tire

Abstract

To provide a tire excellent in operation stability after degradation.SOLUTION: Provided is a tire including a tire member formed of a rubber composition. The rubber composition has a rate of change ΔEB of elongation at the time of breaking before and after heat aging of 8.0% or less. A product (ΔEB×Tt) of the ΔEB(%) and a thickness Tt(mm) of the tire member is less than 30.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] Recently, for tires, from the viewpoints such as consideration for the environment, long-term maintenance of various performances has been desired.

Summary of the Invention

Problems to be Solved by the Invention

[0003] Among them, from the viewpoint of safety, in particular, it is required to maintain the handling stability for a long period of time.

[0004] An object of the present invention is to solve the above problems and provide a tire excellent in handling stability after deterioration.

Means for Solving the Problems

[0005] The present invention is a tire including a tire member composed of a rubber composition, wherein the rubber composition has a change rate ΔEB of elongation at break before and after heat aging of 8.0% or less, and relates to a tire in which the product (ΔEB × Tt) of the ΔEB (%) and the thickness Tt (mm) of the tire member is less than 30.

Effects of the Invention

[0006] The present invention is a tire including a tire member composed of a rubber composition, wherein the rubber composition has a change rate ΔEB of elongation at break before and after heat aging of 8.0% or less, and the product (ΔEB × Tt) of the ΔEB (%) and the thickness Tt (mm) of the tire member is less than 30. Therefore, a tire excellent in handling stability after deterioration can be provided.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Mode for Carrying Out the Invention

[0008] The tire includes a tire member made of a rubber composition. The rubber composition has a change rate ΔEB of elongation at break before and after heat aging of 8.0% or less, and the product (ΔEB×Tt) of the ΔEB (%) and the thickness Tt (mm) of the tire member is less than 30.

[0009] The reason why the above-described effects are obtained by the tire is not necessarily clear, but it is presumed as follows. By suppressing the decrease in elongation at break after deterioration and setting the change rate ΔEB of elongation at break before and after heat aging to 8.0% or less, it is possible to suppress the decrease in handling stability due to rubber deterioration. In addition, by adjusting the product (ΔEB×Tt) of the change rate of elongation at break before and after heat aging and the thickness of the tire member to less than 30, the absolute amount of change in rubber elongation due to deterioration can be suppressed, and the decrease in handling stability can be suppressed. It is presumed that by such an action, the decrease in handling stability is synergistically suppressed, and the handling stability after deterioration can be improved.

[0010] Thus, the tire solves the problem (objective) of improving the handling stability after deterioration by having a configuration that satisfies the relationships of "ΔEB is 8.0% or less" and "ΔEB×Tt is less than 30". That is, the parameters of "ΔEB is 8.0% or less" and "ΔEB×Tt is less than 30" do not define the problem (objective). The problem of the present application is to improve the handling stability after deterioration, and for that purpose, the configuration is such that the parameters are satisfied.

[0011] The tire has a tire member made of a rubber composition.

[0012] The rubber composition (vulcanized rubber composition) has a change rate ΔEB of elongation at break before and after heat aging of 8.0% or less. ΔEB is preferably 7.0% or less, more preferably 6.4% or less, still more preferably 5.8% or less, and particularly preferably 5.2% or less. The smaller ΔEB is, the more desirable it is, that is, it is preferably 0.0%, and the lower limit is not particularly limited.

[0013] The elongation at break EBf before heat aging of the above rubber composition (vulcanized rubber composition) is preferably 400% or more, more preferably 500% or more, still more preferably 540% or more, and particularly preferably 581% or more. The upper limit is preferably 730% or less, more preferably 650% or less, still more preferably 623% or less, and particularly preferably 611% or less. When within the above range, the effect tends to be preferably obtained.

[0014] In this specification, the elongation at break before and after heat aging is a value measured according to JIS K6251. The change rate of elongation at break ΔEB (%) is a value calculated by the following formula using the elongation at break EBf (%) of the sample before heat aging and the elongation at break EBa (%) of the sample after heat aging at -80°C for 168 hours. ΔEB (%) = (|EBf - EBa|) / EBf × 100

[0015] The above rubber composition contains a rubber component. Here, the rubber component is a component that contributes to crosslinking. Generally, a polymer with a weight average molecular weight (Mw) of 10,000 or more and a polymer component that is not extracted by acetone corresponds to the rubber component. The rubber component is in a solid state at normal temperature (25°C).

[0016] The weight average molecular weight of the rubber component is preferably 50,000 or more, more preferably 150,000 or more, still more preferably 200,000 or more, and particularly preferably 270,000 or more. Also, it is preferably 2,000,000 or less, more preferably 1,500,000 or less, still more preferably 1,000,000 or less. When within the above range, the effect tends to be obtained more favorably.

[0017] In this specification, the weight average molecular weight (Mw) can be determined by standard polystyrene conversion based on the measured values obtained by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation). In the case of a polymer having a modifying group, since the modifying group and the silica gel of the column interact with each other and an accurate Mw cannot be obtained, Mw is measured before the modification treatment is carried out.

[0018] The rubber component that can be used in the above rubber composition may be an unmodified rubber or a modified rubber. Examples of the modified rubber include rubbers having a functional group that interacts with a filler such as silica. For example, a terminal-modified rubber (terminal-modified rubber having the above functional group at the terminal) in which at least one terminal of the rubber is modified with a compound (modifying agent) having the above functional group, a main-chain modified rubber having the above functional group in the main chain, a main-chain terminal-modified rubber having the above functional group in the main chain and at the terminal (for example, a main-chain terminal-modified rubber having the above functional group in the main chain and at least one terminal modified with the above modifying agent), and a terminal-modified rubber modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and having a hydroxyl group or an epoxy group introduced therein.

[0019] Examples of the above functional group include an amino group, an amide group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an imide group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group, an epoxy group, etc. These functional groups may have a substituent. Among them, an amino group (preferably an amino group in which the hydrogen atom of the amino group is substituted with an alkyl group having 1 to 6 carbon atoms), an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms), and an alkoxysilyl group (preferably an alkoxysilyl group having 1 to 6 carbon atoms) are preferable.

[0020] Examples of the rubber component include diene rubbers.

[0021] Examples of the diene rubber include isoprene rubber, butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene-butadiene rubber (SIBR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), etc. Examples of the rubber component also include butyl rubber, fluororubber, etc. These may be used alone or in combination of two or more. Further, these rubber components may be subjected to modification treatment or hydrogenation treatment, and extended rubber stretched by oil, resin, liquid rubber component, etc. may also be used. Among the above diene rubbers, from the viewpoint of obtaining more effects, it is desirable to contain at least one of isoprene rubber, BR, and SBR.

[0022] When it is isoprene rubber, BR, or SBR, the mechanism by which more effects are obtained is not clear, but by including these diene rubbers, rubber reinforcement by crosslinking can be realized, and a certain level of handling stability can be ensured. Therefore, it is presumed that the handling stability after deterioration is improved.

[0023] Examples of the isoprene rubber include natural rubber (NR), isoprene rubber (IR), modified NR, denatured NR, denatured IR, etc. As NR, for example, those commonly used in the rubber industry such as SIR20, RSS#3, TSR20, etc. can be used. IR is not particularly limited, and for example, those commonly used in the rubber industry such as IR2200, etc. can be used. Examples of the modified NR include deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), etc., examples of the denatured NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc., and examples of the denatured IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, etc. These may be used alone or in combination of two or more.

[0024] BR is not particularly limited. For example, high-cis BR with a high cis content, BR containing syndiotactic polybutadiene crystals, BR synthesized using a rare earth catalyst (rare earth BR), etc. can be used. These may be used alone or in combination of two or more. Among them, BR preferably contains high-cis BR with a cis content of 90% by mass or more. The cis content is more preferably 95% by mass or more. The cis content can be measured by infrared absorption spectroscopy analysis.

[0025] When there is one type of BR, the cis amount of BR means the cis amount of that BR. When there are multiple types, it means the average cis amount. The average cis amount of BR can be calculated by {Σ(content of each BR × cis amount of each BR)} / total content of all BR. For example, when in 100% by mass of the rubber component, BR with a cis amount of 90% by mass is 20% by mass and BR with a cis amount of 40% by mass is 10% by mass, the average cis amount of BR is 73.3% by mass (=(20×90 + 10×40) / (20 + 10)).

[0026] Also, either non-modified BR or modified BR can be used for BR. Examples of modified BR include modified BR into which a functional group similar to that of modified rubber is introduced. Also, hydrogenated butadiene polymer (hydrogenated BR) can be used for BR.

[0027] SBR is not particularly limited. For example, emulsion polymerization styrene-butadiene rubber (E-SBR), solution polymerization styrene-butadiene rubber (S-SBR), etc. can be used. These may be used alone or in combination of two or more.

[0028] The styrene content of SBR is preferably 5% by mass or more, more preferably 20% by mass or more, still more preferably 25% by mass or more. The styrene content is preferably 60% by mass or less, more preferably 40% by mass or less, still more preferably 35% by mass or less. When within the above range, the effect tends to be obtained more favorably. In this specification, the styrene content 1 can be measured by 1H-NMR measurement.

[0029] When there is one type of SBR, the styrene content of the SBR means the styrene content of that SBR. When there are multiple types, it means the average styrene content. The average styrene content of SBR can be calculated by {Σ(content of each SBR × styrene content of each SBR)} / total content of all SBRs. For example, in 100% by mass of the rubber component, when 85% by mass of SBR has a styrene content of 40% by mass and 5% by mass of SBR has a styrene content of 25% by mass, the average styrene content of SBR is 39.2% by mass (=(85×40 + 5×25) / (85 + 5)).

[0030] The vinyl bond content of SBR is preferably 3% by mass or more, more preferably 5% by mass or more, and still more preferably 7% by mass or more. When the vinyl bond content is within the range of preferably 50% by mass or less, more preferably 40% by mass or less, and still more preferably 30% by mass or less, the effect tends to be obtained more favorably. In addition, in this specification, the vinyl bond content (1,2 - bonded butadiene unit amount) can be measured by infrared absorption spectroscopy.

[0031] The vinyl amount (1,2 - bonded butadiene unit amount) of SBR is the ratio of vinyl bonds when the total mass of the butadiene part in SBR is taken as 100 (unit: % by mass), and vinyl amount [% by mass] + cis amount [% by mass] + trans amount [% by mass] = 100 [% by mass]. When there is one type of SBR, it means the vinyl amount of that SBR. When there are multiple types, it means the average vinyl amount. The average vinyl content of SBR can be calculated by Σ{content of each SBR × (100 [mass%] - styrene content of each SBR [mass%]) × vinyl content of each SBR [mass%]} / Σ{content of each SBR × (100 [mass%] - styrene content of each SBR [mass%])}. For example, in 100 parts by mass of the rubber component, if there are 75 parts by mass of SBR with a styrene content of 40 mass% and a vinyl content of 30 mass%, 15 parts by mass of SBR with a styrene content of 25 mass% and a vinyl content of 20 mass%, and the remaining 10 parts by mass are other than SBR, the average vinyl content of SBR is 28 mass% (={75×(100 [mass%]-40 [mass%])×30 [mass%]+15×(100 [mass%]-25 [mass%])×20 [mass%])} / {75×(100 [mass%]-40 [mass%])+15×(100 [mass%]-25 [mass%])}).

[0032] As the SBR, either non-modified SBR or modified SBR can be used. Examples of the modified SBR include those with functional groups similar to the modified rubber introduced. Also, as the SBR, hydrogenated styrene-butadiene copolymer (hydrogenated SBR) can be used.

[0033] As the above rubber component, for example, a polymer having ethylene units (structural units formed from ethylene: -CH2-CH2-) can also be preferably used. The polymer having the above ethylene units is a polymer having high molecular weight ethylene units, a component that is not extracted by an organic solvent such as acetone from the rubber composition after vulcanization, and is used as the rubber component. Note that it is desirable for the polymer having high molecular weight ethylene units to have the weight average molecular weight of the above rubber component.

[0034] The polymer having the above ethylene units is not particularly limited as long as it is a polymer having ethylene units, but from the viewpoint of obtaining good effects, a multi-component copolymer containing ethylene units, conjugated diene units, and aromatic vinyl units is desirable.

[0035] In the above multi-component copolymer, the conjugated diene units are structural units derived from conjugated diene compounds. Examples of the conjugated diene compound include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, 2-phenyl-1,3-butadiene, 1,3-hexadiene, and the like. These may be used alone or in combination of two or more. Among them, 1,3-butadiene and isoprene are preferred, and 1,3-butadiene is more preferred.

[0036] In the above-mentioned multi-component copolymer, the aromatic vinyl unit is a structural unit derived from an aromatic vinyl compound. Examples of the aromatic vinyl compound include styrene, α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene, 2,4,6-trimethylstyrene, and the like. These may be used alone or in combination of two or more. Among them, styrene and α-methylstyrene are preferred, and styrene is more preferred.

[0037] The above-mentioned multi-component copolymer can be prepared, for example, by copolymerizing ethylene, a conjugated diene compound, and an aromatic vinyl compound, or by copolymerizing a conjugated diene compound and an aromatic vinyl compound, or ethylene, a conjugated diene compound, and an aromatic vinyl compound, and then converting a part of the conjugated diene units into non-conjugated olefin units by hydrogenation. That is, the above-mentioned multi-component copolymer may be a copolymer of ethylene, a conjugated diene compound, and an aromatic vinyl compound, or a copolymer of a conjugated diene compound and an aromatic vinyl compound, or a hydrogenated product (hydrogenated copolymer) of a copolymer of ethylene, a conjugated diene compound, and an aromatic vinyl compound. These may be used alone or in combination of two or more. Among them, from the viewpoint of obtaining better effects, a hydrogenated product of a copolymer of a conjugated diene compound and an aromatic vinyl compound is preferred, and a hydrogenated styrene-butadiene copolymer is more preferred.

[0038] In preparing the above-mentioned multi-component copolymer, the polymerization method is not particularly limited, and random polymerization or block polymerization may be used, but random polymerization is preferred.

[0039] When the above-mentioned copolymer is a hydrogenated copolymer, there are no particular limitations on the hydrogenation method and reaction conditions, and hydrogenation may be carried out by known methods and under known conditions. Usually, it is carried out at 20 to 150 °C under a hydrogen pressure of 0.1 to 10 MPa in the presence of a hydrogenation catalyst. Other methods and conditions related to production are not particularly limited either. For example, the content described in International Publication No. 2016 / 039005 can be applied.

[0040] In the above rubber composition, the content of the isoprene-based rubber in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 30% by mass or more, still more preferably 40% by mass or more, and is preferably 80% by mass or less, more preferably 60% by mass or less, still more preferably 50% by mass or less. When it is within the above range, the effect tends to be preferably obtained.

[0041] In the above rubber composition, the content of BR in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 30% by mass or more, still more preferably 40% by mass or more, and is preferably 80% by mass or less, more preferably 60% by mass or less, still more preferably 50% by mass or less. When it is within the above range, the effect tends to be preferably obtained.

[0042] In the above rubber composition, the content of SBR in 100% by mass of the rubber component is preferably less than 80% by mass, more preferably 50% by mass or less, still more preferably 20% by mass or less. Also, it is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more. When it is within the above range, the effect tends to be preferably obtained. Note that the content of SBR includes the content of hydrogenated SBR.

[0043] When the content of SBR is less than 80% by mass, the mechanism by which more effects are obtained is not clear, but by setting the content of SBR to a predetermined level or less, the heat generation of the rubber can be suppressed, and the progress of deterioration due to heat can be suppressed. Therefore, it is presumed that the handling stability after deterioration is improved.

[0044] In the above rubber composition, the content of the polymer having the ethylene unit in 100% by mass of the rubber component is preferably less than 80% by mass, more preferably 50% by mass or less, and still more preferably 20% by mass or less. Also, it is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 15% by mass or more. When it is within the above range, the effect tends to be preferably obtained. In addition, the content of the hydrogenated product of the copolymer of the conjugated diene compound and the aromatic vinyl compound and the content of the hydrogenated styrene-butadiene copolymer are preferably in the same range.

[0045] The raw materials (monomers) of synthetic rubbers such as SBR and BR may be derived from petroleum or recycled from rubber products such as tires and non-rubber products such as polystyrene. The monomers obtained by recycling (recycled monomers) are not particularly limited, and examples include recycled butadiene and recycled aromatic vinyl. Examples of the butadiene include 1,2-butadiene and 1,3-butadiene. The aromatic vinyl is not particularly limited, and examples include styrene. Among them, it is preferable to use recycled butadiene (recycled butadiene) and / or recycled styrene (recycled styrene) as raw materials.

[0046] The method for producing the recycled monomer is not particularly limited, and examples include synthesis from recycled naphtha obtained by decomposing rubber products such as tires. Also, the method for producing recycled naphtha is not particularly limited, and for example, rubber products such as tires may be decomposed under high temperature and high pressure, decomposed by microwaves, or extracted after mechanical pulverization.

[0047] Furthermore, the raw materials (monomers) of synthetic rubbers such as SBR and BR may be derived from biomass. The monomers derived from biomass (biomass monomers) are not particularly limited, and examples include butadiene derived from biomass and aromatic vinyl derived from biomass. Examples of the butadiene include 1,2-butadiene and 1,3-butadiene. The aromatic vinyl is not particularly limited, and examples include styrene. The method for producing the biomass monomer is not particularly limited, and examples include those by biological and / or chemical and / or physical conversion of animals and plants. Fermentation by microorganisms is typical as the biological conversion, and examples of the chemical and / or physical conversion include those by catalysts, high heat, high pressure, electromagnetic waves, and critical liquids, and combinations thereof. Examples of the biomass sources of these monomers include sugars, wood, plant residues after obtaining useful components, ethanol derived from plants, and biomass naphtha.

[0048] The polymers synthesized from the biomass monomer components (biomass polymers) are not particularly limited, and examples include polybutadiene rubber synthesized from butadiene derived from biomass, and aromatic vinyl / butadiene copolymers synthesized from butadiene derived from biomass and / or aromatic vinyl derived from biomass. Examples of the aromatic vinyl / butadiene copolymer include styrene-butadiene rubber synthesized from butadiene derived from biomass and / or styrene derived from biomass.

[0049] Whether the raw material of the polymer is derived from biomass can be determined by pMC (percent Modern Carbon) measured in accordance with ASTM D6866-10.

[0050] pMC is the ratio of the 14 C concentration of the sample to the 14 C concentration of the standard modern carbon (modern standard reference), and this value is used as an index indicating the biomass ratio of the compound (rubber). The significance of this value will be described below.

[0051] One mole (6.02×10 23 atoms) of carbon atoms contains approximately 6.02×10 11 atoms of 14 C, which is about one trillionth of ordinary carbon atoms. 14 C is called a radioactive isotope, and its half-life is 5,730 years and it decreases regularly. It takes 226,000 years for all of these to decay. Therefore, after carbon dioxide in the atmosphere and the like are taken up by plants and the like and immobilized, in fossil fuels such as coal, oil, and natural gas, which are considered to have passed more than 226,000 years since immobilization, all of the 14 C element has decayed. Therefore, at present in the 21st century, fossil fuels such as coal, oil, and natural gas do not contain 14 any C element at all. Therefore, chemical substances produced from these fossil fuels as raw materials also do not contain 14 any C element.

[0052] On the other hand, 14 C is constantly generated by nuclear reactions of cosmic rays in the atmosphere, and is in balance with the decrease due to radioactive decay. In the atmospheric environment of the earth, 14 the amount of 14 C is constant. Therefore, the -12 C concentration of substances derived from biomass resources that are circulating in the current environment is about 1×10

[0053] This 14 C is generally measured as follows. Using accelerator mass spectrometry based on a tandem accelerator, 13 the 13 C concentration ( 12 C / 14 C) and 14 the 12 C concentration ( 14As a modern standard reference for the concentration of C, the concentration of 14 C in the circulating carbon in nature in 1950 is adopted. As a specific standard substance, the oxalic acid standard provided by NIST (National Institute of Standards and Technology) is used. The specific radioactivity of carbon in this oxalic acid (the radioactivity intensity of 14 C per gram of carbon) is separated for each carbon isotope, 13 For 14 C, it is corrected to a constant value, and the value obtained by applying the decay correction from 1950 AD to the measurement date is used as the value (100%) of the standard

[0054] C concentration. The ratio of this value to the value of the actually measured sample is the pMC value. 14 C concentration is measured, it will show approximately 0 pMC (for example, 0.3 pMC). This value corresponds to a biomass ratio of 0% mentioned above.

[0055] Therefore, using materials such as rubber with a high pMC value, that is, materials such as rubber with a high biomass ratio, in the rubber composition is suitable from the perspective of environmental protection.

[0056] The above rubber composition preferably contains a filler. The filler is not particularly limited, and materials known in the rubber field can be used. For example, inorganic fillers such as carbon black, silica, calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, mica, biochar (BIO CHAR); difficult-to-disperse fillers, etc. can be mentioned. Among them, from the perspective of obtaining more effects, carbon-derived fillers (carbon-containing fillers) such as carbon black and silica are preferred, and carbon black is more preferred.

[0057] In the above rubber composition, the content of the filler (total amount of fillers such as silica and carbon black) is preferably 30 parts by mass or more, more preferably 55 parts by mass or more, still more preferably 60 parts by mass or more, and preferably 200 parts by mass or less, more preferably 150 parts by mass or less, still more preferably 100 parts by mass or less, based on 100 parts by mass of the rubber component. When it is within the above range, the effect tends to be obtained more favorably.

[0058] In the above rubber composition, the carbon black that can be used is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, etc. As commercial products, products of Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin Nippon Carbon Co., Ltd., Columbia Carbon Co., etc. can be used. These may be used alone or in combination of two or more. In addition to carbon black made from conventional mineral oil and the like as raw materials, carbon black made from biomass materials such as lignin as raw materials may also be used. Further, recycled carbon black obtained by decomposing rubber products, plastic products, etc. containing carbon black such as tires may be appropriately used by substituting an equal amount for the above carbon black.

[0059] The nitrogen adsorption specific surface area (N2SA) of the carbon black is preferably 5 m 2 / g or more, more preferably 10 m 2 / g or more, still more preferably 15 m 2 / g or more. Also, the above N2SA is preferably 100 m 2 / g or less, more preferably 80 m 2 / g or less, still more preferably 60 m 2 / g or less. When it is within the above range, the effect tends to be obtained more favorably. The nitrogen adsorption specific surface area of the carbon black is determined according to JIS K6217-2:2001.

[0060] As carbon black, recycled carbon black can be preferably used from the viewpoints of obtaining the above effects and environmental considerations. One type or two or more types of recycled carbon black may be used.

[0061] When recycled carbon black is included, the mechanism by which more effects are obtained is not clear. However, even when using recycled carbon black, since ΔEB is adjusted to 8.0% or less and ΔEB×Tt is less than 30, it has excellent handling stability after deterioration and is also desirable from the viewpoint of environmental considerations. Therefore, it is presumed that the handling stability after deterioration is improved while considering the environment.

[0062] Recycled carbon black is carbon black recovered by pyrolyzing used rubber products such as waste tires.

[0063] Examples of recycled carbon black include recycled carbon black produced through the pyrolysis of waste tires. The pyrolysis of waste tires can be carried out by known methods, such as pyrolysis methods at a temperature of 650°C or higher.

[0064] The average primary particle diameter of recycled carbon black is usually 10 nm or more and 100 nm or less. The lower limit is preferably 12 nm or more, more preferably 15 nm, and the upper limit is preferably 90 nm or less, more preferably 80 nm or less. The average primary particle diameter of carbon black can be observed by a transmission or scanning electron microscope, and more than 400 primary particles of carbon black observed in the field of view are measured, and the average is obtained thereby.

[0065] Commercially available products can be used as recycled carbon black. For example, the product name PB365 manufactured by Enrestec can be mentioned. PB365 is recycled carbon black produced through the pyrolysis of waste tires, and N2SA is 76 m 2 / g. Also, PB365 contains about 17% by mass of ash.

[0066] In the above rubber composition, the content of carbon black (total amount of recycled carbon black and other carbon black) is preferably 30 parts by mass or more, more preferably 55 parts by mass or more, still more preferably 60 parts by mass or more, and preferably 200 parts by mass or less, more preferably 150 parts by mass or less, still more preferably 100 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the effect tends to be obtained more favorably.

[0067] In the above rubber composition, the content of recycled carbon black is preferably 30 parts by mass or more, more preferably 55 parts by mass or more, still more preferably 60 parts by mass or more, and preferably 200 parts by mass or less, more preferably 150 parts by mass or less, still more preferably 100 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the effect tends to be obtained more favorably.

[0068] In the above rubber composition, the usable silica is not particularly limited, and for example, silica prepared by a dry method (anhydrous silica), silica prepared by a wet method (hydrous silica), etc., which are common in the tire industry, can be used. The raw material of silica is not particularly limited, and for example, it may be a raw material derived from a mineral such as quartz, a raw material derived from a living organism such as rice husk (for example, silica using a biomass material such as rice husk as a raw material), or silica recycled from a product containing silica may be used. Among them, hydrous silica prepared by a wet method is preferable because it has many silanol groups. These silicas may be used alone or in combination of two or more.

[0069] Silica using a biomass material as a raw material can be obtained, for example, by extracting a silicate from rice husk ash obtained by burning rice husks using a sodium hydroxide solution, and reacting the silicate with sulfuric acid in the same manner as conventional wet silica to precipitate silicon dioxide, followed by filtration, washing with water, drying, and pulverization.

[0070] Silica recycled from products containing silica can be, for example, silica recovered from products containing silica such as electronic components such as semiconductors, tires, desiccants, and filter materials such as diatomaceous earth. The method of recovery is not particularly limited and includes pyrolysis, decomposition by electromagnetic waves, etc. Among them, silica recovered from electronic components such as semiconductors or tires is preferred.

[0071] When silica crystallizes, it does not dissolve in water and the silicic acid that is its component cannot be utilized. By controlling the combustion temperature and combustion time, crystallization of silica in rice husk ash can be suppressed (see, for example, Japanese Patent Application Laid-Open No. 2009-2594, Akita Prefectural University Web Journal B / 2019, vol. 6, p. 216-222, etc.).

[0072] Amorphous silica extracted from rice husks can be those commercially available from companies such as Wilmar.

[0073] When the above rubber composition contains silica, the content of silica is preferably 30 parts by mass or more, more preferably 55 parts by mass or more, still more preferably 60 parts by mass or more, and preferably 200 parts by mass or less, more preferably 150 parts by mass or less, still more preferably 100 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the effect tends to be obtained more favorably.

[0074] The nitrogen adsorption specific surface area (N2SA) 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. Also, the upper limit of the N2SA of silica is not particularly limited, but is preferably 350 m 2 / g or less, more preferably 300 m 2 / g or less, still more preferably 250 m 2 / g or less. When within the above range, the effect tends to be obtained more favorably. Note that the N2SA of silica is a value measured by the BET method in accordance with ASTM D3037-93.

[0075] Examples of the hardly dispersible filler include microfibrillated plant fibers, short fibrous cellulose, gel-like compounds, etc. Among them, microfibrillated plant fibers are preferred.

[0076] Among the above microfibrillated plant fibers, cellulose microfibrils are preferred in terms of obtaining good reinforcing properties. The cellulose microfibrils are not particularly limited as long as they are derived from natural products. For example, resource biomass such as fruits, grains, and root vegetables, wood, bamboo, hemp, jute, kenaf, and pulp, paper, cloth, agricultural crop residues, food waste, and sewage sludge obtained from these as raw materials, waste biomass such as rice straw, wheat straw, and thinned wood, and cellulose produced by organisms such as jellyfish and acetic acid bacteria. These microfibrillated plant fibers may be used alone or in combination of two or more.

[0077] In this specification, cellulose microfibrils typically mean cellulose fibers having an average fiber diameter within the range of 10 μm or less, and more typically, cellulose fibers having a micro-structure with an average fiber diameter of 500 nm or less formed by the aggregation of cellulose molecules. A typical cellulose microfibril is formed, for example, as an aggregate of cellulose fibers having the above average fiber diameter.

[0078] When the above rubber composition contains a hardly dispersible filler, the content of the hardly dispersible filler is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit of the content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, still more preferably 20 parts by mass or less, and particularly preferably 10 parts by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0079] When the above rubber composition contains silica, it is preferably further contained with a silane coupling agent. The silane coupling agent is not particularly limited, and those known in the rubber field can be used. For example, bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, etc. of the sulfide type, 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, mercapto type such as NXT and NXT-Z manufactured by Momentive, vinyltriethoxysilane, vinyltrimethoxysilane, etc. of the vinyl type, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, etc. of the amino type, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, etc. of the glycidoxy type, 3-nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane, etc. of the nitro type, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, etc. of the chloro type, and the like can be mentioned. As commercially available products, products of Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azmax Co., Ltd., Toray Dow Corning Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

[0080] In the above rubber composition, the content of the silane coupling agent is preferably 0.1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, and particularly preferably 7 parts by mass or more with respect to 100 parts by mass of silica. The upper limit of the content is preferably 50 parts by mass or less, more preferably 20 parts by mass or less, still more preferably 15 parts by mass or less, and particularly preferably 10 parts by mass or less. When it is within the above range, the effect tends to be obtained more favorably.

[0081] It is desirable that the above rubber composition contains a plasticizer. In this specification, the plasticizer is a material that imparts plasticity to the rubber component, and it may be a liquid or a solid at normal temperature (25 °C). These may be used alone or in combination of two or more.

[0082] Examples of the plasticizer include oils, liquid polymers, resins, etc. These may be used alone or in combination of two or more.

[0083] The above oil is not particularly limited, and conventionally known oils such as paraffinic process oil, aromatic process oil, naphthenic process oil and other process oils, low PCA (polycyclic aromatic) process oils such as TDAE, MES, plant-derived oils, and mixtures thereof can be used. These may be used alone or in combination of two or more. From the perspective of life cycle analysis, lubricating oils, waste edible oils, etc. after being used in a rubber mixing mixer, an automobile engine, etc. may be appropriately used. Among them, from the perspective of obtaining more effects, plant-derived oils (also referred to as vegetable oils) are desirable.

[0084] When a vegetable oil is included, the mechanism by which more effects are obtained is not clear, but by blending a vegetable oil, the aggregation of the filler can be suppressed, and the decrease in elongation at break due to deterioration can be suppressed. Therefore, it is presumed that the handling stability after deterioration is improved.

[0085] Examples of the plant-derived oil include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice bran oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil, and the like.

[0086] Examples of the oil include products of Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Corporation, Oleosuisse S.A., H&R AG, Toyokuni Oil Co., Ltd., Showa Shell Sekiyu KK, Fuji Kogyo Co., Ltd., Nisshin Oillio Group, Ltd., and the like.

[0087] Examples of the liquid polymer include a diene-based polymer (liquid rubber) that is liquid at 25°C and a liquid farnesene-based polymer. Examples of the liquid rubber include liquid styrene-butadiene copolymer (liquid SBR), liquid butadiene polymer (liquid BR), liquid isoprene polymer (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), and the like. These may have a polar group-modified terminal or main chain. Further, hydrogenated products thereof can also be used.

[0088] The liquid diene-based polymer preferably has a polystyrene-reduced weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) of 1.0×10 3 ~5.0×10 4 and more preferably 3.0×10 3 ~1.5×10 4 . The lower limit or upper limit of Mw of the liquid diene-based polymer may also be 4500 or 8500. In the present specification, the Mw of the liquid diene-based polymer is a polystyrene-reduced value measured by gel permeation chromatography (GPC).

[0089] As the above liquid diene polymer, for example, products of Sartomer Company, Kuraray Co., Ltd. etc. can be used.

[0090] As the above resin, as a tire compound, resins (resins) usually used can be used, which may be liquid or solid at normal temperature (25°C). For example, aromatic vinyl polymers, coumarone-indene resins, coumarone resins, indene resins, phenolic resins, rosin resins, petroleum resins, terpene resins, acrylic resins and the like can be mentioned. Further, the resin may be a hydrogenated resin (hydrogenated resin). These may be used alone or in combination of two or more. Further, the resin itself may be a copolymer of monomer components derived from a plurality of sources. Among them, aromatic vinyl polymers, petroleum resins, terpene resins, and hydrogenated resins thereof are desirable.

[0091] When using a resin that is solid at normal temperature as the above resin, the softening point is preferably 50°C or higher, more preferably 55°C or higher, still more preferably 60°C or higher, and particularly preferably 85°C or higher. Also, it is preferably 160°C or lower, more preferably 150°C or lower, still more preferably 140°C or lower, and particularly preferably 100°C or lower. When within the above range, the effect tends to be obtained more favorably. When the resin is liquid at normal temperature, the softening point is preferably 20°C or lower, preferably 10°C or lower, and preferably 0°C or lower. In the case of a hydrogenated resin, it is desirable that the softening point is the same as the above. In addition, the softening point of the above resin is the temperature at which the ball drops, measured with a ring and ball softening point measuring device according to the softening point specified in JIS K6220-1:2001.

[0092] The above aromatic vinyl polymer is a polymer containing an aromatic vinyl monomer as a structural unit. For example, resins obtained by polymerizing α-methylstyrene and / or styrene can be mentioned. Specifically, homopolymers of styrene (styrene resins), homopolymers of α-methylstyrene (α-methylstyrene resins), copolymers of α-methylstyrene and styrene, copolymers of styrene and other monomers and the like can be mentioned.

[0093] The above-mentioned coumarone-indene resin is a resin containing coumarone and indene as the main monomer components constituting the resin skeleton (main chain). Examples of monomer components contained in the skeleton other than coumarone and indene include styrene, α-methylstyrene, methyl indene, vinyl toluene, and the like.

[0094] The above-mentioned coumarone resin is a resin containing coumarone as the main monomer component constituting the resin skeleton (main chain).

[0095] The above-mentioned indene resin is a resin containing indene as the main monomer component constituting the resin skeleton (main chain).

[0096] As the above-mentioned phenolic resin, for example, known polymers such as those obtained by reacting phenol with aldehydes such as formaldehyde, acetaldehyde, and furfural in the presence of an acid or alkali catalyst can be used. Among them, those obtained by reacting with an acid catalyst (such as novolak-type phenolic resins) are preferred.

[0097] Examples of the above-mentioned rosin resin include rosin-based resins represented by natural rosin, polymerized rosin, modified rosin, ester compounds thereof, and hydrogenated products thereof.

[0098] Examples of the above-mentioned petroleum resin include C5-based resin, C9-based resin, C5 / C9-based resin, dicyclopentadiene (DCPD) resin, C9 / DCPD resin, and hydrogenated products thereof. Among them, DCPD resin, hydrogenated DCPD resin, C9 / DCPD resin, and C9 / hydrogenated DCPD resin are preferred.

[0099] The above terpene resin is a polymer containing terpenes as constituent units. For example, there are polyterpene resins obtained by polymerizing terpene compounds, aromatic modified terpene resins obtained by polymerizing terpene compounds and aromatic compounds, and the like. Examples of aromatic modified terpene resins include terpene phenol resins using terpene compounds and phenolic compounds as raw materials, terpene styrene resins using terpene compounds and styrene compounds as raw materials, and terpene phenol styrene resins using terpene compounds, phenolic compounds and styrene compounds as raw materials. Examples of terpene compounds include α-pinene, β-pinene, etc., examples of phenolic compounds include phenol, bisphenol A, etc., and examples of aromatic compounds include styrene compounds (styrene, α-methylstyrene, etc.). Among them, aromatic modified terpene resins are preferred.

[0100] The above acrylic resin is a polymer containing acrylic monomers as constituent units. For example, there are styrene acrylic resins such as styrene acrylic resins obtained by copolymerizing an aromatic vinyl monomer component and an acrylic monomer component and having a carboxyl group. Among them, a solvent-free carboxyl group-containing styrene acrylic resin can be preferably used.

[0101] As the above resin, for example, products of Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical, ExxonMobil, KRATON, Nippon Paint Co., Ltd., Nippon Catalyst Co., Ltd., ENEOS Co., Ltd., Arakawa Chemical Industries, Ltd., Tago Chemical Industry Co., Ltd., etc. can be used.

[0102] From the perspective of sustainability, it is desirable to use plant-derived plasticizers such as the above plant-derived oils and farnesene-based polymers as the above plasticizer.

[0103] The farnesene-based polymer is a polymer obtained by polymerizing farnesene and has a structural unit based on farnesene. Farnesene has isomers such as α-farnesene ((3E,7E)-3,7,11-trimethyl-1,3,6,10-dodecatetraene) and β-farnesene (7,11-dimethyl-3-methylene-1,6,10-dodecatriene), but (E)-β-farnesene having the following structure is preferred.

Chemical formula

[0104] The farnesene-based polymer may be a homopolymer of farnesene (farnesene homopolymer) or a copolymer of farnesene and a vinyl monomer (farnesene-vinyl monomer copolymer). These may be used alone or in combination of two or more. Among them, a copolymer of farnesene and a vinyl monomer is preferred.

[0105] Examples of vinyl monomers include aromatic vinyl compounds such as styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 4-tert-butylstyrene, 5-t-butyl-2-methylstyrene, vinyl ethylbenzene, divinylbenzene, trivinylbenzene, divinylnaphthalene, tert-butoxystyrene, vinylbenzyldimethylamine, (4-vinylbenzyl)dimethylaminoethyl ether, N,N-dimethylaminoethylstyrene, N,N-dimethylaminomethylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, 2-t-butylstyrene, 3-t-butylstyrene, 4-t-butylstyrene, vinylxylene, vinylnaphthalene, vinyltoluene, vinylpyridine, diphenylethylene, and tertiary amino group-containing diphenylethylene, and conjugated diene compounds such as butadiene and isoprene. These may be used alone or in combination of two or more. Among them, butadiene is preferred. That is, as the farnesene-vinyl monomer copolymer, a copolymer of farnesene and butadiene (farnesene-butadiene copolymer) is preferred.

[0106] In the farnesene-vinyl monomer copolymer, the copolymerization ratio (farnesene / vinyl monomer) based on the mass of farnesene and the vinyl monomer is preferably 40 / 60 to 90 / 10.

[0107] Farnesene-based polymers with a weight average molecular weight (Mw) of 3000 or more and 300,000 or less can be preferably used. The Mw of the farnesene-based polymer is preferably 8000 or more, more preferably 10,000 or more, and preferably 100,000 or less, more preferably 60,000 or less, and even more preferably 50,000 or less. When within the above range, the effects tend to be more preferably obtained.

[0108] The farnesene-based polymer may be in a liquid state or a solid state at room temperature (25°C). Among them, a liquid farnesene-based polymer in a liquid state at room temperature (25°C) is desirable.

[0109] In the above rubber composition, the content of the plasticizer (total amount of the plasticizer) is preferably 5 parts by mass or more, more preferably 8 parts by mass or more, and still more preferably 10 parts by mass or more with respect to 100 parts by mass of the rubber component. The upper limit is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and still more preferably 13 parts by mass or less. When it is within the above range, the effect tends to be obtained more favorably. Note that the content of the plasticizer includes the amount of oil and resin contained in the oil-extended rubber and the resin-extended rubber.

[0110] In the above rubber composition, the content of the solid plasticizer in a solid state at room temperature (25 ° C) is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and still more preferably 3 parts by mass or more with respect to 100 parts by mass of the rubber component. The upper limit is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and still more preferably 5 parts by mass or less. When it is within the above range, the effect tends to be obtained more favorably. Note that the content of the above resin in a solid state at room temperature (25 ° C) and the above aromatic vinyl polymer in a solid state at room temperature (25 ° C) are preferably in the same range.

[0111] In the above rubber composition, the content of the liquid plasticizer in a liquid state at room temperature (25 ° C) is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and still more preferably 7 parts by mass or more with respect to 100 parts by mass of the rubber component. The upper limit is preferably 25 parts by mass or less, more preferably 20 parts by mass or less, and still more preferably 15 parts by mass or less. When it is within the above range, the effect tends to be obtained more favorably. Note that the content of the liquid plasticizer includes the amount of oil contained in the oil-extended rubber and the amount of liquid resin of the resin-extended rubber extended with the liquid resin. The content of the oil in a liquid state at room temperature (25 ° C) and the content of the vegetable oil are preferably in the same range.

[0112] From the viewpoint of obtaining more effects, it is desirable that the above rubber composition contains a double bond-containing polymer in a liquid state at 25 ° C (hereinafter, also referred to as a double bond-containing low molecular weight polymer (a low molecular weight polymer having a double bond)). In the present specification, the low molecular weight polymer containing double bonds is not included in the rubber component and the plasticizer described above.

[0113] When a low molecular weight polymer containing double bonds is included, the mechanism by which more effects can be obtained is not clear. However, by including a liquid polymer containing double bonds, the reinforcing effect by crosslinking is improved, and a decrease in handling stability due to deterioration can be suppressed. Therefore, it is presumed that the handling stability after deterioration is improved.

[0114] The weight average molecular weight of the above-mentioned low molecular weight polymer containing double bonds is preferably 10,000 or more, more preferably 30,000 or more, still more preferably 50,000 or more, and is preferably 150,000 or less, more preferably 120,000 or less, still more preferably 90,000 or less. When it is within the above range, the effect tends to be obtained more favorably.

[0115] In the above rubber composition, the content of the above-mentioned low molecular weight polymer containing double bonds is preferably 5 parts by mass or more, more preferably 8 parts by mass or more, still more preferably 10 parts by mass or more with respect to 100 parts by mass of the rubber component. The upper limit is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, still more preferably 20 parts by mass or less. When it is within the above range, the effect tends to be obtained more favorably.

[0116] The above-mentioned low molecular weight polymer containing double bonds is not particularly limited as long as it is a low molecular weight polymer having double bonds. Among them, polyoctenamer is desirable. Polyoctenamer includes both cyclic or linear polymers based on cyclooctene and mixtures of such cyclic and linear polymers. In the present specification, polyoctenamer is not included in the plasticizer.

[0117] From the viewpoint of obtaining more effects, polyoctenamer showing a melting temperature or softening temperature of room temperature or higher and 120°C or lower is desirable.

[0118] For the polyoctenamer, for example, VESTENAMER® 8012 (manufactured by Evonik), VESTENAMER® 8020 (manufactured by Evonik), etc. can be used.

[0119] The weight average molecular weight of the polyoctenamer is preferably 10,000 or more, more preferably 30,000 or more, still more preferably 50,000 or more, and is preferably 150,000 or less, more preferably 120,000 or less, still more preferably 90,000 or less. When within the above range, the effect tends to be obtained more favorably.

[0120] In the above rubber composition, the content of the polyoctenamer is preferably 5 parts by mass or more, more preferably 8 parts by mass or more, still more preferably 10 parts by mass or more with respect to 100 parts by mass of the rubber component. The upper limit is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, still more preferably 20 parts by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0121] From the viewpoint of obtaining more effects, it is desirable that the above rubber composition contains a thermoplastic elastomer. In addition, in this specification, the thermoplastic elastomer shall not be included in the rubber component.

[0122] When containing a thermoplastic elastomer, the mechanism by which more effects are obtained is not clear, but by containing a thermoplastic elastomer, the elastic modulus of the rubber composition is improved, and a certain level of handling stability can be imparted. Therefore, it is presumed that the handling stability after deterioration is improved.

[0123] Examples of usable thermoplastic elastomers include, for example, olefin-based thermoplastic elastomers, styrene-based thermoplastic elastomers (elastomeric styrene-isobutylene-styrene block copolymer (SIBS), styrene-isoprene-styrene block copolymer (SIS), styrene-isobutylene block copolymer (SIB), styrene-butadiene-styrene block copolymer (SBS), styrene-ethylene / butene-styrene block copolymer (SEBS), styrene-ethylene / propylene-styrene block copolymer (SEPS), styrene-ethylene / ethylene / propylene-styrene block copolymer (SEEPS), styrene-butadiene / butylene-styrene block copolymer (SBBS), etc.), vinyl chloride-based thermoplastic elastomers, urethane-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, polyester-based thermoplastic elastomers, fluorine-based thermoplastic elastomers, and the like. These may be used alone or in combination of two or more. Among them, urethane-based thermoplastic elastomers (thermoplastic polyurethane elastomers (TPU)) are preferred.

[0124] Examples of thermoplastic polyurethane elastomers (urethane-based thermoplastic elastomers) include those composed of, for example, isocyanate, polyol, and, if necessary, a chain extender.

[0125] The isocyanates constituting the thermoplastic polyurethane elastomer are not particularly limited as long as they are isocyanate compounds having two or more isocyanate groups. For example, aromatic isocyanates such as 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, a mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), 1,5-naphthylene diisocyanate (NDI), 3,3'-bitolylene-4,4'-diisocyanate (TODI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), paraphenylene diisocyanate (PPDI), 4,4'-methylene-bis(phenyl isocyanate); alicyclic isocyanates or aliphatic isocyanates such as 4,4'-dicyclohexylmethane diisocyanate (H 12 MDI), hydrogenated xylylene diisocyanate (H6XDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), etc. These may be used alone or in combination of two or more.

[0126] The polyols (high molecular weight polyols) constituting the thermoplastic polyurethane elastomer include polyether polyols such as polyoxyethylene glycol (PEG), polyoxypropylene glycol (PPG), polyoxytetramethylene glycol (PTMG); condensation polyester polyols such as polyethylene adipate (PEA), polybutylene adipate (PBA), polyhexamethylene adipate (PHMA); lactone polyester polyols such as poly-ε-caprolactone (PCL); polycarbonate polyols such as polyhexamethylene carbonate; acrylic polyols, etc. Among them, from the viewpoint of the riding comfort performance after long-term storage, polyether polyols and polycarbonate polyols are preferred. These may be used alone or in combination of two or more.

[0127] Examples of the chain extender include low molecular weight polyols, polyamines, amino alcohols, etc. Among them, low molecular weight polyols are preferred from the viewpoints of riding comfort performance after long-term storage, etc.

[0128] Examples of the low molecular weight polyol include triols such as glycerin, trimethylolethane, trimethylolpropane, and hexanetriol; tetraols such as pentaerythritol; hexols such as sorbitol, etc. Further, diols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, 1,8-octanediol, aniline-based diol, and bisphenol A-based diol are also included. These may be used alone or in combination of two or more.

[0129] Examples of the polyamine include triamines such as diethylenetriamine and dipropylenetriamine; aliphatic diamines such as ethylenediamine and hexamethylenediamine, alicyclic diamines such as isophoronediamine and piperazine, and diamines such as aromatic diamines. As the aromatic diamine, for example, a monocyclic aromatic diamine having two amino groups bonded to one aromatic ring may be used, or a polycyclic aromatic diamine containing two aminophenyl groups each having at least one amino group bonded to one aromatic ring may be used. Examples of the monocyclic aromatic diamine include types in which amino groups are directly bonded to the aromatic ring such as phenylenediamine, toluenediamine, diethyltoluenediamine, and dimethylthiotoluenediamine; and types in which amino groups are bonded to the aromatic ring via a lower alkylene group such as xylylenediamine. Further, examples of the polycyclic aromatic diamine include diaminodiphenylalkanes (such as 4,4'-diaminodiphenylmethane and its derivatives). These may be used alone or in combination of two or more.

[0130] Thermoplastic polyurethane elastomers can be synthesized by known methods. Examples of the synthesis methods include the one-shot method and the prepolymer method. The one-shot method is a method of polymerizing by reacting isocyanate and polyol etc. all at once. On the other hand, the prepolymer method is a method of polymerizing by reacting isocyanate and polyol etc. in multiple steps. For example, after once synthesizing a urethane prepolymer of low molecular weight, subsequently, a method of polymerizing by reacting the prepolymer with the above-mentioned chain extender.

[0131] Known catalysts can be used for the synthesis of polyurethane. Examples of the catalysts include monoamines such as triethylamine and N,N-dimethylcyclohexylamine; polyamines such as N,N,N’,N’-tetramethylethylenediamine; cyclic diamines such as 1,8-diazabicyclo[5,4,0]-7-undecene (DBU) and triethylenediamine; tin-based catalysts such as dibutyltin dilaurate and dibutyltin diacetate. These may be used alone or in combination of two or more.

[0132] The compositional ratio of isocyanate and polyol in polyurethane is not particularly limited, but the NCO / OH ratio (molar ratio) of the isocyanate group of isocyanate to the hydroxyl group of polyol is preferably 0.5 or more, more preferably 0.7 or more, and still more preferably 0.8 or more. When it is below the above lower limit, since the isocyanate component is too small, the mechanical strength of the urethane tends to decrease. On the other hand, the NCO / OH ratio (molar ratio) is preferably 2.5 or less, more preferably 2.2 or less, and still more preferably 2.0 or less. When it exceeds the above upper limit, since the isocyanate component becomes excessive, it is likely to absorb moisture, and the mechanical strength of the urethane may become low.

[0133] In the above rubber composition, the content of the above thermoplastic elastomer is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, still more preferably 10 parts by mass or less. When it is within the above range, the effect tends to be obtained more favorably. In addition, the content of the thermoplastic polyurethane elastomer (TPU) is preferably in the same range.

[0134] From the viewpoints of crack resistance, ozone resistance, etc., the above rubber composition preferably contains an antioxidant.

[0135] The anti-aging agent is not particularly limited, but examples include naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; p-phenylenediamine-based anti-aging agents such as N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-diphenyl-p-phenylenediamine (DPPD), N,N'-ditoly-p-phenylenediamine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), N,N'-di-2-naphthyl-p-phenylenediamine (DNPD); quinoline-based anti-aging agents such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based anti-aging agents such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; bis, tris, polyphenol-based anti-aging agents such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. Among them, p-phenylenediamine-based anti-aging agents and quinoline-based anti-aging agents are preferred, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and polymers of 2,2,4-trimethyl-1,2-dihydroquinoline are more preferred. As commercially available products, for example, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinsei Chemical Industry Co., Ltd., Flexsys Co., etc. can be used.

[0136] In the above rubber composition, the content of the anti-aging agent is preferably 0.2 parts by mass or more, more preferably 2.0 parts by mass or more, still more preferably 4.0 parts by mass or more, based on 100 parts by mass of the rubber component. The content is preferably 10.0 parts by mass or less, more preferably 6.0 parts by mass or less.

[0137] The above rubber composition preferably contains stearic acid. In the above rubber composition, the content of stearic acid is preferably 0.5 parts by mass or more, more preferably 2.0 parts by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass or less, based on 100 parts by mass of the rubber component.

[0138] As the stearic acid, conventionally known ones can be used. For example, products of NOF Corporation, Kao Corporation, FUJIFILM Wako Pure Chemical Corporation, Chiba Fatty Acids Co., Ltd., etc. can be used.

[0139] The above rubber composition preferably contains zinc oxide. In the above rubber composition, the content of zinc oxide is preferably 0.5 parts by mass or more, more preferably 2.5 parts by mass or more, and preferably 6.0 parts by mass or less, more preferably 4.0 parts by mass or less, based on 100 parts by mass of the rubber component.

[0140] As the zinc oxide, conventionally known ones can be used. For example, products of Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusuitech Co., Ltd., Shoindo Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. can be used.

[0141] The above rubber composition may be blended with wax. In the above rubber composition, the content of wax is preferably 0.5 parts by mass or more, more preferably 1.2 parts by mass or more, and preferably 8.0 parts by mass or less, more preferably 5.0 parts by mass or less, based on 100 parts by mass of the rubber component.

[0142] The wax is not particularly limited, and any wax commonly used in the tire industry can be preferably used. For example, petroleum waxes, mineral waxes, synthetic waxes, plant-derived waxes, etc. can be mentioned. Among them, petroleum waxes and plant-derived waxes are preferred, and petroleum waxes are more preferred. Examples of plant-derived waxes include rice wax, carnauba wax, candelilla wax, etc. Examples of petroleum waxes include paraffin wax, microcrystalline wax, and their selected special waxes, etc., and paraffin wax is preferred. Note that the wax according to this embodiment does not contain stearic acid. As the wax, for example, those commercially available from Ouchi Shinsei Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Paramelt Co., etc. can be used. These waxes may be used alone or in combination of two or more.

[0143] In the above rubber composition, it is preferable to compound sulfur in terms of forming appropriate crosslinked chains in the polymer chain and imparting good performance.

[0144] In the above rubber composition, the sulfur content is preferably 1.0 part by mass or more, more preferably 1.4 part by mass or more, still more preferably 1.6 part by mass or more, based on 100 parts by mass of the rubber component. The content is preferably 7.0 parts by mass or less, more preferably 5.0 parts by mass or less, still more preferably 4.0 parts by mass or less.

[0145] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, soluble sulfur, etc., which are generally used in the rubber industry. As commercially available products, products of Tsuruami Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Kasei Kogyo Co., Ltd., Flexsys Co., Ltd., Nippon Karyu Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

[0146] The above rubber composition preferably contains a vulcanization accelerator. In the above rubber composition, the content of the vulcanization accelerator is not particularly limited and may be freely determined according to the desired vulcanization rate and crosslink density. However, based on 100 parts by mass of the rubber component, it is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, and still more preferably 0.7 parts by mass or more. The upper limit is preferably 8.0 parts by mass or less, more preferably 5.0 parts by mass or less, and still more preferably 4.0 parts by mass or less.

[0147] The type of the vulcanization accelerator is not particularly limited, and those commonly used can be used. Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyldisulfide, and N-cyclohexyl-2-benzothiazylsulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, N-t-butyl-2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, diorthotolylguanidine, and orthotolylbiguanidine. These may be used alone or in combination of two or more. Among them, sulfenamide-based, guanidine-based, and benzothiazole-based vulcanization accelerators are preferred.

[0148] In addition to the above components, the above rubber composition may be appropriately blended with compounding agents commonly used in the tire industry, such as materials such as mold release agents.

[0149] In this specification, various materials containing carbon atoms (for example, rubber, oil, resin, vulcanization accelerator, antioxidant, surfactant, etc.) may be derived from carbon dioxide in the atmosphere. As a method for obtaining the above-mentioned blend from carbon dioxide, carbon dioxide may be directly converted, or methane obtained through a methanation process of synthesizing methane from carbon dioxide may be converted.

[0150] It is desirable that the ratio (Cc / ΔEB) of the content Cc (parts by mass) of carbon black to 100 parts by mass of the rubber component of the rubber composition and the change rate ΔEB (%) of the elongation at break before and after heat aging of the rubber composition (vulcanized rubber composition) exceeds 7.6. Cc / ΔEB is preferably 9.5 or more, more preferably 11.6 or more, and still more preferably 13.2 or more. The upper limit of Cc / ΔEB is preferably 18.0 or less, more preferably 16.0 or less, and still more preferably 15.0 or less. When within the above range, the effect tends to be obtained more favorably.

[0151] When Cc / ΔEB exceeds 7.6, the mechanism by which a more effect is obtained is not clear. However, by satisfying Cc / ΔEB > 7.6, since the rubber is reinforced with carbon black for a certain amount of change, a decrease in handling stability is suppressed. Therefore, it is presumed that the handling stability after deterioration is improved.

[0152] It is desirable that the ratio (Pc×ΔEB) of the content Pc (parts by mass) of the plasticizer to 100 parts by mass of the rubber component of the rubber composition and the change rate ΔEB (%) of the elongation at break before and after heat aging of the rubber composition (vulcanized rubber composition) is less than 80. Pc×ΔEB is preferably 68 or less, more preferably 52 or less, and still more preferably 46 or less. The lower limit of Pc×ΔEB is preferably 10 or more, more preferably 20 or more, and still more preferably 30 or more. When within the above range, the effect tends to be obtained more favorably.

[0153] When Pc×ΔEB is less than 80, the mechanism by which a more effect is obtained is not clear. However, by satisfying Pc×ΔEB < 80, it is possible to suppress the loss of the plasticizer due to deterioration and the resulting change in rigidity, and suppress a decrease in handling stability. Therefore, it is presumed that the handling stability after deterioration is improved.

[0154] It is desirable that the content rate Pr (mass%) of the plasticizer in the rubber composition (100 mass%) is 6.5 mass% or less. Pr is preferably 6.0 mass% or less, more preferably 5.5 mass% or less, still more preferably 5.2 mass%. The lower limit of Pr is preferably 3.0 mass% or more, more preferably 3.5 mass% or more, still more preferably 4.0 mass% or more. When it is within the above range, the effect tends to be obtained better.

[0155] When Pr is 6.5 mass% or less, the mechanism by which more effects are obtained is not clear, but since the content rate of the plasticizer is small, it is possible to suppress the loss of the plasticizer due to deterioration and the resulting change in rigidity, and it is possible to suppress the decrease in handling stability. Therefore, it is presumed that the handling stability after deterioration is improved.

[0156] The rubber composition is kneaded using a rubber kneading device such as an open roll or a Banbury mixer for the above components, and then a crosslinked rubber composition is obtained by a method such as crosslinking.

[0157] As the kneading conditions, in the base kneading step of kneading additives other than the crosslinking agent (vulcanizing agent) and the vulcanization accelerator, the kneading temperature is preferably 100°C or higher, more preferably 120°C or higher, and preferably 180°C or lower, more preferably 170°C or lower. In the finishing kneading step of kneading the vulcanizing agent and the vulcanization accelerator, the kneading temperature is preferably 80°C or higher, and preferably 120°C or lower, more preferably 110°C or lower. Further, the composition kneaded with the vulcanizing agent and the vulcanization accelerator is usually subjected to a vulcanization treatment such as press vulcanization. As the vulcanization temperature, it is preferably 140°C or higher, more preferably 150°C or higher, and preferably 190°C or lower, more preferably 185°C or lower.

[0158] The rubber composition is used for a tire member. Among them, from the viewpoint of obtaining more effects, it is desirable that the tire member is an inner tire member. In addition, in this specification, the tire internal member refers to a member other than the cap tread that contacts the road surface during driving.

[0159] Examples of the tire internal member include carcass ply, base tread, breaker, sidewall, clinch apex, bead apex, etc. Among them, it is preferably used at least for the sidewall.

[0160] The above tire is manufactured by a normal method using the above rubber composition. That is, a composition blended with various additives as required is extruded into the shape of various tire members such as tire internal members at the unvulcanized stage, formed by a normal method on a tire molding machine, bonded together with other tire members to form an unvulcanized tire, and then heated and pressurized in a vulcanizer to manufacture the tire.

[0161] The above tire is not particularly limited, and examples include pneumatic tires, solid tires, airless tires, etc. Among them, pneumatic tires are preferred.

[0162] The above tire is preferably used as a passenger car tire, a large passenger car tire, a large SUV tire, a truck and bus tire, a two-wheeler tire, a racing tire, a winter tire (a studless tire, a snow tire, a stud tire), an all-season tire, a run-flat tire, an aircraft tire, a mine tire, etc.

[0163] The above tire includes a tire member made from the above rubber composition. For the above tire, the product (ΔEB×Tt) of the change rate ΔEB (%) of the elongation at break before and after heat aging of the above rubber composition (the rubber composition after vulcanization) and the thickness Tt of the above tire member is less than 30. ΔEB×Tt is preferably 26 or less, more preferably 20 or less, and still more preferably 16 or less. The lower limit of ΔEB×Tt is preferably 8 or more, more preferably 10 or more, and still more preferably 12 or more. When within the above range, the effect tends to be obtained better.

[0164] In the above tire, the thickness Tt (mm) of the above tire member is preferably 10.0 mm or less, more preferably 5.0 mm or less, still more preferably 4.0 mm or less, and particularly preferably 3.5 mm or less. The lower limit of the thickness Tt of the above tire member is preferably 0.5 mm or more, more preferably 1.0 mm or more, still more preferably 1.5 mm or more, and when it is within the above range, there is a tendency that the effect can be preferably obtained.

[0165] In this specification, the thickness Tt of the tire member means the maximum value of the thicknesses of the respective tire members (such as the sidewall). The thickness at each point on the surface of each tire member is the linear distance measured along the normal line of the surface of each tire member at that point, and the thickness Tt of each tire member is the maximum value of the thicknesses at each point.

[0166] It is desirable that the ratio (Cc / Tt) of the content Cc (parts by mass) of carbon black to 100 parts by mass of the rubber component of the above rubber composition and the thickness Tt (mm) of the above tire member is 15.0 or more. Cc / Tt is preferably 15.7 or more, more preferably 16.5 or more, still more preferably 17.1 or more. Also, the upper limit of Cc / Tt is preferably 20.0 or less, more preferably 19.0 or less, still more preferably 18.5 or less. When it is within the above range, there is a tendency that the effect can be obtained more favorably.

[0167] When Cc / Tt exceeds 15.0, the mechanism by which more effects are obtained is not clear, but since the entire thickness of the tire member is reinforced with carbon black, a decrease in handling stability is suppressed. Therefore, it is presumed that the handling stability after deterioration is improved.

[0168] It is desirable that the ratio (Pc / Tt) of the content Pc (parts by mass) of the plasticizer to 100 parts by mass of the rubber component of the above rubber composition and the thickness Tt (mm) of the above tire member is less than 3.6. Pc / Tt is preferably 3.3 or less, more preferably 3.0 or less, and still more preferably 2.9 or less. Also, the lower limit of Pc / Tt is preferably 1.5 or more, more preferably 2.0 or more, and still more preferably 2.2 or more. When within the above range, the effect tends to be obtained more favorably.

[0169] When Pc / Tt is less than 3.6, the mechanism by which a more remarkable effect is obtained is not clear, but the amount of plasticizer with respect to the thickness of the tire member is small, and it is possible to suppress the loss of the plasticizer due to deterioration and the resulting change in rigidity, and suppress the decrease in handling stability. Therefore, it is presumed that the handling stability after deterioration is improved.

[0170] In the above tire, the groove depth D (mm) of the circumferential groove formed in the tread is preferably 5.5 mm or more, more preferably 6.0 mm or more, and still more preferably 6.5 mm or more, and is preferably 9.5 mm or less, more preferably 9.0 mm or less, and still more preferably 8.5 mm or less. When within the above range, the effect tends to be obtained more favorably.

[0171] In this specification, the groove depth D of the circumferential groove means the distance measured along the normal line of the plane obtained by extending the plane forming the ground contact surface of the outermost surface of the tread from the plane obtained by extending the plane forming the ground contact surface to the deepest groove bottom, and refers to the maximum distance among the groove depths of the provided circumferential grooves.

[0172] It is desirable that the ratio (ΔEB / D) of the change rate ΔEB (%) of the elongation at break before and after heat aging of the above rubber composition to the groove depth D (mm) of the circumferential groove formed in the tread of the above tire is 0.6 or more and 1.5 or less. ΔEB / D is preferably 0.7 or more, more preferably 0.8 or more, and still more preferably 0.9 or more. Also, the upper limit of ΔEB / D is preferably 1.3 or less, more preferably 1.2 or less, and still more preferably 1.1 or less. When within the above range, the effect tends to be obtained more favorably.

[0173] When ΔEB / D is adjusted to a predetermined range, the mechanism by which more effects can be obtained is not clear. However, by setting the change rate ΔEB of the elongation at break before and after heat aging to be equal to or less than a predetermined value and adjusting the groove depth, it is possible to ensure a predetermined handling stability and at the same time suppress a decrease in handling stability due to rubber deterioration. Therefore, it is presumed that the handling stability after deterioration is improved.

[0174] In this specification, dimensions such as thickness are measured with the bead portion of the tire adjusted to the normal rim width. At the time of measurement, the tire is cut out in the tire radial direction, and both bead end portions of the sample are fixed in a state where they are adjusted to the width of the normal rim.

[0175] In this specification, unless otherwise specified, the dimensions of each part of the tire are the values measured in the normal state. The "normal state" refers to the state where the tire is mounted on a standard rim and filled with the standard internal pressure, and is in an unloaded state. Here, the "standard rim" is the rim defined for each tire in the standard system including the standard based on which the tire is designed. For example, in the case of JATMA (Japan Automobile Tire Manufacturers Association), it is the standard rim in the applicable size described in the "JATMA YEAR BOOK"; in the case of ETRTO (The European Tyre and Rim Technical Organisation), it is the "Measuring Rim" described in the "STANDARDS MANUAL"; in the case of TRA (The Tire and Rim Association, Inc.), it is the "Design Rim" described in the "YEAR BOOK". Refer to JATMA, ETRTO, and TRA in this order, and follow the relevant standard if there is an applicable size during the reference. For a tire not defined in the standard, it refers to the rim with the smallest rim diameter and then the narrowest rim width among the rims that can be mounted on the tire and can hold the internal pressure, i.e., the rim that does not cause air leakage between the rim and the tire. Also, the "standard internal pressure" refers to the air pressure defined for each tire in the standard system including the standard based on which the tire is designed. In the case of JATMA, it is the "maximum air pressure"; in the case of ETRTO, it is the "INFLATION PRESSURE"; in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES". Refer to JATMA, ETRTO, and TRA in this order, and follow the relevant standard if there is an applicable size during the reference. For a tire not defined in the standard, it refers to the standard internal pressure (however, 250 KPa or more) of another tire size (defined in the standard) with the standard rim described as the standard rim. In the case where there are multiple standard internal pressures of 250 KPa or more described, it refers to the minimum value among them.

[0176] Hereinafter, an example of the above tire will be described with reference to the drawings, but it is not limited to such a form.

[0177] Figure 1 shows a pneumatic tire 2. In Figure 1, the vertical direction is the radial direction of the tire 2, the left - right direction is the axial direction of the tire 2, and the direction perpendicular to the plane of the paper is the circumferential direction of the tire 2. In Figure 1, the dashed - dotted line CL represents the equatorial plane of the tire 2. The shape of this tire 2 is symmetric with respect to the equatorial plane except for the tread pattern.

[0178] This tire 2 includes a tread 4, a pair of sidewalls 6, a pair of wings 8, a pair of clinches 10, a pair of beads 12, a carcass 14, a belt 16, a band 18, an inner liner 20, and a pair of chafers 22. This tire 2 is of the tubeless type. This tire 2 is mounted on a passenger car.

[0179] The tread 4 has a shape that is convex radially outward. The tread 4 forms a tread surface 24 that contacts the road surface. Grooves 26 are engraved in the tread 4. A tread pattern is formed by these grooves 26. The tread 4 has a base layer 28 and a cap layer 30. The cap layer 30 is located radially outside the base layer 28. The cap layer 30 is laminated on the base layer 28.

[0180] In addition, in Figure 1, an example of the two - layer - structure tread 4 composed of the cap layer 30 and the base layer 28 is shown, but a single - layer - structure tread 4 or a tread 4 having a structure of three or more layers may also be used.

[0181] In the tire 2 of Figure 1, the sidewall 6 extends substantially inward in the radial direction from the end of the tread 4. The radially outer portion of this sidewall 6 is joined to the tread 4. The radially inner portion of this sidewall 6 is joined to the clinch 10.

[0182] In the tire 2 of Figure 1, the sidewall 6 is made of the above - mentioned rubber composition. The sidewall 6 has a change rate ΔEB of elongation at break before and after heat aging of 8.0% or less, and the product (ΔEB×Tt) of the ΔEB(%) and the thickness Tt (mm) of the sidewall is less than 30.

[0183] In the tire 2 of FIG. 1, the thickness Tt of the sidewall 6 is the maximum dimension among the thicknesses of each sidewall at each point on the surface of the sidewall 6, and in the example of FIG. 1, it is indicated by Tt.

[0184] In the tire 2 of FIG. 1, each wing 8 is located between the tread 4 and the sidewall 6. The wing 8 is joined to each of the tread 4 and the sidewall 6.

[0185] Each clinch 10 is located substantially radially inward of the sidewall 6. The clinch 10 is located axially outside the bead 12 and the carcass 14.

[0186] Each bead 12 is located axially inside the clinch 10. The bead 12 includes a core 32 and an apex 34 extending radially outward from this core 32. The core 32 is ring-shaped and includes a wound non-stretchable wire or the like. The apex 34 tapers radially outward.

[0187] The carcass 14 includes a carcass ply 36. In this tire 2, the carcass 14 consists of one carcass ply 36, but it may be composed of two or more plies.

[0188] In this tire 2, the carcass ply 36 is spanned between the beads 12 on both sides and is along the tread 4 and the sidewall 6. The carcass ply 36 is folded back from the axially inner side to the outer side around each core 32. By this folding, a main part 36a and a pair of folded parts 36b are formed in the carcass ply 36. That is, the carcass ply 36 includes the main part 36a and a pair of folded parts 36b.

[0189] Although not shown, examples of the carcass ply 36 include those composed of a number of parallel cords and topping rubber. It is preferable that this carcass 14 has a radial structure.

[0190] The belt 16 is located radially inside the tread 4. The belt 16 is laminated with the carcass 14. The belt 16 is composed of an inner layer 38 and an outer layer 40.

[0191] Although not shown, each of the inner layer 38 and the outer layer 40 may be composed of a number of parallel cords and topping rubber, etc. Each cord is inclined, for example, with respect to the equatorial plane. The inclination direction of the cords of the inner layer 38 with respect to the equatorial plane is opposite to the inclination direction of the cords of the outer layer 40 with respect to the equatorial plane.

[0192] The band 18 is located radially outside the belt 16. In the axial direction, the band 18 has a width equivalent to the width of the belt 16. This band 18 may have a width larger than the width of this belt 16.

[0193] Although not shown, the band 18 may be composed of a cord and topping rubber, etc. The cord is wound in a spiral shape, for example.

[0194] The belt 16 and the band 18 constitute a reinforcing layer. The reinforcing layer may be constituted only by the belt 16.

[0195] The inner liner 20 is located inside the carcass 14. The inner liner 20 is joined to the inner surface of the carcass 14.

[0196] Each chafer 22 is located in the vicinity of the bead 12. In this embodiment, the chafer 22 may be composed of a cloth and rubber impregnated in this cloth, etc. This chafer 22 may be integrated with the clinch 10.

[0197] Figure 2 is an enlarged cross-sectional view showing the vicinity of the tread 4 of the tire 2 in Figure 1. In Figure 2, the vertical direction is the radial direction of the tire 2, the horizontal direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the circumferential direction of the tire 2.

[0198] In this tire 2, the tread 4 has a main groove 42 as a groove 26. As shown in FIGS. 1 and 2, a plurality of, specifically, three main grooves 42 are engraved in this tread 4. These main grooves 42 are arranged at intervals in the axial direction. By engraving three main grooves 42 in this tread 4, four ribs 44 extending in the circumferential direction are formed. That is, the main groove 42 is between the ribs 44 and the ribs 44.

[0199] Each main groove 42 extends in the circumferential direction. The main groove 42 is continuous without interruption in the circumferential direction. The main groove 42 promotes the drainage of water existing between the road surface and the tire 2, for example, in rainy weather. Therefore, even when the road surface is wet, the tire 2 can sufficiently contact the road surface. D in FIG. 2 indicates the groove depth of the circumferential main groove 42 formed in the tread 4.

[0200] In the tire 2, regarding the change rate ΔEB of the elongation at break before and after heat aging of the sidewall 6, the carbon black content Cc with respect to 100 parts by mass of the rubber component, the plasticizer content Pc with respect to 100 parts by mass of the rubber component, the plasticizer content rate Pr (mass %), the thickness Tt (mm) of the sidewall 6, and the groove depth D of the circumferential groove formed in the tread, it is desirable that Cc / ΔEB, Pc×ΔEB, Pr, Cc / Tt, Pc / Tt, ΔEB / D, Tt, and D are within the aforementioned ranges.

Example

[0201] Hereinafter, examples (embodiments) considered preferable for implementation will be shown, but the scope of the present disclosure is not limited to the embodiments.

[0202] Hereinafter, various chemicals used during synthesis and polymerization will be collectively described. The chemicals are purified according to a standard method as necessary. n-Hexane: Manufactured by Kanto Chemical Co., Inc. Styrene: Manufactured by Kanto Chemical Co., Inc. Butadiene: 1,3-butadiene manufactured by Tokyo Chemical Industry Co., Ltd. TMEDA: N,N,N’,N’-tetramethylethylenediamine manufactured by Kanto Chemical Co., Inc. n-butyllithium solution: 1.6 M n-butyllithium hexane solution manufactured by Kanto Chemical Co., Inc.

[0203] Also, the evaluation method of the copolymer will be summarized and explained below.

[0204] (Measurement of hydrogenation rate of conjugated diene part of copolymer) Prepare a 15 mass% concentration solution using carbon tetrachloride as a solvent, and calculate from the spectral reduction rate of the unsaturated bond part of 100 MHz 1 1H-NMR.

[0205] (Measurement of styrene content) Measure 1H-NMR at 25 °C using a JEOL JNM-A 400 NMR apparatus, and determine the styrene content from the ratio of phenyl protons based on styrene units at 6.5 - 7.2 ppm and vinyl protons based on butadiene units at 4.9 - 5.4 ppm obtained from the spectrum. 1

[0206] (Measurement of weight average molecular weight (Mw)) The weight average molecular weight (Mw) of the copolymer is determined by standard polystyrene conversion based on the measured value by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation).

[0207] (Production Example 1 Synthesis of hydrogenated styrene-butadiene copolymer: hydrogenation rate 95 mol%) Into a heat-resistant reaction vessel thoroughly substituted with nitrogen, add 2000 ml of n-hexane, 60 g of styrene, 140 g of butadiene, 0.93 g of TMEDA, and 0.45 mmol of n-butyllithium, and stir at 50 °C for 5 hours to conduct a polymerization reaction. Next, while supplying hydrogen gas at a pressure of 0.4 MPa-Gauge, stir for 20 minutes to react with unreacted polymer terminal lithium to form lithium hydride. Set the hydrogen gas supply pressure to 0.7 MPa-Gauge and the reaction temperature to 90 °C, and perform hydrogenation using a catalyst mainly composed of titanocene dichloride. When the absorption of hydrogen reaches the integrated amount corresponding to the target hydrogenation rate, set the reaction temperature to room temperature, return the hydrogen pressure to normal pressure, withdraw from the reaction vessel, and stir and pour the reaction solution into water to remove the solvent by steam stripping to obtain a hydrogenated styrene-butadiene copolymer. The hydrogenation rate of the hydrogenated styrene-butadiene copolymer is 95 mol%, the weight average molecular weight (Mw) is 450,000, the styrene content is 30 mass%, and the butadiene content is 70 mass%.

[0208] Hereinafter, various chemicals used in the production of tires will be collectively described. The chemicals are purified according to established methods as necessary. NR: TSR20 SBR: Production Example 1 above BR: BR1280 manufactured by LG Chem Carbon black: Showblack N550 (N2SA 42 m 2 / g) manufactured by Cabot Japan Co., Ltd. Recycled carbon black: Manufactured by a known thermal decomposition method (a manufacturing method in which waste tires are heated to 650 °C or higher and thermally decomposed) (N2SA 45 m 2 / g) Oil: VIVATEC 400 / 500 (TDAE oil) manufactured by H&R Vegetable oil: Soybean oil manufactured by Fujifilm Wako Pure Chemical Corporation Resin: Petrotac 100V (C5 / C9 resin, softening point: 94 °C, Mw: 3900, Mn: 1200) manufactured by Tosoh Corporation Polyoktenamer: Vestenamer 8012 (Mw 90000) manufactured by Evonik Thermoplastic elastomer: Nipolon Hard 2500 manufactured by Tosoh Corporation Wax: Sunoc wax manufactured by Ouchi Shinsei Chemical Co., Ltd. Antioxidant 1: Nocrack 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd. Antioxidant 2: Nocrack 224 (2,2,4-trimethyl-1,2-dihydroquinoline polymer) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd. Stearic acid: Stearic acid "Tsubaki" manufactured by NOF Corporation Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powder sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator: Nocceler NS (N-tert-butyl-2-benzothiazylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

[0209] <Preparation of test tires> According to the formulation shown in Table 1, using a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd., materials other than sulfur and vulcanization accelerator are kneaded at 150 °C for 5 minutes to obtain a kneaded product. Sulfur and vulcanization accelerator are added to the kneaded product, and it is kneaded at 80 °C for 5 minutes using an open roll to obtain an unvulcanized rubber composition. The unvulcanized rubber composition is formed into the shape of a sidewall, and on a tire molding machine, it is bonded together with other tire members to form an unvulcanized tire, which is vulcanized at 170 °C for 10 minutes to manufacture a test tire (size 205 / 70R15, passenger car tire).

[0210] Assuming test tires obtained from compositions with formulations and specifications changed according to Table 1, the results calculated based on the following evaluation methods are shown in Table 1. Note that the reference comparison example is as follows. Table 1: Comparative Example 2

[0211] (Thermal aging) In accordance with JIS K6257:2010 "Vulcanized Rubber and Thermoplastic Rubber - Method for Determining Heat Aging Characteristics", the test tire (new) is subjected to heat aging at 80°C for 1 week to obtain a heat-aged tire.

[0212] <Elongation at Break EB before and after heat aging> Regarding the new sample (vulcanized rubber composition) collected from the sidewall of the new tire and the heat-aged sample (vulcanized rubber composition) collected from the sidewall of the heat-aged tire, based on JIS K6251:2010, dumbbell-shaped No. 6 test pieces are prepared from the samples, and using these test pieces, a tensile test is carried out in an atmosphere of 25°C to measure the elongation at break EBf (%) of the new product (before heat aging) and the elongation at break EBa (%) after heat aging. The change rate ΔEB (%) of the elongation at break before and after heat aging is calculated by the following formula. ΔEB(%)=(|EBf - EBa|) / EBf×100

[0213] <Handling stability after deterioration> The heat-aged tire is mounted on a vehicle, and the stability of the control when driving on a test course is subjectively evaluated on a 5-point scale (with a full score of 5 points). The evaluation is carried out by 20 test drivers, and the total value is displayed as an index with the evaluation criterion set to 100. The larger the index, the higher the stability of the control, indicating excellent handling stability after deterioration.

[0214]

Table 1

[0215] The present invention (1) is a tire provided with a tire member composed of a rubber composition, The rubber composition is The change rate ΔEB of the elongation at break before and after heat aging is 8.0% or less, It is a tire in which the product of the ΔEB(%) and the thickness Tt (mm) of the tire member is less than 30.

[0216] The present invention (2) is a tire according to the present invention (1), wherein the rubber composition contains recycled carbon black.

[0217] The present invention (3) is a tire according to the present invention (1) or (2), wherein for the rubber composition, the ratio (Cc / ΔEB) of the content Cc (parts by mass) of carbon black to 100 parts by mass of the rubber component and the change rate ΔEB (%) of the elongation at break before and after heat aging exceeds 7.6.

[0218] The present invention (4) is a tire which is any combination of the present inventions (1) to (3), wherein the rubber composition contains vegetable oil.

[0219] The present invention (5) is a tire which is any combination of the present inventions (1) to (4), wherein for the rubber composition, the product (Pc×ΔEB) of the content Pc (parts by mass) of the plasticizer to 100 parts by mass of the rubber component and the change rate ΔEB (%) of the elongation at break before and after heat aging is less than 80.

[0220] The present invention (6) is a tire which is any combination of the present inventions (1) to (5), wherein the rubber composition contains at least one selected from the group consisting of isoprene rubber, butadiene rubber, and styrene-butadiene rubber.

[0221] The present invention (7) is a tire which is any combination of the present inventions (1) to (6), wherein for the rubber composition, the content of styrene-butadiene rubber in 100% by mass of the rubber component is less than 80% by mass.

[0222] The present invention (8) is a tire which is any combination of the present inventions (1) to (7), wherein the rubber composition contains a double bond-containing polymer in a liquid state at 25°C.

[0223] The present invention (9) is a tire which is any combination of the present inventions (1) to (8), wherein the rubber composition contains a thermoplastic elastomer.

[0224] The present invention (10) is a tire in any combination of any one of the present inventions (1) to (9) in which the content rate Pr (mass%) of the plasticizer is 6.5 mass% or less in the rubber composition.

[0225] The present invention (11) is a tire in any combination of any one of the present inventions (1) to (10) in which the ratio (Cc / Tt) of the content Cc (parts by mass) of carbon black to 100 parts by mass of the rubber component in the rubber composition and the thickness Tt (mm) of the tire member exceeds 15.0.

[0226] The present invention (12) is a tire in any combination of any one of the present inventions (1) to (11) in which the ratio (Pc / Tt) of the content Pc (parts by mass) of the plasticizer to 100 parts by mass of the rubber component in the rubber composition and the thickness Tt (mm) of the tire member is less than 3.6.

[0227] The present invention (13) is a tire in any combination of any one of the present inventions (1) to (12) in which the groove depth D of the circumferential groove formed in the tread is 5.5 mm or more and 9.5 mm or less.

[0228] The present invention (14) is a tire in any combination of any one of the present inventions (1) to (13) in which the ratio (ΔEB / D) of the change rate ΔEB (%) of the elongation at break before and after heat aging of the rubber composition and the groove depth D (mm) of the circumferential groove formed in the tread is 0.6 or more and 1.5 or less.

[0229] The present invention (15) is a tire in any combination of any one of the present inventions (1) to (14) in which the tire member is an inner tire member.

Explanation of symbols

[0230] 2 Pneumatic tire 4 Tread 6 Sidewall 8 Wing 10 Clinch 12 Bead 14 Carcass 16 Belt 18 Band 20 Inner liner 22 Chafer 24 Tread surface 26 Groove 28 Base layer 30 Cap layer 32 Core 34 Apex 36 Carcass ply 36a Main part 36b Folded-back part 38 Inner layer 40 Outer layer 42 Main groove 44 Rib CL Equatorial plane of the tire Tt Thickness of the sidewall D Groove depth of the main groove in the circumferential direction

Claims

1. A tire comprising a tire member composed of a rubber composition, wherein the rubber composition, has a change rate ΔEB of elongation at break before and after heat aging of 8.0% or less, and a product (ΔEB × Tt) of the ΔEB (%) and the thickness Tt (mm) of the tire member is less than 30.

2. The tire according to claim 1, wherein the rubber composition contains recycled carbon black.

3. The tire according to claim 1, wherein a ratio (Cc / ΔEB) of the content Cc (parts by mass) of carbon black to 100 parts by mass of the rubber component and the change rate ΔEB (%) of elongation at break before and after heat aging exceeds 7.

6.

4. The tire according to claim 1, wherein the rubber composition contains vegetable oil.

5. The tire according to claim 1, wherein a product (Pc × ΔEB) of the content Pc (parts by mass) of a plasticizer and the change rate ΔEB (%) of elongation at break before and after heat aging with respect to 100 parts by mass of the rubber component is less than 80.

6. The tire according to claim 1, wherein the rubber composition contains at least one selected from the group consisting of isoprene rubber, butadiene rubber, and styrene-butadiene rubber.

7. The tire according to claim 1, wherein the content of styrene-butadiene rubber in 100% by mass of the rubber component is less than 80% by mass.

8. The tire according to claim 1, wherein the rubber composition contains a double bond-containing polymer in a liquid state at 25°C.

9. The tire according to claim 1, wherein the rubber composition contains a thermoplastic elastomer.

10. The tire according to claim 1, wherein the content rate Pr (%) of the plasticizer is 6.5% by mass or less.

11. The tire according to claim 1, wherein the ratio (Cc / Tt) of the content Cc (parts by mass) of carbon black to 100 parts by mass of the rubber component of the rubber composition and the thickness Tt (mm) of the tire member exceeds 15.

0.

12. The tire according to claim 1, wherein the ratio (Pc / Tt) of the content Pc (parts by mass) of the plasticizer to 100 parts by mass of the rubber component of the rubber composition is less than 3.

6.

13. The tire according to claim 1, wherein the groove depth D of the circumferential groove formed in the tread is 5.5 mm or more and 9.5 mm or less.

14. The tire according to claim 1, wherein the ratio (ΔEB / D) of the change rate ΔEB (%) of the elongation at break of the rubber composition before and after heat aging and the groove depth D (mm) of the circumferential groove formed in the tread is 0.6 or more and 1.5 or less.

15. The tire according to claim 1, wherein the tire member is an inner tire member.

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