JP2006142925A - Pneumatic tire and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire and its manufacturing method solving the problem of a conventional tire having a sealant layer comprising an adhesion rubber and further enhancing blowout prevention performance. <P>SOLUTION: In the tire, a plurality of partitions 8 comprising a cross-linked thin film extending in a thickness direction and tire circumferential direction of the sealant layer are provided in the sealant layer 6 comprising the adhesion rubber provided on a tire inner peripheral surface with a clearance in a tire width direction. In the manufacturing method, a band-like sheet 10 comprising a rubber composition containing peroxide and a rubber component thermally decomposed by peroxide is arranged on a tire inner peripheral surface in the state that a plurality of slits 12 are provided on a surface and a co-agent is inserted to the slit. The rubber composition is denatured to a viscous rubber by heat-treating this to form the sealant layer 6 and a part of the slit is vulcanized/denatured to form the partition comprising the cross-linked thin film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire and a method for manufacturing the same, and more particularly to a pneumatic tire excellent in anti-puncture property and a method for manufacturing the same.

  As a countermeasure when a pneumatic tire is punctured by a nail, a sealant layer made of an adhesive rubber is provided on a tire inner peripheral surface corresponding to a tread portion. Even if a tire has a nail tread that causes a through hole in the tread portion, the adhesive rubber of the sealant layer enters the through hole and performs sealing to maintain the internal pressure. As a specific example, a rubber composition containing polyisobutylene and peroxide is heat-treated to decompose the polyisobutylene component with peroxide to form a sealant layer made of adhesive rubber (Patent Document 1). reference).

However, since the adhesive rubber in the sealant layer formed as described above has fluidity, the adhesive rubber moves to the center in the tire width direction of the tire inner peripheral surface during high-speed running, and the sealant layer in the shoulder region becomes thin. Will occur. For this reason, there is a problem that when the nail is stepped on the shoulder portion of the tread, a sufficient sealing performance (anti-puncture performance) cannot be obtained.
JP-A-53-55802

  An object of the present invention is to provide a pneumatic tire and a method for producing the same, which solves the problem of a tire having a sealant layer made of a conventional adhesive rubber and further improves the anti-puncture performance.

  The pneumatic tire of the present invention that achieves the above object is a pneumatic tire in which a sealant layer made of an adhesive rubber is provided on a tire inner peripheral surface corresponding to at least a tread portion. And the some partition which consists of a bridge | crosslinking thin film extended in a tire circumferential direction provided in the tire width direction at intervals.

  Further, the method for producing a pneumatic tire according to the present invention includes forming a rubber composition containing a peroxide and a thermally decomposable rubber component into the belt-like sheet, and forming the belt-like sheet on the surface thereof with a plurality of slits. The rubber composition is formed by placing the coagent in the slit and arranging the slit in the tire circumferential direction corresponding to at least the tread portion so that the slit is arranged in the tire circumferential direction. The material is modified into viscous rubber to form a sealant layer, and the slit portion is vulcanized and modified to form a partition made of a crosslinked thin film.

  According to the present invention, since the partition made of a plurality of crosslinked thin films is provided in the sealant layer made of adhesive rubber so as to extend in the thickness direction of the sealant layer and the tire circumferential direction, the sealant generated by centrifugal force during high-speed running The flow near the center of the tire width of the layer can be suppressed. Therefore, the thickness of the sealant layer in the shoulder region is maintained and the sealing performance is maintained, so that excellent anti-puncture performance can be obtained.

  In the present invention, a sealant layer made of an adhesive rubber is preferably obtained by heat-treating a rubber composition containing a peroxide and a rubber component thermally decomposable by the peroxide. Examples of rubber components that are thermally decomposable by peroxides include polyisobutylene and butyl rubber having a low isoprene content. The sealant layer is provided on the tire inner circumferential surface corresponding to at least the tread portion so as to extend over one circumference in the tire circumferential direction. The sealant layer may be further provided to extend to the inner wall surface of the sidewall portion.

  The partition provided in the sealant layer is formed by a crosslinked thin film of a rubber component of the sealant layer. That is, a rubber composition containing the peroxide and a thermally decomposable rubber component is molded into a belt-like sheet, a slit is formed on one or both sides of the belt-like sheet, and a coagent is inserted into the slit. By heat-treating this, only the slit portion in which the coagent is inserted can be vulcanized to form a film-like partition.

  The partition is formed so as to extend in the thickness direction in the sealant layer covering the tire inner circumferential surface so as to make one turn, and to extend in the tire circumferential direction, and in the tire width direction. A plurality of sheets are provided at intervals. The partition is preferably endless so as to extend over one circumference in the tire circumferential direction. However, the partition need not be endless as long as it has a circumferential length that substantially suppresses the flow of the viscous rubber, and is not discontinuous. There is no problem.

  The base portion of the partition provided in this way is joined to the inner liner layer on the inner peripheral surface of the tire, or to the cover sheet rubber covering the surface of the sealant layer. Of course, it may be adapted to be bonded to both the inner liner layer and the cover sheet rubber. The height at which the partition rises in the sealant layer in this manner is preferably 50 to 100% of the thickness of the sealant layer.

  FIG. 1 is a schematic longitudinal sectional view illustrating the tread portion of the pneumatic tire of the present invention.

  Reference numeral 1 denotes a tread portion, and 2 denotes a sidewall portion extending from the left and right sides of the tread portion 1 to bead portions (not shown). Inside the tread portion 1 and the sidewall portion 2, a carcass layer 3 that forms a tire skeleton is provided so as to extend to the bead portion. An inner liner layer 4 is provided. Further, two belt layers 5 are provided inside the tread portion 1 so as to cross the belt cords between the layers.

  On the inner peripheral surface of the tire corresponding to the tread portion 1, a sealant layer 6 made of viscous rubber is disposed on the inner portion of the inner liner layer 4 so as to extend around the tire. Further, a cover sheet rubber 7 for preventing stickiness is provided so as to cover the surface of the sealant layer 6. Furthermore, a plurality of partitions 8 made of a crosslinked thin film are provided inside the sealant layer 6. The plurality of partitions 8 are provided at intervals so as to divide the sealant layer 4 in the tire width direction. Moreover, each partition 8 is joined to the inner surface of the cover sheet rubber 7, extends in the thickness direction of the sealant layer 6, and extends in the tire circumferential direction.

  By providing the partition 8 in the sealant layer 6 in this way, the adhesive rubber tire of the sealant layer 6 is restrained from moving in the tire width direction of the sealant layer 6 and the centrifugal force during high-speed running increases. The flow to the center of the width can be suppressed. Therefore, the thickness reduction of the sealant layer in the shoulder region is suppressed, and the puncture prevention performance can be improved. In order to further improve such an effect, it is preferable to set the height of the partition 8 in a range of 50 to 100% of the thickness of the sealant layer 4.

  The number of the partitions 8 in the tire width direction is not particularly limited. The number may be determined according to the tire size and whether the application is for general use or high-speed use.

  FIG. 2 illustrates another embodiment of the pneumatic tire of the present invention.

  This embodiment differs from the embodiment of FIG. 1 in that the base portion of the partition 8 is joined to the inner liner 3 side. The partition 8 extends toward the cover sheet rubber 7 in the sealant layer 6 while being joined to the inner liner 3. In this case as well, as in the embodiment of FIG. 1, the movement of the adhesive rubber can be suppressed during high-speed running, and excellent puncture prevention performance can be maintained.

  In the present invention, the partition 8 may be provided so that the one bonded to the cover sheet rubber 7 side as shown in FIG. 1 and the one bonded to the inner liner 3 side as shown in FIG. The upper end and the lower end of the partition 8 may be simultaneously bonded to the cover sheet rubber 7 and the inner liner 3. That is, the height of the partition 8 is 100% of the thickness of the sealant layer 4.

  In the present invention, as the rubber composition (sealant material) for forming the sealant layer, a rubber composition containing polyisobutylene or a low isoprene-containing butyl rubber and peroxide is preferably used. As the rubber component, a rubber obtained by copolymerizing a small amount of isoprene in addition to polyisobutylene that generates a decomposition polymer is used. Preferably used. The rubber component for the sealant preferably contains 50% by weight or more of the polyisobutylene or copolymer. Examples of other rubber components blended in the rubber composition for sealant include natural rubber, styrene butadiene rubber, and butadiene rubber.

  Further, the peroxide in the rubber composition for sealant is preferably 0.2 to 20 parts by weight with respect to 100 parts by weight of the rubber component. If the amount of peroxide is small, a peroxide-decomposable polymer such as polyisobutylene is not sufficiently decomposed, so that a sufficient anti-puncture effect may not be obtained. Moreover, when there is too much quantity of a peroxide, there exists a tendency for decomposition | disassembly of the polymer of a peroxide decomposition product to progress too much and for the viscosity of a sealant layer to become low too much.

  Examples of the peroxide used in the present invention include acyl peroxides such as benzoyl peroxide and P-chlorobenzoyl peroxide, ketone peroxides such as methyl ethyl ketone peroxide, 1-butyl peroxyacetate, and t-butyl peroxide. Peroxyesters such as oxybenzoate and t-butylperoxyphthalate, alkyl peroxides such as di-t-butylperoxybenzoate and 1,3-bis (1-butylperoxyisopropyl) benzene, t-butylhydro Examples thereof include alkyl groups such as hydroperoxides such as peroxides.

  The partition of the crosslinked thin film formed in the sealant layer is formed by crosslinking the rubber component in the rubber composition with a coagent agent as described later. Specifically, when the rubber component (polyisobutylene or low isoprene-containing butyl rubber) in the rubber composition for sealant is decomposed and modified with peroxide, the coagent crosslinks the same rubber component contrary to the peroxide. Acts as follows. Any coagent agent may be used as long as it functions so that the rubber component of the rubber composition for the sealant is crosslinked. A slit is formed in a belt-shaped sheet formed from the rubber composition, and the coagent is embedded in the slit. Thus, the rubber in the slit portion can be cross-linked into a film to form a partition.

  Preferred coagents include sulfur, thiophenol, unsaturated carboxylic acid esters, etc. Among them, sulfur is particularly optimal.

  The thickness of the sealant layer is preferably about 1 to 4 mm. If the thickness is too thin, the anti-puncture effect will be reduced, and if it is too thick, the tire weight will increase and the fuel efficiency will deteriorate.

  As the rubber for the inner liner, any known rubber can be applied. For example, styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chlorosulfonated polyethylene (CSM), ethylene bromopyrene terpolymer rubber (EPDM), butyl rubber (IIR), chlorinated butyl rubber (Cl-IIR) Rubber materials such as brominated butyl rubber (Br-IIR), hydrin rubber (CHR, CHC), acrylic rubber (ACM), and chloroprene rubber (CR).

  Moreover, the cover sheet layer should just have a function which prevents the sealant layer from sticking. For example, styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chlorosulfonated polyethylene (CSM), ethylene bromopyrene terpolymer rubber (EPDM), butyl rubber (IIR), chlorinated butyl rubber (Cl-IIR) Rubber materials such as brominated butyl rubber (Br-IIR), hydrin rubber (CHR, CHC), acrylic rubber (ACM), and chloroprene rubber (CR).

  The thickness of the cover sheet layer is preferably 0.5 to 2.0 mm. If the thickness is too thin, the strength is reduced and breakage tends to occur. If the thickness is too thick, the tire weight is increased.

  Next, the manufacturing method of the pneumatic tire of the present invention described above will be described.

  First, as shown in FIG. 3, after forming the rubber composition described above as a band-like sheet 10 from a die of an extruder for forming a sealant layer, a plurality of slitter blades 11 are formed on the surface of the band-like sheet 10. As shown in FIG. 4, a slit-shaped sheet 10 is obtained in which a plurality of slits 12 extend in parallel in the longitudinal direction. The slit 12 provided in the belt-like sheet 10 may be only on one side as in the illustrated example, but may be on both sides. The slit 12 is preferably continuous to the entire length in the longitudinal direction, but may be discontinuous as long as it suppresses the movement of the adhesive rubber in the tire width direction. The depth of the slit 12 is preferably 50 to 100% of the thickness of the belt-like sheet 10.

  Next, a coagent is inserted into the slit 12. The coagent may be inserted by dusting if the coagent is powdery, or by pouring if the coagent is liquid. Alternatively, even if it is powdery, it may be once liquidized and then poured.

  In this way, the belt-like sheet 10 in which the coagent is inserted into the slit 12 is attached to the inner peripheral surface of the pneumatic tire tire so as to cover at least the portion corresponding to the tread portion, and further covered thereon. A sheet rubber 7 is pasted. The cover sheet rubber may be unvulcanized rubber or vulcanized rubber. Further, when the belt-like sheet 10 is attached to the inner peripheral surface of the pneumatic tire tire, the surface having the slit 12 is the side on which the cover sheet rubber 7 is applied even if it is on the inner liner 4 side. May be.

  As a pneumatic tire to which the belt-like sheet 10 is attached, it is preferable to use a raw tire before vulcanization, but a vulcanized tire may be used. Further, the tire structure may be a radial tire or a bias tire.

  The coagent insertion process for the slit 12 is preferably performed before being attached to the pneumatic tire as described above from the viewpoint of work efficiency. However, if necessary, it may be performed after being attached to the pneumatic tire. Good.

  Next, the belt-like sheet 10 attached to the pneumatic tire is heat-treated. In the case of a raw tire, this heat treatment is performed simultaneously with the vulcanization of the raw tire. By this heat treatment, the rubber composition constituting the belt-like sheet 10 forms the sealant layer 6 when the rubber components other than the slits 12 are decomposed by peroxide and modified into viscous rubber. The rubber component in the slit 12 is vulcanized by a coagent to form a film-like partition 8. The partition 8 made of the crosslinked thin film is formed so as to be joined to the inner liner 4 when the surface of the belt-like sheet 10 on the slit 12 side is set to the inner liner 4 side. The cover sheet rubber 7 is joined.

  A belt-like sheet is formed using a rubber composition having the following composition, slits having an average depth of 3 mm are formed in the belt-like sheets according to FIGS. 3 and 4, and sulfur is dusted as a coagent in the slits. Got. The belt-like sheet and the cover sheet rubber were attached to the inner peripheral surface of the raw tire, and the cover sheet rubber having a thickness of 1 mm was coated on the sealant layer having a thickness of 3.5 mm by heating and vulcanizing at 160 ° C. for 20 minutes. A pneumatic radial tire having a tire size of 205R / 65R15 was manufactured (Example).

Further, as a comparison, a pneumatic radial tire which is different from the above embodiment except that no slit or coagent was inserted into the belt-like sheet was manufactured (comparative example).

Parts by weight of rubber composition
Polyisobutylene 100
Peroxide (DCP) 16
Carbon black (FEF) 30
Polybutene (molecular weight 2350) 35

  For the above two types of pneumatic tires, the amount of decrease in the thickness of the sealant layer under the belt edge after running for 1 hour at 80 Km / h was measured. The comparative tire was significantly reduced to 3.0 mm.

1 is a partial schematic cross-sectional view illustrating an embodiment of a pneumatic tire of the present invention. It is a partial schematic sectional drawing which illustrates other embodiment of the pneumatic tire of this invention. It is a perspective view explaining the manufacturing process of the pneumatic tire of this invention. It is a perspective view of the strip | belt-shaped sheet | seat obtained by the process of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Carcass layer 4 Inner liner 5 Belt layer 6 Sealant layer 7 Cover sheet rubber 8 Partition

Claims (8)

  In a pneumatic tire in which a sealant layer made of an adhesive rubber is provided at least on an inner peripheral surface of a tire corresponding to a tread portion, a plurality of partitions made of a crosslinked thin film extending in the thickness direction of the sealant layer and the tire circumferential direction in the sealant layer A pneumatic tire provided with an interval in the tire width direction.   The pneumatic tire according to claim 1, wherein a height of the partition is 50 to 100% of a thickness of the sealant layer.   The sealant layer is made of an adhesive rubber formed by heat treatment of a rubber composition containing polyisobutylene or low-isoprene-containing butyl rubber and peroxide, and the partition is formed by a coagent by a coagent during heat treatment of the rubber composition. The pneumatic tire according to claim 1 or 2, comprising a vulcanized modified crosslinked thin film.   The pneumatic tire according to any one of claims 1 to 3, wherein a base portion of the partition is joined to a cover sheet rubber that covers an inner liner layer and / or a surface of the sealant layer on an inner peripheral surface of the tire.   A rubber composition containing a peroxide and a thermally decomposable rubber component is formed on a belt-like sheet, and a plurality of slits are provided on the surface of the belt-like sheet, and a coagent is inserted into the slit. And at least the tire inner circumferential surface corresponding to the tread portion is arranged so that the slits are arranged in the tire circumferential direction, and heat treating this to modify the rubber composition into a viscous rubber to form a sealant layer A method for manufacturing a pneumatic tire, wherein the slit portion is vulcanized and modified to form a partition made of a crosslinked thin film.   The method for producing a pneumatic tire according to claim 5, wherein the rubber component is polyisobutylene or low-isoprene-containing butyl rubber.   The method for manufacturing a pneumatic tire according to claim 5 or 6, wherein the coagent is sulfur. The manufacturing method of the pneumatic tire in any one of Claims 5-7 which makes the depth of the said slit 50 to 100% of the thickness of the said strip | belt-shaped sheet | seat.

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