JP2012102241A - Rubber composition for tread, and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for treads, capable of improving grip performance, grip durability and abrasion resistance in good balance, and pneumatic tires using the same.SOLUTION: The rubber composition for treads comprises a wet masterbatch and specific compounds, wherein the wet masterbatch is obtained by mixing a rubber latex, a filler suspension fluid and a diene-based liquid polymer emulsion.

Description

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

High performance tires such as competition tires are required to have various performances such as grip performance, grip durability, and wear resistance. For example, as a technique for improving the grip performance, a technique of blending a large amount of oil is known, but such a technique reduces the wear resistance.

As another method for improving grip performance, a method is known in which a liquid polymer having a weight average molecular weight smaller than that of a rubber component and liquid at room temperature is blended instead of oil. However, since the crosslink density is reduced by the liquid polymer and the blending adjustment with sulfur is required, thermal sagging (running change) occurs, and sufficient grip durability cannot be obtained. Thus, it has been difficult to improve the grip performance, grip durability, and wear resistance in a balanced manner.

Patent Document 1 describes the use of a hydrogenated liquid polymer, but there is room for improvement in terms of improving the grip performance, grip durability, and wear resistance in a well-balanced manner.

JP 2005-225946 A

The object of the present invention is to solve the above problems and provide a rubber composition for a tread that can improve the grip performance, grip durability, and wear resistance in a well-balanced manner, and a pneumatic tire using the same.

The present invention includes a wet masterbatch, a compound 1 represented by the following formula (1), a compound 2 having a structure represented by the following formula (2), a compound 3 represented by the following formula (3), and At least one selected from the group consisting of hydrates of compound 3, and the wet masterbatch is obtained by mixing a rubber latex, a filler dispersion, and a liquid diene polymer emulsion. The present invention relates to a rubber composition for treads.
R ¹ —S—S— (CH ₂ ) _p —S—S—R ² (1)
(In formula (1), p represents an integer of 2 to 12. R ¹ and R ² are the same or different and each represents a monovalent organic group containing a nitrogen atom.)
_{^{- (R 3 -S x) n}} - (2)
(In Formula (2), R ³ represents — (CH ₂ —CH ₂ —O) _m —CH ₂ —CH ₂ —, m represents an integer of 2 to 5, and x represents an integer of 2 to 6). N represents an integer of 10 to 400.)
_{MO 3 S-S- (CH 2} ) q -S-SO 3 M (3)
(In Formula (3), q represents an integer of 3 to 10. M is the same or different and represents lithium, potassium, sodium, magnesium, calcium, barium, zinc, nickel, or cobalt.)

In the wet masterbatch, the filler dispersion is obtained by dispersing a filler in an aqueous medium, and the liquid diene polymer emulsion is used in a water emulsified liquid diene polymer using a surfactant. An oil droplet emulsion is preferred.

It is preferable that the wet master batch contains 10 to 100 parts by mass of the liquid diene polymer and 40 to 150 parts by mass of the filler with respect to 100 parts by mass of the rubber component in the rubber latex.

In the wet masterbatch, the liquid diene polymer is preferably at least one selected from the group consisting of a liquid styrene butadiene copolymer, a liquid butadiene polymer, and a liquid isoprene polymer.

In the wet masterbatch, the rubber latex is preferably a styrene butadiene rubber latex.

In the wet masterbatch, the filler is preferably carbon black.

In the wet masterbatch, the liquid diene polymer preferably has a weight average molecular weight of 1000 to 60000.

The present invention also relates to a pneumatic tire having a tread produced using the rubber composition.
The pneumatic tire is preferably used as a competition tire.

According to the present invention, since it is a rubber composition for a tread containing a wet masterbatch and a specific compound, grip performance, grip durability, and wear resistance can be improved in a balanced manner. Therefore, it is possible to provide a pneumatic tire such as a racing tire having excellent performance.

The rubber composition for a tread of the present invention contains a wet master batch obtained by mixing a rubber latex, a filler dispersion and a liquid diene polymer emulsion, and at least one of the above compounds 1 to 3.

For example, if a liquid polymer having a different rubber component and skeletal component is used, there are concerns such as deterioration in fracture energy, wear resistance, and reduction in grip performance.In the present invention, such a concern is caused by using the wet masterbatch. It can be wiped off, and the effect of improving the grip performance and wear resistance performance by using the liquid polymer can be obtained well. This is because even if a liquid polymer having a rubber component and a skeleton component are simply mixed, the compatibility of each liquid is low and bleeding of the liquid polymer occurs, but the compatibility is improved by wet masterbatch, and the dispersibility of the liquid polymer is increased. It is guessed that this is because it has risen.

Furthermore, by using a specific compound in combination with the wet masterbatch, a heat-stable crosslinked structure is formed, so that thermal sagging (running change) can also be suppressed. Thus, the above-mentioned combined use significantly improves the wear resistance performance, grip performance, and grip durability, and can improve the above-mentioned performance in a balanced and synergistic manner.

[Wet masterbatch]
The wet masterbatch (WMB) is obtained by mixing (A) rubber latex, (B) filler dispersion, and (C) liquid diene polymer emulsion.

The WMB can be prepared, for example, by mixing (A) to (C), and then coagulating and drying.

((A) rubber latex)
Examples of the rubber latex include natural rubber latex, synthetic diene rubber latex (latex such as butadiene rubber, styrene butadiene rubber, acrylonitrile butadiene rubber, ethylene vinyl acetate rubber, chloroprene rubber, vinyl pyridine rubber, and butyl rubber). Among these, styrene butadiene rubber latex (SBR latex) is preferable because of excellent grip performance.

The concentration of the rubber component (rubber solid content) in the rubber latex is not particularly limited, but is preferably 20 to 80% by mass, more preferably 30 to 60%, from the viewpoint of uniform dispersibility in the rubber latex (100% by mass). % By mass.

The SBR in the SBR latex is not particularly limited, and those generally used in the tire industry such as an emulsion-polymerized styrene butadiene rubber (E-SBR) can be used. Among these, E-SBR is preferable because it has excellent grip performance.

The vinyl content of the SBR is preferably 5% by mass or more, more preferably 15% by mass or more. If the vinyl content is less than 5% by mass, sufficient grip performance may not be obtained. The vinyl content is preferably 50% by mass or less, more preferably 25% by mass or less. When the vinyl content exceeds 50% by mass, the wear resistance tends to deteriorate.
The vinyl content of SBR can be measured by infrared absorption spectrum analysis.

The styrene content of the SBR is preferably 20% by mass or more, more preferably 30% by mass or more. If the styrene content is less than 20% by mass, sufficient grip performance may not be obtained. The styrene content is preferably 50% by mass or less, more preferably 45% by mass or less. If the styrene content exceeds 50% by mass, the fuel efficiency tends to deteriorate.
Incidentally, styrene content of the SBR ^is calculated by H 1 -NMR measurement.

The content of SBR in 100% by mass of the rubber solid content contained in the rubber latex used for WMB is preferably 80% by mass or more, more preferably 90% by mass or more, and still more preferably 100% by mass. If it is less than 80% by mass, the grip performance tends to be insufficient.

((B) Filler dispersion)
Examples of the filler dispersion include those in which a filler is dispersed in an aqueous medium. By using the filler dispersion liquid, the polymer (rubber molecule) and the filler can be mixed in a liquid state, and the filler can be favorably dispersed.

The filler dispersion can be produced by a known method, and can be prepared using, for example, a high-pressure homogenizer, an ultrasonic homogenizer, a colloid mill, or the like. Specifically, the dispersion can be prepared by placing an aqueous medium in a colloid mill, adding a filler while stirring, and then circulating with a surfactant as necessary using a homogenizer. The concentration of the filler in the dispersion is not particularly limited, but is preferably 0.5 to 10% by mass, more preferably 3 to 7 from the viewpoint of uniform dispersibility in the dispersion (100% by mass). % By mass.

As described in the method for producing a dispersion liquid, a surfactant may be appropriately added to the filler dispersion liquid from the viewpoint of dispersibility. The surfactant is not particularly limited, and known anionic surfactants, nonionic surfactants, amphoteric surfactants, and the like can be appropriately used. In the above dispersion, the amount of surfactant added is not particularly limited, but is preferably 0.01 to 3% by mass, more preferably from the viewpoint of uniform dispersibility of the filler in the dispersion (100% by mass). Is 0.05-1 mass%.

As a filler, carbon black, silica, calcium carbonate, alumina, clay, talc, and the like can be arbitrarily selected from those conventionally used in tire rubber compositions. However, grip performance and grip durability can be used. Carbon black is preferred because of its excellent wear resistance balance.

Examples of carbon black that can be used include GPF, FEF, HAF, ISAF, and SAF.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 20 m ² / g or more, more preferably 60 m ² / g or more. If it is less than 20 m < ² > / g, there exists a possibility that reinforcement may be low and sufficient durability may not be acquired. Further, the N ₂ SA of the carbon black is preferably 180 m ² / g or less, more preferably 130 m ² / g or less. When it exceeds 180 m < ² > / g, there exists a possibility that workability may fall.
In addition, the nitrogen adsorption specific surface area of carbon black is calculated | required by A method of JISK6217.

In addition, examples of the aqueous medium include water and alcohol. Among them, water is preferably used.

((C) Liquid diene polymer emulsion)
Examples of the liquid diene polymer emulsion include those obtained by emulsifying a liquid diene polymer using a surfactant, and the compatibility between the rubber component and the liquid diene polymer can be further improved. An oil-in-water emulsion is preferred.

A liquid diene polymer emulsion can be prepared by a known emulsification method. A predetermined amount of a surfactant and water are added to a liquid diene polymer, and a homomixer, a colloid mill, a line mill, a homogenizer, a planetary mixer, a trimix are added. An oil-in-water emulsion can be prepared by applying a shear stress using an emulsifier such as a mixer or a mixer.

In the present invention, the liquid diene polymer is a diene polymer in a liquid state.
The liquid diene polymer is not particularly limited as long as it is a liquid diene polymer. For example, a liquid styrene-butadiene copolymer (rubber), a butadiene polymer (rubber), an isoprene polymer (rubber), Examples thereof include acrylonitrile butadiene copolymer (rubber). Among liquid diene-based polymers, grip performance, grip durability, and wear resistance can be obtained in a balanced manner. Therefore, liquid styrene butadiene copolymer (liquid SBR), liquid isoprene polymer (liquid IR), liquid butadiene heavy Combined (liquid BR) is preferred.

The weight average molecular weight (Mw) of the liquid diene polymer is preferably 1000 or more, more preferably 1500 or more. If Mw is less than 1000, the wear resistance tends to decrease. The Mw of the liquid diene polymer is preferably 60000 or less, more preferably 20000 or less, and still more preferably 15000 or less. When Mw exceeds 60,000, the grip performance under low temperature conditions tends to decrease. In addition, the difference in molecular weight from the rubber component is reduced, and the effect as a plasticizer tends to be hardly exhibited. In addition, in this specification, a weight average molecular weight (Mw) is measured by the method as described in the below-mentioned Example.

The weight average molecular weight (Mw) of the liquid SBR is preferably 2000 or more, more preferably 3000 or more. If Mw is less than 2000, the wear resistance tends to decrease. The Mw of the liquid SBR is preferably 50000 or less, more preferably 40000 or less, and still more preferably 15000 or less. When Mw exceeds 50000, the difference in molecular weight from the rubber component becomes small, and the effect as a plasticizer tends to be hardly exhibited.

The weight average molecular weight (Mw) of the liquid IR is preferably 10,000 or more, more preferably 15000 or more. When Mw is less than 10,000, the wear resistance tends to be lowered. Further, the Mw of the liquid IR is preferably 60000 or less, more preferably 55000 or less. When the Mw of the liquid IR exceeds 60000, the difference in molecular weight from the rubber component becomes small, and the effect as a plasticizer is hardly exhibited. Tend.

The weight average molecular weight (Mw) of the liquid BR is preferably 5000 or more, more preferably 6000 or more. If Mw is less than 5000, liquid BR tends to migrate through the rubber composition, exhibits the same properties as oil, and tends to reduce the effect of improving wear resistance. The Mw of the liquid BR is preferably 50000 or less, more preferably 30000 or less, and still more preferably 20000 or less. When Mw exceeds 50000, the difference in molecular weight from the rubber component becomes small, and the effect as a plasticizer tends to be hardly exhibited.

The glass transition temperature (Tg) of the liquid diene polymer is preferably −90 ° C. or higher, more preferably −60 ° C. or higher, and further preferably −50 ° C. or higher. When Tg is less than −90 ° C., energy loss is low and a desired grip performance tends not to be obtained. Tg is preferably −10 ° C. or lower, and more preferably −15 ° C. or lower. When Tg exceeds -10 ° C, it tends to be hard at low temperatures, and sufficient grip performance tends not to be obtained. In addition, glass transition temperature (Tg) is measured by the method as described in the below-mentioned Example.

The vinyl content of the liquid SBR is preferably 10% by mass or more, more preferably 20% by mass or more. If the vinyl content is less than 10% by mass, sufficient grip performance may not be obtained. The vinyl content is preferably 90% by mass or less, more preferably 75% by mass or less. When the vinyl content exceeds 90% by mass, the wear resistance tends to deteriorate.
The vinyl content of the liquid SBR can be measured by infrared absorption spectrum analysis.

The styrene content of the liquid SBR is preferably 10% by mass or more, more preferably 15% by mass or more. If the styrene content is less than 10% by mass, sufficient grip performance may not be obtained. The styrene content is preferably 60% by mass or less, more preferably 50% by mass or less. When the styrene content exceeds 60% by mass, the softening point becomes high, the rubber becomes hard, and the grip performance may be deteriorated.
Incidentally, styrene content of the liquid SBR ^is calculated by H 1 -NMR measurement.

The concentration of the liquid diene polymer in the emulsion is not particularly limited.

As the surfactant, a known surfactant can be used, but a nonionic surfactant is preferably used from the viewpoint that the liquid diene polymer can be favorably dispersed. Of these, polyoxyalkylene alkyl ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, glycerin fatty acid ester, polyoxyethylene fatty acid ester, polyoxyethylene hydrogenated castor oil and the like are preferable.

Further, in the nonionic surfactant, the hydrophilic part preferably has 2 to 40 repeating units of oxyethylene, and the lipophilic part preferably has an alkyl ether or alkenyl ether structure.

In the above emulsion, the addition amount of the surfactant is not particularly limited, but from the viewpoint of uniform dispersibility of the liquid diene polymer in the emulsion (100% by mass), preferably 0.1 to 10% by mass, More preferably, it is 1-5 mass%.

(mixture)
The mixing method of the rubber latex, the filler dispersion, and the liquid diene polymer emulsion is not particularly limited. For example, the rubber latex is placed in a blender mill, and the filler dispersion is stirred. And a method of dropping a liquid diene polymer emulsion, a method of adding a rubber latex and a liquid diene polymer emulsion to this while stirring a filler dispersion, and stirring a liquid diene polymer emulsion. However, a method of dropping a rubber latex and a filler dispersion liquid is included. Alternatively, a method of mixing a rubber latex stream, a filler dispersion liquid stream, and a liquid diene polymer emulsion stream having a constant flow rate ratio under vigorous hydraulic stirring conditions may be used.

(coagulation)
After the mixing step, solidification is usually performed, but the solidification step is usually performed by adding an acidic compound such as formic acid and sulfuric acid and a coagulant such as a salt such as sodium chloride. In some cases, the mixture may be solidified. In this case, a coagulant may not be used.

(Dry)
After solidification, the obtained solidified product is usually recovered, dehydrated by centrifugation or the like, and further washed and dried to obtain the WMB. Examples of the dryer that can be used for drying include a vacuum dryer, an air dryer, a drum dryer, a band dryer, a hot air dryer, and a kiln type dryer.

(Composition of WMB)
The content of the filler in WMB is preferably 40 parts by mass or more, more preferably 50 parts by mass or more with respect to 100 parts by mass of the rubber component. When the content of the filler is less than 40 parts by mass, grip performance and wear resistance tend to decrease. Moreover, 150 mass parts or less are preferable and, as for content of a filler, 100 mass parts or less are more preferable. If it exceeds 150 parts by mass, the workability tends to deteriorate.

The content of carbon black in WMB is preferably 40 parts by mass or more, more preferably 50 parts by mass or more with respect to 100 parts by mass of the rubber component. The content is preferably 150 parts by mass or less, and more preferably 100 parts by mass or less. If it is out of the above range, there is a tendency similar to that of the filler.

The content of the liquid diene polymer in WMB is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and further preferably 40 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 10 parts by mass, sufficient grip performance may not be obtained. Moreover, this content becomes like this. Preferably it is 100 mass parts or less, More preferably, it is 70 mass parts or less. When it exceeds 100 parts by mass, the wear resistance tends to decrease. In the present specification, the liquid diene polymer is not included in the rubber component.

Of the total amount of 100% by mass of the rubber components (rubber components and other rubber components contained in WMB) contained in the rubber composition of the present invention, the content of the rubber component (rubber solids) contained in the WMB is higher. Preferably, it is 20% by mass or more, more preferably 60% by mass or more. If it is less than 20% by mass, the dispersibility of the liquid diene polymer cannot be sufficiently improved, and grip performance and wear resistance may not be sufficiently improved.

[Other ingredients]
The rubber composition of the present invention can be used by blending other rubber components as required in addition to the above WMB. Examples of other rubber components include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), ethylene propylene diene rubber (EPDM), Examples include chloroprene rubber (CR) and acrylonitrile butadiene rubber (NBR). Of these, SBR and BR are preferable because grip performance, grip durability, and wear resistance can be obtained in a well-balanced manner.
In addition, from the point of being excellent in abrasion resistance, the cis content of BR is preferably 95% by mass or more.

It does not specifically limit as SBR, The thing similar to SBR in the said SBR latex can be used conveniently.

The content of SBR is preferably 20% by mass or more, more preferably 80% by mass in the total amount of 100% by mass of the rubber components (rubber components and other rubber components contained in WMB) contained in the rubber composition of the present invention. That's it. The content may be 100% by mass or 90% by mass or less. When the content is in the above range, grip performance, fuel efficiency and wear resistance are good.

In the SBR (SBR contained in WMB and SBR used elsewhere) contained in the rubber composition of the present invention in 100% by mass, the ratio of SBR contained in WMB is preferably 10% by mass or more, more preferably It is 50 mass% or more. When the proportion is in the above range, the effect of the present invention can be obtained satisfactorily.

When BR is blended in the rubber composition of the present invention, the content of BR (rubber solids) in the total amount of rubber components of 100% by mass is preferably 5% by mass or more, more preferably 10% by mass or more. The content is preferably 40% by mass or less, more preferably 30% by mass or less.

The rubber composition of the present invention includes a compound 1 represented by the following formula (1), a compound 2 having a structure represented by the following formula (2), a compound 3 represented by the following formula (3), and the compound Including at least one selected from the group consisting of 3 hydrates. By using the WMB and the compound together, the compatibility between the rubber component and the liquid diene polymer is improved, and the dispersibility of the liquid diene polymer is improved. Grip durability and wear resistance are obtained at a high level.
R ¹ —S—S— (CH ₂ ) _p —S—S—R ² (1)
(In formula (1), p represents an integer of 2 to 12. R ¹ and R ² are the same or different and each represents a monovalent organic group containing a nitrogen atom.)
_{^{- (R 3 -S x) n}} - (2)
(In Formula (2), R ³ represents — (CH ₂ —CH ₂ —O) _m —CH ₂ —CH ₂ —, m represents an integer of 2 to 5, and x represents an integer of 2 to 6). N represents an integer of 10 to 400.)
_{MO 3 S-S- (CH 2} ) q -S-SO 3 M (3)
(In Formula (3), q represents an integer of 3 to 10. M is the same or different and represents lithium, potassium, sodium, magnesium, calcium, barium, zinc, nickel, or cobalt.)

In formula (1), p is an integer of 2 to 12, preferably 3 to 10, more preferably 4 to 8. When p is 1, thermal stability is poor and the effect of having an alkylene group tends not to be obtained. When _p is 13 or more, it is represented by —SS— (CH ₂ ) _p —S—S—. It tends to be difficult to form a crosslinked chain.

Examples of the alkylene group satisfying the above conditions include ethylene group, trimethylene group, tetramethylene group, pentamethylene group, hexamethylene group, heptamethylene group, octamethylene group, decamethylene group and the like. Among these, a hexamethylene group is preferable because a bridge represented by —SS— (CH ₂ ) _p —S—S— is formed smoothly between the polymers and is thermally stable.

In formula (1), R ¹ and R ² are not particularly limited as long as they are monovalent organic groups containing a nitrogen atom, but those containing at least one aromatic ring are preferred, and a carbon atom is bonded to a dithio group. And those containing a linking group represented by N—C (═S) —. R ¹ and R ² may be the same or different, but are preferably the same for reasons such as ease of production.
For example, what has the following structure can be used suitably as R < ¹ >, R < ² >.

Examples of the compound 1 represented by the above formula (1) include 1,2-bis (N, N′-dibenzylthiocarbamoyldithio) ethane and 1,3-bis (N, N′-dibenzylthiocarbamoyl). Dithio) propane, 1,4-bis (N, N′-dibenzylthiocarbamoyldithio) butane, 1,5-bis (N, N′-dibenzylthiocarbamoyldithio) pentane, 1,6-bis (N, N′-dibenzylthiocarbamoyldithio) hexane, 1,7-bis (N, N′-dibenzylthiocarbamoyldithio) heptane, 1,8-bis (N, N′-dibenzylthiocarbamoyldithio) octane, , 9-bis (N, N′-dibenzylthiocarbamoyldithio) nonane, 1,10-bis (N, N′-dibenzylthiocarbamoyldithio) decane and the like. . Among these, 1,6-bis (N, N′-dibenzylthiocarbamoyldithio) hexane is preferable because it is thermally stable and has excellent polarizability.

In Formula (2), m is 2-5, Preferably it is 2-4. If m is less than 2, there is a tendency that sufficient tensile properties cannot be obtained. Moreover, when m exceeds 5, there exists a tendency for the fall of the tensile characteristic after aging to be large.

In formula (2), x is 2-6, preferably 3-5. When x is less than 2, vulcanization is delayed. Moreover, when x exceeds 6, manufacture of a rubber composition will become difficult.

In formula (2), n is 10 to 400, preferably 50 to 300. If n is less than 10, the organic vulcanizing agent tends to volatilize and handling becomes difficult. On the other hand, if n exceeds 400, the compatibility with rubber deteriorates, and the performance improvement effect may not be sufficient.

As such compound 2, for example, poly-3,6-dioxaoctane-tetrasulfide (such as 2OS4 manufactured by Kawaguchi Chemical Industry Co., Ltd.) can be used.

In formula (3), q is an integer of 3 to 10, preferably 3 to 6. If q is less than 3, the rubber strength and wear resistance may not be sufficiently improved, and if q exceeds 10, the effect of improving rubber strength and wear resistance tends to be small although the molecular weight increases.

In formula (3), M is preferably lithium, potassium, sodium, magnesium, calcium, barium, zinc, nickel or cobalt, more preferably potassium or sodium. Examples of the hydrate of the compound represented by the formula (3) include sodium salt monohydrate and sodium salt dihydrate.

As the compound 3 represented by the formula (3) and its hydrate, a derivative derived from sodium thiosulfate, for example, 1,6-hexamethylene-sodium dithiosulfate. Hydrates are preferred.

In the rubber composition of the present invention, the total content of Compound 1, Compound 2, Compound 3, and the hydrate of Compound 3 is preferably 0.6 with respect to 100 parts by mass of the rubber component (rubber solid content). It is 1 part by mass or more, more preferably 1 part by mass or more. The content is preferably 12 parts by mass or less, more preferably 6 parts by mass or less. If it is less than the lower limit, the improvement effect by these compounds may not be sufficient, and if it exceeds the upper limit, the crosslinking density tends to increase and the grip performance tends to decrease.

The rubber composition of the present invention usually contains sulfur. When the WMB, the compounds 1 to 3, the hydrate of the compound 3 and sulfur are used in combination, the above-described operational effects are exhibited, and the operational effects due to the introduction of different crosslinking forms are also exhibited. The effect of improving performance, grip durability, and wear resistance is sufficiently obtained.

In the rubber composition of the present invention, the sulfur content is preferably 0.5 to 6.0 parts by mass, more preferably 1.0 to 3.0 with respect to 100 parts by mass of the rubber component (rubber solids). Part by mass. When the content is within the above range, the above-mentioned effects can be obtained satisfactorily.

In the rubber composition of the present invention, in addition to the above components, compounding agents generally used in the production of rubber compositions, for example, zinc oxide, stearic acid, various anti-aging agents, softening agents such as resins (resins), Oils, waxes, vulcanization accelerators and the like can be appropriately blended.

As a method for producing the rubber composition of the present invention, known methods 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 can be used for each member of a tire, and among them, it can be suitably used for a tread and a base tread.

[Pneumatic tire]
The pneumatic tire of the present invention is produced by a usual method using the rubber composition.
That is, the rubber composition containing the above components is extruded in accordance with the shape of each tire member such as a tread at an unvulcanized stage, and is molded together with the other tire members by a normal method on a tire molding machine. By doing so, an unvulcanized tire is formed. The unvulcanized tire is heated and pressurized in a vulcanizer to obtain a tire.

The pneumatic tire of the present invention is suitably used as a competition tire, passenger car tire, truck / bus tire, motorcycle tire, high-performance tire, and the like, particularly as a competition tire.

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

The following evaluation was performed for liquid SBR (RICON 100 manufactured by Sartomer), liquid IR (Kuraray LIR-30 manufactured by Kuraray Co., Ltd.) and liquid BR (RICON 142 manufactured by Sartomer). The results are shown in Table 1.

(Measurement of weight average molecular weight (Mw))
The weight average molecular weight (Mw) is measured by gel permeation chromatograph (GPC) (GPC-8000 series, manufactured by Tosoh Corp., detector: differential refractometer, column: TSKGEL SUPERMALTPORE HZ-M, manufactured by Tosoh Corp.). It calculated | required by standard polystyrene conversion based on the value.

(Measurement of glass transition temperature (Tg))
The glass transition temperature (Tg) should be measured in accordance with JIS-K7121, using a differential scanning calorimeter (Q200) manufactured by TA Instruments Japan while raising the temperature at a heating rate of 10 ° C / min. The glass transition onset temperature was determined.

Hereinafter, various chemicals used in Production Examples 1 to 6 will be described together.
SBR latex: LX110 manufactured by Nippon Zeon Co., Ltd. (E-SBR, styrene content: 37.5% by mass, vinyl content: 18% by mass, concentration of rubber component in rubber latex: 40.5% by mass)
Carbon Black: Show Black N220 (N ₂ SA: 111 m ² / g) manufactured by Cabot Japan
Liquid SBR: RICON 100 manufactured by Sartomer (styrene content: 20% by mass, vinyl content: 70% by mass)
Liquid IR: Kuraray LIR-30 manufactured by Kuraray Co., Ltd.
Liquid BR: RICON142 manufactured by Sartomer
Demol N: Surfactant Demol N manufactured by Kao Corporation (sodium salt of β-naphthalene sulfonic acid formalin condensate (anionic surfactant))
New Coal NT-15: New Coal NT-15 manufactured by Nippon Emulsifier Co., Ltd. (nonionic polyoxyethylene alkyl ether type surfactant)

(Production Example 1)
(Preparation of WMB (1))
(Preparation of filler dispersion)
A colloid mill with a rotor diameter of 30 mm was charged with 1900 g of deionized water and 100 g of carbon black, and stirred for 10 minutes at a rotor-stator interval of 1 mm and a rotational speed of 2000 rpm. Subsequently, demole N was added so that it might become a density | concentration of 0.05 mass%, and it circulated 3 times using the pressure type homogenizer, and prepared the filler dispersion liquid.

(Preparation of liquid diene polymer emulsion)
After heating 100 g of liquid SBR to 50 ° C., 300 g of a 5% by mass aqueous solution of New Coal NT-15 was added and stirred to prepare a liquid diene polymer emulsion (oil-in-water emulsion).

(Mixing, coagulation and drying of rubber latex, filler dispersion, and liquid diene polymer emulsion)
Rubber latex (SBR latex), filler dispersion, liquid diene polymer emulsion so that the solid content ratio (mass ratio) of rubber component: filler component: liquid diene polymer component is 100: 60: 50 After the solution became homogeneous, sulfuric acid was added while continuing stirring, and the pH was adjusted to 5 to solidify. The obtained solid was filtered to recover the rubber, and the rubber was washed with pure water until the washed liquid (washing water) had a pH of 7, and dried to obtain WMB (1).

(Production Example 2)
(Preparation of WMB (2))
WMB (2) was obtained under the same conditions as in Production Example 1 except that the liquid SBR was changed to the liquid IR.

(Production Example 3)
(Preparation of WMB (3))
WMB (3) was obtained under the same conditions as in Production Example 1 except that the liquid SBR was changed to the liquid BR.

(Production Example 4)
(Preparation of WMB (4))
Under the same conditions as in Production Example 1 except that the solid content ratio (mass ratio) of the rubber component: filler component: liquid diene polymer component was changed to 100: 70: 55, WMB (4) Obtained.

(Production Example 5)
(Preparation of WMB (5))
WMB (5) was obtained under the same conditions as in Production Example 4 except that the liquid SBR was changed to liquid IR.

(Production Example 6)
(Preparation of WMB (6))
WMB (6) was obtained under the same conditions as in Production Example 4 except that the liquid SBR was changed to liquid BR.

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
SBR: Nipol 9548 manufactured by Nippon Zeon Co., Ltd. (emulsion-polymerized styrene butadiene rubber, styrene content: 35% by mass, containing 37.5 parts by mass of oil with respect to 100 parts by mass of rubber solid content)
BR: BR150B manufactured by Ube Industries, Ltd.
Carbon Black: Show Black N220 (N ₂ SA: 111 m ² / g) manufactured by Cabot Japan
Liquid SBR: RICON 100 manufactured by Sartomer (styrene content: 20% by mass, vinyl content: 70% by mass)
Liquid IR: Kuraray LIR-30 manufactured by Kuraray Co., Ltd.
Liquid BR: RICON142 manufactured by Sartomer
Process oil: Diana Process AH-24 manufactured by Idemitsu Kosan Co., Ltd.
Resin: Escron V120 (coumarone indene resin) manufactured by Nippon Steel Chemical Co., Ltd.
Wax: Sunnock N manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Anti-aging agent: Antigen 6C (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd.
Stearic acid: Stearic acid “椿” manufactured by NOF Corporation
Zinc oxide: Sulfur manufactured by Mitsui Mining & Smelting Co., Ltd .: Powder sulfur heat-resistant crosslinking agent manufactured by Karuizawa Sulfur Co., Ltd. (1): Bulklen VP KA9188 manufactured by LANXESS (1,6-bis (N, N'-dibenzylthio) Carbamoyldithio) hexane)
Heat-resistant crosslinking agent (2): Actor 2OS4 (poly-3,6-dioxaoctane-tetrasulfide) manufactured by Kawaguchi Chemical Industry Co., Ltd.
[Formula: — (R ³ —S _x ) _n — (wherein R ³ = — (CH ₂ —CH ₂ —O) _m —CH ₂ —CH ₂ —, m = 2, x = 4, n = 200 ]]
Heat-resistant crosslinking agent (3): DURALINK HTS (1,6-hexamethylene-sodium dithiosulfate dihydrate) manufactured by Flexis
Vulcanization accelerator (1): Noxeller NS (Nt-butyl-2-benzothiazylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Vulcanization accelerator (2): Noxeller D (N, N'-diphenylguanidine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

In addition, the composition of WMB (1)-(6) obtained by manufacture examples 1-6 is as follows.
WMB (1): SBR (solid content) 100 parts by mass, carbon black 60 parts by mass, liquid SBR 50 parts by mass WMB (2): SBR (solids) 100 parts by mass, carbon black 60 parts by mass, liquid IR 50 parts by mass WMB ( 3): SBR (solid content) 100 parts by mass, carbon black 60 parts by mass, liquid BR 50 parts by mass WMB (4): SBR (solid content) 100 parts by mass, carbon black 70 parts by mass, liquid SBR 55 parts by mass WMB (5) : 100 parts by weight of SBR (solid content), 70 parts by weight of carbon black, 55 parts by weight of liquid IR WMB (6): 100 parts by weight of SBR (solids), 70 parts by weight of carbon black, 55 parts by weight of liquid BR

Examples and Comparative Examples In accordance with the formulation shown in Table 2, materials other than sulfur, a vulcanization accelerator and a heat-resistant crosslinking agent were kneaded for 4 minutes at 150 ° C. using a 1.7 L Banbury mixer and mixed. A kneaded paste was obtained. Next, sulfur, a vulcanization accelerator, and a heat-resistant cross-linking agent were added to the kneaded product obtained, and kneaded for 3 minutes at 80 ° C. using an open roll to obtain an unvulcanized rubber composition.

The obtained unvulcanized rubber composition is formed into a tread shape and bonded together with other tire members to form an unvulcanized tire, press vulcanized at 170 ° C. for 10 minutes, and a test tire ( Size 195 / 65R15) was produced.

The following evaluation was performed about the obtained tire for a test. The results are shown in Table 2.

(Grip performance)
Using the test tire, the vehicle traveled 10 laps on a dry road test course. The test driver evaluated the stability of the control during steering at that time, and the index was displayed with Comparative Example 3 as 100. The larger the value, the higher the grip performance on the dry road surface.

(Grip durability)
The above test tire is run for 10 laps on a dry road test course, and the stability of control during steering is tested with the performance change in the 2nd to 4th laps and the change in performance in the 8th to 10th laps. Was evaluated, and indexed with Comparative Example 3 as 100. The larger the value, the higher the grip durability on dry roads.

(Abrasion resistance)
Using the test tire, the vehicle was run on a test course on an asphalt road surface. The abrasion appearance of the tire after running was evaluated, and the index was displayed with Comparative Example 3 as 100. The larger the value, the higher the wear resistance.

The example using WMB and a specific compound was able to improve the grip performance, grip durability, and wear resistance in a balanced manner as compared with the comparative example. Moreover, from Example 1, Comparative Examples 1, 4 and 7, the improvement effect was obtained synergistically by the combined use of WMB and a specific compound.

Claims (9)

Wet masterbatch, compound 1 represented by the following formula (1), compound 2 having a structure represented by the following formula (2), compound 3 represented by the following formula (3), and water of the compound 3 Including at least one selected from the group consisting of Japanese products,
The wet masterbatch is
A rubber composition for a tread obtained by mixing a rubber latex, a filler dispersion, and a liquid diene polymer emulsion.
R ¹ —S—S— (CH ₂ ) _p —S—S—R ² (1)
(In formula (1), p represents an integer of 2 to 12. R ¹ and R ² are the same or different and each represents a monovalent organic group containing a nitrogen atom.)
_{^{- (R 3 -S x) n}} - (2)
(In Formula (2), R ³ represents — (CH ₂ —CH ₂ —O) _m —CH ₂ —CH ₂ —, m represents an integer of 2 to 5, and x represents an integer of 2 to 6). N represents an integer of 10 to 400.)
_{MO 3 S-S- (CH 2} ) q -S-SO 3 M (3)
(In Formula (3), q represents an integer of 3 to 10. M is the same or different and represents lithium, potassium, sodium, magnesium, calcium, barium, zinc, nickel, or cobalt.) In the wet masterbatch, the filler dispersion is obtained by dispersing a filler in an aqueous medium, and the liquid diene polymer emulsion is used in water to emulsify the liquid diene polymer using a surfactant. The rubber composition for a tread according to claim 1, which is an oil droplet type emulsion. The wet master batch contains 10 to 100 parts by mass of the liquid diene polymer and 40 to 150 parts by mass of the filler with respect to 100 parts by mass of the rubber component in the rubber latex. Tread rubber composition. 4. The wet masterbatch, wherein the liquid diene polymer is at least one selected from the group consisting of a liquid styrene butadiene copolymer, a liquid butadiene polymer, and a liquid isoprene polymer. The rubber composition for a tread as described. The rubber composition for a tread according to any one of claims 1 to 4, wherein in the wet master batch, the rubber latex is a styrene butadiene rubber latex. The rubber composition for a tread according to any one of claims 1 to 5, wherein in the wet masterbatch, the filler is carbon black. The rubber composition for a tread according to any one of claims 1 to 6, wherein in the wet masterbatch, the weight average molecular weight of the liquid diene polymer is 1000 to 60000. A pneumatic tire having a tread produced using the rubber composition according to claim 1. The pneumatic tire according to claim 8, which is used as a racing tire.