JP5809118B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire including an inner liner excellent in adhesiveness and air permeation resistance.

  The inner liner is disposed inside the tire and has a function of reducing the amount of air leakage from the inside of the pneumatic tire to the outside (decreasing air pressure) and improving air permeation resistance. In recent years, tires have been reduced in weight due to a strong social demand for lower fuel consumption of vehicles, and the inner liner has also been reduced in weight.

  At present, the rubber composition for the inner liner uses, for example, a rubber compound mainly composed of butyl rubber (hereinafter also referred to as butyl rubber) including 70 to 100% by mass of butyl rubber and 30 to 0% by mass of natural rubber. The air permeability of tires has been improved. In addition to butylene, the butyl rubber contains about 1% by mass of isoprene, which is combined with sulfur, a vulcanization accelerator, and zinc white to enable crosslinking between rubber molecules. When an inner liner is produced using butyl rubber, a thickness of about 0.6 to 1.0 mm is required for passenger car tires, and a thickness of about 1.0 to 2.0 mm is required for truck and bus tires. In order to reduce the weight of a tire, there is a demand for a polymer that has better air permeation resistance than butyl rubber and that can reduce the thickness of the inner liner layer.

  In order to reduce the weight of the tire, a material containing a thermoplastic resin instead of butyl rubber has been proposed as a composition for the inner liner. However, when a tire is manufactured using an inner liner made of a material containing a thermoplastic resin, the inner liner becomes partly too thin due to the pressure in the vulcanization process. Then, the finished gauge of the inner liner in the tire becomes thinner than the design. When the inner liner is thin, the carcass cord appears to be raised (open thread), which gives the user an impression that the appearance is poor. Furthermore, if the inner liner is thin, the air permeation resistance partially deteriorates, the tire internal pressure decreases, and in the worst case, the tire may burst.

  Further, a large shear strain acts near the shoulder portion of the inner liner while the vehicle is running. When a film containing a thermoplastic resin is used for the inner liner, there has been a problem that peeling due to shear strain is likely to occur at the adhesive interface between the inner liner and the carcass ply, resulting in tire air leakage.

  In order to reduce the weight of the inner liner, a technique using a material containing a thermoplastic elastomer has also been proposed. However, the inner liner made of butyl rubber is thinner than the inner liner made of butyl rubber and has a high air permeation resistance. Is known to be inferior to

  When the vulcanization adhesive strength of the inner liner is small, air is mixed between the inner liner and the insulation rubber or the carcass ply rubber, and an air-in phenomenon appears in which a small balloon appears. Many small spots on the inside of the tire give the user the impression that the appearance is poor. Furthermore, when the vehicle is running, air is the starting point, causing the inner liner and the insulation rubber or carcass ply rubber to peel off, causing cracks in the inner liner and lowering the tire internal pressure, and in the worst case, the tire bursts. There is a risk that.

  Patent Document 1 (Japanese Patent Application Laid-Open No. 2007-291256) includes natural rubber and / or synthetic rubber as a pneumatic tire capable of simultaneously suppressing air pressure reduction, improving durability, and improving fuel efficiency. The following general formula (I) with respect to 100 parts by mass of the rubber component:

  (Wherein m and n are each independently 1 to 100 and x is 1 to 1000). The ethylene-vinyl alcohol copolymer represented by the formula is at least within a range of 15 to 30 parts by mass. There has been proposed a pneumatic tire using the contained rubber composition for an inner liner as an inner liner layer. However, in the technique of Patent Document 1, the thickness of the rubber sheet using the rubber composition is 1 mm, and there is room for improvement in terms of weight reduction of the tire.

  Patent Document 2 (Japanese Patent Laid-Open No. 9-165469) discloses that an inner liner layer is formed using nylon having a low air permeability to improve adhesion to a tire inner surface or a carcass layer that is a rubber composition. Possible pneumatic tires have been proposed. However, in the technique of Patent Document 2, in order to form a nylon film layer, after the nylon film is RFL-treated, it is necessary to bond a rubber paste made of a rubber composition, which causes a problem that the process becomes complicated. .

  Patent Document 3 (Japanese Patent Application Laid-Open No. 2010-13646) proposes to improve adhesion by using petroleum resin or terpene resin as a tackifier for SIBS, which is a thermoplastic elastomer. However, in addition to SIBS, a polyamide-based polymer is blended, and there is a problem that bending crack resistance is lowered.

  In Patent Document 4 (Japanese Patent Laid-Open No. 2010-1000067), natural rosin, terpene, chroman indene resin, petroleum resin or alkylphenol resin is used as a tackifier for a blend of SIBS and a sulfur crosslinkable polymer. Thus, it has been proposed to improve the adhesion of the carcass ply rubber.

  However, in the technology of blending 10 to 300 parts by weight of a polymer capable of sulfur vulcanization with respect to 100 parts by weight of SIBS, when the sulfur crosslinkable polymer is 100 parts by weight or less, SIBS is a matrix (sea part), The sulfur-crosslinkable polymer has a domain structure (island portion), and the adhesive force at the contact interface with the carcass rubber is not improved. In addition, when the sulfur crosslinkable polymer is 100 parts by weight or more, gas barrier properties are reduced except for butyl rubber, adhesive strength is reduced with butyl rubber, and depending on the polymer to be blended, the adhesion becomes high and the thickness is 600 μm or less. There is a problem that a film cannot be produced.

  Patent Document 5 (International Publication No. 2008/029781) manufactures a tire with a strip of a film laminate obtained by blending a thermoplastic resin and a thermoplastic elastomer. By using a laminate, gas barrier properties and adhesiveness can be improved, and bonding between ribbon-like strips is possible. However, with this technique, the gauge at the unvulcanized green cover of the film laminate is constant, and if the gauge is thinned, the tire finish after vulcanization at the buttress portion or the like may be thinned.

JP 2007-291256 A JP-A-9-165469 JP 2010-13646 A JP 2010-1000067 A International Publication No. 2008/029781

  An object of the present invention is to provide a pneumatic tire having an inner liner excellent in adhesion to an adjacent rubber and excellent in air permeation resistance and bending crack growth resistance.

  The present invention is a pneumatic tire provided with an inner liner inside a carcass ply tire mounted between a pair of bead portions, the inner liner having a first layer made of a first polymer composition. The first polymer composition comprises liquid polyisoprene, a maleic anhydride adduct of liquid polyisoprene and a maleic acid monomethyl ester adduct of liquid polyisoprene with respect to 100 parts by mass of the styrene-isobutylene-styrene triblock copolymer. 0.5 parts by mass or more and 70 parts by mass or less of at least one selected from the group consisting 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 portions, wherein the inner liner includes a first layer and a second layer made of a first polymer composition. The first polymer composition has a liquid polyisoprene, a maleic anhydride adduct of liquid polyisoprene, and 100 parts by mass of a styrene-isobutylene-styrene triblock copolymer. 0.5 parts by mass or more and 35 parts by mass or less of at least one selected from the group consisting of maleic acid monomethyl ester adducts of liquid polyisoprene, and the second polymer composition is a styrene-isobutylene-styrene triblock in the polymer component The copolymer is contained in an amount of 10 to 80% by mass, and the second layer is in contact with the carcass ply. It is arranged like.

  In the pneumatic tire of the present invention, the second polymer composition preferably contains at least one of a styrene-isoprene-styrene triblock copolymer and a styrene-isobutylene diblock copolymer.

  In the pneumatic tire of the present invention, it is preferable that the thickness of the first layer is 0.05 mm or more and 0.6 mm or less, and the thickness of the second layer is 0.01 mm or more and 0.3 mm or less.

  In the pneumatic tire of the present invention, the maleic acid monomethyl ester adduct of liquid polyisoprene has an amount of maleic acid monomethyl ester in one molecule of 1% by mass to 10% by mass and a weight average molecular weight of 5,000 or more. It is preferably 50,000 or less.

  In the pneumatic tire of the present invention, the maleic anhydride adduct of liquid polyisoprene has an amount of maleic anhydride in one molecule of 1% by mass to 10% by mass and a weight average molecular weight of 5,000 to 50, 000 or less is preferable.

  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. It is preferable.

  In the pneumatic tire of the present invention, the styrene-isoprene-styrene triblock copolymer has a styrene component content of 10% by mass to 30% by mass and a weight average molecular weight of 100,000 to 290,000. It is preferable.

  In the pneumatic tire of the present invention, the styrene-isobutylene diblock copolymer is linear, the styrene component content is 10% by mass to 35% by mass, and the weight average molecular weight is 40,000 to 120, 000 or less is preferable.

  According to the present invention, it is possible to obtain a pneumatic tire including an inner liner excellent in adhesiveness with an adjacent rubber and excellent in air permeation resistance and bending crack growth resistance.

It is a schematic sectional drawing of the right half of the pneumatic tire in one embodiment of the present invention. It is a schematic sectional drawing which shows the arrangement | positioning state of the inner liner and carcass in one embodiment of this invention. It is a schematic sectional drawing which shows the arrangement | positioning state of the inner liner and carcass in one embodiment of this invention.

[Embodiment 1]
<Pneumatic tire structure>
A structure of a pneumatic tire according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view of the right half of a pneumatic tire. The 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. In addition, a carcass ply 6 provided from one bead portion 4 to the other bead portion, with both ends wound around the bead core 5 and locked, 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. The pneumatic tire 1 uses an inner liner described below as the inner liner 9.

<Inner liner consisting of the first layer>
In one embodiment of the present invention, the inner liner is composed of a first layer made of the first polymer composition.

(First layer)
The first polymer composition used in the first layer is a liquid polyisoprene (hereinafter also referred to as “LIR”) with respect to 100 parts by mass of a styrene-isobutylene / styrene triblock copolymer (hereinafter also referred to as “SIBS”). ), A maleic acid monomethyl ester adduct of liquid polyisoprene (hereinafter also referred to as “maleic acid-modified LIR”), and a maleic anhydride adduct of liquid polyisoprene (hereinafter also referred to as “maleic anhydride-modified LIR”). 0.5 parts by mass or more and 70 parts by mass or less are included.

(Styrene-isobutylene-styrene triblock copolymer)
Due to the isobutylene block of SIBS, the polymer composition containing SIBS has excellent air permeation resistance. Therefore, when a polymer composition containing SIBS is used for the inner liner, a pneumatic tire excellent in 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 composition 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 composition containing SIBS to an inner liner, air permeation resistance can be secured. Therefore, it is not necessary to use a halogenated rubber having a high specific gravity, which has been used for imparting air permeation resistance, such as a halogenated butyl rubber, and the amount used can be reduced even when used. This can reduce the weight of the tire and improve fuel efficiency.

  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 tensile elongation may be lowered, and if it exceeds 400,000, the fluidity and moldability may be deteriorated.

  From the viewpoint of making the air permeation resistance and durability better, the content of the styrene component in SIBS is preferably 10% by mass to 30% by mass, and more preferably 14% by mass 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.

  The SIBS preferably has a molar ratio of isobutylene component to styrene component (isobutylene component / styrene component) of 40/60 to 95/5 from the viewpoint of rubber elasticity of the copolymer.

  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.

(Liquid polyisoprene)
In one embodiment of the present invention, the first polymer composition can include liquid polyisoprene. Liquid polyisoprene is represented by the following formula (II).

  Liquid polyisoprene has the property of being excellent in vulcanization adhesion. Therefore, by blending liquid polyisoprene with SIBS, it is possible to obtain a polymer composition for an inner liner excellent in vulcanization adhesion with an adjacent rubber layer.

  The liquid polyisoprene preferably has a weight average molecular weight of 5,000 or more and 50,000 or less by GPC measurement from the viewpoint of adhesion and fluidity after vulcanization. Further, the weight average molecular weight is more preferably 10,000 or more and 40,000 or less.

  Content of the liquid polyisoprene in a 1st polymer composition is 0.5 to 70 mass parts with respect to 100 mass parts of SIBS. When the content of the liquid polyisoprene is 0.5 parts by mass or more, it is possible to obtain an inner liner having excellent adhesiveness with adjacent rubber. Further, when the content of liquid polyisoprene is 70 parts by mass or less, the content of SIBS in the polymer composition can be sufficiently ensured, so that the inner liner has excellent air permeation resistance and flex crack resistance. Can be obtained. The content of liquid polyisoprene is more preferably 2 parts by mass or more and 45 parts by mass or less with respect to 100 parts by mass of SIBS.

(Adduct of maleic acid monomethyl ester of liquid polyisoprene)
In one embodiment of the present invention, the first polymer composition may include a maleic acid monomethyl ester adduct of liquid polyisoprene. Maleic acid-modified LIR is represented by the following formula (II).

  In the formula (3), the ratio and number of m and n are not particularly limited, but from the viewpoint of adhesion and fluidity after vulcanization, for example, m / n = 1 to 750, m = 20 to 750, n = 1. ~ 20 is preferred.

  Maleic acid-modified LIR has the property of excellent vulcanization adhesion. Therefore, by blending maleic acid-modified LIR with SIBS, a polymer composition for an inner liner excellent in vulcanization adhesion with an adjacent rubber layer can be obtained.

  The maleic acid-modified LIR preferably has a weight average molecular weight of 5,000 or more and 50,000 or less by GPC measurement from the viewpoint of adhesion after vulcanization and fluidity. Further, the weight average molecular weight is more preferably 10,000 or more and 40,000 or less.

  The content of maleic acid-modified LIR in the first polymer composition is 0.5 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of SIBS. When the content of the maleic acid-modified LIR is 5 parts by mass or more, an inner liner excellent in adhesiveness with an adjacent rubber can be obtained. Moreover, since the content of SIBS in the polymer composition can be sufficiently ensured when the content of maleic acid-modified LIR is 70 parts by mass or less, the inner layer has excellent air permeation resistance and flex crack resistance. A liner can be obtained. The content of maleic acid-modified LIR is more preferably 2 parts by mass or more and 45 parts by mass or less with respect to 100 parts by mass of SIBS.

(Moleic anhydride adduct of liquid polyisoprene)
In one embodiment of the present invention, the first polymer composition can include a maleic anhydride adduct of liquid polyisoprene. Maleic anhydride-modified LIR is represented by the following formula (IV).

  In the formula (4), the ratio and number of m and n are not particularly limited, but from the viewpoint of adhesion and fluidity after vulcanization, for example, m / n = 1 to 750, m = 20 to 750, n = 1. ~ 20 is preferred.

  Maleic anhydride-modified LIR has the property of excellent vulcanization adhesion. Therefore, by blending maleic anhydride-modified LIR with SIBS, a polymer composition for an inner liner having excellent vulcanization adhesion with an adjacent rubber layer can be obtained.

  The maleic anhydride-modified LIR preferably has a weight average molecular weight of 5,000 or more and 50,000 or less by GPC measurement from the viewpoint of adhesion and fluidity after vulcanization. Further, the weight average molecular weight is more preferably 10,000 or more and 40,000 or less.

  The content of maleic anhydride-modified LIR in the first polymer composition is 0.5 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of SIBS. When the content of the maleic anhydride-modified LIR is 0.5 parts by mass or more, an inner liner excellent in adhesiveness with an adjacent rubber can be obtained. Moreover, since content of SIBS in a polymer composition can fully ensure that content of maleic anhydride modified LIR is 70 parts by mass or less, it has excellent air permeation resistance and flex crack resistance. An inner liner can be obtained. The content of maleic anhydride-modified LIR is more preferably 2 parts by mass or more and 45 parts by mass or less with respect to 100 parts by mass of SIBS.

  In one embodiment of the present invention, the first polymer composition may contain two or more selected from the group consisting of liquid polyisoprene, maleic acid-modified LIR, and maleic anhydride-modified LIR. In this case, the total content of liquid polyisoprene, maleic acid-modified LIR and maleic anhydride-modified LIR is 0.5 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of SIBS.

(Thickness of the first layer)
The thickness of the first layer is preferably 0.05 mm or greater and 0.6 mm or less. When the thickness of the first layer is less than 0.05 mm, the first layer is broken by the press pressure during vulcanization of the green tire in which the first layer 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 mm or more and 0.4 mm or less.

(Other ingredients)
In the first polymer composition, other reinforcing agents, vulcanizing agents, vulcanization accelerators, various oils, anti-aging agents, softeners, plasticizers, coupling agents, etc. are incorporated into tire or general polymer compositions. Various additives and additives can be blended. Moreover, the content of these compounding agents and additives can also be set to general amounts.

<Inner liner manufacturing method>
The inner liner composed of the first layer can be produced by a usual method of forming various styrene-based thermoplastic elastomers such as extrusion molding or calender molding from various compounding agents of the first polymer composition.

<Pneumatic tire manufacturing method>
The pneumatic tire of the present invention can be produced by applying the above inner liner to a green tire and vulcanizing it together with other members.

  The first polymer composition constituting the inner liner is a composition containing a thermoplastic elastomer, and is in a softened state in a mold at a vulcanization temperature, for example, 150 ° C. to 180 ° C. The softened state means an intermediate state between solid and liquid with improved molecular mobility. The thermoplastic elastomer composition easily adheres and adheres to an adjacent member in a softened state. Therefore, in order to prevent the shape change of the thermoplastic elastomer, the adhesion with the adjacent member, and the fusion, a cooling step is required when manufacturing the tire. In the cooling step, the tire is vulcanized and then rapidly cooled to 50 to 120 ° C. for 10 to 300 seconds to cool the inside of the bladder. As the cooling medium, at least one selected from air, water vapor, water and oil is used. By adopting such a cooling step, the thickness of the inner liner can be reduced.

[Embodiment 2]
<Pneumatic tire structure>
The pneumatic tire in the present embodiment can have the same structure as that in the first embodiment. In the present embodiment, the inner liner used for the pneumatic tire includes a first layer made of the first polymer composition and a second layer made of the second polymer composition.

<First layer>
As the first layer, a layer similar to the first layer described in Embodiment 1 can be used.

  The first polymer composition is composed of 100 parts by mass of styrene-isobutylene-styrene triblock copolymer, liquid polyisoprene, maleic anhydride adduct of liquid polyisoprene, and maleic acid monomethyl ester adduct of liquid polyisoprene. 0.5 mass part or more and 35 mass parts or less are included at least any selected from the group which consists of. When the content of LIR, maleic acid-modified LIR, and maleic anhydride-modified LIR is less than 0.5 parts by mass, sufficient adhesion to the second layer cannot be obtained. On the other hand, if it exceeds 35 parts by mass, the effect of reducing the rolling resistance of the tire tends to be inferior.

<Second layer>
The second polymer composition used for the second layer preferably contains 10% by mass to 80% by mass of a styrene-isobutylene-styrene triblock copolymer in the polymer component.

The SIBS can be the same as the SIBS described in the first embodiment.
The content of the SIBS in the second polymer composition is preferably 10% by mass or more and 80% by mass in the polymer component. When the SIBS is less than 10% by mass, the adhesion with the first layer is lowered, and when the SIBS exceeds 80% by mass, the adhesion with the carcass ply tends to be lowered.

  It is preferable that a 2nd polymer composition contains another styrenic thermoplastic elastomer with SIBS. Here, the styrene-based thermoplastic elastomer refers to a copolymer containing a styrene block as a hard segment. For example, a styrene-isoprene-styrene triblock copolymer (hereinafter also referred to as “SIS”), a styrene-isobutylene diblock copolymer (hereinafter also referred to as “SIB”), a styrene-butadiene-styrene block copolymer ( Hereinafter, also referred to as “SBS”), styrene-ethylene / butene-styrene block copolymer (hereinafter also referred to as “SEBS”), styrene-ethylene / propylene / styrene block copolymer (hereinafter also referred to as “SEPS”). Styrene-ethylene / ethylene / propylene / styrene block copolymer (hereinafter also referred to as “SEEPS”) and styrene / butadiene / butylene / styrene block copolymer (hereinafter also referred to as “SBBS”).

  The styrenic thermoplastic elastomer may have an epoxy group in its molecular structure. For example, Epofriend A1020 manufactured by Daicel Chemical Industries, Ltd. (weight average molecular weight is 100,000, epoxy equivalent is 500). An epoxy-modified styrene-butadiene-styrene copolymer (hereinafter also referred to as “epoxidized SBS”) can be used.

  Of the styrenic thermoplastic elastomers, it is particularly preferable to use a styrene-isoprene-styrene triblock copolymer (SIS) and a styrene-isobutylene diblock copolymer (SIB).

(Styrene-isoprene-styrene triblock copolymer)
Since the isoprene block of SIS is a soft segment, the polymer composition containing SIS tends to be vulcanized and bonded to the rubber component. Therefore, when a polymer composition containing SIS is used for the inner liner, the inner liner is excellent in adhesiveness with the rubber forming the carcass ply, and thus a pneumatic tire having excellent durability can be obtained. .

  The molecular weight of 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 or more and 290,000 or less. 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. The content of the styrene component in the SIS is preferably 10% by mass or more and 30% by mass or less from the viewpoints of tackiness, 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.

(Styrene-isobutylene diblock copolymer)
Since the isobutylene block of SIB is a soft segment, the polymer composition containing SIB tends to be vulcanized and bonded to the rubber component. Therefore, when a polymer composition containing SIB is used for the inner liner, the inner liner is excellent in adhesion to, for example, an adjacent rubber forming a carcass or insulation, so that a pneumatic tire excellent in durability is used. Can be obtained.

  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 or more and 120,000 or less. 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% by mass or more and 35% by mass or less 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 living polymerization method of a general vinyl compound. For example, methylcyclohexane, n-butyl chloride, and cumyl chloride are added to a stirrer, cooled to -70 ° C, and reacted for 2 hours. Thereafter, a large amount of methanol is added to stop the reaction, and vacuum drying at 60 ° C. can produce SIB.

<The thickness of the second layer>
The thickness of the second layer is preferably 0.01 mm or more and 0.3 mm or less. If the thickness of the second layer is less than 0.01 mm, the second layer may be broken by pressing pressure during vulcanization of the raw tire on which the inner liner is disposed, and the vulcanization adhesive force may be reduced. On the other hand, if the thickness of the second layer exceeds 0.3 mm, the tire weight may increase and the fuel efficiency performance may deteriorate. The thickness of the second layer is preferably 0.05 mm or more and 0.2 mm or less.

<Inner liner manufacturing method>
The inner liner in the present embodiment can be manufactured by the same method as the inner liner manufacturing method described in the first embodiment.

<Pneumatic tire manufacturing method>
The pneumatic tire in the present embodiment can be manufactured by the same method as the manufacturing method of the pneumatic tire described in the first embodiment. In addition, when arrange | positioning an inner liner in a raw tire, a 2nd layer is arrange | positioned toward a tire radial direction outer side so that the carcass ply 61 may be contact | connected. When arranged in this manner, the adhesive strength between the second layer and the carcass 6 can be increased in the tire vulcanization 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. Hereinafter, the arrangement | positioning state in the pneumatic tire of an inner liner is demonstrated using FIG. 2 and FIG.

  In FIG. 2, the inner liner PL is composed of a first layer PL1 and a second layer PL2. When the inner liner PL is applied to the inner liner of a pneumatic tire, the second layer PL2 and the carcass are disposed in the tire vulcanization process when the second layer PL2 is disposed facing the outer side in the tire radial direction so as to contact the carcass ply 61. Adhesive strength with 61 can be increased. Therefore, the obtained pneumatic tire can have excellent air permeation resistance and durability since the inner liner and the carcass ply 61 are well bonded.

  In FIG. 3, the inner liner PL has a film made of urethane rubber or silicone rubber as the third layer PL3 between the first layer PL1 and the second layer PL2. When the inner liner PL is applied to an inner liner of a pneumatic tire, if the surface of the second 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 adhesive strength between the layer PL2 and the carcass ply 61 can be increased. Therefore, since the inner liner and the carcass ply 61 are bonded well, it is possible to have excellent air permeation resistance and durability.

<Production of inner liner>
According to the formulation shown in Table 1, various compounding agents were put into a twin-screw extruder (screw diameter: φ50 mm, L / D: 30, cylinder temperature: 220 ° C.) to be pelletized. Thereafter, a polymer sheet for an unvulcanized 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). . The following tests were conducted using the polymer sheet.

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

(Adhesive strength index) = (Adhesive strength of each sample) / (Adhesive strength of sample 1) × 100
The results are shown in Table 1.

<JIS-A hardness>
Test pieces were prepared according to JIS K 6253 “How to obtain hardness of vulcanized rubber and thermoplastic rubber”, and JIS-A hardness was measured at room temperature of 23 ° C. The results are shown in Table 1.

<Production of tire>
The above inner liner polymer sheet is applied to the inner liner portion of a 195 / 65R15 size tire having the structure shown in FIG. 1 to produce a raw tire, and then press vulcanized at 170 ° C. for 20 minutes in the vulcanization step. Went. The following tests were conducted using the tire.

<Static air pressure drop rate test>
A 195 / 65R15 steel radial PC tire was assembled into a JIS standard rim 15 × 6 JJ, an initial air pressure of 300 Kpa was enclosed, and the air was allowed to stand at room temperature for 90 days, and the rate of decrease in air pressure was calculated. The smaller the value, the better the air permeation resistance.

The results are shown in Table 1.
<Bending crack growth test>
In accordance with JIS K 6260 "Dematcher bending crack test method for vulcanized rubber and thermoplastic rubber", a test piece is prepared, a bending crack growth test is performed, and 70% elongation is repeated 1,000,000 times to bend the rubber sheet. After that, the length of the generated crack was measured. Using the obtained numerical value as the standard (100) for Sample 1, the resistance to flex crack growth of each sample was expressed as an index by the following formula. A larger value means that cracks are less likely to grow and can be said to be good.

(Bending crack growth resistance index) = (crack length of each sample) / (crack length of sample 1) × 100
The results are shown in Table 1.

(Note 1) IIR: “Exon Chlorobutyl 1068” manufactured by ExxonMobil Co., Ltd.
(Note 2) SIBS: “Sibusta-SIBSTAR 102T” manufactured by Kaneka Corporation (Shore A hardness 25, styrene component content 25 mass%)
(Note 3) LIR (1): “LIR-30” manufactured by Kuraray (liquid polyisoprene, weight average molecular weight: 28000)
(Note 4) LIR (2): “LIR-403” manufactured by Kuraray Co., Ltd. (maleic anhydride-modified LIR, weight average molecular weight: 34000, number of maleic anhydrides in one molecule: 3)
(Note 5) LIR (3): “LIR-410” manufactured by Kuraray Co., Ltd. (maleic acid-modified LIR, weight average molecular weight: 30000, number of monomethyl maleates in one molecule: 10)
(Note 6) Carbon: “Seast V” manufactured by Tokai Carbon Co., Ltd. (N660, N ₂ SA 27 m ² / g)
<Evaluation results>
Samples 3 to 5 are an inner liner made of a polymer composition containing SIBS and LIR, and a pneumatic tire using the inner liner. Compared to Sample 2 in which the polymer component was 100% by mass of SIBS, the adhesion was improved while maintaining the air permeation resistance.

  Samples 6 to 8 are an inner liner made of a polymer composition containing SIBS and maleic anhydride-modified LIR, and a pneumatic tire using the inner liner. Compared to Sample 2 in which the polymer component was 100% by mass of SIBS, the adhesion was improved while maintaining the air permeation resistance.

  Samples 9 to 11 are an inner liner made of a polymer composition containing SIBS and maleic acid-modified LIR, and a pneumatic tire using the inner liner. Compared to Sample 2 in which the polymer component was 100% by mass of SIBS, the adhesion was improved while maintaining the air permeation resistance.

  Sample 2 is a polymer composition for an inner liner whose polymer component is 100% by mass of SIBS and a pneumatic tire using the same. Air permeation resistance is excellent, but adhesion is poor.

<Production of inner liner>
According to the formulation shown in Table 2, various compounding agents were put into a twin screw extruder (screw diameter: φ50 mm, L / D: 30, cylinder temperature: 220 ° C.) and pelletized. Thereafter, a polymer sheet for an unvulcanized 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). . The following tests were conducted using the polymer sheet.

<Adhesion test>
A rubber sheet having a thickness of 2 mm (formulation: NR / BR / SBR = 40/30/30), a polymer sheet of the second layer and the first layer are stacked in the order described above and added in 20 minutes at 170 ° C. A sample for measuring the adhesive strength was prepared. The peel strength was measured with a tensile tester to obtain a vulcanized adhesive strength. The vulcanized adhesive strength of each sample was expressed as an index using the following calculation formula with sample 29 as the reference (100). In addition, it shows that vulcanization adhesive force is so high that the index | exponent of vulcanization adhesive force is large.

(Adhesive strength index) = (Adhesive strength of each sample) / (Vulcanized adhesive strength of sample 29) × 100
The results are shown in Table 2.

<Manufacture of pneumatic tires>
The polymer sheet for an inner liner is applied to the inner liner portion of a 195 / 65R15 size tire having the structure shown in FIG. 1 to produce a raw tire. went. Then, without removing the tire from the vulcanization mold, it was cooled at 100 ° C. for 3 minutes and then removed from the vulcanization mold. Water was used as the cooling medium. By adopting such a cooling process, a pneumatic tire having a thin inner liner of 0.3 mm could be manufactured.

The following tests were performed using the obtained tires.
<Bending crack growth test>
The flex crack growth test was evaluated based on whether the inner liner was cracked or peeled off. The tire is assembled to a JIS standard rim 15 × 6 JJ, the internal pressure of the tire is set to 150 KPa, which is lower than usual, and the inside of the tire is observed at a load of 600 kg, a speed of 100 km / h, and a traveling distance of 20,000 km. Number was measured. Using the sample 29 as a reference, the flex crack growth resistance of each sample was displayed as an index. It can be said that the larger the value of the index, the better, because cracks are less likely to occur.

(Bending crack growth resistance index) = (number of cracks in sample 29) / (number of cracks in each sample) × 100
<Rolling resistance test>
Using a rolling resistance tester manufactured by Kobe Steel Co., Ltd., the prototype tire was assembled to a JIS standard rim 15 × 6JJ, and the temperature was set to room temperature (30 ° C.) under conditions of a load of 3.4 kN, an air pressure of 230 kPa, and a speed of 80 km / h. And rolling resistance was measured. Then, based on the following calculation formula, with the sample 29 as the reference 100, the rolling resistance change rate (%) of each sample was displayed as an index. It shows that rolling resistance is reduced, so that rolling resistance change rate is large.

Rolling resistance change rate = (rolling resistance of sample 29 / rolling resistance of each sample) × 100
<Static air pressure drop rate test>
A 195 / 65R15 steel radial PC tire was assembled to a JIS standard rim 15 × 6 JJ, an initial air pressure of 300 kPa was enclosed, and the air was left at room temperature for 90 days, and the rate of decrease in air pressure was calculated. The smaller the value, the less the air pressure is reduced.

  The results are shown in Table 2.

(Note 2) SIBS: “Sibusta-SIBSTAR 102T” manufactured by Kaneka Corporation (Shore A hardness 25, styrene component content 25 mass%, weight average molecular weight: 100,000)
(Note 3) LIR (1): “LIR-30” manufactured by Kuraray (liquid polyisoprene, weight average molecular weight: 28000)
(Note 4) LIR (2): “LIR-403” manufactured by Kuraray Co., Ltd. (maleic anhydride-modified LIR, weight average molecular weight: 34000, number of maleic anhydrides in one molecule: 3)
(Note 5) LIR (3): “LIR-410” manufactured by Kuraray Co., Ltd. (maleic acid-modified LIR, weight average molecular weight: 30000, number of monomethyl maleates in one molecule: 10)
(Note 7) SIS: “D1161JP” manufactured by Kraton Polymer Co., Ltd. (styrene component content 15 mass%, weight average molecular weight: 150,000)
(Note 8) SIB: manufactured according to the following manufacturing method.

  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. This 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).

<Evaluation results>
Each sample was evaluated in comparison with sample 29 in which the first layer consisted solely of SIBS and the second layer consisted of 20% SIS and 80% SIBS.

  Samples 12 to 15 and Samples 22 and 23 maintain the air permeation resistance equivalent to that of Sample 29, while maintaining the adhesive strength of the inner liner, the flex crack growth resistance of the pneumatic tire, the rolling resistance and the air permeation resistance. It was excellent.

Samples 16 and 20 had the same performance as sample 29 in all items.
In Samples 17, 21, and 24, the content of LIR, maleic anhydride-modified LIR, or maleic acid-modified LIR in the first polymer composition is 40 parts by mass with respect to 100 parts by mass of SIBS. Compared to sample 29, the rolling resistance increased.

  In samples 18 and 19, the second layer does not contain SIBS. Compared to Sample 29, the adhesion, flex crack growth resistance, rolling resistance and air permeation resistance were inferior.

  In Samples 25 to 28, the first layer does not contain any of LIR, maleic anhydride-modified LIR, and maleic acid-modified LIR. Compared to sample 29, the adhesive strength and the resistance to flex crack growth were inferior.

  Sample 30 had the same effect as sample 29.

  The pneumatic tire of the present invention can be applied to passenger car pneumatic tires, truck / bus tires, light truck tires, and heavy vehicle pneumatic tires.

  1 Pneumatic tire, 2 tread portion, 3 sidewall portion, 4 bead portion, 5 bead core, 6 carcass ply, 7 belt layer, 8 bead apex, 9, PL inner liner, PL1 first layer, PL2 second layer, PL3 Third layer.

Claims (7)

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 has a first layer made of a first polymer composition,
In the first polymer composition, the polymer component comprises a styrene-isobutylene-styrene triblock copolymer, and at least one of a maleic anhydride adduct of liquid polyisoprene and a maleic acid monomethyl ester adduct of liquid polyisoprene, 0.5 parts of at least one selected from the group consisting of a maleic anhydride adduct of liquid polyisoprene and a maleic acid monomethyl ester adduct of liquid polyisoprene with respect to 100 parts by mass of the styrene-isobutylene-styrene triblock copolymer. 70 parts by unrealized inclusive parts by weight
In the liquid polyisoprene maleic acid monomethyl ester adduct, the number of maleic acid monomethyl esters in one molecule is 1 or more and 20 or less,
The maleic anhydride adduct of the liquid polyisoprene is a pneumatic tire in which the number of maleic anhydrides in one molecule is 1 or more and 20 or less . 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 has a first layer composed of a first polymer composition and a second layer composed of a second polymer composition,
In the first polymer composition, the polymer component comprises a styrene-isobutylene-styrene triblock copolymer, and at least one of a maleic anhydride adduct of liquid polyisoprene and a maleic acid monomethyl ester adduct of liquid polyisoprene, 0.5 parts of at least one selected from the group consisting of a maleic anhydride adduct of liquid polyisoprene and a maleic acid monomethyl ester adduct of liquid polyisoprene with respect to 100 parts by mass of the styrene-isobutylene-styrene triblock copolymer. Including not less than 35 parts by mass
In the liquid polyisoprene maleic acid monomethyl ester adduct, the number of maleic acid monomethyl esters in one molecule is 1 or more and 20 or less,
The maleic anhydride adduct of the liquid polyisoprene has 1 to 20 maleic anhydrides in one molecule,
The second polymer composition contains 10% by mass to 80% by mass of a styrene-isobutylene-styrene triblock copolymer in the polymer component,
The pneumatic tire is arranged such that the second layer is in contact with the carcass ply.   The pneumatic tire according to claim 2, wherein the second polymer composition includes at least one of a styrene-isoprene-styrene triblock copolymer and a styrene-isobutylene diblock copolymer.   The pneumatic tire according to claim 2 or 3, wherein the thickness of the first layer is 0.05 mm or more and 0.6 mm or less, and the thickness of the second layer is 0.01 mm or more and 0.3 mm or less. The styrene-isobutylene-styrene triblock copolymer in the first polymer composition has a styrene component content of 10 mass% or more and 30 mass% or less, according to any one of claims 1 to 4 . Pneumatic tire. The pneumatic tire according to claim 3 or 4 , wherein the styrene-isoprene-styrene triblock copolymer has a styrene component content of 10 mass% or more and 30 mass% or less. The pneumatic tire according to claim 3, 4 or 6 , wherein the styrene-isobutylene diblock copolymer is linear and has a styrene component content of 10% by mass or more and 35% by mass or less. .

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