JP5394726B2 - Run-flat tire rubber composition and run-flat tire - Google Patents

Description

The present invention relates to a rubber composition for a run-flat tire and a run-flat tire using the same.

Currently, run-flat tires with a high-strength sidewall reinforcement layer placed inside the sidewall have been put into practical use, and even if the air pressure is lost due to puncture (zero internal pressure), the rigidity of the tire is reduced. Even when it is maintained and repeatedly bent, it is possible to reduce the damage of rubber and to travel safely for a certain distance. As a result, there is no need to always have spare tires, and weight reduction of the entire vehicle can be expected. However, there is a limitation on speed and distance in run flat running during puncture of the run flat tire, and further improvement of the durability of the run flat tire is desired.

As a method of improving the durability of the run flat tire, there is a method of suppressing deformation by increasing the thickness of the reinforcing layer and preventing destruction due to the deformation. However, since the weight of the tire increases, the original purpose of the run flat tire is It is against the weight reduction that is. Another method is to increase the hardness of the reinforcing layer and suppress deformation by increasing the amount of reinforcing filler such as carbon black. However, in the process of kneading and extrusion, the load on the kneading machine is increased and added. Since heat generation increases in post-sulfur properties, improvement in run-flat durability cannot be expected so much.

Patent Document 1 discloses a run flat tire in which performance such as run flat durability is improved by using a rubber composition in which flaky graphite is blended with diene rubber as a sidewall reinforcing rubber layer. However, the use of hydrotalcite and organic resins has not been studied, and there is room for improvement in run flat durability.
JP 2007-297602 A

The present invention solves the above problems and has a rubber composition for run-flat tires having good heat resistance and low heat build-up, and excellent rigidity and durability of run-flat tires, and is produced using the composition. An object of the present invention is to provide a run flat tire having a sidewall reinforcing layer.

The present invention relates to a rubber composition for a run-flat tire containing a rubber component, hydrotalcite and an organic resin.

The organic resin is preferably a petroleum resin.
In the rubber composition, the content of natural rubber in the rubber component 100% by mass is 5 to 50% by mass, the content of butadiene rubber is 20 to 70% by mass, and the content of styrene butadiene rubber is 20 to 70% by mass. It is preferable that Moreover, it is preferable that content of hydrotalcite is 2-70 mass parts and content of organic resin is 2-50 mass parts with respect to 100 mass parts of said rubber components.

The hydrotalcite is represented by the following formula (1);
[(M ₁ ²⁺ ) _(1-x) (M ₂ ³⁺ ) _x (OH ⁻ ) ₂ ] ^{x +} · [(A ⁿ⁻ ) _{x / n} · mH ₂ O] ^x− (1)
(Numbers satisfying _wherein, ^{M 1 2+} is a divalent metal _cation, ^{M 2 3+} is a trivalent metal ^{cation, A n-is} .x representing an n-valent anion 0 <x ≦ 0.5, m is It is preferably a compound represented by 0) or a fired product thereof.

The rubber composition is preferably used for a sidewall reinforcing layer of a run flat tire.

The present invention also relates to a run flat tire having a sidewall reinforcing layer produced using the rubber composition.

According to the present invention, since it is a rubber composition for a run-flat tire in which a hydrotalcite and an organic resin are blended in the rubber component, it has excellent heat resistance and low heat buildup, and is also excellent in rigidity and run-flat durability. Run flat tires can be provided.

The rubber composition for run-flat tires of the present invention contains a rubber component, a hydrotalcite and an organic resin. By blending both components of hydrotalcite and organic resin into the rubber member of the run-flat tire, particularly the reinforcing rubber layer in the sidewall portion, the hydrotalcite can be favorably dispersed in the rubber member. For this reason, high heat resistance and low heat build-up can be imparted to the run-flat tire, and the strength of the rubber can be increased, so that rigidity and run-flat durability can also be improved.

Examples of rubber components include natural rubber (NR), epoxidized natural rubber (ENR), butadiene rubber (BR), styrene butadiene rubber (SBR), isoprene rubber (IR), butyl rubber (IIR), and acrylonitrile butadiene rubber (NBR). ), Diene rubbers such as chloroprene rubber (CR), styrene isoprene butadiene rubber (SIBR), styrene isoprene rubber (SIR), and isoprene butadiene rubber. These may be used alone or in combination of two or more. May be. Among them, it is preferable to use NR, IR, BR, and SBR because excellent heat resistance and low exothermic property are obtained, and at the same time, high run flat durability is obtained, and NR, BR, and SBR are used in combination. More preferably.

The NR is not particularly limited, and for example, those commonly used in the tire industry such as SIR20, RSS # 3, TSR20, and the like can be used. A general IR can be used. The BR is not particularly limited, and for example, BR having a high cis content, BR containing a syndiotactic polybutadiene crystal, and the like can be used. Examples of SBR include those obtained by a solution polymerization method and those obtained by an emulsion polymerization method, but are not particularly limited.

When the rubber component contains NR, the content of NR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, and further preferably 15% by mass or more. If it is less than 5% by mass, the rubber strength tends to decrease. On the other hand, the content of the NR is preferably 50% by mass or less, more preferably 40% by mass or less, and further preferably 35% by mass or less. If it exceeds 50% by mass, sufficient heat resistance and hardness cannot be obtained, and durability tends to decrease.

When the rubber component contains BR, the content of BR in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 25% by mass or more, and further preferably 28% by mass or more. If it is less than 20% by mass, the effect of reducing heat generation tends to be small. 70 mass% or less is preferable, as for content of the said BR, 65 mass% or less is more preferable, and 60 mass% or less is still more preferable. When it exceeds 70 mass%, there exists a tendency for intensity | strength to fall.

When the rubber component contains SBR, the content of SBR in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 30% by mass or more, and further preferably 40% by mass or more. If it is less than 20% by mass, the heat generation of the rubber will be insufficient, the elongation (EB) of the rubber will be insufficient, and the heat resistance may be deteriorated. Moreover, 70 mass% or less is preferable, as for content of the said SBR, 65 mass% or less is more preferable, and 60 mass% or less is still more preferable. When it exceeds 70 mass%, there exists a tendency for the elongation (EB) of rubber to fall.

In the present invention, hydrotalcite and organic resin are used. By using both these components, a run flat tire excellent in heat resistance, rigidity and durability can be obtained. For example, in the reinforced rubber layer, the temperature rises by concentrating on a limited spot, and the destruction of the rubber proceeds. In the present invention, both the hydrotalcite and organic resin components are added, and the hydrotalcite is dispersed in the rubber, whereby the heat resistance is enhanced and the progress of the rubber breakage can be suppressed. It is assumed that flat durability can be obtained.

The hydrotalcite may be either a synthetic product or a natural product and is not particularly limited. For example, the following formula (1);
[(M ₁ ²⁺ ) _(1-x) (M ₂ ³⁺ ) _x (OH ⁻ ) ₂ ] ^{x +} · [(A ⁿ⁻ ) _{x / n} · mH ₂ O] ^x− (1)
(Numbers satisfying _wherein, ^{M 1 2+} is a divalent metal _cation, ^{M 2 3+} is a trivalent metal ^{cation, A n-is} .x representing an n-valent anion 0 <x ≦ 0.5, m is And a fired product thereof can be used. These may be used alone or in combination of two or more.

^Examples of M ₁ ²⁺ include divalent metal cations such as Mg ²⁺ , Mn ²⁺ , Fe ²⁺ , Co ²⁺ , Ni ²⁺ , Cu ²⁺ and Zn ²⁺ , and Mg ²⁺ is particularly preferable. ^Examples of M ₂ ³⁺ include trivalent metal cations such as Al ³⁺ , Fe ³⁺ , Cr ³⁺ , Co ³⁺ , In ³⁺ , and Al ³⁺ is particularly preferable. ^{Further, A} as the ^{n-, OH -, F -,} Cl -, Br -, NO 3-, CO 3 2-, SO 4 2-, Fe (CN) 6 3-, CH 3 COO -, oxalic acid ion , N-valent anions such as salicylate ion, and CO ₃ ²⁻ is particularly preferable. As hydrotalcite, for example, a compound represented by Mg ₆ Al ₂ CO ₃ (OH) ₁₆ .H ₂ O (Perkalite manufactured by Kayaku Akzo Co., Ltd., anion type clay (CO ₃ ⁻ , OH ⁻ )) ), Mg _4.3 Al ₂ (OH) _12.6 CO ₃ · m′H ₂ O (when x = 0.315 in the above formula (1)) Products excluding water (manufactured by Kyowa Chemical Industry Co., Ltd.) can be obtained as commercial products.

The content of the hydrotalcite is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, still more preferably 7 parts by mass or more, and particularly preferably 10 parts by mass or more with respect to 100 parts by mass of the rubber component. . If the amount is less than 2 parts by mass, the effect of addition may not be obtained. The content is preferably 70 parts by mass or less, more preferably 50 parts by mass or less, still more preferably 40 parts by mass or less, and particularly preferably 30 parts by mass or less with respect to 100 parts by mass of the rubber component. When it exceeds 70 mass parts, there exists a tendency for heat resistance and run flat durability to fall.

Although it does not specifically limit as an organic resin, It is preferable to use a petroleum resin from a heat resistant, low heat generating property, or runflat durability viewpoint.

The petroleum resin can be obtained by polymerizing C5 petroleum hydrocarbon. Here, the C5 petroleum hydrocarbon means a C5 fraction obtained by thermal decomposition of naphtha, and specifically, aliphatic diolefins (isoprene, 1,3-pentadiene, etc.) and cyclohexane. Diolefins such as pentadienes (cyclopentadiene, dicyclopentadiene, alkyl-substituted products thereof, mixtures thereof and the like); monoolefins such as 2-methyl-1-butene, 2-methyl-2-butene and cyclopentene; Etc.

Petroleum resins, together with C5 petroleum hydrocarbons, are modified with styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α- Polymerized aromatic olefins such as methylstyrene, vinylnaphthalene, and vinylanthracene may also be used. Examples of other copolymerizable monomers include chain α-olefins and chain diolefins. A preferable blending amount of the copolymerizable monomer is less than 50% by mass in 100% by mass of all monomers.

As the petroleum resin, C5 aliphatic petroleum resin and cyclopentadiene petroleum resin can be preferably used.
Examples of the C5 aliphatic petroleum resin include polymers obtained by polymerizing the above aliphatic diolefins using an aluminum halide catalyst or the like. Examples of the cyclopentadiene-based petroleum resin include polymers obtained by polymerizing the above cyclopentadiene alone or in a mixture, and copolymers with monomers copolymerizable with the cyclopentadiene. Among them, dicyclopentadiene is mainly used. A dicyclopentadiene petroleum resin as a component is preferred.

The softening point of the petroleum resin is preferably 80 ° C. or higher, more preferably 90 ° C. or higher. Below 80 ° C., the resin itself tends to be sticky and difficult to use in the handling of the resin itself. The softening point is preferably 150 ° C. or lower, more preferably 120 ° C. or lower. When it exceeds 150 ° C., it tends to remain undissolved even after kneading, resulting in poor dispersion.

Examples of commercially available petroleum resins include Quinton (manufactured by Nippon Zeon Co., Ltd.), Marcaretz (manufactured by Maruzen Petrochemical Co., Ltd.), and Alcon (manufactured by Arakawa Chemical Industries, Ltd.).

The content of the organic resin is preferably 2 parts by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, and particularly preferably 10 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 2 parts by mass, the hydrotalcite dispersion effect may not be obtained. The content is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, still more preferably 30 parts by mass or less, and particularly preferably 20 parts by mass or less with respect to 100 parts by mass of the rubber component. If it exceeds 50 parts by mass, TB and EB (tensile properties) may be deteriorated and tan δ (exothermic property) may be deteriorated. Moreover, it exists as a foreign material in rubber | gum, and there exists a possibility that reinforcement hardening may be lost.

The blending ratio of hydrotalcite and organic resin (hydrotalcite / organic resin) is preferably 40/60 or more, more preferably 55/45 or more, and still more preferably 70/30 or more on a mass basis. The blending ratio is preferably 95/5 or less, more preferably 90/10 or less, and still more preferably 85/15 or less. When the blending ratio is in the above range, good heat resistance, low heat build-up, and run flat durability can be obtained.

In addition to the above components, the rubber composition of the present invention includes compounding agents conventionally used in the rubber industry, such as fillers such as carbon black and silica, stearic acid, zinc oxide, various anti-aging agents, wax, sulfur. Alternatively, a vulcanizing agent such as a sulfur compound, a vulcanization accelerator, a vulcanization acceleration auxiliary agent, and the like can be appropriately blended as necessary.

The carbon black is not particularly limited, and for example, FEF, GPF, HAF, ISAF, SAF and the like can be used. Carbon black can improve the strength of rubber.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 30 m ² / g or more, more preferably 35 m ² / g or more, from the viewpoint of obtaining sufficient reinforcement and durability. Also, _N 2 SA of carbon black is from the viewpoint of excellent low heat build-is preferably not more than 100 m ² / g, more preferably not more than ^{80m 2 / g, 60m 2 /} g or less is more preferable.
The N ₂ SA of carbon black is determined by the A method of JIS K6217.

The dibutyl phthalate oil absorption (DBP) of carbon black is preferably 50 ml / 100 g or more, more preferably 80 ml / 100 g or more, from the viewpoint that sufficient reinforcing properties can be obtained. The DBP of carbon black is preferably 300 ml / 100 g or less, more preferably 200 ml / 100 g or less, from the viewpoint of excellent fatigue resistance such as elongation at break.
In addition, DBP of carbon black is calculated | required by the measuring method of JISK6217-4.

The content of carbon black is preferably 20 parts by mass or more and more preferably 35 parts by mass or more with respect to 100 parts by mass of the rubber component from the viewpoint of obtaining sufficient rubber strength. Further, the content of carbon black is preferably 80 parts by mass or less, and more preferably 65 parts by mass or less from the viewpoint that the viscosity at the time of kneading is appropriately maintained and processability is excellent.

Examples of the vulcanization accelerator include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N, N′-dicyclohexyl-2- Examples include benzothiazolylsulfenamide (DZ), mercaptobenzothiazole (MBT), dibenzothiazolyl disulfide (MBTS), and diphenylguanidine (DPG). Of these, sulfenamide-based vulcanization accelerators such as TBBS, CBS, and DZ are preferable, and TBBS is particularly preferable because of excellent vulcanization characteristics, low exothermicity after vulcanization, and good run flat durability. .

As the vulcanization accelerating aid, an alkylphenol / sulfur chloride condensate can be suitably used. Thereby, a rubber composition with high hardness can be obtained. Examples of the alkylphenol / sulfur chloride condensate include those represented by the following formula.

（式中、ｎは０又は１〜１０の整数であり、Ｘは２〜４の整数であり、Ｒは炭素数５〜１２のアルキル基である。）

(In the formula, n is 0 or an integer of 1 to 10, X is an integer of 2 to 4, and R is an alkyl group having 5 to 12 carbon atoms.)

From the viewpoint of good dispersibility of the alkylphenol / sulfur chloride condensate in rubber, n is preferably an integer of 1 to 9. Moreover, X is preferably an integer of 2 to 4 and more preferably 2 from the viewpoint that high hardness can be efficiently obtained. When X exceeds 4, it tends to be thermally unstable. When X is 1, the sulfur content (sulfur weight) in the alkylphenol-sulfur chloride condensate decreases. From the viewpoint of good dispersibility in rubber, the lower limit of R is preferably an alkyl group having 5 or more carbon atoms, more preferably 6 or more, and the upper limit is preferably 12 or less carbon atoms, more preferably 9 or less carbon atoms. It is an alkyl group. Specific examples of the alkylphenol / sulfur chloride condensate include Tackrol V200 (Taoka Chemical Co., Ltd.) having an alkyl group of n = 0 to 10, X = 2, R = C ₈ H ₁₇ and a sulfur content of 24% by mass. Manufactured).

The rubber composition of the present invention is produced by a general method. That is, it can be produced by a method of kneading the above components with a Banbury mixer, a kneader, an open roll or the like and then vulcanizing.

The rubber composition of the present invention is used as a rubber member of a run-flat tire, and is particularly preferably used as a reinforcing rubber layer (sidewall reinforcing layer) of a sidewall portion. Due to the presence of the reinforced rubber layer, the vehicle can be supported even when air pressure is lost, and excellent run-flat durability can be imparted. Here, the reinforcing rubber layer in the sidewall portion refers to a lining strip layer disposed inside the sidewall portion of the run flat tire. Specifically, a reinforcing rubber layer (a crescent-shaped reinforcing rubber layer that is disposed from the bead portion to the shoulder portion inside the carcass ply and gradually decreases in thickness in both end directions, as shown in the drawings of JP-A-2004-330822. ) And the like.

The run flat tire of the present invention is produced by a usual method using the rubber composition. That is, if necessary, the rubber composition containing the compounding agent is extruded in accordance with the shape of each member such as a sidewall reinforcing layer of the tire at an unvulcanized stage, and tire molding together with other tire members An unvulcanized tire is formed by molding on a machine by a normal method. This unvulcanized tire is heated and pressurized in a vulcanizer to obtain a run flat tire.

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

(material)
Natural rubber (NR): RSS # 3
Butadiene rubber (BR): BR150B manufactured by Ube Industries, Ltd.
Styrene butadiene rubber (SBR): SBR1502 manufactured by Sumitomo Chemical Co., Ltd.
Carbon black: Diamond Black E (FEF, N ₂ SA: 41 m ² / g, DBP oil absorption: 115 ml / 100 g) manufactured by Mitsubishi Chemical Corporation
Hydrotalcite: Perkalite (Mg ₆ Al ₂ CO ₃ (OH) ₁₆ · H ₂ O) manufactured by Kayaku Akzo Corporation
Petroleum resin: Marukaretsu M-890A manufactured by Maruzen Petrochemical Co., Ltd. (dicyclopentadiene petroleum, resin softening point: 105 ° C.)
Anti-aging agent 6C: Antigen 6C (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd.
Anti-aging agent FR: Antigen FR manufactured by Sumitomo Chemical Co., Ltd. (A product obtained by purifying a reaction product of an amine and a ketone and having no amine residue, a quinoline-based anti-aging agent)
Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Stearate: Sulfur sulfur manufactured by NOF Corporation: Powdered sulfur vulcanization accelerator manufactured by Karuizawa Sulfur Co., Ltd .: Ouchi Shinsei Chemical Industry Co., Ltd. NOxeller NS (N-tert-butyl-2-benzothiazolylsulfenamide)
Vulcanization accelerating adjuvant: Tactrol V200 (Taoka Chemical Industries, Ltd.)

Examples 1-6 and Comparative Examples 1-2
In accordance with the formulation shown in Table 1, using a Banbury mixer, chemicals other than sulfur, a vulcanization accelerator and a vulcanization acceleration auxiliary were kneaded for 4 minutes at 150 ° C. to obtain a kneaded product. Next, using an open roll, sulfur, a vulcanization accelerator and a vulcanization acceleration auxiliary agent are added to the kneaded material obtained, and kneaded for 3 minutes at 80 ° C. to obtain an unvulcanized rubber composition. It was. Furthermore, the obtained unvulcanized rubber composition was press vulcanized for 20 minutes under the condition of 160 ° C. to prepare a vulcanized rubber composition.

As the side wall reinforcing layer, each unvulcanized rubber composition obtained above is formed into the shape of a reinforcing rubber layer (lining strip layer) of the side wall portion of the tire, and is bonded together with other members to be unvulcanized. Sulfur tires were formed and press vulcanized at 160 ° C. for 120 minutes to produce run-flat tires for testing (size: 215 / 45ZR17).

The following evaluation was performed about the produced vulcanized rubber composition and the run flat tire for a test. The evaluation results are shown in Table 1.

(Viscoelasticity test)
Using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd., the complex elastic modulus (E ^* ) and loss tangent (tan δ) were measured under the conditions of a measurement temperature of 70 ° C., an initial strain of 10%, a dynamic strain of ± 1%, and a frequency of 10 Hz. The measured E ^* and tan δ were expressed as an index with Comparative Example 1 as 100 (reference). The larger the E ^* index, the higher the rigidity and the better. Moreover, the larger the index of tan δ, the smaller the heat generation, which is preferable.

(High temperature tensile properties)
In accordance with JIS K 6251 “Vulcanized Rubber and Thermoplastic Rubber-Determination of Tensile Properties”, a No. 3 dumbbell-shaped test piece comprising (vulcanized rubber composition) vulcanized rubber sheet was used, and the measurement temperature was 100 ° C. A tensile test was performed, the elongation at break (EB) was measured, and the measured EB was expressed as an index with Comparative Example 1 being 100 (reference). It shows that heat resistance is so high that an index | exponent is large.

(Run flat durability)
The manufactured test run-flat tire was run on a drum at 80 km / h at an air pressure of 0 kPa, the running distance until the tire broke was measured, and the run-flat durability index of Comparative Example 1 was set to 100. The mileage of each formulation was displayed as an index according to the calculation formula. In addition, it shows that it is excellent in run flat durability, so that a run flat durability index | exponent is large.
(Run flat durability index) = (travel distance of each formulation) / (travel distance of Comparative Example 1) × 100

In the examples in which both components of hydrotalcite and petroleum resin were blended with NR, BR and SBR as rubber components, the low heat build-up was good and the heat resistance, rigidity and run flat durability were also excellent. In Comparative Example 1 in which both components of hydrotalcite and petroleum resin were not blended, these performances were greatly inferior, and in Comparative Example 2 in which no petroleum resin was blended, the performance was also inferior.

Claims (10)

A rubber composition for a run-flat tire comprising a rubber component, hydrotalcite and an organic resin. The rubber composition for a run-flat tire according to claim 1, wherein the organic resin is a petroleum resin. The content of natural rubber in 100% by mass of the rubber component is 5 to 50% by mass, the content of butadiene rubber is 20 to 70% by mass, and the content of styrene butadiene rubber is 20 to 70% by mass. The rubber composition for a run-flat tire as described. The run-flat tire according to any one of claims 1 to 3, wherein the hydrotalcite content is 2 to 70 parts by mass and the organic resin content is 2 to 50 parts by mass with respect to 100 parts by mass of the rubber component. Rubber composition. Hydrotalcite is represented by the following formula (1);
[(M ₁ ²⁺ ) _(1-x) (M ₂ ³⁺ ) _x (OH ⁻ ) ₂ ] ^{x +} · [(A ⁿ⁻ ) _{x / n} · mH ₂ O] ^x− (1)
(Numbers satisfying _wherein, ^{M 1 2+} is a divalent metal _cation, ^{M 2 3+} is a trivalent metal ^{cation, A n-is} .x representing an n-valent anion 0 <x ≦ 0.5, m is Represents a number of 0 or more.)
The rubber composition for run-flat tires according to any one of claims 1 to 4, which is a compound represented by the formula: The rubber composition for a run-flat tire according to any one of claims 1 to 5, wherein the hydrotalcite / organic resin is 40/60 to 95/5 on a mass basis. The rubber composition for a run-flat tire according to any one of claims 1 to 6, comprising carbon black. The rubber composition for a run-flat tire according to any one of claims 1 to 7, comprising a sulfenamide-based vulcanization accelerator and an alkylphenol / sulfur chloride condensate. The rubber composition for a run flat tire according to any one of claims 1 to 8 , which is used for a side wall reinforcing layer. A run-flat tire having a sidewall reinforcing layer produced using the rubber composition according to any one of claims 1 to 9 .