JP6008591B2 - Multilayer structure, inner liner for pneumatic tire, and pneumatic tire - Google Patents

Description

  The present invention relates to a multilayer structure comprising a barrier layer and an elastomer layer, in particular, a multilayer structure having high gas barrier properties and crack resistance and excellent fatigue resistance, and a pneumatic tire using the multilayer structure. The present invention relates to an inner liner and a pneumatic tire including the inner liner.

  Conventionally, a rubber composition mainly composed of butyl rubber, halogenated butyl rubber or the like is used for an inner liner disposed as an air barrier layer on the tire inner surface in order to maintain the internal pressure of the tire. However, these rubber compositions using butyl rubber as the main raw material have low air barrier properties, and therefore when such a rubber composition is used for an inner liner, the thickness of the inner liner has to be about 1 mm.

  On the other hand, an ethylene-vinyl alcohol copolymer (hereinafter sometimes abbreviated as EVOH) is known to have excellent gas barrier properties. The EVOH has an air permeation amount that is 1/100 or less of the above butyl rubber composition for an inner liner, so that even if the thickness is 100 μm or less, the internal pressure retention of the tire can be greatly improved. Therefore, when EVOH is used as an inner liner, it can be used even with a thickness of 100 μm or less, and therefore, it is difficult to break due to bending deformation at the time of tire rolling, and cracks are also difficult to occur. Therefore, it can be said that it is effective to use EVOH for the inner liner of the tire in order to improve the internal pressure retention of the pneumatic tire. For example, Patent Literature 1 discloses a pneumatic tire including an inner liner made of EVOH.

  However, when normal EVOH is used as an inner liner, the effect of improving the internal pressure retention of the tire is great, but normal EVOH has a significantly higher elastic modulus than rubber normally used for tires, so when bent, Breaking or cracking may occur due to deformation. Therefore, when the inner liner made of EVOH is used, the internal pressure retention before using the tire is greatly improved, but the internal pressure retention is lower than that before using the tire after being subjected to bending deformation during rolling of the tire. There was something to do.

  Accordingly, there has been a demand for the development of an inner liner that has high crack resistance and can be made thinner while maintaining gas barrier properties. Therefore, for example, it is conceivable to use a laminate in which an elastic film or sheet having excellent crack resistance and a resin film having good gas barrier properties are joined and integrated. In that case, since an elastic body film etc. are contained in this laminated body, although outstanding gas barrier property is realizable, it becomes a subject. Furthermore, when using the said laminated body as an inner liner, the improvement of the fatigue resistance with respect to long-term use was desired.

JP-A-6-40207

  Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art and provide a multilayer structure having high gas barrier properties and crack resistance and excellent fatigue resistance. Another object of the present invention is to provide an inner liner for a pneumatic tire using such a multilayer structure and a pneumatic tire including the inner liner.

  As a result of diligent studies to achieve the above object, the inventors of the present invention have made the JIS-A hardness of the elastomer layer 80 or less. It is found that the flexibility of the entire multilayer structure can be ensured and the deformation of the multilayer structure can be tracked, so that high gas barrier properties and crack resistance can be ensured and excellent fatigue resistance can be realized. The invention has been completed.

That is, the multilayer structure of the present invention comprises a total of 9 or more barrier layers and elastomer layers, the elastomer layer has a JIS-A hardness of 80 or less , and the barrier layer is 20 ° C., 65%. The elongation at break according to ISO 527 in RH is 100% or less, and the thickness of each barrier layer is 10 μm or less .

The elastomer layer preferably has an elongation at break exceeding 100% in accordance with ISO 527 at 20 ° C. and 65% RH.

  Moreover, it is preferable to laminate | stack the said barrier layer and the said elastomer layer alternately.

The barrier layer, 20 ° C., the oxygen permeability at 65 RH%, preferably not more than ^{10.0cc · mm / m 2 · day} · atm.

  The barrier layer preferably contains one or more resins having a polar group of OH, S, Cl or F. The resin having the polar group is an ethylene-vinyl alcohol copolymer, a modified ethylene-vinyl alcohol copolymer. More preferably, it is at least one selected from coalescence, polyvinyl alcohol, polyvinyl alcohol, nylon, vinyl chloride and ionomer.

  The elastomer layer comprises a polystyrene-based thermoplastic elastomer, a polyolefin-based thermoplastic elastomer, a polydiene-based thermoplastic elastomer, a polyvinyl chloride-based thermoplastic elastomer, a chlorinated polyethylene-based thermoplastic elastomer, a polyurethane-based thermoplastic elastomer, a polyester-based thermoplastic elastomer. It is preferable to include at least one selected from polyamide-based thermoplastic elastomers and fluororesin-based thermoplastic elastomers.

  The barrier layer and the elastomer layer are preferably cross-linked by irradiation with active energy rays, and the multilayer structure preferably has an elastic modulus of 40 Mpa or less at 20 ° C. and 100% strain.

  Furthermore, the inner liner for a pneumatic tire according to the present invention is characterized by using the multilayer structure described above, and the pneumatic tire according to the present invention is provided with the inner liner.

  According to the present invention, it is possible to provide a multilayer structure having high gas barrier properties and crack resistance and excellent fatigue resistance. Moreover, an inner liner for a pneumatic tire using such a multilayer structure and a pneumatic tire including the inner liner can be provided.

It is sectional drawing about an example of the multilayer structure of this invention. It is a fragmentary sectional view about an example of the pneumatic tire of the present invention.

<Multilayer structure>
Hereinafter, the multilayer structure of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of an example of the multilayer structure of the present invention.
As shown in FIG. 1, the multilayer structure 1 of the present invention comprises a total of seven or more barrier layers 2 and elastomer layers 3, and the elastomer layer 3 has a JIS-A hardness of 80 or less. It is characterized by that.

  By laminating a total of seven or more layers of the barrier layer having a high gas barrier property and the elastomer layer having a high toughness, the gas barrier property of the multilayer structure is ensured, and the toughness action of the elastomer layer High crack resistance can be obtained. And, when the JIS-A hardness of the elastomer layer is 80 or less, the flexibility of the entire multilayer structure is ensured, and when the multilayer structure is deformed along with the deformation of rubber when used for an inner liner, etc. Even so, as a result of being able to follow the deformation, excellent fatigue resistance can be realized.

Here, when the JIS-A hardness of the elastomer layer is set to 80 or less, when the JIS-A hardness exceeds 80, the multilayer structure cannot sufficiently secure the desired fatigue resistance. It is because sex cannot be obtained. The JIS-A hardness of the elastomer layer is preferably 75 or less, and more preferably 70 or less.
The lower limit of the JIS-A hardness of the elastomer layer is 20. This is because if the JIS-A hardness is less than 20, it is difficult to form the elastomer layer.
The JIS-A hardness is a standard for measuring the hardness of rubber, and using a spring type hardness tester defined in JIS K6301-1975, an indenter is pushed into the surface of the object to be measured and deformed. The amount of deformation (indentation depth) is measured and digitized.

  Further, by optimizing the JIS-A hardness of the elastomer layer, the elastic modulus of the multilayer structure is preferably 40 Mpa or less at 20 ° C. and 100% strain. This is because when the elastic modulus at 20 ° C. and 100% strain exceeds 40 Mpa, the multilayer structure is not sufficiently flexible, cannot follow deformation, and may deteriorate fatigue resistance. .

  The barrier layer 2 and the elastomer layer 3 are preferably laminated alternately as shown in FIG. This is because better crack resistance can be obtained by alternately laminating the barrier layer 2 and the elastomer layer 3.

  The total number of barrier layers 2 is not particularly limited as long as it is 7 or more, but is preferably 11 or more, more preferably 15 or more from the viewpoint of realizing higher gas barrier properties. Is more preferable. The upper limit of the total number of the barrier barrier layers 2 is not particularly limited, but is preferably 3000 layers or less from the viewpoint of reducing the weight of the multilayer structure 1.

In the multilayer structure of the present invention, as shown in FIG. 1, the thicknesses U1, U2, U3... Un of the elastomer layer 3 and the thicknesses V1, V2, V3. Any of them is preferably in the range of 0.001 to 40 μm. By making the respective thicknesses U and V within the above ranges, crack resistance can be improved by toughening and the number of layers constituting the multilayer structure can be increased, so the overall thickness is the same. However, the gas barrier property and crack resistance of the multilayer structure can be improved as compared with a multilayer structure having a small number of layers.
Further, from the viewpoint of realizing higher crack resistance, the thickness V per one layer of the barrier layer 2 is preferably made thinner, more preferably 10 μm or less.

  For example, polystyrene is mentioned as an example of a material used for a conventional barrier layer. Polystyrene is known as a brittle material, and a layer made of polystyrene may break due to elongation of about 1.5% at room temperature. There is. However, in “Polymer, 1993, vol. 34 (10), 2148-2154”, a layer made of a ductile material and a layer made of polystyrene are laminated, and the thickness of each layer made of polystyrene is 1 μm or less. Thus, it has been reported that a layer made of polystyrene is modified from brittle to ductile. That is, it is considered that even a layer made of a brittle material such as polystyrene can be modified to toughness by making the layer very thin. The present inventors have paid attention to such a concept and have found a multilayer structure capable of achieving both excellent gas barrier properties and crack resistance.

  Moreover, as shown in FIG. 1, the thickness T of the entire multilayer structure 1 of the present invention is preferably in the range of 0.1 to 1000 μm, more preferably in the range of 0.5 to 750 μm, and still more preferably in the range of 1 to 500 μm. If the thickness of the multilayer structure is within the above range, it is suitable as an inner liner for a pneumatic tire, and coupled with limiting the average thickness of one layer of the barrier layer and the elastomer layer, gas barrier properties and crack resistance Etc. can be further improved.

  Moreover, it is preferable that the said barrier layer and the said elastomer layer which comprise the multilayer structure of this invention are bridge | crosslinked by irradiation of an active energy ray. By cross-linking the multilayer structure 1 by irradiation with active energy rays, the affinity between the stacked layers 2 and 3 can be improved and high adhesiveness can be expressed. As a result, the interlayer adhesion of the multilayer structure, and consequently the gas barrier properties and crack resistance can be significantly improved. The active energy rays mean those having energy quanta among electromagnetic waves or charged particle beams, and specific examples include ultraviolet rays, γ rays, electron beams, etc. Among these, improvement of interlayer adhesion From the viewpoint of effects, an electron beam is preferable. When irradiating an electron beam as an active energy ray, the electron beam source is, for example, a Cockroft Walton type, a bandegraft type, a resonant transformer type, an insulated core transformer type, or a linear type, a dynamitron type, a high frequency type, etc. Various electron beam accelerators can be used, the acceleration voltage is usually 100 to 500 kV, and the irradiation dose is usually in the range of 5 to 600 kGy. Moreover, when using an ultraviolet-ray as an active energy ray, it is good to irradiate what contains the ultraviolet-ray with a wavelength of 190-380 nm. There is no restriction | limiting in particular as an ultraviolet-ray source, For example, a high pressure mercury lamp, a low pressure mercury lamp, a metal halide lamp, a carbon arc lamp etc. are used.

(Barrier layer)
The barrier layer constituting the multilayer structure according to the present invention is a layer containing a gas barrier resin in order to realize the air barrier property of the multilayer structure and maintain the internal pressure of the tire.

The barrier layer preferably has an oxygen permeability at 20 ° C. and 65% RH of 10.0 cc · mm / m ² · day · atm or less from the viewpoint of ensuring a high air barrier property of the multilayer structure. - more preferably mm / m is ² · day · atm or less, and more preferably not more than ^{1.0 cc · mm / m 2 ·} day · atm. When the oxygen permeability at 20 ° C and 65% RH exceeds 10.0 cc · mm / m ² · day · atm, the barrier layer must be thickened to increase the internal pressure retention of the tire. The weight cannot be reduced sufficiently.

  Further, the gas barrier resin is not particularly limited as long as a desired air barrier property can be secured. Examples thereof include polyamide resins, ethylene-vinyl alcohol copolymers, modified ethylene-vinyl alcohol copolymers, urethane polymers, olefin polymers, and diene polymers. Moreover, these resin may be used individually by 1 type, and may be used in combination of 2 or more type.

  Further, the gas barrier resin is preferably at least one of resins having a polar group of OH, S, Cl or F. This is because when the gas barrier resin has these polar groups, the cohesive energy density is increased, and as a result, the gas barrier property can be further improved.

Furthermore, the resin having a polar group is preferably at least one selected from an ethylene-vinyl alcohol copolymer or a modified ethylene-vinyl alcohol copolymer, polyvinyl alcohol, nylon, vinyl chloride, and ionomer. This is because such a resin has low oxygen permeability and excellent gas barrier properties.

  The ethylene-vinyl alcohol copolymer (EVOH) preferably has an ethylene content of 25 to 50 mol%, more preferably 30 to 48 mol%, and further preferably 35 to 45 mol%. preferable. If the ethylene content is less than 25 mol%, crack resistance, fatigue resistance and melt moldability may be deteriorated. On the other hand, if it exceeds 50 mol%, sufficient gas barrier properties may not be ensured. The ethylene-vinyl alcohol copolymer preferably has a saponification degree of 90% or more, more preferably 95% or more, and still more preferably 99% or more. If the degree of saponification is less than 90%, gas barrier properties and thermal stability during molding may be insufficient. Further, the ethylene-vinyl alcohol copolymer preferably has a melt flow rate (MFR) of 0.1 to 30 g / 10 minutes under a load of 2160 g at 190 ° C., more preferably 0.3 to 25 g / 10 minutes. .

  The ethylene-vinyl alcohol copolymer preferably has an ethylene content of 3 to 70 mol%, from 10 to 60 mol%, from the viewpoint of improving gas barrier properties, melt moldability and interlayer adhesion of the inner liner. More preferably, it is more preferably 20 to 55 mol%, particularly preferably 25 to 50 mol%. If the ethylene content is less than 3 mol%, the water resistance, hot water resistance, gas barrier properties and melt moldability under high humidity may be deteriorated. On the other hand, if the ethylene content exceeds 70 mol%, the gas barrier of the inner liner may be reduced. May decrease.

  The ethylene-vinyl alcohol copolymer preferably has a saponification degree of 80% or more, more preferably 90% or more, from the viewpoint of improving gas barrier properties, moisture resistance and interlayer adhesion of the inner liner. Is more preferably 95% or more, and particularly preferably 99% or more. On the other hand, the saponification degree of the ethylene-vinyl alcohol copolymer is preferably 99.99% or less. If the saponification degree of EVOH is less than 80%, the melt moldability, gas barrier properties, coloration resistance and moisture resistance of the inner liner may be lowered.

  The ethylene-vinyl alcohol copolymer has a melt flow rate (MFR) of 0.1 to 30 g / 10 min at 190 ° C. and a load of 21.18 N from the viewpoint of obtaining gas barrier properties, crack resistance and fatigue resistance. Preferably, it is 0.3-25 g / 10min.

The ethylene-vinyl alcohol copolymer has a content G (mol%) of 1,2-glycol bond structural units of the following formula:
G ≦ 1.58−0.0244 × E
[Wherein, G is the content (mol%) of 1,2-glycol-bonded structural unit, E is the ethylene unit content (mol%) in EVOH, where E ≦ 64) And the intrinsic viscosity is preferably in the range of 0.05 to 0.2 L / g. By using such EVOH, the obtained inner liner is less dependent on the humidity of the gas barrier property, has good transparency and gloss, and can be easily laminated on a layer made of another resin. The content of the 1,2-glycol-bonded structural unit was determined by changing the EVOH sample to a dimethyl sulfoxide solution according to the method described in “S. Aniya et al., Analytical Science Vol. 1, 91 (1985)”. It can be measured by nuclear magnetic resonance at 90 ° C.

  The modified ethylene-vinyl alcohol copolymer has, in addition to ethylene units and vinyl alcohol units, other repeating units (hereinafter also referred to as structural units), for example, one or more kinds of repeating units derived from these units. It is a polymer. The preferred ethylene content, degree of saponification, melt flow rate (MFR), content of 1,2-glycol bond structural unit and intrinsic viscosity of the modified EVOH are the same as those of the above-mentioned EVOH.

上記式（Ｉ）中、Ｒ^１、Ｒ^２及びＲ^３は、それぞれ独立して、水素原子、炭素数1〜10の脂肪族炭化水素基、炭素数3〜10の脂環式炭化水素基、炭素数6〜10の芳香族炭化水素基又はヒドロキシ基を表す。また、Ｒ^１、Ｒ^２及びＲ^３のうちの一対が結合していてもよい（但し、Ｒ^１、Ｒ^２及びＲ^３のうちの一対が共に水素原子の場合は除く）。また、前記炭素数1〜10の脂肪族炭化水素基、炭素数3〜10の脂環式炭化水素基又は炭素数6〜10の芳香族炭化水素基は、ヒドロキシ基、カルボキシ基又はハロゲン原子を有していてもよい。一方、上記式（ＩＩ）中、Ｒ^４、Ｒ^５、Ｒ^６及びＲ^７は、それぞれ独立して、水素原子、炭素数1〜10の脂肪族炭化水素基、炭素数3〜10の脂環式炭化水素基、炭素数6〜10の芳香族炭化水素基又はヒドロキシ基を表す。また、Ｒ^４とＲ^５又はＲ^６とＲ^７は結合していてもよい（但し、Ｒ^４とＲ^５又はＲ^６とＲ^７が共に水素原子の場合は除く）。また、前記炭素数1〜10の脂肪族炭化水素基、炭素数3〜10の脂環式炭化水素基又は炭素数6〜10の芳香族炭化水素基は、ヒドロキシ基、アルコキシ基、カルボキシ基又はハロゲン原子を有していてもよい。 The modified EVOH preferably has at least one structural unit selected from, for example, the structural units (I) and (II) shown below, and the structural unit is in a proportion of 0.5 to 30 mol% with respect to the total structural units. It is more preferable to contain. Such a modified EVOH can improve the flexibility and processing characteristics of the resin or resin composition, and the interlayer adhesion, stretchability, and thermoformability of the inner liner.

In the above formula (I), R ¹ , R ² and R ³ are each independently a hydrogen atom, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group having 3 to 10 carbon atoms, An aromatic hydrocarbon group or a hydroxy group having 6 to 10 carbon atoms is represented. In addition, a pair of R ¹ , R ² and R ³ may be bonded (except when a pair of R ¹ , R ² and R ³ are both hydrogen atoms). In addition, the aliphatic hydrocarbon group having 1 to 10 carbon atoms, the alicyclic hydrocarbon group having 3 to 10 carbon atoms, or the aromatic hydrocarbon group having 6 to 10 carbon atoms includes a hydroxy group, a carboxy group, or a halogen atom. You may have. On the other hand, in said formula (II), R < ⁴ >, R < ⁵ >, R < ⁶ > and R <^7> are respectively independently a hydrogen atom, a C1-C10 aliphatic hydrocarbon group, and a C3-C10 alicyclic ring. A formula hydrocarbon group, a C6-C10 aromatic hydrocarbon group, or a hydroxy group is represented. R ⁴ and R ⁵ or R ⁶ and R ⁷ may be bonded to each other (except when R ⁴ and R ⁵ or R ⁶ and R ⁷ are both hydrogen atoms). The aliphatic hydrocarbon group having 1 to 10 carbon atoms, the alicyclic hydrocarbon group having 3 to 10 carbon atoms, or the aromatic hydrocarbon group having 6 to 10 carbon atoms is a hydroxy group, an alkoxy group, a carboxy group, or It may have a halogen atom.

  In the modified EVOH, the lower limit of the content of the structural unit (I) and / or (II) with respect to all the structural units is preferably 0.5 mol%, more preferably 1 mol%, and even more preferably 1.5 mol%. On the other hand, in the modified EVOH, the upper limit of the content of the structural unit (I) and / or (II) with respect to all the structural units is preferably 30 mol%, more preferably 15 mol%, still more preferably 10 mol%. By containing the structural units (I) and / or (II) in the specified proportions, the flexibility and processing characteristics of the resin or resin composition, and the interlayer adhesion, stretchability and thermoformability of the inner liner can be achieved. Can be improved.

  In the structural units (I) and (II), examples of the aliphatic hydrocarbon group having 1 to 10 carbon atoms include an alkyl group and an alkenyl group, and examples of the alicyclic hydrocarbon group having 3 to 10 carbon atoms include cyclohexane. Examples thereof include an alkyl group and a cycloalkenyl group, and examples of the aromatic hydrocarbon group having 6 to 10 carbon atoms include a phenyl group.

In the structural unit (I), R ¹ , R ² and R ³ are preferably each independently a hydrogen atom, a methyl group, an ethyl group, a hydroxy group, a hydroxymethyl group or a hydroxyethyl group. Among these, a hydrogen atom, a methyl group, a hydroxy group, or a hydroxymethyl group is more preferable. With such R ¹ , R ² and R ³ , the stretchability and thermoformability of the inner liner can be further improved.

  The method for incorporating the structural unit (I) in EVOH is not particularly limited. For example, in the copolymerization of ethylene and vinyl ester, a monomer further derived into the structural unit (I). And the like. Examples of the monomer derived from the structural unit (I) include alkene such as propylene, butylene, pentene, hexene; 3-hydroxy-1-propene, 3-acyloxy-1-propene, 3-acyloxy-1 -Butene, 4-acyloxy-1-butene, 3,4-diacyloxy-1-butene, 3-acyloxy-4-hydroxy-1-butene, 4-acyloxy-3-hydroxy-1-butene, 3-acyloxy-4 -Methyl-1-butene, 4-acyloxy-2-methyl-1-butene, 4-acyloxy-3-methyl-1-butene, 3,4-diacyloxy-2-methyl-1-butene, 4-hydroxy-1 -Pentene, 5-hydroxy-1-pentene, 4,5-dihydroxy-1-pentene, 4-acyloxy-1-pentene, 5-acyloxy-1-pentene, , 5-diacyloxy-1-pentene, 4-hydroxy-3-methyl-1-pentene, 5-hydroxy-3-methyl-1-pentene, 4,5-dihydroxy-3-methyl-1-pentene, 5,6 -Dihydroxy-1-hexene, 4-hydroxy-1-hexene, 5-hydroxy-1-hexene, 6-hydroxy-1-hexene, 4-acyloxy-1-hexene, 5-acyloxy-1-hexene, 6-acyloxy Alkenes having a hydroxy group or an ester group such as -1-hexene and 5,6-diacyloxy-1-hexene are exemplified. Among these, from the viewpoint of copolymerization reactivity and gas barrier properties of the resulting inner liner, propylene, 3-acyloxy-1-propene, 3-acyloxy-1-butene, 4-acyloxy-1-butene, and 3, 4-diacetoxy-1-butene is preferred. Specifically, propylene, 3-acetoxy-1-propene, 3-acetoxy-1-butene, 4-acetoxy-1-butene, and 3,4-diacetoxy-1-butene are more preferable, and 3,4-diacetoxy- 1-butene is particularly preferred. In addition, when using the alkene which has ester, it is induced | guided | derived to the said structural unit (I) in the case of saponification reaction.

In the structural unit (II), R ⁴ and R ⁵ are preferably both hydrogen atoms. In particular, it is more preferable that R ⁴ and R ⁵ are both hydrogen atoms, one of R ⁶ and R ⁷ is an aliphatic hydrocarbon group having 1 to 10 carbon atoms, and the other is a hydrogen atom. The aliphatic hydrocarbon group in the structural unit (II) is preferably an alkyl group or an alkenyl group. Further, from the viewpoint of particularly emphasizing the gas barrier property of the inner liner, it is preferable that one of R ⁶ and R ⁷ is a methyl group or an ethyl group, and the other is a hydrogen atom. Furthermore, it is also preferable that one of R ⁶ and R ⁷ is a substituent represented by (CH ₂ ) _h OH (where h is an integer of 1 to 8) and the other is a hydrogen atom. In the substituent represented by (CH ₂ ) _h OH, h is preferably an integer of 1 to 4, more preferably 1 or 2, and particularly preferably 1.

上記式（ＩＩＩ）〜（ＩＸ）中、Ｒ^８、Ｒ^９、Ｒ^１０、Ｒ^１１及びＲ^１２は、水素原子、炭素数1〜10の脂肪族炭化水素基（アルキル基又はアルケニル基等）、炭素数3〜10の脂環式炭化水素基（シクロアルキル基又はシクロアルケニル基等）又は炭素数6〜10の芳香族炭化水素基（フェニル基等）を表す。なお、Ｒ^８及びＲ^９又はＲ^１１及びＲ^１２は、同一であってもよく、異なっていてもよい。また、ｉ、ｊ、ｋ、ｐ及びｑは、１〜８の整数を表す。 In addition, the method of incorporating the structural unit (II) in EVOH is not particularly limited, and examples thereof include a method of reacting a monovalent epoxy compound with EVOH obtained by a saponification reaction. Preferred examples of the monovalent epoxy compound include compounds represented by the following formulas (III) to (IX).

In the above formulas (III) to (IX), R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ and R ¹² are a hydrogen atom, an aliphatic hydrocarbon group having 1 to 10 carbon atoms (such as an alkyl group or an alkenyl group), An alicyclic hydrocarbon group having 3 to 10 carbon atoms (such as a cycloalkyl group or a cycloalkenyl group) or an aromatic hydrocarbon group having 6 to 10 carbon atoms (such as a phenyl group) is represented. R ⁸ and R ⁹ or R ¹¹ and R ¹² may be the same or different. Moreover, i, j, k, p, and q represent the integer of 1-8.

  Examples of the monovalent epoxy compound represented by the formula (III) include epoxy ethane (ethylene oxide), epoxy propane, 1,2-epoxybutane, 2,3-epoxybutane, and 3-methyl-1,2- Epoxybutane, 1,2-epoxypentane, 2,3-epoxypentane, 3-methyl-1,2-epoxypentane, 4-methyl-1,2-epoxypentane, 4-methyl-2,3-epoxypentane, 3-ethyl-1,2-epoxypentane, 1,2-epoxyhexane, 2,3-epoxyhexane, 3,4-epoxyhexane, 3-methyl-1,2-epoxyhexane, 4-methyl-1,2 -Epoxyhexane, 5-methyl-1,2-epoxyhexane, 3-ethyl-1,2-epoxyhexane, 3-propyl-1,2-epoxy Xanthone, 4-ethyl-1,2-epoxyhexane, 5-methyl-1,2-epoxyhexane, 4-methyl-2,3-epoxyhexane, 4-ethyl-2,3-epoxyhexane, 2-methyl- 3,4-epoxyhexane, 2,5-dimethyl-3,4-epoxyhexane, 3-methyl-1,2-epoxyheptane, 4-methyl-1,2-epoxyhexane, 5-methyl-1,2- Epoxyheptane, 6-methyl-1,2-epoxyheptane, 3-ethyl-1,2-epoxyheptane, 3-propyl-1,2-epoxyheptane, 3-butyl-1,2-epoxyheptane, 4-ethyl -1,2-epoxyheptane, 4-propyl-1,2-epoxyheptane, 6-ethyl-1,2-epoxyheptane, 4-methyl-2,3-epoxyheptane, -Ethyl-2,3-epoxyheptane, 4-propyl-2,3-epoxyheptane, 2-methyl-3,4-epoxyheptane, 5-methyl-3,4-epoxyheptane, 5-ethyl-3,4 -Epoxyheptane, 2,5-dimethyl-3,4-epoxyheptane, 2-methyl-5-ethyl-3,4-epoxyheptane, 1,2-epoxyheptane, 2,3-epoxyheptane, 3,4- Epoxyheptane, 1,2-epoxyoctane, 2,3-epoxyoctane, 3,4-epoxyoctane, 4,5-epoxyoctane, 1,2-epoxynonane, 2,3-epoxynonane, 3,4-epoxy Nonane, 4,5-epoxynonane, 1,2-epoxydecane, 2,3-epoxydecane, 3,4-epoxydecane, 4,5-epoxydecane, 5,6- Epoxy decane, 1,2-epoxy undecane, 2,3-epoxy undecane, 3,4-epoxy undecane, 4,5-epoxy undecane, 5,6-epoxy undecane, 1,2-epoxy undecane, 2,3-epoxy Dodecane, 3,4-epoxydodecane, 4,5-epoxydodecane, 5,6-epoxydodecane, 6,7-epoxydodecane, epoxyethylbenzene, 1-phenyl-1,2-propane, 3-phenyl-1,2, -Epoxypropane, 1-phenyl-1,2-epoxybutane, 3-phenyl-1,2-epoxypentane, 4-phenyl-1,2-epoxypentane, 5-phenyl-1,2-epoxypentane, 1- Phenyl-1,2-epoxyhexane, 3-phenyl-1,2-epoxyhexane, 4-phenyl-1,2, Epoxyhexane, 5-phenyl-1,2-epoxy hexane, 6-phenyl-1,2-epoxy hexane, and the like.

  Examples of the monovalent epoxy compound represented by the above formula (IV) include methyl glycidyl ether, ethyl glycidyl ether, n-propyl glycidyl ether, isopropyl glycidyl ether, n-butyl glycidyl ether, isobutyl glycidyl ether, tert-butyl glycidyl. Ether, 1,2-epoxy-3-pentyloxypropane, 1,2-epoxy-3-hexyloxypropane, 1,2-epoxy-3-heptyloxypropane, 1,2-epoxy-4-phenoxybutane, , 2-epoxy-4-benzyloxybutane, 1,2-epoxy-5-methoxypentane, 1,2-epoxy-5-ethoxypentane, 1,2-epoxy-5-propoxypentane, 1,2-epoxy- 5-butoxypentane, 1,2-d Xyl-5-pentyloxypentane, 1,2-epoxy-5-hexyloxypentane, 1,2-epoxy-5-phenoxypentane, 1,2-epoxy-6-methoxyhexane, 1,2-epoxy-6 Ethoxyhexane, 1,2-epoxy-6-propoxyhexane, 1,2-epoxy-6-butoxyhexane, 1,2-epoxy-6-heptyloxyhexane, 1,2-epoxy-7-methoxyheptane, 1, 2-epoxy-7-ethoxyheptane, 1,2-epoxy-7-propoxyheptane, 1,2-epoxy-7-butoxyheptane, 1,2-epoxy-8-methoxyoctane, 1,2-epoxy-8- Ethoxyoctane, 1,2-epoxy-8-butoxyoctane, glycidol, 3,4-epoxy-1-butanol, 4, -Epoxy-1-pentanol, 5,6-epoxy-1-hexanol, 6,7-epoxy-1-heptanol, 7,8-epoxy-1-octanol, 8,9-epoxy-1-nonanol, 9, Examples include 10-epoxy-1-decanol, 10,11-epoxy-1-undecanol, and the like.

  Examples of the monovalent epoxy compound represented by the above formula (V) include ethylene glycol monoglycidyl ether, propanediol monoglycidyl ether, butanediol monoglycidyl ether, pentanediol monoglycidyl ether, hexanediol monoglycidyl ether, heptanediol. Examples thereof include monoglycidyl ether and octanediol monoglycidyl ether.

  Examples of the monovalent epoxy compound represented by the formula (VI) include 3- (2,3-epoxy) propoxy-1-propene, 4- (2,3-epoxy) propoxy-1-butene, 5- (2,3-epoxy) propoxy-1-pentene, 6- (2,3-epoxy) propoxy-1-hexene, 7- (2,3-epoxy) propoxy-1-heptene, 8- (2,3- Epoxy) propoxy-1-octene and the like.

  Examples of the monovalent epoxy compound represented by the formula (VII) include 3,4-epoxy-2-butanol, 2,3-epoxy-1-butanol, 3,4-epoxy-2-pentanol, 2 , 3-epoxy-1-pentanol, 1,2-epoxy-3-pentanol, 2,3-epoxy-4-methyl-1-pentanol, 2,3-epoxy-4,4-dimethyl-1- Pentanol, 2,3-epoxy-1-hexanol, 3,4-epoxy-2-hexanol, 4,5-epoxy-3-hexanol, 1,2-epoxy-3-hexanol, 2,3-epoxy-4 , 4-Dimethyl-1-hexanol, 2,3-epoxy-4,4-diethyl-1-hexanol, 2,3-epoxy-4-methyl-4-ethyl-1-hexanol, 3,4-epoxy -5-methyl-2-hexanol, 3,4-epoxy-5,5-dimethyl-2-hexanol, 3,4-epoxy-2-heptanol, 2,3-epoxy-1-heptanol, 4,5-epoxy -3-heptanol, 2,3-epoxy-4-heptanol, 1,2-epoxy-3-heptanol, 2,3-epoxy-1-octanol, 3,4-epoxy-2-octanol, 4,5-epoxy -3-octanol, 5,6-epoxy-4-octanol, 2,3-epoxy-4-octanol, 1,2-epoxy-3-octanol, 2,3-epoxy-1-nonanol, 3,4-epoxy 2-nonanol, 4,5-epoxy-3-nonanol, 5,6-epoxy-4-nonanol, 3,4-epoxy-5-nonanol, 2,3-epoxy Si-4-nonanol, 1,2-epoxy-3-nonanol, 2,3-epoxy-1-decanol, 3,4-epoxy-2-decanol, 4,5-epoxy-3-decanol, 5,6- Examples include epoxy-4-decanol, 6,7-epoxy-5-decanol, 3,4-epoxy-5-decanol, 2,3-epoxy-4-decanol, 1,2-epoxy-3-decanol and the like.

  Examples of the monovalent epoxy compound represented by the above formula (VIII) include 1,2-epoxycyclopentane, 1,2-epoxycyclohexane, 1,2-epoxycycloheptane, 1,2-epoxycyclooctane, , 2-epoxycyclononane, 1,2-epoxycyclodecane, 1,2-epoxycycloundecane, 1,2-epoxycyclododecane and the like.

  Examples of the monovalent epoxy compound represented by the above formula (IX) include 3,4-epoxycyclopentene, 3,4-epoxycyclohexene, 3,4-epoxycycloheptene, 3,4-epoxycyclooctene, 3 , 4-epoxycyclononene, 1,2-epoxycyclodecene, 1,2-epoxycycloundecene, 1,2-epoxycyclododecene, and the like.

  Among the monovalent epoxy compounds, epoxy compounds having 2 to 8 carbon atoms are preferable. In particular, from the viewpoint of easy handling of the compound and reactivity to EVOH, the carbon number of the monovalent epoxy compound is more preferably 2 to 6, and further preferably 2 to 4. The monovalent epoxy compound is particularly preferably a compound represented by the formula (III) or (IV) among the compounds represented by these formulas. Specifically, 1,2-epoxybutane, 2,3-epoxybutane, epoxypropane, epoxyethane, and glycidol are preferable from the viewpoint of reactivity to EVOH and gas barrier properties of the resulting inner liner, and among these, epoxypropane And glycidol are particularly preferred.

  In the present invention, the ethylene-vinyl alcohol copolymer is obtained, for example, by polymerizing ethylene and a vinyl ester to obtain an ethylene-vinyl ester copolymer, and saponifying the ethylene-vinyl ester copolymer. . Further, as described above, the modified ethylene-vinyl alcohol copolymer is obtained by (1) copolymerizing a monomer derived from the structural unit (I) in the polymerization of ethylene and vinyl ester, or (2) It is obtained by reacting a monovalent epoxy compound with EVOH obtained by a saponification reaction. Here, the polymerization method of the ethylene-vinyl alcohol copolymer and the modified ethylene-vinyl alcohol copolymer is not particularly limited, and for example, any of solution polymerization, suspension polymerization, emulsion polymerization, and bulk polymerization may be used. Moreover, any of a continuous type and a batch type may be sufficient.

  Examples of vinyl esters that can be used for the polymerization include vinyl fatty acid such as vinyl acetate, vinyl propionate, and vinyl pivalate.

  Moreover, when manufacturing a modified ethylene-vinyl alcohol copolymer, the monomer which can be copolymerized with these monomers other than ethylene and vinyl ester may be used preferably in a small amount. This copolymerizable monomer includes, in addition to the monomer derived from the above structural unit (I), other alkenes such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, and itaconic acid. Saturated carboxylic acid or its anhydride, salt, monoalkyl ester or dialkyl ester, etc .; Nitriles such as acrylonitrile and methacrylonitrile; Amides such as acrylamide and methacrylamide; Olefins such as vinyl sulfonic acid, allyl sulfonic acid and methallyl sulfonic acid Sulfonic acid or a salt thereof; alkyl vinyl ethers, vinyl ketone, N-vinyl pyrrolidone, vinyl chloride, vinylidene chloride and the like. A vinyl silane compound can also be used as a monomer, and the amount of the vinyl silane compound introduced into the copolymer is preferably 0.0002 mol% or more and 0.2 mol% or less. Examples of the vinylsilane compound include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri (β-methoxy-ethoxy) silane, γ-methacryloyloxypropylmethoxysilane, and the like. Among these vinylsilane compounds, vinyltrimethoxysilane and vinyltriethoxysilane are preferable.

  The solvent that can be used for the polymerization is not particularly limited as long as it is an organic solvent that can dissolve ethylene, vinyl ester, and ethylene-vinyl ester copolymer. Specific examples include alcohols such as methanol, ethanol, propanol, n-butanol and tert-butanol; dimethyl sulfoxide and the like. Among these, methanol is particularly preferable because removal and separation after the reaction is easy.

  Examples of the initiator that can be used for the polymerization include 2,2′-azobisisobutyronitrile, 2,2′-azobis- (2,4-dimethylvaleronitrile), and 2,2′-azobis- (4-methoxy). -2,4-dimethylvaleronitrile), 2,2'-azobis- (2-cyclopropylpropionitrile) and other azonitrile initiators; isobutyryl peroxide, cumylperoxyneodecanoate, diisopropylperoxycarbonate And organic peroxide initiators such as di-n-propyl peroxydicarbonate, t-butylperoxyneodecanoate, lauroyl peroxide, benzoyl peroxide, and t-butyl hydroperoxide.

  The polymerization temperature is usually about 20 to 90 ° C, preferably 40 to 70 ° C. The polymerization time is usually about 2 to 15 hours, preferably 3 to 11 hours. The polymerization rate is usually about 10 to 90%, preferably 30 to 80% with respect to the vinyl ester charged. The resin content in the solution after polymerization is about 5 to 85% by mass, preferably 20 to 70% by mass.

  After polymerization for a predetermined time or after reaching a predetermined polymerization rate, a polymerization inhibitor is added to the resulting copolymer solution as necessary, and unreacted ethylene gas is removed by evaporation. Remove. As a method for removing unreacted vinyl ester, for example, a copolymer solution is continuously supplied from the upper part of the tower filled with Raschig rings at a constant rate, and an organic solvent vapor such as methanol is blown from the lower part of the tower, A method of distilling a mixed vapor of an organic solvent such as methanol and unreacted vinyl ester from the top and taking out a copolymer solution from which unreacted vinyl ester has been removed from the bottom of the column is employed.

  Next, an alkali catalyst is added to the copolymer solution to saponify the copolymer present in the solution. The saponification method can be either a continuous type or a batch type. Examples of the alkali catalyst include sodium hydroxide, potassium hydroxide, alkali metal alcoholate, and the like. The saponification conditions are, for example, in the case of a batch system, the concentration of the alkali catalyst in the copolymer solution is about 10 to 50% by mass, the reaction temperature is about 30 to 65 ° C., and the amount of catalyst used is vinyl ester structural unit 1 It is preferably about 0.02 to 1.0 mole per mole and the saponification time is about 1 to 6 hours.

  The (modified) EVOH after the saponification reaction contains an alkali catalyst, by-product salts such as sodium acetate and potassium acetate, and other impurities. Therefore, it is preferable to remove these by neutralization and washing as necessary. . Here, when the (modified) EVOH after the saponification reaction is washed with water containing almost no metal ions such as ion-exchanged water, chloride ions, etc., part of sodium acetate, potassium acetate, etc. may remain. .

  Specific examples of the nylon include nylon 6, nylon 6-66, nylon MXD6, and aromatic polyamide.

  The polyvinyl alcohol resin (PVA) is a kind of synthetic resin, and is characterized by extremely strong hydrophilicity and soluble in warm water. From the viewpoint of improving gas barrier properties, melt moldability, and interlayer adhesion of the inner liner, the saponification degree is preferably 95 mol% or less, and more preferably 90 mol% or less.

  In the present invention, the polyvinyl alcohol resin can be obtained, for example, by saponifying polyvinyl acetate obtained by polymerizing a vinyl acetate monomer.

  Further, the elongation at break (EB) of the barrier layer is preferably 100% or less. This is because if it exceeds 100%, high gas barrier properties may not be ensured. Here, the elongation at break (EB) was measured at a tensile speed of 500 mm / min with a JIS3 dumbbell under a condition of 20 ° C. and 65% RH in accordance with ISO 527. It means the elongation at the time of cutting.

(Elastomer layer)
The elastomer layer constituting the multilayer structure of the present invention is a layer for imparting crack resistance and crack resistance to the multilayer structure. For example, a layer made of a thermoplastic elastomer or the thermoplastic elastomer exists as a matrix. And a layer made of a thermoplastic elastomer composition. The matrix means a continuous phase. Although the above-mentioned barrier layer has a high gas barrier property and a large effect of improving the internal pressure retention property of the tire, it has a significantly higher elastic modulus than the rubber in the tire, so it breaks or cracks due to deformation at the time of bending. There is a fear. Therefore, by laminating the elastomer layer together with the barrier layer, it is possible to ensure high internal pressure retention and crack resistance of the multilayer structure.
The elastomer layer has a JIS-A hardness of 80 or less. As described above, this is to ensure flexibility of the entire multilayer structure and to obtain desired fatigue resistance.

  The method for setting the JIS-A hardness of the elastomer layer to 80 or less is not particularly limited. For example, the resin constituting the elastomer layer is an elastomer having a JIS-A hardness of 80 or less by adjusting the content ratio of a highly flexible component (soft segment) and a low flexibility component (hard segment). A layer can be obtained.

  Moreover, it is preferable that the elongation at break (EB) of the elastomer layer exceeds 100%. This is because when the elongation at break (EB) is less than 100%, the flexibility of the elastomer layer is insufficient and the desired fatigue resistance may not be obtained. Here, the elongation at break (EB) was measured at a tensile speed of 500 mm / min with a JIS3 dumbbell under a condition of 20 ° C. and 65% RH in accordance with ISO 527. It means the elongation at the time of cutting.

Furthermore, the elastomer layer preferably has an oxygen permeability at 20 ° C. and 65% RH of 10.0 cc · mm / m ² · day · atm or less. This is because if it exceeds 10.0 cc · mm / m ² · day · atm, a sudden drop in internal pressure may not be prevented when a crack occurs in the barrier layer. The oxygen permeability is measured according to JIS K7126-1: 2006 (isobaric method).

  The elastomer component contained in the elastomer layer is not particularly limited. For example, polystyrene-based thermoplastic elastomer, polyolefin-based thermoplastic elastomer, polydiene-based thermoplastic elastomer, polyvinyl chloride-based thermoplastic elastomer, chlorinated polyethylene. Based thermoplastic elastomers, polyurethane based thermoplastic elastomers, polyester based thermoplastic elastomers, polyamide based thermoplastic elastomers, fluororesin based thermoplastic elastomers, and the like. Among these, polyurethane-based thermoplastic elastomers are preferable. In addition, these thermoplastic elastomers may be used individually by 1 type, and may be used in combination of 2 or more type.

  The polystyrene-based thermoplastic elastomer has an aromatic vinyl polymer block (hard segment) and a rubber block (soft segment), and the aromatic vinyl polymer portion forms a physical cross-link and becomes a crosslinking point. On the other hand, the rubber block imparts rubber elasticity. The polystyrene-based thermoplastic elastomer can be classified according to the arrangement pattern of soft segments in the molecule. For example, styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene -Isobutylene-styrene block copolymer (SIBS), styrene-ethylene / butylene-styrene block copolymer (SEBS), styrene-ethylene / propylene-styrene block copolymer (SEPS), etc. A block copolymer of crystalline polyethylene and ethylene / butylene-styrene random copolymer obtained by hydrogenating a block copolymer of butadiene-styrene random copolymer, polybutadiene or ethylene-butadiene random copolymer Obtained by hydrogenating a block copolymer of polymer and polystyrene, for example, also include diblock copolymer of crystalline polyethylene and polystyrene. Among these, styrene-isobutylene-styrene block copolymer (SIBS), styrene-ethylene from the balance of mechanical strength, heat stability, weather resistance, chemical resistance, gas barrier properties, flexibility, workability, etc. / Butylene-styrene block copolymer (SEBS) and styrene-ethylene / propylene-styrene block copolymer (SEPS) are preferred.

  The polyolefin-based thermoplastic elastomer includes a thermoplastic elastomer having a polyolefin block such as polypropylene or polyethylene as a hard segment and a rubber block such as an ethylene-propylene-diene copolymer as a soft segment. Such thermoplastic elastomer includes a blend type and an implant type. Examples of the polyolefin-based thermoplastic elastomer include maleic anhydride-modified ethylene-butene-1 copolymer, maleic anhydride-modified ethylene-propylene copolymer, halogenated butyl rubber, modified polypropylene, and modified polyethylene. You can also.

  Examples of the polydiene thermoplastic elastomer include 1,2-polybutadiene TPE, trans 1,4-polyisoprene TPE, hydrogenated conjugated diene TPE, and epoxidized natural rubber. The 1,2-polybutadiene-based TPE is a polybutadiene containing 90% or more of 1,2-bonds in the molecule, and is crystalline syndiotactic 1,2-polybutadiene as a hard segment and amorphous as a soft segment. It consists of 1,2-polybutadiene. Trans 1,4-polyisoprene-based TPE is polyisoprene having a trans 1,4 structure of 98% or more in the molecule, and includes crystalline trans 1,4 segments as hard segments and soft segments. It consists of amorphous trans 1,4 segments.

The polyvinyl chloride thermoplastic elastomer (TPVC) is generally roughly classified into the following three types.
Type 1: High molecular weight polyvinyl chloride (PVC) / plasticized polyvinyl chloride (PVC) blend type TPVC
It is a thermoplastic elastomer made of high molecular weight PVC for the hard segment and PVC plasticized with a plasticizer for the soft segment. In addition, by using high molecular weight PVC for the hard segment, the function of a crosslinking point is given to the microcrystal part.
Type 2: Partially cross-linked PVC / plasticized PVC blend type TPVC
It is a thermoplastic elastomer using PVC in which a partially crosslinked or branched structure is introduced into a hard segment and PVC plasticized with a plasticizer in a soft segment.
Type 3: PVC / elastomer alloy TPVC
It is a thermoplastic elastomer that uses PVC for the hard segment and rubber such as partially crosslinked nitrile butadiene rubber (NBR) or TPE such as polyurethane TPE and polyester TPE for the soft segment.

  The chlorinated polyethylene-based thermoplastic elastomer is a soft resin obtained by reacting polyethylene with chlorine gas in an aqueous suspension or a solvent such as carbon tetrachloride, and a crystalline polyethylene block is a soft segment in the hard segment. A chlorinated polyethylene (CPE) block is used for the segment. In the CPE block, both components of polyethylene and chlorinated polyethylene are mixed as a mixture having a multi-block or random structure.

The polyester-based thermoplastic elastomer (TPEE) is a multi-block copolymer using polyester as a hard segment in a molecule and polyether or polyester having a low glass transition temperature (Tg) as a soft segment. TPEE can be divided into the following types according to the difference in molecular structure, and polyester / polyether type TPEE and polyester / polyester type TPEE dominate.
(1) Polyester / polyether type TPEE
Generally, it is a thermoplastic elastomer using aromatic crystalline polyester as a hard segment and polyether as a soft segment.
(2) Polyester / Polyester type TPEE
A thermoplastic elastomer using an aromatic crystalline polyester as a hard segment and an aliphatic polyester as a soft segment.
(3) Liquid crystalline TPEE
It is a thermoplastic elastomer using rigid liquid crystal molecules as hard segments and aliphatic polyester as soft segments.

  The polyamide-based thermoplastic elastomer (TPA) is a multi-block copolymer using polyamide as a hard segment and polyether or polyester having a low Tg as a soft segment. The polyamide component constituting the hard segment is selected from nylon 6, 66, 610, 11, 12 and the like, and nylon 6 and nylon 12 are mainly used. As the constituent material of the soft segment, a long-chain polyol such as polyether diol or polyester diol is used. Representative examples of polyether polyols include diol poly (oxytetramethylene) glycol (PTMG), poly (oxypropylene) glycol, and the like. Representative examples of polyester polyols include poly (ethylene adipate) glycol, poly (butylene- 1,4 adipate) glycol and the like.

  The fluororesin-based thermoplastic elastomer is an ABA type block copolymer made of fluororesin as a hard segment and fluororubber as a soft segment. Tetrafluoroethylene-ethylene copolymer or polyvinylidene fluoride (PVDF) is used for the fluororesin constituting the hard segment, and vinylidene fluoride-hexafluoropropylene-tetrafluoro is used for the fluororubber constituting the soft segment. An ethylene terpolymer or the like is used. More specifically, it includes vinylidene fluoride rubber, tetrafluoroethylene-propylene rubber, tetrafluoroethylene-perfluoromethyl vinyl ether rubber, phosphazene fluororubber, fluoropolyether, fluoronitroso rubber, perfluorotriazine. And the like. In addition, fluororesin TPE is microphase-separated like other TPE, and the hard segment forms the crosslinking point.

  The polyurethane-based thermoplastic elastomer (TPU) includes (1) a polyurethane obtained by a reaction of a short-chain glycol and an isocyanate as a hard segment, and (2) a polyurethane obtained by a reaction of a long-chain glycol and an isocyanate as a soft segment. Is a linear multi-block copolymer. Here, polyurethane is a general term for compounds having a urethane bond (—NHCOO—) obtained by polyaddition reaction (urethanization reaction) of isocyanate (—NCO) and alcohol (—OH). In the multilayer structure of the present invention, when the elastomer forming the elastomer layer is TPU, the stretchability and thermoformability can be improved by laminating the elastomer layer. In addition, since the inner liner can improve the interlayer adhesion between the elastomer layer and the barrier layer, it has high durability such as crack resistance, and maintains the gas barrier property and stretchability even when the inner liner is deformed. can do.

  The TPU is composed of a polymer polyol, an organic polyisocyanate, a chain extender and the like. The polymer polyol is a substance having a plurality of hydroxy groups, and is obtained by polycondensation, addition polymerization (for example, ring-opening polymerization), polyaddition or the like. Examples of the polymer polyol include polyester polyol, polyether polyol, polycarbonate polyol, or a cocondensate thereof (for example, polyester-ether-polyol). Among these, polyester polyol or polycarbonate polyol is preferable, and polyester polyol is particularly preferable. In addition, these polymer polyols may be used individually by 1 type, and may be used in combination of 2 or more type.

  Here, for example, according to a conventional method, the polyester polyol may be obtained by condensing a compound capable of forming an ester such as a dicarboxylic acid, an ester thereof, or an anhydride thereof and a low molecular polyol by a direct esterification reaction or an ester exchange reaction. Alternatively, it can be produced by ring-opening polymerization of a lactone.

  It does not specifically limit as dicarboxylic acid which can be used for the production | generation of the said polyester polyol, The dicarboxylic acid generally used in manufacture of polyester is mentioned. Specific examples of the dicarboxylic acid include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, methylsuccinic acid, 2-methylglutaric acid, trimethyladipic acid, 2- C4-C12 aliphatic dicarboxylic acids such as methyloctanedioic acid, 3,8-dimethyldecanedioic acid, 3,7-dimethyldecanedioic acid; cycloaliphatic dicarboxylic acids such as cyclohexanedicarboxylic acid; terephthalic acid, isophthalic acid Examples thereof include aromatic dicarboxylic acids such as acid, orthophthalic acid, and naphthalenedicarboxylic acid. These dicarboxylic acids may be used individually by 1 type, and 2 or more types may be mixed and used for them. Among these, an aliphatic dicarboxylic acid having 6 to 12 carbon atoms is preferable, and adipic acid, azelaic acid or sebacic acid is particularly preferable. These dicarboxylic acids have a carbonyl group that is more likely to react with a hydroxy group, and can greatly improve interlayer adhesion with the barrier layer.

  It does not specifically limit as a low molecular polyol which can be used for the production | generation of the said polyester polyol, The low molecular polyol generally used in manufacture of polyester is mentioned. Specific examples of the low molecular polyol include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,3-butylene glycol, 1, 4-butanediol, neopentyl glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 2-methyl-1,8-octane Diol, 2,7-dimethyl-1,8-octanediol, 1,9-nonanediol, 2-methyl-1,9-nonanediol, 1,10-decanediol, 2,2-diethyl-1,3- C2-C15 aliphatic diol such as propanediol; 1,4-cyclohexanediol, cyclo Cyclohexanedicarboxylic methanol, cyclooctane dimethanol, an alicyclic diol such as dimethyl cyclooctane dimethanol; 1,4-bis (beta-hydroxyethoxy) aromatic dihydric alcohols such as benzene. These low molecular polyols may be used alone or in a combination of two or more. Among these, 3-methyl-1,5-pentanediol, 2-methyl-1,8-octanediol, 2,7-dimethyl-1,8-octanediol, 1,9-nonanediol, 2,8- C5-C12 aliphatic diols having a methyl group in the side chain such as dimethyl-1,9-nonanediol are preferred. The polyester polyol obtained using such an aliphatic diol is likely to react with a hydroxy group, and can greatly improve the interlayer adhesion with the barrier layer. Furthermore, a small amount of a trifunctional or higher functional low molecular polyol can be used in combination with the low molecular polyol. Examples of the trifunctional or higher functional low molecular polyol include trimethylolpropane, trimethylolethane, glycerin, 1,2,6-hexanetriol, and the like.

  Examples of the lactone that can be used to produce the polyester polyol include ε-caprolactone and β-methyl-δ-valerolactone.

  Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, poly (methyltetramethylene) glycol, and the like. These polyether polyols may be used individually by 1 type, and 2 or more types may be mixed and used for them. Among these, polytetramethylene glycol is preferable.

  Examples of the polycarbonate polyol include fats having 2 to 12 carbon atoms such as 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, and 1,10-decanediol. Preferable examples include compounds obtained by polycondensation of a group diol or a mixture thereof by the action of diphenyl carbonate or phosgene.

  The polymer polyol preferably has a lower limit of number average molecular weight of 500, more preferably 600, and even more preferably 700. On the other hand, the upper limit of the number average molecular weight of the polymer polyol is preferably 8,000, more preferably 5,000, and still more preferably 3,000. If the number average molecular weight of the polymer polyol is smaller than the lower limit, the compatibility with the organic polyisocyanate is too high, and the elasticity of the resulting TPU becomes poor. May decrease. On the other hand, if the number average molecular weight of the polymer polyol exceeds the above upper limit, the compatibility with the organic polyisocyanate is lowered, and mixing in the polymerization process becomes difficult. There is a possibility that a stable TPU cannot be obtained. The number average molecular weight of the polymer polyol is a number average molecular weight measured based on JIS-K-1577 and calculated based on the hydroxy group value.

  It does not specifically limit as said organic polyisocyanate, The well-known organic diisocyanate generally used for manufacture of TPU can be used. Examples of the organic diisocyanate include 4,4′-diphenylmethane diisocyanate, tolylene diisocyanate, phenylene diisocyanate, xylylene diisocyanate, 1,5-naphthylene diisocyanate, 3,3′-dichloro-4,4′-diphenylmethane diisocyanate, and toluic acid. Examples include aromatic diisocyanates such as diisocyanates; aliphatic or alicyclic diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, and hydrogenated xylylene diisocyanate. Among these, 4,4'-diphenylmethane diisocyanate is preferable from the viewpoint of improving the strength and crack resistance of the obtained inner liner. These organic polyisocyanates may be used alone or in combination of two or more.

  The chain extender is not particularly limited, and a known chain extender generally used in the production of TPU can be used, and the molecular weight is 300 having two or more active hydrogen atoms capable of reacting with an isocyanate group in the molecule. The following low molecular weight compounds are preferably used. Examples of the chain extender include ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-bis (β-hydroxyethoxy) benzene, 1,4-cyclohexanediol, and the like. . Among these, 1,4-butanediol is particularly preferable from the viewpoint of further improving the stretchability and thermoformability of the obtained inner liner. These chain extenders may be used individually by 1 type, and 2 or more types may be mixed and used for them.

  Examples of the method for producing the TPU include a production method that uses the polymer polyol, the organic polyisocyanate, and a chain extender and that utilizes a known urethanization reaction technique, and uses either a prepolymer method or a one-shot method. May be. In particular, it is preferable to perform melt polymerization in the substantial absence of a solvent, and it is more preferable to perform continuous melt polymerization using a multi-screw extruder.

  In the TPU, the ratio of the mass of the organic polyisocyanate to the total mass of the polymer polyol and the chain extender [isocyanate / (polymer polyol + chain extender)] is preferably 1.02 or less. When the ratio exceeds 1.02, long-term operation stability during molding may be deteriorated.

(Manufacturing method of multilayer structure)
The method for producing the multilayer structure of the present invention is not particularly limited as long as the above-described barrier layer and elastomer layer can be laminated and adhered satisfactorily. For example, co-extrusion, lamination, coating, bonding And known methods such as adhesion. Among them, the method for producing a multilayer structure of the present invention is preferably a method of preparing a plurality of resin compositions and producing a multilayer structure having a barrier layer by a multilayer coextrusion method using these compositions. This is because productivity is high and interlayer adhesion is excellent.

  In the multilayer coextrusion method, the resin or resin composition forming the barrier layer is heated and melted, supplied from different extruders or pumps to the extrusion dies through the respective flow paths, and extruded from the extrusion dies to the multilayers. Then, the multilayer structure of the present invention is formed by laminating and bonding. As this extrusion die, for example, a multi-manifold die, a field block, a static mixer or the like can be used.

  Moreover, the multilayer structure of this invention may be laminated | stacked on the both surfaces or single side | surface with the support layer for supporting this laminated body. The support layer is not particularly limited, and for example, a synthetic resin layer that is usually used as a support layer can be used. In addition, it does not specifically limit as a lamination method to the barrier layer or elastomer layer of a support layer, For example, the adhesion method by an adhesive agent, the extrusion lamination method, etc. are mentioned.

<Inner liner for pneumatic tires>
Next, the inner liner for a pneumatic tire of the present invention and the pneumatic tire of the present invention will be described in detail with reference to the drawings. The inner liner for a pneumatic tire of the present invention is characterized by using the multilayer structure described above.

<Pneumatic tire>
The pneumatic tire according to the present invention includes the inner liner. The multilayer structure described above is applied to the inner liner 12 and can be manufactured by a conventional method.
In the pneumatic tire of the present invention, the rubber constituting the tire and the inner liner 12 can be bonded using an adhesive.

  FIG. 2 is a partial cross-sectional view of an example of the pneumatic tire of the present invention. The tire shown in FIG. 2 has a pair of bead portions 7 and a pair of sidewall portions 8, and a tread portion 9 connected to both sidewall portions 8, and extends in a toroid shape between the pair of bead portions 7. A carcass 10 that reinforces each of these parts 7, 8, and 9, and a belt 11 formed of two belt layers disposed on the outer side in the tire radial direction of the crown part of the carcass 10. An inner liner 12 is disposed on the inner surface of the tire.

  In the illustrated example of the tire, the carcass 10 includes a main body portion extending in a toroidal shape between a pair of bead cores 13 embedded in the bead portion 7, and around each bead core 13 from the inner side to the outer side in the tire width direction. In the tire of the present invention, the number of plies and the structure of the carcass 10 are not limited to this.

  In the illustrated tire, the belt 11 includes two belt layers. However, in the tire of the present invention, the number of belt layers constituting the belt 11 is not limited thereto. Here, the belt layer is usually composed of a rubberized layer of a cord extending obliquely with respect to the tire equatorial plane. In the two belt layers, the cords constituting the belt layer intersect with each other with the equator plane interposed therebetween. Thus, the belt 11 is configured by being laminated. Further, the tire of the illustrated example includes a belt reinforcing layer 14 disposed so as to cover the entire belt 11 outside the belt 11 in the tire radial direction. However, the tire of the present invention includes the belt reinforcing layer 14. The belt reinforcing layer having another structure may be provided. Here, the belt reinforcing layer 14 is usually composed of a rubberized layer of cords arranged substantially parallel to the tire circumferential direction.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

(Elastomer layer)
“Clamylon U9195”, “Clamillon U9185”, “Clamillon U9190”, “Clamylon U9180”, “Clamylon U8175”, “Clamylon U8170” or “Clamylon U8165” manufactured by Kuraray Co., Ltd., which is a thermoplastic polyurethane (TPU), Used as an elastomer layer.

(Barrier layer)
“Eval F101B” manufactured by Kuraray Co., Ltd. was used as a barrier layer of an ethylene-vinyl alcohol copolymer.

(Samples 1 to 7 of Examples and Comparative Examples)
Thereafter, when the barrier layer 1 is used so as to form a multilayer structure having the number of layers and the thickness shown in Table 1 by using the material of each barrier layer and the material of the elastomer layer, 210 In the case of using the C barrier layer 2, a melt at 220 ° C. was supplied from the co-extruder to the feed block, and the melt was extruded from the feed block to produce a multilayer structure.
The multilayer structure thus obtained was rapidly cooled and solidified on a casting drum which was kept at a surface temperature of 25 ° C. and applied with electrostatic force. The cast film obtained by rapid cooling and solidification was pressure-bonded onto a release paper and wound up. In addition, the flow path shape and the total discharge amount were set so that the time from when the melts were merged to when rapidly solidified on the casting drum was about 4 minutes.

  The cast film obtained as described above is subjected to cross-sectional observation with DIGITAL MICROSCOPE VHX-900 (manufactured by KEYENCE) or electron microscope VE-8800 (manufactured by KEYENCE) to determine the average thickness of each layer and the thickness of the multilayer structure. Asked. The results are shown in Table 1.

  Next, for this cast film, an electron beam accelerator [Nisshin High Voltage Co., Ltd., Curetron EB200-100] was used, and each sample was irradiated with an electron beam having an irradiation dose shown in Table 1 at an acceleration voltage of 200 kV. Irradiation gave a cross-linked multilayer film (multilayer structure).

  Next, the sample of the multilayer film produced as described above was evaluated for gas barrier properties, fatigue resistance, and internal pressure retention by the following methods. The results are shown in Table 1.

(1) Gas barrier property The film was conditioned at 20 ° C. and 65% RH for 5 days. Using the two humidity-adjusted films obtained, using MOCON OX-TRAN 2/20 type manufactured by Modern Control Co., in accordance with JIS K7126 (isobaric method) under the conditions of 20 ° C. and 65% RH, The oxygen permeability was measured and the average value was obtained. The gas barrier property is evaluated by an index when the oxygen permeability of Sample 1 is 100, and the smaller the value, the smaller the oxygen permeability and the better the result.

(2) Fatigue resistance (number of cracks after low-temperature drum running test)
An auxiliary layer, which is a rubber composition layer having a thickness of 500 μm, is applied to the above film, and after irradiation with EB, an adhesive (Ogasawara ENR adhesive) is applied and applied to the inner surface as the auxiliary layer. Produced. Using the produced inner liner, as shown in FIG. 3, a pneumatic tire for passenger cars having a size of 195 / 65R15 was produced according to a conventional method.
The produced pneumatic tire was pressed with a load of 6 kN on a drum having a rotation speed corresponding to a speed of 80 km / h at an air pressure of 140 kPa at a normal temperature (20 ° C.) and traveled 20,000 km. The number of cracks on the film surface per 10 cm × 10 cm of the tire shoulder after running was measured as an index of fatigue resistance.

(3) Internal Pressure Retention Property The tire produced as described above was pushed at a pressure of 6 kN on a rotating drum corresponding to a speed of 80 km / h at an air pressure of 140 kPa in an atmosphere of −30 ° C. for 10,000 km. Then, after running the tire (test tire) on a 6JJ × 15 rim, the inner pressure was set to 240 kPa and left for 3 months. Measure the internal pressure after 3 months and use the following formula:
Internal pressure retention = ((240−b) / (240−a)) × 100
The internal pressure retention was evaluated using [wherein, a is the internal pressure (kPa) after 3 months of the test tire and b is the internal pressure (kPa) after 3 months of the test tire of Comparative Example 1]. The value of sample 2 was taken as 100, and the other values were indexed. The larger the index value, the better the internal pressure retention.

  From the results in Table 1, it can be seen that the multilayer structure (multilayer film) of the example can achieve both gas barrier properties and crack resistance at a high level, similarly to the multilayer structure of the comparative example. And it turns out that the multilayer structure of an Example has few cracks compared with the multilayer structure of a comparative example, and shows a high effect about fatigue resistance.

  According to the present invention, it is possible to provide a multilayer structure having high gas barrier properties and crack resistance and particularly excellent fatigue resistance. Moreover, an inner liner for a pneumatic tire using such a multilayer structure and a pneumatic tire including the inner liner can be provided. Thereby, compared with the past, it is industrially useful in that a pneumatic tire having a higher gas barrier property and usable for a long period of time can be obtained.

DESCRIPTION OF SYMBOLS 1 Multilayer structure 2 Barrier layer 3 Elastomer layer 7 Bead part 8 Side wall part 9 Tread part 10 Carcass 11 Belt 12 Inner liner 13 Bead core 14 Belt reinforcement layer

Claims (11)

A total of nine or more barrier layers and elastomer layers,
JIS-A hardness of the elastomer layer is 80 or less ,
The barrier layer has an elongation at break according to ISO 527 at 20 ° C. and 65% RH of 100% or less,
A multilayer structure having a thickness of 10 μm or less per barrier layer .   2. The multilayer structure according to claim 1, wherein the elastomer layer has an elongation at break according to ISO 527 at 20 ° C. and 65% RH of more than 100%.   The multilayer structure according to claim 1, wherein the barrier layer and the elastomer layer are alternately laminated. A method for producing a multilayer structure for producing the multilayer structure according to claim 1,
The method for producing a multilayer structure, wherein the barrier layer and the elastomer layer are crosslinked by irradiation with active energy rays. ^2. The multilayer structure according to claim 1, wherein the barrier layer has an oxygen permeability at 20 ° C. and 65 RH% of 10.0 cc · mm / m ² · day · atm or less.   The multilayer structure according to claim 1, wherein the barrier layer includes one or more resins having a polar group of OH, S, Cl, or F. The resin having a polar group is at least one selected from ethylene-vinyl alcohol copolymer, modified ethylene-vinyl alcohol copolymer, polyvinyl alcohol, polyvinyl alcohol, nylon, vinyl chloride, and ionomer. The multilayer structure according to claim 6 .   The elastomer layer comprises a polystyrene-based thermoplastic elastomer, a polyolefin-based thermoplastic elastomer, a polydiene-based thermoplastic elastomer, a polyvinyl chloride-based thermoplastic elastomer, a chlorinated polyethylene-based thermoplastic elastomer, a polyurethane-based thermoplastic elastomer, a polyester-based thermoplastic elastomer. 2. The multilayer structure according to claim 1, comprising at least one selected from polyamide-based thermoplastic elastomers and fluororesin-based thermoplastic elastomers.   The multilayer structure according to claim 1, wherein the multilayer structure has an elastic modulus of 40 Mpa or less at 20 ° C. and 100% strain. An inner liner for a pneumatic tire using the multilayer structure according to any one of claims 1 to 3 and 5 to 9 . A pneumatic tire comprising the inner liner for a pneumatic tire according to claim 10 .

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