JP2795708B2 - Co-injection multilayer structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Industrial Field of the Invention The present invention relates to beverages, foods, cosmetics, etc., which have good gas barrier properties such as oxygen or carbon dioxide, moisture proof, fragrance retention, flavor barrier properties and good appearance. The present invention relates to a co-injection multi-layer structure, particularly a co-injection stretched multi-layer structure, which has been greatly improved in impact-peeling resistance (hereinafter abbreviated as delamination resistance) used for containers.

B. Conventional technology Stretch blow molding polyester containers are used in many fields due to their excellent transparency and rigidity.However, since gas barrier properties are not always sufficient, storage of foods and the like is limited to short periods. Had been. In order to improve this drawback, various methods have been proposed for forming a multilayer structure by combining EVOH with good gas barrier properties to polyester. That is, there are a co-extrusion molding method, a multi-stage injection molding method, a co-injection molding method, etc. as a method for producing a preform prior to stretching blow, but each has advantages and disadvantages. Among them, the co-injection molding method has a simple apparatus, hardly generates any scrap such as trim, and furthermore, the ethylene-vinyl alcohol copolymer (EVOH) layer is completely covered with the thermoplastic polyester (PET) layer. EVOH layer and PET
Even if there is no adhesive resin (Ad) layer between the layers and the like, it has features such as the appearance of a good multilayer container due to the adhesion effect due to atmospheric pressure, and is currently attracting attention. However,
When the container is filled with food or the like and subjected to an impact such as dropping,
Delamination occurred between PET and EVOH, which was a major problem in appearance. Therefore, the structure of the substrate / Ad / EVOH / Ad / substrate (Japanese Patent Application Laid-Open No. 56-501040) including the Ad layer, or the substrate / Ad / EVOH / Ad / substrate / Ad / EVOH / Ad / substrate (Japanese Patent Laid-Open Nos. 50-135169 and 61-15241)
1, 61-152412, 61-259944), etc., have been studied, but the equipment is very complicated, and it is often difficult to control the thickness of each layer.
The production cost and productivity are inferior to other methods, for example, the coextrusion method (pipe method). Although a method of increasing the delamination resistance by blending an adhesive resin or the like with EVOH or PET has been proposed, it is not necessarily sufficient.

C. Problems to be Solved by the Invention The present invention can provide PET, polycarbonate (PC) and polyamide (P) even without an independent adhesive resin layer.
Prevents interlayer delamination due to impact in a co-injection multilayer structure obtained by co-injection molding of at least one resin (D) selected from A) and an EVOH composition (C), and particularly by co-injection stretch blow molding. The purpose is to do.

D. Means for Solving the Problems The present inventors used a co-injection molding method to form a multilayer preform having a resin (D) in the inner and outer surface layers and an intermediate layer in which various EVOHs were completely encapsulated by the inner and outer layers. Was manufactured, and the parison was heated and stretch blow-molded to produce a container. The container was filled with water and dropped on a concrete floor to evaluate the presence of delamination in order to evaluate the impact resistance interlayer delamination of the container. That is,
We studied the composition of EVOH to prevent delamination. As a result, EV blended with 40 to 2% by weight of thermoplastic polyurethane (B) in 60 to 98% by weight of EVOH (A)
It was found that the OH composition (C) significantly improved the delamination of the container in impact resistance. Further, depending on the raw material brand used or the addition ratio, the container body is disturbed or large gels are scattered, which is a serious problem in appearance. The following formula (I)
It has been found that when a raw material satisfying (III) is used, not only the delamination resistance between impact layers is improved but also a container having a good appearance can be obtained.

1 ≦ N (B) ≦ 7 (I) 0.01 ≦ N (B) / CH (A) ≦ 0.2 (II) 0.01 ≦ MI (0) / MI (2) ≦ 10 (III) where N (B): Nitrogen content of polyurethane (B) (% by weight) CH (A): Ethylene content of EVOH (A) (mol%) MI (0): EVOH composition (C) at 220 ° C. under 10.9 kg load Melt index value (g / 10 minutes) MI (2): The EVOH composition (C) is subjected to 220 ° C.-2 in a nitrogen atmosphere.
Melt index value after heat treatment for hours (g / 10 min) Further examinations revealed that EVOH containing 0.0005 to 0.2 mol% of a vinylsilane compound as EVOH (A)
It is just unexpected that the effect is further increased by using.

By the way, EVOH has lower stretchability than PET, and PET
In the co-injection and co-stretching operations of OH and EVOH, unevenness in the elongation, particularly unevenness and streaks in the longitudinal direction of the bolt are liable to occur, and appearance defects are likely to occur. However, surprisingly, the co-injection stretch blow container molded using the EVOH composition (C) not only significantly improves the impact delamination property,
Surprisingly, it was found that streaks and unevenness, which are likely to occur around the container body, and particularly around the bottom and mouth, were greatly improved.
These facts are clear from the examples described later.

 Hereinafter, the present invention will be described in more detail.

In the present invention, EVOH (A) is a saponified ethylene-vinyl acetate copolymer having an ethylene content of 20 to 60 mol%, preferably 25 to 50 mol%, and a degree of saponification of a vinyl acetate component.
90% or more, preferably 95% or more can be used. If the ethylene content is less than 20 mol%, the melt moldability is poor, while
If it exceeds mol%, the gas barrier properties will be insufficient. Also,
If the degree of saponification is less than 90%, the gas barrier properties and the thermal stability deteriorate. More preferably, the EVOH contains 0.0005 to 0.2 mol% of a silicon compound. 0.0005 mol% of silicon compound (vinylsilane compound)
Beyond this, the effects of improving thermoformability, transparency of the container, reliability of gas barrier properties, etc., are more sufficient. On the other hand, if the content of the vinylsilane compound exceeds 0.5 mol%, gels and buttocks are frequently generated, which not only deteriorates the appearance of the thermoformed container but also lowers the reliability of gas barrier properties. By the way, as the vinylsilane-based compound, the following (X),
Compounds represented by (Y) and (Z) are preferred.

Here, n is 0 to 1, m is 0 to 2, R ¹ is a lower alkyl group, an allyl group, or a lower alkyl group having an allyl group, and R ² is an alkoxyl group having 1 to 40 carbon atoms. The alkoxyl group may have a substituent containing oxygen. R ³ is hydrogen or a methyl group; R ⁴ is a hydrogen atom or a lower alkyl group; R ⁵ is a divalent organic residue in which an alkyl group or a chain carbon atom is bonded to oxygen or nitrogen; R ⁶ is hydrogen A halogen, a lower alkyl group, an allyl group, or a lower alkyl group having an allyl group, R ⁷ is an alkoxyl group or an acyloxyl group (where the alkoxyl group or the acyloxyl group may have a substituent containing oxygen or nitrogen. Good)), R ⁸ is hydrogen, halogen,
R ⁹ is a lower alkyl group, an allyl group, or a lower alkyl group having an allyl group, and R ⁹ is a lower alkyl group. More specifically, R ¹ is a lower alkyl group having 1 to 5 carbon atoms, an allyl group having 6 to 18 carbon atoms, or a lower alkyl group having 1 to 5 carbon atoms having an allyl group having 6 to 18 carbon atoms, R ⁴ Represents a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms, and R ⁵ represents an alkyl group having 1 to 5 carbon atoms or a divalent organic residue in which chain carbon atoms are mutually bonded to oxygen or nitrogen. Show,
R ⁶ is hydrogen, halogen, a lower alkyl group having 1 to 5 carbon atoms,
R 6 represents an allyl group having 6 to 18 carbon atoms or a lower alkyl group having 1 to 5 carbon atoms having an allyl group having 6 to 18 carbon atoms, and R ⁷ is an alkoxyl group or an acyloxyl group (where the alkoxyl group or the acyloxyl group is Or R ⁶ may be hydrogen, halogen, a lower alkyl group having 1 to 5 carbon atoms, an allyl group having 6 to 18 carbon atoms, or an allyl having 6 to 18 carbon atoms. A lower alkyl group having 1 to 5 carbon atoms having a group; R ⁹ represents a lower alkyl group having 1 to 5 carbon atoms; Vinylsilane compound (X),
Specific compound names of (Y) and (Z) include, for example, vinylmethoxysilane, vinylethoxysilane, vinyltri (β-methoxy, ethoxy) silane, and γ-methacryloxypropylmethoxysilane. Among them, vinylmethoxysilane and vinylethoxysilane are preferably used.

In addition, the EVOH does not impair the purpose of the present invention,
Other comonomers [e.g., propylene, butylene, unsaturated carboxylic acids or esters thereof (meth) acrylic acid,
(Meth) acrylic acid esters (methyl, ethyl), etc., and vinylpyrrolidone (N-vinylpyrrolidone, etc.)] can be copolymerized, and further, plasticizers, heat stabilizers, ultraviolet absorbers, antioxidants, coloring It is also free to blend agents, fillers, and other resins (polyamide, partially saponified ethylene-vinyl acetate copolymer, etc.). Further, the preferred melt index (MI) (at 190 ° C. under a load of 2160 g) of the EVOH used in the present invention is 0.1 to 50 g / 10 mi.
n., optimally 0.5 to 20 g / 10 min.

Thermoplastic polyurethane (TPU) used in the present invention
(B) is meltable and usually comprises two or three components such as a high molecular diol and an organic diisoisocyanate and / or a low molecular diol. The details of each component are described below.

The polymer diol is a diol of a polymer compound obtained by polycondensation, addition polymerization (for example, ring-opening polymerization) or polyaddition, and is typically a polyester diol, polyether diol, polycarbonate diol, or a co-condensate thereof. (For example, polyester-ether diol). These may be used alone or as a mixture of two or more. The average molecular weight of these high molecular weight diols is desirably in the range of 500 to 3000, preferably 500 to 2500. If the average molecular weight is too small, the compatibility with the organic diisocyanate is too good, and the elasticity of the resulting polyurethane becomes poor. on the other hand,
If the average molecular weight is too large, the compatibility with the organic diisoisocyanate will be poor and mixing during the polymerization process will not be successful, resulting in the formation of a gel or a stable polyurethane cannot be obtained.

The low molecular weight diol as the second raw material has a molecular weight of
Less than 500 low molecular weight diols, such as ethylene glycol, propylene glycol, 1,4-butanediol,
Aliphatic, alicyclic or aromatic diols such as 1,5-pentane glycol, 3-methylpentane glycol, 1,6-hexanediol, and 1,4-bishydroxyethylbenzene are exemplified. These may be used alone or in combination of two or more.

The organic diisocyanate as the third raw material is 4,4
-Diphenylmethane diisocyanate, tolylene diisocyanate, 2,2-dimethyl-4,4-diphenylmethane diisocyanate, 1,3- or 1,4-bis (isocyanatomethyl) benzene, 1,3- or 1,4- Aromatic, alicyclic or aliphatic diisocyanates such as bis (isocyanatomethyl) cyclohexane, 4,4-dicyclohexylmethane diisocyanate, and isoboron diisocyanate are exemplified. These organic diisocyanates may be used alone or as a mixture of two or more.

Various additives such as a coloring agent, a filler, an antioxidant, and an ultraviolet absorber can be freely added to the TPU as long as the effects of the present invention are not impaired.

By the way, the N (nitrogen) content in the TPU used has a great effect on the performance (delamination resistance, gel, butter, etc.) when blended with EVOH. That is, in the present invention, it is preferable that the formula (I) is satisfied. When the N content exceeds 7% by weight, gels and stripes are liable to be generated, and the effect of improving delamination resistance is small, possibly due to poor thermal stability. On the other hand, when the N content is less than 1% by weight, the effect of improving the delamination resistance is reduced, possibly due to poor compatibility or adhesion with EVOH. And
More preferably, it is 1 to 6% by weight. What is N content?
It is N wt% in TPU when TPU is measured by elemental analysis.

Furthermore, TPU, N content, and ethylene content of EVOH have an important relationship, and in the present invention, it is preferable that the formula (II) is satisfied. When N (B) / CH (A) is more than 0.2, gels and bumps are remarkably generated during film formation, and the effect of improving delamination resistance is small. On the other hand, if it is less than 0.01, the effect of improving delamination resistance is poor. More preferably, it is 0.05 to 0.18.

Further, the change in the melt viscosity of the blend of EVOH (A) and TPU (B) is an important requirement, and in the present invention, it is preferable that the formula (III) is satisfied.

If MI (0) / MI (2) is more than 10, frequent bumps occur on the film surface and the effect of improving the resistance to delamination is poor. On the other hand, if it is less than 0.01, coloring due to decomposition, generation of a gel, and the like are observed, which is not preferable in appearance. Preferably, 5 ≧ MI (0) / MI (2) ≧ 0.5
It is.

Regarding the ratio between MI (A) of EVOH and MI (B) of TPU, 0.05 ≦ MI (B) / MI (A) ≦ 20 is preferable, and 0.0
If it is 5 or less or 20 or more, streaks or uneven flow may occur at the time of film formation, especially at the time of co-extrusion film formation, and the effect of improving not only appearance but also delamination resistance may be insufficient. More preferably, 0.1 ≦ MI (B) / MI (A) ≦ 10. MI (A) is preferably 0.1 g / 10 min ≦ MI (A) ≦ 50 g / 10 min, more preferably 0.5 g / 10 min ≦ MI (A) ≦ 30 g / 10 min. Also, as MI (B), preferably 0.1 g / 10 min ≦ MI
(B) ≦ 70 g / 10 min, more preferably 0.3 g / 10 min ≦ MI (B)
≦ 50 g / 10 minutes.

Also, the blend ratio of EVOH (A) and TPU (B),
It is important that (B) / (A) satisfies a weight ratio of 2/98 to 40/60. Preferably (B) / (A) = 7/93 to 35/65
It is. If the TPU (B) is less than 2%, the effect of improving the impact delamination is not sufficient. If the TPU (B) is more than 40%, gel is likely to be generated and the gas barrier properties are undesirably reduced.

The method of blending EVOH (A) and TPU (B) is not particularly limited, and a dry blend of EVOH and TPU is used as it is, or a Banbury mixer, a single-screw or twin-screw extruder is used. For example, there is a method of pelletizing and drying. If the blend is non-uniform, or if gels and / or lumps are generated or mixed during the blend pelletizing operation, the effect of improving the impact delamination property is likely to be deteriorated. Therefore, it is desirable to use an extruder with a high degree of kneading during the blend pelletizing operation, seal the hopper opening with N ₂ , and extrude at a low temperature. More preferably, there is a method in which a dry blend resin is extruded at a low temperature by using an extruder having a high degree of kneading, the hopper opening is sealed with N _2, and the film is directly extruded at a low temperature.

It is preferable to control the moisture content of the raw materials EVOH (A) and TPU (B) prior to blending. If the water content of the raw material is large, the effect of gelation and lumps, and the improvement of impact resistance delamination will be deteriorated. Therefore, the water content is preferably set to 100 rpm or less, more preferably 50 ppm or less. The drying method is as follows.
It is preferable to dry under vacuum for 24 hours.

When blending and pelletizing, other additives (plasticizer, heat stabilizer, ultraviolet absorber, antioxidant, coloring agent,
It is free to use a filler or another resin as long as the object of the present invention is not hindered. In particular, as a countermeasure against gel generation, a hydrotalcite-based compound, a hindered phenol-based compound, and a hindered amine-based heat stabilizer are used in an amount of 0.01 to 1%.
It is preferable to add by weight%.

Among the resins (D) used in the present invention, PET refers to a polyester containing ethylene terephthalate as a main constituent unit and an ethylene terephthalate unit of 80 mol% or more, preferably 90 mol% or more, and terephthal. It may contain a dicarboxylic acid other than an acid or a glycol component other than ethylene glycol. The dicarboxylic acids other than terephthalic acid include aromatic dicarboxylic acids such as isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl-4,4 dicarboxylic acid, oxalic acid, malonic acid, and succinic acid. , Glutaric acid, adipic acid, pimelic acid,
Aliphatic dicarboxylic acids such as cyclohexanedicarboxylic acid such as aliphatic dicarboxylic acids such as cornic acid, azelaic acid, and sebacic acid can be used, and one or more of these can be used. Among them, isophthalic acid, naphthalenedicarboxylic acid, diphenyl ether dicarboxylic acid and the like are preferable. On the other hand, glycol components other than ethylene glycol include 1,3-propanediol and 1,4-propanediol.
Aliphatic glycols such as butanediol, 1,5-pentanediol, 1,6-hexanediol, 9-nonanediol, diethylene glycol and triethylene glycol;
And alicyclic diols such as cyclohexanediol and cyclohexanedimethanol, and one or more of these can be used. Above all,
Preferred are ethylene glycol, diethylene glycol, cyclohexanediol and the like.

Since the molecular weight of the thermoplastic polyester greatly affects the physical properties of the sheet or the container, the intrinsic viscosity of the thermoplastic polyester is 0.
It is desirably 60 dl / g or more, preferably 0.70 / g or more. Here, the intrinsic viscosity is a value measured at 30 ° C. in a phenol / tetrachloroethane mixed solvent (1: 1 weight ratio). The modified polyester may be freely used with heat stability, a plasticizer, a lubricant, a coloring agent, an ultraviolet absorber, an antistatic agent and the like as long as the effects of the present invention are not impaired.

PA is a linear synthetic polymer having an acid amide bond obtained by condensation of a diamine and a dicarboxylic acid, condensation of an amino acid, and ring opening of a lactam, such as 6 nylon (polycaproamide) and 6,6 nylon (polyhexaamide). Methylene adipamide), 6,10 nylon (polyhexamethylene sebacamide), 11 nylon (polyundecamide), 12 nylon (laurin lactam), 7 nylon (ω-aminoheptanoic acid), 9 nylon (ω-aminononanoic acid) , 6,4 nylon, aromatic polyamide or the like, or a copolymer or blend of two or more of these. It is particularly effective when the ratio of the number of methylene groups to the number of amide groups (CH ₂ / NHCO) is 7 or more, more preferably 8 or more.

On the other hand, PC is a method of transesterifying a diester of carbonic acid obtained from a monofunctional aromatic or aliphatic hydroxy compound with a hydroxy compound, that is, in the absence or presence of a transesterification catalyst under an inert gas atmosphere. And by reacting bisphenyl A with diphenyl carbonate under high temperature and reduced pressure. Also, a method of reacting a dihydroxy compound with a phosgene in the presence of an acid binder, that is, reacting bisphenyl A and phosgene in the presence of an acid binder (eg, caustic, pyridine) at about room temperature. Examples include those obtained by methods. These PCs are used in various fields. For example, according to Tachikawa and Sakajiri, “Plastic Materials Course [17]. Polycarbonate” (Nikkan Kogyo Shimbun, published in 1971),
The production methods and properties thereof are known in detail.

These PET, PA, and PC can be used as a single layer or as a plurality of layers. Further, these resins can be used as a blend layer. In the present invention, PET and PC are more preferably used.

In the present invention, the co-injection multilayer structure means a container precursor (hot parison, cold parison, etc.) obtained by co-injection, and a container obtained by stretching blow molding the same. The co-injection-stretched multilayer structure refers to a container obtained by reheating and stretch-blow-molding a container precursor (parison) among the above-described ones. The multi-layer parison usually uses a molding machine having two or more injection cylinders, and melts the resin (D) and the EVOH composition (C) in a single mold in one or more mold clamping operations, respectively. And / or simultaneously injecting alternately and / or concentric nozzles at different timings from the injection cylinder. For example, the previously injected resin (D) may be on the inner and outer surface layers, the later injected EVOH composition layer and / or the inner resin (D) layer on which the resin (D) has been first injected, and in some cases, Injects the EVOH composition (C) and / or the resin (D) again, and forms a middle layer. The inner layer is completely enclosed by the innermost and outermost resin (D) layers. It is not particularly limited in terms of facilities. The multi-layer parison is heated directly to a warm state or heated to 75 to 150 ° C. by a heating element such as a block heater or an infrared heater,
It is stretched and blown, stretched 1 to 5 times in the machine direction, then blown 1 to 4 times with compressed air, etc., and the resin (D) and / or the EVOH composition (C) are stretched uniaxially or biaxially. Thus, a multilayer stretch blow container is obtained. The heating stretch blow step is not particularly limited in terms of equipment.

Since the conditions for heat-treating the stretch blow container greatly affect the impact delamination resistance of the container, it is more preferable to satisfy the following formula (IV).

(Tp-20)>Tc> Tb (IV) where Tp: melting point or softening point of resin (D) (° C) Tc: heat treatment temperature of container (° C) Tb: melting point or softening point Tc of resin (B) If it is larger than Tp-20, the outermost layer resin (D) is softened and the stretching orientation is lowered, possibly resulting in poor strength of the container. On the other hand, when Tc is lower than Tb, the impact delamination resistance of the multilayer container is not improved. The heat treatment time is preferably about 1 to 100 seconds, and the heat treatment method is not particularly limited, but generally, a method of increasing the mold temperature in the blowing step, or heat treating the mold again under pressure. And heat treatment with hot air or a heat medium. When removing the container having a high temperature after the heat treatment, a method of rapidly cooling the heating mold or the heating medium, a method of again cooling the mold with a cooling mold, and cooling with a cooling mold under pressure may be used.

The co-injection multilayer structure of the present invention is a resin (D), that is, PE
EVOH composition using one or more of T, PA, or PC resin (referred to as base materials 1, 2 etc., and resins different from 1 and 2) and EVOH composition (C) One or more layers each of the EVOH composition and the base layer (the same resin as the innermost and outermost base layers or may be different)
The innermost and outermost base layers are almost completely enclosed with an intermediate layer containing one or more layers. Generally, the base material 1 / EVOH composition / base material 1, the base material 1 / EVOH composition / base material 2 / Base 1, Base 1 / EV
OH composition / substrate 1 / EVOH composition / substrate 1, substrate 1 / EVOH composition / substrate 2 / EVOH composition / substrate 1, and the like. Regarding the thickness of the parison, the total thickness is 2 to 5 mm, the EVOH composition layer is 10 to 100 μm in total, and generally the thinner the EVOH composition, the smaller the number of EVOH composition layers, the further the outer layer side The closer it is, the more likely delamination due to the impact of the container is. Further, the total thickness of the container body is generally 100 to 3000 μ, and can be properly used depending on the application. At this time, the total thickness of the EVOH composition layer is 2 to 200 µ, preferably 5 to 100 µ.

In the co-injection multilayer structure of the present invention, it is not necessary to provide an interlayer adhesive in particular between the EVOH composition layer and the substrate,
It does not prohibit providing this.

Hereinafter, the present invention will be further described with reference to Examples, but the present invention is not limited thereto.

F. Example EVOH having an ethylene content of 48 mol%, a degree of saponification of 99.4%, and a melt index (MI 190 ° C, 2160g load) of 14g / 10min.
(A) EVOH obtained by dry blending 20 parts by weight of a polyester-based polyurethane having an N content of 2.8% by weight with 80 parts by weight (B).
Composition (C), also as PET resin, intrinsic viscosity 0.71 / g
A co-injection stretch blow bottle was made using a co-injection stretch blow molding device (50 HT, 750 ml, 2 pieces) manufactured by Nissei ASB using the isophthalic acid-modified PET. At this time, the extruder tip temperature on the PET side is 250 ° C, the extruder temperature on the EVOH side is 180 ° C, PE
Co-injection stretch blow molding is performed at 240 ° C in the hot runner block where T and EVOH merge, and the average thickness of the body is PET
A multi-layer co-injection stretch blow-molded bottle having 190 μm, the intermediate layer EVOH composition 20 μm, and the outer layer PET 90 μm was obtained. MI (0) / MI at this time
(2) = 4.5.

By the way, in this bottle body, vertical 50mm × horizontal 15mm, thickness 1.0mm, 2.0mm
And 4.0 mm irregularities. The multi-layer container was filled with water, and from the height of 1 m under normal pressure, the body portion was horizontally dropped repeatedly, and delamination occurred at the fifth time.

Examples 2 to 6 and Comparative Examples 1 to 3 Bottles were obtained under the same conditions as in Example 1 except as shown in Table 1. Table 1 shows the results.

G. Effects of the Invention The co-injection multilayer structure of the present invention has a good appearance and good gas barrier property when empty or the contents are filled under normal pressure or high pressure and subjected to impact, without causing interlayer delamination. It is.

Claims (2)

(57) [Claims] (1) Ethylene having an ethylene content of 20 to 60 mol%.
At least one surface selected from thermoplastic polyesters, polyamides and polycarbonates is provided on at least one side of the composition (C) layer comprising 60 to 98% by weight of the vinyl alcohol copolymer (A) and 40 to 2% by weight of the thermoplastic polyurethane (B). A co-injection multilayer structure having a resin (D) layer and satisfying the following formulas (I) and (II). 1 ≦ N (B) ≦ 7 (I) 0.01 ≦ N (B) / CH (A) ≦ 0.2 (II) where (N) B; nitrogen content (% by weight) of polyurethane (B) CH (A) ; Ethylene content (mol%) of EVOH (A) 2. The multilayer structure according to claim 1, wherein the multilayer structure satisfies the following formula (III). 0.01 ≦ MI (0) / MI (2) ≦ 10 (III) where MI (0); melt index value of composition (C) under a load of 220 ° C.-10.9 kg (g / 10 minutes) MI (2) ); Melt index value of the composition (C) after heat treatment at 220 ° C. for 2 hours in a nitrogen atmosphere (g / 10 minutes)