tire

Abstract

The tire uses sustainable cord for the ply cord of the carcass ply to reduce heat generation during driving. [Solution] A tire comprising a tread portion having a cap rubber layer and a carcass portion, wherein sustainable polyester cords are used as ply cords in the carcass ply that constitutes the carcass portion, and the product (tanδ × La) of the loss tangent tanδ of the cap rubber layer measured under the conditions of a temperature of 30°C, an initial strain of 5%, a dynamic strain of 1%, a frequency of 10 Hz, and a deformation mode of tension, and the land ratio La (%) calculated from the contact area of ​​the tread portion satisfies the following formula: tanδ×La≦15

Description

[Technical Field]

[0001] The present invention relates to a tire. [Background technology]

[0002] In recent years, there has been a strong demand for reducing environmental impact and saving resources, and the use of bio-derived cords, recycled cords, etc. (sustainable cords) as ply cords for the carcass ply that constitutes the carcass portion of a tire has been considered (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-23658 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to suppress heat generation during running of a tire that uses sustainable cords for the ply cords of the carcass ply. [Means for solving the problem]

[0005] The present invention provides A tire comprising a tread portion having a cap rubber layer and a carcass portion, A sustainable polyester cord is used as a ply cord in the carcass ply that constitutes the carcass portion, The tire is characterized in that the product (tanδ × La) of the loss tangent tanδ of the cap rubber layer measured under the conditions of a temperature of 30°C, an initial strain of 5%, a dynamic strain of 1%, a frequency of 10 Hz, and a deformation mode of tension, and the land ratio La (%) calculated from the contact area of ​​the tread portion, satisfies the following formula: tanδ×La≦15 [Effects of the Invention]

[0006] According to the present invention, it is possible to suppress heat generation during running of a tire in which sustainable cords are used for the ply cords of the carcass ply. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic cross-sectional view illustrating the structure of a tire according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008] [1] Characteristics of the tire according to the present invention First, the features of the tire according to the present invention will be described.

[0009] 1. Overview The tire according to the present invention includes a tread portion having a cap rubber layer and a carcass portion, and sustainable polyester cords are used as ply cords in the carcass ply constituting the carcass portion. The product (tanδ × La) of the loss tangent tanδ of the cap rubber layer measured under the conditions of a temperature of 30°C, an initial strain of 5%, a dynamic strain of 1%, a frequency of 10 Hz, and a deformation mode of tension, and the land ratio La (%) calculated from the contact area of ​​the tread portion satisfies the following formula: tanδ×La≦15

[0010] These characteristics make it possible to suppress heat generation during running of a tire using sustainable cords for the ply cords, as will be described later.

[0011] 2. Mechanism of effect manifestation in the tire according to the present invention The mechanism by which the tire according to the present invention exerts its heat generation suppression effect during running is believed to be as follows.

[0012] (1) Use of sustainable cord in carcass ply In the present invention, as described above, sustainable polyester cords are used as ply cords in the carcass plies that constitute the carcass.

[0013] Here, "sustainable polyester cord" refers to cord made entirely or partially from sustainable polyester, such as recycled polyester reclaimed from plastic waste such as PET bottles or used clothing, or biopolyester produced using bio-derived raw materials, which can reduce environmental impact and conserve resources.

[0014] However, sustainable polyester cords may not be able to fully demonstrate their performance because their raw materials and / or manufacturing methods differ from those of general-purpose polyethylene terephthalate cords.

[0015] (2) Loss tangent of the cap rubber layer and land ratio Therefore, in the present invention, as described above, the product (tanδ × La) of the loss tangent tanδ of the cap rubber layer measured under the conditions of a temperature of 30°C, an initial strain of 5%, a dynamic strain of 1%, a frequency of 10 Hz, and a deformation mode of tension, and the land ratio La (%) calculated from the contact area of ​​the tread portion satisfies the following formula: tanδ×La≦15

[0016] The loss tangent is a viscoelastic parameter that indicates the energy absorption performance, and the larger the value of the loss tangent, the more the tire absorbs energy and the more likely it is to generate heat in the tread portion.

[0017] On the other hand, the land ratio is the ratio of the actual contact area to the virtual contact area where all the grooves on the surface of the tread are filled. If the land ratio is large, the area in contact with the road surface becomes larger, which causes friction with the road surface and makes the tread more likely to heat up.

[0018] Therefore, in the case of a cap rubber layer with a large loss tangent, it is believed that heat generation in the tread portion during running can be sufficiently suppressed by reducing the land ratio of the tread portion. Conversely, in the case of a tread portion with a large land ratio, it is believed that heat generation in the tread portion during running can be sufficiently suppressed by reducing the loss tangent of the cap rubber layer.

[0019] From the viewpoint of the effect of the present invention (suppression of heat generation during running), the above-mentioned (tan δ×La) is preferably 15 or less, 14 or less, 13 or less, 11 or less, or 10.5 or less. On the other hand, from another viewpoint (from the viewpoint of steering stability), it is preferably 1 or more, 5 or more, 9 or more, 10 or more, 10.5 or more, 11 or more, 13 or more, 14 or more, or 15 or more.

[0020] In the above, the loss tangent can be measured using a dynamic viscoelasticity measuring device (for example, the Iplexer series (registered trademark) manufactured by GABO) on a test piece of 20 mm in length, 4 mm in width, and 1 mm in thickness cut out from the cap rubber layer of the tread portion of the tire so that the long side is in the tire circumferential direction and the thickness direction is in the tire radial direction.

[0021] The loss tangent of the cap rubber layer can be adjusted as appropriate by adjusting, for example, the amount of styrene in the rubber component (polymer), the amount of filler such as silica or carbon black, the content of the softener component, and the content of the resin component in the rubber composition that constitutes the cap rubber layer.

[0022] Specifically, the loss tangent can be increased by, for example, increasing the amount of styrene in the rubber component (polymer), increasing the amount of filler such as silica or carbon black, reducing the content of softener components, or increasing the content of resin components. Conversely, the loss tangent can be decreased by, for example, decreasing the amount of styrene in the polymer, reducing the amount of filler such as silica or carbon black, increasing the content of softener components, reducing the amount of filler such as silica or carbon black, increasing the content of softener components, or reducing the content of resin components.

[0023] The land ratio can be determined from the contact shape of the tire under normal rim, normal internal pressure, and normal load conditions.

[0024] Specifically, a tire is mounted on a standard rim, pressurized to the standard internal pressure, and left to stand at 25°C for 24 hours. Then, ink is applied to the tire tread surface, and the standard load is applied and pressed onto cardboard (camber angle 0°). The contact shape can be obtained by transferring the tire to paper, and the tire is rotated 72° in circumferential directions, transferring the shape to five locations. In other words, five contact shapes are obtained. At this point, the five contact shapes are smoothly connected, with the grooves in the contact shape contours being smoothly joined, and the resulting shape is called the virtual contact surface.

[0025] The land ratio can be calculated by (average area of ​​five contact shapes (black parts) transferred to cardboard / average area of ​​virtual contact surface obtained from five contact shapes) x 100 (%).

[0026] In the above, "genuine rim" refers to the rim specified for each tire by the standard system, including the standard on which the tire is based. For example, for JATMA (Japan Automobile Tire Manufacturers Association), it refers to the standard rim for the applicable size listed in the "JATMA Year Book," for ETRTO (The European Tyre and Rim Technical Organization), it refers to the "Measuring Rim" listed in the "Standards Manual," and for TRA (The Tire and Rim Association, Inc.), it refers to the "Design Rim" listed in the "Year Book." JATMA, ETRTO, and TRA are referenced in that order, and if an applicable size is available at the time of reference, that standard is followed. For tires not specified in the standard, it refers to the rim that can be mounted on the rim and can maintain internal pressure, i.e., the rim with the smallest rim diameter and the next narrowest rim width, among rims that do not leak air from between the rim and tire.

[0027] As with "genuine rims," ​​"regular internal pressure" refers to the air pressure specified for each tire in the standard system, including the standard on which the tire is based. For JATMA, it refers to the maximum air pressure, for ETRTO, it refers to "INFLATION PRESSURE," and for TRA, it refers to the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." As with "genuine rims," ​​JATMA, ETRTO, and TRA are referenced in that order and the corresponding standards are followed. For tires not specified in the standard, it refers to the regular internal pressure (250 KPa or higher) of another tire size (specified in the standard) that is specified using the regular rim as the standard rim. Note that if multiple regular internal pressures of 250 KPa or higher are listed, it refers to the smallest value among them.

[0028] Furthermore, "normal load" refers to the load determined for each tire by each standard in the standard system, including the standard on which the tire is based, and refers to the maximum mass that can be loaded on the tire. In the case of JATMA, it refers to the maximum load capacity, in the case of ETRTO, it refers to the "LOAD CAPACITY", and in the case of TRA, it refers to the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES". As with the above-mentioned "normal rim" and "normal internal pressure", JATMA, ETRTO, and TRA are referenced in that order and their standards are followed. In the case of tires not specified in the standard, the normal load W is calculated as follows: L Ask for. V={(Dt / 2) 2 -(Dt / 2-Ht) 2}×π×Wt W L =0.000011×V+175 W L :Normal load (kg) V: Virtual volume of the tire (mm 3 ) Dt: Tire outer diameter (mm) Ht: tire section height (mm) Wt: tire cross-sectional width (mm)

[0029] [2] More preferred embodiments of the tire according to the present invention The tire according to the present invention can achieve even greater effects by adopting the following aspects.

[0030] 1. Multi-layered tread In the present invention, the tread portion may be formed of only one layer, the cap rubber layer, or may be formed of two layers by providing a base rubber layer inside the cap rubber layer, or may be formed of three layers, or may be formed of four or more layers.

[0031] When the tread portion is multi-layered in this way, the thickness of the cap rubber layer in the entire tread portion is preferably 10% or more, more preferably 70% or more, and even more preferably 80% or more. In addition, in consideration of suppressing heat accumulation inside the tire and suppressing a temperature rise in the cap rubber layer, it is preferable that the loss tangent of the base rubber layer is smaller than that of the cap rubber layer.

[0032] The thickness ratio of the cap rubber layer to the entire tread portion can be calculated by determining the thickness of the cap rubber layer and the thickness of the base rubber layer in the thickness of the tread portion. If a groove exists on the tire equatorial plane, it can be determined by calculating the thickness of the cap rubber layer and the thickness of the base rubber layer at the center of the land portion of the tread portion closest to the equatorial plane.

[0033] The tread portion is a component that forms the contact patch of the tire, and refers to the portion radially outward of components that contain fiber materials such as the carcass, belt layer, belt reinforcing layer, etc. The thickness of the tread portion can be measured by aligning the bead portion with the normal rim width in a cross section cut out in the radial direction of the tire.

[0034] 2. Ply cord and its characteristics (1)Material In the present invention, sustainable polyester cords are used as ply cords, and among various sustainable polyester cords, sustainable polyethylene terephthalate (PET) cords are preferably used. Among sustainable cords with low modulus, sustainable polyethylene terephthalate (PET) cords are preferred as ply cords because they are a highly rigid material.

[0035] (2) Cord diameter As described above, in the present invention, heat generation in the tread portion during running is suppressed by controlling (tan δ×La) to be 15 or less (tan δ×La≦15), but the diameter of the sustainable cord also affects heat generation in the tread portion during running.

[0036] That is, when the diameter of the sustainable cord is small, the tread portion is prone to heat generation, and when the diameter is large, the tread portion is less prone to heat generation.

[0037] Taking this into consideration, and considering the relationship between the diameter of the sustainable cord and (tan δ × La), the ratio ((tan δ × La) / F) of (tan δ × La) to the diameter F (mm) of the sustainable cord is preferably less than 26, less than 25, less than 24, less than 21.5, less than 21, less than 20.6, less than 19.2, or less than 15.5 from the viewpoint of the effects of the present invention (suppression of heat generation during running), and is preferably greater than 1, greater than 5, greater than 10, greater than 14.2, or greater than 15.4. From another viewpoint (durability), it is preferably less than 15.5 or less than 14.3, and from yet another viewpoint (ride comfort), it is preferably greater than 15.4, greater than 19.1, greater than 20.5, greater than 21.4, or greater than 25.

[0038] The diameter of the sustainable cord described above refers to the diameter when the circumscribing circle of the cross section perpendicular to the extension direction of the cord is a perfect circle, and in the case of an ellipse or the like, refers to the equivalent circle diameter (the diameter of a circle when a perfect circle with the same cross-sectional area is assumed).

[0039] In the present invention, the diameter of the sustainable cord is preferably 0.55 mm or more, and more preferably 0.68 mm or more, while the upper limit is preferably 0.98 mm or less, for example.

[0040] (3) Isophthalic acid content When the sustainable polyester cord is a recycled polyester cord regenerated from PET fibers or PET bottles, isophthalic acid may be contained as an impurity, which may destabilize the quality of the sustainable polyester cord. Therefore, the isophthalic acid content in the sustainable polyester cord is preferably less than 0.1 mol%, and 0.0 mol% is particularly preferred. This is believed to result in a sustainable polyester cord of stable quality and stable suppression of heat generation during driving. The isophthalic acid content of the sustainable polyester cord can be measured, for example, by high-performance liquid chromatography (HPLC).

[0041] The relationship between the isophthalic acid content IF (mol %) in the sustainable polyester cord and the above-mentioned ((tan δ×La) / F), ((tan δ×La) / F), is preferably 0.3 or less, 0.25 or less, 0.21 or less, 0.20 or less, 0.19 or less, 0.16 or less, or 0.15 or less from the viewpoint of the effect of the present invention (suppression of heat generation during running), and is preferably 0.1 or more, 0.14 or more, or 0.15 or more. From another viewpoint (durability), it is preferably 0.15 or less, or 0.14 or less. From another viewpoint (ride comfort), it is preferably 0.14 or more, 0.15 or more, 0.19 or more, 0.20 or more, 0.21 or more, or 0.25 or more.

[0042] (4) Strength (tensile strength) The strength S (cN / dtex) of the sustainable polyester cord is preferably 6.0 cN / dtex or more. This allows the carcass to absorb deformation of the tread portion during high-speed running, which is thought to further suppress heat generation during running of the tire. 6.3 cN / dtex or more is more preferable. The upper limit is, for example, preferably 7.0 cN / dtex or less, and more preferably 6.7 cN / dtex or less.

[0043] The strength can be measured in accordance with the method specified in "8.5 Tensile strength and elongation" of JIS L1017:2002 "Test methods for synthetic fiber tire cords" (grab interval 250 mm, pulling speed 300 mm / min).

[0044] In the present invention, the total fineness (dtex) of the sustainable polyester cord is preferably 2200 dtex or more, and more preferably 3340 dtex or more, while the upper limit is preferably, for example, 6600 dtex or less.

[0045] The total fineness of a sustainable polyester cord is the sum of the finenesses of each yarn, including the polyester fiber, that make up the cord, measured in accordance with the method specified in "8.3 Correct fineness" of JIS L1017:2002 "Test methods for synthetic fiber tire cords." For a cord made of a single yarn, the total fineness is equivalent to the fineness of that single yarn, and for a cord made of multiple yarns, the total fineness is equivalent to the sum of the finenesses of the multiple yarns.

[0046] For example, the total fineness of a cord structure of 1700 dtex / 1 (a cord made up of only single yarns with a fineness of 1700 dtex) is 1700 dtex, and the total fineness of a cord structure of 1700 dtex / 2 (a cord made up of two single yarns with a fineness of 1700 dtex twisted together) is 3400 dtex.

[0047] In the present invention, the strength S (cN / dtex), the content IF (mol %) of isophthalic acid in the sustainable polyester cord, and the loss tangent tanδ of the cap rubber layer preferably satisfy the following formulas. S×IF / tanδ≧50

[0048] This is believed to make it possible to reduce manufacturing costs while achieving a longer tire life. It is more preferably 55 or greater, and even more preferably 60 or greater. There is no particular upper limit, but it is preferably less than 200, and more preferably less than 150, for example.

[0049] (5) Ends and Strength The product (S×D) of the strength S (cN / dtex) of the sustainable polyester cord and the number (ends) D (ends / 5cm) of the ply cords (sustainable polyester cords) in the tread portion present in a width of 5cm in a direction perpendicular to the longitudinal direction of the cords is preferably 160 or more (S×D≧160). This allows the carcass portion to adequately absorb deformation of the tread portion during high-speed running, which is thought to further suppress heat generation during running of the tire. It is more preferably 190 or more, 192 or more, or 214 or more. On the other hand, from another perspective (durability), it is preferably 250 or less, 220 or less, 215 or less, or 193 or less.

[0050] In the present invention, the ends of the ply cord are preferably 32 cords / 5 cm or more.

[0051] (6) Intermediate elongation and ends It is preferable that the following formula be satisfied between the intermediate elongation E (%) at a specified load L (cN / dtex) of the sustainable polyester cord and the ends D (ends / 5 cm). 12≦L×D / E≦20

[0052] By appropriately controlling (L×D / E), deformation of the tread portion during high-speed running can be sufficiently absorbed by the carcass portion, which is thought to further suppress heat generation during running of the tire. The lower limit is more preferably 13.6 or more, 14 or more, 14.8 or more, or 14.9 or more. On the other hand, the upper limit is more preferably 15 or less, 14.9 or less, or 13.7 or less.

[0053] The intermediate elongation can be measured in accordance with the test method for "elongation under constant load" in JIS L1017:2002 "Test methods for synthetic fiber tire cords."

[0054] Specifically, when the specified load L described in the next paragraph is 2.0 cN / dtex, the intermediate elongation can be determined by taking a single cord from a vulcanized tire, conducting a tensile test at a temperature of 100±2°C, a gripping distance of 250 mm, and a pulling speed of 300±20 mm / min, and calculating the elongation (%) at a point on the load-elongation curve corresponding to a load of 2.0 cN / dtex.

[0055] In the present invention, the intermediate elongation when the specified load L is 2.0 cN / dtex is preferably 4.3% or more, while the upper limit is preferably, for example, 4.7% or less.

[0056] (7) Breaking Elongation The breaking elongation (%) of the sustainable polyester cord is preferably 10% or more. This is thought to enable the carcass to adequately absorb deformation of the tread portion during high-speed running, further suppressing heat generation during running of the tire. A breaking elongation of 12% or more is more preferable, and a breaking elongation of 13% or more is even more preferable.

[0057] The breaking elongation can be measured in accordance with the method specified in "8.5 Tensile strength and elongation" of JIS L1017:2002 "Testing methods for synthetic fiber tire cords" (grab interval 250 mm, pulling speed 300 mm / min).

[0058] (8) Moisture and heat resistance strength retention rate The moist heat resistance strength retention rate (%) of the sustainable polyester cord is preferably 80% or more. This is thought to enable heat generation during driving to be suppressed for a long period of time. 85% or more is more preferable, and 90% or more is even more preferable.

[0059] The above-mentioned moist heat resistance strength retention rate can be determined by calculating the ratio of the strength after treatment with saturated steam at 135° C. for 48 hours (moist heat treatment) to the strength before treatment.

[0060] 3. Flatness The aspect ratio is the ratio of the tire's cross-sectional height to its cross-sectional width, and by increasing the aspect ratio, the tire's contact area with the road surface can be reduced, thereby suppressing heat generation in the tread. On the other hand, if the aspect ratio is too high, it may result in a decrease in steering stability.

[0061] Considering these points, the specific aspect ratio of the tire according to the present invention is preferably 30% or more, and the upper limit is preferably 60% or less, and more preferably 55 or less.

[0062] The above aspect ratio (%) can be calculated using the following formula using the tire cross-sectional height Ht (mm), cross-sectional width Wt (mm), tire outer diameter Dt (mm), and rim diameter R (mm) when the internal pressure is set to 250 kPa. Oblateness (%)=(Ht / Wt)×100(%) Ht=(Dt-R) / 2

[0063] 4. Land Ratio and Loss Tangent As mentioned above, in the present invention, tan δ×La is controlled to a small value of 15 or less (tan δ×La≦15), but when assembled into a regular rim and under regular internal pressure, the specific land ratio La is preferably 55% or more, more preferably 60% or more. The upper limit is preferably 75% or less, more preferably 70% or less, and even more preferably 65% ​​or less.

[0064] The loss tangent tan δ of the cap rubber layer at a temperature of 30° C. is preferably 0.15 or more, while the upper limit is preferably 0.2 or less, for example.

[0065] [3] Implementation form The present invention will be specifically described below based on embodiments.

[0066] 1. Tire according to this embodiment FIG. 1 is a schematic cross-sectional view illustrating the structure of a tire according to this embodiment, showing a tire meridian cross-section including the rotation axis of the tire in a normal state.

[0067] As shown in Fig. 1, the tire 1 includes a carcass 6 extending from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, and a belt layer 7 disposed radially outward of the carcass 6 and inward of the tread portion 2. C denotes a centerline.

[0068] The carcass 6 is made up of at least one carcass ply 6A (one carcass ply in FIG. 1), and is secured by being folded from the inside to the outside around the bead cores 5 of the bead portions 4 through the tread portion 2 and the sidewall portions 3. In FIG. 1, 6a denotes an inner main body portion of the carcass ply 6A, and 6b denotes an outer folded portion. Between the inner main body portion 6a and the outer folded portion 6b, for example, a bead apex rubber 8 extending from the bead cores 5 radially outward is disposed.

[0069] In this embodiment, the carcass ply 6A uses sustainable polyester cords as ply cords, and is configured by covering both sides of a sustainable polyester cord arrangement body that is aligned at a predetermined end with covering rubber.

[0070] By constructing the carcass portion using such a carcass ply and appropriately controlling the loss tangent of the cap rubber layer and the land ratio of the tread portion, it is possible to suppress heat generation during driving of a tire using sustainable cords in the ply cords.

[0071] 2. Rubber composition forming the cap rubber layer (cap rubber composition) In this embodiment, the cap rubber composition can be obtained by kneading various compounding materials such as a rubber component, a reinforcing agent, an antioxidant, oil, a resin material, and an antioxidant.

[0072] (1) Compounding materials (a) Rubber component The rubber component is not particularly limited, and examples of diene rubbers that can be used include isoprene-based rubbers (natural rubber (NR), isoprene rubber (IR), etc.), styrene butadiene rubber (SBR), butadiene rubber (BR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), and butyl rubber (IIR). These may be used alone or in combination of two or more, and in the present invention, a combination of SBR with BR or isoprene-based rubber is preferred.

[0073] (a) SBR The weight-average molecular weight of SBR is, for example, more than 100,000 and less than 2,000,000. The styrene content of SBR is, for example, preferably more than 5% by mass, more preferably more than 10% by mass, and even more preferably more than 15% by mass. On the other hand, it is preferably less than 40% by mass, more preferably less than 35% by mass, and even more preferably less than 30% by mass. The vinyl content (amount of 1,2-bonded butadiene units) of SBR is, for example, preferably more than 5% by mass, more preferably more than 10% by mass, and even more preferably more than 15% by mass. On the other hand, it is preferably less than 70% by mass, more preferably less than 40% by mass, and even more preferably less than 30% by mass. SBR structural identification (measurement of styrene content and vinyl content) can be performed using, for example, a JNM-ECA series instrument manufactured by JEOL Ltd.

[0074] The SBR is not particularly limited, and examples thereof include emulsion-polymerized styrene-butadiene rubber (E-SBR) and solution-polymerized styrene-butadiene rubber (S-SBR). The SBR may be either unmodified or modified. Hydrogenated SBR, which is obtained by hydrogenating the butadiene portion of SBR, may also be used. Hydrogenated SBR may be obtained by subsequently hydrogenating the BR portion of SBR, or a similar structure may be obtained by copolymerizing styrene, ethylene, and butadiene.

[0075] The modified SBR is preferably an SBR having a functional group that interacts with a filler such as silica. Examples include terminal-modified SBR in which at least one terminal of the SBR has been modified with a compound (modifier) ​​having the above functional group (terminal-modified SBR having the above functional group at the terminal), main-chain-modified SBR in which the main chain has the above functional group, main-chain terminal-modified SBR in which the main chain and the terminals have the above functional group (for example, main-chain terminal-modified SBR in which the main chain has the above functional group and at least one terminal has been modified with the above modifier), and terminal-modified SBR in which the SBR has been modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and in which a hydroxyl group or epoxy group has been introduced.

[0076] Examples of the functional group include an amino group, an amide group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an imide group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group, an epoxy group, etc. These functional groups may have a substituent.

[0077] Furthermore, as the modified SBR, for example, SBR modified with a compound (modifying agent) represented by the following formula can be used.

[0078] [ka]

[0079] In the formula, R 1 , R 2 and R 3 R may be the same or different and represent 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 are the same or different and represent a hydrogen atom or an alkyl group. 4 and R 5 may bond to form a ring structure together with the nitrogen atom, and n represents an integer.

[0080] As the modified SBR modified with a compound (modifier) ​​represented by the above formula, SBR in which the polymerization terminals (active terminals) of solution-polymerized styrene-butadiene rubber (S-SBR) have been modified with a compound represented by the above formula (such as the modified SBR described in JP 2010-111753 A).

[0081] R 1 , R 2 and R 3R is preferably an alkoxy group (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 is preferably an alkyl group (preferably an alkyl group having 1 to 3 carbon atoms). n is preferably 1 to 5, more preferably 2 to 4, and even more preferably 3. In addition, R 4 and R 5 When the groups bond to form a ring structure together with the nitrogen atom, the ring is preferably a 4- to 8-membered ring. The alkoxy group also includes a cycloalkoxy group (such as a cyclohexyloxy group) and an aryloxy group (such as a phenoxy group or a benzyloxy group).

[0082] Specific examples of the modifying agent include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane, etc. These may be used alone or in combination of two or more.

[0083] Modified SBR may also be modified with the following compounds (modifiers): Examples of the modifier include 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 diglycidylated bisphenol A; polyepoxy compounds such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, and polyepoxidized liquid polybutadiene; epoxy group-containing tertiary amines such as 4,4'-diglycidyl-diphenylmethylamine and 4,4'-diglycidyl-dibenzylmethylamine; diglycidylaniline, N,N'-diglycidyl-4-glycidyloxyaniline; Diglycidyl amino compounds such as diglycidyl orthotoluidine, tetraglycidyl meta-xylenediamine, tetraglycidyl aminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidyl aminomethylcyclohexane, and tetraglycidyl-1,3-bisaminomethylcyclohexane; amino group-containing acid chlorides such as bis-(1-methylpropyl)carbamic acid chloride, 4-morpholinecarbonyl chloride, 1-pyrrolidinecarbonyl chloride, N,N-dimethylcarbamic acid chloride, and N,N-diethylcarbamic acid 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-(trippropoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(tributoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldiethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldipropoxy sulfide group-containing silane compounds such as (trimethylsilyl)[3-(methyldibutoxysilyl)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)aminoethyltrimethoxysilane, Alkoxysilanes such as thyltriethoxysilane; (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; and 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-trione , 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-dimethylaminoacetophen, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenylamino)-2-propanone, 1,7-bis(methylethylamino)-4-heptanone, etc. Modification with the above compounds (modifiers) can be carried out by known methods.

[0084] As the SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., ENEOS Material Corporation, Asahi Kasei Corporation, Zeon Corporation, etc. can be used. The SBR may be used alone or in combination of two or more types.

[0085] The amount of SBR in 100 parts by mass of the rubber component is preferably 60 parts by mass or more, and more preferably 70 parts by mass or more, and the upper limit is, for example, preferably 90 parts by mass or less, and more preferably 80 parts by mass or less.

[0086] (b)BR The weight-average molecular weight of the BR is, for example, more than 100,000 and less than 2,000,000. The vinyl content of the BR is, for example, more than 1% by mass and less than 30% by mass. The cis content of the BR is, for example, more than 1% by mass and not more than 98% by mass. The trans content of the BR is, for example, more than 1% by mass and less than 60% by mass. The cis content can be measured by infrared absorption spectroscopy.

[0087] The BR is not particularly limited, and can be a BR with a high cis content (cis content of 90% or more), a BR with a low cis content, a BR containing syndiotactic polybutadiene crystals, etc. The BR can be either unmodified or modified, and the modified BR can be, for example, BR modified with a compound (modifier) ​​represented by the following formula:

[0088] [ka]

[0089] In the formula, R 1 , R 2 and R 3 R may be the same or different and represent 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 are the same or different and represent a hydrogen atom or an alkyl group. 4 and R 5 may bond to form a ring structure together with the nitrogen atom, and n represents an integer.

[0090] The modified BR modified with the compound (modifying agent) represented by the above formula includes BR whose polymerization terminal (active terminal) has been modified with the compound represented by the above formula.

[0091] R 1 , R 2 and R 3 R is preferably an alkoxy group (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 is preferably an alkyl group (preferably an alkyl group having 1 to 3 carbon atoms). n is preferably 1 to 5, more preferably 2 to 4, and even more preferably 3. In addition, R 4 and R 5When the groups bond to form a ring structure together with the nitrogen atom, the ring is preferably a 4- to 8-membered ring. The alkoxy group also includes a cycloalkoxy group (such as a cyclohexyloxy group) and an aryloxy group (such as a phenoxy group or a benzyloxy group).

[0092] Specific examples of the modifying agent include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane, etc. These may be used alone or in combination of two or more.

[0093] The modified BR may also be modified with the following compounds (modifiers): Examples of the modifier include 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 diglycidylated bisphenol A; polyepoxy compounds such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, and polyepoxidized liquid polybutadiene; epoxy group-containing tertiary amines such as 4,4'-diglycidyl-diphenylmethylamine and 4,4'-diglycidyl-dibenzylmethylamine; diglycidylaniline, N,N'-diglycidyl-4-glycidyloxyaniline; Diglycidyl amino compounds such as diglycidyl orthotoluidine, tetraglycidyl meta-xylenediamine, tetraglycidyl aminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidyl aminomethylcyclohexane, and tetraglycidyl-1,3-bisaminomethylcyclohexane; amino group-containing acid chlorides such as bis-(1-methylpropyl)carbamic acid chloride, 4-morpholinecarbonyl chloride, 1-pyrrolidinecarbonyl chloride, N,N-dimethylcarbamic acid chloride, and N,N-diethylcarbamic acid 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-(trippropoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(tributoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldiethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldipropoxy sulfide group-containing silane compounds such as (trimethylsilyl)[3-(methyldibutoxysilyl)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)aminoethyltrimethoxysilane, Alkoxysilanes such as thyltriethoxysilane; (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-trione , 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-dimethylaminoacetophen, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenylamino)-2-propanone, 1,7-bis(methylethylamino)-4-heptanone, etc. Modification with the above compounds (modifiers) can be carried out by known methods. These modified BRs may be used alone or in combination of two or more.

[0094] As the BR, for example, products from Ube Industries, Ltd., ENEOS Materials Corporation, Asahi Kasei Corporation, Zeon Corporation, etc. can be used.

[0095] The amount of BR in 100 parts by mass of the rubber component is preferably 5 parts by mass or more, more preferably 15 parts by mass or more, and is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, and even more preferably 20 parts by mass or less.

[0096] (c) Isoprene rubber Examples of isoprene-based rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR.

[0097] Examples of NR that can be used include those commonly used in the tire industry, such as SIR20, RSS#3, TSR20, and SVR-L. Examples of IR are not particularly limited, and examples of IR that can be used include those commonly used in the tire industry, such as IR2200. Examples of modified NR include deproteinized natural rubber (DPNR) and highly purified 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 alone or in combination of two or more.

[0098] The amount of the isoprene-based rubber per 100 parts by mass of the rubber component is preferably 5 parts by mass or more, and more preferably 15 parts by mass or more, and is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, and even more preferably 20 parts by mass or less.

[0099] (d) Other rubber components The cap rubber composition may contain, as other rubber components, rubbers (polymers) that are generally used in the production of tires, such as nitrile rubber (NBR), as needed.

[0100] The raw materials (monomers) of the above-mentioned synthetic rubbers such as SBR and BR may be derived from underground resources such as petroleum and natural gas, or may be recycled from rubber products such as tires or non-rubber products such as polystyrene.

[0101] Monomers obtained by recycling (recycled monomers) are not particularly limited, and examples thereof include recycled isoprene, recycled butadiene, and recycled aromatic vinyl. Examples of butadienes include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyls include, but are not particularly limited to, styrene. Among these, it is preferable to use recycled isoprene (recycled isoprene), butadiene (recycled butadiene), and / or recycled styrene (recycled styrene) as raw materials.

[0102] The method for producing the recycled monomer is not particularly limited, and examples thereof include synthesis from recycled naphtha obtained by decomposing rubber products such as tires. The method for producing recycled naphtha is also not particularly limited, and examples thereof include decomposing rubber products such as tires under high temperature and pressure, decomposing with microwaves, or mechanically crushing and then extracting.

[0103] Furthermore, the raw materials (monomers) of synthetic rubbers such as IR, SBR, and BR may be derived from biomass. In this specification, biomass refers to materials derived from natural resources such as plants. Examples of biomass include, but are not limited to, agricultural, forestry, and fishery products, sugar, wood chips, plant residues after useful components have been extracted, plant-derived ethanol, and biomass naphtha.

[0104] Monomers derived from biomass (biomass monomers) are not particularly limited and include biomass-derived butadiene and biomass-derived aromatic vinyl. Examples of butadienes include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyls include, but are not limited to, styrene. The method for producing biomass monomers is not particularly limited and includes, for example, biological and / or chemical and / or physical conversion of animals and plants. A representative example of biological conversion is fermentation by microorganisms, and examples of chemical and / or physical conversion include catalytic conversion, high heat conversion, high pressure conversion, electromagnetic wave conversion, critical fluid conversion, and combinations thereof.

[0105] The polymer synthesized from a biomass monomer component (biomass polymer) is not particularly limited, and examples thereof include polybutadiene rubber synthesized from biomass-derived butadiene, and aromatic vinyl / butadiene copolymer synthesized from biomass-derived butadiene and / or biomass-derived aromatic vinyl. Examples of the aromatic vinyl / butadiene copolymer include styrene-butadiene rubber synthesized from biomass-derived butadiene and / or biomass-derived styrene.

[0106] Whether the raw material of a polymer is derived from biomass can be determined by the pMC (percent modern carbon) measured in accordance with ASTM D6866-10.

[0107] pMC is the modern standard reference 14 of sample against C concentration 14 This is the ratio of C concentrations and is a value used as an index of the biomass ratio of a compound. The significance of this value is explained below.

[0108] 1 mole of carbon atoms (6.02 × 10 23 ) contains approximately 6.02 × 10 atoms, which is about one trillionth of the number of ordinary carbon atoms. 11 pieces 14C exists. 14 C is called a radioactive isotope, and its half-life is 5,730 years, and it decreases regularly. It takes 226,000 years for all of it to decay. Therefore, in fossil fuels such as coal, oil, and natural gas, which are thought to have been absorbed and fixed by plants and other organisms more than 226,000 years ago, C was also included in these when it was first fixed. 14 All C elements have decayed. Therefore, in the 21st century, fossil fuels such as coal, oil, and natural gas contain 14 Therefore, chemicals produced from these fossil fuels do not contain any C element. 14 It does not contain any C element.

[0109] on the other hand, 14 C is produced continuously by nuclear reactions in the atmosphere caused by cosmic rays, and in the Earth's atmospheric environment, the amount of C is balanced by the decrease caused by radioactive decay. 14 Therefore, the amount of carbon derived from biomass resources currently circulating in the environment is constant. 14 As mentioned above, the C concentration is approximately 1 × 10 -12 The value is approximately mol %. Therefore, the biomass ratio in a compound can be calculated by using the difference between these values.

[0110] this 14 C is typically measured using accelerator mass spectrometry based on a tandem accelerator. 13 C concentration ( 13 C / 12 C). 14 C concentration ( 14 C / 12 C) is measured. 14 The modern standard reference for the C concentration is the carbon circulating in nature as of 1950. 14The specific standard substance used is the oxalic acid standard provided by NIST (National Institute of Standards and Technology). The specific activity of carbon in this oxalic acid (per gram of carbon) is 14 The radioactivity of C is separated into carbon isotopes, 13 The standard value is the value corrected for decay from 1950 to the measurement date. 14 This is used as the C concentration value (100%). The ratio of this value to the value of the actually measured sample is the pMC value.

[0111] Therefore, if rubber is made from 100% biomass-derived materials, although there are regional differences, it will usually not reach 100 under normal conditions, so it will show a value of approximately 110 pMC. On the other hand, for chemical substances derived from petroleum and other fossil fuels, 14 When the carbon concentration is measured, it will show a value of about 0 pMC (for example, 0.3 pMC), which corresponds to the biomass ratio of 0% mentioned above.

[0112] From the above, it is preferable from the viewpoint of environmental protection (sustainability) to use materials such as rubber with a high pMC value, that is, materials such as rubber with a high biomass ratio (sustainable materials) in a rubber composition.

[0113] (b) Compounding materials other than rubber components (a) Filler The cap rubber composition preferably contains silica or carbon black as a reinforcing agent, but may also contain other fillers, such as calcium carbonate, talc, alumina, clay, aluminum hydroxide, mica, vulcanized rubber particles (rubber powder), etc. When silica is used, it is preferably used in combination with a silane coupling agent.

[0114] (i) Silica Silica has OH groups on its surface and can capture ozone, improving ozone resistance and tire durability. By adding a large amount of silica, such as more than 75 parts by mass, hydrogen bonds are formed on the silica surface and also interact with the rubber component.

[0115] The BET specific surface area of ​​silica is 100m from the viewpoint of obtaining good durability. 2 / g, and preferably greater than 130m 2 / g. On the other hand, it is more preferable that the 2 / g, and preferably less than 200m 2 / g or less is more preferable, and 175m 2 / g or less. The BET specific surface area is the N2SA value measured by the BET method in accordance with ASTM D3037-93.

[0116] The silica is not particularly limited, and for example, silica prepared by a dry method (anhydrous silica) or silica prepared by a wet method (hydrated silica) that is commonly used in the tire industry can be used. Commercially available products that can be used include those from Evonik Industries, Rhodia, Tosoh Silica Corporation, Solvay Japan, Tokuyama Corporation, etc.

[0117] The raw material for silica is not particularly limited, and may be, for example, a mineral-derived raw material such as quartz, a biological raw material such as rice husk (for example, silica made from biomass materials such as rice husk), or silica recycled from a product containing silica. Among them, hydrated silica prepared by a wet method is preferred because it contains a large number of silanol groups. These silicas may be used alone or in combination of two or more.

[0118] Silica made from biomass materials (biomass silica) can be obtained, for example, by extracting silicate from rice husk ash obtained by burning rice husks using a sodium hydroxide solution, and then using this silicate to react with sulfuric acid, as in conventional wet silica, to produce a silicon dioxide precipitate, which is then filtered, washed with water, dried, and pulverized.

[0119] Silica recycled from silica-containing products (recycled silica) can be silica recovered from products containing silica, such as electronic components such as semiconductors, tires, desiccants, and filtering materials such as diatomaceous earth. The recovery method is not particularly limited, and examples include thermal decomposition and decomposition by electromagnetic waves. Among these, silica recovered from electronic components such as semiconductors or tires is preferred.

[0120] When silica crystallizes, it becomes insoluble in water, and its component, silicic acid, cannot be utilized. By controlling the combustion temperature and duration, it is possible to suppress the crystallization of silica in rice husk ash (see, for example, JP 2009-2594 A and Akita Prefectural University Web Journal B / 2019, vol. 6, pp. 216-222).

[0121] Amorphous silica extracted from rice husks may be commercially available from Wilmar Co., Ltd., etc.

[0122] These silicas may be used alone or in combination of two or more. From the viewpoint of environmental protection, it is preferable to use sustainable silica such as biomass silica obtained from biomass as a raw material or recycled silica obtained by recycling used goods or waste materials.

[0123] The content of silica per 100 parts by mass of the rubber component is preferably more than 60 parts by mass, more preferably 70 parts by mass or more, and even more preferably 80 parts by mass or more. The upper limit is, for example, preferably 120 parts by mass or less, and more preferably 100 parts by mass or less.

[0124] (ii) Silane coupling agent When silica is used, it is preferable to use a silane coupling agent in combination in order to enhance the dispersibility of the silica and also to improve the mechanical properties and moldability by reacting with the silica.

[0125] The silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, and bis(4-trimethoxysilylbutyl)trisulfide. Sulfide, 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-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilyl Examples of suitable silane coupling agents include sulfide-based silanes such as ethyl-N,N-dimethylthiocarbamoyl tetrasulfide and 3-triethoxysilylpropyl methacrylate monosulfide, mercapto-based silanes such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and Momentive's NXT and NXT-Z, vinyl-based silanes such as vinyltriethoxysilane and vinyltrimethoxysilane, amino-based silanes such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane, glycidoxy-based silanes such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane, nitro-based silanes such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane, and chloro-based silanes such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Among these, silane coupling agents having a thiocarbonyl group, such as the above-mentioned NXT, are preferred. These silane coupling agents may be used alone or in combination of two or more.

[0126] As the silane coupling agent, for example, products from Evonik Industries, Momentive, Shin-Etsu Silicones Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Dow Corning Toray Co., Ltd., etc. can be used.

[0127] The content of the silane coupling agent is, for example, preferably more than 3 parts by mass, more preferably 5 parts by mass or more, even more preferably 7 parts by mass or more, and even more preferably 8 parts by mass or more, relative to 100 parts by mass of silica. The upper limit is, for example, preferably less than 15 parts by mass, more preferably 12 parts by mass or less, and even more preferably 9 parts by mass or less.

[0128] (iii) Carbon black Carbon black is preferably used for the purpose of improving the crack growth resistance, durability, resistance to ultraviolet degradation, etc. of the tire.

[0129] From the viewpoint of reinforcing properties for rubber, the nitrogen adsorption specific surface area (N2SA) of carbon black is, for example, 30m 2 / g or more, and 2 / g or more is more preferable, and 60m 2 On the other hand, from the viewpoint of heat buildup, it is more preferable that the solubility is 250m / g or more. 2 / g or less, and 150m 2 / g or less is more preferable, and 120m 2 / g or less is more preferable, and 2 The nitrogen adsorption specific surface area of ​​carbon black is measured in accordance with ASTM D4820-93.

[0130] From the viewpoint of rubber rigidity, the dibutyl phthalate (DBP) absorption of carbon black is preferably, for example, 50 ml / 100 g or more, and more preferably 100 ml / 100 g or more. On the other hand, from the viewpoint of rubber deformation compliance, it is preferably 250 ml / 100 g or less, and more preferably 150 ml / 100 g or less. The DBP absorption of carbon black is measured according to ASTM D2414-93.

[0131] The carbon black is not particularly limited, and examples thereof include furnace blacks (furnace carbon black) such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, and ECF; acetylene black (acetylene carbon black); thermal blacks (thermal carbon black) such as FT and MT; and channel blacks (channel carbon black) such as EPC, MPC, and CC, and examples of product numbers include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. These may be used alone or in combination of two or more.

[0132] In addition to mineral oil, the raw material for carbon black may be a biomass material such as lignin or vegetable oil, or a recycled material such as pyrolysis oil obtained by pyrolyzing rubber products such as waste tires. From the viewpoint of environmental protection, it is preferable to use sustainable carbon black, such as biomass carbon black made from biomass materials or recycled carbon black made from recycled materials such as used goods and waste materials.

[0133] The carbon black may be produced by combustion such as a furnace method, by hydrothermal carbonization (HTC), or by thermal decomposition of methane such as a thermal black method.

[0134] Commercially available products include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., Columbia Carbon Co., Ltd., etc. These may be used alone or in combination of two or more.

[0135] The amount of carbon black per 100 parts by mass of the rubber component is preferably 3 parts by mass or more, and more preferably 5 parts by mass or more, and the upper limit is, for example, preferably 15 parts by mass or less, and more preferably 10 parts by mass or less.

[0136] (iv) Other fillers In addition to the above-mentioned carbon black and silica, the cap rubber composition may further contain fillers commonly used in the tire industry, such as graphite, calcium carbonate, talc, alumina, clay, aluminum hydroxide, mica, magnesium sulfate, etc. The content of these fillers is, for example, more than 0.1 parts by mass and less than 150 parts by mass per 100 parts by mass of the rubber component.

[0137] (b) Softener (plasticizer) component In order to impart plasticity to the rubber component during kneading and to properly disperse the powder material, it is preferable to use a softener (plasticizer) component as needed in the cap rubber composition. Note that the term "softener component" as used herein encompasses both softeners that are liquid at 25°C and softeners that are solid at 25°C.

[0138] Examples of softeners include resin components, oils, liquid polymers, and ester-based plasticizers. These softeners may be derived from mineral resources such as petroleum and natural gas, biomass-derived, or naphtha recycled from rubber or non-rubber products. Low-molecular-weight hydrocarbon components obtained by pyrolysis and extraction of used tires or products containing various components may also be used as softeners. Among these, biomass-derived and recycled softeners are preferred as sustainable softeners.

[0139] These softeners may be used alone or in combination of two or more. The content of the softener component per 100 parts by mass of the rubber component is preferably 20 parts by mass or more, and more preferably 30 parts by mass or more. The upper limit is, for example, preferably 80 parts by mass or less, more preferably 70 parts by mass or less, and even more preferably 65 parts by mass or less. The content of the softener component also includes the amount of oil contained in the rubber (oil-extended rubber) etc.

[0140] (i) Oil Examples of oils include mineral oil, vegetable oil, animal oil, etc. From the viewpoint of life cycle assessment, waste oils used in rubber mixers or engines, or refined waste cooking oils used in restaurants may also be used.

[0141] (i-1) Mineral oil In this specification, mineral oil refers to oil derived from mineral resources such as petroleum, natural gas, etc. Examples of mineral oil include paraffinic oil (mineral oil), naphthenic oil, and aromatic oil.

[0142] Specific examples of mineral oils include MES (Mild Extract Solvated), DAE (Distillate Aromatic Extract), TDAE (Treated Distillate Aromatic Extract), TRAE (Treated Residual Aromatic Extract), and RAE (Residual Aromatic Extract).

[0143] Additionally, to address environmental concerns, oils with low polycyclic aromatic compound (PCA) content can be used, such as MES, TDAE, and heavy naphthenic oils.

[0144] Examples of commercially available mineral oils include paraffinic, aromatic, and naphthenic oils, and usable products include those from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Orisoi Co., Ltd., H&R Corporation, Toyokuni Oil Mills Co., Ltd., Showa Shell Sekiyu K.K., and Fuji Kosan Co., Ltd. These may be used alone or in combination of two or more.

[0145] (i-2) Vegetable oil Examples of vegetable oils include linseed oil, rapeseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, rice bran oil, tall oil, sesame oil, perilla oil, castor oil, tung oil, pine oil, pine tar oil, sunflower oil, coconut oil, palm oil, palm kernel oil, olive oil, camellia oil, jojoba oil, macadamia nut oil, peanut oil, grapeseed oil, and wood wax.

[0146] Further examples of vegetable oils include refined oils (such as salad oil) obtained by refining the above oils, interesterified oils, hydrogenated hardened oils, thermally polymerized oils, oxidatively polymerized oils, and waste edible oils recovered from those used as edible oils. Vegetable oils may be liquid or solid at room temperature (25°C). These may be used alone or in combination of two or more.

[0147] The vegetable oil preferably contains acylglycerol, and more preferably triacylglycerol. Acylglycerol refers to a compound in which a hydroxyl group of glycerin is ester-bonded to a fatty acid. The acylglycerol is not particularly limited, and may be 1-monoacylglycerol, 2-monoacylglycerol, 1,2-diacylglycerol, 1,3-diacylglycerol, or triacylglycerol. Furthermore, acylglycerol may be a monomer, a dimer, or a polymer (trimer or higher). Dimer or higher acylglycerols can be obtained by thermal polymerization, oxidative polymerization, or the like. Acylglycerol may be liquid or solid at room temperature (25°C).

[0148] The method for confirming whether or not acylglycerol is contained in the rubber composition is not particularly limited, but may be 1 For example, a rubber composition containing triacylglycerol is immersed in deuterated chloroform at room temperature (25°C) for 24 hours, and after removing the rubber composition, the rubber composition is immersed in deuterated chloroform at room temperature. 1 When H-NMR was measured, signals were observed around 5.26 ppm, 4.28 ppm, and 4.15 ppm when the signal of tetramethylsilane (TMS) was set at 0.00 ppm. These signals are presumed to be signals derived from hydrogen atoms bonded to the carbon atoms adjacent to the oxygen atoms of the ester groups, and therefore the presence of acylglycerol can be confirmed. Here, "around" refers to a range of ±0.10 ppm.

[0149] The fatty acid is not particularly limited and may be either an unsaturated fatty acid or a saturated fatty acid. Examples of unsaturated fatty acids include monounsaturated fatty acids such as oleic acid, and polyunsaturated fatty acids such as linoleic acid and linolenic acid. Examples of saturated fatty acids include butyric acid and lauric acid.

[0150] Among these, it is desirable that the fatty acid contains a fatty acid with few double bonds, i.e., a saturated fatty acid or a monounsaturated fatty acid, and oleic acid is preferred. As a vegetable oil containing such a fatty acid, for example, vegetable oil containing a saturated fatty acid or a monounsaturated fatty acid may be used, or vegetable oil modified by ester exchange or the like may be used. Furthermore, in order to produce vegetable oil containing such a fatty acid, plants may be improved by breeding, genetic modification, genome editing, or the like.

[0151] As the vegetable oil, for example, commercially available products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Orisoi Co., Ltd., H&R Corporation, Toyokuni Oil Mills Co., Ltd., Fuji Kosan Co., Ltd., Nisshin Oillio Group Co., Ltd., etc. can be used.

[0152] (ii) Liquid rubber Liquid rubber is a polymer that is in a liquid state at room temperature (25°C) and is a rubber component that can be extracted by acetone extraction from a vulcanized tire. Examples of liquid rubber include farnesene-based polymers, liquid diene-based polymers, and hydrogenated products thereof.

[0153] Farnesene polymers are polymers obtained by polymerizing farnesene, which has structural 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).

[0154] The farnesene-based polymer may be a homopolymer of farnesene (farnesene homopolymer) or a copolymer of farnesene and a vinyl monomer (farnesene-vinyl monomer copolymer).

[0155] 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).

[0156] The liquid diene polymer has a weight average molecular weight (Mw) of, for example, 1.0 × 10 in terms of polystyrene measured by gel permeation chromatography (GPC). 3 Super, 2.0×10 5 Here, the Mw of the liquid diene polymer is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

[0157] As the liquid rubber, for example, products of Kuraray Co., Ltd., Cray Valley Co., Ltd., etc. can be used.

[0158] (iii) Resin component The cap rubber composition preferably contains a resin component, which is believed to reduce the loss tangent and thereby sufficiently suppress heat generation in the tread portion during running.

[0159] The resin component also functions as a tackifier and may be solid or liquid at room temperature. Specific examples of the resin component include rosin resins, styrene resins, coumarone resins, terpene resins, C5 resins, C9 resins, C5C9 resins, and acrylic resins, and two or more of these may be used in combination. These resin components may be provided with a modifying group capable of reacting with silica, etc., as needed. The content of the resin component per 100 parts by mass of the rubber component is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and even more preferably 30 parts by mass or more. The upper limit is preferably 60 parts by mass or less, and more preferably 50 parts by mass or less.

[0160] Rosin-based resins are resins whose main component is rosin acid, which is obtained by processing pine resin. These rosin-based resins (rosins) can be classified based on whether they are modified or not, and can be divided into unmodified rosin (unmodified rosin) and modified rosin (rosin derivatives). Examples of unmodified rosins include tall rosin (also known as tall oil rosin), gum rosin, wood rosin, disproportionated rosin, polymerized rosin, hydrogenated rosin, and other chemically modified rosins. Modified rosin is a modification of unmodified rosin, and examples include rosin esters, unsaturated carboxylic acid-modified rosin esters, unsaturated carboxylic acid-modified rosin esters, rosin amide compounds, and rosin amine salts.

[0161] Styrenic resins are polymers that use styrene monomers as constituent monomers, and examples thereof include polymers obtained by polymerizing styrene monomers as the main component (50% by mass or more).Specific 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 be copolymerized with them.

[0162] Examples of the 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, α,β-unsaturated carboxylic acids or acid anhydrides thereof such as maleic anhydride, and the like.

[0163] Among the coumarone resins, coumarone-indene resins are preferred. Coumarone-indene resins are resins containing coumarone and indene as monomer components that constitute the resin skeleton (main chain). Monomer components contained in the skeleton other than coumarone and indene include styrene, α-methylstyrene, methylindene, vinyltoluene, etc.

[0164] The hydroxyl value (OH value) of the coumarone-indene resin is, for example, more than 15 mgKOH / g and less than 150 mgKOH / g. The OH value is the amount of potassium hydroxide, expressed in milligrams, required to neutralize acetic acid bonded to hydroxyl groups when acetylating 1 g of the resin, and is a value measured by potentiometric titration (JIS K 0070:1992).

[0165] The softening point of the coumarone-indene resin is, for example, more than 30° C. and less than 160° C. The softening point is the temperature at which the ball drops when the softening point specified in JIS K 6220-1:2001 is measured using a ring and ball softening point tester.

[0166] Terpene resins include polyterpenes, terpene phenols, and aromatic modified terpene resins. Polyterpenes are resins obtained by polymerizing terpene compounds and their hydrogenated products. Terpene compounds are (C5H8) n The hydrocarbons and their oxygen-containing derivatives are represented by the following composition: monoterpenes (C 10 H 16 ), sesquiterpenes (C 15 H 24 ), diterpenes (C 20 H 32 ), and examples thereof include α-pinene, β-pinene, dipentene, limonene, myrcene, alloocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, and γ-terpineol.

[0167] Examples of 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 above-mentioned terpene compounds, as well as hydrogenated terpene resins obtained by hydrogenating the terpene resins. Examples of terpene phenols include resins obtained by copolymerizing the above-mentioned terpene compounds with phenolic compounds, and resins obtained by hydrogenating the above-mentioned resins. Specific examples include resins obtained by condensing the above-mentioned terpene compounds, phenolic compounds, and formalin. Examples of phenolic compounds include phenol, bisphenol A, cresol, and xylenol. Examples of aromatic-modified terpene resins include resins obtained by modifying terpene resins with aromatic compounds, and resins obtained by hydrogenating the above-mentioned resins. The aromatic compound is not particularly limited as long as it is a compound having an aromatic ring, and examples thereof include phenolic compounds such as phenol, alkylphenol, alkoxyphenol, and unsaturated hydrocarbon group-containing phenol; naphthol compounds such as naphthol, alkylnaphthol, alkoxynaphthol, and unsaturated hydrocarbon group-containing naphthol; styrene derivatives such as styrene, alkylstyrene, alkoxystyrene, and unsaturated hydrocarbon group-containing styrene; coumarone, indene, and the like.

[0168] "C5 resin" refers to a resin obtained by polymerizing a C5 fraction. Examples of C5 fractions include petroleum fractions having 4 to 5 carbon atoms, such as cyclopentadiene, pentene, pentadiene, and isoprene. Dicyclopentadiene resin (DCPD resin) is preferably used as a C5 petroleum resin.

[0169] "C9 resin" refers to a resin obtained by polymerizing a C9 fraction, and may be a hydrogenated or modified version. Examples of C9 fractions include petroleum fractions having 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, indene, and methylindene. Specific examples of suitable aromatic vinyl resins include coumarone-indene resins, coumarone resins, indene resins, and aromatic vinyl resins. Preferred aromatic vinyl resins are α-methylstyrene (AMS resin), styrene homopolymers, and copolymers of α-methylstyrene and styrene, with copolymers of α-methylstyrene and styrene being more preferred, due to their economical efficiency, ease of processing, and excellent heat generation. Examples of aromatic vinyl resins that can be used include those commercially available from Kraton, Eastman Chemical Company, and the like.

[0170] "C5C9 resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and may be a hydrogenated or modified resin. Examples of C5 fractions and C9 fractions include the petroleum fractions mentioned above. As the C5C9 resin, for example, commercially available products from Tosoh Corporation, LUHUA, etc. can be used.

[0171] The acrylic resin is not particularly limited, but for example, a solventless acrylic resin can be used.

[0172] Examples of solvent-free acrylic resins include (meth)acrylic resins (polymers) synthesized by high-temperature continuous polymerization (high-temperature continuous bulk polymerization) (methods described in U.S. Pat. No. 4,414,370, JP-A Nos. 59-6207, JP-B Nos. 5-58005, 1-313522, U.S. Pat. No. 5,010,166, and Toa Gosei Kenkyusho Annual Report TREND 2000, Vol. 3, pp. 42-45, etc.), with minimal use of secondary raw materials such as polymerization initiators, chain transfer agents, and organic solvents. In the present invention, (meth)acrylic refers to both methacrylic and acrylic.

[0173] Examples of the monomer components constituting the 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.

[0174] Furthermore, aromatic vinyls such as styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, and divinylnaphthalene may be used together with (meth)acrylic acid or a (meth)acrylic acid derivative as a monomer component constituting the acrylic resin.

[0175] The acrylic resin may be a resin composed solely of a (meth)acrylic component, or a resin containing components other than a (meth)acrylic component, and may have a hydroxyl group, a carboxyl group, a silanol group, or the like.

[0176] As the resin component, for example, products from Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Clayton, Nitto Chemical Co., Ltd., Nippon Shokubai Co., Ltd., ENEOS Corporation, Arakawa Chemical Industries, Ltd., Taoka Chemical Co., Ltd., etc. can be used.

[0177] (c) Wax The cap rubber composition may contain wax. The wax content is, for example, preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and even more preferably 1.5 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is, for example, preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less.

[0178] The wax is not particularly limited, and any wax commonly used in the tire industry can be suitably used. Examples include mineral waxes and plant-derived waxes. Mineral waxes refer to waxes derived from mineral resources such as oil and natural gas. Plant-derived waxes refer to waxes derived from natural resources such as plants. Among these, mineral waxes are preferred.

[0179] Examples of plant-derived waxes include rice wax, carnauba wax, and candelilla wax. Examples of mineral waxes include paraffin wax, microcrystalline wax, and selected special waxes thereof, with paraffin wax being preferred. In the present invention, the wax does not contain stearic acid.

[0180] The wax that can be used may be commercially available waxes from, for example, Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Paramelt Co., Ltd., etc. These waxes may be used alone or in combination of two or more.

[0181] (d) Antiaging agents The cap rubber composition may contain an antioxidant. The content of the antioxidant 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.

[0182] The antioxidant is not particularly limited, and examples thereof include naphthylamine-based antioxidants such as phenyl-α-naphthylamine; diphenylamine-based antioxidants 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 (6PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-diphenyl-p-phenylenediamine (DPPD), and N,N'-ditolyl-p-phenylenediamine. p-phenylenediamine antioxidants such as N-isopropyl-N'-phenyl-p-phenylenediamine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and N,N'-di-2-naphthyl-p-phenylenediamine (DNPD); quinoline antioxidants such as 2,2,4-trimethyl-1,2-dihydroquinoline polymers; monophenol antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. Among these, p-phenylenediamine-based antioxidants and quinoline-based antioxidants are preferred, and polymers of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and 2,2,4-trimethyl-1,2-dihydroquinoline are more preferred. These may be used alone or in combination of two or more.

[0183] As commercially available products, for example, products from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., Flexis, etc. can be used.

[0184] (e) Processing aids The cap rubber composition may contain a processing aid. Examples of processing aids include metal salts (compounds in which the hydrogen atoms of an acid are substituted with metal ions), fatty acid amides, amide esters, and fatty acid esters. These may be used alone or in combination of two or more. Among these, metal salts and fatty acid amides are preferred, and metal salts are more preferred.

[0185] Examples of metals used in metal salts include alkali metals such as potassium and sodium, and alkaline earth metals such as calcium and barium. Magnesium, zinc, nickel, molybdenum, etc. can also be used. Of these, alkali metals are preferred.

[0186] Examples of acids used in metal salts include fatty acids such as lauric acid, myristic acid, palmitic acid, etc. In addition, boric acid, carbonic acid, hydrochloric acid, nitric acid, sulfuric acid, etc. can also be used.

[0187] As commercially available processing aids, products from Kishida Chemical Co., Ltd., Kenei Pharmaceutical Co., Ltd., Struktol Co., Ltd., Performance Additives Co., Ltd., etc. can be used.

[0188] The content of the processing aid is preferably 1 part by mass or more, more preferably 2 parts by mass or more, per 100 parts by mass of the rubber component, and, for example, the upper limit is preferably 6 parts by mass or less, more preferably 4 parts by mass or less.

[0189] (f) Lubricant (stearic acid) The cap rubber composition may contain a lubricant. A lubricant based on a fatty acid derivative such as stearic acid is preferably used as the lubricant. Conventionally known stearic acids can be used, specifically, products from NOF Corporation, NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc., can be used. Struktol WB16 manufactured by Struktol Co., Ltd. can also be used.

[0190] The content of stearic acid is, for example, preferably more than 0.5 parts by mass, more preferably 2.0 parts by mass or more, relative to 100 parts by mass of the rubber component, and the upper limit is preferably less than 10.0 parts by mass.

[0191] (g) Zinc oxide The cap rubber composition may contain zinc oxide. The content of zinc oxide is, for example, preferably more than 0.5 parts by mass, more preferably 3.0 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably less than 10 parts by mass. As the zinc oxide, conventionally known products 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.

[0192] (H) Crosslinking agents and vulcanization accelerators The cap rubber composition preferably contains a crosslinking agent such as sulfur. The content of the crosslinking agent is, for example, preferably more than 0.1 parts by mass, more preferably 2.0 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably less than 10.0 parts by mass. The sulfur content is the pure sulfur content, and when insoluble sulfur is used, it is the content excluding oil content.

[0193] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, etc., which are commonly used in the rubber industry. These may be used alone or in combination of two or more.

[0194] As sulfur, for example, products from Tsurumi Chemical Industry Co., Ltd., Karuizawa Iso Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, Nippon Kanzuri Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used.

[0195] Crosslinking agents other than sulfur may also be used. Specific examples include vulcanizing agents containing sulfur atoms, such as Tackirol V200 manufactured by Taoka Chemical Co., Ltd., DURALINK HTS (sodium 1,6-hexamethylenedithiosulfate dihydrate) manufactured by Flexis, and KA9188 (1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane: hybrid crosslinking agent) manufactured by Lanxess, as well as organic peroxides such as dicumyl peroxide.

[0196] The cap rubber composition preferably contains a vulcanization accelerator. The content of the vulcanization accelerator is, for example, preferably more than 0.3 parts by mass, more preferably 4.0 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably less than 10.0 parts by mass.

[0197] Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiazyl sulfenamide; 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-benzothiazole sulfenamide, Nt-butyl-2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenyl guanidine, di-orthotolyl guanidine, and orthotolyl biguanidine. These may be used alone or in combination of two or more.

[0198] (R) Other In addition to the above-mentioned components, the cap rubber composition may contain additives commonly used in the tire industry, such as organic fillers such as cellulose fibers, organic peroxides, etc. The content of these additives is, for example, more than 0.1 parts by mass and less than 50 parts by mass per 100 parts by mass of the rubber component.

[0199] In the present invention, among the above-mentioned materials, various materials containing carbon atoms (for example, rubber, oil, resin, vulcanization accelerator, antioxidant, surfactant, etc.) may be derived from carbon dioxide in the atmosphere. As a method for obtaining the compound of the present invention from carbon dioxide, carbon dioxide may be directly converted, or methane obtained through a methanation process in which methane is synthesized from carbon dioxide may be converted.

[0200] (2) Preparation of rubber composition The cap rubber composition can be prepared by a general method, for example, a manufacturing method including a base kneading process in which a rubber component and a filler such as silica are kneaded, and a finish kneading process in which the kneaded product obtained in the base kneading process is kneaded with a crosslinking agent.

[0201] The kneading can be carried out using a known (internal) kneading machine such as a Banbury mixer, a kneader, or an open roll.

[0202] The kneading temperature in the base kneading step is, for example, higher than 50° C. and lower than 200° C., and the kneading time is, for example, higher than 30 seconds and lower than 30 minutes. In the base kneading step, in addition to the above components, compounding agents conventionally used in the rubber industry, for example, softeners such as oil, stearic acid, zinc oxide, antioxidants, waxes, vulcanization accelerators, etc., may be appropriately added and kneaded as needed.

[0203] In the final kneading step, the kneaded product obtained in the base kneading step is kneaded with a crosslinking agent. The kneading temperature in the final kneading step is, for example, higher than room temperature and lower than 80°C, and the kneading time is, for example, longer than 1 minute and shorter than 15 minutes. In the final kneading step, in addition to the above components, a vulcanization accelerator, zinc oxide, etc. may be appropriately added and kneaded as necessary.

[0204] The cap rubber composition obtained as described above can then be extruded into a predetermined shape to form a tread.

[0205] 3. Tire manufacturing The tire according to the present embodiment can be manufactured by a conventional method. First, the cap rubber composition obtained as described above is molded into a predetermined shape to manufacture a tread. Next, the tread is assembled with other rubber components on a tire building machine to manufacture an unvulcanized tire.

[0206] When the tread portion has a multi-layer structure of a cap rubber layer and a base rubber layer, the rubber composition for forming the base rubber layer (base rubber composition) can basically be obtained by using the above-mentioned rubber components and compounding materials, appropriately changing the compounding amounts, and kneading them in the same manner. Then, the base rubber composition is extruded together with the cap rubber layer to form a tread rubber of a predetermined shape, and then molded together with other tire components in a tire building machine using a normal method to produce an unvulcanized tire.

[0207] Specifically, an inner liner as a component for ensuring the airtightness of the tire, a carcass as a component for withstanding the load, impact, and inflation pressure to which the tire is subjected, and a belt component, band, etc. as a component for tightly fastening the carcass and increasing the rigidity of the tread are wound around a forming drum, and both ends of the carcass are fixed to both side edges, and bead portions as components for fixing the tire to the rim are arranged and formed into a toroidal shape. After that, a tread is attached to the central portion of the outer periphery to form the tread portion, and sidewalls are attached to the radially outer side to form the side portions, thereby producing an unvulcanized tire.

[0208] The unvulcanized tire thus prepared is then heated and pressurized in a vulcanizer to obtain a tire. The vulcanization process can be carried out by using a known vulcanization method. The vulcanization temperature is, for example, greater than 120°C and less than 200°C, and the vulcanization time is, for example, greater than 5 minutes and less than 15 minutes.

[0209] As described above, the resulting tire has an appropriately controlled (tan δ × La) value, and therefore, heat generation in the tread portion of a tire using sustainable cords for the ply cords of the carcass ply can be sufficiently suppressed during driving.

[0210] The tire according to the present invention is not particularly limited in category and can be used as a passenger car tire, a large passenger car tire, a large SUV tire, a truck / bus tire, a motorcycle tire, a racing tire, a studless tire (winter tire), an all-season tire, a run-flat tire, an aircraft tire, a mining tire, a non-pneumatic tire, etc., but is preferably a passenger car tire. Also, it is preferably a pneumatic tire. [Example]

[0211] Examples (embodiments) that are considered preferable for carrying out the present invention will be shown below, but the scope of the present invention is not limited to these examples.

[0212] The results of an investigation into heat generation suppression performance for tires (tire size: 225 / 55R16, aspect ratio: 55%) made of the various carcasses, treads, and other rubber components shown below are shown at the bottom of Tables 1 and 2.

[0213] 1. Preparation of cap rubber composition A cap rubber composition is prepared using the various compounding materials shown below.

[0214] (1) Compounding materials (a) Rubber component (i) NR:TSR20 (ii) SBR: Modified S-SBR obtained by the method shown in the following (Production Example 1) (styrene content: 25% by mass, vinyl content: 25% by mass) (c) BR: Ubepol BR150B (High-Sys BR) manufactured by Ube Industries (cis content 97% by mass, trans content 2% by mass, vinyl content 1% by mass)

[0215] (Production Example 1) The SBR was prepared according to the following procedure. First, two 10-liter autoclave reactors, each equipped with a stirrer and jacket, were connected in series. Butadiene, styrene, and cyclohexane were mixed in the specified ratios. This mixture was passed through a dehydration column packed with activated alumina and mixed with n-butyllithium in a static mixer to remove impurities. The mixture was then continuously fed into the bottom of the first reactor. 2,2-bis(2-oxolanyl)propane as a polar substance and n-butyllithium as a polymerization initiator were also continuously fed into the bottom of the first reactor at specified rates, maintaining the reactor temperature at 95°C. The polymer solution was continuously withdrawn from the top of the reactor and fed into the second reactor. The temperature of the second reactor is maintained at 95°C, and a mixture of tetraglycidyl-1,3-bisaminomethylcyclohexane (monomer) as a modifier and oligomer components is continuously added at a specified rate as a 1000-fold diluted solution of cyclohexane to carry out the modification reaction. This polymer solution is continuously withdrawn from the reactor, and an antioxidant is continuously added using a static mixer, after which the solvent is removed to obtain the desired modified diene polymer (SBR).

[0216] (b) Compounding materials other than rubber components (a) Carbon black: Diablack N220 manufactured by Mitsubishi Chemical Corporation (N2SA:115m 2 / g) (b) Silica: Ultrasil VN3 manufactured by Evonik Industries (N2SA:175m 2 / g, average primary particle diameter: 17nm) (c) Silane coupling agent: Si266 manufactured by Evonik Industries (Bis(3-triethoxysilylpropyl)disulfide) (d) Resin: Kraton SYLVATRAXX 4401 (α-methylstyrene resin) (E) Oil: Idemitsu Kosan Diana Process NH-70S (Aromatic processed oil) (f) Stearic acid: NOF Corp. bead stearic acid "Tsubaki" (G) Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. (H) Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. (containing 5% oil) (i) Vulcanization accelerator-1: Noccela CZ manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (N-cyclohexyl-2-benzothiazylsulfenamide (CBS)) (J) Vulcanization accelerator 2: Soksil D (DPG) manufactured by Sumitomo Chemical Co., Ltd. (N,N'-diphenylguanidine)

[0217] (2) Manufacture of tread rubber composition (cap rubber composition) According to the formulations shown in Tables 1 and 2, materials other than sulfur and vulcanization accelerator are kneaded for 5 minutes at 150°C using a Banbury mixer to obtain a kneaded mixture. The amounts of each compound are in parts by mass.

[0218] Next, sulfur and a vulcanization accelerator are added to the kneaded mixture, and the mixture is kneaded for 5 minutes at 80°C using an open roll to obtain each cap rubber composition.

[0219] 2. Manufacturing of the tread Using each cap rubber composition obtained above and a base rubber composition prepared separately, the tread portion is manufactured by extrusion processing into a predetermined shape so that the land ratio of the tread portion is the value shown in Tables 1 and 2 (thickness of cap rubber layer / total thickness of tread portion: 80%).

[0220] 3. Carcass ply manufacturing Separately, carcass plies are manufactured to the same specifications, except for using each ply cord with the specifications shown in Tables 1 and 2. In Tables 1 and 2, PET (bio) refers to cord made from bio-polyester produced using bio-derived raw materials, and PET (recycled) refers to cord made from recycled polyester recycled from plastic waste such as PET bottles and used clothing.

[0221] Among the specifications of each ply cord shown in Tables 1 and 2, the strength (S), total fineness (F), intermediate elongation (E), and breaking elongation (E) are values ​​measured in accordance with the method specified in JIS L1017:2002, "Test Methods for Chemical Fiber Tire Cords." The cord diameter (F) is a value measured as the equivalent diameter of the circumscribed circle of a cross section perpendicular to the extension direction, and the ends (D) is a value measured as the number of cords present in a 5-cm width perpendicular to the longitudinal direction. The isophthalic acid content (IF) is a value measured by high-performance liquid chromatography (HPLC), and the moist heat resistance strength retention is a value obtained by calculating the ratio of the strength after 48 hours of treatment with saturated steam at 135°C (moist heat treatment) to the strength before treatment.

[0222] 4. Manufacturing of pneumatic tires Thereafter, the tire is laminated together with other tire components to form an unvulcanized tire having the land ratio shown in Tables 1 and 2, and press-vulcanized at 170°C for 10 minutes to produce test tires for Examples 1 to 6 and Comparative Examples 1 to 3.

[0223] Next, a rubber test piece for viscoelasticity measurement was prepared by cutting out a piece 20 mm long x 4 mm wide x 1 mm thick from the cap rubber layer of the tread portion of each test tire, with the long side in the tire circumferential direction. For each rubber test piece, the loss tangent tanδ was measured using an "IPLEXER (registered trademark)" series manufactured by GABO under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain of 1%, in a deformation mode of tension.

[0224] The thickness direction of the sample is the radial direction of the tire. When the same compounding is used in multiple examples, the average value of the values ​​measured for each test tire is used.

[0225] 5. Parameters Then, (tan δ×La), (tan δ×La) / F, and ((tan δ×La) / F) / (100−IF) are calculated.

[0226] 6. Performance evaluation (evaluation of heat suppression performance) Each test tire was fitted to all wheels of a vehicle (a domestically produced FR vehicle with an engine displacement of 2000cc) and inflated to an internal pressure of 250 kPa (normal internal pressure for a passenger car), and after a break-in run on a test course with a dry asphalt surface at a road surface temperature of 25°C, the vehicle was driven at an average speed of approximately 100 km / h. Immediately after the run, a hole was drilled radially inward from the centre of the tread surface of each test tire, and the temperature was measured 5 mm from the tread surface, and the difference from the air temperature was calculated.

[0227] Next, the result of Comparative Example 1 was set to 100, and the heat generation suppression performance was evaluated by indexing it according to the following formula. A larger value indicates less heat generation and better heat generation suppression performance. Heat generation suppression performance=[(Result of Comparative Example 1) / (Result of test tire)]×100

[0228] [Table 1]

[0229] [Table 2]

[0230] Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-described embodiments. Various modifications can be made to the above-described embodiments within the scope of the same or equivalent to the present invention.

[0231] The present invention (1) is A tire comprising a tread portion having a cap rubber layer and a carcass portion, A sustainable polyester cord is used as a ply cord in the carcass ply that constitutes the carcass portion, The tire is characterized in that the product (tanδ × La) of the loss tangent tanδ of the cap rubber layer measured under the conditions of a temperature of 30°C, an initial strain of 5%, a dynamic strain of 1%, a frequency of 10 Hz, and a deformation mode of tension, and the land ratio La (%) calculated from the contact area of ​​the tread portion, satisfies the following formula: tanδ×La≦15

[0232] The present invention (2) is The tire according to the present invention (1) is characterized in that the (tan δ×La) is 14 or less.

[0233] The present invention (3) is The tire is characterized in that the ratio ((tan δ×La) / F) of (tan δ×La) to the diameter F (mm) of the sustainable cord is less than 26, and is the tire according to the present invention (1) or (2).

[0234] The present invention (4) is The tire according to the present invention (3) is characterized in that the ((tan δ×La) / F) is less than 25.

[0235] The present invention (5) is The tire is characterized in that the sustainable polyester cord is a sustainable polyethylene terephthalate cord, and is any combination with any of the present inventions (1) to (4).

[0236] The present invention (6) is The tire is characterized in that the content of isophthalic acid in the sustainable polyester cord is less than 0.1 mol %, and is any combination with any of present inventions (1) to (5).

[0237] The present invention (7) is The tire is characterized in that the strength S (cN / dtex) of the sustainable polyester cord is 6.0 cN / dtex or more, and is an optional combination with any of the present inventions (1) to (6).

[0238] The present invention (8) is The tire is characterized in that the relationship between the (La × tanδ) and the content IF (mol%) of isophthalic acid in the sustainable polyester cord, ((tanδ × La) / F) / (100-IF), is 0.3 or less, and is an optional combination with any of present inventions (1) to (7).

[0239] The present invention (9) is The tire is characterized in that the relationship (S × IF / tanδ) between the strength S (cN / dtex) of the sustainable polyester cord, the content IF (mol%) of isophthalic acid, and the loss tangent tanδ of the cap rubber layer is 50 or more, and is an optional combination with any of the present inventions (1) to (8).

[0240] The present invention (10) is The tire is characterized in that the product (S×D) of the strength S (cN / dtex) of the sustainable polyester cord and the number D (cords / 5 cm) of the sustainable polyester cords present in a width of 5 cm in a direction perpendicular to the longitudinal direction of the sustainable polyester cord in the tread portion is 160 or more, and is an arbitrary combination with any of present inventions (1) to (9).

[0241] The present invention (11) is The tire according to the present invention (10) is characterized in that the (S×D) is 190 or more.

[0242] The present invention (12) is The tire is characterized in that the relationship (L×D / E) between the intermediate elongation E (%) of the sustainable polyester cord at a specified load L (cN / dtex) and the number D (cords / 5 cm) of the sustainable polyester cord present in a width of 5 cm in a direction perpendicular to the longitudinal direction of the sustainable polyester cord in the tread portion is 12 or more and 20 or less, and is an arbitrary combination with any of present inventions (1) to (11).

[0243] The present invention (13) is The tire according to the present invention (12) is characterized in that the (L×D / E) is 13.6 or more and 15 or less.

[0244] The present invention (14) is The tire is characterized in that the sustainable polyester cord has a breaking elongation of 10% or more, and is any combination with any of the present inventions (1) to (13).

[0245] The present invention (15) is The tire is characterized in that the sustainable polyester cord has a wet heat resistance strength retention rate of 80% or more, and is any combination with any of the present inventions (1) to (14). [Explanation of symbols]

[0246] 1 tire 2 Tread section 3 Sidewall 4 Bead section 5 bead core 6. Carcass 6A carcass ply 6a Inner body part 6b Outer folded part 7 Belt Layer 8 Bead apex rubber C Center line

Claims

1. A tire comprising a tread portion having a cap rubber layer and a carcass portion, A sustainable polyester cord is used as a ply cord in the carcass ply that constitutes the carcass portion, A tire characterized in that the product (tanδ × La) of the loss tangent tanδ of the cap rubber layer measured under the conditions of a temperature of 30°C, an initial strain of 5%, a dynamic strain of 1%, a frequency of 10 Hz, and a deformation mode of tension, and the land ratio La (%) calculated from the contact area of ​​the tread portion, satisfies the following formula: tan δ × La≦15

2. 2. The tire according to claim 1, wherein the (tan δ×La) is 14 or less.

3. The tire according to claim 1 or 2, wherein a ratio ((tan δ×La) / F) of (tan δ×La) to a diameter F (mm) of the sustainable cord is less than 26.

4. 4. The tire according to claim 3, wherein the ((tan δ×La) / F) is less than 25.

5. 3. The tire according to claim 1 or claim 2, wherein the sustainable polyester cord is a sustainable polyethylene terephthalate cord.

6. The tire according to claim 1 or 2, wherein the sustainable polyester cord has an isophthalic acid content of less than 0.1 mol%.

7. 3. The tire according to claim 1, wherein the sustainable polyester cord has a strength S (cN / dtex) of 6.0 cN / dtex or more.

8. The tire according to claim 1 or 2, characterized in that a relationship between the (La × tan δ) and a content IF (mol%) of isophthalic acid in the sustainable polyester cord, ((tan δ × La) / F) / (100−IF), is 0.3 or less.

9. 3. The tire according to claim 1, wherein the relationship between the strength S (cN / dtex), the content IF (mol%) of isophthalic acid in the sustainable polyester cord, and the loss tangent tanδ of the cap rubber layer (S × IF / tanδ) is 50 or more.

10. 3. The tire according to claim 1, wherein the product (S × D) of the strength S (cN / dtex) of the sustainable polyester cord and the number D (cords / 5 cm) of the sustainable polyester cords present in a width of 5 cm in a direction perpendicular to the longitudinal direction of the sustainable polyester cord in the tread portion is 160 or more.

11. 11. The tire according to claim 10, wherein the (S×D) is 190 or more.

12. 3. The tire according to claim 1, wherein a relationship (L×D / E) between an intermediate elongation E (%) of the sustainable polyester cord at a specified load L (cN / dtex) and a number D (cords / 5 cm) of the sustainable polyester cord present in a width of 5 cm in a direction perpendicular to the longitudinal direction of the sustainable polyester cord in the tread portion is 12 or greater and 20 or less.

13. 13. The tire according to claim 12, wherein the (L×D / E) is 13.6 or more and 15 or less.

14. 3. The tire according to claim 1, wherein the sustainable polyester cord has a breaking elongation of 10% or more.

15. The tire according to claim 1 or 2, wherein the sustainable polyester cord has a wet heat resistance strength retention rate of 80% or more.

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