JPH072866B2 - Rubber composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a rubber composition suitable as a tread member for tires for passenger cars and light trucks, and more specifically, it has high impact resilience while maintaining excellent wear resistance. It relates to a rubber composition having a low heat buildup.

[Conventional technology]

There are various varieties of carbon black for rubber reinforcement depending on the properties of the rubber, and these varieties of properties are the main factors that determine the various performances of the composition compounded with the rubber. For this reason, in the case of compounding with rubber, a means for selecting and using carbon black having a variety of characteristics suitable for use as a member is generally used.

For example, fuel-efficient tires have been actively developed in recent years in order to meet the social demands for resource saving and energy saving. A rubber composition containing carbon black in a relatively small amount in a rubber component and having low heat buildup and high impact resilience is effective. However, the rubber compounding of carbon black having a large particle size and a small specific surface area is effective for improving the fuel efficiency, but it is unavoidable that the characteristics such as braking property on a wet road surface and abrasion resistance are deteriorated.

Therefore, if it is possible to simultaneously impart high abrasion resistance and low heat buildup giving high impact resilience to the compounded rubber by using carbon black having a small particle size and a large specific surface area,
It is ideal as a rubber member for tire treads.

The applicant systematically conducts a study to make the above-mentioned antithetic rubber performance compatible by adding more microselective characteristics in addition to the basic characteristics such as particle diameter, specific surface area and structure of the compounded carbon black. The following development proposals have already been made.

Nitrogen adsorption specific surface area (N ₂ SA) is 60 m ² / g or more, compressed DBP is 112
Carbon black capable of simultaneously imparting high reinforcement performance and high impact resilience to compounded rubber in which the Stokes mode diameter and the distribution of aggregates are maintained above a certain value in ml / 100g or more carbon black (Japanese Patent Publication No. 1-53978 Issue), N ₂ SA6
0 m ² / g or more, DBP 108 ml / 100 g or more, the true specific gravity per constant specific surface area is set to a specific range significantly lower than that of known carbon black, and the coloring power and the distribution width per aggregate mode diameter are set to a certain value or more. A rubber composition that combines carbon black to maintain high abrasion resistance and high impact resilience (Japanese Patent Laid-Open No. 59-140241), N ₂ SA of 65 to 84 m ² /
The ratio of g, N ₂ SA / adsorption amount of iodine (IA) is in the range of 1.10 to 1.35, and the relational expression with compression DBP, blackness, iodine adsorption amount and aggregate mode diameter as variables is above a certain value. Carbon black (Japanese Patent Laid-Open No. 3-225639) capable of simultaneously imparting high abrasion resistance and high impact resilience to the compounded rubber set to 3, N ₂ SA 75 to 105 m ² / g, compressed DBP 110 ml / 110 g or more, constant High wear resistance for compounded rubbers whose true specific gravity per specific surface area is set to a specific range lower than that of known carbon black, and particle aggregate void diameter and distribution width per aggregate mode diameter are maintained above a certain value. And carbon black capable of having both high impact resilience (Japanese Patent Laid-Open No. 1-20
1367 publication).

In addition, as for a tire tread rubber in U.S. Patent No. ^{_{4360627, N 2 SA85~95m 2 / g}} , 24M4DBP100~10
Disclosed is a carbon black that achieves high wear resistance and high impact resilience with a Stokes mode diameter distribution (ΔD ₅₀ ) of 180 mμ or more at 4 ml / 100 g and Tint 95 to 105%, and US Pat. No. 4,548,980. No. the specification, as the carbon black characteristics to obtain a high degree of wet grip performance low rolling resistance and required energy savings for a tire tread ^{_{rubber, N 2 SA75~105m 2 / g,}} N 2 SA-IA ≧ 15, N ₂ SA
-CTABSA ≦ 5, 24M4DBP ≦ 110, Tint90 to 110, ΔTint ≦
-3 is shown.

[Problems to be Solved by the Invention]

However, the demand for fuel-efficient tires is becoming more and more advanced, and there is still a strong demand for the development of a low heat-generating rubber composition having high impact resilience while maintaining excellent wear resistance.

In the subsequent research under such a background, the present invention provides a carbon black in which N ₂ SA has a small mode diameter of aggregate intergranular pores per constant aggregate mode diameter in the range of 60 to 100 m ² / g. It was developed by clarifying the fact that rubber properties suitable for tire treads for passenger cars and light trucks can be obtained by compounding with a rubber component.

Therefore, an object of the present invention is to provide a rubber composition having both high wear resistance and low heat build-up, which is suitable for tire treads of passenger cars and light trucks.

[Means for Solving the Problems]

A rubber composition according to the present invention for achieving the above object belongs to a hard system region having a nitrogen adsorption specific surface area (N ₂ SA) of 60 to 100 m ² / g, and has a mode system (p of an intergranular pore). ) Is a furnace carbon black having a selective characteristic according to the following relational formula,
A characteristic feature of the composition is that it is blended in a proportion of 100 parts by weight.

p ≦ 1.543st−55.0 However, p in the above formula refers to the maximum frequency mode diameter in the pore diameter distribution between carbon black aggregate particles measured by a differential scanning calorimeter (DSC), and st is the disc centrifuge device (DCF). ) Refers to the Stokes mode diameter of the carbon black aggregate.

Each characteristic value of carbon black applied to the present invention is a value obtained by the following measuring method.

N ₂ SA (Nitrogen Adsorption Specific Surface Area)-: ASTM D3037-88 "Standard Test Method for Carbon Black-Su
By rface Area by Mitrogen Absorption "Metod B.
The N ₂ SA of IRB # 6 measured by this method was 76 m ² / g.

p-: Indicates the maximum frequency mode diameter in the pore distribution between carbon black aggregate particles measured by a differential scanning calorimeter (DSC), and is measured by the following method.

JIS K6221 (1982) 5 After drying on the basis of the "how to make dry sample", to create a carbon black concentration 0.250 g / cm ³ of the paste were mixed with distilled water of carbon black sample was precisely weighed collected, ultrasonically Disperse well. Immediately after the ultrasonic dispersion treatment, the carbon black paste was precisely weighed in an amount of about 3 to 5 mg, placed in an aluminum sample container and sealed, and then the differential scanning calorimeter (DSC, Mettler) was used.
Set it on DSC30) manufactured by the company and measure in the next step.

Rapid cooling from room temperature to -80 ℃ Heating from -80 ℃ to -5 ℃ at a rate of 10 ℃ / min. After heating from -5 ℃ to -0.1 ℃ at a rate of 1 ℃ / min. 0.1 ° C below the freezing point of water)
Hold for 10 minutes.

Gradually cool from −0.1 ° C to −8 ° C at a rate of 0.1 ° C / min. And record the compensation energy.

Then, read the height (y) of the peak at each temperature (in increments of 0.1 ° C) from the compensation energy chart obtained in the step, and from the formulas (1) and (2) below, the diameter (Dp ) And the same pore distribution curve (ΔV / ΔDp). The maximum frequency mode diameter in this pore distribution curve is p.

Dp = (135.34 / ΔT) +1.14 …… (1) ΔT: freezing point drop width of distilled water Wa: freezing point of distilled water K: factor that takes into account the sensitivity of the SDC device and the mass of the sample The above equations (1) and (2) are equations derived by Brun et al.
Thermochimica Acta, 21 (1977) 59-88 “A NEW METHOD
FOR THE SIMULTANEOUS DETERMINATION OF THE SIZE AND
THE SHAPE OF PORES: THE THERMO POROMETRY ". ASTM D-24 Stand measured by this method
ard Reference Black C-3 (N234) p is 77.6nm
Is.

st-: JISK6221 (1982) 5 Based on "How to make a dry sample", dry carbon black is mixed with a 20 vol% ethanol aqueous solution containing a small amount of a surfactant to prepare a dispersion liquid having a carbon black concentration of 50 mg / l. This is sufficiently dispersed by ultrasonic waves to obtain a sample. A disk centrifuge device (made by Joyes Lobel, UK) was set at a rotation speed of 8000 rpm, and spin liquid (2 wt% glycerin aqueous solution at a temperature of 25 ° C.) was applied to 1
After adding 0 ml, 1 ml buffer solution (20 vol at a temperature of 25 ° C
% Ethanol aqueous solution).

Next, 0.5 ml of the carbon black dispersion liquid at a temperature of 25 ° C. is added with a syringe to start centrifugal sedimentation, and at the same time, a recorder is operated to optically generate a distribution curve of aggregate Stokes equivalent diameter. The Stokes equivalent diameter of the maximum frequency in the obtained distribution curve is defined as st. ASTM D-24 Stand measured by this method
The st of ard Reference Black C-3 (N234) is 80 nm.

In the present invention, if the nitrogen adsorption specific surface area (N ₂ SA) of the furnace carbon black compounded in the rubber component is less than 60 m ² / g, the wear resistance decreases, and if it exceeds 100 m ² / g, the heat generation property increases. Come to do. The maximum frequency mode diameter p in the pore diameter distribution between carbon black particles measured by a differential scanning calorimeter (DSC) is an important characteristic item of the present invention, and this value is equivalent to [1.543st-55.0]. When it becomes the above, it becomes impossible to significantly reduce the heat generation property without decreasing the abrasion resistance of the compounded rubber. Therefore, as the furnace carbon black, the nitrogen adsorption specific surface area (N ₂ SA) is in the range of 60 to 100 m ² / g, and p ≦ 1.543.
When the relational expression of st-55.0 is satisfied, it becomes possible to impart relatively excellent wear resistance and high impact resilience to the rubber composition at the same time.

Fornes carbon black having the characteristics of the present invention is
A combustion chamber provided with a combustion burner and a feed oil injection nozzle mounted in the furnace head in a tangential direction air supply port and in the furnace axial direction,
Using an ordinary oil furnace that is composed of a narrow diameter reaction chamber and a wide diameter reaction chamber that are coaxially connected,
It can be produced by adjusting the supply amount of combustion oil, air, etc., and adding oxygen gas.

The above-mentioned furnace carbon black is compounded in an elastomer such as natural rubber, styrene-butadiene rubber, polybutadiene rubber, isoprene rubber, butyl rubber, and various synthetic rubbers and mixed rubbers that can be reinforced with conventional carbon black according to a conventional method. The compounding ratio of carbon black is 35 to 100 parts by weight with respect to 100 parts by weight of the rubber component, and kneading is performed together with necessary components such as a vulcanizing agent, a vulcanization accelerator, an antioxidant, a vulcanization aid, a softening agent and a plasticizer. To obtain the rubber composition of the present invention.

[Action]

Among the furnace carbon black characteristic items specified in the present invention, the range of particles having a nitrogen adsorption specific surface area (N ₂ SA) of 60 to 100 m ² / g belongs to the hard system region, and the compounded rubber has a high wear resistance and a moderate wear resistance. It is a precondition for maintaining heat generation.
However, if the specific surface area is less than 60 m ² / g is insufficient in terms of wear resistance, on the other hand, if it exceeds 100 m ² / g, the heat buildup increases, especially as a carbon black for fuel-efficient tires. Becomes difficult.

Aggregate of intergranular pores has a mode diameter (p) in which carbon black is strongly fused and bonded (aggregate).
It is a parameter that indicates the properties of the carbon black, and is closely related to the conditions such as the reaction temperature and the degree of combustion gas disturbance during the carbon black formation process. Therefore, there is a correlation that correlates with the structure and the specific surface area, and according to the study by the inventor, it has been confirmed that general carbon blacks marketed have the relations of the following formulas (3) and (4).

p = [75.2 × (DBP) / (N ₂ SA)] ± 3.0 (3) p = (1.543st-42.8) ± 8.0 (4) For example, ASTM D-24 Standard Reference Black C-
The p of 3 (N234) is in the range of 72.6 to 88.6 nm when calculated from st by using the equation (4), but the measured value of st is
It is within the above range at 77.6 nm.

P specified in the present invention is lower than the value calculated from the above formula (4) in relation to st, and particularly, it is positioned at a level equal to or lower than the [1.543st-55.0] value. It has a feature. This is characterized in that the size of the pores between the aggregates is relatively small compared to the size of the aggregate of carbon black itself (Stokes mode diameter), and this unique property makes it possible to improve the wear resistance of the compounded rubber. It has a function of lowering heat generation without damaging it, and effectively improves impact resilience per constant surface area.

The above-mentioned functions act in a comprehensive manner, and it becomes possible to impart the rubber composition with excellent wear resistance and low heat generation performance having high impact resilience.

〔Example〕

 Hereinafter, examples of the present invention will be described in comparison with comparative examples.

Examples, Comparative Examples, Reference Examples Combustion chamber equipped with a tangential air supply port and a combustion burner inserted in the furnace axial direction in the furnace head and a feedstock oil injection nozzle (diameter
800 mm, length 600 mm), a narrow diameter reaction chamber (diameter 160 mm, length 1200 mm) coaxially connected to the combustion chamber, and a wide diameter reaction chamber (diameter 400 mm) continuously connected to each other Was installed.

The raw oil has a specific gravity (15/4 ℃) of 1.073 and a viscosity (Engla 4
0/20 ℃) 2.10, toluene insoluble matter 0.03%, correlation coefficient (BMC
I) 140 aromatic hydrocarbon oil, specific gravity (15/4 ℃) 0.903 as fuel oil, viscosity (Cst / 50 ℃) 16.1, residual carbon content 5.4
%, A hydrocarbon oil with a flash point of 96% was used.

Using the reactor, the feedstock oil and the combustion oil, the production conditions such as the feedstock oil, the fuel oil, the supply amount of air, the presence or absence of the addition of oxygen gas are changed to five types (Examples 1 to 3 and Comparative Examples 1 and 2). ) Furnace carbon black was produced. The characteristics of the obtained carbon black are shown in Table 1 in comparison with the production conditions.
In addition, the reference example in Table 1 is a commercially available hard carbon black, the reference example 1 is N351 [Tokai Carbon Co., Ltd., Seast NH], and the reference example 2 is N347 [Tokai Carbon Co., Ltd., 3H] Reference Example 3 is N339 [SEAST KH manufactured by Tokai Carbon Co., Ltd.].

Next, styrene-butadiene rubber [Japan Synthetic Rubber Co., Ltd.
Manufactured by JSR1712].

Various rubber tests were carried out on each rubber composition obtained by vulcanizing the compound of Table 3 at a temperature of 145 ° C. for 50 minutes, and the results are shown in Table 3.

The rubber characteristic measuring method and measuring conditions were as follows. Among these, tan δ (loss coefficient) is an index of heat generation, and the smaller this value, the lower the heat generation degree.

(1) Abrasion amount Using a Lambourn abrasion tester (mechanical slip mechanism),
The measurement was performed under the following conditions.

Test piece: thickness 10mm, outer diameter 44mm Emery wheel: GC type, grain size # 80, hardness H added carborundum powder: grain size # 80, addition amount about 9g / min. Relative slip ratio between wheel surface and test piece: 24% , 60% Test piece rotation speed: 535 rpm Test load: 4 kg In Table 3, the measured wear amount is shown as a wear resistance index when Reference Example 3 is set to 100. Therefore, the higher the value, the smaller the amount of wear.

(2) tanδ (loss factor) Visco Elastic Spectrometer (manufactured by Iwamoto Seisakusho)
The measurement was performed under the following conditions.

Test piece: thickness 2 mm, length 30 mm, width 5 mm Frequency: 50 Hz Dynamic strain rate: 1.2% Temperature: 60 ° C (3) All other JIS K6301 "vulcanized rubber physical test method".

From the results shown in Table 3, the rubber composition of Example 1 has tan δ and impact resilience which are indexes of abrasion resistance and exothermicity as compared with the rubber composition of Comparative Example 1 in which the N ₂ SA of the compounded carbon black is at the same level. Have been improved together. The rubber composition of Example 2 has the same wear resistance as the rubber compositions of Comparative Example 2 and Reference Example 2 in which the N ₂ SA of the compounded carbon black is at the same level, but the tan δ is decreased and the impact resilience is reduced. Is significantly increased. Further, the rubber composition of Example 3 was improved in wear resistance equivalent to that of the rubber composition of Reference Example 3 in which N ₂ SA of the compounded carbon black was at the same level.
It has tan δ and impact resilience. The effect of simultaneously imparting these wear resistance, low exothermicity and impact resilience is p
This is due to the unique carbon black aggregate characteristics that satisfy ≦ 1.543 st-55.0.

[Effects of the Invention] As described above, according to the present invention, a low heat-generating rubber composition having both excellent abrasion resistance and high impact resilience is provided by selectively regulating micro characteristic items of carbon black different from those of the prior art. You can provide things. Therefore, it can be applied to the tire tread portion for passenger cars and light trucks to effectively reduce fuel consumption.

Claims (1)

[Claims] 1. A nitrogen adsorption specific surface area (N ₂ SA) of 60 to 100 m ² / g
Furnace carbon black which belongs to the hard system region and has a mode diameter (p) of the interaggregate pores having the selective characteristics according to the following relational expression is blended at a ratio of 35 to 100 parts by weight to 100 parts by weight of the rubber component. A rubber composition obtained from. p ≦ 1.543st−55.0 However, p in the above formula refers to the maximum frequency mode diameter in the pore diameter distribution between carbon black aggregate particles measured by a differential scanning calorimeter (DSC), and st is the disc centrifuge device (DCF). ) Refers to the Stokes mode diameter of the carbon black aggregate.