JPH06256579A - Rubber composition - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a rubber composition suitable for use in treads of large tires for trucks, buses and the like, having low heat build-up and high wear resistance. [Constitution] CTAB specific surface area is 100 ~ 160m ² / g, compressed D
BP belongs to the hard system area of 95 to 115 ml / 100 g, and
A rubber composition comprising 100 to parts by weight of a rubber component and 35 to 100 parts by weight of furnace carbon black having the selective properties (1) to (3). (1) 5 ≤ N ₂ SA-IA ≤ 15 (2) 1.13 Dst mode diameter -40.92 ≤ ΔDst ≤ 1.13 Dst mode diameter -30.92 (3) Dp mode diameter ≤ 2.66 Dmp mode diameter -15.516 However, the Dp mode diameter is a difference. The maximum frequency mode diameter and the Dmp mode diameter in the pore size distribution between carbon black particles measured by a scanning calorimeter (DSC) show the same mode diameter measured by the mercury porosimetry.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition suitable as a tread member for large tires mounted on trucks, buses and the like, and more particularly to a rubber composition having both excellent wear resistance and low heat buildup.

[0002]

2. Description of the Related Art There are various varieties of carbon black for rubber reinforcement depending on the characteristics of the rubber, and these varieties characteristics are major factors for determining various performances of a composition compounded with 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, SAF (N110), IS is applied to rubber members, such as large tire treads of trucks and buses, which require a high degree of wear resistance under severe driving conditions.
It is considered effective to apply carbon black having a small particle size and a large specific surface area, such as AF (N220).
However, since this kind of hard carbon black has a property of increasing the heat build-up of the compounded rubber, there is a risk of accelerating the destruction of the internal structure and the aging of the constituent materials due to the heat storage during running when the tire tread is used. . Further, recently, fuel-efficient tires have been actively developed in order to meet social demands for resource saving and energy saving, but imparting low heat-generating property is an essential element for developing fuel-efficient tires. Therefore, if carbon black having a small particle size and a large specific surface area can be simultaneously imparted to the compounded rubber with high abrasion resistance and high repulsion elasticity, it is ideal as a rubber member for a tire tread. It will be

The Applicant has achieved the above-mentioned antithetic rubber performance by adding more microselective properties in addition to the basic properties such as particle size, specific surface area and structure of the compounded carbon black. We are continuing systematically the research to be conducted, and have already made the following development proposals. (1) Nitrogen adsorption specific surface area (N ₂ SA) is 60m ² / g or more, compressed DB
A carbon black having a P of 112 ml / 100 g or more and maintaining the Stokes mode diameter and the distribution of the aggregate at a certain value or more (Japanese Patent Publication No. 1-53978). (2) N ₂ SA 60 m ² / g or more, DBP 108 ml / 100 g or more, the true specific gravity value per constant specific surface area is set to a specific range significantly lower than that of known carbon black, and the coloring power and distribution per aggregate mode diameter are set. A rubber composition containing carbon black having a characteristic of maintaining the width at a certain value or more (JP-A-59-140241). (3) A rubber composition containing carbon black having N ₂ SA in the range of 100 to 200 m ² / g and having an aggregate Stokes size distribution that is relatively broad with respect to the particle size (JP-A-63-112638). Issue). (4) A rubber composition containing carbon black having N ₂ SA in the range of 70 to 185 m ² / g and having ^two maximum points in which the aggregate Stokes diameter distribution is in a specific range (JP-A-63-179941).
Issue). (5) N ₂ SA is in the range of 110 to 155 m ² / g, and DB
A rubber composition containing P, compressed DBP, blackness, N ₂ SA, and carbon black having a value defined by a formula with the adsorption amount of iodine as a variable in a specific range (JP-A-63-29).
No. 7439).

[0005]

According to these prior arts, it is possible to obtain a rubber composition having improved high wear resistance and low heat buildup for a large tire tread. However, the quality requirements for fuel-efficient tires are becoming more and more sophisticated, and under the present circumstances, there is a continuing demand for the development of a rubber composition that achieves both higher levels of wear resistance and low heat build-up.

Based on such a demand, the present invention has been developed by elucidating the technical causal relationship between the particle colloidal properties of carbon black and the compounded rubber performance, which is different from the prior art, and has been developed. Another object of the present invention is to provide a rubber composition having both high wear resistance and low heat build-up, which is suitable as a tread member for large tires intended for buses and the like.

[0007]

The rubber composition according to the present invention for achieving the above object has a CTAB specific surface area of 1
00-160m ² / g, compressed DBP 95-115ml / 100g
, Which is a hard system region, and which is blended in a proportion of 35 to 100 parts by weight with respect to 100 parts by weight of a rubber component, a furnace carbon black having selective characteristics according to the following relational expressions (1) to (3). Is a structural feature. (1) 5 ≤ N ₂ SA-IA ≤ 15 (2) 1.13 Dst mode diameter -40.92 ≤ ΔDst ≤ 1.13 Dst mode diameter -30.92 (3) Dp mode diameter ≤ 2.66 Dmp mode diameter -15.516 However, in the formula (1) N ₂ SA is the nitrogen adsorption specific surface area, and IA is the iodine adsorption amount. The Dst mode diameter of the equation (2) is the Stokes mode diameter of the carbon black aggregate measured by the disc centrifuge (DCF), and ΔDst is the half width of the Stokes diameter distribution. The Dp mode diameter of Eq. (3) is the maximum frequency mode diameter in the pore diameter distribution between carbon black aggregate particles measured by a differential scanning calorimeter (DSC), and the Dmp mode diameter is the carbon black obtained by the mercury injection method. The mode frequency with the maximum frequency in the pore size distribution between aggregate grains is shown.

The values obtained by the following measuring methods are used for the respective characteristics of the carbon black having the above structure. CTAB specific surface area; ASTM D3765-89 "Stan
dard Test Method for Carbon Black-CTAB (Cetyltrimet
hylammonium Bromide) Surface Area ". The measured CTAB specific surface area of IRB # 6 by this method is 77
m ² / g. Compressed DBP (24M4DBP); ASTM D3493-91
“Standard Test Method for Carbon Black −n-Dibuty
l Phthalate Absorption Number of Compressed Sampl
The measured value of the compressed DBP oil absorption of IRB # 6 by this method is 87 ml / 100 g. N ₂ SA (nitrogen adsorption specific surface area); ASTM D3037
-88 "Standard Test Method for Carbon Black-Surf
ace Area by Nitrogen Absorption “Method B.
The N ₂ SA measurement value of IRB # 6 by this method is 76 m ²
/ g. IA (Iodine adsorption amount): According to JIS K6221 (1982) "Testing method for carbon black for rubber", 6.1.1.
The measurement value of iodine adsorption amount of IRB # 6 by this method is 80
It is mg / g.

Dst mode diameter, ΔDst; dry carbon black sample was mixed with a 20 vol% ethanol aqueous solution containing a small amount of a surfactant to prepare a dispersion having a carbon black concentration of 50 mg / l, which was sufficiently dispersed by ultrasonic waves. Let it be a sample. Disk centrifuge device (UK Joyes Lobe
(manufactured by L company) was set at 8000 rpm and 10 ml of spin solution (2 wt% glycerin aqueous solution) was added.
Inject the buffer solution (20 vol% ethanol solution). Next, 0.5 ml of the carbon black dispersion is added with a syringe to start centrifugal sedimentation, and at the same time, the recorder is operated to optically create a Stokes equivalent diameter distribution curve of the carbon black aggregate. The Stokes equivalent diameter of the maximum frequency in the obtained distribution curve is defined as the Dst mode diameter (nm),
The difference between the Stokes equivalent diameters of two points, large and small, at which a frequency of 50% of the maximum frequency is obtained, is ΔDst (nm). I by this measurement method
RB # 6 has a Dst mode diameter of 92 nm and a ΔDst of 68 nm.

Dp mode diameter; JIS K6221 (1982)
After drying according to 5 “How to make a dry sample”, a carbon black sample that has been precisely weighed and mixed with distilled water to make a paste with a carbon black concentration of 0.250 g / cm ³ and sufficiently dispersed with ultrasonic waves. Let Within 10 minutes after ultrasonic dispersion, measurement of the distribution of aggregate intergranular pores is started with a differential scanning calorimeter (DSC, DSC30 manufactured by Mettler). In this case, the amount of the paste to be collected is within the range of about 3 to 5 mg, and after putting it in an aluminum sample container and sealing it, the mass of the paste is confirmed and the paste is set in the DSC device. Then, measure in the next step. Quench from room temperature to -80 ° C. Heat from -80 ° C to -5 ° C at a rate of 10 ° C / min. After heating from −5 ° C. to −0.1 ° C. at a rate of 1 ° C./min., The temperature is kept at −0.1 ° C. (0.1 ° C. lower than the freezing point of distilled water) 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 chart of compensation energy obtained in the step of
From the formulas (1) and (2) below, the pore diameter between aggregate grains (D
p) and the pore size distribution (ΔV / ΔDp). Dp = (135.34 / ΔT) +1.14 (1) ΔV / ΔDp = K · (ΔT) ² / (Wa · y) …… (2) In equations (1) and (2), ΔT is The freezing point depression width of distilled water, Wa is the heat of solidification of distilled water, and K is a coefficient that takes into consideration the sensitivity of the DSC device and the mass of the sample. These expressions are
Guided by Brun et al., Thermochimica Acta, 2
1 (1977) 59-88 “A NEW METHOD FOR THE SIMULTANEOUS
DETERMINATION OF THE SIZE AND THE SHAPE OF PORES:
"THE THERMOPOROMETRY". The Dp mode diameter of IRB # 6 measured by this method is 95.3.
nm.

Dmp mode diameter: 0.2 g of carbon black pellets adjusted to a particle size of 0.25 to 0.50 mm was loaded into a dedicated cell (3 ml) of a mercury porosimeter (Pore Sizer 9300, manufactured by Micromeritics Co., Ltd.). Pressure 2
Mercury is press-fitted in the range of 5 to 2000 lb / in ² , and the pressure at the point where the amount of press-fitted mercury suddenly increases is measured. Calculate the pore size between the aggregates of carbon black from this pressure value,
Dmp mode diameter (nm). In addition, I measured by this method
The RB # 6 has a Dmp mode diameter of 40 nm.

The furnace carbon black having the characteristics of the present invention is provided with a combustion chamber having a tangential air supply port and a combustion burner mounted in the furnace axial direction at the furnace head, and is connected coaxially with the combustion chamber. Using an oil furnace containing a multi-stage narrow-diameter reaction chamber and a wide-diameter reaction chamber with raw oil injection nozzles, split introduction conditions of the raw oil, supply amount of fuel oil and air, and addition conditions of oxygen gas It can be manufactured by adjusting

The above-mentioned furnace carbon black is compounded into an elastomer such as natural rubber, styrene-butadiene rubber, polybutadiene rubber, isoprene rubber, butyl rubber, various other rubbers which can be reinforced with conventional carbon black, and mixed rubber according to a conventional method. The blending 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 carried out 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.

[0014]

[Function] Among the characteristics of the furnace carbon black specified in the present invention, the CTAB specific surface area of 100 to 160 m ² / g
The particle properties of compressed DBP 95 to 115 ml / 100 g belong to the hard system region, and are a precondition for the compounded rubber to retain a high degree of abrasion resistance and an appropriate heat generation property. If the CTAB specific surface area is less than 100 m ² / g, sufficient wear resistance will not be imparted for large tires, while if it exceeds 160 m ² / g, the dispersibility in rubber will deteriorate and the wear resistance will be smooth. Since it does not improve and heat generation also increases, it is particularly difficult to use as carbon black for fuel-efficient tires. Further, if the compressed DBP is less than 95 ml / 100 g, the abrasion resistance becomes insufficient, and if it exceeds 115 ml / 100 g, the viscosity at the time of compounding the rubber becomes high and the workability is deteriorated.

The characteristic of the relational expression (1) is mainly an element for suppressing heat buildup, and when the value of (N ₂ SA-IA) is less than 5, the heat buildup required for a rubber composition for a fuel-efficient tire is obtained. Is insufficiently reduced, and on the other hand, when this value exceeds 15, the viscosity at the time of compounding the rubber becomes high and the practicality becomes poor. Relational expression (2)
Distribution of carbon black (ΔD
If st) becomes too wide, the wear resistance retreats significantly, and conversely, if too narrow, the effect of suppressing heat buildup decreases. Therefore, the range of [1.13 Dst mode diameter -40.92 ≤ ΔDst ≤ 1.13 Dst mode diameter -30.92] regulated by the relational expression (2) is optimal for imparting a high level of wear resistance and low heat buildup to the compounded rubber. It has a wide aggregate distribution range.

The relational expression (3) is also a characteristic element that functions to achieve both high wear resistance and low heat generation. That is, the mode diameter of the interpores of carbon black aggregate particles is a parameter indicating the property of an aggregate (aggregate) in which carbon black is strongly fused and bonded, and its value varies depending on the measuring method. The Dp mode diameter measured by a differential scanning calorimeter (DSC) is the pore diameter between aggregate particles in the state where carbon black is dispersed in distilled water.
The measured value is larger than the Dmp mode diameter obtained by the mercury porosimetry. According to the study by the inventors, it was confirmed that the general carbon blacks on the market have the relationship of the following formula. Dp mode diameter = (2.66 Dmp mode diameter−8.343) ± 5 For example, the measured value of Dp mode diameter of IRB # 6 is 95.3.
However, this value is in the range of the Dp mode diameter (93.1 to 103.1 nm) according to the above formula calculated from the Dmp mode diameter actually measured value of 40 nm. The Dp mode diameter of the carbon black showing the selective characteristics of the present invention is lower than the value calculated from the above equation in relation to the Dmp mode diameter, which is specified by the relational expression (3) (2.66 Dmp mode). When it is located at a level equal to or less than the calculated value of the diameter −15.516), it exerts an effective function for improving abrasion resistance without impairing low heat buildup for the compounded rubber.

The unique properties and functions of the compounded furnace carbon black as described above act comprehensively to impart excellent abrasion resistance performance and low heat generation performance exhibiting a high level of impact resilience to the rubber composition at the same time. It becomes possible.

[0018]

【Example】

Examples 1 to 4, Comparative Examples 1 to 3, Reference Examples 1 to 3 Combustion chamber (diameter 900 mm, length 1000 mm) having a combustion burner installed in the furnace head in the tangential direction air supply port and in the furnace axial direction,
First-stage narrow-diameter reaction chamber (diameter 250 mm, length 500 mm) equipped with a feedstock oil injection nozzle that is coaxially connected to the combustion chamber and penetrates through the furnace wall, second-stage narrow-diameter reaction chamber (diameter 160 mm, length) 600m
m), the third stage narrow diameter reaction chamber (diameter 180 mm, length 600 mm), and the subsequent wide diameter reaction chamber (diameter 400 mm) were installed. Specific gravity (15/4
℃) 1.073, viscosity (Engla 40/20 ℃) 2.1
0, toluene insoluble content 0.03%, correlation coefficient (BMCI) 140
Using aromatic hydrocarbon oil of, the specific gravity (15 /
4 ° C.) 0.903, viscosity (cst / 50 ° C.) 16.1, carbon residue 5.4%, flash point 96 ° C. hydrocarbon oil was used.

Using the above reactor, the feedstock oil and the fuel oil, the production conditions such as the divided feed amount of the feedstock oil, the amount of fuel oil, the amount of air supply, the amount of oxygen gas supply and the like to each narrow-diameter reaction chamber are changed and the furnace carbon is changed. Manufactured black. The characteristics of the obtained carbon black are shown in Table 1 in correspondence with the production conditions. In addition, Table 2 shows the characteristics of commercially available hard carbon black varieties as Reference Examples 1 to 3.

[0020]

[Table 1]

[0021]

[Table 2] Table Note: (1) N220 [Tokai Carbon Co., Ltd., "SEAST 6"] (2) N110 [Tokai Carbon Co., Ltd., "SEAST 9"] (3) Tokai Carbon Co., Ltd., "SEAST 9H" ”

Next, the carbon black samples shown in Tables 1 and 2 were blended with natural rubber at the blending ratio shown in Table 3.

[0023]

[Table 3]

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 40 minutes, and the measurement results are shown in Table 4 (Examples) and Table 5 (Comparative Examples). , Reference example). The rubber properties were measured as follows. Of these, the amount of wear was shown as a relative index when the carbon black of Reference Example 2 was 100. Also, t
An δ (loss coefficient) is an index of exothermicity, and the smaller the measured value, the lower the exothermic degree. Abrasion amount: Lambourn abrasion tester (mechanical slip mechanism)
Was measured under the following conditions. Test piece: thickness 10 mm, outer diameter 44 mm Emery wheel: GC type, grain size # 80, hardness H added carborundum powder: grain size # 80, addition amount about 9 g / mi
n. Relative slip ratio between emery wheel surface and test piece: 24
%, 60% Test piece rotation speed: 535 rpm Test load: 4 kg

Tan δ (loss factor); Visco Elastic Spe
The measurement was performed using a ctrometer (manufactured by Iwamoto Seisakusho) under the following conditions. Specimen: thickness 2 mm, length 30 mm, width 5 mm Frequency: 50 Hz Dynamic strain rate: 1.2% Temperature: 60 ° C. Other characteristics: According to JIS K6301 "Vulcanized rubber physical test method".

[0026]

[Table 4]

[0027]

[Table 5]

From Tables 4 and 5, the results of the examples show tan which is an index of exothermicity as compared with Comparative Examples and Reference Examples which have the same level of N ₂ SA but which do not satisfy the selective characteristic requirements of the present invention.
It can be seen that δ (loss factor) and wear resistance are improved at the same time. Also, it can be seen that the other reinforcing properties are maintained at a high level.

[0029]

As described above, according to the present invention, high repulsion suitable as a tread member for large tires for trucks, buses, etc. is obtained by selectively controlling the micro colloidal properties of carbon black different from the prior art. It is possible to provide a rubber composition having both elasticity and low heat buildup and excellent abrasion resistance. Therefore, it becomes possible to effectively reduce fuel consumption by mounting it on a truck or a bus.

Claims (1)

[Claims] 1. A CTAB specific surface area of 100 to 160 m ² /
g, a compressed carbon DBP belonging to the hard system region of 95 to 115 ml / 100 g and having a selective characteristic according to the following relational expressions (1) to (3), a furnace carbon black was prepared.
A rubber composition containing 35 to 100 parts by weight relative to 0 parts by weight. (1) 5 ≤ N ₂ SA-IA ≤ 15 (2) 1.13 Dst mode diameter -40.92 ≤ ΔDst ≤ 1.13 Dst mode diameter -30.92 (3) Dp mode diameter ≤ 2.66 Dmp mode diameter -15.516 However, in the formula (1) N ₂ SA is the nitrogen adsorption specific surface area, and IA is the iodine adsorption amount. The Dst mode diameter of the equation (2) is the Stokes mode diameter of the carbon black aggregate measured by the disc centrifuge (DCF), and ΔDst is the half width of the Stokes diameter distribution. The Dp mode diameter of Eq. (3) is the maximum frequency mode diameter in the pore diameter distribution between carbon black aggregate particles measured by a differential scanning calorimeter (DSC), and the Dmp mode diameter is the carbon black obtained by the mercury injection method. The mode frequency with the maximum frequency in the pore size distribution between aggregate grains is shown.