JP2012240604A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve separation and crack resistance properties of an inner liner.SOLUTION: The inner liner includes a first layer with a thickness of 0.05 mm to 0.6 mm which is a thermoplastic elastomer composition composed of a mixture of ≥60 mass% of a styrene-isobutylene-styrene triblock copolymer and ≤40 mass% of a C4 polymer as the polymer of the C4 monomer and a second layer with a thickness of 0.01 mm to 0.3 mm which is a thermoplastic elastomer composition composed of a mixture of at least ≥60 mass% of either a styrene-isoprene-styrene triblock copolymer or a styrene-isobutylene diblock copolymer and ≤40 mass% of the C4 polymer, wherein the second layer contacts a carcass ply 6, and the inner liner is characterized in that an average thickness Gs of a buttress region Rs from a tire maximum width position to a corresponding position Lu of a belt layer edge is thinner than an average thickness Gb of a bead region Rb.

Description

  The present invention relates to a pneumatic tire provided with an inner liner.

  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 tire to prevent air leakage from the inside of the pneumatic tire. There is also a demand for weight reduction in an inner liner having the function of:

  At present, the rubber composition for an inner liner 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. Has 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. In order to achieve this, there is a demand for a polymer that has better air permeation resistance than butyl rubber and that can reduce the thickness of the inner liner layer.

  Conventionally, it has been proposed to use a thermoplastic elastomer in order to reduce the weight of the inner liner. However, when the thickness of the thermoplastic elastomer is made thinner than that of butyl rubber, the air permeability and strength are lowered, and the inner liner may be broken by the heat and pressure of the bladder during vulcanization of the tire. Further, a thermoplastic elastomer having a low strength is likely to crack in the inner liner in a buttress portion that undergoes large repeated shear deformation during tire running.

  Patent Document 1 discloses a laminate for improving the adhesion between the inner liner layer and the rubber layer. By providing an adhesive layer on both sides of the inner liner layer, the adhesive layers come into contact with each other at the overlapping portion of the inner liner layer, and are firmly bonded by heating, thereby improving air pressure retention. . However, the adhesive layer for superimposing the inner liner 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 an air permeation-resistant nylon resin and butyl rubber is prepared by dynamic cross-linking to produce an inner liner layer having a thickness of 100 μm. However, nylon resin is hard at room temperature and unsuitable as an inner liner for tires. In addition, the vulcanization adhesion to the rubber layer is not performed only with the mixture obtained by the dynamic crosslinking. Therefore, the adhesion layer for vulcanization is required in addition to the inner liner layer. Therefore, the inner liner member has a complicated structure and many processes. This is disadvantageous from the viewpoint of productivity.

  Prior Document 3 disperses maleic anhydride-modified hydrogenated styrene-ethylene-butadiene-styrene block copolymer in an air-permeable ethylene-vinyl alcohol copolymer 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 inner liner 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. Furthermore, although rubber paste is applied to the surface to be bonded to the tire rubber, a process different from the normal inner liner process is required, resulting in poor productivity.

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

  An object of the present invention is to prevent peeling of an inner liner and improve bending fatigue resistance, air permeation resistance and crack resistance in a pneumatic tire provided with an inner liner.

  The present invention is a pneumatic tire provided with an inner liner inside the tire, wherein the inner liner is a polymer of 60% by mass or more of a styrene-isobutylene-styrene triblock copolymer and a monomer having 4 carbon atoms. A thermoplastic elastomer composition comprising a mixture of a C4 polymer of 40% by mass or less, a first layer having a thickness of 0.05 mm to 0.6 mm, a styrene-isoprene-styrene triblock copolymer, and styrene -A thermoplastic elastomer composition comprising a mixture of at least 60% by mass of an isobutylene diblock copolymer and 40% by mass or less of the C4 polymer, and having a thickness of 0.01 mm to 0.3 mm The second layer is formed of a polymer laminate, and the second layer is disposed so as to contact the rubber layer of the carcass ply. In the inner liner, the average thickness Gs of the buttress region Rs from the tire maximum width position to the corresponding position Lu of the belt layer end is thinner than the average thickness Gb of the bead region Rb extending from the tire maximum width position to the bead toe. It is a pneumatic tire characterized by.

  The styrene-isobutylene-styrene triblock copolymer preferably has a styrene component content of 10 to 30% by mass and a weight average molecular weight of 50,000 to 400,000.

  The C4 polymer is preferably polybutene or polyisobutylene. The C4 polymer preferably has a number average molecular weight of 300 to 3,000, a weight average molecular weight of 700 to 100,000, or a viscosity average molecular weight of 20,000 to 70,000.

  The styrene-isoprene-styrene block 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.

  Further, the styrene-isobutylene block copolymer preferably has a linear molecular chain, a styrene component content of 10 to 35% by mass, and a weight average molecular weight of 40,000 to 120,000.

  The ratio (Gs / Gb) of the average thickness Gs of the buttress region of the inner liner to the average thickness Gb of the bead region is 0.30 to 0.75, and the average thickness Gs of the buttress region of the inner liner is Is preferably 0.05 to 0.45 mm.

  In the present invention, the laminate of the thermoplastic elastomer composition containing the C4 polymer is used for the inner liner, so that the thickness can be reduced while improving the air permeation resistance, and the adhesion to the adjacent rubber layer can be improved. Can improve. And by adjusting the average thickness Gb of the bead region Rb of the inner liner and the average thickness Gs of the buttress region Rs, it is possible to effectively relieve the stress associated with repeated deformation of the tire during running, and bend fatigue and crack resistance. Is improved.

It is a schematic sectional drawing which shows the right half of the pneumatic tire in one embodiment of this invention. It is a schematic sectional drawing of the inner liner in the pneumatic tire of the present invention. It is a schematic sectional drawing of the inner liner in the pneumatic tire of the present invention. It is a schematic sectional drawing of the inner liner in the pneumatic tire of the present invention.

  The present invention is a pneumatic tire provided with an inner liner on the inner side of the tire, and the inner liner is formed of a polymer laminate composed of at least two layers. 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.

  An embodiment of a pneumatic tire according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of the right half of a pneumatic tire for passenger cars. The pneumatic 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. Also, a carcass ply 6 provided from one bead portion 4 to the other bead portion, with both ends folded back and locked around the bead core 5, and at least two sheets on the outer side of the crown portion of the carcass ply 6 A belt layer 7 made of a ply is arranged.

  The belt layer 7 usually intersects two plies made of steel cords or cords such as aramid fibers with respect to the tire circumferential direction so that the cords are usually at an angle of 5 to 30 °. Are arranged as follows. 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. In the carcass ply, organic fiber cords such as polyester, nylon, and aramid are arranged at approximately 90 ° in the tire circumferential direction. In the region surrounded by the carcass ply and the folded portion, the bead core 5 extends from the upper end to the sidewall direction. An extending bead apex 8 is arranged. Further, an inner liner 9 extending from one bead portion 4 to the other bead portion 4 is disposed inside the carcass ply 6 in the tire radial direction.

  In the present invention, from the average thickness Gb of the inner liner 9 in the bead area Rb extending from the tire maximum width position Le to the bead toe Lt, the inner liner 9 in the buttress area Rs extending from the tire maximum width position Le to the corresponding position Lu at the belt layer end. The average thickness Gs is made thin.

  By reducing the thickness of the inner liner in the buttress region Rs, even when shear deformation occurs due to repeated bending deformation in this region during tire running, the stress can be relieved and cracking can be prevented. can do.

  In order to effectively relieve the stress due to bending deformation, the ratio (Gs / Gb) of the average thickness Gs of the buttress region Rs of the inner liner to the average thickness Gb of the bead region Rb is 0.3-0. 75. Further, in order to maintain the air pressure holding performance and also have the effect of relaxing the stress in the buttress region, it is desirable that the average thickness Gs of the buttress region Rs of the inner liner is 0.05 to 0.45 mm.

<Polymer laminate>
In the present invention, the inner liner is a thermoplastic elastomer composition mainly composed of a styrene-isobutylene-styrene triblock copolymer (SIBS), the first layer having a thickness of 0.05 mm to 0.6 mm, and styrene. A second layer having a thickness of 0.01 mm to 0.3 mm, which is a thermoplastic elastomer composition mainly composed of at least one of isoprene-styrene triblock copolymer and styrene-isobutylene diblock copolymer It is formed with the polymer laminated body which consists of these. Here, in the thermoplastic elastomer composition of the first layer and the second layer, C4 polymer, which is a polymer of a monomer having 4 carbon atoms, is mixed in an amount of 40% by mass or less, particularly 0.5 to 40% by mass. Yes.

<First layer>
In the present invention, the first layer is a mixture of 60% by mass or more of styrene-isobutylene-styrene triblock copolymer (SIBS) and 40% by mass or less of a C4 polymer obtained by polymerizing a monomer having 4 carbon atoms. Formed of a thermoplastic elastomer composition.

  Since the styrene-isobutylene-styrene triblock copolymer (SIBS) is derived from the isobutylene block, the polymer film made of SIBS has excellent air permeation resistance. Therefore, when a polymer film made of SIBS is used for the inner liner, a pneumatic tire having excellent 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 inner liner, a pneumatic tire having excellent durability 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. Since SIBS improves air permeation resistance and durability, the content of the styrene component in SIBS is 10 to 30% by mass, preferably 14 to 25% by mass.

  In SIBS, the degree of polymerization of each block is preferably about 10,000 to 150,000 for an isobutylene block and about 5,000 to 30,000 for a styrene block from the viewpoint of rubber elasticity and workability.

  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.

(C4 polymer)
In the present invention, the first layer contains a C4 polymer obtained by polymerizing a monomer unit having 4 carbon atoms together with SIBS. The low molecular weight component of the C4 polymer improves unvulcanized adhesion and vulcanized adhesion between the SIBS first layer and other polymer sheets and rubber layers without impairing the SIBS-derived air permeation resistance. Can be made. Therefore, when the SIBS layer containing the C4 polymer is used for the inner liner portion of the tire, the adhesive strength with the rubber layer forming the adjacent carcass or insulation is improved, and the inner liner and the carcass or the inner liner and the inner liner are formed. The air-in phenomenon during the operation can be prevented.
The number average molecular weight of the C4 polymer by GPC method is preferably 300 to 3,000, more preferably 500 to 2,500. The weight average molecular weight of the polymer by GPC method is preferably 700 to 100,000, and more preferably 1,000 to 80,000. The viscosity average molecular weight of the polymer according to the FCC method is preferably 20,000 to 70,000, and more preferably 30,000 to 60,000.

  Examples of the C4 polymer include polybutene and polyisobutylene. Polybutene is a copolymer having a long-chain hydrocarbon molecular structure obtained by reacting isobutene as a main monomer unit and using normal butene. As the polybutene, hydrogenated polybutene can also be used. Polyisobutylene is a copolymer having a long-chain hydrocarbon molecular structure obtained by polymerizing isobutene as a monomer unit.

Examples of the polybutene include Nisseki polybutene (grade LV7, LV50, LV100, HV15, HV35, HV50, HV100, HV300, HV1900) manufactured by Nippon Oil Corporation. These have a number average molecular weight of 300 to 3000 according to the GPC method. Further, there are Glissopal 550, 1000, 1300 and 2300 manufactured by BASF Corporation. These have a number average molecular weight of 550 to 2300 and a weight average molecular weight of 700 to 4,5000 according to the GPC method. Moreover, Idemitsu polybutene OH, 5H, 2000H (hydrogenation grade), 15R, 35R, 100R, 300R (non-hydrogenation grade) manufactured by Idemitsu Petrochemical Co., Ltd. can be exemplified. These have a number average molecular weight of 350 to 3000 according to ASTM D2503-92.
Examples of polyisobutylene include Tetrax 3T, 4T, 5T, and 6T manufactured by Nippon Oil Corporation. These have a weight average molecular weight of 30,000 to 100,000 according to the NPCC method (GPC method) and a viscosity average molecular weight of 20,000 to 70,000 according to FCC.

(SIBS layer)
In the present invention, the first layer mainly composed of SIBS is also referred to as an SIBS layer. In the present invention, the SIBS layer contains less than 40% by mass, particularly 0.5% by mass or more and 40% by mass or less of a C4 polymer obtained by polymerizing a monomer unit having 4 carbon atoms. If the content of the C4 polymer is less than 0.5% by mass, the vulcanized adhesive strength with carcass or insulation may be reduced, and if it exceeds 40% by mass, the air permeation resistance is reduced. Since the viscosity is lowered, the extrusion processability may be deteriorated. The content of the C4 polymer is preferably 5% by mass or more and 20% by mass or less. On the other hand, the content of SIBS in the SIBS layer is preferably 60% by mass or more and 99.5% by mass or less. If the SIBS content is less than 60% by mass, the air permeation resistance may be reduced. If the SIBS content exceeds 99.5% by mass, the vulcanization adhesion to carcass and insulation may be reduced. It is not preferable. The content of SIBS is more preferably 80% by mass or more and 95% by mass or less.

  The thickness of the SIBS layer as the first layer is 0.05 mm or more and 0.6 mm or less. When the thickness of the SIBS layer is less than 0.05 mm, the SIBS layer may be broken by the press pressure during vulcanization of the raw tire in which the polymer sheet is applied to the inner liner, and an air leak phenomenon may occur in the obtained tire. There is. On the other hand, if the thickness of the SIBS layer exceeds 0.6 mm, the tire weight increases and the fuel efficiency performance decreases. The thickness of the SIBS layer is preferably 0.05 mm or more and 0.4 mm or less.

  The SIBS layer can be obtained by a usual method of forming SIBS into a sheet of thermoplastic resin or thermoplastic elastomer such as extrusion molding or calendar molding.

<Second layer>
In the present invention, the second layer is at least one of a styrene-isoprene-styrene triblock copolymer (hereinafter also referred to as “SIS”) and a styrene-isobutylene diblock copolymer (hereinafter also referred to as “SIB”). This is an elastomer composition comprising a mixture of 60% by mass or more and 40% by mass or less of the C4 polymer, and has a thickness of 0.01 mm to 0.3 mm.

(SIS)
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 inner liner, the inner liner is excellent in adhesiveness with, for example, the rubber layer of the carcass ply, so that a pneumatic tire excellent in durability can be obtained.

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

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

  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.

(SIB)
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 inner liner, the inner liner is excellent in adhesiveness with an adjacent rubber forming a carcass or an insulation, for example, so that a pneumatic tire excellent in durability is obtained. be able to.

  As SIB, it is preferable to use a linear molecular chain from the viewpoint of improving rubber elasticity and adhesiveness. The molecular weight of SIB is not particularly limited, but in order to maintain rubber elasticity and workability, 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 100 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.

(SIS layer, SIB layer)
A thermoplastic elastomer composition in which a C4 polymer is mixed with SIS or SIB is also referred to as SIS layer or SIB layer. C4 polymer is 40 mass% or less with respect to a thermoplastic elastomer, especially 0.5 mass%-40 mass% are mixed. If the content of the C4 polymer is less than 0.5% by mass, the vulcanization adhesion with carcass and insulation may be reduced, and if it exceeds 40% by mass, the air permeation resistance is reduced. Further, since the viscosity is lowered, the extrusion processability may be deteriorated, which is not preferable. The content of the C4 polymer is more preferably 5% by mass or more and 20% by mass or less. On the other hand, the thermoplastic elastomer composition of the second layer, that is, the content of SIS or SIB in the SIS layer or SIB layer is preferably 60% by mass or more and 99.5% by mass or less. If the SIS or SIB content is less than 60% by mass, the viscosity may be low and the extrudability may be deteriorated. If it exceeds 99.5% by mass, the vulcanized adhesive strength with carcass and insulation may be reduced. It is not preferable because it may decrease. The content of SIS or SIB is more preferably 80% by mass or more and 95% by mass or less.

  The thickness of the second layer is 0.01 mm or more and 0.3 mm or less. When the thickness of the second layer is less than 0.01 mm, the second layer may be broken by the press pressure during vulcanization of the raw tire in which the polymer laminate is applied to the inner liner, and the vulcanization adhesive force may be reduced. There is. 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 preferably 0.01 mm or more and 0.2 mm or less.

<Application of inner liner>
Referring to FIG. 1, when the polymer laminate is applied to the inner liner 9 of the pneumatic tire 1, the surface of the first SIBS layer is directed to the innermost side in the tire radial direction, and the second SIS layer or SIB If the surface of the layer is installed facing the outer side in the tire radial direction so as to be in contact with the carcass 6, the second layer and the carcass 6 can be vulcanized and bonded in the vulcanization process of the tire. Therefore, the obtained pneumatic tire 1 can adhere | attach the inner liner 9 and the rubber layer of the carcass 6 well, can prevent air-in, and can have the outstanding air permeation resistance and durability.

<Position of polymer laminate>
Various structures can be adopted as the structure of the polymer laminate used for the inner liner in the present invention. These forms will be described with reference to FIGS. 2 to 4 which are schematic sectional views of the inner liner.

Form 1
As shown in FIG. 2, the polymer laminate 10 includes a SIBS layer 11 as a first layer and a SIS layer 12 as a second layer. When the polymer laminate 10 is applied to an inner liner of a pneumatic tire, the SIS layer 12 and the carcass are disposed in the tire vulcanization process when the SIS layer 12 is installed so as to be in contact with the carcass ply 61 toward the outer side in the tire radial direction. Adhesive strength with 61 can be increased. Therefore, the obtained pneumatic tire can have excellent air permeation resistance and durability because the inner liner and the rubber layer of the carcass ply 61 are well bonded.

Form 2
As shown in FIG. 3, the polymer laminate 10 includes an SIBS layer 11 as a first layer and an SIB layer 13 as a second layer. When the polymer laminate 10 is applied to an inner liner of a pneumatic tire, if the surface of the SIB layer 13 is disposed facing the outer side in the tire radial direction so as to be in contact with the carcass ply 61, the SIB layer 13 and the carcass 61 can be increased in adhesive strength. Therefore, the obtained pneumatic tire can have excellent air permeation resistance and durability because the inner liner and the rubber layer of the carcass ply 61 are well bonded.

Form 3
As shown in FIG. 4, the polymer laminate 10 is configured by laminating a SIBS layer 11 as a first layer, a SIS layer 12 and a SIB layer 13 as a second layer in the order described above. When the polymer laminate 10 is applied to the inner liner 61 of a pneumatic tire, if the surface of the SIB layer 13 is installed facing the outer side in the tire radial direction so as to be in contact with the carcass ply 61, in the tire vulcanization process, The adhesive strength between the layer 13 and the carcass ply 6 can be increased. Therefore, the obtained pneumatic tire can have excellent air permeation resistance and durability because the inner liner and the rubber layer of the carcass ply 61 are well bonded.

<Pneumatic tire manufacturing method>
The polymer laminate 10 can be obtained by subjecting SIBS and / or at least one of SIS and SIB to laminate extrusion such as laminate extrusion or coextrusion in the order described in any of Embodiments 1 to 3, for example.

  A general manufacturing method can be used for the pneumatic tire of the present invention. The polymer laminate 10 can be produced by applying it to an inner liner of a raw tire of the pneumatic tire 1 and vulcanizing it together with other members. When the polymer laminate 10 is arranged on the green tire, the SIS layer 12 or the SIB layer 13 that is the second layer of the polymer laminate 10 is arranged outward in the tire radial direction so as to be in contact with the carcass ply 61. When arranged in this manner, the adhesive strength between the SIS layer 12 or the SIB layer 13 and the carcass 6 can be increased in the tire vulcanization step. The obtained pneumatic tire can have excellent air permeation resistance and durability because the inner liner and the rubber layer of the carcass ply 61 are well bonded.

  In order to adjust the thickness of the inner liner in the bead region Rb and the buttress region Rs, for example, a profile is attached to the extrusion opening of the polymer sheet, and an integrated sheet having a thin buttress region thickness Gs is prepared. This is arranged on the inner surface of the tire as an inner liner.

  The rubber layer of the carcass ply used in the pneumatic tire of the present invention is composed of generally used rubber components such as natural rubber, polyisoprene, styrene-butadiene rubber, polybutadiene rubber, and fillers such as carbon black and silica. Can be used.

  The pneumatic tires of Examples and Comparative Examples were manufactured with the specifications shown in Table 1, Table 2, and Table 3, and the 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.

<Polybutene>
“Nisseki Polybutene Grade HV300” manufactured by Nippon Oil Corporation (number average molecular weight 300)
<Polyisobutylene>
“Tetrax 3T” manufactured by Nippon Oil Corporation (viscosity average molecular weight 30,000, weight average molecular weight 49,000)
<Manufacture of pneumatic tires>
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 inner liner was produced with 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.

  A pneumatic tire is a 195 / 65R15 size tire having the basic structure shown in FIG. 1, and a raw tire is manufactured using the polymer laminate as an inner liner. Molded and manufactured.

  Here, in order to adjust the thickness in the bead region Rb and the buttress region Rs of the inner liner, a profile is attached to the extrusion port of the polymer sheet, and an integrated sheet in which the thickness Gs of the buttress region is reduced is created. This was disposed on the inner surface of the tire as an inner liner.

  In Table 1, Table 2, and Table 3, the thickness of the first layer and the second layer indicates the thickness of the region other than Gs. Except for Comparative Example 1, in all Examples and Comparative Examples, Gb is the total thickness of the first layer and the second layer, and is 0.6 mm.

<Comparative Example 1>
In the inner liner of Comparative Example 1, the following blending components were mixed with a Banbury mixer and formed into a sheet with a calender roll to obtain a polymer film having a thickness of 1.0 mm. The value of Gs / Gb is 1.

IIR (Note 1) 80 parts by mass Natural rubber (Note 2) 20 parts by mass Filler (Note 3) 60 parts by mass (Note 1) IIR used “Exon Chlorobutyl 1068” manufactured by ExxonMobil Corporation.
(Note 2) Natural rubber TSR20 was used.
(Note 3) “Seast V” (N660, nitrogen adsorption specific surface area: 27 m ² / g) manufactured by Tokai Carbon Co., Ltd. was used as the filler.

<Comparative Examples 2-3>
One SIBS layer having a thickness of 0.6 mm manufactured by the above-described method was used as an inner liner. The value of Gs / Gb is 1.

<Comparative Examples 4-9>
A composite layer of 0.40 mm SIBS layer and 0.20 mm SIS layer was used as the inner liner. The value of Gs / Gb is 1 in Comparative Example 4, and 0.75 in Comparative Examples 5 to 9.
Here, the C4 polymer mixed in the first layer or the second layer of Comparative Examples 5 to 8 exceeds 40% by mass.

<Examples 1 to 10>
In Examples 1 to 10, SIBS is used for the first layer and SIS is used for the second layer, and 5% by mass and 40% by mass of polybutene or polyisobutylene are mixed as the C4 polymer. The value of Gs / Gb is 0.75 in Examples 1 to 6, and the value is smaller from Example 7 to Example 10.

<Comparative example 10, Examples 11-19>
Comparative Example 10 and Examples 11 to 19 use SIBS for the first layer and SIB for the second layer. The value of Gs / Gb is highest in Example 11 and lowest in Example 19. In Comparative Example 10, the value of Gs / Gb is 1.

<Comparative Example 11, Examples 20 to 28>
In Comparative Example 11 and Examples 20 to 28, SIBS is used for the first layer, and a composite layer of SIS and SIB is used for the second layer. In Examples 20 to 24, the type and mixing amount of the C4 polymer of the first layer and the second layer are changed. The value of Gs / Gb is 1 in Comparative Example 11, and 0.75 in Examples 20 to 24. In Examples 25 to 28, the value of Gs / Gb is changed, and Example 25 is the highest and Example 28 is the lowest.

<Performance test>
Pneumatic tires were produced using the polymer laminates of Examples and Comparative Examples and the polymer laminates as inner liners, and the following performance tests were performed.

<Peel test>
A test piece was prepared according to JIS-K-6256 “How to determine adhesion between vulcanized rubber and thermoplastic rubber”. A thermoplastic elastomer sheet and a rubber sheet are bonded and vulcanized. After vulcanization, the peel force is measured at the bonding interface. The peel strength of Comparative Example 1 was set to 100, and index evaluation was performed using relative values. It shows that peeling force is so large that an index | exponent is large.

<Bending fatigue test>
A predetermined test piece having a groove in the center was prepared according to JIS-K-6260 “Testing method for demature bending cracking of vulcanized rubber and thermoplastic rubber”. As the inner liner, a sheet having a thickness of 0.3 mm was attached to rubber and vulcanized 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 195 / 65R15 steel radial PC tire manufactured by the above method was assembled into a JIS standard rim 15 × 6 JJ, sealed with an initial air pressure of 300 Kpa, left at room temperature for 90 days, and the rate of decrease in air pressure was calculated.

<Measurement of average thickness>
A 195 / 65R15 steel radial PC tire was divided into 8 equal parts in the circumferential direction, and 8 cut samples cut along the tire radial direction with a width of 20 mm were created at each location, and each of these 8 cut samples was The thickness of the inner liner layer was measured at five points equally divided into five in the buttress region Rs and the bead region Rb. The arithmetic average values of the total 40 measured values were Gs and Gb.

<Crack resistance>
195 / 65R15 steel radial PC tire is assembled to JIS standard rim 15 × 6JJ, filled with regular air pressure, and the maximum load corresponding to this air pressure is applied from the air pressure-addition capacity correspondence table with JATMA YEAR BOOK, speed 80km / The vehicle traveled on the drum at h, and when the damage that could be visually confirmed was generated, the vehicle was stopped and the travel distance was determined. The travel distance of Comparative Example 1 is taken as 100 and is shown as an index. The larger the index, the better the crack resistance.

<Performance evaluation results>
In Tables 1 and 2, Examples 1 to 10 use a polymer laminate including a SIBS layer (thickness 0.4 mm) as a first layer and a SIS layer (thickness 0.2 mm) as a second layer. Yes. Compared with Comparative Examples 1-9, these Examples are generally excellent in peel strength, bending fatigue, sexual air reduction rate, and crack resistance in performance evaluation.

  In Table 2, Examples 11 to 19 use a polymer laminate including an SIBS layer (thickness 0.4 mm) as a first layer and an SIB layer (thickness 0.2 mm) as a second layer. Compared with Comparative Example 10, these examples are comprehensively superior in peel strength, bending fatigue, sexual air reduction rate, and crack resistance in performance evaluation.

  In Table 3, Examples 20 to 28 use a polymer laminate composed of a SIBS layer (thickness 0.4 mm) as a first layer, a SIB layer as a second layer, and a SIS layer (each thickness 0.1 mm). ing. Compared with Comparative Example 11, these examples are generally superior in peel strength, bending fatigue, sexual air reduction rate, and crack resistance in performance evaluation.

  The pneumatic tire of the present invention can be used as a pneumatic tire for trucks and buses, heavy machinery, etc. in addition to a pneumatic tire for passenger cars.

  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 inner liner, 10 polymer laminated body, 11 SIBS layer, 12 SIS layer, 13 SIB layer, Rb bead area, Rs buttress area, Le tire maximum width position, Lt bead toe, Lu belt layer edge corresponding position.

Claims (8)

A pneumatic tire provided with an inner liner on the inside of the tire, wherein the inner liner is
A thermoplastic elastomer composition comprising a mixture of 60% by mass or more of a styrene-isobutylene-styrene triblock copolymer and 40% by mass or less of a C4 polymer that is a polymer of a monomer having 4 carbon atoms, and having a thickness A first layer of 0.05 mm to 0.6 mm;
A thermoplastic elastomer composition comprising a mixture of at least 60% by mass of at least one of a styrene-isoprene-styrene triblock copolymer and a styrene-isobutylene diblock copolymer and 40% by mass or less of the C4 polymer. And a polymer laminate composed of a second layer having 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;
The inner liner is characterized in that the average thickness Gs of the buttress region Rs from the tire maximum width position to the corresponding position Lu of the belt layer end is thinner than the average thickness Gb of the bead region Rb extending from the tire maximum width position to the bead toe. And pneumatic tires.   The pneumatic tire according to claim 1, wherein the styrene-isobutylene-styrene triblock copolymer has a styrene component content of 10 to 30% by mass and a weight average molecular weight of 50,000 to 400,000.   The pneumatic tire according to claim 1, wherein the C4 polymer is polybutene or polyisobutylene.   The pneumatic tire according to claim 1, wherein the C4 polymer has a number average molecular weight of 300 to 3,000, a weight average molecular weight of 700 to 100,000, or a viscosity average molecular weight of 20,000 to 70,000.   The pneumatic tire according to claim 1, wherein the styrene-isoprene-styrene block copolymer has a styrene component content of 10 to 30% by mass and a weight average molecular weight of 100,000 to 290,000.   The styrene-isobutylene block copolymer has a linear molecular chain, a styrene component content of 10 to 35 mass%, and a weight average molecular weight of 40,000 to 120,000. Pneumatic tires.   2. The pneumatic tire according to claim 1, wherein a ratio (Gs / Gb) of an average thickness Gs of the buttress region of the inner liner to an average thickness Gb of the bead region is 0.30 to 0.75.   The pneumatic tire according to claim 1 or 2, wherein an average thickness Gs of a buttress region of the inner liner is 0.05 to 0.45 mm.

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