JPS594631A - Rubber composition - Google Patents

Abstract

PURPOSE:A composition, prepared by incorporating carbon black of high structure with carbon black of low structure with a raw material rubber, having a small hystresis loss and improved wet skid resistance, and suitable for treads in tires. CONSTITUTION:A rubber composition prepared by kneading 100pts.wt. raw material rubber selected from natural rubber, diene type rubber and halogenated butyl rubber with carbon black of high structure, e.g. carbon black N-110, having >=65mg/g iodine absorption and >=95cm<3>/100g dibutyl phthalate oil absorption and carbon black of low structure, e.g. carbon black N-219, having >=65mg/g iodine absorption and <=85cm<3>/100g dibutyl phthalate oil absorption at (40-90): (60-10) weight ratio to make 30-60pts.wt. total amount thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rubber composition that can be used in a low frequency range, that is, from 1 to 40 Hz, particularly from 10 to 40 Hz, by blending a high structure carbon plaque and a low structure carbon black in a specific amount. The present invention relates to a comb composition having low hysteresis loss at around 20 Hz and excellent wet skid resistance.

In recent years, there has been a push to reduce dynamic hysteresis losses in vulcanized rubber used in the tread portion of pneumatic tires in conjunction with the desire to develop low rolling resistance tires.

The vulcanized rubber in this tread is related to wear resistance and exercise performance, so a large amount of highly reinforcing carbon black (15 to 30 voz% of the vulcanized rubber) is used as a filler. Therefore, there is a problem in that the energy loss from the vulcanized comb in the tread portion during dynamic conditions is large, and rolling resistance cannot be reduced.

Recently, there has been a strong demand for tires with significantly reduced rolling resistance, and efforts are being made to reduce the amount of reinforcing carbon black to meet this demand, but tires still do not have sufficiently low rolling resistance performance. In the case of octopus, there is also a problem with the reinforcing properties of the vulcanized rubber.

Further, even if the transfer resistance is significantly reduced, it is not preferable if other properties such as wet braking performance and wear resistance are impaired.

The energy loss characteristics of vulcanized rubber corresponding to transfer resistance are around 10 to 20 Hz as a frequency, 30 to 60 degrees Celsius as an ambient temperature, and 1 to 10% of dynamic strain with a center of 5%. Correspondingly, the lower the value of this loss factor (tan δ), the lower the transfer resistance. In addition, the wet braking performance of a tire is evaluated by measuring the wet skid resistance of vulcanized rubber, and the higher the wet skid resistance, the better the wet braking performance. Similarly, tire abrasion resistance is measured by a pico abrasion test of vulcanized rubber, and the smaller the wear loss, the better the abrasion resistance.

The present invention aims to provide a rubber composition that reduces hysteresis loss while maintaining a high level of vulcanization properties, particularly wet skid resistance, required for a rubber composition for treads, and provides a tire with reduced rolling resistance. Used for treads.

The present inventors have conducted research to reduce dynamic hysteresis loss without significantly changing the various performances required of the vulcanized rubber in the tread, and have developed a vulcanized rubber containing carbon black, which has particularly strong reinforcing properties. We investigated the mechanism by which hysteresis loss occurs in sulfur rubber.

The mechanisms by which this hysteresis loss occurs, which have been previously shown in various literature, include hysteresis loss caused by the raw material rubber, which is the main compounding agent that makes up the vulcanized comb, and carbon black. Although hysteresis loss was thought to be the cause of this loss, the present inventors investigated this mechanism in more detail and found that the following new mechanism is the main factor in practical vulcanized rubber for tread parts. Ta. In other words, vulcanized rubber containing highly reinforcing carbon black is subjected to dynamic strain conditions of 1 to 10% and frequency conditions of 1 to 10%.
Dynamic hysteresis loss when applying dynamic deformation around 40 Hz is mainly caused by energy consumption due to solid friction between carbon aggregates formed by aggregation of carbon black particles, and this is the cause of hysteresis loss. It has become clear that this occurs. After considering how to reduce this adjacency state that tends to cause solid friction between carbon aggregates, we found that it is possible to reduce the adjacency between carbon aggregates by blending two or more types of carbon black with significantly different sizes. The results showed that the dynamic hysteresis loss could be reduced more than expected, and the present invention was achieved. Note that solid friction can be evaluated by measuring the dynamic strain dependence of dynamic viscoelasticity (Rubber Chemistry and Technology, 51(3), pp. 437-523 (1978)).

That is, the present invention provides an iodine adsorption amount of 6 parts by weight for 100 parts by weight of a raw material comb made of at least one selected from natural rubber, diene-based synthetic rubber, and halogenated butyl rubber.
5 my/y or more, dibutyl phthalate) (DBP) oil absorption 95 tyri'/1001 or more carbon black and iodine plate coverage 65 m9/, i9 or more, dibutyl phthalate L/-) (DBP) oil absorption 85 cm3/ 100
,! The weight ratio of carpan black below i' is 40~
The rubber composition is characterized in that a total of 30 to 60 parts by weight is blended at a ratio of 90:60 to 1o.

The raw material rubbers used in the rubber composition of the present invention include Tetra, natural rubber, polyisoprene rubber, styrene-y'methanone copolymer rubber, polybutadiene rubber, etc. It is a blend of at least one kind selected from /I/rubber.

In the coating composition of the present invention, 30 to 60 parts by weight of carbon black are blended with respect to 100 parts by weight of raw rubber. If the amount of carbon black is less than 30 parts by weight, the hysteresis loss is reduced, but the wear resistance is significantly reduced to an unacceptable level. However, if it exceeds 60 parts by weight, the distance between the carbon aggregates becomes closer, resulting in increased hysteresis loss, which is not preferable.

In the present invention, the iodine adsorption amount is 65 my/g or more, D
Carbon black with a BP oil absorption of 95 Cm3/1001 or more (hereinafter referred to as high structure carbon black), such as carbon black N-110XN-220°N-2, N-330, N-339, N-347, etc. Amount 65 mg 7'μ or more, DBP oil absorption 85 cm
3/100! ! Hereinafter, it is essential to mix carbon black (hereinafter referred to as low structure carbon black), such as N-219, N-326, N-327, etc., in the above blending amount range, and the blending weight ratio is ,
The ratio of high structure carbon black to low structure carbon black is 40-90:60-10. As shown here, the undeposited amount is JIS K 6221
The adsorption amount (■) of iodine to carbon blank II was measured based on the regulations, and this value has an inverse correlation with the particle size constituting carbon black. That is, as the amount of undeposited particles increases, the particle size decreases.

The amount of unattached products is 65~/! ! If it is less than 65 to 90 my/, the wear resistance will be poor. For between 90 and 90, the carbon black content is suitable between 45 and 60 parts by weight, and 90 mg.
In order to reduce the transfer resistance when the amount of uncoated carbon black is 30 to 45 parts by weight, it is preferable to set the amount of carbon black in the range of 30 to 45 parts by weight. Also, 'I DBP oil absorption is JIS
Based on the regulations of K6221, carbon black 100I
This is a measurement of the oil absorption amount cm3 of dibutyl phthalate against carbon dioxide, and the value has a correlation with carbon aggregates (generally called strafture). In other words, as the DBP oil absorption increases, carbon aggregates develop to a greater extent. When only one type of carbon black is used, a larger DBP oil absorption is generally advantageous for wear resistance, but hysteresis loss tends to increase, while a smaller DBP oil absorption is disadvantageous for wear resistance. Hysteresis losses will be lower. However, the hysteresis loss can also be significantly reduced by blending a relatively small amount of low structure carbon black with high structure carbon black and incorporating the amount within a specific range into the comb composition. In this way, a special effect can be obtained when two types of carbon black with different DBP oil absorptions are blended, and it is surprising that a significant reduction in dynamic hysteresis loss can be obtained despite a slight decrease in wear resistance. Get results. Judging from this point, it is desirable to use the minimum amount of low structure carbon black, and it is necessary to mix it in a range of 10 to 60% by weight of the total amount of carbon black used.

Since the rubber composition of the present invention is used in the tread portion of a tire, it is necessary that the tire has good motion performance and ride comfort performance, and therefore, the JI
It is necessary that the hardness of the spring-type hardness is in the range of 55 to 70.

The present invention also includes a composition for tire treads, including:
Zinc oxide, stearic acid, anti-aging agent, extender oil, 1j before vulcanization acceleration, sulfur, etc. which are commonly blended in the rubber industry are blended in appropriate amounts.

The present invention will be specifically described below based on Examples and Comparative Examples. All formulations in Table 1 are parts by weight.

Examples 1 to 2 and Comparative Examples 1 to 3 The vulcanization accelerator, compounding ingredients other than sulfur, and raw rubber with the formulation shown in Table 1 were charged into a 1.8 t capacity Gunnoori Tizo mixer, and carbon The blank was mixed until the dispersion was uniform. Furthermore, a vulcanization accelerator and sulfur were kneaded and mixed into the mixture using a roll to prepare a vulcanizable comb composition.

This rubber composition was press-vulcanized at 148° C. for 30 minutes to prepare a sample for physical property measurement, and the vulcanized physical properties were measured and the results are shown in Table 1. The method for measuring the physical properties of vulcanization is as follows.

Vulcanized physical properties were measured in accordance with JIS K 6301. The vinyl abrasion test is expressed as an index based on ASTM D 2228, with the reciprocal of the abrasion loss of Comparative Example 1 being 100, and the higher the index value, the better the abrasion resistance. The loss coefficient (tan δ) was measured using a viscoelastic spectrometer (manufactured by Roki Seisakusho) in a shear type dynamic stimulation mode at 30°C, 60°C, and 100°C at a frequency of 20 Hz.

Measurement was performed using dynamic strain ±5 factors. Also, wet skiing.

The wet skid resistance was measured using a Pretty Sport Pull Skid Tester (manufactured by Stanley) and Safety Walk Outdoor Type B as the road surface, and expressed as an index with Comparative Example 1 set as 100. The higher the index value, the higher the wet skid resistance. indicates that the value is high.

As shown in Table 1, Examples and 2, which used both high-structure carbon black and low-structure carbon black, had better vulcanized physical properties such as modulus than Comparative Example 1, which used only high-structure carbon black. changes only slightly, and the pico wear index also shows a tendency to gradually decrease, but within an acceptable range. On the other hand, tan δ, which is an index of dynamic energy loss, is rapidly decreasing. Wet skid resistance is also improved by incorporating low structure carbon black.

In Comparative Example 2 in which the proportion of low structure carbon black was increased, the tan δ was lowered, but the pico abrasion index was significantly lowered, causing a problem in terms of wear resistance. Comparative Example 3, in which only low structure carbon black was used, was not preferred because the pico wear index further decreased.

Next, the frequency range of the dynamic stimulation in which the rolling resistance of the tire occurs is 1 to 40 Hz, particularly 10 to 20 Hz, and the dynamic strain range is in the range of ±0.2 to ±10%. In this range of stimulation conditions, solid friction caused by adjacent carpin aggregates in the rubber composition, the so-called Payne effect, occupies a major part. In order to evaluate what kind of carbon black is effective in reducing the solid friction of this carbon aggregate, the dynamic strain dependence of the dynamic viscoelasticity of Examples 1 to 2 and Comparative Examples 1 to 3 was first examined. Figure 1 and 2
A comparison is shown in the figure. The dynamic viscoelasticity was determined using a shear-type dynamic stimulation mode at a frequency of 20 H at 30°C and 100°C.
z 1 Measurements were made at dynamic strains of 0.2 inches, 0.5 inches, 1 inch, 2 degrees, 5 inches, and 10 inches.

As can be seen from FIGS. 1 and 2, the jan δ values show almost the same results as shown in Table 1 over a wide dynamic strain range.

As explained above, the rubber composition of the present invention, in which high structure carbon black and low structure carbon black are blended in specific amounts, has a significantly lower loss factor, but has no effect on wet skid performance. I haven't received it. Moreover, since it does not significantly impair other vulcanization properties, it is widely used as a rubber composition for tire treads with reduced rolling resistance.

[Brief explanation of drawings]

Fig. 1 is a graph showing the relationship between dynamic strain @) and tan δ at 3030°C in Examples 1 to 2 and Comparative Examples 1 to 3, and Fig. 2 is a graph showing the relationship between dynamic strain @) and tan δ at 100°C in Examples 1 to 2 and Comparative Examples 1 to 3. Graph showing the relationship between dynamic strain) and tan δ. In addition, in FIG. 1 and FIG. 2, 1 is Comparative Example 1, and 2 is Example 1.
．． 3 represents Example 2, 4 represents Comparative Example 2, and 5 represents Comparative Example 3, respectively. Patent applicant: Yokohama Co., Ltd. Representative Patent Attorney: Tatsuo Ito Representative Patent Attorney: Tetsuya Ito

Claims (1)

[Claims] For 100 parts by weight of raw rubber consisting of at least one selected from natural rubber, diene-based synthetic rubber, and 7'S-rokened butyl rubber, the amount of iodine plate adhesion is 65 m9/I or more, and the oil absorption amount of dibutyl phthalate is 956 n3. A total of 30 to 60 parts by weight of carbon black with an iodine number of 659'I or more and a dibutyl phthalate oil absorption of 85i/100E or less in a weight ratio of 40 to 90:60 to 10. A rubber composition characterized by: