JP5551406B2 - Rubber composition and pneumatic tire - Google Patents

Description

  The present invention relates to a rubber composition and a pneumatic tire. More specifically, the present invention relates to a rubber composition having excellent abrasion resistance and high impact resilience (excellent rolling resistance), and a pneumatic tire using the rubber composition as a tire member. Is.

  Carbon black has a great influence on the performance of the rubber composition when blended in the rubber composition due to physical properties such as specific surface area, structure and surface properties. For this reason, carbon black having different characteristics is selectively used depending on the required performance of the rubber composition and the environmental conditions in which the rubber composition is used.

  The tread rubber that is in contact with the ground is required to have excellent resistance to wear during travel (wear resistance) and low hysteresis loss that occurs when the rubber during travel is deformed and low rolling resistance. In order to achieve both wear resistance and rolling resistance, methods such as high-filling carbon black, a high specific surface area (small particle size), or a method using carbon black having a high structure are being studied ( For example, Patent Documents 1 to 4). However, when these carbon blacks are used, although the wear resistance is improved, the rolling resistance may not be sufficient.

  Further, as a technique for improving the wear resistance of a tire with characteristics other than the specific surface area and structure of carbon black, a technique for improving the sharpness of the distribution of aggregate diameter of carbon black has been proposed (for example, Patent Document 5). ). However, the rubber composition in which the carbon black is blended has reduced heat build-up, and the rolling resistance of a tire using the rubber composition as a tread may not be sufficient. Further, if the sharpness of the aggregate diameter distribution is lowered (increases the broadness), the rolling resistance of the tire can be improved, but at the same time, the wear resistance tends to be lowered. Thus, the method of adjusting only the aggregate diameter distribution of carbon black is not an effective means for achieving both the tire wear resistance and rolling resistance.

  In this way, wear resistance and rolling resistance are in a trade-off relationship, and developments are underway to achieve both performances at a high level, but carbon black that exhibits sufficient characteristics has not yet been found. There is no current situation.

JP 61-1119043 A Japanese Patent Publication No. 6-868 Japanese Patent Laid-Open No. 5-170973 JP-A-6-136289 JP-A-6-279624

  The present invention has been made under such circumstances, and has a rubber composition having high impact resilience (excellent rolling resistance) while having excellent wear resistance, and the rubber composition as a tire member, It aims at providing the pneumatic tire especially used for a tread.

As a result of intensive studies to achieve the above object, the inventors of the present invention used, as a rubber component, carbon black in which the aggregate diameter distribution and the primary particle diameter distribution of the carbon black satisfy a predetermined relationship. It was found that the object can be achieved by a rubber composition blended.
The present invention has been completed based on such findings.

That is, the present invention
[1] the ratio of an electron microscope and weight average primary particle diameter D _wp and the number-based average primary particle diameter _{D np (D wp / D np} ), weight-average aggregate diameter D _wa the number by high-speed disk centrifugation The first region in which the ratio (D _wa / D _na ) with the reference average aggregate diameter D _na satisfies the relationship of the following formula (1), and further, the combustion gas is generated by burning the fuel and the oxygen-containing gas. The diameter of the first region is reduced, the second region is supplied with carbon black raw material to generate carbon black, and the second region is connected via a choke portion, and the diameter is larger than that of the second region. A cylindrical manufacturing apparatus having a third region, wherein the length of the choke portion is 200 to 600 mm, and the ratio of the diameter of the third region to the diameter of the choke portion is 1.8 or more and 4 or less. carbon black, which is produced by the production device, Gore A pneumatic tire using, as a member, a rubber composition obtained by blending 20 to 100 parts by mass with respect to 100 parts by mass of the rubber component ,

[2] The air according to the above [1], wherein the carbon black has a CTAB adsorption specific surface area of 60 to 200 (m ² / g) and a compressed DBP oil absorption (24M4DBP) of 80 to 160 (ml / 100 g). Entered tires,
[3] The pneumatic tire according to claim 2, wherein (D _wp / D _np ) and (D _wa / D _na ) are carbon black satisfying the relationship of the following formula (2):

[4 ] The pneumatic tire according to any one of [ 1] to [3], wherein the member is a tread and / or a tread base.
Is to provide.

  According to the present invention, by using a rubber composition obtained by blending carbon black having a specific property at a predetermined ratio with respect to a rubber component in a tire member, particularly a tread, it has excellent wear resistance. On the other hand, a pneumatic tire having high resilience (excellent rolling resistance) can be provided.

The relationship between D _wp / D _np and D _wa / D _na of carbon black used in the present invention is a table showing. It is a graph showing the relationship between D _wp / D _np and D _wa / D _na of carbon black used in Examples and Comparative Examples. It is sectional drawing of the manufacturing apparatus preferably used by this invention.

First, the rubber composition of the present invention will be described.
[Rubber composition]
The rubber composition of the present invention comprises a ratio (D _wp / D _np ) of a weight-based average primary particle diameter D _wp and a number-based average primary particle diameter D _np by an electron microscope, and a weight-based average aggregate by a high-speed disk centrifugation method. The ratio (D _wa / D _na ) between the diameter D _wa and the number-based average aggregate diameter D _na is the following formula (1):

Carbon black satisfying the above relationship and a rubber component are included.

《Rubber component》
As the rubber component in the rubber composition of the present invention, at least one selected from diene synthetic rubber and natural rubber is used. Examples of the diene synthetic rubber include isoprene rubber (IR), polybutadiene rubber (BR), and styrene-butadiene copolymer rubber (SBR). These rubber components may be used alone or in combination of two or more. May be used in combination.

"Carbon black"
The carbon black used in the rubber composition of the present invention is obtained by _measuring the ratio (D _wp / D _np ) between the weight-based average primary particle diameter D _wp and the number-based average primary particle diameter D _np by an electron microscope and using a high-speed disk centrifugation method. The ratio (D _wa / D _na ) between the weight-based average aggregate diameter D _wa and the number-based average aggregate diameter D _na is the following formula (1):

It is necessary to satisfy the relationship.

(D _wa / D _na and D _wp / D _np)
The measurement of the weight-based average primary particle diameter D _wp and the number-based average primary particle diameter D _np and the calculation of D _wp / D _np using an electron microscope are performed as follows.
First, a carbon black sample is dispersed in chloroform by an ultrasonic cleaning method and then fixed to a carbo support membrane. As a dispersion condition, for example, ultrasonic cleaning may be performed at a frequency of 28 KHz for 30 minutes. This sample was photographed directly with an electron microscope at a magnification of 20000 times and a total magnification of 80000-100,000 times, and the diameter of 1000 carbon black particles randomly selected from the obtained electron micrographs was measured, and a histogram of 3 nm sections was created. To do. When the i-th diameter of this histogram is di and the frequency is ni, the weight-based average primary particle diameter (D _wp ) and the number-based average primary particle diameter (D _np ) are calculated by the following equations. Then, the ratio D _wp / D _np is calculated from the obtained weight-based average primary particle diameter (D _wp ) and number-based average primary particle diameter (D _np ).

The ratio of the weight-average aggregate diameter D _wa the number-based average aggregate diameter D _na by high-speed disk centrifugation (D _wa / D _na) is in compliance with ISO / CD 15825/3, weight average It is a value obtained by measuring the aggregate diameter D _wa (nm) and the number reference average aggregate diameter D _na (nm) and calculating the ratio D _wa / D _na thereof.

D _wp / D _np and D _wa / D _na thus obtained satisfy the relationship of the above formula (1), and the range is shown as in FIG. In addition, as the carbon black aggregate diameter distribution (D _wa / D _na ) increases, the rolling resistance improves, and as the primary particle diameter distribution (D _wp / D _np ) increases, the wear resistance increases. Has the property of lowering.

Until now, when the aggregate distribution ( _Dwa / _Dna ) of carbon black is reduced (when sharpness is increased), the wear resistance of a tire using a rubber composition in which the carbon black is used for the tread is improved. However, rolling resistance decreases, and conversely, when the aggregate diameter distribution (D _wa / D _na ) is increased (decreasing sharpness, that is, increasing broadness), the rolling resistance of the tire is improved. However, it has been known that the wear resistance decreases. The inventor diligently studied this phenomenon, and this phenomenon is caused when the distribution of the primary particle diameter of carbon black (D _wp / D _np ) changes at the same time when the distribution of the aggregate diameter is controlled. Knowledge was obtained. That is, for example, in order to improve the rolling resistance of the tire, when the aggregate diameter distribution (D _wa / D _na ) of carbon black is increased (increased _broadness ), the primary particle diameter distribution (D _wp / D _np ) increases (because the _broadness increases), and as a result, it has been found that the wear resistance is further reduced.

Therefore, in the present invention, only the aggregate diameter distribution (D _wa / D _na ) of carbon black is increased (broadness is increased) and the primary particle diameter distribution (D _wp / D _np ) is decreased ( By increasing the sharpness, the wear resistance and rolling resistance of the tire can be maintained at a high level. That is, the present invention uses the carbon black present in the range where the aggregate diameter distribution is greater than or equal to the distribution of the primary particle diameter in FIG. It is possible to maintain rolling resistance at a high level.

In the carbon black used in the present invention, D _wp / D _np and D _wa / D _na have the following formula (2):

It is preferable to satisfy the relationship. By satisfying the above relationship, the rolling resistance can be improved without lowering the wear resistance of the tire, and it becomes possible to achieve both higher levels of wear resistance and rolling resistance of the tire. preferable.

(Specific surface area and oil absorption)
The CTAB adsorption specific surface area of the carbon black used in the present invention is preferably in the range of 60 to 200 (m ² / g), more preferably in the range of 65 to 160 (m ² / g), and further 70 The range of -150 (m < ² > / g) is preferable. If the adsorption specific surface area is 60 (m ² / g) or more, the wear resistance and rolling resistance of the tire can be improved in a well-balanced manner, and if it is 200 (m ² / g) or less, the resulting rubber composition This is preferable because the viscosity of the unvulcanized rubber does not increase and good processability is obtained. Here, the CTAB adsorption specific surface area is a specific surface area measured by a method of measuring an external surface area not including fine pores of particles, and is a value measured in accordance with ISO6810.

  The compressed DBP oil absorption (24M4DBP) of carbon black used in the present invention is preferably in the range of 80 to 160 (ml / 100 g), more preferably in the range of 85 to 150 (ml / 100 g). Further, a range of 90 to 140 (ml / 100 g) is preferable. If the compressed DBP oil absorption (24M4DBP) is 80 (ml / 100g) or more, the wear resistance and rolling resistance of the tire can be improved in a well-balanced manner, and if it is 160 (ml / 100g) or less, the resulting rubber is obtained. This is preferable because the viscosity of the unvulcanized rubber of the composition does not increase and good processability is obtained. Here, the compressed DBP oil absorption (24M4DBP) is an oil absorption of DBP (dibutyl phthalate) measured for a sample compressed four times at 24000 psi, and is a value measured according to ISO 4656.

  In the rubber composition of the present invention, the amount of carbon black added is preferably 20 to 100 parts by mass, more preferably 30 to 100 parts by mass, and further preferably 30 to 80 parts by mass with respect to 100 parts by mass of the rubber component. preferable. If the amount of carbon black added is within the above range, excellent tire wear resistance and rolling resistance can be obtained.

(Method for producing carbon black)
As long as the carbon black used in the present invention has the above-described properties, there is no limitation on what manufacturing method it is used for. As a method for producing carbon black, a furnace method, a channel method, a thermal method, an acetylene method and the like are generally known, but the furnace method is the most common.
The carbon black used in the present invention is, for example, a first region (combustion region) in which a combustion gas is generated by burning fuel and an oxygen-containing gas such as air. It can be manufactured by a furnace method using a cylindrical manufacturing apparatus having a second region (taper region) for generating carbon black and a third region (reaction region) enlarged from the taper region.

  A preferred embodiment of the manufacturing apparatus will be described with reference to FIG. The manufacturing apparatus shown in FIG. 3 has a first region 1 (combustion region), a second region 2 (tapered region), and a third region 3 (reaction region). The connecting portion has a choke portion 4.

The second region 2 is a region in which carbon black is generated by supplying hydrocarbons or the like as a carbon black raw material to the combustion gas generated in the first region 1 and mainly thermally decomposing the raw material. The shape of the second region 2 becomes gradually narrower than the connection portion with the first region 1 and is connected to the choke portion 4 by the narrow cylindrical portion 5.
The second region 2 is provided with a raw material introduction port 7 for supplying hydrocarbons or the like as a raw material for carbon black into the production apparatus. In order to supply the raw material as uniformly as possible to the second region 2, the raw material introduction ports 7 can be provided in a plurality of rows, for example, as the raw material introduction ports 7-1 to 7-3 shown in FIG. Each of the ports 7-1 to 7-3 can be composed of a plurality of introduction ports.

  The choke portion 4 provided at the connection portion between the second region 2 and the third region 3 is a portion that adjusts the particle diameter of the carbon black obtained. The length of the choke portion 4 may be appropriately selected depending on the desired particle size of the carbon black, but is preferably about 200 to 600 mm, more preferably about 300 to 500 mm in the present invention.

  The third region 3 is a region where the combustion gas accompanied by the carbon black that has passed through the choke portion 4 is cooled to about 1000 ° C. or less to obtain carbon black particles, and has an enlarged diameter larger than that of the choke portion 4. It consists of a cylindrical part 6. The combustion gas is cooled by supplying water or the like from the reaction stop fluid inlet 8. The reaction stop fluid introduction ports 8 can be provided in a plurality of rows such as the reaction stop fluid introduction ports 8-1 to 8-5 shown in FIG.

  Here, the supply amount of oxygen-containing gas such as fuel and air, the supply amount of raw materials, and the supply method thereof are not particularly limited, but the ratio of the diameter of the choke portion 4 to the diameter of the third region 3 is 1.8 or more, preferably 2 or more, and more preferably 2.2 or more. If the ratio of the diameter of the choke portion 4 to the diameter of the third region 3 is within the above range, carbon black satisfying the relationship of the above formulas (1) and (2) can be obtained. The upper limit value of the ratio of the diameter of the choke portion 4 to the diameter of the third region 3 is not particularly limited, but considering the size of the manufacturing apparatus, it may be about 4 or less, preferably 3.5 or less. The above-described method for producing carbon black describes an example of a preferred embodiment, and is not limited to this in obtaining the carbon black of the present invention.

(Other ingredients)
The rubber composition of the present invention preferably contains an amine anti-aging agent and a wax in order to suppress the occurrence and progress of cracks due to ozone.
Examples of the amine-based antiaging agent include 3C (N-isopropyl-N′-phenyl-p-phenylenediamine, 6C [N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine], diphenylamine). And a high-temperature condensate of acetone and the like, and the amount used thereof is preferably 0.1 to 7.0 parts by weight, more preferably 0.5 to 5 parts per 100 parts by weight of the rubber component (A). 0.0 part by mass.
Waxes are also classified as sun crack prevention agents, and have an action of suppressing cracks generated by the action of sunlight or ozone. That is, after vulcanization, it blooms on the surface of the rubber article, blocks the rubber surface and air, reflects sunlight and exhibits its effectiveness. There is no restriction | limiting in particular in the kind of wax, Arbitrary things can be suitably selected and used from the conventionally used waxes. The usage-amount is about 0.1-7.0 mass parts with respect to 100 mass parts of rubber components, Preferably it is 0.5-5.0 mass parts.

The rubber composition of the present invention can contain silica as a reinforcing filler.
Any commercially available silica can be used, among which wet silica, dry silica, and colloidal silica are preferably used, and wet silica is particularly preferably used. The BET specific surface area (measured according to ISO 5794/1) of silica is preferably 100 m ² / g or more, more preferably 150 m ² / g or more, particularly preferably 170 m ² / g or more. Examples of such silicas are those manufactured by Tosoh Silica Co., Ltd., trade names “Nipsil AQ” (BET specific surface area = 190 m ² / g), “Nipsil KQ”, and Degussa's trade name “Ultra Gil VN3” (BET specific surface area = 175 m ^2. / G) can be used.
When silica is used as the reinforcing filler, it is preferable to contain about 1 to 20 parts by mass of the silane coupling agent with respect to 100 parts by mass of silica for the purpose of further improving the reinforcement and low heat build-up. .
The content of silica is usually about 20 to 100 parts by mass, preferably 30 to 80 parts by mass with respect to 100 parts by mass of the rubber component.

In the rubber composition of the present invention, various chemicals usually used in the rubber industry, for example, other than vulcanizing agents, vulcanization accelerators, softeners and amines, are used as long as the effects of the present invention are not impaired. An anti-aging agent, an anti-scorch agent, zinc white, stearic acid and the like can be contained.
As said vulcanizing agent, sulfur etc. are mentioned, The usage-amount is 0.1-10.0 mass parts as a sulfur content with respect to 100 mass parts of rubber components, More preferably, it is 1.0-5. 0 parts by mass. If the amount is less than 0.1 parts by mass, the rupture strength, wear resistance, and low heat build-up of the vulcanized rubber may be reduced. If the amount exceeds 10.0 parts by mass, the rubber elasticity is lost.
The vulcanization accelerator that can be used in the present invention is not particularly limited. For example, M (2-mercaptobenzothiazole), DM (dibenzothiazolyl disulfide), CZ (N-cyclohexyl-2-benzothia). Thiols such as zolylsulfenamide), guanidines such as DPG (diphenylguanidine), or thiurams such as TOT (tetrakis (2-ethylhexyl) thiuram disulfide), and the like. The amount used is preferably 0.1 to 5.0 parts by weight, more preferably 0.2 to 3.0 parts by weight, with respect to 100 parts by weight of the rubber component.

  Moreover, a process oil can be mentioned as a softening agent which can be used with the rubber composition of this invention. Examples of the process oil include paraffinic, naphthenic, and aromatic oils. Aromatics are used for applications that emphasize tensile strength and wear resistance, and naphthenic or paraffinic systems are used for applications that emphasize hysteresis loss and low-temperature characteristics. The amount used is preferably 0 to 100 parts by mass with respect to 100 parts by mass of the rubber component, and if it is 100 parts by mass or less, the deterioration of the tensile strength and low heat build-up (low fuel consumption) of the vulcanized rubber is suppressed. can do.

The rubber composition of the present invention can be prepared by kneading, heating, extruding, etc., the rubber component and carbon black described above and various compounding agents appropriately selected as necessary.
The rubber composition of the present invention thus prepared can provide a pneumatic tire having high impact resilience while having excellent wear resistance.

[Pneumatic tire]
The pneumatic tire of the present invention is characterized by using the above-described rubber composition of the present invention for any of the tire members, and is particularly preferably applied to a tread and / or a tread base. Such a tire has excellent abrasion resistance and high impact resilience (excellent rolling resistance), so that it can be used not only as a tire for passenger cars but also as a heavy load tire.
Examples of the gas filled in the pneumatic tire of the present invention include normal or air having a changed oxygen partial pressure, or an inert gas such as nitrogen. When the rubber composition of the present invention is used for a tread, for example, it is extruded on a tread member, and is pasted and molded by a usual method on a tire molding machine to form a raw tire. The green tire is heated and pressed in a vulcanizer to obtain a tire.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
(1) Measurement of physical properties of carbon black The CTAB adsorption specific surface area of carbon black was measured according to ISO6810, and the compressed DBP oil absorption (24M4DBP) was measured according to ISO4656. The weight-based average primary particle diameter D _wp , the number-based average primary particle diameter D _np , the weight-based average aggregate diameter D _wa , and the number-based average aggregate diameter D _na are measured by the methods described above, and each of the D _wa / D _na and D _wp / D _np were calculated.
(2) Evaluation of Abrasion Resistance Using a rubber composition having a formulation shown in Table 1 as a tread member, a tire for a truck having a tire size of 11R22.5 was made as a trial with a tread having a single layer structure. The test tire is mounted on the drive shaft of a truck, and the amount of wear (reduction in the groove of the tire) after running 40,000 km is measured. The value of Comparative Example 1 using a conventional tire is set to 100, and is expressed as an index. did. It shows that abrasion resistance is so favorable that the value of an index | exponent is large.
(3) Rolling resistance With respect to the above test tire, the rolling resistance at 80 km / h at a normal load and internal pressure was measured by the coasting method, and the value of Comparative Example 1 using a conventional tire was expressed as an index with 100 as the index. The smaller the numerical value, the lower the rolling resistance and the better (the better the rolling resistance).

Preparation Example 1: Preparation of carbon blacks 1 to 4 Under the conditions shown in Table 2, carbon black 1 was prepared using the manufacturing apparatus shown in FIG. The production apparatus includes a first region 1 (diameter: 700, length: 1000) for burning fuel and air, and a second region 2 (upstream end diameter: 700 mm, downstream end) for supplying raw material oil to generate carbon black. Diameter: 230 mm, length: 1200), choke part 4 (diameter: 230 mm, length: 400 mm), and third region (diameter: 576 mm, length: 5000, reaction region diameter ratio / choke region diameter: 2.5) ). The properties of the obtained carbon blacks 1 to 4 are shown in Table 2.

Preparation Example 2: Preparation of carbon blacks 5 to 12 In Preparation Example 1, the conditions shown in Table 2 were used, the size of the third region was diameter: 345 mm, length: 5000, reaction region diameter ratio / choke region diameter: 1 Carbon blacks 5 to 12 were prepared in the same manner as in Preparation Example 1, except that. The properties of the obtained carbon blacks 5 to 12 are shown in Table 2.

Examples 1-4 and Comparative Examples 1-8
In accordance with the formulation shown in Table 1, 12 types of rubber compositions of Examples 1 to 4 and Comparative Examples 1 to 8 were prepared. These 12 kinds of rubber compositions were disposed on a tire tread, and a tire for a tire having a tire size of 11R22.5 was manufactured according to a conventional method. The obtained tire was evaluated for wear resistance and rolling resistance. The evaluation results are shown in Table 2.

[note]
1) Carbon blacks 1 to 12 obtained by preparing the above carbon black
2) Nt-butyl-2-benzothiazolylsulfenamide

Examples 1 and 2 using carbon black in which the relationship between D _wa / D _na and D _wp / D _np satisfies the formulas (1) and (2) as compared with Comparative Example 1 using the conventional tire. Was excellent in terms of wear resistance and rolling resistance, and Examples 3 and 4 were excellent in terms of the balance between wear resistance and rolling resistance. On the other hand, the comparative example using carbon black in which the relationship between D _wa / D _na and D _wp / D _np does not satisfy the formulas (1) and (2) is the same in both points of wear resistance and rolling resistance. It did not have sufficient performance, or could not exhibit sufficient performance in terms of either wear resistance or rolling resistance.

  The present invention provides a rubber composition having excellent wear resistance and high impact resilience (excellent rolling resistance), and a pneumatic tire using the rubber composition for a tire member, particularly a tread. To do. Since the pneumatic tire obtained by the present invention has excellent abrasion resistance and high impact resilience (excellent rolling resistance), it can be used not only as a tire for passenger cars but also as a tire for heavy loads. Can be used.

1. First area (combustion area)
2. Second area (taper area)
3. Third area (reaction area)
4). 4. Choke part 5. Narrow cylindrical part 6. Enlarged cylindrical part Raw material inlet 7-1-3. Raw material inlet 8. Reaction stop fluid inlet 8-1 to 5. Reaction stop fluid inlet

Claims (4)

And the ratio of the weight average primary particle diameter D _wp and the number-based average primary particle diameter D _np by electron microscopy (D _wp / D _np), weight-average aggregate diameter D _wa the number-based average aggregate by high-speed disk centrifugation A ratio (D _wa / D _na ) with the gate diameter D _na satisfies the relationship of the following formula (1), and further, a first region that generates combustion gas by burning fuel and oxygen-containing gas, A second region in which the diameter is reduced from one region, a carbon black raw material is supplied to generate carbon black, and a third region that is connected to the second region via a choke portion and has a larger diameter than the second region The length of the choke part is 200 to 600 mm, and the ratio of the diameter of the third region to the diameter of the choke part is 1.8 or more and 4 or less. The manufactured carbon black is a rubber component A pneumatic tire using as a member a rubber composition obtained by blending 20 to 100 parts by mass with respect to 100 parts by mass .
^2. The pneumatic tire according to claim 1, wherein the carbon black has a CTAB adsorption specific surface area of 60 to 200 (m ² / g) and a compressed DBP oil absorption (24 M4 DBP) of 80 to 160 (ml / 100 g). The pneumatic tire according to claim 2, wherein (D _wp / D _np ) and (D _wa / D _na ) are carbon black satisfying the relationship of the following formula (2).
The pneumatic tire according to claim 1, wherein the member is a tread and / or a tread base.