JPH04123906A - Studless tire - Google Patents

Abstract

PURPOSE:To obtain a studless tire which is excellent in running performance on an ice and snow road and anti-wear performance even in the case of winter use after the elapse of one season by forming the surface and inner layers of a tread of severally different specified rubber compositions. CONSTITUTION:A studless tire has a tread 1 formed of an inner layer 2 and a surface layer 3, and the surface layer 3 covers wholly the inner layer 2, namely including the side of a tread groove 4. in this case, the surface layer 3 is formed of a rubber composition which is below 55 in its initial hardness and made by combining the 20-100 parts by weight of carbon black with the 100 parts by weight of a rubber mostly formed of a natural rubber or a diene series synthetic rubber having a glass transition temperature below -50 deg.C. On the other hand, the inner layer 2 is formed of a rubber composition which is made by combining the 20-100 parts by weight of the carbon black and the 3-30 parts by weight of granular material having leather quality or vegetation guality with the 100 parts by weight of a rubber having the natural rubber or the diene series synthetic rubber having the glass transition temperature below -50 deg.C as a main component.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to studless tires, particularly to improvements in their performance on icy and snowy roads and wear resistance.

[Prior Art] Studless tires are equipped with tread rubber that is flexible even at temperatures below freezing point in order to prevent slipping when driving on icy and snowy roads. By composing the tread rubber with a flexible rubber composition, it is possible to
This is because the red surface deforms, which increases the contact area with the road surface, increases frictional resistance, and improves performance on icy and snowy roads.

By the way, in order to improve performance on icy and snowy roads, natural rubber with a low glass transition temperature has been conventionally used as a rubber composition for the tread of studless tires, as disclosed in JP-A No. 60-31.546. , isoprene rubber, and butadiene rubber mixed with large amounts of softeners such as oil and low-temperature plasticizers have been proposed.

[Problems to be Solved by the Invention] However, this type of tread rubber composition contains a large amount of rubber composition acid compared to that used in the belt adjacent to the tread, the sidewall, or the carcass located below. As the softener gradually transfers to the belt, Zyduol, or carcass, which contains less softener, some of it evaporates, reducing the amount of softener in the tread rubber and increasing the hardness of the tread. A problem has arisen in which braking performance on the road deteriorates. This problem is caused by changing the tires once during the winter.
After a season of use, the problem appears when the blow rod is used in the winter after the second season.

On the other hand, in order to avoid an increase in tread hardness due to migration and disappearance of this softener, avoid using large amounts of softener and
Depending on the amount by which the softener content is reduced, the hardness -1
Another method to consider is to reduce the amount of carbon black that acts directly on the carbon black over a period of time, but in that case, workability and abrasion resistance will decrease, which is not preferred from a practical point of view.

An object of the present invention is to provide a studless tire that has good performance on icy and snowy roads and good wear resistance even when used in winter after the second season.

[Means for solving the problem] As a result of intensive studies to achieve the above objective, we found that the reason why the performance on icy and snowy roads deteriorates after the second winter season is due to the softening of the tread rubber during the first winter season. It is believed that the hardness of L.Red increases by 1-U as the amount of softener decreases, so this invention provides a soft rubber composition with a hardness of 55 or less (at 23° C.) in which the amount of softener decreases over time. The structure is such that the tread is placed on the surface layer of the tread for use in one winter season, and from the second season onwards, a method is adopted to ensure performance on icy and snowy roads by using the inner layer that appears as the surface layer wears away after one season of use. .

The inner layer is preferably a rubber composition containing leather and/or vegetable particles having an average particle diameter of 0.01 to 3 mm.

In this case, the leather used is from cows, horses, pigs, etc., and the plants used are seed shells, fruit kernels, etc., both of which have been ground into granules by a machine or the like. This is because leather has water-absorbing properties and has a special effect that makes it difficult to slip on ice and snow, and a rubber composition containing granulated leather particles retains the anti-slip properties of leather and becomes difficult to slip on ice and snow.

In addition, rubber compositions containing granules obtained by crushing the shells of seeds such as walnuts and camellia fruits, or the kernels of fruits such as peaches and plums, which are harder than ice, improve slip resistance on ice and snow.

If the average particle size of the granules is less than 0.01 mm, the anti-slip effect is small, and if it exceeds 3 wun, the granules tend to fall off from the tread surface, which is not preferred.

This invention relates to a tire whose tread has a two-layer structure of a surface layer and an inner layer. The rubber composition is made of a rubber composition with an initial hardness of 55 or less and contains 20 to 100 parts by weight of carbon black, and the inner layer is made of rubber 100 whose main component is natural rubber and/or diene-based synthetic rubber with a glass transition temperature of 50°C or less. Carbon black 20-100% by weight
Part by weight, granules consisting of leathery and/or vegetable matter 3 to 30
This is a studless tire characterized by being made of a composition containing parts by weight.

The raw material rubber used in the present invention is selected from natural rubber and diene-based synthetic rubber, and in the case of diene-based synthetic rubber, isoprene rubber, styrene-butadiene rubber, butadiene rubber, butadiene-isoprene copolymer with a glass transition temperature of 150°C or less. It is preferably selected from the group of synthetic rubbers including butadiene-isoprene-styrene copolymers.

Small amounts of halogenated butyl rubber, styrene-butadiene copolymers with high styrene content, and dilyl rubber may also be used as modifiers.

In the present invention, the above-mentioned raw material rubber is used for both the surface layer and the inner layer, but foamed rubber may be used for both or either of them. In this case, the tread surface is easily compressed and deformed in accordance with the unevenness of the snow-compacted road surface, increasing the contact area with the road surface and increasing the frictional resistance of the tire as a whole, which is preferable.

In the present invention, in addition to the components listed in -1-, known vulcanizing agents, vulcanization accelerators, vulcanization accelerators, softeners, reinforcing agents, and anti-aging agents are added, and if necessary, blowing agents and foaming auxiliaries are added. additives, vulcanization retarders, and tackifiers are added. Carbon black, silica, and clay are used as reinforcing agents, and raw rubber 100
Preferably, carbon black is 20 to 100 parts by weight, and silica is 5 to 20 parts by weight.

By the way, in this invention, a rubber composition that is soft even below the freezing point is placed on the surface layer of the tread so that it can be used in the winter season, and the thickness of the surface layer is increased in order to have a structure in which the performance is demonstrated in the inner layer from the second season onwards. The problem is how to set the thickness, but based on the knowledge that the tread of a studless tire for a passenger car usually wears down by about 1 mm after driving for 2000 to 3000 km, the thickness of the surface layer should be set to 1 to 1 mm of the tread groove depth. 30%, preferably 3-20%.

The hardness of the surface layer is desirably 55 or less at 23°C, because if the hardness is higher than 55, the performance on icy and snowy roads will be poor.

The amount of the leathery granules and vegetable granules in the rubber composition constituting the inner layer is preferably 3 to 30 parts by weight in total. This is because if the amount of granules blended is less than 3 parts by weight, there is little improvement in performance on icy and snowy roads, while if it exceeds 30 parts by weight, no commensurate improvement in performance can be obtained even if the amount is increased; This is not preferable because it reduces wear resistance.

[Function] This invention is as follows: - [Since this is the same as above, even if the amount of softener decreases over time during the first season of use after manufacturing the tire, a soft rubber composition with a hardness (23°C) of 55 or less. Since the surface layer made of material wears away with use, the hardness of the tread does not increase by 20% and the performance deteriorates as in the case of conventional treads. In addition, after the second season, the inner layer, which is visible after the surface layer is worn out, exhibits performance on icy and snowy roads, so as in the past, the amount of softener decreases over time and the hardness increases by -1, which increases performance. It does not go down and can be used on ice and snow roads even after season 1.

This invention is unique in that it is a studless tire that exhibits its performance on ice and snow even after the second season, but regardless of the season, the softener in the tread can migrate and disappear depending on the mileage, usage environment, etc. , the hardness increases by -1-,
It goes without saying that even if the performance deteriorates, the inner layer can still perform better in place of the worn surface layer.

[Example] Fig. 1 is an enlarged schematic cross-sectional view of essential parts showing an example of a studless tire according to the present invention, in which tread grooves 2 are the inner layer of the tread, and 3 is the surface layer.

In this embodiment, the surface layer 3 covers the inner layer portion 2 over the entire surface including the L/red groove 4 side. T is this surface layer 3
, and D6 is the groove depth of the tread groove 4. Furthermore, the second
As shown in the figure, the tread may have a structure in which the surface layer 3 is mainly covered on the block surface portions 5 of the tread.

Next, 2 parts by weight of sulfur (hereinafter, parts by weight are simply referred to as parts), 51 parts of vulcanization accelerator CB, 1 part of stearic acid, 3 parts of zinc white,
In addition to 1 part of the anti-aging agent, a studless tire with the above structure having a tire size of 165SR13 was manufactured using a rubber composition containing the components listed in Table 1, and its ice l-performance was evaluated.

In addition, as a leather abrasive material, cowhide is mechanically crushed and the average diameter is 0.
．． 11 were used. As the plant H material, mechanically crushed walnut kernels with an average diameter of 0.1 mm were used.

The hardness measurement method is based on JISK6301. In addition, the braking performance on ice is determined by calculating the reciprocal of the braking distance with full braking from a speed of 40 km/hr to 10 the initial performance of Comparative Example 1.
It was expressed as an index as 0. The larger the value, the better the condition. Wear resistance is expressed as an index with the initial performance of the comparative example, which is the depth of the remaining groove in the tread after running 5000 km, as 100. The larger the value, the better the condition.

In Table 1, the initial performance refers to the winter performance within one year after the tire was manufactured, and the next year's performance refers to the winter performance in the second year after the tire was manufactured.

(Margins below) Table 1 shows conventional tires (comparative examples) and 2 tires in which the tread is not composed of two layers, a surface layer and an inner layer, as in the present invention.
), the tire of the present invention has good performance in the next year with no decrease in braking performance on ice. It is also within the practical range in terms of wear resistance. If the thickness T of the surface layer is too thick, the surface layer will not wear out after one season of use, and a surface layer with increased hardness will remain, resulting in a decrease in ice braking performance in the next year (Comparative Example 3) . It can be seen that a tire containing 45 parts by weight of leather H material and vegetable key material granules has poor abrasion resistance in the next year and is not practical (Comparative Example 4).

[Effects of the Invention] As stated in Section 2 below, this invention provides that even if the amount of softener decreases over time during the first season of tire use after manufacture, the surface layer where the softener decreases will wear out over time. As a result, the hardness of the tread does not increase and the performance deteriorates, unlike in the past. In addition, after the second season, the inner layer, visible after the surface layer is worn out, exhibits skid resistance due to the action of leathery and vegetable granules, so there is no drop in performance as in the past, and ice and snow performance is improved. It has been possible to provide a studless tire that can be used satisfactorily on icy and snowy roads even after the second season and has significantly improved tire life.

[Brief explanation of drawings]

FIG. 1 is an enlarged schematic sectional view of a main part showing one embodiment of a studless tire according to the present invention, and FIG. 2 is an enlarged schematic sectional view of a main part showing another embodiment of the same invention. 1...1 Heredit 2...Inner layer part 3...Surface layer

Claims (1)

[Claims] (1) In a tire whose tread has a two-layer structure of a surface layer and an inner layer, the surface layer contains 100 parts by weight of rubber in which most of the rubber is natural rubber and/or diene rubber with a glass transition temperature of -50°C or lower. Against, carbon black 20
~100 parts by weight of a rubber composition with an initial hardness of 55 or less, and the inner layer is a rubber 1 whose main component is natural rubber and/or diene-based synthetic rubber with a glass transition temperature of -50°C or less.
1. A studless tire comprising a composition containing 20 to 100 parts by weight of carbon black and 3 to 30 parts by weight of granules made of leather and/or vegetable matter to 00 parts by weight.