JP5718160B2 - Multilayer structure, inner liner for pneumatic tire, and pneumatic tire - Google Patents

Description

  The present invention relates to a multilayer structure, an inner liner for a pneumatic tire using the multilayer structure, and a pneumatic tire including the inner liner, and in particular, a multilayer structure capable of achieving both gas barrier properties and crack resistance. It is about.

  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 containing butyl rubber as the main raw material have low air barrier properties, and therefore when the 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. Since the EVOH has an air permeation amount of 1/100 or less of the above butyl rubber composition for an inner liner, 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 Document 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.

JP-A-6-40207

  Therefore, an object of the present invention is to provide a multilayer structure capable of solving the above-described problems of the prior art and achieving both gas barrier properties and crack 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 intensive studies to achieve the above object, the present inventor has found that an elastomer layer in a multilayer structure including a certain number or more of barrier layers and elastomer layers whose average thickness is within a specific range. It is found that by applying a layer made of an elastomer composition in which a soft material having a Young's modulus at 23 ° C. lower than that of the elastomer is dispersed in at least one layer, gas barrier properties and crack resistance can be achieved. The invention has been completed.

That is, the multilayer structure of the present invention is
A multilayer structure comprising a total of 7 or more barrier layers and elastomer layers,
The barrier layer has an average thickness of 0.001 to 100 μm, the elastomer layer has an average thickness of 0.001 to 200 μm, the elastomer layer has a functional group that interacts with an elastomer component, and has a molecular weight. It includes at least one layer made of an elastomer composition in which a first soft material of 10,000 or less is dispersed.

  In a preferred example of the multilayer structure of the present invention, the first soft material is a compound having a functional group capable of reacting with a hydroxyl group.

  In another preferred embodiment of the multilayer structure of the present invention, the first soft material is a compound having a molecular weight of 10,000 or less, more preferably a compound having a molecular weight of 5000 or less, and more preferably a molecular weight of 2000 or less. A compound, particularly preferably a compound having a molecular weight of 1000 or less.

  In another preferred embodiment of the multilayer structure of the present invention, the content of the first soft material in the elastomer composition is 10 to 30% by mass.

  In another preferred embodiment of the multilayer structure of the present invention, the first soft material is compatible with the elastomer.

  In another preferred embodiment of the multilayer structure of the present invention, the barrier layer comprises at least one layer comprising a resin composition in which a second soft material having a Young's modulus at 23 ° C. lower than that of the resin is dispersed in the resin. Including.

  In another preferred embodiment of the multilayer structure of the present invention, the barrier layer and the elastomer layer are crosslinked by irradiation with active energy rays.

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

  According to the present invention, a total number of barrier layers and elastomer layers whose average thickness is within a specific range is provided in a certain number or more, and at least one of the elastomer layers has a Young's modulus at 23 ° C. in the elastomer. It is possible to provide a multilayer structure capable of achieving both gas barrier properties and crack resistance, to which a layer made of an elastomer composition in which a soft material lower than the elastomer is dispersed is applied. 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 of an example of the multilayer structure of this invention. It is a fragmentary sectional view of an example of the pneumatic tire of the present invention.

  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 of the present invention needs to include a barrier layer 1 and an elastomer layer 2, and the total number of layers of the barrier layer 1 and the elastomer layer 2 is 7 or more. . With such a multilayer structure, it is possible to prevent defects such as pinholes and cracks generated in a certain layer from progressing to the adjacent layer, so that cracks and breaks throughout the multilayer structure can be prevented, and high Durability such as gas barrier properties and crack resistance can be maintained. Moreover, in order to further exhibit the effect exhibited by the multilayer structure described above, it is preferable that the barrier layers 1 and the elastomer layers 2 are alternately laminated as shown in FIG. Since the barrier layer 1 is more likely to crack than the multilayer structure, it is preferable that the surface of the multilayer structure is formed of the elastomer layer 2. Accordingly, the number of barrier layers is preferably 3 or more, and the number of elastomer layers is preferably 4 or more. In addition, from the viewpoint of sufficiently maintaining the gas barrier properties and crack resistance of the multilayer structure, the total number of barrier layers and elastomer layers needs to be 7 or more, and preferably 11 or more. More preferably, it is 15 layers or more. In addition, the upper limit of the total number of layers of the barrier layer and the elastomer layer is not particularly limited, and is appropriately selected depending on the use, thickness, etc. of the multilayer structure.

  In the multilayer structure of the present invention, the barrier layer 1 has an average thickness of 0.001 to 10 μm and the elastomer layer 2 has an average thickness of 0.001 to 40 μm. By making the average thickness of one layer of the barrier layer and the elastomer layer within the above specified range, the number of layers constituting the multilayer structure can be increased, and the overall thickness is the same but the number of layers is small. Compared with the structure, the gas barrier property and crack resistance of the multilayer structure can be improved.

  For example, polystyrene is an example of a material used for the barrier layer. Polystyrene is known as a brittle material, and a layer made of polystyrene may break due to an elongation of about 1.5% at room temperature. 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 the 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 inventor has paid attention to such a concept and found a multilayer structure capable of achieving both excellent gas barrier properties and crack resistance.

  The barrier layer requires that the lower limit of the average thickness of one layer is 0.001 μm, preferably 0.005 μm, and more preferably 0.01 μm. On the other hand, the upper limit of the average thickness of one layer is required to be 10 μm, preferably 7 μm, more preferably 5 μm, further preferably 3 μm, more preferably 1 μm, still more preferably 0.5 μm, and still more preferably 0.2 μm. 0.1 μm is particularly preferable, and 0.05 μm is most preferable. If the average thickness of one layer in the barrier layer is less than 0.001 μm, it becomes difficult to form a uniform thickness, and the gas barrier property and crack property of the multilayer structure may be deteriorated. On the other hand, if the average thickness of one layer exceeds 10 μm, depending on the thickness of the multilayer structure, it may not be possible to secure a sufficient number of barrier layers constituting the multilayer structure, and gas barrier properties and crack resistance may be reduced. Also, there are cases where toughness cannot be imparted to the barrier layer. Note that the average thickness of one layer in the barrier layer refers to a value obtained by dividing the total thickness of the barrier layers constituting the multilayer structure by the number of the barrier layers.

  For the same reason, the lower limit of the average thickness of one layer of the elastomer layer is required to be 0.001 μm, preferably 0.005 μm, and more preferably 0.01 μm. For the same reason, the upper limit of the average thickness of one layer in the elastomer layer needs to be 40 μm, preferably 20 μm, and more preferably 10 μm. The average thickness of one layer in the elastomer layer refers to a value obtained by dividing the total thickness of the elastomer layers constituting the multilayer structure by the number of layers of the elastomer layer. The total thickness of the elastomer layer is equal to or greater than the total thickness of the barrier layer, that is, the ratio of the total thickness of the elastomer layer to the total thickness of the barrier layer (elastomer layer / barrier layer). It is preferable that the thickness is 1 or more. Thereby, the bending fatigue characteristics until the multilayer structure reaches the whole layer breakage are improved.

  The thickness of the multilayer structure 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-specified 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, Cracking properties and the like can be further improved.

  In the multilayer structure of the present invention, the barrier layer and the elastomer layer are preferably cross-linked by irradiation with active energy rays. By cross-linking the barrier layer and the elastomer layer by irradiation with active energy rays, the affinity between each layer to be laminated 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 rays, and specific examples include ultraviolet rays, γ rays, electron beams, etc. Among them, improvement of interlayer adhesion From the viewpoint of the effect, 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.

  The elastomer layer constituting the multilayer structure of the present invention is a layer composed of an elastomer or a layer composed of an elastomer composition in which the elastomer exists as a matrix. In the multilayer structure of the present invention, the elastomer layer is 23 ° C. in the elastomer. It includes at least one layer made of an elastomer composition in which a first soft material having a Young's modulus lower than that of the elastomer is dispersed. The matrix means a continuous phase. Here, by dispersing the first soft material in the elastomer, the film-forming property of the elastomer composition can be improved. Further, the low-temperature hardness of the formed elastomer composition layer can be reduced, and at low temperatures. The crack resistance can be greatly improved.

  The elastomer layer constituting the multilayer structure of the present invention only needs to contain one or more layers composed of an elastomer composition in which the first soft material is dispersed in the elastomer. As shown in FIG. All the elastomer layers 2 may be layers made of an elastomer composition in which the first soft material 4 having a Young's modulus at 23 ° C. lower than that of the elastomer is dispersed in the elastomer 3. The first soft material 4 in the figure is actually compatible with the elastomer and does not look like a macro, but in the present application, it is shown in the form of particles for convenience of explanation. Moreover, the code | symbols 3 and 4 in a figure are attached | subjected only to the lowest layer of the elastomer layer.

  Although it does not specifically limit as an elastomer used for the said elastomer layer, It is preferable to select from a known thermoplastic elastomer (TPE). Examples of the thermoplastic elastomer include, for example, polystyrene-based thermoplastic elastomers, polyolefin-based thermoplastic elastomers, polydiene-based thermoplastic elastomers, polyvinyl chloride-based thermoplastic elastomers, chlorinated polyethylene-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, and polyesters. -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 above-mentioned 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. Block copolymer of crystalline polyethylene and ethylene / butylene-styrene random copolymer obtained by hydrogenating block copolymer of butadiene-styrene random copolymer, polybutadiene or ethylene-butadiene random copolymer Obtain a block copolymer of the body and the polystyrene by hydrogenating, 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 a solvent such as an aqueous suspension or carbon tetrachloride. 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. Further, in such a multilayer structure, since the interlayer adhesion between the elastomer layer and the barrier layer can be improved, durability such as crack resistance is high, and even if the multilayer structure is deformed and used, gas barrier properties and stretchability are achieved. Can be maintained.

  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 hydroxyl 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, the polyester polyol is, for example, according to a conventional method, a compound capable of forming an ester such as dicarboxylic acid, an ester thereof, or an anhydride thereof and a low molecular polyol are condensed by a direct esterification reaction or transesterification 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 hydroxyl group, and can greatly improve the 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 hydroxyl group, and can greatly improve interlayer adhesion with the barrier layer. Further, 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. Preferred examples include compounds obtained by polycondensation of a group diol or a mixture thereof by the action of diphenyl carbonate or phosgene.

  The above polymer polyol preferably has a lower limit of the 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 above lower limit, the compatibility with the organic polyisocyanate is too high, and the elasticity of the resulting TPU becomes poor. Therefore, the mechanical properties such as stretchability of the resulting multilayer structure and heat There is a possibility that moldability may be lowered. 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. In addition, 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 hydroxyl 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 flex resistance of the resulting multilayer structure. 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 resulting multilayer structure. 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 TPU production method include production methods using the above-mentioned polymer polyol, organic polyisocyanate, and chain extender and utilizing a known urethanization reaction technique, and using either the prepolymer method or the 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.

The soft material (first soft material) used for the elastomer layer needs to have a functional group that interacts with the elastomer component and has a molecular weight of 10,000 or less.
The molecular weight of the first soft material is preferably 5000 or less, more preferably 2000 or less, and even more preferably 1000 or less.

The first soft material is preferably a compound having a functional group that interacts with the elastomer component. When the first soft material has a functional group that interacts with the elastomer component, the soft material can be uniformly dispersed in the elastomer, and the average particle size of the soft material can be reduced.
Here, as the functional group that interacts with the elastomer component, specifically, a hydroxyl group, a carboxyl group, a carboxylate group, an isocyanate group, an isothiocyanate group, an epoxy group, an amino group, a boron-containing group, maleic acid, Examples thereof include a functional group introduced by modification with a compound selected from the group consisting of maleic anhydride and alkoxysilane. Here, the functional group is not limited to those capable of directly reacting with the elastomer molecule or having a high affinity, and includes examples in which the functional group can react with the elastomer molecule by pre-reaction with another agent. The soft material may have two or more of such functional groups.

Examples of the boron-containing group include a boron-containing group that can be converted to a boronic acid group in the presence of a boronic acid group or water. Among the boron-containing groups, the boronic acid group is represented by the following formula (1).

ここで、Ｘ及びＹは水素原子、脂肪族炭化水素基（炭素数１〜２０の直鎖状もしくは分岐状アルキル基、又はアルケニル基等）、脂環式炭化水素基（シクロアルキル基、シクロアルケニル基等）、芳香族炭化水素基（フェニル基、ビフェニル基等）を表し、Ｘ及びＹは同じであってもよいし異なっていてもよい。但し、Ｘ及びＹが共に水素原子の場合は除かれる。また、ＸとＹは結合していてもよい。またＲ^１、Ｒ^２及びＲ^３は上記Ｘ及びＹと同様の水素原子、脂肪族炭化水素基、脂環式炭化水素基、芳香族炭化水素基を表し、Ｒ^１、Ｒ^２及びＲ^３は同じでもよいし異なっていてもよい。またＭはアルカリ金属を表す。更に、上記のＸ、Ｙ、Ｒ^１、Ｒ^２及びＲ^３は他の基、例えば水酸基、カルボキシル基、ハロゲン原子などを有していてもよい。 The boron-containing group that can be converted to a boronic acid group in the presence of water refers to a boron-containing group that can be converted to a boronic acid group represented by the above formula (1) by hydrolysis in the presence of water. . More specifically, water alone, a mixture of water and an organic solvent (toluene, xylene, acetone, etc.), a mixture of a 5% boric acid aqueous solution and the organic solvent, and the like, at room temperature to 150 ° C. It means a functional group that can be converted to a boronic acid group when hydrolyzed for 10 minutes to 2 hours. Representative examples of such functional groups include boronate ester groups represented by the following formula (2), boronic anhydride groups represented by the following formula (3), boronate groups represented by the following formula (4), and the like. Is mentioned.

Here, X and Y are a hydrogen atom, an aliphatic hydrocarbon group (a linear or branched alkyl group having 1 to 20 carbon atoms, or an alkenyl group), an alicyclic hydrocarbon group (a cycloalkyl group, a cycloalkenyl group). Group) and an aromatic hydrocarbon group (phenyl group, biphenyl group, etc.), and X and Y may be the same or different. However, the case where both X and Y are hydrogen atoms is excluded. X and Y may be bonded. R ¹ , R ² and R ³ represent the same hydrogen atom, aliphatic hydrocarbon group, alicyclic hydrocarbon group and aromatic hydrocarbon group as those of X and Y, and R ¹ , R ² and R ³ are It may be the same or different. M represents an alkali metal. Furthermore, the above X, Y, R ¹ , R ² and R ³ may have other groups such as a hydroxyl group, a carboxyl group, and a halogen atom.

  Specific examples of the boronic acid ester group represented by the above formula (2) include boronic acid dimethyl ester group, boronic acid diethyl ester group, boronic acid dibutyl ester group, boronic acid dicyclohexyl ester group, boronic acid ethylene glycol ester group, boron Propylene glycol ester group, boronic acid 1,3-propanediol ester group, boronic acid 1,3-butanediol ester group, boronic acid neopentyl glycol ester group, boronic acid catechol ester group, boronic acid glycerin ester group, boronic acid Examples thereof include a trimethylol ethane ester group, a boronic acid trimethylol propane ester group, and a boronic acid diethanolamine ester group.

  Examples of the boronic acid base represented by the above formula (4) include an alkali metal base of boronic acid. Specific examples include sodium boronate base and potassium boronate base.

  Among such boron-containing groups, a boronic acid cyclic ester group is preferable from the viewpoint of thermal stability. Examples of the boronic acid cyclic ester group include a boronic acid cyclic ester group containing a 5-membered ring or a 6-membered ring. Specific examples include a boronic acid ethylene glycol ester group, a boronic acid propylene glycol ester group, a boronic acid 1,3-propanediol ester group, a boronic acid 1,3-butanediol ester group, and a boronic acid glycerin ester group. .

  The first soft material is preferably a compound having a molecular weight of 10,000 or less, more preferably a compound having a molecular weight of 5000 or less, more preferably a compound having a molecular weight of 2000 or less, and particularly preferably a molecular weight of 1000 or less. It is a compound of this. In addition, when the said soft material is a polymer, the molecular weight of this soft material refers to the weight average molecular weight of polystyrene conversion measured by gel permeation chromatography (GPC).

  The first soft material is preferably in a state where it is homogeneously mixed without causing inconvenient separation (exudation, bloom, etc.) in the elastomer composition. In other words, the first soft material is preferably compatible with the elastomer.

  The first soft material includes butadiene rubber (BR), isoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), natural rubber (NR), butyl rubber (IIR), particularly from the viewpoint of improving crack resistance. , Isobutylene-p-methylstyrene, chlorosulfonated polyethylene rubber (CSM), ethylene propylene rubber (EPM, EPDM), ethylene-butene rubber, ethylene-octene rubber, chloroprene rubber (CR), acrylic rubber (ACM), nitrile rubber (NBR) ), Rubbers such as silicone rubber, hydrogenated rubbers (for example, hydrogenated SBR), modified rubbers (for example, modified natural rubber, brominated-butyl rubber (Br-IIR), chlorinated butyl rubber (Cl-IIR)) , Brominated isobutylene-p-methylstyrene, etc.), liquid rubber (ie low content) It can be used an amount rubber) or the like. From the same viewpoint, the first soft material includes polyethylene (PE), polypropylene (PP), ethylene-butene copolymer, styrene-ethylene-butene-styrene block copolymer (SEBS), and styrene-ethylene. In addition to polymers such as propylene-styrene block copolymer (SEPS), styrene-isobutylene-chloromethylstyrene block copolymer, and polyamide, hydrogenated products, modified products, and the like can be used. More specifically, maleic anhydride-modified hydrogenated styrene-ethylene-butadiene-styrene block copolymer, maleic anhydride-modified ultra-low density polyethylene and the like can be mentioned. In addition, these soft materials may be used individually by 1 type, and may blend and use 2 or more types.

  Moreover, you may use a known plasticizer as said 1st soft material from a viewpoint which is excellent in compatibility with an elastomer and reduces a glass transition point (Tg). Here, as the plasticizer, phthalic acid plasticizers such as dibutyl phthalate, diheptyl phthalate, dioctyl phthalate (DOP), ditridecyl phthalate, and trioctyl melylate; phosphates such as tricresyl phosphate and trioctyl phosphate Plasticizers; fatty acid plasticizers such as tributyl citrate, dioctyl adipate, dioctyl sebacate, and methylacetyl ricinolate; epoxy plasticizers such as epoxidized soybean oil and diisodecyl-4,5-epoxyterolahydrophthalate; N-butyl In addition to amide plasticizers such as benzenesulfonamide, chlorinated paraffin, sunflower oil suitable for diene elastomer, and the like can be mentioned. In addition, these soft materials may be used individually by 1 type, and may blend and use 2 or more types.

  In the multilayer structure of the present invention, the content of the first soft material in the elastomer composition is preferably 5 to 30% by mass. When the content of the first soft material is less than 5% by mass, the low-temperature hardness of the elastomer layer cannot be sufficiently reduced, and there is a possibility that the effect of improving crack resistance may not be sufficiently obtained, and the film formability is improved. There is a risk that it will not be. On the other hand, when the content of the soft material exceeds 30% by mass, the content of the soft material is excessively increased, and the film formability may be deteriorated.

  You may mix | blend a radical crosslinking agent with the said elastomer composition. When the elastomer composition contains a radical crosslinking agent, the crosslinking effect at the time of active energy ray irradiation can be enhanced, and the interlayer adhesion of the multilayer structure can be further improved. Moreover, it is also possible to reduce the irradiation amount of an active energy ray compared with the case where a radical crosslinking agent does not exist in an elastomer composition. The content of the radical crosslinking agent in the elastomer composition is preferably 0.01 to 10% by mass, more preferably 0.05 to 9% by mass, and still more preferably 0.1 to 8% by mass, from the viewpoint of the balance between the crosslinking effect and the economy. Examples of the radical crosslinking agent include trimethylolpropane trimethacrylate, triallyl isocyanurate, triallyl cyanurate, diethylene glycol diacrylate, neophenylene glycol diacrylate, and the like. In addition, these radical crosslinking agents may be used individually by 1 type, and may be used in combination of 2 or more type.

  In addition to the elastomer, soft material, and radical crosslinking agent, the elastomer composition contains a wide variety of additives such as metal salts, heat stabilizers, ultraviolet absorbers, antioxidants, colorants, and fillers described below. They can be appropriately selected and blended within a range that does not impair the object of the present invention. In addition, the content of additives other than the elastomer in the elastomer composition is preferably 50% by mass or less, more preferably 30% by mass or less, and still more preferably 10% by mass or less.

The elastomer or elastomer composition has a melt viscosity (η _1B ) of 1 × 10 ² Pa · s to 1 × 10 ⁴ Pa · s at a temperature of 210 ° C. and a shear rate of 10 / second, a temperature of 210 ° C. and a shear rate. The melt viscosity (η _2B ) at a speed of 1,000 / sec is 1 × 10 ¹ Pa · s to 1 × 10 ³ Pa · s, and the melt viscosity ratio (η _2B / η _1B ) is as follows: It is preferable to satisfy the formula (1B).
−0.8 ≦ (1/2) log ₁₀ (η _2B / η _1B ) ≦ −0.1 (1B)

When the melt viscosity (η _1B ) is less than 1 × 10 ² Pa · s, neck-in and film shaking become significant during extrusion film formation by melt coextrusion lamination or melt extrusion, and the resulting multilayer structure and elastomer before lamination There is a possibility that the thickness unevenness and the reduction of the width of the layer become large, and it becomes impossible to obtain a multilayer structure having a uniform and target size. On the other hand, when the melt viscosity (η _1B ) exceeds 1 × 10 ⁴ Pa · s, film breakage is likely to occur particularly during melt coextrusion lamination or melt extrusion molding under high-speed take-up conditions exceeding 100 m / min. Thus, the high-speed film forming property is remarkably impaired, and die swell tends to occur, and it may be difficult to obtain a thin multilayer structure or an elastomer layer before lamination.

Further, when the melt viscosity (η _2B ) is smaller than 1 × 10 ¹ Pa · s, neck-in and film shake become remarkable at the time of extrusion film formation by melt coextrusion lamination or melt extrusion, and the resulting multilayer structure or There is a possibility that the thickness variation and the reduction of the width of the elastomer layer before lamination are increased. On the other hand, when the melt viscosity (η _2B ) exceeds 1 × 10 ³ Pa · s, the torque applied to the extruder becomes too high, and extrusion spots and weld lines may easily occur.

When the value of (1/2) log ₁₀ (η _2B / η _1B ) calculated from the melt viscosity ratio (η _2B / η _1B ) is smaller than −0.8, extrusion by melt coextrusion lamination or melt extrusion There is a possibility that film breakage is likely to occur at the time of film formation and high-speed film formation property is impaired. On the other hand, when the value of (1/2) log ₁₀ (η _2B / η _1B ) exceeds −0.1, neck-in or film swaying occurs at the time of extrusion film formation by melt coextrusion lamination or melt extrusion. There is a risk that unevenness of thickness or reduction in width may occur in the multilayer structure or the elastomer layer before lamination. From this viewpoint, the value of (1/2) log ₁₀ (η _2B / η _1B ) is more preferably −0.6 or more, and more preferably −0.2 or less. In addition, the value of (1/2) log ₁₀ (η _2B / η _1B ) in the above formula is the melt viscosity (η _1B ) and the melt in the natural logarithmic graph with the melt viscosity as the vertical axis and the shear rate as the horizontal axis. It is determined as the slope of a straight line connecting two points of viscosity (η _2B ).

The elastomer or elastomer composition has a viscosity behavior stability (M ₁₀₀ / M ₂₀ , but M _{20) in} the relationship between the melt kneading time and torque at at least one point at a temperature 10 to 80 ° C. higher than the melting point of the elastomer or elastomer composition. it is preferred that the torque after 20 minutes from the start _{kneading, M 100} is a range value of 0.5 to 1.5 of the representative of the torque after 100 minutes from the start kneading). The viscosity behavior stability value closer to 1 indicates that the viscosity change is smaller and the thermal stability (long run property) is more excellent.

The elastomer layer constituting the multilayer structure of the present invention has an air permeability at 20 ° C. and 65% RH, which usually exceeds 3.0 × 10 ⁻¹¹ cm ³ / (m ² · 24 h · atm). It is preferably in the range of × 10 ^{−9 to} 3.0 × 10 ⁻¹¹ cm ³ / (m ² · 24 h · atm).

  The barrier layer constituting the multilayer structure of the present invention is a layer for imparting gas barrier properties to the multilayer structure, and is preferably a layer composed of a resin or a layer composed of a resin composition in which the resin exists as a matrix. In the multilayer structure of the present invention, it is further preferable that the barrier layer includes at least one layer made of a resin composition in which a second soft material having a Young's modulus at 23 ° C. lower than that of the resin is dispersed in the resin. . The matrix means a continuous phase. Here, by dispersing the second soft material in the resin, the elastic modulus of the resin composition can be lowered, and durability such as crack resistance can be improved.

  The barrier layer constituting the multilayer structure of the present invention is not particularly limited. However, as shown in FIG. 1, all barrier layers 1 have a Young's modulus at 23 ° C. in the resin 5. The layer which consists of a resin composition which disperse | distributed the 2nd soft material 6 lower than this resin may be sufficient. The second soft material 6 in the figure is actually compatible with the resin and does not look like a macro, but in the present application, it is shown in the form of particles for convenience of explanation. Further, reference numerals 5 and 6 in the figure are attached only to the uppermost layer of the barrier layer.

The barrier layer preferably has an air permeability of 8.0 × 10 ⁻¹² cm ³ · cm / cm ² · sec · cmHg or less at 20 ° C. and 65% RH, and 1.0 × 10 ^{−13 to} 3.0 A range of × 10 ⁻¹² cm ³ · cm / cm ² · sec · cmHg is more preferable.

  The resin used for the barrier layer is not particularly limited, but an ethylene-vinyl alcohol copolymer (EVOH), a modified ethylene-vinyl alcohol copolymer (modified EVOH), a polyamide resin, a polyvinylidene chloride resin ( PVDC), polyethylene terephthalate (PET), polyacrylonitrile and the like. Among these, an ethylene-vinyl alcohol copolymer and a modified ethylene-vinyl alcohol copolymer are preferable. The modified EVOH is a compound obtained by, for example, reacting an epoxy compound or the like with EVOH, and has a lower elastic modulus than ordinary EVOH. For this reason, the elasticity modulus of a barrier layer can be reduced and durability, such as crack resistance, can also be improved. In addition, these resin may be used individually by 1 type, and may be used in combination of 2 or more type.

  The ethylene-vinyl alcohol copolymer preferably has an ethylene content of 3 to 70 mol%, and 10 to 60 mol% from the viewpoint of improving gas barrier properties, melt moldability and interlayer adhesion of the multilayer structure. More preferably, it is more preferably 20 to 55 mol%, and 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 multilayer structure There is a risk that the gas barrier properties of the glass will deteriorate.

  From the viewpoint of improving the gas barrier property, moisture resistance and interlayer adhesion of the multilayer structure, the ethylene-vinyl alcohol copolymer preferably has a saponification degree of 80% or more, and preferably 90% or more. More preferably, it 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 multilayer structure may be lowered.

  The ethylene-vinyl alcohol copolymer should have 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, flex resistance and fatigue resistance. Preferably, it is 0.3-25 g / 10min.

The ethylene-vinyl alcohol copolymer has a 1,2-glycol bond structural unit content G (mol%) of the following formula:
G ≦ 1.58−0.0244 × E
[Wherein, G is the content (mol%) of 1,2-glycol-bonded structural units, 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 resulting multilayer structure 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水酸基を表す。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、上記炭素数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、水酸基、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水酸基を表す。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、上記炭素数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、水酸基、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, for example, at least one structural unit selected from the structural units (I) and (II) shown below, and the structural unit is contained 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 multilayer structure.

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 hydroxyl 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 has a hydroxyl group, a carboxy group, or a halogen atom. You may do it. 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 hydroxyl 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 hydroxyl group, an alkoxy group, a carboxy group, or a halogen atom. You may have an atom.

  In the modified EVOH, the lower limit of the content of the structural unit (I) and / or (II) with respect to all structural units is preferably 0.5 mol%, more preferably 1 mol%, still 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 above-specified proportions, flexibility and processing characteristics of the resin or resin composition, interlayer adhesion, stretchability and thermoformability of the multilayer structure 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. An alkyl group, a cycloalkenyl group, etc. are mentioned, A phenyl group etc. are mentioned as a C6-C10 aromatic hydrocarbon 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 hydroxyl group, a hydroxymethyl group or a hydroxyethyl group. More preferably, they are each independently a hydrogen atom, a methyl group, a hydroxyl group or a hydroxymethyl group. With such R ¹ , R ² and R ³ , the stretchability and thermoformability of the multilayer structure 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 from 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 hydroxyl 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 multilayer structure, propylene, 3-acyloxy-1-propene, 3-acyloxy-1-butene, 4-acyloxy-1-butene, and 3 1,4-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 multilayer structure, 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 with respect 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 multilayer structure. Propane 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 the vinyl ester that can be used for the polymerization include 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. Moreover, 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, batchwise, in which 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. .

  The resin composition used for the barrier layer may contain one or more compounds selected from phosphoric acid compounds, carboxylic acids, and boron compounds.

  Specifically, the thermal stability at the time of melt molding of the multilayer structure can be improved by containing a phosphoric acid compound in the resin composition. It does not specifically limit as a phosphoric acid compound, For example, various acids, such as phosphoric acid and phosphorous acid, its salt, etc. are mentioned. The phosphate may be contained in any form of, for example, a first phosphate, a second phosphate, and a third phosphate, and the counter cation species is not particularly limited. Alkaline earth metal ions are preferred. In particular, sodium dihydrogen phosphate, potassium dihydrogen phosphate, sodium hydrogen phosphate, or potassium hydrogen phosphate is preferred because of its high thermal stability improving effect.

  As a minimum of content of a phosphoric acid compound (phosphoric acid radical conversion content of a phosphoric acid compound in a dry resin composition), 1 mass ppm is preferred, 10 mass ppm is more preferred, and 30 mass ppm is still more preferred. On the other hand, as an upper limit of content of a phosphoric acid compound, 10,000 mass ppm is preferable, 1,000 mass ppm is more preferable, and 300 mass ppm is still more preferable. If the content of the phosphoric acid compound is less than 1 ppm by mass, coloring during melt molding may become severe. In particular, since the tendency is remarkable when the heat histories are accumulated, a molded product obtained by molding the resin composition pellet may be poor in recoverability. On the other hand, when the content of the phosphoric acid compound exceeds 10,000 ppm by mass, there is a risk that gels and blisters are likely to occur during molding.

  Moreover, by containing carboxylic acid in a resin composition, the effect of controlling the pH of a resin composition, preventing gelation, and improving thermal stability is acquired. As the carboxylic acid, those having a pKa at 25 ° C. of 3.5 or more are preferable. When a carboxylic acid such as oxalic acid, succinic acid, benzoic acid, or citric acid having a pKa at 25 ° C. of less than 3.5 is contained, it becomes difficult to control the pH of the resin composition, and coloring resistance and interlayer adhesion are reduced. There is a possibility that it cannot be obtained sufficiently. As such carboxylic acid, acetic acid or lactic acid is particularly preferable from the viewpoint of cost and the like.

  As a minimum of content of carboxylic acid (content of carboxylic acid in a dry resin composition), 1 mass ppm is preferred, 10 mass ppm is more preferred, and 50 mass ppm is still more preferred. On the other hand, the upper limit of the carboxylic acid content is preferably 10,000 mass ppm, more preferably 1,000 mass ppm, and even more preferably 500 mass ppm. If the carboxylic acid content is less than 1 ppm by mass, coloring may occur during melt molding. On the other hand, if the content of carboxylic acid exceeds 10,000 ppm by mass, the interlayer adhesion may be insufficient.

Furthermore, the heat stability improvement effect is acquired by containing a boron compound in a resin composition. Specifically, for example, when a boron compound is added to a resin such as (modified) EVOH, a chelate compound is considered to be generated between (modified) EVOH and the boron compound, and by using such (modified) EVOH, It is possible to improve thermal stability and improve mechanical properties over normal (modified) EVOH. The boron compound is not particularly limited, and examples thereof include boric acids, boric acid esters, borates, and hydrogenated boric acids. Specifically, examples of boric acids include orthoboric acid (H ₃ BO ₃ ), metaboric acid, tetraboric acid, and the like, and examples of boric acid esters include triethyl borate, trimethyl borate, and the like. Examples of the borate include alkali metal salts, alkaline earth metal salts, and borax of the various boric acids. Of these, orthoboric acid is preferred.

  The lower limit of the boron compound content (the boron-converted content of the boron compound in the dry resin composition) is preferably 1 ppm by mass, more preferably 10 ppm by mass, and even more preferably 50 ppm by mass. On the other hand, the upper limit of the boron compound content is preferably 2,000 mass ppm, more preferably 1,000 mass ppm, and even more preferably 500 mass ppm. If the content of the boron compound is less than 1 ppm by mass, the effect of improving the thermal stability by adding the boron compound may not be obtained. On the other hand, when the content of the boron compound exceeds 2,000 ppm by mass, gelation tends to occur and there is a risk of forming defects.

  The method for containing the phosphoric acid compound, carboxylic acid or boron compound in the resin composition is not particularly limited. For example, a method of adding and kneading the resin composition to the resin composition when preparing a pellet or the like of the resin composition. Is preferably employed. The method of adding to the resin composition is not particularly limited, but the method of adding as a dry powder, the method of adding in a paste impregnated with a solvent, the method of adding in a suspended state in a liquid, or dissolving in a solvent. The method of adding as a solution can be illustrated. Among these, from the viewpoint of homogeneous dispersion, a method of dissolving in a solvent and adding as a solution is preferable. The solvent used in these methods is not particularly limited, but water is preferably used from the viewpoints of solubility of the additive, cost merit, ease of handling, completeness of work environment, and the like. At the time of these additions, a metal salt, other additives, etc., which will be described later, can be added simultaneously.

  In addition, as another method of containing a phosphoric acid compound, a carboxylic acid or a boron compound, a method of immersing pellets or strands of a resin composition obtained by an extruder or the like in a solution in which those substances are dissolved in a solvent Is preferable in that the substance can be uniformly dispersed. Also in this method, water is preferably used as the solvent for the same reason. By dissolving a metal salt described later in this solution, the metal salt can be contained simultaneously with the phosphoric acid compound and the like.

  The resin composition may contain a compound having a conjugated double bond having a molecular weight of 1,000 or less. By containing such a compound, the hue of the resin composition is improved, and a multilayer structure having a good appearance can be produced. Examples of such a compound include a conjugated diene compound having a structure in which two carbon-carbon double bonds and three carbon-carbon single bonds are alternately connected, three carbon-carbon double bonds, and four carbon-carbon double bonds. Conjugated triene compound having a structure in which carbon-carbon single bonds are alternately connected (preferably 2,4,6-octatriene), 4 or more carbon-carbon double bonds and 5 or more carbon-carbon single bonds And conjugated polyene compounds having a structure in which and are alternately connected. In addition, the compound having a conjugated double bond may include a plurality of conjugated double bonds independently in one molecule, for example, a compound having three conjugated trienes in the same molecule such as tung oil. .

  Examples of the compound having a conjugated double bond include a carboxy group and a salt thereof, a hydroxyl group, an ester group, a carbonyl group, an ether group, an amino group, an imino group, an amide group, a cyano group, a diazo group, a nitro group, a sulfone group, and a sulfoxide. Various functional groups other than conjugated double bonds such as groups, sulfide groups, thiol groups, sulfonic acid groups and salts thereof, phosphoric acid groups and salts thereof, phenyl groups, halogen atoms, nonconjugated double bonds, and triple bonds It may be. Such a functional group may be directly bonded to the carbon atom in the conjugated double bond, or may be bonded to a position away from the conjugated double bond. In addition, the multiple bond in the functional group may be in a position capable of conjugating with a conjugated double bond. For example, 1-phenylbutadiene having a phenyl group, sorbic acid having a carboxy group, etc. Included in compounds with heavy bonds.

  Specific examples of the compound having a conjugated double bond include, for example, 2,4-diphenyl-4-methyl-1-pentene, 1,3-diphenyl-1-butene, and 2,3-dimethyl-1,3-butadiene. 4-methyl-1,3-pentadiene, 1-phenyl-1,3-butadiene, sorbic acid, myrcene and the like.

  The conjugated double bond in the compound having a conjugated double bond is not only an aliphatic conjugated double bond such as 2,3-dimethyl-1,3-butadiene and sorbic acid, but also 2,4-diphenyl. Aliphatic and aromatic conjugated double bonds such as -4-methyl-1-pentene and 1,3-diphenyl-1-butene are also included. However, from the viewpoint of obtaining a multilayer structure having a better appearance, a compound containing a conjugated double bond between the above aliphatic groups is preferable, and a conjugated double bond having a polar group such as a carboxy group and a salt thereof, or a hydroxyl group is included. Also preferred are compounds. Further, a compound having a polar group and containing an aliphatic conjugated double bond is particularly preferable.

  The molecular weight of the compound having a conjugated double bond is preferably 1,000 or less. When the molecular weight exceeds 1,000, the surface smoothness and extrusion stability of the multilayer structure may be deteriorated.

  The lower limit of the content of the compound having a conjugated double bond having a molecular weight of 1,000 or less in the resin composition is preferably 0.1 ppm by mass from the viewpoint of improving the effect exerted by the addition of the compound. 1 mass ppm is more preferable, 3 mass ppm is still more preferable, and 5 mass ppm is especially preferable. On the other hand, the upper limit of the content of the compound is preferably 3,000 ppm by mass, more preferably 2,000 ppm by mass, and 1,500 ppm by mass from the viewpoint of improving the effect exhibited by the addition of the compound. More preferred is 1,000 ppm by mass.

  The method for adding the compound having a conjugated double bond to the resin composition is not particularly limited, but when the resin is (modified) EVOH, the compound after polymerization and before saponification is added. The method of adding is preferable in terms of improving surface smoothness and extrusion stability. The reason for this is not necessarily clear, but it is considered that the compound having a conjugated double bond has an action to prevent alteration of (modified) EVOH before saponification and / or during the saponification reaction.

  The preferred embodiment of the second soft material and the preferred content of the second soft material in the resin composition are the same as those of the first soft material used for the elastomer layer. That is, the second soft material is preferably a compound having a functional group capable of reacting with a hydroxyl group, and specific examples of the functional group capable of reacting with a hydroxyl group are the same as in the case of the first soft material. The second soft material is preferably a compound having a molecular weight of 10,000 or less, more preferably a compound having a molecular weight of 5000 or less, more preferably a compound having a molecular weight of 2000 or less, and particularly preferably a molecular weight. 1000 or less compounds. Furthermore, the second soft material is preferably compatible with the resin. Furthermore, it is preferable that the content rate of the 2nd soft material in the said resin composition is 10-30 mass%.

  Specifically, as the second soft material, butadiene rubber (BR), isoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), natural rubber (NR), butyl rubber (IIR), isobutylene-p- Methyl styrene, chlorosulfonated polyethylene rubber (CSM), ethylene propylene rubber (EPM, EPDM), ethylene-butene rubber, ethylene-octene rubber, chloroprene rubber (CR), acrylic rubber (ACM), nitrile rubber (NBR), silicone rubber, etc. In addition to these rubbers, these hydrogenated rubbers (for example, hydrogenated SBR), modified rubbers (for example, modified natural rubber, brominated-butyl rubber (Br-IIR), chlorinated butyl rubber (Cl-IIR), brominated isobutylene- p-methylstyrene, etc.), liquid rubber (ie, low molecular weight rubber), etc. It is possible. From the same viewpoint, the second soft material includes polyethylene (PE), polypropylene (PP), ethylene-butene copolymer, styrene-ethylene-butene-styrene block copolymer (SEBS), and styrene-ethylene. In addition to polymers such as propylene-styrene block copolymer (SEPS), styrene-isobutylene-chloromethylstyrene block copolymer, and polyamide, hydrogenated products, modified products, and the like can be used. More specifically, maleic anhydride-modified hydrogenated styrene-ethylene-butadiene-styrene block copolymer, maleic anhydride-modified ultra-low density polyethylene and the like can be mentioned. In addition, these soft materials may be used individually by 1 type, and may blend and use 2 or more types.

  Furthermore, a known plasticizer may be used as the second soft material. Here, as the plasticizer, phthalic acid plasticizers such as dibutyl phthalate, diheptyl phthalate, dioctyl phthalate (DOP), ditridecyl phthalate, and trioctyl melylate; phosphates such as tricresyl phosphate and trioctyl phosphate Plasticizers; fatty acid plasticizers such as tributyl citrate, dioctyl adipate, dioctyl sebacate, and methylacetyl ricinolate; epoxy plasticizers such as epoxidized soybean oil and diisodecyl-4,5-epoxyterolahydrophthalate; N-butyl In addition to amide plasticizers such as benzenesulfonamide, chlorinated paraffin, sunflower oil and the like can be mentioned. In addition, these soft materials may be used individually by 1 type, and may blend and use 2 or more types.

  For the same reason as in the case of the elastomer composition, a radical crosslinking agent may be added to the resin composition. Similarly, the content of the radical crosslinking agent in the resin composition is preferably 0.01 to 10% by mass, more preferably 0.05 to 9% by mass, and still more preferably 0.1 to 8% by mass. Specific examples of the radical crosslinking agent are as described above.

  In addition to the resin, phosphoric acid compound, carboxylic acid, boron compound, compound having a conjugated double bond, soft material, radical crosslinking agent, the resin composition includes a metal salt, a thermal stabilizer, and an ultraviolet absorber described later. A wide variety of additives such as antioxidants, colorants, fillers and the like can be appropriately selected and blended within a range that does not impair the object of the present invention. In addition, the content of additives other than the resin in the resin composition is preferably 50% by mass or less, more preferably 30% by mass or less, and still more preferably 10% by mass or less.

The resin or resin composition has a melt viscosity (η _1A ) at a temperature of 210 ° C. and a shear rate of 10 / sec of 1 × 10 ² Pa · s or more and 1 × for the same reason as in the case of the elastomer or elastomer composition. 10 ⁴ Pa · s or less, a melt viscosity (η _2A ) at a temperature of 210 ° C. and a shear rate of 1,000 / sec is 1 × 10 ¹ Pa · s or more and 1 × 10 ³ Pa · s or less, and these It is preferable that the melt viscosity ratio (η _2A / η _1A ) satisfies the following formula (1A).
−0.8 ≦ (1/2) log ₁₀ (η _2A / η _1A ) ≦ −0.1 (1A)

Similarly, the value of (1/2) log ₁₀ (η _2A / η _1A ) calculated from the melt viscosity ratio (η _2A / η _1A ) is more preferably −0.6 or more, and −0 More preferably, it is 2 or less.

The resin or resin composition has a viscosity behavior stability (M ₁₀₀ / M ₂₀ , where M ₂₀ is from the start of kneading) in relation to the melt kneading time and torque at at least one point at a temperature 10 to 80 ° C. higher than the melting point of the resin. The value of the torque after 20 minutes (M ₁₀₀ represents the torque after 100 minutes from the start of kneading) is preferably in the range of 0.5 to 1.5. The viscosity behavior stability value closer to 1 indicates that the viscosity change is smaller and the thermal stability (long run property) is more excellent.

In addition, regarding the relationship between the viscosity of the resin or resin composition and the viscosity of the elastomer or elastomer composition, the elastomer or the melt viscosity (η _2A ) of the resin or resin composition at a temperature of 210 ° C. and a shear rate of 1,000 / sec. The lower limit of the melt viscosity (η _2B ) ratio (η _2B / η _2A ) of the elastomer composition is preferably 0.3, more preferably 0.4, and even more preferably 0.5. On the other hand, the upper limit of the ratio (η _2B / η _2A ) of the melt viscosity (η _2B ) of the elastomer or elastomer composition to the melt viscosity (η _2A ) of the resin or resin composition is preferably 2, and more preferably 1.5. 1.3 is more preferable. By setting the melt viscosity ratio (η _2B / η _2A ) within the above specified range, the appearance of the multilayer structure is improved by the multilayer coextrusion method, and the adhesion between the barrier layer and the elastomer layer is good. Thus, the durability of the multilayer structure can be improved.

  The multilayer structure of the present invention preferably contains a metal salt in at least one of adjacent layers (for example, adjacent barrier layer and elastomer layer). In this case, the interlayer adhesion of the multilayer structure can be greatly improved, and the multilayer structure has excellent durability. The reason why interlayer adhesion can be improved by the inclusion of a metal salt is not necessarily clear, but for example, the bond formation reaction that occurs between the resin constituting the barrier layer and the elastomer constituting the elastomer layer is accelerated by the presence of the metal salt. It is conceivable. Specific examples of such bond formation reactions include a hydroxyl group exchange reaction that occurs between the carbamate group of TPU and the hydroxyl group of EVOH, and an addition reaction of the hydroxyl group of EVOH to the remaining isocyanate group in TPU.

  Although it does not specifically limit as said metal salt, The transition metal salt which belongs to the 4th period of an alkali metal salt, alkaline earth metal salt, or a periodic table is preferable from a viewpoint of improving interlayer adhesiveness more. Among these, alkali metal salts or alkaline earth metal salts are more preferable, and alkali metal salts are particularly preferable.

  Although it does not specifically limit as said alkali metal salt, For example, aliphatic carboxylate, aromatic carboxylate, phosphate, a metal complex etc., such as lithium, sodium, and potassium, are mentioned. Specific examples of the alkali metal salt include sodium acetate, potassium acetate, sodium phosphate, lithium phosphate, sodium stearate, potassium stearate, sodium salt of ethylenediaminetetraacetic acid, and the like. Among these, sodium acetate, potassium acetate, and sodium phosphate are particularly preferable because they are easily available.

  Although it does not specifically limit as said alkaline-earth metal salt, For example, acetate, such as magnesium, calcium, barium, beryllium, or phosphate is mentioned. Among these, magnesium or calcium acetate or phosphate is particularly preferable because it is easily available. When such an alkaline earth metal salt is contained, there is an advantage that the amount of heat-degraded resin adhering to the die of the molding machine during melt molding can be reduced.

  Although it does not specifically limit as a metal salt of the transition metal which belongs to the 4th period of the said periodic table, For example, carboxylate, phosphate, such as titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc And acetylacetonate salts.

  The lower limit of the content of the metal salt (content in terms of metal element in the multilayer structure) is preferably 1 mass ppm, more preferably 5 mass ppm, still more preferably 10 mass ppm, and particularly preferably 20 mass ppm. . On the other hand, the upper limit of the content of the metal salt is preferably 10,000 ppm by mass, more preferably 5,000 ppm by mass, still more preferably 1,000 ppm by mass, and particularly preferably 500 ppm by mass. If the content of the metal salt is less than 1 mass ppm, the effect of improving interlayer adhesion may be reduced. On the other hand, when the content of the metal salt exceeds 10,000 ppm by mass, the appearance of the multilayer structure may be deteriorated.

  The method of containing the metal salt in the resin composition forming the barrier layer or the elastomer composition forming the elastomer layer is not particularly limited, and a phosphoric acid compound or the like is added to the resin composition as described above. The method similar to the method of containing can be employ | adopted.

  In the multilayer structure of the present invention, the peel resistance of adjacent layers (for example, between barrier layers, between elastomer layers, and between a barrier layer and an elastomer layer) is preferably 10 N / 25 mm or more from the viewpoint of interlayer adhesion, and more Preferably it is 15N / 25mm or more, More preferably, it is 20N / 25mm or more. Here, the peel resistance is a value measured by a T-type peel test in accordance with JIS K 6854 at 23 ° C. and 50% RH atmosphere at a pulling speed of 50 mm / min.

  The method for producing the multilayer structure of the present invention is not particularly limited as long as the barrier layer and the elastomer layer can be laminated and adhered satisfactorily. For example, coextrusion, lamination, coating, bonding, adhesion Known methods such as As specific examples of the method for producing a multilayer structure of the present invention, (1) a resin composition containing EVOH and an elastomer composition containing an elastomer are prepared, and a barrier layer and an epoxy composition are produced by a multilayer coextrusion method using these compositions. A method for producing a multilayer structure having an elastomer layer, and (2) a resin composition containing EVOH and an elastomer composition containing an elastomer are prepared, and a plurality of laminates are produced using these, and then a plurality of laminates are prepared. For example, a method of producing a multilayer structure having a barrier layer and an elastomer layer by superimposing the bodies with an adhesive and stretching the bodies is exemplified. Among these, the method (1) is preferable from the viewpoint of high productivity and excellent interlayer adhesion.

  In the multilayer coextrusion method, the resin or resin composition forming the barrier layer and the elastomer or elastomer composition forming the elastomer layer are heated and melted and extruded through different flow paths from different extruders and pumps. The multilayer structure of the present invention is formed by being laminated and bonded after being supplied to the die and extruded from the extrusion die into multiple layers. As this extrusion die, for example, a multi-manifold die, a field block, a static mixer or the like can be used.

  In the multilayer structure of the present invention, a support layer for supporting the laminate may be laminated on both sides or one side of the laminate comprising a barrier layer and an elastomer layer. The support layer is not particularly limited, and for example, a synthetic resin layer or the like usually used as the 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.

  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 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. 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 has a main body portion extending in a toroid 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. Furthermore, 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 radial direction of the tire, but 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.

  The pneumatic tire of the present invention can be manufactured by applying the above-described multilayer structure to the inner liner 12 and using a conventional method. In the pneumatic tire of the present invention, as the gas filled in the tire, normal or air with a changed oxygen partial pressure, or an inert gas such as nitrogen can be used.

  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.

(Synthesis Example 1: EVOH)
A polymerization tank equipped with a cooling device and a stirrer is charged with 20000 parts by weight of vinyl acetate, 2000 parts by weight of methanol, and 10 parts by weight of 2,2′-azobis- (4-methoxy-2,4-dimethylvaleronitrile) as a polymerization initiator. After purging with nitrogen while stirring, ethylene was introduced, the internal temperature was adjusted to 60 ° C., the ethylene pressure was adjusted to 4.5 MPa, the temperature and pressure were maintained for 4 hours, and polymerization was carried out while stirring. Next, 10 parts by mass of sorbic acid (SA) (0.0005% by mass with respect to the charged vinyl acetate) was dissolved in methanol to prepare a methanol solution of 1.5% by mass of sorbic acid, and this was added. The polymerization rate was 45% based on the charged vinyl acetate. The copolymerization reaction liquid obtained after the polymerization is supplied to a tower packed with Raschig rings, and unreacted vinyl acetate is removed from the top of the tower by introducing methanol vapor from the bottom of the tower, and then 40% by mass of methanol of the copolymer. A solution was obtained. The copolymer had an ethylene unit content of 44 mol% and a vinyl acetate unit content of 56 mol%.

  The obtained methanol solution of the copolymer was introduced into the saponification reactor, and then the sodium hydroxide / methanol solution (85 g / L) was 0.5 equivalent to the vinyl acetate component in the copolymer. Then, methanol was further added to adjust the copolymer concentration in the solution to 15% by mass. The temperature inside the reactor was raised to 60 ° C., and the reaction was carried out for 5 hours while blowing nitrogen gas into the reactor. Thereafter, the reaction solution was neutralized with acetic acid to stop the reaction, and the contents were taken out from the reactor and allowed to stand at room temperature. As a result, particulate EVOH was precipitated. The precipitated particles were drained with a centrifuge, and an operation of adding a large amount of water to drain the liquid was repeated to obtain EVOH having a saponification degree of 99.5%.

The obtained EVOH was treated with an aqueous solution containing acetic acid, phosphoric acid and orthoboric acid (OBA) (acetic acid 0.3 g, phosphoric acid 0.06 g, orthoboric acid 0.35 g dissolved in 1 L of aqueous solution) at a bath ratio of 20, After drying, it was pelletized with an extruder to obtain EVOH pellets. The MFR of the EVOH pellets was 1.6 g / 10 min (190 ° C., 21.18 N load). Moreover, the acetic acid content of the pellet was 90 mass ppm, the phosphate compound content was 43 mass ppm in terms of phosphate radical, and the boron compound content was 260 mass ppm in terms of boron. Furthermore, the melt viscosity η _{1A of the} pellet was 3800 Pa · s, η _2A was 590 Pa · s, and (1/2) log ₁₀ (η _2A / η _1A ) was −0.404.

(Examples 1, 3-20 and 22-39)
Resins, resin compositions, elastomers and elastomer compositions for forming the barrier layers and elastomer layers shown in Tables 1 to 10 were prepared, and the barrier layers and the elastomer layers were alternately laminated in the number of layers shown in Tables 1 to 10. In order to form a multilayer structure, a melt at 210 ° C. was supplied from the co-extruder to the feed block, and the melt was extruded and merged from the feed block to produce a multilayer structure. The melt is changed from the feed block so that the thickness of each layer of the multilayer structure becomes uniform by changing the flow path of each layer in the feed block so that it gradually becomes thicker from the surface side toward the center side. It was pushed out.
Moreover, the shape of the slit was designed so that the layer thicknesses of the adjacent barrier layer and elastomer layer were substantially the same. The multilayer structure having a total of 25 layers thus obtained was rapidly cooled and solidified on a casting drum to which a surface temperature was maintained at 25 ° C. and electrostatically applied. 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 Tables 1-10.

  Subsequently, the cast film was irradiated with an electron beam having an irradiation dose shown in Tables 1 to 10 at an acceleration voltage of 200 kV using an electron beam accelerator [manufactured by Nissin High Voltage Co., Ltd., Curetron EB200-100]. Thus, a cross-linked multilayer film was obtained.

(Comparative Example 2)
A single layer film having a thickness of 6 μm was produced according to a conventional method using the EVOH. Moreover, the obtained single layer film was irradiated with an electron beam having an acceleration voltage of 200 kV and an irradiation dose of 200 kGy using an electron beam accelerator [manufactured by Nissin High Voltage Co., Ltd., Curetron EB200-100].

(Comparative Example 21)
Using nylon [Toray Industries, CM1061], a single-layer film having a thickness of 6 μm was produced according to a conventional method. Moreover, the obtained single layer film was irradiated with an electron beam having an acceleration voltage of 200 kV and an irradiation dose of 200 kGy using an electron beam accelerator [manufactured by Nissin High Voltage Co., Ltd., Curetron EB200-100].

  Next, the gas barrier properties, crack resistance, presence or absence of cracks after the low-temperature drum running test, and internal pressure retention of the multilayer film and single-layer film produced as described above were evaluated by the following methods. The results are shown in Tables 1-10. Moreover, the measuring method of the Young's modulus and air permeability in a table | surface is shown below.

(1) Gas barrier property The film was conditioned at 20 ° C. and 65% RH for 5 days. Using two of the obtained humidity-controlled films, the air permeability was measured under the conditions of 20 ° C. and 65% RH using GTR-30X manufactured by GTR Tech, and the average value was obtained. About the result, the average value of the comparative example 1 is displayed as an index, and the lower the index value, the better the gas barrier property.

(2) Crack resistance After making 50 films cut to 21 cm x 30 cm and conditioning each film for 7 days at 0 ° C, according to ASTM F 392-74, manufactured by Rigaku Kogyo Co., Ltd. Using a gelbo flex tester, the number of bendings is 50, 75, 100, 125, 150, 175, 200, 225, 250, 300, 400, 500, 600, 700 The number of pinholes was measured after being bent 800 times, 1000 times, 1500 times. In each bending number, the measurement was performed 5 times, and the average value was defined as the number of pinholes. Taking the number of bends (P) on the horizontal axis and the number of pinholes (N) on the vertical axis, plotting the above measurement results, and obtaining the number of bends (Np1) when the number of pinholes is one by extrapolation. Two digits were used. However, for a film in which no pinholes were observed after 1500 bendings, the number of bendings was increased every 500 times thereafter, and the number of bendings in which pinholes were observed was defined as Np1.
Regarding the number of bendings obtained by the above method, the number of bendings in Comparative Example 1 for Comparative Examples 2 and 3 and Examples 3 to 8, the number of bendings in Comparative Example 9 for Examples 10 to 14, and the comparison for Example 16 The number of bends in Example 15 and Example 18 are indicated by indices when the number of bends in Comparative Example 17 is 100, respectively. In addition, about index value, it shows that there are many frequency | counts of bending and crack resistance is so high that it is large.

(3) Presence or absence of crack after low temperature drum running test Using the film as an inner liner, a pneumatic tire (195 / 65R15) having a structure shown in FIG. Next, the tire was run for 10,000 km in an atmosphere of −30 ° C. under an air pressure of 140 kPa and a weight of 6 km on a rotating drum corresponding to a speed of 80 km / h. The appearance of the inner liner of the tire after running the drum was visually observed to evaluate the presence or absence of cracks.

(4-1) Internal pressure retention (Tables 1 to 4)
The tire was pushed at 10,000 km on a rotating drum corresponding to a speed of 80 km / h with a pressure of 6 kmN at room temperature at an air pressure of 140 kPa. Then, after the tire (test tire) that was traveled was mounted on a 6JJ × 15 rim, the internal 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 Comparative Example 1 was taken as 100, and other values were indexed. The larger the index value, the better the internal pressure retention.

(4-2) Internal pressure retention (Tables 5 to 8)
The tire was pushed at 10,000 km on a rotating drum corresponding to a speed of 80 km / h with a pressure of 6 kmN at room temperature at an air pressure of 140 kPa. Then, after the tire (test tire) that was traveled was mounted on a 6JJ × 15 rim, the internal 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 26]. The value of Comparative Example 20 was taken as 100, and other values were indexed. The larger the index value, the better the internal pressure retention.

(Measurement method of Young's modulus at 23 ° C.)
Using a twin screw extruder manufactured by Toyo Seiki Co., Ltd., a film was formed under the following extrusion conditions to produce a single layer film having a thickness of 100 μm. Next, using this film, a strip-shaped test piece having a width of 15 mm was prepared and left in a temperature-controlled room under conditions of 23 ° C. and 50% RH for 1 week, and then autograph [AG-A500 manufactured by Shimadzu Corporation]. Type] was used to measure an SS curve (stress-strain curve) at 23 ° C. and 50% RH under conditions of a chuck interval of 50 mm and a tensile speed of 50 mm / min, and the Young's modulus from the initial slope of the SS curve. Asked.
Screw: 20 mmφ, full flight cylinder, die temperature setting: C1 / C2 / C3 / die = 200/200/200/200 (° C.)

* 1 Indicates the parts by mass of soft material added to 100 parts by mass of pellets.
* 2 Kuramiron manufactured by Kuraray Co., Ltd.
* 3 Kapox S-6 manufactured by Kao Corporation.
* 4 R-45HT, manufactured by Idemitsu Kosan Co., Ltd.
* 5 Nippon Soda Co., Ltd., Nissan PB series C-1000.
* 7 Sartomer, Ricon 130MA8.
* 8 Ricon 130, manufactured by Sartomer.
* 9 Sunside 550, manufactured by Sanwa Chemical Co., Ltd.
* 13 Ube Industries, UBESTA XPA, polyamide elastomer.
* 14 Tafmer MH7010, a maleic anhydride modified ethylene-butene-1 copolymer elastomer, manufactured by Mitsui Chemicals.
* 15 Tuffmer MP0610, a maleic anhydride modified ethylene-propylene copolymer elastomer, manufactured by Mitsui Chemicals.
* 18 Made by JSR, Dynalon 4630P, modified styrene elastomer.
* 19 Made by JSR, Dynalon 8630P, modified styrene elastomer.
* 20 Mu-ang. Made by Mai Guthrie Public Company, EPOXY PRENE25, epoxidized natural rubber.
* 21 Toray Industries, Inc., CM1061.
* 22 DAICEL EVONIK, E40-S1.
* 24 F216, manufactured by Asahi Kasei Chemicals Corporation.
* 25 TRW-8550FF, manufactured by Teijin Chemicals Limited.

  From the results of Tables 1 to 8, it can be seen that the multilayer structures of Examples can achieve both gas barrier properties and crack resistance as compared with the multilayer structures of Comparative Examples. In addition, the multilayer structures of the examples are excellent in durability at low temperatures.

DESCRIPTION OF SYMBOLS 1 Barrier layer 2 Elastomer layer 3 Elastomer 4 1st soft material 5 Resin 6 2nd soft material 7 Bead part 8 Side wall part 9 Tread part 10 Carcass 11 Belt 12 Inner liner 13 Bead core

Claims (10)

A multilayer structure comprising a total of 7 or more barrier layers and elastomer layers,
The barrier layer has an average thickness of 0.001 to 10 μm, and the elastomer layer has an average thickness of 0.001 to 40 μm.
The elastomer layer has at least one layer comprising an elastomer composition in which a first soft material having a functional group that interacts with an elastomer component, a Young's modulus at 23 ° C. lower than that of the elastomer, and a molecular weight of 10,000 or less is dispersed. A multilayer structure characterized by comprising.   The multilayer structure according to claim 1, wherein the first soft material is a compound having a molecular weight of 5000 or less.   The multilayer structure according to claim 2, wherein the first soft material is a compound having a molecular weight of 2000 or less.   The multilayer structure according to claim 3, wherein the first soft material is a compound having a molecular weight of 1000 or less.   The multilayer structure according to claim 1, wherein the content of the first soft material in the elastomer composition is 10 to 30% by mass.   The multilayer structure according to claim 1, wherein the first soft material is compatible with the elastomer.   The multilayer structure according to claim 1, wherein the barrier layer includes at least one layer made of a resin composition in which a second soft material having a Young's modulus at 23 ° C lower than that of the resin is dispersed in the resin. body.   The multilayer structure according to claim 1, wherein the barrier layer and the elastomer layer are crosslinked by irradiation with active energy rays.   An inner liner for a pneumatic tire using the multilayer structure according to any one of claims 1 to 8. A pneumatic tire comprising the inner liner for a pneumatic tire according to claim 9.

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