JPS63199748A - Rubber composition - Google Patents

Abstract

PURPOSE:To provide a rubber compsn. which has excellent wear resistance, suppresses heat buildup and is useful as a material for the tire tread of automobiles, industrial belts, etc., by blending rubber with specified carbon black. CONSTITUTION:100pts.wt. rubber (A) is blended with 30-80pts.wt. carbon black (B) which as a nitrogen specific surface area (N2SA) of 105-160m<2>/g, 24M4DBP absorption of 90-140ml/100g and in which an agglomeration distribution in a characteristic zone of DELTABP (DBP absorption-24M4DBP absorption) of <=16ml/100g as measured by a centrifugal sedimentation is composed of two peak distributions wherein the mode diameter (Dst (2)) of the distribution of highly agglomerated particles (a second peak) is <=130mmu, a difference between the mode diameter (Dst(1)) of the distribution of lowly agglomerated particles (a first peak) and Dst(2) is 50mmu or smaller and the ratio of the half width of the distribution of lowly agglomerated particles to that of the distribution of highly agglomerated particles is 0.6 or lower, and optionally a vulcanizing agent, a vulcanization accelerator, an antioxidant, a tackifier, a softener, a filler, etc. (C).

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to rubber materials such as treads, side treads, base treads, etc. of automobile tires (passenger car tires, buses, trucks, etc.) and industrial belts; The present invention relates to a rubber composition that has both abrasion resistance and low heat generation properties and can be used as cover rubber for hoses and the like.

[Prior art]

Conventionally, the main characteristics of carbon black for rubber compounding have long been the specific surface area (or particle diameter) shown by the iodine adsorption method, BET adsorption method, etc. and the stratch content shown by the 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 structure of carbon black, the so-called aggregate size and its distribution have a large influence (Japanese Patent Application Laid-Open No. 1986-1986).
636, JP-A-59-86641).

However, if the average aggregate size of carbon black is large, while providing a rubber composition with high rebound resilience, the abrasion resistance decreases, and it is difficult to combine low dynamic properties and abrasion resistance. It was almost impossible to control the distribution alone. Furthermore, in the laboratory, a method of blending two or more types of carbon black to improve dynamic properties has been carried out (Japanese Patent Application Laid-Open No. 59-4631).
Although this is effective in improving dynamic properties, it not only causes a decrease in wear resistance, but also has the disadvantage that a product with uniformity cannot be obtained due to differences in dispersibility due to carbon blank characteristics. be.

[Purpose of the invention]

The present invention is characterized by having both wear resistance and low heat build-up.
An object of the present invention is to provide a rubber composition containing a specific carbon black.

[Structure of the invention]

Therefore, the present invention has a nitrogen specific surface area (NASA) of 105
~160 rrf/g, 24M4DBP oil absorption 90~140m/100g, ΔDBP (DBP oil absorption m-24M4DBP oil absorption) ≦16a//100g, and the aggregate distribution by centrifugal sedimentation method is Carbon black with a two-peak distribution that satisfies the following items,
The gist of the invention is a rubber composition characterized in that it is blended in an amount of 30 to 80 parts by weight per 100 parts by weight of rubber.

■ Most frequent mode diameter of high aggregate distribution (second peak) (
Dst(2)) ≦130+sμ.

■ The most frequent mode diameter of the low aggregate distribution (first peak) (
The difference between Dst (1)) and the most frequent mode diameter (Dst (2)) of the high aggregate distribution (second peak) is 50 mμ or less.

■ The ratio of the half-width of the low aggregate distribution (Dst(1)) to the half-width of the high aggregate distribution (Dst(2)) is 0.6 or less (Δ
Dst(1)/ΔDst(21≦0.6).

Hereinafter, the configuration of the present invention will be explained in detail.

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

(al Nitrogen specific surface area (NASA) is 105-160
rtr/g, 24M4DBP oil absorption 90-140 g
Must be in the characteristic range of af/100g.

Nitrogen specific surface area (N2SA) If it is less than 105m2/g, the wear resistance will be low, and if it exceeds 160m2/g, the heat resistance will be decreased, so it is set to 105-16Onf/g. Also, 2
The reason why the oil absorption amount of 4M4DBP is set to 90-140 m/100 g is that if it is less than 90 mm/100 g, the reinforcing property will not be sufficient and the abrasion resistance will decrease. On the other hand, 140mZ/10
This is because if it exceeds 0 g, the elastic modulus of the compounded rubber will increase, and the chipping resistance will decrease when it is used, for example, in a tread.

ΔDBP (DBP oil absorption - 24M4DBP oil absorption) must be in the characteristic range of 16 m1/100 g 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 mechanical shock is applied to a carbon black-filled rubber composition, the mechanical shock energy is dissipated as heat due to the collapse of the carbon aggregates, so when ΔDBP is high, internal heat generation increases.

If it exceeds 16+af/100g, internal heat generation will increase, which is not preferable.

(C) The aggregate properties obtained by the centrifugal sedimentation method have a two-peak distribution defined by a specific range of mode diameter (Dst) and distribution (ΔDst).

For a two-peak aggregate distribution, it is necessary to identify specific values for each distribution. In other words, it is necessary to satisfy the following three conditions.

Of the two peaks, among the most frequent mode diameters of the low aggregate diameter distribution and the high aggregate diameter distribution (abbreviated as the first mode diameter and second mode diameter, respectively), ■ Dst of the second mode diameter (2 ) shall be 130-μ or less.

(2) The difference between the first mode diameter (Dst(1)) and the second mode diameter is 5On+μ or less.

■ Furthermore, the half-width of the low aggregate distribution (ΔDst(1))
It is necessary that the ratio of the half-width of the high aggregate distribution (ΔDst (21)) satisfies 0.6 or less (ΔDst (1
)/ΔDst(2)≦0.6).

The reason why wear performance and low heat generation performance are maintained at a high level by these regulations is that the product of the present invention has a low mode diameter area (low aggregate distribution area) and a high mode diameter area (low aggregate distribution area) to a level not found in conventional products. The increase in the proportion of thin aggregates that contribute to wear to a degree that was previously unachievable with carbon, as well as the increase in the proportion of fine aggregates that contribute to wear in a certain range (high aggregate distribution area), and the comparison that has a favorable effect on elasticity. This seems to be due to an attempt to increase the occupation ratio of coarse aggregates.

In conventional carbon blends, the overall distribution of aggregates becomes broader compared to before blending, with a decrease in the proportion of thin aggregates and an increase in the proportion of coarse aggregates, compared to the carbon black of the present invention. low wear performance/
It only shows heat generation performance.

When the second mode diameter D s t (2) exceeds 130 mμ, the occupation ratio of coarse aggregates that adversely affect wear resistance increases, resulting in a decrease in wear resistance.

In addition, the first mode diameter (Dst(1)) and the second mode diameter (
If the difference from Dst (2)) exceeds 50-μ, the proportion of thin aggregates will increase relatively too much, making it difficult to disperse carbon black into rubber at the initial stage of mixing. This means that the desired improvement in wear performance cannot be achieved. Furthermore, the aggregate distribution area (ΔDa t) also has an effect on wear performance and heat generation performance, and the half-width of the low aggregate distribution (Δ
Dst (1)) and the half-width of high aggregate distribution (ΔDst
It is essential for the ratio to (21) to be within a certain specific value in order to achieve both wear performance and low heat generation performance.

In other words, the ratio of both distribution widths represents the proportion of occupancy between the fine aggregate portion and the relatively coarse aggregate portion,
When this ratio exceeds 0.6, the occupation ratio of relatively coarse aggregate portions decreases, making it impossible to obtain a rubber composition having the desired low heat generation property.

Therefore, in order to obtain a rubber composition that has both wear resistance and low heat build-up, it is necessary to have aggregate distribution characteristics that simultaneously satisfy the above conditions Φ to ■. It is not possible to have both characteristics.

The centrifugal sedimentation method referred to here is a measurement using a disk centrifage manufactured by Joyce Leble, which takes advantage of the fact that particles with a large Stokes diameter diffuse quickly to detect sedimented particles. This method is to find the size of .

FIG. 1 shows an example of an aggregate distribution curve of carbon black used in the present invention. In the figure, m is the aggregate distribution curve of the carbon black used in the present invention, where the low aggregate distribution curve is indicated by ml, and the high aggregate distribution curve is indicated by m2. In this way, by dividing the two-peak aggregate distribution into each multiple distribution,
Mode diameter of each distribution (Dst), distribution part (ΔDst)
can be easily determined.

The rubber composition of the present invention contains 30 parts by weight of carbon black having the properties (a) to (C) above per 100 parts by weight of rubber.
~80 parts by weight.

As the rubber, various rubbers commonly used as rubber for tires, belts, and hoses can be used, such as natural rubber, styrene-butadiene copolymer rubber, polybutadiene rubber, synthetic polyisoprene rubber, and butyl rubber.

If the blending ratio of carbon black is less than 30 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 80 parts by weight, the desired low heat build-up rubber will not be obtained. 30 to 8 because the composition cannot be obtained.
Must be within 0 parts by weight.

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.

Examples and Comparative Examples Various rubber compositions (Examples 1 to 2, Comparative Examples 1 to 5) were prepared with the formulation contents shown in Table 1 below (all parts by weight and components other than carbon black are the same). .

The properties of each carbon black used in this case are shown in Table 1.The property values were measured using the following measurement method (1).
) to (5).

(mnitrogen specific surface area.

ASTM-03037-78 “5 standard Me
thods of Testing Carbon B
rack-5surface Area by Nitr
on'' Method C to ogen8dSorpt.

(2) Amount of iodine adsorption.

JIS K 622H1982) r Carbon blank test method for rubber J 6.1.1.

(3) DBP oil absorption amount.

According to JIS K 6221 (19B2) r Carbon black test method for rubber J 6.1.2 +1) A method.

+4) 24M4DBP oil absorption.

According to 8 STM-03493.

(5) Particle aggregate distribution half width (ΔDst).

The measurement was carried out by centrifugal sedimentation method using a disk centrifugation manufactured by Joyce Lebre in the following manner.

That is, carbon black dried and precisely weighed according to JIS K 622H1982) 5 method was added to a 20% ethanol aqueous solution, and the carbon black concentration was adjusted to o, oo.
s weight %, and then sufficiently dispersed with ultrasonic waves to prepare a sample. On the other hand, increase the rotation speed of the disk centrifuge to 8
Set to 000 rpm+, spin liquid (distilled water) 10 m
1 to this disk centrifuge, then 0
．． 5- Buffer solution (20% ethanol aqueous solution)
was injected. Next, a sample solution of 0.5 to 1.0-
was added with a syringe to start centrifugal sedimentation, and an aggregate distribution curve as shown in FIG. 1 was created by photoelectric precipitation.

Dst and ΔDst were determined from this curve.

Table 1 shows the vulcanized physical properties of the rubber composition. These vulcanized physical properties are the results of evaluating the viscoelastic properties and Lambourn abrasion of the vulcanized product obtained by kneading a rubber composition containing various carbon blacks and vulcanizing it at 148°C for 30 minutes. It is.

Regarding tanδ, which is an alternative index of exothermicity, a viscoelastic spectrometer (manufactured by Iwamoto Seisakusho ■) was used at a temperature of 10
The values measured at 0° C., distortion rate of 10±2%, and frequency of 20 Hz were used.

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. At this time, a slip is caused between the test piece and the test piece, and the amount of wear of the test piece per unit time is measured. It is expressed as an index with Formulation 1 set as 100. The larger the value, the better.

From Table 1, rubber compositions according to the present invention (Examples 1 and 2)
are the conventional products 5AF (NIIO) and 15AF (N22
Rubber composition containing grade 0) hard carbon black (
It can be seen that while having the wear resistance of Comparative Examples 1 and 2), tan δ, which is an alternative index of heat generation, is maintained at a low level.

Comparative example 4 is a blend of conventional varieties (SAP/HAF =
50% 150%). It can be seen that this rubber composition maintains low heat build-up, but its abrasion resistance is significantly lower than that of the present invention.

〔Effect of the invention〕

As described 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 that is excellent in wear resistance and low heat build-up. This rubber composition is extremely effective when used as tread rubber for tires, especially tires for large vehicles and tires for passenger cars.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between aggregate diameter and aggregate distribution of various carbon blacks.

Claims (1)

[Claims] Nitrogen specific surface area (N_2SA) 105 to 160 m^2/g
, 24M4DBP oil absorption 90-140ml/100g,
ΔDBP (DBP oil absorption amount - 24M4DBP oil absorption amount) ≦1
Carbon black, which is in the characteristic range of 6 ml/100 g and has a bimodal aggregate distribution that satisfies the following items by centrifugal sedimentation, is added at 30 to 8 mL per 100 parts by weight of rubber.
A rubber composition characterized in that it contains 0 parts by weight. (1) The most frequent mode diameter (Dst(2)) of the high aggregate distribution (second peak) is ≦130 mμ. (2) The difference between the most frequent mode diameter (Dst(1)) of the low aggregate distribution (first peak) and the most frequent mode diameter (Dst(2)) of the high aggregate distribution (second peak) is 50 mμ or less . (3) The ratio of the half-width of the low aggregate distribution (Dst(1)) to the half-width of the high aggregate distribution (Dst(2)) is 0.6 or less (
ΔDst(1)/ΔDst(2)≦0.6).