JP2012162262A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire for reducing the internal pressure drop in the tire, reducing crack growth of an inner liner caused by repetitive bending deformation caused by tire travel, and also reducing rolling resistance, the pneumatic tire having the inner liner.SOLUTION: This pneumatic tire includes the inner liner on the tire inside of a carcass ply installed between a pair of bead parts. In the pneumatic tire, the inner liner is constituted of a first layer arranged on the tire inside, and a second layer arranged so as to contact with a rubber layer of the carcass ply. The first layer is a thermoplastic elastomer composition mainly constituted of a styrene-isobutylene-styrene block copolymer. The second layer is a thermoplastic elastomer composition including a styrene-isoprene-styrene block copolymer, and also including the styrene-isobutylene-styrene block copolymer by 10-80 mass% of a thermoplastic elastomer component.

Description

  The present invention relates to a pneumatic tire including an inner liner, and more particularly to a pneumatic tire that reduces crack growth of an inner liner due to repeated bending deformation during tire running, reduces a decrease in tire internal pressure, and reduces rolling resistance.

  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, air leakage from the inside of a pneumatic tire to the outside is reduced by being arranged inside the tire. Therefore, the inner liner that improves the air permeation resistance has also been reduced in weight.

  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. Further, the rubber compound mainly composed of butyl rubber contains about 1% by mass of isoprene in addition to butylene, which enables crosslinking between rubber molecules together with sulfur, a vulcanization accelerator, and zinc white. When the butyl rubber is used for the inner liner, a thickness of about 0.6 to 1.0 mm is usually required 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, in order to reduce the weight of a tire, a film made of a material containing a thermoplastic resin instead of the rubber composition has been proposed. However, if a tire is manufactured using a thin inner liner made of a thermoplastic resin, the pressure in the vulcanization process is partially reduced so that the finished gauge of the inner liner of the tire product becomes thinner than the design. In addition to the impression that the carcass cord is raised at that location (open thread), the inner liner with a thin finish will give the user an impression that the appearance is poor, and if the inner liner is thin, the gas barrier property will be partially degraded Therefore, the tire internal pressure decreases, and in the worst case, the tire may burst.

  The inner liner is subjected to a large shear strain in the vicinity of the shoulder when the tire is running. When a material containing a thermoplastic resin is used as the inner liner, there is a problem that due to this shear strain, peeling is likely to occur at the adhesive interface between the inner liner and the carcass ply, resulting in tire air leakage.

  In order to reduce the weight of the inner liner, a technique using a thermoplastic elastomer material has also been proposed. However, a material that is thinner than a butyl rubber inner liner and has high air permeation resistance is inferior to a butyl rubber inner liner in vulcanization adhesion to insulation rubber and carcass ply rubber adjacent to the inner liner. I know.

  When the vulcanization adhesive strength of the inner liner is low, air is mixed between the inner liner and the insulation rubber or the carcass rubber, and a so-called air-in phenomenon occurs in which a small balloon appears. Many small spots on the inside of the tire give the user an impression that the appearance is poor, and air is the starting point during driving, causing separation and cracking in the inner liner, resulting in a decrease in tire internal pressure. In such a case, the tire may burst.

  In Patent Document 1, it is proposed to improve adhesion by using petroleum resin or terpene resin as a tackifier for SIBS, which is a thermoplastic elastomer. However, in addition to SIBS, a polyamide-based polymer is blended, and there is a problem that bending crack resistance is lowered.

  Patent Document 2 describes the adhesion of carcass ply rubber using a natural rosin, terpene, chroman indene resin, petroleum resin or alkylphenol resin as a tackifier to a blend of SIBS and sulfur crosslinkable polymer. It has been proposed to improve.

  However, in the technology of blending 10 to 300 parts by weight of a polymer capable of sulfur vulcanization with respect to 100 parts by weight of SIBS, when the sulfur crosslinkable polymer is 100 parts by weight or less, SIBS is a matrix (sea part), The sulfur-crosslinkable polymer has a domain structure (island portion), and the adhesive force at the contact interface with the carcass rubber is not improved. In addition, when the sulfur crosslinkable polymer is 100 parts by weight or more, gas barrier properties are reduced except for butyl rubber, adhesive strength is reduced with butyl rubber, and depending on the polymer to be blended, the adhesion becomes high and the thickness is 600 μm or less. There is a problem that a film cannot be produced.

  In Patent Document 3, a tire is manufactured using a strip of a film laminate in which a thermoplastic resin and a thermoplastic elastomer are blended. By using a laminate, gas barrier properties and adhesiveness can be improved, and bonding between ribbon-like strips is possible. However, with this technique, the gauge at the unvulcanized green cover of the film laminate is constant, and if the gauge is thinned, the tire finish after vulcanization at the buttress portion or the like may be thinned.

JP 2010-13646 A JP 2010-1000067 A International Publication No. 2008-029781

  The present invention provides a pneumatic tire including an inner liner that reduces a decrease in the internal pressure of the tire, reduces crack growth of the inner liner due to repeated bending deformation accompanying tire running, and further reduces rolling resistance. The purpose is to do.

  The present invention is a pneumatic tire provided with an inner liner inside a tire of a carcass ply mounted between a pair of bead portions, wherein the inner liner includes a first layer disposed inside the tire, The second layer is disposed so as to be in contact with the rubber layer of the carcass ply, and the first layer is a thermoplastic elastomer composition mainly composed of a styrene-isobutylene-styrene block copolymer, and the second layer. The layer includes the styrene-isoprene-styrene block copolymer, and further relates to the pneumatic tire which is a thermoplastic elastomer composition containing 10-80% by mass of the styrene-isobutylene-styrene block copolymer of the thermoplastic elastomer component. .

  The thickness of the first layer is preferably 0.05 mm to 0.6 mm, and the thickness of the second layer is preferably 0.01 mm to 0.3 mm. The styrene-isobutylene-styrene block 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.

  Further, 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.

  In the present invention, the inner liner is composed of a first layer mainly composed of SIBS and a second layer made of a styrenic thermoplastic elastomer containing SIS and SIBS. Preferably, the first layer or the second layer has a tackifier. Therefore, vulcanization adhesion between the first layer and the second layer can be improved. As a result, the adhesion between the first layer and the carcass ply is also strengthened, and the occurrence of air-in between the first layer / carcass ply, the first layer / second layer, and the carcass ply / second layer can be prevented. The tire durability performance is improved.

It is a schematic sectional drawing of the right half of the pneumatic tire of this invention. FIGS. 2A and 2B are schematic cross-sectional views showing an arrangement state of the inner liner and the carcass.

<Tire structure>
In the present invention, a pneumatic tire having an inner liner on the inner side of the tire will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of the right half of a pneumatic tire. In the figure, a 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. In addition, a carcass ply 6 provided from one bead portion 4 to the other bead portion, with both ends wound around the bead core 5 and locked, 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.

<Inner liner>
In the present invention, the inner liner is composed of a first layer disposed inside the tire and a second layer disposed so as to contact the rubber layer of the carcass ply. The first layer is a thermoplastic elastomer composition mainly composed of a styrene-isobutylene-styrene block copolymer (hereinafter also referred to as “SIBS”), and the second layer is a styrene-based thermoplastic containing SIS and SIBS. It is an elastomer composition, and the thermoplastic elastomer composition of at least one of the first layer and the second layer contains 0.1 to 100 parts by mass of a tackifier with respect to 100 parts by mass of the thermoplastic elastomer. It is characterized by.

<First layer>
The first layer is made of a thermoplastic elastomer composition mainly composed of a styrene-isobutylene-styrene block copolymer (SIBS). Due to the isobutylene block of SIBS, the polymer film made of SIBS has excellent air permeation resistance. Therefore, when a polymer 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.

  When a pneumatic tire is manufactured by applying a polymer film made of SIBS to the inner liner, air permeation resistance can be secured. Therefore, it is not necessary to use a halogenated rubber having a high specific gravity, which has been used for imparting air permeation resistance, such as a halogenated butyl rubber, and the amount used can be reduced even when used. This can reduce the weight of the tire and improve fuel efficiency.

  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 first layer is broken by pressing pressure during vulcanization of a green tire in which the polymer laminate is applied to the inner liner, and an air leak phenomenon occurs in the obtained tire. 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.

  The first layer is mainly SIBS. That is, 90 mass% or more of SIBS is included in the thermoplastic elastomer component. Here, as the thermoplastic elastomer, a styrene thermoplastic elastomer, a urethane thermoplastic elastomer, or the like can be used.

<Second layer>
The second layer includes a styrene-isoprene-styrene block copolymer (SIS), and further includes a styrene-isobutylene-styrene block copolymer (SIBS) in a thermoplastic elastomer component of 10 to 80% by mass of the thermoplastic elastomer component. It is a composition.

  The second layer may include a styrenic thermoplastic elastomer as another thermoplastic elastomer. Here, the styrene thermoplastic elastomer refers to a copolymer containing a styrene block as a hard segment. For example, styrene-isobutylene block copolymer (hereinafter also referred to as “SIB”), styrene-butadiene-styrene block copolymer (hereinafter also referred to as “SBS”), styrene-ethylene butene-styrene block copolymer. Combined (hereinafter also referred to as “SEBS”), styrene-ethylene / propylene / styrene block copolymer (hereinafter also referred to as “SEPS”), styrene / ethylene / ethylene / propylene / styrene block copolymer (hereinafter referred to as “SEPS”). "SEEPS"), and styrene-butadiene-butylene-styrene block copolymer (hereinafter also referred to as "SBBS").

  The styrenic thermoplastic elastomer may have an epoxy group in its molecular structure. For example, Epofriend A1020 manufactured by Daicel Chemical Industries, Ltd. (weight average molecular weight is 100,000, epoxy equivalent is 500). An epoxy-modified styrene-butadiene-styrene copolymer (epoxidized SBS) can be used.

  The second layer contains styrene-isoprene-styrene copolymer (SIS) as a main component. Since the isoprene block of SIS is a soft segment, a polymer film made of SIS is easily vulcanized and bonded to a 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. The content of the styrene component in the SIS is preferably 10 to 30% by mass from the viewpoints of tackiness, adhesiveness, and rubber elasticity.

In the present invention, the polymerization degree 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 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 block 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.

  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. The polymerization degree of each block in the 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 living polymerization method of a general vinyl compound. For example, methylcyclohexane, n-butyl chloride, and cumyl chloride are added to a stirrer, cooled to -70 ° C, and reacted for 2 hours. Thereafter, a large amount of methanol is added to stop the reaction, and vacuum drying at 60 ° C. can produce SIB.

  The SIB layer used as an additional layer can be formed by a usual method of forming a styrenic thermoplastic elastomer into a film such as extrusion molding or calendering of SIB. The thickness of the second layer is preferably 0.01 mm to 0.3 mm. If 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 may increase and the fuel efficiency performance may deteriorate. The thickness of the second layer is further preferably 0.05 to 0.2 mm.

<SIBS mixture>
In the present invention, the second layer is composed of a mixture of SIS and SIBS. Here, the blending amount of SIBS is adjusted in a range of 10 to 80% by mass, preferably 30 to 70% by mass of the thermoplastic elastomer component. When the SIBS is less than 10% by mass, the adhesion with the first layer is lowered, and when the SIBS exceeds 80% by mass, the adhesion with the carcass ply tends to be lowered.

<Tackifier>
In this invention, 0.1-100 mass parts of tackifiers can be mix | blended with respect to 100 mass of thermoplastic elastomers at least any one of a 1st layer and a 2nd layer. Here, the “tackifier” refers to an additive for enhancing the tackiness of the thermoplastic elastomer composition, and examples thereof include the following tackifiers. The tackifier preferably has a weight average molecular weight Mw of 1 × 10 ² to 1 × 10 ⁶ and a softening point in the range of 50 ° C. to 150 ° C. When the weight average molecular weight is less than 1 × 10 ² , the viscosity is low, and the formability of the sheet is disadvantageous. On the other hand, when the weight average molecular weight exceeds 1 × 10 ⁶ , adhesion to the first layer and the second layer is sufficient. Disappear.

[C9 petroleum resin]
C9 petroleum resin is obtained by thermally decomposing naphtha to obtain useful compounds such as ethylene, propylene, butadiene, etc., but the remaining C5-C9 fraction (mainly C9 fraction) from which they have been removed is in a mixed state. It is an aromatic petroleum resin obtained by polymerization as it is. For example, as trade names, Alcon P70, P90, P100, P125, P140, M90, M100, M115, and M135 (all manufactured by Arakawa Chemical Industries, Ltd., softening point 70 to 145 ° C.), and Imabe S100 and S110 , P100, P125, P140 (all manufactured by Idemitsu Petrochemical Co., Ltd., aromatic copolymer hydrogenated petroleum resin, softening point 100-140 ° C., weight average molecular weight 700-900, bromine number 2.0-6.0 g) / 100 g) and Petcoal XL (manufactured by Tosoh Corporation).

[C5 petroleum resin]
C5 petroleum resin is obtained by thermally decomposing naphtha to obtain useful compounds such as ethylene, propylene and butadiene, but the remaining C4 to C5 fractions (mainly C5 fractions) from which they have been removed are mixed. It is an aliphatic petroleum resin obtained by polymerization as it is. Product names include Highletz G100 (Mitsui Petrochemical Co., Ltd., softening point 100 ° C.), Marcarez T100AS (Maruzen Oil Co., Ltd., softening point 100 ° C.), and Escorez 1102 (Tonex Corp., softening) The point is 110 ° C.).

[Terpene resin]
As product names, YS Resin PX800N, PX1000, PX1150, PX1250, PXN1150N, Clearon P85, P105, P115, P125, P135, P150, M105, M115, K100 (all manufactured by Yashara Chemical Co., Ltd., softening point 75-160 ° C) )

[Aromatic modified terpene resin]
As product names, there are YS resins TO85, TO105, TO115, and TO125 (all manufactured by Yashara Chemical Co., Ltd., softening point: 75 to 165 ° C.).

[Terpene phenol resin]
As product names, Tamanol 803L, 901 (Arakawa Chemical Industries, softening point 120 ° C to 160 ° C), YS Polystar U115, U130, T80, T100, T115, T145, T160 (all manufactured by Yashara Chemical Co., Ltd.) , Softening point 75-165 ° C).

[Coumarone resin]
There is a coumarone resin (manufactured by Kobe Oil Chemical Co., Ltd.) having a softening point of 90 ° C.

[Coumaron Inden Oil]
As a trade name, there is 15E (manufactured by Kobe Oil Chemical Co., Ltd., pour point 15 ° C.).

[Rosin ester]
As product names, Ester gum AAL, A, AAV, 105, AT, H, HP, HD (all manufactured by Arakawa Chemical Industries, softening point 68 ° C. to 110 ° C.), and Harrier Star TF, S, C, There are DS70L, DS90, and DS130 (all manufactured by Harima Kasei Co., Ltd., softening point 68 ° C to 138 ° C).

[Hydrogenated rosin ester]
As trade names, there are Superesters A75, A100, A115, and A125 (all manufactured by Arakawa Chemical Industries, Ltd., softening point 70 ° C to 130 ° C).

[Alkylphenol resin]
As a trade name, there is Tamanoru 510 (manufactured by Arakawa Chemical Industries, Ltd., softening point 75 ° C. to 95 ° C.).

[DCPD]
As a trade name, there is Escoretz 5300 (manufactured by Tonex Co., Ltd., softening point 105 ° C.)

  As for the tackifier, the fully hydrogenated petroleum resin of C9 petroleum resin has good compatibility with SIB, and can improve the adhesion without deteriorating the gas barrier property. It also has the effect of lowering the viscosity and can be advantageously used for film extrusion.

  The tackifier is blended in the range of 0.1 to 100 parts by mass, preferably 1 to 50 parts by mass with respect to 100 parts by mass of the thermoplastic elastomer of the first layer. When the tackifier is less than 0.1 parts by mass, the vulcanization adhesive strength with the second layer is not sufficient, while when it exceeds 100 parts by mass, the tackiness becomes too high, and the workability and productivity are reduced. The gas barrier property is further lowered.

  The second layer is disposed between the first layer inside the tire and the carcass ply, and adhesion between them is required. Then, the said tackifier is mix | blended in 0.1-100 mass parts with respect to 100 mass parts of thermoplastic elastomer of a 2nd layer, Preferably, it is 1-50 mass parts. When the tackifier is less than 0.1 parts by mass, the vulcanization adhesive strength with the first layer is not sufficient. On the other hand, when it exceeds 100 parts by mass, the tackiness becomes too high, and the workability and productivity are reduced. The gas barrier property is further lowered.

<Polymer laminate>
In the present invention, a polymer laminate composed of the first layer and the second layer is used as the inner liner. Here, the first layer and the second layer are thermoplastic elastomer compositions, which are in a softened state in a mold at a vulcanization temperature, for example, 150 ° C. to 180 ° C. The softened state means an intermediate state between solid and liquid with improved molecular mobility. In addition, the thermoplastic elastomer composition is easy to stick and adhere to an adjacent member in a softened state. Therefore, in order to prevent the shape change of the thermoplastic elastomer, the adhesion with the adjacent member, and the fusion, a cooling step is required when manufacturing the tire. In the cooling step, the tire is vulcanized and then rapidly cooled to 50 to 120 ° C. for 10 to 300 seconds to cool the inside of the bladder. As the cooling medium, at least one selected from air, water vapor, water and oil is used. By adopting such a cooling step, it is possible to form a thin inner liner having an inner liner in the range of 0.05 to 0.6 mm.

  Next, the arrangement state with the carcass ply in the vulcanized tire of the inner liner is illustrated in FIG. In FIG. 2A, 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 inner liner of a pneumatic tire, the SIS layer PL2 and the carcass are disposed in the tire vulcanization process when the SIS layer PL2 is disposed facing the carcass ply 61 and facing outward 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.

  In FIG. 2B, the polymer laminate PL is configured by laminating a SIBS layer PL1 as a first layer, an intermediate layer PL3, and a SIS layer PL2 as a second layer in the order described above. When the polymer laminate PL is applied to an inner liner of a pneumatic tire, when the surface of the SIS layer PL2 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 SIS layer The adhesive strength between PL2 and the carcass ply 61 can be increased. Therefore, since the inner liner and the rubber layer of the carcass ply 61 are adhered well, it is possible to have excellent air permeation resistance and durability.

<Pneumatic tire manufacturing method>
A general manufacturing method can be used for the pneumatic tire of the present invention. A strip is manufactured using the polymer laminate PL, and an inner liner is manufactured by the method described above. It can be manufactured by applying the inner liner to the raw tire of the pneumatic tire 1 and vulcanizing it together with other members. When the polymer laminate PL is arranged on the green tire, the SIS layer PL2 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 carcass ply 61. When arranged in this manner, the adhesive strength between the SIS layer PL2 which is the second layer made of the styrene-based thermoplastic elastomer composition and the carcass 6 can be increased in the tire vulcanizing 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.

<Polymer laminate>
The thermoplastic elastomer (SIB, SIBS and SIS) used for the production of the polymer laminate comprising the first layer and the second layer of the present invention was 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. This 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]
“Sibstar SIBSTAR 102 (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.

<Inner liner manufacturing method>
Styrenic thermoplastic elastomers such as 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 prepared 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).

<Manufacture of pneumatic tires>
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, and then pressed at 170 ° C. for 20 minutes in the vulcanization process. Vulcanization was performed. Then, without removing the tire from the vulcanization mold, it was cooled at 100 ° C. for 3 minutes and then removed from the vulcanization mold. Water was used as the cooling medium. By adopting such a cooling process, the inner liner could be manufactured with a thin film of 0.3 mm.

(Note 1) Tackifier A: C9 petroleum resin, Alcon P140 (Arakawa Chemical Industries, softening point 140 ° C., weight average molecular weight Mw: 900).
(Note 2) Tackifier B: terpene resin, YS resin PX1250 (manufactured by Yashara Chemical Co., Ltd., softening point: 125 ° C., weight average molecular weight Mw: 700).
(Note 3) Tackifier C: hydrogenated rosin ester, super ester A125 (Arakawa Chemical Industries, softening point 125 ° C., weight average molecular weight Mw: 700).

<Comparative Examples 1-4, Examples 1-6, Reference Examples 1-10>
Comparative Examples 1 and 2 are examples in which no tackifier is blended in either the first layer or the second layer, Comparative Example 3 is an example in which 0.05 part by weight of tackifier is blended in the second layer, or Comparative Example 4 is an example in which 110 parts by mass of a tackifier is blended in the second layer. Examples 1 and 2 and Reference Examples 1 and 2 are examples in which SIBS is contained in the second layer, and Reference Examples 3 to 8 are examples in which a tackifier is blended in the second layer. Examples 3 to 6 and Reference Examples 9 and 10 are examples in which SIBS and a tackifier are used in combination in the second layer.

  Each of Examples 1 to 6 and Reference Examples 1 to 10 are superior to Comparative Example 1 in vulcanization adhesion, flex crack growth, rolling resistance change rate, and static air reduction rate.

<Comparative Example 5, Comparative Example 6, Examples 7-14, Reference Examples 11-18>
Comparative Example 5 is an example in which 0.05 part by mass of the tackifier is blended in the first layer, and Comparative Example 6 is an example in which 110 parts by mass of the tackifier is blended in the first layer. Reference Examples 11 and 12 are examples in which a tackifier is blended in the first layer, Examples 7 and 8 are examples in which a tackifier is blended in the first layer, and SIBS is blended in the second layer, Reference Examples 13 to 18 is an example in which a tackifier is blended in the first layer and the second layer, and Examples 9 to 14 are examples in which a tackifier is blended in the first layer and a tackifier and SIBS are blended in the second layer. is there.

  In Examples 7 to 14 and Reference Examples 11 to 18, since a predetermined amount of the tackifier was blended in the first layer or the second layer, the vulcanized adhesive force, the flex crack growth property, and the rolling resistance compared to Comparative Examples 5 and 6. Overall rate of change and static air drop are excellent.

<Performance test>
The following performance evaluation was performed on the pneumatic tire manufactured as described above.

<Vulcanization adhesion>
The unvulcanized rubber sheets of the first layer and the carcass ply layer and the first layer and the second layer are laminated and vulcanized at 170 ° C. for 20 minutes to prepare a sample for measuring the vulcanized adhesive force. The peel strength was measured with a tensile tester to obtain a vulcanized adhesive strength. By the following formula, the vulcanization adhesive strength of each formulation was displayed as an index based on Comparative Example 1. In addition, it shows that vulcanization adhesive force is so high that the index | exponent of vulcanization adhesive force is large.

Vulcanization adhesion index = (vulcanization adhesion of each formulation) / (vulcanization adhesion of Comparative Example 1) × 100
<Bending crack growth test>
The durability running test was evaluated based on whether the inner liner was cracked or peeled off. The prototype tire is assembled to a JIS standard rim 15 × 6 JJ, the tire internal pressure is set to 150 KPa, which is lower than usual, the load is 600 kg, the speed is 100 km / h, the traveling distance is 20,000 km, the inside of the tire is observed, cracks, The number of peels was measured. Using Comparative Example 1 as a reference, the crack growth property of each formulation was displayed as an index. A larger index value indicates a smaller flex crack growth.

Flex crack growth index = (number of cracks in Comparative Example 1) / (number of cracks in each formulation) × 100
<Rolling resistance index>
Using a rolling resistance tester manufactured by Kobe Steel Co., Ltd., the prototype tire was assembled to a JIS standard rim 15 × 6JJ, and the temperature was set to room temperature (30 ° C.) under conditions of a load of 3.4 kN, an air pressure of 230 kPa, and a speed of 80 km / h. And rolling resistance was measured. And based on the following formula, the comparative example 1 was made into the reference | standard 100, and the rolling resistance change rate (%) of the Example was displayed by the index | exponent. It shows that rolling resistance is reduced, so that rolling resistance change rate is large.

Rolling resistance index = (Rolling resistance of Comparative Example 1 / Rolling resistance of Example) × 100
<Static air pressure drop rate test>
The prototype tire was assembled in a JIS standard rim 15 × 6 JJ, filled with an initial air pressure of 300 kPa, and allowed to stand at room temperature for 90 days to calculate the rate of decrease in air pressure. The smaller the value, the less the air pressure is reduced.

  The pneumatic tire of the present invention can be applied to passenger car pneumatic tires, truck / bus tires, light truck tires, and heavy vehicle pneumatic 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 inner liner, PL polymer laminated body, PL1 SIBS layer, PL2 SIS layer, PL3 SIB layer.

Claims (4)

A pneumatic tire having an inner liner on the inside of a carcass ply tire mounted between a pair of bead parts,
The inner liner is composed of a first layer disposed inside the tire and a second layer disposed so as to contact the rubber layer of the carcass ply,
The first layer is a thermoplastic elastomer composition mainly composed of a styrene-isobutylene-styrene block copolymer,
The second layer is a thermoplastic elastomer composition comprising a styrene-isoprene-styrene block copolymer and further containing 10-80% by mass of a styrene-isobutylene-styrene block copolymer in a thermoplastic elastomer component. Tires.   The pneumatic tire according to claim 1, wherein the thickness of the first layer is 0.05 mm to 0.6 mm, and the thickness of the second layer is 0.01 mm to 0.3 mm.   The pneumatic tire according to claim 1, wherein the styrene-isobutylene-styrene block 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 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.

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