JP5005609B2 - Rubber composition and pneumatic tire using the same - Google Patents

Description

  The present invention relates to a rubber composition and a pneumatic tire using the same.

  In recent years, while higher performance and higher horsepower of automobiles have progressed, awareness of safety has increased, and the demand for grip performance on tires has increased. For example, various performances during high-speed traveling are listed as one of them. In particular, the tire tread has a problem that heat is generated as the vehicle travels, and grip performance deteriorates due to high temperatures.

  Conventionally, as a technique for improving grip performance, for example, a technique of increasing the glass transition point (Tg) by increasing the amount of bound styrene and the amount of vinyl bond of styrene-butadiene rubber is known. However, there is a risk that the wear resistance is lowered, or the grip performance at a low temperature is lowered and brittle fracture is caused. As a technique for improving grip performance, a technique of blending a large amount of oil is also known. In this case, however, the wear resistance is lowered. In addition, a method of blending a resin having a high Tg with a rubber composition for a tire tread is also known. However, the grip performance under high temperature conditions could not be sufficiently improved.

  In order to solve these problems, for the purpose of providing a rubber composition for tires exhibiting high grip performance, diene rubber is selected from the group consisting of 2,2,6,6-tetramethylpiperidine and its derivatives. A tire rubber composition containing at least one selected compound, at least one compound selected from the group consisting of a protonic acid and a phenol derivative, and carbon black has been developed (Patent Document 1).

  However, there is still room for improvement in grip performance.

JP-A-2005-112922

  An object of this invention is to provide the rubber composition which can improve the grip performance in a medium temperature-high temperature range, and a pneumatic tire using the same.

  The present invention relates to a rubber composition comprising (A) a rubber component, (B) at least one nitrogen compound selected from the group consisting of piperidine derivatives, imidazoles and caprolactams, and (C) benzoxazine.

  Further, (D) an acid is preferably contained.

  Furthermore, it is preferable to contain (E) a compound containing an ionic bond.

  Furthermore, it is preferable to contain (F) a magnetic substance.

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

  According to the present invention, by containing (A) a rubber component, (B) a nitrogen compound, and (C) a benzoxazine, a rubber composition that can improve grip performance in an intermediate temperature to high temperature region, and The used pneumatic tire can be provided.

  The rubber composition of the present invention contains (A) a rubber component, (B) a nitrogen compound, and (C) a benzoxazine.

  The (A) rubber component, (B) nitrogen compound, and (C) benzoxazine contained in the rubber composition of the present invention will be described below.

  Examples of the rubber component (A) include natural rubber (NR), isoprene rubber (IR), styrene butadiene rubber (SBR), butadiene rubber (BR), butyl rubber (IIR), halogenated butyl rubber (X-IIR), and acrylonitrile. Examples include butadiene rubber (NBR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), and halides of copolymers of isomonoolefin and paraalkylstyrene, which are usually used in the rubber industry. There is no restriction | limiting in particular, You may use individually or in combination of 2 or more types. Among them, NR, SBR or BR is preferable, and SBR is more preferable because it has sufficient strength and exhibits excellent wear resistance.

  The amount of bound styrene of SBR is preferably 10% by weight or more, more preferably 20% by weight or more, further preferably 30% by weight or more, and particularly preferably 35% by weight or more. When the amount of bound styrene of SBR is less than 10% by weight, there is a tendency that a sufficient improvement effect of grip performance cannot be obtained under medium temperature and high temperature conditions. The amount of bound styrene in SBR is preferably 60% by weight or less, more preferably 50% by weight or less, and further preferably 45% by weight or less. When the amount of bound styrene in SBR exceeds 60% by weight, the rubber becomes hard, the contact area with the road surface decreases, and high grip performance tends to be not obtained.

  The nitrogen compound (B) preferably contains hydrogen bonds, and by adding such a nitrogen compound to the rubber composition, the grip performance under intermediate temperature conditions (30 to 50 ° C.) is improved. be able to.

  The nitrogen compound (B) preferably has one or more cyclic structures containing nitrogen. If no annular structure containing nitrogen is included, the high temperature grip performance tends not to be improved.

  The nitrogen compound (B) used in the present invention is at least one nitrogen compound selected from the group consisting of piperidine derivatives, imidazoles, and caprolactams. Among these, imidazoles are preferable because they are general-purpose products and easily available.

（式中、Ｒ¹は１価の鎖状の炭化水素基、−ＯＨ、−ＮＨ₂または−ＳＨ、ａは０〜４の整数であり、ａ個のＲ¹はそれぞれ同一でも異なっていてもよく、Ｒ¹の合計炭素数は１０以下である）で表されるイミダゾール類（Ｉ）が好ましいが、化学式（２）：

（式中、Ｒ²およびＲ³は１価の鎖状の炭化水素基、−ＯＨ、−ＮＨ₂または−ＳＨ、Ｒ⁴は２価の鎖状の炭化水素基であり、Ｘは窒素原子をｄ個含む環状構造であり、Ｘは二重結合を含んでいてもよい。また、ｂは０〜３の整数、ｃは０〜５の整数、ｄは１〜６の整数であり、ｂ個のＲ²、ｃ個のＲ³はそれぞれ同一でも異なっていてもよく、ｄ個のＮは隣接していても隣接していなくてもよい）、または化学式（３）：

（式中、Ｒ⁵は１価の鎖状の炭化水素基、−ＯＨ、−ＮＨ₂または−ＳＨ、ｅは０〜４の整数であり、ｅ個のＲ⁵はそれぞれ同一でも異なっていてもよく、Ｒ⁵の合計炭素数は１１〜１５である）で表されるイミダゾール類（ＩＩ）、もしくはイミダゾール類（Ｉ）とイミダゾール類（ＩＩ）の混合物を使用してもよい。 When imidazoles are used as the nitrogen compound (B), the nitrogen compound (B) has the chemical formula (1):

(In the formula, R ¹ is a monovalent chain hydrocarbon group, —OH, —NH ₂ or —SH, a is an integer of 0 to 4, and a R ¹ may be the same or different. The total number of carbon atoms of R ¹ is preferably 10 or less), but the imidazoles (I) represented by formula (2):

(Wherein R ² and R ³ are monovalent chain hydrocarbon groups, —OH, —NH ₂ or —SH, R ⁴ is a divalent chain hydrocarbon group, and X is a nitrogen atom. a cyclic structure including d, X may include a double bond, b is an integer of 0 to 3, c is an integer of 0 to 5, d is an integer of 1 to 6, and b R ² and c R ^{3 s} may be the same or different, and d N may be adjacent or non-adjacent), or chemical formula (3):

(In the formula, R ⁵ is a monovalent chain hydrocarbon group, —OH, —NH ₂ or —SH, e is an integer of 0 to 4, and e R ⁵ may be the same or different. Well, the total carbon number of R ⁵ is 11 to 15), or a mixture of imidazoles (I) and imidazoles (II) may be used.

In the chemical formula (1), R ¹ is preferably a monovalent chain hydrocarbon group, —OH, —NH ₂ and —SH. Among them, a monovalent chain hydrocarbon group is more preferable, an alkyl group is more preferable, and —CH ₃ is particularly preferable because there is little steric hindrance and the reaction with the protonic acid (D) easily occurs effectively. preferable.

The number a of the substituents R ¹ is preferably an integer of 0 to 4, for the reason that can be a number of substituents R ¹ is large, the steric hindrance, 0 or 1 are more preferable.

Further, the total carbon number of R ¹ is preferably 10 or less, and more preferably 5 or less. When the total carbon number of R ¹ is 11 or more, the steric hindrance is large, hydrogen bonds cannot be formed effectively, and a sufficient improvement effect of grip performance tends not to be obtained.

などがあげられる。なかでも、

が好ましい。 As imidazoles satisfying the chemical formula (1), for example,

Etc. Above all,

Is preferred.

In the chemical formula (2), R ² and R ³ are preferably a monovalent chain hydrocarbon group, —OH, —NH ₂ and —SH. Among these, as R ² , a monovalent chain hydrocarbon group is preferable, an alkyl group is more preferable, because there is little steric hindrance and reaction with a protonic acid (D) is likely to occur effectively. CH ₃ or —C ₂ H ₅ is more preferred. R ³ is preferably —NH ₂ . Note that b R ² and c R ³ may be the same or different. The number b of the substituent R ² is preferably an integer of 0 to 3, and the number of substituents should not be too large. It is more preferable to use 2 for the reason that the number of steric hindrances is smaller.

The number c of the substituent R ³ is preferably an integer of 0 to 5, and more preferably 2.

  X is a cyclic structure containing d nitrogen atoms, and X may contain a double bond.

  The number d of N in X is preferably an integer of 1 to 6, and more preferably 3. Note that d Ns may or may not be adjacent.

などがあげられる。なかでも、

が好ましい。 As such a cyclic structure X, for example,

Etc. Above all,

Is preferred.

R ⁴ is preferably a divalent chain hydrocarbon group, more preferably an alkylene group, and further preferably —C ₂ H ₄ —.

などがあげられる。なかでも、汎用品で入手しやすいという理由から、

が好ましい。 As imidazoles satisfying the chemical formula (2), for example,

Etc. Above all, because it is easy to obtain with general-purpose products,

Is preferred.

In chemical formula (3), R ⁵ is preferably a monovalent chain hydrocarbon group, —OH, —NH ₂ and —SH.

The number e of the substituent R ⁵ is an integer of 0 to 4, and 0 or 1 is preferable because the steric hindrance is small.

The total carbon number of R ⁵ is preferably an integer of 11 to 15. When the total carbon number of R ⁵ is 16 or more, there is a tendency that it does not easily react with the protonic acid due to steric hindrance.

などがあげられる。 As imidazoles satisfying the chemical formula (3), for example,

Etc.

  When a piperidine derivative is used as the nitrogen compound (B), for example, 2,2,6,6-tetramethylpiperidine, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1 , 2,2,6,6-pentamethyl-4-piperidyl) sebacate, 1- [2- {3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy} ethyl] -4- { 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy} -2,2,6,6-tetramethylpiperidine, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine 8-acetyl-3-dodecyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro [4,5] decane-2,4-dione, poly [{6- (1,1, 3,3- Tramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6,6 -Tetramethyl-4-piperidyl) imino}], 1,2,2,6,6-tetramethyl-4-piperidyl-methacrylate, 2,2,6,6-tetramethyl-4-piperidyl-methacrylate, etc. 2,2,6,6-tetramethylpiperidine and its derivatives, among which 2,2,6,6-tetramethylpiperidine or its derivatives are preferable, and 2,2,6,6-tetramethylpiperidine Derivatives are more preferred.

  When imidazoles are used as the nitrogen compound (B), for example, imidazole, 1-methylimidazole, 2-methylimidazole, N-acetylimidazole, 2-mercapto-1-methylimidazole, benzimidazole, 2-mercaptobenzimidazole. , 2-phenylimidazole, 1-benzyl-2-methylimidazole and the like. Among them, since the structure is simple, an acid approaches nitrogen and easily forms a hydrogen bond, 2-methylimidazole, imidazole or 1-methylimidazole is preferred.

  When caprolactams are used as the nitrogen compound (B), for example, ε-caprolactam can be mentioned.

  The nitrogen compound (B) used in the present invention is at least one nitrogen compound selected from the group consisting of piperidine derivatives, imidazoles, and caprolactams.

  As the nitrogen compound (B), among at least one compound selected from the group consisting of piperidine derivatives, imidazoles and caprolactams, imidazoles are preferred because they are free of steric hindrance and easily form a bond with an acid. 2-methylimidazole is more preferred. The above compounds may be used singly or in combination of two or more, but when used in combination of two or more, the effect of combining two or more compounds having hydrogen bonds may be used. Is difficult to obtain, and the rubber strength is lowered, which is not preferred.

  The nitrogen compound (B) may be used alone or in combination of two or more. However, combining two or more of the nitrogen compounds (B) is less effective and further reduces the rubber strength. Is preferably used. However, the combination of imidazole (I) and imidazole (II) is preferable because the low-temperature characteristics can be improved while maintaining high-temperature grip performance.

  The compounding amount of the nitrogen compound (B) is preferably 0.1 parts by weight or more and more preferably 2 parts by weight or more with respect to 100 parts by weight of the rubber component (A). When the compounding amount of the nitrogen compound (B) is less than 0.1 part by weight, the grip performance improving effect due to the nitrogen compound (B) tends to be difficult to obtain. Further, the compounding amount of the nitrogen compound (B) is preferably 30 parts by weight or less, and more preferably 20 parts by weight or less. When the compounding amount of the nitrogen compound (B) exceeds 30 parts by weight, the effect of adding the compound (B) becomes difficult to obtain, and the cost tends to increase.

  Benzoxazine (C) is a compound represented by the following general formula, and has a benzoxazine ring as a basic skeleton. This compound has no volatile by-products when heated, and is cured by ring-opening polymerization of the benzoxazine ring, and the cured product has excellent heat resistance and flame retardancy. It attracts attention as a substitute for thermosetting resins such as resins, epoxy resins, unsaturated polyester resins and bismaleimide resins.

（式中、ｎは１〜４の整数を表す。Ｒ₁は低級アルキル基、シクロアルキル基、アリール基、アリル基またはアラルキル基を表す。Ｒ₂は水素原子、低級アルキル基、シクロアルキル基、アリール基、アリル基、アラルキル基または、以下に示される１〜４価の有機基を表す。）

(In the formula, n represents an integer of 1 to 4. R ₁ represents a lower alkyl group, a cycloalkyl group, an aryl group, an allyl group, or an aralkyl group. R ₂ represents a hydrogen atom, a lower alkyl group, a cycloalkyl group, An aryl group, an allyl group, an aralkyl group, or a monovalent to tetravalent organic group shown below)

（式中、ｎは１〜４の整数を表す。Ｒ₁は水素原子、低級アルキル基、シクロアルキル基、アリール基、アリル基またはアラルキル基を表す。Ｒ₂は低級アルキル基、シクロアルキル基、アリール基、アリル基、アラルキル基または、以下に示される１〜４価の有機基を表す。）

(In the formula, n represents an integer of 1 to 4. R ₁ represents a hydrogen atom, a lower alkyl group, a cycloalkyl group, an aryl group, an allyl group or an aralkyl group. R ₂ represents a lower alkyl group, a cycloalkyl group, An aryl group, an allyl group, an aralkyl group, or a monovalent to tetravalent organic group shown below)

  Benzoxazine (C) can improve high temperature grip performance by blending benzoxazine in the rubber composition.

  Examples of benzoxazine (C) include (1) Pd type, (2) Fa type, and the like. (1) Pd type and (2) Fa type benzoxazine (C) are commercially available and have the advantage of being readily available.

で表される（１）Ｐ−ｄ型が好ましい。 When (1) Pd type is used as benzoxazine (C), benzoxazine (C) has the following chemical formula:

(1) Pd type represented by these is preferable.

で表される（２）Ｆ−ａ型が好ましい。 Furthermore, when (2) Fa type is used as benzoxazine (C), benzoxazine (C) has the following chemical formula:

(2) Fa type represented by these is preferable.

  Benzoxazine (C) can be used alone. When two or more kinds are combined, improvement of grip performance can be expected in a wider range.

  The blending amount of benzoxazine (C) is preferably 0.5 parts by weight or more and more preferably 1 part by weight or more with respect to 100 parts by weight of the rubber component (A) because grip performance can be improved. Further, the amount of benzoxazine (C) is preferably 20 parts by weight or less, more preferably 10 parts by weight or less, based on 100 parts by weight of the rubber component (A) because the cost can be reduced.

  The present invention preferably contains (D) an acid.

  Examples of the acid (D) include protonic acids such as carboxylic acids and phenolic compounds, and phenolic compounds are preferred because of their low crosslinking inhibition.

（式中、Ｒ⁷は１価の鎖状の炭化水素基、−ＯＨ、−ＮＨ₂または−ＳＨ、ｆは０〜５の整数であり、ｆ個のＲ⁷はそれぞれ同一でも異なっていてもよく、Ｒ⁷の合計炭素数は１０以下である）で表されるカルボン酸が好ましい。 As the carboxylic acid, R ⁶ —COOH (R ⁶ is a monovalent chain hydrocarbon group having 1 to 10 carbon atoms) or chemical formula (4):

(Wherein R ⁷ is a monovalent chain hydrocarbon group, —OH, —NH ₂ or —SH, f is an integer of 0 to 5, and f R ^{7 s} may be the same or different. The total carbon number of R ⁷ is preferably 10 or less).

R ⁶ is preferably a monovalent chain hydrocarbon group having 10 or less carbon atoms, and a methyl group is more preferable because it is easily available.

Acetic acid, propionic acid, etc. can be used as the carboxylic acid represented by R ⁶ —COOH.

In the chemical formula (4), R ⁷ is preferably a monovalent chain hydrocarbon group, —OH, —NH ₂ and —SH.

The number f of the substituent R ⁷ is an integer of 0 to 4, and 0 is preferable because it is easily available.

Further, the total carbon number of R ⁷ is preferably 10 or less, and more preferably 5 or less. When the total carbon number of R ⁷ is 11 or more, the steric hindrance is large, and it tends to be difficult to react with the protonic acid.

などがあげられる。 As the carboxylic acid satisfying the chemical formula (4), for example,

Etc.

（式中、Ｒ⁸は１価の鎖状の炭化水素基、−ＯＨ、−ＮＨ₂または−ＳＨ、ｇは０〜５の整数であり、ｇ個のＲ⁸はそれぞれ同一でも異なっていてもよく、Ｒ⁸の合計炭素数は１０以下である）で表されるフェノール系化合物が好ましい。 As a phenolic compound, chemical formula (5):

Wherein R ⁸ is a monovalent chain hydrocarbon group, —OH, —NH ₂ or —SH, g is an integer of 0 to 5, and g R ⁸ may be the same or different. The total number of carbon atoms of R ⁸ is preferably 10 or less).

In the chemical formula (5), R ⁸ is preferably a monovalent chain hydrocarbon group, —OH, —NH ₂ and —SH. Among these, a monovalent chain hydrocarbon group, —OH is more preferable, an alkyl group or —OH is more preferable, and —C ₂ H ₅ , —C (CH ₃ ), — OH is particularly preferred.

The number g of the substituent R ⁸ is preferably an integer of 0 to 5, and more preferably 0 to 3 because the steric hindrance is small.

Further, the total carbon number of R ⁸ is preferably 10 or less. When the total carbon number of R ⁸ is 11 or more, the steric hindrance is large, and it tends to be difficult to react with the protonic acid.

などがあげられる。 Examples of the phenolic compound satisfying the chemical formula (5) include:

Etc.

Hereinafter, R ⁶ —COOH, an acid satisfying the chemical formula (4) or the chemical formula (5) is referred to as a proton acid (small), and the other proton acid is referred to as a proton acid (large).

  (D) The compounding amount of the acid is preferably 1 part by weight or more and more preferably 5 parts by weight or more with respect to 100 parts by weight of the rubber component (A). (D) If the compounding quantity of an acid is less than 1 weight part, there exists a tendency which is not enough to react with a nitrogen compound (B). Further, the blending amount of (D) acid is preferably 20 parts by weight or less, and more preferably 10 parts by weight or less. (D) When the amount of the acid exceeds 20 parts by weight, crosslinking tends to be inhibited.

  As a combination of imidazoles and (D) acid, a combination of imidazoles (II) and protonic acid (large) is not preferable because steric hindrance is great and hydrogen bonds cannot be effectively obtained. Any combination of imidazoles (I) and proton acids (small), imidazoles (II) and proton acids (small), imidazoles (I) and proton acids (large) is preferred. In consideration of steric hindrance, the combination of imidazoles (I) and protonic acids (small) is most preferable.

  The present invention preferably contains (E) a compound containing an ionic bond.

  (E) The compound containing an ionic bond is, for example, an organometallic compound. By blending such an organometallic compound in the rubber composition, grip performance under high temperature conditions (around 100 ° C.) can be improved.

  (E) Examples of the compound containing an ionic bond include organic carboxylic acid metal salts and thiocarboxylic acid salts, but organic carboxylic acid metal salts are preferred because they are easily available.

  Examples of organic carboxylic acid metal salts include aromatic carboxylic acid metal salts such as benzoic acid metal salts and naphthoic acid metal salts, acetic acid metal salts, propionic acid metal salts, acrylic acid metal salts, methacrylic acid metal salts, and oxalic acid metal salts. The carboxylic acid metal salt which does not contain an aromatic ring is mentioned, and the carboxylic acid metal salt which does not contain an aromatic ring is preferred.

  Carboxylic acid metal salts that do not contain aromatic rings (carboxylic acid metal salts that do not contain multiple bonds) include carboxylic acid metal salts that do not contain multiple bonds, such as acetic acid metal salts, propionic acid metal salts, oxalic acid metal salts, and acrylic acid. Carboxylic acid metal salts containing multiple bonds, such as metal salts and metal methacrylates, are mentioned, and dispersion of crosslinks can be suppressed and the crosslink density can be improved. Therefore, carboxylic acid metal salts containing no multiple bonds are more preferred.

  Examples of carboxylic acid metal salts that do not contain multiple bonds include organic monocarboxylic acid metal salts such as acetic acid metal salts and propionic acid metal salts, and organic dicarboxylic acid metal salts such as oxalic acid metal salts. More preferred are monocarboxylic acid metal salts.

  Examples of the organic carboxylic acid metal salt satisfying the above conditions include magnesium acetate, calcium propionate, calcium acetate, magnesium propionate and the like, but since they are generally commercially available and easy to obtain, magnesium acetate or calcium propionate is used. preferable.

  Examples of the thiocarboxylate include thioacetate and thiopropionate.

  (E) The compound containing an ionic bond may be used alone or in combination of two or more, but when two or more are used in combination, two or more compounds having an ionic bond are used in combination. However, it is difficult to obtain the effect of the combination, and further, the rubber strength is lowered, which is not preferable.

  (E) As for content of the compound containing an ionic bond, 0.1 weight part or more is preferable with respect to 100 weight part of rubber components (A), and 1 weight part or more is more preferable. When the content of the compound containing (E) ionic bond is less than 0.1 part by weight, the grip performance improving effect due to containing the compound containing (E) ionic bond tends to be difficult to obtain. Moreover, (E) 30 weight part or less is preferable and, as for content of the compound containing an ionic bond, 20 weight part or less is more preferable. (E) When the content of the compound containing an ionic bond exceeds 30 parts by weight, the tackiness tends to increase.

  The present invention preferably contains (F) a magnetic substance.

  Generally, when a magnetic material such as a ferrite magnet is blended as it is in a diene rubber, the rubber strength is lowered, so that it cannot be used as a rubber composition for treads. By blending the (F) magnetic material (also referred to as magnetic carbon black in the present invention) contained in the magnetic material, the magnetic materials can be repeatedly attracted and repelled in the diene rubber, and high tan δ can be generated. As a result, grip performance in a wide temperature range can be improved.

  (F) The magnetic substance is a composite fine particle of carbon black and a decomposition product of a transition metal compound which is a magnetic fine particle. (F) The magnetic substance is specifically obtained by the production methods described in JP-A Nos. 63-199272 and 63-205369.

  (F) The compounding quantity of a magnetic body is 10 weight part or more with respect to 100 weight part of diene rubber (A), and 20 weight part or more is preferable. (F) When the content of the magnetic material is less than 10 parts by weight, there is a tendency that tan δ is not improved. The content of (F) magnetic substance is 200 parts by weight or less, preferably 150 parts by weight or less. (F) When the content of the magnetic substance exceeds 200 parts by weight, the dispersibility tends to deteriorate.

  (F) The magnetic material preferably has a magnetic flux density of 100 to 1000 mT.

(F) The specific surface area of the magnetic material is preferably 80 m ² / g or more, and more preferably 100 m ² / g or more. When the specific surface area is less than 80 m ² / g, grip performance tends to be lowered. Further, the specific surface area of the magnetic carbon black (B) is preferably 280 m ² / g or less, and more preferably 200 m ² / g or less. When the specific surface area exceeds 280 m ² / g, the workability tends to decrease.

  (F) The average particle size of the magnetic material is preferably 30 nm or more, and more preferably 200 nm or more. If the average particle size is less than 30 nm, the dispersibility tends to be poor. Further, the average particle size of the (F) magnetic substance is preferably 200 nm or less, and more preferably 180 nm or less. When the average particle diameter exceeds 200 nm, the wear resistance tends to decrease.

  (F) The average primary particle diameter of carbon black in the magnetic material is preferably 10 nm or more, and more preferably 15 nm or more. When the average primary particle diameter is less than 10 nm, the produced magnetic material (magnetic carbon black) becomes small, and the dispersibility tends to deteriorate. Moreover, (F) The average primary particle diameter of carbon black in the magnetic material is preferably 200 nm or less, and more preferably 180 nm or less. (F) When the average primary particle diameter of the magnetic material exceeds 200 nm, the produced magnetic material (magnetic carbon black) becomes large, so that the wear resistance tends to decrease. (F) The average primary particle diameter of the magnetic fine particles in the magnetic material is preferably 20 nm or more, and more preferably 30 nm or more. When the average primary particle diameter is less than 20 nm, the magnetism tends to be small. Moreover, (F) The average primary particle diameter of the magnetic fine particles in the magnetic material is preferably 200 nm or less, more preferably 100 nm or less, and particularly preferably 90 nm or less. (F) When the average primary particle diameter of the magnetic material exceeds 200 nm, the wear resistance tends to decrease. The average primary particle diameter of the magnetic fine particles in the magnetic substance (F) is preferably larger than the average primary particle diameter of the carbon black in the magnetic substance (magnetic carbon black) from the viewpoint of imparting ferromagnetism.

  Specific examples of the transition metal compound used as a raw material for the magnetic fine particles include metallocene of at least one metal selected from Fe, Co, and Ni, a carbonyl complex compound, an inorganic salt, or an organic acid salt. . Among these, ferrocene using Fe as a transition metal is preferable because it is easily available.

  The content of the magnetic fine particles is preferably 1% by weight or more, more preferably 5% by weight or more, and still more preferably 10% by weight or more in the magnetic substance (F). When the content of the magnetic fine particles is less than 1% by weight, tan δ is not improved and grip performance tends not to be improved. Further, the content of the magnetic fine particles is preferably 50% by weight or less, more preferably 30% by weight or less, and still more preferably 20% by weight or less in the magnetic substance (F). When the content of the magnetic fine particles exceeds 50% by weight, the magnetic fine particles cannot be fused and bonded to the carbon black particles.

  In addition, the rubber composition of the present invention preferably contains a reinforcing filler.

  Examples of reinforcing fillers include carbon black, silica, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, talc, and clay. Black is preferred.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 80 m ² / g or more, and more preferably 100 m ² / g or more. When N ₂ SA of carbon black is less than 80 m ² / g, grip performance and wear resistance tend to decrease. Further, N ₂ SA of carbon black is preferably 280 m ² / g or less, and more preferably 200 m ² / g or less. When N ₂ SA of carbon black exceeds 280 m ² / g, workability tends to be lowered.

  When carbon black is contained as a reinforcing filler, the content of carbon black is preferably 10 parts by weight or more, more preferably 20 parts by weight or more with respect to 100 parts by weight of the rubber component (A). When the content of carbon black is less than 10 parts by weight, the wear resistance tends to decrease. The carbon black content is preferably 200 parts by weight or less, and more preferably 150 parts by weight or less. When the content of carbon black exceeds 200 parts by weight, processability tends to be lowered.

  The rubber composition for tires of the present invention preferably further contains oil.

  Examples of the oil include process oils such as aroma oil, naphthenic oil, and paraffin oil, and oils derived from natural resources such as vegetable oils.

  When oil is contained, the oil content is preferably 10 to 200 parts by weight, more preferably 20 to 150 parts by weight, including the oil-extended oil, with respect to 100 parts by weight of the rubber component (A). If the oil content is less than 10 parts by weight, the wet grip performance tends to be insufficient, and if it exceeds 150 parts by weight, the wear resistance tends to be remarkably reduced.

  The rubber composition for tires of the present invention preferably further contains a tackifying resin.

  Examples of the tackifying resin include coumarone resin, phenolic resin, terpene resin, and xylene resin. In the present invention, the tackifying resin is also referred to as a resin.

  The softening point of the tackifying resin is preferably 40 to 200 ° C, more preferably 60 to 180 ° C. When the softening point of the tackifying resin is less than 40 ° C., the grip performance under a high temperature condition tends to decrease, and when it exceeds 200 ° C., the dispersibility during kneading tends to decrease.

  When the tackifying resin is contained, the content of the tackifying resin is preferably 1 to 50 parts by weight and more preferably 5 to 30 parts by weight with respect to 100 parts by weight of the rubber component (A). If the content of the tackifying resin is less than 1 part by weight, there is a tendency that sufficient grip performance cannot be obtained, and if it exceeds 50 parts by weight, excessive tackiness is exhibited and processing tends to be difficult.

  The rubber composition of the present invention comprises (A) a rubber component, (B) a nitrogen compound, (C) a benzoxazine, (D) an acid, (E) a compound containing an ionic bond, (F) a magnetic material, and a reinforcing material. In addition to fillers, oils and tackifying resins, compounding agents conventionally used in the rubber industry, such as various anti-aging agents, vulcanizing agents such as stearic acid, zinc oxide and sulfur, various vulcanization accelerators, etc. Can be blended.

  The rubber composition of the present invention is used for tires, and is particularly suitable as a tread among tire members because it is excellent in both medium temperature grip performance and high temperature grip performance.

  The tire of the present invention is produced by a usual method using the rubber composition of the present invention as a tread. That is, the rubber composition is extruded into a tread shape at an unvulcanized stage and bonded together with other tire members on a tire molding machine by an ordinary method to form an unvulcanized tire. The unvulcanized tire can be heated and pressurized in a vulcanizer to obtain the tire of the present invention.

  Examples of tires include passenger car tires, competition tires, and the like. However, since particularly excellent grip performance can be obtained, use as a competition tire is also preferable.

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

ベンゾオキサジン２：（Ｃ）ベンゾオキサジン、四国化成工業株式会社製の（２）Ｆ−ａ型

チッ素化合物１：（Ｂ）チッ素化合物、日本合成化学製のイミダゾール

チッ素化合物２：（Ｂ）チッ素化合物、日本合成化学製の１−メチルイミダゾール

チッ素化合物３：（Ｂ）チッ素化合物、イオン系窒素化合物、日本合成化学製のイオン性液体（１−エチル−３−メチルイミダゾロウムソルト）

酸１：（Ｄ）酸、大内新興化学工業（株）製のノクセラーＮＳ３０（４，４’−ブチリデンビス−（３−メチル−６−ｔｅｒｔ−ブチルフェノール））

酸２：（Ｄ）酸、和光純薬工業（株）製のフェノール

酸３：（Ｄ）酸、和光純薬工業（株）製の安息香酸

酢酸マグネシウム：（Ｅ）イオン結合を含む化合物、キシダ化学（株）製
プロピオン酸カルシウム：（Ｅ）イオン結合を含む化合物、和光純薬工業（株）製
酢酸カルシウム：（Ｅ）イオン結合を含む化合物、和光純薬工業（株）製
磁性金属粉１：（Ｆ）磁性体、フェライト磁石、戸田工業（株）製のＦＨ８０１
磁性流体２：（Ｆ）磁性体、シグマハイケミカル製のＡ−２００
磁性流体３：（Ｆ）磁性体、シグマハイケミカル製のＮ−５０４（イソパラフィンと四三酸化鉄（マグネタイト）の混合物）
磁性流体４：（Ｆ）磁性体、シグマハイケミカル製のＰ−２０６（ポリオレフィン［Ｃ_nＨ_2n+2］とフェライト［鉄、マンガン、亜鉛酸化物、（ＭｎＯ）_n（ＺｎＯ）_nＦ₂Ｏ₃］の混合物）
硫黄：鶴見化学工業（株）製の粉末硫黄
加硫促進剤：大内新興化学工業（株）製のノクセラーＮＳ（Ｎ−ｔｅｒｔ−ブチル−２−ベンゾチアゾリルスルフェンアミド） Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
Styrene butadiene rubber (SBR): (A) rubber component, Toughden 4350 manufactured by Asahi Kasei Co., Ltd. (amount of bound styrene: 39% by weight, containing 50 parts by weight of oil with respect to 100 parts by weight of rubber solid)
Carbon black: Dia Black A (N110, N ₂ SA: 130 m ² / g) manufactured by Mitsubishi Chemical Corporation
Anti-aging agent 6C: Santoflex 13 (N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine) manufactured by Flexis
Anti-aging agent 224: Nocrack 224 (2,2,4-trimethyl-1,2-dihydroquinoline polymer) manufactured by Flexis
Stearic acid: Nippon Oil & Fats Co., Ltd. Zinc Oxide: Mitsui Metal Mining Co., Ltd. Zinc Oxide Type 2 Aroma Oil: Japan Energy Co., Ltd. Process X-260
Tackifying resin: Resin, Neopolymer 140 manufactured by Nippon Petrochemical Co., Ltd. (softening point: 140 ° C.)
Benzoxazine 1: (C) benzoxazine, (1) Pd type made by Shikoku Chemicals Co., Ltd.

Benzoxazine 2: (C) benzoxazine, (2) Fa type manufactured by Shikoku Kasei Kogyo Co., Ltd.

Nitrogen compound 1: (B) Nitrogen compound, imidazole manufactured by Nippon Synthetic Chemical

Nitrogen compound 2: (B) Nitrogen compound, 1-methylimidazole manufactured by Nippon Synthetic Chemical

Nitrogen compound 3: (B) Nitrogen compound, ionic nitrogen compound, ionic liquid manufactured by Nippon Synthetic Chemical (1-ethyl-3-methylimidazolium salt)

Acid 1: (D) acid, Noxeller NS30 (4,4'-butylidenebis- (3-methyl-6-tert-butylphenol)) manufactured by Ouchi Shinsei Chemical Co., Ltd.

Acid 2: (D) acid, phenol manufactured by Wako Pure Chemical Industries, Ltd.

Acid 3: (D) acid, benzoic acid manufactured by Wako Pure Chemical Industries, Ltd.

Magnesium acetate: (E) a compound containing an ionic bond, Kishida Chemical Co., Ltd. calcium propionate: (E) a compound containing an ionic bond, Wako Pure Chemical Industries, Ltd. calcium acetate: (E) a compound containing an ionic bond , Wako Pure Chemical Industries, Ltd. magnetic metal powder 1: (F) magnetic material, ferrite magnet, Toda Kogyo FH801
Magnetic fluid 2: (F) Magnetic material, A-200 manufactured by Sigma High Chemical
Magnetic fluid 3: (F) magnetic material, Sigma High Chemical N-504 (mixture of isoparaffin and iron trioxide (magnetite))
Magnetic fluid 4: (F) Magnetic material, P-206 (polyolefin [C _n H _{2n + 2} ] and ferrite [iron, manganese, zinc oxide, (MnO) _n (ZnO) _n F ₂ O) manufactured by Sigma High Chemical ₃ ] mixture)
Sulfur: Powdered sulfur vulcanization accelerator manufactured by Tsurumi Chemical Industry Co., Ltd .: Noxeller NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

Examples 1-4 and Comparative Examples 1-4
In accordance with the formulation shown in Table 1, components other than sulfur and a vulcanization accelerator were kneaded for 3 minutes at 150 ° C. using a BP Banbury mixer (base kneading) to obtain a kneaded product. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded material, and kneaded for 5 minutes under the condition of 50 ° C. using an open roll to obtain an unvulcanized rubber sheet. Further, the obtained unvulcanized rubber sheet was press vulcanized for 12 minutes under the condition of 170 ° C. to produce vulcanized rubber sheets of Examples 1 to 4 and Comparative Examples 1 to 4, and further into a predetermined shape. A cart tire of a size (11 × 7.10-5) was produced by pasting.

(Degree of crosslinking (SWELL))
The obtained vulcanized rubber sheet was extracted with toluene, and the volume change rate (SWELL) before and after extraction was measured. In addition, it shows that the dispersion | variation in bridge | crosslinking can be suppressed and it is so preferable that SWELL is small.

(Viscoelasticity test)
Using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd., viscoelasticity (complex elastic modulus) of a vulcanized rubber sheet at 40 ° C. and 100 ° C. under conditions of initial strain of 10%, dynamic strain of 2%, and vibration frequency of 10 Hz. E ′ and loss tangent tanD) were measured. In both the viscoelasticity test at 40 ° C. and the viscoelasticity test at 100 ° C., the larger E ′, the higher the rigidity and the better, and the larger tan δ, the higher the grip force and the better the grip performance. It shows that.

(Tensile test)
In accordance with JIS K 6251 “Vulcanized Rubber and Thermoplastic Rubber-Determination of Tensile Properties”, a tensile test was conducted using a No. 3 dumbbell-shaped rubber test piece made of the vulcanized rubber sheet, and the stress at 300% elongation ( M300) was measured. And the tensile strength index | exponent of the comparative example 1 was set to 100, and M300 of each mixing | blending was displayed as an index | exponent with the following formula. In addition, it shows that it is excellent in abrasion abrasion resistance, so that a tensile strength index | exponent is large.
(Tensile strength index) = (M300 of each formulation) / (M300 of Comparative Example 1) × 100

(Actual vehicle evaluation)
The unvulcanized rubber sheet is formed into a tread shape, bonded to another tire member, and press vulcanized at 170 ° C. for 12 minutes to obtain a test cart tire (size: 11 × 7.10− 5) was produced.

  The manufactured cart tire was mounted on a test cart, and the test course of 2 km per lap was run for 8 weeks. The grip performance of the reference blended tire was 3 points, and the test driver made a sensory evaluation with a maximum score of 5 points. The initial grip performance indicates the grip performance of the first to fourth laps, and the second half grip performance indicates the grip performance of the fifth to eighth laps. Furthermore, the tire appearance of the reference blend after running was given 3 points, and the wear appearance of each blend was evaluated relative to a maximum of 5 points.

  The evaluation results of the test are shown in Tables 1-6.

  Table 1 shows a rubber composition containing (A) a rubber component, (B) at least one nitrogen compound selected from the group consisting of piperidine derivatives, imidazoles and caprolactams, and (C) benzoxazine (Example 1). -4), (D) rubber composition containing Examples (Examples 2 to 4), (E) rubber composition containing compounds containing ionic bonds (Examples 3 and 4), and (F) The rubber composition (Example 4) containing a magnetic body and the evaluation result in those tires are shown.

  Table 2 shows the evaluation results of Examples in which the type and blending amount of (C) benzoxazine were changed based on Example 1.

  Table 3 shows the evaluation results of the examples in which the type and blending amount of the (B) nitrogen compound were changed using Example 1 as a reference.

  Table 4 shows the evaluation results of Examples in which the type and blending amount of (D) acid were changed based on Example 2.

  Table 5 shows the evaluation results of Examples in which the type and amount of the compound containing (E) ionic bond were changed with Example 3 as a reference.

  Table 6 shows the evaluation results of Examples in which the type and blending amount of (F) magnetic material were changed with Example 4 as a reference.

Claims (5)

(A) rubber component,
(B) b imidazole compound or al least one nitrogen compound and (C) a rubber composition containing a benzoxazine selected. The rubber composition according to claim 1, further comprising (D) an acid. The rubber composition according to claim 1 or 2, further comprising (E) a compound containing an ionic bond. Furthermore, the rubber composition of Claim 1, 2, or 3 containing (F) magnetic body. A pneumatic tire using the rubber composition according to claim 1, 2, 3 or 4.