JPH0222348A - Rubber composition for tire tread - Google Patents

Abstract

PURPOSE:To obtain the subject rubber composition excellent in abrasion resistance and low heat build-up properties and suitable as tread rubber in tires for large-sized cars or passenger cars by blending rubber with a specific amount of specified carbon black. CONSTITUTION:A composition obtained by blending 100 pts.wt. one or more rubbers selected from the group consisting of natural rubber and diene-based synthetic rubber (e.g., styrene-butadiene copolymer rubber or polybutadiene rubber) with carbon black having 100-115m<2>/g nitrogen adsorption specific surface area, <=18ml/100g DBP defined by the formula, 95-105ml/100g 24M4DBP oil absorption, 1.03-1.10 ratio of the nitrogen adsorption specific surface area/ iodine adsorption, <=0.914 half-value width ratio of the (002) face peak by an X-ray diffractometry and 3.40-3.62Angstrom spacing of the (002) face.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rubber composition for tire treads that has excellent wear resistance and low fuel consumption.

[Conventional technology]

Conventionally, the main characteristics of carbon black for rubber compounding have long been the specific surface area (or particle diameter) determined by iodine adsorption method, BET adsorption method, etc., and the stracture determined by DBP oil absorption.

A rubber composition blended with carbon black is required to have both low heat build-up and high reinforcing properties, particularly when used as a rubber material such as a tread portion or a base tread portion of an automobile tire.

However, as the particle size of the carbon black used becomes larger or the struture becomes smaller, the heat generation property decreases and improves, but on the other hand, the reinforcing property tends to deteriorate, which is a trade-off. Therefore, it has been extremely difficult to impart high reinforcing properties to a rubber composition while maintaining low heat generation properties.

For the dynamic properties of carbon black filled rubber compositions,
In recent years, it has become clear that in addition to the specific surface area and stracture of carbon black, the so-called aggregate size and its distribution have a large effect (Japanese Patent Laid-Open No. 59-8
6636, JP-A-59-86641).

However, if the average aggregate size of the carbon blank is large, it will give a rubber composition with high elasticity (Ω elasticity), but the abrasion resistance will decrease. It was almost impossible to control the size and distribution alone.Furthermore, in the laboratory, methods have been used to improve dynamic properties by blending two or more types of carbon black. 59-4631), although this is effective in improving dynamic properties, it not only causes a decrease in wear resistance, but also causes differences in dispersibility due to carbon black characteristics, making it difficult to produce products with uniformity. The problem is that it cannot be obtained.

[Problem to be solved by the invention]

The present invention has both wear resistance and low heat generation property.
An object of the present invention is to provide a rubber composition containing a specific carbon black.

[Means to solve the problem]

In the present invention, 35 to 35 parts by weight of carbon black having the following characteristics are added to 100 parts by weight of at least one rubber selected from the group consisting of natural rubber and diene-based synthetic rubber.
The gist of the invention is a rubber composition for a tire tread, characterized in that it contains 70 parts by weight.

■Nitrogen adsorption specific surface area (N, SA) is 100-115m
“7g.

■ ΔDBP defined by the formula below is 18d/100g
below.

ΔD B P (rn1/100g)=D B P −
24M4DBP■ 24M4DBP oil absorption is 9
5-105ml 100g.

■ Nitrogen adsorption specific surface area (N2SA) (m2/g) /
The ratio of iodine adsorption amount (I8) (g/g) is 1.03 to 1
．． 10゜■ The half-width ratio of the (002) plane peak by X-ray diffraction method (diffraction peak half-width of sample/N220 diffraction peak half-width) is 0.914 or less, and the interplanar spacing of the (002) plane is 3.40~ 3.62 people.

This means will be explained in detail below.

(1) The carbon black used in the present invention is as follows (a
) to (d).

(a) Nitrogen specific surface area (N, SA) is 100 to 115
m"7g, 24M4DBP oil absorption 1i95~105m
Must be in the characteristic region of Z/100g.

If the nitrogen specific surface area (NSA) is less than 100 m''/g, the wear resistance will be low, and if it exceeds 115 m''7 g, the heat resistance will decrease, so it is set at 100 to 115 m''7 g.
4M/lDBP oil absorption 95-105 mZ/100g
The reason for this is that if it is less than 95ml/100g, the reinforcing property will not be sufficient and the wear resistance will decrease;
This is because if it exceeds 100 g, the elastic modulus of the compounded rubber will increase, and when used in the tread portion, the chipping resistance will decrease.

(bl ΔD E P (DBP oil absorbing mother-24F14
0BP oil absorption) is in the characteristic range of 18ml/100g or less.

ΔDBP indicates the proportion of temporary structure, and is known to be a measure of the degree of collapse of temporary carbon aggregates during mixing. When a carbon black-filled rubber composition is subjected to a mechanical shock, the mechanical shock energy is dissipated as heat due to the collapse of carbon aggregates, and therefore, when ΔDI3P is high, internal heat generation increases. If it exceeds 18 ml/100 g, internal heat generation will increase, which is not preferable.

(The CI NtSA/18 ratio is in the characteristic range of 1.03 to 1.10.

The value indicated by the N25A/IA ratio is thought to be related to the chemical activity of the carbon black surface toward many types of rubber molecules, and if this value is less than 1.03, it will lead to an increase in heat generation, which is undesirable. If the value is larger than .10, the elastic modulus of the compounded rubber increases and the chipping resistance decreases.

(d+ The spacing of the (002) plane is 3.40 to 3.62
For humans, the half-width ratio of the diffraction peak is 0.914 or less.

In addition to the above-mentioned four requirements, the carbon black of the present invention is required to have a specific interplanar spacing and a diffraction peak half width when measured by X-ray diffraction.

If the spacing between the (002) planes is less than 3.40, the heat generation property will decrease, but at the same time, the reinforcing property will also decrease, which is not preferable.

If the content exceeds 3.62, heat resistance deteriorates. Furthermore, if the half-width ratio of the diffraction peak exceeds 0.914, the heat resistance will be significantly reduced, which is not preferable.

In FIG. 1, the vertical axis CPS represents the intensity of the diffraction line, and the horizontal axis represents the incident angle 2θ (degrees). In Figure 1, d is d (002
), and f and g indicate the intensities of the diffraction lines used as background.

e is the intersection point drawn perpendicularly to the background from the maximum intensity d of the diffraction line, a and c are the intersection points of the two halves of the line and the diffraction curve, and i is the half width. Each point above (a
-g) is the intensity of this diffraction curve and the bank ground,
It is obtained by drawing the smoothest curve to remove irregularities in the curve due to minute fluctuations.

(2) The rubber composition of the present invention comprises carbon black having the properties (al to (d)) based on 100 parts by weight of at least one rubber selected from the group consisting of natural rubber and diene rubber. 35 to 70 parts by weight.

As the diene rubber, various rubbers commonly used as tire rubbers can be used, such as styrene-butadiene copolymer rubber, polybutadiene rubber, synthetic polyisoprene rubber, and butyl rubber.

If the blending ratio of carbon black is less than 35 parts by weight based on 100 parts by weight of rubber, the desired highly reinforcing rubber composition will not be obtained, while if it exceeds 70 parts by weight, the desired low heat build-up rubber will not be obtained. 35 to 7 because the composition cannot be obtained.
It must be within the range of 0 times the last part.

In addition to carbon black, the rubber composition of the present invention may contain, if necessary, a vulcanizing agent such as sulfur, a vulcanization accelerator, a vulcanization accelerating aid, an anti-aging agent, a tackifier, a softening agent, It may also contain fillers and the like.

Examples and comparative examples are shown below.

[Example, comparative example]

Various rubber compositions (Examples 1 to 6, Comparative Examples 1 to 8) were prepared using the formulation contents shown in Table 1 below (all parts by weight and components other than carbon blank were the same).

Table 1 shows the properties of each carbon black used in this case. In addition, the characteristic value is measured by the following measurement method + 1
) to (5).

(1) Nitrogen specific surface area.

ASTM-03037-78'''5 standard M
methods of Testing Carbon
Black-3surface Area by
Nitrogen Ads.

rption″Method C.

(2) Amount of iodine adsorption.

According to JIS K 6221 (1982) r Carbon black test method for rubber J 6.1.1.

(3) DBP oil absorption amount.

According to JIS K 6221 (1982) r Carbon black test method for rubber J 6.1.2 (1) A method.

(4) 24M4DBP oil absorption amount.

8 According to STM-D3493.

(5) X-ray diffraction method.

The d (002) and half width of carbon black are Co
It was determined by a transmission method using Kα rays and a pinhole slit. The half width ratio (R) of the diffraction peak is N
The value is expressed by the following formula based on the half width of the (002) diffraction peak of 220.

This R was calculated from the peak width measured under the following conditions.

The half-width H of the measured peak is the sum of the true half-width from the sample itself and the half-width a from the device. H=
L+a, therefore, in N220 selected as the standard,
The measured half width H(N220) is H(N220) =
L (N220) + a. Further, the half width H (sample) measured in the sample = L (sample) + a.

The diffraction peak of carbon black is broad, and H≧
Therefore, the formula becomes as follows.

H(N220) L (N220) measurement was performed under the following conditions using an X-ray diffraction apparatus manufactured by Rigaku Corporation (trade name: Rotaflex).

Voltage 40KV, current 50111A% Coka, Fe filter used, Drive Axis 2θ/θ5CA
N 5PEED 1.5DEC/MIN, pinhole slit 21111φ, receiving slit 1° ×
B.

The sample was placed in a sample molding die (φ-40+n) with a diameter of 0.65 mm.
g of powdered carbon blank was put therein, a load of 20 tons (5 minutes) was applied using a tablet-forming press, and the obtained plate sample was subjected to X-ray diffraction.

Table 1 shows the vulcanized physical properties of the rubber composition. The physical properties of this vulcanization were evaluated by kneading a rubber composition containing various types of carbon black and vulcanizing it at 148°C for 30 minutes, and evaluating the viscoelastic properties and Lambourne abrasion (abrasion resistance) of the vulcanizate obtained. This is a record of the results.

For tan δ, which is an alternative index of heat generation, a viscoelastic spectrometer (Iwaki Seisakusho f) 1! 1) at a temperature of 100° C., a strain rate of 10±2%, and a frequency of 2011z.

Regarding Lambourn wear, a test piece disk and a polishing disk are rotated in contact with each other without making an angle using a Lambourn type abrasion tester, and at this time slip is caused between the test piece and the polishing disk.
Measure the amount of wear on the test piece per unit time. Mixture 1 to 1
00 and expressed as an index. The larger the value, the better.

(Left space below the wooden page) From Table 1, rubber compositions according to the present invention (Examples 1.2.
3.4.5.6) has better wear resistance than the conventional rubber composition (Comparative Example 1) containing l5AF (N220) class hard carbon black, and has a lower tan δ, which is an alternative index of heat generation. It can be seen that it is held at the level. Comparative Example 2.3 is the half width of the X-ray diffraction peak, d (002)
The carbon black properties excluding the interplanar spacing satisfy the claimed scope of the rubber composition of the present invention, but tan δ
It can be seen that the amount is significantly increased compared to the present invention. Comparative Example 4 is a rubber composition containing a conventional type of HA F (N339) class carbon black, but the rubber composition of the present invention (Example 1) has better wear resistance and better wear resistance than Comparative Example 4.
It can be seen that the heat resistance is good. Furthermore, the rubber composition of the present invention (Example 2.3.4.5.6) is different from the rubber composition outside the scope of the present invention ( It can be seen that compared to Comparative Example 5.7.8), the tan δ was significantly reduced, that is, the heat generation property was significantly improved. Comparative Example 6 has a specific surface area (N,
Regarding properties other than SA), the rubber composition blended with carbon black falls within the scope of the present patent claims, but compared to the rubber composition within the scope of the present invention (Example 4), it has better heat resistance,
It is clear that the wear resistance is inferior.

〔Effect of the invention〕

As explained above, according to the present invention, by blending a specific amount of specific carbon black into rubber, it is possible to obtain a rubber composition for a tire tread that is excellent in wear resistance and low heat build-up.

This rubber composition for tire treads is extremely effective when used as tread rubber for tires for large vehicles and tires for passenger cars.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an X-ray diffraction curve of carbon black.

Claims (1)

[Scope of Claims] 35 to 70 parts by weight of carbon black having the following characteristics is blended with 100 parts by weight of at least one rubber selected from the group consisting of natural rubber and diene-based synthetic rubber. A rubber composition for a tire tread, characterized by: (1) Nitrogen adsorption specific surface area (N_2SA) is 100-11
5m^2/g. (2) ΔDBP defined by the following formula is 18ml/10
Less than 0g. ΔDBP (ml/100g) = DBP-24M4DBP (3) 24M4DBP oil absorption amount is 95-105ml/10
0g. (4) Nitrogen adsorption specific surface area (N_2SA) (m^2/g)
/ iodine adsorption amount (IA) (mg/g) ratio is 1.03
~1.10. (5) The half-width ratio of the (002) plane peak by X-ray diffraction method (diffraction peak half-width of the sample/diffraction peak half-width of N220) is 0.914 or less, and the interplanar spacing of the (002) plane is 3.4.
0-3.62 Å.