RU2279988C2 - Tire - Google Patents

Abstract

FIELD: rubber industry; tires.

SUBSTANCE: invention relates to pneumatic tire designed for running on ice. Proposed tire has layer of foam rubber of surface in contact with road pavement, expansion ratio of foam rubber layer being 3-50%. To form layer of foam rubber, rubber mix is used containing natural caoutchouc and polybutadiene caoutchouc as rubber component, carbon soot, silicon dioxide, organic fibers (a) free from microparticles and organic fibers (b) containing microparticles, ratio of mixing of organic fibers (a) free from microparticles with organic fibers (b) containing microparticles being within 98/2-2/98.

EFFECT: provision of perfect running on ice (braking and adhesion characteristics on plane), convenience and ease of manufacture of tire.

9 cl, 12 ex, 2 tbl, 4 dwg

Description

FIELD OF THE INVENTION

The invention relates to a tire, for example, a pneumatic tire intended for movement on ice, and more particularly, to a tire that has excellent performance on ice, and is also convenient and simple to manufacture in a factory.

State of the art

Since the controlled use of studded tires began, tire tread research has been actively pursued with the specific goal of improving tire braking and traction performance on a road surface covered with ice and / or snow (hereinafter referred to as ice performance). On the surface of the road covered with ice and / or snow, the formation of a film of water is possible due to frictional heating in the contact area between the surface of the road covered with ice and / or snow and a tire, etc., as a result of which the resulting water film reduces the coefficient of friction in the area of contact between the road surface covered with ice and / or snow and the tire. For this reason, the performance on ice largely depends on the function of removing the water film, the edge effect and the effect of spikes in the tire tread. In order to improve the performance of the tire on ice, it is necessary to further strengthen the influence of the water film removal function, the edge effect and the spike effect in the tire tread.

To give the tire the function of removing a water film, numerous microscopic drain channels (the depth and width of which is approximately 100 μm) are formed on the surface of the tire. Thus, these microscopic drainage channels remove a film of water, increasing the coefficient of friction in the contact area of the tire with the road surface covered with ice and / or snow. However, in this case, the problem arises that although it is possible to improve the performance on ice at the initial stage of tire operation, as the tire gradually deteriorates as a result of increased mileage, its performance on ice irreversibly deteriorates.

A measure to prevent the deterioration of performance on ice, even if the tire is worn, consider the formation of shells in the tread. In this regard, JP-A-4-38207 indicates that foam rubber is applied to the tire tread to form microscopic drain channels on the tread surface. However, even when the rim wears out while increasing the tire mileage, short fibers that are not substantially parallel to the wear surface are not easy to remove from the tread, as a result of which the initially provided microscopic drain channels cannot always be formed efficiently, and the coefficient of friction on the road surface covered with ice and / or snow, does not undergo a significant increase. In addition, the removal of short fibers from the tread is highly dependent on traffic conditions and the like, so that the problem is that it is impossible to improve performance on ice with a guarantee.

In addition, JP-A-11-48264 indicates that the rubber composition containing the foaming agent is mixed with organic fibers, which reduces the viscosity compared to the viscosity of the rubber composition at a temperature corresponding to the maximum vulcanization temperature, before vulcanization of the rubber composition. At the same time, when the tire tread is created using such a rubber mixture, the effect of forming microscopic drain channels arises on the tire tread surface, enhancing the influence of the water film removal function, but in this case, there is still an activity field for enhancing the edge effect and the spike effect (effect scratching).

In addition, in accordance with JP-A-2001-233993 proposed to give organic fiber different functionalities. For example, it is proposed to include in an organic fiber having a predetermined diameter, microparticles having a predetermined particle size, such as glass microparticles, aluminum hydroxide microparticles, alumina microparticles, iron microparticles, (meth) acrylic microparticles, epoxy microparticles, etc. ., for the formation of organic fibers containing microparticles, with the aim of introducing them into the rubber component for the tire. To further enhance the influence of the water film removal function, as well as to enhance the edge effect in the tire, it is proposed to use a resin with a viscosity lower than the viscosity of the rubber component during a period when the rubber temperature is used in such a rubber mixture containing organic fibers containing microparticles and a rubber component the mixture reaches a maximum vulcanization temperature during vulcanization, as an organic fiber material.

Through the use of organic fibers containing microparticles, the effect of the removal function of the water film, the effect of increasing the coefficient of friction and the edge effect are enhanced. However, organic fiber, which includes such microparticles, must be made somewhat thicker in diameter, which worsens the extruded surface, leading to a decrease in the convenience and ease of use at the plant, and also affects the foam layer forming microscopic drainage channels during extrusion.

Summary of the invention

Therefore, the object of the invention is to solve the aforementioned problems of conventional technology and to develop a tire having excellent performance on ice (braking and traction performance on a plane), the development of which made a proper attempt to use organic fibers containing microparticles to improve comfort and ease of use at the plant and the guaranteed formation of microscopic drainage channels exhibiting the function of removing a film of water and showing enough their edge effect or the effect of spikes.

Various studies have been carried out and it has been found that when rubber compounds are mixed not only with organic fibers containing microparticles, but also with an adequate amount of organic fibers containing no microparticles, deterioration of the extruded surface during extrusion can be prevented by the preferred use of microparticles having a hardness of Mohs exceeding the hardness of the ice, as a result of which a significant scratching effect can be developed on a part of the surface of the tread rubber, i.e. the use of such solid microparticles in the case of the formation of shells on a part of the surface of the rubber of the tread promotes the formation of microscopic drainage channels that more strongly exhibit the edge effect and the effect of spikes on this part of the surface, therefore, it becomes possible to sufficiently exhibit the function of removing a film of water formed on the road surface covered with ice and / or snow, which leads to an absolutely excellent performance on ice, as well as convenience and ease of use; as a result of these studies, the invention was made.

The aforementioned problem is solved by selecting the following design, described below.

(1) A tire containing a foam rubber layer located on a surface substantially in contact with the road surface, the foam rubber layer having an expansion ratio of 3-50% and containing predetermined amounts of at least natural rubber and polybutadiene rubber as a rubber component, natural rubber is 20-70 mass parts, and polybutadiene rubber is 30-80 mass parts per 100 mass parts of the rubber component, and 5-55 mass parts of carbon black per 100 mass parts of the rubber component, 5-55 mass the output parts of silica per 100 mass parts of the rubber component, as well as the specified amounts of (a) organic fibers not containing microparticles, and (b) organic fibers containing microparticles.

(2) The tire described in paragraph (1), in which the total amount of organic fibers (a) not containing microparticles and organic fibers (b) containing microparticles is in the range of 1-5 mass parts per 100 mass parts of the rubber component .

(3) The tire described in paragraph (1) or (2), in which the mixing ratio of organic fibers (a) not containing microparticles with organic fibers (b) containing microparticles is in the range 98 / 2-2 / 98 .

(4) The tire described in paragraph (1) or (2), in which the mixing ratio of the organic fibers (a) not containing microparticles with the organic fibers (b) containing microparticles is in the range 95 / 5-5 / 95 .

(5) A tire as described in any one of (1) to (4), wherein in the organic fibers (b) containing microparticles, the microparticles are contained in an amount of 5-50 parts by mass per 100 parts by mass of the organic fiber.

(6) The tire described in any one of paragraphs (1) to (4), in which the microparticles in the organic fibers (b) containing the microparticles have a Mohs hardness of at least 2 and an average particle size of 10-30 μm, and not less than 80 mass percent according to the calculation of the frequency distribution of particle sizes are in the range of 10-50 microns.

(7) The tire described in any one of (1) to (4), wherein the organic fiber used in the organic fibers (a) not containing microparticles and the organic fibers (b) containing microparticles has a diameter of 0.01 -0.1 mm and a length of 0.5-20 mm.

(8) A tire as described in any one of (1) to (4), wherein the microparticles in (b) organic fibers containing microparticles have a frequency count of at least 20 weight percent at the peak value of the particle size distribution.

(9) The tire described in any one of (1) to (4), in which the microparticles in the organic fibers (b) containing the microparticles have a characteristic ratio of not less than 1.1 and comprise an angular portion (angular portions).

(10) The tire described in any one of (1) to (4), wherein the microparticles in (b) organic fibers containing microparticles are selected from inorganic microparticles and organic microparticles.

(11) The tire described in any one of (1) to (4), wherein the resin in the organic fiber is at least one high molecular weight polymer resin selected from polyethylene and polypropylene resins and has a melting point of not more than 190 ° C.

Brief Description of the Drawings

The following is a description of the invention with reference to the accompanying drawings, in which:

figure 1 presents the conditional section of the tire corresponding to the invention;

on figa and 2b presents the conditional section of the tread part in the tire corresponding to the invention, carried out in the circumferential direction and the direction of its width, respectively; and

figure 3 presents a conditional view illustrating the theory of orientation of organic fibers containing microparticles in a given direction.

DETAILED DESCRIPTION OF THE INVENTION

A tire according to the invention is a tire containing a layer of foam rubber disposed on a surface substantially in contact with a road surface, and specifically, a pneumatic tire comprising a layer of foam rubber which comprises enclosed closed cells located on a tire tread surface of at least a measure substantially in contact with a road surface, as shown in FIGS. 1-3.

For example, as shown in FIG. 1, the tire 1 according to the invention comprises a pair of bead parts 2, a radial carcass 3, toroidally extending between the bead parts 2, a belt belt 4 located on the outer peripheral surface of the corona part of the carcass 3 for manifesting the rim effect, and a tread 5, consisting of a running part 6 and a base part 7. In addition, the inner structure of the tire 1, with the exception of the tread 5, is similar to a conventional radial tire, so its description is omitted.

The surface of the tread 5, i.e. the running portion 6 is a foam rubber layer 6A as shown in FIG. This foam rubber layer 6A contains numerous long cells 12 surrounded by a protective layer 14, the structure of which is such that (a) the microparticle-free organic fibers are oriented and (b) the microparticle-containing organic fibers are in the tire circumferential direction. Thus, there is a protective layer 14 containing microparticles 20, and a protective layer 14 not containing microparticles.

There are no specific restrictions on the manufacturing method of tire 1. For example, a new tire is obtained by vulcanization in a given mold at a given temperature under a given pressure. As a result, the unvulcanized tread is vulcanized to produce a tire 1 having a running part consisting of a foam rubber layer 6A according to the invention.

In addition, when the uncured running portion 6 is heated in the mold, which is described in more detail below, the organic fibers (a) not containing microparticles and the organic fibers (b) containing microparticles melt (or soften), as a result of which their viscosity decreases (to melt viscosity), and the gas generated due to the expansion reaction of the foaming agent mixed into the rubber is stored in the rubber matrix, as well as in the spaces between organic fibers having a relatively low viscosity during melting. As a result, as shown in FIG. 2, after cooling, numerous long cells 12 appear in the foam rubber layer 6A, oriented in the tire circumferential direction (arrow A) of the tire.

The foam rubber layer 6A has long cells 12, spherical shells 18 and the like, as shown in FIG. During the tire run, on the surface of the foam rubber layer 6A due to wear of the tread surface, the lower parts 13 of the long cells 12 and the recessed parts 19 of the spherical shells 18 are revealed. Long cells are scattered in the tire 1 throughout the entire foam rubber layer 6A, so that even if part of the surface layer , containing organic fibers, undergoes further thinning due to wear, then new lowered parts 13 and buried parts 19 are revealed, as a result of which it is possible to successfully maintain high performance on ice. In addition, the protective layers 14 of organic fibers (b) containing microparticles, and the microparticles 20 themselves exhibit not only wear resistance in part of the surface layer, but also a sufficient edge effect and the effect of spikes, so that an additional improvement in the performance on ice is possible.

The foam rubber layer 6A in the running portion 6 of the tread has an expansion ratio of 3-50%. The foam rubber layer contains at least natural rubber and polybutadiene rubber as a rubber component, while natural rubber is 20-70 mass parts, and polybutadiene rubber is 30-80 mass parts per 100 mass parts of the rubber component, and 5-55 mass parts of carbon black per 100 mass parts of the rubber component, 5-55 mass parts of silica per 100 mass parts of the rubber component, as well as predetermined amounts of (a) organic fibers not containing microparticles, and (b) organic fibers, soda rusting microparticles.

The following is a detailed description of the foam rubber layer.

Although the rubber component in the foam rubber layer contains a predetermined amount of at least natural rubber and polybutadiene rubber, it may also contain other rubber (other rubbers).

The amount of natural rubber in the rubber component should preferably be 20-70 mass parts, and more preferably 30-50 mass parts per 100 mass parts of the rubber component. In addition, the amount of polybutadiene rubber should preferably be 30-80 mass parts, and more preferably 50-70 mass parts per 100 mass parts of the rubber component. When the amount of natural rubber exceeds 70 parts by mass or when the amount of butadiene rubber is less than 30 parts by mass, there is a danger that this will adversely affect the performance of the tire, so that the performance on ice will deteriorate. On the other hand, when the amount of polybutadiene rubber exceeds 80 parts by mass or when the amount of natural rubber is less than 20 parts by mass, there is a problem with the convenience and ease of use of the tire.

According to the purpose of the application, another rubber suitable for incorporation into the rubber component may be selected, and it may include, for example, a styrene butadiene copolymer (SBR) and the like.

When used in a tire tread, the rubber component should preferably have a glass transition temperature of no higher than -60 ° C. When a rubber component having such a glass transition temperature is used in a tread or the like, sufficient elasticity of the rubber-like material is maintained even in the low-temperature region, which makes it possible to exhibit an acceptable performance on ice.

In the foam rubber layer, since carbon black improves the dynamic properties of this rubber layer and improves workability, etc., well-known varieties of carbon black can be appropriately used to select each of such parameters as the absorption value I ₂ , the specific surface area of CTAB ( cetyltrimethylammonium bromide), N ₂ absorption value, DBP (dibutyl phthalate) absorption value, and the like. in a suitable range. Carbon black species can be mentioned, for example, such as SAF (furnace soot with ultra-high abrasion resistance), ISAF-LH (furnace soot with very high abrasion resistance for low hysteresis rubber), HAF (furnace soot with high abrasion resistance), HAF- HS (furnace soot with high abrasion resistance for tires assembled in a half-bottom drum), etc.

Carbon black is included in the foam rubber layer in an amount of 5-55 mass parts, and preferably 10-50 mass parts per 100 mass parts of the rubber component. When the amount of carbon black exceeds 55 mass parts, tire performance deteriorates, which negatively affects the performance of the tire on ice, and when the amount of carbon black is less than 5 weight percent, it also negatively affects the performance of the tire on ice.

The silica used in the foam rubber layer is not only silicon dioxide, but also a filler based on silicic acid, and it specifically includes silicic anhydride, silica hydrate, and silicates such as calcium silicate, aluminum silicate, and the like.

Silica is included in the foam rubber layer in an amount of 5-55 parts by mass, and preferably 30-50 parts by mass per 100 parts by mass of the rubber component. When the amount of silica exceeds 55 mass parts, tire performance deteriorates, which negatively affects the performance of the tire on ice, and when the amount of silica is less than 5 weight percent, this also negatively affects the performance of the tire on ice.

In addition, the foam rubber layer according to the invention contains predetermined amounts of (a) microparticle-free organic fibers and (b) microparticle-containing organic fibers.

When organic fibers (b) containing microparticles are included in the foam rubber layer, the effects of increased water drainage and increased friction appear on the tire tread surface, which improves the performance on ice. However, when a material having a relatively high hardness is used to introduce microparticles into organic fibers (b) containing microparticles, there may be a risk that this material will adversely affect the surface of the molded tire body during extrusion of unvulcanized rubber due to the relationship with the size of the organic fiber containing microparticles, and will cause deterioration in machinability at the plant. Therefore, it is preferable that the foam rubber layer contains mixed in a predetermined ratio organic fibers (a) that do not contain microparticles, and organic fibers (b) that contain microparticles. This mixing ratio of organic fibers (a) containing no microparticles with organic fibers (b) containing microparticles is preferably in the range 98 / 2-2 / 98, and more preferably 95 / 5-5 / 95.

In the present invention, the total amount of organic fibers (a) containing no microparticles and organic fibers (b) containing microparticles in a foam rubber layer is preferably in the range of 1-5 parts by weight, and more preferably 1.5-3 parts by weight 100 mass parts of the rubber component. When this total amount is less than 1 mass part, the effect of mixing organic fibers or the effect of scratching may not be sufficiently manifested, and a sufficient improvement in the performance on ice will not be realized corresponding to these effects. Moreover, if the content exceeds 5 mass parts, the usability of the extrusion is reduced, causing deterioration of the extruded surface, as well as cracking or other undesirable manifestation in the vulcanized rubber or tire tread.

The following is a description of the organic fiber used in organic fibers (a) not containing microparticles, and in organic fibers (b) containing microparticles. In addition, in both cases (a) and (b), organic fibers of the same material, shape, diameter, length, etc., are not necessarily used. Other types of fibers may be used. In any case, it is desirable to use an organic fiber having the following properties.

There are no specific restrictions on the material of organic fiber used in organic fibers (a) that do not contain microparticles, and in organic fibers (b) that contain microparticles, so that it can be selected in accordance with the purpose of use. However, in the invention, it is preferable to use a resin having a viscosity characteristic such that the viscosity drops compared to the viscosity of the rubber matrix in the rubber component when the temperature approaches the maximum vulcanization temperature during vulcanization due to the aforementioned relationship with the rubber component. That is, the resin for organic fiber has such a thermophysical characteristic that it melts (including softening) when the rubber mixture approaches the maximum vulcanization temperature. When the resin for organic fiber has such a thermophysical characteristic, the aforementioned long cells are able to function as a microscopic drain channel that can be easily formed in the vulcanizate obtained by vulcanizing the rubber compound.

In addition, in the sense in which it is used in this description, the term "maximum vulcanization temperature" means the maximum temperature of the rubber mixture achieved during vulcanization. For example, in the case of vulcanization in the mold, the rubber mixture reaches a maximum temperature during the time during which the rubber mixture is in the mold and is removed from it, and then cooled. The maximum vulcanization temperature can be measured, for example, by immersing a thermocouple in a rubber compound. It is also possible to measure the viscosity of the rubber matrix with a cone viscometer, capillary viscometer, etc.

Therefore, as the resin used in the invention, the aforementioned high molecular weight polymer resin having a melting point below the maximum vulcanization temperature and the like is preferable. Such a crystalline high molecular weight polymer resin melts rapidly in the rubber composition during vulcanization with an increase in the difference between the melting temperature and the maximum vulcanization temperature, so that the time of falling viscosity of the high molecular weight polymer resin is reduced compared to the viscosity of the rubber matrix. Therefore, when the high molecular weight polymer resin is melted, the gases existing in the rubber composition, including gas generated from the foaming agent mixed into the rubber composition, are collected inside the high molecular weight polymer resin having a viscosity lower than the viscosity of the rubber matrix. As a result, cells having a resin layer containing microparticles deposited on a rubber matrix, i.e. in vulcanized rubber in an undisturbed state, capsule-shaped long cells coated with a high molecular weight polymer resin are effectively formed. In the foam rubber layer forming the running portion of the tire tread, capsule-shaped long cells appear on the tread surface during tire run, and their lowered parts formed due to the implementation of the wear function as microscopic drain channels essentially exhibit a marginal effect and a stud effect in addition to the effect removing a film of water.

In contrast, when the melting point of the resin for organic fiber is close to the maximum vulcanization temperature of the rubber composition, the resin does not melt quickly in the initial stage of vulcanization, but melts in the last stage of vulcanization. At the last stage of vulcanization, part of the gas existing in the rubber mixture is taken into the matrix of vulcanized rubber, and is not collected inside the molten resin. As a result, the effective formation of long cells, operating essentially as a microscopic drainage channel, does not occur. In addition, if the melting temperature of the resin for organic fiber is too low, then when the organic fibers are mixed and mixed with the rubber compound, this causes the fusion of organic fibers with each other, leading to unsatisfactory dispersion of the organic fibers. In the latter case, the effective formation of long cells, working essentially as a microscopic drain channel, also does not occur. Therefore, it is preferable to select the melting temperature of the resin for the organic fiber so that the resin does not melt and does not soften at the temperature that occurs at each step before vulcanization, and that the viscosity of the resin changes in opposition to the viscosity of the rubber matrix during vulcanization.

There are no specific restrictions on the upper limit of the melting temperature of organic fiber, except that it should be lower than the maximum vulcanization temperature of the rubber matrix, but in the preferred embodiment, it should be at least 10 ° C, and in the more preferred embodiment - at least 20 ° C lower than the maximum vulcanization temperature. Although the industrial vulcanization temperature of the rubber composition is generally at most 190 ° C., the melting temperature of the resin is usually set, for example, to not exceed 190 ° C., preferably not to exceed 180 ° C., and more preferably not to exceed 170 ° C.

In addition, the melting temperature of the resin can be measured using a well-known device for measuring the melting temperature. For example, such a melting point may be a peak melting point measured with a digital signal transducer (DSC) measuring device.

The organic fiber of the invention can be made from a crystalline high molecular weight polymer resin and / or a non-crystalline (amorphous) high molecular weight polymer resin. However, as mentioned above, at a certain temperature, a strong change in viscosity occurs due to phase transformation, and viscosity control is carried out simply so that in the preferred embodiment, the organic fiber is formed from organic material containing a large amount of crystalline high molecular weight polymer resin, and in a more preferred variant formation occurred only from crystalline high molecular weight polymer resin.

As a crystalline high molecular weight polymer resin, homopolymers, copolymers and mixtures thereof having a wide melting temperature, such as polyethylene (PE), polypropylene (PP), polybutylene, polybutylene succinate, polyethylene succinate, syndiotactic 1,2-polybutadiene (SPB) can be used ), polyvinyl alcohol (PVA), polyvinyl chloride (PVC), etc. In addition, an additive may be added to these resins. You can use one additive or a combination of two or more additives. Among these crystalline high molecular weight polymer resins, polyolefins and copolymers of polyolefins are preferred. Polyethylene (PE) and polypropylene (PP) are more preferable from the point of view that they have a lower melting point, and it’s easy to handle them.

As a non-crystalline high molecular weight polymer resin, polymethyl methacrylate (PMMA), a copolymer of acrylonitrile, butadiene and styrene (ABS), polystyrene (PS), polyacrylonitrile, their copolymers, mixtures thereof, etc. can be used. It is possible to use one such resin or a combination of two or more resins.

In organic fibers (a) containing no microparticles and organic fibers (b) containing microparticles, it is preferred that the organic fiber has a length of 0.5-20 mm, and more preferably 1-10 mm. When organic fibers having such a length are present in the vulcanized rubber constituting the foam rubber layer, they effectively exhibit an edge and spike effect, and together with the foaming agent or the like, which are described below, can effectively form long cells capable of functioning, essentially like a microscopic drain channel. When the length of the organic fiber is less than 0.5 mm, the above-mentioned effects may not be manifested sufficiently, and when it exceeds 20 mm, the organic fibers are interwoven with each other, as a result of which there is a tendency for dispersibility to deteriorate.

It is also preferred that the organic fiber has a diameter of 0.01-0.1 mm, and more preferably 0.015-0.09 mm. When the diameter of the organic fiber is less than 0.01 mm, shearing is easily caused, so that the edge effect and the effect of the spikes may not be manifested sufficiently, and if the diameter exceeds 0.1 mm, there are problems with machinability.

The microparticles contemplated by the invention contained in organic fibers (b) containing microparticles include inorganic microparticles and organic microparticles. Suitable microparticles are glass microparticles, aluminum hydroxide microparticles, alumina microparticles, iron microparticles, and the like. As the mentioned organic microparticles, the above-mentioned microparticles of (meth) acrylic resin, epoxy microparticles and the like can be used. It is possible to use one variety of such particles or a combination of two or more of their varieties. Among them, organic microparticles are preferred in that they provide an excellent scratch effect on ice.

The microparticles used in the invention should preferably have a Mohs hardness of not less than 2, and more preferably not less than 5. When the Mohs hardness of these microparticles is not less than the ice hardness (1-2) or not less than 2, possibly more intense manifestation of the effect of scratching on the surface of the foam rubber layer in the tread. Thus, the resulting tire has a large coefficient of friction with the road surface covered with ice and / or snow, and excellent performance on ice (the performance of braking and traction of the tire on a plane, shown on the road surface covered with ice and / or snow).

As microparticles having such a high hardness, we mention microparticles of gypsum, calcite, fluorite, orthoclase, quartz, garnet, etc. In particular, as preferred microparticles having a Mohs hardness of at least 5, mention is made of silica glass microparticles (hardness 6.5), quartz (hardness 7.0), fused alumina (hardness 9.0), and the like. Among these materials, silicate glass, alumina (alumina) and the like are cheap and easy to use.

Among these particles, preferably not less than 80 weight percent, and more preferably not less than 90 weight percent, according to the calculation of the particle size distribution frequencies carried out for the microparticles, are in the range of 10-50 μm, and the average particle size is in the range of 10-30 μm.

When the particle size in the aforementioned frequency count is less than 10 μm, the microparticles are easily aggregated with each other in the manufacture of organic fibers (b) containing microparticles, and there is a tendency to deteriorate their dispersibility. In addition, when such organic fibers are used in the tire, the scratching effect or the spike effect may not be sufficiently manifested. And when said size exceeds 50 μm, defects such as fiber breakage often occur during the manufacture of organic fibers (b) containing microparticles, as a result of which it may not be possible to efficiently obtain the desired organic fibers (b) containing microparticles.

It is also preferable that the microparticles in the organic fibers (b) containing microparticles have a frequency count of at least 20 percent of their mass, preferably not less than 25 percent of their mass, and more preferably not less than 30 percent of the mass, at the peak value of the particle size distribution. When counting the frequencies of microparticles at the peak value shows that there are at least 20 mass percent of such microparticles, the particle size distribution curve obtained for microparticles becomes small in radius of curvature and the particle size becomes the same. As a result, when forming an organic fiber containing microparticles, it is difficult to break the fibers; moreover, when such organic fibers are used in a tire, proper performance on ice occurs. In contrast, when counting the frequencies of microparticles at the peak value shows that there are less than 20 mass percent of such microparticles, when the fibers are formed, their breakage is easy, and the spread of performance on ice also easily occurs. In addition, when the particle size is in the above range, and this particle size becomes large, the performance of the tire on ice is improved.

In the sense in which it is used in this description, the term "frequency counting" means the mass percentage of microparticles falling within the width of the division interval when the particle size is divided into segments of 2 μm wide in the distribution of particle sizes (on the particle size distribution curve) and the term “counting frequencies at a peak value” means counting frequencies within the width of a division interval that includes the maximum peak value on the particle size distribution curve.

The microparticles preferably have a characteristic ratio of not less than 1.1, and also contains an angular portion (angular portions). In particular, the characteristic ratio is not less than 1.2, and more preferably not less than 1.3. In addition, the expression "the presence of the angular part (angular parts)" means that the surface of the microparticle as a whole is neither a spherical surface, nor a surface outlined by smooth curves.

As microparticles in the invention, microparticles already containing an angular part (angular parts) can be used. However, even if the microparticles have a spherical shape, by spraying during operation it is possible to form an angular part (angular parts) on the surface of the microparticles. In addition, a set of angular parts may already be present in the microparticle.

The shape of the microparticles can be determined by observing the microparticles in an electron microscope. When the characteristic ratio, which is the ratio of the size along the major axis to the size along the minor axis in the microparticle, is not less than 1.1, it is possible to effectively sharpen the angular part (s) that are formed on the surface of the microparticle. If organic fibers containing such microparticles are used in a tire or similar product, the edge or tire effect can be significantly enhanced.

In an organic fiber containing microparticles, it is preferred that the amount of microparticles contained therein is 5-50 parts by mass, and more preferably 7-50 parts by mass per 100 parts by mass of an organic fiber forming resin. When the number of microparticles is less than 5 parts by weight, there is a danger that the scratching effect in the rubber product or the edge effect and the effect of tires in the tire tread may not be manifested sufficiently, and when said amount is more than 50 parts by weight, when forming an organic fiber containing microparticles, defects such as fiber rupture and the like often occur, and therefore there is a danger that it will not be possible to efficiently produce organic fibers containing microparticles.

In order to form cells after vulcanization in accordance with the invention, the foaming agent is mixed into the rubber composition before the foam rubber layer is formed. Through the use of a foaming agent and the above-described organic fibers, long cells are formed in the vulcanized rubber or the foam rubber layer of the tread, which form microscopic drain channels providing a performance characteristic for removing the water film.

As a foaming agent, we mention dinitrosopentamethylenetetramine (DNPT), azodicarbonamide (ADCA), dinitrosopentastyrene tetramine, a benzenesulfonyl hydrazide derivative, hydroxybenzenesulfonyl hydrazide (OBSN), ammonium nitroxide, and azobenzo, and nitrosamide -N, N'-dinitrosophthalamide, toluenesulfonylnidrazide, p-toluenesulfonylsemicarbazide, p, p'-hydroxybis (besolnosulfonylsemicarbazide) and the like.

Among these foaming agents, dinitrosopentamethylenetetramine (DNPT) and azodicarbonamide (ADCA) are preferred from the viewpoint of processability, and particularly azodicarbonamide (ADCA) is particularly preferred. It is possible to use one such substance or a combination of two or more such substances. Due to the action of the foaming substance, the resulting vulcanized rubber is converted into foam rubber, which allows to achieve a high degree of pricing.

In the invention, it is preferable to use a foaming agent together with an auxiliary foaming agent. As an auxiliary foaming agent, we will mention auxiliary agents commonly used in the manufacture of foam products, such as urea, zinc stearate, zinc benzenesulfinate, zinc white, and the like. Among them, urea, zinc stearate and zinc benzenesulfinate are preferred. You can use one such tool or a combination of two or more of these tools.

The amount of foaming agent in the mixture is determined appropriately in accordance with the intended use, but in the preferred embodiment, it is 1-10 mass parts per 100 mass parts of the rubber component. The foaming agent may be mixed with the rubber matrix or present in each of the organic fibers. In addition, you can use industrially supplied products for a similar purpose.

In the content range that does not adversely affect the technical essence of the invention, other components can be used in the proposed technical solution. As another component, various additives commonly used in the rubber industry can be appropriately selected and used in accordance with the purpose of application, in addition to a vulcanizing agent such as sulfur and the like; it can be a vulcanization accelerator, such as dibenzothiazyl disulfide, etc., an accelerator activator, a sulfidation inhibitor, such as N-cyclohexyl-2-benzothiazylsulfenamide, N-oxide-ethylenebenzothiazyl sulfenamide, etc., an ozone antidetetrant (additive, protection ozone layer), coloring agent, antistatic agent, dispersing agent, lubricant, antioxidant, emollient, inorganic filler such as carbon black or silica and the like. It is possible to use one such substance or a combination of two or more such substances.

When forming a foam rubber layer in accordance with the invention, the aforementioned rubber mixture is ground, heated and extruded in the following manner under the following conditions.

When grinding, there are no specific restrictions on the grinding device, for example, on the volume of loading in the grinding device, the rotational speed of its rotor, grinding temperature, grinding time, etc., so that they can be selected in accordance with the intended use. As a grinding device, it is preferable to use commercially available devices.

When heating and extrusion, there are no specific restrictions on the conditions of heating and extrusion devices, for example, during heating or extrusion, etc., so that they can be selected in accordance with the intended use. As a heating or extrusion device, it is preferable to use commercially available devices. In addition, since a foaming agent is present in the rubber composition, the heating and extrusion temperatures are suitably selected in a range that does not cause foaming. In particular, it is desirable to have an extrusion temperature of about 90-110 ° C.

In the invention, it is preferable to orient the aforementioned organic fibers in the direction of extrusion during extrusion and the like. To effectively carry out such an orientation, the fluidity of the rubber composition is controlled within a limited temperature range. In particular, the viscosity of the rubber composition is varied so as to increase fluidity by appropriately introducing a processing aid such as a plasticizer such as aromatic oil, naphthenic oil, paraffin oil, synthetic ester oil and the like, and a liquid polymer such as liquid polyisoprene rubber, liquid polybutadiene rubber and the like. into the rubber compound.

Upon receipt of the foam rubber layer of the invention, it is preferable to orient the organic fibers (a) not containing microparticles and the organic fibers (b) containing microparticles in a direction parallel to the contact surface of the tread with the ground, or in the tire circumferential direction. Thus, it is possible to improve the drainage property in the direction of tire run and effectively improve its performance on ice.

Describing the method of co-orientation of organic fibers in the foam rubber layer illustrated in FIG. 3, we note that the rubber mixture 16 containing organic fibers 15 containing microparticles is extruded through the extruder matrix 17, reducing the cross-sectional area of the flow channel towards the outlet to ensure a constant the orientation direction of the organic fibers 15 containing microparticles, etc. In this case, the organic fibers 15 containing microparticles and the like in the rubber composition 16 are gradually aligned before extrusion along the extrusion direction (indicated by arrow P) during extrusion into the matrix 17, so the longitudinal directions of these organic fibers are essentially are fully oriented in the direction of extrusion (indicated by arrow P) when the rubber mixture is extruded from the head 17. The degree of orientation of the organic fibers 15 containing microparticles and the like in the rubber mixture 16 of change due to the degree of reduction of the cross-sectional area of the flow channel, the speed of extrusion, the viscosity of the rubber compound 16 before vulcanization, etc.

The invention does not impose specific restrictions on the method and conditions of vulcanization, so that they can be properly selected in accordance with the type of rubber compound, etc. In the case of obtaining a layer of foam rubber for the tread in accordance with the invention, it is preferable to conduct vulcanization in the mold. From the point of view of vulcanization temperature, it is preferable that the maximum vulcanization temperature of the rubber mixture during vulcanization is not lower than the melting temperature of the resin constituting the organic fiber, as mentioned above. If the maximum vulcanization temperature is lower than the melting temperature of the resin, the organic fibers do not melt, as a result of which the gas resulting from pricing will not be able to get into the resin, and long cells will not form effectively in the foam rubber layer. There are no particular restrictions on the vulcanization device, and industrially supplied devices can preferably be used as such.

In the tread (foam rubber layer) of the tire according to the invention, the lowered portions of the long cells obtained on the tread surface are directive, therefore, they function as a drain channel providing efficient drainage. In addition, the lowered part has a protective layer, in particular a protective layer containing microparticles, so that this part exhibits exceptional peeling resistance, the ability to maintain the shape of the drain channel, wear resistance, the properties of the drain channel to remain under load, and the like. In the tire according to the invention, long cells exist over the entire foam rubber layer, so that the various functionalities of the lowered part are manifested from the initial stage to the final stage of operation, as a result of which the performance on ice becomes even better.

The degree of expansion of the foam rubber layer should preferably be in the range of 3-50%, in particular 15-40%. When the degree of expansion is less than 3%, the volume of the reduced part in the tread becomes small, so that it is not possible to significantly improve the performance on ice, and when the degree of expansion exceeds 50%, the performance on ice is satisfactory, but the number of shells in the tread becomes larger due to of which an unfavorable in terms of durability reduction of the fracture stress occurs. In addition, “expansion ratio, Vs” means the total expansion ratio in vulcanized rubber or tread and can be calculated using the following equation:

Vs = (ρ ₀ / ρ ₁ -1) × 100 (%),

where ρ ₁ is the density (g / cm ³ ) of vulcanized rubber (foam rubber), and ρ ₀ is the density (g / cm ³ ) of the solid-phase part of vulcanized rubber (foam rubber). In this case, the density of the rubber (foam rubber) after vulcanization and the density of the solid phase part of the rubber (foam rubber) after vulcanization are calculated, for example, based on the mass measured in ethanol and the mass measured in air.

In the invention, it is preferable that the average size of the length of the cell formed in the foam rubber layer is about 10-500 microns. When this average size is 10 μm, the performance of draining the microscopic drain channel formed on the surface of the rubber may decrease, and when this size exceeds 500 μm, the rubber may decrease resistance to cuts and resistance to chipping pieces, as well as wear resistance on a dry road surface . Since it is necessary to suppress the sliding of the tire tread on ice, the invention can be applied to obtain a tread for a tire with a retreadable tread, a solid tire, and the like. In addition, if the tire is a pneumatic tire, then an inert gas such as nitrogen gas and the like can be used as the gas to fill the inside of the tire in addition to air.

Although the specific embodiment discussed above has been described with respect to a tread having a two-layer structure, there are no particular restrictions on the tread structure, so that it can also have a single-layer structure. In addition, it is possible to adopt a multilayer structure dividing in the radial direction, a structure dividing in the tire circumferential direction or in the tread width direction. In any case, it is preferable that at least a portion of the surface tread layer consist of a foam rubber layer according to the invention.

The following are examples illustrating the invention and are not restrictive.

Examples 1-5, comparative examples 1-12

To form the foam rubber layer used in each of the examples and comparative examples, a rubber mixture containing natural rubber, cis-1,4-polybutadiene rubber (trademark UBEROL 150L, supplier of Ube Industries, Ltd.), carbon black (N134 (N ₂ SA: 142 m ² / g), supplier Asahi Carbon Co., Ltd.), silica (Nipsil AQ, supplier Nippon Silica Co., Ltd.), silane (organosilicon) size (Si69, supplier Degussa), aromatic oil, stearic acid, antioxidant (IPPD: N-isopropyl-N'-phenyl-p-phenylenediamine), zinc oxide, vulcanization accelerator (MBTS: 2,2-dibenzothiazyl isulfide; CBS: N-cyclohexyl-2-benzothiazylsulfenamide), sulfur, foaming agent (DNPT: dinitrosopentamethylenetetramine), urea, (a) microparticle-free organic fibers, and (b) microparticle-based organic fibers, if properly selected relations (a) / (b). Miscible amounts of rubber components are presented in tables 1 and 2.

In addition, the vulcanization temperature of each rubber compound during vulcanization was measured by immersing a thermocouple in the rubber compound. This temperature exceeds the temperature of the resin for the organic fiber while approaching the maximum vulcanization temperature, and the viscosity of the resin becomes lower than the viscosity of the rubber matrix during vulcanization of the rubber compound.

In addition, the viscosity (melt viscosity) of the organic fiber resin at a maximum vulcanization temperature is 6 - according to the results of measurements with a conical viscometer (measure the change in torque and measure the pressure change of the foam, while the torque of the rubber is determined as the viscosity of the rubber, and the measurement ends at the maximum value torque). On the other hand, the viscosity (fluid viscosity) of the rubber composition at the maximum vulcanization temperature is 11, when the torque is measured with an error in time using a Model 1-C conical viscometer, the supplier is Monsanto, changing the temperature and applying a constant amplitude input signal with a frequency 100 cycles per minute, and the minimum torque value is defined as viscosity (assigned pressure: 0.59 MPa; holding pressure: 0.78 MPa; closing pressure: 0.78 MPa; amplitude angle: ± 5 °).

A tread (foam rubber layer) is formed for the tire using the above-described rubber composition, and then a radial tire for a passenger car is made, which, according to the test results, has a tire size of 185 / 70R13, in accordance with normal manufacturing conditions.

The manufacturability of the rubber compound and the performance on ice are evaluated respectively by the following methods.

Performance on ice

The test tire is installed on each of the four wheels of a passenger car with an engine capacity of 1600 cubic centimeters, and then braking on an icy road at a temperature of -1 ° C to evaluate the performance on ice represented by the following equation, provided that the tire corresponding to the comparative Example 1 is a control bus.

Performance on ice = (stopping distance of the control tire / stopping distance of the tire other than the control tire) × 100.

Manufacturability

The processability associated with the extruded surface is evaluated by measuring the surface roughness of the rubber after extrusion using a surface roughness measuring device. When the surface roughness (Ra) does not exceed 50 μm, machinability is considered acceptable (symbol: O).

The results of the changes are presented in tables 1 and 2.

The composition of the mixture (in mass parts) Example one 2 3 four fifty Natural rubber fifty fifty fifty fifty fifty 4-cis-1,4-polybutadiene rubber fifty fifty fifty fifty fifty Carbon black thirty thirty thirty thirty thirty Silica thirty thirty thirty thirty thirty Silane (organosilicon) sizing 3.0 3.0 3.0 3.0 3.0 Aromatic oil fifteen fifteen fifteen fifteen fifteen Stearic acid 2 2 2 2 2 Antioxidant (IPPD) 2.5 2.5 2.5 2.5 2.5 Zinc oxide 2 2 2 2 2 Vulcanization Accelerator (MBTS) 0.6 0.6 0.6 0.6 0.6 Vulcanization Accelerator (CBS) 1.2 1.2 1.2 1.2 1.2 Sulfur 1.3 1.3 1.1 1.3 1.3 Foaming Agent (DNPT) 2.5 2.5 2.5 2.5 2.5 Urea 2.5 2.5 2.5 2.5 2.5 (a) Organic microparticle fibers (*) 0.1 0.25 one 0.86 3 (b) Organic fibers containing microparticles (*) 1.9 4.75 one 0.05 3 (a) / (b) 5/95 5/95 50/50 95/5 50/50 The degree of expansion (%) 25 25 25 25 25 Performance on ice 105 113 108 98 113 Manufacturability O O O O Δ (*) Raw materials for organic fiber: polyethylene resin (melting point: 132 ° C), microparticle content (in mass percent): 15, average microparticle size (μm): 20, fiber diameter (μm): 32, fiber length ( mm): 2.

table 2 The composition of the mixture (in mass parts) Comparative example one 2 3 four 5 6 7 8 9 10 eleven 12 Natural rubber 70 twenty fifty fifty fifty one hundred 80 fifty fifty fifty fifty fifty 4-cis-1,4-polybutadiene rubber thirty 80 fifty fifty fifty - twenty fifty fifty fifty fifty fifty Carbon black 55 55 55 thirty 5 thirty thirty 60 - thirty thirty thirty Silica 5 5 5 thirty 55 thirty thirty - 60 thirty thirty thirty Silane (organosilicon) sizing 0.5 0.5 0.5 3.0 5.5 3.0 3.0 - 6.0 3.0 3.0 3.0 Aromatic oil fifteen fifteen fifteen fifteen fifteen fifteen fifteen fifteen fifteen fifteen fifteen fifteen Stearic acid 2 2 2 2 2 2 2 2 2 2 2 2 Antioxidant (IFPD) 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Zinc oxide 2 2 2 2 2 2 2 2 2 2 2 2 Vulcanization Accelerator (MBTS) 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 Vulcanization Accelerator (CBS) 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 Sulfur 1.3 1.3 1.3 1.3 1.1 1.3 1.3 1.3 1.1 1.3 1.3 1.3 Foaming Agent (DNPT) 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Urea 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 (a) Organic microparticle fibers (*) - - - - - one one one one 2 - - (b) Organic fibers containing microparticles (*) 2 2 2 2 2 one one one one - 6 four (a) / (b) 0/100 0/100 0/100 0/100 0/100 50/50 50/50 50/50 50/50 100/0 0/100 0/100 The degree of expansion (%) 25 25 25 25 25 25 25 25 25 25 25 25 Performance on ice one hundred 105 103 105 108 93 94 93 95 95 105 98 Manufacturability × × × × × O O O O O × O (*) Raw materials for organic fiber: polyethylene resin (melting point: 132 ° C), microparticle content (in mass percent): 15, average microparticle size (μm): 20, fiber diameter (μm): 32, fiber length ( mm): 2.

As can be seen from the results shown in tables 1 and 2, the mixtures of examples 1-5 are excellent in both performance on ice and manufacturability. As shown in comparative examples 1-5, tires provided with a foam rubber layer not containing organic fiber containing microparticles exhibit poor processability. As shown in comparative examples 6-9, when the mixed amounts of the main ingredients, such as natural rubber, polybutadiene rubber, carbon black, silica and the like, are outside the adequate ranges, an acceptable improvement in performance on ice cannot be obtained. As shown in comparative examples 10-13, when the ratio of organic fibers (a) containing no microparticles and organic fibers (b) containing microparticles is outside the acceptable range, neither the performance on ice nor the processability can be improved.

In the tire according to the invention, the microparticle-free organic fibers (a) and the microparticles (b) organic fibers are included in the mixture in a predetermined mixing ratio, whereby various of the above-mentioned problems inherent in conventional technology can be solved. That is, trying to realize the preferred use of organic fibers containing microparticles improves the convenience and ease of use at the plant, and you can also create tires with excellent performance on ice (performance characteristics of braking and traction on a plane) in which microscopic drainage is reliably formed channels exhibiting a performance characteristic of removing a film of water, as well as sufficiently exhibiting an edge effect and / or spike effect.

Claims (9)

1. A tire containing a foam rubber layer located on a surface substantially in contact with a road surface, the foam rubber layer having an expansion ratio of 3-50%, for the formation of which a rubber mixture containing predetermined amounts of at least natural rubber and polybutadiene is used rubber as a rubber component, while natural rubber is 20-70 parts by weight, and polybutadiene rubber is 30-80 parts by weight. per 100 parts by weight rubber component, and 5-55 parts by weight carbon black per 100 parts by weight rubber component, 5-55 parts by weight silica per 100 parts by weight a rubber component, the mixing ratio of organic fibers (a) not containing microparticles with organic fibers (b) containing microparticles is in the range 98 / 2-2 / 98, and the total amount of organic fibers (a) not containing microparticles, and organic fibers (b) containing microparticles, is in the range of 1-5 parts by weight per 100 parts by weight rubber component. 2. The tire according to claim 1, in which the mixing ratio of organic fibers (a) not containing microparticles with organic fibers (b) containing microparticles is in the range 95 / 5-5 / 95. 3. A tire according to any one of claims 1 and 2, wherein in the organic fibers (b) containing microparticles, the microparticles are contained in an amount of 5-50 parts by weight per 100 parts by weight organic fiber. 4. A tire according to any one of claims 1 and 2, in which the microparticles in the organic fibers (b) containing microparticles have a Mohs hardness of at least 2 and an average particle size of 10-30 μm, and not less than 80 wt.% According to the calculation Particle size distribution frequencies are in the range of 10-50 microns. 5. The tire according to any one of claims 1 and 2, in which the organic fiber used in organic fibers (a) not containing microparticles and organic fibers (b) containing microparticles has a diameter of 0.01-0.1 mm and 0.5-20 mm long. 6. The tire according to any one of claims 1 and 2, in which the microparticles in organic fibers (b) containing microparticles have a frequency count of at least 20 wt.% At the peak value of the particle size distribution. 7. A tire according to any one of claims 1 and 2, in which the microparticles in the organic fibers (b) containing microparticles have a characteristic ratio of not less than 1.1 and comprise an angular portion (angular portions). 8. A tire according to any one of claims 1 and 2, in which the microparticles in the organic fibers (b) containing microparticles are selected from inorganic microparticles and organic microparticles. 9. A tire according to any one of claims 1 and 2, in which the resin in the organic fiber is at least one high molecular weight polymer resin selected from polyethylene and polypropylene resins and has a melting point of not more than 190 ° C.

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