JPH05170976A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To obtain the subject product, having a tread part composed of a composition prepared by blending a rubber component with specific PVA powder and staple fiber oriented in a specified direction and improved in frictional force on ice and snow roads, especially on ice without impairing the runnability on open roads. CONSTITUTION:The objective product having a tread part, composed of a rubber composition prepared by blending 100 pts.wt. rubber component with 1-15 pts.wt. PVA powder having 10-70cPs viscosity, >=80mol% saponification degree and 30-1000mum average grain diameter and staple fiber 17 and having <=8 difference in JIS hardness between 20 and -10 deg.C. Most of the staple fiber 17 is oriented along the surface (a) and sides (b) of a block 16 in the tread part. Cellulosic staple fiber such as rayon is preferred as the staple fiber. Furthermore, the staple fiber preferably has >=1mum average diameter, 1000-3000mum average length and 10-100 ratio of the length/the diameter so as to orient in the flow direction of the rubber in extrusion molding of the tread part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a studless air having improved frictional force (braking performance, drivability) on ice and snow roads, especially on ice, without impairing running performance on general roads (dry roads, wet roads). Containing tires.

[0002]

2. Description of the Related Art Conventionally, when a car travels in winter in a cold snowy area, a spiked tire with a spiked tire is used, or a tire chain is attached to the outer circumference of the tire for snowy or icy roads. We are safe. However, a spiked tire or a tire equipped with a tire chain is likely to cause road wear or damage, which becomes dust and causes pollution, which is a major environmental problem.

In order to solve such a safety problem and an environmental problem, a studless tire having a braking property and a drivability on a snowy road and an icy road without using spikes or chains is rapidly prevailing at present. .. As this studless tire, for example, sand is compounded into a tread rubber (Japanese Patent Laid-Open No. 61-150803) or metal fiber is compounded.
(Japanese Patent Laid-Open No. 63-34206), blending metals (Japanese Patent Laid-Open No.
Japanese Patent Laid-Open No. 2-281052) has proposed a vehicle tire designed to improve the performance on ice. However, since the rubber hardness of this automobile tire is relatively high, the effect of improving friction on ice was insufficient. Further, as the tire wears, these sands, metal fibers, and metals scatter to cause dust pollution, which becomes a major environmental problem.

It has also been proposed to use foamed rubber for the tread rubber (Japanese Patent Laid-Open No. 62-283001, Japanese Laid-Open Patent Publication No. Sho 62-283001).
63-89547 publication). However, in the tire in this case, although the frictional force on the icy and snowy road is good, since the block rigidity of the foamed rubber is low, the edge effect and the drainage effect due to the closed cells are not sufficient, and the wear resistance and the general road ( There is a problem that running performance on dry roads and wet roads is reduced.

Further, there has been proposed a pneumatic tire in which a water absorbing agent which is a water-insoluble hydrophilic substance is blended with a tread rubber to improve the performance on ice (JP-A-60-259).
No. 503). However, although this tire absorbs water on the road surface while traveling on the ice and snowy road, it has a problem that the frictional force on ice cannot be sufficiently improved because the drainage is insufficient. A studless tire in which a water-insoluble polymer powder is mixed with a tread rubber has also been proposed (JP-A-3-159803). However, in this tire, there is a difference in hardness between 0 ° C. and room temperature, resulting in a large hardness at 0 ° C., and there is a drawback that the on-ice property cannot be sufficiently improved.

[0006]

The object of the present invention is to improve the frictional force (braking performance, drivability) on ice and snow roads, especially on ice, without impairing the running performance on general roads (dry roads, wet roads). To provide a pneumatic tire.

[0007]

The pneumatic tire of the present invention comprises a rubber composition in which the tread portion is blended with 1 to 15 parts by weight of polyvinyl alcohol powder with respect to 100 parts by weight of the rubber component, and short fibers. The difference in JIS hardness at 20 ° C and -10 ° C of the tread portion is 8 or less, the polyvinyl alcohol powder has a viscosity of 10 to 70 cps, and a saponification degree of 80 mol% or more,
It has an average particle size of 30 to 1000 μm and is characterized in that most of the short fibers are oriented along the block surface and side surfaces of the tread portion.

As described above, in the present invention, since the polyvinyl alcohol powder is used for the tread portion, the polyvinyl alcohol powder present as particles in the tread portion during traveling on the ice and snow road surface is dissolved by the water on the road surface or naturally on the tread surface. Since the particles of the polyvinyl alcohol powder that do not fall off from the surface of the tread surface are well absorbed by the water on the road surface, the grip force on the road surface is increased and the frictional force on ice can be improved. Further, even when traveling on a wet road, since polyvinyl alcohol powder absorbs water on the road surface well and polyvinyl alcohol powder that has absorbed water on the road surface immediately falls off from the tread surface, drainage becomes good, Driving performance is not impaired. Further, when traveling on a dry road, since the blending amount of polyvinyl alcohol powder in the tread portion is small, it does not affect the decrease in rigidity of the tread so much, so that the dry road traveling performance is not impaired. In addition, it is generally important to lower the hardness at low temperatures, for example, at -10 ° C, in order to improve the running performance on ice and snow roads, and on the high temperature side, for example, at 20 ° C to maintain performance on general roads. It is effective to keep the hardness at high. In the present invention, JI at 20 ℃ and -10 ℃ of the tread portion
Since the difference in S hardness is 8 or less, the flexibility of the polyvinyl alcohol powder in the matrix rubber is maximized while maintaining flexibility at low temperatures, while sacrificing running performance and wear resistance on general roads. There is nothing to do. Furthermore, in the present invention, since the short fibers are used, the tread rubber (rubber composition) that constitutes the tread portion can be softened and the rigidity of the tread rubber can be sufficiently maintained, that is, that of the soft rubber. Since the rigidity can be reinforced, it is possible to achieve a high level of compatibility with the rigidity of the tread surface and the adhesion effect (that the tread surface reaches the ice surface of the snow and snow road and follows the surface shape of the ice surface).

The structure of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a meridional direction half-section explanatory view of an example of a pneumatic tire of the present invention. In FIG. 1, a pneumatic tire A of the present invention has a pair of left and right bead portions 11, 11.
And a pair of left and right sidewall portions 12 and 12 connected to these bead portions 11 and 11, and a tread portion 13 arranged between these sidewall portions 12 and 12. Left and right bead parts 11,1
A carcass layer 14 is mounted between 1 and the tread portion 13
In, the belt layer 15 is arranged so as to surround this outer circumference. 10 is the tread surface.

In the present invention, the tread portion 13 contains polyvinyl alcohol powder in an amount of 1 to 15 with respect to 100 parts by weight of the rubber component.
It is composed of a rubber composition and short fibers mixed in parts by weight,
And the JIS hardness difference at -10 ° C is 8 or less. (1) If the difference in JIS hardness between 20 ° C and -10 ° C is more than 8, as a result, the JIS hardness at -10 ° C will be too high or the JIS hardness at 20 ° C will be too low. , Which are not good for ice and snow road performance and general road performance,
The blending effect of the polyvinyl alcohol powder is not sufficiently exhibited.

The rubber component is not particularly limited, and those normally used as tread rubber may be used. For example, natural rubber (NR), butadiene rubber
(BR), styrene-butadiene copolymer rubber (SB
R) and so on. Polyvinyl alcohol powder has a viscosity of 10
~ 70cps, saponification degree 80mol% or more, average particle size 30 ~ 1000μ
with m. When the viscosity is less than 10 cps, the polyvinyl alcohol powder is easily dissolved during vulcanization, and the polyvinyl alcohol powder is less likely to exist as particles in the tread portion after vulcanization. If the viscosity exceeds 70 cps, the water absorption capacity of polyvinyl alcohol powder will decrease. Further, if the saponification degree is less than 80 mol%, the water absorption capacity of the polyvinyl alcohol powder will be reduced. If the average particle size is less than 30 μm, the improvement of the performance on ice will be insufficient, and if it exceeds 1000 μm, the running performance on general roads such as dry road running performance (abrasion resistance etc.) will be deteriorated.

The polyvinyl alcohol powder is blended in an amount of 1 to 15 parts by weight with respect to 100 parts by weight of the rubber component. If it is less than 1 part by weight, the improvement of the performance on ice will be insufficient, and if it exceeds 15 parts by weight, the abrasion resistance will be deteriorated. A compounding agent such as carbon black or sulfur is appropriately blended with the rubber composition thus formed, if necessary. The polyvinyl alcohol powder is present in the tread portion 13 in the form of particles after tire vulcanization molding.

(2) Examples of the short fibers include natural fibers such as cotton and silk, cellulosic fibers, chemical fibers such as polyamide fibers represented by nylon fibers, polyester fibers, polyvinyl alcohol fibers such as vinylon. Inorganic fibers such as carbon fibers can be used. Cellulose short fibers such as rayon are preferable. Metal short fibers such as steel short fibers and copper-based metal short fibers may be used.

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. 2 and 3. 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 oriented in the tire circumferential direction EE ′ along the surface a and the side surface b of the block 16 of the tread portion 13.

To obtain such short fiber orientation,
In extrusion molding of 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, short fibers 17
If the length is too short, they will be randomly arranged in the tread rubber and will not be oriented. Therefore, the short fibers have an average diameter of 1 μm or more and an average length of 100 to 5000 μ.
m, preferably 1000 to 3000 μm, and the length / diameter ratio is 10 to 1000.

Thus, the short fibers 17 are formed on the surface a and the side surface b
In the block 16 in which the orienting is performed, the rigidity of the entire block is remarkably high, but the elastic modulus anisotropy that the elastic modulus in the direction perpendicular to the orientation direction, that is, from the surface to the inward direction is not so high is exhibited. Therefore, in the present invention, a dynamic Young's modulus of dynamic Young's modulus E ₁ and the block radial block circumferential E ₂ is, is possible to orientation of the short fibers 17 so as to satisfy the following formula and formula preferable.

1.03 ≤ E ₁ / E ₂ ... 3 [MPa] ≤ E ₂ ≤ 20 [MPa] ...

[0018]

[Examples] Various kinds of tires having a tire size of 11R22.5 14PR were prepared by forming a tread portion with a rubber composition having a compounding content (parts by weight) shown in Table 1, and the tires (conventional examples, Examples 1 to 1) were prepared.
4, Comparative Examples 1 to 7) were evaluated as follows. The results are shown in Table 1. In Table 1, polyvinyl alcohol powder is abbreviated as PVA powder. A large vehicle (2D) was used as the test vehicle. JIS hardness difference : Cut out a test piece from the tread portion of each test tire, measure the hardness at a temperature of 20 ° C and -10 ° C according to the method specified in JIS-K 6301, and then measure the difference. Was calculated. Braking performance on icy road surface : Running on an ice plate at an initial speed of 40 km / h, the braking distance when braking was measured, and the conventional tire (conventional example) was set to 100 and indexed. The larger the value, the better the braking.

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 smooth smoothed snowy 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. Driving stability (dry road surface) : The results (average value) obtained by scoring the feel of each tire by 5 test drivers by the 10-point method are shown as an index with respect to the conventional tire. The larger the value, the better the steering stability. Abrasion resistance (dry road surface) : After running 20,000 km on a dry road surface under the conditions of design normal load and air pressure specified in JATMA, the wear amount of each tire is shown as an index against the wear amount of conventional tires. The larger the value, the better the wear resistance. Dynamic Young's modulus (circumferential direction and radial direction) [MPa] : A sample is cut from the side of the tread block of each test tire in the circumferential direction (same as the tire circumferential direction) and in the radial direction with respect to the tire rotation axis, and Toyo Seiki ( Using a viscoelastic spectrometer manufactured by K.K., a sample with a length between chucks of 10 mm, a width of 5 mm, and a thickness of 2 mm was measured at a frequency of 20 Hz, initial strain of 10%, dynamic strain of ± 2%,
The measurement was carried out at a temperature of 0 ° C. The larger the value, the higher the rigidity.

[0020]

Note) * 1 PVA powder F: viscosity 43 cps, saponification degree 88 mol%, average particle size 100 μm. * 2 PVA powder G ... Viscosity 62cps, Saponification degree 97.9mol%,
Average particle size 750 μm. * 3 PVA powder D ... Viscosity 5.2cps, Saponification degree 88mol%,
Average particle size 800 μm. * 4 PVA powder E ... Viscosity 43 cps, saponification degree 88 mol%, average particle size 1500 μm. * 5 Short fiber A: Cellulose short fiber, average diameter 12 μm,
Average length 1500 μm * 6 Short fiber B ... Carbon short fiber, average diameter 1 μm, average length 5 μm * 7 Short fiber C ... Nylon short fiber, average diameter 10 μm, average length 8000 μm * 8 N- (1,3-dimethyl) -N '-Phenyl-p-phenylenediamine. * 9 N-tert-butyl-2-benzothiazole / sulfenamide. * 10 Polymer BR: cis component 98%, Tg-103 ° C. * 11 Polymer SBR: Styrene content 24.6% by weight, vinyl content in butadiene portion 15% by weight, Tg-51 ° C.

The viscosity of the PVA powder is a value measured with a Heppler viscometer at 20 ° C. and 4% aqueous solution viscosity. The saponification degree is a value that represents the proportion of hydroxyl groups in mol%. In Table 1, the conventional example is a rubber composition for a tread portion of a conventional studless tire, in which PVA powder and short fibers are not mixed. Examples 1 to 4 are rubber compositions within the scope of the present invention, and both general road running performance and ice / snow road running performance can be achieved. Comparative Example 1 is a rubber composition using a PVA powder having a viscosity outside the range of the present invention, and the running performance on ice and snow roads is not improved. Comparative Example 2 is a rubber composition using PVA powder having an average particle diameter outside the range of the present invention, and the abrasion resistance is significantly reduced. In Comparative Example 3 and Comparative Example 4, the length of the short fiber is outside the range of the present invention, and the improvement of the running performance on ice and snow roads is insufficient. In Comparative Example 5, the PVA powder content was outside the range of the present invention, and the wear resistance was significantly reduced. Comparative Example 6
Indicates that the short fiber is not mixed and the steering stability is reduced. In Comparative Example 6, the difference in JIS hardness is outside the range of the present invention, and the running performance on ice and snow roads is not improved.

[0023]

As described above, according to the present invention, the polyvinyl alcohol powder and the short fibers are used in the tread portion, so that the running on ice and snowy roads can be performed without impairing the running performance on general roads (dry roads, wet roads). It is possible to improve the performance.

[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.

FIG. 3 is a sectional view taken along line KK ′ 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

Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location C08K 7/02 KDW 7167-4J // (C08L 21/00 29:04)

Claims (2)

[Claims] 1. A tread portion comprising a rubber composition in which 1 to 15 parts by weight of polyvinyl alcohol powder is mixed with 100 parts by weight of a rubber component and short fibers, and the tread portion has JIS hardness at 20 ° C. and −10 ° C. Difference of 8 or less, the polyvinyl alcohol powder has a viscosity of 10 to 70 cps, a saponification degree of 80 mol% or more, and an average particle size of 30 to 1000 μm, and most of the short fibers are on the block surface and side surfaces of the tread portion. Pneumatic tires oriented along. 2. Short fibers having an average diameter of 1 μm or more and 100 to 100 μm.
The pneumatic tire of claim 1 having an average length in the range of 5,000 μm.