JP2012214167A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire having an inner liner for reducing rolling resistance, and improving low-temperature durability.SOLUTION: This pneumatic titre 1 includes an inner liner 9 inside a carcass ply 6. The inner liner 9 is formed of a laminate including an inside first layer and a second layer adjacent to the carcass ply 6. The first layer is constituted of an elastomer composition including 99.5-60 mass% of a styrene-isobutylene-styrenetriblock copolymer and 0.5-40 mass% of a styrene-maleic anhydride copolymer, and is 0.05-0.6 mm in thickness. The second layer is constituted of an elastomer composition including any of a styrene-isoprene-styrenetriblock copolymer and a styrene-isobutylenediblock copolymer, and is 0.01-0.3 mm in thickness. In the inner liner 9, thickness Ge in a shoulder position Pe is larger than a thickness Gc in a crown central position Pc.

Description

  The present invention relates to a pneumatic tire provided with an inner liner having different thicknesses on the tire inner surface.

  The inner liner is disposed inside the tire and has a function of reducing the 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 air permeability such as a butyl rubber has been conventionally 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 rubber composition.

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

  On the other hand, pneumatic tires are required to reduce fuel consumption, and attempts have been made to reduce rolling resistance by reducing the weight of the tire. 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, thereby improving air pressure retention. . However, the adhesive layer for overlaying 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, an inner liner layer having a thickness of 100 μm is made of a mixture of nylon resin having good air permeation resistance and butyl rubber by dynamic crosslinking. 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, a flexible gas barrier layer is prepared by dispersing maleic anhydride-modified hydrogenated styrene-ethylene-butadiene-styrene block copolymer in an ethylene-vinyl alcohol copolymer having good air barrier properties. . 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. The soft resin-dispersed modified ethylene-vinyl alcohol copolymer has a soft resin dispersed therein, but the matrix-modified ethylene-vinyl alcohol copolymer has poor flex 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.

  Patent Document 4 achieves an improvement in low-temperature durability by designing the thickness at the shoulder portion to be larger than the thickness at the tire crown portion. However, increasing the thickness dimension increases the weight, which is not preferable from the viewpoints of low fuel consumption and manufacturing cost.

JP-A-9-19987 Patent No. 2999188 JP 2008-24219 A JP 2005-343379 A

  An object of the present invention is to reduce rolling resistance and improve low-temperature durability in a pneumatic tire provided with an inner liner by reducing the weight of the tire.

  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 on the tire inner side and the carcass. Formed of a multi-layer laminate including a second layer disposed adjacent to the ply, wherein the first layer is 99.5 to 60% by mass of a styrene-isobutylene-styrene triblock copolymer as a polymer component; The styrene-isoprene-styrene is composed of an elastomer composition containing 0.5 to 40% by mass of a styrene-maleic anhydride copolymer, and has a thickness of 0.05 mm to 0.6 mm. It is composed of an elastomer composition containing at least one of a triblock copolymer and a styrene-isobutylene diblock copolymer, and has a thickness of 0.01 mm It is 0.3 mm, the inner liner is a pneumatic tire, wherein the thickness Ge shoulder position Pe is greater than the thickness Gc at the crown center position Pc.

  In the pneumatic tire 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 an intersection with the boundary line is formed. The shoulder position Pe, the intersection between the boundary line of the carcass ply and the inner liner 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 thick part of the inner liner 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 side. .

  In the present invention, the thick part of the inner liner is preferably formed in a region having a width of 50% or less of the shoulder width Wc from the shoulder position Pe to the crown center position Pc side.

  Furthermore, 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 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. In the present invention, the thick portion 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. The inner liner preferably has a thickness Ge at the shoulder position Pe of 160% to 520% with respect to the thickness Gc at the crown center position Pc.

  In the pneumatic tire of the present invention, the styrene / maleic anhydride copolymer composition ratio is in the range of 50/50 to 90/10 in terms of molar ratio, and the weight average molecular weight is in the range of 4,000 to 20,000. It is preferable that the acid value of maleic anhydride is 50-600.

  Furthermore, in the pneumatic tire of the present invention, 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 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, it is preferable that the styrene-isobutylene diblock copolymer is 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 specific thermoplastic elastomer composition for the inner liner, and the thickness of the inner liner in the tire shoulder portion is thicker than other portions, so that the air permeability is maintained and the adjacent carcass ply Can improve the adhesion. Furthermore, it is excellent in low temperature durability and can reduce rolling resistance accompanying weight reduction.

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. It is a schematic sectional drawing of the inner liner of the pneumatic tire of this invention. It is a schematic sectional drawing of the inner liner of the pneumatic tire of this invention. It is a schematic sectional drawing of the inner liner of the pneumatic tire of this invention. It is a schematic sectional drawing of the inner liner of the pneumatic tire of this invention.

  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 is usually formed between two plies made of cords such as steel cords or aramid fibers with respect to the tire circumferential direction so that the cords are usually at an angle of 5 to 30 ° in the tire circumferential direction. They are arranged to cross each other. 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 or metal cords such as steel are arranged at approximately 90 ° in the tire circumferential direction. A bead apex 8 extending from the upper end in the sidewall direction is disposed. 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.

  Here, in the present invention, the position, distance and width relating to the inner liner 9 are defined as follows.

<Shoulder position Pe>
In the tire meridian cross 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. 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 and the inner liner 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. .

<Shoulder distance Wc>
A distance along the contour line of the inner liner 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 of the inner liner 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 is Gc, the thickness at the shoulder position Pe is Ge, and the thickness at the maximum width position Ps is Gs.

  The thick portion of the inner liner 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 formed in a region having a width of 100% or less of the shoulder distance Wc. In particular, the thickness portion is more preferably in the range of 10% to 50% of the shoulder distance Wc.

The thick portion of the inner liner 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. preferable. 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 thickness Ge of the shoulder position Pe is preferably 160% to 520% with respect to the thickness Gc at the crown central position Pc in the present invention, and the shoulder position Pe with respect to the thickness Gs of the maximum width position Ps. The thickness Ge is desirably 160% to 520%. When the thickness Ge of the shoulder position Pe is less than 160%, the effect of suppressing bending deformation and shear deformation of the shoulder portion is small, and when it exceeds 520%, the effect of reducing the weight of the inner liner is small. The thickness Ge of the shoulder position Pe is more preferably 200% to 520% 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.

<Inner liner>
The pneumatic tire according to the present invention includes an inner liner on a tire inner side of a carcass ply mounted between a pair of bead portions, and the inner liner is provided on a first layer disposed on the inner side of the tire and the carcass ply. It is formed of a multi-layer polymer laminate including a second layer disposed adjacently.

  Here, the first layer includes a styrene-isobutylene-styrene triblock copolymer (SIBS) and a styrene-maleic anhydride copolymer, 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 in the range of 0.01 mm to 0.3 mm. It is.

<First layer>
The first layer of the inner liner of the present invention is composed of 99.5 to 60% by mass of a styrene-isobutylene-styrene triblock copolymer as a polymer component and 0.5 to 40% by mass of a styrene-maleic anhydride copolymer. %, And the thickness is 0.05 mm to 0.6 mm. Hereinafter, the first layer is also referred to as “SIBS layer”.

  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.

  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 such as a halogenated butyl rubber which has been used for imparting conventional air permeation resistance, and the amount used can be reduced even when used. As a result, the weight of the tire can be reduced, and the effect of improving fuel consumption can be obtained.

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

The SIBS is a copolymer in which the degree of polymerization of each block is 10,000 to 1 for isobutylene from the viewpoint of rubber elasticity and handling (becomes liquid when the degree of polymerization is less than 10,000).
About 50,000, and preferably 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.

  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 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.

<Mixing with SMA>
The styrene-maleic anhydride copolymer used in the first layer is a styrene-maleic anhydride copolymer base resin (hereinafter also referred to as SMA base resin), or a styrene-maleic anhydride copolymer base resin. The ester resin of a styrene-maleic anhydride copolymer having a monoester group and a monocarboxylic acid group (hereinafter also referred to as SMA ester resin) and a styrene-maleic anhydride copolymer base resin, which are obtained by conversion into ammonium, are ammonium. It describes as a concept containing the aqueous solution of ammonium salt of styrene-maleic anhydride copolymer (hereinafter also referred to as SMA resin ammonium salt aqueous solution) dissolved in a salt.

  The styrene-maleic anhydride copolymer is used as a polymer surfactant and a highly functional cross-linking agent in dispersion and emulsification, and has excellent vulcanization adhesiveness with rubber. Moreover, since the wettability is given to rubber, the adhesive effect is also excellent.

  In one embodiment of the present invention, the polymer composition for an inner liner can improve vulcanization adhesion with rubber while maintaining air barrier properties by blending SMA with SIBS.

  In the polymer component of the polymer composition for the inner liner, the SMA content is 0.5 to 40% by mass. When the content of SMA is 0.5% by mass or more, an inner liner excellent in adhesiveness with adjacent rubber can be obtained. Moreover, when the SMA content is 40% by mass or less, an inner liner having excellent air permeation resistance and durability can be obtained. The content of SMA in the polymer component is more preferably 2 to 30% by mass.

(Styrene-maleic anhydride copolymer-based resin)
In one embodiment of the present invention, the SMA preferably contains a styrene-maleic anhydride copolymer base resin from the viewpoints of tackiness before vulcanization and adhesion after vulcanization. The SMA base resin preferably has a styrene component / maleic anhydride component molar ratio of 50/50 to 90/10 from the viewpoints of a high softening point and high thermal stability.

  The SMA base resin preferably has a weight average molecular weight of 4,000 to 20,000 from the viewpoint of adhesion after vulcanization and fluidity. Furthermore, the weight average molecular weight is more preferably 5,000 to 15,000. In the SMA base resin, the maleic anhydride component in the styrene-maleic anhydride copolymer preferably has an acid value of 50 to 600 from the viewpoint of unvulcanized adhesiveness. Furthermore, the acid value of the maleic anhydride component is more preferably 95 to 500.

(Ester resin of styrene-maleic anhydride copolymer)
In one embodiment of the present invention, the styrene-maleic anhydride copolymer is a styrene-maleic anhydride copolymer having a monoester group and a monocarboxylic acid group obtained by esterifying an SMA base resin. It is preferable that the ester resin (hereinafter also referred to as SMA ester resin) is included.

The SMA ester resin has the property of being excellent in vulcanization adhesion. Therefore,
By blending SMA ester resin with SIBS, a polymer composition for an inner liner excellent in vulcanization adhesion with a rubber layer can be obtained. The SMA ester resin preferably has a styrene component / maleic anhydride component molar ratio of 50/50 to 90/10 from the viewpoint of vulcanization adhesion.

  The SMA ester resin preferably has a weight average molecular weight of 5,000 to 12,000 from the viewpoint of adhesion after vulcanization and fluidity. Furthermore, the weight average molecular weight is more preferably 6,000 to 11,000.

  In the SMA ester resin, the maleic anhydride component preferably has an acid value of 50 to 400 from the viewpoint of adhesion to unvulcanized rubber. Furthermore, the acid value of the maleic anhydride component is more preferably 95 to 290. The SMA ester resin can be produced, for example, by introducing a base resin and alcohol into a reaction vessel and heating and stirring in an inert gas atmosphere.

(Styrene-maleic anhydride copolymer ammonium salt aqueous solution)
In one embodiment of the present invention, the styrene-maleic anhydride copolymer is a styrene-maleic anhydride copolymer aqueous ammonium salt solution (hereinafter also referred to as an SMA ammonium salt aqueous solution) in which an SMA base resin is dissolved in an ammonium salt. ) Is preferably included.

  The SMA ammonium salt aqueous solution has a property of excellent wettability. Therefore, the polymer composition for inner liners excellent in adhesiveness can be obtained by mix | blending SMA ammonium salt aqueous solution with SIBS. The SMA ammonium salt aqueous solution preferably has a solid content of 10.0 to 45.0% from the viewpoint of adhesion to unvulcanized rubber and molding processability. The aqueous SMA ammonium salt solution preferably has a pH of 8.0 to 9.5 from the viewpoint of tackiness.

  An aqueous SMA ammonium salt solution causes exothermic reaction when water is added to a reaction vessel, base resin is added with vigorous stirring, and ammonium hydroxide is gradually added. Then, it can manufacture by heating to predetermined temperature and continuing stirring until melt | dissolution is completed.

<Other ingredients>
The polymer composition for the inner liner includes other reinforcing agents, vulcanizing agents, vulcanization accelerators, various oils, anti-aging agents, softeners, plasticizers, coupling agents, etc. for tires or general polymer compositions. Various compounding agents and additives blended in can be blended. Moreover, the content of these compounding agents and additives can also be set to general amounts.

<Second layer>
In the present invention, the second layer is also referred to as a SIS layer containing a styrene-isoprene-styrene triblock copolymer (hereinafter also referred to as “SIS”) and a styrene-isobutylene diblock copolymer (hereinafter referred to as “SIB”). ) Including at least one of the SIB layers. Since the isoprene block of the styrene-isoprene-styrene triblock copolymer (SIS) is a soft segment, the polymer film made of SIS is easily vulcanized and bonded to the rubber component. Therefore, when a polymer film made of SIS is used for the 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 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 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.

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

  The content of the styrene component in the SIB is preferably 10 to 35% by mass from the viewpoints of tackiness, adhesiveness, and rubber elasticity. In the present invention, the polymerization degree of each block in SIB is preferably about 300 to 3,000 for isobutylene and about 10 to 1,500 for styrene from the viewpoint of rubber elasticity and handling.

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

  The SIB layer can be obtained by forming SIB into a film by an ordinary method of forming a thermoplastic resin or thermoplastic elastomer into a film such as extrusion molding or calendering. The thickness of the second layer is 0.01 mm to 0.3 mm. Here, the thickness of the second layer refers to the thickness of the SIS layer when the second layer is composed only of the SIS layer, and the thickness of the SIB layer when the second layer is composed of only the SIB layer. When a layer consists of two layers of an SIS layer and an SIB layer, it means the total thickness of the SIS layer and the SIB layer. When the thickness of the second layer is less than 0.01 mm, the second layer 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 further preferably 0.05 to 0.2 mm.

<Form 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. 3 to 6 which are schematic sectional views of the inner liner.

Form 1
As shown in FIG. 3, 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.

Form 2
As shown in FIG. 4, the polymer laminate PL is composed of a SIBS layer PL1 as a first layer and a SIB layer PL3 as a second layer. When the polymer laminate PL is applied to an inner liner of a pneumatic tire, if the surface of the SIB layer PL3 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 The adhesive strength between PL3 and the carcass 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 3
As shown in FIG. 5, the polymer laminate PL is configured by laminating a SIBS layer PL1 as a first layer, a SIS layer PL2 and a SIB layer PL3 as second layers in the order described above. When the polymer laminate PL is applied to an inner liner of a pneumatic tire, if the surface of the SIB layer PL3 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 The adhesive strength between PL3 and the carcass ply 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 4
As shown in FIG. 6, the polymer laminate PL is configured by laminating an SIBS layer PL1 as a first layer, an SIB layer PL3 as a second layer, and an SIS layer PL2 in the order described above. When the polymer laminate PL is applied to an 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.

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

<Pneumatic tire manufacturing method>
A general manufacturing method can be used for the pneumatic tire of the present invention. The polymer laminate PL can be manufactured by applying it to the inner liner of the green tire 1 and vulcanizing it together with other members. When the polymer laminate PL is arranged on the green tire, the SIS layer PL2 or the SIB layer PL3, which is the second layer of the polymer laminate PL, is arranged outward in the tire radial direction so as to be in contact with the carcass ply 61. When arranged in this manner, the adhesion strength between the SIS layer PL2 or SIB layer PL3 and the carcass ply 61 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.

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.

  The pneumatic tires of Examples and Comparative Examples were manufactured according to the specifications shown in Table 1 and Table 2, and the performance was evaluated. SIB, SIBS, SIS and SMA 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.

<SMA>
SMA (1): styrene-maleic anhydride copolymer, SMA 1000 (acid value 490) manufactured by Sartomer.

SMA (2): esterification of styrene-maleic anhydride copolymer, SMA 1440 (acid value 200) manufactured by Sartomer.
SMA (3): Ammonium salt aqueous solution of styrene-maleic anhydride copolymer, SMA 1000H (pH 9.0) manufactured by Sartomer.

<Manufacture of pneumatic tires>
The mixture of SIBS and SMA (1) to SMA (3), 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).

  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 of the crown center region of the inner liner, the maximum tire width region and the shoulder region, a profile is attached to the extrusion port of the polymer sheet, and the thickness Ge of the shoulder region is reduced. A sheet was prepared and placed on the inner surface of the tire as an inner liner.

(Note 1) In Tables 1 to 3, “region (wc / ws) (%)” means the ratio wc (%) of the distance wc extending from the shoulder position Pe in the crown center position Pc direction to the distance Wc, and the shoulder position A ratio ws (%) with respect to the distance Ws of the distance ws extending in the direction of the maximum width position Ps around Pe is shown.
(Note 2) In Tables 1 to 3, G _c1 and G _s1 mean the thicknesses of Pc and Ps of the first layer, and G _c2 and G _s2 mean the thicknesses of Pc and Ps of the second layer. To do. G _c is obtained as the sum of G _c1 and G _c2 , and G _s is obtained as the sum of G _s1 and G _s2 .

<Performance test>
The following performance evaluation was performed on the pneumatic tire manufactured as described above. The low temperature durability and rolling resistance were tested using a pneumatic tire having a tire size of 195 / 65R15.

<Peel test>
A peel test was conducted according to JIS-K-6256 “How to determine adhesion between vulcanized rubber and thermoplastic rubber”. First, the polymer sheet having a thickness of 0.3 mm, the rubber sheet having a thickness of 2 mm (formulation: NR / BR / SBR = 40/30/30) and the reinforced canvas fabric were stacked in the order described above under the condition of 170 ° C. A test specimen for peeling was produced by heating under pressure for 12 minutes. A peel test was performed using the obtained test piece, and the adhesive force between the polymer sheet for the inner liner and the rubber sheet was measured. The size of the test piece was 25 mm wide, and the test was performed at room temperature of 23 ° C. With Comparative Example 1 as the reference value 100, the peel strength index was calculated from the obtained numerical value by the following formula. The larger the value, the better the adhesion.

(Peeling strength index) = (Adhesive strength of each formulation) / (Adhesive strength of Comparative Example 1) × 100
The results are shown in Table 1.

<Low temperature durability>
The low temperature durability test was performed at an atmospheric temperature of −20 ° C. with a tire pressure of 120 kPa, a load factor of 60%, and a speed of 80 Km / h. The low temperature durability shown in the figure is expressed as an index based on Comparative Example 1 by measuring the travel distance when a crack occurs in the inner liner. The higher the value, the better the low temperature durability.

<Rolling resistance>
For rolling resistance, tan δ of each formulation was measured using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.) at a temperature of 70 ° C., an initial strain of 10%, and a dynamic strain of 2%. The tan δ of 100 was expressed as an index according to the following formula. The larger the index, the better the rolling resistance.

Rolling resistance index = (tan δ of Comparative Example 1) / (tan δ × 100 of each formulation)
<Comparative Examples 1-2, Examples 1-3>
The first layer of the inner liners of Comparative Examples 1 and 2 is composed of a composition containing 100% SIBS. And the comparative example 2 has the thick part formed in the shoulder part. Examples 1 to 3 are composed of compositions in which 2 to 30% by mass of SMA (1) is mixed in the first layer. All of the second layers are SIS layers. Examples 1 to 3 are excellent in overall peel strength, rolling resistance and low temperature durability.

<Comparative Examples 3-4, Examples 4-6>
The first layer of the inner liners of Comparative Examples 3 to 4 is composed of a composition containing 100% SIBS. In Comparative Example 4, a thick portion is formed in the shoulder portion. Examples 4-6 are comprised with the composition by which 2-30 mass% of SMA (1) is mixed with the 1st layer. All of the second layers are SIB layers. Examples 4 to 6 are generally excellent in peeling force, rolling resistance and low temperature durability.

<Comparative Examples 5-6, Examples 7-12>
Comparative Example 5 and Examples 7 to 9 are examples in which a thick part was formed in the shoulder part of the inner liner and the thickness was changed. Regarding the first layer, Comparative Example 5 is a mixture of 100% SIBS, and Examples 7 to 9 are a mixture of 80% of SIBS and 20% of SMA (1). In each of the second layers, SIS is used. Examples 7 to 9 are generally excellent in peeling force, rolling resistance and low temperature durability.

  Comparative Example 6 and Examples 10 to 12 are examples in which a thick part was formed in the shoulder part of the inner liner and the thickness was changed. Regarding the first layer, Comparative Example 6 is a mixture of 100% SIBS, and Examples 10 to 12 are a mixture of 80% SIBS and 20% SMA (1). SIB is used for all the second layers. Examples 7 to 9 are generally excellent in peeling force, rolling resistance and low temperature durability.

<Examples 13 to 24>
Examples 13 to 18 are examples of compositions in which one or more SMA (1), SMA (2) and SMA (3) were mixed in the first layer and mixed in a total of 20% by weight. In each of the second layers, SIS is used. Examples 13 to 18 are generally excellent in peeling force, rolling resistance and low temperature durability.

  Examples 19 to 24 are examples of compositions in which one type of SMA (1), SMA (2), and SMA (3) and two or more types were mixed in the first layer in a total of 20% by weight. SIB is used for all the second layers. Examples 18 to 22 are excellent in overall peel strength, rolling resistance and low temperature durability.

  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, PL polymer laminated body, PL1 SIBS layer, PL2 SIS layer, PL3 SIB layer, Pe shoulder position, Pc crown center position, Ps tire maximum width position,
Te tread end.

Claims (10)

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 formed of a multi-layer polymer laminate including a first layer disposed inside a tire and a second layer disposed adjacent to the carcass ply,
The first layer contains 99.5 to 60% by mass of a styrene-isobutylene-styrene triblock copolymer and 0.5 to 40% by mass of a styrene-maleic anhydride copolymer as polymer components. The thickness is 0.05 mm to 0.6 mm,
The second layer is composed of an elastomer composition containing at least one of a styrene-isoprene-styrene triblock copolymer and a styrene-isobutylene diblock copolymer, and has a thickness of 0.01 mm to 0.3 mm. ,
The pneumatic tire according to claim 1, wherein the inner liner has a thickness Ge at a shoulder position Pe larger than a thickness Gc at a 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 of 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,
2. The pneumatic tire according to claim 1, wherein 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.   3. The pneumatic tire according to claim 1, wherein a thick portion of the inner liner is formed in a region having a width of 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 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 520% with respect to a thickness Gc at a crown central position Pc.   The copolymer composition ratio of styrene / maleic anhydride is in the range of 50/50 to 90/10 in molar ratio, the weight average molecular weight is in the range of 4,000 to 20,000, and the acid value of maleic anhydride is The pneumatic tire according to claim 1, which is 50 to 600.   The air according to any one of claims 1 to 7, 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.   2. The pneumatic according to claim 1, wherein the styrene-isobutylene diblock copolymer is linear, has a styrene component content of 10 to 35 mass%, and a weight average molecular weight of 40,000 to 120,000. tire.

Images