JP7293870B2 - Rubber composition and tire - Google Patents

Description

The present invention relates to rubber compositions and tires.

Rubber compositions used for tires and the like are required to have performance such as steering stability performance during running and wet grip performance when applied to tires. , performance improvements have been made.

For example, Patent Literature 1 discloses a technique of blending a specific modified diene rubber and a specific silica to provide good tire physical properties.

WO2013/125614

An object of the present invention is to solve the above problems and to provide a rubber composition and a tire that can be controlled to a desired hardness.

The present invention relates to a rubber composition containing a rubber component and a soft magnetic material and satisfying the following formulas (1) and (2).

The soft magnetic material is preferably carbonyl iron powder.
The rubber composition is preferably a tread rubber composition.

The present invention also relates to a tire using said rubber composition.

According to the present invention, it is a rubber composition that contains a rubber component and a soft magnetic material and satisfies the above formulas (1) and (2), so it provides a rubber composition that can be controlled to a desired hardness. .

BRIEF DESCRIPTION OF THE DRAWINGS It is an example of the schematic diagram which shows the mechanism of hardness change of the rubber composition of this invention. It is an example of the schematic diagram which shows the measurement of Young's modulus (E).

[Rubber composition (vulcanized)]
The rubber composition of the present invention contains a rubber component and a soft magnetic material, and satisfies the formulas (1) and (2). Such a rubber composition can control the hardness of the rubber composition by a magnetic field, and can be adjusted to a desired hardness by conditions such as the strength of the magnetic field. In particular, even when a magnetic field is applied and deformation is repeated under load, the change in Young's modulus can be maintained. For example, when applied to a tire, the change in Young's modulus can be maintained by applying a magnetic field.

Although the reason why such effects are obtained is not clear, it is speculated as follows.
The rubber composition satisfies the formula (1), i.e., a rubber composition whose Young's modulus increases by 10% or more when a predetermined magnetic field is applied as compared to the Young's modulus of the rubber composition when no magnetic field is applied. be. For example, by applying a magnetic field from the outside, soft magnetic materials such as iron powder (metal fillers, etc.) are magnetically polarized (functioning like small magnets), and an attractive force acts as a magnetic interaction between the soft magnetic materials. . Since this attractive force suppresses the movement of the soft magnetic material, the rubber becomes hard and deformation is suppressed. That is, since the rubber can be hardened by applying an external magnetic field, the hardness of the rubber can be controlled by the magnetic field. Therefore, for example, when wet (dry road surface), no external magnetic field is applied, and by softening the rubber, good wet grip performance can be imparted. Good steering stability can also be imparted by applying heat and hardening the rubber.

Furthermore, the rubber composition satisfies the formula (2), that is, the change in the acetone extraction amount of the rubber composition after compression under predetermined conditions and the acetone extraction amount before compression is within 10%. is. For example, if a plasticizer (acetone extractable component) such as various oils or liquid polymers is blended into a rubber composition, when a magnetic field is applied, the magnetic bodies inside the rubber will have the necessary viscosity to align in the direction of the magnetic field. This makes it easy to adjust the hardness of the rubber depending on whether or not the magnetic field is applied. If there is little change in the extracted amount of the acetone-extracted component before and after compression, the extracted component can be retained inside the rubber even under conditions where the rubber composition is repeatedly subjected to deformation, so that the rubber can be maintained over time. It is also possible to adjust the hardness of From the above, it is speculated that it is possible to adjust the hardness to a desired value, and that the magnitude of change in Young's modulus can be maintained even when magnetic field application and repeated deformation are performed, especially in a state where there is a load. It is speculated that it can provide excellent steering stability and wet grip performance.

(rubber component)
Examples of rubber components include isoprene rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), Diene rubbers such as styrene-isoprene-butadiene copolymer rubber (SIBR) can be mentioned. The isoprene rubber includes natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, modified IR, and the like. Among these, SBR, BR, and isoprene-based rubber are preferred, and SBR is more preferred, from the viewpoint of imparting performance such as hardness adjustment function, wet grip performance when applied to tires, and steering stability. In addition, a rubber component may be used independently and may be used in combination of 2 or more type.

SBR is not particularly limited, and for example, emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc. can be used.

The SBR content in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 50% by mass or more, still more preferably 70% by mass or more, and particularly preferably 90% by mass or more. By making it more than the lower limit, there is a tendency that good wet grip performance and steering stability can be obtained. The upper limit of the SBR content is not particularly limited, and may be 100% by mass.

The styrene content of SBR is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 25% by mass or more. By making it more than the lower limit, there is a tendency that good wet grip performance can be obtained. Also, the styrene content is preferably 50% by mass or less, more preferably 45% by mass or less. By making it below the upper limit, not only can good steering stability be obtained, but the temperature dependence of grip performance tends to decrease, and stable wet grip performance tends to be obtained during running.
In the present invention, the styrene content of SBR is calculated by H ¹ -NMR measurement.

The vinyl content of SBR (vinyl content in the butadiene component of SBR) is preferably 20% by mass or more, more preferably 25% by mass or more. By making it more than the lower limit, there is a tendency that good wet grip performance can be obtained. The vinyl content is preferably 60% by mass or less, more preferably 55% by mass or less. By making it below the upper limit, there is a tendency to obtain excellent wet grip performance in a wide temperature range.
The vinyl content (1,2-bonded butadiene unit content) can be measured by infrared absorption spectrometry.

As SBR, both non-oil-extended SBR and oil-extended SBR can be used, but oil-extended SBR can be preferably used. Oil-extended SBR is obtained by extending SBR using an extender oil. Thus, the dispersibility of silica can be improved by containing oil-extended SBR that has been oil-extended in advance with an extender oil.

Examples of extender oils used for extending SBR include naphthenic, paraffinic, and aromatic oil-extended oils. As a method of oil extension, for example, a method of adding an extender oil after completion of polymerization, removing the solvent and drying by a conventionally known method, and the like can be mentioned. The amount of extender oil used is preferably 5 to 100 parts by mass, more preferably 10 to 50 parts by mass, and even more preferably 10 to 40 parts by mass based on 100 parts by mass of SBR.

As SBR, modified SBR can be used in addition to non-modified SBR. The modified SBR may be an SBR having a functional group that interacts with a filler such as silica. SBR (end-modified SBR having the above functional group at the end), main chain-modified SBR having the above-mentioned functional group in the main chain, main chain end-modified SBR having the above-mentioned functional group in the main chain and end (for example, the main chain Main chain end modified SBR having the above functional group and at least one end modified with the above modifying agent), or modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule, hydroxyl group and terminal-modified SBR into which an epoxy group is introduced.

Examples of the above functional groups include amino group, amido group, silyl group, alkoxysilyl group, isocyanate group, imino group, imidazole group, urea group, ether group, carbonyl group, oxycarbonyl group, mercapto group, sulfide group, disulfide group, sulfonyl group, sulfinyl group, thiocarbonyl group, ammonium group, imide group, hydrazo group, azo group, diazo group, carboxyl group, nitrile group, pyridyl group, alkoxy group, hydroxyl group, oxy group, epoxy group and the like. . In addition, 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), an alkoxysilyl group ( An alkoxysilyl group having 1 to 6 carbon atoms is preferred.

In the rubber composition, the rubber component is modified with an acrylamide compound represented by the following formula (I) from the viewpoint of imparting performance such as hardness adjustment function, wet grip performance when applied to tires, and steering stability. A modified diene rubber A, a diene rubber modified with a silicon or tin compound represented by the following formula (II) and a modifying compound represented by the following formula (III), or a diene rubber represented by the following formula (III) A blend rubber with modified diene rubber B modified with a modifying compound can be preferably used.

（式中、Ｒ^１は水素又はメチル基を表す。Ｒ^２及びＲ^３はアルキル基を表す。ｎは整数を表す。） The modified diene rubber A is a diene rubber modified with an acrylamide compound represented by the following formula (I). This is a diene rubber in which the ends of the polymer are modified with an acrylamide compound.

(In the formula, R ¹ represents hydrogen or a methyl group. ^{R 2} and R ³ represent alkyl groups. n represents an integer.)

In formula (I), R ² and R ³ are preferably C 1-4 alkyl groups. n is preferably an integer of 2-5.

Specific examples of the acrylamide compounds include N,N-dimethylaminomethylacrylamide, N,N-ethylmethylaminomethylacrylamide, N,N-diethylaminomethylacrylamide, N,N-ethylpropylaminomethylacrylamide, N,N- Dipropylaminomethylacrylamide, N,N-butylpropylaminomethylacrylamide, N,N-dibutylaminomethylacrylamide, N,N-dimethylaminoethylacrylamide, N,N-ethylmethylaminoethylacrylamide, N,N-diethylaminoethyl acrylamide, N,N-ethylpropylaminoethylacrylamide, N,N-dipropylaminoethylacrylamide, N,N-butylpropylaminoethylacrylamide, N,N-dibutylaminoethylacrylamide, N,N-dimethylaminopropylacrylamide, N,N-ethylmethylaminopropylacrylamide, N,N-diethylaminopropylacrylamide, N,N-ethylpropylaminopropylacrylamide, N,N-dipropylaminopropylacrylamide, N,N-butylpropylaminopropylacrylamide, N, N-dibutylaminopropylacrylamide, N,N-dimethylaminobutylacrylamide, N,N-ethylmethylaminobutylacrylamide, N,N-diethylaminobutylacrylamide, N,N-ethylpropylaminobutylacrylamide, N,N-dipropyl aminobutylacrylamide, N,N-butylpropylaminobutylacrylamide, N,N-dibutylaminobutylacrylamide; and methacrylamides thereof. Among them, N,N-dimethylaminopropylacrylamide is preferred.

（式中、Ｒはアルキル基、アルケニル基、シクロアルケニル基又は芳香族炭化水素基を表す。Ｍはケイ素又はスズを表す。Ｘはハロゲンを表す。ａは０～２の整数を表す。ｂは２～４の整数を表す。）

（式中、Ｒ^４～Ｒ^６は同一若しくは異なって炭素数が１～８のアルキル基を表す。Ｒ^７～Ｒ^１２は同一若しくは異なって炭素数が１～８のアルコキシ基又はアルキル基を表す。ｐ～ｒは同一若しくは異なって１～８の整数を表す。） The modified diene rubber B is a diene rubber modified with a silicon or tin compound represented by the following formula (II) and a modifying compound represented by the following formula (III), or a diene rubber represented by the following formula (III) It is a diene rubber modified with a modifying compound. The former is a diene-based rubber in which the terminal of a polymer coupled with a silicon or tin compound is modified with a modifying compound, and the latter is a diene-based rubber in which the terminal of the polymer is modified with a modifying compound.

(Wherein, R represents an alkyl group, an alkenyl group, a cycloalkenyl group or an aromatic hydrocarbon group. M represents silicon or tin. X represents a halogen. a represents an integer of 0 to 2. b represents represents an integer from 2 to 4.)

(In the formula, R ⁴ to R ⁶ are the same or different and represent an alkyl group having 1 to 8 carbon atoms. R ⁷ to R ¹² are the same or different and represent an alkoxy group or an alkyl group having 1 to 8 carbon atoms. .p to r are the same or different and represent an integer of 1 to 8.)

The silicon compound and tin compound represented by formula (II) function as a coupling agent for the diene rubber. Silicon compounds include tetrachlorosilicon, tetrabromosilicon, methyltrichlorosilicon, butyltrichlorosilicon, dichlorosilicon, bistrichlorosilylsilicon, and the like. Tin compounds include tetrachlorotin, tetrabromotin, methyltrichlorotin, butyltrichlorotin, dichlorotin, bistrichlorosilyltin, and the like.

In formula (III), R ⁴ to R ⁶ are preferably methyl group, ethyl group, propyl group or butyl group, R ⁷ to R ¹² are preferably methoxy group, ethoxy group, propoxy group or butoxy group, p to r are Integers from 2 to 5 are preferred.

Specific examples of modified compounds represented by formula (III) include 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate and 1,3,5-tris(3-triethoxysilylpropyl)isocyanate. nurate, 1,3,5-tris(3-tripropoxysilylpropyl)isocyanurate, 1,3,5-tris(3-tributoxysilylpropyl)isocyanurate and the like. Among them, 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate is preferred.

The modified diene rubbers A and B can be obtained, for example, by preparing the rubbers A and B separately and then mixing them. In this case, the modified diene-based rubbers A and B can be prepared by the following manufacturing methods.

The modified diene rubber A is an active conjugated diene polymer having an alkali metal terminal obtained by polymerizing a conjugated diene monomer or a conjugated diene monomer and an aromatic vinyl monomer in a hydrocarbon solvent using an alkali metal catalyst. It can be prepared by reacting the combination with an acrylamide compound represented by the above formula (I).

Conjugated diene monomers include 1,3-butadiene, isoprene, 1,3-pentadiene (piperine), 2,3-dimethyl-1,3-butadiene, 1,3-hexadiene, and the like. Among them, 1,3-butadiene and isoprene are preferable from the viewpoint of physical properties of the resulting polymer and availability in industrial practice.

Examples of aromatic vinyl monomers include styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene and divinylnaphthalene. Of these, styrene is preferred from the viewpoint of the physical properties of the resulting polymer and availability in industrial practice.

The hydrocarbon solvent is not particularly limited as long as it does not deactivate the alkali metal catalyst, and examples thereof include aliphatic hydrocarbons, aromatic hydrocarbons, and alicyclic hydrocarbons. Specific examples include propane having 3 to 12 carbon atoms, n-butane, iso-butane, n-pentane, iso-pentane, n-hexane, cyclohexane, benzene, toluene and xylene.

Alkali metal catalysts include metals such as lithium, sodium, potassium, rubidium and cesium, and hydrocarbon compounds containing these metals. Preferred alkali metal catalysts include lithium or sodium compounds having 2 to 20 carbon atoms, specifically ethyllithium, n-propyllithium, iso-propyllithium, n-butyllithium, sec-butyl lithium, t-octyllithium, n-decyllithium, phenyllithium and the like.

As a monomer for polymerization, a conjugated diene monomer alone may be used, or a conjugated diene monomer and an aromatic vinyl monomer may be used in combination. When a conjugated diene monomer and an aromatic vinyl monomer are used in combination, the ratio of the two is preferably 50/50 to 90/10, more preferably 55/45 to 85/15 in terms of mass ratio of conjugated diene monomer/aromatic vinyl monomer. is.

In the polymerization, it is possible to use commonly used substances such as an alkali metal catalyst, a hydrocarbon solvent, a randomizer, and a vinyl bond content modifier for conjugated diene units, and the method for producing the polymer is not particularly limited. .

In order to adjust the vinyl bond content of the conjugated diene portion, various compounds can be used as the Lewis basic compound, but ether compounds or tertiary amines are preferred in terms of industrial availability. . Ether compounds include cyclic ethers such as tetrahydrofuran, tetrahydropyran and 1,4-dioxane; aliphatic monoethers such as diethyl ether and dibutyl ether; and aliphatic diethers such as ethylene glycol dimethyl ether. Moreover, triethylamine, tripropylamine, etc. are mentioned as a tertiary amine compound.

The amount used when adding the acrylamide compound to the active conjugated diene polymer having an alkali metal terminal to produce the modified diene rubber A is the same as the alkali metal catalyst used when adding the alkali metal. It is usually 0.05 to 10 mol, preferably 0.2 to 2 mol, per 1 mol.

Since the reaction between the acrylamide compound and the active conjugated diene polymer having an alkali metal terminal occurs rapidly, the reaction temperature and reaction time can be selected in a wide range. It's time. In the reaction, the active conjugated diene-based polymer and the acrylamide compound are brought into contact. For example, a diene-based polymer is prepared using an alkali metal catalyst, and the acrylamide compound is added to the polymer solution. A method of adding a fixed amount and the like can be mentioned.

After completion of the reaction, the coagulation method used in the production of rubber by ordinary solution polymerization, such as addition of a coagulant from the reaction solvent or steam coagulation, can be used as it is, and the coagulation temperature is not limited at all. The resulting modified diene rubber A has an acrylamide compound introduced at the molecular end.

On the other hand, the modified diene rubber B is an active conjugated diene having an alkali metal terminal obtained by polymerizing a conjugated diene monomer or a conjugated diene monomer and an aromatic vinyl monomer in a hydrocarbon solvent using an alkali metal catalyst. (a) the silicon or tin compound (coupling agent) represented by the above formula (II), and then reacting the modified compound represented by the above formula (III) with the system polymer, or ( b) can be prepared by reacting a modified compound represented by the above formula (III).

An active conjugated diene-based polymer having an alkali metal terminal is obtained in the same manner as the modified diene-based rubber A is prepared. In (a) above, the silicon or tin compound is usually used in the range of 0.01 to 0.4 equivalents of halogen atoms per equivalent of terminal alkali metal atoms of the active conjugated diene polymer. The coupling reaction is usually carried out in the range of 20°C to 100°C. Furthermore, the reaction of the modified compound in (a) and (b) above can be carried out in the same manner as the reaction of the acrylamide compound described above. The resulting modified diene rubber B has a modified compound introduced at the molecular end.

The modified diene rubbers A and B are preferably a mixture obtained by preparing the rubbers A and B in one batch. In this case, for example, the mixture is prepared by reacting the active conjugated diene-based polymer having an alkali metal terminal with the acrylamide compound, the silicon or tin compound and the modified compound, or the modified compound. can.

Specifically, an active conjugated diene-based polymer having an alkali metal terminal is prepared by the same method as described above, (c) an acrylamide compound is added to the polymer solution, and then a silicon or tin compound is added as necessary. (coupling agent) and then adding a modifying compound, or (d) simultaneously adding an acrylamide compound, a modifying compound, and optionally a silicon or tin compound to the polymer solution. The above mixture is obtained.

In this case, the reaction with the acrylamide compound and modified compound and the coupling reaction can be carried out in the same manner as described above. The resulting mixture contains a modified diene rubber A having an acrylamide compound introduced at the molecular end and a modified diene rubber B having a modifying compound introduced at the molecular end.

The blend of the modified diene rubbers A and B in the present invention having a weight average molecular weight in a specific range is prepared by adding a conjugated diene monomer or a conjugated diene monomer and an aromatic vinyl monomer to an alkali metal Also included are those containing a mixture obtained by reacting two or more modifiers with an active conjugated diene-based polymer having an alkali metal terminal obtained by polymerization using a system catalyst.

That is, in the above description, the mixture obtained by reacting the active conjugated diene-based polymer with a specific modifier was described, but not limited to such a form, any modifier of two or more A mixture obtained by reacting is also included in the present invention. The mixture can be obtained by, for example, reacting an active conjugated diene-based polymer having an alkali metal terminal prepared in the same manner as described above with two or more conventionally known terminal modifiers in one batch.

The modified diene rubbers A and B used in the rubber composition of the present invention have a weight-average molecular weight of both rubbers as a whole (weight-average molecular weight measured for the entire composition comprising the modified diene rubbers A and B) of 300,000. or more, preferably 500,000 or more, more preferably 600,000 or more. The (Mw) is 1,400,000 or less, preferably 1,200,000 or less, more preferably 1,000,000 or less.

The overall molecular weight distribution (Mw/Mn) of the modified diene rubbers A and B is preferably 4 or less, more preferably 3.5 or less, and even more preferably 3 or less.

In this specification, the number average molecular weight (Mn) and weight average molecular weight (Mw) of both rubbers and the aromatic vinyl polymer described later are determined by gel permeation chromatography (GPC) (GPC manufactured by Tosoh Corporation). 8000 series, detector: differential refractometer, column: TSKGEL SUPER MALTPORE HZ-M (manufactured by Tosoh Corporation).

As the modified diene rubbers A and B, modified butadiene rubber (modified BR) and modified styrene butadiene rubber (modified SBR) are preferable, and modified SBR is more preferable, from the viewpoint of improving the performance balance.

When the modified diene rubbers A and B are modified SBR, the total vinyl bond content in the butadiene portion of the rubbers A and B is preferably 20% by mass or more, more preferably 25% by mass or more. Also, the vinyl bond content is preferably 60% by mass or less, more preferably 55% by mass or less.

When the modified diene rubbers A and B are modified SBR, the total styrene content of the rubbers A and B is preferably 10% by mass or more, more preferably 15% by mass or more, and still more preferably 25% by mass or more. . Also, the styrene content is preferably 50% by mass or less, more preferably 45% by mass or less.

In the rubber composition, the compounding ratio (A/B (mass ratio)) of the modified diene rubbers A and B is preferably 5/95 to 95/5, more preferably 10/90 to 90/10, and still more preferably is between 20/80 and 80/20.

In the rubber composition, the total content of the modified diene rubbers A and B in 100% by mass of the rubber component is preferably 2% by mass or more, more preferably 5% by mass or more, and still more preferably 10% by mass or more. The upper limit of the total content is not particularly limited, and may be 100% by mass.

As a commercially available rubber component such as SBR, for example, rubber such as SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Co., Ltd., Asahi Kasei Co., Ltd., Nippon Zeon Co., etc. can be used.

(soft magnetic material)
The soft magnetic material is not particularly limited, and known inorganic soft magnetic materials and organic soft magnetic materials can be used. Specifically, iron, carbonyl iron, iron nitride, nickel, cobalt, Fe—Ni alloy, Fe—Co alloy, Fe—Cr alloy, Fe—Si alloy, Fe—Al alloy, Fe—Cr—Si alloy, Fe - Iron alloys such as Cr-Al alloys and Fe-Si-Al alloys, Mg-Zn ferrites, Mn-Zn ferrites, Mn-Mg ferrites, Cu-Zn ferrites, Mg-Mn-Sr ferrites, Ni-Zn ferrites, etc. Examples include materials such as ferrite-based substances. Among them, carbonyl iron (carbonyl iron powder) is preferable from the viewpoint of control of magnetic force. Carbonyl iron powder is a material obtained by removing CO by vaporizing and decomposing carbonyl iron (Fe(CO) ₅ ).

In the rubber composition, the content of the soft magnetic material is preferably 100 parts by mass or more, more preferably 200 parts by mass or more, and still more preferably 250 parts by mass or more with respect to 100 parts by mass of the rubber component. By making it more than the lower limit, there is a tendency that the Young's modulus can be made sufficiently high when a magnetic force is applied. Although the upper limit of the content is not particularly limited, it is preferably 1000 parts by mass or less, more preferably 700 parts by mass or less, and still more preferably 550 parts by mass or less. By making it below the upper limit, there is a tendency that good dispersibility can be obtained.

The soft magnetic material preferably has an average particle size of 2 to 20 μm, more preferably 5 to 15 μm. The average particle size is determined by measuring the 50% by mass particle size by a laser diffraction light scattering method. As a measuring instrument, for example, a laser diffraction/scattering particle distribution analyzer LA-950S2 manufactured by Horiba Ltd. can be used.

すなわち、磁束密度３００ｍＴ（ミリテスラ）の磁場を印加した状態でのゴム組成物のヤング率Ｅ_３００／磁場を印加しない状態（非印加状態）でのゴム組成物のヤング率Ｅ_０が１．１０以上である。ゴムの硬さ調整の観点から、Ｅ_３００／Ｅ_０≧１．１２が好ましく、Ｅ_３００／Ｅ_０≧１．１４がより好ましく、Ｅ_３００／Ｅ_０≧１．１６が更に好ましい。上限は特に限定されないが、Ｅ_３００／Ｅ_０≦２．００が好ましく、Ｅ_３００／Ｅ_０≦１．７０がより好ましく、Ｅ_３００／Ｅ_０≦１．５０が更に好ましい。 The rubber composition (vulcanized) satisfies the following formula (1).

That is, the Young's modulus E ₃₀₀ of the rubber composition in the state of applying a magnetic field with a magnetic flux density of 300 mT (millitesla) / the Young's modulus E ₀ of the rubber composition in the state of not applying a magnetic field (non-applied state) is 1.10 or more. is. From the viewpoint of rubber hardness adjustment, E ₃₀₀ /E ₀ ≧1.12 is preferred, E ₃₀₀ /E ₀ ≧1.14 is more preferred, and E ₃₀₀ /E ₀ ≧1.16 is even more preferred. Although the upper limit is not particularly limited, E ₃₀₀ /E ₀ ≤ 2.00 is preferable, E ₃₀₀ /E ₀ ≤ 1.70 is more preferable, and E ₃₀₀ /E ₀ ≤ 1.50 is even more preferable.

From the viewpoint of rubber hardness adjustment, E ₃₀₀ (Young's modulus of the rubber composition under application of a magnetic field of 300 mT) is preferably ≧22.0 MPa, more preferably E ₃₀₀ ≧24.0 MPa, and E ₃₀₀ ≧25.0 MPa. More preferred. Although the upper limit is not particularly limited, E ₃₀₀ ≤ 40.0 MPa is preferable, E ₃₀₀ ≤ 35.0 MPa is more preferable, and E ₃₀₀ ≤ 32.0 MPa is even more preferable.

From the viewpoint of rubber physical properties, E ₀ (Young's modulus of the rubber composition in a non-applied state) is preferably ≧20.0 MPa, more preferably E ₀ ≧21.0 MPa, and even more preferably E ₀ ≧22.0 MPa. Although the upper limit is not particularly limited, E ₀ ≤ 35.0 MPa is preferable, E ₀ ≤ 30.0 MPa is more preferable, and E ₀ ≤ 28.0 MPa is even more preferable.

Here, E ₃₀₀ and E ₀ can be adjusted depending on the types and amounts of chemicals (especially rubber components and fillers) blended in the rubber composition. For example, E ₃₀₀ and E ₀ can be adjusted by appropriately adjusting the type and amount of the soft magnetic material, and increasing the blending amount tends to increase E ₃₀₀ and E ₀ , especially E ₃₀₀ . Also, E ₃₀₀ and E ₀ tend to increase when a high-molecular-weight rubber component is used or when the amount of filler is increased, and when a plasticizer such as oil or liquid polymer is added, they tend to decrease.

Methods for satisfying E ₃₀₀ /E ₀ ≧1.10 include (a) a method of adjusting the type and amount of the soft magnetic material, and (b) the type of plasticizer (acetone extractable component) such as various oils and liquid polymers. (c) a method of using a styrene-butadiene rubber as a rubber component, (d) a method of using a modified rubber (e) a method using a high-molecular-weight rubber component; (f) a method of adjusting the type and amount of various fillers;

The Young's modulus E ₃₀₀ and E ₀ can be measured by the method described in Examples below. For example, the application of a magnetic field with a magnetic flux density of 300 mT can be performed by applying an alternating magnetic field, and in that case, the frequency of 50 Hz, 60 Hz, etc. and the application time can be appropriately selected. The direction in which the magnetic field is applied may be selected from the direction in which the soft magnetic material is desired to be oriented or the direction in which the soft magnetic material is already oriented. Specifically, a method of applying voltage by the method described in Examples below is adopted.

すなわち、４００ＭＰａで１分間圧縮した後のゴム組成物のアセトン抽出量ＡＥ_４００／当該圧縮前のゴム組成物のアセトン抽出量ＡＥ_０が０．９０～１．１０である。磁場を印加した際のゴム内部での軟磁性材料の配向性の観点から、０．９２≦ＡＥ_４００／ＡＥ_０≦１．０８が好ましく、０．９３≦ＡＥ_４００／ＡＥ_０≦１．０７がより好ましく、０．９４≦ＡＥ_４００／ＡＥ_０≦１．０６が更に好ましい。 The rubber composition (vulcanized) satisfies the following formula (2).

That is, the acetone extraction amount AE ₄₀₀ of the rubber composition after compression for 1 minute at 400 MPa/acetone extraction amount AE ₀ of the rubber composition before compression is 0.90 to 1.10. From the viewpoint of the orientation of the soft magnetic material inside the rubber when a magnetic field is applied, 0.92 ≤ AE ₄₀₀ /AE ₀ ≤ 1.08 is preferable, and 0.93 ≤ AE ₄₀₀ /AE ₀ ≤ 1.07. More preferably, 0.94≦AE ₄₀₀ /AE ₀ ≦1.06.

AE ₄₀₀ ≧40.0% by mass is preferable, AE ₄₀₀ ≧44.0% by mass is more preferable, and AE ₄₀₀ ≧46 from the viewpoint of the orientation of the soft magnetic material inside the rubber when a magnetic field is applied and the physical properties of the rubber. 0 mass % is more preferred. Although the upper limit is not particularly limited, _AE400≤60.0 % by mass is preferable, _AE400≤55.0 % by mass is more preferable, and _AE400≤53.0 % by mass is even more preferable.

AE _{0 ≧40.0% by mass is preferable, AE 0 ≧} 44.0% by mass is more preferable, and AE ₀ ≧46 from the viewpoint of the orientation of the soft magnetic material inside the rubber when a magnetic field is applied and the physical properties of the rubber. 0 mass % is more preferred. Although the upper limit is not particularly limited, AE ₀ ≦60.0% by mass is preferable, AE ₀ ≦55.0% by mass is more preferable, and AE ₀ ≦53.0% by mass is even more preferable.

Here, AE ₄₀₀ and AE ₀ can be adjusted depending on the type and amount of chemicals (in particular, various oils, plasticizers such as liquid polymers (acetone extractable components)) blended in the rubber composition. For example, AE ₄₀₀ and AE ₀ can be adjusted by appropriately adjusting the types and amounts of oil and plasticizer, and AE ₄₀₀ and AE ₀ tend to increase as the compounding amount increases.

Methods for satisfying 0.90 ≤ AE ₄₀₀ /AE ₀ ≤ 1.10 include (a) a method of adjusting the type and amount of plasticizers (acetone extractable components) such as various oils and liquid polymers (farnesene-based polymers, A method using a crosslinkable softening agent such as a liquid diene polymer, etc.), (b) a method using a plasticizer highly compatible with the rubber component (a method using an oil having a SP value close to that of the rubber component, etc.), ( c) a method using styrene-butadiene rubber as the rubber component, (d) a method using a modified rubber, and (e) a method using a high-molecular-weight rubber component, and the like can be used alone or in combination.

The acetone extraction amount AE can be measured by a method for measuring the acetone extraction amount based on JIS K 6229:2015, specifically by the method described in Examples below.

FIG. 1 is an example of a schematic diagram showing a hardness change mechanism of a rubber composition containing the rubber component and the soft magnetic material described above and satisfying the formulas (1) and (2). Since the rubber composition 1a to which no magnetic field is applied has no magnetic attraction between the soft magnetic materials 2, the hardness of the rubber is soft (does not change), while the magnetic field is applied by the magnetic force (magnetic field) 3. In the rubber composition 1b in which there is a magnetic attraction between the soft magnetic materials 2, the movement of the soft magnetic material 2 is suppressed by the attraction, and the rubber becomes hard. Such a hardness adjustment function can provide steering stability in dry conditions and wet grip performance.

(Plasticizer)
From the viewpoint of the orientation of the soft magnetic material inside the rubber, the rubber composition preferably contains a plasticizer (acetone extractable component) such as oil or liquid polymer.

The content of the oil is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, and even more preferably 40 parts by mass or more from the viewpoint of wet grip performance and the like, based on 100 parts by mass of the rubber component. From the viewpoint of steering stability and the like, the upper limit is preferably 90 parts by mass or less, more preferably 70 parts by mass or less, and even more preferably 65 parts by mass or less.
The content of oil also includes the amount of oil contained in the rubber (oil-extended rubber).

Oils include, for example, process oils, vegetable oils, or mixtures thereof. As the process oil, for example, paraffinic process oil, aromatic process oil, naphthenic process oil, etc. can be used. Vegetable oils 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. These may be used alone or in combination of two or more. Among them, from the viewpoint of compatibility with rubber components such as SBR, process oils are preferable, and aromatic process oils are more preferable.

As oil, for example, Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Co., Ltd., Orisoi Co., Ltd., H&R, Toyokuni Oil Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kosan Co., Ltd. etc. products can be used.

A liquid polymer is a polymer that is in a liquid state at room temperature (25° C.). Examples of liquid polymers include farnesene-based polymers and liquid diene-based polymers. Among them, farnesene-based polymers and the like can be preferably used from the viewpoint of wet grip performance and the like.

A farnesene-based polymer is a polymer obtained by polymerizing farnesene, and has structural units based on farnesene. Farnesene includes 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, which has the following structure, is preferred.

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

Vinyl monomers include styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 4-tert-butylstyrene, 5- t-butyl-2-methylstyrene, vinylethylbenzene, divinylbenzene, trivinylbenzene, divinylnaphthalene, tert-butoxystyrene, vinylbenzyldimethylamine, (4-vinylbenzyl)dimethylaminoethyl ether, N,N-dimethylaminoethyl styrene, N,N-dimethylaminomethylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, 2-t-butylstyrene, 3-t-butylstyrene, 4-t-butylstyrene, vinylxylene, Examples include aromatic vinyl compounds such as vinylnaphthalene, vinyltoluene, vinylpyridine, diphenylethylene, and tertiary amino group-containing diphenylethylene, and conjugated diene compounds such as butadiene and isoprene. These may be used individually by 1 type, and may use 2 or more types together. Among them, butadiene is preferred. That is, the farnesene-vinyl monomer copolymer is preferably a copolymer of farnesene and butadiene (farnesene-butadiene copolymer).

A liquid farnesene-based polymer can be suitably used as the farnesene-based polymer. The liquid farnesene-based polymer is a farnesene-based polymer that is liquid at room temperature (25° C.) and has a weight average molecular weight (Mw) of 3,000 to 300,000. The Mw of the liquid farnesene polymer is preferably 8,000 or more, more preferably 10,000 or more, and is preferably 100,000 or less, more preferably 60,000 or less, and still more preferably 50,000 or less.

The glass transition temperature (Tg) of the farnesene-based polymer is preferably −100° C. or higher, more preferably −78° C. or higher, and preferably −10° C. or lower, more preferably −30° C. or lower, further preferably − 54°C or less. Within the above range, the effects of the present invention tend to be obtained more favorably.
In addition, Tg is a value measured according to JIS-K7121:1987 using a differential scanning calorimeter (Q200) manufactured by TA Instruments Japan Co., Ltd. under the condition of a temperature increase rate of 10 ° C./min. .

The melt viscosity of the farnesene-based polymer is preferably 0.1 Pa·s or more, more preferably 0.7 Pa·s or more, and preferably 500 Pa·s or less, more preferably 100 Pa·s or less, and still more preferably 13 Pa·s. s or less. Within the above range, the effects of the present invention tend to be obtained more favorably.
The melt viscosity is a value measured at 38°C using a Brookfield viscometer (manufactured by BROOKFIELD ENGINEERING LABS. INC.).

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

The content of the farnesene polymer is preferably 5 parts by mass or more, more preferably 15 parts by mass or more, still more preferably 25 parts by mass or more, and preferably 70 parts by mass or less with respect to 100 parts by mass of the rubber component. , more preferably 50 parts by mass or less, and still more preferably 45 parts by mass or less. When it is within the above range, there is a tendency that good blendability of the soft magnetic material can be obtained by applying a magnetic field.

As the farnesene-based polymer, for example, products of Kuraray Co., Ltd. can be used.

3. The liquid diene polymer preferably has a polystyrene equivalent weight average molecular weight (Mw) of 1.0×10 ³ to 2.0×10 ⁵ as measured by gel permeation chromatography (GPC). It is more preferably 0×10 ³ to 1.5×10 ⁴ .
In addition, in this specification, Mw of a liquid diene polymer is a polystyrene conversion value measured by gel permeation chromatography (GPC).

Liquid diene-based polymers include liquid styrene-butadiene copolymer (liquid SBR), liquid butadiene polymer (liquid BR), liquid isoprene polymer (liquid IR), liquid styrene-isoprene copolymer (liquid SIR), and the like. be done.

The content of the liquid polymer (the total content of the liquid farnesene-based polymer, the liquid diene-based polymer, etc.) is preferably 5 parts by mass or more, more preferably 15 parts by mass or more, and still more preferably 100 parts by mass of the rubber component. is 25 parts by mass or more, preferably 70 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 45 parts by mass or less. When it is within the above range, there is a tendency that good blendability of the soft magnetic material can be obtained by applying a magnetic field.

(other fillers)
Examples of fillers other than soft magnetic materials that can be used in the rubber composition include those known in the rubber field, such as silica, carbon black, calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, and mica. . Among them, silica and carbon black are preferable.

Examples of silica used in the rubber composition include dry silica (anhydrous silica) and wet silica (hydrous silica). Among them, wet-process silica is preferable because it has many silanol groups.

The silica content is preferably 30 parts by mass or more, more preferably 80 parts by mass or more, relative to 100 parts by mass of the rubber component. By making it more than the lower limit, there is a tendency that good steering stability and wet grip performance can be obtained. Although the upper limit of the content is not particularly limited, it is preferably 150 parts by mass or less, more preferably 130 parts by mass or less, and still more preferably 120 parts by mass or less. By making it below the upper limit, there is a tendency that good dispersibility can be obtained.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 80 m ² /g or more, more preferably 120 m ² /g or more, still more preferably 150 m ² /g or more. By making it more than the lower limit, there is a tendency that good wet grip performance and steering stability can be obtained. The N ₂ SA of silica is preferably 250 m ² /g or less, more preferably 220 m ² /g or less, and even more preferably 200 m ² /g or less. By making it below the upper limit, there is a tendency that good dispersibility can be obtained.
The N ₂ SA of silica is a value measured by the BET method according to ASTM D3037-93.

As silica, for example, products of Degussa, Rhodia, Tosoh Silica, Solvay Japan, Tokuyama, etc. can be used.

The tread rubber composition preferably contains a silane coupling agent together with silica.
The silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, Bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (2-triethoxysilylethyl) trisulfide, 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- sulfides such as triethoxysilylpropyl methacrylate monosulfide; mercaptos such as 3-mercaptopropyltrimethoxysilane and 2-mercaptoethyltriethoxysilane; vinyls such as vinyltriethoxysilane and vinyltrimethoxysilane; Amino compounds such as propyltriethoxysilane and 3-aminopropyltrimethoxysilane, glycidoxy compounds such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane, 3-nitropropyltrimethoxysilane, Nitro-based agents such as 3-nitropropyltriethoxysilane and chloro-based agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane can be mentioned. Commercially available products such as Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Dow Corning Toray Co., Ltd., and the like can be used. These may be used alone or in combination of two or more. Among them, sulfide-based and mercapto-based silane coupling agents are preferred.

When a silane coupling agent is contained, the content of the silane coupling agent is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and preferably 20 parts by mass with respect to 100 parts by mass of silica. Below, more preferably 15 mass parts or less.

Carbon black that can be used in the rubber composition includes GPF, FEF, HAF, ISAF, SAF and the like, but is not particularly limited. Commercially available products include Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Co., Ltd., Lion Corporation, Shin Nikka Carbon Co., Ltd., and Columbia Carbon Co., Ltd. can. By blending carbon black, reinforcing properties are obtained, and abrasion resistance and the like are remarkably improved.

The content of carbon black is preferably 1 part by mass or more, more preferably 10 parts by mass or more with respect to 100 parts by mass of the rubber component. By setting it to the lower limit or more, there is a tendency that the effect of blending carbon black can be obtained. Also, the content of the carbon black is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 60 parts by mass or less. By making it below the upper limit, there is a tendency that good dispersibility can be obtained.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 80 m ² /g or more, more preferably 100 m ² /g or more, still more preferably 105 m ² /g or more. If it is at least the lower limit, there is a tendency that good reinforcing properties can be obtained. Although the upper limit of N ₂ SA of carbon black is not particularly limited, it is preferably 180 m ² /g or less, more preferably 150 m ² /g or less, still more preferably 130 m ² /g or less.
The nitrogen adsorption specific surface area of carbon black is obtained by method A of JIS K6217.

(other ingredients)
The rubber composition may contain wax.
The wax is not particularly limited, and includes petroleum waxes such as paraffin wax and microcrystalline wax; natural waxes such as plant waxes and animal waxes; synthetic waxes such as polymers of ethylene and propylene. These may be used alone or in combination of two or more. Among them, petroleum waxes are preferred, and paraffin waxes are more preferred.

As the wax, for example, products of Ouchi Shinko Kagaku Kogyo Co., Ltd., Nippon Seiro Co., Ltd., Seiko Kagaku Co., Ltd., etc. can be used.

When wax is contained, the content is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, and preferably 20 parts by mass or less, based on 100 parts by mass of the rubber component. More preferably, it is 10 parts by mass or less.

The rubber composition may contain an antioxidant.
Examples of anti-aging agents 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; -Isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, etc. p-phenylenediamine-based antioxidants; quinoline-based antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; 2,6-di-t-butyl-4-methylphenol, Monophenol anti-aging agents such as styrenated phenol; inhibitors and the like. These may be used alone or in combination of two or more. Among them, p-phenylenediamine antioxidants and quinoline antioxidants are preferred.

As the anti-aging agent, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Kagaku Kogyo Co., Ltd., Flexis, etc. can be used, for example.

When an antioxidant is contained, its content is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 10 parts by mass or less, with respect to 100 parts by mass of the rubber component. More preferably, it is 5 parts by mass or less.

The rubber composition may contain stearic acid.
Conventionally known stearic acid can be used, for example, products of NOF Corporation, NOF, Kao Corporation, Fuji Film Wako Pure Chemical Industries, Ltd., Chiba Fatty Acids Co., Ltd. can be used.

When stearic acid is contained, the content is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 10 parts by mass or less, or more, relative to 100 parts by mass of the rubber component. It is preferably 5 parts by mass or less.

The rubber composition may contain zinc oxide.
As the zinc oxide, conventionally known ones can be used, for example, products of Mitsui Kinzoku Mining Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. can be used.

When zinc oxide is contained, the content is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 10 parts by mass or less, or more, relative to 100 parts by mass of the rubber component. It is preferably 5 parts by mass or less.

The rubber composition preferably contains sulfur.
Sulfur includes powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur and the like commonly used in the rubber industry. These may be used alone or in combination of two or more.

As sulfur, for example, products of Tsurumi Chemical Industry Co., Ltd., Karuizawa Io Co., Ltd., Shikoku Kasei Kogyo Co., Ltd., Flexis Co., Ltd., Nippon Kantan Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used.

When sulfur is contained, the content is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and preferably 10 parts by mass or less, based on 100 parts by mass of the rubber component. More preferably 5 parts by mass or less, still more preferably 3 parts by mass or less.

The rubber composition preferably contains a vulcanization accelerator.
Vulcanization accelerators include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiazylsulfenamide; tetramethylthiuram disulfide (TMTD ), tetrabenzyl thiuram disulfide (TBzTD), tetrakis (2-ethylhexyl) thiuram disulfide (TOT-N) and other thiuram vulcanization accelerators; N-cyclohexyl-2-benzothiazolesulfenamide, Nt-butyl- 2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N,N'-diisopropyl-2-benzothiazolesulfenamide, etc. 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 vulcanization accelerators and guanidine-based vulcanization accelerators are preferred.

When a vulcanization accelerator is contained, its content is preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more, and preferably 10 parts by mass with respect to 100 parts by mass of the rubber component. parts or less, more preferably 7 parts by mass or less.

In addition to the above components, the rubber composition may further contain other compounding agents commonly used in the tire industry (such as organic cross-linking agents). The content of these compounding agents is preferably 0.1 to 200 parts by mass with respect to 100 parts by mass of the rubber component.

[Method for producing rubber composition (vulcanized)]
The rubber composition (vulcanized) can be produced, for example, by kneading each of the above components using a rubber kneading device such as an open roll or Banbury mixer, followed by vulcanization. During production, the unvulcanized rubber composition obtained by kneading is vulcanized as it is. First, a magnetic field is applied to the unvulcanized rubber composition to orient the soft magnetic material, and then vulcanized. method.

In the case of a manufacturing method in which an arrangement operation is performed first, for example, the following manufacturing method can be used.
First, each of the above components is kneaded using a rubber kneading device such as an open roll or Banbury mixer to prepare an unvulcanized rubber composition. At this point, the soft magnetic material is randomly distributed inside the unvulcanized rubber composition. Next, a magnetic field is applied to the unvulcanized rubber composition using an electromagnet or the like. By applying a magnetic field, the soft magnetic materials are aligned in the direction of the magnetic field to form columnar clusters. The magnetic field application conditions are not particularly limited, and may be appropriately set according to the orientation state of the soft magnetic material. For example, conditions of magnetic flux density of 50 mT to 1 T and application time of 180 minutes or less (15 to 120 minutes, etc.) can be adopted. After the magnetic field is applied, the unvulcanized rubber composition is vulcanized, and during vulcanization, the soft magnetic material is aligned inside the rubber to maintain the state in which columnar clusters are formed. As a result, a rubber composition (vulcanized) in which the soft magnetic material is dispersed in the rubber and aligned (orientated) in the same direction can be produced. In addition, there is a tendency that the Young's modulus is greatly improved by applying a magnetic field when the alignment work is performed compared to when the alignment work is not performed.

As kneading conditions for producing the unvulcanized rubber composition, in the base kneading step for kneading additives other than the vulcanizing agent and the vulcanization accelerator, the kneading temperature is usually 100 to 180° C., preferably 120 to 170°C. In the finishing kneading step of kneading the vulcanizing agent and the vulcanization accelerator, the kneading temperature is usually 120°C or lower, preferably 85 to 110°C. As for the vulcanization conditions of the unvulcanized rubber composition in which the vulcanizing agent and the vulcanization accelerator are kneaded, the vulcanization temperature is usually 140 to 190°C, preferably 150 to 185°C.

The rubber composition is preferably used for treads (cap treads), but is also used for other members such as sidewalls, base treads, undertreads, clinch apex, bead apex, breaker cushion rubber, and carcass cord covering rubber. , insulation, chafer, inner liner, etc., and the side reinforcing layer of run-flat tires.

The tire of the present invention is manufactured by a conventional method using the above rubber composition.
That is, the rubber composition blended with the above components is extruded in an unvulcanized stage according to the shape of each tire member such as a tread, and a magnetic field is applied as necessary to orient the soft magnetic material. An unvulcanized tire is formed by molding the obtained unvulcanized tire member together with other tire members by a conventional method on a tire building machine. A tire is obtained by heating and pressurizing this unvulcanized tire in a vulcanizer.

Examples of the tire include pneumatic tires and airless (solid) tires, among which pneumatic tires are preferred. Tires can be used as tires for passenger cars, tires for large passenger cars, tires for large SUVs, tires for heavy loads such as trucks and buses, tires for light trucks, tires for two-wheeled vehicles, tires for racing (high performance tires), and the like. It can also be used for all-season tires, summer tires, studless tires (winter tires), and the like.

EXAMPLES The present invention will be specifically described based on Examples, but the present invention is not limited to these.

(Production example 1)
A stainless steel polymerization reactor with an internal volume of 20 liters was washed, dried, and purged with dry nitrogen. solution 5.22 mmol) was added, and polymerization was carried out at 65° C. for 3 hours while stirring. After completion of polymerization, 1.57 mmol (0.245 g) of N,N-dimethylaminopropylacrylamide and 3.66 mmol (2.251 g) of 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate were added. . After reacting for 30 minutes with stirring, 10 ml of methanol was added and the mixture was further stirred for 5 minutes. After that, the contents of the polymerization reaction vessel were taken out, 10 g of 2,6-di-t-phthyl-p-cresol (Sumilyzer BHT manufactured by Sumitomo Chemical Co., Ltd.; hereinafter the same) and 141 g of oil were added, and most of the hexane was evaporated. After that, it was dried under reduced pressure at 55° C. for 12 hours to obtain a rubber mixture.

Various chemicals used in Examples and Comparative Examples are described below.
Modified diene rubbers A and B: Production Example 1 (modified SBR, amount of extender oil: 18 parts by mass per 100 parts by mass of SBR)
Carbonyl iron powder: BASF CIP CM (average particle size 10 μm)
Oil: Diana Process NH-70S (aromatic process oil) manufactured by Idemitsu Kosan Co., Ltd.
Liquid polymer: FB-823 manufactured by Kuraray (liquid farnesene-butadiene copolymer, Tg-78°C, Mw 50,000, farnesene/butadiene ratio = 80/20)
Epoxy resin: Mitsubishi Chemical grade 827
Zinc oxide: Type 2 zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Paulownia sulfur manufactured by NOF Corporation: HK200-5 (powder sulfur containing 5% oil) manufactured by Hosoi Chemical Industry Co., Ltd.
Vulcanization accelerator CZ: Noxceler CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.

<Examples and Comparative Examples (without arranging work)>
According to the blending contents shown in Table 2 (the amount of sulfur indicates the amount of pure sulfur), using a 1.7 L Banbury mixer, among the blended materials, the materials shown in Step 1 were kneaded at 150 ° C. for 3 minutes, and the kneaded product was obtained. Obtained. Next, the material shown in step 2 was added to the kneaded material obtained in step 1, and kneaded at 80°C for 3 minutes using an open roll to obtain an unvulcanized rubber composition.
The obtained unvulcanized rubber composition was press vulcanized at 150° C. for 20 minutes to obtain a vulcanized rubber sheet (vulcanized).

<Examples and comparative examples (with arrangement work)>
According to the blending contents shown in Table 2 (the amount of sulfur indicates the amount of pure sulfur), using a 1.7 L Banbury mixer, among the blended materials, the materials shown in Step 1 were kneaded at 150 ° C. for 3 minutes, and the kneaded product was obtained. Obtained. Next, the material shown in step 2 was added to the kneaded material obtained in step 1, and kneaded at 80°C for 3 minutes using an open roll to obtain an unvulcanized rubber composition.
A magnetic field is applied to the obtained unvulcanized rubber composition using a magnetic field generator (NK029 manufactured by Niroku Seisakusho) in the thickness direction of the unvulcanized rubber composition to orient the soft magnetic material in the direction of the magnetic field. (Applied conditions: DC magnetic field (300 mT), temperature: room temperature, application time: 24 hours).
The unvulcanized rubber composition in which the magnetic material was oriented and obtained by the magnetic field application was press vulcanized at 150° C. for 20 minutes to obtain a vulcanized rubber sheet (vulcanized).

Using the obtained vulcanized rubber sheet, the following evaluations were carried out.

[Young's modulus (E)]
A test piece prepared from each vulcanized rubber sheet was measured using a precision universal tester (AG-IS 500N manufactured by Shimadzu Corporation) under the following measurement conditions, with no magnetic field applied, and Young's modulus (MPa) in the applied state. were measured respectively (Young's modulus was measured from the gradient of stress from 4% to 20% strain). The application state was measured under the following magnetic field application conditions.
(Measurement condition)
Cylindrical test piece: diameter 28 mm, height 14 mm
Deformation: compression deformation (compression direction: direction shown in FIG. 2)
Temperature: Room temperature Load: 0N to 400N
Compression speed: 1mm/min
Strain: 0% to 20%
(magnetic field application conditions)
As shown in FIG. 2, a magnet was placed under the cylindrical test piece, and a compression test was performed under the same measurement conditions as above.
Magnetic flux density: DC magnetic field (300mT, neodymium magnet)
Magnetic field direction: parallel to compression direction

[Acetone extraction amount (AE)]
For each vulcanized rubber sheet, the amount of substances extracted by acetone contained in the vulcanized rubber sheet before compression and after compression (extraction amount: mass% ) were measured (method A). The vulcanized rubber sheet was compressed under the following compression conditions.
(Compression conditions)
A compression test was carried out under the following conditions using a test piece made from a vulcanized rubber sheet.
Cylindrical test piece: diameter 28 mm, height 14 mm
Compressive load: 400MPa
Temperature: Room temperature Compression time: 2 minutes

From Table 2, it can be seen that the rubber compositions of Examples containing a rubber component and a soft magnetic material and satisfying the above formulas (1) and (2) can adjust the hardness of the rubber to a desired hardness by applying a magnetic field. Met. Also, by using this hardness control, it was possible to impart good steering stability and wet grip performance. Furthermore, since there was little change in the amount of acetone extracted before and after the compression test, it was possible to adjust the hardness of the rubber over time by applying a magnetic field when applied to a tire that was repeatedly subjected to deformation.

1a rubber composition (no magnetic field applied)
1b rubber composition (with magnetic field applied)
2 Soft magnetic material 3 Magnetic force (magnetic field)

Claims (4)

A rubber composition for tires containing a rubber component and a soft magnetic material and satisfying the following formulas (1) and (2),
A rubber composition for a tire, wherein the content of the soft magnetic material is 100 parts by mass or more relative to 100 parts by mass of the rubber component.

2. The rubber composition for tires according to claim 1, wherein the soft magnetic material is carbonyl iron powder. The rubber composition for tires according to claim 1 or 2, which is a rubber composition for treads . A tire using the tire rubber composition according to any one of claims 1 to 3.

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