JP2013060138A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire in which an adhesion property between an inner liner and a tire member adjacent to it is enhanced, air permeation resistance is improved, and rolling resistance is reduced by reducing the weight.SOLUTION: The inner liner 9 of the pneumatic tire 1 includes a polymer laminate body comprising: a first layer having a thermoplastic elastomer composition containing 60-99.9 mass% of a styrene-isobutylene-styrene triblock copolymer in a polymer component, and 0.1-50 pts.mass of lamellar clay minerals with an organic compound intercalated therein to 100 pts.mass of the polymer component; and a second layer of a thermoplastic elastomer composition containing at least either a styrene-isoprene-styrene triblock copolymer or a styrene-isobutylene diblock copolymer. The second layer is arranged in a manner of abutting on a carcass ply 6. In the inner liner 9, a thickness Ge at a shoulder position Pe is larger than a thickness Gc at a crown central position Pc.

Description

  The present invention relates to a pneumatic tire provided with an inner liner composed of a plurality of layers of a thermoplastic elastomer composition on the inner surface of the tire.

  The inner liner of a pneumatic tire is disposed inside the tire and has a function of reducing air leakage from the inside of the pneumatic tire to the outside and maintaining the tire internal pressure constant. As a material having such a function, a rubber composition having low gas permeability such as butyl rubber is used. On the other hand, in order to reduce the weight of the tire, a film made of a material containing a thermoplastic resin may be used instead of the butyl rubber composition.

  Generally, the inner liner is subjected to a large shear strain in the vicinity of the shoulder portion when the tire is used. Therefore, 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.

  Conventionally, there has been a problem of reducing fuel consumption in a pneumatic tire, and for this purpose, a method of reducing rolling resistance by reducing the weight of the tire has been adopted. Therefore, a technique using a thermoplastic elastomer for the inner liner has also been proposed. However, if the thickness is made thinner than the inner liner of butyl rubber, it is difficult to achieve both air permeation resistance and weight reduction. Further, the strength of the inner liner is reduced by reducing the thickness, and there is a problem that the inner liner is broken or deformed by the heat and pressure of the bladder during the vulcanization process.

  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, so that air pressure retention is improved. . However, the adhesive layer for overlapping the inner liner layer comes into contact with the bladder in a heated state in the vulcanization process, and there is a problem of sticking 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 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.

  In Patent Document 3, the low temperature durability is improved by designing the thickness of the shoulder portion to be larger than the thickness of the tire crown portion. However, increasing the thickness dimension increases the weight, which is not preferable from the viewpoint of low fuel consumption and manufacturing cost.

JP-A-9-19987 Japanese Patent No. 2999188 JP 2005-343379 A

  The present invention, in a pneumatic tire having an inner liner, maintains a thin layer of the inner liner to improve adhesion of adjacent tire members, and also improves air permeation resistance, tensile properties at high temperatures and bending fatigue properties. And it aims at providing the pneumatic tire which reduced rolling resistance by weight reduction of a tire further.

  The present invention is a pneumatic tire provided with an inner liner on the inside of a carcass ply tire mounted between a pair of bead portions, wherein the inner liner is a polymer of a styrene-isobutylene-styrene triblock copolymer. It comprises a thermoplastic elastomer composition containing 60% by mass to 99.9% by mass in the component and 0.1 to 50 parts by mass of a layered clay mineral obtained by intercalating an organic compound with respect to 100 parts by mass of the polymer component. A polymer laminate comprising a first layer and a second layer of a thermoplastic elastomer composition comprising at least one of a styrene-isoprene-styrene triblock copolymer and a styrene-isobutylene diblock copolymer, The second layer is disposed in contact with the carcass ply, and the inner liner is Than the thickness Gc at down center position Pc is a pneumatic tire, wherein the thickness Ge shoulder position Pe is thick.

  In another embodiment of the present invention, in the tire meridional section, the normal line L is drawn in the tire inner diameter direction from the ground contact end Te of the tread portion with respect to the boundary line between the carcass ply and the inner liner, and the intersection with the boundary line is defined as a shoulder. The position Pe is defined as an intersection of the boundary line between the carcass ply and the inner liner and the tire center line CL as a crown center position Pc, and a distance along the contour line of the inner liner from the shoulder position Pe to the crown center position Pc. When the shoulder distance Wc is set, the thick portion of the inner liner is formed in a region having a width of at least 10% of the shoulder distance Wc from the shoulder position Pe to the crown center position Pc side. Tire.

  The thick portion of the inner liner is preferably formed in a region having a width of at least 50% or less of the shoulder width Wc from the shoulder position Pe to the crown center position Pc.

  When the distance along the contour of the inner liner from the shoulder position Pe of the inner liner to the tire maximum width position Ps is a side distance Ws, the thick part of the inner liner is It is preferable that a region having a width of at least 20% of the side distance Ws is formed on the maximum width position Ps side.

  Furthermore, the thick part of the inner liner is preferably formed in a region having a width of 100% or less of the maximum width distance Ws on the side of the maximum width position Ps from the shoulder position Pe.

  In the pneumatic tire of the present invention, it is preferable that the inner liner has a thickness Ge at a shoulder position Pe of 160% to 300% with respect to a thickness Gc at a crown center position Pc.

  In the present invention, the styrene-isobutylene-styrene triblock copolymer used for the inner liner 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 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 molecular chain of the styrene-isobutylene diblock copolymer is preferably linear, the styrene component content is 10 to 35% by mass, and the weight average molecular weight is 40,000 to 120,000.

  The tire of the present invention uses a thermoplastic elastomer composition containing a layered clay mineral intercalated with an organic compound as an inner liner, and the inner liner has a thickness ranging from the tire maximum width position to the crown center position in the tire cross section. By adjusting to a specific range, the overall thickness of the inner liner is reduced to reduce the rolling resistance by reducing the weight, while maintaining the air permeation resistance by forming a thick part at the tire shoulder. It is possible to improve the bending fatigue.

It is a schematic sectional drawing of the right half of the pneumatic tire of this invention. It is an expansion schematic sectional drawing of the tread part of FIG.

  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 at least two polymer laminates. The first layer is made of styrene-isobutylene-styrene triblock copolymer (SIBS). The second layer includes at least one of styrene-isoprene-styrene triblock copolymer (SIS) and styrene-isobutylene diblock copolymer (SIB). The second layer is disposed in contact with the rubber layer of the carcass ply, and the inner liner is formed such that the thickness Ge at the shoulder position Pe is thicker than the thickness Gc at the crown central position Pc.

  An embodiment of a pneumatic tire according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of the right half of the pneumatic tire, and FIG. 2 is an enlarged schematic cross-sectional view of the tread portion thereof. 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. 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 generally intersects at least 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. Note that a topping rubber layer can be provided on the outer sides of both ends 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 specification, the position, distance and width related to the inner liner 9 are defined as follows.

<Shoulder position Pe>
In the tire meridian cross section, a normal line L is drawn from the contact end Te of the tread portion in the tire inner diameter direction with respect to the boundary line between the carcass ply 6 and the inner liner 9, and an intersection point with the boundary line is defined as a shoulder position Pe. Here, the ground contact edge Te of the tread portion is defined as an intersection point obtained by extending the outer contour line of the tread portion and the outer contour line of the shoulder portion.

<Crown center position Pc>
The intersection of the boundary line between the carcass ply and the inner liner and the tire center line CL is defined as a crown center position Pc.

<Maximum width position Ps>
The maximum width position Ps is the intersection of the line parallel to the tire rotation axis and the boundary line of the carcass ply 6 and the inner liner 9 passing through the maximum width position Le of the outer contour line when the tire is filled with the specified internal pressure and the standard rim is mounted. And

<Shoulder distance Wc>
A distance along the contour line of the inner liner 9 from the shoulder position Pe to the crown center position Pc is defined as a shoulder distance Wc.

<Side distance Ws>
A distance along the contour line of the inner liner 9 from the shoulder position Pe to the tire maximum width position Ps is defined as a side distance Ws.

<Inner liner thickness>
The thickness of the crown center position Pc of the inner liner 9 is Gc, the thickness at the shoulder position Pe is Ge, and the thickness at the maximum width position Ps is Gs.

  The thick part of the inner liner 9 is preferably formed in a region having a width of at least 10% of the shoulder distance Wc from the shoulder position Pe to the crown center position Pc. On the other hand, the thick portion is preferably formed in a region having a width of 100% or less of the shoulder distance Wc. Further, the thick part is more preferably in the range of 10% to 50% of the shoulder distance Wc.

  The thick part of the inner liner 9 has a width of at least 20% of the side distance Ws on the side of the maximum width position Ps from the shoulder position Pe, and is formed in a region having a width of 100% or less. Is preferred. By setting the thick portion within the range of 20% to 100% of the side distance Ws from the shoulder position Pe, it is possible to suppress the deformation of the shoulder portion that is severely bent and deformed during tire running, and to effectively reduce the stress in this region. Can be achieved. Furthermore, the thick part is more preferably in the range of 20% to 80% of the side distance Ws from the shoulder position Pe.

  In the present invention, the inner liner has a thickness of the thick portion, that is, a thickness Ge of the shoulder position Pe is 160% to 300% with respect to the thickness Gc at the crown center position Pc, and the thickness of the maximum width position Ps. The thickness Ge of the shoulder position Pe is preferably 110% to 350% with respect to the thickness Gs. When the thickness Ge of the shoulder position Pe is less than 160%, the bending deformation and shear deformation of the shoulder portion are not sufficiently suppressed, and when it exceeds 300%, the effect of reducing the weight of the inner liner cannot be sufficiently expected. The thickness Ge of the shoulder position Pe is more preferably 200% to 300% with respect to the thickness Gc at the crown center position Pc.

  The thick portion preferably has a structure in which the thickness is gradually reduced from the shoulder position Pe in the crown central position Pc direction and the maximum width position Ps direction. By forming the thick part of the inner liner as described above, even when bending deformation and shear deformation accompanying repeated deformation in this region occur during tire running, the stress can be relieved. Generation of cracks can be prevented.

  The average thickness of the region excluding the thick portion of the first layer is 0.05 to 1.0 mm, preferably 0.1 to 0.7 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, when the thickness of the first layer exceeds 1.0 mm, the tire weight increases and the fuel efficiency performance decreases.

  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.

  In the present invention, the thick portion formed in the shoulder portion is adjusted such that the thickness of at least one of the first layer and the second layer of the inner liner is increased in the shoulder portion. A thick part can also be formed by laminating layers.

<Polymer laminate>
The polymer laminate used for the inner liner of the present invention includes a first layer having a thickness of 0.05 mm to 1.0 mm containing a styrene-isobutylene-styrene triblock copolymer (hereinafter also referred to as “SIBS”), A second layer containing at least one of a styrene-isoprene-styrene triblock copolymer (SIS) and a styrene-isobutylene diblock copolymer (SIB), and the thickness of the second layer is 0.01 mm to 0.3 mm.

<First layer>
The first layer is a thermoplastic elastomer composition containing, as a polymer component, a styrene-isobutylene-styrene triblock copolymer in an amount of 60 mass% to 99.9 mass% in the polymer component. On the other hand, it contains 0.1 to 50 parts by mass of a layered clay mineral intercalated with an organic compound.

  In the present invention, the first layer includes 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 inner liner, a pneumatic tire having excellent air permeation resistance can be obtained. Furthermore, since the molecular structure other than aromatic is completely saturated, SIBS has excellent durability with suppressed deterioration hardening.

  The molecular weight of SIBS is preferably 50,000 to 400,000 in terms of weight average molecular weight by GPC measurement from the viewpoint of fluidity, molding process, rubber elasticity and the like. If the weight average molecular weight is less than 50,000, the tensile strength and tensile elongation may be reduced, and if it exceeds 400,000, the extrusion processability may be deteriorated. From the viewpoint of improving air permeation resistance and bending fatigue resistance, SIBS has a styrene component content of 10 to 30% by mass, preferably 14 to 23% by mass.

  In the SIBS, the degree of polymerization of each block in the copolymer is preferably about 10,000 to 150,000 for isobutylene and about 5,000 to 30,000 for styrene.

  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.

  As a polymer component contained in the first layer, a styrene-based thermoplastic elastomer, a urethane-based thermoplastic elastomer, a rubber component, and a thermoplastic resin can be included, and these components are 0.01% by mass to 60% by mass in the polymer component. Range.

<Organized layered clay mineral>
In the present invention, the first layer has a layered clay mineral intercalated with an organic compound (hereinafter also referred to as “organized layered clay mineral”) in an amount of 0.1 to 50 parts by mass with respect to 100 parts by mass of the polymer component. Some are mixed. In the organically treated layered clay mineral, the organic compound intercalates between the layers of the layered clay mineral, so that the layers are expanded and the dispersibility to the polymer is improved.

  The layered clay mineral is a kind of layered silicate mineral, and its crystal structure is composed of three layers of silicate tetrahedral layer-alumina octahedral layer-silicate tetrahedral layer, and the unit layer is about 10 mm (1 nm) wide It has a very thin plate shape of 0.1 to 1 μm.

  A typical example of the layered clay mineral is montmorillonite. Montmorillonite becomes deficient in positive charge when a part of Al as the central atom of the alumina octahedron layer in the crystal structure is replaced with Mg, and each crystal layer itself is negatively charged. , K +, Ca 2+, Mg 2+, and the like are sandwiched between them to neutralize the lack of electric charge and become stable. Therefore, montmorillonite exists in a state in which a number of crystal layers are overlapped.

  When water contacts the surface of the montmorillonite plate crystal layer, water molecules hydrate to the exchangeable cations between the layers, and the layers expand. Further, by intercalating an organic compound between layers using the cation exchange property of montmorillonite, the layers are expanded and the dispersibility in organic solvents and polymers is improved.

  Examples of layered clay minerals include montmorillonite (especially sodium montmorillonite, magnesium montmorillonite and calcium montmorillonite), bentonite, kaolinite, nonlite, beidellite, vorconskite, hectorite, saponite, sauconite, sobokite, stevensite, subfolder Mite minerals such as phyllosilicates such as smite, vermiculite and other smectite clays, illite and illite / smectite mixtures (lectretite, talosobite, ladykite and mixtures of the above clay compounds with illite) or attapulgite and sepiolite hydrotals Site-based layered compounds are exemplified. Of these, smectite clay is preferable, and montmorillonite clay is particularly preferable. Bentonite containing a smectite clay mineral may be used. These layered clay minerals are generally obtained by collecting natural minerals and performing a predetermined refining operation. These synthetic clays can be used interchangeably.

  Examples of the organic compound used as the intercalant include an organic compound having a polar group that is easily ionized in the molecule. An organic compound having a polar group causes a strong interaction with the surface of a layer covered with negative ions such as oxygen ions of smectite clay minerals, and enters (intercalates) the layered clay mineral. It is thought to expand and expand.

  As the organic compound, those having an alkyl group having 6 or more carbon atoms and having a polar group ionizing at the terminal are preferable. Examples thereof include those having a hydroxyl group or a carboxyl group, aldehydes, amines, amides, or quaternary ammonium salts.

  Examples of the organic compound having a hydroxyl group include aliphatic alcohols such as octyl alcohol and nonyl alcohol, alcohols such as aromatic alcohol substituted with an alkyl group, and phenols.

  Examples of organic compounds having a carboxyl group include linear aliphatics such as stearic acid, palmitic acid, and lauric acid, linear alkenoic acids such as oleic acid, dienoic acids such as linoleelaidic acid, and polyunsaturated acids such as trienoic acid. Examples include aliphatic acids.

Examples of aldehydes include hexyl aldehyde.
As amines or amides, polar organic compounds having one or more amines or amides, such as alkylamines, aminocycloalkanes and aminocycloalkane substituents, cycloaliphatic diamines, aliphatic amines, alkylaromatic amines, alkyldiaryls Examples include amines, aliphatic amides, etc., including primary, secondary, and / or tertiary amines or amides. Of these, alkylamines, aliphatic amines, alkylaromatic amines, and alkyldiarylamines are preferable. The above organic compounds can be used alone or in combination of two or more.

  Preferred amines include 1-hexylamine, 1-heptylamine, 1-octylamine, 1-nomylamine, 1-dodecylamine, 1-hexadecylamine, 1-octadecylamine, primary amines such as oleylamine, di-n Secondary amines such as dodecylamine, di-n-hexadecylamine, di-n-octadecylamine, dimethyl-n-octylamine, dimethyl-n-decylamine, dimethyl-n-tetradecylamine, dimethyl-n-hexa Tertiary amines such as decylamine, dimethyl-n-octadecylamine, dimethyloleylamine, di-n-decylmethylamine dicocoalkylmethylamine, tri-n-octylamine, tri-n-decylamine, tri-n-hexadecyl Aliphatic amines such as amines can be mentioned.

  Preferable amides include hexylamide, heptylamide, octylamide, nonylamide, lauramide, myristamide, palmitamide, steramide, palmamid, oleamide, linoleamide and the like.

  Moreover, what has a nitrile group or a lactam group, a pyridine, ester, surfactant, ethers etc. can also be used as an organic compound which has a polar group.

  Examples of the quaternary ammonium salt include dimethyl distearyl ammonium salt, trimethyl stearyl ammonium salt, dimethyl dioctadecyl ammonium, dimethyl benzyl octadecyl ammonium, and trimethyl octadecyl ammonium.

  As a method for intercalating an organic compound into the layered clay mineral, a known method can be employed. For example, in order to bring a montmorillonite clay mineral into contact with an organic compound, the layered clay mineral is preliminarily mixed with about 20 times the mass of water, and then the organic compound and the montmorillonite clay mineral are brought into contact with each other. There is a way to obtain clay minerals. The cation exchange amount of the organic compound in the organically treated layered clay mineral is preferably 50 to 200 meg / 100 g.

  The compounding amount of the organically treated layered clay mineral is 0.1 to 50 parts by mass, more preferably 0.5 to 30 parts by mass with respect to 100 parts by mass of the polymer component. When the blending amount of the organically treated layered clay mineral is less than 0.1 parts by mass, the air permeability resistance and the tensile property at high temperature of the first layer are deteriorated. Moreover, when the compounding amount of the organically treated layered clay mineral exceeds 50 parts by mass, the hardness of the first layer becomes too large, and the bending fatigue property is lowered.

<Second layer>
In the present invention, the second layer has at least one of an SIS layer containing a styrene-isoprene-styrene triblock copolymer (SIS) and an SIB layer containing a styrene-isobutylene diblock copolymer (SIB). .

  Since the isoprene block of the styrene-isoprene-styrene triblock copolymer (SIS) is a soft segment, the polymer film made of SIS is easy to vulcanize and adhere to the rubber component, improving the adhesion to the rubber layer of the carcass ply. A pneumatic tire excellent in durability can be obtained.

  From the viewpoint of rubber elasticity and moldability, the molecular weight of the SIS is preferably 100,000 to 290,000 in terms of weight average molecular weight as measured by GPC. 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 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.

  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, for example, adhesion to adjacent rubber forming carcass and insulation. And a pneumatic tire excellent in bending fatigue can be obtained.

  SIB preferably has a linear molecular chain from the viewpoint of rubber elasticity and adhesiveness. The molecular weight of SIB is preferably 40,000 to 120,000 in terms of weight average molecular weight by GPC measurement from the viewpoint of rubber elasticity and moldability. 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 SIS layer and the SIB layer can be obtained by forming a SIB into a film by an ordinary method of forming a thermoplastic resin or a thermoplastic elastomer into a film such as extrusion molding or calendar molding.

  The average thickness excluding the thick portion of the second layer is preferably 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 may be broken by the press pressure during vulcanization of the green 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 further preferably 0.05 to 0.2 mm.

<Method for producing polymer laminate>
The polymer laminate can be obtained by subjecting SIBS and / or at least one of SIS and SIB to laminate extrusion such as laminate extrusion or coextrusion, and the obtained polymer laminate can be used as an inner liner.

<Pneumatic tire manufacturing method>
A conventional manufacturing method can be adopted for the pneumatic tire of the present invention. The polymer laminate is applied to the inner liner of the green tire 1 and molded together with other members. This can be produced by putting a raw tire into a mold and vulcanizing it by a conventional method. When the polymer laminate is disposed on the green tire, the SIS layer or SIB layer, which is the second layer of the polymer laminate, is disposed outward in the tire radial direction so as to be in contact with the carcass ply 6. When arranged in this manner, the adhesion strength between the SIS layer or SIB layer and the carcass can be increased in the tire vulcanization step. In the obtained pneumatic tire, since the inner liner and the rubber layer of the carcass ply are well bonded, excellent air permeation resistance and bending fatigue resistance can be improved.

  In order to adjust the thickness of the inner liner by the thickness Ge of the shoulder position Pe, the thickness Gc of the crown center position Pc, and the thickness Gs of the maximum width position Ps, for example, a profile is attached to the extrusion port of the polymer sheet. Then, an integrated sheet having a predetermined thickness Ge in the vicinity of the shoulder position is prepared, and this is disposed 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.

  With the specifications shown in Table 1, pneumatic tires of Examples and Comparative Examples were manufactured, and tire performance was evaluated. Here, 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>
“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.

<Organized layered clay mineral>
“BENTONE 34” manufactured by Rheox was used. Here, the layered clay mineral is a hectorite clay mineral, the organic compound is dimethyl distearyl ammonium salt, and the cation exchange amount of the organic compound is 100 meg / 100 g.

<Manufacture of pneumatic tires>
The composition containing SIBS, SIS and SIB was 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).

  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. Molded and manufactured.

  Here, in order to adjust the thickness of the shoulder part of the inner liner, a profile is attached to the extrusion port of the polymer sheet, and an integrated sheet with a thick shoulder part Ge is created, and this is used as the inner liner. Arranged on the inner surface of the tire.

(Note 1) In Table 1, “Uneven thickness range (wc / ws) (%)” means the ratio wc (%) of the distance extending in the crown center position Pc direction around the shoulder position Pe to the shoulder position Pe and the shoulder position Pe. A ratio ws (%) of the distance extending in the direction of the maximum width position Ps with respect to Ws.
(Note 2) In Table 1, the value of the thickness ratio (Ge / Gs) of the thick part is the same as the value of (Ge / Gc).

<Performance test>
The performance test was carried out by the following method. Regarding the performance of pneumatic tires, the following performance evaluation was performed using tires having a tire size of 195 / 65R15.

(A) High temperature tensile test According to JIS-K-6251 “Vulcanized rubber and thermoplastic rubber-Determination of tensile properties”
Using a No. 3 dumbbell-shaped test piece consisting of a thermoplastic sheet and a vulcanized rubber sheet, the specimen was left for 2 minutes in a temperature atmosphere at 100 ° C., and then a tensile test was carried out. Was measured.

(B) Bending fatigue test A predetermined test piece having a groove in the center was prepared in accordance with JIS-K-6260 "Demach bending cracking test method for vulcanized rubber and thermoplastic rubber". The inner liner made of a thermoplastic resin was prepared by attaching a sheet having a thickness of 0.3 mm to rubber and vulcanizing it to prepare a predetermined test piece. A cut was made in advance in the center of the groove of the test piece, bending deformation was repeatedly applied, and crack growth was measured.

The crack length was measured at an atmospheric temperature of 30 ° C., a strain of 30%, and a period of 5 Hz, and the number of repetitions required for a crack to grow by 1 mm was calculated at 700,000, 1.4 million, and 2.1 million times. The unit is the number of times × 10 ⁴ / mm, and the larger the numerical value, the better the cracks are less likely to grow.

(C) Air permeability test The air permeability of the thermoplastic resin sheet and the vulcanized rubber sheet was measured according to the ASTM-D-1434-75M method. A numerical value of 10 or less, particularly 5 or less, indicates that the air permeation is the smallest and the air barrier property is good.

(D) Rolling resistance Using a rolling resistance tester manufactured by Kobe Steel Co., Ltd., a steel radial tire having a tire size of 195 / 65R15 is assembled to 6JJ applied to JIS machine Acrim 15, load 3.4 kN, air pressure 230 kPa, speed 80 km. The rolling resistance was measured by running at room temperature (38 ° C.) under the conditions of / hour. Then, the rolling resistance change rate (%) of each example and comparative example was displayed as an index according to the following calculation formula on the basis of comparative example 1. In addition, it shows that rolling resistance is reduced, so that rolling resistance change rate is small. That is, it is preferable that the value is large as a negative value.

(Rolling resistance change rate) = (Rolling resistance of each Example−Rolling resistance of Comparative Example 1) ÷ (Rolling resistance of Comparative Example 1) × 100
(E) Static air drop rate A pneumatic tire with a size of 195 / 65R15 is assembled into a JIS standard rim 15 x 6 JJ, sealed with an initial air pressure of 300 KPa, and left at room temperature for 90 days to calculate the air pressure drop rate. It was set as the value of the dynamic air drop rate.

<Comprehensive evaluation>
Comprehensive evaluation was performed according to the following method.

Each of the above performance evaluations (c) to (e) was superior to Comparative Example 1, and the value of (b) exceeding 5000 times × 10 ⁴ / mm was designated as “A” evaluation.

Each of the performance evaluations of the above (c) to (e) was superior to that of Comparative Example 1, and the value of (b) exceeding 4000 to 5000 times × 10 ⁴ / mm was designated as “B” evaluation.

<Comparative Examples 1-4, Examples 1-9>
Comparative Example 1 uses a composition in which 80 parts by mass of SIBS and 20 parts by mass of NR (in Table 1, the mixing amount is described in parentheses) are mixed in the first layer. Comparative Examples 1 to 3 are examples in which no organically treated layered clay mineral is blended, and Comparative Example 4 is an example in which 80 parts by mass of the organically treated layered clay mineral is blended.

  In Comparative Examples 1 to 4, although the inner liner is thick, the air permeation amount is large and the static air reduction rate is low. The rolling resistance change rate is also a low value.

  Examples 1-9 are excellent in the bending fatigue resistance compared with the comparative examples 2-4 which have a thick part, there are few air permeation | transmission amounts, and they are excellent in the performance of rolling resistance change rate and static air fall rate. Although the comparative example 1 is excellent in bending fatigue property, the air permeation amount is increased.

  The pneumatic tire provided with the inner liner of the present invention can be widely used not only for pneumatic tires for passenger cars but also for pneumatic tires provided with inner liners for trucks, buses, heavy machinery and the like.

  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, Pe shoulder position, Pc crown center position, Ps tire maximum width Position, Te tread edge.

Claims (9)

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 contains a styrene-isobutylene-styrene triblock copolymer in a polymer component in an amount of 60% by mass to 99.9% by mass, and an organic compound is intercalated with respect to 100 parts by mass of the polymer component. A thermoplastic elastomer composition containing 0.1 to 50 parts by mass of a thermoplastic elastomer composition and at least one of a styrene-isoprene-styrene triblock copolymer and a styrene-isobutylene diblock copolymer A polymer laminate composed of a second layer of the composition;
The second layer is disposed in contact with the carcass ply;
The pneumatic tire is characterized in that the inner liner has a thickness Ge at the shoulder position Pe larger than a thickness Gc at the crown central position Pc.   In the tire meridional section, a normal line L is drawn in the tire inner diameter direction from the ground contact end Te of the tread portion with respect to the boundary line between the carcass ply and the inner liner, and an intersection with the boundary line is defined as a shoulder position Pe. When the intersection between the liner boundary line and the tire center line CL is the crown center position Pc, and the distance along the contour of the inner liner from the shoulder position Pe to the crown center position Pc is the shoulder distance Wc, The pneumatic tire according to claim 1, wherein the thick part of the liner is formed in a region having a width of at least 10% of the shoulder distance Wc from the shoulder position Pe to the crown center position Pc side.   The pneumatic part according to claim 1 or 2, wherein the thick portion of the inner liner is formed in a region having a width of at least 50% or less of the shoulder width Wc from the shoulder position Pe to the crown center position Pc side. tire.   When the distance along the contour of the inner liner from the shoulder position Pe of the inner liner to the tire maximum width position Ps is defined as a side distance Ws, the thick portion of the inner liner has the maximum width from the shoulder position Pe. The pneumatic tire according to any one of claims 1 to 3, wherein the pneumatic tire is formed in a region having a width of at least 20% of the side distance Ws on the position Ps side.   The thick part of the inner liner is formed in a region having a width of 100% or less of the maximum width distance Ws from the shoulder position Pe to the maximum width position Ps side. The described pneumatic tire.   The pneumatic tire according to any one of claims 1 to 5, wherein the inner liner has a thickness Ge at a shoulder position Pe of 160% to 300% with respect to a thickness Gc at a crown central position Pc.   The air according to any one of claims 1 to 6, 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. Enter tire.   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. Pneumatic tire.   The molecular chain of 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. The pneumatic tire according to any one of the above.

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