JP5612727B2 - Rubber composition for tire and pneumatic tire - Google Patents

Description

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

Sulfur, which is widely used in rubber compositions for tires such as breaker toppings, base treads, clinch, sidewalls, and inserts, has an S8 structure and a polarity similar to that of ethylene glycol when dissolved in a polymer. Therefore, it is generally difficult to uniformly disperse in low-polar natural rubber, butadiene rubber, and styrene butadiene rubber.

Therefore, a method of reducing the amount of S8 used by using a sulfur-containing hybrid crosslinking agent (1,6-bis (N, N′-dibenzylthiocarbamoyldithio) hexane), an alkylphenol / sulfur chloride condensate, etc. has been proposed. However, the sulfur-containing hybrid crosslinking agent is generally expensive, and the alkylphenol / sulfur chloride condensate itself has poor dispersibility, resulting in deterioration in elongation at break and wear resistance.

In addition, steel cord coating rubber contains a relatively large amount of sulfur for cord adhesion, but most of the sulfur is present as a poorly dispersed mass without being involved in crosslinking. The crosslink density becomes non-uniform and the elongation at break tends to decrease significantly. Therefore, it is desired to provide a compounded rubber having sulfur dispersed uniformly in the rubber and having an excellent elongation at break.

On the other hand, various tire members are also required to have performance such as steering stability and low fuel consumption. For example, tin-modified butadiene rubber, which has a strong binding force to the filler, is used to maintain fuel handling performance while maintaining steering stability. It has been proposed to improve.

However, the effects of improving the elongation at break and low fuel consumption by the above-mentioned methods are still unsatisfactory, and further improvement is required in terms of significantly improving both of these performances while maintaining steering stability. It has been. For example, Patent Document 1 discloses that a specific styrene butadiene rubber and coumarone indene resin are used to improve grip performance, but improvement in fuel efficiency and elongation at break have not been studied.

JP 2006-124601 A

An object of the present invention is to solve the above problems and provide a rubber composition for a tire and a pneumatic tire that can achieve both low fuel consumption and elongation at break.

The present invention includes isoprene-based rubber, sulfur and a coumarone indene resin having a softening point of -20 to 45 ° C, and the content of the coumarone indene resin is 0.5 to 20 parts by mass with respect to 100 parts by mass of the rubber component. It is related with the rubber composition for tires which is.

The sulfur content is preferably 0.5 to 7 parts by mass with respect to 100 parts by mass of the rubber component. The coumarone indene resin content is preferably 0.5 to 10 parts by mass and the sulfur content is 1.3 to 7 parts by mass with respect to 100 parts by mass of the rubber component.

The rubber composition is preferably a rubber composition for breaker topping, base tread, sidewall, clinch, tie gum, bead apex, strip apex or sidewall reinforcing layer.

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

According to the present invention, since it is a rubber composition for tires containing a predetermined amount of isoprene-based rubber, sulfur and coumarone indene resin having a specific softening point, both low fuel consumption and elongation at break can be achieved.

The rubber composition for tires of the present invention is obtained by blending a predetermined amount of a coumarone indene resin having a softening point of -20 to 45 ° C with respect to isoprene-based rubber and sulfur. Thereby, while maintaining steering stability, the elongation at break and fuel efficiency can be remarkably improved, and these performances can be improved in a well-balanced manner. Although this reason is not necessarily clear, it is estimated as follows.

Although it is difficult to uniformly disperse sulfur in low-polar isoprene-based rubber, when a coumarone indene resin having a specific softening point is blended, the resin and sulfur (especially oxygen atoms contained in the coumarone indene resin) Sulfur) is attracted by van der Waals force, whereby the sulfur surface is coated with the resin, and the surface energy of sulfur is reduced (cohesive force is reduced). As a result, the difference in the SP value between the sulfur surface and the isoprene-based rubber is reduced, so that the dispersion of sulfur is promoted. In addition, the resin itself has a good dispersibility and imparts lubricity to the polymer chain. Is uniformly dispersed throughout the rubber composition. Therefore, the cross-linking between the polymers is made uniform in the vulcanization process, so that both the fuel economy and the elongation at break are improved and the durability is excellent while maintaining the steering stability. In addition, performance such as adhesion to a steel cord and wear resistance is improved.

Examples of the isoprene-based rubber include natural rubber (NR), isoprene rubber (IR), and liquid isoprene rubber (L-IR). 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. Moreover, it does not specifically limit as IR, A general thing can be used in the tire industry. Among these, NR is preferable from the viewpoint that good fuel economy and elongation at break can be obtained.

In the tire rubber composition, the content of the isoprene-based rubber in 100% by mass of the rubber component is preferably 10 to 100% by mass. Within the above range, good fuel economy and elongation at break can be obtained.

In the case of the rubber composition for breaker topping, the content of the isoprene-based rubber in 100% by mass of the rubber component is preferably 70% by mass or more, more preferably 90% by mass or more, and further preferably 100% by mass. If it is less than 70% by mass, sufficient elongation at break may not be obtained.

In the case of the rubber composition for base tread, the content of isoprene-based rubber in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 50% by mass or more. If it is less than 20% by mass, sufficient elongation at break may not be obtained. The content is preferably 90% by mass or less, more preferably 70% by mass or less. If it exceeds 90% by mass, sufficient fuel economy tends not to be obtained.

In the case of a rubber composition for sidewalls and sidewall reinforcing layers (sidewall inner layer reinforcing layers), the content of isoprene rubber in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 30% by mass or more. It is. If it is less than 10% by mass, sufficient rubber strength may not be obtained. The content is preferably 70% by mass or less, more preferably 60% by mass or less. When it exceeds 70 mass%, sufficient bending crack growth resistance tends to be not obtained.

The rubber component that can be used in the present invention other than the isoprene-based rubber is not particularly limited, and is styrene butadiene rubber (SBR), butadiene rubber (BR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR). And diene rubbers such as styrene-isoprene-butadiene copolymer rubber (SIBR). Of these, SBR and BR are preferred in the case of rubber compositions for base treads and sidewall inner layer reinforcing layers, because they provide a good balance of fuel efficiency, elongation at break, handling stability, and durability. In the case of a rubber composition, BR is preferable.

The SBR is not particularly limited, but it is a compound represented by the following formula (1) described in JP 2010-111753 A, from the viewpoint that low fuel consumption and elongation at break are obtained in a high dimension. The modified one can be suitably used.

（式中、Ｒ^１、Ｒ^２及びＲ^３は、同一若しくは異なって、アルキル基、アルコキシ基（好ましくは炭素数１〜８、より好ましくは炭素数１〜６、更に好ましくは炭素数１〜４のアルコキシ基）、シリルオキシ基、アセタール基、カルボキシル基（−ＣＯＯＨ）、メルカプト基（−ＳＨ）又はこれらの誘導体を表す。Ｒ^４及びＲ^５は、同一若しくは異なって、水素原子又はアルキル基（好ましくは炭素数１〜４のアルキル基）を表す。ｎは整数（好ましくは１〜５、より好ましくは２〜４、更に好ましくは３）を表す。）

(In formula, R < ¹ >, R < ² > and R < ³ > are the same or different, and are an alkyl group and an alkoxy group (preferably C1-C8, More preferably C1-C6, More preferably C1-C4 An alkoxy group), a silyloxy group, an acetal group, a carboxyl group (—COOH), a mercapto group (—SH), or a derivative thereof, and R ⁴ and R ⁵ are the same or different and represent a hydrogen atom or an alkyl group (preferably Represents an alkyl group having 1 to 4 carbon atoms, and n represents an integer (preferably 1 to 5, more preferably 2 to 4, more preferably 3).

R ¹ , R ² and R ³ are preferably alkoxy groups, and R ⁴ and R ⁵ are preferably hydrogen atoms. As a result, low fuel consumption and high elongation at break can be obtained.

Specific examples of the compound represented by the above formula (1) include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyldimethylmethoxysilane, 3-aminopropylmethyldimethoxysilane, 2- Examples include dimethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, and 3-dimethylaminopropyltrimethoxysilane. These may be used alone or in combination of two or more.

Examples of the method for modifying the styrene butadiene rubber with the compound (modifier) represented by the above formula (1) are described in JP-B-6-53768, JP-B-6-57767, JP-T2003-514078, and the like. A conventionally known method such as a known method can be used. For example, it can be modified by bringing a styrene butadiene rubber into contact with a modifier. Specifically, after a styrene butadiene rubber is prepared by anionic polymerization, a predetermined amount of the modifier is added to the rubber solution to polymerize the styrene butadiene rubber. Examples thereof include a method of reacting a terminal (active terminal) with a modifier.

The amount of bound styrene of SBR is preferably 5% by mass or more, more preferably 8% by mass or more from the viewpoint that good steering stability can be obtained. On the other hand, it is preferably 21% by mass or less, more preferably 13% by mass or less, from the viewpoint that good fuel economy can be obtained.
In the present invention, the styrene content of SBR is calculated by H ¹ -NMR measurement.

In the case of the rubber composition for base tread, the content of SBR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more. If it is less than 5% by mass, the above-described improvement effect by SBR may not be sufficiently obtained. The content is preferably 50% by mass or less, more preferably 30% by mass or less. If it exceeds 50% by mass, sufficient elongation at break and resistance to flex crack growth may not be obtained.

In the case of the rubber composition for a sidewall inner layer reinforcing layer, the content of SBR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 25% by mass or more. If it is less than 5% by mass, there is a possibility that the physical property stability and reversion property under high temperature cannot be sufficiently obtained during deflate running. The content is preferably 60% by mass or less, more preferably 45% by mass or less. When it exceeds 60% by mass, the exothermic property tends to decrease.

The BR is not particularly limited, but in the case of a rubber composition for a base tread, lithium starts from the point that low fuel consumption, flex crack growth resistance, elongation at break, handling stability, and durability are obtained in a balanced manner. A tin-modified BR having a tin atom content of 50 to 3000 ppm, a vinyl content of 5 to 50% by mass and a molecular weight distribution of 2 or less is preferred. From the same point, in the case of the rubber composition for the sidewall and the sidewall inner layer reinforcing layer, BR containing 1,2-syndiotactic polybutadiene crystal (SPB-containing BR) is preferable.

The tin-modified BR is obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and the end of the tin-modified BR molecule is bonded with a tin-carbon bond. It is preferable.

Examples of the lithium initiator include lithium compounds such as alkyl lithium and aryl lithium. Examples of tin compounds include tin tetrachloride and butyltin trichloride.

The tin atom content of the tin-modified BR is 50 ppm or more. If it is less than 50 ppm, tan δ tends to increase. The tin atom content is 3000 ppm or less, preferably 300 ppm or less. If it exceeds 3000 ppm, the extrudability of the kneaded product tends to deteriorate.

The molecular weight distribution (Mw / Mn) of the tin-modified BR is 2 or less. When Mw / Mn exceeds 2, tan δ tends to increase. The lower limit of the molecular weight distribution is not particularly limited, but is preferably 1 or more.
In the present specification, the weight average molecular weight (Mw) and the number average molecular weight (Mn) are gel permeation chromatograph (GPC) (GPC-8000 series, manufactured by Tosoh Corporation), detector: differential refractometer, column: It can be determined by standard polystyrene conversion based on the measured value by TSKEL SUPERMALTPORE HZ-M manufactured by Tosoh Corporation.

The vinyl content of the tin-modified BR is 5% by mass or more. If it is less than 5% by mass, it is difficult to produce tin-modified BR. The vinyl content is 50% by mass or less, preferably 20% by mass or less. If it exceeds 50% by mass, the dispersibility of carbon black is poor and the tensile strength tends to decrease.
The vinyl content can be measured by infrared absorption spectrum analysis.

As the SPB-containing BR, a general-purpose product in the tire industry can be used, but from the viewpoint that the above-described performance can be satisfactorily obtained, 1,2-syndiotactic polybutadiene crystals are chemically bonded to BR and dispersed.

The melting point of the 1,2-syndiotactic polybutadiene crystal is preferably 180 ° C. or higher, more preferably 190 ° C. or higher, and preferably 220 ° C. or lower, more preferably 210 ° C. or lower. If it is less than the lower limit, the effect of improving the steering stability by the SPB-containing BR may not be sufficiently obtained, and if it exceeds the upper limit, the workability tends to deteriorate.

In the SPB-containing BR, the content of 1,2-syndiotactic polybutadiene crystals (the content of boiling n-hexane insoluble matter) is preferably 2.5% by mass or more, more preferably 10% by mass or more. If it is less than 2.5% by mass, the reinforcing effect (E *) and the resistance to flex crack growth may be insufficient. The content is preferably 20% by mass or less, more preferably 18% by mass or less. When it exceeds 20 mass%, workability tends to deteriorate.

In the case of the rubber composition for base tread, the content of BR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more. If the amount is less than 5% by mass, the above-described improvement effect by BR may not be sufficiently obtained. The content is preferably 50% by mass or less, more preferably 30% by mass or less. If it exceeds 50 mass%, there is a possibility that sufficient elongation at break cannot be obtained.

In the case of the rubber composition for a sidewall, the BR content in 100% by mass of the rubber component is preferably 30% by mass or more, more preferably 40% by mass or more. If the amount is less than 30% by mass, the above-described improvement effect by BR may not be sufficiently obtained. The content is preferably 80% by mass or less, more preferably 70% by mass or less. If it exceeds 80 mass%, there is a possibility that sufficient elongation at break and tearability may not be obtained.

In the rubber composition for a sidewall inner layer reinforcing layer, the BR content in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 20% by mass or more. If the amount is less than 5% by mass, the above-described improvement effect by BR may not be sufficiently obtained. The content is preferably 60% by mass or less, more preferably 40% by mass or less. If it exceeds 60% by mass, high-temperature durability during deflate running may be insufficient.

Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur.
In the tire rubber composition, the sulfur content is preferably 0.5 parts by mass or more, more preferably 1.3 parts by mass or more, and preferably 7 parts by mass with respect to 100 parts by mass of the rubber component. Below, more preferably 6 parts by mass or less. Within the above range, excellent fuel efficiency and elongation at break can be obtained.

In the case of the rubber composition for the breaker topping and the sidewall inner layer reinforcing layer, the sulfur content is based on 100 parts by mass of the rubber component from the viewpoint that excellent fuel efficiency, elongation at break, and adhesion can be obtained. , Preferably it is 4-7 mass parts.

The rubber composition of the present invention contains a coumarone indene resin having a softening point of -20 to 45 ° C. The coumarone indene resin is a resin containing coumarone and indene as monomer components constituting the resin skeleton (main chain), and monomer components contained in the skeleton other than coumarone and indene include styrene and α-methylstyrene. , Methylindene, vinyltoluene and the like.

The softening point of the coumarone indene resin is −20 ° C. or higher, preferably −10 ° C. or higher. If it is lower than -20 ° C, there is a possibility that the effect of improving fuel economy and elongation at break cannot be obtained sufficiently. The softening point is 45 ° C. or lower, preferably 40 ° C. or lower. When it exceeds 45 ° C., fuel economy and elongation at break tend to deteriorate.
The softening point of the coumarone indene resin is a temperature at which the sphere descends when the softening point specified in JIS K 6220-1: 2001 is measured with a ring and ball softening point measuring device.

In the rubber composition for a tire, the content of the coumarone indene resin having the specific softening point is 0.5 parts by mass or more, preferably 1 part by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 0.5 parts by mass, there is a possibility that the fuel economy and the effect of improving elongation at break cannot be sufficiently obtained. The content is 20 parts by mass or less, preferably 10 parts by mass or less, more preferably 5 parts by mass or less. When it exceeds 20 parts by mass, the hardness is insufficient and the steering stability tends to deteriorate.

The rubber composition of the present invention may contain other coumarone indene resin. Among them, the softening point is 70 to 70 from the viewpoint of obtaining good grip properties, elongation at break, handling stability, and adhesive processability. It is preferable to blend a coumarone indene resin at 120 ° C. The content of the coumarone indene resin having a softening point of 70 to 120 ° C. is preferably 0.5 to 8 parts by mass with respect to 100 parts by mass of the rubber component from the viewpoint that these performances can be obtained in a balanced manner. is there.

The rubber composition of the present invention preferably contains carbon black. As a result, good reinforcing properties can be obtained, and excellent wear resistance, durability, steering stability, UV degradation resistance, and the like can be obtained.

In the case of the rubber composition for breaker topping, the nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 40 m ² / g or more, and more preferably 70 m ² / g or more. If it is less than 40 m ² / g, sufficient elongation at break may not be obtained. The N ₂ SA is preferably 200 m ² / g or less, more preferably 90 m ² / g or less. When it exceeds 200 m ² / g, there is a possibility that sufficient fuel efficiency cannot be obtained.

In the case of the rubber composition for the base tread, the sidewall, and the sidewall inner layer reinforcing layer, the nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 30 m ² / g or more. If it is less than 30 m ² / g, there is a possibility that sufficient elongation at break cannot be obtained. The _N 2 SA is preferably at most 100 m ² / g, more preferably at most ^{50 m} 2 / g. When it exceeds 100 m ² / g, there is a possibility that sufficient fuel efficiency cannot be obtained.
Incidentally, _N 2 SA of carbon black, JIS K 6217-2: determined by 2001.

In the case of the rubber composition for breaker topping, the content of carbon black is preferably 20 parts by mass or more, more preferably 50 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 20 parts by mass, sufficient hardness and elongation at break may not be obtained. The content is preferably 100 parts by mass or less, more preferably 70 parts by mass or less. If it exceeds 100 parts by mass, sufficient fuel economy may not be obtained.

In the case of the base tread rubber composition, the carbon black content is preferably 3 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 3 parts by mass, sufficient reinforcement may not be obtained. The content is preferably 50 parts by mass or less, more preferably 10 parts by mass or less. If it exceeds 50 parts by mass, sufficient fuel economy may not be obtained.

In the case of the rubber composition for a sidewall and a sidewall inner layer reinforcing layer, the content of carbon black is preferably 20 parts by mass or more, more preferably 30 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 20 parts by mass, sufficient hardness and elongation at break may not be obtained. The content is preferably 80 parts by mass or less, more preferably 60 parts by mass or less. If it exceeds 80 parts by mass, sufficient fuel economy may not be obtained.

The rubber composition of the present invention may contain silica and is preferably blended particularly in the case of base treads, breaker toppings, and sidewall rubber compositions. In addition, when using a silica (especially when using 15 mass parts or more with respect to 100 mass parts of rubber components), in order to accelerate | stimulate dispersion | distribution of a silica, it is preferable to use together with a well-known silane coupling agent.

In the case of the rubber composition for base tread, the nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 50 m ² / g or more, more preferably 100 m ² / g or more, and preferably 200 m ² / g or less. More preferably, it is 130 m ² / g or less. Within the above range, the effects of the present invention can be obtained satisfactorily.
The _N 2 SA of silica is a value measured by the BET method in accordance with ASTM D3037-81.

In the case of the rubber composition for base tread, the content of silica is preferably 10 to 60 parts by mass, more preferably 25 to 45 parts by mass with respect to 100 parts by mass of the rubber component. Within the above range, excellent fuel efficiency can be obtained.

When the rubber composition of the present invention is a rubber composition for breaker topping, it preferably contains organic acid cobalt. Since the organic acid cobalt serves to crosslink the cord (steel cord) and the rubber, the adhesion between the cord and the rubber can be improved. Examples of the organic acid cobalt include cobalt stearate, cobalt naphthenate, and cobalt neodecanoate.

The content of the organic acid cobalt is preferably 0.05 to 0.5 parts by mass, more preferably 0.05 to 0.3 parts by mass in terms of the amount of cobalt metal with respect to 100 parts by mass of the rubber component. . If the amount is less than 0.05 parts by mass, sufficient adhesion may not be obtained. If the amount exceeds 0.5 parts by mass, the elongation at break tends to decrease.

In the case where the rubber composition of the present invention is a rubber composition for a sidewall inner layer reinforcing layer, it contains an alkylphenol / sulfur chloride condensate because good fuel economy, elongation at break, handling stability, and durability can be obtained. It is preferable.

（式中、Ｒ^６、Ｒ^７及びＲ^８は、同一若しくは異なって、炭素数４〜１２のアルキル基を表す。ｘ及びｙは、同一若しくは異なって、２〜４の整数を表す。ｔは０〜２５０の整数を表す。） The alkylphenol / sulfur chloride condensate is not particularly limited, but a compound represented by the following formula (2) is preferable from the viewpoint of excellent performance.

(Wherein R ⁶ , R ⁷ and R ⁸ are the same or different and represent an alkyl group having 4 to 12 carbon atoms. X and y are the same or different and represent an integer of 2 to 4. t is Represents an integer of 0 to 250.)

t is preferably an integer of 0 to 100 and more preferably an integer of 1 to 10 from the viewpoint of good dispersibility of the alkylphenol / sulfur chloride condensate in the rubber component. x and y are both preferably 2 because high hardness can be efficiently expressed. R ^{6 to} R ⁸ are preferably an alkyl group having 4 to 12 carbon atoms and more preferably an alkyl group having 6 to 9 carbon atoms from the viewpoint of good dispersibility of the alkylphenol / sulfur chloride condensate in the rubber component.

（式中、ｔは０〜１００の整数を表す。） Specific examples of the alkylphenol / sulfur chloride condensate include Takkol V200 (following formula (3)) manufactured by Taoka Chemical Industry Co., Ltd.

(In the formula, t represents an integer of 0 to 100.)

The content of the alkylphenol / sulfur chloride condensate is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 10 parts by mass or less, based on 100 parts by mass of the rubber component. Preferably it is 7 mass parts or less. Within the above range, fuel economy, elongation at break, handling stability, and durability can be obtained in a well-balanced manner.

In addition to the components described above, the rubber composition of the present invention contains compounding agents generally used in the production of rubber compositions such as various anti-aging agents, waxes, stearic acid, zinc oxide, oils, vulcanizing agents, vulcanizing agents, A sulfur accelerator or the like can be appropriately blended.

When the rubber composition of the present invention is a rubber composition for a base tread, the total content of oil, a coumarone indene resin having a softening point of -20 to 45 ° C., and other coumarone indene resins is effective for the present invention. From the point of being sufficiently obtained, the amount is preferably 2 to 30 parts by mass, more preferably 6 to 25 parts by mass with respect to 100 parts by mass of the rubber component.

As a method for producing the rubber composition of the present invention, a known method can be used. For example, the above components are kneaded using a rubber kneader such as an open roll or a Banbury mixer, and then vulcanized. Can be manufactured.

The rubber composition of the present invention can be suitably used for each member of a tire, such as a breaker, sidewall reinforcing layer (side wall inner layer reinforcing layer), base tread, sidewall, clinch, tie gum, bead apex, strip apex, etc. It can be suitably used for tire members other than these treads, and can be particularly suitably used for breakers, sidewall reinforcing layers, base treads, and sidewalls.

The breaker is a member arranged inside the tread and outside the carcass in the radial direction. Specifically, the breaker is a member shown in FIG. 3 of Japanese Patent Application Laid-Open No. 2003-94918. The side wall reinforcing layer (side wall inner layer reinforcing layer) is a lining strip layer (insert layer) arranged inside the side wall portion of the run-flat tire, and specifically, a drawing of Japanese Patent Application Laid-Open No. 2004-330822. It is a reinforced rubber layer shown in FIG. The base tread is, for example, an inner surface layer of a tread having a two-layer structure.

The pneumatic tire of the present invention can be produced by a usual method using the rubber composition. That is, the rubber composition is extruded in accordance with the shape of each member of the tire at an unvulcanized stage, molded by a normal method on a tire molding machine, and bonded together with other tire members, and unvulcanized. Form a tire. This unvulcanized tire can be heated and pressurized in a vulcanizer to produce a tire.

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

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
NR: TSR20
Non-modified SBR: Nipol 1502 (E-SBR, bound styrene content: 23.5% by mass, non-modified) manufactured by Nippon Zeon Co., Ltd.
High cis BR: VCR617 (SPB-containing BR, SPB content: 17% by mass, SPB melting point: 200 ° C., content of boiling n-hexane insoluble matter: 15-18% by mass) manufactured by Ube Industries, Ltd.
Modified SBR: HPR340 manufactured by JSR Corporation (modified S-SBR, amount of bound styrene: 10% by mass, Tg: -64 ° C., coupled with alkoxysilane and introduced at the terminal, by the compound represented by formula (1) Modification (R ^{1 to} R ³ = methoxy group, R ^{4 to} R ⁵ = hydrogen atom, n = 3)
Modified BR: BR1250H manufactured by Nippon Zeon Co., Ltd. (tin-modified BR polymerized using a lithium initiator, vinyl content: 10 to 13% by mass, Mw / Mn: 1.5, tin atom content: 250 ppm)
Carbon black N326: Mitsubishi Chemical Co., Ltd. DIABLACK ^{_{N326 (N 2 SA: 84m 2}} / g, DBP oil absorption of 74cm ^3/100 g)
Carbon Black N550: Show Black N550 (N ₂ SA: 41 m ² / g) manufactured by Cabot Japan
Silica: Z115Gr (N ₂ SA: 115 m ² / g) manufactured by Rhodia Co., Ltd.
Silane coupling agent: Si266 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa
Anti-aging agent 6PPD: Antigen 6C (N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd.
Wax: Ozoace 0355 manufactured by Nippon Seiki Co., Ltd.
Stearate: Zinc Hana manufactured by NOF Co., Ltd .: Zinc Hana 2 manufactured by Mitsui Mining & Smelting Co., Ltd. Cobalt stearate: cost-F manufactured by Dainippon Ink & Chemicals, Inc. (cobalt content: 9. 5% by mass)
10% oil-containing insoluble sulfur: Seimisulfur manufactured by Nippon Kiboshi Kogyo Co., Ltd. (60% or more insoluble sulfur by carbon disulfide, oil content: 10% by mass)
20% oil-containing insoluble sulfur: Kristex HSOT20 (insoluble sulfur containing 80% by mass of sulfur and 20% by mass of oil) manufactured by Flexis Co., Ltd.
DCBS: Noxeller DZ (N, N′-dicyclohexyl-2-benzothiazylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
TBBS: Noxeller NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
V200: Takiroll V200 manufactured by Taoka Chemical Co., Ltd. (alkylphenol-sulfur chloride condensate represented by the above formula (3), sulfur content: 24% by mass)
Oil: VivaTec400 (TDAE oil) manufactured by H & R Co., Ltd.
Petroleum C5 resin: Marukaretsu resin (C5 petroleum resin, softening point: 100 ° C.) manufactured by Maruzen Petrochemical Co., Ltd.
Resin C10: NOVARES C10 manufactured by Rutgers Chemicals (liquid coumarone indene resin, softening point: 5 to 15 ° C.)
Resin C30: NOVARES C30 manufactured by Rutgers Chemicals (coumarone indene resin, softening point: 20-30 ° C.)
Resin C80: NOVARES C80 manufactured by Rutgers Chemicals (coumarone indene resin, softening point: 75 to 85 ° C.)
Resin C100: NOVARES C100 manufactured by Rutgers Chemicals (coumarone indene resin, softening point: 95 to 105 ° C.)
Resin C120: NOVARES C120 manufactured by Rutgers Chemicals (coumarone indene resin, softening point: 115 to 125 ° C.)

According to the formulation shown in Tables 1 to 4, chemicals other than sulfur and a vulcanization accelerator were kneaded using a 1.7 L Banbury mixer. Next, using a roll, sulfur and a vulcanization accelerator were added to the obtained kneaded product and kneaded to obtain an unvulcanized rubber composition.
The obtained unvulcanized rubber composition was press vulcanized at 170 ° C. for 12 minutes to obtain a vulcanized rubber composition.

Further, an unvulcanized tire is prepared by using the obtained unvulcanized rubber composition for a breaker, a side wall reinforcing layer, a base tread, and a side wall, and vulcanized to test tires (size: 245 / 40R18). Was made.
The obtained unvulcanized rubber composition, vulcanized rubber composition, and test tire were evaluated as follows, and the results are shown in Tables 1 to 4.

(Viscoelasticity test)
Using a viscoelastic spectrometer VES manufactured by Iwamoto Seisakusho Co., Ltd., the complex elastic modulus E * () of the vulcanized rubber composition under the conditions of a temperature of 70 ° C., a frequency of 10 Hz, an initial strain of 10% and a dynamic strain of 2%. MPa) and loss tangent tan δ were measured. In addition, it shows that rigidity is high and steering stability is excellent, so that E * is large, and heat_generation | fever property is low, and low-fuel-consumption property is excellent, so that tan (delta) is small.

(Tensile test)
Using a No. 3 dumbbell-shaped test piece made of a vulcanized rubber composition, a tensile test was performed at room temperature in accordance with JIS K 6251 “Vulcanized rubber and thermoplastic rubber-Determination of tensile properties”. The elongation EB (%) was measured. It shows that it is excellent in elongation at break, so that EB is large.

(Durability: Breaker, Base tread)
A test tire applied to a breaker or base tread is placed in an oven, deteriorated at 80 ° C. for 3 weeks, and then subjected to a load overload condition of 140% with respect to the maximum load (maximum air pressure condition) of JIS standard. The distance traveled until the occurrence of abnormality such as swelling of the tread when the drum was run was measured. The traveling distance of Comparative Examples 1 and 15 was set to 100, and the traveling distance of each formulation was displayed as an index. In addition, it shows that it is excellent in durability, so that an index | exponent is large.

(Durability: Sidewall reinforcement layer)
The test tire applied to the sidewall reinforcing layer was run on the drum at a speed of 80 km / hr at an air pressure of 0 kPa, and the running distance until the tire broke was measured. The travel distance of Comparative Example 9 was set to 100, and the travel distance of each formulation was displayed as an index. In addition, it shows that run flat durability is excellent, so that an index | exponent is large.

(Durability: Side wall)
The test tire applied to the side wall is set to a low internal pressure of 150 kPa (1.5 Bar) according to JIS standards, and is run at 80 km / h under a 140% overload load condition. Was measured. The traveling distance of Comparative Example 21 was set to 100, and the traveling distance of each formulation was displayed as an index. In addition, it shows that it is excellent in durability, so that an index | exponent is large.

In Examples where NR and sulfur were blended with a coumarone indene resin (C10, C30) having a softening point of -20 to 45 ° C, a petroleum resin or a coumarone indene resin having a high softening point was used instead of C10 or C30. Compared to the comparative example used, both elongation at break and rolling resistance could be improved while maintaining steering stability. In addition, the durability of the tire was improved.

When rubber compositions for clinch, tie gum, bead apex, strip apex are prepared using isoprene-based rubber (NR, IR, L-IR, epoxidized NR) and C10 or C30, etc., these rubbers Even in the composition, E *, tan δ and EB were excellent. Further, the test tires produced by applying to clinch, tie gum, bead apex and strip apex were excellent in durability.

Claims (12)

Including isoprene-based rubber, sulfur and a coumarone indene resin having a softening point of -20 to 45 ° C;
The rubber composition for base treads whose content of the coumarone indene resin is 0.5 to 20 parts by mass with respect to 100 parts by mass of the rubber component. The rubber composition for base treads according to claim 1, comprising carbon black having a nitrogen adsorption specific surface area of 30 to 100 m ² / g. The rubber composition for base treads according to claim 1 or 2, comprising a styrene-butadiene rubber and / or a tin-modified butadiene rubber modified with a compound represented by the following formula (1).

(Wherein R ¹ , R ² and R ³ are the same or different and each represents an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group, a mercapto group or a derivative thereof. R ⁴ and R ⁵ are (The same or different, and represents a hydrogen atom or an alkyl group. N represents an integer.) The rubber composition for a base tread according to any one of claims 1 to 3, wherein the content of the isoprene-based rubber in 100% by mass of the rubber component is 20 to 90% by mass. The rubber composition for a base tread according to claim 3, wherein the content of butadiene rubber in 100% by mass of the rubber component is 5 to 50% by mass. The rubber composition for base treads according to any one of claims 1 to 5, comprising 10 to 45 parts by mass of silica with respect to 100 parts by mass of the rubber component. The rubber composition for base treads according to any one of claims 1 to 6, comprising 3 to 50 parts by mass of carbon black with respect to 100 parts by mass of the rubber component. The rubber composition for a base tread according to claim 3, wherein the content of the styrene butadiene rubber in 100% by mass of the rubber component is 5 to 30% by mass. Furthermore, the rubber composition for base treads in any one of Claims 1-8 containing the coumarone indene resin of 70-120 degreeC of softening points. The rubber composition for base tread according to any one of claims 1 to 9, wherein a sulfur content is 0.5 to 7 parts by mass with respect to 100 parts by mass of the rubber component. The content of the coumarone indene resin having a softening point of -20 to 45 ° C. is 0.5 to 10 parts by mass and the content of sulfur is 1.3 to 7 parts by mass with respect to 100 parts by mass of the rubber component. The rubber composition for base treads in any one of Claims 1-10. The pneumatic tire which has a base tread produced using the rubber composition in any one of Claims 1-11.