JP3283953B2 - Rubber composition - Google Patents

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 to be mounted on trucks, buses, etc., and more specifically, low heat generation having high rebound resilience while maintaining excellent wear resistance. Rubber composition.

[0002]

2. Description of the Related Art There are various types of carbon blacks for reinforcing rubber according to their characteristics, and the characteristics of these types are major factors for determining various properties of a composition mixed with rubber. For this reason, when compounding with rubber, a means for selecting and using carbon black having a variety of characteristics suitable for the purpose of the member is generally used.

[0003] For example, in recent years, fuel-efficient tires have been actively developed to meet the social demands for resource saving and energy saving, but such fuel-efficient tires have a relatively small particle size. A rubber composition having low heat build-up and high rebound resilience obtained by blending a large variety of carbon black in a relatively small amount with a rubber component is effective. However, rubber compounding of carbon black with a large particle diameter and a small specific surface area is effective for the purpose of improving fuel economy performance,
Deterioration of surface characteristics such as braking performance and abrasion resistance on wet road surfaces is inevitable. Therefore, if carbon black having a small particle diameter and a large specific surface area can simultaneously impart high abrasion resistance and low heat generation to give high rebound resilience to a compounded rubber, it is ideal as a rubber member for a tire tread. It will be.

[0004] The applicant of the present invention has achieved the above-mentioned reciprocal rubber performance by adding more microselective characteristics in addition to the basic characteristics such as the particle size, specific surface area and structure of the carbon black compound. We have been systematically conducting research to make this possible, 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
Carbon black in which the Stokes mode diameter and distribution of aggregates are maintained at a certain value or more in carbon black having a P of 112 ml / 100 g 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 per specific surface area is set to a specific range which is 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 property of maintaining the width at a certain value or more (JP-A-59-140241). (3) A rubber composition containing carbon black having an N ₂ SA in the range of 100 to 200 m ² / g and having an agglomerate Stokes diameter distribution which is relatively broad with respect to the particle diameter (JP-A-63-112638) No.). (4) A rubber composition containing carbon black having an N ₂ SA in the range of 70 to 185 m ² / g and having ^two maximum points in the Stokes diameter distribution in a specific range (Japanese Patent Laid-Open No. 63-177991).
No.). (5) N ₂ SA is in the range of 110 to 155 m ² / g and DB
P, compressed DBP, blackness, N ₂ SA and a rubber composition containing carbon black having a specific range defined by a formula using iodine adsorption as a variable (Japanese Patent Laid-Open No. 63-29)
No. 7439). (6) Nitrogen adsorption specific surface area (N ₂ SA) is 60 to 160 m ² / g, D
It belongs to the hard region where the BP oil absorption is 90 to 150 ml / 100 g, and the mode diameter (Dp) of the aggregate intergranular pore is Dp.
.Ltoreq.1.543.times. (Dst mode diameter) -30.0], a rubber composition containing a furnace carbon black satisfying the relational expression (Japanese Patent Application No. 3-173129).

[0005]

According to these prior arts, it is possible to obtain a rubber composition having both improved abrasion resistance and improved rebound resilience for use in large tire treads.
However, quality requirements for fuel-efficient tires are becoming more and more advanced, and at present, there is a continuing demand for the development of rubber compositions having both higher levels of rebound resilience and abrasion resistance.

The present invention has been developed based on such a demand by elucidating the technical consequences of the colloidal properties of carbon black different from those of the prior art and the performance of a compounded rubber. Another object of the present invention is to provide a rubber composition having both high abrasion resistance and low heat generation, which is suitable as a tread member of a large tire for a bus or 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 100-120ml / 100
g belongs to the hardware domain and the following relational expressions (1) to (3)
The composition is characterized in that furnace carbon black having selective characteristics according to (1) is blended at a ratio of 35 to 100 parts by weight with respect to 100 parts by weight of the rubber component. (1) 5 ≦ N ₂ SA−IA ≦ 15 (2) 0.636 Dst mode diameter + 5.88 ≦ ΔDst ≦ 0.639 Dst mode diameter + 15.88 (3) Dp mode diameter ≧ 2.66Dmp mode diameter + 0.516 where (1 ) In the formula, N ₂ SA indicates a nitrogen adsorption specific surface area, and IA indicates an iodine adsorption amount. The Dst mode diameter in the equation (2) is the Stokes mode diameter of the carbon black aggregate measured by a disk centrifuge (DCF), and ΔDst is the half width of the Stokes diameter distribution. The Dp mode diameter in the equation (3) is the maximum frequency mode diameter in the pore diameter distribution between the carbon black aggregate particles measured by a differential scanning calorimeter (DSC), and the Dmp mode diameter is the carbon black obtained by the mercury intrusion method. The mode diameter of the maximum frequency in the pore diameter 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-mentioned structure. CTAB specific surface area; ASTM D3765-89 "Stan
dard Test Method for Carbon Black-CTAB (Cetyltrimet
hylammonium bromide) Surface Area ". The measured value of the 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
According to e "compression DBP oil absorption measurements of IRB # 6 by this method is 87ml / 100g N ₂ SA (nitrogen adsorption specific surface area);.. ASTM D3037
−88 ”Standard Test Method for Carbon Black-Surf
ace Area by Nitrogen Absorption "According to Method B.
The N ₂ SA measurement of IRB # 6 by this method is 76 m ²
/ g. IA (Iodine adsorption amount): According to JIS K6221 (1982) "Test method for carbon black for rubber", section 6.1.1.
The measured value of the iodine adsorption amount of IRB # 6 by this method is 80
mg / g.

Dst mode diameter, ΔDst; A dry carbon black sample is 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 is sufficiently dispersed by ultrasonic waves. Let it be a sample. Disc Centrifuge (Joyes Lobe, UK)
l) was set to 8000 rpm, 10 ml of spin solution (2 wt% glycerin aqueous solution) was added, and then 1 ml
Buffer solution (20 vol% ethanol aqueous solution). Then, 0.5 ml of the carbon black dispersion is added by a syringe to start centrifugal sedimentation, and at the same time, the recorder is operated to optically create a distribution curve of the Stokes equivalent diameter of the carbon black aggregate. The Stokes equivalent diameter of the maximum frequency in the obtained distribution curve is defined as Dst mode diameter (nm),
The difference between Stokes equivalent diameters at two points, large and small, at which a frequency of 50% of the maximum frequency is obtained is defined as ΔDst (nm). I by this measurement method
The Dst mode diameter of RB # 6 is 92 nm, and ΔDst is 68 nm.

Dp mode diameter: JIS K6221 (1982)
5 After drying on the basis of the "how to make dry sample", carbon black concentration to create a 0.250 g / cm ³ of the paste were mixed with distilled water of carbon black sample precisely weighed collected, thoroughly dispersed with an ultrasonic Let it. Within 10 minutes after the ultrasonic dispersion, the distribution measurement of the pores between aggregates is started using a differential scanning calorimeter (DSC, DSC30 manufactured by Mettler). In this case, the amount of the collected paste is in the range of about 3 to 5 mg. After sealing in a sample container made of aluminum, the mass of the paste is confirmed, and the paste is set in the DSC device. Next, measurement is performed in the next step. Cool rapidly 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., It is kept at -0.1 ° C (a temperature lower than the freezing point of distilled water by 0.1 ° C) for 10 minutes. Cool gradually from -0.1 ° C to -8 ° C at a rate of 0.1 ° C / min. And record the compensation energy. Then, from the compensation energy chart obtained in
Read the height (y) of the mountain (in increments of 0.1 ° C),
From the equation (2), the pore diameter (Dp) between the aggregate grains and the pore diameter distribution (ΔV / ΔDp) are obtained. 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 drop width of distilled water, Wa is the freezing heat of distilled water, and K is a coefficient taking into account the sensitivity of the DSC apparatus 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: After loading 0.2 g of carbon black pellets adjusted to a particle size of 0.25 to 0.50 mm into a dedicated cell (3 ml) of a mercury porosimeter (Pore Sizer 9300, manufactured by Micromeritics), Pressure 2
Mercury is injected in the range of 5 to 2000 lb / in ² , and the pressure at which the amount of injected mercury sharply increases is measured. From this pressure value, the pore diameter between aggregate particles of carbon black is calculated,
Dmp mode diameter (nm). In addition, I measured by this method
The Dmp mode diameter of RB # 6 is 40 nm.

The furnace carbon black having the characteristics of the present invention is provided in a combustion chamber having a tangential air supply port on a furnace head and a combustion burner mounted in a furnace axial direction, and is coaxially connected to the combustion chamber. Using an oil furnace consisting of a multi-stage narrow-diameter reaction chamber and a wide-diameter reaction chamber having a feed oil injection nozzle, divided feed conditions for feed oil, supply amounts of fuel oil and air, and oxygen gas addition conditions It can be manufactured by adjusting such factors.

The above-mentioned furnace carbon black is blended with an elastomer such as natural rubber, styrene butadiene rubber, polybutadiene rubber, isoprene rubber, butyl rubber, other various rubbers which can be reinforced with conventional carbon black, or a mixed rubber 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 is kneaded together with necessary components such as a vulcanizing agent, a vulcanization accelerator, an antioxidant, a vulcanization aid, a softener, and a plasticizer. Thus, the rubber composition of the present invention is obtained.

[0014]

In the furnace carbon black characteristic items specified in the present invention, the CTAB specific surface area is 100 to 160 m ² / g.
The particle properties of the compressed DBP of 100 to 120 ml / 100 g belong to the hard system region, and are prerequisites for maintaining high abrasion resistance and moderate heat generation in the compounded rubber. When the CTAB specific surface area is less than 100 m ² / g, sufficient abrasion resistance is not provided for large tires. On the other hand, when the CTAB specific surface area exceeds 160 m ² / g, heat generation increases, and especially as carbon black for fuel-efficient tires Is difficult to use. Also, if the compression DBP is 100
If it is less than 100 ml / 100 g, the abrasion resistance becomes insufficient and
If it exceeds 20 ml / 100 g, the viscosity at the time of compounding the rubber will increase, and the processability will decrease.

The characteristic of the relational expression (1) mainly serves as a factor for suppressing heat build-up. If the value of (N ₂ SA-IA) is less than 5, the heat build-up required for a rubber composition for a fuel-efficient tire is required. On the other hand, if this value exceeds 15, the viscosity at the time of compounding the rubber becomes high and the practicality becomes poor. Equation (2)
Aggregate distribution of carbon black (ΔD
In the case of st), if it is too wide, the regression of wear resistance becomes large, and if it is too narrow, the effect of suppressing heat build-up decreases. Therefore, [0.639 Dst mode diameter + 5.88 ≦ ΔDst ≦ 0.639 Dst mode diameter + 15.88] regulated by relational expression (2)
However, the aggregate distribution range is optimal for imparting a high level of wear resistance and low heat build-up to the compounded rubber.

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 carbon black aggregate intergranular pores is a parameter indicating the properties of aggregates (aggregates) in which carbon black is firmly fused and bonded, and the value differs depending on the measurement method. Since the Dp mode diameter measured by a differential scanning calorimeter (DSC) is the pore diameter between aggregate particles in a state where carbon black is dispersed in distilled water, it is smaller than the Dmp mode diameter obtained by the mercury intrusion method. The measured value increases. According to the study by the inventors, it has been confirmed that the general carbon black on the market has the following relationship. Dp mode diameter = (2.66 Dmp mode diameter−8.343) ± 5 For example, the actual measured value of the Dp mode diameter of IRB # 6 is 95.3.
This value falls within the range of the Dp mode diameter (93.1 to 103.1 nm) calculated from the Dmp mode diameter measured value of 40 nm by the above equation. The Dp mode diameter of carbon black exhibiting the selective characteristics of the present invention is higher than the value calculated from the above equation in relation to the Dmp mode diameter, and this is specified by the relational expression (3) (2.66 Dmp mode diameter). (Diameter + 0.516) When it is positioned at a level equal to or higher than the calculated value, it functions effectively to improve the low heat build-up of the compounded rubber without impairing the wear resistance.

[0017] The unique properties and functions of the above-mentioned compounded furnace carbon black act collectively to give the rubber composition excellent wear resistance and low heat generation performance exhibiting a high level of rebound resilience. Becomes possible.

[0018]

【Example】

Examples 1 to 4, Comparative Examples 1 to 3, Reference Examples 1 to 3 A combustion chamber (900 mm in diameter, 1000 mm in length) having a tangential air supply port in the furnace head and a combustion burner mounted in the axial direction of the furnace.
A first-stage narrow-diameter reaction chamber (diameter 200 mm, length 600 mm) and a second-stage narrow-diameter reaction chamber (diameter 160 mm, length) each having a feed oil injection nozzle coaxially connected to the combustion chamber and penetrating through the furnace wall. 500m
m), a third-stage narrow-diameter reaction chamber (diameter 200 mm, length 500 mm), and a subsequent wide-diameter reaction chamber (diameter 450 mm) were installed. The specific gravity (15/4
° C) 1.073, viscosity (engler 40/20 ° C) 2.1
0, toluene insoluble content 0.03%, correlation coefficient (BMCI) 140
Of aromatic hydrocarbon oil, specific gravity (15 /
A hydrocarbon oil having a temperature of 4 ° C) of 0.903, a viscosity (cst / 50 ° C) of 16.1, a residual carbon content of 5.4%, and a flash point of 96 ° C was used.

Using the above-mentioned reactor, raw material oil and fuel oil, furnace carbon was produced by changing the production conditions such as the divided supply amount of fuel oil, the amount of fuel oil, the amount of air supply, and the amount of oxygen gas supplied to each narrow-diameter reaction chamber. Black was manufactured. The properties of the obtained carbon black are shown in Table 1 in association with the production conditions. Table 2 shows the characteristics of commercially available hard carbon black products 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, each of the carbon black samples shown in Tables 1 and 2 was blended with natural rubber at a blending ratio shown in Table 3.

[0023]

[Table 3]

Each rubber composition obtained by vulcanizing the compound of Table 3 at a temperature of 145 ° C. for 40 minutes was subjected to various rubber tests, and the measurement results were shown in Table 4 (Example) and Table 5 (Comparative Example). , Reference Example). In addition, the measurement of the rubber property was based on the following. Among these, the amount of wear was shown by a relative index when the carbon black of Reference Example 2 was set to 100. Also, t
an δ (loss coefficient) is an index of heat build-up, and a smaller measured value indicates a lower heat build-up. Wear: Lambourn abrasion tester (mechanical slip mechanism)
Was measured under the following conditions. Test piece: thickness 10mm, outer diameter 44mm Emery wheel: GC type, particle size # 80, hardness H Carburundum powder with addition: particle size # 80, addition amount about 9g / 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 coefficient); Visco Elastic Spe
The measurement was performed using a ctrometer (manufactured by Iwamoto Seisakusho) 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. Other properties: According to JIS K6301 “Vulcanized rubber physical test method”.

[0026]

[Table 4]

[0027]

[Table 5]

From Tables 4 and 5, it can be seen that the results of the Examples show relatively high abrasion resistance compared to Comparative Examples and Reference Examples which have the same level of N ₂ SA but do not meet the selective characteristics requirements of the present invention. It is recognized that tan δ (loss coefficient), which is an index of heat build-up, is simultaneously improved, and the rebound resilience is greatly improved.
It can also be seen that other reinforcing properties are maintained at a high level. On the other hand, in Comparative Example 1 in which ΔDst was lower than the requirement of the present invention, although the abrasion resistance was at the same level as that of Example 3 in which the specific surface area was almost equal, tan δ was reduced, and conversely ΔDst
In Comparative Example 2 where is high, tan δ is slightly lower than that in Example 3, but the wear resistance is largely reduced. Comparative Example 3 having a small Dp mode diameter shows intermediate characteristics between Comparative Example 1 and Comparative Example 2, and the improvement width is smaller than that of the example.

[0029]

As described above, according to the present invention, by selectively restricting the micro-colloidal properties of carbon black different from those of the prior art, an excellent and excellent tread member for large tires for trucks, buses and the like is obtained. It is possible to provide a low heat generation rubber composition having abrasion resistance and high rebound resilience. Therefore, it can be mounted on trucks and buses to achieve effective fuel economy.

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Claims (1)

(57) [Claims] 1. A CTAB specific surface area of 100 to 160 m ² /
g, furnace carbon black having a compressed DBP belonging to a hard region of 100 to 120 ml / 100 g and having selective properties according to the following relational expressions (1) to (3):
A rubber composition blended in an amount of 35 to 100 parts by weight with respect to 00 parts by weight. (1) 5 ≦ N ₂ SA−IA ≦ 15 (2) 0.639 Dst mode diameter + 5.88 ≦ ΔDst ≦ 0.639 Dst mode diameter + 15.88 (3) Dp mode diameter ≧ 2.66Dmp mode diameter + 0.516 where (1 ) In the formula, N ₂ SA indicates a nitrogen adsorption specific surface area, and IA indicates an iodine adsorption amount. The Dst mode diameter in the equation (2) is the Stokes mode diameter of the carbon black aggregate measured by a disk centrifuge (DCF), and ΔDst is the half width of the Stokes diameter distribution. The Dp mode diameter in the equation (3) is the maximum frequency mode diameter in the pore diameter distribution between the carbon black aggregate particles measured by a differential scanning calorimeter (DSC), and the Dmp mode diameter is the carbon black obtained by the mercury intrusion method. The mode diameter of the maximum frequency in the pore diameter distribution between aggregate grains is shown.