JPH10231384A - Rubber composition for studless tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition enhanced in frictional forces on ice or snow roads and improved in performances on the ice or snow roads by compounding a dienic rubber with activated carbon particles having a specific average particle diameter in a specific ratio. SOLUTION: This composition is obtained by compounding (A) 100 pts.wt. of a dienic rubber (e.g. the blend of >=40 pts.wt. of natural rubber with one or more other dienic rubbers) with (B) 1-10 pts.wt. of activated carbon particles (e.g. coconut husk activated carbon) having an average particle diameter of 30-500μm and preferably an inner specific surface area of 1000-3000m<2> /g and, if necessary, (C) a reinforcing filler such as carbon black having a nitrogen specific surface area N2 SA of 70-200m<2> /g and a DBP oil-absorbing amount of 80-150ml/100g, sulfur, a vulcanization accelerator, a filler, a softening agent, a plasticizer, a low mol.wt. polymer (weight-average mol.wt. of 1000-60000), a low hardness rubber, short fibers, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rubber composition for a studless tire, and more particularly to a rubber composition for a studless tire having improved frictional force on an icy road.

[0002]

2. Description of the Related Art Spike tires and chains attached to tires have been used for running tires on icy and snowy roads, but these cause environmental problems such as generation of dust.
Studless tires have been developed as alternative tires for running on snowy roads. Studless tires are generally reduced to about 1/10 of the coefficient of friction on a normal road surface and become slippery on a frozen road surface. Therefore, the studless tire is devised from the material and design aspects to increase the frictional force of the tire. In terms of materials, rubbers having good low-temperature properties that are hard to be hardened even at low temperatures have been developed. In addition, various improvements in frictional force on ice by blending special additives have been proposed, but compared to spiked tires, the performance of studless tires on icy and snowy roads is not yet sufficient, and further improvement is desired. .

[0003]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a rubber composition for a tire tread capable of improving the performance of a studless tire on ice and snow by increasing the frictional force of the studless tire on ice and snow. It is in.

[0004]

According to the present invention, an average particle size of 30 to 500 .mu.m per 100 parts by weight of diene rubber is used.
The present invention provides a rubber composition for a studless tire, comprising 1 to 10 parts by weight of activated carbon particles of

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, as a rubber composition used for a studless tire, particularly a tread portion thereof, a diene rubber or carbon black generally used in a conventional rubber composition for a studless tire is used. (Preferably nitrogen specific surface area N ₂ SA 70 to ²⁰⁰ m ² / g,
DBP oil absorption: 80 to 150 ml / 100 g), and further, by blending activated carbon particles having an average particle size of 30 to 500 μm with a rubber composition containing an inorganic reinforcing filler such as silica and carbon carbide, oil and the like. As a result, the water removal / drainage effect due to the increase in the height and the edge effect (digging effect) due to the mixing of the hard substance can be obtained, and the frictional force on the icy and snowy road can be increased.

Examples of the diene rubber used in the present invention include natural rubber (NR), polyisoprene rubber (IR), and various styrene-butadiene copolymer rubbers (S
BR), various polybutadienes (BR), and the like. In particular, in consideration of low-temperature performance, it is preferable to use a blend rubber with another diene rubber containing at least 40 parts by weight of natural rubber.

According to the present invention, the diene rubber 100
By mixing 1 to 10 parts by weight, preferably 1 to 5 parts by weight, more preferably 1 to 3 parts by weight of activated carbon particles having an average particle size of 30 to 500 μm with respect to parts by weight, irregularities are formed on the rubber surface, The effect of trapping or removing water generated on the road is obtained, and the frictional force on the snowy and snowy road is improved by the cohesive friction. The blending amount of activated carbon particles is diene rubber 100
Less than 1 part by weight per part by weight is not preferable because surface irregularities required for trapping or removing water are not formed.
Exceeding 0 parts by weight is not preferable because the contact area of the tire surface with the ice and snow road surface is reduced and the frictional force on ice is reduced.
If the average particle size of the activated carbon used is less than 30 μm, surface irregularities required for trapping or removing water are not formed. Conversely, if the average particle size exceeds 500 μm, the ground contact area decreases and the frictional force on ice decreases, which is not preferable.

[0008] The activated carbon compounded in the rubber composition of the present invention is activated carbon conventionally used as an adsorbent or a catalyst, particularly woody activated carbon such as wood, palm nuts, sawdust and charcoal, particularly coconut shell activated carbon. These activated carbons which can be preferably used are those obtained by carbonizing the above-mentioned woody raw material, then activating, purifying and pulverizing it. The activated carbon obtained is remarkably porous and has an internal specific surface area of 1,000.
It is about 0 to 3,000 m ² / g.

The rubber composition for a studless tire according to the present invention comprises, in addition to a diene rubber, a tire comprising a reinforcing filler, sulfur, a vulcanization accelerator, an antioxidant, a filler, a softener, a plasticizer, and the like. Additives and special compounding agents that are generally compounded for low-molecular-weight polymers (for example, a weight-average molecular weight of 1,000 to 6) not as a rubber component but as a plasticizer.
000), low-hardness rubber, short fibers, and the like. Such a compound can be vulcanized by a general method to produce a tire tread. The amount of these additives may be a general amount.

[0010]

EXAMPLES The present invention will be further described below with reference to Examples and Comparative Examples, but it goes without saying that the scope of the present invention is not limited to these Examples.

Examples 1 to 5 and Comparative Examples 1 to 3 The respective components were blended according to the blending contents (parts by weight) shown in Table I, and the raw material rubber and the blending agent except for the vulcanization accelerator and sulfur were used.
After mixing with a 7 liter Banbury mixer for 5 minutes,
The mixture was kneaded with a vulcanization accelerator and sulfur with an 8-inch test kneading roll machine for 4 minutes to obtain a rubber composition. These rubber compositions were press-vulcanized at 160 ° C. for 20 minutes to prepare target test pieces, and the friction coefficient on ice was measured. The results of a friction test on ice of the obtained vulcanized product are as shown in Table I.

[0012]

[Table 1]

The friction test on ice is performed by detecting a resistance (frictional force) when a rubber test piece is pressed with a constant load on an ice surface placed in a temperature-controlled constant temperature chamber and slid at a constant speed. Done. The friction test conditions on ice shown in the examples and comparative examples were as follows: ice temperature −3 ° C., speed 10 to 25 km.
/ Hr, a load is applied to the test piece so that the contact pressure is 3 kg / cm ² . The results are as shown in Table I. In addition, the result was shown as an index with the value of Comparative Example 1 being 100.

[0014]

As described above, by adding a specific activated carbon to a diene rubber according to the present invention, a remarkable improvement in frictional force on ice is recognized, and the rubber composition is most suitable as a rubber composition for a studless tire.

Claims (2)

[Claims] 1. A rubber composition for a studless tire comprising 100 parts by weight of a diene rubber and 1 to 10 parts by weight of activated carbon particles having an average particle size of 30 to 500 μm. 2. The activated carbon is coconut shell activated carbon.
Or the rubber composition according to 2.