JP5342683B1 - Pneumatic tire - Google Patents

Abstract

Provided is a pneumatic tire provided with an inner liner having excellent air permeation resistance and good adhesion to an adjacent rubber.
A pneumatic tire 1 including an inner liner 9 inside a tire of a carcass ply 6, wherein the inner liner includes a first polymer composition including a styrene-isobutylene-styrene triblock copolymer. And a second layer comprising a second polymer composition comprising at least one of a styrene-isoprene-styrene triblock copolymer and a styrene-isobutylene diblock copolymer, at least one of which is an epoxidized styrene -A butadiene-styrene triblock copolymer is contained in an amount of 0.5 mass% to 40 mass%, and the inner liner has a thickness Ge at the shoulder position Pe larger than a thickness Gc at the crown central position Pc, and the thickness Ge is 0. .2 mm or more and 1.9 mm or less.
[Selection] Figure 1

Description

  The present invention relates to a pneumatic tire provided with an inner liner.

  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 butyl 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 have low fuel consumption, and there is a problem of reducing rolling resistance by reducing the weight of the tire. For this reason, a technology that uses a thermoplastic elastomer for the inner liner has also been proposed, but if the thickness is made thinner than the inner liner of the butyl rubber, the strength of the inner liner decreases, and the heat and pressure of the bladder during the vulcanization process There was a problem that the inner liner was broken or deformed.

  Furthermore, it has been found that a thermoplastic elastomer having high air permeation resistance is inferior to a butyl rubber in vulcanization adhesion with an insulation rubber or a carcass rubber adjacent to the inner liner. If the vulcanization adhesive strength of the inner liner is low, air is mixed between the inner liner and the insulation rubber or the carcass rubber, and a so-called air-in phenomenon occurs in which a small balloon appears. The presence or absence of air-in does not affect the performance of the tire, but gives the user the impression that the appearance is poor.

  Patent Document 1 (Japanese Patent Application Laid-Open No. 9-019987) discloses a polyamide-based resin and a polyester-based resin as a laminate suitable for a pneumatic tire having an air permeation preventive layer such as an inner liner layer that keeps air pressure constant. At least one gas barrier layer (A) selected from the group consisting of a polyarylate-based resin, a polyamide-based alloy and a polyester-based alloy and an adhesive layer (B) are laminated in at least two layers, and at least one of them A laminated body of a laminated film and a rubber layer, which is provided with a laminated film irradiated with an electron beam from the surface and in which the adhesive layer (B) is heat bonded to the rubber layer (R), is disclosed.

  The laminate has a problem that the adhesive layer comes into contact with the bladder in the vulcanization process in a heated state, and sticks to the bladder.

  In Patent Document 2 (Japanese Patent No. 2999188), as a thermoplastic elastomer composition having air permeation resistance, the elastomer composition (A) is a dispersed phase, the thermoplastic resin composition (B) is a matrix, and A thermoplastic elastomer composition is disclosed in which the thermoplastic resin composition is a blend of two or more thermoplastic resins. In the examples, nylon resin is used as the thermoplastic resin composition, but nylon resin is hard at room temperature and unsuitable as an inner liner for tires. Furthermore, the thermoplastic elastomer composition does not vulcanize and adhere to the rubber layer. Therefore, when the thermoplastic elastomer is used for the inner liner, an adhesive layer for vulcanization is further required, which is disadvantageous from the viewpoint of productivity.

  In prior art document 3 (Japanese Patent Laid-Open No. 2008-024219), maleic anhydride-modified hydrogenated styrene-ethylene-butadiene-styrene block copolymer is dispersed in an ethylene-vinyl alcohol copolymer having good air barrier properties. A flexible gas barrier layer is also disclosed. Also disclosed is an inner liner layer produced by sandwiching the gas barrier layer with a thermoplastic polyurethane layer and further applying rubber glue (70/30 of butyl rubber / natural rubber is dissolved in toluene) on the surface to be bonded to the tire rubber. ing.

  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. Further, 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 bending fatigue properties 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 manufacturing process is required, resulting in poor productivity.

  Prior document 4 (Japanese Patent Laid-Open No. 2005-343379) discloses an inner liner designed so that the thickness at the shoulder portion is larger than the thickness at the tire crown portion in order to effectively suppress the occurrence of cracks in the inner liner layer. A layer is disclosed. However, when the thickness dimension is increased, the weight increases, which causes a problem from the viewpoint of reducing the fuel consumption of the tire.

JP-A-9-019987 Japanese Patent No. 2999188 JP 2008-024219 A JP 2005-343379 A

  The present invention provides a pneumatic tire provided with an inner liner having excellent air permeation resistance and good adhesion to an adjacent rubber, and a pneumatic tire with reduced rolling resistance and excellent low-temperature durability. For the purpose.

  The present invention relates to a pneumatic tire having an inner liner on the inner side of a carcass ply tire mounted between a pair of bead portions, the inner liner comprising a polymer laminate, and the polymer laminate is a styrene-isobutylene. A first layer having a thickness of 0.05 mm or more and 0.8 mm or less comprising a first polymer composition containing a styrene triblock copolymer, a styrene-isoprene-styrene triblock copolymer and a styrene-isobutylene diblock copolymer A second layer having a thickness of 0.01 mm or more and 0.8 mm or less comprising a second polymer composition containing at least one of the coalesced, and at least one of the first polymer composition and the second polymer composition is an epoxy Containing 0.5% by mass or more and 40% by mass or less of a modified styrene-butadiene-styrene triblock copolymer The second layer is disposed so as to be in contact with the rubber layer of the carcass ply, and the inner liner has a thickness Ge at the shoulder position Pe larger than a thickness Gc at the crown center position Pc, and the thickness Ge is 0.2 mm or more. It is 1.9 mm or less.

  In the pneumatic tire of the present invention, in the tire meridional section, the normal line L is drawn from the ground contact end Te of the tread portion toward the inner diameter of the tire with respect to the boundary line between the carcass ply and the inner liner, and the intersection point with the boundary line is defined as the shoulder position Pe. The intersection of the boundary line between 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 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 side.

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

  In the pneumatic tire of the present invention, when the distance along the contour of the inner liner from the shoulder position Pe of the inner liner to the tire maximum width position Ps is a side distance Ws, the thick part of the inner liner is the shoulder position Pe. Is preferably formed in a region having a width of at least 20% of the side distance Ws on the side of the maximum width position Ps.

  In the pneumatic tire of the present invention, the thick part of the inner liner is preferably formed in a region having a width of 100% or less of the side distance Ws from the shoulder position Pe to the tire maximum width position Ps side.

  In the pneumatic tire of the present invention, the inner liner preferably has a thickness Ge at the shoulder position Pe of 120% or more and 500% or less with respect to the thickness Gc at the crown center position Pc.

  In the pneumatic tire of the present invention, the styrene-isobutylene-styrene triblock copolymer has a styrene component content of 10% by mass to 30% by mass and a weight average molecular weight of 50,000 to 400,000. preferable.

  In the pneumatic tire of the present invention, the epoxidized styrene-butadiene-styrene triblock copolymer has a weight average molecular weight of 10,000 to 400,000 and a styrene component content of 10% by mass to 30% by mass. The epoxy equivalent is preferably 50 or more and 1,000 or less.

  According to the present invention, a pneumatic tire provided with an inner liner having excellent air permeation resistance and good adhesion to an adjacent rubber, and a pneumatic tire with reduced rolling resistance and excellent low-temperature durability. Can be obtained.

It is a schematic sectional drawing of the right half of the pneumatic tire in one embodiment of the present 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 in one embodiment of the present invention.

<Pneumatic tire>
A pneumatic tire according to an embodiment of 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 FIG. 1, a pneumatic tire 1 includes 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.

<Tire maximum width position Ps>
When the tire is filled with the specified internal pressure and the standard rim is mounted, 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 is defined as the tire maximum width position Ps. To do.

<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 side. 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. Furthermore, the thick portion is preferably formed in a region having a width of at least 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 relieve the stress in this region. Can be achieved. Furthermore, it is preferable that the thick part is formed in a 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 larger than a thickness Gc at the crown center position Pc. For this reason, the durability of the inner liner at the shoulder portion is improved, and it is possible to suppress tearing and deformation due to a decrease in strength of the inner liner, and a decrease in adhesive force, and as a result, it is possible to effectively suppress tire air leakage. it can.

  The thickness Ge of the shoulder position Pe is not less than 0.2 mm and not more than 1.9 mm. When Ge is less than 0.2 mm, tearing and deformation are likely to occur during tire travel. When Ge exceeds 1.9 mm, the effect of reducing the weight of the inner liner cannot be obtained sufficiently. Ge is preferably 0.3 mm or more and 1.9 mm or less.

  The thickness Ge of the shoulder position Pe is preferably 120% or more and 500% or less with respect to the thickness Gc at the crown center position Pc. 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 thickness Ge of the shoulder position Pe is more preferably 200% or more and 500% or less with respect to the thickness Gc at the crown center position Pc.

  The thickness Ge of the shoulder position Pe is preferably 120% or more and 500% or less with respect to the thickness Gs of the maximum width position Ps.

  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>
In one embodiment of the present invention, the polymer laminate used for the inner liner is formed of at least two polymer laminates. The first layer is made of a first polymer composition containing a styrene-isobutylene-styrene triblock copolymer (hereinafter also referred to as SIBS), and has a thickness of 0.05 mm or more and 0.8 mm or less. The second layer includes a second polymer composition containing 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 thickness is 0.01 mm or more and 0.8 mm or less. At least one of the first polymer composition and the second polymer composition includes an epoxidized styrene-butadiene-styrene triblock copolymer.

<First layer>
In one embodiment of the invention, the first layer comprises a first polymer composition comprising a styrene-isobutylene-styrene triblock copolymer (SIBS). Due to the isobutylene block of SIBS, the polymer film containing SIBS has excellent air permeation resistance. Therefore, when a polymer film containing 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 containing 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 or more and 400,000 or less from the viewpoint of fluidity, molding process, rubber elasticity, and the like. If the weight average molecular weight is less than 50,000, the tensile strength and 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 content of the styrene component in SIBS of 10% by mass to 30% by mass, preferably 14% by mass 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 content of SIBS in the first polymer composition is preferably 60% by mass or more and 100% by mass or less. If the SIBS content is less than 60% by mass, sufficient air permeation resistance cannot be obtained. The content of SIBS is more preferably 80% by mass or more and 99.5% by mass or less.

  The first polymer composition may further include an epoxidized styrene-butadiene-styrene triblock copolymer (hereinafter also referred to as epoxidized SBS).

  Epoxidized SBS is a thermoplastic elastomer in which a hard segment is a polystyrene block and a soft segment is a butadiene block, and an unsaturated double bond portion contained in the butadiene block is epoxidized.

  Since the epoxidized SBS has a styrene block, the epoxidized SBS is excellent in melt adhesion with the second layer containing SIS and SIB having the styrene block. Therefore, when the first layer containing epoxidized SBS and the second layer containing SIS or SIB are arranged adjacent to each other and vulcanized, a polymer laminate in which the first layer and the second layer are well bonded is obtained. Can do.

  The molecular weight of the epoxidized SBS is not particularly limited, but from the viewpoint of rubber elasticity and moldability, the weight average molecular weight by GPC method is preferably 10,000 or more and 400,000 or less. If the weight average molecular weight is less than 10,000, the size may be too soft and the dimensions may not be stable, and if it exceeds 400,000, it may be too hard to extrude thinly, which is not preferable.

  The content of the styrene component in the epoxidized SBS is preferably 10% by mass or more and 30% by mass or less from the viewpoints of tackiness, adhesiveness, and rubber elasticity.

The epoxidized SBS preferably has a molar ratio of butadiene units to styrene units (butadiene units / styrene units) of 90/10 to 70/30. In the epoxidized SBS, the degree of polymerization of each block is preferably about 500 to 5,000 for a butadiene block and about 50 to 1,500 for a styrene block from the viewpoint of rubber elasticity and handling.

  The epoxy equivalent of the epoxidized SBS is preferably from 50 to 1,000 from the viewpoint of adhesiveness.

  The content of epoxidized SBS in the first polymer composition can be 0.5 mass% or more and 40 mass% or less. If the content of epoxidized SBS is less than 0.5% by mass, sufficient adhesive force cannot be obtained. On the other hand, if it exceeds 40% by mass, productivity is greatly deteriorated due to over-adhesion, which is not preferable. The content of epoxidized SBS is more preferably 5% by mass or more and 30% by mass or less.

  The thickness of the 1st layer containing SIBS is 0.05 mm or more and 0.8 mm or less. The thickness of the first layer means the average thickness of the first layer. 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 0.8 mm, the tire weight increases, and the fuel efficiency performance decreases. The thickness of the first layer is preferably 0.05 mm or more and 0.4 mm or less.

  The first layer can be obtained by forming the first polymer composition containing SIBS into a film by an ordinary method of forming a thermoplastic resin or a thermoplastic elastomer into a film such as extrusion molding or calendar molding.

<Second layer>
In one embodiment of the invention, the second layer is from a second polymer composition comprising at least one of a styrene-isoprene-styrene triblock copolymer (SIS) and a styrene-isobutylene diblock copolymer (SIB). Become.

  Since the isoprene block of the styrene-isoprene-styrene triblock copolymer (SIS) is a soft segment, the polymer film containing SIS is easily vulcanized and bonded to the rubber component. Therefore, when a polymer film containing 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.

  The degree of polymerization of each block in the 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.

  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 containing SIB is used for the inner liner, the inner liner is excellent in adhesiveness with an adjacent rubber forming a carcass or 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 second polymer composition may further include an epoxidized styrene-butadiene-styrene triblock copolymer (also referred to as epoxidized SBS).

The epoxidized SBS can be the same as the first polymer composition.
Epoxidized SBS has a soft segment composed of a butadiene block, and thus is easily vulcanized and bonded to a rubber component. Therefore, when the second layer containing the epoxidized SBS is disposed and vulcanized adjacent to a rubber layer forming, for example, carcass or insulation, the second layer and the rubber layer can be bonded well. Therefore, when a polymer laminate including an epoxidized SBS layer is used for the inner liner, adhesion between the polymer laminate and the adjacent rubber layer can be improved.

  The thickness T2 of the second layer can be 0.01 mm or more and 0.8 mm or less. The thickness of the second layer means the average thickness of the second 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 0.8 mm, the tire weight increases and the fuel efficiency performance decreases. The thickness of the second layer is preferably 0.05 mm or more and 0.2 mm or less.

  The second layer can be obtained by forming the second polymer composition into a film by an ordinary method of forming a thermoplastic resin or a thermoplastic elastomer into a film such as extrusion molding or calendar molding.

<Position of polymer laminate>
As shown in FIG. 3, the polymer laminate PL is composed of a first layer PL1 and a second layer PL2. When the polymer laminate PL is applied to an inner liner of a pneumatic tire, if the second layer PL2 is disposed so as to contact the carcass ply 61 toward the outer side in the tire radial direction, the second layer PL2 is used in the tire vulcanization process. The adhesion strength between 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.

<Method for producing polymer laminate>
The polymer laminate in one embodiment of the present invention can be produced, for example, by the following method. The first layer and the second layer are produced by extrusion molding or calendar molding. The first layer and the second layer are bonded together to produce a polymer laminate. Moreover, each pellet of the first polymer composition and the second polymer composition can also be produced by laminate extrusion such as laminate extrusion or coextrusion.

<Pneumatic tire manufacturing method>
The pneumatic tire in one embodiment of the present invention can be manufactured, for example, by the following method.

  A green tire is produced by applying the polymer laminate of the present invention to the inner liner portion. The polymer laminate is disposed with the second layer facing outward in the tire radial direction so as to contact the carcass and insulation. With this arrangement, the second layer and the adjacent rubber layer such as carcass or insulation can be vulcanized and bonded in the tire vulcanization step. Therefore, in the obtained pneumatic tire, since the inner liner is well bonded to the adjacent rubber layer, it can have excellent air permeation resistance and durability.

  Regarding the thickness of the inner liner, 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 are the conditions when extruding the first layer and the second layer ( The desired thickness can be obtained by adjusting the extrusion speed and the number of revolutions of extrusion).

  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.

  Next, the green tire is mounted on a mold and heated while being pressurized at 150 to 180 ° C. for 3 to 50 minutes with a bladder to obtain a vulcanized tire. Next, it is preferable to cool the obtained vulcanized tire at 50 to 120 ° C. for 10 to 300 seconds.

  A pneumatic tire uses a polymer laminate as an inner liner. Since SIBS, SIS, SIB and epoxidized SBS constituting the polymer laminate are thermoplastic elastomers, when heated to, for example, 150 to 180 ° C. in the step of obtaining a vulcanized tire, Become. Since the thermoplastic elastomer in the softened state is more reactive than the solid state, it is fused to the adjacent member. That is, the inner liner in contact with the outer surface of the expanded bladder is softened by heating and fused to the bladder. If an attempt is made to remove the vulcanized tire from the mold while the inner liner and the outer surface of the bladder are fused, the inner liner peels off from the adjacent insulation or carcass, resulting in an air-in phenomenon. In addition, the tire shape itself may be deformed.

  Therefore, the thermoplastic elastomer used for the inner liner can be solidified by immediately cooling the obtained vulcanized tire at 120 ° C. or lower for 10 seconds or longer. When the thermoplastic elastomer is solidified, the fusion between the inner liner and the bladder is eliminated, and the releasability when the vulcanized tire is taken out from the mold is improved.

  The cooling temperature is preferably 50 to 120 ° C. When the cooling temperature is lower than 50 ° C., it is necessary to prepare a special cooling medium, which may deteriorate productivity. When the cooling temperature exceeds 120 ° C., the thermoplastic elastomer is not sufficiently cooled, and the inner liner remains fused to the bladder when the mold is opened, which may cause an air-in phenomenon. The cooling temperature is more preferably 70 to 100 ° C.

  The cooling time is preferably 10 to 300 seconds. If the cooling time is shorter than 10 seconds, the thermoplastic elastomer is not sufficiently cooled, and the inner liner remains fused to the bladder when the mold is opened, which may cause an air-in phenomenon. When the cooling time exceeds 300 seconds, the productivity is deteriorated. The cooling time is more preferably 30 to 180 seconds.

  The step of cooling the vulcanized tire is preferably performed by cooling the inside of the bladder. Since the inside of the bladder is hollow, a cooling medium adjusted to the cooling temperature can be introduced into the bladder after the vulcanization process is completed.

  The process of cooling the vulcanized tire can be performed by cooling the inside of the bladder and installing a cooling structure in the mold.

  As the cooling medium, it is preferable to use one or more selected from the group consisting of air, water vapor, water, and oil. Among these, it is preferable to use water that is excellent in cooling efficiency.

<Production of polymer laminate>
With the specifications shown in Tables 1 to 3, polymer laminates of Examples and Comparative Examples were produced, and performance was evaluated. SIB, SIBS, SIS, and epoxidized SBS 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.

  In Example 23, SIBS having a weight average molecular weight of 200,000 was used, and in Example 24, SIBS having a weight average molecular weight of 300,000 was used.

(SIS)
D1161JP (styrene component content 15 mass%, weight average molecular weight: 150,000) manufactured by Kraton Polymer Co., Ltd. was used.

(Epoxidized SBS)
“Epofriend A1020” (epoxidized styrene-butadiene-styrene triblock copolymer, weight average molecular weight 100,000, styrene component content 40 mass%, epoxy equivalent 500) manufactured by Daicel Chemical Industries, Ltd. was prepared. .

  Each of the raw materials of the first layer and the second layer was pelletized with a twin screw extruder (screw diameter: φ50 mm, L / D: 30, cylinder temperature: 220 ° C.). The obtained pellets were co-extruded using a T-die extruder (screw diameter: φ80 mm, L / D: 50, die grip width: 500 mm, cylinder temperature: 220 ° C.), and the thicknesses shown in Tables 1 to 3 were used. A polymer laminate having the first and second layers was prepared. As Comparative Example 1, a polymer sheet consisting of only the first layer was prepared.

<Production of pneumatic tire>
In order to adjust the thickness Ge of the shoulder position Pe of the inner liner and the thickness Gc of the crown center position Pc, a polymer layer is formed by attaching a profile to the extrusion port of the polymer sheet and reducing the thickness Gc of the crown center position Pc. The body was made. The obtained polymer laminate was applied to the inner liner portion of the tire to prepare a raw tire. This was disposed on the inner surface of the tire as an inner liner. The polymer laminate was arranged such that the first layer of the polymer laminate was disposed on the innermost side in the radial direction of the green tire, and the second layer was in contact with the carcass layer of the green tire. The green tire was press-molded in a mold at 170 ° C. for 20 minutes to produce a 195 / 65R15 size vulcanized tire.

  After the vulcanized tire was cooled at 100 ° C. for 3 minutes, the vulcanized tire was taken out of the mold to obtain a pneumatic tire.

The following evaluation was performed about the polymer laminated body and the pneumatic tire.
<Adhesiveness>
A peel test was conducted according to JIS K 6256 “Vulcanized Rubber and Thermoplastic Rubber—How to Determine Adhesiveness”. First, a polymer laminate and a rubber sheet (formulation: NR / BR / SBR = 40/30/30) are bonded and vulcanized so that the second layer of the polymer laminate is in contact with the rubber sheet, and then a peeling test. A piece was made. A peel test was performed using the obtained test piece, and the adhesion between the polymer laminate and the rubber sheet was measured. The size of the test piece was 25 mm wide, and it was performed under a room temperature condition of 23 ° C. The adhesion index was calculated by the following calculation formula using the obtained numerical value as a reference (100) as a reference. The larger the value, the better the adhesion.

(Adhesiveness index) = (Adhesive strength of each polymer laminate) / (Adhesive strength of Comparative Example 1) × 100
<Rolling resistance>
For rolling resistance, tan δ of each polymer laminate was measured using a viscoelastic spectrometer VES (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 higher the index, the lower the rolling resistance.

(Rolling resistance index) = (tan δ of Comparative Example 1) / (tan δ of each polymer laminate) × 100
<Low temperature durability>
Low temperature durability was measured in terms of atmospheric temperature -20 ° C, tire pressure 120 kPa, load rate 60%, speed 80 Km / h, and the distance traveled when a crack occurred in the inner liner was measured. Based on the distance, it was displayed as an index according to the following formula. The larger the value, the better the low temperature durability.

(Low temperature durability index) = (travel distance of each pneumatic tire) / (travel distance of Comparative Example 1) × 100
<Static air pressure reduction rate>
The pneumatic tire was assembled into a JIS standard rim 15 × 6 JJ, sealed with an initial air pressure of 300 Kpa, left at room temperature for 90 days, and the rate of decrease in air pressure was calculated.

<With or without air-in>
The inside of the vulcanized tire was visually inspected and evaluated according to the following criteria.

A: The number of air-ins is zero.
B: The number of air-ins having a diameter of 5 mm or less is 1 to 3.

  C: The number of air-ins having a diameter of 5 mm or less is 4 or more, or the number of air-ins having a diameter of 5 mm or more is 1 or more.

  The results are shown in Tables 1 to 3.

  (* 1) In the uneven thickness range (CL (%) / SW (%)), CL (%) and SW (%) indicate the following.

CL (%) = distance from shoulder position Pe of thick part to crown center position Pc / shoulder distance Wc × 100
SW (%) = distance from shoulder position Pe of thick part to maximum width position Ps side / side distance Ws × 100
<Evaluation results>
Comparative Example 1 is a polymer sheet made of SIBS and used as a reference.

  In Examples 1 to 3 and 10 to 24, the first layer includes SIBS and epoxidized SBS. While having air permeation resistance equivalent to that of Comparative Example 1, adhesion and low temperature durability were improved, and rolling resistance was reduced.

  In Examples 4 to 6, the second layer includes SIS and epoxidized SBS. While having air permeation resistance equivalent to that of Comparative Example 1, adhesion and low temperature durability were improved, and rolling resistance was reduced.

  In Examples 7 to 9, the second layer includes SIB and epoxidized SBS. While having air permeation resistance equivalent to that of Comparative Example 1, adhesion and low temperature durability were improved, and rolling resistance was reduced.

  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.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  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 1st layer, PL2 2nd Layer, Pe shoulder position, Pc crown center position, Ps tire maximum width position, ground contact edge of Te tread portion, Wc shoulder distance, Ws side distance.

Claims (8)

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 made of a polymer laminate,
The polymer laminate is a first layer having a thickness of 0.05 mm or more and 0.8 mm or less comprising a first polymer composition containing a styrene-isobutylene-styrene triblock copolymer;
A second layer having a thickness of 0.01 mm or more and 0.8 mm or less, comprising a second polymer composition containing at least one of a styrene-isoprene-styrene triblock copolymer and a styrene-isobutylene diblock block copolymer,
At least one of the first polymer composition and the second polymer composition contains 0.5% by mass or more and 40% by mass or less of an epoxidized styrene-butadiene-styrene triblock copolymer,
The second layer is disposed in contact with the rubber layer of the carcass ply;
The inner liner has a thickness Ge at the shoulder position Pe larger than a thickness Gc at the crown central position Pc.
The thickness Ge is 0.2 mm or more and 1.9 mm or less,
Pneumatic tire. 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 a 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. The intersection of the boundary line between the inner liner and the tire center line CL is a crown center position Pc, and the distance along the contour line of the inner liner from the shoulder position Pe to the crown center position Pc is a shoulder distance Wc. When
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 the thick portion of the inner liner is formed in a region having a width of at least 50% 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 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 portion of the inner liner is formed in a region having a width of 100% or less of the side distance Ws from the shoulder position Pe to the maximum tire 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 120% or more and 500% or less with respect to a thickness Gc at a crown center position Pc.   The styrene-isobutylene-styrene triblock copolymer has a styrene component content of 10% by mass or more and 30% by mass or less, and a weight average molecular weight of 50,000 or more and 400,000 or less. The described pneumatic tire.   The epoxidized styrene-butadiene-styrene triblock copolymer has a weight average molecular weight of 10,000 to 400,000, a styrene component content of 10% by mass to 30% by mass, and an epoxy equivalent of 50 or more. The pneumatic tire according to any one of claims 1 to 7, which is 1,000 or less.

Images