JP2758462B2 - Rubber composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a rubber composition used for tires, hoses, conveyor belts, and the like, and particularly requires high reinforcing properties and low heat generation in a high-severity region. It relates to an improved rubber composition.

(Prior art) In rubber compounds such as treads of truck and bus tires that require extremely high abrasion resistance, highly reinforcing carbon black such as ISAF has been used in the past.
As the economic demands of the market increase, obtaining even higher abrasion resistance has become an important point in determining the commercial value.

Conventional methods for improving abrasion resistance include increasing the amount of carbon black, reducing the amount of softeners such as process oils, changing the amount of compounding, or further reinforcing the use of ISAF carbon black. SA with excellent properties
For example, use of F-grade carbon black has been performed.

Techniques for improving low heat build-up include decreasing the amount of carbon black, increasing the particle size, and increasing the DCF (Disc Ce).
ntrifuge) broadening of the aggregate size distribution in the measurement.

(Problems to be Solved by the Invention) However, increasing / decreasing the amount of carbon black, changing the grade, and controlling the aggregate size distribution cause a trade-off relationship between the reinforcing property and the low heat build-up. In other words, it is possible to increase the reinforcing property to a certain extent by increasing the amount of carbon black, but on the contrary, it results in lowering the low heat build-up. On the other hand, when the amount of carbon black is reduced, the opposite phenomenon occurs. Further, when the carbon black is atomized, for example, when the carbon black is changed from ISAF to SAF, the reinforcing property increases, but the low heat build-up property decreases. Furthermore, broadening of the aggregate size distribution leads to lower heat generation, but conversely reduces the reinforcing property.

On the other hand, when the amount of the softening agent such as the process oil is reduced, both the reinforcing property and the low heat generation property are improved, but the workability is greatly reduced.

As described above, a rubber composition in which both the reinforcing property and the low heat buildup have been sufficiently improved has not been known.

Therefore, the object of the present invention is, particularly in a high-severity region,
An object of the present invention is to provide a rubber composition having improved reinforcing properties and low heat build-up.

(Means for Solving the Problems) As a result of intensive studies and studies to solve the above problems, the present inventors have found that the above problems can be solved by using carbon black satisfying specific characteristics requirements. As a result, the present invention has been completed.

That is, the present invention provides a rubber composition containing natural rubber and / or a diene-based synthetic rubber and carbon black,
The carbon black is represented by the following formula: TD / IV <0.52 (IV in the formula is a pore volume (cc) determined by a mercury porosimeter method.
/ 100g), TD indicates the volume (cc / 100g) of the pore that occupies the maximum peak of the pore distribution in the mercury porosimeter method)
The present invention relates to a rubber composition which satisfies a characteristic condition represented by the following formula:

In the present invention, the carbon black adsorbed amount of cesyltrimethylammonium bromide (CTAB value) is 10%.
In 5 m ² / g or more and a dibutyl phthalate compressed oil absorption ₍₂₄ M
₄ DBP oil absorption) is preferably 85 ml / 100 g or more.

Examples of the diene-based synthetic rubber which is one of the rubber components used in the present invention include synthetic polyisobrene rubber, polybutadiene rubber, styrene butadiene rubber, butyl rubber and the like, and these may be used alone or in combination of two or more. Can be used.

Next, a method of measuring mercury porosimeter for carbon black, which is a key of the present invention, will be described.

First, as a device to be used, a mercury porosimeter (Pore Seizer 9310) manufactured by Micromeritics Co., Ltd. is prepared, and 0.2 g of pellet-like carbon black is loaded in a dedicated cell (3 ml). After that, pressure 0.17 ~ 327kg / cm ² (16 ~ 30,000 1b
Inject mercury within the range of / inch ² ). The corrected value of the amount of mercury injected (cc) within this range per 100 g of carbon black is defined as IV (cc / 100 g). In addition, in this injection, there is a position where the injection amount of mercury sharply increases. For example, IRB
(Industry Reference Black) # 6
The peak position exists at 465Å. This position is measured in 5 ° units in diameter. Further, from this point, the amount of mercury injected until the void diameter becomes 50 ° is measured (this value is ΔIV for convenience). Here, twice the value of ΔIV (2 × ΔI
V) is defined as TD.

(Operation) In the present invention, it is necessary to use carbon black whose IV and TD defined by the mercury porosimeter method satisfy the following formula: TD / IV <0.52. This means that the relative amount of minute voids is reduced.

That is, by paying attention only to the pore diameter of carbon black and shifting the relative amount of minute pores to the “large pore diameter” side compared to the conventional product (see FIG. 2), the rubber composition accompanying the decrease in dispersibility Although it has been proposed that a decrease in abrasion resistance can be effectively prevented (Japanese Patent Laid-Open No. 64-1362), in the present invention, the amount of peak voids, that is, minute voids, is relatively reduced. (See FIG. 1), it is intended to obtain low heat generation based on dispersibility, workability, and further improvement in wear resistance by balancing with aggregates. The relatively increased larger voids (the IV-TD region in the above definition) have a greater contribution to reinforcing properties, particularly under large deformation.

As described above, in the present invention, low heat generation is achieved by controlling the connected state of the carbon black particles, instead of the conventional rough measurement methods such as the surface area of nitrogen adsorption (N ₂ SA) and the oil absorption of dibutyl phthalate (DBP). It solves the trade-off between sex and reinforcement. The value of 0.52 in the above equation is a numerical value obtained empirically.

In the present invention, the reason why the CTAB value is preferably 105 m ² / g or more is that when the CTAB value is smaller than this, the reinforcing property is reduced and the effect of the present invention is hardly exhibited. Further, the reason why the oil absorption of ₂₄ M ₄ DBP is preferably 85 ml / 100 g or more is that if the oil absorption is smaller than this value, the dispersibility and reinforcement in rubber are not sufficiently improved, and the effect of the present invention is not improved. This is because it is difficult to appear.

(Examples) Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

First, a method for measuring the characteristic value of carbon black and a method for measuring physical properties of rubber will be described.

Method for measuring characteristic value of carbon black The mercury posimeter method is as described above.

CTAB value conforms to ASTM D3765-85, also ₂₄ M ₄ DBP value A
Based on STM D3493-84.

Rubber physical property measuring method The Mooney viscosity was based on JIS 6300-1974.

The reinforcing property (wear resistance index) was calculated by the following formula by measuring the wear loss amount using a Lambourn tester.

The slip ratio was changed by changing the rotation speed of the sample (50%, 20%). It is considered that the higher the slip ratio, the higher the severe abrasion.

The low heat build-up (Tan δ) was measured using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. under the conditions of a tensile dynamic strain of 1% and a frequency of 50 Hz at 25 ° C. The test piece is about 2m thick
m, width 5 mm, using a slab sheet, the distance between the samples was 2 cm, and the initial load was 100 g. The lower the value of Tan δ obtained here, the lower the heat generation.

Rubber compositions using various carbon blacks having different properties in the compounding systems shown in Table 1 below were kneaded with a Banbury mixer, and the Mooney viscosity was measured first. The vulcanizate (vulcanization conditions: 145 ° C. × 30 minutes) was measured and evaluated for its wear resistance index and low heat build-up (Tan δ). The results obtained are shown in Tables 2 to 5 below.

As reference values, the mercury porosimeter characteristics and colloidal characteristics (CTAB value, ₂₄ M ₄ DBP value).

From the results of Tables 2 to 5, the rubber compositions using carbon black satisfying the characteristic requirements of the present invention (Examples 1 to 7)
Indicates that the vulcanizate is superior in wear resistance, particularly in the high-severity region, and low heat build-up as compared with those not satisfying the requirements (Comparative Examples 1 to 4).

(Effects of the Invention) As described above, in the rubber composition of the present invention, carbon black is used as a reinforcing agent in consideration of the connection of particles satisfying specific requirements. Reinforcement (abrasion resistance) and low heat generation were significantly improved.

For this reason, the rubber composition of the present invention is used not only for treads of various tires but also for various rubber products such as conveyor belts and hoses, in particular, to improve the abrasion resistance and low heat build-up of the products, and thus to improve the products. Performance can be improved.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an improvement in performance based on a relationship between a peak void amount and a large void diameter conventionally devised, and FIG. 2 is a diagram showing a relationship between a peak void amount and a large void diameter in the present invention. It is explanatory drawing which shows the performance improvement based on.

Claims (2)

(57) [Claims] 1. A rubber composition containing natural rubber and / or a diene-based synthetic rubber and carbon black, wherein the carbon black is represented by the following formula: TD / IV <0.52 (where IV is the pore volume by a mercury porosimeter method) cc
/ 100g), TD indicates the volume (cc / 100g) of the pore that occupies the maximum peak of the pore distribution in the mercury porosimeter method)
A rubber composition characterized by satisfying the characteristic condition represented by: 2. The carbon black has a cesyltrimethylammonium bromide adsorption amount (CTAB value) of at least 105 m ² / g and a dibutyl phthalate compressed oil absorption ( ₂₄ M ₄ DBP oil absorption) of at least 85 ml / 100 g. 3. The rubber composition according to item 1.