JP2008050452A - Rubber composition for tire and pneumatic tire produced by using the composition as bead filler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition having improved balance of elongation at break and high elastic modulus. <P>SOLUTION: The rubber composition for tire comprises (A) 100 pts.wt. of a diene rubber containing (i) 50-90 pts.wt. of natural rubber and/or polyisoprene rubber and (ii) 10-50 pts.wt. of a styrene-butadiene copolymer rubber and (B) 0.1-6 pts.wt. of a carboxylic acid-containing disulfide amine salt compound expressed by formula (I). The invention further provides a pneumatic tire produced by using the composition as a bead filler. <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 particularly, a tire rubber composition having an improved balance between elongation at break and high elastic modulus, and a pneumatic tire using the same as a bead filler. About.

  In a pneumatic tire, the bead filler needs to use rubber having a high elastic modulus in order to suppress the movement of the bead portion and the carcass turn-up edge and prevent edge separation. In addition, it is desirable to use a rubber having a high elastic modulus from the viewpoint of reducing the weight of the tire and improving the handling stability. On the other hand, when the elastic modulus is generally increased, the elongation at break decreases, and as a result, the edge separation occurs without being able to cope with the deformation of the edge portion, so that the rubber used for the bead filler has a high elastic modulus. And high break elongation are required (see Patent Documents 1 and 2).

Japanese Patent Laid-Open No. 05-098081 JP-A-11-140230

  Accordingly, an object of the present invention is to provide a rubber composition having an improved balance between elongation at break and high elastic modulus suitable for use as a bead filler for pneumatic tires.

（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０．１〜６重量部
を含んでなるタイヤ用ゴム組成物並びにそれをビードフィラーに用いた空気入りタイヤが提供される。 According to the present invention, a diene comprising (A) 50 to 90 parts by weight of natural rubber (NR) and / or polyisoprene rubber (IR) and (ii) 10 to 50 parts by weight of styrene-butadiene copolymer rubber (SBR) 100 parts by weight of rubber 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 0.1 to 6 parts by weight of an amine salt compound of a carboxylic acid-containing disulfide represented by formula (1) and a pneumatic tire using the same as a bead filler are provided.

  According to the present invention, a rubber composition having an improved balance between elongation at break and high elastic modulus can be obtained by using a vulcanization accelerator containing an amine salt compound of a carboxylic acid-containing disulfide.

  As a result of advancing research to solve the above problems, the present inventors have determined that a specific rubber composition containing NR and / or IR and SBR has an amine salt compound of a carboxylic acid-containing disulfide of the formula (I) ( By using the vulcanization accelerator containing B), the balance between the elongation at break and the high elastic modulus of the rubber composition was successfully improved.

  According to the invention, (i) natural rubber (NR) and / or polyisoprene rubber (IR) 50-90 parts by weight, preferably 60-85 parts by weight and (ii) styrene-butadiene copolymer rubber (SBR) The amine salt compound (B) of the carboxylic acid-containing disulfide represented by the above general formula (I) is added in an amount of 0.1 to 100 parts by weight of the rubber component (A) comprising 10 to 50 parts by weight, preferably 15 to 40 parts by weight. 1 to 6 parts by weight is blended.

In a preferred embodiment of the present invention, in addition to the components (A) and (B), a sulfenamide vulcanization accelerator (C) and sulfur (D) are blended with 100 parts by weight of the component (A). . The blending amounts of the components (B), (C) and (D) preferably satisfy the relationship of the following formula (1).
1.2 ≦ (D) / [(B) / 2 + (C)] ≦ 3.0 (1)
If this ratio is small, the elongation at break is low, and there is a risk that improvement in high-speed durability may be reduced. On the other hand, if the ratio is large, the effect of improving the elastic modulus is reduced, and improvement in high-speed durability may be reduced. Absent.

  According to the present invention, 0.1 to 6 parts by weight, preferably 1 to 5 parts by weight of the carboxylic acid-containing disulfide amine salt compound of the formula (I) is added per 100 parts by weight of the diene rubber. If the compounding amount of the amine salt compound (I) of the carboxylic acid-containing disulfide is small, the elastic modulus is low, which is not preferable. On the other hand, if the amount is too large, the rubber becomes too hard and the elongation at break is insufficient.

  In the rubber composition according to the present invention, as the rubber component (A), (i) NR and / or IR and (ii) SBR are blended in the ratio as described above. If the blending amount of NR and / or IR is small (that is, if the blending amount of SBR is large), the elongation at break is lowered and high-speed durability is lowered, which is not preferable. Conversely, the blending amount of NR and / or IR is large. (In other words, when the amount of SBR is small), the elongation at break is high, but this is not preferable because the elastic modulus is lowered and the extrusion processability is deteriorated. In addition, NR, IR, and SBR used in the present invention may be any that can be used for tires and the like. The rubber composition of the present invention may contain a small amount of any diene rubber other than NR, IR and SBR and other rubbers as long as the object of the present invention is not impaired.

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.

  The vulcanization accelerator used in the rubber composition of the present invention may consist only of an amine salt compound of a carboxylic acid-containing disulfide, but in addition to the amine salt compound of the carboxylic acid-containing disulfide, unvulcanized in the art. The sulfenamide vulcanization accelerator (C) generally used as a rubber vulcanization accelerator is blended with sulfur (D), and the blending ratio satisfies the relationship of the above formula (1). preferable.

  Examples of the sulfenamide-based vulcanization accelerator that can be used in the rubber composition according to the present invention include N-cyclohexyl-2-benzothiazolylsulfenamide and Nt-butyl-2-benzothiazolylsulfene. Examples include amide, N-oxydiethylene-2-benzothiazolylsulfenamide, N, N′-dicyclohexyl-2-benzothiazolylsulfenamide, and the like.

  In addition to the sulfur, examples of the vulcanizing agent that can be included in the rubber composition according to the present invention include organic peroxides, quinone dioximes, metal oxides, and alkylphenol-formaldehyde resins.

  In addition to the components described above, the rubber composition according to the present invention is used for tires such as reinforcing agents (fillers) such as carbon black and silica, various oils, anti-aging agents, plasticizers, and other rubber compositions. Various additives that are generally blended can be blended, and such additives are kneaded by a general method using a general-purpose rubber kneader such as a roll, a Banbury mixer, a kneader, etc. And 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 bead filler or the like schematically shown in FIG. 1 and used as it is in a conventional general pneumatic tire production line. Can do.

  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 1, Examples 1-8 and Comparative Examples 1-3
Sample preparation In the formulation shown in Table I, the ingredients other than the vulcanization accelerator and sulfur were kneaded for 5 minutes in a 1.7 liter Banbury mixer (temperature controlled 60 ° C x 60 rpm) and released when the temperature reached 160 ° C. A master batch was obtained. This master batch was kneaded by turning the vulcanization accelerator and sulfur 10 times left and right with an open roll to obtain a rubber composition.

  Next, the rubber composition thus obtained was vulcanized in a 15 × 15 × 0.2 cm mold at 150 ° C. for 30 minutes to prepare a vulcanized rubber sheet, which was formed into a sample shape necessary for the following test method. The physical properties of the vulcanized rubber were measured. The results are shown in Table I.

Rubber property evaluation test method Breaking elongation: A dumbbell No. 3 type sample was stretched at a speed of 500 mm / min in accordance with JIS 6251, and the breaking elongation at 20 ° C. was measured. The results are shown as an index with the value of the standard example being 100. It shows that breaking elongation is so high that this figure is large.
Storage elastic modulus E ′: Based on JIS 6394, the storage elastic modulus E ′ at 20 ° C. and 100 ° C. was measured at an initial strain of 10%, an amplitude of 2%, and a frequency of 20 Hz. The results are shown as an index with the value of the standard example being 100. A larger value indicates a higher elastic modulus.

High-speed durability : A tire with a 265 / 70R16 all-season pattern was prepared using bead fillers extruded using each rubber composition in a 4.5 "pin type cold feed extruder. Comparative Example 2 was a bead filler. Production of the tire for evaluation was stopped due to poor extrusion shape.After completion of the JIS D-4230 high-speed durability test with a drum diameter of 1707 mm, the test was continued at a speed of 10 km / hr every 30 minutes until the tire broke. The distance traveled until breakage was indicated by an index with the distance traveled by the tire using the rubber composition of the standard example as 100. The larger this value, the better the high-speed durability.

Table I footnote * 1: Thai natural rubber STR20
* 2: Styrene butadiene copolymer rubber made by Nippon Zeon Co., Ltd. Nipol 1502
* 3: Carbon black seast 3 manufactured by Tokai Carbon Co., Ltd.
* 4: Three types of zinc oxide manufactured by Shodo Chemical Industry Co., Ltd. * 5: Industrial stearic acid manufactured by Chiba Fatty Acid Co., Ltd. * 6: Idemitsu Kosan Co., Ltd. Diana Process Oil AH-20
* 7: Sumitomo Chemical Co., Ltd. Antigen RD-G
* 8: Flexsys Co., Ltd. Christex HS OT 20
* 9: Ouchi Shinsei Chemical Co., Ltd. Noxeller NS-F
* 10: Compound A synthesized in Preparation Example 1

  As is apparent from the results in Table I, Examples 1 and 2 are examples in which a predetermined amount of the vulcanization accelerator of the present invention was used alone, with high breaking elongation, high elastic modulus, and high-speed durability improved. . On the other hand, Comparative Example 1 uses the vulcanization accelerator of the present invention alone in excess of the upper limit and has a high elastic modulus but is not sufficient in breaking elongation and high-speed durability.

  Example 3 is an example in which the vulcanization accelerator of the present invention is used in combination with a sulfenamide-based vulcanization accelerator, which has high elongation at break, high elastic modulus, and high-speed durability. Example 4 is an example in which the lower limit of the vulcanization accelerator of the present invention is used, and in combination with the sulfenamide vulcanization accelerator, a slight improvement is observed. In Example 5, when the vulcanization accelerator of the present invention and the amount of sulfur are within the specified range of the formula (1), high elongation at break and improvement in high-speed durability are observed. However, although Example 6 is an example of the present invention, when the value of the formula (1) of the vulcanization accelerator and the amount of sulfur used in the preferred embodiment of the present invention exceeds 3.0, the elastic modulus is improved. It shows that the effect and the improvement effect of high-speed durability are reduced.

  Example 7 is a case where the vulcanization accelerator of the present invention alone is used at a predetermined amount and at the upper limit of the ratio of NR / SBR, but the elastic modulus is equal to that of the standard example, but the high breaking elongation is improved due to high elongation at break. To do. In Comparative Example 2, a predetermined amount of the vulcanization accelerator of the present invention is used alone and NR / SBR is used in excess of NR, and a high elongation at break can be obtained, but the elastic modulus decreases. Moreover, the extrudability deteriorated and the tire for evaluation could not be manufactured.

  Example 8 is an example in which a predetermined amount of the vulcanization accelerator of the present invention is used alone and NR / SBR is used at the NR lower limit (SBR upper limit), but the improvement in breaking elongation is small, but the high elastic modulus and high-speed durability are high. improves. On the other hand, Comparative Example 3 is an example in which the vulcanization accelerator of the present invention is used alone in a predetermined amount, but NR / SBR is used below the NR lower limit (exceeding the SBR upper limit), and has a high elastic modulus but is not broken. Elongation decreased and high speed durability deteriorated.

  In the present invention, the use of the carboxylic acid-containing disulfide amine salt compound (I) as a vulcanization accelerator in specific NR / IR and SBR rubber compositions improves the balance between high modulus and high elongation at break. Therefore, it is useful as a bead filler for pneumatic tires.

It is a meridian half section view of the typical pneumatic tire which shows typically the bead filler using the rubber composition concerning the present invention with other parts.

Claims (3)

(A) (i) natural rubber and / or polyisoprene rubber 50 to 90 parts by weight and (ii) 100 parts by weight of diene rubber containing 10 to 50 parts by weight of styrene-butadiene copolymer rubber, 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 0.1 to 6 parts by weight of an amine salt compound of a carboxylic acid-containing disulfide represented by the formula: It further contains a sulfenamide-based vulcanization accelerator (C) and sulfur (D), and has a net sulfur content (D), an amine salt compound (B) of the carboxylic acid-containing disulfide, and a sulfenamide-based vulcanization accelerator (C The rubber composition for tires according to claim 1, wherein the blending amount thereof satisfies the following formula (1).
1.2 ≦ (D) / [(B) / 2 + (C)] ≦ 3.0 (1)   A pneumatic tire using the rubber composition according to claim 1 as a bead filler.

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