JPH06256580A - Rubber composition - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a low heat-generating rubber composition having excellent wear resistance and impact resilience suitable as a tire tread member for light trucks and truck buses. [Composition] Nitrogen adsorption specific surface area (N ₂ SA) is 100 ~ 140m ² / g,
Furnace carbon black, which has a selective property of DBP oil absorption of 100 to 130 ml / 100 g and has a blackness of 35% to 100 parts by weight of the rubber component, is selected.
A rubber composition containing 100 to 100 parts by weight. Blackness ≤ 0.39 × N ₂ SA + 72.0 However, the value of blackness is the percentage of the reflectance of the carbon black paste prepared by ultrasonic dispersion with respect to the reference carbon black (IRB # 6).

Description

Detailed Description of the Invention

[0001]

The present invention relates to a rubber composition suitable as a tire tread member for a light truck or a truck bus,
More particularly, it relates to a rubber composition having a low heat buildup and having a high impact resilience while maintaining excellent wear resistance.

[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, in recent years, fuel-efficient tires have been actively developed in order to meet social demands for resource saving and energy saving, but such a fuel-efficient tire has a relatively small particle size. A rubber composition containing a large amount of carbon black of a large variety in a rubber component in a relatively small amount and having low heat buildup and high impact resilience is effective. However, the compounding of carbon black rubber with a large particle size and a small specific surface area is effective for the purpose of improving fuel economy performance,
The deterioration of surface properties such as braking performance and wear resistance on wet road surfaces cannot be avoided. Therefore, it is ideal as a rubber member for a tire tread if it is possible to simultaneously impart high abrasion resistance and low heat buildup that gives high impact resilience to a compounded rubber by using carbon black having a small particle size and a large specific surface area. Will be things.

The Applicant has the above-mentioned antithetic rubber performance,
In terms of the characteristics of the carbon black to be compounded, especially basic characteristics such as particle size, specific surface area, structure, etc., in addition to the basic characteristics such as microscopic selective characteristics, we are continuing systematically research to achieve both. We are making development proposals. (1) Nitrogen adsorption specific surface area (N ₂ SA) is 60m ² / g or more, compressed DB
Carbon black with a P of 112 ml / 100 g or more, which maintains the Stokes mode diameter and distribution of the aggregate above a certain value, is a carbon black capable of simultaneously imparting high reinforcing performance and high impact resilience to compounded rubber. 1-53978
Issue). (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 having a high abrasion resistance and a high impact resilience, which is blended with carbon black having a characteristic of keeping the width above a certain value (JP-A-59).
-140241 publication). (3) N ₂ SA is 65 to 84 m ² / g, and the ratio of N ₂ SA / iodine adsorption amount (IA) is 1.10 to 1.35.
A carbon black (special characteristics) that can simultaneously impart high abrasion resistance and high impact resilience to a compounded rubber in which a relational expression with variables such as BP, blackness, iodine adsorption amount and aggregate mode diameter is set to a certain value or more. (Kaisho 62-58792). (4) N ₂ SA 75-105 m ² / g, compressed DBP 110 ml
/ 100 g or more, set the true specific gravity per constant specific surface area to a specific range lower than that of known carbon black, and maintain the particle aggregate void diameter and the distribution width per aggregate mode diameter above a certain value. Further, a carbon black (Japanese Patent Laid-Open No. 1-201367) that allows a compounded rubber to have both high abrasion resistance and high impact resilience. (5) Nitrogen adsorption specific surface area (N ₂ SA) belongs to the hard system region of 60 to 100 m ² / g, and the mode diameter (Dp) of the inter-aggregate pores is Dp ≦ 1.543 × (Dst mode diameter) −55.0 ] Furnace carbon black that satisfies the relational expression of
A low heat-generating rubber composition having excellent abrasion resistance while maintaining a high level of impact resilience (JP-A-4-209640).

In addition, US Pat. No. 4,360,627 discloses N ₂ SA85 for tire tread rubber.
~ 95m ² / g, 24M4 DBP100 ~ 104ml / 100g, T
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 int 95 to 105%, and US Pat. No. 4,548,980 discloses N _{2 is used} as a carbon black property for obtaining low rolling resistance and high wet grip performance required for energy-saving tires.
SA 75-105 m ² / g, N ₂ SA-IA ≧ 15, N ₂ S
A-CTABSA≤5, 24M4 DBP≤110, Tint
90 to 110 and ΔTint ≦ −3 are shown.

[0006]

[Problems to be Solved by the Invention] However, the quality requirements for fuel-efficient tires are becoming more sophisticated, and the development of a rubber composition that achieves both abrasion resistance and impact resilience (low heat build-up) at a higher level The current situation is that

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. It is an object of the present invention to provide a low heat-generating rubber composition having a high degree of wear resistance and impact resilience, which is suitable as a tire tread for trucks and truck buses.

[0008]

[Means for Solving the Problems]
The rubber composition according to the present invention has a nitrogen adsorption specific surface area (N ₂S
A) is 100-140m²/ g, DBP oil absorption is 100-13
It belongs to the 0ml / 100g hardware area and has a blackness of
A fanness carbon black with selective characteristics that satisfies the relational expression.
35-100 parts by weight for 100 parts by weight of the rubber component
The composition is characterized in that it is mixed in the ratio of. Blackness ≦ 0.39 × N₂ SA + 72.0 However, the value of blackness is the value of the carbon produced by ultrasonic dispersion.
Black carbon paste standard carbon black (IRB # 6)
It is assumed that the ratio of the reflectance to that is expressed as a percentage.

The values obtained by the following measuring methods are used for the respective characteristics of the carbon black having the above structure. (1) Nitrogen adsorption specific surface area (N ₂ SA); ASTM D3037-
88 "Standard Test Method for Carbon Black-Surfac
e Area by Nitrogen Absorption "Method B. The N ₂ SA measurement value of IRB # 6 by this method is 76 m ² / g
Is. (2) DBP oil absorption amount; JIS K6221 (1982) "Test method for carbon black for rubber", oil absorption amount A in 6.1.2
By law. The measured DBP oil absorption of IRB # 6 by this method is 99.0 ml / 100 g.

(3) Blackness; 0.5 g of dry carbon black treated according to the method of preparing a dry sample according to JIS K6221 (1982) is put in a sample bottle, and dibutyl phthalate is added as a dispersion medium and dispersed by an ultrasonic homogenizer. . The obtained carbon black paste is formed as a thin film on a glass plate using a film applicator (film thickness 0.003 inch) and measured with a reflectometer. The blackness is calculated by the following formula from the measured reflectance of the sample (carbon black paste thin film) and the reflectance of the standard sample IRB # 6. Blackness = [(reflectance of IRB # 6) / (reflectance of sample)] x 100

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 coaxially connected to the combustion chamber. Using an oil furnace that consists of a multi-stage narrow-diameter reaction chamber and a wide-diameter reaction chamber with a feed oil injection nozzle, adjust the feed-in oil split introduction conditions, fuel oil and air supply amounts, and oxygen gas addition conditions Can be manufactured.

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.

[0013]

[Function] Among the characteristic items of the furnace carbon black specified in the present invention, the nitrogen adsorption specific surface area (N ₂ SA) is 100 to 14
The particle properties in the range of 0 m ² / g and the DBP oil absorption amount of 100 to 130 ml / 100 g belong to the hard system region, and are a precondition for the compounded rubber to maintain a high degree of abrasion resistance and an appropriate heat generation property. If the nitrogen adsorption specific surface area is less than 100 m ² / g, it becomes insufficient in terms of wear resistance, while if it exceeds 140 m ² / g, the heat generation property increases, and it is particularly suitable for use as a carbon black for fuel-efficient tires. It will be difficult. DBP oil absorption is 1
If it is less than 00 ml / 100 g, sufficient abrasion resistance cannot be imparted, and if it exceeds 130 ml / 100 g, the viscosity at the time of compounding the rubber becomes high and the workability deteriorates.

The blackness of the carbon black paste prepared by ultrasonic dispersion is one of the parameters showing the properties of the aggregate (aggregate) in which carbon black is firmly fused and bonded, and the reaction in the process of carbon black formation. It is closely related to conditions such as temperature and degree of disturbance of combustion gas. Therefore, it has a high correlation with the surface area of carbon black, and according to the study of the inventor, the nitrogen adsorption specific surface area (N ₂ S
A) is 100-140 m ² / g, DBP oil absorption is 100-13
It was confirmed that the blackness of commercial carbon black in the range of 0 ml / 100 g is in the relation of the following formula. Blackness = 0.39 × N ₂ SA + 80.6 ± 3.0

Therefore, the blackness specified in the present invention is characterized by being lower than the value calculated from the above formula in relation to the nitrogen adsorption specific surface area (N ₂ SA), and this selective It is presumed that the properties of the compound rubber effectively function to improve the impact resilience of the compounded rubber without impairing the wear resistance and to impart low heat buildup.

The characteristic properties and functions of the compounded furnace carbon black as described above act in a comprehensive manner to allow the rubber composition to have both excellent abrasion resistance and high impact resilience exhibiting low heat buildup. It will be possible.

[0017]

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

Examples 1 to 3 and Comparative Examples 1 to 3 A combustion chamber (diameter 900 mm, length 1000 mm) having a tangential air supply port on the furnace head and a combustion burner mounted in the furnace axial direction,
First stage narrow diameter reaction chamber (diameter 250 mm, length 450 mm), second stage narrow diameter reaction chamber (diameter 200 mm, length) that is equipped with a feedstock oil injection nozzle that is coaxially connected to the combustion chamber and penetrates through the furnace wall (500 mm)
An oil furnace consisting of a large-diameter reaction chamber and a subsequent large-diameter reaction chamber (diameter 450 mm) was installed. Specific gravity (1
5/4 ℃) 1.073, viscosity (Engla 40/20 ℃) 2.
10, toluene insoluble content 0.03%, correlation coefficient (BMCI) 14
Aromatic hydrocarbon oil of 0 was used, and the specific gravity (1
5/4 ° C) 0.903, viscosity (cst / 50 ° C) 16.1, residual carbon content 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. Comparative Examples 2 and 3 are commercially available hard carbon blacks.

[0020]

[Table 1] Table Note: 1) "Cast 6" manufactured by Tokai Carbon Co., Ltd. 2) "Cast 9" manufactured by Tokai Carbon Co., Ltd.

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

[0022]

[Table 2]

Various rubber tests were conducted on each rubber composition obtained by vulcanizing the compound of Table 2 at a temperature of 145 ° C. for 40 minutes, and the measurement results are shown in Table 3. The rubber properties were measured as follows. Of these, the abrasion resistance index was shown as a relative index when the carbon black of Comparative Example 3 was 100. Further, tan δ (loss coefficient) is an index of heat generation, and the smaller the measured value, the lower the heat generation degree.

(1) Amount of wear: Measured under the following conditions using a Lambourn wear tester (mechanical slip mechanism). 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 (2) tan δ (loss factor); Visco Elastic Spectrometer
(Manufactured by Iwamoto Seisakusho) was used and 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) Other characteristics: According to JIS K6301 "vulcanized rubber physical test method" .

[0025]

[Table 3]

From the results shown in Table 3, the rubber compositions of Examples 1 to 3 satisfying the requirements of the present invention have the same level of N ₂ SA as compared with Comparative Examples which deviate from the selective characteristic requirements of the present invention. Ta, which is an index of heat generation, while maintaining equivalent wear resistance
It can be seen that nδ (loss coefficient) is significantly decreased and other reinforcing properties are maintained at a high level.

[0027]

As described above, according to the present invention, a low heat-generating rubber composition having excellent wear resistance and impact resilience by selectively regulating the microscopic property of carbon black different from the prior art. Can be provided. Therefore, it can be applied to a tire tread member for a light truck or a truck bus to effectively reduce fuel consumption.

Claims (1)

[Claims] 1. A nitrogen adsorption specific surface area (N ₂ SA) of 100 to 14
Rubber component 1 is a furnace carbon black having a selective property of 0 m ² / g, a DBP oil absorption of 100 to 130 ml / 100 g, and a blackness satisfying the following relational expression.
A rubber composition blended in a proportion of 35 to 100 parts by weight with respect to 00 parts by weight. Blackness ≦ 0.39 × N ₂ SA + 72.0 However, the value of the blackness is expressed as a percentage of the reflectance of the carbon black paste prepared by ultrasonic dispersion with respect to the reference carbon black (IRB # 6). To do.