Tire

Abstract

A tire which is provided with a tread part, wherein: the ratio of the weight G (kg) of the tire to the maximum load capacity WL (kg) of the tire, namely, G / WL is 0.0131 or less; the tread part comprises at least one rubber layer which is composed of a rubber composition that contains a rubber component and a reinforcing filler; the rubber composition has a tanδ at 30°C of more than 0.15 and a complex elastic modulus at 30°C (E*30) of less than 8.0 MPa; and the ratio of the tanδ at 30°C to the weight G, namely, (tanδ at 30°C) / G is 0.016 or more.

Description

Technical Field

[0001] The present disclosure relates to a tire.

Background Art

[0002] In pneumatic tires, weight reduction is required from the viewpoint of improving fuel efficiency. Patent Document 1 describes a predetermined tire with reduced rubber volume for weight reduction.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, a light tire with reduced rubber volume has room for improvement in wet grip performance.

[0005] An object of the present disclosure is to provide a tire with improved wet grip performance.

Means for Solving the Problems

[0006] As a result of intensive studies, it has been found that a tire with improved wet grip performance can be obtained by setting the ratio of the tire weight G (kg) to the maximum load capacity W

[0007] (kg) of the tire, the tan δ and complex elastic modulus of the rubber composition constituting the tread, and the tan δ with respect to the tire weight within a predetermined range. L (kg) of the tire weight G (kg) (G / W L) is 0.0131 or less, the tread has at least one rubber layer made of a rubber composition containing a rubber component and a reinforcing filler, the tanδ (tanδ at 30°C) of the rubber composition is more than 0.15, and the complex elastic modulus (E* at 30°C) 30 ) is less than 8.0 MPa, and relates to a tire in which the ratio of the tanδ at 30°C to G (tanδ at 30°C / G) is 0.016 or more.

Effect of the Invention

[0008] According to the present disclosure, a tire with improved wet grip performance is provided.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0010] A tire according to an embodiment of the present disclosure is a tire provided with a tread, wherein the ratio of the tire weight G (kg) to the maximum load capacity W L (kg) of the tire (G / W L ) is 0.0131 or less, the tread has at least one rubber layer made of a rubber composition containing a rubber component and a reinforcing filler, the tanδ of the rubber composition at 30°C is more than 0.15, and the complex elastic modulus (E* at 30°C) 30 ) is less than 8.0 MPa, and it is a tire in which the ratio of the tanδ at 30°C to G (tanδ at 30°C / G) is 0.016 or more.

[0011] The tanδ of the rubber composition at 30°C and the complex elastic modulus (E* at 30°C)30 ) By satisfying the above requirements, the resulting tire has improved wet grip performance. Although not intending to be bound by theory, the reason is considered as follows.

[0012] A tire that is light in weight relative to its maximum load capacity is less likely to relieve the input from the road surface, so it tends to vibrate easily and have a high vibration frequency. Therefore, when the tanδ at 30 °C of the tread rubber is made larger than a predetermined value according to the tire weight, it becomes easier to convert high-frequency vibrations into thermal energy, so that the heat generation of the tread rubber is promoted and the wet grip performance can be improved. Furthermore, by making the complex elastic modulus (E* 30 ) smaller than a predetermined value, it is considered that the effect of improving the wet grip performance can be further enhanced because it becomes easier to convert vibration energy into thermal energy.

[0013] The ratio of the 30 °C tanδ to the G (30 °C tanδ / G) is 0.016 or more, preferably 0.017 or more, more preferably 0.018 or more, still more preferably 0.019 or more, and particularly preferably 0.020 or more. Also, the upper limit value of 30 °C tanδ / G is not particularly limited from the viewpoint of the effects of the present disclosure, but is preferably 0.080 or less, more preferably 0.070 or less, still more preferably 0.060 or less, and particularly preferably 0.050 or less.

[0014] In this specification, the maximum load capacity W L(kg) represents the load capacity value (kg) when the tire with its load index (LI) is filled with the maximum air pressure (kPa) under the usage conditions defined by the JATMA standard. For tires of sizes without specific definitions in the JATMA standard, when the tire is filled with 250 kPa of air, with the tire section width being Wt (mm), the tire section height being Ht (mm), and the tire outer diameter being Dt (mm), the values calculated by the following formulas (1) and (2) shall be used. Note that Wt is the maximum width between the outer surfaces of the sidewalls excluding patterns or characters on the tire side surface in the normal state. Ht is the distance from the bottom surface of the bead part to the outermost surface of the tread, and is half of the difference between the tire outer diameter and the rim diameter nominal value. V = {(Dt / 2) 2 -(Dt / 2 - Ht) 2}×π×Wt ···(1) W L = 0.000011×V + 100 ···(2)

[0015] The reinforcing filler contains silica, and preferably, the ratio of the carbon black content to the silica content in the reinforcing filler is 0.21 or less.

[0016] Preferably, the rubber composition contains 4.0 parts by mass or more of a resin component with respect to 100 parts by mass of the rubber component.

[0017] Preferably, the specific gravity of the rubber composition is 1.270 or less.

[0018] The tread part has land parts partitioned by two or more circumferential grooves continuously extending in the tire circumferential direction. When the distance between the extension line of the land part and the extension line of the deepest part of the groove bottom of the circumferential groove is H, preferably, a rubber layer composed of the rubber composition is disposed in at least a part of the region of the distance H from the outermost surface of the land part radially inward.

[0019] H / E* 30is preferably 1.33 or less, more preferably 1.30 or less, still more preferably 1.27 or less, still more preferably 1.25 or less, still more preferably 1.22 or less, and particularly preferably 1.20 or less. Since the tire of the present disclosure is light in weight and has a small complex elastic modulus, there is a concern about a decrease in handling stability performance. Therefore, by making the depth of the circumferential groove shallower according to the complex elastic modulus, the handling stability performance can be improved. Note that H / E* 30 The lower limit of is not particularly limited from the viewpoint of the effects of the present disclosure, but is preferably 0.70 or more, more preferably 0.75 or more, still more preferably 0.80 or more, and particularly preferably 0.85 or more.

[0020] The tread portion has a pair of shoulder land portions partitioned by the circumferential grooves and a center land portion located between the pair of shoulder land portions, and the ratio of the total area of the center land portion to the total area of the entire land portion is preferably 0.35 to 0.80.

[0021] The tread portion has two or more circumferential grooves continuously extending in the tire circumferential direction, a width direction groove, and sipes, and the ratio of the total groove area to the ground contact area of the tread portion is preferably 0.15 to 0.35.

[0022] The ratio of the total area of the circumferential grooves to the ground contact area of the tread portion is preferably 0.09 to 0.16, and the ratio of the total area of the width direction groove and the sipes to the ground contact area of the tread portion is preferably 0.08 to 0.14.

[0023] The ratio La / Lb of the circumferential length La of the tire to the total Lb of the length Lb1 of the edge components in the width direction of the width direction groove and the total Lb2 of the length of the edge components in the width direction of the sipes is preferably 0.10 to 0.20.

[0024] The tread portion preferably has sipes whose both ends do not open to the circumferential grooves.

[0025] The tread portion includes a first rubber layer that constitutes the tread surface and a second rubber layer adjacent to the inner side in the radial direction of the first layer, and it is preferable that at least one of the first rubber layer and the second rubber layer is composed of the rubber composition, and it is more preferable that the first rubber layer is composed of the rubber composition.

[0026] It is preferable that the deepest part of the groove bottom of the circumferential groove is formed so as to be located on the inner side in the tire radial direction than the outermost part of the second rubber layer.

[0027] The ratio (t2 / t1) of the thickness t2 of the rubber of the second layer to the thickness t1 of the first rubber layer is preferably 5 / 95 to 60 / 40.

[0028] In this specification, "tire weight" is represented by G (kg). However, G is the weight of the tire alone without including the weight of the rim. Also, when a sound deadening material, a sealant, a sensor, etc. are attached to the tire inner cavity, G is a value including the weights of these. Note that the tire weight G can be varied by a conventional method, that is, it can be increased by increasing the specific gravity of the tire or increasing the thickness of each member of the tire, and it can be decreased conversely.

[0029] The tire according to the present disclosure has a maximum load capacity W L (kg) to the ratio of the tire weight G (kg) (G / W L ) is, from the viewpoint of the effects of the present disclosure, 0.0131 or less, more preferably 0.0130 or less, further preferably 0.0129 or less, still further preferably 0.0128 or less, and particularly preferably 0.0127 or less. Also, the lower limit value of the G / W L is not particularly limited from the viewpoint of the effects of the present disclosure, but can be, for example, 0.0080 or more, 0.0090 or more, 0.0100 or more, 0.0110 or more, 0.0115 or more, 0.0120 or more, 0.0121 or more.

[0030] The maximum load capacity W L(kg) is preferably 300 or more, more preferably 400 or more, still more preferably 450 or more, and particularly preferably 500 or more from the viewpoint of better exhibiting the effects of the present disclosure. Further, the maximum load capacity W L (kg) can be, for example, 1300 or less, 1200 or less, 1100 or less, 1000 or less, 900 or less, 800 or less, 700 or less, 650 or less from the viewpoint of better exhibiting the effects of the present disclosure. Note that the maximum load capacity W L can be increased by increasing the virtual volume V of the space occupied by the tire, and conversely, can be decreased.

[0031] "Normal rim" is the rim defined for each tire in the standard system including the standard on which the tire is based. In the case of JATMA, it is the "standard rim"; in the case of TRA, it is the "Design Rim"; and in the case of ETRTO, it is the "Measuring Rim". In the case of a tire of a size not defined in the above standard system, it refers to the narrowest rim among the rims with the smallest diameter that can be rim-assembled to the tire and does not cause air leakage between the rim and the tire.

[0032] "Normal internal pressure" is the air pressure defined for each tire in the standard system including the standard on which the tire is based. In the case of JATMA, it is the "maximum air pressure"; in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and in the case of ETRTO, it is the "INFLATION PRESSURE". In the case of a tire of a size not defined in the above standard system, the normal internal pressure is 250 kPa.

[0033] "Normal state" means that the tire is rim-assembled to the normal rim and filled with the normal internal pressure, and moreover, it is in a no-load state. In the case of a tire of a size not defined in the above standard system, it means that the tire is rim-assembled to the above minimum rim and filled with 250 kPa, and moreover, it is in a no-load state.

[0034] FIG. 1 is an enlarged cross-sectional view schematically showing a part of a tread of a tire. In FIG. 1, the vertical direction is the tire radial direction, the left-right direction is the tire width direction, and the direction perpendicular to the paper surface is the tire circumferential direction. In the present disclosure, unless otherwise specified, the dimensions and the like of each part of the tire are values measured in the normal state.

[0035] The groove depth H of the circumferential groove 1 is obtained by the distance between the extension line 4 of the land part 2 and the extension line 5 of the deepest part of the groove bottom of the circumferential groove 1. Note that, for example, when there are a plurality of circumferential grooves 1, the groove depth H can be the distance between the extension line 4 of the land part 2 and the extension line 5 of the deepest part of the groove bottom of the circumferential groove 1 having the deepest groove depth among the plurality of circumferential grooves 1 (the left circumferential groove 1 in FIG. 1). In the tire of the present disclosure, it is preferable to dispose a rubber layer formed of the above-described predetermined rubber composition in at least a part of the region of the distance H from the outermost surface (tread surface 3) of the land part 2 inward in the tire radial direction. Further, in the tire of the present disclosure, two or more rubber layers are present in the region of the distance H from the outermost surface of the land part 2 inward in the tire radial direction, and at least one of the two or more rubber layers is preferably formed of a predetermined rubber composition. When the rubber layer is composed of two or more layers, at least one of the two or more rubber layers may be formed of the above-described predetermined rubber composition.

[0036] The tread portion of the tire of the present disclosure includes a first rubber layer 6 and a second rubber layer 7 (hereinafter, may be simply referred to as "first layer 6" and "second layer 7"), the outer surface of the first layer 6 constitutes the tread surface 3, and the second layer 7 is adjacent to the first layer 6 inward in the radial direction. The first layer 6 typically corresponds to a cap tread. The second layer 7 typically corresponds to a base tread or an under tread. Further, as long as the object of the present disclosure is achieved, one or two or more rubber layers may be further provided between the second layer 7 and the belt layer. In the tire of the present disclosure, it is preferable that at least one of the first layer 6 and the second layer 7 is formed of a predetermined rubber composition, and it is more preferable that the first layer 6 is formed of a predetermined rubber composition.

[0037] One of the circumferential grooves 1 shown on the left side of FIG. 1 is formed such that the deepest part of the groove bottom of the circumferential groove 1 is located radially inside the tire than the outermost part of the second layer 7. Specifically, the second layer 7 has a recess recessed radially inside the tire with respect to the outermost part, and a part of the first layer 6 is formed with a predetermined thickness inside the recess of the second layer 7. The circumferential groove 1 is formed so as to enter inside the recess of the second layer 7 beyond the outer surface of the second layer 7. Note that the circumferential groove 1 may be formed with a groove depth that does not reach the outer surface of the second layer 7, like the circumferential groove 1 shown on the right side of FIG. 1.

[0038] In FIG. 1, double-headed arrow t1 is the thickness of the first layer 6, and double-headed arrow t2 is the thickness of the second layer 7. In FIG. 1, the midpoint in the tire width direction of the land portion 2 is shown as symbol P. The straight line indicated by symbol N passes through point P and is a straight line (normal line) perpendicular to the tangent plane at this point P. In this specification, the thicknesses t1 and t2 are measured along the normal line N drawn from point P on the tread surface at a position where there is no groove in the cross section of FIG. 1.

[0039] In the present disclosure, the thickness t1 of the first layer 6 is not particularly limited, but is preferably 1.0 mm or more, more preferably 2.0 mm or more, and still more preferably 3.0 mm or more. Also, the thickness t1 of the first layer 6 is preferably 10.0 mm or less, more preferably 9.0 mm or less, and still more preferably 8.0 mm or less.

[0040] In the present disclosure, the thickness t2 of the second layer 7 is not particularly limited, but is preferably 0.5 mm or more, more preferably 1.0 mm or more, and still more preferably 1.5 mm or more. Also, the thickness t2 of the second layer 7 is preferably 8.0 mm or less, more preferably 6.0 mm or less, and still more preferably 4.0 mm or less.

[0041] The ratio t2 / t1 of t1 to t2 is preferably 5 / 95 or more, more preferably 8 / 92 or more, still more preferably 10 / 90 or more, still more preferably 12 / 88 or more, still more preferably 15 / 85 or more, still more preferably 20 / 80 or more, and particularly preferably 25 / 75 or more, from the viewpoint of suppressing blowout of the tire and maintaining wet grip performance. Further, from the viewpoint of wet grip, it is preferably 60 / 40 or less, more preferably 55 / 45 or less, still more preferably 50 / 50 or less, and particularly preferably 40 / 60 or less.

[0042] Fig. 2 shows a schematic view of the contact surface when the tread is pressed against a flat surface. The tread 10 constituting the tire according to the present disclosure has, as shown in Fig. 1, a circumferential groove 1 that continuously extends in the tire circumferential direction C (in the example of Fig. 1, it extends linearly along the tire circumferential direction), and lateral grooves 21 and sipes 22 and 23 that extend in the width direction.

[0043] The tread portion 10 has a plurality of circumferential grooves 1 that continuously extend in the circumferential direction C. In Fig. 1, three circumferential grooves 1 are provided, but the number of circumferential grooves is not particularly limited, and may be, for example, 2 to 5. Further, in the present disclosure, the circumferential groove 1 extends linearly along the circumferential direction, but is not limited to such a mode, and may extend, for example, in a wave shape, a sine wave shape, or a zigzag shape along the circumferential direction.

[0044] The tread portion 10 has land portions 2 partitioned by a plurality of circumferential grooves 1 in the tire width direction W. The shoulder land portions 11 are a pair of land portions formed between the circumferential groove 1 and the tread end Te. The center land portion 12 is a land portion formed between the pair of shoulder land portions 11. In Fig. 1, two center land portions 12 are provided, but the number of center land portions is not particularly limited, and may be, for example, 1 to 5.

[0045] Preferably, the land portion 2 is provided with transverse grooves and / or sipe that cross the land portion 2. More preferably, the land portion 2 has sipe with neither or only one end opening into the circumferential groove 1. In FIG. 2, the shoulder land portion 11 is provided with a plurality of shoulder transverse grooves 21 whose ends open into the circumferential groove 1, and a plurality of shoulder sipe 22 whose both ends do not open into the circumferential groove 1, and the center land portion 12 is provided with a plurality of shoulder sipe 23 whose both ends do not open into the circumferential groove 1, but the present invention is not limited to such an embodiment.

[0046] In the present disclosure, the "groove" including the circumferential groove and the transverse groove refers to a recess having a width greater than at least 2.0 mm. On the other hand, in this specification, the "sipe" refers to a narrow cut having a width of 2.0 mm or less, preferably 0.5 to 2.0 mm.

[0047] In the present disclosure, when the length of the tire in the circumferential direction C is La, the sum of the lengths of the edge components in the width direction W of the width direction grooves 21 is Lb1, and the sum of the lengths of the edge components in the width direction W of the sipe 22 and 23 is Lb, La / Lb is preferably 0.10 or more, more preferably 0.11 or more, still more preferably 0.12 or more, and particularly preferably 0.13 or more. Also, La / Lb is preferably 0.20 or less, more preferably 0.19 or less, still more preferably 0.18 or less, and particularly preferably 0.17 or less. By setting La / Lb within the above range, the deformation of the tread portion 10 can be within a predetermined range, the area of the land portion 2 can be ensured to be a predetermined value or more, and when the rubber composition described later is used for the tread, the handling stability during high-speed driving can be improved.

[0048] The "length of the edge component in the width direction W" of the width direction grooves 21 and the sipe 22 and 23 refers to the projected length in the width direction W of the width direction grooves 21 and the sipe 22 and 23 (the width direction component among the width direction component and the circumferential direction component).

[0049] The ratio of the total area of the center land part 12 to the area of the entire land part 2 is preferably 0.35 or more, more preferably 0.40 or more, and even more preferably 0.45 or more. By setting the ratio of the total area of the center land part 12 to the area of the entire land part 2 within the above range, the volume of the center land part can be increased and the land rigidity can be increased, so that better handling stability can be obtained. Further, from the viewpoint of the effects of the present disclosure, the ratio of the total area of the center land part 12 to the area of the entire land part 2 is preferably 0.80 or less, more preferably 0.70 or less, even more preferably 0.60 or less, and particularly preferably 0.55 or less.

[0050] The ratio of the total groove area to the ground contact area of the tread part 10 is preferably 0.15 or more, more preferably 0.17 or more, and even more preferably 0.20 or more. Also, the ratio of the total groove area to the ground contact area of the tread part 10 is preferably 0.35 or less, more preferably 0.32 or less, and even more preferably 0.30 or less.

[0051] The ratio of the total area of the circumferential grooves 1 to the ground contact area of the tread part 10 is preferably 0.09 or more, more preferably 0.10 or more, and even more preferably 0.11 or more. Also, the ratio of the total area of the circumferential grooves 1 to the ground contact area of the tread part 10 is preferably 0.16 or less, more preferably 0.15 or less, and even more preferably 0.14 or less.

[0052] The ratio of the total area of the widthwise grooves 21 and the sipes 22, 23 to the ground contact area of the tread part 10 is preferably 0.08 or more, more preferably 0.09 or more, and even more preferably 0.10 or more. Also, the ratio of the total area of the widthwise grooves 21 and the sipes 22, 23 to the ground contact area of the tread part 10 is preferably 0.14 or less, more preferably 0.13 or less, and even more preferably 0.12 or less.

[0053] By setting the ratios of the total groove area, the total circumferential groove area, and the total area of the widthwise grooves and sipes to the ground contact area within the above ranges, the rigidity of the tread land can be increased, and due to the synergistic effect with the flexibility of the rubber in the rubber composition for the tread according to the present disclosure, high handling stability can be exhibited during high-speed driving, and the riding comfort at low temperatures can be improved. When the ratios of the total groove area, the total circumferential groove area, and the total area of the widthwise grooves and sipes to the ground contact area are less than the above ranges, the proportion of the land part becomes too large, so the drainage performance and grip performance tend to decrease. On the other hand, when the ratios of the total groove area, the total circumferential groove area, and the total area of the widthwise grooves and sipes to the ground contact area exceed the above ranges, sufficient rigidity of the tread land cannot be obtained, so the handling stability tends to decrease.

[0054] In addition, in this specification, the "ground contact area of the tread part" means the ground contact area of the tread part in a state where all the grooves of the tread part 2 are filled. Further, the ground contact area of the tread part, the total area of the circumferential grooves, the total area of the widthwise grooves, and the total area of the sipes are values measured when the tread is pressed against a flat surface under an unloaded state with the maximum load capacity loaded while mounted on a standard rim and filled with the standard internal pressure.

[0055] The rubber composition constituting the at least one rubber layer has a tanδ (tanδ at 30°C) exceeding 0.15, preferably 0.16 or more, and more preferably 0.17 or more under the conditions of an initial strain of 5%, a dynamic strain of 1%, and a frequency of 10 Hz at 30°C. By setting the tanδ at 30°C of the rubber composition constituting the rubber layer (preferably the first layer 6) within the above range, the wet grip performance tends to be good. Also, the upper limit value of the tanδ at 30°C of the rubber composition is not particularly limited from the viewpoint of the effects of the present disclosure, but from the viewpoint of low fuel consumption performance, it is preferably 0.50 or less, more preferably 0.40 or less, still more preferably 0.35 or less, and particularly preferably 0.30 or less. In the present disclosure, the tanδ at 30°C can be measured for a vulcanized rubber test piece cut out from each rubber layer of the tread portion of the tire such that the tire circumferential direction is the long side using a dynamic viscoelasticity measuring device.

[0056] The rubber composition constituting the at least one rubber layer has a complex elastic modulus (E* 30 ) of less than 8.0 MPa, preferably 7.8 MPa or less, and more preferably 7.6 MPa or less under the conditions of an initial strain of 5%, a dynamic strain of 1%, and a frequency of 10 Hz at 30°C. By setting the E* 30 of the rubber composition constituting the rubber layer (preferably the first layer 6) within the above range, the wet grip performance tends to be good. Also, the lower limit value of the E* 30 of the rubber composition is not particularly limited from the viewpoint of the effects of the present disclosure, but is preferably 4.0 MPa or more, more preferably 4.5 MPa or more, still more preferably 5.0 MPa or more, and particularly preferably 5.5 MPa or more. In the present disclosure, the E* 30 can be measured for a vulcanized rubber test piece cut out from each rubber layer of the tread portion of the tire such that the tire circumferential direction is the long side using a dynamic viscoelasticity measuring device.

[0057] The specific gravity of the rubber composition constituting the at least one rubber layer is preferably 1.270 or less, more preferably 1.260 or less, still more preferably 1.250 or less, still more preferably 1.240 or less, and particularly preferably 1.230 or less, from the viewpoint of handling stability performance. On the other hand, the lower limit value of the specific gravity is not particularly limited from the viewpoint of the effects of the present disclosure, but is preferably 1.160 or more, more preferably 1.165 or more, and still more preferably 1.170 or more. The specific gravity can be increased, for example, by increasing the silica content, and conversely, can be decreased by decreasing the silica content. In the present specification, the specific gravity of the rubber composition refers to the specific gravity of the vulcanized rubber composition and is measured based on JIS K 2249-4:2011.

[0058] The manufacturing procedure of a tire including the tread which is one embodiment of the present disclosure will be described in detail below. However, the following description is an exemplification for explaining the present disclosure and is not intended to limit the technical scope of the present disclosure only to this description scope. In the present specification, when indicating a numerical range using "~", it includes the numerical values at both ends thereof.

[0059] [Rubber composition] The tire of the present disclosure can more effectively improve the wet grip performance by the cooperation of the structure of the tire described above, particularly the shape of the tread, and the physical properties of the rubber composition described above.

[0060] <Rubber component> The rubber composition according to the present disclosure preferably contains at least one selected from the group consisting of isoprene rubber, styrene-butadiene rubber (SBR), and butadiene rubber (BR) as a rubber component. The rubber component may be a rubber component containing SBR and BR, or may be a rubber component containing isoprene rubber, SBR, and BR. The rubber component may also be a rubber component consisting only of SBR and BR, or may be a rubber component consisting only of isoprene rubber, SBR, and BR.

[0061] [Isoprene rubber] Examples of isoprene rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, denatured NR, denatured IR, etc. As NR, for example, SIR20, RSS#3, TSR20, etc., which are common in the tire industry, can be used. IR is not particularly limited, and for example, IR2200, etc., which are common in the tire industry, can be used. Examples of modified NR include deproteinized natural rubber (DPNR), high-purity natural rubber, etc., examples of denatured NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc., and examples of denatured IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, etc. These isoprene rubbers may be used alone or in combination of two or more.

[0062] When contained in the rubber component, the content in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 25% by mass or more, still more preferably 30% by mass or more, and particularly preferably 35% by mass or more from the viewpoints of processability and durability performance. On the other hand, the upper limit value of the content in the isoprene-based rubber component is not particularly limited, but from the viewpoint of obtaining good ride comfort performance due to the damping property in the tread portion, it is preferably 85% by mass or less, more preferably 80% by mass or less, still more preferably 75% by mass or less, and particularly preferably 70% by mass or less.

[0063] (SBR) SBR is not particularly limited, and examples include solution-polymerized SBR (S-SBR), emulsion-polymerized SBR (E-SBR), modified SBRs thereof (modified S-SBR, modified E-SBR), etc. Examples of modified SBR include SBRs with modified terminals and / or main chains, modified SBRs coupled with tin, silicon compounds, etc. (condensates, those having a branched structure, etc.). Furthermore, hydrogenated products of these SBRs (hydrogenated SBR) etc. can also be used. Among them, S-SBR is preferred, and modified S-SBR is more preferred.

[0064] Examples of the modified SBR include those modified with functional groups commonly used in this field. Examples of the above functional groups include, for example, amino groups (preferably amino groups in which the hydrogen atoms of the amino group are substituted with alkyl groups having 1 to 6 carbon atoms), amide groups, silyl groups, alkoxysilyl groups (preferably alkoxysilyl groups having 1 to 6 carbon atoms), 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 (preferably alkoxy groups having 1 to 6 carbon atoms), hydroxyl groups, oxy groups, epoxy groups, etc. These functional groups may have substituents. Examples of the substituents include functional groups such as amino groups, amide groups, alkoxysilyl groups, carboxyl groups, and hydroxyl groups. Examples of the modified SBR also include hydrogenated ones, epoxidized ones, tin-modified ones, etc.

[0065] As the SBR, extended SBR or non-extended SBR can be used. When using extended SBR, the amount of oil extension of SBR, that is, the content of the oil extender oil contained in SBR, is preferably 10 to 50 parts by mass with respect to 100 parts by mass of the rubber solid content of SBR.

[0066] The SBRs listed above may be used alone or in combination of two or more. As the SBRs listed above, for example, those commercially available from Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., ZS Elastomer Co., Ltd., etc. can be used.

[0067] From the viewpoint of ensuring damping properties in the tread portion and wet grip performance, the styrene content of SBR is preferably 15% by mass or more, more preferably 20% by mass or more, and still more preferably 25% by mass or more. Further, from the viewpoints of temperature dependence of grip performance and abrasion resistance performance, it is preferably 60% by mass or less, more preferably 50% by mass or less, and still more preferably 45% by mass or less. In the present specification, the styrene content of SBR is 1 calculated by H-NMR measurement.

[0068] From the viewpoints of ensuring reactivity with silica, rubber strength, and abrasion resistance performance, the vinyl content of SBR is preferably 10 mol% or more, more preferably 13 mol% or more, and still more preferably 16 mol% or more. Further, from the viewpoints of preventing an increase in temperature dependence, wet grip performance, elongation at break, and abrasion resistance performance, the vinyl content of SBR is preferably 70 mol% or less, more preferably 65 mol% or less, and still more preferably 60 mol% or less. In the present specification, the vinyl content (1,2-bonded butadiene unit amount) of SBR is measured by infrared absorption spectroscopy.

[0069] From the viewpoint of abrasion resistance performance, the weight average molecular weight (Mw) of SBR is preferably 150,000 or more, more preferably 200,000 or more, and still more preferably 250,000 or more. Further, from the viewpoints of crosslinking uniformity, etc., Mw is preferably 2,500,000 or less, more preferably 2,000,000 or less, and still more preferably 1,500,000 or less. The Mw of SBR can be determined by standard polystyrene conversion based on the measured value by gel permeation chromatography (GPC) (for example, GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTIPORE HZ-M manufactured by Tosoh Corporation).

[0070] When contained in the rubber component, the content in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 15% by mass or more, still more preferably 20% by mass or more, and particularly preferably 25% by mass or more from the viewpoints of ensuring damping properties in the tread portion and wet grip performance. Further, from the viewpoint of improving durability performance by suppressing heat generation in the tread portion, it is preferably 85% by mass or less, more preferably 80% by mass or less, still more preferably 75% by mass or less, and particularly preferably 70% by mass or less.

[0071] (BR) BR is not particularly limited. For example, BR with a cis content of less than 50 mol% (low-cis BR), BR with a cis content of 90 mol% or more (high-cis BR), rare-earth-based butadiene rubber synthesized using a rare-earth element-based catalyst (rare-earth-based BR), BR containing syndiotactic polybutadiene crystals (BR containing SPB), modified BR (high-cis modified BR, low-cis modified BR), etc., which are common in the tire industry, can be used. Examples of the modified BR include BR modified with the same functional groups as those described for the above SBR. These BRs may be used alone or in combination of two or more.

[0072] As the high-cis BR, for example, those commercially available from Nippon Zeon Co., Ltd., Ube Industries, Ltd., JSR Corporation, etc. can be used. By containing high-cis BR, the low-temperature properties and abrasion resistance can be improved. The cis content is preferably 95 mol% or more, more preferably 96 mol% or more, still more preferably 97 mol% or more, and particularly preferably 98 mol% or more. In this specification, the cis content (cis-1,4-bonded butadiene unit amount) is a value calculated by infrared absorption spectrum analysis.

[0073] As the rare earth-based BR, it is synthesized using a rare earth element-based catalyst, and the vinyl content is preferably 1.8 mol% or less, more preferably 1.0 mol% or less, still more preferably 0.8 mol% or less, and the cis content is preferably 95 mol% or more, more preferably 96 mol% or more, still more preferably 97 mol% or more, particularly preferably 98 mol% or more. As the rare earth-based BR, for example, those commercially available from Lanxess Co., Ltd. can be used.

[0074] The SPB-containing BR is not simply one in which 1,2-syndiotactic polybutadiene crystals are dispersed in BR, but one in which they are dispersed after chemically bonding to BR. As such SPB-containing BR, those commercially available from Ube Industries, Ltd. can be used.

[0075] As the modified BR, a modified butadiene rubber (modified BR) modified with a functional group containing at least one element selected from the group consisting of silicon, nitrogen, and oxygen at the terminal and / or in the main chain is preferably used.

[0076] Other modified BRs include those obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and in which the terminals of the modified BR molecules are bonded by tin-carbon bonds (tin-modified BR), etc. Also, the modified BR may be either non-hydrogenated or hydrogenated.

[0077] From the viewpoint of preventing low-temperature brittleness, the glass transition temperature (Tg) of BR is preferably -14°C or lower, more preferably -17°C or lower, still more preferably -20°C or lower. On the other hand, the lower limit value of the Tg is not particularly limited, but from the viewpoint of abrasion resistance, it is preferably -150°C or higher, more preferably -120°C or higher, still more preferably -110°C or higher. The glass transition temperature of BR is a value measured by performing differential scanning calorimetry (DSC) under the condition of a heating rate of 10°C / min in accordance with JIS K 7121.

[0078] The weight average molecular weight (Mw) of BR is preferably 300,000 or more, more preferably 350,000 or more, and even more preferably 400,000 or more from the viewpoint of wear resistance performance. Further, from the viewpoints such as crosslinking uniformity, etc., it is preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,000,000 or less. Incidentally, the Mw of BR can be determined by standard polystyrene conversion based on the measured value by gel permeation chromatography (GPC) (for example, GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTIPORE HZ-M manufactured by Tosoh Corporation).

[0079] From the viewpoint of wear resistance performance, the content in 100% by mass of the rubber component when containing BR is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more. Further, from the viewpoint of wet grip performance, it is preferably 40% by mass or less, more preferably 35% by mass or less, even more preferably 30% by mass or less, and particularly preferably 25% by mass or less.

[0080] (Other rubber components) As the rubber component according to the present disclosure, it may contain the above-mentioned isoprene rubber, SBR, and rubber components other than BR. As other rubber components, crosslinkable rubber components generally used in the tire industry can be used. For example, isoprene rubbers other than styrene isoprene rubber (SIR), styrene isoprene butadiene rubber (SIBR), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), etc., SBR, and diene rubbers other than BR; rubber components other than diene rubbers such as butyl rubber (IIR), halogenated butyl rubber, ethylene propylene rubber, polynorbornene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), and hydrin rubber can be mentioned. These other rubber components may be used alone or in combination of two or more. The rubber component according to the present disclosure preferably contains 80% by mass or more of diene rubber, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 98% by mass or more, and may be a rubber component consisting only of diene rubber.

[0081] <Reinforcing filler> The rubber composition according to the present disclosure preferably contains silica as a reinforcing filler, and more preferably contains carbon black and silica. Further, the reinforcing filler may be a reinforcing filler consisting only of carbon black and silica.

[0082] (Silica) The silica is not particularly limited, and for example, silica prepared by a dry method (anhydrous silica), silica prepared by a wet method (hydrous silica), etc., which are common in the tire industry, can be used. Among them, hydrous silica prepared by a wet method is preferred because it has many silanol groups. These silicas may be used alone or in combination of two or more.

[0083] From the viewpoints of ensuring the reinforcing property and the damping property in the tread portion, the nitrogen adsorption specific surface area (N2SA) of the silica is preferably 140 m 2 / g or more, more preferably 150 m 2 / g or more, further preferably 160 m 2 / g or more, and particularly preferably 170 m 2 / g or more. Also, from the viewpoints of heat generation property and processability, it is preferably 350 m 2 / g or less, more preferably 300 m 2 / g or less, further preferably 250 m 2 / g or less. Note that the N2SA of the silica in this specification is a value measured by the BET method in accordance with ASTM D3037-93.

[0084] The average primary particle diameter of silica is preferably 20 nm or less, more preferably 18 nm or less. The lower limit value of the average primary particle diameter is not particularly limited, but is preferably 1 nm or more, more preferably 3 nm or more, and still more preferably 5 nm or more. By the average primary particle diameter of silica being within the above range, the dispersibility of silica can be further improved, and the reinforcing property, fracture property, and abrasion resistance can be further improved. The average primary particle diameter of silica can be observed by a transmission or scanning electron microscope, and by measuring 400 or more primary particles of silica observed in the field of view and averaging them.

[0085] From the viewpoint of ensuring the damping property in the tread part and the wet grip performance, the content of silica with respect to 100 parts by mass of the rubber component is preferably 30 parts by mass or more, more preferably 35 parts by mass or more, still more preferably 40 parts by mass or more, and particularly preferably 45 parts by mass or more. Also, from the viewpoint of reducing the specific gravity of the rubber and achieving weight reduction, it is preferably 110 parts by mass or less, more preferably 100 parts by mass or less, still more preferably 95 parts by mass or less, and particularly preferably 90 parts by mass or less.

[0086] (Carbon black) The carbon black is not particularly limited, and general ones in the tire industry such as GPF, FEF, HAF, ISAF, SAF, etc. can be used. Specifically, N110, N115, N120, N125, N134, N135, N219, N220, N231, N234, N293, N299, N326, N330, N339, N343, N347, N351, N356, N358, N375, N539, N550, N582, N630, N642, N650, N660, N683, N754, N762, N765, N772, N774, N787, N907, N908, N990, N991, etc. can be preferably used. In addition to these, in-house synthetic products, etc. can also be preferably used. These carbon blacks may be used alone or in combination of two or more.

[0087] The nitrogen adsorption specific surface area (N2SA) of the carbon black is preferably 50 m 2 / g or more from the viewpoints of weather resistance and reinforcing property, and 80 m2 More preferably, it is 100 m 2 / g or more, and even more preferably. Also, from the viewpoints of dispersibility, low fuel consumption performance, fracture characteristics, and durability performance, 250 m 2 / g or less is preferable, and 220 m 2 / g or less is more preferable. Note that the N2SA of the carbon black in this specification is a value measured in accordance with Method A of JIS K 6217-2 "Basic Characteristics of Carbon Black for Rubber - Part 2: Method for Determining Specific Surface Area - Nitrogen Adsorption Method - Single Point Method".

[0088] When containing carbon black, the content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more from the viewpoints of weather resistance and reinforcement. Also, from the viewpoint of low fuel consumption performance, 40 parts by mass or less is preferable, 30 parts by mass or less is more preferable, 20 parts by mass or less is even more preferable, and 18 parts by mass or less is particularly preferable.

[0089] (Other reinforcing fillers) As reinforcing fillers other than silica and carbon black, those generally used in the tire industry, such as aluminum hydroxide, calcium carbonate, alumina, clay, talc, etc., can be blended.

[0090] The ratio of the content of carbon black to the content of silica is preferably 0.40 or less, more preferably 0.30 or less, even more preferably 0.21 or less, even more preferably 0.17 or less, even more preferably 0.13 or less, and particularly preferably 0.10 or less. By setting the ratio of the content of carbon black to the content of silica within the above range, while maintaining the rigidity in the high strain region, the E* of the rubber composition 30 can be further reduced, so that the wet grip performance can be further improved. On the other hand, the lower limit value of the ratio of the content of carbon black to the content of silica is not particularly limited, and can be, for example, 0.01 or more, 0.02 or more, 0.05 or more, and it may also be a reinforcing filler that does not contain carbon black.

[0091] The total content of the reinforcing filler with respect to 100 parts by mass of the rubber component is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, still more preferably 45 parts by mass or more, and particularly preferably 50 parts by mass or more from the viewpoints of ensuring reinforcement and attenuation in the tread portion. From the viewpoint of the effects of the present disclosure, it is preferably 120 parts by mass or less, more preferably 110 parts by mass or less, still more preferably 100 parts by mass or less, and particularly preferably 95 parts by mass or less.

[0092] (Silane coupling agent) Silica is preferably used in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and in the tire industry, any silane coupling agent that has been conventionally used in combination with silica can be used. For example, the following mercapto-based silane coupling agents; sulfide-based silane coupling agents such as bis(3-triethoxysilylpropyl)disulfide and bis(3-triethoxysilylpropyl)tetrasulfide; thioester-based silane coupling agents such as 3-octanoylthio-1-propyltriethoxysilane, 3-hexanoylthio-1-propyltriethoxysilane, and 3-octanoylthio-1-propyltrimethoxysilane; vinyl-based silane coupling agents such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based silane coupling agents such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and 3-(2-aminoethyl)aminopropyltriethoxysilane; glycidoxy-based silane coupling agents such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based silane coupling agents such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; chloro-based silane coupling agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane; etc. are mentioned. Among them, it is preferable to contain a sulfide-based silane coupling agent and / or a mercapto-based silane coupling agent. These silane coupling agents may be used alone or in combination of two or more.

[0093] The mercapto-based silane coupling agent is preferably a compound represented by the following formula (3) and / or a compound containing a bonding unit A represented by the following formula (4) and a bonding unit B represented by the following formula (5).

Chemical formula

Chemical formula

Chemical formula

[0094] Examples of the compound represented by the formula (3) include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and the compound represented by the following formula (6) (Si363 manufactured by Evonik Degussa Co., Ltd.), etc. Among them, the compound represented by the following formula (6) can be preferably used. These may be used alone or in combination of two or more. [Chemical formula]

[0095] Examples of the compound containing the bonding unit A represented by the formula (4) and the bonding unit B represented by the formula (5) include those commercially available from Momentive Co., Ltd. and others. These may be used alone or in combination of two or more.

[0096] From the viewpoint of enhancing the dispersibility of silica, the content of the silane coupling agent relative to 100 parts by mass of silica is preferably 1.0 part by mass or more, more preferably 3.0 part by mass or more, and still more preferably 5.0 part by mass or more. From the viewpoint of preventing the deterioration of the abrasion resistance performance, it is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and still more preferably 15 parts by mass or less.

[0097] <Resin component> The rubber composition according to the present disclosure preferably contains a resin component. The resin component is not particularly limited, and examples thereof include petroleum resins, terpene resins, rosin resins, phenolic resins, etc. commonly used in the tire industry. These resin components may be used alone or in combination of two or more.

[0098] Examples of the petroleum resin include C5-based petroleum resins, aromatic-based petroleum resins, and C5C9-based petroleum resins. These petroleum resins may be used alone or in combination of two or more.

[0099] As used herein, the term "C5 petroleum resin" refers to a resin obtained by polymerizing a C5 fraction. Examples of the C5 fraction include petroleum fractions corresponding to 4 to 5 carbon atoms such as cyclopentadiene, pentene, pentadiene, and isoprene. As the C5 petroleum resin, dicyclopentadiene resin (DCPD resin) is preferably used.

[0100] As used herein, the term "aromatic petroleum resin" refers to a resin obtained by polymerizing a C9 fraction, which may be hydrogenated or modified. Examples of the C9 fraction include petroleum fractions corresponding to 8 to 10 carbon atoms such as vinyltoluene, alkylstyrene, indene, and methylindene. Specific examples of the aromatic petroleum resin include, for example, coumarone-indene resin, coumarone resin, indene resin, and aromatic vinyl resin, which are preferably used. As the aromatic vinyl resin, due to economic reasons, ease of processing, and excellent heat generation properties, a homopolymer of α-methylstyrene or styrene, or a copolymer of α-methylstyrene and styrene is preferred, and a copolymer of α-methylstyrene and styrene is more preferred. As the aromatic vinyl resin, for example, those commercially available from companies such as Kraton Corporation and Eastman Chemical Company can be used.

[0101] As used herein, the term "C5C9 petroleum resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, which may be hydrogenated or modified. Examples of the C5 fraction and the C9 fraction include the above-mentioned petroleum fractions. As the C5C9 petroleum resin, for example, those commercially available from companies such as Tosoh Corporation and LUHUA can be used.

[0102] As terpene resins, there may be mentioned polyterpene resins composed of at least one selected from terpene compounds such as α-pinene, β-pinene, limonene, dipentene, etc.; aromatic modified terpene resins using the terpene compounds and aromatic compounds as raw materials; terpene phenol resins using terpene compounds and phenolic compounds as raw materials; and those obtained by subjecting these terpene resins to hydrogenation treatment (hydrogenated terpene resins). Examples of the aromatic compounds used as raw materials for the aromatic modified terpene resins include styrene, α-methylstyrene, vinyltoluene, divinyltoluene, etc. Examples of the phenolic compounds used as raw materials for the terpene phenol resins include phenol, bisphenol A, cresol, xylenol, etc.

[0103] The rosin resins are not particularly limited, and examples thereof include natural resin rosin and rosin modified resins obtained by modifying it by hydrogenation, disproportionation, dimerization, esterification, etc.

[0104] The phenolic resins are not particularly limited, and examples thereof include phenol formaldehyde resins, alkylphenol formaldehyde resins, alkylphenol acetylene resins, oil-modified phenol formaldehyde resins, etc.

[0105] From the viewpoint of wet grip performance, the softening point of the resin component is preferably 60°C or higher, more preferably 65°C or higher. Also, from the viewpoints of processability and improvement of the dispersibility between the rubber component and the filler, it is preferably 150°C or lower, more preferably 140°C or lower, and even more preferably 130°C or lower. In the present specification, the softening point can be defined as the temperature at which the sphere drops when measured with a ring and ball type softening point measuring device in accordance with the softening point specified in JIS K 6220-1:2001.

[0106] From the viewpoint of achieving a good balance between wet grip performance and handling stability performance, aromatic petroleum resins are preferred as the resin component, and aromatic vinyl resins are more preferred.

[0107] When containing a resin component, the content relative to 100 parts by mass of the rubber component is preferably 2.0 parts by mass or more, more preferably 3.0 parts by mass or more, still more preferably 4.0 parts by mass or more, and particularly preferably 5.0 parts by mass or more. By setting the content of the resin component within the above range, while improving the heat generation performance in the high-frequency region, the adhesive friction can also be improved, and the wet grip performance tends to be further improved. Further, from the viewpoint of durability performance, it is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, still more preferably 30 parts by mass or less, and particularly preferably 20 parts by mass or less.

[0108] <Other compounding agents> In the rubber composition according to the present disclosure, in addition to the above components, compounding agents generally used in the conventional tire industry, such as oils, waxes, processing aids, anti-aging agents, stearic acid, zinc oxide, vulcanizing agents such as sulfur, vulcanization accelerators, etc. can be appropriately contained.

[0109] Examples of the oil include process oil, vegetable oil, animal oil, etc. Examples of the process oil include paraffinic process oil, naphthenic process oil, aromatic process oil, etc. Further, a process oil with a low content of polycyclic aromatic compound (PCA) compounds for environmental measures can be mentioned. Examples of the low-PCA content process oil include Treated Distillate Aromatic Extract (TDAE) obtained by re-extracting oil aromatic process oil, aroma alternative oil which is a mixed oil of asphalt and naphthenic oil, mild extraction solvates (MES), and heavy naphthenic oil, etc.

[0110] When contained, the content relative to 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 2 parts by mass or more, still more preferably 3 parts by mass or more, further more preferably 5 parts by mass or more, further more preferably 8 parts by mass or more, and particularly preferably 12 parts by mass or more from the viewpoint of processability. Also, from the viewpoints of low fuel consumption performance and durability performance, it is preferably 80 parts by mass or less, more preferably 60 parts by mass or less, and still more preferably 40 parts by mass or less. In the present specification, the oil content includes the amount of oil contained in the oil-extended rubber.

[0111] When contained, the content relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1 part by mass or more from the viewpoint of the weather resistance of the rubber. Also, from the viewpoint of preventing whitening of the tire due to blooming, it is preferably 10 parts by mass or less, more preferably 5 parts by mass or less.

[0112] As the processing aid, a fatty acid metal salt for the purpose of reducing the viscosity of the rubber and ensuring mold release property during unvulcanization, and those commercially available as compatibilizers widely from the viewpoint of suppressing micro-layer separation of the rubber component can be used.

[0113] When contained, the content relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1 part by mass or more from the viewpoint of exerting the effect of improving processability. Also, from the viewpoints of abrasion resistance and breaking strength, it is preferably 10 parts by mass or less, more preferably 8 parts by mass or less.

[0114] The anti-aging agent is not particularly limited, and examples thereof include amine-based, quinoline-based, quinone-based, phenol-based, imidazole-based compounds, and anti-aging agents such as metal carbamates.

[0115] When contained, the content relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1 part by mass or more from the viewpoint of ozone crack resistance of the rubber. Also, from the viewpoints of abrasion resistance performance and wet grip performance, it is preferably 10 parts by mass or less, more preferably 5 parts by mass or less.

[0116] When containing stearic acid, the content based on 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1 part by mass or more, from the viewpoint of processability. Also, from the viewpoint of vulcanization rate, it is preferably 10 parts by mass or less, more preferably 5 parts by mass or less.

[0117] When containing zinc oxide, the content based on 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1 part by mass or more, from the viewpoint of processability. Also, from the viewpoint of wear resistance performance, it is preferably 10 parts by mass or less, more preferably 5 parts by mass or less.

[0118] As the vulcanizing agent, sulfur is preferably used. As sulfur, powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, etc. can be used.

[0119] When containing sulfur as the vulcanizing agent, the content based on 100 parts by mass of the rubber component is preferably 0.1 part by mass or more, more preferably 0.3 part by mass or more, further preferably 0.5 part by mass or more, from the viewpoint of ensuring a sufficient vulcanization reaction. Also, from the viewpoint of deterioration prevention, it is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, further preferably 3.0 parts by mass or less. In addition, when using oil-containing sulfur as the vulcanizing agent, the content of the vulcanizing agent is the total content of pure sulfur contained in the oil-containing sulfur.

[0120] Examples of vulcanizing agents other than sulfur include alkylphenol sulfur chloride condensates, sodium 1,6 - hexamethylene - dithiolsulfate dihydrate, 1,6 - bis(N,N’ - dibenzylthiocarbamoyldithio)hexane), etc. These vulcanizing agents other than sulfur that are commercially available from companies such as Tago Chemical Industry Co., Ltd., Rancess Co., Ltd., Flexsys Co., etc. can be used.

[0121] Examples of the vulcanization accelerator include sulfenamide-based, thiazole-based, thiuram-based, thiourea-based, guanidine-based, dithiocarbamic acid-based, aldehyde-amine-based or aldehyde-ammonia-based, imidazoline-based, or xanthate-based vulcanization accelerators. These vulcanization accelerators may be used alone or in combination of two or more. Among them, from the viewpoint of more preferably obtaining the desired effect, one or more vulcanization accelerators selected from the group consisting of sulfenamide-based, guanidine-based, and thiazole-based vulcanization accelerators are preferable, and it is more preferable to combine a sulfenamide-based vulcanization accelerator and a guanidine-based vulcanization accelerator.

[0122] Examples of the sulfenamide-based vulcanization accelerator include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazolylsulfenamide (DCBS), and the like. Among them, N-tert-butyl-2-benzothiazolylsulfenamide (TBBS) and N-cyclohexyl-2-benzothiazolylsulfenamide (CBS) are preferable.

[0123] Examples of the guanidine-based vulcanization accelerator include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicatechol borate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, 1,3-di-o-cumenyl-2-propionylguanidine, and the like. Among them, 1,3-diphenylguanidine (DPG) is preferable.

[0124] Examples of the thiazole-based vulcanization accelerator include 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, di-2-benzothiazolyldisulfide, and the like. Among them, 2-mercaptobenzothiazole is preferable.

[0125] When containing a vulcanization accelerator, the content relative to 100 parts by mass of the rubber component is preferably 1.0 part by mass or more, more preferably 1.5 parts by mass or more, and still more preferably 2.0 parts by mass or more. Further, the content of the vulcanization accelerator relative to 100 parts by mass of the rubber component is preferably 8.0 parts by mass or less, more preferably 7.0 parts by mass or less, still more preferably 6.0 parts by mass or less, and particularly preferably 5.0 parts by mass or less. By setting the content of the vulcanization accelerator within the above range, the breaking strength and elongation tend to be ensured.

[0126] The rubber composition according to the present disclosure can be produced by a known method. For example, it can be produced by kneading each of the above components using a rubber kneading device such as an open roll or a closed kneader (Banbury mixer, kneader, etc.).

[0127] The kneading process includes, for example, a base kneading process of kneading compounding agents and additives other than the vulcanizing agent and the vulcanization accelerator, and a final kneading (F kneading) process of adding the vulcanizing agent and the vulcanization accelerator to the kneaded product obtained in the base kneading process and kneading them. Further, the base kneading process can be divided into a plurality of processes if desired. The kneading conditions are not particularly limited. For example, in the base kneading process, kneading is performed at a discharge temperature of 150 to 170°C for 1 to 10 minutes, and in the final kneading process, kneading is performed at 70 to 110°C for 1 to 5 minutes.

[0128] [Tire] The tire of the present disclosure is suitable for passenger car tires, truck / bus tires, large SUV tires, racing tires, motorcycle tires, etc., and can be used as respective summer tires, winter tires, and studless tires. In the present specification, a passenger car tire is a tire assumed to be mounted on an automobile traveling on four wheels, and refers to one having a maximum load capacity of 1000 kg or less.

[0129] A tire provided with a tread composed of the above rubber composition can be manufactured by a conventional method. That is, an unvulcanized rubber composition in which each of the above components is compounded as necessary with respect to the rubber component is extruded according to the shape of at least one rubber layer constituting the tread, and is bonded together with other tire members on a tire molding machine and molded by a conventional method to form an unvulcanized tire. By heating and pressurizing this unvulcanized tire in a vulcanizer, a tire can be manufactured. The vulcanization conditions are not particularly limited, and for example, a method of vulcanizing at 150 to 200 ° C for 10 to 30 minutes can be mentioned.

Examples

[0130] Hereinafter, the present disclosure will be described based on examples, but the present disclosure is not limited only to these examples.

[0131] Hereinafter, various chemicals used in the examples and comparative examples are collectively shown. NR: TSR20 SBR: Modified solution-polymerized SBR produced in Production Example 1 described below (styrene content: 30% by mass, vinyl content: 52 mol%, Mw: 250,000, non-oil product) BR: UBEPOL BR (registered trademark) 150B manufactured by Ube Industries, Ltd. (cis content: 97 mol%, Tg: -108 ° C, Mw: 440,000) Carbon black: Diamond Black N220 manufactured by Mitsubishi Chemical Corporation (N2SA: 115m 2 / g) Silica: ULTRASIL (registered trademark) VN3 manufactured by Evonik Degussa GmbH (N2SA: 175m 2 / g, average primary particle diameter: 17 nm) Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa GmbH Oil: VivaTec 400 (TDAE oil) manufactured by H&R Resin component: Sylvares SA85 manufactured by Clayton (copolymer of α-methylstyrene and styrene, softening point: 85 ° C) Zinc oxide: Zinc white No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Camellia bead stearic acid manufactured by NOF Corporation Sulfur: HK-200-5 (powder sulfur containing 5% oil) manufactured by Hosoi Chemical Industry Co., Ltd. Vulcanization accelerator 1: Nocceler CZ (N-cyclohexyl-2-benzothiazolylsulfenamide (CBS)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Nocceler D (1,3-diphenylguanidine (DPG)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0132] Production Example 1: Synthesis of SBR Cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene were charged into a nitrogen-substituted autoclave reactor. After adjusting the temperature of the reactor contents to 20°C, n-butyllithium was added to initiate polymerization. Polymerization was carried out under adiabatic conditions, and the maximum temperature reached 85°C. When the polymerization conversion rate reached 99%, 1,3-butadiene was added, and polymerization was continued for another 5 minutes. Then, N,N-bis(trimethylsilyl)-3-aminopropyltrimethoxysilane was added as a modifier to carry out the reaction. After the polymerization reaction was completed, 2,6-di-tert-butyl-p-cresol was added. Subsequently, the solvent was removed by steam stripping and dried with a hot roll adjusted to 110°C to obtain SBR.

[0133] (Examples and Comparative Examples) According to the formulation shown in Table 1, using a 1.7 L sealed Banbury mixer, chemicals other than sulfur and vulcanization accelerators were kneaded for 1 to 10 minutes until the discharge temperature reached 150 to 160°C to obtain a kneaded product. Next, using a twin-screw open roll, sulfur and vulcanization accelerators were added to the obtained kneaded product and kneaded for 4 minutes until the temperature reached 105°C to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press-vulcanized at 170°C for 12 minutes to prepare a test vulcanized rubber composition.

[0134] Also, using the obtained unvulcanized rubber composition, it was extruded into the shape of the first layer (thickness: 3.0 mm) of the tread using an extruder equipped with a die of a predetermined shape, and laminated together with the second layer (thickness: 3.0 mm) of the tread and other tire members to produce an unvulcanized tire, which was press-vulcanized at 170 °C for 12 minutes to produce each test tire described in Tables 2 to 5.

[0135] The following evaluations were performed on the obtained vulcanized rubber composition for testing and the test tires. The evaluation results are shown in Tables 2 to 5.

[0136] <Measurement of tanδ and complex elastic modulus E*> Each vulcanized rubber test piece after vulcanization was prepared by cutting out from each rubber layer of the tread portion of each test tire with a length of 20 mm × width of 4 mm × thickness of 2 mm such that the tire circumferential direction was the long side. For each rubber test piece, tanδ and complex elastic modulus (E*) were measured under the conditions of a temperature of 30 °C, an initial strain of 5%, a dynamic strain of 1%, and a frequency of 10 Hz using a dynamic viscoelasticity measuring device (Iplexer series manufactured by GABO). The results are shown in Table 1. The thickness direction of the sample was the tire radial direction.

[0137] <Wet grip performance> Each test tire was filled with 250 kPa of air, mounted on all four wheels of an automobile with an exhaust volume of 2000 cc, and while driving on a wet asphalt road surface at an initial speed of 100 km / h, the brake was depressed and the braking distance was measured. Regarding the value of the reciprocal of the braking distance, the braking distance of the reference example (Example 1 in Tables 2 and 3, Example 9 in Table 4, and Example 13 in Table 5) was set to 100 and expressed as an index. The larger the index, the better the wet grip performance.

[0138] <Handling stability performance> Each test tire was filled with air at 250 kPa and mounted on all four wheels of an automobile with a displacement of 2000 cc, and actual vehicle running was performed on a test course with a dry asphalt surface. Based on the feelings during straight running, lane change, acceleration, and deceleration at a speed of 120 km / h by the test driver, the handling characteristics were evaluated. The evaluation was carried out with integer values from 1 to 10, and the total score of 10 test drivers was calculated based on the evaluation criteria that the higher the score, the better the handling characteristics. The total score of the reference example (Example 1 in Tables 2 and 3, Example 9 in Table 4, and Example 13 in Table 5) was converted to a reference value (100), and the evaluation results of each test tire were indexed and displayed in proportion to the total score.

[0139]

Table 1

[0140]

Table 2

[0141]

Table 3

[0142]

Table 4

[0143]

Table 5

[0144] From the results in Tables 1 to 5, it can be seen that the tires of the present disclosure with the tire weight relative to the maximum load capacity of the tire and the tanδ and complex elastic modulus of the rubber composition constituting the tread within a predetermined range have improved wet grip performance. Also, in a preferred embodiment, it can be seen that the handling stability performance is also improved.

[0145] <Embodiment> Examples of embodiments of the present disclosure are shown below.

[0146] 〔1〕A tire including a tread portion, wherein the ratio (G / W L of the tire weight G (kg) to the maximum load capacity W L ) of the tire is 0.0131 or less (preferably 0.0130 or less, more preferably 0.0129 or less, still more preferably 0.0128 or less, particularly preferably 0.0127 or less), the tread has at least one rubber layer made of a rubber composition containing a rubber component and a reinforcing filler, the tanδ (30°C tanδ) of the rubber composition at 30°C is more than 0.15 (preferably 0.16 or more, more preferably 0.17 or more), and the complex elastic modulus (E* 30 ) at 30°C is less than 8.0 MPa (preferably 7.8 MPa or less, more preferably 7.6 MPa or less), and the ratio (30°C tanδ / G) of the 30°C tanδ to the G is 0.016 or more (preferably 0.017 or more, more preferably 0.018 or more, still more preferably 0.019 or more, particularly preferably 0.020 or more). 〔2〕The tire according to the above 〔1〕, wherein the reinforcing filler contains silica, and the ratio of the content of carbon black to the content of silica in the reinforcing filler is 0.21 or less (preferably 0.17 or less, more preferably 0.13 or less, still more preferably 0.10 or less). 〔3〕The tire according to the above 〔1〕 or 〔2〕, wherein the rubber composition contains 4.0 parts by mass or more (preferably 4.0 to 40 parts by mass, more preferably 5.0 to 30 parts by mass) of a resin component with respect to 100 parts by mass of the rubber component. 〔4〕The tire according to any one of the above 〔1〕 to 〔3〕, wherein the specific gravity of the rubber composition is 1.270 or less (preferably 1.260 or less, more preferably 1.250 or less, still more preferably 1.240 or less, particularly preferably 1.230 or less). 〔5〕The tread portion has land portions partitioned by two or more circumferential grooves that continuously extend in the tire circumferential direction. When the distance between the extension line of the land portion and the extension line of the deepest part of the groove bottom of the circumferential groove is defined as H, a rubber layer composed of the rubber composition is disposed in at least a part of the region of distance H radially inward from the outermost surface of the land portion. The tire according to any one of the above items 〔1〕 to 〔4〕. 〔6〕H / E* 30 is 1.30 or less (preferably 1.27 or less, more preferably 1.25 or less, still more preferably 1.22 or less, particularly preferably 1.20 or less). The tire according to item 〔5〕 above. 〔7〕The tread portion has a pair of shoulder land portions partitioned by the circumferential grooves and a center land portion located between the pair of shoulder land portions. The ratio of the total area of the center land portion to the total area of the land portions is 0.35 to 0.80 (preferably 0.40 to 0.70, more preferably 0.45 to 0.60). The tire according to item 〔5〕 or 〔6〕 above. 〔8〕The tread portion has two or more circumferential grooves that continuously extend in the tire circumferential direction, width direction grooves, and sipes. The ratio of the total groove area to the contact area of the tread portion is 0.15 to 0.35 (preferably 0.17 to 0.32, more preferably 0.20 to 0.30). The tire according to any one of the above items 〔1〕 to 〔7〕. 〔9〕The total area of the circumferential grooves with respect to the contact area of the tread portion is 0.09 to 0.16 (preferably 0.10 to 0.15, more preferably 0.11 to 0.14), and the total area of the width direction grooves and sipes with respect to the contact area of the tread portion is 0.08 to 0.14 (preferably 0.09 to 0.13, more preferably 0.10 to 0.12). The tire according to item 〔8〕 above. 〔10〕The ratio La / Lb of the circumferential length La of the tire to the total Lb of the length Lb1 of the width direction edge components of the width direction grooves and the length Lb2 of the width direction edge components of the sipes is 0.10 to 0.20 (preferably 0.11 to 0.29, more preferably 0.12 to 0.18, still more preferably 0.13 to 0.17). The tire according to item 〔8〕 or 〔9〕 above. 〔11〕The tire according to any one of 〔8〕to 〔10〕above, wherein the tread portion has sipes whose both ends do not open into the circumferential grooves. 〔12〕The tire according to any one of 〔1〕to 〔11〕above, wherein the tread portion includes a first rubber layer constituting the tread surface and a second rubber layer adjacent to the inner side in the radial direction of the first layer, and at least one of the first rubber layer and the second rubber layer is composed of the rubber composition. 〔13〕The tire according to 〔12〕above, wherein the deepest part of the groove bottom of the circumferential groove is formed to be located on the inner side in the tire radial direction than the outermost part of the second rubber layer. 〔14〕The tire according to 〔12〕or 〔13〕above, wherein the ratio (t2 / t1) of the thickness t2 of the rubber of the second layer to the thickness t1 of the first rubber layer is 5 / 95 to 60 / 40 (preferably 15 / 85 to 65 / 45, more preferably 25 / 75 to 50 / 50).

Explanation of symbols

[0147] 1 ··· Circumferential groove 2 ··· Land portion 3 ··· Tread surface 4 ··· Extension line of the land portion 5 ··· Extension line of the deepest part of the groove bottom of the circumferential groove 6 ··· First layer 7 ··· Second layer 8 ··· Extension line of the outermost part of the second layer 10 ··· Tread portion 11 ··· Center land portion 12 ··· Shoulder land portion 21 ··· Groove in the width direction 22, 23 ··· Sipes

Claims

1. A tire having a tread portion, The ratio (G / W) of the tire weight G (kg) to the maximum load capacity W L (kg) of the tire is 0.0131 or less, L and wherein the tread portion has at least two rubber layers made of a rubber composition containing a rubber component and a reinforcing filler, the tread portion includes a first rubber layer constituting a tread surface and a second rubber layer adjacent to the inner side in the radial direction of the first rubber layer, a ratio (t2 / t1) of the thickness t2 of the second rubber layer to the thickness t1 of the first rubber layer is 5 / 95 to 60 / 40, The tanδ (tanδ at 30°C) of at least one rubber composition among the rubber composition constituting the first rubber layer and the rubber composition constituting the second rubber layer is more than 0.15, and the complex elastic modulus (E* 30 ) at 30°C is less than 8.0 MPa, and a ratio (30°C tanδ / G) of the 30°C tanδ to the G is 0.016 or more.

2. The tire according to claim 1, wherein the reinforcing filler contains silica, and a ratio of the content of carbon black to the content of silica in the reinforcing filler is 0.21 or less.

3. The tire according to claim 1 or 2, wherein the rubber composition contains 4.0 parts by mass or more of a resin component with respect to 100 parts by mass of the rubber component.

4. The tire according to any one of claims 1 to 3, wherein a specific gravity of the rubber composition is 1.270 or less.

5. the tread portion has land portions partitioned by two or more circumferential grooves continuously extending in the tire circumferential direction, when a distance between an extension line of the land portion and an extension line of the deepest part of the groove bottom of the circumferential groove is H, a rubber layer made of the rubber composition is disposed in at least a part of a region of a distance H from the outermost surface of the land portion toward the inner side in the radial direction.

6. H / E* 30 The tire according to claim 5, wherein H / E* is 1.30 or less.

7. the tread portion has a pair of shoulder land portions partitioned by the circumferential grooves and a center land portion located between the pair of shoulder land portions, and a ratio of a total area of the center land portions to an area of the entire land portion is 0.35 to 0.

80.

8. the tread portion has two or more circumferential grooves continuously extending in the tire circumferential direction, a width direction groove, and sipes, and a ratio of a total groove area to a contact area of the tread portion is 0.15 to 0.

35.

9. a ratio of a total area of the circumferential grooves to the contact area of the tread portion is 0.09 to 0.16, and a ratio of a total area of the width direction groove and the sipes to the contact area of the tread portion is 0.08 to 0.

14.

10. The ratio La / Lb of the circumferential length La of the tire to the total Lb of the sum Lb1 of the lengths of the edge components in the width direction of the width direction grooves and the sum Lb2 of the lengths of the edge components in the width direction of the sipes is 0.10 to 0.

20. The tire according to claim 8 or 9.

11. The tread portion has sipes whose both ends do not open to the circumferential grooves. The tire according to any one of claims 8 to 10.

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