JP2001206984A - Method for producing carbon black/silica-filled rubber composition and pneumatic tire for heavy duty - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a carbon black/silica-filled rubber composition which is capable of producing a tire having excellent performances of abrasion resistance and heat generation performances balanced at a high level in excellent productivity and has excellent kneading workability. SOLUTION: (A) a process for dispersing carbon black to a natural rubber and/or (B) a diene-based synthetic rubber to give a composition and a process for dispersing silica to the composition obtained by the process (A) are successively carried out to produce the objective carbon black/silica filled rubber composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a carbon black / silica filled rubber composition and a pneumatic tire for heavy loads. More specifically, the present invention provides a carbon black / silica-filled rubber composition which can provide a tire having excellent performance in which abrasion resistance and heat generation performance are balanced at a high level with high productivity and good kneading workability. The present invention relates to a method for efficiently producing the same, and a heavy-duty pneumatic tire using the rubber composition for a tread rubber.

[0002]

2. Description of the Related Art Hitherto, as a method for improving abrasion resistance of a tread rubber or the like in a pneumatic tire, a method of using high-grade carbon black, a method of increasing a filling amount of carbon black, and the like have been adopted. Particularly, in a heavy-duty pneumatic tire used for a heavy-duty truck or the like, a method using silica is adopted because it is desired that abrasion resistance and heat generation performance (low heat generation) are balanced at a high level. ing. However, in this silica, due to hydrogen bonding of silanol groups, which are surface functional groups, the particles tend to agglomerate, which tends to cause poor dispersion. In addition, if the amount of silica is increased in order to further improve the wear resistance, the kneading workability is deteriorated, and further, the dispersion is caused poorly. This leads to unfavorable situations such as an increase in kneading time due to the formation, a decrease in productivity due to an increase in the number of kneading stages, and a reduction in wear resistance and heat generation performance. Therefore, in order to solve such a problem, for example, an attempt has been made to use a processability improver. However, this method is effective in lowering the viscosity and the like, but deteriorates the heat generation performance and increases the cost. However, there is a problem that the method is not sufficiently satisfactory.

[0003]

SUMMARY OF THE INVENTION The present invention relates to a carbon black / silica blend system in such a situation.
The kneading workability is good, the dispersibility of the reinforcing filler is good, and the abrasion resistance and the heat generation performance are efficiently improved. It is an object of the present invention to provide a method for manufacturing and a heavy-duty pneumatic tire using the composition obtained by this method.

[0004]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors disperse the reinforcing filler in two stages, that is, in the first stage, After adding carbon black and kneading and dispersing, in the second stage, by adding silica and dispersing it, and preferably, in the first stage, kneading at a higher temperature than the second stage, In the second stage, the rubber drop temperature 1
It has been found that by kneading at 45 ° C. or less, a desired rubber composition can be obtained with high productivity and the object can be achieved. The present invention has been completed based on such findings. That is, the present invention provides (A) a step of dispersing carbon black in natural rubber and / or a diene-based synthetic rubber; and (B) a composition obtained in the above (A) step.
An object of the present invention is to provide a method for producing a carbon black / silica-filled rubber composition, which comprises sequentially performing a step of dispersing silica. The present invention also provides a heavy-duty pneumatic tire using the carbon black / silica-filled rubber composition obtained by the above-described production method as a tret rubber.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the method of the present invention, a natural rubber and / or a diene-based synthetic rubber is used as a rubber component. Here, as the diene-based synthetic rubber, for example, polyisoprene synthetic rubber (IR), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR) ). The natural rubber and the diene-based synthetic rubber of the rubber component may be used alone or in combination of two or more. In the method of the present invention, for the rubber component,
(A) a step of dispersing carbon black and (B) a step of dispersing silica in the composition obtained in step (A) are sequentially performed. The carbon black used in the step (A) is not particularly limited, and any one can be appropriately selected from those conventionally used as a reinforcing filler for rubber. Examples of the carbon black include FEF, SRF, HAF, ISAF, S
AF and the like can be mentioned, and among them, HAF, ISAF and SAF which are excellent in wear resistance are preferable.

[0006] The carbon black preferably has a nitrogen adsorption specific surface area (BET) in the range of 120 to 160 m ² / g. If the BET is less than 120 m ² / g, it is difficult to obtain sufficient abrasion resistance, and if it exceeds 160 m ² / g, the heat generation performance tends to decrease. The BET is A
It is a value measured according to STM D3037-88. The compounding amount of the carbon black is the same as that of the rubber component 1
It is preferably 70 parts by weight or less based on 00 parts by weight. If the amount exceeds 70 parts by weight, the heat generation performance may be reduced, or dispersion may be poor, and the abrasion resistance and the like may be deteriorated. On the other hand, if the amount is too small, the abrasion resistance becomes insufficient. Considering heat generation performance, abrasion resistance, dispersibility, etc., the compounding amount of this carbon black is
A range of 30 to 60 parts by weight is more preferred.

In the step (A), together with carbon black, various chemicals usually used in the rubber industry, such as a vulcanizing agent, a vulcanization accelerator, and aging, as long as the object of the present invention is not impaired. An inhibitor, an anti-scorch agent, a softener, zinc white, stearic acid and the like can be contained. In the present invention, in the step (A), carbon black and, if desired, the above-mentioned various chemicals are blended with the rubber component and kneaded to disperse the carbon black. For the purpose of constructing a reinforcing structure by the above, it is advantageous that the temperature is higher than the kneading temperature in the step (B) to be described later, and it is desirable to control the rubber falling temperature within the range of 150 to 160 ° C. Next, in the step (B), silica is added to the composition obtained in the step (A) and dispersed.

This silica has a nitrogen adsorption specific surface area (BE)
T) is in the range of 160 to 260 m ² / g, and the dibutyl phthalate oil absorption (DBP) is in the range of 160 to 260 ml / 100 g. If the BET is less than 160 m ² / g or the DBP is less than 160 ml / 100 g, the abrasion resistance may be insufficient, while the BET may exceed 260 m ² / g,
When the DBP exceeds 260 ml / 100 g, poor dispersion is caused, and heat generation performance and abrasion resistance are reduced. From the viewpoint of the balance between wear resistance and heat generation performance, the BET is more preferably in the range of 180 to 240 m ² / g, and the DBP is in the range of 170 to 240 ml / 1.
A range of 00 g is more preferred. The BET is 3
This is a value measured in accordance with ASTM D4820-93 after drying at 00 ° C. for 1 hour, and DBP is ASTM D2
It is a value measured according to 414-93. Examples of the silica include wet silica (hydrous silicic acid), dry silica (silicic anhydride), calcium silicate, aluminum silicate, and the like. Of these, wet silica is particularly preferable.

In the present invention, the amount of silica in the step (B) is 5 to 100 parts by weight of the rubber component.
The range is preferably from 30 to 30 parts by weight. If the amount is less than 5 parts by weight, the effect of improving abrasion resistance may not be sufficiently exhibited, and if it exceeds 30 parts by weight, heat generation performance may be reduced. In consideration of the effect of improving the wear resistance and the heat generation performance, the amount of the silica is more preferably in the range of 7 to 25 parts by weight. In the present invention, in this step (B), a silane coupling agent can be used in combination, if desired. The silane coupling agent is not particularly limited, and known silane coupling agents conventionally used in rubber compositions,
For example, bis (3-triethoxysilylpropyl) polysulfide, γ-mercaptopropyltriethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, N-β
(Aminoethyl) -γ-aminopropyltrimethoxysilane and the like can be used. The amount of the silane coupling agent optionally used is generally selected in the range of 1 to 30% by weight based on the silica. If this amount is less than 1% by weight, the effect as a coupling agent is not sufficiently exhibited, and if it exceeds 30% by weight, gelation of the rubber component may be caused, and the slip at the time of kneading is large, and the kneading time is reduced. Tend to be longer. In consideration of the effect as a coupling agent, prevention of gelation, kneading time, and the like, a more preferable amount of the silane coupling agent is in the range of 10 to 20% by weight. This (B)
In the process, the kneading temperature is preferably as low as possible because the gel properties of the silica are likely to be poor due to gelation of the silica.
It is preferable to control the temperature within the range of 0 ° C. Thereby, good sheet properties can be maintained, and good tire productivity can be maintained.

The kneading temperature in the steps (A) and (B) may be, for example, the number of kneading revolutions of a Banbury mixer used for kneading, the volume of the rubber composition to be charged, the kneading time, the setting of the ram raising time, and the like. Can be controlled. The rubber falling temperature in the steps (A) and (B) is a value obtained by measuring the temperature of the rubber on the under roll at the end of kneading. The heavy duty pneumatic tire of the present invention uses the rubber composition obtained as described above for a tread rubber, and can be manufactured, for example, as follows. First, the rubber composition is extruded into a member for tread in an unvulcanized stage, processed into a sheet, and then pasted on a tire molding machine by a usual method to form a green tire. Next, the green tire is heated and pressurized in a vulcanizer to obtain the heavy duty pneumatic tire of the present invention.

[0011]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Examples 1 to 5 and Comparative Example 5 After preparing various rubber compositions on the basis of the compounding contents and kneading conditions shown in Table 1, these rubber compositions were used as tread rubber, and 1800R25 was used under ordinary vulcanization conditions.
A prototype tire was made.

The Mooney viscosity of the rubber composition, the dispersibility in the vulcanized rubber, and the heat generation performance and wear resistance of the tire were determined according to the following methods. (1) Mooney viscosity of rubber composition According to JIS K6300, Mooney viscosity [ML _{1 +} 4/130 ° C.] was measured at 130 ° C.
Exponential notation. (2) Dispersibility The test piece was taken out from the vulcanized rubber, and the macrodispersibility was measured using
The value of 1 / σ was determined by measuring with an M (scanning electron microscope), and the value was indicated as an index by setting Comparative Example 1 to 100. The larger the value, the better the dispersibility. (3) Heat generation performance Conduct a drum test under constant speed and step load conditions.
The temperature was measured at a fixed position inside the tread portion, and the index was indicated by setting Comparative Example 1 to 100. The smaller the numerical value, the lower the exothermic temperature and the lower the exothermicity. (4) Abrasion resistance From the average value of the reduced groove depth after traveling for 2000 hours, the following formula was obtained: Wear resistance = [(reduced groove depth of tire of Comparative Example 1 or 4) / (of the test tire) The wear resistance was determined by the following formula: x100. The larger the value, the better the wear resistance.

[0013]

[Table 1]

[0014]

[Table 2]

[Note] 1) Kneading conditions Batch: Carbon black and silica are charged in the same stage. Split: Carbon black is charged in step (A) and silica is charged in step (B). 2) Number of stages: 3) Coupling agent : Bis (3-ethoxysilylpropyl) tetrasulfide 4) Anti-aging agent 3C: N-phenyl-N '-(1,3-
(Dimethylbutyl) -p-phenylenediamine 5) Vulcanization accelerator CZ: N-cyclohexyl-2-benzothiazylsulfenamide 6) Sheet properties ：: The surface is smooth. ：: The surface is slightly uneven. Δ: There are many irregularities on the surface. X: There is a feeling of stiffness. 7) Abrasion resistance: No marks indicate values of Comparative Example 1 as 100, and * marks indicate values of Comparative Example 4 as 100.

[0016]

According to the present invention, a tire having a good dispersibility of a reinforcing filler, a high level of abrasion resistance and a high level of exothermic performance and excellent performance by improving the sheet properties is provided with good productivity. Thus, a carbon black / silica filled rubber composition having good kneading workability can be efficiently produced.

Claims (8)

[Claims] 1. A step of dispersing (A) carbon black in natural rubber and / or a diene-based synthetic rubber;
(B) A method for producing a carbon black / silica-filled rubber composition, which comprises sequentially subjecting the composition obtained in the above step (A) to a step of dispersing silica. 2. The silica dispersion kneading temperature in the step (B) is controlled to a rubber falling temperature of 145 ° C. or lower.
The manufacturing method as described. 3. The method according to claim 1, wherein the kneading temperature of carbon black in step (A) is controlled to be higher than the kneading temperature of silica in step (B). 4. The method according to claim 1, wherein in the step (A), 70 parts by weight or less of carbon black is added to 100 parts by weight of natural rubber and / or diene-based synthetic rubber and dispersed. 5. In the step (B), silica (5-3) is added to 100 parts by weight of natural rubber and / or diene-based synthetic rubber.
5. The method according to claim 1, wherein 0 parts by weight are added and dispersed. 6. The silica used in the step (B) has a nitrogen adsorption specific surface area of 160 to 260 m ² / g and a dibutyl phthalate oil absorption (DBP) of 160 to 260 ml / 10 g.
The method according to any one of claims 1 to 5, wherein the amount is 0 g. 7. The production method according to claim 1, wherein a silane coupling agent is used in the step (B). 8. A heavy-duty pneumatic tire using the carbon black / silica-filled rubber composition obtained by the production method according to claim 1 as a tread rubber.