Vulcanized rubber composition for studless tires and studless tire

Abstract

Provided is a vulcanized rubber composition for studless tires that is obtained by vulcanizing a rubber composition which contains a rubber component and a filler. The filler contains recycled carbon black. When the recycled carbon black is measured with a grindometer, there are not less than three lines having a length of not less than 10 mm, and among the particles which give lines having a length of not less than 10 mm, the particle size of the third-largest particles is not more than 20 μm. The vulcanized rubber composition has a plurality of voids.

Description

Vulcanized rubber composition for studless tires, and studless tires

[0001] This invention relates to a vulcanized rubber composition for studless tires and to studless tires.

[0002] Conventionally, in the case of tires primarily used in winter, such as studless tires, various studies have been conducted, particularly on the tire tread, in order to improve braking performance and traction (ice performance) on icy and snowy road surfaces.

[0003] For example, Patent Document 1 discloses a rubber composition containing a rubber component comprising natural rubber, polybutadiene rubber, and styrene-butadiene copolymer rubber in predetermined proportions, and 50 to 90 parts by mass of a filler substantially containing silica and carbon black per 100 parts by mass of the rubber component, wherein the distribution ratio (Si distribution ratio) of the total silica to the phase containing polybutadiene rubber and styrene-butadiene copolymer rubber (SB phase) is 50% by mass or more, and it is shown that applying such a rubber composition to the tread member of a tire improves ice performance.

[0004] International Publication No. 2019 / 116701

[0005] Incidentally, in recent years, from the perspective of social sustainability, there has been a demand for the use of so-called sustainable materials in businesses and products, such as materials derived from biological resources (biomass resources) and materials derived from recycled resources. There is also a demand to increase the proportion of sustainable materials (hereinafter sometimes referred to as the "sustainability rate") in the various components used in tires. For example, recycled carbon black is known as a material derived from recycled resources.

[0006] Here, if conventional recycled carbon black is used as a filler in the rubber composition instead of unused carbon black in order to improve the proportion of sustainable materials in studless tires, there is a risk that other tire rubber properties other than ice performance (e.g., crack resistance after degradation, high-temperature tensile strength after degradation) may deteriorate.

[0007] Therefore, the object of the present invention is to provide a vulcanized rubber composition for studless tires that contributes to improved sustainability compared to conventional recycled carbon black, while minimizing adverse effects on tire rubber properties and maintaining performance, and a studless tire using the vulcanized rubber composition in the tread portion.

[0008] In other words, the gist of the present invention that solves the above problems is as follows.

[0009] [1] A vulcanized rubber composition for studless tires, comprising a rubber composition containing a rubber component and a filler, wherein the filler contains recycled carbon black, the recycled carbon black is such that when measured with a grind gauge, three or more lines with a length of 10 mm or more are observed, and the particle size of the third largest particle among the particles that produce the lines with a length of 10 mm or more is 20 μm or less, and the vulcanized rubber composition has a plurality of voids.

[0010] [2] The vulcanized rubber composition for studless tires according to [1], wherein, in the measurement of the recycled carbon black using a grind gauge, a paste of the recycled carbon black is prepared as a measurement sample in accordance with JIS K5101-1-5.

[0011] [3] The vulcanized rubber composition for studless tires according to [1] or [2], wherein, in the measurement of the recycled carbon black using a grind gauge, the applied load is set to 0.4 to 0.5 kN and the rotation speed of the glass plate is set to 90 to 110 r / min in accordance with JIS K5101-1-5, and the paste of the recycled carbon black is prepared as the measurement sample.

[0012] [4] The vulcanized rubber composition for studless tires according to any one of [1] to [3], wherein the rubber composition further contains a void introducing agent.

[0013] [5] The vulcanized rubber composition for studless tires according to any one of [1] to [4], wherein the rubber composition contains a foaming agent as a void introducing agent and a foaming aid.

[0014] [6] The vulcanized rubber composition for studless tires according to any one of [1] to [5], wherein the rubber composition further contains a resin component and a liquid plasticizer, the resin component is at least one selected from the group consisting of terpene resins and rosin resins, the content of the resin component in the rubber composition is 15 parts by mass or more per 100 parts by mass of the rubber component, and the content of the liquid plasticizer in the rubber composition is 30 parts by mass or less per 100 parts by mass of the rubber component.

[0015] A studless tire having a vulcanized rubber composition for studless tires described in any of [7], [1] to [6] used in the tread portion, wherein the tread surface of the tread portion is divided into a plurality of blocks by a plurality of circumferential main grooves extending in the tire circumferential direction and a plurality of widthwise grooves extending in the tire width direction, a plurality of sipes and a plurality of shallow grooves are provided on the surface of the blocks so as to extend in opposite directions in the tire width direction with respect to one direction in the tire circumferential direction, the depth of the shallow grooves is less than the depth of the sipes, the inclination angle θ1 of the sipes with respect to the tire circumferential direction is greater than 0° and less than 90°, the inclination angle θ2 of the shallow grooves with respect to the tire circumferential direction is greater than 0° and less than 90°, and the magnitude of the difference between the inclination angle θ1 and the inclination angle θ2 is 30° or less.

[0016] According to the present invention, compared to conventional methods using recycled carbon black, it is possible to provide a vulcanized rubber composition for studless tires that contributes to improved sustainability while minimizing adverse effects on tire rubber properties and maintaining performance, and a studless tire using the vulcanized rubber composition in the tread portion.

[0017] This is an explanatory diagram illustrating an example of measurement results using a grind gauge. This is a schematic diagram showing a plurality of voids present in a vulcanized rubber composition according to one embodiment of the present invention. This is a schematic diagram showing a cross-section of voids present in a vulcanized rubber composition according to one embodiment of the present invention. This is a schematic unfolded diagram showing the tread pattern in the tread portion of a studless tire according to one embodiment of the present invention. This is a schematic diagram showing the water flow when θ1 = 60° and θ2 = 15°. This is a schematic diagram showing the water flow when θ1 = θ2 = 60°.

[0018] The vulcanized rubber composition for studless tires and the studless tires of the present invention will be described in detail below, based on embodiments thereof.

[0019] <Definitions> The compounds described herein may be derived in part or in whole from fossil resources, from biological resources such as plant resources, or from recycled resources such as used tires. They may also be derived from a mixture of two or more of fossil resources, biological resources, or recycled resources.

[0020] <Vulcanized Rubber Composition for Studless Tires> A vulcanized rubber composition for studless tires according to one embodiment of the present invention (hereinafter sometimes referred to as "the vulcanized rubber composition of this embodiment") is a vulcanized rubber composition for studless tires obtained by vulcanizing a rubber composition (meaning an unvulcanized rubber composition) containing a rubber component and a filler, wherein the filler contains recycled carbon black, the recycled carbon black is such that when measured with a grind gauge, three or more lines with a length of 10 mm or more are confirmed, and the particle size of the third largest particle among the particles that produce the lines with a length of 10 mm or more is 20 μm or less, and the vulcanized rubber composition has a plurality of voids.

[0021] The vulcanized rubber composition of this embodiment not only uses recycled carbon black as a filler, but also uses recycled carbon black in which, when measured with a grind gauge, three or more lines with a length of 10 mm or more are confirmed, and the particle size of the third largest particle among the particles that produce such lines of 10 mm or more is 20 μm or less. In this way, by using at least recycled carbon black, the vulcanized rubber composition of this embodiment can contribute to improved sustainability. Furthermore, in the grind gauge measurement of recycled carbon black, there is a high correlation between the evaluation results and the durability of the rubber composition, particularly the performance after degradation. By using recycled carbon black that is judged to have good dispersibility in grind gauge measurement (recycled carbon black in which the particle size of the third largest particle is 20 μm or less), the deterioration of the durability of the rubber composition, particularly the performance after degradation, can be suppressed. In other words, by using recycled carbon black in which the third largest particle size is 20 μm or less, the adverse effects on tire rubber properties (e.g., crack resistance after degradation, high-temperature tensile strength after degradation) are significantly smaller compared to using conventional recycled carbon black, and performance can be maintained.

[0022] (Multiple voids) As shown in Figure 2, the vulcanized rubber composition 110 of this embodiment has multiple voids 120, which gives it appropriate flexibility and makes it easier to adhere to icy road surfaces. In addition, the vulcanized rubber composition 110 having multiple voids 120 allows water on the road surface or water that has risen on the ice to be absorbed into the voids on the surface, removing water from the road surface (functioning as a drainage channel). Therefore, by using this vulcanized rubber composition, the ice performance and wet performance of the resulting studless tire can be improved.

[0023] The voids, as shown in Figure 3, are multiple holes formed in the vulcanized rubber composition 110, with an average diameter of approximately 1 to 500 μm. Here, the diameter of the voids refers to the largest diameter D of the voids 120 (if the voids are not spherical, the maximum distance D between any two points on the inner wall of the voids). The average diameter of the voids is the average value of the diameter D of the voids 120 present in the vulcanized rubber composition 110 of this embodiment. This average diameter can be calculated by observing the cross-section of the vulcanized rubber composition with a digital microscope (for example, the "VHX-100" manufactured by Keyence Corporation) and taking the average value of the diameters of all voids present in one field of view (2.5 mm × 2.5 mm). In the vulcanized rubber composition of this embodiment, since the shape and size of the voids do not change significantly within a single vulcanized rubber composition, the average value of the voids in one field of view can be used as the average diameter of the voids.

[0024] The vulcanized rubber composition of this embodiment preferably has a porosity of 5 to 45%. If the porosity is 5% or more, ice performance can be improved more reliably. From a similar viewpoint, the porosity is more preferably 7% or more, and even more preferably 15% or more. On the other hand, if the porosity is 45% or less, even if there are multiple voids, the decrease in abrasion resistance can be suppressed more effectively. From a similar viewpoint, the porosity is more preferably 40% or less, and even more preferably 37% or less. The above porosity refers to the percentage of the volume of the voids in the vulcanized rubber composition (volume %). The method for measuring the above porosity is not particularly limited, and for example, the porosity can be measured using a hydrometer (ViBRA hydrometer "DMA-220" manufactured by Shinko Denshi Co., Ltd.).

[0025] Here, the method for creating voids in the vulcanized rubber composition is not particularly limited. Depending on the void conditions and the equipment used to manufacture the vulcanized rubber composition of this embodiment, known techniques can be used to form the voids. For example, as will be described later, voids can be created in the vulcanized rubber composition by blending a foaming agent, foaming aid, etc., into the rubber composition before vulcanization. The void ratio can be controlled by changing the vulcanization conditions or by the content of void-introducing agents such as foaming agents and composite fibers. Another method for creating voids in the vulcanized rubber composition is to blend rubber powder into the rubber composition before vulcanization. In this method, the rubber powder falls off from the surface of the vulcanized rubber composition, and as a result, voids can be formed near the surface of the vulcanized rubber composition. In this case, the diameter of the voids and the void ratio can be adjusted by adjusting the particle size and number of the rubber powder particles.

[0026] The rubber composition that forms the basis of the vulcanized rubber composition of this embodiment (meaning the unvulcanized rubber composition; hereinafter sometimes referred to as "the rubber composition of this embodiment") will be described below.

[0027] (Rubber component) The rubber composition of this embodiment contains a rubber component, which provides the composition with rubber elasticity. The sustainability rate of the rubber component is preferably 30% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 100% by mass. Hereinafter, in this specification, "sustainability rate" refers to the total mass ratio of components derived from biological resources (biomass resources) and components derived from recycled resources in the material in question.

[0028] In this specification, the term "biomass resources" refers to carbon-neutral organic resources of biological origin, excluding fossil resources (such as petroleum, coal, and natural gas). These biological resources may be edible or inedible, but are preferably inedible, as they do not compete with food resources and are considered to be resources that can be used effectively.

[0029] In this specification, the term "recycled resources" refers to resources obtained by recycling products that have been used, collected without being used, or discarded. For example, recycled resources include resources obtained by recycling used rubber products such as used tires.

[0030] The rubber component is preferably derived from biological resources and recycled resources. Here, the proportion of the monomer component derived from biological resources in 100 mol% of the monomer component constituting the rubber derived from biological resources is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, even more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may also be 100 mol%. Similarly, the proportion of the monomer component derived from recycled resources in 100 mol% of the monomer component constituting the rubber derived from recycled resources is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, even more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may also be 100 mol%.

[0031] The aforementioned rubber component is a component that contributes to crosslinking, and typically has a weight-average molecular weight (Mw) of 10,000 or more, preferably 50,000 or more, more preferably 150,000 or more, even more preferably 200,000 or more, and also preferably 5,000,000 or less, more preferably 2,000,000 or less, and even more preferably 1,500,000 or less. In this specification, the weight-average molecular weight (Mw) of the rubber component can be determined, for example, by converting it to standard polystyrene based on measurements obtained by gel permeation chromatography (GPC).

[0032] The rubber component is preferably a diene-based rubber, and among the diene-based rubbers, isoprene-based rubber and butadiene-based rubber are preferred.

[0033] Examples of isoprene-based rubbers include natural rubber and synthetic isoprene rubber. The origin of natural rubber is not particularly limited; for example, it may be derived from the Para rubber tree, guayule, or Russian dandelion. Natural rubber may be modified or altered, and synthetic isoprene rubber may also be altered. These isoprene-based rubbers may be used individually or in combination of two or more. Natural rubber is preferred as the isoprene-based rubber.

[0034] Examples of the butadiene-based rubber include butadiene rubber and styrene-butadiene rubber. Here, it is preferable that the butadiene used as a raw material for the butadiene-based rubber is derived from biological resources or recycled resources.

[0035] Examples of the styrene-butadiene rubber include emulsion-polymerized styrene-butadiene rubber and solution-polymerized styrene-butadiene rubber.

[0036] The isoprene-based rubber and the butadiene-based rubber preferably have a sustainability rate of 30% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 100% by mass.

[0037] Furthermore, in order to keep the overall sustainability rate of the rubber component within the aforementioned range, it is preferable to use natural rubber as the rubber component, or to use polymers synthesized using monomer components derived from biological resources or recycled resources. It is also possible to use mass balance certified synthetic rubber to keep the sustainability rate within the aforementioned range.

[0038] The ratio of each monomer unit (for example, units derived from isoprene, units derived from butadiene, and units derived from aromatic vinyl compounds) in the entire rubber component can be appropriately adjusted depending on the member to which it is applied. The ratio of each monomer unit in the entire rubber component can be adjusted, for example, by appropriately combining the isoprene-based rubber and butadiene-based rubber mentioned above. The ratio of cis-bonded units in the butadiene-derived units can also be appropriately adjusted depending on the member to which it is applied. In this specification, "monomer unit" means a constituent unit of a polymer, "unit derived from isoprene" means a constituent unit in a polymer composed of isoprene, which is a monomer (including isoprene units in natural rubber), "unit derived from butadiene" means a constituent unit in a polymer composed of butadiene, which is a monomer, and "unit derived from aromatic vinyl compounds" means a constituent unit in a polymer composed of aromatic vinyl compounds, which are monomers. In this specification, the ratio of each monomer unit is measured by NMR.

[0039] In addition to the isoprene-based rubber, butadiene rubber, and styrene-butadiene copolymer rubber mentioned above, the rubber component may also include diene-based rubbers such as acrylonitrile-butadiene rubber, chloroprene rubber, butyl rubber, and styrene-isoprene-butadiene copolymer rubber. These rubber components may be used individually or in combination of two or more.

[0040] The rubber component may have functional groups that interact with fillers such as carbon black and silica introduced through modification. Examples of such functional groups include amino groups, amide groups, isocyanate groups, imino groups, imidazole groups, urea groups, ammonium groups, imide groups, hydrazo groups, azo groups, diazo groups, carboxyl groups, nitrile groups, pyridyl groups, alkoxy groups, hydroxyl groups, oxy groups, epoxy groups, ether groups, carbonyl groups, oxycarbonyl groups, silyl groups, alkoxysilyl groups, mercapto groups, sulfide groups, disulfide groups, sulfonyl groups, sulfinyl groups, and thiocarbonyl groups. These functional groups may also have substituents. These functional groups may be introduced into the rubber component individually or in combination of two or more. Among these, amino groups, alkoxy groups, and alkoxysilyl groups are preferred, and substituted amino groups in which the hydrogen atoms of the amino group are replaced by alkyl groups having 1 to 6 carbon atoms, alkoxy groups having 1 to 6 carbon atoms, and alkoxysilyl groups having 1 to 6 carbon atoms are even more preferred.

[0041] The functional group can be introduced, for example, by reacting a compound having the functional group (modifier) ​​with the rubber component. The compound having the functional group (modifier) ​​is a modifying functional group that interacts with fillers such as silica and carbon black, and can be a nitrogen-containing functional group, a silicon-containing functional group, or an oxygen-containing functional group. Examples of nitrogen-containing functional groups include amino group-containing compounds, examples of silicon-containing functional groups include silicon halides and hydrocarbyloxysilane compounds, and examples of oxygen-containing functional groups include alkoxy group-containing compounds, alkylene oxide group-containing compounds, and trialkylsilyloxy group-containing compounds. More specifically, examples include compounds described in WO2016 / 194316 and WO2019 / 117256. These modifiers may be used individually or in combination of two or more.

[0042] The aforementioned rubber derived from sustainable materials (materials derived from biological resources or materials derived from recycled resources) can be manufactured, for example, using monomer components derived from biological resources or monomer components derived from recycled resources, and, if necessary, monomer components derived from fossil resources, in the same manner as conventional methods for manufacturing synthetic rubber derived from fossil resources.

[0043] For example, the method described in Japanese Patent Publication No. 2022-179158 can be used to prepare rubber derived from biological resources.

[0044] As the butadiene obtained from the aforementioned biological resources, butadiene derived from alkyl alcohols (preferably ethanol and butanol, more preferably butanol), butadiene derived from alkenes (preferably ethylene), and butadiene derived from unsaturated carboxylic acids (preferably tigric acid) can be suitably used.

[0045] -Rubber component of embodiment (A)- In one embodiment, the rubber component preferably includes natural rubber (NR) and butadiene rubber (BR). The butadiene rubber (BR) may be modified or not. The origin of the natural rubber (NR) is not particularly limited, and examples include that derived from the Para rubber tree, guayule, or Russian dandelion. Furthermore, the natural rubber may be modified natural rubber, and examples of modified natural rubber include deproteinized natural rubber and high-purity natural rubber.

[0046] The inclusion of natural rubber in the rubber component improves the fracture strength of the rubber composition, which in turn reduces the rolling resistance of the tire, improves fuel efficiency, and also improves the wear resistance of the tire. In the above embodiment, the natural rubber content is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, even more preferably 40 parts by mass or more, and also preferably 90 parts by mass or less, more preferably 80 parts by mass or less, even more preferably 70 parts by mass or less, and even more preferably 60 parts by mass or less.

[0047] Furthermore, by including butadiene rubber in the rubber component, a good balance can be achieved between the tire's ice performance and wear resistance. The type of butadiene rubber is not particularly limited. For example, high-cis polybutadiene can be used as the butadiene rubber, in which case it is preferable that the cis-1,4 bond content be 90% by mass or more. By using high-cis polybutadiene, the wear resistance of the tire can be further improved. In the above embodiment, the content of butadiene rubber is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, even more preferably 40 parts by mass or more, and also preferably 90 parts by mass or less, more preferably 80 parts by mass or less, even more preferably 70 parts by mass or less, and even more preferably 60 parts by mass or less.

[0048] In the above embodiment, the rubber component preferably further contains styrene-butadiene rubber (SBR). Further inclusion of styrene-butadiene rubber in the rubber component can improve the wet performance of the tire. The styrene-butadiene rubber (SBR) is not particularly limited, and examples include solution-polymerized styrene-butadiene rubber (S-SBR) and emulsion-polymerized styrene-butadiene rubber (E-SBR), among which emulsion-polymerized styrene-butadiene rubber (E-SBR) is preferred. Furthermore, the styrene-butadiene rubber may or may not be modified. The proportion of styrene-butadiene rubber in the rubber component is preferably 5% by mass or more. In this case, the wet performance of the tire can be further improved. The proportion of styrene-butadiene rubber in the rubber component is not particularly limited, but is preferably 50% by mass or less.

[0049] In the above embodiment, the rubber component may include other rubber components such as synthetic isoprene rubber (IR) in addition to the natural rubber, butadiene rubber, and styrene-butadiene rubber mentioned above. These other rubber components may or may not be modified. Furthermore, the proportion of other rubber components in the rubber component is preferably in the range of 0 to 30% by mass, and more preferably in the range of 0 to 15% by mass.

[0050] -Rubber component of embodiment (B)- In one embodiment, the rubber component preferably contains 35% by mass or more of natural rubber. In this case, the compatibility properties of the rubber component can be further enhanced, thereby improving ice performance and wet performance. From a similar viewpoint, the proportion of natural rubber in the rubber component is preferably 50% by mass or more, and more preferably 60% by mass or more. On the other hand, there is no particular upper limit to the proportion of natural rubber in 100% by mass of the rubber component, but it is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less. The natural rubber may be unmodified or modified.

[0051] In the above embodiment, the proportion of butadiene rubber in the rubber component is preferably 65% ​​by mass or less. In this case, ice performance and wet performance can be better maintained. From a similar viewpoint, the proportion of butadiene rubber in the rubber component is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 38% by mass or less, and even more preferably 35% by mass or less. On the other hand, the lower limit of the proportion of butadiene rubber in 100% by mass of the rubber component is not particularly limited, but is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more. The butadiene rubber may be unmodified or modified.

[0052] In the above embodiment, the rubber component may include other components of the natural rubber and butadiene rubber described above. Examples of other rubber components include isoprene rubber (IR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), polysulfide rubber, silicone rubber, fluororubber, urethane rubber, etc. These other rubber components may be modified. These other rubber components may be used individually or in combination of two or more. Furthermore, these other rubber components may not be used at all (i.e., the rubber component may consist only of natural rubber (NR) and butadiene rubber (BR)). In particular, in the above example, the rubber component does not have to contain styrene-butadiene rubber (SBR).

[0053] -Rubber component of embodiment (C)- In one embodiment, the rubber component preferably includes a modified conjugated diene polymer having (meth)acrylic acid ester in its molecule (hereinafter sometimes referred to as "(meth)acrylic acid ester modified polymer"). Since (meth)acrylic acid ester is hydrophilic, by using a polymer in which (meth)acrylic acid ester is incorporated into the molecule as the rubber component, the rubber surface can be made hydrophilic, thereby greatly improving ice performance. In addition, since the (meth)acrylic acid ester modified polymer has a (meth)acrylic acid ester portion in its molecule, it is possible to suppress deterioration of performance such as abrasion resistance when hydrophilic materials (such as some resin components) are added to the rubber composition.

[0054] The term "(meth)acrylic acid ester" refers to acrylic acid esters and / or methacrylic acid esters. Furthermore, "having a (meth)acrylic acid ester in the molecule" means that the (meth)acrylic acid ester is incorporated into the molecule in the form of a functional group (such as an acryloyl group or methacryloyl group).

[0055] The (meth)acrylic acid ester is preferably an alkoxyalkyl (meth)acrylic acid ester.

[0056] The (meth)acrylic acid ester content in the (meth)acrylic acid ester modified polymer is preferably 0.5 to 10 mol%. A (meth)acrylic acid ester content of 1 mol% or more in the (meth)acrylic acid ester modified polymer provides sufficient hydrophilicity, resulting in superior ice performance. Furthermore, a (meth)acrylic acid ester content of 10 mol% or less in the (meth)acrylic acid ester modified polymer suppresses a decrease in performance such as abrasion resistance. From a similar viewpoint, the (meth)acrylic acid ester content in the (meth)acrylic acid ester modified polymer is preferably 2 to 7 mol%, and more preferably 3 to 6 mol%. The (meth)acrylic acid ester content in the (meth)acrylic acid modified polymer can be measured by NMR.

[0057] Furthermore, the (meth)acrylic acid-modified polymer is preferably having a glass transition temperature of -100 to -50°C. In this case, superior ice performance can be achieved. From a similar viewpoint, the glass transition temperature of the (meth)acrylic acid-modified polymer is more preferably -90°C or higher, and more preferably -70°C or lower. The glass transition temperature of the (meth)acrylic acid-modified polymer can be measured using a differential scanning calorimeter (for example, DSC, manufactured by T.A. Instruments Japan, "DSCQ2000") in accordance with JIS K 7121-1987.

[0058] The conjugated diene polymer constituting the (meth)acrylic acid ester-modified polymer is not particularly limited, but is preferably a homopolymer of conjugated diene units or a copolymer having aromatic vinyl units and conjugated diene units. Examples of conjugated diene compounds as monomers include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, 2-phenyl-1,3-butadiene, and 1,3-hexadiene, among which 1,3-butadiene and isoprene are preferred. On the other hand, examples of aromatic vinyl compounds as monomers include styrene, p-methylstyrene, m-methylstyrene, p-tert-butylstyrene, α-methylstyrene, chloromethylstyrene, and vinyltoluene.

[0059] The conjugated diene polymer constituting the (meth)acrylic acid ester-modified polymer preferably has a vinyl bond content of 10 to 20 mol% for the 1,3-butadiene units. If the vinyl bond content is 10 mol% or more, the strength of the (meth)acrylic acid-modified polymer can be increased. If the vinyl bond content is 20 mol% or less, the hardness of the rubber increases, and deterioration of ice performance can be effectively suppressed. From a similar viewpoint, the vinyl bond content of the 1,3-butadiene units is more preferably 13 mol% or more, and more preferably 18 mol% or less.

[0060] The (meth)acrylic acid ester-modified polymer can be produced, for example, by copolymerizing a conjugated diene polymer with a (meth)acrylic acid ester monomer. The polymerization method is not particularly limited and may be a known emulsion polymerization method or a solution polymerization method, but emulsion polymerization is preferred from the viewpoint of industrial productivity.

[0061] In the above embodiment, the proportion of (meth)acrylic acid ester-modified polymer in the rubber component is preferably 5 to 50% by mass. A proportion of 5% by mass or more can more reliably improve ice performance, and a proportion of 50% by mass or less can more reliably suppress deterioration of performance such as abrasion resistance. From a similar viewpoint, the proportion of (meth)acrylic acid ester-modified polymer in the rubber component is more preferably 10% by mass or more, and more preferably 45% by mass or less.

[0062] Other rubber components besides (meth)acrylic acid ester-modified polymers include diene rubbers. Furthermore, among diene rubbers, it is preferable that the rubber component contains natural rubber and either butadiene rubber or styrene-butadiene rubber. By using these rubbers together with (meth)acrylic acid ester-modified polymers as rubber components, it is possible to maintain good cut resistance and abrasion resistance while also improving ice performance.

[0063] (Filler) The rubber composition of this embodiment contains a filler. The inclusion of a filler improves the reinforcing properties of the rubber composition. Examples of fillers include carbon black, silica, talc, clay, aluminum hydroxide, and titanium oxide.

[0064] The amount of filler in the rubber composition is preferably in the range of 40 to 100 parts by mass per 100 parts by mass of the rubber component. When the amount of filler in the rubber composition is 40 parts by mass or more per 100 parts by mass of the rubber component, the reinforcing properties of the base rubber are improved, and the durability of the tire is improved. Furthermore, when the amount of filler in the rubber composition is 100 parts by mass or less per 100 parts by mass of the rubber component, the workability in the mixing of the rubber composition is improved, and the fuel efficiency of the tire is also improved.

[0065] -Carbon Black- Carbon black can reinforce rubber compositions and improve their abrasion resistance. As carbon black, plant-derived carbon black or carbon black obtained through recycling (also called "recycled carbon black") can be used.

[0066] From the viewpoint of further improving the wear resistance of the rubber composition and the tire to which it is applied, the carbon black content in the rubber composition 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, per 100 parts by mass of the rubber component. Furthermore, from the viewpoint of the workability of the rubber composition, the carbon black content in the rubber composition is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 70 parts by mass or less, per 100 parts by mass of the rubber component.

[0067] --Recycled Carbon Black-- As stated above, the rubber composition of this embodiment requires that the filler contain recycled carbon black. In this specification, recycled carbon black refers to carbon black obtained by recovering from raw materials that are waste materials that have been recycled. Examples of such waste materials include waste rubber, used tires, and waste oil. Waste rubber is not limited to that generated from rubber products, but refers to all discarded rubber, including unwanted scraps generated during the production or repair of rubber products. Examples of scraps include buffing powder and peeling rubber. Buffing powder is, for example, fine rubber generated in the buffing process that removes the tread portion remaining on the base tire during tire retreading. Peeling rubber is, for example, long pieces of rubber, 1 to 2 cm wide, that are peeled off from the surface of rubber products such as tires. Peeling rubber is generated by using a U-shaped or V-shaped knife like a peeler to scrape the surface of rubber products such as tires. Furthermore, waste rubber is not limited to cross-linked rubber, but also includes unvulcanized rubber. Rubber products include, for example, finished products such as tires and rubber hoses, as well as rubber parts or components used in the manufacturing process of these finished products. Used tires may be retreaded, or they may be tires discarded for any reason, such as tires resulting from tire replacement or vehicle scrapping, or End-of-Life Tires (ELTs) that have reached the end of their lifespan as tires. Waste oil is not limited to that generated when plastics and rubber are decomposed, but also includes used oils discharged from industry, such as animal and vegetable oils, lubricating oils, insulating oils, and cutting oils. Among these, waste oils that do not contain any non-organic composition, such as those derived from silicone rubber or polyvinyl chloride, are desirable. Furthermore, waste oils that contain carbon black or rubber containing carbon black are desirable. "Recycled carbon black" is different from carbon black that is directly manufactured using hydrocarbons such as petroleum, natural gas, and coal as raw materials, i.e., carbon black that is not recycled. Note that "used" here includes not only those that have been discarded after being actually used, but also those that were manufactured but discarded without actually being used.

[0068] Furthermore, it is preferable that the recycled carbon black is obtained by thermal decomposition of a vulcanized rubber product containing carbon black. Recycled carbon black obtained by thermal decomposition of a vulcanized rubber product containing carbon black is readily available because a large amount of vulcanized rubber product containing carbon black exists and it can be easily obtained by thermal decomposition. Moreover, it is preferable that the recycled carbon black is obtained from the solid residue generated by the thermal decomposition of the vulcanized rubber product containing carbon black. When a rubber product containing carbon black is thermally decomposed, solid residue and volatile components (oil) are obtained, and recycled carbon black can be recovered from either. When recovering carbon black from volatile components, it is possible to recover oil with a specific gravity suitable for producing carbon black and use it to produce carbon black using an existing carbon black production method (for example, Japanese Patent Publication No. 2015-520259). In this case, unlike carbon black recovered from solid residue, there are advantages such as the absence of impurities and the absence of mixtures of different grades. Furthermore, in the production of environmentally friendly carbon black, there are various options besides the oil obtained by recovering volatile components from the thermal decomposition of rubber mentioned above, such as using vegetable oil or oil derived from waste plastics. However, edible resources such as vegetable oil present challenges in securing sufficient quantities due to other uses such as food, and the environmental impact associated with the expansion of cultivated land must also be considered. Similarly, oil derived from waste plastics is used for other purposes such as horizontal recycling of plastics, so supply issues are also a concern. On the other hand, when using volatile components (oil) produced by the thermal decomposition of vulcanized rubber products, particularly tires, the tire industry has a system for continuing to use existing materials, making it possible to continue using existing materials and reduce the consumption of new materials in new tire manufacturing, thereby contributing to reducing the environmental burden on the industry. The grade of carbon black is not particularly limited, but examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762.

[0069] Furthermore, when recycled carbon black is recovered from solid residue, it is more preferably carbon black that has undergone surface treatment or surface modification. Examples of surface treatment or surface modification include hydrofluoric acid treatment, acid treatment such as hydrochloric acid or sulfuric acid, or treatment with peroxides. Surface treatment or surface modification may be carried out at room temperature, preferably at 70°C or higher, more preferably at 90°C or higher, and particularly preferably at 90°C to 100°C.

[0070] Furthermore, recycled carbon black can be obtained from the pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3427975, "Rubber Chemistry and Technology," Vol. 85, No. 3, pp. 408-449 (2012), particularly pp. 438, 440, and 442, states that it can be obtained by the 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 Patent No. 6856781 (Comparison of Surface Morphology and Chemistry of Pyrolysis Carbon Black and Commercial Carbon Black, PowderTechnology 160 (2005) 190-193).

[0071] Recycled carbon black may lack functional groups on its surface, or it may be treated to contain functional groups on its surface. Treatment to contain functional groups on the surface of recycled carbon black can be carried out by conventional methods. For example, in European Patent Application Publication No. 3173251, carbon black obtained from a thermal decomposition process is treated with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl groups and / or carboxyl groups on its surface. In addition, in Japanese Patent No. 6856781, carbon black obtained from a thermal decomposition process is treated with an amino acid compound containing at least one thiol group or disulfide group to obtain carbon black with an activated surface. The recycled carbon black according to this embodiment also includes carbon black that has been treated to contain functional groups on its surface.

[0072] Furthermore, for the thermal decomposition of cross-linked rubber products (vulcanized rubber products) such as used tires, one example is a thermal decomposition method at a temperature of 650°C or higher.

[0073] Furthermore, the recycled carbon black used in this embodiment must, when measured with a grind gauge, show at least three lines with a length of 10 mm or more, and the particle size of the third largest particle among those particles that produce such lines of 10 mm or more is 20 μm or less.

[0074] The measurement using the grind gauge described above is for evaluating the dispersibility of carbon black and can be performed in accordance with the descriptions in JIS K5101-1-5 (especially regarding the preparation of paste) and JIS K5400 (especially regarding the method of evaluation by the manner in which linear traces are generated).

[0075] The range of the grind gauge used is preferably 0 to 25 μm, from the viewpoint of accurately measuring particle size and from the viewpoint of ease of measurement. However, a grind gauge with an upper limit of 20 μm is also usable, as it can determine whether the particle size of the third largest particle is 20 μm or less.

[0076] JIS K5101-1-5 describes a method for preparing a paste of recycled carbon black as a measurement sample in grind gauge measurements. The paste of recycled carbon black can be prepared in accordance with JIS K5101-1-5 as a measurement sample for grind gauge measurements. By preparing the paste of recycled carbon black in accordance with JIS K5101-1-5, the accuracy of grind gauge measurements can be further improved.

[0077] In one embodiment, the accuracy of grind gauge measurement can be further improved by appropriately adjusting the viscosity of the paste. In one embodiment, it is preferable to prepare a paste (measurement sample) containing recycled carbon black by blending recycled carbon black and zinc oxide with epoxidized soybean oil. Here, the blending ratio of the paste is not particularly limited, but it is preferable to use about 8 to 12 g of recycled carbon black and about 160 to 200 g of zinc oxide per 100 mL of epoxidized soybean oil.

[0078] Furthermore, in the measurement of recycled carbon black using a grind gauge, the paste of recycled carbon black can be prepared as a measurement sample by setting the applied load to 0.4 to 0.5 kN and the rotation speed of the glass plate to 90 to 110 r / min, in accordance with JIS K5101-1-5. In this case, the accuracy of the grind gauge measurement can be further improved.

[0079] When the recycled carbon black is measured with a grind gauge, three or more lines with a length of 10 mm or more can be observed. If the number of lines with a length of 10 mm or more is less than three, it is considered that the recycled carbon black being measured is too minute, and therefore cannot be sufficiently detected. In addition, while several lines caused by particles in the sample are observed when measuring with a grind gauge, in this embodiment, in accordance with JIS standards, lines with a length of 10 mm or more are not considered, and lines with a length of 10 mm or more are considered.

[0080] Furthermore, in this embodiment, in accordance with JIS standards, among the lines with a length of 10 mm or more, the line caused by the largest particle and the line caused by the second largest particle are judged to be abnormal values, and from the viewpoint of improving measurement accuracy, attention is paid to the line caused by the third largest particle and its particle size is confirmed. Here, the smaller the particle size of the third largest particle in the recycled carbon black, the better the dispersibility of the recycled carbon black in the rubber composition when the recycled carbon black is blended into the rubber composition, and the more likely it is that the durability of the rubber composition will improve. As described above, in the case of the recycled carbon black, if the particle size of the third largest particle among the particles that cause the line with a length of 10 mm or more is 20 μm or less, the dispersibility of the recycled carbon black in the rubber composition is improved, and the durability of the rubber composition can be effectively improved.

[0081] Figure 1 shows an explanatory diagram of an example of measurement results using a grind gauge. In the measurement using grind gauge 1, several lines attributable to particles in the sample are observed. In this embodiment, in accordance with JIS standards, lines 2 with a length of less than 10 mm are not considered, and lines 3 with a length of 10 mm or more are considered. Furthermore, among the lines 3 with a length of 10 mm or more, line 31 attributable to the largest particle and line 32 attributable to the second largest particle are judged to be abnormal values. In this embodiment, from the viewpoint of improving measurement accuracy, attention is paid to line 33 attributable to the third largest particle. The scale 4 at the location where line 33 attributable to the third largest particle appears is read, and this reading is taken as the particle size of the third largest particle. In this specification, the measurement of recycled carbon black using a grind gauge is performed by the method described in the examples.

[0082] The recycled carbon black in which the third largest particle size is 20 μm or less can be manufactured by various methods. For example, recycled carbon black in which the third largest particle size is 20 μm or less can be manufactured by further grinding the recycled carbon black produced by a general method from recycled waste by extending the grinding process for a longer time or increasing the grinding intensity.

[0083] The recycled carbon black preferably has an ash content of 20% by mass or less. If the ash content in the recycled carbon black is 20% by mass or less, a tire with sufficient reinforcement can be obtained. Considering the reinforcement of the tire, the ash content of the recycled carbon black is more preferably 10% by mass or less, even more preferably 6% by mass or less, even more preferably 5% by mass or less, even more preferably 4% by mass or less, even more preferably 3% by mass or less, even more preferably 2% by mass or less, and particularly preferably 1% by mass or less. Here, in this specification, the ash content of carbon black is determined according to ASTM D8474 / D1506.

[0084] The aforementioned ash content specifically includes zinc oxide, zinc sulfide, silica, iron compounds (iron oxide), calcium oxide, aluminum oxide, magnesium oxide, and the like. In the case of recycled carbon black produced from solid residue obtained by thermal decomposition of waste, a certain amount of ash remains even after various processes to remove it. In this embodiment, the presence of ash in recycled carbon black is permitted. The lower limit of the ash content of the recycled carbon black used in this embodiment may be 0.5% by mass.

[0085] The recycled carbon black preferably contains one or more elements selected from the group consisting of Zn (zinc), Fe (iron), and Cu (copper). Such recycled carbon black can maintain the physical properties of the rubber composition while retaining components that may affect the deterioration of the rubber composition's properties, thus simplifying processing steps such as purification to completely remove components that may affect the deterioration of the rubber composition's properties.

[0086] Furthermore, the recycled carbon black may contain Zn (zinc). The Zn in the recycled carbon black originates from, for example, zinc oxide used as a vulcanization aid. If the Zn content in the recycled carbon black exceeds a certain amount, the physical properties of the rubber composition will deteriorate, but if it is below a certain amount, the deterioration of the physical properties of the rubber composition can be suppressed. However, the recycled carbon black may also not contain Zn.

[0087] If the recycled carbon black contains Zn, the Zn content in the recycled carbon black is preferably 2.5% by mass or less. A lower Zn content in the recycled carbon black is preferable, but a Zn content of 2.5% by mass or less can suppress a decrease in the physical properties of the rubber composition. From the viewpoint of suppressing a decrease in the physical properties of the rubber composition, the Zn content is more preferably 2.0% by mass or less, even more preferably 1.5% by mass or less, even more preferably 1.0% by mass or less, and particularly preferably 0.5% by mass or less. The Zn content may also be 0.01% by mass or more, or 0.05% by mass or more. The above upper and lower limits can be combined as appropriate.

[0088] Methods to keep the Zn content in recycled carbon black within the above range include, for example, acid treatment and analyzing the amount of Zn contained in the raw rubber to be recycled in advance, and using some or all of the raw rubber with a low Zn content.

[0089] The Fe content in the recycled carbon black is preferably 0% by mass or more and 0.1% by mass or less. A lower Fe content in the recycled carbon black is preferable, but if the Fe content is 0.1% by mass or less, the deterioration of the physical properties of the rubber composition can be suppressed. From the viewpoint of suppressing the physical properties of the rubber composition, the Fe content in the recycled carbon black is more preferably 0.09% by mass or less, even more preferably 0.08% by mass or less, even more preferably 0.07% by mass or less, even more preferably 0.06% by mass or less, even more preferably 0.05% by mass or less, even more preferably 0.04% by mass or less, and most preferably 0.03% by mass or less. Furthermore, the Fe content in the recycled carbon black may be 0.01% by mass or more, or 0.02% by mass or more. The above upper and lower limits can be combined as appropriate.

[0090] The Cu content in the recycled carbon black is preferably 0% by mass or more and 0.05% by mass or less. A lower Cu content in the recycled carbon black is preferable, but if the Cu content is 0.05% by mass or less, the deterioration of the physical properties of the rubber composition can be suppressed. From the viewpoint of suppressing the physical properties of the rubber composition, the Cu content in the recycled carbon black is more preferably 0.04% by mass or less, even more preferably 0.03% by mass or less, even more preferably 0.02% by mass or less, and even more preferably 0.01% by mass or less. Furthermore, the Cu content in the recycled carbon black may be 0.01% by mass or more, or 0.02% by mass or more. The above upper and lower limits can be combined as appropriate.

[0091] The recycled carbon black may contain components other than Zn, Fe, and Cu as described above. "Components other than Zn, Fe, and Cu" refers to components other than Zn, Fe, and Cu in the ash. Examples of components other than Zn, Fe, and Cu in the ash include Si (silicon), S (sulfur), Ca (calcium), K (potassium), Br (bromine), Mg (magnesium), Cl (chlorine), P (phosphorus), Co (cobalt), Na (sodium), and Al (aluminum).

[0092] The recycled carbon black may contain silicon (Si). Preferably, the Si content in the recycled carbon black is 0% by mass or more and 1.0% by mass or less. A Si content of 1.0% by mass or less in the recycled carbon black suppresses a decrease in the physical properties of the rubber composition. From a similar viewpoint, the Si content in the recycled carbon black is more preferably 0.5% by mass or less, and even more preferably 0.3% by mass or less. Furthermore, it is also preferable that the Si content in the recycled carbon black is 0% by mass, i.e., the recycled carbon black is substantially Si-free. On the other hand, the Si content in the recycled carbon black may be 0.01% by mass or more, or 0.05% by mass or more. The above upper and lower limits can be combined as appropriate.

[0093] The recycled carbon black may contain sulfur (S). The S content in the recycled carbon black is preferably 0.4% by mass or more, and more preferably 0.5% by mass or more. Furthermore, the S content in the recycled carbon black is preferably 2.0% by mass or less, more preferably 1.8% by mass or less, and even more preferably 1.0% by mass or less. The above upper and lower limits can be combined as appropriate.

[0094] The recycled carbon black may contain Ca (calcium). The Ca content in the recycled carbon black is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.5% by mass or more, even more preferably 0.7% by mass or more, and even more preferably 0.8% by mass or more. Furthermore, the Ca content in the recycled carbon black is preferably 1.5% by mass or less, more preferably 1.2% by mass or less, and even more preferably 1.1% by mass or less. The above upper and lower limits can be combined as appropriate.

[0095] The recycled carbon black used in this embodiment has a nitrogen adsorption specific surface area (N) determined by the BET method. ２ SA) 40-100m ２ It is preferable that the amount be / g, and 50 to 90 m ２ It is more preferable that the amount be / g, and 55 to 75 m ２ It is particularly preferable that the amount of OAN oil absorbed is 70 to 120 mL / 100 g, more preferably 75 to 110 mL / 100 g, and particularly preferably 80 to 100 mL / 100 g. In this specification, the specific surface area of ​​nitrogen adsorption of carbon black by the BET method (N ２ SA) is the statistical thickness specific surface area (STSA), which is determined according to ASTM D6556. In this specification, the amount of OAN absorbed by carbon black is determined according to ASTM D2414.

[0096] The recycled carbon black preferably has a pH of 4 to 12, more preferably 5 to 11, and particularly preferably 6 to 10. Herein, in this specification, the pH of the recycled carbon black is determined according to ASTM D1512.

[0097] The recycled carbon black preferably has a toluene staining transmittance of 60% or more, more preferably 70% or more, and particularly preferably 80% or more. Herein, in this specification, the toluene staining transmittance of recycled carbon black is determined according to ASTM D1618.

[0098] The recycled carbon black preferably has a heating loss of 3% by mass or less at 125°C, more preferably 2.5% by mass or less, and particularly preferably 2% by mass or less. Hereinafter, the heating loss of the recycled carbon black at 125°C is determined according to ASTM D1509.

[0099] The recycled carbon black preferably has a sulfur content of 5% by mass or less, more preferably 3.5% by mass or less, and particularly preferably 3% by mass or less.

[0100] The recycled carbon black preferably has a 35-mesh sieve residue of 20 ppm by mass or less, more preferably 15 ppm by mass or less, and particularly preferably 10 ppm by mass or less. Here, in this specification, the 35-mesh sieve residue of the recycled carbon black is determined according to ASTM D1514.

[0101] The recycled carbon black preferably has a 325-mesh (44 μm) sieve residue of 1,000 ppm by mass or less, more preferably 700 ppm by mass or less, and particularly preferably 300 ppm by mass or less. Here, in this specification, the 325-mesh (44 μm) sieve residue of the recycled carbon black is determined according to ASTM D1514.

[0102] The recycled carbon black preferably has a pellet hardness of 100 cN or less, more preferably 90 cN or less, and particularly preferably 80 cN or less. Hereinafter, the pellet hardness of the recycled carbon black is determined according to ASTM D5230.

[0103] The recycled carbon black preferably has a pellet fine powder content of 10% by mass or less, more preferably 7% by mass or less, and particularly preferably 5% by mass or less. Hereinafter, the pellet fine powder content of the recycled carbon black is determined according to ASTM D1508.

[0104] The recycled carbon black preferably has a particle size (D97) of 25 μm or less, more preferably 15 μm or less, and particularly preferably 10 μm or less. Hereinafter, the particle size (D97) of the recycled carbon black is determined using a laser diffraction particle size analyzer, with the refractive index of water being 1.33 and the refractive index of the filler being 1.75.

[0105] The recycled carbon black preferably contains 50% or more by volume of particles 5 μm or smaller, more preferably 70% or more by volume, and particularly preferably 80% or more by volume.

[0106] The recycled carbon black preferably has an oil absorption rate (COAN) of 50 to 110 mL / 100 g, more preferably 60 to 100 mL / 100 g, and particularly preferably 70 to 90 mL / 100 g. Hereinafter, the oil absorption rate (COAN) of the compressed sample of recycled carbon black is determined according to ASTM D3493.

[0107] --Carbon Black Other Than Recycled Carbon Black-- The rubber composition of this embodiment may further contain, in addition to the recycled carbon black described above, carbon black other than recycled carbon black (virgin carbon black) as a filler. Examples of carbon black other than recycled carbon black include plant-derived carbon black, such as that derived from castor oil and pine resin oil. The grade of the carbon black is not particularly limited, and examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, etc. Commercially available carbon black can be used, and examples of commercially available carbon black include products from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., Birla Carbon, etc. These carbon blacks may be used individually or in combination of two or more types.

[0108] -Silica- The filler may contain silica. The type of silica is not particularly limited. Examples include wet silica, colloidal silica, calcium silicate, aluminum silicate, etc. Among the above, wet silica is preferred, and precipitated silica is more preferred. These silicas may be used individually or in combination of two or more types.

[0109] From the viewpoint of reducing environmental impact, silica derived from silicate plants is preferred. These silicate plants include, for example, mosses, ferns, horsetails, plants of the Cucurbitaceae family, Urticaceae family, and grasses. Among these plants, grasses are preferred. Among grasses, silica derived from rice husks (hereinafter also referred to as "rice husk silica") is particularly preferred from the viewpoint of availability. Further examples of silica include silicon wafer scraps used as raw materials for semiconductors, silica recycled from glass bottles, etc., and used in manufacturing.

[0110] The silica has a nitrogen adsorption specific surface area (N ２The nitrogen adsorption specific surface area (N ２ SA) of silica is preferably 50 m ２ / g or more, more preferably 100 m ２ / g or more, still more preferably 150 m ２ / g or more, and preferably 350 m ２ / g or less, more preferably 250 m ２ / g or less, still more preferably 230 m ２ / g or less, and even more preferably 200 m ２ / g or less. In the present specification, the nitrogen adsorption specific surface area (N ２ SA) of silica is a value measured by the BET method in accordance with ASTM D3037-93.

[0111] The content of silica in the rubber composition can be appropriately adjusted depending on, for example, the applicable tire category, tire member, target performance, etc. For example, the content of silica in the rubber composition is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, more preferably 30 parts by mass or more, more preferably 50 parts by mass or more, more preferably 70 parts by mass or more, still more preferably 80 parts by mass or more, even more preferably 100 parts by mass or more, particularly preferably 110 parts by mass or more, and preferably 300 parts by mass or less, more preferably 200 parts by mass or less, still more preferably 180 parts by mass or less, and particularly preferably 150 parts by mass or less, based on 100 parts by mass of the rubber component.

[0112] The ratio of silica in the total content of silica and carbon black is not particularly limited and can be appropriately adjusted depending on, for example, the applicable tire category, tire member, target performance, etc. For example, in the case of the tread rubber of a passenger car tire, the ratio of silica in the total content of silica and carbon black is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, and preferably 98% by mass or less. [[ID=​​​​​​​​​​​​​​​​(Silane coupling agent) When the filler contains silica, it is preferable that the rubber composition contains a silane coupling agent in order to improve the effect of the silica. Examples of the silane coupling agent include bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl- Examples include N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl) tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, and dimethoxymethylsilylpropylbenzothiazolyl tetrasulfide. These silane coupling agents may be used individually or in combination of two or more.

[0114] Furthermore, bioethanol can also be used as a raw material for silane coupling agents.

[0115] (Void-introducing agent) The rubber composition of this embodiment preferably further contains a void-introducing agent. By containing a void-introducing agent, the rubber composition can form a plurality of voids on the surface or inside, or on the surface and inside, of the vulcanized rubber composition.

[0116] Examples of the void-introducing agents include foaming agents, metal sulfate salts, thermally expandable microcapsules, porous cellulose particles, and lignin derivatives. These void-introducing agents may be used individually or in combination of two or more. In particular, from the viewpoint of ice surface performance, it is preferable to use a foaming agent as the void-introducing agent.

[0117] The content of the void-introducing agent in the rubber composition of this embodiment is not particularly limited, but from the viewpoint of obtaining a desired void ratio and maintaining abrasion resistance, it is preferably 0.1 to 20 parts by mass, more preferably 0.3 to 10 parts by mass, and even more preferably 0.5 to 5 parts by mass per 100 parts by mass of the rubber component.

[0118] - Foaming Agent - The rubber composition of this embodiment contains a foaming agent as a void-introducing agent, which allows bubbles to be generated in the vulcanized rubber by the foaming agent during the vulcanization of the rubber composition, thereby forming multiple voids in the vulcanized rubber composition. Specific examples of foaming agents include, for example, azodicarbonamide (ADCA), dinitrosopentamethylenetetramine (DPT), dinitrosopentastyrenetetramine, benzenesulfonyl hydrazide derivatives, p,p'-oxybisbenzenesulfonyl hydrazide (OBSH), carbonates such as ammonium carbonate, sodium carbonate, and potassium carbonate, inorganic foaming agents such as bicarbonates (bicarbonates) such as ammonium bicarbonate, sodium bicarbonate, and potassium bicarbonate, nitrogen-generating nitrososulfonyl azo compounds, N,N'-dimethyl-N,N'-dinitrosofthalamide, toluenesulfonyl hydrazide, p-toluenesulfonyl semicarbazide, and p,p'-oxybisbenzenesulfonyl semicarbazide. Among these, from the viewpoint of ease of manufacturing and processing, azodicarbonamide (ADCA), dinitrosopentamethylenetetramine (DPT), and inorganic blowing agents are preferred as blowing agents, and it is more preferable that they contain at least sodium bicarbonate. These blowing agents may be used individually or in combination of two or more.

[0119] The amount of the foaming agent in the rubber composition is not particularly limited, but is preferably 1 to 10 parts by mass, and more preferably 2 to 8 parts by mass, per 100 parts by mass of the rubber component.

[0120] -Metal Sulfate- The rubber composition of this embodiment contains a metal sulfate as a void-introducing agent, causing the metal sulfate to protrude from the tire surface obtained by vulcanizing the rubber composition, performing a claw function without the disadvantage of being abrasive. Subsequently, the metal sulfate gradually exits from the rubber matrix, creating voids that function as storage volumes and passages for draining the water film from the ice surface. Under these conditions, the contact between the tire surface (e.g., the tread surface) and the ice is no longer lubricated. Magnesium sulfate is an example of a metal sulfate that improves the coefficient of friction.

[0121] The metal sulfate salt is preferably composed of micrometer-sized particles. Specifically, the average particle size and median particle size (both expressed by mass) are preferably 1 μm to 1 mm, and the median particle size is more preferably 2 μm to 800 μm. When the average particle size and median particle size are 1 μm or larger, the target technical effect (i.e., the formation of appropriate fine roughness) is easily obtained. Furthermore, when the average particle size and median particle size are 1 mm or smaller, especially when the rubber composition is used as a tread, a decrease in aesthetics can be suppressed (it is possible to suppress the appearance of overly obvious particles on the tread surface), and the grip performance on melted ice is less likely to be impaired.

[0122] For all these reasons, the median particle size of the metal sulfate is preferably 2 μm to 500 μm, and more preferably 5 μm to 200 μm. This particularly preferred particle size range appears to correspond to the optimal compromise between the desired surface roughness on the one hand and good contact between the rubber composition and the road surface on the other hand. From a similar viewpoint, the content of the metal sulfate in the rubber composition is preferably 5 to 40 parts by mass, more preferably 10 to 35 parts by mass, per 100 parts by mass of the rubber component.

[0123] -Thermally Expandable Microcapsules- The thermally expandable microcapsules consist of a shell made of thermoplastic resin containing a thermally expandable substance. The shell of the thermally expandable microcapsules can be made of a nitrile polymer. The thermally expandable substance contained within the microcapsule shell has the property of vaporizing or expanding upon heat, and examples include at least one selected from the group consisting of hydrocarbons such as isoalkanes and n-alkanes. Examples of isoalkanes include isobutane, isopentane, 2-methylpentane, 2-methylhexane, and 2,2,4-trimethylpentane, while examples of n-alkanes include n-butane, n-propane, n-hexane, n-heptane, and n-octane. These hydrocarbons may be used individually or in combination. A preferred form of the thermally expandable substance is one in which a hydrocarbon that is gaseous at room temperature is dissolved in a hydrocarbon that is liquid at room temperature. By using such a hydrocarbon mixture, sufficient expansion force can be obtained from low to high temperatures within the vulcanization molding temperature range (150°C to 190°C) of unvulcanized tires.

[0124] Examples of such thermally expandable microcapsules include "EXPANCEL 091DU-80" or "EXPANCEL 092DU-120" manufactured by Expancel GmbH in Sweden, or "Matsumoto Microsphere F-85D" or "Matsumoto Microsphere F-100D" manufactured by Matsumoto Oil & Fat Pharmaceutical Co., Ltd.

[0125] The content of thermally expandable microcapsules in the rubber composition is preferably 0.1 to 10 parts by mass, and more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the rubber component.

[0126] -Porous Cellulose Particles- By including porous cellulose particles as a void-introducing agent in the rubber composition of this embodiment, porous cellulose particles can be exposed on the tire surface of the vulcanized rubber composition obtained by vulcanizing the rubber composition. In such a vulcanized rubber composition, water on the icy or snowy road surface is absorbed by the porous cellulose particles, and water between the tire and the road surface can be removed. Furthermore, because the presence of cellulose, a polysaccharide, causes interaction between the tire and water on the icy or snowy road surface, the interaction between the tire and water by the modified polyoxyalkylene glycol can be further enhanced.

[0127] The porous cellulose particles described above are typically cellulose particles having a porous structure with a void ratio of 75 to 95%, and when incorporated into a rubber composition, they can significantly improve ice performance. A void ratio of 75% or more in the porous cellulose particles provides excellent ice performance improvement, while a void ratio of 95% or less increases the strength of the particles. The void ratio is more preferably 80 to 90%. The void ratio of the porous cellulose particles can be determined by measuring the volume of a certain mass of sample (i.e., porous cellulose particles) with a graduated cylinder, determining the bulk density, and using the following formula: Void ratio [%] = {1 - (bulk density of sample [g / ml]) / (true density of sample [g / ml])} × 100 Here, the true density of cellulose is 1.5.

[0128] The particle size of the porous cellulose particles is not particularly limited, but from the viewpoint of abrasion resistance, it is preferable that the average particle size is 1000 μm or less. The lower limit of the average particle size is not particularly limited, but it is preferable that it is 5 μm or more. The average particle size is more preferably 100 to 800 μm, and even more preferably 200 to 800 μm.

[0129] Such porous cellulose particles are commercially available from Rengo Co., Ltd. as "Viscopearl," and are also described in Japanese Patent Publication No. 2001-323095, Japanese Patent Publication No. 2004-115284, etc., and can be suitably used. The content of porous cellulose particles in the rubber composition is preferably 0.3 to 20 parts by mass per 100 parts by mass of rubber component. A content of 0.3 parts by mass or more enhances the effect of improving ice performance, and a content of 20 parts by mass or less prevents the rubber hardness from becoming too high, thereby suppressing a decrease in abrasion resistance. The content of porous cellulose particles is more preferably 1 to 15 parts by weight, and even more preferably 3 to 15 parts by mass.

[0130] -Lignin Derivatives- The rubber composition of this embodiment can enhance its ice performance by containing a lignin derivative as a void-introducing agent. Ligninsulfonates are preferably used as the lignin derivative. Examples of ligninsulfonates include alkali metal salts, alkaline earth metal salts, ammonium salts, and alcoholamine salts of ligninsulfonic acid, and at least one of these can be included in the composition. Preferably, alkali metal salts and / or alkaline earth metal salts of ligninsulfonic acid are used, such as potassium salts, sodium salts, calcium salts, magnesium salts, lithium salts, and barium salts, and mixed salts of these are also acceptable.

[0131] (Foaming aid) The rubber composition of this embodiment preferably further contains a foaming aid. In particular, when a foaming agent is used as a void introduction agent in the rubber composition of this embodiment, it is preferable to use a foaming aid in combination. In other words, the rubber composition of this embodiment preferably contains a foaming agent as a void introduction agent and a foaming aid. In this case, the foaming reaction can be promoted, the degree of completion of the reaction can be increased, and unwanted deterioration over time can be suppressed.

[0132] Examples of foaming agents include urea, zinc stearate, zinc benzenesulfinate, and zinc oxide. These foaming agents may be used individually or in combination of two or more.

[0133] The total content of the foaming agent and the foaming aid is preferably 1 to 30 parts by mass per 100 parts by mass of the rubber component. When the total content of the foaming agent and the foaming aid is 1 part by mass or more, the rubber composition can be sufficiently foamed during vulcanization, and a high foaming rate of the vulcanized rubber composition can be maintained. On the other hand, when the total content of the foaming agent and the foaming aid is 30 parts by mass or less, a decrease in the foaming rate can also be suppressed. From a similar viewpoint, the total content of the foaming agent and the foaming aid is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, more preferably 25 parts by mass or less, and more preferably 20 parts by mass or less, per 100 parts by mass of the rubber component.

[0134] In the rubber composition of this embodiment, the mass ratio of the foaming aid to the foaming agent (foaming aid / foaming agent) is preferably 1.1 to 3.3. If the mass ratio is 1.1 or higher, the rubber composition foams sufficiently during vulcanization, and the foaming rate of the vulcanized rubber composition can be increased. On the other hand, if the mass ratio is 3.3 or lower, the foaming rate can be well maintained. From a similar viewpoint, the mass ratio of the foaming aid to the foaming agent (foaming aid / foaming agent) is more preferably 1.2 or higher, even more preferably 1.3 or higher, even more preferably 3.2 or lower, even more preferably 3.1 or lower, even more preferably 2.9 or lower, even more preferably 2.7 or lower, even more preferably 2.5 or lower, and particularly preferably 2.3 or lower.

[0135] Furthermore, from the viewpoint of the foaming rate of the vulcanized rubber composition and the wet performance of the tire, the content of the foaming aid is preferably in the range of 4 to 14 parts by mass, and more preferably in the range of 6 to 14 parts by mass, per 100 parts by mass of the rubber component.

[0136] (Liquid Plasticizer) The rubber composition of this embodiment preferably further contains a liquid plasticizer. Here, "liquid plasticizer" refers to a compounding agent that is liquid at 25°C (room temperature) and has the effect of softening the rubber composition. The liquid plasticizer is not particularly limited and includes oils, liquid polymers, etc., and among these, oil is preferred. These liquid plasticizers may be used individually or in combination of two or more.

[0137] The aforementioned oils refer to the drawstring oils contained in rubber components and the liquid oils added as compounding agents to rubber compositions. Examples include vegetable oils, process oils, oils obtained by recycling vegetable oils or process oils, or mixtures thereof. From the viewpoint of reducing environmental impact, vegetable oils and recycled oils are preferred as oils. Examples of vegetable oils include palm oil, castor oil, cottonseed oil, soybean oil, linseed oil, rapeseed oil, coconut oil, peanut oil, pine oil, pine tar, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil, and coconut oil. Examples of process oils include paraffinic process oils, aromatic process oils, and naphthenic process oils. Commercially available oils can be used as the aforementioned oils. Examples of commercially available oils that can be used include those from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Co., Ltd., Orisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Showa Shell Sekiyu K.K., Nisshin Oillio Group Ltd., Fuji Kosan Co., Ltd., and others. These oils may be used individually or in combination of two or more types.

[0138] The liquid polymer is preferably a liquid diene polymer. Examples of liquid diene polymers include liquid styrene-butadiene copolymer (liquid SBR), liquid polybutadiene (liquid BR), liquid polyisoprene (liquid IR), liquid styrene-isoprene copolymer (liquid SIR), liquid styrene-butadiene-styrene block copolymer (liquid SBS block polymer), liquid styrene-isoprene-styrene block copolymer (liquid SIS block polymer), liquid polyfarnesene, liquid farnesene-butadiene copolymer, and the like. These liquid polymers may be hydrogenated, or their ends or main chains may be modified with functional groups (polar groups). These liquid polymers may be used individually or in combination of two or more. The above liquid polymers are not included in the definition of "rubber components."

[0139] In this embodiment, the liquid plasticizer content in the rubber composition is preferably 30 parts by mass or less per 100 parts by mass of the rubber component. In this case, good ice and snow performance and wet grip performance can be obtained while suppressing deterioration of wear resistance and handling stability. From a similar viewpoint, the liquid plasticizer content is preferably 28 parts by mass or less, and more preferably 25 parts by mass or less, per 100 parts by mass of the rubber component. Furthermore, from the viewpoint of obtaining even better ice and snow performance and wet grip performance, the liquid plasticizer content in the rubber composition of this embodiment is preferably 5 parts by mass or more, and more preferably 10 parts by mass or more, per 100 parts by mass of the rubber component. However, the liquid plasticizer content in the rubber composition of this embodiment may also be 0 parts by mass per 100 parts by mass of the rubber component.

[0140] (Resin component) The rubber composition of this embodiment preferably further contains a resin component. In particular, the rubber composition of this embodiment preferably contains a resin component when it contains the liquid plasticizer described above. By including a resin component in the rubber composition, processability and productivity can be improved, and wet performance and ice performance when applied to tires can be enhanced. The above resin component may be used alone or in combination of two or more types.

[0141] The aforementioned resin component is preferably at least one selected from the group consisting of terpene resins and rosin resins. By using terpene resins and / or rosin resins, compatibility with the rubber component is improved, so that excellent wet performance and ice performance can be achieved even with a small amount. Furthermore, by using terpene resins and / or rosin resins, stickiness caused by the resin component can be suppressed, and productivity can be improved. Moreover, since terpene resins and rosin resins are naturally derived and sustainable resins, by incorporating terpene resins and / or rosin resins into the rubber composition, the sustainability rate of the studless tire to which the rubber composition is applied can be improved, and the environmental burden can be further reduced.

[0142] The aforementioned resin component may include other resin components besides the terpene-based resin and rosin-based resin described above. Examples of such other resin components include C ５ based resin, C ５ -C ９ based resin, C ９ Examples include resins such as cyclopentadiene resins, aromatic resins, coumarone resins, indene resins, coumarone-indene resins, olefin resins, polyurethane resins, and acrylic resins. These other resin components may be used individually or in combination of two or more.

[0143] The resin component may be hydrogenated, that is, it may be a hydrogenated resin. Furthermore, the resin component may have functional groups that interact with fillers such as carbon black and silica introduced through modification. Examples of such functional groups include amino groups, amide groups, isocyanate groups, imino groups, imidazole groups, urea groups, ammonium groups, imide groups, hydrazo groups, azo groups, diazo groups, carboxyl groups, nitrile groups, pyridyl groups, alkoxy groups, hydroxyl groups, oxy groups, epoxy groups, ether groups, carbonyl groups, oxycarbonyl groups, silyl groups, alkoxysilyl groups, mercapto groups, sulfide groups, disulfide groups, sulfonyl groups, sulfinyl groups, and thiocarbonyl groups.

[0144] The aforementioned terpene resins are solid resins obtained by polymerizing turpentine oil, which is obtained simultaneously when rosin is obtained from pine trees, or polymer components separated therefrom, using a Friedel-Crafts type catalyst. Examples include β-pinene resin and α-pinene resin. Terpene resins also include terpene-aromatic compound resins, and typical examples of such terpene-aromatic compound resins include terpene-phenol resin and styrene-terpene resin. Terpene-phenol resins can be obtained by reacting terpenes with various phenols using a Friedel-Crafts type catalyst, or by further condensation with formalin. Styrene-terpene resins can be obtained by reacting styrene with terpenes using a Friedel-Crafts type catalyst. There are no particular restrictions on the terpenes used as raw materials, but monoterpene hydrocarbons such as α-pinene and limonene are preferred, those containing α-pinene are more preferred, and α-pinene is particularly preferred.

[0145] Examples of rosin-based resins include natural resin rosin, modified rosin (including rosin derivatives and modified rosin derivatives), etc. Examples of natural resin rosin include gum rosin contained in raw pine resin and tall oil, tall oil rosin, and wood rosin. Examples of modified rosin include polymerized rosin and its partially hydrogenated rosin; glycerin ester rosin, its partially hydrogenated rosin and fully hydrogenated rosin; pentaerythritol ester rosin, its partially hydrogenated rosin and polymerized rosin; etc. Furthermore, from the viewpoint of further improving the wet performance, ice performance, and productivity of the rubber composition, it is preferable that the resin component includes at least a rosin-based resin.

[0146] Said C ５ C resins are C ５ This refers to the resin obtained by polymerizing the fraction. ５The fraction typically includes olefinic hydrocarbons such as 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene, and diolefinic hydrocarbons such as 2-methyl-1,3-butadiene, 1,2-pentadiene, 1,3-pentadiene, and 3-methyl-1,2-butadiene. ５ Examples of resins include aliphatic hydrocarbon resins and alicyclic hydrocarbon resins. Examples of aliphatic hydrocarbon resins include C ５ Examples include petroleum resins manufactured by polymerizing 1,3-pentadiene, a petroleum fraction of the C system, as the main raw material. For example, the "Quinton 100" series (A100, B170, K100, M100, R100, N295, U190, S100, D100, U185, P195N, etc.) manufactured by Nippon Zeon Corporation. ５ Examples of petroleum resins produced by polymerizing petroleum fractions include the "Escolets" series from ExxonMobile (1102, 1202(U), 1304, 1310, 1315, 1395, etc.) and the "Hi-Rets" series from Mitsui Chemicals, Inc. (G-100X, -T-100X, -C-110X, -R-100X, etc.). Examples of alicyclic hydrocarbon resins include C ５ Cyclopentadiene-based petroleum resin, C, manufactured using cyclopentadiene extracted from the fraction as the main raw material. ５ Examples include dicyclopentadiene-based petroleum resins manufactured using dicyclopentadiene in the fraction as the main raw material. Examples of the above-mentioned dicyclopentadiene-based petroleum resins include the "Quinton 1000" series (1325, 1345, etc.) manufactured by Nippon Zeon Corporation. Examples of the above-mentioned dicyclopentadiene-based petroleum resins include the "Marcaretz M" series (M-890A, M-845A, M-990A, etc.) manufactured by Maruzen Petrochemical Co., Ltd.

[0147] The resin component preferably has a softening point of 30°C or higher, more preferably 60°C or higher, more preferably 80°C or higher, more preferably higher than 110°C, more preferably 116°C or higher, more preferably 120°C or higher, more preferably 123°C or higher, and even more preferably 127°C or higher. Furthermore, from the viewpoint of processability, the resin component preferably has a softening point of 160°C or lower, more preferably 150°C or lower, more preferably 145°C or lower, more preferably 141°C or lower, and even more preferably 136°C or lower. In this specification, the softening point of the resin component is the temperature at which the sphere drops when the softening point specified in JIS K 6220-1:2015 (ISO 28641:2010) is measured using a ring-type softening point measuring device.

[0148] The content of the resin component in the rubber composition is not particularly limited, but for example, it is preferably in the range of 5 to 100 parts by mass per 100 parts by mass of the rubber component. When the content of the resin component is 5 parts by mass or more per 100 parts by mass of the rubber component, the workability of the rubber composition is improved. Furthermore, when the content of the resin component is 100 parts by mass or less per 100 parts by mass of the rubber component, deterioration of the abrasion resistance and other properties of the rubber composition can be suppressed. From a similar viewpoint, the content of the resin component in the rubber composition is more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more, per 100 parts by mass of the rubber component. Also from a similar viewpoint, the content of the resin component in the rubber composition is more preferably 60 parts by mass or less, and even more preferably 50 parts by mass or less, per 100 parts by mass of the rubber component.

[0149] (Other Components) In addition to the components described above, the rubber composition of this embodiment may further contain various additives used in rubber products, particularly tires, such as antioxidants, zinc oxide, sulfur, vulcanization accelerators, waxes, stearic acid, organic peroxides, cellulose nanofibers, solid fine particles such as eggshells, rice husks, and walnut flour, and rubber powder obtained by crushing used rubber products. Furthermore, the rubber composition of this embodiment may further contain organic acids (monocarboxylic acids, dicarboxylic acids, tricarboxylic acids, etc.), composite fibers, and the like.

[0150] - Rubber composition of embodiment (A) - In one embodiment, the rubber composition may be a rubber composition containing a rubber component, a filler, and a resin component, wherein the rubber component contains natural rubber and butadiene rubber, the filler contains silica, and the resin component has a weight-average molecular weight of 200 g / mol or more and 3300 g / mol or less.

[0151] The rubber component in the above embodiment corresponds to the rubber component in embodiment (A) described above.

[0152] In the above embodiment, including silica in the filler can further improve the ice performance and wear resistance of the tire. The previously described information regarding silica can be applied.

[0153] In the above embodiment, the CTAB specific surface area of ​​the silica (cetyltrimethylammonium bromide adsorption specific surface area) is 70 m². ２ / g or more 250m ２ It can be less than or equal to / g. Note that the CTAB specific surface area refers to the value measured in accordance with ASTM D3765-92. However, the adsorption cross-section per molecule of cetyltrimethylammonium bromide on the silica surface is 0.35 nm. ２ The specific surface area (m²) is calculated from the amount of adsorption of CTAB. ２ Let the CTAB specific surface area be ( / g).

[0154] In the above embodiment, the silica content is preferably 5 to 100 parts by mass, more preferably 10 to 50 parts by mass, and even more preferably 10 to 45 parts by mass, per 100 parts by mass of the rubber component. If the silica content is 5 parts by mass or more per 100 parts by mass of the rubber component, the abrasion resistance and ice performance of the vulcanized rubber composition can be further improved, and if it is 100 parts by mass or less, deterioration of workability during mixing of the rubber composition and deterioration of the tire's fuel efficiency can be suppressed.

[0155] In the above embodiment, the filler is silica and carbon black, as well as the following general formula (1): nM・xSiO ｙ ・zH ２O ... (1) [wherein M is at least one selected from the group consisting of aluminum, magnesium, titanium, calcium, and zirconium, oxides or hydroxides of these metals, hydrates thereof, or carbonates of these metals; n, x, y, and z are integers from 1 to 5, integers from 0 to 10, integers from 2 to 5, and integers from 0 to 10, respectively] may include an inorganic compound represented by this formula.

[0156] Examples of inorganic compounds represented by the general formula (1) include alumina (Al) such as γ-alumina and α-alumina. ２ O ３ Alumina monohydrate (Al) such as boehmite and diaspore. ２ O ３ ・H ２ O), aluminum hydroxide [Al(OH) ] such as gibbsite and bayerite ３ ], aluminum carbonate [Al ２ (CO ３ ) ３ ], magnesium hydroxide [Mg(OH) ２ ], magnesium oxide (MgO), magnesium carbonate (MgCO2) ３ ), talc (3MgO・4SiO ２ ・H ２ O), attapulgite (5MgO・8SiO ２ 9H ２ O), Titanium White (TiO ２ ), Titanium Black (TiO ２ｎ－１ ), calcium oxide (CaO), calcium hydroxide [Ca(OH) ２ ], magnesium aluminum oxide (MgO・Al ２ O ３ ), clay (Al ２ O ３ ・2SiO ２ ), kaolin (Al ２ O ３ ・2SiO ２ ・2H ２ O), pyrophyllite (Al ２ O ３ 4SiO ２ ・H ２ O), Bentonite (Al ２ O ３4SiO ２ ・2H ２ O), aluminum silicate (Al ２ SiO ５ Al ４ 3SiO ４ ・5H ２ O, etc.), magnesium silicate (Mg ２ SiO ４ MgSiO ３ (etc.), calcium silicate (Ca ２ SiO ４ (e.g.), aluminum calcium silicate (Al ２ O ３ CaO・2SiO ２ (etc.), magnesium calcium silicate (CaMgSiO) ４ ), calcium carbonate (CaCO3) ３ ), zirconium oxide (ZrO ２ ), zirconium hydroxide [ZrO(OH) ２ nH ２ O], Zirconium carbonate [Zr(CO) ３ ) ２ Examples include crystalline aluminosilicates containing hydrogen, alkali metals, or alkaline earth metals to correct the charge, such as various zeolites.

[0157] The average particle size of the inorganic compound represented by the general formula (1) is preferably 0.01 to 10 μm, and more preferably 0.05 to 5 μm, from the viewpoint of balancing wear resistance and ice performance.

[0158] In the above embodiment, the filler content is preferably 60 to 100 parts by mass, and more preferably 60 to 80 parts by mass, per 100 parts by mass of rubber component. When the filler content per 100 parts by mass of rubber component is 60 parts by mass or more, the wear resistance of the tire is further improved, and the durability of the tire is also further improved. Furthermore, when the filler content per 100 parts by mass of rubber component is 100 parts by mass or less, the workability in kneading the rubber composition is further improved.

[0159] In the above embodiment, the proportion of silica in the filler is preferably 20% by mass or more and 70% by mass or less. If the proportion of silica in the filler is 20% by mass or more, the ice performance can be further improved. Also, if the proportion of silica in the filler is 70% by mass or less, the wear resistance can be further improved. From a similar viewpoint, the proportion of silica in the filler is more preferably 30% by mass or more, even more preferably 40% by mass or more, and even more preferably 60% by mass or less.

[0160] In the above embodiment, by using a resin component with a weight-average molecular weight of 200 g / mol or more and 3300 g / mol or less, the rubber composition has low adhesion and does not adhere easily to manufacturing equipment, resulting in excellent workability during manufacturing. Furthermore, by applying a rubber composition with low adhesion to studless tires, durability can be improved. In addition, by using a resin component with a weight-average molecular weight of 200 g / mol or more and 3300 g / mol or less, the ice performance of the tire can be further improved.

[0161] If the weight-average molecular weight of the resin component is 200 g / mol or more, the resin component is less likely to precipitate from the tire, and the effects of the resin component can be fully expressed. Furthermore, if the weight-average molecular weight of the resin component is 3300 g / mol or less, the adhesion to the rubber composition can be reduced, and the resin component is more compatible with the rubber component.

[0162] The weight-average molecular weight of the resin component is preferably 500 g / mol or more, more preferably 550 g / mol or more, more preferably 600 g / mol or more, more preferably 650 g / mol or more, and even more preferably 700 g / mol or more, from the viewpoint of suppressing the precipitation of the resin component from the tire and more sufficiently suppressing the deterioration of the tire's appearance. Furthermore, the weight-average molecular weight of the resin component is preferably 3200 g / mol or less, more preferably 3100 g / mol or less, even more preferably 3000 g / mol or less, even more preferably 2900 g / mol or less, even more preferably 2800 g / mol or less, even more preferably 2700 g / mol or less, even more preferably 2600 g / mol or less, particularly preferably 2500 g / mol or less, and most preferably 2400 g / mol or less, from the viewpoint of improving compatibility with the rubber component and further enhancing the effect of the resin component.

[0163] Regarding other resin components, the previously described information can be used as a reference.

[0164] - Rubber composition of embodiment (B) - In one embodiment, the rubber composition comprises a rubber component, a filler, and C ５ A rubber composition containing a resin, wherein the proportion of natural rubber in the rubber component is 35% by mass or more, the proportion of butadiene rubber in the rubber component is 65% by mass or less, the content of the filler is 55 parts by mass or more per 100 parts by mass of the rubber component, the proportion of carbon black in the filler is 70% by mass or more, and the proportion of silica in the filler is 0% by mass or more and 20% by mass or less.

[0165] The rubber component in the above embodiment corresponds to the rubber component in embodiment (B) described above.

[0166] In the above aspect, by having the content of the filler be 55 parts by mass or more with respect to 100 parts by mass of the rubber component, the wear resistance performance as the tread portion of the tire can be improved. From the same viewpoint, the content of the filler with respect to 100 parts by mass of the rubber component is more preferably 65 parts by mass or more, still more preferably 75 parts by mass or more, and even more preferably 80 parts by mass or more. On the other hand, the upper limit of the content of the filler with respect to 100 parts by mass of the rubber component is not particularly limited, but from the viewpoint of low rolling resistance, it is preferably 120 parts by mass or less, more preferably 110 parts by mass or less, and still more preferably 100 parts by mass or less.

[0167] In the above aspect, by having the proportion of carbon black in the filler be 70% by mass or more, the wear resistance performance as the tread portion of the tire can be improved. From the same viewpoint, the proportion of carbon black in the filler is more preferably 75% by mass or more, still more preferably 80% by mass or more, and may also be 100% by mass (that is, the filler consists only of carbon black).

[0168] In the above aspect, the proportion of silica in the filler is more preferably 5% by mass or more, still more preferably 10% by mass or more, from the viewpoint of effectively suppressing the decrease in wear resistance performance accompanying the addition of the resin component.

[0169] In the above aspect, C [[ID=L10]]<ID= ５ The content of the C ５ series resin is preferably 5 parts by mass or more and 18 parts by mass or less with respect to 100 parts by mass of the rubber component. If the content of the C ５ series resin is 5 parts by mass or more, a further improvement effect on the ice grip performance and wet grip performance can be obtained, and if it is 18 parts by mass or less, the adhesion of the rubber composition can be suppressed within a range that does not cause problems in workability. From the same viewpoint, the content of the above C

[0170] series resin with respect to 100 parts by mass of the rubber component is more preferably 8 parts by mass or more, and still more preferably 12 parts by mass or more. ５ The C <ID= ５ series resin is preferably a hydrogenated C ５Because the resin system has higher compatibility with rubber components, it can further improve ice grip performance and wet grip performance, and it is not hydrogenated C ５ Compared to conventional resins, it can improve manufacturing efficiency.

[0171] In the above embodiment, the rubber composition further contains a liquid plasticizer, preferably in an amount of 5 parts by mass or more and 16 parts by mass or less per 100 parts by mass of the rubber component. If the liquid plasticizer content is 5 parts by mass or more, the effect of improving ice grip performance and wet grip performance is greatly enhanced. On the other hand, if it is 16 parts by mass or less, the viscosity of the rubber composition that has decreased due to the addition of the resin component can be adjusted (improved), and the workability of manufacturing the rubber composition and the vulcanized rubber composition is improved.

[0172] -Rubber composition of embodiment (C)- In one embodiment, the rubber composition may contain a rubber component and a filler, wherein the rubber component contains a modified conjugated diene polymer having a (meth)acrylic acid ester in its molecule, the filler contains silica, the silica content is 30 to 70 parts by mass per 100 parts by mass of the rubber component, and the proportion of silica in the filler is 55% by mass or more.

[0173] The rubber component in the above embodiment corresponds to the rubber component in embodiment (C) described above.

[0174] In the above embodiment, if the silica content per 100 parts by mass of rubber component is 30 parts by mass or more, the contact area with the road surface when the vulcanized rubber composition is applied to the tire will increase, and the ice performance can be further improved. Also, if the silica content per 100 parts by mass of rubber component is 70 parts by mass or less, deterioration of the processability and abrasion resistance of the rubber composition can be suppressed. From a similar viewpoint, the silica content per 100 parts by mass of rubber component is more preferably 35 parts by mass or more, even more preferably 40 parts by mass or more, even more preferably 65 parts by mass or less, and even more preferably 60 parts by mass or less.

[0175] In the above embodiment, if the proportion of silica in the filler is 55% by mass or more, the contact area with the road surface when the vulcanized rubber composition is applied to the tire will increase, and the ice performance can be further improved. On the other hand, there is no particular upper limit to the proportion of silica in the filler, but from the viewpoint of suppressing deterioration of the processability and wear resistance of the rubber composition, it is preferable that it be 80% by mass or less. From a similar viewpoint, the proportion of silica in the filler is more preferably 60% by mass or more, and more preferably 75% by mass or less.

[0176] In the above embodiment, it is preferable that the rubber composition contains a fatty acid amide. Fatty acid amides can promote the imparting of hydrophilicity to the rubber surface and increase viscous resistance, thereby further improving the ice performance of the vulcanized rubber composition.

[0177] Examples of fatty acid amides include caproic acid amide, lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, oleic acid amide, erucic acid amide, methylenebisstearate amide, ethylenebisstearate amide, and ethylenebisoleic acid amide. Furthermore, from the viewpoint of achieving superior ice performance, the fatty acid amide is preferably a fatty acid bis-amide, and more preferably an ethylenebis-fatty acid amide.

[0178] The amount of fatty acid amide is preferably 0.1 to 10 parts by mass per 100 parts by mass of the rubber component. If the amount of fatty acid amide is 0.1 parts by mass or more per 100 parts by mass of the rubber component, a sufficient improvement in ice performance can be obtained. Furthermore, if the amount of fatty acid amide is 10 parts by mass or less per 100 parts by mass of the rubber component, a decrease in the performance of the rubber composition, such as abrasion resistance and reinforcing properties, can be suppressed.

[0179] (Method for producing rubber composition and vulcanized rubber composition) The method for preparing the rubber composition of this embodiment is not particularly limited, and known methods can be used. For example, it can be obtained by mixing a predetermined rubber component, a filler such as carbon black, and other components using a mixer such as a Banbury mixer, roll mixer, or internal mixer. Alternatively, components other than the crosslinking accelerator and crosslinking agent may be mixed in a non-production (non-pro) stage, and the crosslinking accelerator and crosslinking agent may be added to the mixture and mixed in a production (pro) stage to prepare the rubber composition.

[0180] Furthermore, the vulcanized rubber composition of this embodiment can be obtained by vulcanizing the rubber composition described above. There are no particular restrictions on the apparatus, method, conditions, etc., for vulcanization, and they can be appropriately selected according to the purpose. Examples of vulcanization apparatus include molding vulcanizers that use molds for vulcanizing rubber compositions. As for the vulcanization conditions, the temperature is, for example, about 100 to 190°C.

[0181] <Studless Tire> A studless tire according to one embodiment of the present invention (hereinafter sometimes referred to as "the tire of this embodiment") uses the vulcanized rubber composition of this embodiment described above in the tread portion. In other words, the tire of this embodiment has a tread portion made of the vulcanized rubber composition of this embodiment described above. The tire of this embodiment is characterized in that the tread surface of the tread portion is divided into a plurality of blocks by a plurality of circumferential main grooves extending in the tire circumferential direction and a plurality of widthwise grooves extending in the tire width direction; a plurality of sipes and a plurality of shallow grooves are provided on the surface of the blocks so as to extend in opposite directions in the tire width direction with respect to one direction in the tire circumferential direction; the depth of the shallow grooves is smaller than the depth of the sipes; the inclination angle θ1 of the sipes with respect to the tire circumferential direction is greater than 0° and less than 90°; the inclination angle θ2 of the shallow grooves with respect to the tire circumferential direction is greater than 0° and less than 90°; and the magnitude of the difference between the inclination angle θ1 and the inclination angle θ2 is 30° or less.

[0182] The tire of this embodiment has a tread made of the vulcanized rubber composition of this embodiment. Compared to conventional methods using recycled carbon black, it contributes to improved sustainability while minimizing adverse effects on the rubber properties of the tire and maintaining performance. Furthermore, because the tread surface of the tire of this embodiment has the above-described configuration, it has excellent grip performance on ice as well as excellent wet grip performance. The configuration of the tread surface of the tire of this embodiment will be described in detail below.

[0183] Here, "tread" refers to the entire circumferential surface of the tire that comes into contact with the road surface when a pneumatic tire is mounted on the applicable rim, filled to the specified internal pressure, and subjected to the maximum load. "Circumferential main groove" and "widthwise groove" refer to grooves with a groove width (opening width) of 2 mm or more, and "sipe" refers to a sipe width that partially closes when in contact with the road, for example, a sipe width of 0.3 mm or more and 0.6 mm or less. Here, "groove width" and "sipe width" refer to the opening width when a pneumatic tire is mounted on the applicable rim, filled to the specified internal pressure, and unloaded. Furthermore, the "depth" of sipes and shallow grooves refers to the maximum depth when a pneumatic tire is mounted on the applicable rim, filled to the specified internal pressure, and unloaded. Furthermore, the "inclination angle" of sipes and shallow grooves refers to the inclination angle of a virtual line connecting the endpoints with respect to the tire's circumferential direction if the sipes or shallow grooves are not straight in a plan view. Furthermore, measurements for sipes and shallow grooves should be taken in the opposite direction to the tire circumferential direction relative to the tire width direction (see Figure 4).

[0184] Furthermore, "applicable rim" refers to an industrial standard valid in the region where the tire is produced and used, and is described or will be described in the future in publications such as the JATMA YEAR BOOK of JATMA (Japan Automobile Tire Manufacturers Association) in Japan, the STANDARDS MANUAL of ETRTO (The European Tyre and Rim Technical Organization) in Europe, and the YEAR BOOK of TRA (The Tire and Rim Association, Inc.) in the United States, as the standard rim for the applicable size (Measuring Rim in ETRTO's STANDARDS MANUAL, Design in TRA's YEAR BOOK) The term "rim" refers to the rim of the wheel (i.e., the "rim" of the wheel mentioned above includes not only current sizes but also sizes that may be included in the industry standards in the future. An example of a "size to be listed in the future" is the size listed as "FUTURE DEVELOPMENTS" in the ETRTO 2013 edition). However, if the size is not listed in the industry standards, it refers to the rim with a width corresponding to the tire bead width. Furthermore, "specified internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity of a single wheel in the applicable size and ply rating as described in JATMA, etc. For sizes not listed in the industry standards, "specified internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity specified for each vehicle on which the tire is mounted. Furthermore, "maximum load capacity" refers to the load corresponding to the maximum load capacity mentioned above.

[0185] Figure 4 is a schematic unfolded view showing the tread pattern of the tread portion of the tire of this embodiment. The internal structure of the tire is not particularly limited, but according to convention, the tire may include a pair of bead portions, a pair of sidewalls connected to the bead portions, and a tread portion connected to the sidewall portions. Furthermore, the tire may include a carcass that toroidally straddles the pair of bead portions, and a reinforcing layer such as a belt on the radially outer side of the crown portion of the carcass.

[0186] As shown in Figure 4, this tire has a plurality of circumferential main grooves 202 extending in the circumferential direction of the tire on the tread surface 201 of the tread portion, and a plurality of land portions 203 are demarcated between the circumferential main grooves 202, or between the circumferential main grooves 202 and the tread edge TE.

[0187] In the illustrated example, three circumferential main grooves 202 are formed. The circumferential main groove 202a is located in one half of the tire width direction with the tire equatorial plane CL as the boundary, the circumferential main groove 202b extends along the tire equatorial plane CL, and the circumferential main groove 202c is located in the other half of the tire width direction with the tire equatorial plane CL as the boundary. On the other hand, the number of circumferential main grooves 202 is not limited to three; there can be multiple grooves. In the illustrated example, all of the circumferential main grooves 202 extend straight in the tire circumferential direction, but they can also extend in a zigzag, bent, or curved manner. Also, in the illustrated example, the circumferential main grooves 202 extend in the tire circumferential direction (without inclination), but they can also extend with an inclination angle of 5° or less relative to the tire circumferential direction. The groove width (opening width) of the circumferential main grooves 202 can be, for example, 2 mm to 12 mm. The groove depth (maximum depth) of the circumferential main groove 202 can be, for example, 5 mm to 12 mm.

[0188] In the illustrated example, four land portions 203 are formed. Land portions 203a and 203b are located in one half of the tire width direction, with the tire equatorial plane CL as the boundary, while land portions 203c and 203d are located in the other half of the tire width direction, with the tire equatorial plane CL as the boundary. On the other hand, the number of land portions 203 corresponds to the number of circumferential main grooves 202, and there should be three or more. It is also possible that any of the land portions 203 are located on the tire equatorial plane CL.

[0189] Each land area 203 is provided with multiple widthwise grooves 204 extending in the tire width direction. In the illustrated example, the multiple widthwise grooves 204 are arranged at approximately equal intervals in the tire circumferential direction on each land area 203, thereby dividing the land area 203 into multiple (approximately identical) blocks 205.

[0190] In the illustrated example, the widthwise grooves 204 all extend straight, but they can also extend in a zigzag, bent, or curved manner. Furthermore, the widthwise grooves 204 can extend in the tire width direction, or they can extend at an inclination angle of 60° or less (or 45° or less, or 30° or less) with respect to the tire width direction. The groove width (opening width) of the widthwise grooves 204 can be, for example, 2 mm to 12 mm. The groove depth (maximum depth) of the widthwise grooves 204 can be, for example, 5 mm to 12 mm. In the illustrated example, the widthwise grooves 204 that demarcate the land area 203a and the widthwise grooves 204 that demarcate the land area 203b are located in a straight line, and the widthwise grooves 204 that demarcate the land area 203c and the widthwise grooves 204 that demarcate the land area 203d are also located in a straight line. With such a configuration, drainage performance can be further improved. On the other hand, the widthwise groove 204 that demarcates the land portion 203a and the widthwise groove 204 that demarcates the land portion 203b do not have to be located on a straight line (their virtual extensions may be offset from each other in the tire circumferential direction), and the widthwise groove 204 that demarcates the land portion 203c and the widthwise groove 204 that demarcates the land portion 203d do not have to be located on a straight line (their virtual extensions may be offset from each other in the tire circumferential direction). Also, in the illustrated example, the widthwise groove 204 located in one half of the tire width direction with respect to the tire equatorial plane CL as the boundary is inclined in the opposite direction to the tire circumferential direction with respect to the tire width direction, but they may be inclined in the same direction to the tire circumferential direction with respect to the tire width direction.

[0191] In this way, multiple blocks 205 are demarcated by multiple circumferential main grooves 202 extending in the circumferential direction of the tire and multiple widthwise grooves 204 extending in the width direction of the tire. In the illustrated example, the blocks 205 are approximately parallelogram-shaped in this plan view, but are not limited to this shape.

[0192] As shown in Figure 4, the surface of the block 205 is provided with a plurality of sipes 206 and a plurality of shallow grooves 207, extending in opposite directions in the tire width direction relative to one direction in the tire circumferential direction. Furthermore, the sipes 206 and shallow grooves 207 intersect with each other. Thus, in this embodiment, because the surface of the block 205 is provided with a plurality of sipes 206 and a plurality of shallow grooves 207, the sipes 206 and shallow grooves 207 can remove the water film, especially when the tire is new, thereby improving ice grip performance and wet grip performance.

[0193] In the illustrated example, four sipes 206 are arranged on each block 205. The number of sipes 206 can be any number, and is not limited to four. Also, in the illustrated example, the four sipes 206 are arranged at equal intervals in the circumferential direction of the tire so that the size of the block pieces partitioned by the sipes 206 is approximately the same. On the other hand, the sipes 206 do not necessarily have to be arranged at equal intervals in the circumferential direction of the tire. In the illustrated example, the sipes 206 are flat sipes that extend in a straight line when viewed from above, but they may also extend in a zigzag pattern. The sipes 206 can also be so-called three-dimensional sipes, in which the inner wall surface of the sipe has an uneven surface along the depth direction of the sipe. In this example, both ends of the sipes 206 open into the circumferential main groove 202, but one or both ends may terminate within the block 205.

[0194] In this embodiment, the inclination angle θ1 of the sipe 206 with respect to the tire circumferential direction is greater than 0° and less than 90°. If the inclination angle θ1 is 0°, the edge component in the tire width direction (edge ​​component in the tire circumferential direction) due to the sipe 206 will be reduced. Also, if the inclination angle θ1 is 90°, the edge component in the tire circumferential direction (edge ​​component in the tire width direction) due to the sipe 206 will be reduced.

[0195] In this embodiment, the sipe depth (maximum depth) of the sipe 206 is not particularly limited, but can be, for example, 5 to 8 mm.

[0196] In the illustrated example, 15 shallow grooves 207 are arranged in each block 205. The number of shallow grooves 207 can be any number and is not limited to 15. Also, in the illustrated example, the 15 shallow grooves 207 are arranged at equal intervals in the tire circumferential direction so that the size of the block pieces partitioned by the shallow grooves 207 is approximately the same. The pitch interval of the shallow grooves 207 in the tire circumferential direction can be, for example, 1.0 to 3.0 mm. On the other hand, the shallow grooves 207 do not necessarily have to be arranged at equal intervals in the tire circumferential direction. In the illustrated example, the shallow grooves 207 extend in a straight line in a plan view, but they may also extend in a zigzag pattern. In this example, both ends of the shallow grooves 207 open into the circumferential main grooves 202, but one or both ends may terminate within the block 205.

[0197] In this embodiment, the inclination angle θ2 of the shallow groove 207 with respect to the tire circumferential direction is greater than 0° and less than 90°. If the inclination angle θ2 is 0°, the edge component in the tire width direction (edge ​​component in the tire circumferential direction) due to the shallow groove 207 will be reduced. Also, if the inclination angle θ2 is 90°, the edge component in the tire circumferential direction (edge ​​component in the tire width direction) due to the shallow groove 207 will be reduced.

[0198] In this embodiment, the groove depth (maximum depth) of the shallow groove 207 is smaller than the depth (maximum depth) of the sipe 206. The groove depth (maximum depth) of the shallow groove 207 is not particularly limited, but can be, for example, 0.1 to 0.3 mm. Such shallow grooves 207 can be removed early, for example, by break-in driving.

[0199] Furthermore, in this embodiment, the magnitude of the difference between the inclination angle θ1 and the inclination angle θ2 is 30° or less (the absolute value of θ1 - θ2 is 30° or less). In this way, the sipes 206 and shallow grooves 207 are provided so as to extend in opposite directions in the tire width direction with respect to one direction in the tire circumferential direction, and the magnitude of the difference between the inclination angle θ1 and the inclination angle θ2 is 30° or less (including the case where it is 0). As a result, water flows uniformly through the sipes 206 and shallow grooves 207, making it less likely for water to overflow, thus improving drainage function and effectively improving ice grip performance and wet grip performance.

[0200] The inclination angle θ1 is preferably 45° or more, more preferably 60° or more, and even more preferably 75° or more. In this case, by increasing the edge component of the sipe 206 in the tire width direction (edge ​​component relative to the tire circumferential direction), the function of wiping water in the tire circumferential direction is improved, thereby further improving ice grip performance and wet grip performance. In this example, the sipe 206 has the same inclination angle relative to the tire circumferential direction as the width direction groove 204, but it can be made different.

[0201] The inclination angle θ2 is preferably 45° or more, more preferably 60° or more, and even more preferably 75° or more. In this case, the edge component of the shallow groove 207 in the tire width direction (edge ​​component relative to the tire circumferential direction) is increased, improving the function of wiping water in the tire circumferential direction, thereby further improving ice grip performance and wet grip performance.

[0202] Furthermore, the difference between the inclination angle θ1 and the inclination angle θ2 is preferably 15° or less, more preferably 10° or less, even more preferably 5° or less, and particularly preferably 0°. In this case, water can be made to flow uniformly through the sipes 206 and shallow grooves 207, further improving ice grip performance and wet grip performance. However, even when the difference between the inclination angle θ1 and the inclination angle θ2 is greater than 15° and 30° or less, it may still be preferable from the viewpoint of ensuring the rigidity of the land portion and improving ground contact by preventing any parts of the block piece partitioned by the sipes 206 and shallow grooves 207 from having too small an acute angle.

[0203] Furthermore, the groove width (opening width) of the shallow groove 207 is preferably 0.75 to 1.0 times the sipe width (opening width) of the sipe 206. In this way, when the widths of the sipe 206 and the shallow groove 207 are nearly equal within the above range, water flows more uniformly when the difference between the inclination angle θ1 and the inclination angle θ2 is within the above range, ice grip performance and wet grip performance can be further improved. The groove width (opening width) of the shallow groove 207 is not particularly limited, but can be, for example, 0.3 to 0.4 mm.

[0204] Next, we will explain the behavior of water on ice, focusing on the inclination angle of the sipes 206 and shallow grooves 207 with respect to the tire circumferential direction, in a tire in which sipes 206 and shallow grooves 207 are provided on the block 205. Figure 5A schematically shows the water flow when θ1 = 60° and θ2 = 15°. Figure 5B schematically shows the water flow when θ1 = θ2 = 60°. As schematically shown in Figures 5A and 5B, when the difference in inclination angle with respect to the tire circumferential direction between the sipes 206 and shallow grooves 207 is large (Figure 5A), as schematically shown by the difference in thickness of the arrows, more water flows to the side with the smaller inclination angle with respect to the tire circumferential direction (shallow grooves 207 in Figure 5A), resulting in an uneven flow and making water overflow more likely. In contrast, when the difference in inclination angle between the sipe 206 and the shallow groove 207 with respect to the tire circumferential direction is small (including when it is 0) (Figure 5B), water flows uniformly through the sipe 206 and the shallow groove 207, resulting in less water overflow and improved drainage function.

[0205] In this embodiment, the tire has multiple sipes 206 and multiple shallow grooves 207 on the surface of the block 205. Therefore, especially when new, the water film can be removed by both the sipes 206 and the shallow grooves 207, thereby improving ice grip performance. The sipes 206 and shallow grooves 207 are provided so as to extend in opposite directions in the tire width direction with respect to one direction in the tire circumferential direction, and the difference between the inclination angle θ1 and the inclination angle θ2 is 30° or less. As schematically explained in Figure 5B, water flows uniformly through the sipes 206 and shallow grooves 207, resulting in less water overflow, improved drainage function, and further improved ice grip performance.

[0206] Furthermore, the tire of this embodiment comprises a cap rubber located on the outermost surface of the tread portion and a base rubber located radially inward of the cap rubber, and the vulcanized rubber composition of this embodiment described above may be used for the cap rubber located on the outermost surface of the tread portion. In this case, the tread surface of the cap rubber can take the configuration described above (a configuration in which sipes and shallow grooves are provided in a predetermined manner).

[0207] In the case of a tire comprising the cap rubber and base rubber described above, the base rubber can be made, for example, using a rubber composition (rubber composition for base rubber) containing a rubber component and a filler.

[0208] In the above-mentioned base rubber composition, the rubber component preferably contains 50% by mass or more of natural rubber. Including natural rubber in the rubber component can increase the fracture strength of the tread rubber, and as a result, improve the durability of the tire. From a similar viewpoint, in the above-mentioned base rubber composition, the proportion of natural rubber in the rubber component is more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and may also be 100% by mass. When other rubber components are used in combination, the proportion of natural rubber in the rubber component is preferably 95% by mass or less, and more preferably 90% by mass or less.

[0209] The rubber component in the above-mentioned base rubber composition preferably further contains styrene-butadiene rubber (SBR) in addition to natural rubber. Including styrene-butadiene rubber together with natural rubber in the rubber component can improve the wet performance of the tire. The styrene-butadiene rubber (SBR) is not particularly limited, and examples include solution-polymerized styrene-butadiene rubber (S-SBR) and emulsion-polymerized styrene-butadiene rubber (E-SBR), among which emulsion-polymerized styrene-butadiene rubber (E-SBR) is preferred. Furthermore, the styrene-butadiene rubber may or may not be modified. In addition, the proportion of styrene-butadiene rubber in the rubber component is preferably 5% by mass or more. In this case, the wet performance of the tire can be further improved. Furthermore, the proportion of styrene-butadiene rubber in the rubber component is not particularly limited, but is preferably 50% by mass or less.

[0210] The rubber components in the above-mentioned base rubber composition may include, in addition to the natural rubber and styrene-butadiene rubber mentioned above, other rubber components such as synthetic isoprene rubber (IR) and butadiene rubber (BR). These other rubber components may or may not be modified. Furthermore, the proportion of other rubber components in the rubber component is preferably in the range of 0 to 30% by mass, and more preferably in the range of 0 to 15% by mass.

[0211] The above-mentioned base rubber composition may or may not further contain at least one of a resin component and a liquid plasticizer. The previously described information can be applied to the resin component and liquid plasticizer.

[0212] The above-mentioned base rubber composition preferably contains a total amount of the resin component and the liquid plasticizer of 30 parts by mass or less per 100 parts by mass of the rubber component. In this case, the fracture characteristics at high temperatures can be improved. From a similar viewpoint, the total amount of the resin component and the liquid plasticizer in the above-mentioned base rubber composition is preferably 28 parts by mass or less, more preferably 26 parts by mass or less, more preferably 24 parts by mass or less, even more preferably 22 parts by mass or less, or even 0 parts by mass, per 100 parts by mass of the rubber component.

[0213] The tire (studless tire) of this embodiment can be used, for example, as a tire for construction vehicles, trucks and buses, aircraft, and passenger cars, and is particularly preferred as a passenger car tire or a truck and bus tire. This is because the vulcanized rubber composition used as the material for the tread has excellent wet performance and wear resistance, which offers significant advantages when used as a passenger car tire or a truck and bus tire.

[0214] In this embodiment, the tire is preferably a pneumatic tire, and as the gas used to fill the pneumatic tire, in addition to ordinary air or air with adjusted oxygen partial pressure, inert gases such as nitrogen, argon, and helium can be used.

[0215] In manufacturing the tire of this embodiment, for example, an unvulcanized rubber composition may be used for molding, and then vulcanized to obtain the tire. Alternatively, a pre-vulcanized rubber composition may be used to obtain semi-vulcanized rubber, and then the semi-vulcanized rubber may be used for molding, and then fully vulcanized to obtain the tire.

[0216] The present invention will be described in more detail below with reference to examples, but these examples are for illustrative purposes only and do not limit the present invention in any way.

[0217] <Evaluation 1> Two types of rubber compositions having the compound compositions shown in Table 1 were prepared, and these rubber compositions were vulcanized at 145°C for 33 minutes to obtain vulcanized rubber test pieces.

[0218] (Sustainable material ratio) For each of the prepared rubber compositions, the sustainable material ratio was evaluated by calculating the total mass ratio of components derived from biomass resources (bioresources) and components derived from recycled resources (recycled resources). The results are shown in Table 1.

[0219] (Tensile strength (crack resistance)) The obtained vulcanized rubber test pieces were punched out into JIS No. 3 dumbbells, and the obtained samples were subjected to a tensile test in accordance with JIS K 6251:2004 at room temperature, and the tensile strength (TB) before heat deterioration (initial) and after heat deterioration (100 °C × 24 hours) was measured. The results are shown in Table 1. The larger the numerical value, the better the fracture resistance, that is, the crack resistance.

[0220]

[0221] *1 Butadiene rubber: manufactured by UBE Elastomer Co., Ltd., trade name "BR150L" *2 Virgin carbon black: manufactured by Asahi Carbon Co., Ltd., trade name "N550", nitrogen adsorption specific surface area (N ２ SA) = 40 m ２ / g, OAN oil absorption = 121 mL / 100 g *3 Recycled carbon black: manufactured by Enrestec Co., Ltd., trade name "PB365", ash content = 17% by mass *4 Antioxidant A: manufactured by Ouchi Shinsei Chemical Industry Co., Ltd., trade name "Nocrack 6C" *5 Antioxidant B: manufactured by Ouchi Shinsei Chemical Industry Co., Ltd., trade name "Nocrack 224" *6 Oil: manufactured by ENEOS Co., Ltd., trade name "A / Omix" *7 Fatty acid: manufactured by Miyoshi Oil & Fat Co., Ltd., trade name "MXST" *8 Other chemicals: total amount of sulfur, vulcanization accelerator, resin, and wax, at the same ratio in each rubber composition

[0222] From Table 1, it can be seen that replacing carbon black (virgin carbon black) with recycled carbon black among various materials contained in the rubber composition contributes to improving sustainability, while the tensile strength before and after heat deterioration decreases, that is, the crack resistance deteriorates.

[0223] <Evaluation 2> As test carbon blacks, recycled carbon black 1 and recycled carbon black 2 were prepared.

[0224] Next, 3.75 g of zinc oxide, 0.20 g of the carbon black under test, and 2.00 mL of epoxidized soybean oil were mixed to obtain a mixture. The obtained mixture was kneaded for 5 to 10 minutes to form a paste, and the sample paste was prepared. In accordance with JIS K5101-1-5, the paste was prepared using a Toyo Seiki Huber Mahler (model: H3) under conditions of a load of 0.4536 kN and a glass plate rotation speed of 100 r / min. In accordance with JIS K5400, each sample paste was placed on a grind gauge and stretched with a scraper. The grind gauge used had a range of 0 to 25 μm. It was confirmed that three or more continuous lines of 10 mm or more appeared, and the scale reading at the location where the line caused by the third largest particle among the particles that produced the continuous lines of 10 mm or more appeared was read, and this reading was taken as the particle size of the third largest particle. The same procedure was performed a total of four times, and the average particle size of the third largest particle from the four measurements was calculated. The results are shown in Table 2.

[0225] Furthermore, regarding the carbon black used in the test, the nitrogen adsorption specific surface area (N) was calculated according to ASTM D6556. ２ SA was measured. The results are shown in Table 2.

[0226] Furthermore, the Zn, Fe, and Cu content of the tested carbon black was measured by X-ray fluorescence analysis (XRF). The results are shown in Table 2.

[0227] Furthermore, the ash content of the tested carbon black was measured according to ASTM D8474 and D1506. The results are shown in Table 2.

[0228]

[0229] (Preparation of Rubber Compositions) Using recycled carbon black 1 or recycled carbon black 2 as described above, rubber compositions were prepared according to the formulations shown in Table 3. Other chemicals included antioxidants, oils, fatty acids, sulfur, and vulcanization accelerators, and the same types and amounts were added in the reference comparative example and reference example. Commercially available chemicals commonly used in the preparation of rubber compositions were used. The amounts added were also the amounts commonly used in the preparation of rubber compositions. For each rubber composition prepared, the sustainable material ratio was evaluated by calculating the total mass ratio of components derived from biological resources (biomass resources) and components derived from recycled resources (recycled resources). The results are shown in Table 3.

[0230] (High-temperature tensile strength after degradation) Each rubber composition was vulcanized at 145°C for 33 minutes to obtain vulcanized rubber. The obtained vulcanized rubber was subjected to thermal degradation at 100°C for 48 hours in an air atmosphere. A tensile test was performed at 100°C in accordance with JIS K6251:2017, and the tensile strength was measured. The high-temperature tensile strength (fracture resistance) after degradation was expressed as an index using the following formula, with the tensile strength of the test piece of Reference Example 1 set to 100. The results are shown in Table 3. High-temperature tensile strength index after degradation = (Tensile strength of the test piece / Tensile strength of the test piece of Reference Example 1) × 100 A higher high-temperature tensile strength index after degradation indicates that the vulcanized rubber is less prone to fracture and has superior post-degradation performance (fracture resistance).

[0231] (Crack resistance after thermal degradation) The rubber composition to be tested was pre-treated by thermal degradation at 100°C for 24 hours in an air atmosphere. A strip-shaped test piece was prepared from the rubber composition with a 0.5 mm hole drilled in the lengthwise direction in the center. Using this test piece, a dc / dn test (using Shimadzu Corporation's "ServoPulsa") was performed, applying repeated fatigue at a frequency of 5 Hz and 80°C with a strain of 30-100%, and the tear energy [J / m] after 1950 cycles was measured. ２ The crack propagation rate was calculated when the common logarithm of [ ] was 3.9. The crack propagation rate obtained by the above process was normalized by the reciprocal of the formulation data for each example, using the formulation data of Reference Example 1 as a control (index value 100). The results are shown in Table 3. A larger index value indicates a lower crack propagation rate and superior crack resistance after thermal degradation.

[0232]

[0233] *11 Natural rubber: RSS#3 *12 Butadiene rubber: Manufactured by UBE Elastomers, product name "BR150L" *13 Virgin carbon black: Manufactured by Asahi Carbon, N550

[0234] Tables 2 and 3 show that the reference example using recycled carbon black with a particle size of 20 μm or less for the third largest particle size exhibits better high-temperature tensile strength after degradation compared to the reference comparative example using recycled carbon black with a particle size of more than 20 μm for the third largest particle size. Furthermore, the reference example also showed better crack resistance after thermal degradation compared to the reference comparative example.

[0235] Based on these evaluations, it can be seen that by using recycled carbon black in which the third largest particle size measured with a grind gauge is 20 μm or less, it is possible to significantly suppress adverse effects on tire rubber properties and maintain performance while contributing to improved sustainability.

[0236] <Evaluation 3 (Relationship between Zn content in carbon black and rubber properties)> Carbon black (CB) and styrene-butadiene rubber with different ash, Zn, and sulfur content were kneaded according to the formulations shown in Table 4 to prepare rubber compositions for each example.

[0237] Furthermore, the Zn and S content of the carbon black used was measured by X-ray fluorescence analysis. The results are shown in Table 4.

[0238] Furthermore, the ash content of the carbon black used was measured by thermogravimetric analysis (TGA, RIGAKU Corporation) using the following procedure. The sample was heated from room temperature to 550°C under a nitrogen atmosphere, and then heated to maintain 550°C under an air atmosphere, and the loss on heating was measured. The loss on heating (mass%) when the sample was heated from room temperature to 550°C under a nitrogen atmosphere was defined as "Loss on heating 1," and the loss on heating (mass%) when heated to maintain 550°C under an air atmosphere was defined as "Loss on heating 2." The ash content was calculated using the following formula. The results are shown in Table 4. Ash content (mass%) = 100 - Loss on heating 1 - Loss on heating 2

[0239] For each example of rubber composition, vulcanized rubber was obtained by vulcanization at 145°C for 33 minutes. Tensile strength was measured for each vulcanized rubber by performing a tensile test at room temperature in accordance with JIS K6301-1995. The tensile strength of the test specimen of the standard rubber composition was set to 100, and the index was expressed using the following formula. The results are shown in Table 4. Tensile strength index = (Tensile strength of test specimen other than the standard rubber composition / Tensile strength of test specimen of the standard rubber composition) × 100 A larger index indicates that the vulcanized rubber is less prone to fracture and has superior tensile strength.

[0240] For each example of rubber composition, a viscoelasticity test was performed using TA Instruments' "ARES-G2" under the conditions of a frequency of 15 Hz, shear strain of 10%, and temperature of 50°C, and the storage modulus (G') was measured. The evaluation results were indexed with the standard rubber composition as the control (index value 100). The results (viscoelasticity) are shown in Table 4. A higher index indicates a higher G', and a better rubber property for application in products such as tires.

[0241]

[0242] *21 SBR: Styrene-butadiene rubber, product name "#1500" *22 CB1: Carbon black, recycled carbon black equivalent to N330 *23 CB2: Carbon black, recycled carbon black equivalent to N330 *24 CB3: Carbon black, recycled carbon black equivalent to N330 *25 CB5: Carbon black, virgin (new) carbon black equivalent to N330

[0243] Table 4 shows that when carbon black with reduced Zn content is applied to a rubber composition, the deterioration of the rubber composition's physical properties is suppressed.

[0244] According to the present invention, compared to conventional methods using recycled carbon black, it is possible to provide a vulcanized rubber composition for studless tires that contributes to improved sustainability while minimizing adverse effects on tire rubber properties and maintaining performance, and a studless tire using the vulcanized rubber composition in the tread portion.

[0245] 1: Grind gauge 2: Line less than 10 mm in length 3: Line 10 mm or longer 31: Line caused by the largest particle 32: Line caused by the second largest particle 33: Line caused by the third largest particle 4: Scale mark at the location where the line caused by the third largest particle appears 110: Vulcanized rubber composition for studless tires 120: Void 201: Tread 202: Main circumferential groove 203: Land area 204: Width direction groove 205: Block 206: Sipe 207: Shallow groove CL: Tire equatorial plane TE: Tread edge

Claims

1. A vulcanized rubber composition for studless tires, comprising a rubber component and a filler, obtained by vulcanizing a rubber composition, wherein the filler contains recycled carbon black, the recycled carbon black is such that when measured with a grind gauge, three or more lines with a length of 10 mm or more are observed, and the particle size of the third largest particle among the particles that produce the lines with a length of 10 mm or more is 20 μm or less, and the vulcanized rubber composition has a plurality of voids.

2. The vulcanized rubber composition for studless tires according to claim 1, wherein, in the measurement of the recycled carbon black using a grind gauge, a paste of the recycled carbon black is prepared as the measurement sample in accordance with JIS K5101-1-5.

3. The vulcanized rubber composition for studless tires according to claim 1, wherein, in the measurement of the recycled carbon black using a grind gauge, the applied load is set to 0.4 to 0.5 kN and the rotation speed of the glass plate is set to 90 to 110 r / min in accordance with JIS K5101-1-5, and the paste of the recycled carbon black is prepared as the measurement sample.

4. The vulcanized rubber composition for studless tires according to claim 1, wherein the rubber composition further contains a void-introducing agent.

5. The vulcanized rubber composition for studless tires according to claim 1, wherein the rubber composition contains a foaming agent as a void-introducing agent and a foaming aid.

6. The vulcanized rubber composition for studless tires according to claim 1, wherein the rubber composition further contains a resin component and a liquid plasticizer, the resin component is at least one selected from the group consisting of terpene resins and rosin resins, the content of the resin component in the rubber composition is 15 parts by mass or more per 100 parts by mass of the rubber component, and the content of the liquid plasticizer in the rubber composition is 30 parts by mass or less per 100 parts by mass of the rubber component.

7. A studless tire using the vulcanized rubber composition for studless tires described in claim 1 in the tread portion, wherein the tread surface of the tread portion is divided into a plurality of blocks by a plurality of circumferential main grooves extending in the tire circumferential direction and a plurality of widthwise grooves extending in the tire width direction, a plurality of sipes and a plurality of shallow grooves are provided on the surface of the blocks so as to extend in opposite directions in the tire width direction with respect to one direction in the tire circumferential direction, the depth of the shallow grooves is less than the depth of the sipes, the inclination angle θ1 of the sipes with respect to the tire circumferential direction is greater than 0° and less than 90°, the inclination angle θ2 of the shallow grooves with respect to the tire circumferential direction is greater than 0° and less than 90°, and the magnitude of the difference between the inclination angle θ1 and the inclination angle θ2 is 30° or less.

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