JP2012076505A - Tire for truck/bus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve air permeation resistance, bending fatigue performance and crack resistance, in a tire for a truck/bus.SOLUTION: In this tire for the truck/bus, a tire inner surface is covered with an air blocking layer, and the air blocking layer is positioned at its end part in an area being set to 1 mm or less in a thickness and being 120 mm or less along a bead base line from the tow tip of a bead part. The air blocking layer is constituted of a polymer laminated body constituted of a first layer having a thickness of 0.05-0.6 mm formed of a styrene-isobutylene-styrene tri-block copolymer and a second layer having a thickness of 0.01-0.3 mm including at least any of a styrene-isoprene-styrene tri-block copolymer and a styrene-isobutylene di-block copolymer, and the second layer is arranged on the carcass ply side.

Description

  The present invention relates to a truck / bus tire having an air barrier layer.

  In recent years, tires have been made lighter due to the strong social demand for low fuel consumption of vehicles, and among the tire components, they are placed inside the tires to reduce air leakage from the inside of the pneumatic tire to the outside. The air barrier layer that is (air permeation resistant) is also required to be lightweight.

  Currently, the rubber composition for an air barrier layer improves the air permeation resistance of a tire by using a rubber compound mainly composed of butyl rubber including, for example, 70 to 100% by mass of butyl rubber and 30 to 0% by mass of natural rubber. Things have been done. In addition to butylene, the rubber compound mainly composed of butyl rubber contains about 1% by mass of isoprene, which, when combined with sulfur, vulcanization accelerator, and zinc white, enables co-crosslinking between adjacent rubber layers. I have to. The butyl rubber usually requires a thickness of about 0.6 to 1.0 mm for passenger car tires and about 1.0 to 2.0 mm for truck and bus tires. Therefore, there is a demand for a polymer that is more excellent in air permeation resistance than butyl rubber and that can reduce the thickness of the air barrier layer.

  Patent Document 1 discloses a laminate for improving the adhesion between the air barrier layer and the rubber layer. This is because by providing adhesive layers on both sides of the air barrier layer, the adhesive layers come into contact with each other at the overlapping portion of the air barrier layer, and are firmly bonded by heating, thereby improving air pressure retention. . However, the adhesive layer for superimposing the air barrier layer comes into contact with the bladder in a heated state in the vulcanization process, and there is a problem that it adheres to and adheres to the bladder.

  In Patent Document 2, a mixture of a nylon resin having good air permeability and butyl rubber is prepared by dynamic crosslinking to produce an air blocking layer having a thickness of 100 μm. However, nylon resin is hard at room temperature and is not suitable as an air barrier layer for tires. In addition, since the vulcanization adhesion to the rubber layer is not performed only by the mixture by dynamic crosslinking, an adhesive layer for vulcanization is required in addition to the air barrier layer. This is disadvantageous from the viewpoint of productivity.

  Prior Document 3 disperses a maleic anhydride-modified hydrogenated styrene-ethylene-butadiene-styrene block copolymer in an ethylene-vinyl alcohol copolymer having good air barrier properties to produce a flexible gas barrier layer. . In addition, the thermoplastic polyurethane layer has an sandwich sandwich structure, and rubber paste (70/30 of butyl rubber / natural rubber is dissolved in toluene) is applied to the surface to be bonded to the tire rubber to produce an air barrier layer. However, the modified ethylene-vinyl alcohol copolymer dispersed in a flexible resin has low adhesive strength and may be peeled off from the thermoplastic polyurethane layer. In the modified ethylene-vinyl alcohol copolymer dispersed with a flexible resin, the flexible resin is dispersed, but the EVOH of the matrix is poor in bending fatigue and breaks during running of the tire. Further, rubber glue is applied to the surface to be bonded to the tire rubber, but a process different from the manufacturing process of the normal air barrier layer is required, resulting in poor productivity.

  Prior document 4 describes a specific oxygen permeation amount in which a flexible resin having a Young's modulus lower than that of a copolymer is dispersed in a matrix made of a modified ethylene-vinyl alcohol copolymer instead of the inner liner or the inner liner. An air barrier layer having a predetermined thickness including a layer made of the above resin composition is disposed at least near the toe tip of the tire bead portion, so that a heavy load intended to improve tire air retention and bead portion durability. It relates to heavy duty tires.

  However, even in this technique, the adhesiveness between the air barrier layer and the inner liner or carcass rubber is insufficient, and the bending fatigue property is not always satisfactory.

JP-A-9-19987 Patent No. 2999188 JP 2008-24219 A JP 2009-173114 A

  An object of the present invention is to improve air permeation resistance, bending fatigue resistance, and crack resistance in a truck / bus tire having an air barrier layer.

  The present invention relates to a truck / bus tire whose inner surface is covered with an air barrier layer, wherein the air barrier layer has a thickness of 1 mm or less and a region of 120 mm or less along a bead base line from a toe tip of a bead portion. The air blocking layer includes a styrene-isobutylene-styrene triblock copolymer first layer having a thickness of 0.05 mm to 0.6 mm, and a styrene-isoprene- A polymer laminate comprising at least one of a styrene triblock copolymer and a styrene-isobutylene diblock copolymer, and a second layer having a thickness of 0.01 mm to 0.3 mm; A tire for trucks and buses, characterized in that the layer is disposed on the carcass ply side.

  Further, the present invention provides a truck / bus tire having an inner liner on an inner surface of the tire, wherein an air barrier layer that forms an overlapping portion in contact with the inner surface of the inner liner is disposed, and the air barrier layer has a thickness of 1 mm or less, the end is located in a region of 120 mm or less along the bead base line from the overlapped portion through the toe tip of the bead, and the air blocking layer is made of styrene-isobutylene-styrene tri A first layer made of a block copolymer having a thickness of 0.05 mm to 0.6 mm, and at least one of a styrene-isoprene-styrene triblock copolymer and a styrene-isobutylene diblock copolymer, It is comprised by the polymer laminated body which consists of a 2nd layer which is 0.01 mm-0.3 mm, It is characterized by the above-mentioned.

  Furthermore, in the tire for trucks and buses having an inner liner on the tire inner surface, and the inner liner is covered with an air barrier layer, the air barrier layer has a thickness of 1 mm or less and extends from the toe tip of the bead portion to the tire inner surface. The toe end portion is located in a region of 35 mm or less in the direction along the direction of the first, and the air blocking layer is a first 0.05 mm to 0.6 mm thick made of a styrene-isobutylene-styrene triblock copolymer. A polymer laminate comprising a layer and a second layer having a thickness of 0.01 mm to 0.3 mm, comprising at least one of a styrene-isoprene-styrene triblock copolymer and a styrene-isobutylene diblock copolymer The second layer is disposed adjacent to the inner liner.

In the present invention, the styrene-isobutylene-styrene triblock copolymer preferably has a styrene component content of 10 to 30% by mass. The styrene-isoprene-styrene triblock copolymer preferably has a styrene component content of 10 to 30% by mass and a weight average molecular weight of 100,000 to 290,000. Furthermore, the styrene-isobutylene diblock copolymer is preferably linear, has a styrene component content of 10 to 35% by mass, and a weight average molecular weight of 40,000 to 120,000.
It is preferable that tow rubber is disposed so as to cover the end portion of the air blocking layer in the toe portion of the truck / bus tire of the present invention. The tow rubber contains 20 to 40% by mass of a butyl rubber and a rubber component. A rubber composition comprising at least one of halogenated butyl rubber.

  The tire for trucks and buses according to the present invention uses the polymer laminate as an air barrier layer, so that the air in the tire lumen is blocked from the outside of the tire and the internal pressure can be maintained. Adhesion with the layer can be increased. A truck / bus tire using this polymer laminate as an air barrier layer at a predetermined position in the bead portion is excellent in peeling force from an adjacent inner liner, and is improved in bending fatigue and air barrier properties.

It is a schematic sectional drawing which shows the right half of the tire for trucks and buses in embodiment of this invention. It is a bead part expanded sectional view of the tire for trucks and buses in an embodiment of the invention. It is a bead part expanded sectional view of the tire for trucks and buses in an embodiment of the invention. It is a bead part expanded sectional view of the tire for trucks and buses in an embodiment of the invention. It is a bead part expanded sectional view of the tire for trucks and buses in an embodiment of the invention. It is a bead part expanded sectional view of the tire for trucks and buses in an embodiment of the invention. It is a schematic sectional drawing of the air barrier layer in embodiment of this invention. It is a schematic sectional drawing of the air barrier layer in embodiment of this invention. It is a schematic sectional drawing of the air barrier layer in embodiment of this invention. It is a schematic sectional drawing of the air barrier layer in embodiment of this invention.

  The present invention is a pneumatic tire provided with an air barrier layer on a tire inner surface, and the air barrier layer is formed of at least two polymer laminates. The first layer is made of styrene-isobutylene-styrene triblock copolymer (SIBS) and has a thickness in the range of 0.05 mm to 0.6 mm. The second layer includes at least one of styrene-isoprene-styrene triblock copolymer (SIS) and styrene-isobutylene diblock copolymer (SIB), and has a thickness of 0.01 mm to 0.3 mm. The second layer is disposed in contact with the rubber layer of the carcass ply.

<Embodiment 1>
A schematic sectional view of a tire for trucks and buses of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of the right half of a truck / bus tire, and FIG. 2 is an enlarged view of a bead portion thereof. The truck / bus tire 1 has a tread portion 2 and sidewall portions 3 and bead portions 4 so as to form a toroid shape from both ends of the tread portion. Further, a bead core 5 is embedded in the bead portion 4. Further, a carcass ply 6 provided from one bead portion 4 to the other bead portion and folded and locked at both ends around the bead core 5, and on the outer side of the crown portion of the carcass ply 6 are four sheets. A belt layer 7 made of a ply is disposed.

  The belt layer 7 usually intersects four plies made of a cord such as a steel cord or an aramid fiber with respect to the tire circumferential direction so that the cord is usually at an angle of 5 to 30 °, Or they are partly arranged in the same direction. In addition, a topping rubber layer can be provided on both outer sides of the belt layer to reduce peeling at both ends of the belt layer. The carcass ply generally has steel cords arranged at approximately 90 ° in the tire circumferential direction, and a bead apex 8 extending in the side wall direction from the upper end of the bead core 5 is disposed in a region surrounded by the carcass ply and its folded portion. The An air blocking layer 9 extending from one bead portion 4 to the other bead portion 4 is disposed on the inner side in the tire radial direction of the carcass ply 6.

  Further, a bead reinforcement layer 10 made of a steel cord, an aramid fiber cord or a nylon fiber cord is disposed in a region where the carcass ply 6 turns the bead core 5 back.

  In the truck / bus tire of the present invention, as shown in the figure, it is not necessary to provide an inner liner. In this case, however, the inner surface of the tire is covered with an air blocking layer 9 disposed directly inside the tire of the carcass ply 6. Will be covered.

  1 and 2, the air barrier layer 9 covers the inner surface of the tire and is folded back from the toe tip P in the tire width direction, and further extends along the bead base line L from the toe tip P to the bead base line width Wb. It arrange | positions so that the lower end part 9e may be located in an area | region. Here, the bead baseline width Wb is usually in the range of 100 to 120 mm in the truck / bus tire. If the air blocking layer 9 is disposed from the toe tip P to a region exceeding 120 mm in the direction along the bead base line L, the air blocking layer 9 reaches a portion in contact with the rim, and the rim mounting property may be deteriorated. .

  By disposing the air blocking layer 9, it is possible to prevent the bead portion from being repeatedly deformed during running of the tire layer and to pass air between the bead portion and the bead base portion and air from entering the tire from the outside of the tire. Allows internal pressure maintenance. Furthermore, by suppressing the ingress of oxygen from the outside of the tire, it is possible to reduce the deterioration of the air barrier layer and greatly improve the durability of the bead portion.

  A rubber chafer 12 for reinforcing the bead portion is disposed in the bead region in contact with the bead base and the rim flange. A tow rubber 13 is disposed on the toe portion so as to cover the lower end portion 9e of the air blocking layer. The tow rubber 13 is a rubber composition in which 20 to 40% by mass of the rubber component is composed of at least one of butyl rubber and halogenated butyl rubber.

<Embodiment 2>
FIG. 3 shows another embodiment of the present invention. The air barrier layer 9 is disposed so that the lower end portion 11e of the inner liner located in the bead portion forms an overlapping portion with the inner liner 11 at least in the bead portion region. Here, the inner liner 11 is disposed between the carcass ply 6 and the air blocking layer 9. The air barrier layer 9 has a lower end portion 9e located in the region of the bead base line width Wb along the bead base line L through the toe tip P from the lower end portion 11e of the inner liner. Here, the bead baseline width Wb is normally 120 mm.

  As shown in FIG. 3, the air barrier layer 9 forms an overlapping portion with a part of the inner liner, so that the non-uniformity of the air barrier layer end due to the shrinkage of the air barrier layer when unvulcanized can be compensated. If the air blocking layer 9 is disposed from the toe tip P to a region exceeding 120 mm in the direction along the bead base line L, the air blocking layer 9 reaches a portion in contact with the rim, and the rim mounting property may be deteriorated. . A tow rubber 13 is disposed on the toe portion so as to cover the lower end portion 9e of the air blocking layer. The tow rubber 13 is a rubber composition in which 20 to 40% by mass of the rubber component is composed of at least one of butyl rubber and halogenated butyl rubber.

  In the present invention, the inner liner may be a generally used rubber composition, for example, a butyl rubber or a halogenated butyl rubber, a butyl rubber, isoprene rubber, natural rubber, or the like, or a thermoplastic elastomer.

<Embodiment 3>
In FIG. 4, the air blocking layer 9 is disposed so as to cover the inner liner lower end portion 11e so as to be located on the inner side in the tire width direction.

  In the air blocking layer 9, it is preferable that the other lower end portion 9e is located in a region of the bead base line width Wb in a direction along the bead base line L from one end portion forming the overlapping portion through the toe tip P. Here, the bead baseline width Wb is normally 120 mm.

  As shown in FIG. 4, the air barrier layer 9 overlaps with a part of the inner liner, thereby making it possible to compensate for the non-uniformity of the air barrier layer end due to the shrinkage of the air barrier layer when unvulcanized. If the air blocking layer 9 is disposed from the toe tip P to a region exceeding 120 mm in the direction along the bead base line L, the air blocking layer 9 reaches a portion in contact with the rim, and the rim mounting property may be deteriorated. . And the toe rubber | gum 13 is arrange | positioned so that this lower end part 9e may be coat | covered in a toe part. The tow rubber 13 is a rubber composition in which 20 to 40% by mass of the rubber component is composed of at least one of butyl rubber and halogenated butyl rubber.

<Embodiment 4>
In the truck / bus tire of the present invention shown in FIG. 5, an inner liner 11 is disposed adjacent to the inside of the carcass ply 6 and an air blocking layer 9 is disposed inside thereof. The air barrier layer 9 is disposed such that its end 9e is located in a region (Hb) of 35 mm or less in the direction along the tire inner surface from the toe tip P. And the toe rubber | gum 13 is arrange | positioned so that the lower end part 9e of an air interruption layer may be coat | covered in a toe part. The tow rubber 13 is a rubber composition in which 20 to 40% by mass of the rubber component is composed of at least one of butyl rubber and halogenated butyl rubber.

<Embodiment 5>
In FIG. 6, the air blocking layer 9 is disposed so as to be located on the inner side of the inner liner in the tire width direction. The air blocking layer 9 forms an overlapping portion with the inner liner 11 so as to cover the lower end portion 11e of the inner liner located at the bead portion. The lower end portion 9e of the air blocking layer 9 is located in a region (Hb) of 35 mm or less in the direction along the tire inner surface from the toe tip P. A tow rubber 13 is disposed so as to cover the lower end portion 9e of the air blocking layer in the toe portion. The tow rubber 13 is a rubber composition in which 20 to 40% by mass of the rubber component is composed of at least one of butyl rubber and halogenated butyl rubber.

<Air barrier layer>
In the present invention, a specific polymer laminate is used for the air barrier layer. The polymer laminate includes a first layer made of styrene-isobutylene-styrene triblock copolymer (SIBS) having a thickness of 0.05 mm to 0.6 mm, styrene-isoprene-styrene triblock copolymer (SIS), and styrene. -It consists of a 2nd layer containing at least one of isobutylene diblock copolymer (SIB), and the thickness of the said 2nd layer is 0.01 mm-0.3 mm.

<First layer>
In one embodiment of the present invention, the first layer is made of a styrene-isobutylene-styrene triblock copolymer (SIBS). Due to the isobutylene block of SIBS, the polymer film made of SIBS has excellent air permeation resistance. Therefore, when a polymer film made of SIBS is used for the air barrier layer, a pneumatic tire excellent in air permeation resistance can be obtained.

  Further, SIBS has excellent durability because its molecular structure other than aromatic is completely saturated, thereby preventing deterioration and hardening. Therefore, when a polymer film made of SIBS is used for the air barrier layer, a pneumatic tire having excellent durability can be obtained.

  When a pneumatic tire is manufactured by applying a polymer film made of SIBS to the air barrier layer, air permeation resistance can be secured. Therefore, it is not necessary to use a halogenated rubber having a high specific gravity such as a halogenated butyl rubber which has been used for imparting conventional air permeation resistance, and the amount used can be reduced even when used. As a result, the weight of the tire can be reduced, and the effect of improving fuel consumption can be obtained.

  The molecular weight of SIBS is not particularly limited, but the weight average molecular weight by GPC measurement is preferably 50,000 to 400,000 from the viewpoints of fluidity, molding process, rubber elasticity and the like. If the weight average molecular weight is less than 50,000, the tensile strength and the tensile elongation may be lowered, and if it exceeds 400,000, the extrusion processability may be deteriorated. From the viewpoint of improving air permeation resistance and durability, SIBS has a styrene component content in SIBS of 10 to 30% by mass, preferably 14 to 23% by mass.

  The SIBS is a copolymer in which the degree of polymerization of each block is about 10,000 to 150,000 for isobutylene from the viewpoint of rubber elasticity and handling (becomes liquid when the degree of polymerization is less than 10,000), and styrene. Then, it is preferable that it is about 5,000-30,000.

  SIBS can be obtained by a living cationic polymerization method of a general vinyl compound. For example, JP-A-62-48704 and JP-A-64-62308 disclose that living cationic polymerization of isobutylene and other vinyl compounds is possible. By using isobutylene and other compounds as vinyl compounds, It is disclosed that a polyisobutylene-based block copolymer can be produced.

  Since SIBS does not have double bonds other than aromatics in the molecule, it is more stable to ultraviolet rays than a polymer having double bonds in the molecule, such as polybutadiene, and therefore has weather resistance. It is good. Furthermore, although it has no double bond in the molecule and is a saturated rubber-like polymer, the refractive index (nD) at 20 ° C. of light with a wavelength of 589 nm is the Polymer Handbook (1989: Wiley). (Polymer Handbook, Willy, 1989)) is 1.506. This is significantly higher than other saturated rubbery polymers such as ethylene-butene copolymers.

  The thickness T1 of the first layer made of SIBS is 0.05 to 0.6 mm. When the thickness of the first layer is less than 0.05 mm, the vulcanization of the raw tire in which the polymer laminate is applied to the air barrier layer causes the first layer to be broken by the press pressure, and the resulting tire has an air leak. Phenomena may occur. On the other hand, if the thickness of the first layer exceeds 0.6 mm, the tire weight increases and the fuel efficiency performance decreases. The thickness of the first layer is preferably 0.05 to 0.4 mm. The first layer can be obtained by forming SIBS into a film by an ordinary method of forming a thermoplastic resin or thermoplastic elastomer into a film such as extrusion molding or calendar molding.

<Second layer>
In the present invention, the second layer is also referred to as a SIS layer composed of a styrene-isoprene-styrene triblock copolymer (hereinafter also referred to as “SIS”) and a styrene-isobutylene diblock copolymer (hereinafter referred to as “SIB”). At least one of the SIB layers.

  Since the isoprene block of the styrene-isoprene-styrene triblock copolymer (SIS) is a soft segment, the polymer film made of SIS is easily vulcanized and bonded to the rubber component. Therefore, when a polymer film made of SIS is used for the air barrier layer, the air barrier layer is excellent in adhesiveness with, for example, a rubber layer of a carcass ply, so that a pneumatic tire having excellent durability can be obtained. it can.

  The molecular weight of the SIS is not particularly limited, but from the viewpoint of rubber elasticity and moldability, the weight average molecular weight by GPC measurement is preferably 100,000 to 290,000. If the weight average molecular weight is less than 100,000, the tensile strength may be lowered, and if it exceeds 290,000, the extrusion processability is deteriorated. It is preferable that content of the styrene component in SIS is 10-30 mass% from a viewpoint of adhesiveness, adhesiveness, and rubber elasticity.

  In the present invention, the degree of polymerization of each block of SIS is preferably about 500 to 5,000 for isoprene and about 50 to 1,500 for styrene from the viewpoint of rubber elasticity and handling.

  The SIS can be obtained by a general vinyl compound polymerization method, for example, a living cationic polymerization method. The SIS layer can be obtained by forming the SIS into a film by a usual method of forming a thermoplastic resin or a thermoplastic elastomer into a film such as extrusion molding or calendar molding.

  Since the isobutylene block of the styrene-isobutylene diblock copolymer (SIB) is a soft segment, the polymer film made of SIB is easily vulcanized and bonded to the rubber component. Therefore, when a polymer film made of SIB is used as an air barrier layer, the air barrier layer has excellent adhesion to, for example, an adjacent rubber that forms a carcass or insulation, so that the pneumatic tire has excellent durability. Can be obtained.

  It is preferable to use a linear SIB from the viewpoint of rubber elasticity and adhesiveness. The molecular weight of SIB is not particularly limited, but from the viewpoint of rubber elasticity and moldability, the weight average molecular weight by GPC measurement is preferably 40,000 to 120,000. If the weight average molecular weight is less than 40,000, the tensile strength may be lowered, and if it exceeds 120,000, the extrusion processability may be deteriorated.

  The content of the styrene component in the SIB is preferably 10 to 35% by mass from the viewpoints of tackiness, adhesiveness, and rubber elasticity.

  In the present invention, the polymerization degree of each block in SIB is preferably about 300 to 3,000 for isobutylene and about 10 to 1,500 for styrene from the viewpoint of rubber elasticity and handling.

  The SIB can be obtained by a general vinyl compound polymerization method, for example, a living cationic polymerization method. For example, in International Publication No. 2005/033035, methylcyclohexane, n-butyl chloride and cumyl chloride are added to a stirrer, cooled to −70 ° C., reacted for 2 hours, and then a large amount of methanol is added. A production method is disclosed in which the reaction is stopped and vacuum-dried at 60 ° C. to obtain SIB.

  The SIB layer can be obtained by forming SIB into a film by an ordinary method of forming a thermoplastic resin or thermoplastic elastomer into a film such as extrusion molding or calendering.

  The thickness T2 of the second layer is 0.01 mm to 0.3 mm. Here, the thickness of the second layer refers to the thickness of the SIS layer when the second layer is composed only of the SIS layer, and the thickness of the SIB layer when the second layer is composed of only the SIB layer. When a layer consists of two layers of an SIS layer and an SIB layer, it means the total thickness of the SIS layer and the SIB layer. When the thickness of the second layer is less than 0.01 mm, the second layer is broken by the press pressure during vulcanization of the raw tire in which the polymer laminate is applied to the air barrier layer, and the vulcanization adhesion force is reduced. There is a fear. On the other hand, if the thickness of the second layer exceeds 0.3 mm, the tire weight increases and the fuel efficiency performance decreases. The thickness of the second layer is further preferably 0.05 to 0.2 mm.

<Form of polymer laminate>
In the present invention, various structures can be adopted as the structure of the polymer laminate used for the air barrier layer. These forms will be described with reference to FIGS. 7 to 10, which are schematic sectional views of the air blocking layer.

Form 1
As shown in FIG. 7, the polymer laminate PL is composed of a SIBS layer PL1 as a first layer and a SIS layer PL2 as a second layer. When the polymer laminate PL is applied to an air barrier layer of a pneumatic tire, if the SIS layer PL2 is placed outward in the tire radial direction so as to be in contact with the inner liner or the carcass ply 61, in the tire vulcanization process, The adhesive strength between the layer PL2 and the inner liner or the carcass ply 61 can be increased. Therefore, the obtained pneumatic tire can have excellent air permeation resistance and durability because the air barrier layer and the inner liner or the rubber layer of the carcass ply 61 are well bonded.

Form 2
As shown in FIG. 8, the polymer laminate PL is composed of a SIBS layer PL1 as a first layer and a SIB layer PL3 as a second layer. When the polymer laminate PL is applied to an air barrier layer of a pneumatic tire, if the surface of the SIB layer PL3 is disposed outwardly in the tire radial direction so as to be in contact with the inner liner or the carcass ply 61, the tire vulcanizing step In this case, the adhesive strength between the SIB layer PL3 and the inner liner or the carcass 61 can be increased. Therefore, the obtained pneumatic tire can have excellent air permeation resistance and durability because the air barrier layer and the inner liner or the rubber layer of the carcass ply 61 are well bonded.

Form 3
As shown in FIG. 9, the polymer laminate PL is configured by laminating a SIBS layer PL1 as a first layer, a SIS layer PL2 and a SIB layer PL3 as second layers in the order described above. When the polymer laminate PL is applied to a pneumatic tire, if the surface of the SIB layer PL3 is placed outward in the tire radial direction so as to be in contact with the inner liner or the carcass ply 61, the SIB layer is used in the tire vulcanization process. The adhesive strength between PL3 and the inner liner or carcass ply 61 can be increased. Therefore, the obtained pneumatic tire can have excellent air permeation resistance and durability because the air barrier layer and the inner liner or the rubber layer of the carcass ply 61 are well bonded.

Form 4
As shown in FIG. 10, the polymer laminate PL is configured by laminating an SIBS layer PL1 as a first layer, an SIB layer PL3 as a second layer, and an SIS layer PL2 in the order described above. When the polymer laminate PL is applied to an air barrier layer of a pneumatic tire, if the surface of the SIS layer PL2 is installed so as to be in contact with the inner liner or the carcass ply 61 toward the outer side in the tire radial direction, the tire vulcanizing step , The adhesive strength between the SIS layer PL2 and the inner liner or the carcass ply 61 can be increased. Therefore, the obtained pneumatic tire can have excellent air permeation resistance and durability because the air barrier layer and the inner liner or the rubber layer of the carcass ply 61 are well bonded.

<Method for producing polymer laminate>
The polymer laminate PL can be obtained by subjecting SIBS and / or SIS and SIB to laminate extrusion such as laminate extrusion or coextrusion in the order described in any one of forms 1 to 4, for example.

<Method of manufacturing tires for trucks and buses>
A general manufacturing method can be used for the truck / bus tire of the present invention. The polymer laminate PL can be manufactured by applying it to the air barrier layer of the raw tire of the truck / bus tire 1 and vulcanizing it together with other members. When the polymer laminate PL is arranged on the raw tire, the SIS layer PL2 or SIB layer PL3, which is the second layer of the polymer laminate PL, is arranged outward in the tire radial direction so as to be in contact with the inner liner or the carcass ply. . By arranging in this way, in the tire vulcanizing step, the adhesive strength between the SIS layer PL2 or SIB layer PL3 and the inner liner or carcass ply can be increased. The obtained tire can have excellent air permeation resistance and durability because the air barrier layer and the inner liner or the carcass ply are well bonded.

  With the specifications shown in Table 1, Table 2, and Table 3, tires for trucks and buses of Examples and Comparative Examples were manufactured, and performance was evaluated. SIB, SIBS and SIS used for the first layer and the second layer were prepared as follows.

<SIB>
To a 2 L reaction vessel equipped with a stirrer, 589 mL of methylcyclohexane (dried with molecular sieves), 613 ml of n-butyl chloride (dried with molecular sieves), and 0.550 g of cumyl chloride were added. After cooling the reaction vessel to −70 ° C., 0.35 mL of α-picoline (2-methylpyridine) and 179 mL of isobutylene were added. Further, 9.4 mL of titanium tetrachloride was added to initiate polymerization, and the reaction was allowed to proceed for 2.0 hours while stirring the solution at -70 ° C. Next, 59 mL of styrene was added to the reaction vessel, and the reaction was continued for another 60 minutes, and then a large amount of methanol was added to stop the reaction. After removing the solvent and the like from the reaction solution, the polymer was dissolved in toluene and washed twice with water. The toluene solution was added to a methanol mixture to precipitate a polymer, and the obtained polymer was dried at 60 ° C. for 24 hours to obtain a styrene-isobutylene diblock copolymer.

Styrene component content: 15% by mass
Weight average molecular weight: 70,000
<SIBS>
Shibstar SIBSTAR 102T (Shore A hardness 25, styrene component content 25 mass%, weight average molecular weight: 100,000) manufactured by Kaneka Corporation was used.

<SIS>
D1161JP (styrene component content 15 mass%, weight average molecular weight: 150,000) manufactured by Kraton Polymer Co., Ltd. was used.
<Manufacture of tires for trucks and buses>
The above SIBS, SIS and SIB were pelletized with a twin screw extruder (screw diameter: φ50 mm, L / D: 30, cylinder temperature: 220 ° C.). Thereafter, an air barrier layer was produced by a T-die extruder (screw diameter: φ80 mm, L / D: 50, die lip width: 500 mm, cylinder temperature: 220 ° C., film gauge: 0.3 mm) or an inflation co-extruder. .

  In the 11R22.5 14PR size truck / bus tire having the basic structure shown in FIG. 1 and the bead portion structure shown in FIGS. 2 to 6, a raw tire is manufactured using the polymer laminate as an air barrier layer. In the vulcanization process, a vulcanized tire was manufactured by press molding at 150 ° C. for 35 minutes. In Tables 1 to 3, the comparative example and the example in which the bead portion structure is not shown are structures that do not correspond to FIGS. 2 to 6.

<Comparative Examples 1-3>
In Comparative Examples 1 to 3, the air blocking layer was not disposed, and the following components were mixed as an inner liner with a Banbury mixer and formed into a sheet with a calendar roll to obtain a polymer film having a thickness of 1.0 mm.

IIR (Note 1) 90 parts by weight Natural rubber (Note 2) 10 parts by weight Filler (Note 3) 50 parts by weight (Note 1) IIR: “Exon Chlorobutyl 1068” manufactured by ExxonMobil Corporation.
(Note 2) TSR20.
(Note 3) “Seast V” (N660, nitrogen adsorption specific surface area: 27 m ² / g) manufactured by Tokai Carbon Co., Ltd.

<Examples 1 to 5, Comparative Example 4>
Examples 1 to 5 and Comparative Example 4 have a structure in which no inner liner is disposed. In Examples 1 to 5, SIBS is used for the first layer and SIS or SIB is used for the second layer as the air blocking layer. In Comparative Example 4, only the SIBS layer is disposed as the air blocking layer.

<Examples 6 to 16>
Examples 6 to 8 have a structure in which no inner liner is disposed, and SIBS is used for the first layer of the air blocking layer, and a composite layer of SIS and SIB is used for the second layer. The air barrier layer is disposed over the entire tire inner surface.

  In Examples 9 to 16, an inner liner is disposed, SIBS is used for the first layer of the air blocking layer, and a composite layer of SIS and SIB is used for the second layer. In Examples 9 to 11, the air barrier layer is disposed over the entire inner surface of the tire. In Examples 12 to 16, the upper end of the air barrier layer is located 50 mm from the toe tip P. In addition, the same inner liner as in Comparative Examples 1 to 3 was used.

<Examples 17 to 20>
Examples 17 to 20 have a structure in which an inner liner is not disposed, and SIBS is used for the first layer of the air blocking layer, and a composite layer of SIS and SIB is used for the second layer. And the mixing ratio of butyl rubber of tow rubber is changed.

<Performance test>
The tires for trucks and buses of Examples and Comparative Examples were manufactured as described above, and the following performance tests were performed.

<Peel test>
An air barrier layer (polymer laminate or polymer sheet) and a carcass rubber sheet (components: natural rubber and SBR) were layered and heated under pressure at 170 ° C. for 12 minutes to prepare a peeling test piece. The polymer laminate was stacked so that the SIS layer or SIB layer was in contact with the rubber sheet. Using the obtained test piece, a peel test was performed according to JIS K 6256 “Vulcanized Rubber and Thermoplastic Rubber—How to Obtain Adhesiveness”, and the peel force between the air barrier layer and the rubber sheet was measured. The size of the test piece was 25 mm wide, and the peel test was performed at room temperature of 23 ° C. The larger the value, the greater the peel force between the air barrier layer and the rubber sheet.

<Bending fatigue test>
A predetermined test piece having a groove at the center was prepared in accordance with JIS K 6260 “Demach flex cracking test method for vulcanized rubber and thermoplastic rubber”. The air barrier layer was vulcanized by attaching a sheet having a thickness of 0.3 mm to rubber to prepare a predetermined test piece. An incision was made in advance at the center of the groove of the test piece, and a test was conducted to measure crack growth by repeatedly bending and deforming. The crack length was measured at an ambient temperature of 23 ° C., a strain of 30%, and a period of 5 Hz, and the number of repetitions of bending deformation required for the crack to grow by 1 mm was calculated. Using the value of Comparative Example 1 as a reference (100), the flexural fatigue properties of the polymer laminates of Examples and Comparative Examples were expressed as indices. It can be said that the larger the numerical value, the better the cracks are less likely to grow. For example, the index of Example 1 is obtained by the following formula.

(Bending fatigue index) = (Number of repetitions of bending deformation of Example 1) / (Number of repetitions of bending deformation of Comparative Example 1) × 100
<Static air pressure drop rate test>
The tire for 11R22.5PR truck and bus manufactured by the above method was assembled in a JIS standard rim, sealed with an initial air pressure of 900 Kpa, left at room temperature for 90 days, and the rate of decrease in air pressure was calculated.

<Performance evaluation results>
<Examples 1 to 5, Comparative Example 4>
Examples 1 to 5 and Comparative Example 4 have a structure in which no inner liner is disposed. In Examples 1 to 5, SIBS is used for the first layer as the air blocking layer, SIS or SIB is used for the second layer, and the lower end thereof extends to the vicinity of the toe tip. Excellent in strength, flex fatigue, and static air drop rate.

Since the comparative example 4 does not use the second layer for the air blocking layer, the peeling force is remarkably inferior.
<Examples 6 to 16>
Examples 6-8 are structures which do not arrange an inner liner. The air barrier layer uses SIBS for the first layer and a composite layer of SIS and SIB for the second layer, and is disposed over the entire tire inner surface. Compared with Comparative Example 1, these examples are generally superior in peel strength, flex fatigue, and static air reduction rate.

  Examples 9 to 16 have a structure in which an inner liner is disposed. The air barrier layer uses SIBS for the first layer and a composite layer of SIS and SIB for the second layer, and is disposed over the entire tire inner surface. Compared with Comparative Example 1, the peel strength, the bending fatigue property, and the static air drop rate are comprehensively excellent. Compared with Comparative Example 1, these examples are generally superior in peel strength, flex fatigue, and static air reduction rate.

<Examples 17 to 20>
Examples 17 to 20 have a structure in which an inner liner is not disposed, and SIBS is used for the first layer of the air blocking layer, and a composite layer of SIS and SIB is used for the second layer. Examples 18 and 19 in which the mixing ratio of tow rubber to butyl rubber is 20 to 40% by mass are excellent in an overall balance of peeling force, bending fatigue property and static air decrease rate.

  The truck / bus tire of the present invention is a concept including a so-called heavy vehicle tire and the like, and can be applied to these tires.

  DESCRIPTION OF SYMBOLS 1 Pneumatic tire, 2 tread part, 3 side wall part, 4 bead part, 5 bead core, 6 carcass ply, 7 belt layer, 8 bead apex, 9 air barrier layer, 9e lower end of air barrier layer, 10 bead reinforcement layer, 11 inner liner, 12 rubber chafer, 13 toe rubber, P toe tip, PL polymer laminate, PL1 SIBS layer, PL2 SIS layer, PL3 SIB layer.

Claims (7)

In truck and bus tires where the inner surface of the tire is covered with an air barrier layer,
The air blocking layer has a thickness of 1 mm or less, an end thereof is located in a region of 120 mm or less from the toe tip of the bead portion along the bead base line, and
The air barrier layer includes a first layer made of styrene-isobutylene-styrene triblock copolymer having a thickness of 0.05 mm to 0.6 mm, a styrene-isoprene-styrene triblock copolymer, and a styrene-isobutylene diblock copolymer. It is composed of a polymer laminate including at least one of polymers and a second layer having a thickness of 0.01 mm to 0.3 mm, and the second layer is disposed on the carcass ply side. The truck / bus tire described above. In a truck bus tire having an inner liner on the tire inner surface,
An air blocking layer is formed to form an overlapping portion in contact with the inner surface of the inner liner of the tire;
The air barrier layer has a thickness of 1 mm or less, and an end thereof is located in a region of 120 mm or less along the bead base line from the overlapping portion through the toe tip of the bead portion, and
The air barrier layer includes a first layer made of styrene-isobutylene-styrene triblock copolymer having a thickness of 0.05 mm to 0.6 mm, a styrene-isoprene-styrene triblock copolymer, and a styrene-isobutylene diblock copolymer. The truck / bus tire according to claim 1, wherein the tire is made of a polymer laminate including at least one of polymers and a second layer having a thickness of 0.01 mm to 0.3 mm. In a tire for trucks and buses having an inner liner on the inner surface of the tire and the inner liner covered with an air barrier layer,
The air barrier layer has a thickness of 1 mm or less, a toe end is located in a region of 35 mm or less in a direction along the tire inner surface from a toe tip of the bead part, and
The air barrier layer includes a first layer made of styrene-isobutylene-styrene triblock copolymer having a thickness of 0.05 mm to 0.6 mm, a styrene-isoprene-styrene triblock copolymer, and a styrene-isobutylene diblock copolymer. It is composed of a polymer laminate including at least one of polymers and a second layer having a thickness of 0.01 mm to 0.3 mm, and the second layer is disposed adjacent to the inner liner. The truck / bus tire described above.   The tire for trucks and buses according to any one of claims 1 to 3, wherein the styrene-isobutylene-styrene triblock copolymer has a styrene component content of 10 to 30% by mass.   The styrene-isoprene-styrene triblock copolymer has a styrene component content of 10 to 30% by mass and a weight average molecular weight of 100,000 to 290,000. Truck and bus tires.   The styrene-isobutylene diblock copolymer is linear, the styrene component content is 10 to 35 mass%, and the weight average molecular weight is 40,000 to 120,000. Truck and bus tires as described in 1.   7. The rubber component according to claim 1, wherein 20 to 40% by mass of the rubber component is tow rubber made of a rubber composition comprising at least one of butyl rubber and halogenated butyl rubber, and an end portion of the air blocking layer is coated. Truck and bus tires.

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