JP5670699B2 - Pneumatic tire - Google Patents

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 gas permeability such as 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 easily occurs at the adhesive interface between the inner liner and the carcass ply, and tire air leakage occurs.

On the other hand, pneumatic tires are required to have low fuel consumption, and there is a problem of reducing rolling resistance by reducing the weight of the tire. Therefore, a technique of using a thermoplastic elastomer have been proposed in the inner liner, both standing in air permeability and weight reduction when thinner than the inner liner of butyl rubber is difficult. 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 overlapping the inner liner layer comes into contact with the bladder in a heated state in the vulcanization process, and there is a problem of sticking to the bladder.

  In Patent Document 2, a mixture of a nylon resin having good air permeability and butyl rubber is prepared by dynamic crosslinking to produce an inner liner layer having a thickness of 100 μm. However, nylon resin is hard at room temperature and unsuitable as an inner liner for tires. In addition, the vulcanization adhesion to the rubber layer is not performed only with the mixture obtained by the dynamic crosslinking. Therefore, the adhesion layer for vulcanization is required in addition to the inner liner layer. Therefore, the inner liner member has a complicated structure and many processes. This is disadvantageous from the viewpoint of productivity.

  Prior Document 3 disperses a maleic anhydride-modified hydrogenated styrene-ethylene-butadiene-styrene block copolymer in an ethylene-vinyl alcohol copolymer having good air barrier properties to produce a flexible gas barrier layer. . In addition, the thermoplastic polyurethane layer has an sandwich sandwich structure, and rubber paste (70/30 of butyl rubber / natural rubber is dissolved in toluene) is applied to the surface to be bonded to the tire rubber to produce an inner liner layer.

  However, the modified ethylene-vinyl alcohol copolymer dispersed in a flexible resin has low adhesive strength and may be peeled off from the thermoplastic polyurethane layer. In the modified ethylene-vinyl alcohol copolymer dispersed with a flexible resin, the flexible resin is dispersed, but the EVOH of the matrix is poor in bending fatigue and breaks during running of the tire. Furthermore, although rubber paste is applied to the surface to be bonded to the tire rubber, a process different from the normal inner liner process is required, resulting in poor productivity.

  Prior document 4 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-A-9-19987 Patent No. 2999188 JP 2008-24219 A JP 2005-343379 A

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

  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 is (A) styrene-isobutylene-styrene triblock A first layer having a thickness of 0.05 mm to 0.6 mm composed of a combination, and (B) at least one of a styrene-isoprene-styrene triblock copolymer and a styrene-isobutylene diblock copolymer, It is composed of a polymer laminate composed of a second layer of 0.01 mm to 0.3 mm, the second layer is disposed so as to contact the rubber layer of the carcass ply, and the inner liner is at a crown center position Pc. The present invention relates to a pneumatic tire characterized in that the thickness Ge at the shoulder position Pe is thicker than the thickness Gc at.

  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 the intersection with the boundary line is defined as a shoulder. The position Pe is defined as an intersection of the boundary line between the carcass ply and the inner liner and the tire center line CL as a crown center position Pc, and a distance along the contour line of the inner liner from the shoulder position Pe to the crown center position Pc. When the shoulder distance Wc is set, the thick portion of the inner liner is formed in a region having a width of at least 10% of the shoulder distance Wc from the shoulder position Pe to the crown center position Pc side. To do.

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

  Further, 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 part of the inner liner extends from the shoulder position Pe to the outermost position. It is preferable to form in a region having a width of at least 20% of the maximum width distance Ws on the large position Ps side.

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

  In the inner liner, the thickness Ge of the shoulder position Pe is preferably 120% to 500% with respect to the thickness Gc at the crown center position Pc.

  In 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 100,000.

  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.

  In the tire of the present invention, a specific thermoplastic elastomer material is used for the inner liner, and since the tire shoulder portion is thickened, the overall thickness can be reduced while maintaining air barrier properties, and adhesion to an adjacent carcass ply is also achieved. Can be increased. 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.

  The present invention is a pneumatic tire provided with an inner liner on the inner side of the tire, and the inner liner is formed of at least two polymer laminates. The first layer is made of styrene-isobutylene-styrene triblock copolymer (SIBS) and has a thickness in the range of 0.05 mm to 0.6 mm. The second layer includes at least one of styrene-isoprene-styrene triblock copolymer (SIS) and styrene-isobutylene diblock copolymer (SIB), and has a thickness of 0.01 mm to 0.3 mm. The second layer is disposed in contact with the rubber layer of the carcass ply.

  An embodiment of a pneumatic tire according to the present invention will be described with reference to the drawings. FIG. 1 is a 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 usually intersects two plies made of steel cords or cords such as aramid fibers with respect to the tire circumferential direction so that the cords are usually at an angle of 5 to 30 °. Are arranged as follows. In addition, a topping rubber layer can be provided on both outer sides of the belt layer to reduce peeling at both ends of the belt layer. In the carcass ply, organic fiber cords such as polyester, nylon, and aramid are arranged at approximately 90 ° in the tire circumferential direction. In the region surrounded by the carcass ply and the folded portion, the bead core 5 extends from the upper end to the sidewall direction. An extending bead apex 8 is arranged. Further, an inner liner 9 extending from one bead portion 4 to the other bead portion 4 is disposed inside the carcass ply 6 in the tire radial direction.

  Here, in the present invention, the position, distance and width in 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 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 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 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 60% 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 inner liner has a thickness Ge at the shoulder position Pe of 120% to 500% with respect to the thickness Gc at the crown center position Pc, and the shoulder position Pe with respect to the thickness Gs at the maximum width position Ps. The thickness Ge is desirably 120% to 500%. If the thickness of Ge of the shoulder position Pe is less than 1 2 0% inhibition of bending deformation and shear deformation of the shoulder portion is insufficient, and the effect of weight reduction of the inner liner exceeds 500% can not be sufficiently expected. The thickness Ge of the shoulder position Pe is more preferably 200% to 500% 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.

<Polymer laminate>
The polymer laminate used for the inner liner of the present invention includes a first layer made of styrene-isobutylene-styrene triblock copolymer (SIBS) having a thickness of 0.05 mm to 0.6 mm, 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.

<First layer>
In one embodiment of the present invention, the first layer is made of a styrene-isobutylene-styrene triblock copolymer (SIBS). Due to the isobutylene block of SIBS, the polymer film made of SIBS has excellent air permeation resistance. Therefore, when a polymer film made of SIBS is used for the inner liner, a pneumatic tire having excellent air permeation resistance can be obtained.

  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 about 10,000 to 150,000 for isobutylene from the viewpoint of rubber elasticity and handling (becomes liquid when the degree of polymerization is less than 10,000), and styrene. Then, it is preferable that it is about 5,000-30,000.

  SIBS can be obtained by a living cationic polymerization method of a general vinyl compound. For example, JP-A-62-48704 and JP-A-64-62308 disclose that living cationic polymerization of isobutylene and other vinyl compounds is possible. By using isobutylene and other compounds as vinyl compounds, It is disclosed that a polyisobutylene-based block copolymer can be produced.

  Since SIBS does not have double bonds other than aromatics in the molecule, it is more stable to ultraviolet rays than a polymer having double bonds in the molecule, such as polybutadiene, and therefore has weather resistance. It is good. Furthermore, although it has no double bond in the molecule and is a saturated rubber-like polymer, the refractive index (nD) at 20 ° C. of light with a wavelength of 589 nm is the Polymer Handbook (1989: Wiley). (Polymer Handbook, Willy, 1989)) is 1.506. This is significantly higher than other saturated rubbery polymers such as ethylene-butene copolymers.

  The thickness T1 of the first layer made of SIBS is 0.05 to 0.6 mm. When the thickness of the first layer is less than 0.05 mm, the first layer is broken by pressing pressure during vulcanization of a green tire in which the polymer laminate is applied to the inner liner, and an air leak phenomenon occurs in the obtained tire. May occur. On the other hand, if the thickness of the first layer exceeds 0.6 mm, the tire weight increases and the fuel efficiency performance decreases. The thickness of the first layer is preferably 0.05 to 0.4 mm. The first layer can be obtained by forming SIBS into a film by an ordinary method of forming a thermoplastic resin or thermoplastic elastomer into a film such as extrusion molding or calendar molding.

<Second layer>
In the present invention, the second layer is also referred to as a SIS layer composed of a styrene-isoprene-styrene triblock copolymer (hereinafter also referred to as “SIS”) and a styrene-isobutylene diblock copolymer (hereinafter referred to as “SIB”). 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 T2 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 has 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 SIBS and / or SIS and SIB to laminate extrusion such as laminate extrusion or coextrusion in the order described in any one of forms 1 to 4, for example.

<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 the SIB layer PL3 and the carcass 6 can be increased in the tire vulcanizing step. The obtained pneumatic tire can have excellent air permeation resistance and durability because the inner liner and the rubber layer of the carcass ply 61 are well bonded.

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

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

With the specifications shown in Table 1 and Table 2, pneumatic tires of Examples , Reference Examples, and Comparative Examples were manufactured, and performance was evaluated. SIB, SIBS and SIS used for the first layer and the second layer were prepared as follows.

<SIB>
To a 2 L reaction vessel equipped with a stirrer, 589 mL of methylcyclohexane (dried with molecular sieves), 613 ml of n-butyl chloride (dried with molecular sieves), and 0.550 g of cumyl chloride were added. After cooling the reaction vessel to −70 ° C., 0.35 mL of α-picoline (2-methylpyridine) and 179 mL of isobutylene were added. Further, 9.4 mL of titanium tetrachloride was added to initiate polymerization, and the reaction was allowed to proceed for 2.0 hours while stirring the solution at -70 ° C. Next, 59 mL of styrene was added to the reaction vessel, and the reaction was continued for another 60 minutes, and then a large amount of methanol was added to stop the reaction. After removing the solvent and the like from the reaction solution, the polymer was dissolved in toluene and washed twice with water. The toluene solution was added to a methanol mixture to precipitate a polymer, and the obtained polymer was dried at 60 ° C. for 24 hours to obtain a styrene-isobutylene diblock copolymer.

Styrene component content: 15% by mass
Weight average molecular weight: 70,000
<SIBS>
“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.

<Manufacture of pneumatic tires>
The above SIBS, SIS and SIB were pelletized with a twin screw extruder (screw diameter: φ50 mm, L / D: 30, cylinder temperature: 220 ° C.). Thereafter, an inner liner was prepared with a T-die extruder (screw diameter: φ80 mm, L / D: 50, die lip width: 500 mm, cylinder temperature: 220 ° C., film gauge: 0.3 mm).

  A pneumatic tire is a 195 / 65R15 size tire having the basic structure shown in FIG. 1, and a raw tire is manufactured using the polymer laminate as an inner liner, and then pressed at 170 ° C. for 20 minutes in the vulcanization process. Molded and manufactured.

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

(Note 1) In Tables 1 and 2, the thickness (mm) of the air barrier layer is shown.
(Note 2) In Tables 1 and 2, the thickness (mm) of the adhesive layer is shown.
(Note 3) In Tables 1 and 2, “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.

<Comparative Examples 1, 2, 3>
The inner liners of Comparative Examples 1, 2, and 3 are composed of a laminate of an air barrier layer and an adhesive layer. A 0.8 mm thick sheet of chlorobutyl rubber (“Exon Chlorobutyl 1068” manufactured by ExxonMobil Co., Ltd.) was used as the air barrier layer. In addition, natural rubber (TSR20) was used as the adhesive layer to form a sheet having a thickness of 0.8 mm. In Tables 1 and 2, the thickness of the air barrier layer is described in parentheses in the first layer row, and the thickness of the adhesive layer is described in parentheses in the second layer row.

  Comparative Example 1 is an example in which a thick part is not formed, and Comparative Examples 2 and 3 are examples in which a thick part is formed at the shoulder position Pe using a conventional inner liner material.

< Examples 3, 5, 7, 8 and Reference Examples 1, 2, 4, 6 >
In Reference Examples 1, 2, 4, and 6, SIBS is used for the first layer and SIS is used for the second layer, and the value of Ge / Gc is changed. The value of Ge / Gc is smaller in Reference Example 1, the largest reference example 6.

  In Examples 3, 5, 7, and 8, SIBS is used for the first layer and SIB is used for the second layer, and the value of Ge / Gc is changed. Example 3 is the smallest and Example 8 is the largest. In Comparative Example 3, an air person fault is used for the first layer, an adhesive layer is used for the second layer, and the value of Ge / Gc is 500%.

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

<Low temperature durability, rolling resistance>
A rhinoceros and size 195 / 65R15 pneumatic tire was used to test low temperature durability and rolling resistance.

  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.

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

Rolling resistance index = tan δ of Comparative Example 1 / tan δ of each formulation × 100
<Performance evaluation results>
Reference examples 1, 2, 4, and 6 have configurations using SIBS for the first layer and SIS for the second layer. Low temperature durability tends to improve from Reference Example 1 where the value of Ge / Gc is the smallest, 200%, to Reference Example 6 where the value of Ge / Gc is 400%. Conversely, the rolling resistance is Reference Example 1 is the best, and Reference Example 6 is less effective.

  Examples 3, 5, 7, and 8 have a configuration using SIBS for the first layer and SIB for the second layer. Low temperature durability tends to improve from Example 3 where the value of Ge / Gc is 267%, which is the smallest, to Example 8 where the value of Ge / Gc is 500%. Example 3 is the best, and Example 8 is less effective.

It turns out that Comparative Examples 1-3 is inferior to an Example and a reference example in the balance of low temperature durability and rolling resistance.

  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 edge.

Claims (9)

A pneumatic tire having an inner liner on the inside of a carcass ply tire mounted between a pair of bead parts,
The inner liner includes (A) a first layer having a thickness of 0.05 mm to 0.6 mm made of a styrene-isobutylene-styrene triblock copolymer, and (B) a styrene-isobutylene diblock copolymer, or , A polymer laminate comprising a styrene-isobutylene diblock copolymer and a styrene-isoprene-styrene triblock copolymer , and a second layer having a thickness of 0.01 mm to 0.3 mm, A pneumatic tire characterized in that two layers are disposed so as to contact a rubber layer of a carcass ply, and 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.   The pneumatic tire according to claim 1 or 2, wherein a thick portion of the inner liner is formed in a region having a width of at least 50% or less of the shoulder width Wc from the shoulder position Pe to the crown center position Pc side. . 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 position Ps side, the side distance pneumatic tire according to claim 1, which is formed in a region having at least 20% of the width of Ws. The thick portion of the inner liner, the shoulder from a position Pe to the maximum width position Ps side, any one of the widest distance claim is formed in a region having 100% or less of the width of Ws 1 to 3 The pneumatic tire according to item . The inner liner to a thickness Gc at the crown center position Pc, the pneumatic tire according to any one of claims 1 to 5 thick Ge shoulder position Pe is 120% to 500%. The styrene - isobutylene - styrene pneumatic tire according to any one of claims 1 to 6 triblock copolymer styrene component content of 10 to 30 mass%. The styrene - isoprene - styrene tri-block copolymer, the pneumatic tire according to any one of claims 1 to 7 styrene component content of 10 to 30 mass%. The styrene - isobutylene diblock copolymer is linear, pneumatic tire according to any one of claims 1 to 7 styrene component content of 10 to 35 wt%.

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