Tire

Abstract

Provided is a tire capable of achieving both wet grip performance during high-speed travel and wear resistance at low temperatures. A pneumatic tire having a tread portion comprising a rubber composition containing 50 parts by mass or more of silica with respect to 100 parts by mass of a rubber component containing more than 50% by mass of a butadiene rubber and a styrene butadiene rubber, when the total styrene content in the rubber component is 25 mass% or less, ABR is the content (mass%) of the butadiene rubber in the rubber component, and L is the ground contact area ratio (%) of the tread surface of the tread portion, ABR and L satisfy the following formula. (1) ABR * Lgt; 3000, 3000.

Description

Technical Field

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

[0002] Various methods for improving wet grip performance and wear resistance have been studied so far. For example, Patent Document 1 discloses a tire rubber composition containing a diene rubber (A) containing a specified amount of a specific conjugated diene rubber represented by a specified formula, silica having a CTAB adsorption specific surface area within a specified range, and a silane coupling agent represented by a specified formula, and a pneumatic tire using the same for a tire tread. [Prior art literature] [Patent Literature]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-141405 Summary of the invention [Problems to be solved by the invention]

[0004] However, since wet grip performance and wear resistance are basically contradictory properties, it is difficult to improve both at the same time, and further improvement in balancing the performance of both is sought.

[0005] An object of the present invention is to provide a tire that can achieve both wet grip performance during high-speed running and wear resistance at low temperatures.

Methods to solve the problem

[0006] The present invention relates to the following tire. A pneumatic tire, characterized in that: It is a pneumatic tire having a tread portion. The tread portion is composed of a rubber composition containing 50 parts by mass or more of silica per 100 parts by mass of the rubber component. The rubber component contains more than 50% by mass of butadiene rubber and styrene butadiene rubber, The total amount of styrene in the rubber component is 25% by mass or less, The content (mass %) of the butadiene rubber in the rubber component is denoted as A BR , when the contact area ratio (%) of the tread of the tread portion is L, A BR and L satisfy the following formula. (1) A BR ×L>3000 [Effects of the invention]

[0007] According to the present invention, it is possible to provide a tire that can achieve both wet grip performance during high-speed running and wear resistance performance at low temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

[0009] A tire according to one embodiment of the present invention is a pneumatic tire having a tread portion. The tread portion is composed of a rubber composition containing 50 parts by mass or more of silica per 100 parts by mass of the rubber component. The rubber component contains more than 50% by mass of butadiene rubber and styrene butadiene rubber, The total amount of styrene in the rubber component is 25% by mass or less, The content (mass %) of the butadiene rubber in the rubber component is denoted as A BR , when the contact area ratio (%) of the tread of the tread portion is L, A BR and L satisfy the following formula. (1) A BR ×L>3000

[0010] Although not wishing to be limited by theory, the principle of achieving both wet grip performance during high-speed running and wear resistance at low temperatures in the present invention can be considered as follows.

[0011] That is, it is considered that (1) by making the main polymer of the rubber component of the rubber composition constituting the tread portion a butadiene rubber (BR), the wear resistance is improved; (2) by containing a certain amount or more of silica, the road followability of the tread portion is improved, thereby improving the wet grip performance; (3) by making the rubber component further contain styrene butadiene rubber (SBR) and by making the total styrene content in the rubber component below a certain value, SBR becomes easily compatible with BR, and the silica is easily dispersed in the BR phase in the SBR domin where it is easily distributed, thereby effectively reinforcing the BR, maintaining the wear resistance, and improving the wet grip performance; (4) the glass transition temperature of the rubber composition containing the rubber component with a low total styrene content becomes low, so that the temperature dependence is reduced, and the grip performance when the tire is heated due to high-speed running and the wear resistance performance during the period of low temperature are not easily reduced; (5) by maintaining the contact area ratio of the tread surface at a large level, the contact area is increased, thereby dispersing the wear energy input from the road to the tread surface, and thus the wear of the tread can be suppressed. In this way, it is considered that the synergistic effect of (1) to (5) can achieve both wet grip performance during high-speed running and wear resistance performance at low temperatures.

[0012] The total amount of styrene (mass %) is referred to as A STY When A BR , L and A STY It is preferable to satisfy the following formula. (2) (A BR / A STY )×L>130

[0013] It can be considered that A BR Towards a larger direction, L to a larger direction, and A STY The smaller the size, the better the wet grip performance at high speeds and the wear resistance at low temperatures.

[0014] The rubber composition contains at least one hydrocarbon resin, and the content of the hydrocarbon resin in the rubber composition is preferably 5% by mass or more.

[0015] It is considered that since hydrocarbon resins tend to be distributed preferentially in the SBR phase region like silica, by further combining a certain amount of hydrocarbon resin or more, the SBR phase region where the hydrocarbon resin tends to be distributed preferentially is dispersed in the BR phase, which is beneficial to both wet grip performance and wear resistance.

[0016] The content of the silica is preferably 100 parts by mass or more based on 100 parts by mass of the rubber component.

[0017] It is considered that the road surface following property of the tread portion is further improved by silica, and the wet grip performance is improved.

[0018] The glass transition temperature of the rubber composition is preferably lower than -30°C.

[0019] This is considered to be because the temperature dependency of the rubber composition is reduced, and the grip performance when the tire is heated by high-speed running and the wear resistance performance when the temperature is low are less likely to decrease.

[0020] The right side of formula (1) is preferably 3250, more preferably 3500.

[0021] It is considered that by increasing the product of the content of butadiene rubber and the ground contact area ratio, improvement in wear resistance can be expected.

[0022] The content of the butadiene rubber in the rubber component is A BR It is preferably less than 70 mass %.

[0023] It is considered that as the butadiene rubber content in the rubber component increases, the wear resistance at low temperatures tends to improve. However, since Tg decreases, the loss in the temperature range generally considered to contribute to wet grip (tan δ at 0°C) also decreases, and the balance with the wet grip performance during high-speed running is disrupted. Therefore, in order to achieve both performance and stability, it is necessary to set the content to less than 70% by mass.

[0024] The glass transition temperature of the styrene butadiene rubber is preferably lower than -30°C.

[0025] It is considered that as the glass transition temperature of the rubber composition decreases, the grip performance when the tire generates heat due to high-speed running and the wear resistance performance when the temperature is low are less likely to decrease.

[0026] The tread surface has two or more circumferential main grooves extending in the tire circumferential direction and a land portion divided by the circumferential main grooves. When a pair of the land portions located at the outermost sides in the tire width direction among the land portions are provided as shoulder land portions, the shoulder land portions preferably have at least one opening area greater than 0.1 mm 2 Less than 15mm 2 of small holes.

[0027] It is considered that the small holes contribute to improving drainage, so drainage in the shoulder region is improved, and wet grip performance is improved.

[0028] The tread surface has more than two circumferential main grooves extending along the circumferential direction of the tire and a ground contact portion divided by the circumferential main grooves. When a pair of ground contact portions located at the outermost sides in the tire width direction are set as shoulder ground contact portions, the shoulder ground contact portion preferably has at least one circumferential fine groove.

[0029] It is considered that the circumferential fine grooves contribute to improving drainage, so drainage in the shoulder region is improved, and wet grip performance is improved.

[0030] The tread surface preferably has a widened circumferential groove whose groove width widens toward the inner side in the tire radial direction.

[0031] It is considered that the widened circumferential groove increases in width as the tread portion wears, and the drainage performance of the tire after wear is improved, thereby improving the wet grip performance.

[0032] The widened circumferential groove is preferably present at a land portion located on the tire centerline, or, when a circumferential main groove is present on the tire centerline, at a land portion closest to the tire centerline.

[0033] It is considered that the drainage after the tire is worn is improved in the center portion in the tire width direction, and the wet grip performance is improved.

[0034] [definition] The “normal state” refers to a state where the wheel is assembled on a normal rim and filled with a normal internal pressure without load.

[0035] "Dimensions of each part of the tire" are: unless otherwise specified, the "dimensions of each part of the tire" that appear on the outer surface of the tire are the values ​​specified under the normal state. On the other hand, the "dimensions of each part of the tire" that exist inside the tire are the values ​​specified when the tire is cut with a plane containing the tire rotation axis and the cut tire piece is kept at the rim width of the normal rim.

[0036] "Regular rims" refer to rims whose standards are specified for each tire in the standard system including the standards on which the tire is based, for example, standard rims in applicable sizes listed in the JATMA Yearbook of JATMA (Japan Automobile Tire Association), "Measuring Rim" listed in the Standards Manual of the European Tire and Rim Technical Organisation (ETRTO), and "Design Rim" listed in the Yearbook of the Tire and Rim Association, Inc. (TRA). Reference is made to JATMA, ETRTO, and TRA in that order, and when referring to applicable sizes, the applicable sizes are followed. In addition, for tires not specified in the standards, the rim with the smallest diameter, followed by the rim with the smallest rim width, is a rim that can be assembled and can maintain internal pressure, that is, a rim that does not leak air between the rim and the tire.

[0037] "Regular internal pressure" means: in the standard system including the standard on which the tire is based, the air pressure specified for each tire by the standard, for example, the maximum value recorded in the "maximum air pressure" of JATMA, the "INFLATION PRESSURE" of ETRTO, and the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" of TRA. As in the case of regular rims, reference is made to JATMA, ETRTO, and TRA in this order, and when making references, the standard is followed if there is an applicable size. In addition, in the case of a tire not specified in the above standards, the regular internal pressure (including 250 kPa or more) of other tire sizes (including tires specified in the standards) recorded with the above regular rim as the standard rim is referred to. When multiple regular internal pressures of 250 kPa or more are recorded, the minimum value among them is referred to.

[0038] "Normal load" is the load specified for each tire in the standard system including the standard on which the tire is based. For example, it refers to the maximum value recorded in JATMA's "Maximum load capacity", ETRTO's "LOAD CAPACITY", and TRA's "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES". As with the normal rim and normal internal pressure, it is referenced in the order of JATMA, ETRTO, and TRA. When referencing, if there is an applicable size, follow the standard. At the same time, if it is a tire not specified in the above standards, the normal load W is calculated according to the following calculation: L In addition, in this specification, "maximum load capacity" has the same meaning as the above-mentioned normal load. W L =0.000011×V+175 V=[(Dt / 2) 2 -(Dt / 2-Ht) 2}×π×Wt V: Virtual volume of the tire (mm 3 ) Dt: Tire outer diameter Dt (mm) Ht: Tire section height (mm) Wt: tire section width (mm)

[0039] The "contact area ratio L (%)" is calculated by the following formula from the total contact area and the effective contact area of ​​the tire. Ground contact area ratio L (%) = (effective ground contact area / total ground contact area) × 100

[0040] The "total contact area" is the area of ​​the tread region obtained from the profile of the tire when it is pressed on the ground. The total contact area can be obtained by assembling the tire on a regular rim, loading it with a regular internal pressure, leaving it at 25°C for 24 hours, applying ink to the tire tread surface, loading the tire with a regular load (maximum load capacity) and pressing it vertically on a cardboard (camber angle of 0°), and transferring the ink. The total contact area is the average of the five areas obtained by rotating the tire 72 degrees in sequence and performing the above transfer operation at a total of five locations.

[0041] The "effective contact area" is the area of ​​the tread of the tire that contacts the ground when the tire is pressed against the ground. The effective contact area can be obtained by assembling the tire on a regular rim, loading it with a regular internal pressure, leaving it at 25°C for 24 hours, applying ink to the surface of the tire tread, loading the tire with a regular load (maximum load capacity) and pressing it vertically on a cardboard (camber angle of 0°), and transferring the ink. The effective contact area is the average of the five areas obtained by rotating the tire 72 degrees in sequence and performing the above transfer operation at a total of five locations.

[0042] "Total styrene content (mass %)" refers to the total content of styrene parts contained in the total amount of rubber components, which can be calculated by Σ(styrene content (mass %) in each rubber component × content (mass %) of each rubber component in the total amount of rubber components / 100). For example, in 100% by mass of the rubber component, when styrene butadiene rubber with a styrene content of 40% by mass is 85% by mass, styrene butadiene rubber with a styrene content of 25% by mass is 5% by mass, and butadiene rubber with a styrene content of 0% by mass is 10% by mass, the total styrene content in the rubber component is 35.25% by mass (=40×85 / 100+25×5 / 100+0×10 / 100).

[0043] The “hydrocarbon resin content” refers to the total content of at least one hydrocarbon resin contained in the rubber composition.

[0044] The "content of plasticizer" also includes the amount of plasticizer in the rubber component extended by the plasticizer. Similarly, the "content of oil" also includes the amount of oil contained in the oil-extended rubber.

[0045] "Circumferential main groove" means: a circumferential groove extending continuously along the circumference of the tire, wherein the groove width in the tire width direction on the tread surface is 4 mm or more. The circumferential main groove may extend in a straight line along the circumference, or may extend in a wave, sinusoidal or zigzag shape along the circumference. The widened circumferential groove described below is not included.

[0046] "Contact portion" refers to the area of ​​the tread surface divided by the circumferential main groove, which is the part where the tire contacts the road surface. Among the contact portions, the pair of contact portions located on the outermost sides in the tire width direction are called shoulder contact portions, and the contact portion in the area sandwiched by the shoulder contact portions is called the center contact portion. When there is only one circumferential main groove, there is only the shoulder contact portion, and there is no center contact portion.

[0047] "Small holes" refer to small holes on the tread surface that extend from the inside of the tread to the tread surface. The small holes exist independently and are not connected to the circumferential grooves, lateral grooves, etc.

[0048] "Circumferential fine grooves" refer to circumferential grooves that extend continuously in the circumferential direction of the tire and have a groove width of less than 4 mm in the tire width direction on the tread surface. Circumferential fine grooves may extend in a straight line in the circumferential direction, or in a wave, sinusoidal or zigzag shape in the circumferential direction. The widened circumferential grooves described below are not included.

[0049] "Expanded circumferential groove" means a circumferential groove that continuously extends along the circumference of the tire, and is configured so that the groove width in the tire width direction is the smallest at the tread surface and expands inward in the tire radial direction. The expanded circumferential groove may extend in a straight line along the circumference, or may extend in a wave-like, sinusoidal or zigzag shape along the circumference.

[0050] [Measurement method] "Styrene content (mass %)" by 1 H-NMR measurement and calculation.

[0051] “Vinyl content (1,2-bonded butadiene unit amount) (mol %)” is calculated by infrared absorption spectrum analysis in accordance with JIS K 6239-2:2017.

[0052] The “cis content (cis-1,4-bonded butadiene unit amount) (mol %)” is calculated by infrared absorption spectrum analysis in accordance with JIS K 6239-2:2017.

[0053] The "glass transition temperature (Tg) (°C)" is measured by using a differential scanning calorimeter (Q200) manufactured by TA Instruments Japan Co., Ltd. while heating at a heating rate of 10°C / min in accordance with JIS K 7121. In the present invention, Tg of styrene butadiene rubber, butadiene rubber, etc. is particularly measured.

[0054] "Glass transition temperature (Tg) of rubber composition" refers to the temperature (tanδ peak temperature) corresponding to the maximum value of the temperature distribution curve in the range of -60°C to 40°C obtained by measuring the temperature distribution curve of tanδ using a dynamic viscoelasticity measuring device (e.g., EPLEXOR series manufactured by GABO Corporation) under the conditions of frequency 10 Hz, initial strain 10%, dynamic strain ±0.5%, and heating rate 2°C / min. In addition, in the measurement in the range of -60 to 40°C, when the tanδ value increases or decreases monotonically with the increase in temperature, the glass transition temperature of the rubber composition is set to 40°C or -60°C, respectively. In addition, in the range of -60°C to 40°C, when there are two or more points showing the maximum value, the point with the lowest temperature is set to the glass transition temperature.

[0055] The “weight average molecular weight (Mw)” can be determined by converting the measured value into standard polystyrene based on gel permeation chromatography (GPC) (e.g., GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTIPORE HZ-M manufactured by Tosoh Corporation).

[0056] “N2SA of carbon black” is measured according to JIS K 6217-2:2017.

[0057] "N2SA of silica" is measured by the BET method according to ASTM D3037-93.

[0058] The "average primary particle size" is obtained by taking a photograph of the particles with a transmission or scanning electron microscope and taking the arithmetic average of the particle sizes of 400 particles. For the particle size, when the shape of the particle is roughly circular, the diameter of the circle is set as the particle size, and when it is needle-shaped or rod-shaped, the short diameter is set as the particle size. In other cases, the equivalent circle diameter calculated from the electron microscope image is set as the particle size. The equivalent circle diameter can be obtained by setting it to "the positive square root of [4×(area of ​​the particle) / π]". The average primary particle size is applicable to silica, carbon black, etc.

[0059] The "softening point" is defined as the temperature at which a ball falls when the softening point specified in JIS K 6220-1:2001 is measured using a ring and ball softening point measuring apparatus.

[0060] [tire] The pneumatic tire of the present invention will be described below with reference to the accompanying drawings as appropriate. However, the accompanying drawings are only for illustration and the present invention is not to be construed in a limited manner based on the accompanying drawings.

[0061] The pneumatic tire of the present invention is characterized in that it is a pneumatic tire having a tread portion, wherein the tread portion is composed of a predetermined rubber composition, and in the rubber composition, the content (mass %) of butadiene rubber in the rubber component is set to A BR , when the contact area ratio (%) of the tread surface in the tread portion is L, A BR and L satisfy the following formula. (1) A BR ×L>3000

[0062] <Formula (1)> In the pneumatic tire of the present invention, the contact area ratio L (%) of the tread surface is calculated from the total contact area and the effective contact area of ​​the tire as defined above.

[0063] Figure 1 Indicates the area of ​​the tread obtained from the profile of the tire when it is pressed against the ground when calculating the total contact area. As described above, this profile can be obtained by assembling the tire on a regular rim, loading it with a regular internal pressure, leaving it at 25°C for 24 hours, applying ink to the tread surface of the tire, loading the tire with a regular load (maximum load capacity) and pressing it vertically on a cardboard (camber angle of 0°) to transfer the ink. Figure 1 CL is the tire center line.

[0064] The contact area ratio is preferably 60% or more, more preferably 61% or more, further preferably 62% or more, further preferably 63% or more, further preferably 64% or more, further preferably 65% ​​or more. In addition, the contact area ratio is preferably 80% or less, further preferably 75% or less, further preferably 70% or less.

[0065] The right side of formula (1) is preferably 3250, more preferably 3500, further preferably 3750, further preferably 4000. On the other hand, for A BR There is no particular upper limit to the value of ×L, and it may be, for example, 6500, or 6000, or 5000.

[0066] <Formula (2)> The pneumatic tire of the present invention is preferably: the total amount of styrene (mass %) in the rubber component contained in the rubber composition is A STY When A BR , L and A STY Satisfies the following formula. (2) (A BR / A STY )×L>130

[0067] The right side of formula (2) is preferably 200, more preferably 300, further preferably 360, further preferably 450, further preferably 550, further preferably 600. On the other hand, for (A BR / A STY There is no particular upper limit for the value of )×L, and for example, it can be 750, or 700, or 650.

[0068] <Glass Transition Temperature of Rubber Composition> In the rubber composition constituting the tread portion of the pneumatic tire of the present invention, the glass transition temperature (° C.) of the rubber composition is preferably lower than -30° C.

[0069] From the viewpoint of reducing the temperature dependency of the rubber composition, the glass transition temperature is preferably less than -33°C, more preferably less than -37°C, further preferably less than -40°C, and further preferably less than -42°C. On the other hand, the lower limit of the glass transition temperature is not particularly limited, and may be, for example, greater than -50°C, greater than -47°C, or greater than -45°C.

[0070] The glass transition temperature can be appropriately adjusted according to the type and amount of the rubber component constituting the rubber composition, and the type and amount of additives other than the rubber component.

[0071] <Small hole> The pneumatic tire of the present invention preferably has a tread surface having two or more circumferential main grooves extending in the tire circumferential direction and a land portion divided by the circumferential main grooves, and when a pair of land portions located at the outermost sides in the tire width direction of the land portions are set as shoulder land portions, the shoulder land portions have at least one opening area greater than 0.1 mm 2 Less than 15mm 2 of small holes.

[0072] Figure 2 An embodiment of the pneumatic tire of the present invention including the above-mentioned small holes is shown. Figure 2 In the embodiment, small holes 4 are formed on a pair of contact portions 3 in the shoulder region of the tread surface. The small holes help to improve drainage, so the drainage in the shoulder region is improved, which helps to improve wet grip performance. For example, it can be considered that in actual use, the shoulder contact portion or the central contact portion on one side is worn first, and even if the remaining shoulder contact portion hardens over time, the small holes can ensure drainage, making it easy to improve wet grip performance after wear. The opening area of ​​the small holes on the tread surface is preferably greater than 0.1 mm 2 , more preferably greater than 0.5 mm 2 , more preferably greater than 1.0 mm 2 , especially preferably greater than 1.5 mm 2In addition, the opening area of ​​the small holes on the tread surface is preferably less than 15 mm 2 , more preferably less than 10 mm 2 , more preferably less than 7.0 mm 2 , preferably less than 5.0 mm 2 The depth of the deepest part of the small hole is preferably 3% or more of the deepest part of the circumferential main groove, more preferably 5% or more. In addition, the depth of the deepest part of the small hole is preferably 80% or less of the deepest part of the circumferential main groove, more preferably 60% or less, and further preferably 40% or less.

[0073] <Circumferential fine groove> The pneumatic tire of the present invention is preferably: the tread surface has more than two circumferential main grooves extending along the circumferential direction of the tire and a ground contact portion divided by the above-mentioned circumferential main grooves, and when a pair of ground contact portions located at the outermost sides in the tire width direction are set as shoulder ground contact portions, the above-mentioned shoulder ground contact portions have at least one circumferential fine groove.

[0074] Figure 3 An embodiment of the pneumatic tire of the present invention including the above-mentioned circumferential narrow grooves is shown. Figure 3 In the tire, a pair of land portions 3 present in the shoulder region of the tread surface are formed with circumferential narrow grooves 5. The circumferential narrow grooves contribute to improved drainage, so drainage in the shoulder region is improved, contributing to improved wet grip performance.

[0075] <Wide Circumferential Groove> The pneumatic tire of the present invention preferably has a tread surface with a widened circumferential groove whose groove width widens toward the inner side in the tire radial direction.

[0076] Figure 4 An embodiment of the pneumatic tire of the present invention including the above-mentioned widened circumferential groove is shown. Figure 4 In the embodiment, linear widened circumferential grooves 6 are formed on two land portions 3 adjacent to the circumferential main groove 2 passing through the center line of the tire. The widened circumferential grooves can extend in a wave shape, a sine shape or a sawtooth shape in the circumferential direction. In addition, there is no particular limitation on the land portion where the widened circumferential groove is formed, but it is preferably formed on the land portion located on the center line of the tire, or when there is a circumferential main groove on the center line of the tire, it is preferably formed like Figure 4 The ground contact portion closest to the tire center line is formed like the widened circumferential groove 6. In addition, the ground contact portion closest to the tire center line refers to the ground contact portion where the distance between the inner end of the ground contact portion in the tire width direction and the tire center line is the smallest.

[0077] Figure 5 It is a diagram showing a cross section of the widened circumferential groove 6 . Figure 5In the embodiment, the groove width of the widened circumferential groove increases monotonically toward the inner side in the tire radial direction, but the increase in the groove width is not limited to such a form, and for example, it may increase while repeating slight increases and decreases in a curved or stepped manner.

[0078] [Rubber composition] The rubber composition constituting the tread portion of the pneumatic tire of the present invention will be described below.

[0079] The rubber composition according to the present invention contains 50 parts by mass or more of silica based on 100 parts by mass of the rubber component.

[0080] <Rubber ingredients> The rubber component contains: more than 50% by mass of butadiene rubber (BR) and styrene butadiene rubber (SBR). In addition, the rubber component may also be a rubber component containing other rubber components other than BR and SBR such as isoprene rubber (IR rubber). Furthermore, the rubber component may also be a rubber component consisting only of more than 50% by mass of BR and SBR.

[0081] (SBR) As SBR, there is no particular limitation, and examples include solution polymerization SBR (S-SBR), emulsion polymerization SBR (E-SBR), and modified SBRs (modified S-SBR, modified E-SBR) thereof. As modified SBR, examples include SBRs with modified ends and / or main chains, and modified SBRs (condensates, substances with branched structures, etc.) coupled with tin or silicon compounds, etc. Among them, S-SBR and modified SBR are preferred. Furthermore, hydrides (hydrogenated SBR) of these SBRs, etc., may also be used. SBR may be used alone or in combination of two or more.

[0082] Examples of the S-SBR that can be used in the present invention include S-SBR manufactured and commercially available from JSR Corporation, Sumitomo Chemical Co., Ltd., Ube Industries, Ltd., Asahi Kasei Corporation, and ZS Elasteromers Corporation.

[0083] From the viewpoint of suppressing the temperature dependency of the rubber composition, it is preferred that the styrene content of SBR is less, for example, preferably less than 40 mass %, more preferably less than 30 mass %, more preferably less than 20 mass %, further preferably less than 15 mass %. There is no particular restriction on the lower limit of the styrene content, which is usually greater than 1 mass %, or greater than 3 mass %, or greater than about 5 mass %. In addition, the styrene content of SBR is measured by the above-mentioned determination method.

[0084] From the viewpoint of ensuring reactivity with silica and wet grip performance, rubber strength and wear resistance, the vinyl content of SBR is preferably greater than 10 mol%, more preferably greater than 13 mol, and more preferably greater than 15 mol. In addition, from the viewpoint of preventing temperature correlation from increasing and elongation at break and wear resistance, the vinyl content of SBR is preferably less than 50 mol, more preferably less than 40 mol, and more preferably less than 30 mol. In addition, the vinyl content (1,2-bonded butadiene unit amount) of SBR is determined by the above-mentioned determination method.

[0085] From the viewpoint of suppressing the temperature dependency of the rubber composition, the glass transition temperature (Tg) of SBR is preferably less than -30°C. The Tg of SBR is preferably less than -40°C, more preferably less than -50°C, and further preferably less than -55°C. In addition, the Tg is usually greater than -80°C, or greater than -70°C, or greater than -65°C. In addition, the Tg of SBR is measured by the above-mentioned measurement method.

[0086] From the viewpoint of wet grip performance, the weight average molecular weight (Mw) of SBR is preferably greater than 200,000, more preferably greater than 250,000, and further preferably greater than 300,000. In addition, from the viewpoint of crosslinking uniformity, the weight average molecular weight is preferably less than 2 million, more preferably less than 1.8 million, and further preferably less than 1.5 million. In addition, the weight average molecular weight of SBR is measured by the above-mentioned measurement method.

[0087] From the viewpoint of wet grip performance, the content of SBR in the rubber component is preferably greater than 25% by mass, more preferably greater than 30% by mass, and further preferably greater than 35% by mass. On the other hand, from the viewpoint of the effect of the invention, the content of SBR in the rubber component is preferably less than 50% by mass, more preferably less than 48% by mass, and further preferably less than 45% by mass.

[0088] (BR) There are no particular limitations on the BR, and for example, BR having a cis content of less than 50 mol% (low cis BR), BR having a cis content of more than 90 mol% (high cis BR), rare earth-based butadiene rubber synthesized using a rare earth element catalyst (rare earth-based BR), BR containing syndiotactic polybutadiene crystals (BR containing SPB), and modified BR (high cis-modified BR, low cis-modified BR) commonly used in the tire industry can be used. As the modified BR, there can be mentioned BR modified with the same functional groups as described above for the SBR. One type of BR can be used alone, or two or more types can be used in combination.

[0089] As high cis BR, for example, commercially available materials such as Zeon Co., Ltd., Ube Industries, Ltd., and JSR Co., Ltd. can be used. By containing high cis BR, low temperature characteristics and wear resistance can be improved. The cis content is preferably greater than 95 mol%, more preferably greater than 96 mol%, and further preferably greater than 97 mol%. In addition, in this specification, the cis content (cis-1,4-bonded butadiene unit amount) is a value calculated by infrared absorption spectrum analysis.

[0090] The rare earth BR is synthesized using a rare earth element catalyst, and the vinyl content is preferably less than 1.8 mol%, more preferably less than 1.6 mol%, and further preferably 1.5 mol% or less, and the cis content is preferably greater than 95 mol%, more preferably greater than 96 mol%, and further preferably 97 mol% or more. As the rare earth BR, for example, commercially available products such as those produced by Lanxess Co., Ltd. can be used.

[0091] Examples of SPB-containing BR include 1,2-syndiotactic polybutadiene crystals dispersed in BR instead of simply being dispersed in BR, but being dispersed by chemical bonding with BR. As such SPB-containing BR, products commercially available from Ube Industries, Ltd. and the like can be used.

[0092] As the modified BR, a modified butadiene rubber (modified BR) in which the terminal and / or the main chain is modified with a functional group containing at least one element selected from silicon, nitrogen and oxygen can be preferably used.

[0093] Other modified BRs include those obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and further, BRs in which the ends of the modified BR molecules are bonded by tin-carbon bonds (tin-modified BRs), etc. In addition, the modified BR may be unhydrogenated modified BR or any hydrogenated modified BR.

[0094] From the viewpoint of wear resistance, the weight average molecular weight (Mw) of BR is preferably greater than 300,000, more preferably greater than 350,000, and further preferably greater than 400,000. In addition, from the viewpoint of crosslinking uniformity, etc., it is preferably less than 2 million, more preferably less than 1 million, and further preferably less than 500,000. In addition, Mw can be obtained by the above-mentioned measurement method.

[0095] The rubber component of the present invention contains more than 50% by mass of BR. From the viewpoint of wear resistance, the content of BR in the rubber component (A BR ) is preferably greater than 51% by mass, more preferably greater than 53% by mass, and still more preferably greater than 55% by mass. In addition, from the viewpoint of wet grip performance, A BRIn one embodiment, it is preferably less than 90% by mass, more preferably less than 85% by mass, further preferably less than 80% by mass, and further preferably less than 75% by mass. BR In other embodiments, it is preferably less than 70 mass %, more preferably less than 65 mass %, and even more preferably less than 60 mass %.

[0096] (Other rubber components) The rubber component to which the present invention relates may also contain rubber components other than SBR and BR. For other rubber components, crosslinkable rubber components that can be commonly used in the tire industry can be used, for example, isoprene-based rubber (IR-based rubber), styrene-isoprene-butadiene copolymer rubber (SIBR), styrene-isobutylene-styrene block copolymer (SIBS), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), hydrogenated nitrile rubber (HNBR), butyl rubber (IIR), ethylene-propylene rubber, polynorbornene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), chloroether rubber, etc. can be cited. Other rubber components can be used alone or in combination of two or more.

[0097] As IR rubber, for example, isoprene rubber (IR) and natural rubber, which are common materials in the tire industry, can be used. Natural rubber may contain, in addition to non-modified natural rubber (NR), modified natural rubbers such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), high-purity natural rubber, and grafted natural rubber. Isoprene rubber may be used alone or in combination of two or more.

[0098] The NR is not particularly limited, and products generally used in the tire industry can be used, and examples thereof include SIR20, RSS#3, and TSR20.

[0099] When other rubber components are contained, from the viewpoint of the effect of the present invention, the content of the other rubber components in the rubber component is preferably less than 15% by mass, more preferably less than 10% by mass, and further preferably less than 5% by mass. On the other hand, the lower limit of the content of the other rubber components in the rubber component is not particularly limited and can be 0% by mass, for example, it can also be greater than 1% by mass, greater than 2% by mass, or greater than 3% by mass.

[0100] (Total styrene content) Total styrene content (A STY) means: as defined above, it is the total content (mass %) of the styrene part contained in the total amount of the rubber component. In the present invention, the total styrene amount in the rubber component is 25 mass % or less. The total styrene amount is preferably less than 20 mass %, more preferably less than 15 mass %, and further preferably less than 10 mass %. In addition, the total styrene amount is usually 3 mass % or more, or 4 mass % or more, or about 5 mass % or more.

[0101] <Packing> The rubber composition according to the present invention contains 50 parts by mass or more of silica as a filler relative to 100 parts by mass of the rubber component.

[0102] The rubber composition according to the present invention may contain carbon black as a filler in addition to silica. It is more preferable to contain silica and carbon black as the filler, and the filler may consist of silica and carbon black alone.

[0103] (Silicon Dioxide) As silicon dioxide, there is no particular limitation, for example, silicon dioxide (anhydrous silicon dioxide) prepared by a dry method, silicon dioxide (hydrous silicon dioxide) prepared by a wet method, and other silicon dioxide commonly used in tire industries can be used. In addition, from the viewpoint of environmental load, silicon dioxide (for example, amorphous silicon dioxide refined from rice husks) using biomass materials as raw materials can also be used. Among them, for the reason that there are more silanol groups, hydrous silicon dioxide prepared by a wet method is preferably used. Silica can be used alone or in combination of two or more.

[0104] Silica made from biomass materials as raw materials, for example, can be obtained by extracting silicate from rice husk ash obtained by burning rice husks with a sodium hydroxide solution, and filtering the silicate and sulfuric acid-generated silica precipitate in the same way as conventional wet silica, washing, drying, and crushing. If the silica is crystallized, it is insoluble in water, and the silicic acid as the component cannot be used. By managing the combustion temperature and combustion time, the crystallization of silica in the rice husk ash can be suppressed (see Japanese Patent Publication No. 2009-2594, Akita Prefectural University Online Journal B / 2019, vol. 6, p. 216-222, etc.). Amorphous silica extracted from rice husks can use commercially available substances such as Wilmar.

[0105] From the viewpoint of low fuel consumption and wear resistance, the nitrogen adsorption specific surface area (N2SA) of silica is preferably greater than 140 m 2 / g, more preferably greater than 150m 2 / g, more preferably greater than 160m 2 / g, more preferably 175m 2In addition, from the viewpoint of low fuel consumption performance and processability, it is preferably less than 350 m 2 / g, more preferably less than 300m 2 / g, more preferably less than 250m 2 / g. In addition, the N2SA of silica is measured by the above-mentioned measurement method.

[0106] The average primary particle size of silicon dioxide is preferably greater than 10nm, more preferably greater than 12nm, and more preferably greater than 14nm. In addition, the average primary particle size is preferably less than 26nm, more preferably less than 24nm, and more preferably less than 22nm. In addition, the average primary particle size of silicon dioxide is measured by the above-mentioned determination method.

[0107] From the viewpoint of wet grip performance, the content of silica relative to 100 parts by mass of the rubber component is preferably greater than 70 parts by mass, more preferably greater than 80 parts by mass, further preferably greater than 90 parts by mass, further preferably greater than 100 parts by mass. In addition, from the viewpoint of wear resistance, the content is preferably less than 200 parts by mass, more preferably less than 150 parts by mass, further preferably less than 130 parts by mass.

[0108] (Carbon Black) As carbon black, products commonly used in the tire industry can be appropriately used, for example, GPF, FEF, HAF, ISAF, SAF, etc. can be mentioned. In addition, from the perspective of life cycle assessment, in addition to the above-mentioned carbon black, carbon black using lignin as a raw material or recycled carbon black obtained by thermal cracking of products containing carbon black such as tires can also be used. Carbon black can be used alone or in combination of two or more.

[0109] From the perspective of reinforcement, the nitrogen adsorption specific surface area (N2SA) of carbon black is preferably greater than 10 m 2 / g, more preferably greater than 30m 2 / g, more preferably greater than 50m 2 / g. In addition, from the viewpoint of low fuel consumption performance and processability, it is preferably less than 200m 2 / g, more preferably less than 175m 2 / g, more preferably less than 150m 2 / g. In addition, the N2SA of carbon black is measured by the above-mentioned measurement method.

[0110] The average primary particle size of carbon black is preferably greater than 10 nm, more preferably greater than 12 nm, and further preferably greater than 14 nm. In addition, the average primary particle size is preferably less than 26 nm, more preferably less than 24 nm, and further preferably less than 22 nm. In addition, the average primary particle size of carbon black is measured by the above-mentioned measurement method.

[0111] When carbon black is contained, from the viewpoint of wear resistance and wet grip performance, the content thereof is preferably greater than 1 part by mass, more preferably greater than 3 parts by mass, and further preferably greater than 5 parts by mass relative to 100 parts by mass of the rubber component. In addition, from the viewpoint of low fuel consumption performance, the content is preferably less than 50 parts by mass, more preferably less than 30 parts by mass, and further preferably less than 10 parts by mass.

[0112] When both silica and carbon black are contained, the content of silica is preferably greater than the content of carbon black from the viewpoint of balancing low fuel consumption performance, wet grip performance and wear resistance. The proportion of silica relative to the total content of silica and carbon black is preferably greater than 80% by mass, more preferably greater than 90% by mass, and further preferably greater than 95% by mass.

[0113] (Other fillers) As fillers, in addition to carbon black and silica, other fillers may be further used. Such fillers are not particularly limited, and for example, any of the fillers commonly used in the tire industry such as aluminum hydroxide, alumina, calcium carbonate, magnesium sulfate, talc, clay, and biochar may be used. Other fillers may be used alone or in combination of two or more.

[0114] From the viewpoint of wear resistance, the total content of fillers relative to 100 parts by mass of the rubber component is preferably greater than 40 parts by mass, more preferably greater than 60 parts by mass, and even more preferably greater than 80 parts by mass. In addition, from the viewpoint of low fuel consumption performance and elongation at break, it is preferably less than 250 parts by mass, more preferably less than 200 parts by mass, and even more preferably less than 150 parts by mass.

[0115] (Silane coupling agent) Silica is preferably used in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and any silane coupling agent that has been used in combination with silica in the tire industry can be used, for example, thioester silane coupling agents such as 3-octanoylthio-1-propyltriethoxysilane, 3-hexanoylthio-1-propyltriethoxysilane, and 3-octanoylthio-1-propyltrimethoxysilane; mercapto silane coupling agents such as substances represented by the following chemical formula; sulfide silane coupling agents such as bis(3-triethoxysilylpropyl) disulfide and bis(3-triethoxysilylpropyl) tetrasulfide; vinyltriethoxysilane , vinyl trimethoxysilane and other vinyl silane coupling agents; 3-aminopropyl triethoxysilane, 3-aminopropyl trimethoxysilane, 3-(2-aminoethyl) aminopropyl triethoxysilane and other amino silane coupling agents; γ-glycidyloxypropyl triethoxysilane, γ-glycidyloxypropyl trimethoxysilane and other glycidyloxy silane coupling agents; 3-nitropropyl trimethoxysilane, 3-nitropropyl triethoxysilane and other nitro silane coupling agents; 3-chloropropyl trimethoxysilane, 3-chloropropyl triethoxysilane and other chlorinated silane coupling agents, etc. Among them, thioester silane coupling agents and / or sulfide silane coupling agents are preferred. The silane coupling agent can be used alone or in combination of two or more.

[0116] The mercapto-based silane coupling agent is preferably a compound represented by the following chemical formula (1) and / or a compound containing a bonding unit A represented by the following chemical formula (2) and a bonding unit B represented by the following chemical formula (3).

Chemical formula 1

Chemical formula 2

Chemical formula 3

[0117] As the compound represented by formula (1), for example, 3-mercaptopropyl trimethoxysilane, 3-mercaptopropyl triethoxysilane, 2-mercaptoethyl trimethoxysilane, 2-mercaptoethyl triethoxysilane or a compound represented by the following chemical formula (4) (Si363 manufactured by Evonik Degussa) etc. can be cited, and the compound represented by the following chemical formula (4) can be preferably used. These can be used alone or in combination of two or more.

Chemistry 4

[0118] Examples of the compound containing the bonding unit A represented by the chemical formula (2) and the bonding unit B represented by the chemical formula (3) include those manufactured and commercially available from Momentive Corporation and the like.

[0119] When a silane coupling agent is contained, from the viewpoint of improving the dispersibility of silica, its content relative to 100 parts by mass of the rubber component (the total amount when multiple silane coupling agents are used in combination) is preferably greater than 0.5 parts by mass, more preferably greater than 1.0 parts by mass, further preferably greater than 2.0 parts by mass, and further preferably greater than 4.0 parts by mass. Furthermore, from the viewpoint of preventing a decrease in wear resistance, it is preferably less than 20 parts by mass, more preferably less than 12 parts by mass, further preferably less than 10 parts by mass, and further preferably less than 9.0 parts by mass.

[0120] From the viewpoint of improving the dispersibility of silica, the content of the silane coupling agent relative to 100 parts by mass of silica is preferably greater than 1.0 parts by mass, more preferably greater than 3.0 parts by mass, and further preferably greater than 5.0 parts by mass. In addition, from the viewpoint of cost and processability, it is preferably less than 20 parts by mass, more preferably less than 15 parts by mass, and further preferably less than 12 parts by mass.

[0121] <Plasticizer> The rubber composition according to the present invention preferably contains a plasticizer. Examples of the plasticizer include hydrocarbon resins, oils, liquid rubbers, and ester plasticizers.

[0122] (Hydrocarbon resin) Hydrocarbon resin refers to a polymer having a skeleton formed by hydrocarbons, which is a solid substance at 25°C. Hydrocarbon resins may also generally contain oxygen elements derived from carboxyl groups, hydroxyl groups, coumarone, etc. As hydrocarbon resins, there are no particular limitations, and petroleum resins, terpene resins, rosin resins, phenolic resins, etc. commonly used in the tire industry can be cited. As hydrocarbon resins, for example, commercially available substances from Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Kraton, Eastman Chemical, Nippon Paint Chemical Co., Ltd., LUHUA, Nippon Shokubai Co., Ltd., ENEOS Co., Ltd., Arakawa Chemical Industries, Ltd., and Taoka Chemical Industries, Ltd. can be used. Hydrocarbon resins can be used alone or in combination of two or more.

[0123] Petroleum resin As the petroleum resin, there can be used C5-based petroleum resin, aromatic petroleum resin, C5C9-based petroleum resin, etc. The petroleum resin may be used alone or in combination of two or more.

[0124] C5 petroleum resin refers to a resin obtained by polymerizing a C5 fraction. Examples of C5 fractions include petroleum fractions corresponding to 4 to 5 carbon atoms such as cyclopentadiene, pentene, pentadiene, and isoprene, and may also be hydrogenated products or modified products thereof. As C5 petroleum resin, dicyclopentadiene resin (DCPD resin) may be preferably used.

[0125] Aromatic petroleum resins refer to resins obtained by polymerizing C9 fractions, and may also be hydrogenated products or modified products thereof. As C9 fractions, for example, petroleum fractions corresponding to 8 to 10 carbon atoms such as vinyltoluene, alkylstyrene, indene, and methylindene can be cited. As specific examples of aromatic petroleum resins, for example, coumarone indene resins, coumarone resins, indene resins, and aromatic vinyl resins can be preferably used.

[0126] As the aromatic vinyl resin, α-methylstyrene or a homopolymer of styrene, or a copolymer of α-methylstyrene and styrene is preferred, and a copolymer of α-methylstyrene and styrene is more preferred, because of economic efficiency, easy processing, and excellent heat generation.

[0127] The C5C9-based petroleum resin refers to a resin obtained by copolymerizing the above-mentioned C5 fraction and the above-mentioned C9 fraction, and may be a hydrogenated product or a modified product thereof. Examples of the C5 fraction and the C9 fraction include the above-mentioned petroleum fractions.

[0128] 《Terpene resins》 Examples of terpene resins include polyterpene resins composed of at least one selected from terpene compounds such as α-pinene, β-pinene, limonene, and dipentene; aromatic modified terpene resins using the above terpene compounds and aromatic compounds as raw materials; terpene phenol resins using terpene compounds and phenolic compounds as raw materials; and substances obtained by hydrogenating these terpene resins (hydrogenated terpene resins). As the raw material for the aromatic modified terpene resin, i.e., aromatic compounds, for example, styrene, α-methylstyrene, vinyltoluene, divinyltoluene, etc. can be listed. As the raw material for the terpene phenol resin, i.e., phenolic compounds, for example, phenol, bisphenol A, cresol, xylenol, etc. can be listed. The terpene resin can be used alone or in combination of two or more.

[0129] 《Rosin-based resin》 The rosin-based resin is not particularly limited, and examples thereof include natural resin rosin, and rosin-modified resins obtained by modifying the rosin by hydrogenation, disproportionation, dimerization, esterification, etc. The rosin-based resin may be used alone or in combination of two or more.

[0130] 《Phenolic resin》 The phenolic resin is not particularly limited, and examples thereof include phenol formaldehyde resin, alkylphenol formaldehyde resin, alkylphenol acetylene resin, oil-modified phenol formaldehyde resin, etc. The phenolic resin may be used alone or in combination of two or more.

[0131] Softening Point From the viewpoint of wet grip performance, the softening point of the hydrocarbon resin is preferably higher than 60° C., more preferably higher than 70° C., and even more preferably higher than 80° C. In addition, from the viewpoint of processability and improvement of the dispersibility of the rubber component and the filler, it is preferably lower than 150° C., more preferably lower than 140° C., and even more preferably lower than 130° C. The softening point is measured by the above-mentioned measurement method.

[0132] 《Glass transition temperature (Tg)》 From the perspective of excellent compatibility with the rubber component, the Tg of the hydrocarbon resin is preferably 110° C. or less, more preferably 105° C. or less, and even more preferably 100° C. or less. From the perspective of excellent compatibility with the rubber component, the Tg is preferably -35° C. or more, more preferably 0° C. or more, and even more preferably 30° C. or more. In addition, Tg is measured by the above-mentioned measurement method using a differential scanning calorimeter.

[0133] 《Weight average molecular weight (Mw)》 From the perspective of low volatility and good grip, the Mw of the hydrocarbon resin is preferably greater than 500, more preferably greater than 600, and further preferably greater than 650. In addition, from the perspective of being easy to entangle with the polymer and not easy to fall off, and thus having excellent dry grip, the Mw is preferably less than 15000, more preferably less than 13000, and further preferably less than 11000. By making the Mw within the above range, the obtained rubber composition has excellent processability, and the heat build-up and elongation at break can be improved. In addition, the Mw is measured by the above-mentioned measurement method.

[0134] 《Content>> From the viewpoint of wet grip performance, the rubber composition of the present invention preferably contains at least one hydrocarbon resin, and the rubber composition of the present invention preferably contains the hydrocarbon resin in the rubber composition at a content of 5% by mass or more. The content of the resin in the rubber composition is preferably greater than 6% by mass, more preferably greater than 7% by mass, more preferably greater than 10% by mass, and more preferably greater than 12% by mass. In addition, from the viewpoint of suppressing heat generation, the content of the hydrocarbon resin in the rubber composition is preferably less than 100% by mass, more preferably less than 80% by mass, more preferably less than 60% by mass, particularly preferably less than 50% by mass, more particularly preferably less than 35% by mass, and most preferably less than 25% by mass.

[0135] (Oil) Examples of the oil include process oil, vegetable oil, animal oil, and the like. Examples of the process oil include paraffinic process oil, cycloparaffinic process oil, and aromatic process oil. In addition, due to environmental measures, process oils with a low content of polycyclic aromatic compounds (PCA) may also be used. Examples of the process oil with a low PCA content include shallow solvent extracted oil (MES), treated aromatic oil (TDAE), and heavy cycloparaffinic oil. One type of oil may be used alone, or two or more types may be used in combination.

[0136] When oil is contained, from the viewpoint of processability, the content is preferably greater than 5 parts by mass, more preferably greater than 10 parts by mass, and further preferably greater than 15 parts by mass relative to 100 parts by mass of the rubber component. Furthermore, from the viewpoint of wear resistance, the content is preferably less than 120 parts by mass, more preferably less than 80 parts by mass, and further preferably less than 40 parts by mass. In addition, in this specification, the content of oil also includes the amount of oil contained in the oil-increased rubber.

[0137] (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. The liquid rubber may be used alone or in combination of two or more.

[0138] When liquid rubber is contained, its content relative to 100 parts by mass of the rubber component is preferably greater than 1 part by mass, more preferably greater than 2 parts by mass, further preferably greater than 3 parts by mass, further preferably greater than 5 parts by mass. In addition, the content of liquid rubber is preferably less than 50 parts by mass, more preferably less than 40 parts by mass, further preferably less than 20 parts by mass.

[0139] (Ester plasticizer) As the ester plasticizer, for example, 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), dilauryl 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), tricresyl phosphate (TXP), etc. The ester plasticizer may be used alone or in combination of two or more.

[0140] (Plasticizer content) From the viewpoint of wet grip performance, the content of the plasticizer relative to 100 parts by mass of the rubber component is preferably greater than 5 parts by mass, more preferably greater than 10 parts by mass, and further preferably greater than 15 parts by mass. Furthermore, from the viewpoint of processability, the content is preferably less than 120 parts by mass, more preferably less than 80 parts by mass, and further preferably less than 60 parts by mass.

[0141] <Other compounding agents> The rubber composition of the present invention may contain, in addition to the above components, compounding agents commonly used in the tire industry, such as processing aids, zinc oxide, stearic acid, wax, antioxidants, vulcanizing agents, and vulcanization accelerators.

[0142] (Processing Aids) As processing aids, for example, fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and amide esters, mixtures of fatty acid metal salts and fatty acid amides, etc. can be cited. One type of processing aid can be used alone, or two or more types can be used in combination. As processing aids, for example, commercially available substances from Schill+Seilacher, Performance-Additives, etc. can be used.

[0143] When a processing aid is contained, its content is preferably greater than 0.5 parts by mass, more preferably greater than 1 part by mass, and further preferably greater than 1.5 parts by mass relative to 100 parts by mass of the rubber component from the viewpoint of exerting an effect of improving processability. In addition, from the viewpoint of wear resistance and breaking strength, it is preferably less than 10 parts by mass, more preferably less than 8.0 parts by mass, and further preferably less than 5.0 parts by mass.

[0144] (Zinc Oxide) When zinc oxide is contained, its content is preferably greater than 0.5 parts by mass, more preferably greater than 1.0 parts by mass, and even more preferably greater than 1.5 parts by mass relative to 100 parts by mass of the rubber component from the viewpoint of processability. In addition, from the viewpoint of wear resistance, it is preferably less than 10 parts by mass, more preferably less than 7 parts by mass, and even more preferably less than 5 parts by mass.

[0145] (Stearic Acid) When stearic acid is present, from the viewpoint of processability, its content relative to 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and further preferably 1.5 parts by mass or more. In addition, from the viewpoint of vulcanization speed, it is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

[0146] (wax) When wax is contained, the content is preferably greater than 0.5 parts by mass, more preferably greater than 1.0 parts by mass, and further preferably greater than 1.3 parts by mass relative to 100 parts by mass of the rubber component from the viewpoint of weather resistance of the rubber. Furthermore, from the viewpoint of preventing tire whitening due to blooming, the content is preferably less than 10 parts by mass, more preferably less than 7.0 parts by mass, and further preferably less than 5.0 parts by mass.

[0147] (Antioxidant) As antioxidant, there is no particular limitation, for example, antioxidants such as amine, quinoline, quinone, phenol, and imidazole compounds, and metal carbamates can be cited, preferably N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, N-cyclohexyl-N'-phenyl-p-phenylenediamine and other phenylenediamine antioxidants, and quinoline antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline, 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline. Antioxidants can be used alone or in combination of two or more.

[0148] When an antioxidant is contained, from the viewpoint of the ozone cracking resistance of the rubber, its content relative to 100 parts by mass of the rubber component is preferably greater than 0.5 parts by mass, more preferably greater than 1.0 parts by mass, and further preferably greater than 1.5 parts by mass. In addition, from the viewpoint of wear resistance and wet grip performance, it is preferably less than 10 parts by mass, more preferably less than 7 parts by mass, and further preferably less than 5 parts by mass.

[0149] (Vulcanizing agent) As the vulcanizing agent, sulfur can be preferably used. As sulfur, powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, etc. can be used. The vulcanizing agent can be used alone or in combination of two or more.

[0150] When sulfur is contained as a vulcanizing agent, its content relative to 100 parts by mass of the rubber component is preferably greater than 0.1 parts by mass, more preferably greater than 0.3 parts by mass, and further preferably greater than 0.5 parts by mass from the viewpoint of ensuring sufficient vulcanization reaction. In addition, from the viewpoint of preventing deterioration, it is preferably less than 5.0 parts by mass, more preferably less than 4.0 parts by mass, and further preferably less than 3.0 parts by mass. In addition, when sulfur containing oil is used as a vulcanizing agent, the content of the vulcanizing agent is set to the total content of pure sulfur contained in the sulfur containing oil.

[0151] Examples of the vulcanizing agent other than sulfur include alkylphenol / sulfur chloride condensate, sodium 1,6-hexamethylenedithiosulfate dihydrate, 1,6-bis(N,N'-dibenzylthiocarbamoyldisulfide)hexane, etc. These vulcanizing agents other than sulfur can be commercially available from Taoka Chemical Industry Co., Ltd., Lanxess Co., Ltd., Flexis Co., Ltd., etc.

[0152] (Vulcanization accelerator) Examples of the vulcanization accelerator include sulfenamide-based, thiazole-based, thiuram-based, thiourea-based, guanidine-based, dithiocarbamic acid-based, aldehyde-amine-based or aldehyde-ammonia-based, imidazoline-based, or xanthate-based vulcanization accelerators. The vulcanization accelerator may be used alone or in combination of two or more.

[0153] Among them, it is preferred that the vulcanization accelerator contains at least one vulcanization accelerator selected from sulfenamide-based, guanidine-based and thiazole-based vulcanization accelerators, and it is more preferred that the vulcanization accelerator consists of a sulfenamide-based vulcanization accelerator and a guanidine-based vulcanization accelerator.

[0154] Examples of the sulfenamide vulcanization accelerator include N-tert-butyl-2-benzothiazolesulfenamide (TBBS), N-cyclohexyl-2-benzothiazolesulfenamide (CBS), and N,N-dicyclohexyl-2-benzothiazolesulfenamide (DCBS). Among them, N-cyclohexyl-2-benzothiazolesulfenamide (CBS) is preferred.

[0155] Examples of the guanidine vulcanization accelerator include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicatecholborate, 1,3-di-o-cumylguanidine, 1,3-di-o-biphenylguanidine, and 1,3-di-o-cumyl-2-propionylguanidine. Among them, 1,3-diphenylguanidine (DPG) is preferred.

[0156] Examples of the thiazole vulcanization accelerator include 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, di-2-benzothiazole disulfide, etc. Among them, 2-mercaptobenzothiazole is preferred.

[0157] When a vulcanization accelerator is contained, its content relative to 100 parts by mass of the rubber component is preferably greater than 1 part by mass, more preferably greater than 1.5 parts by mass, and further preferably greater than 2 parts by mass. In addition, the content of the vulcanization accelerator relative to 100 parts by mass of the rubber component is preferably less than 8 parts by mass, more preferably less than 7 parts by mass, and further preferably less than 6 parts by mass. By setting the content of the vulcanization accelerator within the above range, it tends to be possible to ensure the breaking strength and elongation.

[0158] [manufacture] Any of the rubber compositions of the present invention 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 mill or a closed mixer (Banbury mixer, kneader, etc.).

[0159] The kneading process, for example, includes the following basic kneading process: kneading the compounding agents and additives other than the vulcanizing agent and the vulcanization accelerator, and the final kneading process (F kneading): adding the vulcanizing agent and the vulcanization accelerator to the kneaded material obtained in the basic kneading process and kneading. Furthermore, the above-mentioned basic kneading process can also be decomposed into multiple processes as needed.

[0160] The kneading conditions are not particularly limited, and examples thereof include kneading at a discharge temperature of 150 to 170° C. for 3 to 10 minutes in the basic kneading step and kneading at 70 to 110° C. for 1 to 5 minutes in the final kneading step.

[0161] The pneumatic tire of the present invention can be manufactured by conventional methods using the above-mentioned unvulcanized rubber composition. That is, the pneumatic tire of the present invention can be manufactured by: extruding the unvulcanized rubber composition on an extruder with a die head of a specified shape according to a specified tread shape, laminating it together with other tire components on a tire molding machine, molding it into an unvulcanized tire by conventional methods, and heating and pressurizing the unvulcanized tire in a vulcanizer. The vulcanization conditions are not particularly limited, and for example, a method of vulcanizing at 150 to 200° C. for 10 to 30 minutes can be cited.

[0162] [use] The pneumatic tire of the present invention can be used for any purpose, for example, it can be used as a tire for a passenger car, a tire for a large passenger car, a tire for a light truck, a tire for a large SUV, a racing tire, or a tire for a motorcycle. Among them, it is preferred to use a tire for a passenger car or a tire for a light truck. Here, a tire for a passenger car refers to a tire that is installed on a four-wheel vehicle as a prerequisite, and the maximum load capacity in the JATMA standard is a tire of less than 1000 kg, and a tire for a light truck refers to a tire of less than 1400 kg under the same standard.

[0163] The tire of the present invention can be used as a summer tire, a winter tire, or a studless tire of the above tires. Among them, winter tires and studless tires used at low temperatures are preferred. [Example]

[0164] Although the present invention is described based on the examples, the present invention is not limited to the examples.

[0165] [Various medicines] The following summarizes various reagents used in Examples and Comparative Examples. NR:TSR20 SBR1: SLR6430 manufactured by TRINSEO (S-SBR, styrene content: 40% by mass, vinyl bond content: 24 mol%, Tg: -30°C, Mw: 1.01 million, oil-extended product containing 37.5 parts by weight of oil per 100 parts by weight of the rubber component) SBR2: Styrene butadiene rubber synthesized by the following Preparation Example 1 (modified S-SBR, styrene content: 20 mass%, vinyl content: 20 mol%, Tg: -60°C, Mw: 800,000) SBR3: Styrene butadiene rubber synthesized by the following Preparation Example 2 (modified S-SBR, styrene content: 15% by mass, vinyl content: 30 mol%, Tg: -60°C, Mw: 800,000) BR1: UBEPOL BR (registered trademark) 150B manufactured by Ube Industries, Ltd. (vinyl content: 1.5 mol%, cis content: 97 mol%, Tg: -108°C, Mw: 440,000) BR2: ASAPRENE N103 manufactured by Asahi Kasei Corporation (modified BR whose terminal is modified by a mixture of tetraglycidyl-1,3-bisaminomethylcyclohexane and its oligomer components, vinyl content: 12 mol%, cis content: 36% by mass, Tg: -90°C, Mw: 550,000) CB (carbon black): SHOBLACK N134 (N2SA: 148m 2 / g, average primary particle size: 18nm) Silicon dioxide: ULTRASIL (registered trademark) VN3 (N2SA: 175m 2 / g, average primary particle size: 18nm) Coupling agent (silane coupling agent): Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa Oil: VivaTec500 (TDAE oil) manufactured by H&R Hydrocarbon resin 1: Sylvatraxx 4401 manufactured by Kraton Corporation (aromatic vinyl resin (copolymer of styrene and α-methylstyrene), Mw: 700, softening point: 85° C., Tg: 34° C.) Hydrocarbon resin 2: PR395 manufactured by ExxonMobil Corporation (C5C9-based resin, Mw: 880, softening point: 117.8°C, Tg: 68°C) Zinc oxide: Zinc oxide No. 2 manufactured by Mitsui Mining and Smelting Co., Ltd. Stearic acid: NOF Corporation's stearic acid beads "TSUBAKI" Wax: SUNNOC N manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Antioxidant 1: Antigen 6C (6PPD, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd. Antioxidant 2: NOCRAC 224 (TMQ, 2,2,4-trimethyl-1,2-dihydroquinoline polymer) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Sulfur: Powdered sulfur manufactured by Karuizawa Sulfur Co., Ltd. Vulcanization accelerator 1: NOCCELER CZ (CBS, N-cyclohexyl-2-benzothiazole sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: NOCCELER D (DPG, 1,3-diphenylguanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0166] [Manufacturing example] Preparation Example 1: Synthesis of SBR2 Adjust the ratio of styrene and 1,3-butadiene so that the styrene content in the target product is 20% by mass. Add cyclohexane, tetrahydrofuran, styrene and 1,3-butadiene to a nitrogen-substituted autoclave reactor. After adjusting the temperature of the contents of the reactor to 20°C, add n-butyl lithium to start polymerization. Polymerize under adiabatic conditions. When the polymerization conversion rate reaches 99%, add 1,3-butadiene to further polymerize it, then add methyltriethoxysilane as a modifier to carry out a modification reaction. After the reaction is completed, add 2,6-di-tert-butyl-p-cresol. Then, remove the solvent by steam stripping and dry it by a hot roller adjusted to 110°C to obtain SBR2.

[0167] Preparation Example 2: Synthesis of SBR3 Adjust the ratio of styrene and 1,3-butadiene so that the styrene content in the target product is 15% by mass. Add cyclohexane, tetrahydrofuran, styrene and 1,3-butadiene to a nitrogen-substituted autoclave reactor. After adjusting the temperature of the contents of the reactor to 20°C, add n-butyl lithium to start polymerization. Polymerize under adiabatic conditions. When the polymerization conversion rate reaches 99%, add 1,3-butadiene to further polymerize it, and then add 3-[bis-(trimethylsilyl)amino]propyltriethoxysilane as a modifier to carry out a modification reaction. After the reaction is completed, add 2,6-di-tert-butyl-p-cresol. Then, remove the solvent by steam stripping and dry it by a hot roller adjusted to 110°C to obtain SBR3.

[0168] [Examples and Comparative Examples] According to the compounding recipe shown in each table, a 1.7L closed Banbury mixer was used to mix the reagents other than sulfur and vulcanization accelerator for 1 to 10 minutes until the discharge temperature was 150 to 160°C to obtain a kneaded product. Then, sulfur and a vulcanization accelerator were added to the obtained kneaded product using a twin-screw open roll mill, and kneaded for 4 minutes until the temperature was 105°C to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was formed into a prescribed tread shape according to each table, and an unvulcanized tire was made by bonding it with other tire components, and press-vulcanized for 12 minutes at 170°C to obtain each test tire (tire 1: 225 / 60R16 98H, tire 2: 275 / 55R20 117T XL).

[0169] The tread surface of each test tire has at least circumferential main grooves and transverse grooves. There are three circumferential main grooves, one of which passes through the tire centerline, and the other two are arranged at equal intervals from the main groove passing through the tire centerline to the outside in the tire width direction. In addition, there are no small holes, circumferential thin grooves, or widened circumferential grooves.

[0170] <Evaluation> The results of the measurements of the test tires according to the following methods are described in the corresponding columns of the following table.

[0171] (Ground area ratio) For each test tire, the total contact area and the effective contact area based on the above definition were obtained, and the contact area ratio (%) was calculated.

[0172] (High-speed wet grip performance) Each test tire was installed as all tires of the vehicle (tire 1: domestic FF passenger car, displacement 2000cc, tire 2: domestic 4WD passenger car, displacement 3000cc), and the vehicle was driven on a test route on a wet asphalt road at a speed of 100km / h. 20 test drivers evaluated the grip performance during driving with a score of 1 to 5, and the total score was calculated. The result was expressed as an index with the benchmark comparative example as 100. The larger the index, the better the operating stability during driving, indicating that the high-speed wet grip performance is excellent.

[0173] (Low temperature wear resistance) Each test tire was installed as all tires of a vehicle (tire 1: domestic FF passenger car, displacement 2000cc, tire 2: domestic 4WD passenger car, displacement 3000cc), and the vehicle was driven on an asphalt test route for 20,000 km at an outdoor temperature of 10°C or less, and the amount of reduction in tread thickness from the start of driving was measured. The result was expressed as an index, with the benchmark comparative example as 100. The larger the index, the smaller the reduction, indicating excellent low-temperature wear resistance.

[0174]

Table 1

[0175]

Table 2

[0176] [Implementation Method] Preferred embodiments are shown below.

[0177] [1] A pneumatic tire, characterized in that: It is a pneumatic tire having a tread portion. The tread portion is composed of a rubber composition, and the rubber composition contains 50 parts by mass or more, preferably 70 parts by mass or more, more preferably 80 parts by mass or more, and even more preferably 90 parts by mass or more of silica per 100 parts by mass of the rubber component. The rubber component contains more than 50% by mass of butadiene rubber and styrene butadiene rubber, The total amount of styrene in the rubber component is 25% by mass or less, The content (mass %) of the butadiene rubber in the rubber component is denoted as A BR , when the contact area ratio (%) of the tread surface of the tread portion is L, A BR and L satisfy the following formula. (1) A BR ×L>3000 [2] The pneumatic tire according to [1], wherein the total styrene amount (mass %) is A STY When A BR , L and A STY Satisfies the following formula, (2) (A BR / A STY )×L>130 The right side of formula (2) is preferably 200, more preferably 300, further preferably 360, further preferably 450, further preferably 550, further preferably 600. [3] The pneumatic tire according to [1] or [2], wherein the rubber composition contains at least one hydrocarbon resin, and the content of the hydrocarbon resin in the rubber composition is 5 mass % or more, preferably greater than 6 mass %, more preferably greater than 7 mass %, further preferably greater than 10 mass %, and further preferably greater than 12 mass %. [4] A pneumatic tire according to any one of [1] to [3], wherein the content of the silica relative to 100 parts by mass of the rubber component is greater than 70 parts by mass, preferably 80 parts by mass or more, more preferably 90 parts by mass or more, and even more preferably 100 parts by mass or more. [5] The pneumatic tire according to any one of [1] to [4], wherein the glass transition temperature of the rubber composition is less than -30°C, preferably less than -33°C, more preferably less than -37°C, further preferably less than -40°C, and further preferably less than -42°C. [6] The pneumatic tire according to any one of [1] to [5], wherein the right side of the formula (1) is 3250. [7] The pneumatic tire according to any one of [1] to [5], wherein the right side of formula (1) is 3500, preferably 3750, and more preferably 4000. [8] The pneumatic tire according to any one of [1] to [7], wherein the content of the butadiene rubber in the rubber component is BR It is less than 70 mass %, preferably less than 65 mass %, and more preferably less than 60 mass %. [9] The pneumatic tire according to any one of [1] to [8], wherein the glass transition temperature of the styrene-butadiene rubber is less than -30°C, preferably less than -40°C, more preferably less than -50°C, and even more preferably less than -55°C.

[10] The pneumatic tire according to any one of [1] to [9], wherein the tread surface has: two or more circumferential main grooves extending in the tire circumferential direction; and a land portion divided by the circumferential main grooves. When a pair of land portions located at the outermost sides in the tire width direction of the land portions are set as shoulder land portions, the shoulder land portions have at least one opening area greater than 0.1 mm 2 Less than 15mm 2 , preferably greater than 0.5 mm 2 Less than 10mm 2 , more preferably greater than 0.5 mm 2 , less than 7.0mm 2 , more preferably greater than 1.0 mm 2 , less than 5.0mm 2 of small holes.

[11] The pneumatic tire according to any one of [1] to

[10] , wherein the tread surface has: two or more circumferential main grooves extending in the tire circumferential direction; and a land portion divided by the circumferential main grooves. When a pair of land portions located outermost in the tire width direction among the land portions are provided as shoulder land portions, the shoulder land portions have at least one circumferential narrow groove.

[12] The pneumatic tire according to any one of [1] to

[11] , wherein the tread surface has a widened circumferential groove whose groove width widens toward the inside in the tire radial direction.

[13] The pneumatic tire according to

[12] , wherein the widened circumferential groove exists at a contact portion located on the tire center line, or, when a circumferential main groove exists on the tire center line, exists at a contact portion closest to the tire center line.

Claims

1. A pneumatic tire, characterized in that: It is a pneumatic tire having a tread portion. The tread portion is composed of a rubber composition, wherein the rubber composition contains 50 parts by mass or more of silica based on 100 parts by mass of the rubber component. The rubber component contains more than 50% by mass of butadiene rubber and styrene butadiene rubber, The total amount of styrene in the rubber component is 25% by mass or less, The content of the butadiene rubber in the rubber component is defined as A. BR , when the contact area ratio of the tread surface of the tread portion is set to L, A BR and L satisfy the following formula, (1) A BR ×L>3000, Among them, A BR The unit of is mass % and the unit of L is %.

2. The pneumatic tire according to claim 1, wherein: The total styrene amount is set as A STY When A BR , L and A STY Satisfies the following formula, (2) (A BR / A STY )×L>130, Among them, A STY The unit is mass %.

3. The pneumatic tire according to claim 1 or 2, wherein: The rubber composition contains at least one hydrocarbon resin, and the content of the hydrocarbon resin in the rubber composition is 5% by mass or more.

4. The pneumatic tire according to claim 1 or 2, wherein: The content of the silica is 100 parts by mass or more based on 100 parts by mass of the rubber component.

5. The pneumatic tire according to claim 1 or 2, wherein: The rubber composition has a glass transition temperature of less than -30°C.

6. The pneumatic tire according to claim 1 or 2, wherein: The right side of formula (1) is 3250.

7. The pneumatic tire according to claim 6, wherein: The right side of formula (1) is 3500.

8. The pneumatic tire according to claim 1 or 2, wherein: The content of the butadiene rubber in the rubber component is A BR Less than 70 mass %.

9. The pneumatic tire according to claim 1 or 2, wherein: The glass transition temperature of the styrene butadiene rubber is less than -30°C.

10. The pneumatic tire according to claim 1 or 2, wherein: The tread surface has: two or more circumferential main grooves extending in the tire circumferential direction, and a land portion divided by the circumferential main grooves. When a pair of land portions located at the outermost sides in the tire width direction of the land portions are set as shoulder land portions, the shoulder land portions have at least one opening area greater than 0.1 mm 2 Less than 15mm 2 of small holes.

11. The pneumatic tire according to claim 1 or 2, wherein: The tread surface has: two or more circumferential main grooves extending in the tire circumferential direction, and a land portion divided by the circumferential main grooves. When a pair of land portions located outermost in the tire width direction among the land portions are defined as shoulder land portions, the shoulder land portions have at least one circumferential narrow groove.

12. The pneumatic tire according to claim 1 or 2, wherein: The tread surface has a widened circumferential groove whose groove width widens toward the inner side in the tire radial direction.

13. The pneumatic tire according to claim 12, wherein: The widened circumferential groove exists in the ground contact portion located on the tire center line, or, when a circumferential main groove exists on the tire center line, exists in the ground contact portion closest to the tire center line.

14. The pneumatic tire according to claim 1 or 2, wherein: The rubber composition contains less than 200 parts by mass of silica based on 100 parts by mass of the rubber component.

15. The pneumatic tire according to claim 1 or 2, wherein: A BR The value of ×L is less than 6500.

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