JP2000319451A - Tread rubber composition and studless tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a studless tire which shows good abrasion resistance, excellent road holding property on a snow and ice road and less decrease of the road holding property even after a long term running and a tread rubber composition which gives a tread for the tire. SOLUTION: A tread rubber composition comprises 100 pts.wt. of a diene- based rubber as a matrix and 5 to 20 pts.wt. of a particle dispersed in the matrix to enhance a road holding property, the particle being a crushed particle of a hard rubber having an average particle diameter of 100 to 3,000 μm, the hard rubber containing 100 pts.wt. of a rubber component, 5 to 30 pts.wt. of a short fiber having a diameter(D) of 1 to 50 μm, length(L) of 100 to 3,000 μm and an aspect ratio (L/D) of 10 to 500 and a thermosetting resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a tread rubber composition and a studless tire.

[0002]

2. Description of the Related Art Various studless tires have been developed in order to improve the grip performance of vehicle tires on snow and ice. For example, pulverized shells such as fir and walnut are contained in a matrix of the tire tread. There is known one that is dispersed to improve grip.

[0003] However, in recent years, higher performance has been demanded for gripping properties, and a tire tread using the above-mentioned pulverized material cannot satisfy such a high level demand. In addition, the pulverized material has a problem that it is worn out in a short time or falls off from the tread surface, so that the grip property is rapidly reduced.

[0004]

The problem to be solved by the present invention is to have good abrasion resistance and excellent grip on snow and ice road surfaces, and this grip is hardly reduced even after long running. It is to provide a studless tire and a tread rubber composition from which a tread of the tire can be obtained.

[0005]

Means for Solving the Problems To solve the above-mentioned problems, the present inventor analyzed the problems in the above-mentioned pulverized materials in detail, and found that the problem that the pulverized materials are worn in a short time is high in abrasion resistance. The problem can be solved if the short fibers and the thermosetting resin are solidified with a binder to form particles, and the problem of the pulverized material falling off the tread surface can be solved by using a rubber component similar to the matrix component of the tread as a binder during vulcanization. It was considered that the dispersed particles were adhered to the matrix to improve the adhesiveness, which could be eliminated. In this way, instead of the traditional natural grounds,
The idea was to blend hard rubber particles obtained from a composition containing a rubber component, short fibers and a thermosetting resin into a tread. By repeating various experiments, optimizing the components of the hard rubber particles, it was confirmed that good abrasion resistance and excellent grip properties were obtained, and that the grip properties were not easily reduced even after long running, The present invention has been reached.

That is, the tread rubber composition according to the present invention is obtained by blending 100 parts by weight of a diene rubber serving as a matrix with 5 to 20 parts by weight of particles dispersed in the matrix to improve grip. A rubber composition, wherein the particles have an average particle size of 1
The rubber is a pulverized particle of 00 to 3000 μm, wherein the hard rubber contains a rubber component, a short fiber, and a thermosetting resin, and 5 to 30 parts by weight of the short fiber is mixed with 100 parts by weight of the rubber component. Obtained from the composition, wherein the short fibers are:
Diameter (D) 1-50 μm, Length (L) 100-3000
It is a fiber having a length of 10 μm and an aspect ratio (L / D) of 10 to 500.

A studless tire according to the present invention is a studless tire provided with a tread, wherein the studless tire is obtained from the tread rubber composition.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION First, the diene rubber and particles (hard rubber particles) constituting the tread rubber composition of the present invention will be described in detail, and then the tread rubber composition and studless tire will be described. (Diene rubber) Diene rubber used in the present invention,
It is a main component of the tread rubber composition, serving as a tread matrix.

Examples of the diene rubber include diene rubbers such as natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR), and butadiene rubber (BR). Or two or more are used. Of these, natural rubber and / or butadiene rubber are preferred because they are unlikely to become hard at low temperatures.

The diene rubber may contain styrene-butadiene rubber (SBR), isoprene-isobutylene rubber (IIR), halogenated butyl rubber (X-IIR), etc. in addition to the diene rubber. [Hard rubber particles and raw materials thereof] The hard rubber particles used in the present invention are particles made of hard rubber obtained by solidifying specific short fibers and a thermosetting resin with a rubber component of the same quality as the matrix, and are dispersed in the matrix. It is a component that imparts good abrasion resistance and excellent grip properties on snow and ice road surfaces to the tread, and does not reduce the grip properties even after long-term running. The hard rubber particles are particles obtained by pulverizing hard rubber obtained by vulcanizing or semi-vulcanizing a rubber composition described below.

The hard rubber is preferably semi-vulcanized rather than vulcanized. This is because, when the tread rubber composition is vulcanized, it is vulcanized together with a diene rubber which serves as a matrix of the tread rubber composition, so that the adhesive strength increases. The average particle size of the hard rubber particles is 100 to 3000 μm
And preferably 100 to 2000 μm, more preferably 100 to 1000 μm. If the average particle size of the hard rubber particles is less than 100 μm, the tread becomes too hard, and the grip of the tread on a snow and ice road surface decreases. On the other hand, when the average particle size of the hard rubber particles exceeds 3000 μm, the difference in wear resistance between the tread rubber and the hard rubber appears remarkably, and the appearance of the tread surface after running for a long period of time is not good. become.

The hardness of the hard rubber particles is not particularly limited, and is preferably 80 or more, more preferably 90 or more, as measured with a type A durometer. If the hardness of the hard rubber particles is less than 80, the grip of the tread on a snow and ice road surface may be reduced. The shape of the hard rubber particles is not particularly limited, and may be spherical or flat.

The rubber composition for obtaining the above-mentioned hard rubber particles contains a rubber component, short fibers and a thermosetting resin. The rubber component is a component that becomes a binder that solidifies the short fibers and the thermosetting resin into particles by being vulcanized or semi-vulcanized. Since the rubber component and the diene rubber serving as the base material of the tread rubber composition adhere during vulcanization, the short fibers are fixed in the tread.

As the rubber component, natural rubber; styrene
Butadiene rubber (SBR), butadiene rubber (BR),
Diene-based synthetic rubbers such as isoprene rubber (IR); polynorbornene resins, etc., and one or more of them can be used. The rubber component may include components other than the above. The short fiber is a component that supplementarily enhances the wear resistance of the hard rubber particles and the entire tread, imparts excellent grip to the tread on snow and ice road surfaces, and does not decrease the grip even after long-term running.

The dimensional relationship of short fibers will be described. The diameter (D), length (L) and aspect ratio (L / D)
Is D = 1-50 μm, L = 100-3000 μm, L
/ D = 10-500. The size of the short fiber is diameter 5 ~
20 μm, length 300-1500 μm, aspect ratio 3
It is preferably from 0 to 200. If the diameter and / or length of the short fiber is larger than the above range, the dispersion of the short fiber becomes poor, and after vulcanization, it becomes a breaking nucleus to cause rubber sprinkling and the like, resulting in reduced wear resistance and snow and ice road surface. The grip of the tread is reduced. If it is smaller than the above range, the dispersion of the short fibers is also poor in this case, and the quality is not stable. When the aspect ratio is less than 10, it becomes difficult to orient the short fibers in a desired direction, the strength is reduced, and the grip properties are reduced. On the other hand, if the aspect ratio exceeds 500,
Also in this case, the dispersion of the short fibers becomes poor, and it becomes difficult to orient the short fibers in a desired direction. In short, when the dimensional relationship of the short fibers is as described above, the degree of dispersion of the short fibers in the vulcanized rubber is good, and the short fibers give the tread a sufficient reinforcing property, and the grip properties of the tread on the snow and ice road surface and Greatly improves wear resistance.

The material of the short fiber is not particularly limited, and examples thereof include nylon; polyester; rayon; aramid such as Kevlar; vinylon; cotton; More than one species can be used. In order to improve the adhesiveness (conformity) between the short fiber and the rubber component, the short fiber is a resorcinol-formalin initial condensate / latex mixture (RFL)
It is preferable that the surface is treated by the above method. Examples of the surface treatment method of the short fibers include a method of immersing the fibers in RFL and drying at 220 to 240 ° C. for 5 to 10 minutes.

The amount of the short fibers is not particularly limited, but is, for example, 5 to 30 parts by weight, preferably 10 to 25 parts by weight, per 100 parts by weight of the rubber component. If the blending amount of the short fibers is less than 5 parts by weight, abrasion resistance and grip properties of the tread on snow and ice road surfaces may be reduced. If the short fiber content exceeds 30 parts by weight, processability is poor,
The strength of the hard rubber particles obtained by vulcanization or semi-vulcanization decreases, and rubber chipping may occur. That is, when the blending amount of the short fibers is within the above range, the workability is good, and the wear resistance and the grip property of the tread on the snow and ice road surface are easily maintained for a long period of time.

The thermosetting resin is a component for improving the wear resistance of the hard rubber particles and the tread as a whole. The thermosetting resin is not particularly limited as long as it is a thermosetting resin. For example, a phenol / formaldehyde resin and the like can be mentioned, and one or two or more kinds are used. Among these, a phenol-formaldehyde resin such as a thermosetting phenol resin prepared for addition to rubber is preferable.

The amount of the thermosetting resin is not particularly limited. For example, the amount is preferably 10 to 30 parts by weight, more preferably 15 to 30 parts by weight, per 100 parts by weight of the rubber component.
20 parts by weight. If the amount of the thermosetting resin is less than 10 parts by weight, the hardness is not sufficient, the abrasion resistance may be reduced, and the grip performance on snow and ice road surfaces may not be improved. On the other hand, if the compounding amount of the thermosetting resin exceeds 30 parts by weight, the resin may be cured during kneading or the like, and may not be processed thereafter.

The rubber composition may contain a reinforcing filler other than the above short fibers in order to further improve the reinforcing properties (abrasion resistance, rubber chipping resistance, hardness, etc.). Examples of the reinforcing filler include powders made of white fillers such as silica, clay, talc, calcium carbonate, basic magnesium carbonate, and alumina, in addition to carbon black. The blending amount is not particularly limited, and a necessary amount can be appropriately used.

If necessary, the rubber composition may further contain, for example, a softening agent such as a process oil; a vulcanization aid such as zinc oxide and stearic acid; a mercaptobenzothiazole (M
BT), dibenzothiazyl disulfide (MBTS),
It is composed of a thiazole-based accelerator such as N-tert-butyl-2-benzothiazolylsulfenamide (TBBS) and N-cyclohexyl-2-benzothiazylsulfenamide (CBS), hexamethylenetetramine (HMT), and the like. Additives such as a vulcanization accelerator; sulfur; a foaming agent; an antioxidant; The amounts of these additives are not particularly limited, and the necessary amounts can be appropriately used.

As a method for producing the rubber composition, a known method can be adopted. For example, a method in which the above-mentioned raw materials are kneaded using a rubber kneading apparatus such as a Banbury mixer or a kneader according to JIS K6299. No. Hard rubber particles are produced by grinding hard rubber obtained by vulcanizing or semi-vulcanizing a rubber composition. The vulcanization here refers to vulcanization of tc (80) or more in a vulcanization test according to JIS K6300, and semi-vulcanization refers to vulcanization of at least tc (10) and less than tc (80). [Tread Rubber Composition and Studless Tire] The tread rubber composition of the present invention is a composition containing the diene rubber and hard rubber particles as essential components.

The mixing ratio of the hard rubber particles is 5 to 20 parts by weight, preferably 10 to 20 parts by weight, based on 100 parts by weight of the diene rubber. If the compounding ratio of the hard rubber particles is less than 5 parts by weight based on 100 parts by weight of the diene rubber, improvement in wear resistance and grip properties of the tread on snow and ice road surfaces cannot be expected. On the other hand, diene rubber 100
If the amount exceeds 20 parts by weight with respect to the weight part, the performance on the snow and ice road surface is reduced due to the effect that the entire tread becomes hard.

The tread rubber composition of the present invention may contain the above-mentioned reinforcing filler such as carbon black in order to obtain a sufficient hardness when used in a studless tire. The tread rubber composition of the present invention may contain the additives exemplified in the description of the hard rubber particles, if necessary.

As a method for producing the tread rubber composition of the present invention, a known method can be applied. The above-mentioned components are obtained by kneading under ordinary methods and conditions using, for example, a kneader such as a Banbury mixer or a twin-screw roller. The tread of the studless tire according to the present invention is obtained from the tread rubber composition of the present invention. The tread is a portion that is always in contact with the road surface, and therefore, the studless tire has excellent grip properties on snow and ice road surfaces, has low grip characteristics even after long-term running, and has good wear resistance. .

The studless tire of the present invention is prepared by producing a raw tire from which a tire is made using the tread rubber composition, and then placing the raw tire in a mold vulcanizer at, for example, 150 to 180 ° C. It can be produced by vulcanizing for 8 to 40 minutes.

[0027]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples. However, the present invention is not limited to the following Examples. In the following, “parts” indicates “parts by weight” and “%” indicates “% by weight”. Prior to Examples and Comparative Examples, basic blending components used for these were prepared. -Production of Hard Rubber A- Each component shown in Table 1 was kneaded by a method according to JIS K6299 using a Banbury mixer and a roll machine to prepare a rubber composition A. Next, the rubber composition A was molded and vulcanized using a sheet mold (2 mm thick) to obtain a hard rubber A. The vulcanization temperature was 150 ° C and 50%
The time corresponding to the vulcanization was taken as the vulcanization time. Separately, the vulcanization temperature was 150 ° C and the time corresponding to 95% vulcanization was determined by JIS.
It was measured according to K6300 and is shown in Table 1 with the time corresponding to 50% vulcanization.

The hardness of the rubber composition A after vulcanization is determined by a vulcanization temperature of 1
After vulcanization at 50 ° C. for 5 minutes, it was measured using a type A durometer according to the method specified in JIS K6253. The results are shown in Table 1. —Production of Hard Rubber AA and Hard Rubbers B to G— In the same manner as for the hard rubber A, a rubber composition AA and a rubber composition BG are prepared from the components shown in Table 1, respectively. And hard rubbers B to G were produced.
In the rubber composition AA, the vulcanization temperature was 150 ° C.
The time corresponding to 5% vulcanization was taken as the vulcanization time. Separately, the vulcanization temperature was 150 ° C. and the time corresponding to 50% vulcanization was also measured. In the rubber composition AA, at a vulcanization temperature of 150 ° C.,
After vulcanization for 12 minutes, the vulcanization hardness was measured.

[0029]

[Table 1]

* 1 Kevlar (Kevlar, aramid fiber) manufactured by DuPont was used as the short fiber. In the rubber compositions A, AA and BD, Kevlar E / E 6F722 (trade name) which is a mixture with natural rubber (NR) was used instead of using Kevlar fiber alone. The ratio of Kevlar fiber to NR (Kevlar fiber / NR) in Kevlar E / E 6F722 is 30/1.
00. In Table 1, the composition of Kevlar E / E 6F722 is divided into NR and Kevlar fibers, and the short fibers are represented by the weight of only Kevlar fibers.
The NR included in F722 is shown in Table 1 with the NR added separately. For rubber compositions F and G, prototypes that were a mixture of Kevlar and natural rubber (NR) were used as described above.

* 2 Showa Cabot Co., Ltd., Carbon Black Showa Black N220 * 3 Sumitomo Durez Co., Ltd., Sumilite Resin PR12
686 * 4 TBBS N-tert-butyl-2-benzothiazolylsulfenamide, manufactured by Sanshin Chemical Co., Ltd., Suncellar NS * 5 HMT hexamethylenetetramine, manufactured by Ouchi Shinkosha Co., Ltd., Noxeller H -Example 1-Hard rubber A Was crushed using a cladding roll and a gliding roll which are usually used for crushing rubber, and passed through a sieve to produce hard rubber A particles having an average particle diameter of 1000 μm.

Next, the average particle size of the hard rubber particles is 10
15 parts of 00 μm hard rubber A particles, 60 parts of natural rubber,
Butadiene rubber (BR150B, manufactured by Ube Industries) 40
Parts, 60 parts of carbon black (Showa Black N220, manufactured by Showa Cabot), 10 parts of naphthenic oil (Process P-200, manufactured by Japan Energy), 1.5 parts of wax (Sunnoc, manufactured by Ouchi Shinkosha), aging prevention 1.5 parts of an agent (antigen 6C, manufactured by Sumitomo Chemical Co., Ltd.), 2.5 parts of stearic acid (tsubaki stearic acid, manufactured by NOF Corporation) and 3.0 parts of zinc oxide (two types of zinc oxide, manufactured by Mitsui Kinzoku Co., Ltd.) After blending, 1.0 part of sulfur (manufactured by Tsurumi Chemical Co.) and 1.5 parts of N-tert-butyl-2-benzothiazylsulfenamide (TBBS) as a vulcanization accelerator were further blended, and a Banbury mixer was added. To prepare a tread rubber composition (1). Table 1 shows the compounding amount, type and particle size of the hard rubber particles among the components.

The tread rubber composition (1) was extruded into a tread shape using an extruder, and then vulcanized at 165 ° C. for 20 minutes to produce a studless tire (1). In addition,
The tire specification was 185 / 70R14. -Example 2 and Comparative Examples 1 to 11-The same as Example 1 except that the hard rubber A particles having an average particle diameter of 1000 µm and the compounding amount thereof were changed as shown in Tables 2 and 3 in Example 1. And tread rubber composition (2) and comparative rubber compositions (1) to (1), respectively.
1) was prepared. The hard rubber particles described in Tables 2 and 3 were produced in the same manner as in Example 1.

Next, the tread rubber composition (2) and the comparative tread rubber compositions (1) to (11) are extruded into a tread shape using an extruder, respectively, and the studless tire (2) and the comparative studless tire ( 1)
To (11). The tires obtained in the above Examples and Comparative Examples were evaluated as described below. An initial braking index on ice tire was mounted on a car, and the initial speed was 30 km / h on the ice floe measurement road on the Nayoro Test Course in Hokkaido of Sumitomo Rubber Industries.
h from the deceleration at the time of lock braking with h
The braking index on ice was determined by setting the index at 100 to 100, and the results are shown in Tables 2 and 3. The greater the index value, the greater the braking force. Brake index on ice after traveling 5000 km The tire on which the result of the initial on-ice braking index was good was traveled 5000 km on a dry road, and then the on-ice braking index was obtained under the same conditions as described above. The results are shown in Tables 2 and 3.

[0035]

[Table 2]

[0036]

[Table 3]

<Evaluation Results> Examples 1 and 2 are superior to Comparative Example 1 containing no hard rubber particles in the initial grip on snow and ice road surfaces. Also hard to lower. Example 1 and Comparative Examples 2 and 3
From the comparison with, even if the compounding amount of the hard rubber particles is too small,
Even if the amount is too large, the initial grip property is reduced. The latter reason may be due to the tread becoming too hard.

From the comparison between Example 1 and Comparative Examples 4 and 5, the initial grip properties are reduced when the particle size of the hard rubber particles is too small, and the initial grip properties are reduced when the particle size of the hard rubber particles is too large. Good, but the grip after running 5000 km is reduced. The reason is that in the former, the tread is too hard, and in the latter, after traveling 5000 km,
This is probably because the hard rubber particles fall off and large irregularities are formed on the tread surface.

From the comparison between Example 1 and Comparative Example 6, when the hardness of the hard rubber particles is low, the initial grip properties are reduced. From the comparison between Example 1 and Comparative Examples 7 to 9, the initial grip properties are reduced when the blending amount of the short fibers in the hard rubber particles is too small, and the initial gripping properties are good when the blending amount is too large. However, grip performance after traveling 5000 km is reduced.
It is considered that the latter reason is that if the blending amount of the short fibers is too large after traveling 5,000 km, chipping of rubber or the like occurs.

From the comparison between Example 1 and Comparative Examples 10 to 11, when the aspect ratio of the short fibers in the hard rubber particles is too small (short fibers are too short) and too large (short fibers are too long) Means that the initial grip is good, but 500
The grip after running at 0 km is reduced in each case. The latter reason is considered to be due to the fact that the dispersibility of the short fibers in the hard rubber particles is low, and the short fibers are used as nuclei to cause chipping of the rubber and decrease the wear resistance.

[0041]

The studless tire according to the present invention comprises:
It has good abrasion resistance and excellent grip on snow and ice road surfaces, and this grip is unlikely to decrease even after long-term running. The tread rubber composition according to the present invention can be used for producing the above studless tire.

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) C08L 61/04 C08L 61/04 F term (reference) 4J002 AB014 AB024 AC011 AC012 AC031 AC032 AC061 AC062 AC081 AC082 BE064 BK002 CC033 CF054 CL004 CL064 FA044 FB264 FD010 FD020 FD022 FD023 FD024 FD030 FD140 FD150 GN01

Claims (2)

[Claims] 1. A tread rubber composition comprising 100 parts by weight of a diene rubber serving as a matrix and 5 to 20 parts by weight of particles dispersed in the matrix for improving gripping properties. Crushed particles having an average particle size of 100 to 3000 μm made of a hard rubber, wherein the hard rubber contains a rubber component, a short fiber, and a thermosetting resin, and the short fiber is 5 to 5 parts by weight of the rubber component. The short fiber is obtained from a rubber composition containing 30 parts by weight, and has a diameter (D) of 1 to 50 μm and a length (L) of 100 to 30.
A tread rubber composition, which is a fiber having a thickness of 00 µm and an aspect ratio (L / D) of 10 to 500. 2. A studless tire having a tread, wherein the tread is obtained from the tread rubber composition according to claim 1.