JP3316249B2 - 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 for use as a tire tread member for passenger cars and light trucks, and more particularly to a rubber composition having low heat build-up and having excellent abrasion resistance while maintaining high rebound resilience. About things.

[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 present applicant has proposed the above-mentioned reciprocal rubber performance,
Research has been systematically continued to combine the characteristics of the carbon black to be blended by adding more microselective characteristics in addition to the basic characteristics such as particle size, specific surface area, and structure. We are making 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 having a Stokes mode diameter and the same distribution of aggregates maintained at a certain value or more, and capable of simultaneously imparting a high reinforcing performance and a high rebound resilience to a compounded rubber. 1-53978
No.). (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 having both high abrasion resistance and high rebound resilience blended with carbon black having the property of maintaining the width at or above a certain value (JP-A-59
-140241). (3) N ₂ SA is 65 to 84 m ² / g, and the ratio of N ₂ SA / absorbed iodine (IA) is in the range of 1.10 to 1.35;
A carbon black that can impart high abrasion resistance and high rebound resilience to a compounded rubber at the same time, with a relational expression having variables of BP, blackness, iodine adsorption amount and agglomerate mode diameter set to a certain value or more. JP-A-62-58792). (4) N ₂ SA is 75 to 105 m ² / g, compressed DBP 110 ml
/ 100g or more, set the true specific gravity value per specific surface area to a specific range lower than that of the known carbon black, and maintain the particle aggregate void diameter and the distribution width per aggregate mode diameter above a certain value. Carbon black (Japanese Patent Application Laid-Open No. 1-201367), which is capable of having both high abrasion resistance and high rebound resilience in a compounded rubber. (5) The nitrogen adsorption specific surface area (N ₂ SA) belongs to a hard type region of 60 to 100 m ² / g, and the mode diameter (Dp) of the pores between the aggregate grains is Dp ≦ 1.543 × (Dst mode diameter) −55.0 Formulated with furnace carbon black that satisfies the relationship
A low heat build-up rubber composition having excellent wear resistance while maintaining a high level of rebound resilience (JP-A-4-209640).

In addition, US Pat. No. 4,360,627 discloses an N ₂ SA85 for tire tread rubber.
^{~95m 2 / g, 24M4 DBP100~104ml /} 100g, T
A carbon black which achieves high abrasion resistance and high rebound resilience at an int of 95 to 105% and a distribution of aggregate Stokes mode diameter (ΔD ₅₀ ) of 180 mμ or more is disclosed, and US Pat. No. 4,548,980 discloses: As carbon black characteristics for obtaining low rolling resistance and high wet grip performance required for energy-saving tires, N ₂
SA 75 to 105 m ² / g, N ₂ SA-IA ≧ 15, N ₂ S
A-CTABSA ≦ 5, 24M4 DBP ≦ 110, Tint
90 to 110, ΔTint ≦ −3 are shown.

[0006]

However, quality requirements for fuel-efficient tires are becoming increasingly sophisticated, and there is a continuing need for the development of rubber compositions that achieve both higher levels of rebound resilience and wear resistance. is the current situation.

The present invention has been developed based on such a demand by elucidating the technical consequences between 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 low heat generating rubber composition having high rebound resilience and abrasion resistance suitable for treads of tires for light and light trucks.

[0008]

The rubber composition according to the present invention for achieving the above object has a CTAB specific surface area of 6%.
0-100m ² / g, compressed DBP 110-130ml / 100g
Of a hard carbon region having a selective property according to the following relational formulas (1) to (3): 35 to 100 parts by weight with respect to 100 parts by weight of the rubber component. Is a structural feature. (1) 10 ≦ N ₂ SA-IA ≦ 20 (2) 1.13 Dst mode diameter −57.64 ≦ ΔDst ≦ 1.13 Dst mode diameter −47.64 (3) Dp mode diameter ≦ 2.66 Dmp mode diameter −15.516 N ₂ SA indicates the specific surface area of nitrogen adsorption, and IA indicates the amount of adsorbed iodine. 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 as the characteristics of the carbon black having the above-described 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 the equations (1) and (2), ΔT is The freezing point drop width of distilled water, Wa is the solidification heat of distilled water, and K is a coefficient taking into account 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: 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 5-2000 lb / in ² and the pressure at the point where 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 the furnace head and a combustion burner mounted in the furnace axis 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 with a raw oil injection nozzle, split feed conditions for feed oil, supply amounts of fuel oil and air, oxygen gas addition conditions, etc. Can be manufactured by adjusting

The above-mentioned furnace carbon black is blended with an elastomer such as natural rubber, styrene-butadiene rubber, polybutadiene rubber, isoprene rubber, butyl rubber, various rubbers which can be reinforced with conventional carbon black, and 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.

[0015]

In the furnace carbon black characteristic items specified in the present invention, the CTAB specific surface area is 60 to 100 m ² / g.
Particles having a compressed DBP in the range of 110 to 130 ml / 100 g belong to the hard type region, and are prerequisites for maintaining the compounded rubber with high abrasion resistance and moderate heat generation. If the CTAB specific surface area is less than 60 m ² / g, the abrasion resistance becomes insufficient, while if it exceeds 100 m ² / g, the heat generation increases, and it is particularly difficult to use the carbon black for fuel-efficient tires. Becomes In addition, compressed DBP is 110ml / 1
If it is less than 00 g, sufficient abrasion resistance cannot be imparted, and 130 g
If the amount exceeds ml / 100g, the viscosity at the time of rubber compounding becomes high, and the processability decreases.

The characteristic of the relational expression (1) is a factor which mainly suppresses the heat build-up. If the value of (N ₂ SA-IA) is less than 10, the heat build-up required for the rubber composition for a fuel-efficient tire is required. On the other hand, when this value exceeds 20, the viscosity at the time of compounding the rubber becomes high and the practicality becomes poor. Equation (2)
Aggregate distribution of carbon black (ΔD
When st) is larger than the value on the right side (1.13 Dst mode diameter -47.64), the regression of wear resistance increases, and when it is smaller than the left side (1.13 Dst mode diameter -57.64), the effect of suppressing heat generation decreases. Accordingly, [1.13Dst mode diameter−57.64 ≦ ΔDst ≦ 1.13Dst mode diameter−47.64] regulated by the relational expression (2)
Is the optimum aggregate distribution range 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 the carbon black exhibiting the selective characteristics of the present invention is further 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 diameter). When it is positioned at a level equal to or less than the calculated value of the diameter (-15.516), it performs an effective function to improve the wear resistance without impairing the rebound resilience of the compounded rubber.

[0018] The unique properties and functions of the above-mentioned compounded furnace carbon black act collectively to simultaneously provide the rubber composition with a high level of resilience and abrasion resistance exhibiting low heat build-up. It becomes possible.

[0019]

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

Examples 1-4, Comparative Examples 1-3, Reference Examples 1
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 axis direction;
First-stage narrow-diameter reaction chamber (diameter 220 mm, length 400 mm) and second-stage narrow-diameter reaction chamber (diameter 190 mm, length) each having a feed oil injection nozzle coaxially connected to the combustion chamber and penetrating the furnace wall. 500m
m), a third-stage narrow-diameter reaction chamber (diameter 240 mm, length 400 mm), and a subsequent wide-diameter reaction chamber (diameter 450 mm) were installed. The specific gravity (15/4
℃) 1.073, viscosity (engler 40/20 ℃) 2.10, toluene insoluble content 0.03%, correlation coefficient (BMCI) 140 used aromatic hydrocarbon oil, as fuel oil, specific gravity (15/4 ℃) 0.903,
A hydrocarbon oil having 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.

[0022]

[Table 1]

[0023]

[Table 2] Table Note: (1) N351 [Tokai Carbon Co., Ltd., Seast NH] (2) N347 [Tokai Carbon Co., Ltd., Seast 3H] (3) N339 [Tokai Carbon Co., Ltd., Seast KH]

Next, the carbon black samples shown in Tables 1 and 2 were compounded in oil-extended styrene-butadiene rubber [JSR1712, manufactured by Nippon Synthetic Rubber Co., Ltd.] at the compounding ratio shown in Table 3.

[0025]

[Table 3]

Each rubber composition obtained by vulcanizing the composition of Table 3 at a temperature of 145 ° C. for 50 minutes was subjected to various rubber tests. The measurement results are shown in Tables 4 (Examples and Comparative Examples) and 5 (Reference Example) In addition, the measurement of the rubber property was based on the following. Among them, the abrasion amount was indicated by a relative index when the carbon black of Reference Example 3 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: JIS K6301 “Vulcanized rubber physical test method”.

[0028]

[Table 4]

[0029]

[Table 5]

From Tables 4 and 5, the results of the Examples show that tan which is an index of exothermicity is higher than that of Comparative Examples and Reference Examples which have the same level of N ₂ SA but do not satisfy the selective characteristic requirements of the present invention.
It is recognized that the high abrasion resistance performance is significantly improved while δ (loss coefficient) is equal to or less than that. It can also be seen that other reinforcing properties are maintained at a high level. On the other hand, in Comparative Example 1 having a large Dp mode diameter, the range of improvement in characteristics is smaller than that of the embodiment. Comparative Example 2 has the same level of abrasion resistance as Example 2 in which the specific surface area is equal because ΔDst is low, but tan δ is high. Conversely, in Comparative Example 3 in which ΔDst is high, tan δ is slightly lower, but the wear resistance is largely reduced.

[0031]

As described above, according to the present invention, the low heat build-up property which shows excellent wear resistance while maintaining high rebound resilience by selectively controlling the micro colloidal properties of carbon black different from the prior art. A rubber composition can be provided. Therefore, the present invention can be applied to a tire tread member for a passenger car or a light truck to achieve effective fuel saving.

Claims (1)

(57) [Claims] (1) a CTAB specific surface area of 60 to 100 m ² / g;
Furnace carbon black having a compressed DBP belonging to a hard system region of 110 to 130 ml / 100 g and having selective properties according to the following relational expressions (1) to (3) was obtained by adding a rubber component 100
A rubber composition blended at a ratio of 35 to 100 parts by weight with respect to parts by weight. (1) 10 ≦ N ₂ SA-IA ≦ 20 (2) 1.13 Dst mode diameter −57.64 ≦ ΔDst ≦ 1.13 Dst mode diameter −47.64 (3) Dp mode diameter ≦ 2.66 Dmp mode diameter −15.516 N ₂ SA indicates the specific surface area of nitrogen adsorption, and IA indicates the amount of adsorbed iodine. 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.