JP5053452B1 - Pneumatic tire - Google Patents

Abstract

[PROBLEMS] To improve the adhesion of an inner liner, improve air permeation resistance and low temperature durability, and reduce rolling resistance by reducing the weight of a tire.
An inner liner provided on the inner side of a carcass ply 6 is a rubber selected from a styrene-isobutylene-styrene triblock copolymer in an amount of 5% by mass to 40% by mass, natural rubber, isoprene rubber and butyl rubber. A first layer containing 60% by mass to 95% by mass of a component, a styrene-isoprene-styrene triblock copolymer and a styrene-isoprene-styrene diblock copolymer of 10% by mass to 85% by mass, natural A polymer laminate composed of a second layer containing 15% by mass to 90% by mass of a rubber component selected from rubber, isoprene rubber and butyl rubber, wherein the second layer is in contact with the carcass ply, and the inner liner is a crown The thickness of the shoulder position Pe is 120% to 50% with respect to the thickness Gc at the central position Pc. It is%.
[Selection] Figure 1

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.

  Prior art document 1 realizes 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 viewpoint of low fuel consumption and manufacturing cost.

JP 2005-343379 A

  The present invention provides a pneumatic tire provided with an inner liner, which maintains the inner liner layer thin, improves the adhesion of adjacent tire members, improves air permeation resistance and low temperature durability, and further reduces the weight of the tire. An object of the present invention is to provide a pneumatic tire in which rolling resistance is reduced by the conversion.

The pneumatic tire of 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 parts, and the inner liner includes:
(A) The styrene-isobutylene-styrene triblock copolymer is 5% by mass or more and 40% by mass or less, and at least one rubber component selected from the group consisting of natural rubber, isoprene rubber and butyl rubber is 60% by mass or more. A first layer comprising a polymer composition containing 95% by weight or less;
(B) 10% to 85% by mass of at least one of styrene-isoprene-styrene triblock copolymer and styrene-isobutylene diblock copolymer, and further from the group consisting of natural rubber, isoprene rubber and butyl rubber A second layer comprising a polymer composition containing at least one selected rubber component in an amount of 15% by mass to 90% by mass;
A polymer laminate comprising:
The second layer is disposed in contact with the carcass ply;
The inner liner is characterized in that the thickness Ge at the shoulder position Pe is 120% to 500% with respect to the thickness Gc at the crown central position Pc.

  The first layer is 0.1 parts by mass or more and 5 parts by mass or less of sulfur, 1 part by mass or more and 5 parts by mass or less of stearic acid, and 0.1 parts by mass or more of zinc oxide with respect to 100 parts by mass of the polymer component. And 8 parts by mass or less, preferably 0.1 to 5 parts by mass of an antioxidant, and 0.1 to 5 parts by mass of a vulcanization accelerator. .

  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 used, the thick portion of the inner liner is a pneumatic tire 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. .

  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. 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. It is desirable to form on the position Ps side in a region having a width of at least 20% of the side distance Ws.

  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 tire of the present invention uses a polymer composition comprising a mixture of SIBS and a rubber component in the first layer and dynamically cross-linked for the inner liner, and the thickness of the inner liner is changed from the tire maximum width position to the crown center position in the tire cross section. By adjusting the area to a specific range, the overall inner liner layer thickness is reduced to reduce the rolling resistance by reducing the weight, and the thicker portion is formed on the tire shoulder to improve air permeability. Low temperature durability can be improved while maintaining.

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 a styrene-isobutylene-styrene triblock copolymer (hereinafter also referred to as “SIBS”). The second layer includes at least one of a styrene-isoprene-styrene triblock copolymer (hereinafter also referred to as “SIS”) and a styrene-isobutylene diblock copolymer (hereinafter also referred to as “SIB”). 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 Gc, Ge, Gs>
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 Gc at the crown center position Pc, that is, a thickness Ge at the shoulder position Pe of 120% to 500%. When the thickness Ge of the shoulder position Pe is less than 120%, the bending deformation and shear deformation of the shoulder portion are not sufficiently suppressed, and when it exceeds 500%, the effect of reducing the weight of the inner liner cannot be sufficiently expected.

  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.

<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 (SIBS), and a styrene-isoprene-styrene triblock. The second layer contains at least one of a copolymer (SIS) and a styrene-isobutylene diblock copolymer (SIB), and the thickness of the second layer is 0.01 mm to 0.3 mm.

  And the average thickness of the area | region except the thick part of a polymer laminated body is the range of 0.06 mm-1.3 mm. When the thickness of the polymer laminate is less than 0.06 mm, when the polymer laminate is applied to the inner liner and the raw tire is vulcanized, the polymer laminate is broken by press pressure, and the vulcanized tire There is a risk that air leakage will occur. On the other hand, if the thickness of the polymer laminate exceeds 1.3 mm, the tire weight increases and the fuel efficiency performance decreases. The thickness of the polymer laminate is preferably 0.25 mm or more and 0.8 mm or less.

  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.

<First layer>
(Polymer composition)
The first layer contains 60% by mass or more of styrene-isobutylene-styrene triblock copolymer (SIBS) and at least one rubber component selected from the group consisting of natural rubber, isoprene rubber and butyl rubber. It consists of a polymer composition containing 0.1 parts by mass or more and 5 parts by mass or less of sulfur with respect to 100 parts by mass of the polymer component containing at least 95% by mass.

  The polymer composition includes SIBS, a rubber component, and sulfur. When a rubber component and sulfur are added to SIBS and heated and mixed, the rubber component and sulfur are vulcanized during the heating and mixing to form a sea-island structure in which SIBS is a matrix (sea) and the rubber component is an island.

  The polymer composition having a sea-island structure has air permeation resistance derived from a matrix phase composed of SIBS. Furthermore, the rubber component forming the island phase has adhesiveness before vulcanization with an adjacent member containing the rubber component, and also vulcanizes with the rubber component of the adjacent member during heating and mixing. Also has adhesiveness. Therefore, the sheet made of the polymer composition is excellent in air permeation resistance, and at the same time, has adhesiveness before vulcanization with adjacent members and vulcanization adhesion.

(Styrene-isobutylene-styrene triblock copolymer)
Since SIBS contains an isobutylene block, the polymer laminate has excellent air permeation resistance. Furthermore, since the molecular structure other than aromatic is completely saturated, SIBS has excellent durability with suppressed deterioration hardening. Therefore, when a polymer laminate including SIBS is used for the inner liner, a pneumatic tire excellent in air permeation resistance and durability can be obtained.

  As for the molecular weight of SIBS, it is preferable that the weight average molecular weight by GPC method is 50,000 or more and 400,000 or less from a viewpoint of hold | maintaining fluidity | liquidity, a shaping | molding process, and rubber elasticity. 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.

  SIBS generally contains 10% to 40% by mass of styrene units. The content of styrene units in SIBS is preferably 10% by mass or more and 30% by mass or less from the viewpoint of better air permeation resistance and durability.

  SIBS preferably has a molar ratio of isobutylene units to styrene units (isobutylene units / styrene units) of 40/60 to 95/5 from the viewpoint of rubber elasticity of the copolymer. In SIBS, the polymerization degree of each block is preferably about 10,000 to 150,000 for an isobutylene block and about 5,000 to 30,000 for a styrene block.

  SIBS can be obtained, for example, by a living cationic polymerization method. JP-A-62-48704 and JP-A-64-62308 disclose that living cationic polymerization of isobutylene and other vinyl compounds is possible, and polyisobutylene is obtained by using isobutylene and other compounds as vinyl compounds. It is disclosed that block copolymers of the system can be produced.

  Since SIBS does not have double bonds other than aromatics in the molecule, it is more stable to ultraviolet rays and has weather resistance than a polymer having double bonds in the molecule such as polybutadiene. It is good.

  The content of SIBS is 5% by mass or more and 40% by mass or less in the polymer component of the polymer composition. If the SIBS content is less than 5% by mass, the air permeation resistance of the polymer sheet may be lowered. On the other hand, when the content of SIBS exceeds 40% by mass, the vulcanization adhesive strength with the adjacent member may be insufficient. The content of SIBS is preferably 10% by mass or more and 30% by mass or less in the polymer component from the viewpoint of ensuring air permeation resistance.

(Rubber component)
The polymer composition constituting the polymer laminate includes a rubber component. The rubber component can give the polymer composition tackiness before vulcanization with an adjacent member containing the rubber component. Furthermore, the vulcanization reaction with sulfur can provide the polymer composition with vulcanization adhesion to adjacent members such as carcass and insulation.

  The rubber component contains at least one selected from the group consisting of natural rubber, isoprene rubber and butyl rubber, and among them, natural rubber is preferable from the viewpoint of breaking strength and adhesiveness.

  The content of the rubber component is 60% by mass or more and 95% by mass or less in the polymer component of the polymer composition. When the content of the rubber component is less than 60% by mass, the viscosity of the polymer composition is increased and the extrusion processability is deteriorated. Therefore, there is a possibility that the sheet cannot be thinned when the polymer laminate is produced. On the other hand, if the content of the rubber component exceeds 95% by mass, the air permeation resistance of the sheet may be reduced. The content of the rubber component is preferably 70% by mass or more and 90% by mass or less in the polymer component from the viewpoints of tackiness before vulcanization and vulcanization adhesion.

(sulfur)
The polymer composition includes sulfur. As sulfur, sulfur generally used in the rubber industry during vulcanization can be used. Of these, insoluble sulfur is preferably used. Here, the insoluble sulfur refers to sulfur obtained by heating and quenching natural sulfur S ₈ to increase the molecular weight so that S _x (x = 100,000 to 300,000) is obtained. By using insoluble sulfur, blooming that normally occurs when sulfur is used as a rubber vulcanizing agent can be prevented.

  The sulfur content is 0.1 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the polymer component. When the sulfur content is less than 0.1 parts by mass, the vulcanization effect of the rubber component cannot be obtained. On the other hand, when the sulfur content exceeds 5 parts by mass, the hardness of the polymer composition increases, and when the polymer laminate is used for the inner liner, the durability performance of the pneumatic tire may be reduced. The sulfur content is further preferably 0.3 parts by mass or more and 3.0 parts by mass or less.

(Polymer composition compounding agent)
The polymer composition may contain compounding agents such as stearic acid, zinc oxide, anti-aging agent, and vulcanization accelerator.

  Stearic acid functions as a vulcanization aid for the rubber component. The content of stearic acid is preferably 1 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the polymer component. If the content of stearic acid is less than 1 part by mass, the effect as a vulcanization aid cannot be obtained. On the other hand, when the content of stearic acid exceeds 5 parts by mass, the viscosity of the polymer composition is lowered, and the breaking strength may be lowered. The content of stearic acid is further preferably 1 part by mass or more and 4 parts by mass or less.

Zinc oxide functions as a vulcanization aid for the rubber component. The content of zinc oxide is preferably 0.1 parts by mass or more and 8 parts by mass or less with respect to 100 parts by mass of the polymer component. When the content of zinc oxide is less than 0.1 part by mass, the effect as a vulcanization aid cannot be obtained. On the other hand, when the content of zinc oxide exceeds 8 parts by mass, the hardness of the polymer composition increases, and when the polymer sheet is used for the inner liner, the durability performance of the pneumatic tire may be lowered. The content of zinc oxide is further preferably 0.5 parts by mass or more and 6 parts by mass or less.

  The anti-aging agent has a function of preventing a series of deteriorations such as oxidative deterioration, heat deterioration, ozone deterioration, fatigue deterioration and the like called aging. Anti-aging agents are classified into primary anti-aging agents composed of amines and phenols and secondary anti-aging agents composed of sulfur compounds and phosphites. The primary anti-aging agent has the function of stopping hydrogenation to various polymer radicals to stop the chain reaction of auto-oxidation, and the secondary anti-aging agent shows a stabilizing action by changing hydroxy peroxide to a stable alcohol. is there.

  Examples of the anti-aging agent include amines, phenols, imidazoles, phosphorus and thioureas. One type of anti-aging agent may be used alone, or two or more types may be used in combination. Of these, N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine is preferably used.

  The content of the antioxidant is preferably 0.1 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the polymer component. When the content of the anti-aging agent is less than 0.1 parts by mass, the anti-aging effect cannot be obtained. On the other hand, when the content of the anti-aging agent exceeds 5 parts by mass, a blooming phenomenon occurs in the polymer composition. The content of the antioxidant is further preferably 0.3 parts by mass or more and 4 parts by mass or less.

  As the vulcanization accelerator, thiurams, thiazoles, thioureas, dithiocarbamates, guanidines and sulfenamides can be used. A vulcanization accelerator may be used individually by 1 type, or may combine 2 or more types. Of these, dibenzothiazyl sulfide is preferably used.

  The content of the vulcanization accelerator is preferably 0.1 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the polymer component. When the content of the vulcanization accelerator is less than 0.1 parts by mass, the vulcanization acceleration effect cannot be obtained. On the other hand, when the content of the vulcanization accelerator exceeds 5 parts by mass, the hardness of the polymer composition increases, and when the polymer sheet is used for the inner liner, the durability performance of the pneumatic tire may be reduced. Furthermore, the raw material cost of the polymer composition increases. The content of the vulcanization accelerator is further preferably 0.3 parts by mass or more and 4 parts by mass or less.

<Second layer>
In the present invention, the second layer contains at least one of a styrene-isoprene-styrene triblock copolymer and a styrene-isobutylene diblock copolymer in an amount of 10% by mass to 85% by mass, and further includes natural rubber, isoprene rubber, and It consists of a polymer composition containing 15% by mass or more and 90% by mass or less of at least one rubber component selected from the group consisting of butyl rubber.

  The second layer has at least one of an SIS layer containing styrene-isoprene-styrene triblock copolymer (SIS) and an SIB layer containing 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 polymer composition of the second layer contains at least one selected from the group consisting of natural rubber, isoprene rubber and butyl rubber as a rubber component in a range of 15% by mass to 90% by mass of the polymer component. By mixing the rubber component in this range, the polymer composition can be given adhesiveness before vulcanization with an adjacent member containing the rubber component. Furthermore, vulcanization adhesion with adjacent members such as the first layer, carcass, and insulation can be imparted to the polymer composition by dynamic vulcanization.

  When the rubber component content is less than 15% by mass in the polymer component of the polymer composition, the viscosity of the polymer composition increases and the extrusion processability deteriorates. However, there is a possibility that the sheet cannot be thinned. On the other hand, if the content of the rubber component exceeds 90% by mass, the air permeation resistance of the sheet may be reduced.

  The second layer can be obtained by forming 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.

  The average thickness excluding the thick portion of the second layer is preferably 0.01 mm to 0.3 mm. 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)
In the present invention, the first layer of the polymer laminate used for the inner liner can be produced, for example, by the following method. Each compounding agent is put into a twin-screw extruder and kneaded under conditions of about 150 to 280 ° C. and 50 to 300 rpm to obtain pellets of a polymer composition dynamically crosslinked with SIBS, a rubber component, sulfur and the like. The obtained pellets are put into a T-die extruder to obtain a first layer having a desired thickness. The first layer layer can be formed into a sheet and simultaneously bonded to the second layer to form a polymer laminate. The polymer laminate can be produced by laminate extrusion such as laminate extrusion or coextrusion.

  In the twin screw extruder, SIBS, which is a thermoplastic elastomer, becomes a matrix phase and the rubber component becomes an island phase and is dispersed. Further, in the twin-screw extruder, the rubber component and the additive component react, and the rubber component that is an island phase undergoes a crosslinking reaction. Since the rubber component is dynamically cross-linked in a twin screw extruder, it is called so-called dynamic cross-linking. Even if the rubber component is cross-linked in a twin-screw extruder, the matrix phase of the system is composed of a thermoplastic elastomer component, so that the shear viscosity of the entire system is low and extrusion is possible.

The pellets of the dynamically crosslinked polymer composition obtained by the twin-screw extruder have the rubber component crosslinked, but the thermoplastic elastomer component in the matrix phase retains the plasticity, and the plasticity of the entire polymer composition It plays a role to produce. Therefore, since the polymer composition exhibits plasticity even in T-die extrusion, it can be formed into a sheet shape.

  Further, since the rubber component of the pellet of the dynamically crosslinked polymer composition is crosslinked, the pneumatic tire is used when a pneumatic tire is manufactured by applying the polymer sheet prepared using the pellet to the inner liner. Even when heated, the inner liner can be prevented from entering the carcass layer.

  The second layer can employ the same manufacturing method as the first layer, but after mixing SIB or SIS, rubber components with sulfur and additives with a Banbury mixer, extrusion molding, calender molding, thermoplastic resin, thermoplastic A general method for forming the elastomer into a sheet can be employed.

<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 0 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.

  Table 1 shows the composition (A1 to A5) of the first layer of the polymer laminate, and Table 2 shows the composition (B1 to B6) of the second layer of the polymer laminate. The pneumatic tires of Examples and Comparative Examples were manufactured according to the specifications shown in Table 3 by combining the combinations of the first layer and the second layer, and the tire performance was evaluated. Here, the polymer components and the compounding agents used in the polymer compositions of the first layer and the second layer are as follows.

(Note 1) IIR: “Exon Chlorobutyl 1066” manufactured by ExxonMobil Co., Ltd.
(Note 2) SIBS: “Sibstar SIBSTAR 102T” manufactured by Kaneka Corporation (styrene-isobutylene-styrene triblock copolymer, weight average molecular weight 100,000, styrene unit content 25 mass%, Shore A hardness 25) .
(Note 3) Stearic acid: “Lunac stearate S30” manufactured by Kao Corporation.
(Note 4) Zinc oxide: “Zinc Hana 1” manufactured by Mitsui Kinzoku Mining Co., Ltd.
(Note 5) Anti-aging agent: “NOCRACK 6C” (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine) manufactured by Ouchi Shinsei Chemical Co., Ltd.
(Note 6) Vulcanization accelerator: “Noxeller DM” (di-2-benzothiazolyl disulfide) manufactured by Ouchi Shinsei Chemical Co., Ltd.
(Note 7) Sulfur: “Powder sulfur” manufactured by Tsurumi Chemical Co., Ltd.
(Note 8) SIS: “D1161JP” manufactured by Kraton Polymer Co., Ltd. (styrene-isoprene-styrene triblock copolymer, weight average molecular weight 150,000, styrene unit content 15 mass%).
(Note 9) SIB: 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 to a 2 L reaction vessel equipped with a stirrer. 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
(Note 10) Butyl rubber: “Exon Chlorobutyl 1066” manufactured by ExxonMobil Co., Ltd.

<Manufacture of pneumatic tires>
The polymer 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, a T-die extruder (screw diameter: φ80 mm, L / D: 50, die lip width: 500 mm, cylinder temperature: 220 ° C.) a first layer having a thickness of 0.25 mm and a second layer having a thickness of 0.05 mm Were manufactured and bonded together to produce a polymer laminate.

  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 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 Tables 3 and 4, “region (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 Tables 3 and 4, 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) Vulcanization adhesion index of first layer and second layer The polymer laminate is heated at 170 ° C. for 20 minutes to prepare a sample for measurement of vulcanization adhesion. The peel strength was measured by a tensile peel test to obtain a vulcanized adhesive strength. By the following formula, the vulcanization adhesive strength of each blending example was displayed as an index with Comparative Example 7 as a reference (100). The larger the vulcanized adhesive strength index, the stronger the vulcanized adhesive strength.
(Vulcanization adhesion index) = (Vulcanization adhesion of each formulation example) ÷ (Vulcanization adhesion of Comparative Example 7) × 100.

(B) 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.

(C) Low temperature durability Under the atmospheric temperature of -20 ° C, the tire pressure is 120kPa, the load factor is 60 (%), the speed is 80km / hour, and the distance traveled when the inner liner is cracked is measured. did. The relative value was displayed as an index with the travel distance of Comparative Example 7 as 100.

(D) Rolling resistance Using a rolling resistance tester manufactured by Kobe Steel, Ltd., a steel radial tire having a tire size of 195 / 65R15 was assembled into a JIS standard rim 15 × 6JJ, a load of 3.4 kN, an air pressure of 230 kPa, and a speed of 80 km. The rolling resistance was measured by running at room temperature (38 ° C.) under the conditions of / hour. And the rolling resistance of each Example and the comparative example was displayed by the index | exponent on the basis of the comparative example 7 with the following formula. It shows that rolling resistance is reduced, so that an index value is large.
(Rolling resistance change rate) = (Rolling resistance of Comparative Example 7) ÷ (Rolling resistance of each blending example) × 100
<Comprehensive evaluation>
Comprehensive evaluation was performed based on each performance evaluation of said (a)-(d). Evaluation criteria for comprehensive evaluation A and comprehensive evaluation B are as follows.

Overall evaluation A
(A)-(d) satisfy | fills all the following conditions.
(A) The vulcanization adhesion index of the first layer and the second layer is greater than 100.
(B) Static air drop rate is less than 2.5.
(C) Low temperature durability (index) is greater than 100.
(D) Rolling resistance (index) is greater than 100.

Overall evaluation B
Any of (a) to (d) satisfies the following one condition.
(A) The vulcanized adhesion index of the first layer and the second layer is 100 or less.
(B) Static air drop rate is 2.5 or more.
(C) Low temperature durability (index) is 100 or less.
(D) Rolling resistance (index) is 100 or less.

<Examples 1-7>
In Table 3, Examples 1 and 2 are pneumatic tires using a polymer laminate using the polymer composition of Formulation A1 as the first layer and the polymer composition of Formulation B1 as the second layer. The thickness (Ge) of the thick portion is 0.36 mm in Example 1 and 1.5 mm in Example 2.

  In each of the polymer laminates of Examples 1 and 2, the vulcanized adhesion index of the first and second polymer laminates was 200, and excellent characteristics were obtained. In addition, excellent performance was obtained in terms of static air drop rate, low temperature durability and rolling resistance of pneumatic tires.

  Examples 3 and 4 are pneumatic tires using a polymer laminate using the polymer composition of Formulation A1 as the first layer and the polymer composition of Formulation B3 as the second layer. And the thickness (Ge) and thickness ratio (Ge / Gc) of a thick part differ. In each of the polymer laminates of Examples 3 and 4, the first and second polymer laminates had a vulcanization adhesion index of 220, and excellent characteristics were obtained. In addition, excellent performance was obtained in terms of static air drop rate, low temperature durability and rolling resistance of pneumatic tires.

  Examples 5 and 6 are pneumatic tires using a polymer laminate using the polymer composition of Formulation A2 as the first layer and the polymer composition of Formulation B2 as the second layer. And the thickness (Ge) and thickness ratio (Ge / Gc) of a thick part differ. In each of the polymer laminates of Examples 5 and 6, the vulcanized adhesion index of the polymer laminates of the first layer and the second layer was 210, and excellent characteristics were obtained. In addition, excellent performance was obtained in terms of static air drop rate, low temperature durability and rolling resistance of pneumatic tires.

  Example 7 is a pneumatic tire using a polymer laminate using a polymer composition of Formulation A2 as the first layer and a polymer composition of Formulation B4 as the second layer. In the polymer laminate of Example 7, the vulcanized adhesion index of the polymer laminate of the first layer and the second layer was 218, and excellent characteristics were obtained. In addition, excellent performance was obtained in terms of static air drop rate, low temperature durability and rolling resistance of pneumatic tires.

<Comparative Examples 1-10>
In Table 4, Comparative Example 1 is a pneumatic tire using a polymer laminate using the polymer composition of Formulation A1 as the first layer and the polymer composition of Formulation B1 as the second layer. In the polymer laminate of Comparative Example 1, the vulcanized adhesive strength index of the polymer laminate of the first layer and the second layer was 200, and excellent characteristics were obtained. In addition, the static air drop rate and rolling resistance of the pneumatic tire were satisfactory. However, the low temperature durability was the same level as that of Comparative Example 7 and was insufficient.

  Comparative Example 2 is a pneumatic tire using a polymer laminate using the polymer composition of Formulation A1 as the first layer and the polymer composition of Formulation B1 as the second layer. In the polymer laminate of Comparative Example 2, the first layer and the second layer polymer laminate have a vulcanization adhesion index of 200 and excellent characteristics are obtained, and the static air reduction rate of the pneumatic tire is satisfactory. Is performance. However, although low temperature durability was superior to Examples 1 and 2, rolling resistance was inferior to Comparative Example 7.

  Comparative Examples 3 and 4 are pneumatic tires using a polymer laminate using the polymer composition of Formulation A1 as the first layer and the polymer composition of Formulation B1 as the second layer. The polymer laminate of the first and second layers of the polymer laminate has a vulcanization adhesion index of 220, which provides excellent characteristics, and the static air reduction rate of the pneumatic tire is satisfactory. Comparative Example 3 shows no improvement in low temperature durability, and Comparative Example 4 is inferior in rolling resistance.

  Comparative Example 5 is a pneumatic tire using a polymer laminate using the polymer composition of Formulation A2 as the first layer and the polymer composition of Formulation B2 as the second layer. The vulcanized adhesion index of the polymer laminate of the first layer and the second layer in the polymer laminate was 210, and excellent characteristics were obtained. However, the static air drop rate and rolling resistance of pneumatic tires are inferior.

  In Comparative Examples 6 to 10, both the first layer and the second layer use a polymer composition different from the polymer composition of the present invention. In all cases, the vulcanization adhesion index, static air drop rate, low temperature durability and rolling resistance are totally inferior.

  The pneumatic tire using the polymer laminate of the present invention as an inner liner can be widely used not only for pneumatic tires for passenger cars but also for pneumatic tires having 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 (6)

A pneumatic tire provided with an inner liner on the inner side of a carcass ply tire mounted between a pair of bead parts, the inner liner,
(A) The styrene-isobutylene-styrene triblock copolymer is 5% by mass or more and 40% by mass or less, and at least one rubber component selected from the group consisting of natural rubber, isoprene rubber and butyl rubber is 60% by mass or more. A first layer comprising a polymer composition containing 95% by weight or less;
(B) 10% to 85% by mass of at least one of styrene-isoprene-styrene triblock copolymer and styrene-isobutylene diblock copolymer, and further from the group consisting of natural rubber, isoprene rubber and butyl rubber A second layer comprising a polymer composition containing at least one selected rubber component in an amount of 15% by mass to 90% by mass;
A polymer laminate comprising:
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 a shoulder position Pe of 120% to 500% with respect to a thickness Gc at a crown central position Pc.   The first layer is 0.1 parts by mass or more and 5 parts by mass or less of sulfur, 1 part by mass or more and 5 parts by mass or less of stearic acid, and 0.1 parts by mass or more of zinc oxide with respect to 100 parts by mass of the polymer component. 2. A polymer composition comprising 8 parts by mass or less, an anti-aging agent in an amount of 0.1 to 5 parts by mass, and a vulcanization accelerator in an amount of 0.1 to 5 parts by mass. Pneumatic tire described in 2.   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, 3. The pneumatic tire according to claim 1, wherein the thick portion 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.   The thick part of the said inner liner is formed in the area | region which has a width | variety of 50% or less of the said shoulder width Wc from the said shoulder position Pe to the crown center position Pc side. Pneumatic 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 4, 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 portion of the inner liner is 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 described pneumatic tire.

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