JP2008050441A - Rubber composition for tire and pneumatic tire using the same for side wall - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition suitable for a side wall of pneumatic tire, the rubber composition which is highly balanced among cutting resistance, crack resistance and aging resistance. <P>SOLUTION: The rubber composition for a tire comprises (A) 100 pts.wt. of a diene rubber comprising (1) 60-20 pts.wt. of a natural rubber and/or a polyisoprene rubber and (2) 40-80 pts.wt. of a polybutadiene rubber containing ≥5 wt.% of a n-hexane insoluble content having syndiotactic-1,2-polybutadiene as a principal component in a matrix component of high cis-1,4-polybutadiene, and (B) 0.2-5 pts.wt. of an amine salt compound of carboxylic acid-containing disulfide expressed by formula (I). The pneumatic tire using the same for a side wall is also provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a tire rubber composition and a pneumatic tire using the same, and more specifically, a tire rubber composition in which cut resistance, crack resistance and aging resistance are balanced in the next order, and the rubber composition for a sidewall. It relates to the used pneumatic tire.

  The tire sidewall of a pneumatic tire is required to have high trauma resistance (cut resistance), fatigue resistance (crack resistance) and aging resistance. As a method for improving crack resistance, soft carbon such as FEF is used. Is known (see Non-Patent Document 1), but when soft carbon is used, there is a problem that the damage resistance is lowered, and it is required to balance the above performance in a high order. Yes.

Carbon Black Handbook <Third Edition> (Carbon Black Association) 247 pages

  Accordingly, an object of the present invention is to provide a rubber composition suitable for use in a pneumatic tire, particularly for a side wall compound, in which the above physical properties, that is, cut resistance, crack resistance and aging resistance, are balanced in high order. is there.

（式中、Ｒ₁ ，Ｒ₂ 及びＲ₃ は、独立に、水素又は炭素数１〜２０のヘテロ原子及び／又は置換基を有してもよい有機基であり、Ｘは炭素数２〜２０のヘテロ原子及び／又は置換基を有してもよい有機基である。）
で表されるカルボン酸含有ジスルフィドのアミン塩化合物０．２〜５重量部
を含んでなるタイヤ用ゴム組成物並びにそれをサイドウォールに用いた空気入りタイヤが提供される。 According to the present invention, (A) (1) 60-20 parts by weight of natural rubber and / or polyisoprene rubber and (2) syndiotactic-1,2-polybutadiene as a matrix component of high cis 1,4-polybutadiene. 100 parts by weight of a diene rubber containing 40 to 80 parts by weight of a polybutadiene rubber containing 5% by weight or more of an n-hexane insoluble component as a main component, and (B) Formula (I):

(In the formula, R ₁ , R ₂ and R ₃ are independently hydrogen or an organic group which may have a heteroatom having 1 to 20 carbon atoms and / or a substituent, and X is 2 to 20 carbon atoms. The hetero atom and / or the organic group which may have a substituent.
A rubber composition for tires comprising 0.2 to 5 parts by weight of an amine salt compound of a carboxylic acid-containing disulfide represented by the formula, and a pneumatic tire using the rubber composition for a sidewall are provided.

  According to the present invention, by using the diene rubber (A) and the vulcanization accelerator containing the amine salt compound (B) of the carboxylic acid-containing disulfide, the desired physical properties are balanced in a high order. A rubber composition blend suitable for use as a sidewall compound can be obtained.

  As a result of advancing research to solve the above-mentioned problems, the present inventors have used the vulcanization accelerator containing the diene rubber (A) and the amine salt compound (B) of a carboxylic acid-containing disulfide. The present inventors have found a rubber composition suitable for use as a side wall compound that balances physical properties, that is, trauma resistance (cut resistance), fatigue resistance (crack resistance), and aging resistance.

  According to the present invention, the diene rubber (A) comprises (1) natural rubber (NR) and / or polyisoprene rubber (IR) 60 to 20 parts by weight, preferably 50 to 30 parts by weight, and (2) high Polybutadiene rubber (BR) 40 containing a syndiotactic-1,2-polybutadiene as a main component and an n-hexane insoluble content of 5 wt% or more in a matrix component of cis 1,4-polybutadiene (for example, cis content 94.7% or more). -80 parts by weight, preferably 50-70 parts by weight. If the blending amount of NR and / or IR in the diene rubber is small, it is not preferable because the strength is insufficient, and if it is large, it is not preferable because crack resistance is insufficient. Further, if the amount of BR is small, it is not preferable because crack resistance is insufficient. On the other hand, if the amount is too large, strength is insufficient.

  As the NR and IR, any NR and IR that can be blended in the rubber composition for tires can be used, and the polybutadiene rubber (2) can be obtained by, for example, the method described in page 23 of the monthly report of the Japan Chemical Society, January 1988 issue. For example, it is commercially available as a VCR series from Ube Industries.

  The rubber composition of the present invention can contain a small amount (20% by weight or less of the rubber component) of other diene rubbers in addition to the rubber component. Any diene rubber can be used, specifically other polybutadiene rubber, chloroprene rubber, styrene-butadiene copolymer rubber, ethylene-propylene-diene copolymer rubber, acrylonitrile-butadiene copolymer For example, united rubber can be used.

  According to the present invention, the amine salt compound of the carboxylic acid-containing disulfide of the general formula (I) is 0.2 to 5 parts by weight, preferably 0.5 to 4 parts by weight per 100 parts by weight of the diene rubber (A). Part mix. If the amount of the amine salt compound (I) of the carboxylic acid-containing disulfide is small, the hardness is unsatisfactory, and conversely, if too large, the elongation at break is insufficient.

The carboxylic acid-containing disulfide amine salt compound used in the present invention (that is, the disulfide amine salt compound of the present invention) is a compound represented by the above formula (I), the details of which are filed on Aug. 14, 2006. Japanese Patent Application No. 2006-221258 (the contents of this application are incorporated herein by reference). Specifically, in the formula (I), R ₁ , R ₂ and R ₃ can be each independently hydrogen or an organic group having 1 to 20 carbon atoms, preferably 1 to 12 carbon atoms, Examples of such an organic group include a chain hydrocarbon group such as a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, and a stearyl group, and a cyclic hydrocarbon group such as a cyclopropyl group, a cyclobutyl group, and a cyclohexyl group. Is mentioned. In the chain of these organic groups, you may have hetero atoms, such as a nitrogen atom, an oxygen atom, and a sulfur atom. Examples of such an organic group include a methoxypropyl group, a methoxyethyl group, a tetrahydrofurfuryl group, a hydroxyethyl group, and a hydroxycyclohexyl group. R ₁ and R ₂ together with the nitrogen atom to which they are bonded, a heterocyclic group such as imidazole group, triazole group, pyrazole group, aziridine group, pyrrolidine group, piperidine group, morpholine group, thiamorpholine group It may be formed. In the case where R ₁ and R ₂ form a heterocyclic group together with the nitrogen atom to which they are bonded, they may further have a substituent on the heterocyclic ring. Examples of this substituent include alkyl groups such as methyl and ethyl; halogen groups such as bromo and chloro; hydroxyl groups, alkoxy groups, carboxyl groups, and ester groups.

  In the formula (I), X is a chain hydrocarbon group or alicyclic hydrocarbon group having 2 to 20 carbon atoms, preferably 2 to 12 carbon atoms, which may have a substituent, and aromatic. An organic group selected from a hydrocarbon group and a heterocyclic group. Examples of the organic group include a methylene group, an ethylene group, a propylene group, a hexylene group, a cyclobutylene group, a cyclohexylene group, a phenylene group, a thiazole group, a thiadiazole group, and a pyridylnaphthylene group. When X is a chain hydrocarbon group or an alicyclic hydrocarbon group, X has a heteroatom selected from the group consisting of a nitrogen atom, an oxygen atom, and a sulfur atom in the carbon chain. Alternatively, it may have an alkyl group such as methyl or ethyl, a halogen group such as bromo or chloro, a hydroxyl group, a carboxyl group, or an ester group.

As shown in the following reaction formula (1), the disulfide amine salt compound (I) according to the present invention is a disulfide compound having a carboxylic acid in one molecule represented by the formula (II) (wherein X represents the above As defined above) and an amine of formula (III) (wherein R ₁ , R ₂ and R ₃ are as defined above) can be produced. This reaction does not require an oxidant or a catalyst, and an appropriate solvent (for example, an aliphatic alcohol such as methanol, ethanol or propanol, an ether such as diethyl ether or tetrahydrofuran, or a ketone such as acetone or 2-butanone). Etc.) can be produced by mixing and reacting the compounds of formula (II) and formula (III).

  According to another aspect of the present invention, the disulfide amine salt compound (I) comprises a thiol compound (IV) containing a carboxylic acid in one molecule and an amine (III) as shown in the following reaction formula (2). ) In the presence of an oxidizing agent.

  In the reaction formulas (1) and (2), the amine (III) is stoichiometrically excessive (for example, 1.01 to 1.15 equivalents) relative to the disulfide compound (II) or the thiol compound (IV). ).

  Specific examples of the carboxylic acid-containing disulfide compound (II) used as a starting material in the reaction formula (1) include, for example, dithiodiglycolic acid, dithiodipropionic acid, dithiosalicylic acid, dithiobis (2-nitrobenzoic acid) Etc. On the other hand, examples of the thiol compound represented by the formula (IV) used in the reaction formula (2) include mercaptoacetic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, thiosalicylic acid, and thionicotinic acid.

  On the other hand, specific examples of the amine represented by the above formula (III) include, for example, methylamine, ethylamine, propylamine, butylamine, hexylamine, isobutylamine, tert-butylamine, dimethylamine, diethylamine, dipropylamine, diisopropyl. Amine, cyclopropylamine, cyclobutylamine, cyclohexylamine, N-methylcyclohexylamine, N-ethylcyclohexylamine, dicyclohexylamine, 2-methylcyclohexylamine, exo-2-aminonorbornane, 2-methoxyethylamine, bis (2-methoxy) Ethyl) amine, tetrafurfurylamine, morpholine, thiomorpholine, 1-methylpiperazine, 2-methylimidazole, ethanolamine, 2-aminocyclohexanol , Piperazine, 2-piperazine methanol, 2-piperazine ethanol, 1- (2-hydroxyethyl) piperazine, trimethylamine, triethylamine, tri-propyl amine.

  Although there is no restriction | limiting in particular as an oxidizing agent which can be used for the said Reaction formula (2), The following compound is mentioned. Chlorates such as sodium chlorate, potassium chlorate and ammonium chlorate; perchlorates such as sodium perchlorate and potassium perchlorate; inorganic peroxides such as lithium peroxide, sodium peroxide and potassium peroxide Chlorites such as sodium chlorite and potassium chlorite; bromates such as sodium bromate and potassium bromate; nitrates such as sodium nitrate, potassium nitrate and ammonium nitrate; sodium iodate, potassium iodate, iodine Iodates such as calcium acid; Permanganates such as potassium permanganate and sodium permanganate; Dichromates such as sodium dichromate and potassium dichromate; Periodates such as sodium periodate Periodate such as metaperiodic acid; chromic anhydride (chromium trioxide) ), Etc .; lead oxides such as lead dioxide; iodine oxides such as diiodine pentoxide; nitrites such as sodium nitrite and potassium nitrite; hypochlorites such as calcium hypochlorite; Chlorinated isocyanuric acid such as trichlorinated isocyanuric acid; peroxodisulfates such as ammonium peroxodisulfate; peroxoborate salts such as ammonium peroxoborate; perchloric acid; hydrogen peroxide; nitric acid; chlorine fluoride, trifluoride Halogenated compounds such as bromine, bromine pentafluoride, iodine pentafluoride and iodine; water-soluble chelate compounds of copper such as copper ethylenediaminetetraacetate and copper nitrilotripropionate; organic compounds such as dimethyl sulfoxide; oxygen and the like. When oxygen is used as the oxidizing agent, air can also be used as the oxygen source. These may be used alone or in combination as long as there is no danger. Of these, sodium chlorate, sodium perchlorate, sodium peroxide, sodium chlorite, hydrogen peroxide, iodine, copper ethylenediaminetetraacetate, copper nitrilotripropionate and oxygen are easy to react and high in efficiency. preferable.

  Examples of the solvent that can be used in the reaction include aliphatic alcohols such as methanol, ethanol, propanol, isopropanol, and butanol, ethers such as diethyl ether, tetrahydrofuran (THF), and isopropyl ether, and ketones such as acetone and 2-butanone. And nitrogen-containing organic solvents such as acetonitrile and dimethylformamide (DMF). These solvents may be used alone or in the form of a mixed solvent. Of these, aliphatic alcohols, ethers, and ketones are preferred because they are highly soluble in disulfides, thiols, and amines and can be easily removed from the reaction product.

  Although there is no limitation in particular in the reaction temperature of the said reaction, it is preferable to exist in the range of 0 to 100 degreeC. Below 0 ° C, the reaction time is slow, and at temperatures above 100 ° C, undesirable side reactions of the product may occur. This reaction temperature is more preferably in the range of 20 ° C to 70 ° C.

  Even if the vulcanization accelerator used in the rubber composition of the present invention consists only of an amine salt compound of a carboxylic acid-containing disulfide, in addition to the amine salt compound of the carboxylic acid-containing disulfide, What is generally used as a vulcanization accelerator may be included. The amine salt compound of the carboxylic acid-containing disulfide of the present invention is not limited to the other compounds as long as the desired vulcanization promoting effect and heat aging resistance can be improved without impeding the vulcanization promoting action of the carboxylic acid-containing disulfide amine salt compound. It can be used in an arbitrary ratio with respect to the total amount of the vulcanization accelerator.

  In addition to the carboxylic acid-containing disulfide amine salt compound, for example, a sulfenamide-based or thiuram-based vulcanization accelerator may be used in combination with the rubber composition according to the present invention. By using this vulcanization accelerator, vulcanization of the rubber component can be further accelerated. Examples of the sulfenamide-based vulcanization accelerator include N-cyclohexyl-2-benzothiazolylsulfenamide, Nt-butyl-2-benzothiazolylsulfenamide, N-oxydiethylene-2-benzo Examples include thiazolylsulfenamide and N, N′-dicyclohexyl-2-benzothiazolylsulfenamide. Examples of thiuram-based vulcanization accelerators include tetrakis (2-ethylhexyl) thiuram disulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetramethylthiuram monosulfide, tetrabenzylthiuram disulfide, and dipentamethylenethiuram tetrasulfide. .

  Specific examples of the vulcanizing agent that can be included in the rubber composition according to the present invention include sulfur, organic peroxide, quinone dioxime, metal oxide, and alkylphenol-formaldehyde resin.

  In addition to the components described above, the rubber composition according to the present invention includes reinforcing agents (fillers) such as carbon black and silica, vulcanization or crosslinking agents, various oils, anti-aging agents, plasticizers for tires, etc. Various additives that are generally compounded for rubber compositions of the above can be compounded, and such additives are general methods, using general-purpose rubber kneaders such as rolls, Banbury mixers, kneaders, etc. And kneaded into a composition that can be used for vulcanization or crosslinking. As long as the amount of these additives is not contrary to the object of the present invention, a conventional general amount can be used.

  The rubber composition according to the present invention can be suitably used for a typical pneumatic tire sidewall schematically shown in FIG. 1, and can be used as it is in a conventional general pneumatic tire production line. .

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, it cannot be overemphasized that the scope of the present invention is not limited to these Examples.

Preparation Example 1: Synthesis of disulfide amine salt compound A:
In 1000 g of methanol, 306.4 g (1 mol) of dithiosalicylic acid and 218.2 g (2.2 mol) of cyclohexylamine were added and reacted at room temperature for 30 minutes. After completion of the reaction, methanol was removed under reduced pressure, followed by filtration, washing twice with acetone and drying, to obtain 499.2 g (yield 99%) of Compound A as a white powder represented by the following formula.

¹ HNMR (400 MHz, DMSO-d6) δ in ppm: 1.0-1.3, 1.5, 1.7, 1.9, 2.9, 7.1, 7.2, 7.5, 7 .8
Elemental analysis value (%): C26H36N204S2
Calculated values: C, 61.87; H, 7.19; N, 5.55; S, 12.71
Measurement: C, 61.54; H, 7.28; N, 5.56; S, 12.72

Standard example, Examples 1-4 and Comparative Examples 1-4
Sample preparation In the formulation shown in Table I, when the vulcanization accelerator and the components excluding sulfur were kneaded with a 1.7 liter Banbury mixer (temperature control 60 ° C. × rotation speed 60 rpm) and the temperature reached 160 ° C. A master batch was obtained by discharge. The masterbatch was kneaded by turning the vulcanization accelerator and sulfur 10 times each left and right with an open roll to obtain a rubber composition.

  Next, the obtained rubber composition was vulcanized in a sample-shaped mold required for each test at 150 ° C. for 30 minutes to prepare a vulcanized rubber sample, and the physical properties of the vulcanized rubber were tested by the following test methods. Was measured. The results are shown in Table I.

Rubber Property Evaluation Test Method Breaking Elongation: Based on JIS K 6251, a dumbbell No. 3 type sample was left to age in a gear oven at 90 ° C. for 48 hours, and then the breaking elongation was measured. The results are shown as an index with the value of the standard example being 100. The larger this value, the better the crack resistance.
Hardness: Measured according to JIS K 6253. The results are shown as an index with the value of the standard example being 100. Larger values indicate better cut resistance.

  Bending fatigue resistance: The length of a crack after bending a test piece which was left to stand in a gear oven at 90 ° C. for 48 hours and bent 100,000 times at room temperature was measured by a demach bending test according to JIS K 6260. (Stroke was 40 mm, speed was 300 ± 10 rpm). The result was expressed as an index with the value of the standard example as 100. A larger index value indicates a smaller amount of crack growth and better bending fatigue resistance.

Table I footnote * 1: RSS # 3
* 2: Nipol BR1220 manufactured by Nippon Zeon Co., Ltd.
* 3: VCR412 manufactured by Ube Industries, Ltd. (cis content: 94.7%, n-hexane insoluble content: 12%)
* 4: Seest N manufactured by Tokai Carbon Co., Ltd.
* 5: Diana Process Oil AH-20 manufactured by Idemitsu Kosan Co., Ltd.
* 6: Antigen 6C manufactured by Sumitomo Chemical Co., Ltd.
* 7: Zinc Oxide Co., Ltd. 3 types of zinc oxide * 8: Nippon Oil & Fats Co., Ltd. Bead stearic acid * 9: FLEXSYS SANTOCURE TBBS
* 10: Compound A synthesized in Preparation Example 1
* 11: Fine powdered sulfur with Jinhua seal oil manufactured by Tsurumi Chemical Co., Ltd.

  The standard example shows a conventional typical formulation, and the comparative example 1 is an example in which the blending amount of a normal sulfenamide vulcanization accelerator is increased to increase the hardness, but the elongation at break / aging fatigue resistance after aging Decreases. Comparative Examples 2 and 3 are examples in which polybutadiene rubber VCR is used in a normal vulcanization system. The hardness increases but the elongation at break / bending fatigue resistance after aging decreases. Comparative Example 4 uses the carboxylic acid-containing disulfide amine salt compound used in the present invention, but does not use BR (VCR) and has low hardness.

  In contrast, Examples 1 and 2 are examples in which the carboxylic acid-containing disulfide amine salt compound of the present invention is used alone and in combination with a VCR, and the balance of elongation at break / hardness / flexural fatigue resistance after aging is balanced. It has been improved. Examples 3 and 4 are examples in which the carboxylic acid-containing disulfide amine salt compound of the present invention and other conventional sulfenamide vulcanization accelerators were used in combination with a VCR. The balance of later bending fatigue resistance is improved.

  As described above, according to the present invention, by using a vulcanization accelerator including a specific rubber composition (A) and an amine salt compound (B) of a carboxylic acid-containing disulfide, it has high trauma resistance (cut resistance). ), A rubber composition useful as a sidewall compound that balances fatigue resistance (crack resistance) and aging resistance in a high order.

It is a meridian half cross-sectional view of a typical pneumatic tire schematically showing a sidewall using the rubber composition according to the present invention together with other parts.

Claims (2)

(A) (1) 60 to 20 parts by weight of natural rubber and / or polyisoprene rubber and (2) n-based mainly on syndiotactic-1,2-polybutadiene as a matrix component of high cis 1,4-polybutadiene 100 parts by weight of a diene rubber containing 40-80 parts by weight of a polybutadiene rubber containing 5% by weight or more of hexane-insoluble matter and (B) Formula (I):

(In the formula, R ₁ , R ₂ and R ₃ are independently hydrogen or an organic group which may have a heteroatom having 1 to 20 carbon atoms and / or a substituent, and X is 2 to 20 carbon atoms. The hetero atom and / or the organic group which may have a substituent.
A rubber composition for tires comprising 0.2 to 5 parts by weight of an amine salt compound of a carboxylic acid-containing disulfide represented by the formula:   A pneumatic tire using the rubber composition according to claim 1 as a sidewall.

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