JPH06287356A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To obtain a composition being excellent in wet skid properties and wear resistance and improved in fuel consumption by kneading a material containing a specified wet-process styrene/butadiene/carbon black masterbatch and a specified premix of carbon black with a natural rubber. CONSTITUTION:A rubber composition obtained by kneading a material containing a wet-process styrene/butadiene/carbon black masterbatch obtained by dispersing at least 40wt.%, based on the total carbon black to be contained in the rubber composition, carbon black (of an iodine adsorption of 100mg/g or above) in a rubber latex containing a styrene/butadiene rubber component of a combined styrene content of 25-45wt.% and a Mooney viscosity (ML1+4, 100 deg.C) of 55 or above and a premix prepared by previously kneading at least 10wt.%, based on the total carbon black to be contained in the rubber composition, carbon black with a natural rubber is provided.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a rubber composition containing a diene copolymer rubber, natural rubber and carbon black, and a pneumatic tire having a tread processed by using the composition in a tread portion.

[0002]

2. Description of the Related Art In recent years, with the demand for safety and low fuel consumption for automobiles, attempts to simultaneously improve wet skid resistance, low fuel consumption, and reinforcement as a rubber material for tires are included in the rubber material. Made from both sides of polymer and carbon black.

For example, Japanese Patent Publication No. 62-10530 discloses that
Random copolymerization of styrene and 1.3 butadiene,
It has a bond of at least one metal selected from silicon, germanium, tin and lead with butadienyl in the main chain, and the content of bonded styrene is 3 to 30% by weight and 1.2 vinyl bond of butadiene moiety. Content is 60-95
It has been shown that a rubber composition for tires containing a blended rubber of styrene-butadiene copolymer rubber and natural rubber in an amount of wt% and carbon black has improved running safety and rolling resistance.

Further, JP-A-61-141741 discloses that a rubber composition containing a butadiene copolymer modified with an isocyanate compound and having a glass transition temperature of −70 ° C. or more is excellent in wet skid resistance, rolling friction resistance and tensile strength. Is disclosed. Further, Japanese Patent Publication No. 61-362 discloses a method for modifying a diene polymer rubber with a benzophenone compound, and describes that impact resilience is improved.

However, the fuel consumption characteristics obtained by these modification techniques are insufficient for the recent trend toward low fuel consumption.
The styrene-butadiene rubber (modified SBR) produced by the above-mentioned modification technique is generally prepared by an anionic polymerization method in many cases, and in this polymerization method, a high molecular weight component is small and abrasion resistance is poor in many cases. When this modified SBR is combined with carbon black having a small particle size, abrasion resistance is improved, but fuel consumption cannot be satisfactory. On the other hand, in the case of carbon black, the fuel economy is improved by increasing the particle size, but in this case, there is a drawback that the wear resistance is greatly reduced and the reinforcing property is deteriorated.

Further, JP-A-1-272644 discloses that optimum rolling resistance and wet skid resistance are obtained by combining SBR obtained by emulsion polymerization and carbon black in a wet carbon black masterbatch method. . However, the SBR obtained by the emulsion polymerization method contains a large amount of high molecular weight components and has good wear resistance, but poor fuel economy, and carbon black can be satisfactorily dispersed by the wet masterbatch method. It has not yet reached the desired fuel economy characteristics. Furthermore, SBR obtained by emulsion polymerization method
And a polymer having a low Tg such as natural rubber and polybutadiene have been blended, and wet skid resistance, rolling resistance, and abrasion resistance have been tried, but satisfactory results have not been obtained.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems of the prior art.
Provided is a rubber composition containing a butadiene-based copolymer rubber, natural rubber and carbon black, which is excellent in wet skid resistance and abrasion resistance and at the same time has improved fuel economy. It is to provide a pneumatic tire used for a tread having excellent properties.

[0008]

As a result of repeated studies on the above-mentioned problems, the present inventors have found that a styrene-butadiene copolymer rubber latex in which carbon black is dispersed,
It was found that a rubber composition for a tire tread with improved fuel economy is obtained by separately producing a pre-kneaded product obtained by previously kneading a natural rubber with carbon black, and kneading these, and a tire tread of the present invention. A pneumatic tire having a rubber composition for tread and a tread has been completed. That is,

The rubber composition for tire tread of the present invention comprises
(A) Solid content 100% of a rubber latex (abbreviated as SBR latex) containing a styrene-butadiene rubber (abbreviated as SBR) component having a bound styrene content of 25 to 45% by weight and a Mooney viscosity (ML _{1 + 4} 100 ° C.) of 55 or more. To 40 parts by weight of the total carbon black contained in the rubber composition for a tire tread (a) (wet process styrene-butadiene-carbon obtained by dispersing an iodine adsorption amount of 100 mg / g or more). Black masterbatch (abbreviated as wet carbon black masterbatch), and (b) 10% by weight or more of the total carbon black contained in the rubber composition (b) (iodine adsorption amount 80 mg / g or less) and natural rubber. And a pre-kneaded product obtained by previously kneading and are kneaded together. , Preferably, SBR
The weight content ratio of the solid content of the latex to the natural rubber is 2: 8 to 8: 2, and the content of carbon black is 20 to 100 parts by weight with respect to 100 parts by weight of all the rubber components.

The pneumatic tire having the tread of the present invention is characterized in that the tread portion is processed using the rubber composition for a tire tread of the present invention.

The SBR latex used in the composition of the present invention is obtained by emulsifying and dispersing a 1,3-butadiene monomer and a styrene monomer in an aqueous medium using an emulsifier, and adding a polymerization initiator to carry out a polymerization reaction. Manufactured by a conventionally known method of causing it. As the emulsifier used, anionic surfactants such as fatty acid soap, rosin acid soap, sodium naphthalenesulfonate and sodium alkylbenzenesulfonate are usually used. As the polymerization initiator, a redox initiator is used in the cold rubber processing method in which polymerization is performed at 0 to 20 ° C. As the redox initiator, cumene hydroperoxide, a combination of organic acid compounds such as diisopropylbenzene hydroperoxide and ferrous sulfate is generally used, and as a reducing agent,
Sulfoxylate and the like are used together. Usually, when the polymerization reaction rate reaches 55 to 65%, a polymerization terminator such as sodium dimethyldithiocarbamate or diethylhydroxylamine is added to terminate the polymerization reaction.

The bound styrene content of the SBR is 25-4.
It is 5% by weight. If it is less than 25% by weight, Tg tends to be low,
Wet skid resistance is poor. If it exceeds 45% by weight, rolling resistance and wear resistance are deteriorated. The Mooney viscosity is 55 ML _{1 + 4} (100 ° C.) or higher. If it is less than 55, the amount of low molecular weight components increases, the fuel economy deteriorates, and the rolling resistance decreases.

The composition of the present invention comprises a wet kneaded carbon black masterbatch obtained by previously dispersing the carbon black (a) in the SBR latex and a pre-kneaded product obtained by kneading the natural rubber with the carbon black (b) in advance. ) And (3) are separately produced, and kneading is performed in a state where carbon black is unevenly distributed.

The wet SBR carbon black masterbatch is prepared by mixing 20 to 90 parts by weight of the desired carbon black (a) with 100 parts by weight of the solid content of the SBR latex. In this case, the carbon black to be mixed is added to the rubber latex in the state of an aqueous dispersion (slurry), the obtained rubber latex master batch is coagulated with an acid such as sulfuric acid, and then washed with water, filtered and dried. It is processed to obtain a wet carbon black masterbatch. The rubber latex masterbatch can usually be mixed with aroma oil.

Also, carbon black (b) is used as the natural rubber.
The preliminary kneaded product (b) obtained by previously kneading is obtained by kneading with a commonly used Banbury mixer.

The carbon black (a) to be dispersed in the SBR latex must have an iodine adsorption amount of 100 mg / g or more. If it is less than 100 mg / g, the particle size is large and S
The BR reinforcing property is poor, so that the wear resistance of the entire rubber composition is reduced. If SBR and carbon black are simply dry blended without using a wet carbon masterbatch, the Mooney viscosity will be as high as 55 or higher, and because the carbon black is fine particles, the kneading property will be poor and the carbon black will not be uniformly dispersed in the SBR. . Therefore, heat generation becomes high, and fuel consumption and wear resistance are poor. When the amount of carbon black is 40% by weight or less of the total carbon black contained in the rubber composition for tire tread, the effect of improving fuel economy and wear resistance is small.

Carbon black (b) preliminarily kneaded with natural rubber must have an iodine adsorption amount of 80 mg / g or less. If it exceeds 80 mg / g, the amount of heat generated becomes large, and there is no effect of improving fuel economy. The content is 10% by weight or more of the amount of carbon black contained in the entire composition. If it is less than 10% by weight, the effect of uneven distribution of carbon black is not exerted and the amount of heat generation is increased, which is not preferable.

The content of total carbon black in the composition is 20 to 100 parts by weight with respect to 100 parts by weight of total rubber. If it exceeds 100 parts by weight, the dispersion of carbon black is insufficient and the fracture resistance and resistance are high. The abrasion resistance is lowered, and if it is less than 20 parts by weight, the reinforcing property is deteriorated, which is not preferable. The weight ratio of the isomorphic component of the rubber latex containing the SBR component to the natural rubber in the composition is 2: 8 to 8: 2, preferably 4: 6 to.
It is 6: 4.

When the carbon black-dispersed SBR latex and the pre-kneaded product are kneaded (sometimes referred to as the main kneading) during the production of the composition of the present invention, aromatic oil, stearic acid, and an antioxidant may be added as necessary. Can be mixed. Although a part of the carbon black of the entire composition may be mixed in the main kneading, the amount thereof is preferably 50% by weight or less of the total carbon black in the composition.

The composition of the present invention contains, in addition to carbon black, softening agents such as aroma oil and spindle oil, antioxidants, vulcanization accelerators, vulcanization accelerators such as stearic acid and zinc white, vulcanizing agents and the like. The rubber compounding agent can be compounded with the rubber within the usual range. It is preferable that these compounding agents are mixed with a softening agent, an antioxidant, stearic acid and the like in the first stage during the main kneading, and are kneaded with a vulcanization accelerator and a vulcanizing agent in the second stage at low temperature. .

A preferred embodiment of the pneumatic tire having a tread of the present invention is a tread portion having a cap and a base.
In a pneumatic tire having a layered structure, the base portion is processed using the composition. Further, the pneumatic tire may be reinforced with any of organic fiber cords such as nylon, vinylon, polyester and Kepler or organic fiber cords such as steel, glass and carbon, and the carcass has either a radial structure or a bias structure. It may be present, but it is preferably a radial structure.

[0022]

The present invention will be described below with reference to examples.
The invention is not limited to these examples. Various measurements in the examples were carried out as follows.

Bound styrene content: The styrene content of the copolymer characteristics was determined by using an analytical curve using the absorbance of the phenyl group at 699 cm ^-1 by an infrared spectrometer.

Abrasion resistance: The amount of abrasion loss was measured using a Lambourn abrasion tester, and the comparative example 1 was expressed as an index, and the larger the numerical value, the better. Wet skid resistance: Measured at room temperature (25 ° C) using a Stanley portable skid resistance tester. An asphalt surface sprayed with water at 20 ° C was selected as the contact road surface. Comparative Example 1 was set to 100 and displayed as an index, and the larger the value, the better. Fuel economy (rolling friction resistance): tan δ at 60 ° C. is shown as an index of rolling friction resistance. Tan δ was measured at 1% with a spectrometer manufactured by Iwamoto Seisakusho. The copolymer used in the examples was prepared by the following method.

Example 1 Preparation of wet carbon black masterbatch: bound styrene content 40%, Mooney viscosity 80ML _{1 + 4} (100
℃) SBR latex containing SBR (solid content 100 parts by weight), ISAF carbon black (Iodine adsorption amount 1
A slurry in which 50 parts by weight of 19 mg / g) was dispersed in water was added to obtain a carbon black-SBR latex masterbatch. Sulfuric acid was added to this to coagulate, washed with water, filtered, and dried to obtain a wet carbon black masterbatch. Preparation of pre-kneaded product: 100 parts by weight of natural rubber and 50 parts by weight of FEF carbon black (iodine adsorption amount: 45 mg / g) were kneaded for 3 minutes at 50 rpm with a OOC type Banbury mixer, a filling rate of 60% and a starting temperature of 70 ° C. , Made a preliminary paste. Main kneading: Next, the wet carbon black masterbatch and the preliminary kneading product were put together, and 5 parts by weight of aromatic oil, 3 parts by weight of stearic acid and an antioxidant (Ouchi Shinko Chemical Industry Co., Ltd., trade name "810NA") were added.
1.0 part by weight was added, and the mixture was kneaded at 60 rpm, a filling rate of 70%, and a starting temperature of 100 ° C. for 3 minutes. To 100 parts by weight of the obtained kneaded product, 3.0 parts by weight of zinc white, 1.5 parts by weight of sulfur, and 1.0 part by weight of vulcanization accelerator (Ouchi Shinko Chemical Industry Co., Ltd., trade name "MSA") were added. , 5 at 80 ℃ start
Kneading was carried out at 0 rpm for 1 minute to obtain a rubber composition for tire tread. After press vulcanizing this composition at 150 ° C. for 40 minutes,
Predetermined tests were performed at room temperature. The results are shown in Table 1.

Examples 2 to 5 As shown in Table 1, the same procedure as in Example 1 was performed except that the SBR latex used was changed. Only in Example 3, I
A portion of SAF carbon was added.

Comparative Examples 1-3, 5 Based on Table 2, the same procedure as in Example 1 was carried out. Comparative Example 4 SBR and a pre-kneaded product were kneaded without making a wet masterbatch. Others were the same as in Example 1.

Comparative Examples 6 to 7 As shown in Table 2, a masterbatch and a preliminary kneaded product were not prepared,
Natural rubber, SBR, and carbon black were dry blended. Others are the same as in the first embodiment.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

INDUSTRIAL APPLICABILITY The present invention provides a rubber composition for a tread and a pneumatic tire, which have excellent wet skid resistance and abrasion resistance and at the same time have fuel economy as a rubber material for a tire.

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Claims (4)

[Claims] 1. A vulcanizable rubber composition for a tire tread containing carbon black in a blend system of a styrene-butadiene copolymer and natural rubber, comprising: (a) a bound styrene content of 25 to 45% by weight and a Mooney viscosity (ML _{1). +4} 100 ° C.) 40% by weight or more of the total carbon black contained in the rubber composition for a tire tread with respect to 100 parts by weight of solids of a rubber latex containing a styrene-butadiene rubber component of 55 or more (a ) (Iodine adsorption amount of 100 mg / g or more) is obtained by dispersing the wet method styrene-butadiene-carbon black masterbatch, and (b) 10% by weight or more of the total carbon black contained in the rubber composition (carbon black ( b) A pre-kneaded product obtained by previously kneading (natural iodine adsorption amount 80 mg / g or less) and natural rubber Tire tread rubber composition characterized by comprising kneaded materials containing. 2. The weight content ratio of the solid content of the rubber latex containing the styrene-butadiene rubber component to the natural rubber is 2: 8 to 8: 2, and the content of carbon black is 100 parts by weight of the total rubber component. 20 to 100 parts by weight of the rubber composition for a tire tread according to claim 1. 3. A rubber latex containing a styrene-butadiene rubber component having a styrene bond content of 25 to 45% by weight and a Mooney viscosity (ML _{1 + 4} 100 ° C.) of 55 or more based on 100 parts by weight of the solid content of the rubber latex. Wet method styrene-butadiene-carbon black masterbatch obtained by dispersing 40% by weight or more of the total carbon black contained in the rubber composition for tire tread (a) (adsorption amount of iodine 100 mg / g or more). (B) A pre-kneaded product obtained by previously kneading 10% by weight or more of the total carbon black contained in the rubber composition (b) (adsorbed iodine amount of 80 mg / g or less) and natural rubber is mixed. A tread characterized by being processed by using a rubber composition for a tire tread capable of being kneaded and kneaded in a tread portion. Pneumatic tire to. 4. The weight ratio of the solid content of the rubber latex containing the styrene-butadiene rubber component to the natural rubber is 2: 8.
The pneumatic tire with a tread according to claim 3, wherein the content of carbon black is 20 to 100 parts by weight with respect to 100 parts by weight of all rubber components.