JPH03210342A - Tread rubber of studless tire - Google Patents

Abstract

PURPOSE:To prepare the title rubber excellent in the braking and driving performance on a frozen road by using a sponge rubber made from a rubber compsn. obtd. by compounding a raw material rubber with leather particles and specific vegetable particles in a specified ratio to make at least the surface layer. CONSTITUTION:At least the surface layer is made up of a sponge rubber made from a rubber compsn. prepd. by compounding 100 pts.wt. raw material rubber comprising a natural and/or diene rubber, 3-30 pts.wt. leather particles (e.g. particles of hide), and 3-30 pts.wt. vegetable particles obtd. by grinding seed shells or fruit pits (e.g. particles of walnut shell).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tread rubber for a studless tire suitable for mounting on a vehicle that runs both on roads with icy surfaces and on roads under normal conditions.

[Prior art] In the past, spiked tires with many hard metal studs planted in the tread were commonly used for vehicles that often drive on icy and snowy roads, but as the number of vehicles increased, spiked tires These studs stick into the road and dig up the surface of the road, resulting in an increase in dust particles and road damage, which has become a social problem. A so-called studless tire has been proposed, which can be used on icy and snowy roads without any need for protection.

Incidentally, the tread of a studless tire uses a rubber composition that increases the coefficient of friction between the tread, ice, and the road surface. As a way to increase the coefficient of friction,
As described in JP-A-60-137946, a rubber composition containing wear-resistant, high-hardness particles such as alumina with a particle size of 0.01 to 0.5 mm is used, and alumina A method of protruding from the tread surface to form fine irregularities on the tread surface to increase the coefficient of friction, or a low solidification temperature oil or cold-resistant plastic such as polyester described in JP-A-60-137945. Attempts have been made to use a rubber composition that has a low hardness and shows little change in hardness even when the temperature is lower than 1 freezing point by blending a large amount of the agent.

JP-A-62-283001 and JP-A-63-9040
No. 2 has a foaming ratio of 1 to 100% as an improvement on the above method.
A method of using foamed rubber for the tread has been proposed.

[Problems to be Solved by the Invention] However, in the method of blending alumina granules, the slip resistance cannot be improved unless the blending amount is increased.

However, there is a problem in that when a large amount is added, the wear resistance is significantly reduced. Furthermore, in the method of lowering the hardness by blending a low freezing point oil or a cold-resistant plasticizer, the wear resistance decreases, and the hardness changes during long-term use, resulting in a decrease in the slip resistance.

Fine irregularities occur on the tread surface of tires using rubber compositions containing alumina granules or foamed rubber for the tread rubber, and these irregularities are one of the factors that increase the coefficient of friction on the tread surface and improve slip resistance. It is believed that By the way, tires generate heat while driving, and the internal temperature is 0.
℃ or higher, the surface of the compacted snow covering the road melts due to the simultaneous action of this heat and the ground pressure of the tire or sunlight, forming a thin film of water on top of it, and this water acts as a lubricant, causing the tread surface to melt. There is a problem that the anti-slip effect is reduced due to the uneven surface.

An object of the present invention is to provide a tread rubber for a stud-type tire that uses new means other than the above-mentioned methods to improve slip resistance, and has improved slip resistance through the interaction of these measures.

[Means for solving the problem] The inventors conducted research focusing on the fact that animals can pull oak without slipping on ice and snow surfaces, and found that leather has a special effect that makes it difficult to slip on ice. The present invention was developed based on the discovery that a rubber composition containing granulated leather particles retains the anti-slip effect of leather and becomes difficult to slip on ice. Furthermore, the tread is made from foamed rubber made from a rubber composition containing granules made by crushing the shells of seeds such as walnuts and camellias, or the kernels of peaches and plums, which have water absorbency and are harder than water. The present invention is based on improving the slip resistance on ice by configuring this structure.

That is, this invention provides 100 parts by weight of one or more raw material rubbers selected from natural rubber and diene-based synthetic rubber, and 3 to 30 parts by weight of leathery granules and pulverized seeds or fruit kernels. This is a tread rubber for a studless tire, which is a foamed rubber composition containing 3 to 30 parts by weight of vegetable granules, and has at least the surface layer portion.

Raw material rubbers used in the present invention include natural rubber, isoprene rubber with a glass transition temperature of 150°C or less, butadiene rubber in styrene, butadiene rubber, butadiene-isoprene copolymer, and synthetic rubber of butadiene-isoprene-styrene copolymer. selected from the group. Small amounts of halogenated butyl rubber, high styrene content styrene-butadiene copolymers, and nitrile rubber may also be used as modifiers.

In the present invention, in addition to the above-mentioned components, known vulcanizing agents, vulcanization accelerators, vulcanization accelerating aids, softeners, reinforcing agents, foaming agents, foaming aids, and anti-aging agents are added, and if necessary, vulcanization sulfur retarder,
A tackifier is added. Carbon black, silica, and clay are used as reinforcing agents, and the preferable range is 20 to 100 parts by weight of carbon black, and 5 to 20 parts by weight when using silica, per 100 parts by weight of raw rubber.

[Function] Since the present invention is as described above, even if a thin film of water is formed on the compacted snow due to the melting point drop due to the heat of the tire that has become over 0°C due to sunlight or heat generation while driving and the ground pressure, Even if the tires are floating on a film of water,
The leathery granules exposed on the tread surface have a high affinity for water and are easily wetted, so they break this water film and bring the tire surface into contact with the ice surface, making it easier to get wet with water than previously used. It is thought that this improves slip resistance, which could not be achieved with alumina granules.

Therefore, the larger the particle size of the leathery granules is, the better the action of breaking this water film is, but if the particle size is too large, the workability in the tread manufacturing process will be poor, and the water contained in the leather will be released during vulcanization. The average particle size is preferably in the range of 0.01 to 0.5 mm, since the crushed leather material foams and becomes brittle, and in particular, a particle size exceeding 0.5 mm is not preferable because it interferes with the vulcanization reaction of the rubber. Furthermore, if there is a large amount of water contained in the leather, it will not volatilize during mixing and will remain, and for the purpose of preventing foaming during vulcanization, the moisture content of the leather is preferably 25% or less of the weight of the leather.

It is preferable to mix 3 to 30 parts by weight with respect to 100 parts by weight of raw rubber; if it is less than 3 parts, the anti-slip effect will be small;
If the amount exceeds 0 parts by weight, the effect commensurate with the increased amount will not be obtained even if the amount is increased, and the wear resistance will deteriorate on the contrary, which is not preferable.

Since the action of the present invention takes advantage of the hydrophilic properties of leather, it is not limited to granules made by physically crushing leather, but may also be made into granules by physicochemical treatment, such as gelatin granules.

On the other hand, on the surface of compacted snow, water that melts due to solar radiation or a rise in temperature seeps into the compacted snow and refreezes at night, but when this water turns into ice, its volume increases, so it repeats melting and freezing. During this process, the surface of the compacted snow becomes uneven. Since the tread rubber of the present invention is foamed rubber, it can be easily compressed and deformed, and the tread surface deforms according to the unevenness of the road surface, increasing the contact area with the road surface and increasing the frictional resistance of the tire as a whole. growing.

Furthermore, when the tread surface is compressed when it makes contact with the ground, the hardness of the plant-based granules is greater than the hardness of the compacted snow surface, so they protrude from the tread surface, destroying the air bubbles contained in the compacted snow surface, forming minute irregularities, and compressing the road surface. This increases the coefficient of friction of the tread and subsequently creates a large frictional resistance between the tread surface and the tread surface.

The true specific gravity of the tread rubber composition is do, and the apparent specific gravity of the tread surface layer corresponding to 30% of the groove depth in the tread pattern is d.
When the foaming ratio expressed as (do/d-1) x 100% is smaller, the smaller the expansion ratio, the less the slip resistance improvement effect (because the compression deformation is smaller), the larger the foaming ratio, the lower the apparent wear resistance. decreases, so in practice the foaming ratio is 0.1 to 2.
0%, preferably in the range 1-5% of foamed rubber is used.

The size of the vegetable granules is preferably approximately the same size as air bubbles in compacted snow, or slightly smaller, with an average particle size of 0.01 to 0.
．． A 5mm one is used. If the particle size is smaller than 0.01 mm, the effect of improving slip resistance will be small, and if it is larger than 0.5 mm, the effect of improving slip resistance will be small and wear resistance will decrease. The greater the amount of compounding, the greater the effect of improving slip resistance, but as the amount of combined columns increases, workability in the tread rubber manufacturing process tends to decrease, and wear resistance tends to decrease. It is preferably 3 to 30 parts by weight. From the viewpoint of abrasion resistance and workability, the total amount of the crushed leather and vegetable granules is preferably 6 to 40 parts by weight.

In addition, vegetable granules are hydrophilic and easily wetted by the water in the water film, so they have a greater effect on breaking the water film than water-repellent granules such as alumina and silica sand, and are effective in improving slip resistance on wet compacted snow surfaces. is large.

[Example] Examples and comparative examples will be described below. Parts simply indicate parts by weight. Note that this invention is not limited to the following examples.

30 parts of natural rubber, 70 parts of solution polymerized styrene-butadiene rubber
part, zinc white 3 parts, stearic acid 2 parts, anti-aging agent (N-
(1,3-dimethyl-butyl)-N-phenyl-P-
1 part of vulcanization accelerator (N-cyclohexyl-2-benzothiazyl-sulfenamide)
．． 4 parts of sulfur, 2 parts of paraffin wax, 1 part of paraffin wax, and 50 parts of naphthenic process oil, the ingredients shown in Table 1 were added and mixed according to the usual method, and a tire size 185/70R13 for passenger cars was prepared. Radial tires were manufactured and subjected to ice braking tests and wear tests. Table 1 shows the results.

In the ice braking test, the test tire was mounted on the test vehicle, and the test vehicle was driven at 40 km/h on a compressed snow road, and the short distance it skidded from the point where the brake was applied to the stop was measured. expressed as an index (larger is preferable).

Note that the temperature during the test was -7 to -8°C.

In the wear test, the amount of wear was determined by running on a dry road surface for 110,000 km, and the amount of wear was determined from the change in the groove depth of the tread pattern, and the reciprocal of the amount was expressed as an index with Comparative Example Tire 11 set as 100 (the larger the number, the better the wear resistance).

Leather granules 1: Mechanically crushed cowhide with an average particle size of 0.1 mm.

Leather granules 2: Gelatin granules with an average particle size of 0.05m
m.

Leather granules 3: Crushed cowhide, particle size 0.4m
Exceeds m.

Walnut shell granules: Mechanically crushed, average particle size 0, 1mm (Note) Comparative Example Tire 5 was not heat cured.

Example Tire 1.2.3 and Comparative Example Tire 9 in Table 1.
As is clear from No. 10, the braking performance of tires without leathery granules is poor. Also, Example Tire 1.2
．． 3 and Comparative Example Tire 7 show that the braking performance of tires without walnut shell granules is poor, while the braking performance of tires containing both leathery granules and vegetable granules is good. .

On the other hand, from Example Tire 1.2.3 and Comparative Example Tire 6, the braking performance improves with increasing blending amount of leathery granules; As the braking performance increases, the content deteriorates and the braking performance does not reach saturation, so it is preferable to use up to 30 parts from the viewpoint of braking performance and abrasion resistance.

From Example Tire 1.3 and Comparative Example Tire 8, the walnut shell granules had the same tendency as the leathery granules;
It is preferable to keep it up to 100%.

[Effects of the Invention] As explained above, according to the present invention, braking performance and driving performance on icy road surfaces can be significantly improved without substantially impairing wear resistance.

Claims (1)

[Claims] (1) 3 to 3 parts by weight of leathery granules per 100 parts by weight of one or more types of raw material rubber selected from natural rubber and diene-based synthetic rubber
A stud dress characterized in that at least the surface layer is made of foamed rubber of a rubber composition containing 30 parts by weight and 3 to 30 parts by weight of vegetable granules obtained by crushing seed shells or fruit kernels. Tire tread rubber.