JP2003292821A - Carbon black and its rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carbon black which is suitable for a tire tread use, imparting excellent abrasion resistance and grip properties to a compound rubber while well-balancing them, and to provide a rubber composition. <P>SOLUTION: The carbon black has selective characteristics expressed by the following formulae: (1) 160≤CTAB≤220, (2) -40≤N<SB>2</SB>SA-IA≤-10, (3) 1.3×CTAB-155<N<SB>2</SB>SA-CTAB, (4) 110≤24M4DBP≤130, (5) 40≤DBP-24M4 DBP≤60 and (6) ΔDst≤0.75×24M4DBP-43, and the rubber composition is obtained by compounding the carbon black by the ratio of 50-180 pts.wt. to 100 pts.wt. of a diene rubber component. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to carbon black suitable for a tire tread having excellent steering stability and wear resistance, and a rubber composition containing the same.

[0002]

2. Description of the Related Art In recent years, as automobiles have been improved in performance and roads have been developed, there is a strong demand for tires having excellent steering stability and wear resistance. It is important to improve the grip performance (road surface gripping force) of the rubber composition in order to improve the steering stability (braking performance on the road surface). To that end, increase the hysteresis loss of the rubber composition. Is required.

Conventionally, as a means for increasing the hysteresis loss of a rubber composition for a tire tread, a styrene-butadiene copolymer rubber (SB having a large amount of styrene bonds is used.
A method of filling R) with a large amount of carbon black has been adopted. However, the rubber composition in which a large amount of carbon black is mixed and filled has problems that the hardness becomes too high, the frictional resistance with the road surface becomes small, and the rubber structure of the tire deteriorates due to remarkable heat generation during running.

Therefore, from the viewpoint of the characteristics of the carbon black to be blended, a rubber composition having both high grip performance and abrasion resistance for tire tread has been actively developed. For example, the present applicant has a nitrogen adsorption specific surface area (N ₂ SA) of 120 to 1 for the purpose of achieving both grip performance and wear resistance.
Carbon black for rubber compounding (hardness of 65 m ² / g, DBP oil absorption of 120 ml / 100 g or more, and having a limited characteristic relation value (G value) for reducing the particle size while suppressing the surface activity. Kaihei 2-32137), Dst 70
Below, the nitrogen adsorption specific surface area / iodine adsorption amount is 0.85
0.98, DBP oil absorption amount -24M4 DBP shows a high level of wear resistance and grip performance even if the specific surface area or DBP oil absorption amount is not high by blending carbon black with less than 20, and processing is performed even with a higher specific surface area. A rubber composition (Japanese Unexamined Patent Publication No. 3-174470) that exhibits a high degree of abrasion resistance without impairing the properties and abrasion resistance has been developed.

Further, the present applicant has found that the diene rubber component 100
In weight parts, (1) 125 ≤ CTAB ≤ 160, (2) 115
≦ DBP ≦ 150, (3) 1.20 ≦ DBP / 24M4DB
P, (4) Blackness ≧ 0.53 × CTAB + 65.
50 to 1 of carbon black having the selective characteristics of 8
A rubber composition compounded in a proportion of 80 parts by weight (Japanese Patent Laid-Open No. Hei 5)
-32826), (1) 140 ≦ CTAB ≦ 180,
(2) -10 <N ₂ SA-IA <0, (3) 110 ≦ 24M4
DBP ≦ 130, (4) 20 ≦ DBP-24M4 DBP ≦ 4
It has been proposed to develop a rubber composition (Japanese Patent Laid-Open No. 6-256577) in which carbon black having a selective characteristic of 0, (5) ΔDst ≦ 0.5Dst + 23 is blended at a ratio of 50 to 180 parts by weight.

[0006]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention Based on the above-mentioned prior art, the present inventors further researched on improvement and compatibility of grip performance and abrasion resistance of a rubber composition, and as a result, the ratio of carbon black Set the relationship of colloidal properties that represent surface area, aggregates, etc. to a specific range, and CTAB
By relatively increasing the porosity (N ₂ SA-CTAB) with respect to 24A4 and sharpening the distribution width (ΔDst) of the aggregate with respect to the absorption amount of 24M4DBP, it is possible to suppress deterioration of wear resistance and to grip. It was confirmed that the performance could be significantly improved.

The present invention has been completed on the basis of this finding, and an object thereof is to impart a high level of wear resistance and grip performance to compounded rubber in a well-balanced manner, and to use it for tire tread applications. It is an object of the present invention to provide a carbon black that is preferably used and a rubber composition containing the carbon black.

[0008]

The carbon black according to the present invention for achieving the above object is characterized in that it has the following selective characteristics. (1) 160 ≤ CTAB ≤ 220 (2) -40 ≤ N ₂ SA-IA ≤ -10 (3) 1.3 x CTAB-155 <N ₂ SA-CTAB (4) 110 ≤ 24 M4DBP ≤ 130 (5) 40 ≦ DBP-24M4DBP ≦ 60 (6) ΔDst ≦ 0.75 × 24M4DBP-43 However, CTAB is CTAB specific surface area (m ² / g), N ₂ SA is nitrogen adsorption specific surface area (m ² / g), IA is Elemental adsorption amount (mg / g),
DBP is the DBP absorption (cm ³ / 100g), 24M4 DBP is the compressed DBP absorption (cm ³ / 100g), ΔDst is the half-width (nm) of the Stokes diameter distribution of the carbon black aggregate measured by the disc centrifuge (DCF). ).

The rubber composition according to the present invention is characterized in that the above-mentioned carbon black is blended in a proportion of 50 to 180 parts by weight with respect to 100 parts by weight of the diene rubber component.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In order to achieve the object of the present invention, it is necessary to satisfy all the carbon black characteristics specified in the above constitutions (1) to (6). That is, among the characteristics of carbon black, (1) CTAB specific surface area is a prerequisite characteristic requirement of the particle size level of carbon black particles when carbon black is compounded and filled in the rubber component, and this value is 160 m. If it is less than ² / g, it is not possible to simultaneously impart a sufficient level of grip performance and abrasion resistance to the compounded rubber, while if it exceeds 220 m ² / g, the Mooney viscosity will increase when compounded into the rubber component and kneading will occur. Workability is reduced, and dispersibility of carbon black in rubber is reduced.

(2) If the value of (N ₂ SA-IA) exceeds -10, the grip performance of the compounded rubber is insufficient, and if it is less than -40, the wear resistance retreats significantly. In addition, (3) [1.
The requirement of 3 × CTAB-155 <(N ₂ SA-CTAB)] indicates that the carbon black surface has a high porosity (N ₂ SA-CTAB) per constant CTAB, and the porosity is 1.3 × CTAB-. If the value is less than or equal to 155,
No improvement in both grip performance and wear resistance can be seen.

24M4DBP improves the dispersibility of carbon black in rubber and is a structural factor involved in the reinforcing effect of compounded rubber. The value of 24M4DBP satisfies (4) 110≤24M4DBP≤130. There is a need. If the value of 24M4DBP is less than 110 (cm ³ / 100g), the shearing stress applied during kneading when compounded in the rubber component will be insufficient, resulting in a decrease in wear resistance. on the other hand,
130 (cm ³ / 100g) reduced exceeding the dispersibility viscosity becomes high during the rubber compounding and resulting in deterioration of the processability of the rubber composition.

(5) (DBP-24M4DBP) is a parameter indicating the structure strength of carbon black, and is a factor relating to the structure level in rubber. If this value is less than 40, the grip performance of the rubber composition will be insufficient, while if it exceeds 60, the structure will be destroyed at the time of compounding into the rubber component, resulting in deterioration of dispersibility and workability. The skid performance is significantly reduced.

Further, (6) (ΔDst ≦ 0.75 × 24M4D
The requirement of BP-43) is characterized by the narrow distribution width of aggregates per constant 24M4 DBP and the relatively sharp distribution, and ΔDst is 0.75 × 24M4.
If it exceeds DBP-43, it becomes impossible to improve the grip performance and wear resistance, and achieve both of them.

The carbon black of the present invention is CTAB,
_{N 2 SA-IA, (N} 2 SA-CTAB)> 1.3 × C
TAB-155, 24M4DBP, DBP-24M4DB
By setting the selective characteristics of P and ΔDst ≦ 0.75 × 24M4DBP-43 in a specific range, it becomes possible to effectively improve the grip performance and wear resistance of the compounded rubber, and to achieve both functions. As a result, it can be suitably used as a rubber composition for a tire tread, which is excellent in steering stability and wear resistance, as compared with a conventional rubber composition containing a comparable type of carbon black.

The values obtained by the following measuring methods are used for the respective characteristics of the carbon black in the above constitution. CTAB specific surface area (m ² / g); JIS K6217 (1997)
"Testing method for basic performance of carbon black for rubber" 8
And the CTAB adsorption specific surface area. The measured value of IRB # 6 by this measuring method is 77 m ² / g.

N ₂ SA (nitrogen adsorption specific surface area) (m ² / g);
JIS K6217 (1997) "Testing method for basic performance of carbon black for rubber", item 7, nitrogen adsorption specific surface area, 7.4
According to the term C method. The measured value of IRB # 6 by this measuring method is 76 m ² / g.

IA (adsorption amount of iodine) (mg / g); JIS
K6217 (1997) "Testing method of basic performance of carbon black for rubber", item 6, Iodine adsorption amount. The measured value of IRB # 6 by this measuring method is 80 mg / g.

DBP absorption (ml / 100g); JIS K6
217 (1997) “Testing method for basic performance of carbon black for rubber”, item 9, DBP absorption, item 9.2, method A. The measured value of IRB # 6 by this measuring method is 99 ml / 100 g
Is.

24M4DBP absorption (ml / 100g); JIS
K6217 (1997) "Testing method for basic performance of carbon black for rubber", item 10, according to DBP absorption of compressed sample. The measured value of IRB # 6 by this measuring method is 87 ml.
/ 100g.

Full width at half maximum of Stokes diameter distribution of aggregate ΔDst (nm); JIS K6221-82 5. A 20% by volume ethanol aqueous solution containing a small amount of a surfactant in a dried carbon black sample based on “How to prepare a dried sample” To prepare a dispersion liquid having a carbon black concentration of 50 mg / l, which is sufficiently dispersed by ultrasonic waves to obtain a sample. A disk centrifuge device (manufactured by Joyes Lobel, UK) was set at a rotation speed of 8000 rpm, 10 ml of a spin solution (2% by weight glycerin aqueous solution at a temperature of 25 ° C) was added, and then 1 ml of a buffer solution (20 volumes at a temperature of 25 ° C). % Ethanol aqueous solution). Next, after adding 0.5 ml of the carbon black dispersion liquid at a temperature of 25 ° C. with a syringe, centrifugal sedimentation was started, and at the same time, the recorder was operated and the distribution curve shown in FIG. The elapsed time from the start, the vertical axis represents the absorbance at a specific point that changes with the centrifugal sedimentation of carbon black. Each time T is read from this distribution curve and substituted into the following equation (Equation 1) to calculate the Stokes equivalent diameter corresponding to each time.

[0022]

[Equation 1]

In Equation 1, η is the viscosity of the spin liquid (0.935
cp), N is the disk rotation speed (8000 rpm), r ₁ is the radius of the carbon black dispersion liquid injection point (4.56 cm), r ₂ is the radius to the absorbance measurement point (4.82 cm), and ρ _CB is the density of the carbon black. (g / cm ³ ), ρ ₁ is the spin liquid density (1.00178
g / cm ³ ).

The Stokes equivalent diameter (mode diameter) of the maximum frequency in the Stokes equivalent diameter-absorbance distribution curve (FIG. 2) thus obtained is defined as Dst (nm), and 50% of the maximum frequency is obtained. The difference (half-value width) of the obtained Stokes equivalent diameters of two points, large and small, is defined as ΔDst (nm). The ΔDst of IRB # 6 by this measuring method is 68 nm.

In the rubber composition of the present invention, carbon black having the above-mentioned properties is added to a diene rubber component 100 such as styrene-butadiene copolymer rubber or polybutadiene rubber.
It is compounded at a ratio of 50 to 180 parts by weight with respect to parts by weight. If the blending ratio is less than 50 parts by weight, a sufficient reinforcing effect cannot be obtained, so that the wear resistance and grip performance are low. If the blending ratio exceeds 180 parts by weight, the viscosity increases during compounding and kneading with the rubber component, resulting in poor kneading processability. This is because it is significantly reduced. At the time of compounding, a rubber composition is obtained by kneading together with commonly used necessary components such as a vulcanizing agent, a vulcanization accelerator, an antiaging agent, a vulcanization aid, a softening agent and a plasticizer.

The carbon black having the selective characteristics of the present invention comprises a combustion chamber having a combustion burner mounted in the furnace head in a tangential direction air supply port and in the furnace axial direction, and is coaxially connected to the combustion chamber. Using a multi-stage narrow diameter reaction chamber equipped with a feed oil supply nozzle, and a reaction furnace composed of a wide diameter reaction chamber,
It can be produced by controlling the feedstock oil introduction conditions, the amounts of fuel oil and feedstock oil supplied, the reaction time (the residence time of the combustion gas from the final feedstock oil introduction position to the stop of the reaction), and the like.

[0027]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples.

(1) Production of carbon black Examples 1 to 6 and Comparative Examples 9, 11, 15 Carbon black was produced using the reaction furnace shown in FIG. The reactor shown in FIG. 3 is equipped with a tangential combustion air introduction duct 9 and an axial combustion burner 10 at the furnace head, and the downstream outlet gradually converges to an inner diameter of 900 mm and a length of 1000.
mm (convergence part length 300 mm) combustion chamber 1, first-stage narrow-diameter reaction chamber 2 (internal diameter 180 mm, length 500 mm) coaxially connected to the combustion chamber, second-stage narrow-diameter reaction chamber 3 (internal diameter 200 mm) , Length 300 mm), 3rd stage narrow diameter reaction chamber 4 (internal diameter 190 mm, length 300 mm), and subsequent wide diameter reaction chamber 5 (internal diameter 400 m)
m, length 8000 mm), the first stage narrow diameter reaction chamber 2 has a first feedstock oil supply nozzle 6 and a second stage narrow diameter reaction chamber 3
Is equipped with a second feedstock oil supply nozzle 7, and the wide diameter reaction chamber 5 is equipped with a cooling water nozzle 8 for stopping the reaction. Using this reactor, carbon blacks having different characteristics were produced by changing the amounts of feed oil, fuel oil, and air supplied to the first-stage narrow-diameter reaction chamber and the second-stage narrow-diameter reaction chamber, respectively. As the base oil, specific gravity (15/4 ° C) 1.073, viscosity (Engla 40
/ 20 ℃) 2.10, toluene insoluble content 0.03%, aromatic hydrocarbon oil with correlation coefficient (BMCI) 140, fuel oil specific gravity (15/4 ℃) 0.903, viscosity (Cst / 50 ° C) 16.
1. Hydrocarbon oil having a residual carbon content of 5.4% and a flash point of 96 ° C. was used.

Comparative Examples 7 to 8, 10, 12 to 14 Carbon black was produced using the reaction furnace shown in FIG. The reactor shown in FIG. 4 is equipped with a tangential combustion air introduction duct 9 and an axial combustion burner 10 at the furnace head, and the downstream outlet gently converges to an inner diameter of 900 mm and a length of 1000.
mm (convergence part length 300 mm) combustion chamber 1, first-stage narrow-diameter reaction chamber 2 (internal diameter 180 mm, length 500 mm) coaxially connected to the combustion chamber, second-stage narrow-diameter reaction chamber 3 (internal diameter 200 mm) , Length 300 mm and subsequent wide diameter reaction chamber 5 (inner diameter 400 mm,
Length 8000 mm) and the first stage narrow diameter reaction chamber 2
Is equipped with a first feedstock oil supply nozzle 6, a second feedstock oil supply nozzle 7 in the second stage narrow diameter reaction chamber 3, and a cooling water nozzle 8 for stopping the reaction in the wide diameter reaction chamber 5. Using this reactor, carbon blacks having different characteristics were produced by changing the amounts of feed oil, fuel oil, and air supplied to the first-stage narrow-diameter reaction chamber and the second-stage narrow-diameter reaction chamber, respectively. The same feed oil and fuel oil as in the example were used.

The manufacturing conditions applied to Tables 1 and 2 are shown in Tables 3 and 4, respectively.
The characteristics of the carbon black obtained in Example No. Corresponding to.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

[0034]

[Table 4]

(2) Preparation of rubber composition Next, using each of the carbon blacks of Tables 3 and 4, the styrene-butadiene rubber was compounded at the compounding ratio shown in Table 5, and the compound was heated at a temperature of 145 ° C. for 50 minutes. It was vulcanized to prepare a rubber composition.

[0036]

[Table 5]

(3) Rubber Property Test With respect to each rubber composition obtained, the loss coefficient (tan δ) which is an index of grip performance and the pico-wear amount showing wear resistance were measured. The obtained results are shown in Tables 6 and 7, and the relationship between the pico abrasion resistance (index) and the loss coefficient (index) is shown in FIG. The measurement was performed by the following method.

Loss coefficient (tan δ); manufactured by Iwamoto Manufacturing Co., Ltd.
It measured on the following conditions using Visco Elastic Spectrometer. The measurement results are the measured values (tan δ) of Comparative Example 7.
Is shown as an index [(tan δ measured value) / (tan δ of Comparative Example 7)] × 100. Therefore,
The larger the index value, the better the grip performance. Test piece: Thickness 2mm, length 30mm, width 5mm Frequency: 50Hz Dynamic strain rate: ± 1% Temperature: 60 ° C

Pico abrasion test; using a pico abrasion tester,
It was measured according to ASTM D2228. The measurement results are shown as an index [(wear amount of Comparative Example 7) / (sample wear amount)] × 100 when the wear amount of Comparative Example 7 is 100. Therefore, the larger the index value, the better the wear resistance.

[0040]

[Table 6] Note: * 1 Index when Comparative Example 7 is 100

[0041]

[Table 7] Note: * 1 Index when Comparative Example 7 is 100

From Tables 3 to 4, Tables 6 to 7 and FIG. 5, at least the rubber compositions of Examples 1 to 6 in which carbon black satisfying all the selective characteristic requirements of the present invention was blended with styrene-butadiene rubber, were obtained. Compared with the rubber compositions of Comparative Examples 7 to 15 in which one of the selective characteristic requirements is deviated, carbon black is compounded, and the loss index and the index showing wear resistance are large, and the high-level grip performance and wear resistance are well balanced. It is recognized that it has been granted.

[0043]

As described above, according to the carbon black of the present invention, it becomes possible to impart high balance abrasion resistance and grip performance to the compounded rubber in a well-balanced manner. Therefore, it is extremely useful as a carbon black which is excellent in handling stability and wear resistance and which is preferably used for a high-performance tire tread and a rubber composition containing the carbon black.

[Brief description of drawings]

FIG. 1 is a distribution curve showing the change in absorbance due to centrifugal sedimentation of carbon black and the time elapsed since the carbon black dispersion was added during the measurement of Dst.

FIG. 2 is a distribution curve showing the relationship between the Stokes equivalent diameter and the absorbance obtained when measuring Dst.

FIG. 3 is a schematic cross-sectional view illustrating a reaction furnace used to produce the carbon black of the present invention.

FIG. 4 is a schematic cross-sectional view illustrating a reaction furnace used for producing a carbon black of a comparative example.

FIG. 5 is a graph showing the relationship between pico abrasion resistance (index) and loss coefficient (index) according to examples and comparative examples.

[Explanation of symbols]

1 combustion chamber 2 1st stage narrow diameter reaction chamber 3 2nd stage narrow diameter reaction chamber 4 3rd stage narrow diameter reaction chamber 5 Wide diameter reaction chamber 6 1st feed oil supply nozzle 7 Second feed oil supply nozzle 8 Cooling water nozzle 9 Combustion air introduction duct 10 Burner for combustion

Continued front page    (72) Inventor Ryusuke Harada             Tokai Ka, 1-2-3 Kita-Aoyama, Minato-ku, Tokyo             Carbon Co., Ltd. F-term (reference) 4J002 AC021 AC031 AC081 DA036                       GN01                 4J037 AA02 BB15 BB18 BB19 BB33                       BB36 DD05 DD07 DD17 FF18

Claims (2)

[Claims] 1. A carbon black having the following selective characteristics. (1) 160 ≤ CTAB ≤ 220 (2) -40 ≤ N ₂ SA-IA ≤ -10 (3) 1.3 x CTAB-155 <N ₂ SA-CTAB (4) 110 ≤ 24 M4DBP ≤ 130 (5) 40 ≦ DBP-24M4DBP ≦ 60 (6) ΔDst ≦ 0.75 × 24M4DBP-43 However, CTAB is CTAB specific surface area (m ² / g), N ₂ SA is nitrogen adsorption specific surface area (m ² / g), IA is Elemental adsorption amount (mg / g),
DBP is the DBP absorption (cm ³ / 100g), 24M4 DBP is the compressed DBP absorption (cm ³ / 100g), ΔDst is the half-width (nm) of the Stokes diameter distribution of the carbon black aggregate measured by the disc centrifuge (DCF). ). 2. Based on 100 parts by weight of the diene rubber component,
A rubber composition comprising the carbon black according to claim 1 in an amount of 50 to 180 parts by weight.