JPH06228371A - Rubber composition - Google Patents

Abstract

PURPOSE:To obtain a rubber compsn. which has a high abrasion resistance and low heat build-up properties. CONSTITUTION:100 pts.wt. rubber component comprising a natural rubber and/or a synthetic diene rubber is compounded with 20-70 pts.wt. carbon black which has a CATB (specific surface area as determined by cetyltrimethylammonium bromide adsorption) of 60-110m<2>/g, a 24M4DBP of 127-150ml/100g, a DELTAD50/Dst of 0.50-0.85, and a DELTAD10/Dst of 1.00-1.60.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a rubber composition suitable for tires. More specifically, the present invention relates to a rubber composition for tires, which is excellent in low heat buildup and excellent in abrasion resistance, and particularly suitable for passenger car tires.

[0002]

2. Description of the Related Art Conventionally, low reinforcing carbon black having a low specific surface area is used as the carbon black in order to ensure the low heat build-up of rubber. Reduce the blending ratio of carbon black. Disc Centrifuge (DC
F) Broadening of the aggregate size distribution of carbon black in the measurement.

On the other hand, in order to improve wear resistance,
Highly reinforced carbon black having a high specific surface area is used as the carbon black. Increase the blending ratio of carbon black. Means are taken to sharpen the aggregate size distribution in DCF measurements.

Since these conditions conflict with each other,
There is a problem that abrasion resistance decreases when trying to secure low heat build-up, and low heat buildup when trying to improve wear resistance. In this way, it is impossible to make both properties compatible with each other by the conventional means, and it has been desired to develop a rubber composition having both properties.

Japanese Unexamined Patent Publication (Kokai) No. 62-290738 describes a method of improving wear resistance by controlling the distribution of aggregates of carbon black. However, even if it is applied to low-reinforcing carbon black having a low specific surface area, there is a limit to improvement in wear resistance.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rubber composition excellent in low heat build-up and also excellent in abrasion resistance, particularly a rubber composition for a tret which is suitable for passenger car tires. is there.

[0007]

Means for Solving the Problems As a result of intensive studies on the colloidal properties of carbon black in order to solve the above problems, the present inventors have found that a rubber composition of a rubber composition can be obtained by blending carbon black having specific properties. The present invention has been completed by finding that low heat build-up can be improved while maintaining wear resistance.

That is, the present invention has a cetyltrimethylammonium bromide adsorption specific surface area (CTAB) of 60 to 110 m ^{2 with} respect to 100 parts by weight of at least one rubber component selected from the group consisting of natural rubber and diene synthetic rubber. / G, the 24M4DBP oil absorption is 127 to 150 ml / 100 g, the ΔD ₅₀ / Dst is 0.50 to 0.85, and the ΔD ₁₀ / Dst is 1.00 to 20 to 70 carbon black satisfying the four conditions of 1.60
It is a rubber composition prepared by blending parts by weight.

Examples of the diene-based synthetic rubber that can be used in the present invention include, but are not limited to, isoprene rubber, butadiene rubber, butyl rubber, and styrene-butadiene copolymer rubber.

CTAB is cetyltrimethylammonium bromide. Generally, the nitrogen adsorption method is used to measure the specific surface area of carbon black, which is an excellent evaluation method.However, some types of carbon black have pores of about several angstroms in a large part of the entire surface. Rubber cannot enter the pores. Therefore, the evaluation of the specific surface area of the pores to the extent that rubber can penetrate can be solved by using large adsorbed molecules. One of the large adsorbed molecules is C
It is TAB. Therefore, it has been adopted as a method for evaluating the specific surface area of the pores of carbon black into which rubber can penetrate, and m ² /
It is represented by g. Measured according to ASTM D3765-89.

24M4DBP oil absorption is 24,000ps
The DBP oil absorption was calculated after applying repeated compression four times at the pressure i, and the DBP oil absorption due to the deformable / destructive structural form (secondary structure) caused by the so-called van der Waals force was eliminated. Based on the structural form of the non-destructive true structure (primary structure), D
It is an index for evaluating the skeletal structural characteristics of carbon black mainly composed of a primary structure, which is used when determining the BP oil absorption, and is a value measured according to ASTM D3493.

[0012] Dst is a value in which the most frequent value, that is, the largest aggregate diameter, is represented by the sootkes equivalent diameter when the distribution of aggregates (aggregates) of carbon black is examined, and is expressed in nm.
The measurement of Dst uses a disk centrifuge (DCF) manufactured by Joyce-Rable, by a centrifugal sedimentation method.
Measurement is performed by the following method. The carbon black dried in advance is precisely weighed and mixed with a 20% 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. This is used as a sample.

The rotation speed of the disc centrifuge is set to 6
The speed is set to 000 rpm, 10 ml of the spin solution (2% glycerin aqueous solution) is added, and then 1 ml of the buffer solution (ethanol aqueous solution) is injected. Then, 0.5 ml of the sample was added with a syringe, and then centrifugal sedimentation was started all at once, and a distribution curve of the distribution of aggregates formed by the photoprecipitation method was drawn, and a sootx equivalent diameter corresponding to the peak of the curve was obtained.
st (nm).

The width (half-value width) of the distribution curve at a position of 50% of the frequency (wt%) of the most frequent value is ΔD ₅₀ , and the width of the distribution curve at a position of 10% of the most frequent value is ΔD ₁₀ . 1). In order to express the degree of sharpness of the distribution curve in a non-dimensional manner, the characteristic values ΔD ₅₀ / Dst and ΔD 10 / Dst are used.

In the present invention, CTAB is 60 m ² / g.
If less than 110, wear resistance is significantly reduced, while 110
If it exceeds m ² / g, the low heat build-up property is significantly deteriorated, and therefore CTAB needs to be in the range of 60 to 110 m ² / g. It is preferably in the range of 75 to 110 m ² / g.

When 24M4DBP is less than 127 ml / 100 g, the improvement of abrasion resistance is small, and when it exceeds 150 ml / 100 g,
The workability is significantly reduced.

As described above, ΔD ₅₀ / Dst is a characteristic value representing the degree of variation in the distribution of carbon black aggregates. The smaller the value, the higher the homogeneity of carbon black and the greater the reinforcing effect. If this value is less than 0.50, workability and low heat buildup deteriorate, and if it exceeds 0.85, the improvement in wear resistance becomes small. Therefore, ΔD ₅₀ / Dst needs to be in the range of 0.50 to 0.85. Preferably 0.50 to 0.7
The range is 5.

As a result of a detailed study on the distribution of aggregates of carbon black, the present inventors have found that there is a carbon black having a broader lower portion of the distribution curve although the value of ΔD ₅₀ / Dst is small. Discovered that since the component on the large particle size side increased, the original homogenization could not be achieved and the wear resistance deteriorated. Since this region cannot be detected by the conventional index of ΔD ₅₀ / Dst, a new characteristic value of ΔD ₁₀ / Dst was introduced. This value is 1.
When it is less than 00, workability and low heat buildup are significantly deteriorated, and 1.6
If it exceeds 0, the improvement in wear resistance becomes small. Therefore ΔD ₁₀ /
The value of Dst needs to be in the range of 1.00 to 1.60. The range of 1.00 to 1.50 is preferable.

This index is effective and ΔD ₁₀ / Dst, especially when combined with high structure carbon black.
By limiting the ratio to 1.00 to 1.60, a carbon black having a high structure and a uniform aggregate distribution can be obtained, and a high wear resistance, which cannot be obtained with a specific surface area of this range, can be maintained. be able to. The carbon black of the present invention can be produced using a conventional oil furnace in the following manner. That is, a raw material of a highly aromatic component having a uniform composition is used and sprayed into a narrow region in the furnace by using a nozzle that also sprays oil droplets having a smaller distribution into the reaction furnace. Further, the reaction time can be made uniform by setting the conditions such that the temperature in the furnace and the flow of the combustion gas are smaller.

[0020]

The present invention will be described in more detail with reference to the following examples, but it goes without saying that the present invention is in no way limited by these examples. A rubber component consisting of 30 parts by weight of natural rubber and 70 parts by weight of styrene-butadiene copolymer rubber, 45 parts by weight of carbon black having the characteristic values shown in Table 1, 3 parts by weight of stearic acid, and Zn
5 parts by weight of O, 2 parts by weight of antioxidant (6C), 0.6 part by weight of vulcanization accelerator (CZ), and 1.5 parts by weight of sulfur were kneaded and vulcanized.

With respect to this rubber composition, a Lambourn abrasion resistance index was measured as a characteristic value showing abrasion resistance, and a tan δ index was measured as a characteristic value showing low heat generation. The composition and the result are shown in Table 1 and FIG.

The Lambourn abrasion resistance index, which is a wear resistance test, was shown by indexing the slip ratio as 60% and the conventional example as 100. The larger the value, the better the abrasion resistance.

The internal loss (tan δ) was measured by using a viscoelasticity spectrometer manufactured by Iwamoto Seisakusho Co., Ltd.
%, Frequency 50 Hz and 50 ° C.
The test piece is a slab sheet with a thickness of about 2 mm and a width of 5 mm.
The distance between the test clips was 2 cm, and the initial load was 100 g.
As a measure of low exothermicity, the tan δ index has a conventional example of 1
It was shown as an index as 00. The smaller the value, the better the low heat buildup. In FIG. 2, the Lambourn abrasion resistance index is plotted on the abscissa and the tan δ index is plotted on the ordinate, and the values of the examples, comparative examples, and conventional examples are plotted. The rubber composition is better as it goes to the lower right direction. From this, it is clear that the rubber composition of the present invention is excellent in both wear resistance and low heat buildup.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

As compared with the conventional rubber composition containing carbon black, it is possible to obtain a rubber having excellent abrasion resistance and low heat buildup.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a distribution curve of carbon black aggregates, and is an explanatory diagram of Dst, ΔD ₅₀ , and ΔD ₁₀ .

FIG. 2 is a Lambourn wear index on the horizontal axis and ta on the vertical axis.
The figure which plotted the value about the rubber composition of an Example, a comparative example, and a prior art example by taking ndelta index is shown, and it is a good rubber composition, so that it goes to the lower right direction.

Claims (1)

[Claims] 1. A cetyltrimethylammonium bromide adsorption specific surface area (CTAB) of 60 to 110 m ² / g relative to 100 parts by weight of at least one rubber component selected from the group consisting of natural rubber and diene-based synthetic rubber. Within the range, 24M4 DBP oil absorption is within the range of 127 to 150 ml / 100g, ΔD ₅₀ / Dst is within the range of 0.50 to 0.85, and ΔD ₁₀ / Dst is within the range of 1.00 to 1.60. A rubber composition comprising 20 to 70 parts by weight of carbon black satisfying the following four conditions: