is 2.0 × 10 －３ 7. The motorcycle tire according to claim 6, wherein the tensile strength is equal to or less than N·m.

8. The bending rigidity of the steel cord is 1.5 × 10 －３ 8. The motorcycle tire according to claim 7, wherein the tensile strength is 1.0 N·m or less.

9. The bending rigidity value FR and the complex modulus E of the steel cord ＊ (MPa) and the product (FR × E ＊ ) is 25 x 10 －３ 3. The motorcycle tire according to claim 1, wherein the tensile strength is MPa·N·m or less.

10. The (FR x E ＊ ) is 15 x 10 －３ 10. The motorcycle tire according to claim 9, wherein the tensile strength is MPa·N·m or less.

11. The (FR x E ＊ ) is 10 x 10 －３ 11. The motorcycle tire according to claim 10, wherein the tensile strength is MPa·N·m or less.

12. 3. The motorcycle tire according to claim 1, wherein the coating rubber of the belt layer contains organic acid cobalt.

13. 13. The motorcycle tire according to claim 12, wherein the content of the organic cobalt acid is 0.05 parts by mass or more in terms of cobalt per 100 parts by weight of the rubber component.

14. The belt layer is multi-layered, 3. The motorcycle tire according to claim 1, wherein an average distance D (mm) between steel cords in at least one pair of belt layers adjacent to each other in the radial direction of the tire in the multilayered belt layers is 0.6 mm or less.

15. The belt layer is multi-layered, 3. The motorcycle tire according to claim 1, wherein in at least one set of the multilayered belt layers adjacent in the radial direction of the tire, an angle formed by steel cords in each belt layer in a tread portion in the tire circumferential direction is 65° or less.

16. 16. The motorcycle tire according to claim 15, wherein the angle formed by the steel cords in the belt layers in the tire circumferential direction is 60 degrees or less.

17. The belt layer is multi-layered, 3. The motorcycle tire according to claim 1, wherein, in adjacent belt layers, a ratio (L2 / L1) of a length L2 (mm) in the tire width direction of an outer belt layer in the tire radial direction to a length L1 (mm) in the tire width direction of an inner belt layer in the tire radial direction exceeds 1.

00.

18. 3. The motorcycle tire according to claim 1, wherein the rubber composition of the tread portion contains 25% by mass or less of styrene in the rubber component and has a Tg of −18° C. or higher.

19. 3. The motorcycle tire according to claim 1, wherein the tread portion is divided in the tire width direction into an inner region and an outer region sandwiching the inner region.

20. The motorcycle tire according to claim 19, wherein the rubber composition constituting the outer region of the tread portion contains 25% by mass or less of styrene in the rubber component and has a Tg of −18° C. or higher.

21. 3. The motorcycle tire according to claim 1, wherein a ratio (Lm / Tw) of a maximum length Lm (mm) of the belt layer in the tire width direction to a tread width Tw (mm) is 1.00 or more.

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