Tire

Abstract

To provide a tire improved in wet grip performance.SOLUTION: A tire comprising a tread portion, wherein a tread surface of the tread portion comprises four circumferential main grooves, a crown rib defined by the circumferential main grooves, and a pair of middle ribs adjacent to the crown rib across the circumferential main grooves, A total sea ratio N (%) of the crown rib and the middle rib is greater than 0 and less than 15, the tread portion is formed from a rubber composition containing a rubber component, a filler, and a plasticizer, the plasticizer contains a copolymer resin containing cyclopentadiene as a monomer component, and N / P is less than 3.0, where P (parts by mass) is a total amount of the plasticizer per 100 parts by mass of the rubber component in the rubber composition.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] In recent years, there has been a demand for improved wet grip performance of tires. Patent Document 1 describes a tire rubber composition that uses a rubber component containing predetermined amounts of a predetermined conjugated diene rubber and a conjugated diene polymer, and further contains predetermined amounts of a predetermined silica and a predetermined tetrazine compound, thereby improving wet grip performance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-41035 Summary of the Invention [Problem to be solved by the invention]

[0004] However, there is still room for improvement in the wet grip performance of tires.

[0005] An object of the present invention is to provide a tire with improved wet grip performance. [Means for solving the problem]

[0006] The present invention relates to the following tire. A tire having a tread portion, a tread surface of the tread portion having four circumferential main grooves, a crown rib defined by the circumferential main grooves, and a pair of middle ribs adjacent to the crown rib and spaced apart by the circumferential main grooves; The total sea ratio N (%) of the crown rib and the middle rib is greater than 0 and less than 15, the tread portion is made of a rubber composition including a rubber component, a filler, and a plasticizer, the plasticizer contains a copolymer resin containing cyclopentadiene as a monomer component, When the total amount of the plasticizer relative to 100 parts by mass of the rubber component in the rubber composition is P (parts by mass), Tires with an N / P ratio of less than 3.0. [Effects of the Invention]

[0007] According to the present invention, a tire with improved wet grip performance can be provided. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing a schematic representation of a tread pattern of a tire according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] A tire according to one embodiment of the present invention will now be described. The tire according to this embodiment has a tread portion, and the tread surface of the tread portion has four circumferential main grooves, a crown rib defined by the circumferential main grooves, and a pair of middle ribs adjacent to the crown rib and separated by the circumferential main grooves, the crown rib and the middle ribs having a total sea ratio N (%) greater than 0 and less than 15, the tread portion being made of a rubber composition containing a rubber component, a filler, and a plasticizer, the plasticizer containing a copolymer resin containing cyclopentadiene as a monomer component, and where P (parts by mass) is the total amount of the plasticizer per 100 parts by mass of the rubber component in the rubber composition, N / P is less than 3.0.

[0010] Although not intending to be bound by theory, the reason why wet grip performance is improved in the present invention is thought to be as follows.

[0011] That is, (1) the tread portion has four circumferential main grooves, which can expel water from the road surface, which is thought to contribute to improved wet grip performance. (2) The tread portion has a crown rib and a pair of middle ribs, and the total sea-to-sea ratio N (%) of the crown rib and the middle rib is greater than 0 and less than 15, which ensures a certain level of contact area with the road surface at the center of the tire's contact patch, which is thought to contribute to improved wet grip performance. (3) Copolymer resins containing cyclopentadiene as a monomer component are less likely to leach out of the rubber component because the cyclopentadiene and / or dicyclopentadiene moieties (DCPD moieties) are highly compatible with the rubber component. In addition, copolymer resins containing cyclopentadiene as a monomer component are bulky. Therefore, the inclusion of this copolymer resin in a rubber composition imparts flexibility without compromising the reinforcing effect, which is thought to contribute to maintaining the wet grip performance of the tire. (4) By keeping the N / P ratio below 3.0, when the plasticizer content is increased, the S ratio of the crown rib and middle rib can also be increased, which is believed to ensure wet grip performance. Furthermore, it is believed that the cooperation of the above (1) to (4) achieves the remarkable effect of improving wet grip performance.

[0012] The N (%) is preferably less than 12, and more preferably less than 9. It is believed that the smaller the value of N, the more effectively the present invention can improve wet grip performance.

[0013] Crown rib sea ratio N c (%) is preferably less than 3. This is thought to further improve wet grip performance, as it ensures a certain level of contact area with the road surface at the center of the tire contact patch.

[0014] Middle rib sea ratio N m (%) is preferably less than 17. By making the sea-to-surface ratio of the middle rib less than 17%, it is possible to ensure a certain level of contact area with the road surface even at the middle rib, which is thought to further improve wet grip performance.

[0015] The land portion further has a shoulder rib, and the shoulder rib has a sea ratio N S (%) is preferably greater than 20.

[0016] By having shoulder ribs, drainage performance can be achieved even in areas close to the tire's contact edge, and it is thought that by increasing the sea ratio of the shoulder ribs to more than 20%, wet grip performance can be further improved.

[0017] The rubber component preferably contains 90% by mass or more of butadiene rubber.

[0018] Cyclopentadiene and / or dicyclopentadiene moieties (DCPD moieties) have particularly high compatibility with SBR or BR, so it is thought that wet grip performance is further maintained by including 90% by mass or more of a butadiene-based rubber.

[0019] The filler preferably contains silica in an amount of 60 mass % or more.

[0020] By including a certain percentage or more of silica in the filler, it is possible to improve flexibility while suppressing the heat generation of the rubber, making it easier for it to undergo small deformations, which is thought to contribute to improved wet grip performance.

[0021] The plasticizer preferably contains a copolymer resin containing styrene and cyclopentadiene as monomer components.

[0022] The ratio of tan δ at 0° C. (0° C. tan δ) of the rubber composition to N (0° C. tan δ / N) is preferably greater than 0.06.

[0023] By setting 0°C tanδ / N to a certain level or higher, it is thought that energy loss at the tread surface will be more likely to occur even on wet roads, and that the crown portion will be more likely to contact the road surface when the tire is rolling, making it possible to further improve wet grip performance.

[0024] When the total amount of copolymer resins containing cyclopentadiene as a monomer component per 100 parts by mass of the rubber component in the rubber composition is D (parts by mass), D×N is preferably 80 or more.

[0025] By ensuring that D × N is above a certain level, even when the content of copolymer resin containing cyclopentadiene as a monomer component is low and compatibility with the rubber component due to the DCPD portion is difficult to achieve, it is possible to reduce N and ensure a certain level of contact area with the road surface at the center of the tire's contact patch, thereby ensuring wet grip performance.

[0026] N / P is preferably less than 1.0. It is believed that the smaller the N / P value, the more effectively the present invention improves wet grip performance.

[0027] The tire according to this embodiment is preferably for use in an electric vehicle.

[0028] [Definition] "Normal condition" means that the tire is mounted on a normal rim, inflated to the normal internal pressure, and unloaded. Unless otherwise specified, the tire must be in normal condition.

[0029] Unless otherwise specified, the "dimensions of each part of the tire" are values ​​that are specified when the tire appears on its outer surface in a normal state, while those that exist inside the tire or on a cut surface of the tire are values ​​that are specified when, for example, the tire is cut along a plane that includes the tire rotation axis and the cut tire piece is maintained within the rim width of a normal rim.

[0030] "Genuine rim" refers to the rim specified for each tire in the standard system that includes 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. In the case of a tire not specified in the above standards, it refers to the narrowest rim among the smallest diameter rims that can be mounted on the tire and can maintain internal pressure (i.e., no air leaks from between the rim and tire).

[0031] "Normal internal pressure" refers to the air pressure specified for each tire in the standard system that includes the standard on which the tire is based. For example, for JATMA, it is "maximum air pressure," for ETRTO, it is "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 regular rims, refer to JATMA, ETRTO, and TRA in that order, and follow that standard if there is an applicable size at the time of reference. In the case of tires not specified in the above standards, it refers to the normal internal pressure (250kPa or more) of another tire size (defined in the standard) that is specified using the regular rim as the standard rim, and if there are multiple normal internal pressures of 250kPa or more listed, it refers to the smallest value among them.

[0032] "Normal load (kg)" is the load specified for each tire in the standard system including the standard on which the tire is based, for example, "Maximum Load Capacity" for JATMA, "Load Capacity" for ETRTO, and the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA. As with normal rims and normal internal pressures, JATMA, ETRTO, and TRA should be referenced in that order, and if there is an applicable size at the time of reference, that standard should be followed. For tires not specified in the above standards, the maximum load capacity W calculated separately should be used. L is the normal load.

[0033] "Maximum load capacity W L (kg)" is calculated using the following formula: "V" is the virtual volume of the tire (mm 3 ), "Dt" is the outer diameter (mm) of the tire in its normal state, "Ht" is the tire's cross-sectional height (mm) in the tire's radial direction in a cross section of the tire taken along a plane including the tire's rotation axis, and "Wt" is the tire's cross-sectional width (mm) in its normal state. Ht can be calculated by (Dt-R) / 2, where R is the tire rim diameter. Wt is the value obtained by excluding any patterns or letters on the tire sidewall. Note that maximum load capacity is synonymous with the normal load mentioned above.

[0034]

number

[0035] The "tread portion" refers to a component that includes the portion that forms the tire's contact surface, and in the case where the tire includes components that form the tire skeleton from steel or textile materials, such as a belt layer, a belt reinforcing layer, and a carcass layer, the "tread portion" is a component that is located radially outward of these components in the tire radial cross section.

[0036] In this specification, a "circumferential main groove" refers to a circumferential groove that extends continuously in the circumferential direction of the tire and has a groove depth of 3.0 mm or more at its deepest portion. In this specification, "four circumferential main grooves" refers to the first four circumferential main grooves, counting from the circumferential main groove with the widest groove width. The circumferential grooves may extend linearly in the circumferential direction, or may extend in a wavy, sinusoidal, or zigzag pattern.

[0037] "Groove width" means the maximum distance between groove edges on the tread surface in a direction perpendicular to the extension direction of the groove.

[0038] "Groove depth" refers to the linear distance between the line connecting the ends of the groove on the tread surface and the lowest point of the groove in the tire radial direction in a cross section of the tire taken along a plane including the tire rotation axis. If the groove depth of the groove varies in the tire width direction and / or circumferential direction, the maximum value of this linear distance is the groove depth of the groove.

[0039] The "land portion" refers to the portion of the tread that comes into contact with the ground when the tire is pressed against the ground, and is the portion of the tread that constitutes the effective contact area, which will be described later.

[0040] A "rib" refers to a land area defined by a tire ground contact edge or a circumferential main groove, in which no specific lateral grooves are formed. In the case of a rib defined by two circumferential main grooves, the "specific lateral groove" refers to a lateral groove that connects to both adjacent circumferential main grooves and has a maximum groove depth of 3.0 mm or more. In the case of a rib defined by a tire ground contact edge and a circumferential main groove, the "specific lateral groove" refers to a lateral groove that connects from the tire ground contact edge to the circumferential main groove and has a maximum groove depth of 3.0 mm or more. The land area having the "specific lateral groove" is called a block.

[0041] A "crown rib" refers to a rib that exists on the tire equator when a circumferential main groove does not exist on the tire equator. When a circumferential main groove exists on the tire equator, a "crown rib" refers to a rib that is adjacent to the circumferential main groove in the tire width direction, and when there are two adjacent ribs, both of them are crown ribs.

[0042] The "middle rib" is a rib that is adjacent to the outer side in the tire width direction of the circumferential main groove that is adjacent to the outer side in the tire width direction of the crown rib. The outer end of the middle rib in the tire width direction may be the contact edge, or another rib (for example, a shoulder rib, which will be described later) may be located further outward in the tire width direction than the outer end of the middle rib in the tire width direction.

[0043] The "shoulder rib" is a rib adjacent to the outer side in the tire width direction of the circumferential main groove adjacent to the outer side in the tire width direction of the middle rib. The outer end of the shoulder rib in the tire width direction may be the contact edge, or another rib may be located further outward in the tire width direction than the outer end of the shoulder rib in the tire width direction.

[0044] The "contact area" is the area of ​​the tread obtained from the outline of the tire when pressed against the ground. It is obtained by mounting the tire on a standard rim, inflating it to the standard internal pressure, leaving it to stand at 25°C for 24 hours, then applying ink to the surface of the tire tread, applying a standard load (a load equal to the maximum load capacity) to the tire, and pressing it perpendicularly against cardboard (camber angle 0°) to transfer the ink. The contact area is measured for each rib. The area of ​​the contact area of ​​each rib is called the total contact area of ​​each rib.

[0045] The "effective contact area" is the area of ​​the tread that comes into contact with the tire when it is pressed against the ground. It is obtained by assembling the tire on a standard rim, inflating it to the standard internal pressure, leaving it to stand at 25°C for 24 hours, then applying ink to the surface of the tire tread, applying a standard load (a load equal to the maximum load capacity) to the tire, and pressing it perpendicularly against cardboard (camber angle 0°) to transfer the ink. The effective contact area is measured for each rib. The area of ​​the effective contact area of ​​each rib is called the effective contact area of ​​each rib.

[0046] The "total sea ratio N (%) of the crown rib and middle rib" is calculated using the following formula. N (%) = {1 - (total effective ground contact area of ​​crown rib and middle rib / total ground contact area of ​​crown rib and middle rib)} x 100 When there are two crown ribs, the total effective contact area and total gross contact area refer to the combined areas of the two crown ribs and the two shoulder ribs.

[0047] Crown rib seam ratio N c (%)" is calculated using the following formula: N c (%) = {1-(total effective contact area of ​​crown ribs / total total contact area of ​​crown ribs)} x 100 When there are two crown ribs, the total effective contact area and total gross contact area refer to the combined areas of the two crown ribs.

[0048] Middle rib sea ratio N m (%)" is calculated using the following formula: N m (%) = {1-(total effective contact area of ​​middle ribs / total total contact area of ​​middle ribs)} x 100

[0049] Shoulder rib seam ratio s (%)" is calculated using the following formula: N s (%) = {1-(total effective contact area of ​​shoulder ribs / total total contact area of ​​shoulder ribs)} x 100 When there are two shoulder ribs, the total effective contact area and total total contact area refer to the combined areas of the two shoulder ribs.

[0050] "Contact width TW" is the maximum width of the contact area in the tire width direction. TW is determined by mounting a tire on a standard rim, inflating it to the standard internal pressure, and leaving it at 25°C for 24 hours. Then, ink is applied to the tire tread surface, and the tire is pressed vertically onto cardboard (camber angle 0°) under a standard load (a load equal to the maximum load capacity). The ink is then transferred to form a copy of the contact area, and the maximum width in the tire width direction is calculated from the contact area. The same transfer process is repeated at five locations, rotating the tire 72 degrees each time, and the average of the five maximum widths obtained is taken as TW.

[0051] "Plasticizer" is a material that imparts plasticity to rubber components and is a component that is extracted from rubber compositions using acetone. Plasticizers include those that are liquid (fluid) at 25°C and those that are solid at 25°C. However, this does not include waxes and stearic acid, which are commonly used in the tire industry.

[0052] The "total amount P of plasticizer per 100 parts by mass of the rubber component" includes the amount of plasticizer in the rubber component extended by the plasticizer.

[0053] The "loss tangent of a rubber composition" is the loss tangent (tanδ) under various conditions measured in extension mode using a dynamic viscoelasticity measuring device (for example, the Iplexer series manufactured by GABO). The sample used for dynamic viscoelasticity measurement is a vulcanized rubber composition having a length of 20 mm, a width of 4 mm, and a thickness of 1 mm. When preparing a sample by cutting it out from a tire, if the component from which the sample is prepared is a tread portion, a belt layer, or an inner liner, the length direction of the sample should be aligned with the tire circumferential direction, and the thickness direction of the sample should be aligned with the tire radial direction. If the component from which the sample is prepared is a sidewall, a clinch, a bead apex, or a side reinforcing layer, the length direction of the sample should be aligned with the tangent direction to the tire circumference, and the thickness direction of the sample should be aligned with the tire width direction.

[0054] "0°C tan δ" is the loss tangent (tan δ) measured under the conditions of a temperature of 0°C, a frequency of 10 Hz, an initial strain of 10%, a dynamic strain of ±2.5%, and an extension mode.

[0055] The "rubber component of the rubber composition" is a component that contributes to crosslinking within the rubber composition, and generally has a weight average molecular weight (Mw) of 10,000 or more.

[0056] The "glass transition temperature of the rubber component" refers to the static glass transition temperature of each rubber component determined by a differential scanning calorimeter (for example, Q200 manufactured by TA Instruments Japan Co., Ltd.).

[0057] "Styrene content" is measured by pyrolysis gas chromatography and NMR measurement ( 1 H-NMR and 13 The amount of components such as "styrene content" is calculated by C-NMR. Unlike physical property values ​​such as complex modulus (E*), the amount of components such as "styrene content" has a true value that is independent of the measurement method, so it is preferable to use a measurement method with as high accuracy as possible. In this specification, "pyrolysis gas chromatography" refers to a method in which a sample is heated in a pyrolysis device, the individual components contained in the gas phase components generated by this heating are separated using a separation column, and each isolated component is analyzed.

[0058] "Vinyl content (amount of 1,2-bonded butadiene units)" can be measured by pyrolysis gas chromatography or NMR measurement ( 1 H-NMR and 13 It is calculated using C-NMR. As with the "styrene content," there is a true value for the "vinyl content" that is independent of the measurement method, so it is preferable to use a measurement method with as high accuracy as possible.

[0059] "Cis content (cis-1,4-bonded butadiene unit amount)" is measured by infrared absorption spectroscopy or NMR measurement ( 1 H-NMR and 13This is a value measured by C-NMR and is applied to rubber components that have repeating units derived from butadiene, such as BR. As with the "styrene content," there is a true value for the "cis content" that is independent of the measurement method, so it is preferable to use a measurement method with as high accuracy as possible.

[0060] The "weight average molecular weight (Mw)" can be determined by converting the measured value into standard polystyrene equivalents using gel permeation chromatography (GPC) (for example, a GPC-8000 series manufactured by Tosoh Corporation, a differential refractometer as the detector, and a TSKgel SuperMultipore HZ-M column manufactured by Tosoh Corporation). This applies to, for example, SBR, BR, plasticizers, etc.

[0061] The "nitrogen adsorption specific surface area (N2SA) of carbon black" is measured in accordance with JIS K 6217-2:2017.

[0062] The "nitrogen adsorption specific surface area (N2SA) of silica" is measured by the BET method in accordance with ASTM D3037-93.

[0063] The "average primary particle size" is a value obtained by photographing particles with a transmission or scanning electron microscope and calculating the arithmetic mean of the particle sizes of 400 particles. If the particle shape is spherical, the particle size is the diameter of the sphere, and if the particle shape is non-spherical, the particle size is calculated from the microscope image as the circle-equivalent diameter (positive square root of {4 × (particle area) / π}).

[0064] The "softening point of the resin" is the temperature at which the ball drops when the softening point specified in JIS K 6220-1:2015 7.7 is measured using a ring and ball softening point tester.

[0065] [tire] A tire according to one embodiment of the present invention will be described below with reference to the drawings. The tire according to this embodiment has a tread portion, and the tread surface of the tread portion has four circumferential main grooves, a crown rib defined by the circumferential main grooves, and a pair of middle ribs adjacent to the crown rib and separated by the circumferential main grooves. The total sea-to-sea ratio N (%) of the crown ribs and middle ribs is greater than 0 and less than 15, and when P (parts by mass) is the total amount of plasticizer per 100 parts by mass of the rubber component in the rubber composition constituting the tread portion, N / P is less than 3.0. Note that the embodiment described below is merely an example, and the tire according to this embodiment is not limited to the following embodiment.

[0066] Fig. 1 is a diagram showing a schematic representation of a tread pattern of a tire according to one embodiment of the present invention, in which W indicates the tire width direction, C indicates the tire circumferential direction, and TW indicates the tire contact patch width.

[0067] The tread surface of the tire according to this embodiment has four circumferential main grooves 2. In Fig. 1, the groove widths of the four circumferential main grooves 2 are wider for the two circumferential main grooves closer to the tire equator and narrower for the pair of circumferential main grooves closer to the tire contact edge, but this is not limiting, and all four circumferential main grooves 2 may have the same groove width.

[0068] In Fig. 1, no circumferential main groove exists on the tire equator, and the crown rib 3 exists on the tire equator CL. The crown rib 3 is provided with a plurality of lateral grooves 7d having a tire width direction component and a maximum groove depth of less than 3.0 mm. One end of each lateral groove 7d opens into the circumferential main groove and the other end terminates within the crown rib. Although the crown rib according to this embodiment is not limited to this form, it is preferable that the crown rib have lateral grooves.

[0069] Crown rib sea ratio N C From the viewpoint of wet grip performance, N is preferably less than 8%, more preferably less than 5%, and even more preferably less than 3%. Cmay be 0%, but is preferably greater than 1%.

[0070] Middle rib sea ratio N m In order to ensure a certain level of contact area with the road surface even at the middle rib and improve wet grip performance, the seam ratio N of the middle rib is preferably less than 17%, more preferably less than 15%, even more preferably less than 10%, and particularly preferably less than 8%. m is preferably more than 2%, more preferably more than 3%.

[0071] A pair of middle ribs 4 are adjacent to the crown rib 3 across the circumferential main groove 2. In FIG. 1, the middle rib 4 is provided with lateral grooves 7c. The deepest part of the lateral grooves 7c is less than 3.0 mm. From the viewpoint of wet grip performance, it is preferable that the middle rib according to this embodiment has lateral grooves. In FIG. 1, the lateral grooves 7c are connected to the circumferential main grooves, but the lateral grooves of the middle rib are not limited to this form and may be closed lateral grooves that terminate within the middle rib.

[0072] The total sea ratio N of the crown rib and the middle rib is more than 0%, preferably more than 2%, more preferably more than 5%, and even more preferably more than 7%. The total sea ratio N of the crown rib and the middle rib is less than 15%, preferably less than 14%, more preferably less than 12%, even more preferably less than 10%, and especially preferably less than 9%. N is N C and N m is equal to the sum of

[0073] The tread surface in FIG. 1 has one shoulder rib 5. The tread surface according to this embodiment preferably has a shoulder rib. In FIG. 1, the shoulder rib 5 is provided with a lateral groove 7e with a maximum groove depth of less than 3.0 mm. When the tread surface according to this embodiment has a shoulder rib, the shoulder rib preferably has a lateral groove from the viewpoint of wet grip performance. In FIG. 1, the lateral groove 7e is connected to the circumferential main groove 2 and the tire ground contact edge, but this is not limited to this form. The lateral groove 7e may be a closed lateral groove that does not connect to the circumferential main groove and / or the tire ground contact edge and terminates within the shoulder rib. When the tread surface according to this embodiment has a shoulder rib, the lateral groove of the shoulder rib preferably opens to the tire ground contact edge from the viewpoint of wet grip performance.

[0074] Shoulder rib seam ratio N S From the viewpoint of wet grip performance, the seam ratio N of the shoulder rib is preferably more than 10%, more preferably more than 15%, even more preferably more than 20%, and particularly preferably more than 22%. S is preferably less than 40%, more preferably less than 35%, and even more preferably less than 30%.

[0075] In Fig. 1, the tread surface has a plurality of lateral grooves 7a that communicate from the tire ground contact edge to the circumferential main groove and have a maximum groove depth of 3.0 mm or more, and a plurality of shoulder blocks 6 that are partitioned by the lateral grooves 7a. In Fig. 1, the shoulder blocks 6 have lateral grooves 7b that communicate with the circumferential main grooves 2 but do not communicate with the tire ground contact edge, but this is not limited to this.

[0076] The tan δ at 0°C (0°C tan δ) of the rubber composition constituting the tread portion according to the present embodiment is preferably 0.50 or more, more preferably 0.55 or more, and even more preferably 0.60 or more. The tan δ at 0°C is preferably 0.80 or less, more preferably 0.75 or less, and even more preferably 0.70 or less.

[0077] The tan δ of the rubber composition can be adjusted appropriately by changing the types and amounts of the rubber components, fillers, plasticizers, etc., which will be described later. For example, the 0°C tan can be increased by increasing the content of the plasticizer in the rubber composition.

[0078] The ratio of 0°C tan δ to N (0°C tan δ / N) is preferably greater than 0.04, more preferably greater than 0.06, and even more preferably greater than 0.08. 0°C tan δ / N is preferably less than 0.20, more preferably less than 0.18, even more preferably less than 0.15, and particularly preferably less than 0.10.

[0079] When the total amount of plasticizers per 100 parts by mass of the rubber component in the rubber composition constituting the tread portion according to this embodiment is P (parts by mass), N / P is less than 3.0, preferably less than 2.0, more preferably less than 1.0, and even more preferably less than 0.50. N / P is preferably greater than 0.05, more preferably greater than 0.10. P will be described later.

[0080] When the total amount of copolymer resin containing cyclopentadiene as a monomer component per 100 parts by mass of the rubber component in the rubber composition constituting the tread portion according to this embodiment is defined as D (parts by mass), D×N is preferably 80 or more, more preferably 100 or more, and even more preferably 140 or more. Furthermore, D×N is preferably 300 or less, more preferably 280 or less, and even more preferably 250 or less. D will be described later.

[0081] [Rubber composition] The rubber composition constituting the tread portion according to this embodiment will be described below. The rubber composition according to this embodiment contains a rubber component, a filler, and a plasticizer, and the plasticizer contains a copolymer resin containing cyclopentadiene as a monomer component.

[0082] <Rubber component> The rubber composition according to the present embodiment preferably contains a diene rubber as the rubber component, and more preferably contains a butadiene rubber among diene rubbers.

[0083] As the diene rubber, any of those commonly used in the tire industry can be suitably used. Specific examples include isoprene rubber, butadiene rubber, styrene-isoprene rubber (SIR), chloroprene rubber (CR), etc. These diene rubbers may be used alone or in combination of two or more.

[0084] Butadiene-based rubber is a rubber component made of a polymer containing butadiene as a polymer unit. Examples of butadiene-based rubber include styrene butadiene rubber (SBR), butadiene rubber (BR), butadiene-isoprene copolymer rubber, acrylonitrile butadiene rubber (NBR), and styrene isoprene butadiene rubber (SIBR). These butadiene-based rubbers may be used alone or in combination of two or more. The rubber component according to this embodiment preferably contains BR or SBR, and more preferably uses BR and SBR in combination. The rubber component may also be made up of only BR and SBR.

[0085] The rubber composition according to the present embodiment preferably contains BR and SBR as diene rubbers, but may contain BR, SBR, and an isoprene-based rubber, or may be a rubber component consisting solely of BR, SBR, and an isoprene-based rubber.

[0086] (SBR) The SBR is not particularly limited, and examples thereof include solution-polymerized SBR (S-SBR), emulsion-polymerized SBR (E-SBR), and modified SBRs thereof (modified S-SBR, modified E-SBR). Modified SBRs include SBRs whose ends and / or main chains are modified, and modified SBRs (condensates, those having a branched structure, etc.) coupled with tin, silicon compounds, etc. Furthermore, hydrogenated products of these SBRs (hydrogenated SBRs) can also be used. These SBRs may be used alone or in combination of two or more.

[0087] As the SBR, either oil-extended or non-oil-extended SBR can be used. In this specification, commercially available SBRs from JSR Corporation, Sumitomo Chemical Co., Ltd., UBE Corporation, Asahi Kasei Corporation, ZS Elastomers Co., Ltd., ARLANXEO, etc. can be used.

[0088] From the viewpoint of compatibility with copolymer resins containing cyclopentadiene as a monomer component, the styrene content of SBR is preferably greater than 10% by mass, more preferably greater than 15% by mass, and even more preferably greater than 20% by mass. On the other hand, the styrene content of SBR is preferably less than 55% by mass, more preferably less than 50% by mass, and even more preferably less than 45% by mass. If the styrene content of SBR exceeds 55% by mass, styrene groups are adjacent to each other, the polymer becomes too hard, and crosslinking tends to become non-uniform. This results in significant changes in performance with temperature changes, making it difficult to obtain stable grip performance. The styrene content of SBR is measured by the above-mentioned measurement method.

[0089] The vinyl content of SBR is preferably more than 10 mol%, more preferably more than 15 mol%, and even more preferably more than 18 mol%. The vinyl content of SBR is preferably less than 70 mol%, more preferably less than 65 mol%, and even more preferably less than 60 mol%. In this specification, the vinyl content of SBR is measured by the above-mentioned measurement method.

[0090] From the viewpoint of wet grip performance, the glass transition point (Tg) of SBR is preferably -80°C or higher, more preferably -70°C or higher, and even more preferably -65°C or higher. From the viewpoint of fuel economy performance, the Tg of SBR is preferably -55°C or lower. The Tg of SBR is measured by the above-mentioned measurement method.

[0091] The weight average molecular weight (Mw) of SBR is preferably more than 200,000, more preferably more than 300,000, even more preferably more than 400,000, and particularly preferably more than 500,000. From the viewpoint of crosslink uniformity, Mw is preferably less than 2,000,000, more preferably less than 1,500,000, and even more preferably less than 1,000,000. The Mw of SBR is measured by the above-mentioned measurement method.

[0092] From the viewpoint of compatibility with copolymer resins containing cyclopentadiene as a monomer component, the content of SBR in the rubber component is preferably more than 40% by mass, more preferably more than 50% by mass, even more preferably more than 60% by mass, and particularly preferably more than 70% by mass, and is preferably less than 90% by mass, more preferably less than 85% by mass.

[0093] (BR) The BR is not particularly limited, and can be one commonly used in the tire industry, such as BR with a cis content of less than 50 mol% (low-cis BR), BR with a cis content of 90 mol% or more (high-cis BR), rare earth butadiene rubber (rare earth BR) synthesized using a rare earth catalyst, BR containing syndiotactic polybutadiene crystals (SPB-containing BR), modified BR (high-cis modified BR, low-cis modified BR), etc. These BRs may be used alone or in combination of two or more.

[0094] As the high-cis BR, for example, commercially available products from Zeon Corporation, UBE Corporation, JSR Corporation, etc. can be used. The inclusion of high-cis BR can improve low-temperature properties and wear resistance. The cis content of the high-cis BR is preferably more than 95 mol%, more preferably more than 96 mol%, and even more preferably more than 97 mol%. The cis content of BR is measured by the above-mentioned measurement method.

[0095] The rare earth BR is synthesized using a rare earth catalyst and has a vinyl content of preferably less than 1.8 mol%, more preferably less than 1.6 mol%, and even more preferably 1.5 mol% or less, and a cis content of preferably more than 95 mol%, more preferably more than 96 mol%, and even more preferably 97 mol% or more. As the rare earth BR, for example, commercially available products from LANXESS K.K. can be used.

[0096] The SPB-containing BR is not simply 1,2-syndiotactic polybutadiene crystals dispersed in the BR, but is dispersed after being chemically bonded to the BR. As such SPB-containing BR, commercially available products from UBE Corporation and the like can be used.

[0097] Examples of modified BR include BR modified with functional groups similar to those described above for SBR, and also preferably used are modified butadiene rubbers (modified BRs) whose terminals and / or main chains are modified with functional groups containing at least one element selected from the group consisting of silicon, nitrogen, and oxygen.

[0098] Other examples of modified BR include tin-modified BR, which is obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and in which the terminals of the modified BR molecule are further bonded with a tin-carbon bond (tin-modified BR).Modified BR may be either non-hydrogenated or hydrogenated.

[0099] From the viewpoint of abrasion resistance, the weight-average molecular weight (Mw) of BR is preferably more than 300,000, more preferably more than 350,000, and even more preferably more than 400,000. From the viewpoint of crosslinking uniformity, etc., it is preferably less than 2,000,000, more preferably less than 1,000,000, and even more preferably less than 500,000. The Mw of BR can be determined by the above-mentioned method.

[0100] The content of BR in the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. The content of BR in the rubber component is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less.

[0101] The content of the butadiene rubber in the rubber component is preferably more than 50% by mass, more preferably 60% by mass or more, even more preferably 70% by mass or more, still more preferably 80% by mass or more, particularly preferably 90% by mass or more, and can be 100% by mass.

[0102] When a diene rubber other than a butadiene rubber is contained as the rubber component, it is preferable that an isoprene rubber is contained.

[0103] (Isoprene rubber) Examples of isoprene-based rubbers that can be used include those commonly used in the tire industry, such as isoprene rubber (IR) and natural rubber. Natural rubber includes unmodified natural rubber (NR) as well as modified natural rubbers such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), highly purified natural rubber, and grafted natural rubber. These isoprene-based rubbers may be used alone or in combination of two or more.

[0104] The NR is not particularly limited, and those commonly used in the tire industry can be used, such as SIR20, RSS#3, and TSR20.

[0105] When an isoprene-based rubber is contained, the content of the isoprene-based rubber in the rubber component is preferably more than 5% by mass, more preferably more than 10% by mass, and even more preferably more than 20% by mass, and preferably less than 60% by mass, and more preferably less than 50% by mass.

[0106] (Other rubber components) The rubber component may contain a rubber component other than the diene rubber (non-diene rubber) to the extent that it does not affect the effects of the invention. Examples of non-diene rubbers include rubber components commonly used in the tire industry, such as butyl rubber, ethylene propylene rubber, polynorbornene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), and hydrin rubber. These other rubber components may be used alone or in combination of two or more. In addition to the above rubber components, a known thermoplastic elastomer may or may not be contained.

[0107] (Rubber components synthesized from recycled and biomass-derived raw materials) Monomers, which are structural units of synthetic rubbers such as IR, 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. Monomers obtained by recycling (recycled monomers) are not particularly limited, and examples include recycled polyisoprene, recycled butadiene, and recycled aromatic vinyl compounds. Examples of butadienes include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyl compounds include, but are not limited to, styrene. Among these, recycled polyisoprene (recycled isoprene), recycled butadiene (recycled butadiene), and / or recycled styrene (recycled styrene) are preferably used as raw materials.

[0108] 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.

[0109] Furthermore, the monomers that are the structural units of polymers 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.

[0110] Monomers derived from biomass (biomass monomers) are not particularly limited, and examples thereof include biomass-derived butadiene and biomass-derived aromatic vinyl compounds. Examples of butadienes include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyl compounds include, but are not limited to, styrene. The method for producing biomass monomers is not particularly limited, and examples include 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.

[0111] Polymers synthesized from biomass monomer components (biomass polymers) are not particularly limited and include polybutadiene rubber synthesized from biomass-derived butadiene, aromatic vinyl / butadiene copolymers synthesized from biomass-derived butadiene and / or biomass-derived aromatic vinyl compounds, etc. Examples of the aromatic vinyl / butadiene copolymers include styrene-butadiene rubber synthesized from biomass-derived butadiene and / or biomass-derived styrene.

[0112] Whether a polymer's raw material is biomass-derived can be determined by its pMC (percent modern carbon) measured in accordance with ASTM D6866-10. pMC is the modern standard reference carbon. 14 of sample against C concentration 14This 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.

[0113] 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 14 C exists. 14 The half-life of C is 5730 years, 14 C is decreasing regularly. Therefore, in the case of 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 they were 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 elements.

[0114] on the other hand, 14 C is constantly produced by cosmic rays undergoing nuclear reactions in the atmosphere. 14 The amount of C is balanced between radioactive decay and nuclear reaction, and in the Earth's atmospheric environment, 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.

[0115] 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 / 12C) is measured. 14 The modern standard reference for the C concentration is the carbon circulating in nature as of 1950. 14 The 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.

[0116] 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 above-mentioned biomass ratio of 0%.

[0117] From the above, it is preferable in terms of environmental protection to use a material such as rubber having a high pMC value, that is, a material such as rubber having a high biomass ratio, in a rubber composition.

[0118] [Filler] The rubber composition according to the present embodiment contains a filler, and the filler preferably contains silica, more preferably contains carbon black and silica. Alternatively, the filler may be a filler consisting of only carbon black and silica.

[0119] <Silica> The silica is not particularly limited, and can be, for example, silica prepared by a dry method (anhydrous silica), silica prepared by a wet method (hydrated silica), or other silica commonly used in the tire industry. The raw material for silica is not particularly limited, and can 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 silica-containing product. Among these, hydrated silica prepared by a wet method is preferred because it contains a large number of silanol groups. Silica can be used alone or in combination of two or more types.

[0120] Silica made from biomass materials can be obtained, for example, by extracting silicate from rice husk ash obtained by burning rice husks using a sodium hydroxide solution, and then reacting the silicate with sulfuric acid in the same manner as conventional wet-process silica to produce a silicon dioxide precipitate, which is then filtered, washed with water, dried, and pulverized.

[0121] Silica recycled from silica-containing products can be, for example, 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.

[0122] When silica crystallizes, it becomes insoluble in water, and its component, silicic acid, cannot be utilized. By controlling the combustion temperature and duration, the crystallization of silica in rice husk ash can be suppressed (see, for example, JP 2009-2594 A, Akita Prefectural University Web Journal B / 2019, vol. 6, pp. 216-222). Amorphous silica extracted from rice husks can be commercially available from Wilmar, Inc.

[0123] From the viewpoint of reinforcement, the nitrogen adsorption specific surface area (N2SA) of silica is 100m 2 / g or more is preferable, and 150m 2 / g is more preferable, and 170m2 From the viewpoint of heat buildup and processability, it is more preferable that the tensile strength is more than 250 m / g. 2 / g is preferable, and 200m 2 / g is more preferable, and 180m 2 / g or less is more preferable. The N2SA of silica is measured by the above-mentioned measurement method.

[0124] From the viewpoint of reinforcing properties, the average primary particle diameter of silica is preferably more than 10 nm, more preferably more than 12 nm, and even more preferably more than 15 nm. The average primary particle diameter is preferably less than 25 nm, and more preferably less than 20 nm. The average primary particle diameter of silica is measured by the above-mentioned measurement method.

[0125] The silica content in the filler is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more. The silica content in the filler is preferably 95% by mass or less. However, the silica content in the filler may be 100% by mass.

[0126] From the viewpoint of wet grip performance, the content of silica per 100 parts by mass of the rubber component is preferably more than 30 parts by mass, more preferably more than 40 parts by mass, and even more preferably 50 parts by mass or more. Also, the content of silica per 100 parts by mass of the rubber component is preferably less than 120 parts by mass, more preferably less than 100 parts by mass, and even more preferably less than 80 parts by mass.

[0127] <Silane coupling agent> Silica is preferably used in combination with a silane coupling agent.Silane coupling agent is not particularly limited, but for example, sulfide-based silane coupling agent such as bis(3-triethoxysilylpropyl) disulfide, bis(3-triethoxysilylpropyl) tetrasulfide; mercapto-based silane coupling agent such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane; vinyl-based silane coupling agent such as vinyltriethoxysilane, vinyltrimethoxysilane; 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane Examples of suitable silane coupling agents include amino-based silane coupling agents such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based silane coupling agents such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based silane coupling agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Among these, sulfide-based silane coupling agents and / or mercapto-based silane coupling agents are preferred. Examples of suitable silane coupling agents include those commercially available from Evonik Degussa GmbH and Momentive GmbH. These silane coupling agents may be used alone or in combination.

[0128] The content of the silane coupling agent is preferably more than 5 parts by mass, more preferably more than 7 parts by mass, per 100 parts by mass of silica from the viewpoint of improving the dispersibility of silica, and is preferably less than 15 parts by mass, more preferably less than 10 parts by mass, and even more preferably less than 9 parts by mass from the viewpoint of cost and processability.

[0129] The content of the silane coupling agent per 100 parts by mass of the rubber component (the total amount when multiple silane coupling agents are used) is preferably more than 2 parts by mass, more preferably more than 3 parts by mass, and even more preferably more than 5 parts by mass from the viewpoint of improving the dispersibility of silica, and is preferably less than 12 parts by mass, more preferably less than 10 parts by mass, and even more preferably less than 8 parts by mass from the viewpoint of preventing a decrease in abrasion resistance.

[0130] <Carbon black> Carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. The raw material for carbon black may be a biomass material such as lignin or vegetable oil, or pyrolysis oil obtained by pyrolysis of waste tires. Carbon black may be produced by combustion, such as in a furnace process, by hydrothermal carbonization (HTC), or by thermal decomposition of methane, such as in a thermal black process. Commercially available carbon black 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., and Columbia Carbon Co., Ltd. One type of carbon black may be used alone, or two or more types may be used in combination.

[0131] In addition to the above, from the viewpoint of life cycle assessment, carbon black may be made from a biomass material such as lignin, or recycled carbon black obtained by pyrolysis and purification of a product containing carbon black, such as a tire.

[0132] As used herein, "recycled carbon black" refers to carbon black obtained by crushing used tires or other products containing carbon black and calcining the crushed material, and refers to carbon black in which, when subjected to oxidative combustion by heating in air as measured by thermogravimetry in accordance with JIS K 6226-2:2003, the proportion of the mass of ash (ash content), which is the non-combustible component, is 13% by mass or more. In other words, the proportion of the mass (carbon content) of the recycled carbon black lost due to oxidative combustion is 87% by mass or less. Recycled carbon black is sometimes expressed as rCB.

[0133] Recycled carbon black can be obtained from the pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3427975, citing "Rubber Chemistry and Technology," Vol. 85, No. 3, pp. 408-449 (2012), particularly pp. 438, 440, and 442, describes the carbon black as being obtained by pyrolysis of organic materials at 550-800°C in the absence of oxygen, or by vacuum pyrolysis at relatively low temperatures (

[0027] ). Carbon black obtained from such pyrolysis processes typically lacks functional groups on its surface, as mentioned in

[0004] of Japanese Patent Publication No. 6856781 (Comparison of the Surface Morphology and Chemistry of Pyrolytic Carbon Black with Commercial Carbon Black, Powder Technology 160 (2005) pp. 190-193).

[0134] Recycled carbon black may lack functional groups on its surface, or may be treated to include functional groups on its surface. Treatment to include functional groups on the surface of recycled carbon black can be carried out by conventional methods. For example, in European Patent Application Publication No. 3,173,251, carbon black obtained from a pyrolysis process is treated with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl and / or carboxyl groups on its surface. Furthermore, in Japanese Patent Publication No. 6,856,781, carbon black obtained from a pyrolysis process is treated with an amino acid compound containing at least one thiol or disulfide group to obtain surface-activated carbon black. The recycled carbon black of this embodiment also includes carbon blacks treated to include functional groups on their surfaces.

[0135] As the recycled carbon black, commercially available products from Strable Green Carbon, LD Carbon, etc. can be used.

[0136] The nitrogen adsorption specific surface area (N2SA) of carbon black is 80m from the viewpoint of reinforcement. 2 / g or more is preferable, and 90m 2 / g is more preferable, and 100m 2 / g or more is more preferable, and 110m 2 From the viewpoint of heat buildup and processability, it is particularly preferable that the tensile strength is more than 200 m / g. 2 / g is preferred, and 150m 2 / g is more preferable, and 120m 2 / g or less is more preferable. The N2SA of carbon black is measured by the above-mentioned measurement method.

[0137] The average primary particle size of carbon black is preferably greater than 15 nm, more preferably greater than 18 nm, and even more preferably greater than 20 nm. The average primary particle size is preferably less than 50 nm, more preferably less than 40 nm, and even more preferably less than 30 nm. The average primary particle size of carbon black is measured by the above-mentioned measurement method.

[0138] The amount of carbon black per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, and is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less, per 100 parts by mass of the rubber component.

[0139] <Other fillers> The filler may contain fillers other than silica and carbon black. The other fillers are not particularly limited, but may include, for example, fillers that have been commonly used in the tire industry, such as aluminum hydroxide, calcium carbonate, alumina, clay, and talc.

[0140] <Plasticizer> The rubber composition according to the present embodiment contains a plasticizer, and as the plasticizer, contains a copolymer resin containing cyclopentadiene as a monomer component.

[0141] A plasticizer is a material that imparts plasticity to rubber components and encompasses both liquid and solid plasticizers at 25°C. Examples of plasticizers include resins, oils, liquid rubbers, and ester-based plasticizers. These plasticizers may be derived from mineral resources such as petroleum and natural gas, biomass-derived materials, or naphtha recycled from rubber and 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 plasticizers. Plasticizers may be used singly or in combination.

[0142] The content P of the plasticizer (total content when two or more types are contained) per 100 parts by mass of the rubber component is preferably 15 parts by mass or more, more preferably 18 parts by mass or more, even more preferably 20 parts by mass or more, and particularly preferably 25 parts by mass or more. On the other hand, from the viewpoint of fuel economy, the content is preferably less than 120 parts by mass, more preferably less than 100 parts by mass, and even more preferably less than 80 parts by mass.

[0143] <Copolymer resin containing cyclopentadiene as a monomer component> The copolymer resin containing cyclopentadiene as a monomer component is not particularly limited as long as it contains cyclopentadiene as a monomer component, and may further contain other monomer components described below. In addition, these may be hydrogenated or modified.

[0144] The monomer component other than cyclopentadiene is not particularly limited, but is preferably a monomer component commonly used in petroleum resins, more preferably the C9 fraction described below, and even more preferably styrene and / or indene. The "styrene" constituting the monomer component may be a compound having a styrene structure other than styrene, such as styrene, α-methylstyrene, vinyltoluene, and chlorostyrene.

[0145] The copolymer resin containing cyclopentadiene as a monomer component is preferably a copolymer resin containing styrene and cyclopentadiene and / or dicyclopentadiene as monomer components, and may be a hydrogenated or modified copolymer resin.

[0146] As the copolymer resin containing cyclopentadiene as a monomer component, for example, those commercially available from ExxonMobil Corporation, ENEOS Corporation, Nippon Zeon Co., Ltd., Maruzen Petrochemical Co., Ltd., etc., can be used. One type of such resin may be used alone, or two or more types may be used in combination.

[0147] When a copolymer resin containing cyclopentadiene as a monomer component further contains styrene as a monomer component, the styrene content in 100% by mass of the copolymer resin is, from the viewpoint of the effects of the present invention, preferably 0.5% by mass or more, more preferably 0.8% by mass or more, even more preferably 1.0% by mass or more, even more preferably 2.0% by mass or more, even more preferably 3.0% by mass or more, even more preferably 4.0% by mass or more, and even more preferably 5.0% by mass or more. The upper limit of the styrene content is not particularly limited, but can be, for example, less than 50% by mass, less than 40% by mass, less than 30% by mass, or less than 10% by mass.

[0148] From the viewpoint of the effects of the present invention, the softening point of the copolymer resin containing cyclopentadiene as a monomer component is preferably above 70° C., more preferably above 80° C., even more preferably above 90° C., and particularly preferably above 100° C. Furthermore, from the viewpoint of improving processability and dispersibility of the rubber component and the filler, the softening point is preferably below 150° C., more preferably below 140° C., and even more preferably below 130° C. The softening point of the resin is measured by the above-mentioned measurement method.

[0149] The total content D of copolymer resins containing cyclopentadiene as a monomer component per 100 parts by mass of the rubber component is preferably more than 5 parts by mass, more preferably more than 10 parts by mass, even more preferably more than 15 parts by mass, even more preferably more than 19 parts by mass, and particularly preferably more than 22 parts by mass. From the viewpoint of processability, the content is preferably less than 100 parts by mass, more preferably less than 80 parts by mass, even more preferably less than 60 parts by mass, and particularly preferably less than 40 parts by mass.

[0150] (Other resins) The rubber composition according to the present embodiment may contain a resin other than the copolymer resin containing cyclopentadiene as a monomer component. The other resin is not particularly limited, but may be a resin commonly used in the tire industry, such as an aromatic vinyl resin, a C9 resin, a C5 resin, a C5C9 resin, a terpene resin, a rosin resin, or a phenolic resin. The resin may be used alone or in combination of two or more.

[0151] <Aromatic vinyl resin> In this specification, the term "aromatic vinyl resin" refers to a resin containing at least one aromatic vinyl compound selected from the group consisting of styrene, α-methylstyrene, vinyltoluene, p-chlorostyrene, etc. as a monomer component (excluding copolymer resins containing cyclopentadiene as a monomer component). As the aromatic vinyl resin, a homopolymer of α-methylstyrene or styrene or a copolymer of α-methylstyrene and styrene is preferred, and a copolymer of α-methylstyrene and styrene is more preferred, because they are economical, easy to process, and have excellent heat generation properties. As the aromatic vinyl resin, commercially available products from Kraton, Eastman Chemical Company, Mitsui Chemicals, Inc., etc., can be used. One type of the resin may be used alone, or two or more types may be used in combination.

[0152] <C9 resin> As used herein, the term "C9 resin" refers to a resin obtained by polymerizing a C9 fraction (excluding copolymer resins containing cyclopentadiene as a monomer component), and may be a polymer obtained by polymerizing a C9 fraction alone or a copolymer obtained by copolymerizing a C9 fraction with other components. Examples of C9 fractions include petroleum fractions having 8 to 10 carbon atoms selected from the group consisting of alkylstyrenes such as vinyltoluene, coumarone, indene, and methylindene. Specific examples of C9 resins include coumarone-indene resins, coumarone resins, and indene resins. These resins may be used singly or in combination.

[0153] <C5 resin> In this specification, "C5 resin" refers to a resin obtained by polymerizing a C5 fraction other than cyclopentadiene, and may be a hydrogenated or modified version of such a resin. Examples of C5 fractions other than cyclopentadiene include at least one petroleum fraction having 4 to 5 carbon atoms selected from the group consisting of dicyclopentadiene, isoprene, pentane, isopentane, neopentane, pentene, pentadiene, etc. Such resins may be used alone or in combination of two or more.

[0154] <C5C9 resin> The term "C5C9 resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and may be a hydrogenated or modified resin. As the C5C9 petroleum resin, for example, commercially available products from Tosoh Corporation, LUHUA, etc. can be used. The resin may be used alone or in combination of two or more.

[0155] <Terpene resin> Terpene resins refer to resins containing at least one terpene compound selected from the group consisting of α-pinene, β-pinene, limonene, dipentene, etc., as the most abundant monomer component, preferably at least 50 mol %, and may be hydrogenated or modified. Specific examples of terpene resins include polyterpene resins containing only one or more of the terpene compounds as monomer components; aromatic-modified terpene resins containing the terpene compound and an aromatic compound as monomer components; and terpene phenolic resins containing the terpene compound and a phenolic compound as monomer components. Examples of aromatic compounds that serve as monomer components for aromatic-modified terpene resins include at least one selected from the group consisting of styrene, α-methylstyrene, vinyltoluene, divinyltoluene, etc. Examples of phenolic compounds that serve as monomer components for terpene phenolic resins include at least one selected from the group consisting of phenol, bisphenol A, cresol, xylenol, etc. These resins may be used alone or in combination.

[0156] <Rosin-based resin> The rosin-based resin refers to a resin containing at least one rosin acid compound selected from the group consisting of abietic acid, neoabietic acid, palustric acid, isopimaric acid, etc., and may be a hydrogenated or modified version of such a rosin-based resin. Examples of the rosin-based resin include, but are not limited to, natural rosin and rosin-modified resins obtained by modifying rosin through hydrogenation, disproportionation, dimerization, esterification, etc. Such resins may be used singly or in combination of two or more.

[0157] <Phenol-based resin> The phenolic resin refers to a resin containing a phenolic compound such as phenol or cresol as the monomer component with the largest content, preferably 50 mol% or more. Examples of the phenolic resin include, but are not limited to, phenol-formaldehyde resin, alkylphenol-formaldehyde resin, alkylphenol-acetylene resin, and oil-modified phenol-formaldehyde resin. These resins may be used alone or in combination of two or more.

[0158] ≪Softening point≫ From the viewpoint of wet grip performance, the softening point of the resin is preferably above 80° C., more preferably above 90° C., and even more preferably above 100° C. Furthermore, from the viewpoint of processability and improving the dispersibility of the rubber component and the filler, the softening point is preferably below 150° C., more preferably below 140° C., and even more preferably below 130° C. The softening point of the resin is measured by the above-mentioned measurement method.

[0159] (Plasticizers other than resins) Plasticizers other than resins, such as oil, liquid rubber, and ester-based plasticizers, will now be explained.

[0160] (oil) Examples of oils include mineral oil, vegetable oil, and animal oil. From the viewpoint of life cycle assessment, waste oils used in rubber mixers and engines, and refined waste cooking oils used in restaurants may also be used. One type of oil may be used alone, or two or more types may be used in combination.

[0161] As used herein, mineral oil refers to oil derived from mineral resources such as petroleum and natural gas. Examples of mineral oil include paraffinic oil (mineral oil), naphthenic oil, and aromatic oil. Specific examples of mineral oil include mild extracted solvate (MES), distillate aromatic extract (DAE), treated distillate aromatic extract (TDAE), treated residual aromatic extract (TRAE), and residual aromatic extract (RAE). Furthermore, as an environmental measure, oils with a low content of polycyclic aromatic compounds (PCA) can also be used. Examples of low PCA oils include MES, TDAE, and heavy naphthenic oil.

[0162] In this specification, examples of vegetable oils include linseed oil, rapeseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, rice 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 Japan wax. Further examples of vegetable oils include refined oils (such as salad oil) obtained by refining the above oils, interesterified oils obtained by interesterifying the above oils, hardened oils obtained by hydrogenating the above oils, thermally polymerized oils obtained by thermally polymerizing the above oils, oxidatively polymerized oils obtained by oxidizing the above oils, and waste edible oils recovered from edible oils. Vegetable oils may be liquid or solid at 25°C.

[0163] The vegetable oil according to this embodiment preferably contains acylglycerol, and more preferably triacylglycerol. In this specification, acylglycerol refers to a compound in which a hydroxyl group of glycerin is esterified with 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, the 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. The acylglycerol may be liquid or solid at 25°C.

[0164] The method for confirming whether the rubber composition contains the acylglycerol is not particularly limited, but may be any of the following: 1 For example, a rubber composition containing triacylglycerol is immersed in deuterated chloroform at 25°C for 24 hours, and after removing the rubber composition, the 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 carbon atoms adjacent to the oxygen atoms of the ester group. In this paragraph, "around" refers to a range of ±0.10 ppm.

[0165] 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.

[0166] 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 a vegetable oil containing such a fatty acid, plants may be improved by breeding, genetic modification, or the like.

[0167] 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.

[0168] Examples of animal oils include fish oil, beef tallow, and oleyl alcohol derived from these.

[0169] When oil is contained, the content per 100 parts by mass of the rubber component is preferably 5 parts by mass or more, more preferably 8 parts by mass or more, and even more preferably 10 parts by mass or more from the viewpoint of processability. Moreover, the content of oil is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 30 parts by mass or less from the viewpoint of the effects of the present invention.

[0170] (liquid rubber) The liquid rubber is not particularly limited as long as it is a polymer that is in a liquid state at room temperature (25°C), and examples thereof include liquid butadiene rubber (liquid BR), liquid styrene butadiene rubber (liquid SBR), liquid isoprene rubber (liquid IR), liquid styrene isoprene rubber (liquid SIR), liquid farnesene rubber, etc. One type of liquid rubber may be used alone, or two or more types may be used in combination.

[0171] (ester plasticizer) Examples of ester-based plasticizers include dibutyl adipate (DBA), diisobutyl adipate (DIBA), dioctyl adipate (DOA), di-2-ethylhexyl azelate (DOZ), dibutyl sebacate (DBS), diisononyl adipate (DINA), diethyl phthalate (DEP), dioctyl phthalate (DOP), diundecyl phthalate (DUP), dibutyl phthalate (DBP), dioctyl sebacate (DOS), tributyl phosphate (TBP), trioctyl phosphate (TOP), triethyl phosphate (TEP), trimethyl phosphate (TMP), thymidine triphosphate (TTP), tricresyl phosphate (TCP), and trixylenyl phosphate (TXP). One type of ester-based plasticizer may be used alone, or two or more types may be used in combination.

[0172] [Other compounding agents] In addition to the rubber component, filler, and plasticizer, the rubber composition according to the present embodiment may contain compounding agents that are generally used in the tire industry, such as processing aids, vulcanized rubber particles, wax, stearic acid, zinc oxide, antioxidants, vulcanizing agents, and vulcanization accelerators, as appropriate.

[0173] (processing aids) Examples of processing aids include fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, mixtures of fatty acid metal salts and amide esters, and mixtures of fatty acid metal salts and fatty acid amides. These processing aids may be used alone or in combination of two or more. Examples of processing aids that can be used include those commercially available from Schill + Seilacher, Performance Additives, etc.

[0174] When a processing aid is contained, the content thereof per 100 parts by mass of the rubber component is preferably more than 0.5 parts by mass, more preferably more than 1 part by mass, and even more preferably more than 1.5 parts by mass from the viewpoint of improving processability, and is preferably less than 10 parts by mass, more preferably less than 8.0 parts by mass, and even more preferably less than 5.0 parts by mass from the viewpoint of abrasion resistance and breaking strength.

[0175] (vulcanized rubber particles) The vulcanized rubber particles are particles made of vulcanized rubber, and specifically, rubber powder as specified in JIS K 6316:2017 can be used. From the standpoint of environmental considerations and cost, recycled rubber powder produced from crushed waste tires is preferred. One type of vulcanized rubber particle may be used alone, or two or more types may be used in combination.

[0176] The vulcanized rubber particles are not particularly limited, and may be unmodified vulcanized rubber particles or modified vulcanized rubber particles.

[0177] As commercially available vulcanized rubber, for example, products from Lehigh, Muraoka Rubber Industries, Ltd., etc. can be used.

[0178] (wax) The wax is not particularly limited, and any wax commonly used in the tire industry can be suitably used, such as 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. 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. The wax according to this embodiment does not contain stearic acid. Waxes commercially available from, for example, Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Paramelt Co., Ltd., etc. can be used. One type of wax may be used alone, or two or more types may be used in combination.

[0179] When wax is contained, the content per 100 parts by mass of the rubber component is preferably more than 0.5 parts by mass, more preferably more than 1.0 part by mass, and even more preferably more than 1.5 parts by mass from the viewpoint of weather resistance of the rubber, and is preferably less than 10 parts by mass, more preferably less than 7.0 parts by mass, and even more preferably less than 5.0 parts by mass from the viewpoint of preventing whitening of the tire due to bloom.

[0180] (stearic acid) When stearic acid is contained, the content per 100 parts by mass of the rubber component is preferably more than 0.5 parts by mass, more preferably more than 1.0 part by mass, and even more preferably more than 1.5 parts by mass from the viewpoint of processability, and is preferably less than 10 parts by mass, more preferably less than 8.0 parts by mass, and even more preferably less than 5.0 parts by mass from the viewpoint of vulcanization rate.

[0181] (zinc oxide) When zinc oxide is contained, the content per 100 parts by mass of the rubber component is preferably more than 0.5 parts by mass, more preferably more than 1.0 part by mass, and even more preferably more than 1.5 parts by mass from the viewpoint of processability, and preferably less than 10 parts by mass, more preferably less than 8.0 parts by mass, and even more preferably less than 5.0 parts by mass from the viewpoint of abrasion resistance.

[0182] (anti-aging agent) The antioxidant is not particularly limited, but 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), N,N'-ditolyl ... p-phenylenediamine-based antioxidants such as diphenyldiamine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and N,N'-di-2-naphthyl-p-phenylenediamine (DNPD); quinoline-based antioxidants such as 2,2,4-trimethyl-1,2-dihydroquinoline polymers; monophenol-based antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol-based antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. 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. Commercially available products that can be used include those from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., and Flexis Co., Ltd. One type of antioxidant may be used alone, or two or more types may be used in combination.

[0183] When an antioxidant is contained, the content per 100 parts by mass of the rubber component is preferably more than 1 part by mass, more preferably more than 2 parts by mass, and even more preferably more than 3 parts by mass from the viewpoint of ozone crack resistance of the rubber, and is preferably less than 10 parts by mass, more preferably less than 8 parts by mass, and even more preferably less than 5 parts by mass from the viewpoint of abrasion resistance and wet grip performance.

[0184] (vulcanizing agent) Sulfur is preferably used as the vulcanizing agent. Examples of sulfur that can be used include powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. The vulcanizing agent may be used alone or in combination of two or more.

[0185] When sulfur is contained as a vulcanizing agent, the content per 100 parts by mass of the rubber component is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, from the viewpoint of ensuring a sufficient vulcanization reaction. Furthermore, from the viewpoint of preventing deterioration, the content is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, and even more preferably 3.0 parts by mass or less. When oil-containing sulfur is used as the vulcanizing agent, the content of the vulcanizing agent is the total content of pure sulfur contained in the oil-containing sulfur.

[0186] Examples of vulcanizing agents other than sulfur include alkylphenol-sulfur chloride condensate, sodium 1,6-hexamethylene-dithiosulfate dihydrate, and 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane. These vulcanizing agents other than sulfur are commercially available from Taoka Chemical Co., Ltd., Lanxess K.K., Flexis, and the like. One vulcanizing agent may be used alone, or two or more may be used in combination.

[0187] (Vulcanization accelerator) Examples of vulcanization accelerators include sulfenamide-based, thiazole-based, thiuram-based, thiourea-based, guanidine-based, dithiocarbamic acid-based, aldehyde-amine-based or aldehyde-ammonia-based, imidazoline-based, and xanthate-based vulcanization accelerators. Among these, sulfenamide-based, thiazole-based, and guanidine-based vulcanization accelerators are preferred. One type of vulcanization accelerator may be used alone, or two or more types may be used in combination.

[0188] Examples of sulfenamide vulcanization accelerators include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazolylsulfenamide (DCBS), etc. Among these, N-cyclohexyl-2-benzothiazolylsulfenamide (CBS) is preferred.

[0189] Examples of the thiazole vulcanization accelerator include 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, etc. Among these, 2-mercaptobenzothiazole is preferred.

[0190] Examples of guanidine vulcanization accelerators include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicatechol borate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, 1,3-di-o-cumenyl-2-propionylguanidine, etc. Among these, 1,3-diphenylguanidine (DPG) is preferred.

[0191] When a vulcanization accelerator is contained, the content thereof per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 1.5 parts by mass or more. The content thereof per 100 parts by mass of the rubber component is preferably 8 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 6 parts by mass or less. By setting the content of the vulcanization accelerator within the above range, breaking strength and elongation tend to be ensured.

[0192] <Various materials containing carbon atoms> In this specification, various materials containing carbon atoms (for example, rubber, oil, resin, vulcanization accelerator, antioxidant, surfactant, etc.) may be derived from atmospheric carbon dioxide. The various materials may be obtained from carbon dioxide by directly converting carbon dioxide or by converting methane obtained through a methanation process in which methane is synthesized from carbon dioxide.

[0193] [Manufacturing method] The rubber composition can be produced by a known method, for example, by kneading the above-mentioned components using a rubber kneading device such as an open roll or an internal kneader (such as a Banbury mixer or kneader).

[0194] The kneading process may include, for example, a base kneading process in which compounding ingredients and additives other than the vulcanizing agent and vulcanization accelerator are kneaded, and a final kneading (F kneading) process in which the vulcanizing agent and vulcanization accelerator are added to the kneaded product obtained in the base kneading process and kneaded. Furthermore, the base kneading process may be divided into multiple processes as desired. When the base kneading process is divided, the method may be (1) a method in which some of the compounding ingredients and additives are pre-mixed to form a masterbatch, and then the remaining compounding ingredients and additives are added to the resulting masterbatch and kneaded, or (2) a method in which all of the compounding ingredients and additives to be kneaded in the base kneading process are kneaded at once, and then the kneaded product is remilled one or more times. In the above method (1), the number of masterbatches is not limited and may be two or more. Furthermore, when the number of masterbatches is two or more, all of the compounding ingredients and additives used in the base kneading process may be allocated to one of the masterbatches.

[0195] The kneading conditions are not particularly limited, but examples include a method in which the base kneading step involves kneading for 3 to 10 minutes at a discharge temperature of 150 to 170°C, and a method in which the final kneading step involves kneading for 1 to 5 minutes at 70 to 110°C. The vulcanization conditions are not particularly limited, but examples include a method in which vulcanization is carried out for 10 to 30 minutes at 150 to 200°C.

[0196] The tire according to the present embodiment can be manufactured by a conventional method using the rubber composition. That is, the unvulcanized rubber composition is extruded to match the shape of the tread portion, and the unvulcanized tread portion is bonded together with other tire components in a tire building machine by a conventional method, and molded to form an unvulcanized tire. The unvulcanized tire thus obtained is then heated and pressurized in a vulcanizer. The vulcanization conditions are not particularly limited, and examples thereof include a method of vulcanizing at 150 to 200°C for 10 to 30 minutes.

[0197] [Application] In this specification, the term "tire" refers to pneumatic tires, non-pneumatic tires, etc., with pneumatic tires being preferred. Pneumatic tires can be used for passenger car tires, large passenger car tires, large SUV tires, heavy-duty tires, light truck tires, motorcycle tires, racing tires (high-performance tires), etc. Among these, they can be suitably used as heavy-duty tires, and are optimally used as tires for electric vehicles (EVs). In this specification, heavy-duty tires refer to tires intended to be mounted on four-wheeled automobiles and having a maximum load capacity of 1000 kg or more. The maximum load capacity of heavy-duty tires is preferably 1200 kg or more, and more preferably 1400 kg or more.

[0198] Examples (working examples) that are considered preferable for carrying out the present invention are shown below, but the scope of the present invention is not limited to these working examples. Rubber compositions and tires obtained according to the tables were examined using the various chemicals shown below, and the results calculated based on the evaluation methods below are shown in the tables.

[0199] <Various chemicals> The chemicals used in the examples and comparative examples are summarized below. NR:TSR20 SBR: Modified SBR produced in Production Example 1 described below (styrene content: 30% by mass, vinyl content: 20% by mole, Tg: -51°C, Mw: 880,000) BR: UBEPOL BR (registered trademark) 150B (unmodified BR, cis content: 97 mol%, Mw: 440,000) manufactured by UBE Corporation Carbon black: Seast N220 (N2SA: 114m) manufactured by Tokai Carbon Co., Ltd. 2 / g, average primary particle diameter: 22nm) Silica: Ultrasil VN3 (N2SA: 175 ml) manufactured by Evonik Degussa 2 / g, average primary particle diameter: 18nm) Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa Resin 1: Oppa PR383 manufactured by ExxonMobil (hydrogenated DCPD-C9 resin, containing styrene and cyclopentadiene as monomer components, Mw: 770, softening point: 103°C, styrene content: 1.78% by mass) Resin 2: ExxonMobil Oppera PR-120 (hydrogenated DCPD resin, containing cyclopentadiene as a monomer component, softening point: 120°C) Resin 3: SYLVATARAXX4401 (α-methylstyrene resin, Mw: 700, softening point: 85°C) manufactured by Kraton Oil: Idemitsu Kosan Co., Ltd. Diana Process NH-70S (aromatic process oil) Wax: Ozoace wax (paraffin wax) manufactured by Nippon Seiro Co., Ltd. Antioxidant 1: Nocrac 6C (6PPD) (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Antioxidant 2: Nocrac FR (2,2,4-trimethyl-1,2-dihydroquinoline polymer) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Stearic acid: Camellia stearic acid beads manufactured by NOF Corporation Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Co., Ltd. Vulcanization accelerator 1: Noccela CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Noccelaer D (1,3-diphenylguanidine (DPG)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0200] Manufacturing example: SBR manufacturing Cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene are charged into a nitrogen-purged autoclave reactor. The ratio of styrene to 1,3-butadiene is adjusted so that the styrene content is 30% by mass. After adjusting the temperature of the reactor contents to 20°C, n-butyllithium is added to initiate polymerization. Polymerization is carried out under adiabatic conditions, reaching a maximum temperature of 85°C. When the polymerization conversion rate reaches 99%, 1,3-butadiene is added, and the polymerization is continued for another 5 minutes. After GPC confirms the formation of a polymer with a molecular weight of 880,000, N,N-bis(trimethylsilyl)-3-aminopropyltrimethoxysilane is added as a modifier and the reaction is continued. After the polymerization reaction is complete, 2,6-di-tert-butyl-p-cresol is added. The solvent is then removed by steam stripping, and the mixture is dried on a heated roll heated to 110°C to obtain SBR.

[0201] Examples and Comparative Examples According to the formulations shown in Tables 1 and 2, a 1.7 L closed-type Banbury mixer is used to knead the chemicals other than sulfur and the vulcanization accelerator for 1 to 10 minutes until the discharge temperature reaches 150 to 160°C, yielding a kneaded mixture. Next, a two-screw open roll is used to add sulfur and the vulcanization accelerator to the kneaded mixture, which is then kneaded for 4 minutes until the temperature reaches 105°C, yielding an unvulcanized rubber composition. The unvulcanized rubber composition is extruded to the shape of the tread using an extruder equipped with a predetermined die, and then bonded together with other tire components to produce unvulcanized tires. These are then vulcanized at 170°C to obtain test tires (size: 245 / 40R19).

[0202] <Measurement of tan δ at 0°C> A rubber test specimen measuring 20 mm in length, 4 mm in width, and 1 mm in thickness was cut from the tread of each test tire, with the long side aligned in the tire circumferential direction and the thickness aligned in the tire radial direction. The loss tangent of each rubber test specimen was measured using a GABO Iplexer series under the following conditions: temperature 0°C, frequency 10 Hz, initial strain 10%, dynamic strain ±2.5%, and extension mode.

[0203] <Wet grip performance> Each test tire was fitted to all wheels of a vehicle (domestic FF 2000cc), and the braking distance from an initial speed of 100 km / h on a wet asphalt road surface was measured, and the measurement results were expressed as an index using the following calculation formula. The higher the index, the shorter the braking distance and the better the wet grip performance. In the wet grip performance index, Comparative Example 1 is used as the reference comparative example. (Wet grip performance index) = (braking distance of the reference comparative example) / (braking distance of each test tire) × 100

[0204] [Table 1]

[0205] [Table 2]

[0206] <Embodiment> Examples of embodiments of the present invention are given below. [1] A tire having a tread portion, a tread surface of the tread portion having four circumferential main grooves, a crown rib defined by the circumferential main grooves, and a pair of middle ribs adjacent to the crown rib and spaced apart by the circumferential main grooves; The total sea ratio N (%) of the crown rib and the middle rib is greater than 0 and less than 15, the tread portion is made of a rubber composition including a rubber component, a filler, and a plasticizer, the plasticizer contains a copolymer resin containing cyclopentadiene as a monomer component, When the total amount of the plasticizer relative to 100 parts by mass of the rubber component in the rubber composition is P (parts by mass), A tire having an N / P ratio of less than 3.0, preferably less than 2.0. [2] The tire according to [1] above, wherein N (%) is less than 12. [3] The tire according to [1] or [2] above, wherein N (%) is less than 9. [4] Sea ratio N of crown rib c (%) is less than 3. [5] Middle rib sea ratio N m The tire according to any one of the above [1] to [4], wherein (%) is less than 17, preferably less than 15, more preferably less than 10, and even more preferably less than 8. [6] The tread surface further has one or two shoulder ribs, and the shoulder ribs have a seam ratio N S The tire according to any one of the above [1] to [5], wherein (%) is greater than 20, preferably greater than 22. [7] The tire according to any one of the above [1] to [6], wherein the rubber component contains 90% by mass or more of a butadiene-based rubber. [8] The tire according to any one of the above [1] to [7], wherein the filler contains silica in an amount of 60% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. [9] The tire according to any one of the above [1] to [8], wherein the plasticizer contains a copolymer resin containing styrene and cyclopentadiene as monomer components.

[10] The tire according to any one of the above [1] to [9], wherein the ratio (0°C tanδ / N) of tanδ at 0°C of the rubber composition to N (0°C tanδ) is greater than 0.06, preferably greater than 0.08.

[11] When the total amount of copolymer resins containing cyclopentadiene as a monomer component relative to 100 parts by mass of the rubber component in the rubber composition is D (parts by mass), The tire according to any one of the above [1] to

[10] , wherein D×N is 80 or more, preferably 100 or more, and more preferably 140 or more.

[12] The tire according to any one of the above [1] to

[11] , wherein N / P is less than 1.0, preferably less than 0.5.

[13] The tire according to any one of [1] to

[12] above, which is for an electric vehicle. [Explanation of symbols]

[0207] CL Tire Equator W Tire width direction C Circumferential direction of tire TW tire contact width 1 Tread 2 Circumferential main groove 3 Crown Rib 4. Middle Rib 5 Shoulder Ribs 6 Shoulder Block 7 Yokomizo 7a Lateral grooves with a maximum depth of 3.0 mm or more 7b Lateral grooves with a maximum depth of less than 3.0 mm 7c Lateral grooves with a maximum depth of less than 3.0 mm 7d Lateral grooves with a maximum depth of less than 3.0 mm 7e Lateral grooves with a maximum depth of less than 3.0 mm

Claims

1. A tire having a tread portion, a tread surface of the tread portion having four circumferential main grooves, a crown rib defined by the circumferential main grooves, and a pair of middle ribs adjacent to the crown rib and spaced apart by the circumferential main grooves; a total sea ratio N (%) of the crown rib and the middle rib is greater than 0 and less than 15; the tread portion is made of a rubber composition including a rubber component, a filler, and a plasticizer, the plasticizer contains a copolymer resin containing cyclopentadiene as a monomer component, When the total amount of the plasticizer relative to 100 parts by mass of the rubber component in the rubber composition is P (parts by mass), A tire having an N / P ratio of less than 3.

0.

2. The tire of claim 1, wherein said N(%) is less than 12.

3. 3. The tire according to claim 1, wherein said N(%) is less than 9.

4. Sea ratio N of crown rib c 3. The tire of claim 1, wherein (%) is less than 3.

5. Middle rib sea ratio N m 3. The tire of claim 1, wherein the % is less than 17.

6. The tread surface further has one or two shoulder ribs, and the shoulder ribs have a sea ratio N S 3. The tire of claim 1, wherein (%) is greater than 20.

7. The tire according to claim 1 or 2, wherein the rubber component contains 90% by mass or more of a butadiene-based rubber.

8. The tire according to claim 1 or 2, wherein the filler contains silica in an amount of 60% by mass or more.

9. 3. The tire according to claim 1, wherein the plasticizer contains a copolymer resin containing styrene and cyclopentadiene as monomer components.

10. The tire according to claim 1 or 2, wherein a ratio (0°C tan δ / N) of tan δ at 0°C of the rubber composition to N (0°C tan δ) is greater than 0.

06.

11. When the total amount of copolymer resins containing cyclopentadiene as a monomer component relative to 100 parts by mass of the rubber component in the rubber composition is D (parts by mass), 3. The tire according to claim 1, wherein D×N is 80 or more.

12. 3. The tire of claim 1 or 2, wherein N / P is less than 1.

0.

13. The tire according to claim 1 or 2, which is for an electric vehicle.

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