JPH06328907A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve running performance on ice and snow and improve wear resistance and blend processing property by constituting a tread section out of matrix rubber, powder rubber having low hardness, liquid polymer, and short fiber and letting these have the predetermined performance. CONSTITUTION:A tread section 13 is composed of a compound in which powder rubber composition having average particle size of less than 1000mum and low hardness, hollow minute particles, low molecular weight diene polymer having average molecular weight of 6,000 to 60,000, and short fiber having aspect ratio of 10 to 1000 are blended with matrix rubber. In addition, when carbon black is blended with powder rubber having low hardness, the amount is 20 weight parts or less per 100 weight parts of rubber, and the blending amount of powder rubber having low hardness is 1 to 10 weight parts per 100 weight parts of matrix rubber. Also, the blending amount of diene system polymer having low molecular weight is 5 to 50 weight parts per 100 weight parts of matrix rubber. Conequently, it is possible to suppress reduction of wear resistance and improve running performance on a road covered with ice and snow at the initial time of running and after a vehicle starts to run without reducing running performance on an ordinary wet road.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire having improved running performance on ice and snow, and particularly improved running performance on ice and snow while suppressing deterioration in wear resistance.

[0002]

2. Description of the Related Art Conventionally, when a car travels in winter in cold snowy regions, spiked tires with spiked tires are used, or a tire chain is attached to the outer periphery of the tire to allow snow to run on ice or ice. It is safe. However, a spiked tire or a tire equipped with a tire chain is apt to be worn or damaged on the road, which becomes dust and causes pollution, which is a serious environmental problem. In order to solve such a safety problem and an environmental problem, studless tires which have braking performance and drivability on snowy roads and icy roads without using spikes or chains are rapidly prevailing at present.

As this studless tire, a matrix of a low-hardness vulcanized rubber composition having a high adhesion effect (that the tread surface adheres to the icy road surface and follows the surface shape of the icy road surface) in order to improve the frictional force on ice is used as a matrix. A tire having a tread portion formed by compounding with rubber has been proposed (JP-A-63)
-92659, JP 63-172750, JP 4-382
See Japanese Patent Application Laid-Open No. 09 and Japanese Patent Application Laid-Open No. 3-10907).

However, JP-A-63-92659 discloses a pneumatic tire containing a soft powder vulcanized rubber having a glass transition point of -50 ° C. or less and a particle size of 1000 μm or less. The adhesion effect was not sufficient and the performance on ice was not always satisfactory.

On the other hand, Japanese Unexamined Patent Publication No. 60-139503 discloses a studless tire using a tread rubber containing high hardness rubber particles. However, since the adhesion effect of the rubber particles themselves is low, the performance on ice is not always required. It was not satisfactory.

Further, Japanese Patent Application Laid-Open No. 4-38209 discloses that low hardness rubber particles and short fibers are blended, but since the rubber particles have a relatively large particle size, they have wear resistance and mixing processability. Was insufficient in terms of. Further, in Japanese Patent Laid-Open No. 3-10907, the average particle size of 0.5-
It has been proposed that a 3 mm low-hardness vulcanized rubber composition be blended with a matrix rubber to improve the performance on ice. However, this pneumatic tire also does not have a sufficient matrix rubber adhesion effect and the performance on ice is not always satisfactory. Not going.

[0007]

As described above, the conventional techniques have problems that the frictional force on ice is not sufficient and that the mixing workability is difficult. Therefore, it is an object of the present invention to solve the problems of the prior art and to provide a pneumatic tire having excellent wear resistance and mixing workability, as well as significantly improving running performance on ice and snow. .

[0008]

According to the present invention, the tread portion is composed of a matrix rubber, a low hardness powder rubber, a liquid polymer and a short fiber, and the low hardness powder rubber has an average particle size of less than 1000 μm, Hardness Powder rubber containing or not containing 20 parts by weight or less of carbon per 100 parts by weight, the compounding amount is 1 to 10 parts by weight per 100 parts by weight of matrix rubber, and the liquid polymer is a low molecular weight diene having an average molecular weight of 6,000 to 60,000. -Based polymer whose compounding amount is matrix rubber 1
There is provided a pneumatic tire having 5 to 50 parts by weight per 00 parts by weight, and the short fibers having an aspect ratio (ratio of length / diameter) of 10 to 1000.

The structure of the pneumatic tire according to the present invention is not particularly limited, and a pneumatic tire having any conventionally known structure, and pneumatic tire structures of various structures currently under development may be used. The tread portion may have the above-described configuration.

An example thereof will be described below with reference to the attached FIG. FIG. 1 is a meridional direction half-section explanatory view of a preferred example of the pneumatic tire of the present invention. In FIG. 1, a pneumatic tire A of the present invention includes a pair of left and right bead portions 11, 11 and a pair of left and right sidewall portions 12, 12 connected to these bead portions 11, 11 and between these sidewall portions 12, 12. It consists of a tread portion 13 that is arranged. A carcass layer 14 is mounted between the pair of left and right bead portions 11, 11, and a belt layer 15 is arranged in the tread portion 13 so as to surround the outer periphery thereof. 10 is the tread surface.

In the present invention, as described above, the tread portion 13 is a low hardness vulcanized rubber composition having an average particle size of less than 1000 μm,
From a mixture of hollow fine particles with an average particle size of 10 to 120 μm and an average wall thickness of 0.1 to 15 μm, a low molecular weight diene polymer with an average molecular weight of 6,000 to 60,000 and short fibers with an aspect ratio of 10 to 1000 in a matrix rubber. Composed.

In the present invention, the kind of the matrix rubber compounded in the rubber compound constituting the tread portion is not particularly limited, but preferably natural rubber, polyisoprene rubber, polybutadiene rubber, styrene-butadiene copolymer weight. A united rubber or a blend of these is used. Compounding agents such as carbon black and a softening agent are appropriately mixed with this matrix rubber by a conventional method.

The carbon black is not particularly limited in kind as long as it is usually used for treads. The compounding amount of carbon black is raw rubber 1
The amount is preferably 40 to 100 parts by weight with respect to 00 parts by weight, and less than 40 parts by weight is not preferable because the reinforcing property is poor and the abrasion resistance tends to be low. If it exceeds 100 parts by weight, heat generation tends to increase, which is not preferable.

In the rubber compound constituting the tread portion in the present invention, the average particle size is less than 1000 μm, preferably 10 to 4
Compound a low hardness powder rubber of 00 μm. This average particle size is 10
When it exceeds 00 μm, the wear resistance of the pneumatic tire is deteriorated and the mixing processability during the production of the pneumatic tire is deteriorated, which is not preferable.

The low hardness powder rubber is preferably a rubber compound previously vulcanized so that its shape is maintained even after tire vulcanization. Examples of the raw rubber include natural rubber, polyisoprene rubber, polybutadiene rubber, and the like. A styrene-butadiene copolymer rubber, a halogenated butyl rubber, or a blend of two or more of these can be used.
Carbon black may or may not be blended,
When compounded, it should be 20 parts by weight or less per 100 parts by weight of rubber. This is because when the compounding amount of carbon black is increased, the modulus difference from the matrix rubber is reduced and the adhesion effect is reduced, so that the performance on ice is not improved. In addition, it is preferable not to mix carbon black.

In the present invention, the compounding amount of the low hardness powder rubber in the rubber compound constituting the tread part is 1 to 10 parts by weight per 100 parts by weight of the matrix rubber, and 2 to 4 parts by weight is particularly preferable. If the blending amount is less than 1 part by weight, the improvement of the performance on ice is insufficient, and conversely, if it exceeds 10 parts by weight, the abrasion resistance decreases, which is not preferable.

In the present invention, the liquid polymer used as a softening agent in the rubber compound constituting the tread portion, that is, the low molecular weight diene polymer is GPC (gel permeation ch
romatgraphy: measured by gel permeation chromatography, and the molecular weight converted to polystyrene is 6,000.
It is a low molecular weight diene-based polymer of -60,000. The measurement conditions of GPC are as follows. Solvent: THF (tetrahydrofuran) Concentration: 0.05 wt% Flow rate: 1 ml / min Column temperature: 40 ° C Column: Ultra Styragel (trade name) If the molecular weight of this low molecular weight diene polymer is less than 6,000, it will be It is not preferable because it has a migration property and the purpose of blending cannot be achieved, and conversely, when the molecular weight exceeds 60,000, the softening effect becomes small and the desired physical properties cannot be obtained, which is not preferable.

The low-molecular-weight diene-based polymer used in the present invention is an arbitrary diene-based polymer (for example, butadiene polymer, isoprene polymer, acrylonitrile-butadiene copolymer, fragrance, etc.) as long as it does not bleed out from the surface of the raw rubber. Group vinyl butadiene copolymers) and the preferred diene-based polymer is a butadiene polymer having 70% or more, preferably 75% or more, of cis 1.4 bonds. This is because when the cis bond is less than 70%, the low temperature hardness becomes high (hard) and the performance on ice tends to deteriorate. Further, the low molecular weight diene-based polymer used in the present invention is one having a general formula> C = N ⁺ <functional group (for example, N-methyl-2-pyrrolidone, N-methyl-β-propiolactam etc.) at the end. Although generally known, the effect obtained by the present invention does not depend on the terminal structure of the low molecular weight polymer, but is obtained by its basic structure.
Therefore, it may have a terminal functional group, and its type does not matter.

According to the invention, a molecular weight of 6,000 to 60,000,
Preferably, 6,000 to 50,000 low molecular weight diene-based polymer is added in an amount of 5 to 50 parts by weight, preferably 5 to 30 parts by weight, based on 100 parts by weight of the matrix rubber. If the blending amount of this low molecular weight diene polymer is less than 5 parts by weight, the blending amount will be too small to be effective, and if it exceeds 50 parts by weight, the Mooney viscosity of the unvulcanized rubber will be lowered and the workability will be deteriorated to be practical. Not.

In the present invention, the rubber composition constituting the tread portion further has an aspect ratio of 10 to 1000, preferably 10
~ 300 short fibers are blended. As such short fibers,
For example, natural fibers such as cotton and silk, cellulosic fibers, polyamide fibers, polyester fibers, chemical fibers such as polyvinyl alcohol fibers such as vinylon, and inorganic fibers such as carbon fibers can be used. Preferable are polyamide fibers represented by nylon fibers or cellulosic short fibers such as rayon. In particular, for example, γ
-A master batch containing 50 parts by weight of nylon 6 fibers with an average length of 30 μm and an average diameter of 0.3 μm surface-treated with aminopropyltrimethoxysilane per 100 parts by weight of natural rubber (commercially available as UBEPOL-HE from Ube Industries, Ltd.) Can be preferably used. Metal short fibers such as steel short fibers and copper-based metal short fibers may be used. Two or more kinds of these short fibers may be used in combination.

The amount of the short fibers mixed with the rubber is not particularly limited, but is preferably 1 to 15 parts by weight, and particularly preferably 1 to 5 parts by weight, based on 100 parts by weight of the matrix rubber. In the present invention, the short fibers are oriented along the block surface and side surfaces of the tread portion 13. The orientation of the short fibers is shown in FIGS. FIG. 2 is an explanatory plan view of a tread portion of an example of the pneumatic tire of the present invention, and FIG. 3 is a sectional view taken along the line KK ′. As shown in FIGS. 2 and 3, the short fibers 17 are
The tread portion 13 is oriented in the tire circumferential direction EE ′ along the surface a and the side surface b of the block 16. As described above, most of the short fibers are preferably oriented along the block surface and the side surface of the tread portion (along the circumferential direction).

To obtain such short fiber orientation,
When extruding the tread portion 13, it is used that fibers having a certain length / diameter ratio tend to be aligned in the flow direction of the rubber that is the matrix. Such a tendency is that when the tire is vulcanized, the unvulcanized tread rubber flows along the mold by the protrusions of the mold, and as a result, the short fibers 17 are oriented along the protrusions of the mold. This allows
The short fibers 17 are oriented along the surface a and the side surface b of the block 16 of the tread portion 13. However, the short fibers 17
If it does not have a constant aspect ratio, it will be randomly arranged in the tread rubber and will not be oriented. Therefore, the short fibers have an aspect ratio of 10 to 1000, preferably 10 to 1000.
Must be 300, preferably 0.05 mean diameter
The average diameter is preferably 0.05 to 0.8 μm and 1 to 100 μm, more preferably 1 to 5000 μm and more preferably 1 to 5000 μm in average length, and more preferably short fibers prevent deterioration of abrasion resistance and are excellent in orientation.
It is a polyamide-based short fiber having an average length within the range of μm. If the aspect ratio exceeds 1000, the fraction of the short fibers in the matrix rubber becomes poor and sufficient orientation cannot be obtained, which is not preferable.

In the block 16 in which the short fibers 17 are oriented on the surface a and the side surface b as described above, the rigidity of the entire block is remarkably high, but the elastic modulus in the direction perpendicular to the orientation direction, that is, from the surface to the inward direction is not so high. Anisotropy of elastic modulus is expressed. Due to this anisotropy, the block rigidity of the soft base rubber, which has a high adhesion effect, can be reinforced, and the block edge effect and the rubber adhesion effect can be maximized, so that the performance on ice and snow roads is of course better than on ordinary roads. Performance can also be improved.

The rubber compound used in the present invention may optionally contain various additives commonly used for tires, in addition to the above-mentioned essential components. can do. Examples of such optional additives include vulcanization accelerators, antioxidants, fillers and plasticizers. The pneumatic tire according to the present invention can be manufactured by using a general method and apparatus except that the above rubber compound is vulcanized to form a tread portion.

[0025]

According to the present invention, the above-mentioned specific low hardness powder rubber, hollow fine particles, liquid polymer and short fibers are compounded in the matrix rubber of the rubber compound constituting the tread portion of the pneumatic tire. By compounding rubber, a micro low modulus part is created in the rubber, the followability to the road surface on ice is improved, and the powdered rubber in contact with the road surface brings a high adhesion effect, and the specific short fiber By using together, the block of low hardness powder rubber is reinforced,
Sufficient frictional force on ice can be obtained even in a region where the amount of powdered rubber is relatively small, and further abrasion resistance, mixing processability, etc. are improved.

Further, according to the present invention, by using a specific liquid polymer as a softening agent, it is possible to cover the wear which is reduced in the blending of the low hardness powder rubber, and to prevent the change of the rubber with time due to the migration of the softening agent. Can be suppressed.

[0027]

The present invention will be described in more detail below with reference to Examples and Comparative Examples, but it goes without saying that the technical scope of the present invention is not limited to these Examples. Examples 1 to 4 and Comparative Examples 1 to 7 Using the tread rubber compounds having the compounding contents (parts by weight) shown in Table 1, pneumatic radial tires having the structure shown in FIG. 1 were prepared by a conventional method. The size of this tire is 185 /
70 R13 85Q The cord angle of the carcass layer 4 was set to approximately 90 ° with respect to the tire circumferential direction. The following evaluation was performed using a 1600cc FF car as a test car. The results are shown in Table 1.

Dynamic Young's modulus (circumferential direction and radial direction) [MPa
] : A sample was cut from the side of the tread block of each test tire after running 7,000 km on a new and dry road surface in the circumferential direction (same as the tire circumferential direction) and the radial direction with respect to the tire rotation axis, and manufactured by Toyo Seiki Co., Ltd. Using a viscoelastic spectrometer, the length between chucks is 10 mm, width is 5 mm, and thickness is 2
The mm sample was measured under the conditions of a frequency of 20 Hz, an initial strain of 10%, a dynamic strain of ± 2%, and a temperature of 0 ° C. The larger the value, the greater the rigidity.

Braking performance on ice: 30 km on ice
The braking distance at the time of braking was measured by running at / h, and the index was displayed with the conventional tire (control example) preliminary running (300 km) as 100. The larger the value, the better the braking. All tires were preliminarily run on a dry road for 300 km before they were tested.

Driving performance on a snowy road surface: By repeatedly braking a compressed snowy road surface with a passenger car, a climbing test with a 5% (2.9 °) slope is performed on a slippery compressed snowy road surface with a smooth road surface,
The zero-start method was used to measure the uphill acceleration time in the 30m section, which was shown as an index for conventional tires. The larger the value, the better the drivability. All tires were preliminarily run on a dry road for 300 km before they were tested.

Braking performance on wet road surface : Running on an asphalt road surface with water removed at an initial speed of 40 km / h, the braking distance when braking was measured, and the conventional tire (control example) was set to 100 and expressed as an index. The larger the value, the better the braking. All tires were preliminarily run on a dry road for 300 km before they were tested.

Abrasion resistance (dry road surface) : 20,000 dry road surfaces under the conditions of design normal load and air pressure specified in JATMA.
After traveling for km, the wear amount of each tire was shown as an index with respect to the wear amount of the conventional tire (control example). The larger the number,
It shows that the wear resistance is good.

Mixing workability : The mixing of the mixed rubber, the sheeting property, the bagging on the roll, the state of the extruded product, etc.
Scored on a perfect score. The higher the score, the better.

[0034]

[Table 1]

[0035]

[Table 2]

(1) BR ... Moss component 98%, Tg-103 ° C. (2) N- (1,3-dimethyl) -N'-phenyl-p
-Phenylenediamine (3) N-tert-butyl-2-benzothiazole-sulfenamide (4) Low hardness powder rubber A ... NR pure rubber vulcanized rubber pulverized product (average particle size 200 µm, carbon 0 phr) (5 ) Low hardness powder rubber B ... NR pure rubber vulcanized rubber crushed product (average particle size 1500 μm, carbon 0 phr) (6) Low hardness powder rubber C ... NR pure rubber vulcanized rubber crushed product (average particle size 200 μm, carbon 40 phr) (7) Short fibers A ... Nylon 6 short fibers, average length 30 μm, average diameter 0.3 μm (8) Short fibers B ... Cellulose short fibers, average length 1500 μ
m, average diameter 12 μm (9) short fiber C ... carbon short fiber, average length 5 μm, average diameter 1 μm (10) short fiber D ... polyester short fiber, average length 8000 μ
m, average diameter 5 μm (11) Liquid polymer A ... Liquid BR Mw = 15000 1.4 cis-80% (12) Liquid polymer B ... Liquid SBR Mw = 5000, S
t = 30% by weight (13) Liquid polymer C ... Liquid SBR Mw = 65000, S
t = 30% by weight

As shown in Table 1, the control example was a conventional typical tire formulation, but without the low hardness powder rubber and short fibers. In Table 2, this conventional tire is set to 100, and the evaluation values of other examples are shown as indexes. Examples 1 to 1 according to the present invention
The tire of No. 4 had no change in braking performance on wet roads, almost no deterioration in wear resistance was observed, and the initial and aging performance on ice and snow was remarkably improved as compared with the conventional tire. In addition, the reference example shows data relating to another application of the present applicant in which low hardness powder rubber and short fibers are blended.

On the other hand, the compounding of Comparative Example 1 is not practical because the particle size of the powdered rubber exceeds 1000 μm, and the abrasion resistance is significantly reduced. In the blend of Comparative Example 2, the amount of carbon in the powder rubber is large, so that the performance improvement in the ice and snow road is not recognized. In Comparative Example 3, the blend amount of the powder rubber is too large, and the wear resistance is remarkably lowered. In Comparative Examples 4 and 5, the short fiber aspect ratio was out of the range of the present invention, and therefore no improvement in performance was observed in the ice and snow road. In Comparative Example 6, since the liquid polymer had a molecular weight of less than 6,000, the performance on ice was deteriorated over time. In Comparative Example 7, since the molecular weight of the liquid polymer exceeds 60,000, the softening effect is insufficient, no improvement in on-ice performance is observed, and the change over time is large.

[0039]

As described above, according to the present invention,
By blending a specific low-hardness powder rubber, liquid rubber and short fibers in the tread portion, the deterioration of wear resistance is greatly reduced without impairing the running performance on general wet roads,
It is possible to significantly improve the ice and snow road running performance in the initial stage and after the running.

[Brief description of drawings]

FIG. 1 is a meridional direction half-section explanatory view of an example of a pneumatic tire of the present invention.

FIG. 2 is an explanatory plan view of a tread portion of an example of a pneumatic tire of the present invention.

3 is a cross-sectional view taken along the line K-K 'in FIG.

[Explanation of symbols]

 10 ... Tread surface 11 ... Bead part 12 ... Sidewall 13 ... Tread part 14 ... Carcass layer 15 ... Belt layer 16 ... Block 17 ... Short fiber

Claims (2)

[Claims] 1. A tread portion comprising a matrix rubber, a low hardness powder rubber, a liquid polymer and a short fiber, wherein the low hardness powder rubber has an average particle size of less than 1000 μm and 20 parts by weight of carbon per 100 parts by weight of the low hardness powder rubber. Parts or less, the compounding amount is 1 to 10 parts by weight per 100 parts by weight of the matrix rubber, and the liquid polymer has an average molecular weight.
A low molecular weight diene polymer of 6,000 to 60,000 in an amount of 5 to 50 parts by weight per 100 parts by weight of matrix rubber, and the short fibers have an aspect ratio (ratio of length / diameter).
Pneumatic tires that are 10 to 1000. 2. Short fibers having an average diameter of 0.05 to 0.8 μm and 1
The pneumatic tire according to claim 1, wherein the pneumatic tire is a polyamide-based short fiber having an average length within the range of 100 µm.