JPH11310009A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent ice braking performance from changing on a wet frozen road by specifying the average grain size and cover thickness of the powder rubber covering a tread section. SOLUTION: The tread section of this pneumatic tire is preferably covered with a layer made of powder rubber with the average grain size of 50-500 μm and having the thickness of 1000-3000 μm. If the grain size of the powder rubber is below 50 μm, the irregularities on the surface are made too fine, and the primarily required difference between an irregular face and a lubricating face is eliminated. If the grain size is too large, large irregularities are formed, edge portions are decreased, and the desired frictional force is not obtained. If the thickness of the powder rubber layer is below 1000 μm, it is at a level difficult to manufacture. If the thickness becomes too thick to exceed 3000 μm, the powder rubber layer having a very low reinforcing property occupies a large portion of the tread section, the primary cap tread rubber portion is reduced, and the abrasion resistance as a tire is lowered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having a tread for maintaining and improving initial performance and performance after running wear in a snow or studless tire having excellent on-snow performance and on-ice performance.

[0002]

2. Description of the Related Art Conventionally, as a pneumatic tire suitable for running on an ice burn, a spike tire gripping the ice burn with a spike pin has been frequently used. However, in recent years, when traveling on a normal road surface with a spike tire, the problem of spike pins shaving the road surface and causing dust pollution has been highlighted. Therefore, studless tires have attracted attention as pneumatic tires that can sufficiently grip an ice burn without using a spike pin. In recent years, attention has been paid to braking performance on ice in a wet ice burn (black ice burn) at around 0 ° C., and improvements have been made. As a tread rubber composition used for generally used studless tires, foamed rubber, which is said to be particularly suitable for wet ice burn at around 0 ° C., is excavated by the edge portion of the open pores on the tread surface and increases friction. The purpose is to aim at the adhesive friction due to the action of removing the water film at the edge portion. In addition, vulcanized powder rubber (Japanese Patent Application Laid-Open No. 63-92659) and foamed rubber powder (Japanese Patent Application Laid-Open No. 2-279743), which have the same role as the foamed rubber, are arranged in a scattered manner. Studless tires are also known.

Further, there is a studless tire having a tread composed of a rubber mixed with a hard substance which does not chemically bond to a rubber component such as a cellulose fiber, a nylon fiber, and a water-soluble resin (Japanese Patent Application Laid-Open No. 2-167353, Kaiping 4
-41535, JP-A-3-159803). In this studless tire, the hard material exposed on the tread drops off during running, and the dropout hole generated by the dropout is
An increase in digging friction due to an edge portion similar to the foamed hole and an adhesive friction due to a water film removing action can be obtained. However, most of the commercially available studless tires have very smooth cap tread treads, reflecting the vulcanized mold surface at the time of manufacture. However, the ice and snow performance of tread rubber that gives micro unevenness to the tread surface such as foamed rubber or rubber compounded with foreign matter is the performance after running wear that appears due to the tread wear, and the initial performance when the cap tread surface is smooth. Is considered to be at a low level. Further, Japanese Patent Application Laid-Open No. 7-195573 discloses a method of processing a tread surface in which braking performance on ice does not change from the beginning of traveling to the time of wear after traveling, and a studless tire using the same. However, such a tire requires a complicated operation process for processing the tread surface, and some of such tires do not always exhibit satisfactory initial braking performance.

[0004]

Therefore, according to the present invention, a pneumatic tire for a studless tire whose braking performance on ice in a wet ice barn (black ice barn) at around 0 ° C. does not change from the beginning of traveling to the time of abrasion after traveling. The purpose is to provide. Another object of the present invention is to effectively utilize powdered rubber from the viewpoint of recycling.

[0005]

According to the present invention, in a pneumatic tire provided with a tread, the tread surface of the tread is made of powdered rubber having an average particle size of 50 to 500 μm and having a thickness of 100 μm.
A pneumatic tire having a tread covered with 0 to 3000 μm is provided.

Further, according to the present invention, the tread portion is a tread rubber composition for a studless tire for ice and snow surfaces, and the tread portion is made of natural rubber, polyisoprene, polybutadiene and styrene butadiene copolymer. A tread rubber composition comprising 3 to 50 parts by weight of a hard substance which does not chemically bond to rubber with 100 parts by weight of a base rubber component composed of one or more kinds selected from the group consisting of: Has been surface-treated with 2 to 10 parts by weight of an adhesive for powdered rubber based on 100 parts by weight of powdered rubber, and the adhesive for powdered rubber is at least one selected from rubber latex or liquid rubber. The rubber component of the powdered rubber is natural rubber, polyisoprene, polybutadiene and styrene butadiene copolymer, or Isobutene, a pneumatic tire having a tread and each characterized in that one or more members selected from the group consisting of polyethylene propylene is provided.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION A pneumatic tire according to the present invention
In a pneumatic tire having a tread, the tread tread portion has a thickness of 10 μm by powder rubber having an average particle size of 50 μm or more.
A pneumatic tire having a tread covered with 00 μm to 3000 μm, preferably using powdered rubber treated with a specific adhesion imparting agent, wherein the tread portion has tread rubber for a studless tire for ice and snow surfaces. It is a tire containing. Preferably, the tread portion is natural rubber,
3 to 50 parts by weight of a hard substance that does not chemically bond to rubber is added to 100 parts by weight of a base rubber component composed of one or more kinds selected from the group consisting of polyisoprene, polybutadiene and styrene butadiene copolymer. It is a pneumatic tire having a tread rubber compounded. According to the present invention, in applying the powdered rubber to the tread tread portion, it is important that only the vulcanized powdered rubber is pseudo-vulcanized by applying pressure and heat of 120 ° C. or more to adhere. is there. In the present invention, in particular, when the vulcanized powder rubber is formed into a sheet by pressing, it is inspired that the surface state has a very uneven surface, and this is used as a braking surface on ice, and the tread surface of the studless tire is used as a braking surface. It is applied to

[0008] In the pneumatic tire of the present invention, the tread portion has an average particle size of 50 to 500 µm, preferably 1 to 500 µm.
With a powder rubber of 00 to 300 μm, a thickness of 1000 to 30
Those covered with a layer of 00 μm, preferably 1500 to 3000 μm are suitable. The particle size of this powder rubber is 50 μm
If it is less than 3, the unevenness on the surface becomes too fine, and the difference between the originally required uneven surface and the lubricated surface is lost. On the other hand, if the particle size is too large, a large uneven surface is formed, the edge portion is reduced, and a desired frictional force cannot be obtained. If the thickness of the powder rubber layer is less than 1000 μm, it is at a difficult level in production. On the other hand, if the thickness exceeds 3000 μm, the powder rubber layer having very low reinforcing properties occupies a large area of the tread portion, and the original tread portion becomes large. The amount of the cap tread rubber decreases, and the wear resistance of the tire decreases. Since the powder rubber layer needs only to have surface irregularities at the initial stage of traveling, it is more than 1500 μm to 30 μm.
Most preferably, it is not more than 00 μm.

The tread rubber composition used in the tread portion of the pneumatic tire of the present invention has no problem as long as it is a rubber composition for a tread used in a general studless tire for ice and snow surfaces. For example, foamed rubber, a rubber composition in which vulcanized powder rubber or foamed rubber powder is arranged in a scattered manner,
Further, a rubber composition mixed with a hard substance which does not chemically bond to a rubber component such as a cellulose fiber, a nylon fiber or a water-soluble resin is used. Among them, a rubber composition mixed with a water-soluble resin is preferable. When foamed rubber is mixed, the performance on ice can be significantly increased by increasing the foaming rate, but at the same time, the hardness is reduced by foaming. In the case of studless, when the rigidity of the tread is reduced, the blocks fall down due to the fine sipe being cut, and the ground contact area is reduced, thereby reducing the performance on ice and the steering stability. But,
In the case of mixing of a hard substance, there is no space like a bubble, and the hardness does not decrease. In the case of mixing of a water-soluble resin, an effect of absorbing water and removing a water film is added, in addition to an edge effect due to surface irregularities at the time of falling off the running material, as compared with other hard substances.

When the above-mentioned water-soluble resin is used, its shape may be a powder having an average particle diameter of 20 to 1000 μm or an average length of 20 to 1000 μm, and an aspect ratio of 10 to 10 μm.
It is desirable to use at least one or more of 1,000 short fibrous bodies. Examples of the type include sodium carboxymethylcellulose, polyvinyl alcohol, alkylacrylamide, vinylpyrrolidone derivatives, and hydroxyethyl methacrylate.The most preferably used is an oxyalkylene group represented by the following general formula. And the oxyalkylene group content in the polyvinyl alcohol-based resin containing an oxyalkylene group is preferably 5 to 20% by weight. This is because the oxyalkylene group-containing polyvinyl alcohol having a specific structure has extremely high water solubility in a low temperature range. This makes it possible to quickly remove the water film on the ice. Further, since the oxyalkylene group-containing polyvinyl alcohol has biodegradability, it does not cause environmental pollution even if it is eluted on the road surface.

[0011]

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Regarding the treatment for imparting adhesion of the powdered rubber in the present invention, the performance can be sufficiently obtained by the untreated powdered rubber, but the unvulcanized molded product (the tread portion is covered with the untreated powdered rubber). When vulcanizing the raw tire), the extra rubber escape route (vent hole) on the vulcanized mold surface of the tread tread
Powdered rubber gets into the machine. When the tire exits the vulcanization mode after vulcanization, the rubber that escaped from the vent hole at the same time escapes.However, untreated powdered rubber has only a pseudo-crosslinking level of reinforcing properties, so if you pull out the clogged one, it will break in the middle, I get stuck in the hall. The clogging of the vent hole is very important in tire production, and if it occurs frequently, the production efficiency is reduced. Therefore, it is necessary to treat the powdered rubber with the adhesion imparting agent to enhance the reinforcing property and suppress the clogging of the vent hole.

The adhesion-imparting agent used in the present invention includes, for example, rubber latex, liquid rubber, and organic solvent, and is preferably a diene-based rubber latex and liquid rubber. Examples of the rubber latex include rubber latex such as natural rubber, styrene-butadiene rubber, butadiene rubber, and styrene-butadiene rubber modified with carboxy. Preferably, natural rubber, butadiene rubber, and styrene butadiene rubber are used. These emulsions usually have a solid content of 40 to 60% by weight. The liquid rubber is preferably a polyisoprene, polybutadiene, styrene butadiene copolymer having a molecular weight of 3,000 to 150,000. The amount of the treatment with the adhesion-imparting agent is preferably 2 to 10 parts by weight based on 100 parts by weight of the powder rubber in terms of performance and operation. If it is less than 2 parts by weight, the desired treatment is insufficient, and if it exceeds 10 parts by weight, the surface irregularities required for the performance on ice cannot be obtained.

The rubber component of the powdered rubber used in the present invention is, for example, one or more selected from the group consisting of natural rubber, polyisoprene, polybutadiene and styrene-butadiene copolymer, or polyisobutene and polyethylene propylene. Preferably, Particularly preferred are one or more selected from natural rubber, polyisoprene, and polybutadiene. Basically, the use of powder rubber can provide surface irregularities, but the lower the rubber hardness at lower temperatures, the better the adhesive friction at low temperatures. Therefore, one or two or more selected from natural rubber, polyisoprene, and polybutadiene having a low glass transition temperature and a low hardness at a low temperature are preferable.

The rubber component of the powdered rubber used in the present invention contains a filler such as carbon black and additives such as a vulcanization accelerator and an antioxidant. May be blended in a usual amount. Further, regarding the method for imparting adhesion to the trade tread of the powder rubber, the treated powder rubber is directly sprayed on the tread tread,
Any of a method of pressurizing and vulcanizing or a method of laminating the treated powder rubber to a predetermined thickness in advance and laminating it on the tread tread, pressing and vulcanizing may be employed.

The tread rubber composition in the tread portion is blended with a filler such as carbon black or the like usually used for tread rubber, an additive such as a vulcanization accelerator or an antioxidant with respect to the rubber component of the tread. Further, a predetermined hard substance that does not chemically bond with the rubber component is blended, and then a tread is manufactured according to a normal manufacturing method.

[0017]

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

Method for Producing Powdered Rubber The components shown in Table 1 below were used to knead the components other than the vulcanized system with an internal mixer, and then the master batch and the vulcanized system were mixed with a roll mill to obtain 160. ° C, 20
Vulcanized rubber obtained by vulcanization per minute was freeze-pulverized at -200 ° C. or lower using liquid nitrogen, and then selected with a Tyler mesh to obtain powdered rubber of each particle size. Table 2 shows a list of powdered rubber of each particle size.

[0019]

[Table 1]

[0020]

[Table 2]

[0021] processing method Table 3 below powder rubber showing a list of powdered rubber process compounding. A predetermined amount of rubber latex or liquid rubber is added to powdered rubber. Since rubber latex has water, the water is evaporated at room temperature. Powdered rubber to which rubber latex or liquid rubber has been added is mixed at 120 ° C. using an internal mixer at 1 ° C.
Knead for 0 minutes. When carbon, zinc oxide and stearic acid are added, they are added at this time and kneaded at the same time. The addition of the vulcanization accelerator and sulfur, once cooled the kneaded material,
Next, the mixture is kneaded with an internal mixer and the process is completed at 100 ° C. About the obtained processed material, in order to confirm the reinforcing property,
Press vulcanization was performed at 160 ° C. for 20 minutes to prepare a target test piece. Reinforcement was confirmed by the tensile strength in the tensile test and the elongation at break. Tensile test is JIS K6
251 was performed.

[0022]

[Table 3]

According to the results of a tensile test performed on the test pieces shown in Table 3 above, rubber latex,
Those treated with the liquid rubber (S2 to S9) have improved tensile strength and elongation at break in any case, which indicates that they work advantageously for clogging of vent holes and the like.

Preparation method of cap tread rubber In the composition shown in Table 4 below, each component except for the vulcanization system was mixed for 5 to 6 minutes by a closed mixer, and the masterbatch was released when the temperature reached 165 ° C ± 5 ° C. The vulcanization accelerator and sulfur were again kneaded with a closed mixer and released at 110 ° C. to obtain a rubber composition. At this time, various polyvinyl alcohols, nylon short fibers, vulcanized powder rubber and the like were mixed in the first closed mixer, and the foaming agent was mixed in the same step as the vulcanizing system.

[0025]

[Table 4]

The tire manufacturing method used in the evaluation of the tire manufacturing method does not deviate from a general one. That is, a component material such as an inner liner, a carcass, a belt, a side tread, and a cap tread is attached to produce an uncured green tire. It is placed in a tire mold and vulcanized. Therefore, here, a method for covering the cap tread with powdered rubber will be described. An adhesive having the following composition is applied to the tread surface of the rubber member for the cap tread after the extrusion process. After the powder rubber is entirely covered on the coated surface, excess powder rubber is removed until the powder rubber is slightly thicker than a predetermined thickness. The powdered rubber covering the tread is pressed with a roller jig or the like, and the specified thickness is again measured at ± 500 μm.
If it is thicker than specified, start over. If it is thinner, add powder rubber. The surface-treated powdered rubber, which is formed into a sheet, is extruded to a specified thickness by a roll mill or the like, and then pasted on the cap tread tread.

Adhesive composition n-hexane 1000 g PIR 100 g zinc oxide 5 g stearic acid 2 g antioxidant 1 g sulfur 1.5 g vulcanization accelerator NS 1 g (Note) n-hexane: n-hexane (Kanto Chemical) PIR: Nipol IR 2200 (manufactured by Zeon Corporation) Zinc oxide: Zinc flower No. 3 Stearic acid: Industrial stearic acid Antioxidant: N-phenyl-N '-(1,3-dimethylbutyl) -p-phenylenediamine Sulfur: 5% Oil-extended powder sulfur Vulcanization accelerator NS: N-tert-butyl-2-benzothiazolylsulfenamide

The following test methods were used for tire evaluation. Actual vehicle braking test on ice Tire size 175 / 70R 13 (Steel radial tire) Rim 13 × 5J Air pressure 200kPa Vehicle 1500cc passenger car Test temperature -2 ° C ~ 0 ° C Near brake at initial speed 40km / h and measure distance to stop I do. The distance is displayed as an index. (The tire after running in Example 1 is set to 100), and the larger the numerical value, the better. (Before running) No preliminary running, that is, the tire cap tread tread reflects a smooth vulcanized mold surface. (After running) I made a preliminary run on the asphalt road for 300 km.
Accordingly, the powder rubber covering the tread disappears, and the cap tread rubber appears.

Running Life Test Tire Size 175 / 70R 13 (Steel Radial Tire) Rim 13 × 5J Air Pressure 200kPa Vehicle 1500cc Passenger Car Under the above conditions, the distance when the asphalt surface was run and the cap tread tread became 3 mm from the groove bottom. Is displayed as an index. (The tire after running in Example 4 is set to 100),
The higher the value, the better.

Standard Example 1, Examples 1 to 7 and Comparative Examples 1 to
2 The results of the actual tire evaluation when the type of powder rubber was changed
It is shown in Table 5 below.

[Table 5]

According to the evaluation results in Table 5, the performance on ice is not changed before and after running in any of the examples 1 to 7 in contrast to the case of the standard example 1 in which the performance on ice is largely changed before and after running. The powder rubber composition using NR, IR, and BR exhibits high braking performance on ice before traveling.
Further, as shown in Comparative Examples 1 and 2, if the particle diameter of the powdered rubber is too small or too large, the braking performance on ice is reduced.

Examples 8 to 13 Table 6 below shows the results of evaluation of the actual tires on the difference in the cap tread rubber composition.

[Table 6]

According to the evaluation results in Table 6, Examples 8 to 13 are shown.
As shown in the above, in all the cap tread rubber compositions, the performance on ice before and after running does not change. In addition, comparing Example 4 with Example 9, the addition of the oxyalkylene group-containing polyvinyl alcohol according to Example 4 before and after traveling was better than the case where the polyvinyl alcohol according to Example 9 was added as a hard substance. High braking ability on ice. On the other hand, as shown in Example 13, when the same hard substance is added in a small amount, the braking performance on ice after traveling decreases.

Examples 14 to 19 Table 7 below shows the results of evaluation of actual tires when the surface treatment type and amount of the powder rubber were changed.

[Table 7]

According to the evaluation results in Table 7, Examples 14 to 1
As shown in FIG. 8, when the treatment type and amount of the powder rubber are changed within a predetermined range, the braking performance on ice before and after traveling does not change in any case. However, as shown in Example 19, when the processing is performed with an excess amount exceeding the predetermined amount, the braking performance on ice before traveling decreases.

Examples 20 to 21 and Comparative Example 3 Table 8 below shows the evaluation results of the actual tires when the thickness of the rubber powder covering the tread surface of the cap tread was changed.

[Table 8]

According to the evaluation results in Table 8, Examples 20 to 2
As shown in FIG. 3, in a specific thickness range, the running life is not reduced without changing the braking performance on ice before and after running, but when the range is exceeded, the running life is significantly reduced.

[0038]

As described above, according to the present invention, it is possible to obtain a pneumatic tire capable of maintaining the initial performance and the performance after running wear of a studless tire having excellent performance on snow and performance on ice.

Claims (6)

[Claims] 1. A pneumatic tire having a tread having a tread whose tread surface is covered with powdered rubber having an average particle diameter of 50 to 500 μm to a thickness of 1000 to 3000 μm. 2. The pneumatic tire having a tread according to claim 1, wherein the tread portion is a cap tread rubber composition for a studless tire for ice and snow surfaces. 3. The rubber composition according to claim 1, wherein the tread portion comprises a rubber and 100 parts by weight of a base rubber component comprising one or more selected from the group consisting of natural rubber, polyisoprene, polybutadiene and styrene-butadiene copolymer. The pneumatic tire having a tread according to claim 1 or 2, which is a tread rubber composition containing 3 to 50 parts by weight of a hard substance that does not chemically bond. 4. The tread according to claim 1, wherein the powdered rubber is surface-treated with 2 to 10 parts by weight of an adhesive for powdered rubber based on 100 parts by weight of the powdered rubber. A pneumatic tire having: 5. The pneumatic tire having a tread according to claim 4, wherein the adhesion imparting agent for powdered rubber is at least one selected from rubber latex and liquid rubber. 6. The rubber component of the powder rubber is one or more selected from the group consisting of natural rubber, polyisoprene, polybutadiene and styrene-butadiene copolymer, or polyisobutene and polyethylene propylene. A pneumatic tire having the tread according to any one of claims 1 to 5.