JPH1058918A - Pneumatic tire and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep operational stability high and also provide excellent performance on the ice enough to meet the level required by the market. SOLUTION: A raw tire case on which a fiber 24 whose strength is deteriorated by vulcanization more than that before vulcanization and a tread including blowing agent are stuck is vulcanized. When tread rubber is worn, running performance is improved due to recessed sections 22A formed by spherical independent closed cells 22 and groove-like recessed sections 24A formed after the fiber 24 is separated from the rubber. Since the strength of the fiber 24 has been deteriorated by vulcanization, the fiber 24, when exposed out of rubber face, is immediately separated from the rubber. Since the groove-like recessed sections 24A work to discharge the water in the tire contacting the road face, its water absorption performance is hard to be saturated, ensuring an increase in the performance μ on the ice.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention provides a pneumatic tire capable of maintaining a high level of handleability and abrasion resistance and improving the performance on ice required by the market.

[0002]

2. Description of the Related Art At present, studless tires using foam rubber for a tread have been proposed for the purpose of improving running performance on ice and snow.

Further, it is known that, when micro-grooves are formed on the surface, μ on ice is improved as compared with foamed rubber in which bubbles are independently present.

[0004]

As a method for forming microscopic grooves on the rubber surface, a foamed rubber containing short fibers as disclosed in JP-A-4-38207 is disclosed as a technique. Short fibers that do not adhere to rubber as described therein curl due to heat shrinkage during vulcanization, and fibers are pushed into grooves and sipes of the mold and bent in the tread rubber. For this reason, even if the tread wears due to running, the fibers do not separate from the rubber, micro-grooves are not formed as originally intended, and μ on ice was not sufficiently improved.

The present invention has been made in consideration of the above-described circumstances, and has as its object to provide a pneumatic tire and a method for manufacturing a pneumatic tire capable of improving the on-ice performance required by the market by reliably increasing μ on ice. is there.

[0006]

According to the present invention, there is provided a pneumatic tire in which a belt and a tread are sequentially arranged on the outer periphery of a crown portion of a carcass layer straddling a toroid between a pair of bead cores. The tread is characterized in that it has a rubber layer containing fibers that have been degraded into a fibril shape by vulcanization or have a lower strength than before vulcanization.

[0007] The tread of the pneumatic tire according to the first aspect has a rubber layer containing fibers whose strength has been deteriorated by the vulcanization as compared to before the vulcanization. The fibril state is promoted in the rubber, leading to destruction, and the fibers that appear on the ground surface due to wear of the rubber are immediately separated from the rubber.

When the fiber comes off, a groove-like concave portion is formed on the ground surface, and the concave portion absorbs water in the ground surface, thereby improving the performance on ice. In particular, since the groove-shaped recess has an action of draining water in the ground contact surface, the water absorbing ability is hardly saturated, and μ on ice can be reliably increased.

The fibers may have such a strength that they are broken by coming into contact with the road surface and are immediately separated from the rubber, or may be degraded into fibrils by vulcanization.

The fiber whose strength is deteriorated by vulcanization as compared with that before vulcanization may be a fiber whose strength is deteriorated by the temperature at the time of vulcanization. A material which reacts and deteriorates in strength may be used.

The term "fiber" as used herein refers to a long member whose length is at least 20 times the outer diameter.

According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the fiber is a polyethylene terephthalate having a terminal carboxyl group of 35 eq / ton or more.

The polyethylene terephthalate having a terminal carboxyl group of 35 eq / ton or more used in the pneumatic tire according to the second aspect is characterized in that, during vulcanization, the amine in the rubber (for example, urea as an auxiliary of a foaming agent, vulcanization) Accelerators generated during vulcanization) are hydrolyzed and deteriorated by acting as a catalyst. In addition, it is more preferable that the terminal carboxyl group is 50 eq / ton or more, because the deterioration is further deteriorated. When the terminal carboxyl group is less than 35 eq / ton, it is difficult to deteriorate.

According to a third aspect of the present invention, in the pneumatic tire according to the first aspect, the fiber is an aromatic polyester having a phenoxy structure.

An aromatic polyester having a phenoxy structure used in the pneumatic tire according to claim 3 is:
During vulcanization, the amine in the rubber (for example, urea as an auxiliary of a foaming agent, which is generated during vulcanization from a vulcanization accelerator) is hydrolyzed and degraded by acting as a catalyst.

According to a fourth aspect of the present invention, in the pneumatic tire according to any one of the first to third aspects,
It is characterized in that the fibers are short fibers.

In the pneumatic tire according to the fourth aspect, since the fibers are short fibers, the groove-shaped concave portions appearing on the worn rubber surface have a short length. In the rubber vulcanized with the fiber as the short fiber, the range in which the rubber does not exist is intermittent compared to the rubber vulcanized with the fiber as the long fiber, so that uneven wear hardly occurs. In particular, when it is necessary to improve the uneven wear property, it is preferable to make the direction of the fiber random. The short fibers referred to in the present invention are those having a length of less than 5 mm.

According to a fifth aspect of the present invention, in the pneumatic tire according to any one of the first to third aspects,
It is characterized in that the fibers are long fibers.

In the pneumatic tire according to the fifth aspect, since the fibers are long fibers, the groove-shaped concave portions appearing on the worn rubber surface have a long length. In addition, the long recess can hold a large amount of water. In particular, a concave portion whose end is connected to the main groove or sipe is effective because absorbed water can be discharged to the main groove or sipe. In addition, the long fiber referred to in the present invention means a fiber having a length of 5 mm or more.

According to a sixth aspect of the present invention, in the pneumatic tire according to any one of the first to fifth aspects,
The fiber is oriented along the tire circumferential direction.

In the pneumatic tire according to the sixth aspect, since the longitudinal direction of the fiber is oriented along the circumferential direction of the tire, the groove-shaped concave portion appearing on the rubber surface has the longitudinal direction corresponding to the circumferential direction of the tire, and the inside of the ground contact surface. The drainage of the vehicle can be improved, and the braking performance on ice can be improved.

According to a seventh aspect of the present invention, in the pneumatic tire according to any one of the first to sixth aspects,
The rubber layer is a foamed rubber.

In the pneumatic tire according to the seventh aspect, since the water absorption and drainage effect and the edge effect by the foam of the foamed rubber are added, the performance on ice of the tire is further improved.

[0024] In the method for manufacturing a pneumatic tire according to claim 8, a green tread containing a fiber which is degraded into a fibril shape by vulcanization or whose strength is lower than before vulcanization is applied to a crown portion of a green tire case. The green tire case to which the green tread is bonded is then vulcanized and molded with a predetermined mold.

In the method for manufacturing a pneumatic tire according to the present invention, first, a raw tread containing a fiber which is degraded into a fibril shape by vulcanization or whose strength is lower than that before vulcanization is applied to a crown portion of a green tire case. paste. Next, when the green tire case to which the green tread is attached is vulcanized and molded with a predetermined mold, the rubber is cured and the fibers are deteriorated.

The pneumatic tire of the present invention can be easily prepared by kneading a predetermined amount of a fiber whose strength is deteriorated by vulcanization as compared with that before vulcanization into a rubber composition for forming a raw tread, and then performing a normal tire forming step. Can be formed.

[0027] The pneumatic tire thus formed has a rubber layer in the tread containing a fiber whose strength is deteriorated by the vulcanization compared with that before the vulcanization. Fibers that break down in the rubber and appear on the ground surface due to wear of the rubber are immediately released from the rubber.

When the fiber comes off, a groove-shaped concave portion is formed in the ground contact surface, and the concave portion absorbs water in the contact surface, thereby improving the performance on ice. In particular, since the groove-shaped recess has an action of draining water in the ground contact surface, the water absorbing ability is hardly saturated, and μ on ice can be reliably increased.

The fibers may have such a strength that they are broken by coming into contact with the road surface and are immediately separated from the rubber, or may be degraded into fibrils by vulcanization.

The fiber whose strength is deteriorated by vulcanization as compared with the fiber before vulcanization may be a fiber whose strength is deteriorated by the temperature at the time of vulcanization. A material which reacts and deteriorates in strength may be used.

The term “fiber” as used herein refers to a long member having a length of 20 times or more the outer diameter.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A pneumatic tire 10 according to one embodiment of the present invention will be described with reference to FIGS.

The pneumatic tire of this embodiment (size: 1)
85 / 70R13) 10 is a pneumatic tire having a radial structure in which a belt and a tread as a reinforcing layer are sequentially arranged on the outer periphery of a crown portion of a carcass straddling a pair of bead cores in a toroidal manner. The internal structure other than the tread is not different from the structure of a general radial tire, and therefore the description is omitted.

As shown in FIG. 1, a plurality of blocks 18 are formed on the tread 12 by a plurality of circumferential grooves 14 and a plurality of lateral grooves 16 intersecting with the circumferential grooves 14. Further, the block 18 is formed with a sipe 19 extending in the tire width direction in order to improve braking performance and traction performance on ice.

As shown in FIG. 2, the tread 12 is composed of an upper cap portion 12A directly in contact with the road surface and a lower base portion 12B disposed adjacent to the inside of the tire of the cap portion 12A. And a so-called cap-base structure.

The base portion 12B is made of a low-heat-generating non-foamed normal rubber. As shown in FIG. 3, the cap portion 12A is made of a foamed rubber containing a myriad of substantially spherical spherical closed cells 22. It is used. Also, the cap part 12
Fibers 24 deteriorated by vulcanization are dispersed in the foamed rubber of A. (Manufacturing method) Next, a method of manufacturing the pneumatic tire 10 of the present embodiment will be described.

The foam rubber forming the cap portion 12A is:
A rubber compound using a specific carbon black in a specific part by weight and a foaming agent and a circular fiber 2 degraded by vulcanization.
4 and heating and pressurizing according to a normal tire manufacturing method.

The fibers 24 may be kneaded with a predetermined amount of rubber, a compounding agent, a foaming agent, and the like, for example, using a Banbury mixer. When the rubber kneaded with the fibers 24 is put into an extruder and extruded from a die whose flow path cross-sectional area decreases toward the outlet, the direction of the fibers, that is, the longitudinal direction of the fibers is gradually aligned along the extrusion direction, When coming out of the die, the longitudinal direction of the fiber is aligned with the extrusion direction, so if you cut the raw rubber member extruded from the die in the desired direction,
A rubber member having a uniform fiber direction can be obtained, and this can be used as the rubber of the cap portion 12A. Raw cap part 1 made of rubber member made in this way
2A is pasted on a raw base portion 12B which has been pasted on a crown portion of a green tire case in advance, and vulcanized at a predetermined temperature and a predetermined pressure in a predetermined mold to thereby vulcanize and mold the present embodiment. The pneumatic tire 10 can be formed.

The rubber component contained in the tread 12 is, for example, a natural rubber, a polyisopropylene rubber, a polybutadiene rubber, a butyl rubber, a styrene-butadiene copolymer rubber having a low styrene content, or a polymer thereof.
A mixture of more than one species. By using these polymers, the tread 12 can have sufficient rubber elasticity at a low temperature.

As the foaming agent, for example, a system in which urea is used in combination with dinitrosopentamethylenetetraamine, and a benzenesulfonylhydrazide derivative, in particular, oxybisbenzenesulfonylhydrazide, are preferable in view of production processability.

The fiber 24 has a strength that does not bend or break when kneaded with rubber or extruded from an extruder, and is broken when the rubber comes into contact with a road surface after being vulcanized, and is easily separated from the rubber. Use a material whose strength decreases so as to be separated.

As the fiber 24, for example, PET (polyethylene terephthalate) having a terminal carboxyl group of 35 eq / ton or more, preferably 50 eq / ton or more, or an aromatic polyester having a phenoxy structure can be used.

The aromatic polyester having a PET and a phenoxy structure having a terminal carboxyl group of 35 eq / ton or more, desirably 50 eq / ton or more is used as an amine component in rubber during vulcanization (for example, as an auxiliary agent for a foaming agent). Urea, vulcanization accelerators, etc., which are generated during the vulcanization reaction) are hydrolyzed by the catalytic role to reduce the strength,
Alternatively, it may be deteriorated in a fibril shape. Usually, PET for tires (for example, used for ply cords, etc.)
Has a terminal carboxyl group of less than 35 eq / ton to ensure strength and fatigue resistance.

The fiber 24 of this embodiment has a thickness of 20 μm.
m, a PET short fiber having a length of 2 mm and a terminal carboxyl group of 35 eq / ton or more. The content of the fiber 24 is 10 phr.

When a rubber composition formed by kneading the fiber 24, a predetermined amount of rubber, a compounding agent, a foaming agent, and the like is heated in a mold, a gas is generated by the foaming agent and countless spherical closed cells are formed. 22 are formed.

The foaming rate Vs of the foamed rubber is 5 to 50.
% Is desirable, preferably 5 to 30%. The foaming rate Vs of the foamed rubber is Vs = (ρ ₀ / ρ ₁ -1) × 1
Where ρ ₁ is the density (g / cm) of the foamed rubber.
³ ), ρ ₀ is the density (g / cm ³ ) of the solid phase portion of the foamed rubber. If the foaming ratio Vs of the foamed rubber is less than 5%, flexibility at low temperatures cannot be obtained, and if it exceeds 50%, the wear resistance is reduced and the wear resistance on a dry road surface becomes practically insufficient. Absent.

The average cell diameter of the spherical closed cells 22 is 5 to 15
0 μm is desirable, and preferably 10 to 100 μm. When the average cell diameter of the spherical closed cells 22 is less than 5 μm, the effect of improving the ice and snow performance is small.
During running, deformation of the block, clogging of the sipe 19, etc. may occur, resulting in reduced performance on snow, reduced cut resistance, increased chipping of the block, and difficulty in obtaining a stable shape during manufacturing. Therefore, it is not preferable.

The rubber of the cap portion 12A of the present embodiment is
The foaming ratio Vs is 20%, and the average foaming diameter of the spherical closed cells 22 is 25 μm.

The thickness of the fiber 15 is 5 μm or more and 15 μm or more.
It is preferably 0 μm or less. The thickness of the fiber 24 is 5
If it is less than μm, the width of the concave portion formed after the fibers 24 are detached becomes narrow, and the water absorbing power is undesirably reduced. On the other hand, if the thickness of the fiber 24 is larger than 150 μm, the abrasion resistance and the steering stability on a dry road surface deteriorate, which is not preferable.

Next, the operation of the present embodiment will be described. When the pneumatic tire 10 of the present embodiment is run, the fibers 24 having reduced strength are broken in the rubber due to expansion and contraction of the rubber,
The fibers 24 appearing on the ground surface due to wear of the rubber are immediately separated from the rubber. Thereby, as shown in FIG. 4, the groove-shaped concave portion 24A and the spherical closed cell 2
2 and the concave portion 22A appears.

The fibers 24 may have such a strength that they are broken by coming into contact with the road surface and are immediately separated from the rubber, or may be decomposed (crushed) by vulcanization.

When the pneumatic tire 10 is run on ice, a water film is formed between the tire and the ice due to the contact pressure, but the countless recesses 2 formed on the contact surface of the tread 12 are formed.
The water in the ground contact surface is quickly absorbed by 2A and 24A. Furthermore, the drainage to the rear side in the tire rotation direction within the ground contact surface is improved by the groove-shaped concave portion 24A whose longitudinal direction is substantially the circumferential direction of the tire, so that especially the braking performance on ice is improved.

In the above embodiment, the cap portion 12
Although the fibers 24 dispersed in the rubber of A are short fibers having a length of 2 mm, the fibers 24 may be long fibers having a length of 5 mm or more. By making the fibers 24 long fibers, the groove-shaped concave portions 24A appearing on the worn rubber surface have a long length, and can absorb and hold a large amount of water. In particular, the groove-shaped recess 24A whose end is connected to the circumferential groove 14, the lateral groove 16, the sipe 19, etc.
This is effective because it can be discharged to the lateral groove 16 and the sipe 19.

The direction of the fibers 24 dispersed in the rubber of the cap portion 12A may be the tire axial direction or may be random.

If the direction of the fiber 24 is the tire axial direction, the direction of the groove-shaped concave portion 24A is the tire axial direction, and the edge component in the tire axial direction increases, so that traction performance on ice can be improved.

The fibers 24 whose strength is reduced by hydrolysis are used, but any material may be used as long as the strength is reduced after vulcanization.

Although the cross section of the fiber 24 of the above embodiment is circular, shapes other than circular (for example, square,
Square, oval, etc.).

In the above-described embodiment, the example in which the rubber containing the fiber 24 is used for the cap portion 12A has been described.
It is sufficient that at least one rubber layer including the rubber layer 4 is provided on the tread 12, and the arrangement portion may not be the outermost layer. For example, if the rubber layer containing the fibers 24 is exposed in the middle to late stages of wear, it is possible to compensate for the decrease in the drainage effect due to the decrease in the circumferential grooves 14 and the lateral grooves 16.

Further, the pneumatic tire 10 of the above embodiment
Was for passenger cars, but the present invention can of course be applied to tires for trucks and buses other than tires for passenger cars.

The present invention can be freely combined with tire shapes such as sipe and block shapes. (Test Example) The braking performance on ice and the feeling performance on ice were compared using a conventional tire, two kinds of working tires to which the present invention was applied, and two kinds of comparative tires.

Test method for brake performance on ice Mount the tire on a 2000cc class domestic car and drive on a flat road on ice. did. The result was expressed as an index with the reciprocal of the distance taken as 100 for a conventional tire. The larger the value, the better the braking performance on ice.

Test Method of Feeling Performance on Ice The tire was mounted on a domestic 2000CC class passenger car, run on an ice test course, and handling on ice was evaluated by feeling.

The results are shown as indexes with the conventional tire being 100. The larger the value, the better the feeling performance on ice.

Next, the working tire and the comparative tire will be described. For each tire, the tire size is 185 / 70R13
In each of the treads, four blocks are arranged in the tire width direction, and the size of the blocks is 35 mm in the tire circumferential direction and 3 mm in the tire width direction.
0 mm. The sipe formed in the block has a width of 0.4 mm and an interval in the tire circumferential direction of about 7 mm.

Table 1 shows the other specifications and the results of the tests on the braking performance on ice and the feeling performance on ice.

[0066]

[Table 1]

As shown in Table 1 above, the working tires 1 and 2 to which the present invention was applied exhibited higher on-ice braking performance than the comparative tires.

When the fiber direction is oriented in the tire circumferential direction, the feeling on ice can be ensured to be equal to or more than that of the comparative tire.

[0069]

As described above, since the pneumatic tire according to the first aspect has the above-described structure, it is possible to obtain an excellent performance on ice required by the market by reliably increasing μ on ice. It has an excellent effect.

Since the pneumatic tire according to claim 2 has the above-described structure, the fibers in the rubber can be hydrolyzed by causing the amine in the rubber to act as a catalyst during vulcanization, thereby reducing the strength. Has excellent effects.

Since the pneumatic tire according to claim 3 has the above-mentioned structure, the fibers in the rubber can be hydrolyzed by causing the amine in the rubber to act as a catalyst during vulcanization, thereby reducing the strength. Has excellent effects.

The pneumatic tire according to the fourth aspect has the above-described configuration, and thus has an excellent effect that uneven wear can be suppressed.

The pneumatic tire according to the fifth aspect has the above-described structure, and thus has an excellent effect that uneven wear can be suppressed.

The pneumatic tire according to the sixth aspect has the above-described structure, and therefore has an excellent effect that a large amount of water can be retained in the concave portion formed in the ground contact surface, and the performance of absorbing moisture can be improved. Having. Further, the concave portion whose end is connected to the main groove or the sipe is more effective because the absorbed water can be discharged to the main groove or the sipe.

The pneumatic tire according to the seventh aspect has the above-described configuration, and thus has an excellent effect that the performance on ice can be further improved.

According to the method of manufacturing a pneumatic tire according to the eighth aspect, there is an excellent effect that a pneumatic tire having a reliably increased μ on ice can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a plan view of a tread of a pneumatic tire according to one embodiment of the present invention.

FIG. 2 is a cross-sectional view of a block taken along a tire circumferential direction.

FIG. 3 is an enlarged sectional view of a rubber constituting a cap portion.

FIG. 4 is an enlarged sectional view of the vicinity of a worn tread contact surface.

[Explanation of symbols]

 Reference Signs List 10 Pneumatic tire 12 Tread 22 Spherical closed cell 24 Fiber

Claims (8)

[Claims] 1. A pneumatic tire in which a belt and a tread are sequentially arranged on the outer periphery of a crown portion of a carcass layer straddling in a toroidal manner between a pair of bead cores, and the tread is formed into a fibril shape by vulcanization. A pneumatic tire comprising a rubber layer containing fibers that have been deteriorated or whose strength has been deteriorated before vulcanization. 2. The fiber has a terminal carboxyl group of 35 eq.
The pneumatic tire according to claim 1, wherein the pneumatic tire is polyethylene terephthalate of at least / ton. 3. The pneumatic tire according to claim 1, wherein the fiber is an aromatic polyester having a phenoxy structure. 4. The pneumatic tire according to claim 1, wherein the fibers are short fibers. 5. The pneumatic tire according to claim 1, wherein the fibers are long fibers. 6. The pneumatic tire according to claim 1, wherein the fibers are oriented along a tire circumferential direction. 7. The pneumatic tire according to claim 1, wherein the rubber layer is a foamed rubber. 8. A green tread containing fibers which are degraded into fibrils by vulcanization or whose strength is lower than that before vulcanization is attached to a crown portion of a green tire case, and thereafter, the green tread to which the green tread is attached is attached. A method for manufacturing a pneumatic tire, comprising vulcanizing a tire case with a predetermined mold.